HomeMy WebLinkAboutCC_2021_01_26_San Luis Obispo County MJHMP Plan 4_16_2020_Complete San Luis Obispo County
Multi-Jurisdictional Hazard Mitigation Plan
2019 Update
October 2019
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Table of Contents
TABLE OF CONTENTS
Section 1 Promulgation and Adoption.............................................................................................1-1
1.1 County of San Luis Obispo Board of Supervisors 2005 Adoption........................................1-1
1.2 County of San Luis Obispo Board of Supervisors 2011 Adoption........................................1-2
1.3 San Luis Obispo County Flood Control and Water Conservation District 2013 Adoption
................................................................................................................................................................................1-3
1.4 County of San Luis Obispo Board of Supervisors 2013 Adoption........................................1-4
1.5 County of San Luis Obispo Board of Supervisors 2019-2020 Plan Adoption Resolution
................................................................................................................................................................................1-4
Section 2 Executive Summary............................................................................................................2-1
2.1 Plan Description.......................................................................................................................................2-1
2.2 Plan Purpose and Authority.................................................................................................................2-2
Section 3 Planning Process.................................................................................................................3-1
3.1 Background on Mitigation Planning in San Luis Obispo County.........................................3-1
3.2 What's New in the Plan Update.........................................................................................................3-1
3.2.1 Changes in Jurisdictional Participation..........................................................................3-2
3.2.2 Plan Section Review and Analysis - 2019 Update.....................................................3-2
3.3 Local Government Participation.........................................................................................................3-5
3.4 Planning Process......................................................................................................................................3-7
3.4.1 Phase 1: Organize Resources.............................................................................................3-8
3.4.2 Phase 2: Assess Risks ........................................................................................................3-20
3.4.3 Phase 3: Develop the Mitigation Plan ........................................................................3-21
3.4.4 Phase 4: Implement the Plan and Monitor Progress............................................3-22
Section 4 San Luis Obispo County Profile........................................................................................4-1
4.1 County History..........................................................................................................................................4-1
4.2 Geography..................................................................................................................................................4-1
4.3 Cities and Communities........................................................................................................................4-3
4.4 Population and Demographics Profile............................................................................................4-6
4.4.1 Social Vulnerability.............................................................................................................4-10
4.5 Economy...................................................................................................................................................4-19
4.6 Climate......................................................................................................................................................4-21
4.7 Transportation Systems......................................................................................................................4-22
4.8 Governing Body.....................................................................................................................................4-22
4.9 Land Use...................................................................................................................................................4-22
4.10 Development Trends.........................................................................................................................4-23
Section 5 Risk Assessment..................................................................................................................5-1
5.1 Hazard Identification and Prioritization..........................................................................................5-2
5.1.1 Methodology and Results................................................................................................5-2
5.1.2 Disaster Declaration History............................................................................................5-5
5.1.3 Climate Change Considerations Summary.............................................................5-10
Table of Contents
5.1.4 Overview of Hazard Identification and Risk Assessment..................................5-11
5.2 Assest Summary....................................................................................................................................5-12
5.2.1 Assets Expsoure.......................................................................................................................5-12
5.3 Hazard Analysis and Risk Assessment..........................................................................................5-32
5.3.1 Adverse Weather: General...............................................................................................5-32
5.3.2 Adverss Weather: Thunderstorm/Heavy Rain/Dense Fog/Freeze...................5-35
5.3.3 Adverse Weather: High Wind/Tornado......................................................................5-54
5.3.4 Adverse Weather: Extreme Heat...................................................................................5-68
5.3.5 Agricultural Pest Infestation, Plant Disease, Marine Invasive Species and Tree
Mortality.................................................................................................................................5-78
5.3.6 Biological Agents (Naturally Occurring).....................................................................5-91
5.3.7 Coastal Storm/Coastal Erosion/Sea Level Rise......................................................5-101
5.3.8 Dam Incidents.....................................................................................................................5-137
5.3.9 Drought and Water Shortage......................................................................................5-152
5.3.10 Earthquakes, Faults, and Liquefaction.......................................................................5-168
5.3.11 Flooding................................................................................................................................5-213
5.3.12 Landslides and Debris Flow...........................................................................................5-250
5.3.13 Soil Hazards: Land Subsidence....................................................................................5-263
5.3.14 Tsunami and Seiche.........................................................................................................5-269
5.3.15 Wildfires................................................................................................................................5-281
5.3.16 Hazardous Materials Incidents....................................................................................5-297
Section 6 Capability Assessment.......................................................................................................6-1
6.1 San Luis Obispo County's Mitigation Capabilities Overview..................................................6-1
6.1.1 San Luis Obispo County's Regulatory Mitigation Capabilities.............................6-3
6.1.2 Combining Designations..................................................................................................6-17
6.2 San Luis Obispo County's Administrative and Technical Mitigation Capabilities.......6-18
6.2.1 Department of Planning and Building........................................................................6-18
6.2.2 Office of Emergency Services.........................................................................................6-18
6.2.3 Environmental Health Services Division.....................................................................6-19
6.2.4 Public Works Department................................................................................................6-19
6.2.5 Local Boards, Commissions, Committees..................................................................6-20
6.2.6 State and Federal Programs............................................................................................6-21
6.3 San Luis Obispo County's Fiscal Mitigation Capabilities.......................................................6-22
6.4 Hazard Specific Mitigation Capabilities.......................................................................................6-23
6.4.1 Adverse Weather capabilities.........................................................................................6-23
6.4.2 Agricultural Pest Infestation and Plant Disease Capabilities..............................6-23
6.4.3 Biological Agents (Naturally Occurring) Capabilities............................................6-24
6.4.4 Coastal Storm Capabilities...............................................................................................6-24
6.4.5 Dam Failure Capabilities...................................................................................................6-24
6.4.6 Drought and Subsidence Capabilities.........................................................................6-25
6.4.7 Earthquake Capabilities....................................................................................................6-26
6.4.8 Flood Capabilities................................................................................................................6-27
6.4.9 Hazardous Materials Capabilities.................................................................................6-29
6.4.10 Landslide Risk Reduction Capabilities........................................................................6-30
6.4.11 Tsunami Capabilities..........................................................................................................6-30
Table of Contents
6.4.12 Wildfire Capabilities...........................................................................................................6-31
6.4.13 Climate Change Capabilities...........................................................................................6-34
6.5 Opportunities for Enhancement.....................................................................................................6-35
Section 7 Mitigation Strategy............................................................................................................7-1
7.1 Goals and Objectives..............................................................................................................................7-1
7.2 Identification and Analysis of Mitigation Actions.......................................................................7-3
7.2.1 Prioritization Process............................................................................................................7-5
7.3 Mitigation Action Plan...........................................................................................................................7-6
7.3.1 Progress of Previous Mitigating Actions.......................................................................7-7
7.3.2 Updated Mitigation Action Plan......................................................................................7-9
Section 8 Implementation and Monitoring.....................................................................................8-1
8.1 Implementation........................................................................................................................................8-1
8.1.1 Role of Hazard Mitigation Planning Committee in Implementation and
Maintenance............................................................................................................................8-2
8.1.2 Process for Incorporation into Existing Planning Mechanisms............................8-2
8.2 Maintenance Monitoring and Evaluation.......................................................................................8-3
8.2.1 Maintenance/Monitoring Schedule................................................................................8-4
8.2.2 Maintenance and Evaluation Process.............................................................................8-4
8.2.3 Disaster Proclamation or Declaration............................................................................8-5
8.3 Continued Public Involvement...........................................................................................................8-5
List of Jurisdictional Annexes
Annex A City of Arroyo Grande
Annex B City of Atascadero
Annex C City of Grover Beach
Annex D City of Morro Bay
Annex E City of Paso Robles
Annex F City of Pismo Beach
Annex G City of San Luis Obispo
Annex H Avila Beach CSD
Annex I Ground Squirrel Hollow CSD
Annex J Heritage Ranch CSD
Annex K Los Osos CSD
Annex L Nipomo CSD
Annex M Oceano CSD
Annex N San Miguel CSD
Annex O San Simeon CSD
Annex P Templeton CSD
Annex Q Cayucos Sanitary District
Annex R Port San Luis Harbor District
Annex S San Luis Obispo Flood Control and Water Conservation District
Annex T South San Luis Obispo County Sanitation District
List of Appendices
Appendix A Hazard Mitigation Planning Committee
Table of Contents
Appendix B Mitigation Categories and Alternatives
Appendix C Planning Process Documentation
Appendix D Jurisdictional Adoption Resolutions
Appendix E Critical Facilities
Appendix F Climate Change Adaptation Planning Guide Consistency Summary
Appendix G References
Acknowledgements
San Luis Obispo County Board of Supervisors
Debbie Arnold, Chair
Adam Hill,Vice Chair
Lynn Compton
Bruce Gibson
John Peschong
County Planning& Building
Trevor Keith, Director
Rob Fitzroy, Deputy Director
Airlin Singewald, Division Manager
Brian Pedrotti, Supervising Planner
Jillian Ferguson, Project Manager
Kylie Hensley, Long Range Planner
County Office of Emergency Services
Joe Guzzardi, Emergency Services Manager
Scott Milner, Emergency Services Coordinator
Consulting Team -Wood Environment and Infrastructure Solutions, Inc.
Jeff Brislawn, Project Manager
Scott Field, Senior Planner
Dan Gira, Senior Planner
Julia Pujo, Senior Planner
Table of Contents
Amy Carr, Planner
Marta Blanco Castano, GIS Analyst/ Planner
Kaylan Lamb, Planner
Hannah Thomas, Planner
Members of the Hazards Mitigation Committee:
Rebecca Whiteside, Planning & Building GIS Robert Hill, Sustainability and Natural Resources
Analyst, County of San Luis Obispo Official, City of San Luis Obispo
Kate Ballantyne, Public Works Deputy Director, Chris Read, Sustainability Manger, City of San Luis
County of San Luis Obispo Obispo
Mladen Bandov, Public Works Water Resources James Blattler, Administrative Analyst, City of San
Engineer, County of San Luis Obispo Luis Obispo Fire Department
Lynda Auchinachie,Agriculture Department Mychal Jones, Plant Superintendent/Chief Plant
Environmental Resource Specialist, County of San Operator, South San Luis Obispo County
Luis Obispo Sanitation District
Stephen Lieberman, Fire Chief, City of Arroyo Rick Koon, District Manager, Cayucos Sanitary
Grande District
Camilla Karamanlis, Program Analyst, City of Chris Munson, Facilities Manager, Port San Luis
Arroyo Grande Harbor District
Matt Downing, Planning Manager, City of Arroyo Brad Hagemann, General Manager, Avila Beach
Grande Community Services District
Tom Peterson, Fire Marshall, City of Atascadero Dan Gilmore, General Manager, Ground Squirrel
Hollow Community Services District
Casey Bryson, Fire Chief, City of Atascadero Scott Duffield, General Manager, Heritage Ranch
Community Services District
John Peters, Chief of Police, City of Grover Beach Renee Osborne, General Manger, Los Osos
Community Services District
Steve Knuckles, Fire Chief, City of Morro Bay Rob Roberson, Interim General Manager/Fire
Chief, San Miguel Community Services District
Matt Vierra, Fire Marshall, City of Morro Bay Scott Young, Assistant Fire Chief, San Miguel
Community Services District
Jonathan Stornetta, Fire Chief, City of Paso Courtney Murguia, Office Manager—Grace
Robles Environmental, San Simeon Community Services
District
Mike Gruver,Associate Planner, City of Pismo Carey Casciola, Business&Accounting Manager,
Beach Oceano Community Services District
Keith Aggson, Fire Chief, City of San Luis Obispo Nicole Miller,Account Administrator, Oceano
Community Services District
Rodger Maggio, Fire Marshall, City of San Luis Jeff Brilz, General Manager,Templeton
Obispo Community Services District
Bill White, Fire Chief,Templeton Community
Services District
Section 1
Adoption Resolutions
SECTION 1 ADOPTION RESOLUTIONS
The following is a record of adoption of this plan by San Luis Obispo County since its inception in 2005.
Jurisdictional adoption resolutions can be referenced in Appendix D.
1.1 County of San Luis Obispo Board of Supervisors 2005 Adoption
Adoption by Local Governing Body: §201.6(c)(5)
November 1, 2005
To the Citizens, Visitors, Employees, and Officials of San Luis Obispo County:
As the costs of damage from natural disasters continue to increase, the County of San Luis Obispo realizes
the importance of identifying effective ways to reduce vulnerability to disasters. Natural hazard mitigation
plans assist communities in reducing risk from natural hazards by identifying resources, information, and
strategies for risk reduction, while helping to guide and coordinate mitigation activities.
As a result the County of San Luis Obispo has developed this Local Hazard Mitigation Plan (LHMP) which
provides guidance on how to reduce risk from natural hazards. This LHMP works in conjunction with
other County plans, including the General Plan, and hazard mitigation plans developed for specific
programs such as flood control and fire prevention.
This letter promulgates the San Luis Obispo County Local Hazard Mitigation Plan and constitutes the
adoption of the Plan. This Local Hazard Mitigation Plan becomes effective on approval by the San Luis
Obispo County Board of Supervisors on the date indicated below.
Original signed by Shirley Bianchi
Chairperson, Board of Supervisors November 1, 2005
County of San Luis Obispo
Section 1
Adoption Resolutions
1.2 County of San Luis Obispo Board of Supervisors 2011 Adoption
Adoption by Local Governing Body: §201.6(c)(5)
August 16, 2011
To the Citizens, Visitors, Employees, and Officials of San Luis Obispo County:
As the costs of damage from natural disasters continue to increase, the County of San Luis Obispo
continues to realize the importance of identifying effective ways to reduce vulnerability to disasters.
Natural hazard mitigation plans assist communities in reducing risk from natural hazards by identifying
resources, information, and strategies for risk reduction, while helping to guide and coordinate mitigation
activities.
As a result the County of San Luis Obispo has developed this updated and revised Local Hazard Mitigation
Plan (LHMP) which provides guidance on how to reduce risk from natural hazards.
The LHMP works in conjunction with other County plans, including the General Plan, and hazard
mitigation plans developed for specific programs such as flood control and fire prevention.
This letter promulgates the San Luis Obispo County Local Hazard Mitigation Plan and constitutes the
adoption of the Plan. This Local Hazard Mitigation Plan becomes effective on approval by the San Luis
Obispo County Board of Supervisors on the date indicated below.
Original signed by Adam Hill
Chairperson, Board of Supervisors August 16, 2011
County of San Luis Obispo
Section 1
Adoption Resolutions
1.3 San Luis Obispo County Flood Control and Water Conservation District 2013
Adoption
Adoption by Local Governing Body: §201.6(c)[5]
December 10,2013
To the Citizens_ Visitors. F111pkn•ces.and Officials ofsan Luis Obispo Cnuttty:
As the costs of datnage from natural disasters continue to increase.tits County ul'Saii
Luis Obispo continues to realize the importance of identifying effective■vivs to reduce
vutnerabil4v to disasters. Natural hazard mitigation plans assist communities in reducing risk
from natural hazards by identifying resources, inforination,and strategies for risk reduction.
►►Nic helping to guide and coordinate mitigation activities.
As a result.the Cnuntr of Sall 1.0 is Obispo has developed this updated and revised
Local Hazard Mitigation 11latt(LI-IMP)which provides muidance on how to reduce risk front
natural hazards.
The L1IMP works in conjunction with the other County plans, iticluding the General
Plan,and hazard mitieption plans developed for specific programs such as flood control and
fire prevention.
'Ili is letter promulgates the San l.uis Obispo County Local Hazzrd Mitigation Pian and
constitutes the adoption of the flan.This Local Hazard Mitigation Plan becomes of eeti.c un
approval by tite Sart Luis Obispo County Flood Control and Water Conservation Districl on
the date indicated bclo►v_
r
Bruce Gibson
Acting Chairperson.Board ol'Supervisors December 10,2013
San [.tis Ol:tispo CountV Blood Control
And Water Conservation District
ObispoSan Luis
Section 1
Adoption Resolutions
1.4 County of San Luis Obispo Board of Supervisors 2013 Adoption
Adoptiott by Local Goveming Body-. §201.6(c){a)
December 10. 2013
Co [lee Citizens, Visitors,Empiovecs.and Officials of San Luis Obispo County-
As the costs of'damagc I'rorn natura14isame"colitill lie it) increase, 111 County of'San
Luis Obispo continues to realixc ilia importance of idcntifving effective ways to reduce
vuIncrabiIity to disasters.Nat uraI heard mitigation plans assist communities in reducing risk
lr«ni natural hazards by idcnlifying resources, intorneation,and strategics Ior risk reduction,
while lie[ping to guide and coordinate: oil itigalioil activities.
As a result. the County of Sate Luis Obispo has do-eloped ill is updated and revised
Local I laziird Mitigation Plan(I.i IMF') which provides guidance on leo►► to reduce risk from
natural linyards.
The LIIN111 works in conJunction with the other Coumv places, incIuding the General
PIan. and hazard initigaIion plans developed for specific programs such as flood comroI and
fire pre►enf lore.
I'leis letter prom telgates the Sari Luis Obispu Court} Local f lazard l41itigaticm flan and
cceristitures the aLtoption of, be I,Ian.'rhis Local Hazard MiIigation Plan beenmes effective on
approval lay the San Luis Obispo Coil 111% Board of Supervisors nn the Bite indicated he tow.
Bruce Gibson 1
Acting Chairperson, Board of Supervisors December 10.2U 13
1.5 County of San Luis Obispo Board of Supervisors 2019-2020 Plan Adoption
Resolution
lution
ObispoSan Luis
Section 2
Executive Summary
SECTION 2 EXECUTIVE SUMMARY
2.1 Plan Description
The mounting cost of disaster recovery in the nation and State of California over the past decades has
prompted a renewed interest in proactively determining effective ways to minimize hazard vulnerability,
Hazard mitigation planning plays an important role in building resilience through identifying
vulnerabilities and potential solutions in mitigation actions.The County of San Luis Obispo, its
municipalities and its special districts have to develop this local hazard mitigation plan, which underwent a
comprehensive update in 2019.The goal of this plan is to arrive at practical, meaningful, attainable and
cost-effective mitigation solutions to reduce vulnerability to the identified hazards and ultimately reduce
both human and financial losses from hazard events.
The following jurisdictions participated in the development of this plan:
Lead Jurisdiction:
• County of San Luis Obispo
Municipalities:
• City of Arroyo Grande
• City of Atascadero
• City of Grover Beach
• City of Morro Bay
• City of Paso Robles
• City of Pismo Beach
• City of San Luis Obispo
Community Services Districts:
• Avila Beach CSD
• Ground Squirrel Hollow CSD
• Heritage Ranch CSD
• Los Osos CSD
• Nipomo CSD
• Oceano CSD
• San Miguel CSD
• San Simeon CSD
• Templeton CSD
Special Districts:
• San Luis Obispo County Flood Control and Water Conservation District
• Cayucos Sanitary District
• Port San Luis Harbor District
• South San Luis Obispo County Sanitation District
Development of this mitigation plan included assessing mitigation capabilities, securing political support,
and soliciting input and approval from each of the involved communities.
Section 2
Executive Summary
Risk assessments were performed that identified and evaluated priority natural and human-caused
hazards that could impact the County and its jurisdictions. Historical hazard events are described.The
future probability of these identified hazards and their impact on communities within the County is
described.
Vulnerability assessments summarize the identified hazards' impact to critical structures, infrastructure,
and future development. Estimates of potential dollar losses to vulnerable structures are presented.
The risk and vulnerability assessments were used to determine mitigation goals and objectives to
minimize long-term vulnerabilities to the identified hazards.These goals and objectives were the
foundation behind the development of a comprehensive range of specific attainable mitigation actions.
This plan was originally developed in 2005, updated in 2011 and 2013, and underwent a comprehensive
update in 2019. A significant change to the plan in 2019 was the inclusion of the municipalities and
special districts, broadening it from a County-specific plan to a multi-jurisdictional document prepared in
coordination with the participating entities and input from the public.This plan entails adopting,
implementing, assigning responsibility, monitoring, and reviewing this hazard mitigation plan overtime,
to ensure the goals and objectives are being achieved and the plan remains a relevant document.
2.2 Plan Purpose and Authority
The Disaster Mitigation Act (DMA) of 2000, also commonly known as "The 2000 Stafford Act
Amendments" (the Act), constitutes an effort by the Federal government to reduce the rising cost of
disasters. The Act stresses the importance of mitigation planning and disaster preparedness prior to an
event.
Section 322 of the DMA requires local governments to develop and submit mitigation plans in order to
qualify for the Federal Emergency Management Agency's (FEMA) Hazard Mitigation Assistance (HMA)
grant program funds. For disasters declared after November 1, 2004, San Luis Obispo County must have a
Local Hazard Mitigation Plan (LHMP) approved pursuant to §201.6 in order to receive HMA funding. The
LHMP is written to meet the statutory requirements of DMA 2000 (P.L. 106-390), enacted October 30,
2000 and 44 CFR Part 201 — Mitigation Planning, Interim Final Rule, published February 26, 2002. The
HMA grants include the Hazard Mitigation Grant Program (HMGP), Pre-Disaster Mitigation (PDM)
program, and the Flood Mitigation Assistance (FMA) program. Additional FEMA mitigation funds include
the HMGP Post Fire funding associated with Fire Management Assistance Grant (FMAG) declarations, the
Building Resilient Infrastructure and Communities (BRIC) funding associated with the 2018 Disaster
Recovery Reform Act (DRRA), and the Rehabilitation of High Hazard Potential Dams (HHPD) Grant
Program.
To facilitate implementation of the DMA 2000, the Federal Emergency Management Agency (FEMA)
created an Interim Final Rule (the Rule), published in the Federal Register in February of 2002 at section
201 of 44 CFR.The Rule spells out the mitigation planning criteria for States and local communities.
Specific requirements for local mitigation planning efforts are outlined in section §201.6 of the Rule. In
March 2013 FEMA released The Local Mitigation Planning Handbook (Handbook) as the official guide for
local governments to develop, update and implement local mitigation plans. The Handbook complements
and references the October 2011, FEMA Local Mitigation Plan Review Guide (Guide) in order to help
"Federal and State officials assess Local Mitigation Plans in a fair and consistent manner." Local
jurisdictions must demonstrate that proposed mitigation actions are based upon a sound planning
Section 2
Executive Summary
process that accounts for the inherent risk and capabilities of the individual communities as stated in
section §201.5 of the Rule. Throughout the 2019 update of this LHMP the Handbook and Guide was
consulted for the purpose of ensuring thoroughness, diligence, and compliance with the DMA 2000
planning requirements.
The 2019 update occurred concurrent with the update of the County General Plan Safety Element update
to ensure consistency with hazards and mutually reinforcing policies. In addition to following the DMA
requirements the update addressed the following State of California legislation requirements that relate
to the General Plan and LHMP:
• Senate Bill (SB) 379: Requires inclusion of climate adaptation strategies in General Plan Safety
Elements and encourages inclusion of climate change discussion in LHMP updates;
• SB 1000 requires environmental justice and social equity considerations in the General Plan update;
these considerations were also addressed in the inclusion of social vulnerability and related discussion
in Section 4 San Luis Obispo County Profile and mitigation action prioritization criteria detailed in
Section 7.
• Assembly Bill (AB) 2140 which recommends adoption by reference or incorporation of the LHMP into
the Safety Element of the General Plan, following LHMP approval.
This Local Hazard Mitigation Plan was prepared jointly by the County of San Luis Obispo;the Cities of
Arroyo Grande, Atascadero, Grover Beach, Morro Bay, Paso Robles, Pismo Beach, and San Luis Obispo; the
Community Services Districts of Avila Beach, Ground Squirrel Hollow, Heritage Ranch, Los Osos, Nipomo,
Oceano, San Miguel, San Simeon, and Templeton; and special districts including the San Luis Obispo
County Flood Control and Water Conservation District, the Cayucos Sanitary District, the Port San Luis
Harbor District, and the South San Luis Obispo County Sanitation District. The risk assessment and
mitigation strategies within this plan were developed jointly to benefit all of the above jurisdictions and
make them more resilient to future disasters.
Section 3
Planning Process
SECTION 3 PLANNING PROCESS
DMA -. . .
An open public involvement process is essential to the development of an effective plan. In order to develop a more
comprehensive approach to reducing the effects of natural disasters, the planning process shall include:
(1) An opportunity for the public to comment on the plan during the drafting stage and prior to plan approval;
(2) An opportunity for neighboring communities, local and regional agencies involved in hazard mitigation
activities, and agencies that have the authority to regulate development as well as businesses, academia,
and other private and non-profit interests to be involved in the planning process;and
(3) Review and incorporation, if appropriate, of existing plans,studies, reports, and technical information.
[The plan shall document]the planning process used to develop the plan, including how it was prepared, who was
involved in the process, and how the public was involved.
3.1 Background on Mitigation Planning in San Luis Obispo County
The primary purpose of the San Luis Obispo County Multi-Jurisdictional Hazard Mitigation Plan (LHMP)
update is to reduce or eliminate long-term risk to people and property from natural hazards and their
effects on the San Luis Obispo County planning area. San Luis Obispo County recognized the need and
importance of a Local Hazard Mitigation Plan (LHMP) and initiated its development in 2005 after receiving
a grant from the Federal Emergency Management Agency(FEMA), which also served as the primary
funding source for this plan.The original LHMP was developed in 2005, updated in 2011, and most
recently in 2013 with final approval from FEMA in 2014.Additional details on the previous planning effort
can be referenced in the 2014 Plan.
The plan underwent a comprehensive update in 2019. The planning process followed during the update
was similar to what was used in the original plan development. This planning process utilized the input
from a multi jurisdictional Hazard Mitigation Planning Committee (HMPC). A significant change from the
2014 Plan is the inclusion of all of the incorporated communities within the planning area (seven), nine
community service districts, and four special districts. Wood Environment & Infrastructure Solutions, Inc
(Wood) was procured to assist with the update in 2019. The process is described further in this section
and documented in Appendix C.
3.2 What's New in the Plan Update
A local jurisdiction must review and revise its plan to reflect
changes in development,progress in local mitigation efforts,
• and changes in priorities, and resubmit it for approval within
5 years in order to continue to be eligible for mitigation
project grant funding.
The updated LHMP complies with Federal Emergency Management Agency(FEMA) guidance and
California Office of Emergency Services guidelines for Local Hazard Mitigation Plans.The update followed
the requirements noted in the Disaster Mitigation Act (DMA) of 2000 and FEMA's 2013 Local Hazard
Mitigation Planning Handbook.
Section 3
Planning Process
This LHMP update involved a comprehensive review and update of each section of the 2014 plan and
includes an assessment of the progress in evaluating, monitoring and implementing the mitigation
strategy outlined in the initial plan. The planning process provided an opportunity to review jurisdictional
priorities related to hazard significance and mitigation action, and revisions were made where applicable
to the plan and the municipal annexes. Another major change in priority was the desire to expand the
LHMP into a multi jurisdictional plan (see subsection 3.2.1). Only the information and data still valid from
the 2014 plan was carried forward as applicable into this LHMP update.
3.2.1 Changes in Jurisdictional Participation
A significant change to the 2019 Plan is that it is now a multi jurisdictional HMP. Previously in the 2014
Plan, the only additional jurisdiction covered by the LHMP was the San Luis Obispo County Flood Control
and Water Conservation District (FCWCD).The FCWCD continued to participate in the 2019 planning
process, in addition to four(4) other special districts, nine (9) community service districts (CSD) and
participation from all seven (7) incorporated municipalities in the County. The municipalities previously
had been covered by separate LHMPs. All of the municipalities previously had local hazard mitigation
plans, which were used as the basis to inform and update jurisdictional annexes. As such, this Plan
constitutes an LHMP update for those jurisdictions and also for the County, County FCWCD, Los Osos CSD
and the South San Luis Obispo County Sanitation District, which were also covered by previous LHMPs.
One Community Service District (CSD), Oceano, had recently completed and submitted its LHMP to FEMA
for approval in 2019; this plan was approved by FEMA in 2019 as a single jurisdictional plan. The LHMP is
included in its entirety as an annex for easy reference and coordination on mitigation activities, and to be
considered for inclusion as part of the next five year update of the County multi jurisdictional HMP. The
Cambria CSD and Cambria Healthcare District have a FEMA-approved LHMP (February 2018) and are not
covered in this plan. This Plan constitutes a new LHMP for the following jurisdictions:
Community Service Districts:
• Avila Beach CSD
• Ground Squirrel Hollow CSD
• Heritage Ranch CSD
• Nipomo CSD
• San Miguel CSD
• San Simeon CSD
• Templeton CSD
Special Districts:
• Cayucos Sanitary District
• Port San Luis Harbor District
3.2.2 Plan Section Review and Analysis - 2019 Update
During the 2019 plan update, the HMPC updated each of the sections of the previously approved plan to
include new information.Wood developed a summary of each section in the plan and guided the HMPC
through the elements that needed updating during the kickoff meeting in January 2019. This included
analyzing each section using FEMA's local plan update guidance (2013) to ensure that the plan met the
latest requirements. In addition, the FEMA Local Mitigation Plan Review Tool that was provided with the
Section 3
Planning Process
approval of the 2014 version of this plan was reference, in particular the 2014 FEMA comments on
opportunities for improvement were considered and addressed in the 2019 update. The HMPC and Wood
determined that nearly every section of the plan would need revision to align the plan with the latest
FEMA planning guidance and requirements. A summary of the changes in this plan update is highlighted
in the table below.
Table 3-1 San Luis Obispo County Hazard Mitigation Plan Update Highlights
Plan Section Summary of Plan Review,Analysis,and Updates
1. Promulgation and Includes history of previous adoptions
Adoption Plan will be re-adopted as part of the update process
2. Introduction and
Revised to reflect updated plan and 2019 planning process
Executive Summary
Describes and documents the planning process for the 2019 update, including
coordination among agencies
Describes how 2014 plan was integrated with/into other planning efforts.
3. Planning Process Removed 2014 planning process info.
Describes changes to jurisdictional participation
Describes 2019 public participation process
Describes the Hazard Mitigation Planning Committee
Describes the 10 step process followed for the update
Updated with recent census data and current economy description
4.County Profile Updated land use and development trends
Drought and Coastal Storm are now profiled as separate hazards and are no longer part of
Adverse Weather
Extreme heat has been added as a hazard under Adverse Weather
Marine invasive species has been added to Agricultural pest infestation and plant disease
Vector borne disease has been added to Biological Agents
Discussion on levee failure has been added to Flood
5. Hazard Assessment Debris Flow has been added to Landslides
Coastal storms and sea level rise have been added to Coastal Erosion
Subsidence was added as a standalone hazard profile
Climate change information has been added to each hazard profile
Updated list of disaster declarations to include recent data.
Updated tables to include recent National Center for Environmental Information data.
Updated past occurrences for each hazard to include recent data.
2014 Plan on Vulnerability Assessment is now included with the Risk Assessment section as
subsections by hazard.
Updated critical facilities identified from the 2014 plan.
Updated growth and development trends to include recent Census and local data sources.
5. Risk Assessment Updated historic and cultural resources using local/state/national sources.
Updated property values for vulnerability and exposure analysis, using updated building
information based on assessor's data.
Updated estimate flood losses using the latest Digital Flood Insurance Rate Map (DFIRM)
and assessor's data.
Section 3
Planning Process
Plan Section Summary of Plan Review,Analysis,and Updates
Updated National Flood Insurance Program (NFIP) data and Repetitive Loss structure data
from the previous plan.
Incorporated new hazard loss estimates since 2014, as applicable.
Used updated GIS inventory data to assess wildfire threat to the County
Updated HAZUS-MH Level I earthquake vulnerability analysis data
Updated information regarding specific vulnerabilities to hazards, including maps and
tables of specific assets at risk,specific critical facilities at risk, and specific populations at
risk.
Updated maps in plan where appropriate.
Reviewed mitigation capabilities and update to reflect current capabilities.
6.Capability Added capability summary tables for regulatory,administrative/technical, and fiscal
Assessment mitigation capabilities.
Added capabilities for new hazards profiled in Section 5.
Added information on how capabilities could be expanded or enhanced.
Indicated what actions have been implemented that may reduce previously identified
vulnerabilities.
Updated mitigation strategy based on the results of the updated risk assessment,
completed mitigation actions, and implementation obstacles and opportunities since the
completion of the 2014 plan.
Reviewed and updated goals and objectives based on HMPC input.
Included updated information on how actions are prioritized, or how priorities changed.
7. Mitigation Strategy Reviewed mitigation actions from the 2014 plan and developed a status report for each,-
identified
ach;identified if actions have been completed, deleted, or deferred/carried forward. Updated
priorities on actions.
Identify examples of successful implementation to highlight positive movement on actions
identified in 2014 plan.
Identified new mitigation actions proposed by the HMPC with more detail on
implementation than the previous plan.
Developed a summary table of mitigation actions for all participating jurisdictions.
Reviewed and updated procedures for monitoring,evaluating,and updating the plan.
8. Implementation and Revised to reflect current methods.
Monitoring Updated the system for monitoring progress of mitigation activities by identifying
additional criteria for plan monitoring and maintenance.
Added a process for incorporation of the HMP into existing mechanisms
Developed annexes for new participating jurisdictions in 2019.
Moved previous information in 2014 plan on San Luis Obispo County Flood Control and
Water Conservation District into jurisdictional annex
A City of Arroyo Grande
B City of Atascadero
Jurisdictional Annexes C City of Grover Beach
D City of Morro Bay
E City of Paso Robles
F City of Pismo Beach
G City of San Luis Obispo
H Avila Beach CSD
Section 3
Planning Process
Plan Section Summary of Plan Review,Analysis,and Updates
I Ground Squirrel Hollow CSD
J Heritage Ranch CSD
K Los Osos CSD
L Nipomo CSD
M Oceano CSD
N San Miguel CSD
O San Simeon CSD
P Templeton CSD
Q SD -Cayucos Sanitary District
R SD - Port San Luis Harbor District
S SD -San Luis Obispo FCWCD
T SD -South San Luis Obispo County Sanitation District
Appendix A: Hazard Mitigation Planning Committee
Appendix B: Mitigation Categories,Alternatives, and Selection Criteria
Appendix C: Planning Process Documentation
Appendices Appendix D:Jurisdiction Adoption Resolutions
Appendix E: Critical Facilities
Appendix F:Climate Change Adaptation Planning Guide Consistency Summary
Appendix G:Climate Change Adaptation and Resilience Statutory Consistency Summary
Appendix H: References
3.3 Local Government Participation
In the 2019 plan update, the following jurisdictions participated in the planning process and will be
adopting the updated plan following FEMA approval. As noted previously, all participants are new to the
SLO County LHMP except for San Luis Obispo Flood Control and Water Conservation District which
participated in the 2014 planning process.All incorporated cities in the County participated in this
planning process as well as four(4) special districts, nine (9) community service districts (CSD.The County
and the municipalities have the authority to regulate development within their jurisdictions;the County
has authority for regulating development within the unincorporated areas including the CSDs.
Lead Jurisdiction:
• County of San Luis Obispo
Municipalities:
• City of Arroyo Grande
• City of Atascadero
• City of Grover Beach
• City of Morro Bay
• City of Paso Robles
• City of Pismo Beach
• City of San Luis Obispo
Community Service Districts:
0 Avila Beach CSD
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• Ground Squirrel Hollow CSD
• Heritage Ranch CSD
• Los Osos CSD
• Nipomo CSD
• San Miguel CSD
• San Simeon CSD
• Templeton CSD
Special Districts:
• San Luis Obispo County Flood Control and Water Conservation District
• Cayucos Sanitary District
• Port San Luis Harbor District
• South San Luis Obispo County Sanitation District
The DMA planning regulations and guidance stress that each local government seeking FEMA approval of
their mitigation plan must participate in the planning effort in the following ways:
• Participate in the process as part of the HMPC
• Detail areas within the planning area where the risk differs from that facing the entire area
• Identify potential mitigation actions
• Formally adopt the plan
For the San Luis Obispo County planning area's HMPC, "participation" meant the following:
• Providing facilities for meetings
• Attending and participating in the HMPC meetings
• Completing and returning Wood Plan Update Guide worksheets
• Collecting and providing other requested data (as available)
• Identifying mitigation actions for the plan
• Reviewing and providing comments on plan drafts and jurisdictional annexes
• Informing the public, local officials, and other interested parties about the planning process and
providing opportunity for them to comment on the plan
• Coordinating, and participating in the public input process
• Coordinating the formal adoption of the plan by the governing boards
The County and all jurisdictions with annexes to this plan and seeking FEMA approval met all of these
participation requirements. In most cases one or more representatives for each jurisdiction attended the
multi jurisdictional meetings described in Table 3.2 Schedule of Planning Meetings and brought together
a local planning team to help collect data, identify mitigation actions and implementation strategies, and
review and provide data on annex drafts. In some cases, the jurisdictions had limited capacity to attend or
had conflicts with HMPC meetings; in these cases, alternative forms of communication were used to
provide input into the process.Appendix C provides additional information and documentation of the
planning process.
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3.4 Planning Process
Wood established the planning process for the San Luis Obispo County Multi-Jurisdictional Hazard
Mitigation Plan using the DMA planning requirements and FEMA's associated guidance.The original
FEMA planning guidance is structured around a four-phase process:
1. Organize Resources
2. Assess Risks
3. Develop the Mitigation Plan
4. Implement the Plan and Monitor Progress
Into this process, Wood integrated a more detailed 10-step planning process used for FEMA's Community
Rating System (CRS) and Flood Mitigation Assistance programs.Thus, the modified 10-step process used
for this plan meets the requirements of major grant programs including: FEMA's Hazard Mitigation Grant
Program, Pre-Disaster Mitigation program, Flood Mitigation Assistance Program, and flood control
projects authorized by the U.S.Army Corps of Engineers.
In 2013, FEMA released the Local Mitigation Planning Handbook that has become the official guide for
local governments to develop, update and implement local mitigation plans. While the requirements
under§201.6 have not changed, the Handbook provides guidance to local governments on developing or
updating hazard mitigation plans to meet the requirements under the Code of Federal Regulations (CFR)
Title 44— Emergency Management and Assistance §201.6, Local Mitigation Plans for FEMA approval and
eligibility to apply for FEMA Hazard Mitigation Assistance grant programs. It also offers practical
approaches, tools, worksheets and local mitigation planning examples for how communities can engage
in effective planning to reduce long-term risk from natural hazards and disasters.The Handbook
complements and liberally references the Local Mitigation Plan Review Guide (October 1, 2011), which is
the official guidance for Federal and State officials responsible for reviewing local mitigation plans in a fair
and consistent manner.
Table 3-2 shows how the modified 10-step process fits into FEMA's four-phase process, and how these
elements correspond to the tasks in the FEMA Mitigation Planning Handbook.
Table 3-2 San Luis Obispo County Hazard Mitigation Planning Process
HandbookFEMA's 4-Phase DMA Process Modified 10-Step CRS Process FEMA Local Mitigation Planning
1) Organize Resources
201.6(c)(1) 1) Organize the Planning Effort 1: Determine the planning area and
resources
201.6(b)(1) 2) Involve the Public 2: Build the planning team -44 CFR
201.6 (C)(1)
3:Create an outreach strategy-44 CFR
201.6(b)(2) and (3) 3) Coordinate with Other 201.6(b)(1)
Departments and Agencies 4: Review community capabilities -44
CFR 201.6 (b)(2)&(3)
2)Assess Risks
201.6(c)(2)(i) 4) Identify the Hazards
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ModifiedFEMA's 4-Phase DMA Process
Handbook Tasks
5:Conduct a risk assessment-44 CFR
201.6(c)(2)(ii) 5)Assess the Risks 201.6 (C)(2)(i)44 CFR
201.6(C)(2)(ii)&(iii)
3) Develop the Mitigation Plan
201.6(c)(3)(i) 6) Set Goals 6: Develop a mitigation strategy-44
201.6(c)(3)(ii) 7) Review Possible Activities CFR 201.6(c)(3)(i);44 CFR 201(c)(3)(ii)
201.6(c)(3)(iii) 8) Draft an Action Plan and 44 CFR 201.6(c)(3)(iii)
4) Implement the Plan and Monitor Progress
201.6(c)(5) 9)Adopt the Plan 7: Review and adopt the plan
10) Implement, Evaluate, and 8: Keep the plan current
201.6(c)(4) Revise the Plan 9:Create a safe and resilient
community-44 CFR 201.6(c)(4)
3.4.1 Phase 1: Organize Resources
Planning Step 1: Organize the Planning Effort
The 2019 planning process and update of the LHMP had its roots in the development of a grant
application. The County Office of Emergency Services (OES) wrote the grant and in the process solicited
commitments from local government jurisdictions that were interested in participating. With an
understanding of the number of jurisdictions and their commitment to participate, the grant application
was approved and awarded to the County in 2018. A request for proposals was utilized to bring on a
qualified planning consultant. The update process was formally initiated in January 2019 under the
coordination of the County of San Luis Obispo Planning & Building Department as the lead entity, in
coordination with OES, so that the effort could be coordinated with a parallel effort to update the General
Plan Safety Element.Wood worked with the Planning & Building staff and OES to establish the framework
and organization for development of the plan.Wood assisted County staff with coordination with other
governmental agencies and public process elements to develop the updated LHMP for San Luis Obispo
County. Organizational efforts were initiated with a series emails to inform and educate jurisdictions
within the County of the purpose and need for an update to the countywide hazard mitigation plan.
Representatives from participating jurisdictions and HMPC members from the 2014 plan were used as a
starting point for the invite list, with additional invitations extended as appropriate throughout the
planning process. The HMPC was re-established as a result of this effort. Membership of the HMPC is
detailed in Appendix A.
Planning Meetings
The planning process officially began with a kickoff meeting on January 25, 2019.The meeting covered
the scope of work and an introduction to the DMA requirements. Participants were provided with a Local
Hazard Mitigation Plan Update Workbook, which included worksheets to facilitate the collection of
information necessary to support update of the plan. Using FEMA guidance, Wood designed these
worksheets to capture information on past hazard events, identify hazards of concern to each of the
participating jurisdictions, quantify values at risk to identified hazards, inventory existing capabilities, and
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record possible mitigation actions. A copy of Wood's Local Hazard Mitigation Plan Update Guide for this
project is included in Appendix C. The County and each jurisdiction seeking FEMA approval of their plan
completed and returned the worksheets in either the Local Hazard Mitigation Plan Update Workbook or
shared their most recent local hazard mitigation plan for incorporation into the plan document.
During the planning process, the HMPC communicated through face-to-face meetings, email, and
telephone conversations. Draft documents were posted on a Google Drive and in some cases emailed so
that the HMPC members could easily access and review them. The HMPC formally met four times during
the planning period (January 25, 2019—April 30, 2019). The purposes of these meetings are described in
Table 3.2. The planning consultant sent meeting handouts ahead of time to the participating jurisdictions
to review and provide feedback before or at the meeting. In addition to these meetings some jurisdictions
held meetings with subcommittees to discuss the needed input for the plan update. In a couple cases
some municipalities were not able to attend the planning workshops due to scheduling conflicts or
limited staff capacity. A planner in the County Planning & Building Department— Long Range Division and
the planning consultant worked with the jurisdictions individually in those cases to obtain necessary
information and input into the planning process. This was done through direct emails from the planning
consultant and follow-up phone conversations with the consultant and the County Planner where
necessary.
Table 3-3 Schedule of Planning Meetings
Meeting
Meeting Type Meeting Topic Date(s) Location(s)
HMPC#1 Kick-off meeting: introduction to DMA,the planning January 25, 2019 San Luis Obispo
process, planning for public involvement and hazard
identification
HMPC#2 Hazard Identification and Risk Assessment results, March 19, 2019 San Luis Obispo
capability assessment updates
HMPC#3 Update of mitigation goals and objectives, capabilities, April 25, 2019 San Luis Obispo
previous mitigation action progress
HMPC#4 Development and prioritization of mitigation action April 30,2019 San Luis Obispo
recommendations
HMPC Meeting#1 -Kickoff Meeting
On January 25, 2019, the Planning Team convened in person to discuss the process for completing the
update of this plan. The kickoff meeting was well attended with thirty-three (33) individuals present.The
audience was a mix of county departments, local governments, special districts and stakeholders.
Representatives from the County department included: Planning & Building, Office of Emergency Services,
Public Works and the Agricultural Department. All participating municipalities and Community Service
Districts had representatives present at the meeting. Stakeholders present at the meeting included
representatives from the San Luis Obispo County Fire Safe Council, and a Professor of City and Regional
Planning from Cal Poly, San Luis Obispo.A complete list of those in attendance at the kickoff meeting can
be found in the sign-in sheets in Appendix C.
Following introductions, Wood reviewed the DMA requirements and the suggested planning process to
follow to meet the requirements as well as the expected schedule of the process. The roles of the HMPC
and stakeholder was discussed including the participation requirements for the different roles.
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Planning Process
During the kickoff meeting the Planning Team validated the identified hazards within the 2014 plan with
minor revisions and collaboratively prioritized the hazards for the purpose of identifying which are "of
most concern"to the County. More details are included in Section 5 Risk Assessment.
The group also discussed other agencies that should be part of this planning process, as well as related
planning efforts to be coordinated with and recent studies to be incorporated. Part of this discussion was
also related to creating a public outreach strategy to involve the public throughout the planning process.
Suggestions on public involvement tools included,
• Outreach through social media
• Posting information on local government websites
• Utilize City of San Luis Obispo's City Hall web platform
• Create and disseminate an online public survey
The kickoff meeting ended with Wood sharing handouts to assist in the planning process.These handouts
included the Local Hazard Mitigation Plan Update Workbook which outlined data collection needs for
each participating jurisdiction.
HMPC Meeting #2 — Risk and Goals
On March 19, 2019, the HMPC convened in person to discuss the results of the risk and vulnerability
assessment.Twenty-four (24) members of the HMPC were present for the discussion. Wood began the
meeting with a presentation on the results the risk assessment for natural hazards, results for hazardous
material incidents were presented at the next meeting. A handout summarizing the hazard significance for
each jurisdiction was shared for Planning Team to review.The group went through each hazard together
and discussed the results as well as shared any local insight to inform the HIRA update. Refer to the
meeting summary in Appendix C for notes related to each hazard discussed. Part of this discussion was
also related to development trends.
Following the discussion on the results of the risk assessment, the group was provided a handout that
summarized current goals and objectives from the County HMP,jurisdictional HMPs and the State HMP.
Wood explained this update process provides an opportunity to review the previous plan's goals to
determine if they are still valid, comprehensive, and reflect current priorities and updated risk assessment.
The group was also encouraged to share their jurisdiction's goal statements with their local planning
teams prior to the next meeting to discuss if changes are necessary.
Wood shared with group that the online public survey had been opened and already received thirty(30)
responses at that time.A link was shared with the HMPC to easily distribute by email and for posting on
websites.The meeting ended with a review of the next steps and planning process schedule.
HMPC Meeting#3—Goals, Capabilities, and Action Status
The HMPC reconvened on April 25, 2019 to discuss goal revisions and updates, updates to the capability
assessment and status of mitigation actions from the previous County and jurisdictional HMPs.The
meeting began with a status update of the planning process and a review of the additional vulnerability
assessment data related to hazardous material incidents.This was followed by discussion on the revised
goals, with some additional adjustments suggested by the group. The capability assessment update was
also discussed; it was emphasized that each jurisdiction should consider options for enhancing or
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expanding their mitigation capabilities. Progress on mitigation actions was also summarized in
anticipation of developing new actions in a subsequent meeting.
HMPC Meeting#4— Mitigation Action Workshop
On April 30th, 2019, the HMPC convened in person to identify new mitigation actions to include in the
updated plan. This encompassed a review of possible mitigation activities, alternatives, and related
climate adaptation strategies.The group also discussed criteria for mitigation action selection and
prioritization. This was followed by a brainstorming session to elicit the development of new mitigation
actions. Entities responsible for new mitigation action implementation were identified. A sticky dot
exercise was used as an initial prioritization on the new mitigation actions. Mitigation action worksheets
were distributed to allow additional details to be added following the workshop.
Planning Step 2: Involve the Public
Involving the public assures support from the community at large and is a required part of the planning
process per the DMA 2000. Early discussions with the San Luis Obispo County planning staff and input
received in the first HMPC meeting established the initial plan for public involvement in the plan update.
Public outreach began with the creation of an online public survey that was shared with each participating
jurisdiction to post on their websites and disseminate via email to local stakeholders. The public outreach
activities described here were conducted with participation from and on behalf of all jurisdictions
participating in this plan.
Throughout the planning process public workshops were held to inform the public of the purpose of the
DMA and the hazard mitigation planning process for the San Luis Obispo County planning area.At each
workshop the public in attendance were provided comment cards to leave any comments related to the
County's Hazard Mitigation Plan as well as provide their contact information if they would like to receive
ongoing updates and information related to the planning process.
At the kick-off meeting, the HMPC discussed additional options for public involvement and agreed to an
approach using established public information mechanisms and resources within the community. Public
involvement activities included press releases, website postings, flyer development and distribution, public
meetings, and the collection of public comments on the draft plan.To promote the first workshop County
staff reached out to local media outlets to inform the public of the opportunity to participate and posted
on several community calendars. Posts were created on the following community calendars:
• KSBY
• KCBX
• KEYT/ KCOY
• New Times/Santa Maria Sun
• Paso Robles Daily News
• Santa Maria Times
• Tribune
• Cambrian News
• Pacific Coast Business Times
County-wide stakeholders were identified, and invites were also sent to:
• Cal Poly MCRP Professors
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Planning Process
• Cambria CSD
• SLO Fire Safe Council
• California Department of Corrections and Rehabilitation - Associate Warden California Men's Colony
(CMC)
• Department of State Hospitals
• Xolon Salinan Tribe
• Tenet Health
• SLO COG
• Coastal Commission
• Head of Safety Committee Cayucos
• Safety and Emergency Plans Templeton
• Paso Robles Joint Unified School District
• San Luis Coastal Unified School District
• Assistant Superintendent, Lucia Mar Schools
Figure 3-1 below is the flyer the County HMPC used to advertise the first public workshop on March
19,2019. Press releases can be found in Appendix C.
Figure 3-1 San Luis Obispo County's Flyer for Public Workshop #1, March 19, 2019
COUNTYSLO I iL HAZARD
MITIGATION , UPDATE
PUBLIC WORKSHOP
IDENTIFY HAZARDS, VULNERABILITIES, AND
ASSETS AT RISK
March 19, 2019 15:30 . .
995 Palm Street, San Luis Obispo
(San Luis Obispo Library)
Take our - survey:
https:flwww.surveymonkey.com/r/SLOH MPupdate
Snacks will be
wood. provided!
San Luis Obispo County Local Hazard Mitigation Plan I October 2019 Page 3-12
Section 3
Planning Process
Online Public Survey
During the plan update's drafting stage, an online public survey was developed as a tool to gather public
input.The survey was for the public to provide feedback to the San Luis Obispo County Multi-
jurisdictional Hazard Mitigation Planning Committee on reducing hazard impacts.The survey provided an
opportunity for public input during the planning process, prior to finalization of the plan update. The
survey gathered public feedback on concerns about hazards and input on strategies to reduce their
impacts. The survey was released in March and closed on May 14th. The HMPC provided links to the
public survey by distributing it using social media, email, and posting the link on websites. The County
provided laptops that could be used to fill out the survey at the first public meeting, as well as flyers with
the survey link as handouts.
Section 3
Planning Process
Figure 3-2 Example of Public Survey Response
Wildfire Fuels
Treatment...
Assistance
with Qefensi...
Continued
Partici patio...
Critical
Facilities—
Generators for
critical...
P Lanni ng f Zoning
Public
EducationlAw...
Stormwate r
Drainage
Forest
Healt hf W ater...
Flood
Mitigation
Education and ■
Discounts on...
FlooBuyout
uyo ■
Property buyoutut
Public
Education I...
Warning and
Notification...
Landslidelmudsl
ide mitigation
Evacuation
route...
Hazardous Tree
Remova[
0% 10% 20°' 3046 40% 50% 6W. 70% $4?6 9040 100°�
Three hundred and twenty-two (322) people filled out the survey online. Results showed that the public
perceives the most significant hazards to be wildfire, earthquake and drought and water shortage. Figure
3-1 above, shows the responses to question 3 of the survey, which solicited the public's opinion on the
mitigation actions that should have the highest priority in the updated hazard mitigation plan. Wildfire
fuels treatment projects, evacuation route development, hazardous tree removal, and public education
and awareness of hazards were cited as the most popular mitigation actions. This information was shared
ObispoSan Luis County Local . Mitigation Plan I October 2r ' Page
Section 3
Planning Process
with the HMPC during the update of the mitigation strategy as a source of potential mitigation ideas.A
summary of all the survey data and documentation of the public feedback can be found in Appendix C.
Public Workshops
Two public workshops were held during the planning process to inform the public, receive input to
integrate into the plan update and keep the public updated on the progress being made in the planning
process.
The first workshop was held on March 19, 2019 with fifteen (15) members of the public were present.The
intent of the first was to introduce the public to the hazard mitigation planning process for the County's
Plan Update as well as answer any questions and gather public input to be integrated into the plan
update. In addition it was an opportunity to help staff identify risks, hazards and vulnerabilities from the
public's perspective. The HMPC received three comment cards from meeting that helped to inform the
Planning Team on the public initial thoughts on hazard mitigation and hazards in their community each
can be found in Appendix C.
The second public workshop was held on April 30, 2019 and was well attended with thirteen members of
the public, as well as stakeholders from Cal Poly and the County Farm Bureau. The primary intent of the
second workshop was to gather feedback on mitigation strategies to reduce the identified hazard
vulnerabilities, answer questions and collect input to share with the HMPC.This workshop was also an
opportunity to inform the public on the Safety Element update of the County's General Plan and how that
effort related to the County's Hazard Mitigation Plan. Two local news stations (KEYT and KSBY) were also
present at the meeting and each reported on the planning process and shared the link to the online
public survey in TV broadcast segments the following morning.
Example press releases and sign in sheets are located in Appendix C. Prior to finalizing the plan the draft
was available online on the San Luis Obispo County website.
Table 3-4 Public Meeting Schedule
Meeting Topic Meeting Date Meeting Location
Introduce the Disaster Mitigation Act of 2000 and the March 19,2019 San Luis Obispo Library,
hazard mitigation planning process for the County's plan City of San Luis Obispo
update. Reviewed the results of the risk assessment and
discussed mitigation action strategies.
Discuss and gather feedback on mitigation strategies to April 30, 2019 Ludwick Community
reduce identified hazard vulnerabilities,answer questions Center, City of San Luis
and collect input to share with the HMPC for the plan Obispo
update.Shared the progress on the update to the General
Plan Safety Element and how it relates to the HMP.
Introduce public review draft of plan and solicit feedback. October 14,2019 November 15, 2019
Public Review Period
On October 14, 2019, a public review draft of this plan was released for comment and made available for
download via the County Planning & Building Department website. Comments were collected through
November 13, 2019. The draft plan was advertised through social media, mass emailing and an
advertisement through the media mechanisms noted previously.An electronic comment form through
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Planning Process
SurveyMonkey was provided with the draft plan. Two comments were received and are documented in
Appendix C. One comment received related to providing evacuation routes and integrate evacuation
planning into this plan.While detailed evacuation routes are outside the scope of this plan, the County
does have a number of evacuation plans which are noted in subsection 6.1 that include hazard-specific
plans for dam and levee failure, wildfire (West Atascadero, Parkhill, Avila, Cambria, Upper Los Berros, Suey
Creek), tsunami, and Diablo Canyon radiological incidents. The former Director of the County's Office of
Emergency Services also reviewed and provided input to the committee on portions of Section 4,
Community Profile and Section 5 Hazard Identification and Risk Assessment;this resulted in edits in those
sections to clarify correct or enhance the existing information where applicable.
Planning Step 3: Coordinate with Other Departments and Agencies
Early in the planning process, state and local agencies and organizations were invited to participate as
stakeholders in the process. Stakeholders include local and regional agencies involved in hazard
mitigation activities or those beyond the County and local government that have the authority to regulate
development, including the California Coastal Commission and the Xolon Salinan Tribe. Stakeholders
could participate in various ways, either by contributing input at HMPC meetings, being aware of planning
activities through an email group, providing information to support the effort, or reviewing and
commenting on the draft plan. Based on their involvement in other hazard mitigation planning efforts,
and status in the County, representatives from the following agencies and organizations were invited to
participate as stakeholders in the process; an asterisk indicates they participated in HMPC meetings:
• Cal Poly, San Luis Obispo*
• Cambria CSD
• Oceano CSD*
• SLO Fire Safe Council*
• Associate Warden CMC
• Department of State Hospitals*
• Xolon Salinan Tribe
• Tenet Health
• San Luis Obispo Council of Governments (SLOCOG)
• Coastal Commission
• Retired Cal Poly professor/citizen*
The majority of the listed stakeholders were invited to participate in the planning process, which included
an invitation to attend the kickoff meeting. Several opportunities were provided for the above groups to
participate in the planning process. At the beginning of the planning process, invitations were extended
to these groups via an email from the Planning & Building staff project manager to actively participate on
the HMPC. They were also invited via email to the public meetings discussed previously.
Coordination with key agencies, organizations, and advisory groups throughout the planning process
allowed the HMPC to review common problems, development policies, and mitigation strategies as well
as identifying any conflicts or inconsistencies with regional mitigation policies, plans, programs and
regulations. Phone calls and emails were used during plan development to directly coordinate with key
individuals representing other regional programs.
As noted by the asterisks next to the above names, many of these groups found it beneficial to participate
on the HMPC or attend public meetings. Others assisted in the process by providing data directly as
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requested in the Local Hazard Mitigation Plan Update Guide or through data contained on their websites.
Further as part of the both HMPC and public outreach processes, all groups were invited to review and
comment on the plan prior to submittal to Cal OES and FEMA.
As part of the public review and comment period for the draft plan, key agencies were again specifically
solicited to provide any final input to the draft plan document. This input was solicited both through
membership on the HMPC and by direct emails to key groups and associations to review and comment
on the plan. As part of this targeted outreach, these key stakeholders were also specifically invited to
attend the HMPC and public meeting to discuss any outstanding issues and to provide input on the draft
document and final mitigation strategies.
In summary, several opportunities were provided for the groups listed above to participate in the planning
process. At the beginning of the planning process, invitations were extended to these groups to actively
participate on the HMPC. Specific participants from these groups are detailed in Appendix A. Others
assisted in the process by providing data directly as requested or through data contained on their
websites or as maintained by their offices. Further as part of the public outreach process, all groups were
invited to attend the public meetings and to review and comment on the plan prior to submittal to Cal
OES and FEMA. In addition, as part of the review of the draft plan, key agency stakeholders were
contacted, and their comments specifically solicited. Emergency managers in adjacent counties (Kern,
Monterey, and Santa Barbara) were contacted by the County emergency services coordinator via email
and asked to provide comments on the public review draft of the plan.The Emergency Manager for Santa
Barbara County provide comments during this review period. The comments were integrated into Section
4 Community Profile to provide clarity and make the plan more accurate.
This process accomplished as part of planning steps two and three in the FEMA Local Mitigation Planning
Handbook.
Incorporation of Existing Plans and Other Information
The coordination and synchronization with other community planning mechanisms and efforts are vital to
the success of this plan. To have a thorough evaluation of hazard mitigation practices already in place,
appropriate planning procedures should also involve identifying and reviewing existing plans, policies,
regulations, codes, tools, and other actions are designed to reduce a community's risk and vulnerability
from natural hazards. San Luis Obispo County uses a variety of mechanisms to guide growth and
development. Integrating existing planning efforts, mitigation policies, and action strategies into this plan
establishes a credible, comprehensive document that weaves the common threads of a community's
values together. The development and update of this plan involved a comprehensive review of existing
plans, studies, reports, and initiatives from the County of San Luis Obispo and each participating
municipality that relate to hazards or hazard mitigation. A high-level summary of the key plans, studies
and reports is summarized in the table below. Information on how they informed the update are noted
and incorporated where applicable.
Section 3
Planning Process
Table 3-5 Summary of Review of Key Plans, Studies and Reports
Plan,Study, Report Name How Plan informed LHMP
County of San Luis Obispo General Plan and Elements Provided background information on the county
(Safety,Agricultural, Conservation and Open Space, including some information related to jurisdictions.The
Land Use) elements were used to provide information on risk and
vulnerabilities to hazards and the existing policies the
County has in place related to hazards and mitigation.
Municipal General Plans (including Safety Elements, Informed the municipal annexes and in some cases the
Land Use Elements,and Housing Elements) community service district annexes on past hazard
events, mitigation policies,combining designations and
existing and projected development
Local Hazard Mitigation Plans (City of Atascadero, City Informed the HIRA sections, mitigation action plans and
of Morro Bay,City of Paso Robles, City of Pismo Beach, capability assessments for the applicable annexes
City of San Luis Obispo, Los Osos CSD and the City
Arroyo Grande/City Grover Beach/Lucia Mar Unified
School District/South San Luis Obispo County Sanitation
District)
Area Plans (Estero, Inland, North Coast, San Luis Bay Informed the community and district profiles
Coastal, South County Coastal)
Community Plans (Avila Beach, San Miguel, Nipomo, Informed the community service district profiles
Los Osos)
Urban Water Management Plans (Arroyo Grande, Informed the drought and water shortage sections of
Atascadero) the applicable annexes
San Luis Obispo County Flood Insurance Study Reviewed for information on past floods and flood
problems to inform risk assessment(Section 4)
Utilized Digital Flood Insurance Rate Maps effective
January 2016 to update maps and flood risk assessment
in Section 4.
State of California Multi-Hazard Mitigation Plan (draft Reviewed information on climate change and hazard
2018) assessment data to ensure consistency with this plan
update
Reviewed list of hazards to inform risk assessment
(Section 4)
Reviewed goals for consistency during the update of
the Fresno Multi-jurisdictional Hazard Mitigation Plan
NOAA National Centers for Environmental Information- Reviewed information on climate change to inform risk
State Climate Summaries assessment(Section 4)
California Department of Finance/U.S.Census Bureau, Informed the background on the community including
American Community Survey, 2013-2017 demographic trends
2018 Economic Profile, San Luis Obispo Chamber of Informed the economic section of the Community
Commerce Profile including the top employers in the County
California County Level Economic Forecast 2018-2050, Informed the development trends section of the
California Department of Transportation Office of State Community Profile and how the State is forecasting the
Planning County's growth in terms of population,economy and
housing production
County of San Luis Obispo EnergyWise Plan, Inform climate change projections and possible effects
ClimateWise Integrated Climate Change Adaptation on the County and the"climate change considerations"
Planning in San Luis Obispo,California's Fourth Climate for each hazard profiled
Section 3
Planning Process
Plan,Study, Report Name How Plan informed LHMP
Change Assessment:Central Coastal Region Report
2( 018)
San Luis Obispo County Integrated Regional Water Informed the background section on adverse weather in
Management Plan (Draft 2019) and San Luis Obispo general. Including how the county is divided into
County Stormwater Resource Plan watershed groups and annual precipitation information
USDA Risk Management Agency Crop Indemnity Informed the adverse weather section vulnerability
Reports, 2015-2018 assessment on how crops have been impacted by
weather events in the past.Also informed the Drought
and Agricultural Pests and Disease sections of the HIRA
California Climate Adaptation Strategy, 2018 and Informed the Extreme Heat profile and climate change
California OES Contingency Plan for Excessive Heat considerations
Emergencies (2014)
Dam and Levee Failure Evacuation Plan,County of San Informed the Dam Failure profile and vulnerability
Luis Obispo assessment and provided information on levees of
concern in the Flood profile.Also informed applicable
jurisdictional annexes
Land Subsidence from Groundwater Use in California Informed the Land Subsidence profile
(2013)James W. Borchers and Michael Carpenter,
Luhdorff&Scalmanni Consulting Engineers
Tsunami Response Plan,County of San Luis Obispo Informed the Tsunami profile the base plan HIRA and
applicable jurisdictional annexes
Community Wildfire Protection Plan, San Luis Obispo Informed the Wildfire profile in the base plan HIRA and
County(March 2019) applicable jurisdictional annexes
Community Health Assessment,County of San Luis Provided background information on the county and
Obispo Health Agency informed the biological agents
Other technical data, reports and studies were reviewed and considered, as appropriate, during the
collection of data to support Planning Steps 4 and 5, which include the hazard identification, vulnerability
assessment, and capability assessment. Information from the following agencies and groups in were
reviewed in the development and update of this plan. Specific references relied on in the development of
this plan are also sourced throughout the document as appropriate.
• California Department of Forestry and Fire Protection
• California Department of Parks and Recreation Office of Historic Preservation
• California Department of Transportation
• California Department of Public Health
• California Natural Resources Agency
• California Department of Water Resources
• California Geological Survey
• County of San Luis Obispo Agricultural Department
• County of San Luis Obispo Public Health Department
• County of San Luis Obispo Information Technology Department
• County of San Luis Obispo Planning and Building Department
• County of San Luis Obispo Public Works Department
• County of San Luis Obispo Office of Emergency Services
Section 3
Planning Process
• California Coastal Commission
• California Water Foundation
• San Luis Obispo County Flood Control and Water Conservation District
• National Oceanic and Atmospheric Administration National Climatic Data Center
• National Register of Historic Places
• Natural Resource Conservation Service
• National Weather Service
• U.S. Fish and Wildlife Service
• U.S. Geological Survey
• Western Regional Climate Center
• San Luis Tribune
• Center for Western Weather and Water Extremes
Integration of 2014 Plan into Other Plans and Planning Mechanisms
In addition, the 2014 hazard mitigation was incorporated into several County plans and planning
mechanisms. The risk assessment informed the update of the County Emergency Operations Plan.
Mitigation projects were proposed as part of County work plans for actual implementation related to
drought and fire. On December 3, 2013, the County Board of Supervisors approved an amendment to the
San Luis Obispo General Plan Safety Element by Resolution 2013-296. Through this amendment effective
January 2, 2014, the Local Hazard Mitigation Plan was incorporated by reference in compliance with
California Assembly Bill 2140, stating:
"The San Luis Obispo County Local Hazard Mitigation Plan presents a comprehensive risk
assessment of natural hazards that have the potential to affect San Luis Obispo County.The Local
Hazard Mitigation Plan was developed by the County in accordance with the federal Disaster
Mitigation Act of 2000, adopted by the Board of Supervisors and approved by the Federal
Emergency Management Agency.The Local Hazard Mitigation Plan suggests possible mitigation
measures for reducing the effects of the potential hazards. It is incorporated by this reference into
the Safety Element and should be consulted when addressing known hazards to ensure the
general health and safety of people within San Luis Obispo County. The goals and policies within
this Safety Element support and are consistent with the recommended mitigation strategy within
the Local Hazard Mitigation Plan."
The 2019 HMP update was coordinated with and done in parallel with the update of the 1999 Safety
Element of the County General Plan to ensure consistency of policies.
Several of the participating jurisdictions previously participated in other single or multi jurisdictional
plans, primarily the municipalities. Where those plans have been integrated into other planning
mechanisms is noted in the 'Mitigation Planning History and 2019 Process' in the jurisdictional annexes.
3.4.2 Phase 2: Assess Risks
Planning Step 4: Identify the Hazards
Wood led the HMPC in an effort to review the list of hazards identified in the 2014 plan and document all
the hazards that have, or could, impact the planning area, including documenting recent drought, flood,
wildfire and winter storm events. Data collection worksheets were used in this effort to aid in determining
hazards and vulnerabilities and where risk varies across the planning area.The profile of each of these
Section 3
Planning Process
hazards was then updated in 2019 with information from the HMPC and additional sources. Web
resources, existing reports and plans, and existing GIS layers were used to compile information about past
hazard events and determine the location, previous occurrences, probability of future occurrences, and
magnitude/severity of each hazard. Geographic information systems (GIS) were used to display, analyze,
and quantify hazards and vulnerabilities where data permitted. The potential for climate change to affect
the frequency and intensity of the hazards was summarized based on latest available science, where
applicable.A more detailed description of the hazard identification and risk assessment process and the
results are included in Section 5 Risk Assessment.
Planning Step 5:Assess the Risks
After updating the profiles of the hazards that could affect the County, the HMPC collected information to
describe the likely impacts of future hazard events on the participating jurisdictions.This step included
two parts: a vulnerability assessment and a capability assessment.
Vulnerability Assessment—Participating jurisdictions updated their assets at risk to natural hazards—
overall and in identified hazard areas.These assets included total number and value of structures; critical
facilities and infrastructure; natural, historic, and cultural assets; and economic assets.The HMPC also
analyzed development trends in hazard areas.The latest DFIRM was used to refine the estimate flood
losses during the update, where available for the NFIP participating communities.
Capability Assessment—The HMPC also conducted a capability assessment update to review and
document the planning area's current capabilities to mitigate risk and vulnerability from natural hazards.
By collecting information about existing government programs, policies, regulations, ordinances, and
emergency plans, the HMPC can assess those activities and measures already in place that contribute to
mitigating some of the risks and vulnerabilities identified. This information for the County is included in
Section 6 and in the respective jurisdictional annexes.This addressed FEMA planning task 4: Review
community capabilities - 44 CFR 201.6 (b)(2) & (3).
Results of the risk assessment was presented, and comments discussed at the second meeting of the
HMPC in April 2019.
A more detailed description of the risk assessment process and the results are included in Section 5 Risk
Assessment.
3.4.3 Phase 3: Develop the Mitigation Plan
Planning Step 6: Set Goals
Wood facilitated a discussion session with the HMPC to review the 2014 plan's goals and objectives.The
HMPC discussed definitions and examples of goals, objectives, and actions and considered the goals of
the state hazard mitigation plan and other relevant local plans when reviewing and revising the goals and
objectives. The resulting updated goals and objectives are presented in Section 7 Mitigation Strategy.
Planning Step 7: Review Possible Activities
Wood facilitated a discussion at an HMPC meeting to review the alternatives for mitigating hazards. This
included a brainstorming session with the HMPC to identify a comprehensive range of mitigation actions
for each identified hazard, and a method of selecting and defending recommended mitigation actions
using a series of selection criteria. More specifics on the process and the results of this collaborative
process are captured in Section 7 Mitigation Strategy.
Section 3
Planning Process
As part of the review of mitigation options long term climate change adaptation strategies were also
discussed. HMPC members were encouraged to incorporate climate change adaptation measures into
the mitigation strategy of their respective jurisdictions utilizing resources and guidance available on the
Cal-Adapt website.
Planning Step 8: Draft an Action Plan
Based on input from the HMPC regarding the draft risk assessment and the goals and activities identified
in Planning Steps 6 and 7, Wood produced a complete first draft of the plan. This complete was shared
electronically with the HMPC for review and comment. Other agencies were invited to comment on this
draft as well. HMPC and agency comments were integrated into the second draft, which was advertised
and distributed to collect public input and comments. Wood integrated comments and issues from the
public, as appropriate, along with additional internal review comments and produced a final draft for the
California Office of Emergency Services and FEMA Region IX to review and approve, contingent upon final
adoption by the governing boards of each participating jurisdiction.
3.4.4 Phase 4: Implement the Plan and Monitor Progress
Planning Step 9: Adopt the Plan
In order to secure buy-in and officially implement the plan, the plan was adopted by the governing
boards of each participating jurisdiction on the dates included in the adoption resolutions in Appendix D:
Adoption Resolutions. The final plan will be included in the safety element of the County General Plan and
result in the County's eligibility for Assembly Bill (AB) 2140.This adoption makes the jurisdiction eligible
for consideration for part or all of its local costs on eligible public assistance to be provided by State share
funding through the California Disaster Assistance Act.
Planning Step 10: Implement, Evaluate, and Revise the Plan
The true worth of any mitigation plan is in the effectiveness of its implementation. Up to this point in the
plan update process, all of the HMPC's efforts have been directed at researching data, coordinating input
from participating entities, and updating and developing appropriate mitigation actions. Each
recommended action includes key descriptors, such as hazard(s) addressed, lead manager and priority, to
help initiate implementation. An overall implementation strategy is described in Section 8 Plan
Implementation and Monitoring.
Finally, there are numerous organizations within the San Luis Obispo County planning area whose goals
and interests' interface with hazard mitigation. Coordination with these other planning efforts, as
addressed in Planning Step 3, is paramount to the ongoing success of this plan and of mitigation in San
Luis Obispo County and is addressed further in Section 8. A plan update and maintenance schedule and a
strategy for continued public involvement are also included in Section 8.
Implementation and Maintenance Process: 2014 Plan
The 2014 LHMP included a process for implementation and maintenance which was generally followed,
with some variation. Implementation of the plan including the status of mitigation actions is captured in
Section 7 and the jurisdictional annexes. In general, the County and participating jurisdictions have made
progress in the implementation of the plan. Successes of note are detailed in Section 7. An updated
implementation and maintenance section can be referenced in Section 8.
Section 4
San Luis Obispo County Profile
SECTION 4 SAN LUIS OBISPO COUNTY PROFILE
4.1 County History
The area that today comprises San Luis Obispo County was home to the Chumash people thousands of
years before the present age.Important settlements existed in many coastal areas such as Morro Bay and
Los Osos.
Mission San Luis Obispo de Tolosa was founded on September 1, 1772 in the area that is now the City of
San Luis Obispo. The namesake of the mission, city and county is Saint Louis of Toulouse, the young
bishop of Toulouse (Obispo and Tolosa in Spanish) in 1297.
San Luis Obispo County, the 16th largest County in California, is one of the original 27 California counties
created by Act of the State Legislature on February 18, 1850.
4.2 Geography
Located along California's Central Coast, San Luis Obispo County is midway (190 miles/306 kilometers)
between Los Angeles and San Francisco and is accessible north-to-south by U.S. Highway 101 and scenic
Highway 1. Routes from the east include State Highways 41, 46, 58 and 166. San Luis Obispo County is
bordered by Santa Barbara County to the south, Monterey County to the north and Kern County to the
east. Kings County shares a small border with San Luis Obispo County at the north east corner of the
County.
The County encompasses 3,316 square miles or 2,114,750 acres and stretches along 80 miles of coastline.
The highest point is Caliente Mountain (5,104 feet). The lowest point is sea level.
A series of ancient volcanic peaks, referred to as the "nine sisters", lie between Morro Bay and San Luis
Obispo. Most notable of the peaks is Morro Rock, often called the sentinel of the Pacific Ocean.
The Central Coast of California is susceptible to a number of natural hazards. This HMP profiles the most
significant of these hazards. Historical data, catastrophic potential, relevance to the jurisdiction, and the
probability and potential magnitude of future occurrences were all used to reduce and prioritize the list of
hazards to those most relevant to San Luis Obispo County.
The following map shows the geography of the County.
Section 4
San Luis Obispo County Profile
Figure 4-1 San Luis Obispo County
I
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intended for planning purposes only.
Data Source: San Luis Obispo County, '11V
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San Luis Obispo County Local Hazard Mitigation Plan I October
r
+ Section 4
San Luis Obispo County Profile
4.3 Cities and Communities
The incorporated cities within San Luis Obispo County are:
• Arroyo Grande 0 Paso Robles
• Atascadero 0 Pismo Beach
• Grover Beach 0 San Luis Obispo
• Morro Bay
Unincorporated communities and Census Designated Places (CDP) include:
• Avila Beach • Los Osos-Baywood Park
• Blacklake 0 Los Ranchos
• Callender 0 Nipomo
• California Valley 0 Oak Shores
• Cambria • Oceano
• Cayucos 0 Pozo
• Cholame 0 San Miguel
• Creston • San Simeon
• Edna • Santa Margarita
• Garden Farms 0 Shandon
• Halcyon . Templeton
• Harmony 0 Whitley Gardens
• Lake Nacimiento 0 Woodlands
• Los Berros
In addition to traditionally noted cities and communities, areas such as the Camp Roberts military
installation, Camp San Luis, and California Polytechnic State University-San Luis Obispo can be considered
communities in and of themselves. San Luis Obispo County works and interacts with these institutions in
many ways similar to how the County interacts with other communities outside the scope of this plan.
However, it is recognized these listed entities fall under the authority and jurisdiction of the State of
California and/or the U.S. Government.
Additionally, the County contains several Community Services Districts (CSDs) or other special districts.
California state law allows residents of an unincorporated area to initiate the formation of a community
services district to provide any of a wide variety of services, including water, garbage collection,
wastewater management, security, fire protection, public recreation, street lighting, mosquito abatement,
conversion of overhead utilities to underground, library services, ambulance services, and graffiti
abatement. A CSD may span unincorporated areas, multiple cities and/or counties. Once a CSD is formed,
the residents elect a board to oversee CSD management and operations.
Following is a list of all CSDs and special districts in San Luis Obispo County. Districts that are participating
jurisdictions in this plan update process are bolded. Figure 4-2 shows the CSDs and special districts that
participated in the 2019 planning process.
San Luis Obispo County LocalOctober 2019 Page 4-3
Section 4
San Luis Obispo County Profile
• Arroyo Grande Cemetery District • Garden Farms Community Water District
• Atascadero Cemetery District 0 Ground Squirrel Hollow CSD
• Atascadero Public Financing Authority • Heritage Ranch CSD
• Atascadero Unified School District Educational • Independence Ranch CSD
Facilities Corporation • Linne CSD
• Avila Beach CSD 0 Los Osos CSD
• California Valley CSD 0 Nipomo CSD
• Cambria Cemetery District 0 Nipomo Lighting District
• Cambria Community Healthcare District 0 Oceano CSD
• Cambria CSD • Paso Robles Cemetery District
• Cayucos Fire Protection District 0 Paso Robles Joint Unified School District
• Cayucos Sanitary District Educational Facilities Corporation
• Cayucos-Morro Bay Cemetery District • Pismo Beach Public Financing Authority
• Central California Schools Financing Authority 0 Port San Luis Harbor District
• Central Coast Cities Joint Powers Self- 0 San Luis Obispo County Air Pollution District
Insurance Fund - Compensation 0 San Luis Obispo County Financing Authority
• Central Coast Cities Joint Powers Self- • San Luis Obispo County Flood Control and
Insurance Fund-Liability Water Conservation District
• City of Arroyo Grande Public Financing 0 San Luis Obispo County Integrated Waste
Authority Management Authority
• City of Pismo Beach Public Facilities 0 San Luis Obispo Public Financing Authority
Corporation 0 San Miguel Cemetery District
• Coastal San Luis Resource Conservation 0 San Miguel CSD
District 0 San Simeon CSD
• County Service Area No. 1 0 Santa Margarita Cemetery District
• County Service Area No. 7 0 Santa Margarita Fire Protection
• County Service Area No. 9 0 Schools Insurance Program for Employees
• County Service Area No. 10 0 Shandon Cemetery District
• County Service Area No. 12 0 South San Luis Obispo County Sanitation
• County Service Area No. 16 District
• County Service Area No. 17 • Squire Canyon CSD
• County Service Area No. 18 0 Templeton Cemetery District
• County Service Area No. 21 • Templeton CSD
• County Service Area No. 22 0 Templeton Unified School District Educational
• County Service Area No. 23 Facilities Corporation
• Creston Hills Ranch CSD 0 Upper Salinas/Las Tablas Resource
• EI Paso de Robles Public Financing Authority Conservation District
• Five Cities Fire Authority
Section 4
San Luis Obispo County Profile
Figure 4-2 Participating Districts
,l
MONTEREY KINGS
� r
-- -------------- ----- ----------- ------------- _ ------------- — ------ ;
San Miguel � -
41 g 41 i
I' r
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- Heritage Ranch San Simeon ,,,,[Port San Luis Harbor District
- Los Osos
Templeton
Map compiled EQ019; D 10 20 Miles pN
intended for planning purposes only.
Data Source, San Luis Obispo County, Ii,`51
US Census TIGER Database,CA Open
Data Portal,LAFCO
San Luis Obispo County Local Hazard Mitigation Plan I October 2019
Section 4
San Luis Obispo County Profile
4.4 Population and Demographics Profile
This section was updated in 2019 using data from the 2012-2017 American Community Survey (ACS) 5-
Year Estimates.
Population
The U.S. Census Bureau estimated San Luis Obispo County's total population of 280,119 as of 2017. This
constitutes a 4% increase in population from the 2014 plan (269,637 persons). The tables below list the
total population estimates for each jurisdiction, and shows how they have changed in the last five years.
Table 4-1 San Luis Obispo County Population Change, 2012-2017
Jurisdiction 2012 2013 2014 i i 017,
San Luis Obispo County 270,121 272,094 274,184 276,517 278,680 280,119 +4%
Arroyo Grande City 17,284 17,411 17,536 17,720 17,842 17,971 +4%
Atascadero City 28,441 28,613 28,792 29,084 29,516 29,797 +5%
Avila Beach CDP* NA NA 1,166 1,270 1,242 1,080 -7%
Cayucos CDP 2,431 2,475 2,553 2,758 2,987 2,847 +17%
Grover Beach City 13,194 13,253 13,337 13,409 13,484 13,524 +3%
Los Osos CDP 14,874 14,177 14,778 15,388 15,603 15,714 +6%
Nipomo CDP 16,747 17,256 17,115 16,727 16,456 16,706 +0%
Oceano CDP 7,543 7,453 7,355 7,857 8,262 7,788 +3%
Paso Robles City 29,770 30,144 30,522 30,863 31,178 31,409 +6%
Pismo Beach City 7,721 7,746 7,789 7,890 7,984 8,060 +4%
San Luis Obispo City 45,328 45,584 45,911 46,337 46,716 46,997 +4%
San Miguel CDP 2,822 2,621 2,638 2,461 2,696 2,824 +0%
San Simeon CDP 513 534 477 284 325 523 +2%
Templeton CDP 7,200 7,525 7,753 7,377 7,525 7,989 +11%
Source:U.S.Census Bureau American Community Survey,www.census.gov/. Avila Beach data not available prior to 2014.
Note:Data for Census Designated Places(CDP)may not have the same boundaries as the participating Community Service Districts.
Table 4-2 and Table 4-3 show several key demographic and social characteristics of San Luis Obispo
County, how those characteristics have changed over the last five year, and how those characteristics
compare to the rest of the state and nation.
ObispoSan Luis
Section 4
San Luis Obispo County Profile
Table 4-2 San Luis Obispo County Demographic and Social Characteristics, 2012-2017
San Luis Obispo . -
Population 270,121 280,119 3.7%
Median Age 39.3 39.0 -0.8%
Total Housing Units 117,318 120,182 2.4%
Housing Occupancy Rate 86.7% 87.4% 0.7%
%of Housing Units with no Vehicles Available 4.5% 4.5% 0.0%
Median Home Value $449,300 $499,800 11.2%
Unemployment 8.7% 4.8% -3.9%
Mean Travel Time to Work(minutes) 20.9 21.8 4.3%
Median Household Income $59,628 $67,175 12.7%
Per Capita Income $30,218 $33,972 12.4%
%of Individuals Below Poverty Level 13.7% 13.8% 0.1%
#of Households 101,708 105,044 3.3%
Average Household Size 2.49 2.51 0.8%
•of Population Over 25 with High School Diploma 89.5% 90.5% 1.0%
•of Population Over 25 with Bachelor's Degree or Higher 31.5% 34.0% 2.5%
•with Disability 11.1% 11.1% 0.0%
•Speak English less than "Very Well" 6.7% 6.8% 0.1%
Source:U.S.Census Bureau American Community Survey www.census.gov/
Table 4-3 Demographic and Social Characteristics Compared to the State and Nation
Median Age 39.0 36.1 37.8
Housing Occupancy Rate 87.4% 92.1% 87.8%
0/0 Of Housing Units with no Vehicles Available 4.5% 7.4% 8.8%
Median Home Value $499,800 $443,400 $193,500
Unemployment 4.8% 7.7% 6.6%
Mean Travel Time to Work(minutes) 21.8 28.8 26.4
Median Household Income $67,175 $67,169 $57,652
Per Capita Income $33,972 $33,128 $31,177
%of Individuals Below Poverty Level 13.8% 15.1% 14.6%
Average Household Size 2.51 2.96 2.63
•of Population Over 25 with High School Diploma 90.5% 82.5% 87.3%
•of Population Over 25 with bachelor's degree or Higher 34.0% 32.6% 30.9%
•with Disability 11.1% 10.6% 12.6%
•Speak English less than "Very Well" 6.8% 18.4% 8.5%
Source:U.S.Census Bureau American Community Survey www.census.gov/
Table 4-4 and Figure 4-3 breakdown the demographics of the county by sex, race, and age.
San Luis Obispo County Local Hazard Mitigation Plan I October 2019 -4-7
Section 4
San Luis Obispo County Profile
Table 4-4 Demographics by Race and Sex
San Luis Obispo County Population
Total Population 280,119 ---
Male 142,182 50.8%
Female 137,937 49.2%
Hispanic or Latino 62,174 22.2%
White alone 194,355 69.4%
Black alone 4,958 18.0%
Asian alone 9,998 3.6%
American Indian and Alaska Native alone 1,237 0.4%
Native Hawaiian and Other Pacific Islander alone 280 0.1%
Some other race alone 109 0.0%
Two or more races alone 7,008 2.5%
Source:U.S.Census Bureau American Community Survey www.census.gov/
Figure 4-3 San Luis Obispo County Population By Age
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Housing Characteristics
The 2010 United States Census documented 117,315 housing units, 13 percent of which were vacant. The
table below presents the 2017 American Community Survey estimates for types of housing units.
San Luis Obispo County Local Hazard Mitigation Plan I October
Section 4
San Luis Obispo County Profile
Table 4-5 Types and Total Amounts of Housing Units in San Luis Obispo County
Type of housing units Total
1-unit detached 80,791 67%
1-unit attached 6,527 5.4%
2 units 3,878 3.2%
3 or 4 units 7 6,190 5.2%
5 to 9 units 5,035 4.2%
10 to 19 units 3,117 2.6%
20 or more units 4,180 3.5%
Mobile home 10,185 8.5%
Boat, RV,van, etc. 279 0.2%
Total housing units 120,182 100%
Source:U.S.Census Bureau American Community Survey www.census.gov/
Occupied Housing Unit Characteristics:According to the 2017 American Community Survey, San Luis
Obispo had 120,182 total housing units, of which 105,044 (87.4%were occupied. 60 percent of the
occupied housing units were owner-occupied and 40% renter-occupied. More than half the total housing
units (52.4%) were built in 1980 or later. However nearly half of residents (45.3%) had been in their current
housing for eight years or less. Only 4.5% of occupied housing units have no vehicles available for private
use, considerably below state and national averages (7.4%and 8.8% respectively). 67.6% of occupied
housing units use utility gas for heating, with another 17.9% using electric heating.
Housing Costs: The median value of owner-occupied housing units in 2017 was $499,800; this represents
an 11.2% increase since 2012, and is 12.7% above the average in California. More than 70% of owner-
occupied units were valued between $300,000 and $999,999. Eight percent were valued at $1,000,000 or
more. Most owner-occupied units had a mortgage (67.5%).The median rent cost during this time was
$1,326, and 45.9% of renters were paying 35% or more of their income for housing.
Households and Families:In 2017 the average household size was 2.51 persons. There were 105,044
total households, 66,465 (63.3%) of which were family households (62.4%).
Income and Employment: The median household income in 2017 was $67,175, a 12.7% increase over
2010; this is statistically the same as the statewide average ($67,169). Per capita income increased similarly
during this period, from $30,218 in 2012 to $33,972 in 2017.There were 137,680 people in the labor force,
with an unemployment rate of 4.8%, down from 8.7% in 2012. Figure 4-4 shows the number of people
earning different income levels in the County as of 2017.
Section 4
San Luis Obispo County Profile
Figure 4-4 Income Distribution in San Luis Obispo County
20,000
15,000
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Source:U.S.Census Bureau American Community Survey www.census.gov/
Poverty:In 2017, 13.8%of county residents lived in poverty. 12.9% of related children under 18 were
below the poverty level, compared with 6% of people 65 years old and over. 6.6% of all families had
incomes below the poverty level, although that number increases to 20.5%for families with a female
householder and no husband present.
Language:Among people at least five years old living in San Luis Obispo County in 2017, 81.8% spoke
primarily English at home. Spanish was spoken in 14% of homes.A total of 6.8% households reported
they spoke English less than "very well", which is well below the statewide and national averages (18.4%
and 8.5% respectively). Since the 2010 census there has been a slight decrease (1.5%) in English as the
primary language spoken at home, in the same time period the percentage of individuals who speak
Spanish at home and households that reported to speak English less than "very well" increased by 0.9%.
Education: In 2017, 90.5% of people 25 years and over had at least graduated from high school and 34
percent had a bachelor's degree or higher.The total school enrollment in San Luis Obispo County was
77,327 for persons 3 years and over. Nursery school and kindergarten enrollment was 6,484 and
elementary or high school enrollment was 33,824 children. College or graduate school enrollment was
37,019.
People with Disabilities: 30,019 persons (11.1%) were living with some form of disability in 2017.This in
unchanged from 2012 and is close to statewide and national averages (10.6% and 12.6% respectively).
Health Insurance Coverage.As of 2017, 91.4% of residents had health insurance coverage, including
73.4%with private insurance (alone or with public coverage) and 32.8%with public coverage alone or with
private coverage.
4.4.1 Social Vulnerability
Social vulnerability considerations were included in the update of this plan in 2019 to identify areas across
the County that might be more vulnerable to hazard impacts based on a number of factors.A social
vulnerability index (SoVI) was developed by the Center for Disease Control's (CDC) Agency for Toxic
San Luis Obispo County Local Hazard Mitigation Plan I October 2019 Page 4-10
Section 4
San Luis Obispo County Profile
Substances and Disease Registry (ATSDR) and their Geospatial Research, Analysis & Services Program
teams, as a way to portray communities' capacities to prepare for and respond to natural and man-made
disasters. The SoVI does so by providing insight into particularly vulnerable populations to in turn assist
emergency response planners and even public health officials identify communities more likely to require
additional support before, during, and after a hazardous event. The CDC's SoVI create county- and state-
level maps to show relative vulnerability and hence provide key socially and spatially relevant information
on communities' populations, and these maps compare the SoVI based on Census Tracts. The overall
social vulnerability based on the SoVI data is shown for the County of San Luis Obispo by Census Tracts in
Figure 4-5 below, based on statewide ranking. This overall index combines four main themes of
vulnerability, namely: socioeconomic status; household composition and disability; minority status and
language; and housing and transportation, which in turn are comprised of subcategories for a total of 15
variables accounting for various vulnerability factors. For additional information on the CDC's SoVI, refer
to their documentation and materials online at https:Hsvi.cdc.gov/.
Based on this data, the areas with the highest level of social vulnerability in the county are Grover Beach,
Oceano, southwestern San Luis Obispo City, southeastern Atascadero, southeastern and western Paso
Robles, San Miguel, and the Adelaida region.
Section 4
San Luis Obispo County Profile
Figure 4-5 Overall Social Vulnerability in San Luis Obispo based on the SoVI, by Census Tracts
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FINAL-FOR EXTERNAL USE
San Luis Obispo County Local Hazard Mitigation Plan I October
Section 4
San Luis Obispo County Profile
San Luis Obispo County Planning & Building staff also applied the CDC methodology to refine Census
Tract level summaries into finer scale aggregation units associated with Census Designated Places (CDP),
to provide social vulnerability perspectives on more tangible community centers. The results of this CDP
based analysis further informs the vulnerability of people as discussed for each hazard in Section 5; the
SoVI data was further used to inform the County's General Plan Safety Element update in 2019. The
overall social vulnerability of the County by CDP is portrayed in Figure 4-6. Additional maps using the
CDPs and the four main vulnerability themes of the SoVI are shown in Figure 4-7 (socioeconomic
vulnerability theme), Figure 4-8 (household composition and disability vulnerability theme), Figure 4-9
(minority status and language vulnerability theme), and Figure 4-10 (housing and transportation
vulnerability theme). For additional information on the CDC's SoVI, refer to their documentation and
materials online at https:Hsvi.cdc.gov/.
Section 4
San Luis Obispo County Profile
Figure 4-6 Overall Social Vulnerability in San Luis Obispo based on the SoVI, by Census Designated Place
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San Luis Obispo County Local Hazard Mitigation Plan I October 2019
Section 4
San Luis Obispo County Profile
Figure 4-7 Socioeconomic Vulnerability in San Luis Obispo by Census Designated Place
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Data Portal,CDC SVI 2016
San Luis Obispo County Local Hazard Mitigation Plan I October 2019
Section 4
San Luis Obispo County Profile
Figure 4-8 Household Composition and Disability Vulnerability in San Luis Obispo by Census Designated Place
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Planning&Building Data Source:San Luis Obispo County,
US Can sus TIGER Database,CA Open
Data Portal,CDC SVI 2016
San Luis Obispo County Local Hazard Mitigation Plan I October 2019
Section 4
San Luis Obispo County Profile
Figure 4-9 Minority and Language Vulnerability in San Luis Obispo by Census Designated Place
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Planning&BullJong Data Source:San Luis Obispo County,
US Census TIGER Database,CA Open
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San Luis Obispo County Local Hazard Mitigation Plan I October 2019
Section 4
San Luis Obispo County Profile
Figure 4-10 Housing and Transportation Vulnerability in San Luis Obispo by Census Designated Place
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blannwn;&Piuilding Data Source:San Luis Obispo County. 1
US Census TIGER Database.CA Open
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San Luis Obispo County Local Hazard Mitigation Plan I October 2019
Section 4
San Luis Obispo County Profile
Environmental Justice Considerations
iii - -. i
The environmental justice element, or related environmental justice goals,policies, and objectives integrated in other
elements,shall do all of the following:
(A) Identify objectives and policies to reduce the unique or compounded health risks in disadvantaged
communities by means that include, but are not limited to, the reduction of pollution exposure, including the
improvement of air quality, and the promotion of public facilities,food access,safe and sanitary homes, and
physical activity.
(8) Identify objectives and policies to promote civil engagement in the public decision-making process.
(C) Identify objectives and policies that prioritize improvements and programs that address the needs of
disadvantaged communities.
In 2016 California passed Senate Bill 1000 (SB 1000), the Planning for Healthy Communities Act, requiring
cities and counties with disadvantaged communities to include environmental justice (EJ) in their General
Plans when they are updating two or more elements of their General Plan concurrently on or after January
1, 2018. Environmental justice is defined by state law as "the fair treatment of people of all races, cultures,
and incomes with respect to the development, adoption, implementation, and enforcement of
environmental laws, regulations, and policies" (Gov. Code § 65040.12e). SB 1000 defines disadvantaged
environmental justice (EJ) communities as those that either 1) rank in the top 2511 percentile of the
CalEnviroScreen Index, or 2) are low-income and disproportionately affected by exposure to
environmental pollution and other hazards that can lead to negative health effects or environmental
degradation. This two-part definition creates a "black and white" baseline and another that allows a city or
county to cater to its communities through its broad language. Per the first definition, no areas in San Luis
Obispo County contain disadvantaged communities. Per the second definition, local jurisdictions may
subjectively interpret how to identify disadvantaged communities based on a regional analysis.
This LHMP addresses these considerations to a degree in the social vulnerability assessment for each
hazard in Section 5 and prioritization criteria for mitigation actions in Section 7. Prioritization criterial
includes a 'Social' element which considers applying a higher priority to actions that relate to social
equity, benefits disadvantaged communities, or addresses vulnerable populations. In addition, the County
of San Luis Obispo adopted Mitigation Action C.1.3 to increase involvement of disadvantaged
communities in disaster preparedness activities and prioritize programs that address their needs and
incorporated these requirements into the Safety Element of the General Plan during a process parallel to
this LHMP update. Other cities and counties may choose to identify disadvantaged communities within
their jurisdictions and incorporate the SB 1000 requirements into their planning processes.
4.5 Economy
Table 4-6 breaks down San Luis Obispo County's labor force by industry as of 2017. The largest sector of
employment is in educational services, health care, & social assistance, which makes up 22.2% of jobs in
the County. They're followed by the arts, entertainment, recreation, accommodation, &food services
sector(11.8%), retail trade (10.8%), and the professional, scientific, and management, and administrative
and waste management services sector(10.0%).
Section 4
San Luis Obispo County Profile
Table 4-6 San Luis Obispo County Employment by Industry (2017)
Industry #Employed
Population (2017) 280,119
In Labor Force 137,680
Agriculture,forestry,fishing and hunting,and mining 4,480
Armed Forces 1,817
Construction 10,235
Manufacturing 8,841
Wholesale trade 2,820
Retail trade 14,851
Transportation and warehousing,and utilities 5,845
Information 2,012
Finance and insurance,and real estate and rental and leasing 5,842
Professional,scientific,and management,and administrative and waste management services 13,821
Educational services,and health care and social assistance 30,501
Arts,entertainment,and recreation,and accommodation and food services 16,229
Other services,except public administration 6,676
Public administration 7,124
Unemployed 6,586
Source:U.S.Census Bureau American Community Survey 2012-2017 5-Year Estimates,www.census.gov/
The San Luis Obispo Chamber of Commerce published a 2018 Community Economic Profile for the City of
San Luis Obispo with additional information about San Luis Obispo County. This section was updated in
2013 to reflect the latest data from the San Luis Obispo Chamber of Commerce.
Employers: The table below reflects the top 25 employers in San Luis Obispo County as reported by the
California Employment Development Department.
Table 4-7 Top 25 Employers—San Luis Obispo County
Company/Organization
Employees
Employer Name Location Industry Employees
Atascadero State Hospital Atascadero Hospitals 1,000-4,999
Cal Poly State University San Luis Obispo Schools-Universities&Colleges 1,000-4,999
Academic
Glenair Inc Paso Robles Communications Consultants 1,000-4,999
Pacific Gas&Electric Co San Luis Obispo Electric Companies 1,000-4,999
San Luis Obispo County EMS San Luis Obispo Government Offices-County 1,000-4,999
AMI Sierra Vista Radiology San Luis Obispo Physicians&Surgeons 500-999
California Mid-State Fair Paso Robles Concert Venues 500-999
Cuesta College Paso Robles Junior-Community College-Tech 500-999
Institutes
Division of Juvenile Justice Paso Robles State Govt-Correctional 500-999
Institutions
Medi-Cal Eligibility Info San Luis Obispo Government Offices-County 500-999
San Luis Obispo County Local Hazard Mitigation Plan I October 2019 Page 0
Section 4
San Luis Obispo County Profile
Company/Organization
_�i Employees
Mental Marketing Atascadero Advertising-Agencies& 500-999
Counselors
Sierra Vista Regional Med Ctr San Luis Obispo Hospitals 500-999
Trust Rcm San Luis Obispo Billing Service 500-999
Arroyo Grande Community Hosp Arroyo Grande Hospitals 250-499
Child Abuse-Neglect-Child San Luis Obispo Business Management 250-499
Consultants
County Office of Education San Luis Obispo Schools 250-499
French Hospital Medical Ctr San Luis Obispo Hospitals 250-499
Hearst Castle 11119 San Simeon I National Monuments 50-499
Madonna Inn Resort San Luis Obispo Resorts 250-499
Morro Bay Art Assn Gallery Morro Bay Art Galleries&Dealers 250-499
Ramirez Farm Labor Shandon Labor Contractors 250-499
San Luis Obispo County Social San Luis Obispo Government Offices-County 250-499
San Luis Obispo Sheriff's Dept San Luis Obispo Sheriff 250-499
Social Services Dept San Luis Obispo Government Offices-County 250-499
Source:California Employment Development Department
Agriculture:The agriculture industry in San Luis Obispo is a crucial part of the local economy, providing
employment and income directly for those in agriculture, as well as driving growth in the tourism industry.
Total crop values in 2017 were $925 million.The top 20 leading agriculture crops are listed in Table 5-3 in
the Risk Assessment section.
4.6 Climate
The climate and air quality of San Luis Obispo County are directly related to its physical characteristics.
The coastal lowlands and plains are bounded on the east by the Santa Lucia Mountains and experience a
maritime climate.That climate is somewhat modified locally by elevation and distance from the ocean, as
well as the mountains.The north and northeastern portions of the County include the upper end of the
Salinas Valley,where the maritime climate is substantially modified by the intervening mountains.The
Carrizo Plain in the east and southeastern portion of the County is climatically high desert.
Because the County is located along the California coast,the weather is normally under the influence of a
high-pressure system located to the west.As a result, a common weather pattern includes afternoon and
evening onshore winds.
San Luis Obispo County has a pleasant, Mediterranean climate year-round, averaging 315 days of
sunshine per year.
• Winter: 64°F/317 - Cool and Sunny
• Spring: 757/447 - Breezy and Cool
• Summer: 947/547 -Warm Coastal Mornings/Sunny Days
• Fall: 777/437 -Warm Days and Cool Nights
San Luis Obispo County Local Hazard Mitigation Plan I October
Section 4
San Luis Obispo County Profile
The 2010 &2011 Annual Air Quality Report issued by the San Luis Obispo Air Pollution Control District
notes that the County overall had good air quality. However ozone levels exceeding both federal and
state standards were measured on numerous days in the rural eastern portion of the county due to
transported pollution. Smoke from wildfires can often adversely affect air quality. South County air quality
was impacted by dust blown from the dune complex along the coast of the Five Cities area. Only one
exceedance of the federal PM10 standard occurred in 2010, but numerous exceedances of the state
standard were recorded during this time frame.The County attained both federal and state standards for
fine particulate matter, carbon monoxide, nitrogen dioxide, sulfur dioxide, hydrogen sulfide, and visibility.
An overview of the effects of climate change on San Luis Obispo County can be found in subsection 5.1.3.
4.7 Transportation Systems
The County contains major transportation arteries including U.S. Highway 101, California State Highways
1, 41,46, 58, and 166, and the Union Pacific Railroad. The County has a regional airport near the southern
portion of the City of San Luis Obispo which offers service to larger commercial airports to the north and
south (Los Angeles and San Francisco, as well as flights to Phoenix). In addition to air transportation, the
County is also served with scheduled rail service by Amtrak, and motor bus service by companies such as
Greyhound and Orange Belt Stages, as well as a number of tour coach operators, and local transit
systems.
4.8 Governing Body
The Board of Supervisors serves as the Legislative body of the County of San Luis Obispo for the planning
and provision of services related to public needs and the requirements of State and Federal laws.
California law provides for five Supervisors to be elected by district. Each Supervisor is elected for a four-
year term. Two of the Supervisors' terms are staggered so that all Supervisors are not standing for
election at the same time.As the elected representative of the people of San Luis Obispo County, the
Board of Supervisors establishes overall County priorities and sets policy.
The San Luis Obispo County Flood Control and Water Conservation District is operated by the County
Water Resources Division of Public Works.The District (Public Works Department) is the designated
County agency responsible for managing, planning, and maintaining drainage and flood control facilities
in the unincorporated public areas where no other agency has assumed an active role in such activities.
The District has a regional role in the County and can work with individual cities or communities when
requested. The County Board of Supervisors also serves as the governing body for the Flood Control
District.
4.9 Land Use
Existing land use within San Luis Obispo County is varied with respect to types of uses, ownership,
character, and intensity. Land uses include:
• Rural residential 0 Recreational open space
• Single family detached 0 Other open space
• Single family attached 0 Heavy industrial
• High-density residential (apartments) 0 Warehouse
• Mobile homes 0 Vacant
Section 4
San Luis Obispo County Profile
• Agriculture 0 Retail /Office
• Water 0 Tourist/Commercial recreation
• Utilities 0 Light industrial/ Business park
• Public facilities 0 Mineral extraction
• Schools
4.10 Development Trends
While the population of San Luis Obispo County is expected to continue growing, there are Land Use
policies and elements within the County General Plan to help assure orderly development.
The California Department of Transportation's Office of State Planning prepared the California County-
Level Economic Forecast 2018-2050. Highlights of the forecast for San Luis Obispo County include:
• From 2018 to 2023, employment growth is expected to average 0.9 percent per year.
• The largest employment gains will be observed in education and healthcare, leisure services, and
government. Together, these sectors will account for 61 percent of net job creation during the 2018-
2023 period.
• Average salaries are currently below the California average, and will remain so over the foreseeable
future. In San Luis Obispo County, inflation-adjusted salaries are expected to rise by an average of 1.8
percent per year between 2018 and 2023, which will be similar to statewide growth.
• Over the forecast period, an average of 970 homes will be authorized per year. Because San Luis
Obispo County has large amounts of buildable land, housing production will spread out into single-
family communities, rather than be forced up into multifamily skyscrapers.
• The population is expected to increase by 0.4 percent annually through 2023. Net migration will
account for almost all population growth. Because the County has an old population base, the
number of deaths will be approximately equal to the number of births during the forecast period.
Table 4-8 San Luis Obispo County Economic Forecast, 2017-2050
ObispoSan Luis
Population (people) 279,967 298,795
Net Migration (people) 1,326 710
Registered Vehicles (thousands) 315 355
Households (thousands) 105.7 124.9
New Homes Permitted (homes) 1,111 303
Total Taxable Sales (billions) $5.36 $19.35
Personal Income (billions) $16.14 $54.75
Real Per Capita Income(dollars) $56,044 $85,431
Inflation Rate (%change in CPI) 2.7 1.9
Real Farm Crop Value (millions) 967.2 1234.3
Real Industrial Production (millions) 2,493 4,698
Unemployment Rate (percent) 3.3 3.8
Employment(thousands ofjobs)
Total Wage&Salary 123.8 144.5
Farm 5.2 6.4
Section 4
San Luis Obispo County Profile
San Luis Obispo County 2018 2050
Construction 7.7 5.5
Manufacturing 7.3 7.9
Transportation&Utilities 4.1 3.9
Wholesale&Retail Trade 17.5 22.3
Financial Activities 4.2 4.4
Professional Services 10.7 13.4
Information 1.4 1.4
Health&Education 15.7 19.7
Leisure 19.3 23.5
Government 24.8 29.5
Source:California County-Level Economic Forecast 2018-2050,California Department of Transportation
Analysis of development trends in the County can be found in subsection 5.2, to include analysis of
building permits.Additional discussion on development trends can be found in the Future Development
section of each hazard profile in the Section 5.
ObispoSan Luis
Section 5
Risk Assessment
SECTION 5 RISK ASSESSMENT
DMA Requirement§201.6(c)(2):
[The plan shall include]A risk assessment that provides the factual basis for activities proposed in the strategy to
reduce losses from identified hazards. Local risk assessments must provide sufficient information to enable the
jurisdiction to identify and prioritize appropriate mitigation actions to reduce losses from identified hazards.
Risk, for the purposes of this plan and as defined by FEMA, is a combination of hazard, vulnerability, and
exposure. "It is the impact that a hazard would have on people, services, facilities, and structures in a
community and refers to the likelihood of a hazard event resulting in an adverse condition that causes
injury or damage."
The risk assessment process identifies and profiles relevant hazards and assesses the exposure of lives,
property, and infrastructure to these hazards. The process allows for a better understanding of a
jurisdiction's potential risk to hazards and provides a framework for developing and prioritizing mitigation
actions to reduce risk from future hazard events.
This risk assessment builds upon the methodology described in the 2013 FEMA Local Mitigation Planning
Handbook, which recommends a four-step process for conducting a risk assessment:
1. Describe Hazards
2. Identify Community Assets
3. Analyze Risks
4. Summarize Vulnerability
In essence, the risk assessment evaluates potential loss from hazards by assessing the vulnerability of the
county's population, build environment, critical facilities, and other assets. Data collected through this
process has been incorporated into the following sections of this section:
Subsection 5.1: Hazard Identification - identifies the hazards that threaten the Planning Area and
describes why some hazards have been omitted from further consideration.
Subsection 5.2: Asset Summary - describes the methodology for inventorying assets as the basis for
determining vulnerability of the planning area to the identified hazards.
Subsection 5.3: Hazard Analysis and Risk Assessment - discusses the threat to the Planning Area and
describes previous occurrences of hazard events and the likelihood of future occurrences (2013 FEMA
Local Mitigation Planning Handbook Risk Assessment Step 1). It also includes a vulnerability assessment
considering assets at risk, critical facilities, and future development trends (2013 FEMA Local Mitigation
Planning Handbook Risk Assessment Steps 2, 3 and 4).
This risk assessment covers the entire geographical area of San Luis Obispo County. Since this plan is a
multi-jurisdictional plan, the HMPC was required to evaluate how the hazards and risks vary from
jurisdiction to jurisdiction. While these differences are noted in this section, they are expanded upon in
the annexes of the participating jurisdictions. If no additional data is provided in an annex, it should be
assumed that the risk and potential impacts to the affected jurisdiction are similar to those described here
for the entire San Luis Obispo County planning area.
County of San Luis Obispo Local October 2019
Section 5
Risk Assessment
5.1 Hazard Identification and Prioritization
[The risk assessment shall include a]description of the type of all-natural hazards that can affect the jurisdiction.
The first step in developing a risk assessment is identifying the hazards. The San Luis Obispo County
HMPC conducted a hazard identification study to determine the hazards that threaten the planning area.
5.1.1 Methodology and Results
The Central Coast region of California is susceptible to a number of hazards. This HMP profiles the most
significant of these hazards. Historical data, catastrophic potential, relevance to the jurisdiction, and the
probability and potential magnitude of future occurrences were all used to reduce and prioritize the list of
hazards to those most relevant to San Luis Obispo County.
Using existing natural hazards data and input gained through planning meetings during both the 2014
HMP and 2019 update, the HMPC agreed upon a list of hazards that could affect San Luis Obispo County.
The following table explains the changes in the hazards profiled in 2014 and the 2019 update. Bolded
hazards are new to the plan.
Table 5-1 Updates to Hazards Profiled, 2014 Plan and 2019 Update
2019 Hazards How and Why Identified R.I.T.T. -Mm
Adverse weather:extreme heat, In 2014 Plan Extreme heat added;drought removed
freeze, hail,wind,dense fog,tornado, and addressed as a separate hazard
thunderstorm
Agricultural pest infestation and plant In 2014 Plan Tree mortality included.
disease, marine invasive species
Biological agents (naturally occurring) In 2014 Plan Pandemic flu,food and water borne
illness.Also addressed in other planning
mechanisms but a concern to county and
history of events. Include Vector Borne
Disease
Coastal Storm/Coastal Erosion/Sea In 2014, sea level rise
Level Rise recommended by HMPC
Dam Incidents New in 2014, recommended Includes flooding from excess releases
by HMPC and 2014 FEMA and failures.
review; identified in local
HMPs; in GP Safety Element
Drought and Water Shortage In 2014 Plan as part of Separated out from adverse weather as its
adverse weather own hazard as nature of hazard is unique
and different consequences; includes
ground and surface water shortage,-
agricultural
hortage;agricultural and viticulture impacts
Earthquake(including fault rupture, In 2014 Plan
groundshaking, liquefaction)
Floods In 2014 Plan Includes riverine and stormwater drainage
and levee failure;coastal flooding
addressed in coastal storms section
Section 5
Risk Assessment
2019 Hazards • • Why Identified •
Landslides and Debris Flow In 2014 Plan Debris flow included due to potential from
wildfire burns
Subsidence New in 2014, recommended Consequence of drought due to overdraft
by HMPC; identified in Paso of aquifers.
Robles HMP
Tsunami and seiche In 2014 Plan
Wildfire In 2014 Plan
Human Caused:Hazardous New in 2014, recommended Includes Fixed Facility and Transportation,
Materials by HMPC; In 1999 General Radiological Accidents, Oil spills, Natural
Plan Safety Element;County Gas Pipeline Rupture&Storage Facilities
EOP and several emergency
response plans
Climate Change/Long term climate In 2014 Plan Climate change considerations
variability incorporated in the hazard profiles to
describe how the frequency and intensity
of hazards could be altered in the future
In alphabetical order, the natural hazards identified and investigated for the San Luis Obispo County
Multi-Jurisdictional Hazard Mitigation Plan include:
• Adverse Weather
- Extreme Heat
- Thunderstorm/Heavy Rain/ Lightening/Freeze/Hail/Dense Fog
- High Wind/Tornado
• Agricultural Pest Infestation and Plant Disease/Marine Invasive Species
• Biological Agents (naturally occurring)
• Coastal Storm/Coastal Erosion/Sea Level Rise
• Dam Incidents
• Drought and Water Shortage
• Earthquake
• Flood
- Levee Failure
• Landslide and Debris Flow
• Subsidence
• Tsunami
• Wildfire
Human Caused Hazards
• Hazardous Materials
- Fixed Facility
- Transportation
- Radiological Accidents
- Oil Spills
- Natural Gas Pipeline Rupture &Storage Facilities
Section 5
Risk Assessment
The 2019 HMP update included a significant re-evaluation of the hazards with the latest, best available
data. Hazards data from San Luis Obispo County, California Governor's Office of Emergency Services (CA-
OES), FEMA, the National Oceanic and Atmospheric Administration, and many other sources were
examined to assess the significance of these hazards to the planning area. The update process included a
comprehensive, parcel-level risk analysis with GIS where available data permitted. Many new maps and
tables were added that capture the potential losses. Additional details on the loss analysis, including a
breakdown of hazard losses by jurisdiction and property type can be referenced in Appendix E and the
jurisdictional annexes.
Overall Hazard Significance Summary
Overall hazard significance was based on a combination of Geographic Area, Probability of Future
Occurrence and Potential Magnitude/Severity as defined below. The individual ratings are based on or
interpolated from the analysis of the hazards in the sections that follow. During the 2019 San Luis Obispo
County HMP update the individual ratings and significance of the hazards was revisited and updated.
Public concern was also considered via input at public meetings and an online survey.
Table 5-2 San Luis Obispo County Hazard Significance
Geographic Probability of Future Magnitude/ Overall
Area Occurrence Severity(Extent) Significance
Adverse Weather: Significant Likely Negligible Medium
Thunderstorm/Heavy
Rain/Hail/Lig hting/Dense
Fog/Freeze
Adverse Weather: High Significant Likely Negligible Low
Wind/Tornado
Adverse Weather: Extreme Extensive Occasional Negligible Low
Heat
Agricultural Pest Infestation Limited Highly Likely Negligible Medium
and Disease
Biological Extensive Occasional Critical Medium
Dam Incidents Limited Unlikely Critical Medium
Drought and Water Extensive Likely Critical High
Shortage
Earthquake Extensive Occasional Critical High
Flood Significant Likely Critical Medium
Landslides and Debris Flow Significant Likely Critical Medium
Coastal Storm/Coastal Limited Likely Limited Medium
Erosion/Sea Level Rise
Subsidence Significant Occasional Negligible Low
Tsunami and Seiche Significant Occasional Limited Medium
Wildfire Extensive Likely Critical High
Human Caused: Hazardous Limited Highly Likely Negligible Low
Materials
Section 5
Risk Assessment
Geographic Area Magnitude/Severity(Extent)
Limited: Less than 10%of planning area Catastrophic—More than 50 percent of property severely damaged;
Significant: 10-50%of planning area shutdown of facilities for more than 30 days;and/or multiple deaths
Extensive: 50-100%of planning area Critical-25-50 percent of property severely damaged;shutdown of
facilities for at least two weeks;and/or injuries and/or illnesses result in
Probability of Future Occurrences permanent disability
Highly Likely: Near 100%chance of occurrence in Limited-10-25 percent of property severely damaged;shutdown of
next year or happens every year. facilities for more than a week;and/or injuries/illnesses treatable do not
Likely: Between 10 and 100%chance of occurrence result in permanent disability
in next year or has a recurrence interval of 10 years or Negligible—Less than 10 percent of property severely damaged,
less. shutdown of facilities and services for less than 24 hours;and/or
Occasional:Between 1 and 10%chance of injuries/illnesses treatable with first aid
occurrence in the next year or has a recurrence
interval of 11 to 100 years. Significance
Unlikely:Less than 1%chance of occurrence in next Low:minimal potential impact
100 years or has a recurrence interval of greater than Medium:moderate potential impact
every 100 years. High:widespread potential impact
Other Hazards Considered
Other hazards were noted by the HMPC and public to potentially consider in the HMP update. Some of
these hazards have the potential to do damage or harm but since the focus of this plan is on natural
hazards, per the DMA requirements, they are not profiled further; in some cases they are currently
addressed in other planning mechanisms or have had limited historic impacts:
• Expansive Soils
• Radon
• Tree mortality/hazardous trees in developed areas
• Human-Wildlife conflicts
• Energy Shortage
• Civil Disturbance/Disorder
• Terrorism
• Cyber Threat
• Transportation Incidents/emergencies
• Well Stimulation & Hydraulic Fracturing
5.1.2 Disaster Declaration History
One method the HMPC used to identify hazards was researching past events that triggered federal and
state emergency or disaster declarations in the planning area. Federal and state disaster declarations may
be granted when the severity and magnitude of an event surpasses the ability of the local government to
respond and recover. Disaster assistance is supplemental and sequential.When the local government's
capacity has been surpassed, a state disaster declaration may be issued, allowing for the provision of state
assistance. Should the disaster be so severe that both the local and state governments' capacities are
exceeded, a federal emergency or disaster declaration may be issued allowing for the provision of federal
assistance. In other words, a presidential disaster declaration puts federal recovery programs in place to
help disaster victims, business, and public agencies.
The federal government may issue a disaster declaration through FEMA, the U.S. Department of
Agriculture (USDA), or the Small Business Administration (SBA). FEMA also issues emergency declarations,
which are more limited in scope and without the long-term federal recovery programs of major disaster
declarations (Farm Service Agency 2018). The quantity and types of damage are the determining factors.
This section focuses on state and federal disaster and emergency declarations.
County of San Luis Obispo Local October 2019
Section 5
Risk Assessment
The communities throughout San Luis Obispo are among the many in California that are susceptible to
disaster. Details on federal and state disaster declarations were obtained by the HMPC, FEMA, and the
California Office of Emergency Services (Cal OES) and compiled in chronological order in Table 5-3.A
review of state and federal declared disasters indicates that San Luis Obispo County received 26 state
proclamations between 1950 and March 2017, 22 of which also received federal disaster declarations. Of
the 26 state declarations, 19 were associated with flooding (13 of the flooding events which were related
to severe winter storms and heavy rains; 1 was associated with coastal flooding; and 3 were flooding and
mudslides); 3 were for drought (not including declaration issued by the USDA); 2 were for freeze; ; 1 was
for earthquake; and 2 were for wildfire.
Since 2012, there have been 13 drought declarations issued by the Secretary of Agriculture in San Luis
Obispo County, 9 of which were Fast Track Secretarial disaster designations.According to the Secretary of
Agriculture, a Fast Track designation is for a severe drought and provides an automatic designation when
during the growing season any portion of the county meets the severe drought intensity value for eight
consecutive weeks. Refer to the Drought hazard profile for more information of Disaster Declarations from
the Secretary of Agriculture related to drought events.
This disaster history(combined federal and state) suggests that San Luis Obispo County experiences a
major event worthy of a disaster declaration every 2.6 years.The County has a 39 percent chance of
receiving a disaster declaration in any given year. With the exception of the declarations for earthquake
and wildfire, every declaration resulted directly or indirectly from severe weather. Similarly, most disaster-
related injuries to people and damage to property and crops resulted from severe weather. Further, a
review of these events helps San Luis Obispo County and its jurisdictions identify risk reduction targets
and ways to improve capabilities to avoid large-scale hazard events in the future.
Table 5-3 San Luis Obispo County's State and Federal Disaster Declarations, 1950-2018
M1 State 11 Federal
Hazard Type � Disaster# 1 Proclamation 11 Declaration ..
Floods OCD 50-01 1950 11/21/50 -- Statewide 9 deaths;
$32,183,000
Floods DR-28 1955 12/22/55 12/23/55 Statewide 74 deaths,-
$200,000,000
eaths;$200,000,000
Severe Storms -- 1958 4/2/58 4/4/58 Statewide 13 deaths;
—Flood several injuries
$24,000,000
Severe Storms -- 1963 2/14/164 -- Northern California— --
-Flood Boundaries of SLO county
and 3 other counties up to
the Oregon Border
Severe Winter DR-223 1967 12/1/1966 1/2/1967 San Luis Obispo (and 7 $28,761,041
Storms—Flood other counties)
Flood DR-253 1969 -- 1/26/1969 San Joaquin County(and 47 deaths; 161
39 other counties) injuries
$300,000,000
Section 5
Risk Assessment
State Federal
Hazard Type Disaster# Year � Proclamation Declaration Location �. . -
Offshore Oil -- 1969 -- -- Coastal Areas of Souther
Platform Spill California
Severe Winter DR-364 1973 1/30/1973 2/8/1973 San Luis Obispo County $17,998,250
Storms— (and 5 other counties)
Coastal
Flooding
Drought -- 1976 2/9/76, -- San Luis Obispo County $2,664,000,000
2/13/76, (and 30 other counties)
2/24/76,
3/26/76,
7/6/76
Drought EM-3023 1977 -- 1/20/1977 San Luis Obispo County --
Severe Winter DR-547 1978 2/1/1978 2/15/1978 San Luis Obispo County 14 deaths, 21
Storms- Flood (and 13 other counties) injuries,
$117,802,785
Severe Winter DR-677 1982 12/8/1982- 2/9/1983 San Luis Obispo County $523,617,032
Storms- Flood - 3/21/1982 (and 43 other counties)
1983
Wildfire—Las DR-739 1985 7/1/1985 7/18/1985 San Luis Obispo County 3 deaths,470
Pilitas Fire (and 6 other counties) injuries,
$64,845,864
Burned 75,000
acres from Las
Pilitas area to
SLO. Portions of
the City of SLO
was evacuated.
Train -- 1986 -- -- Grover Beach Evacuations,
Derailment Road closures
Freeze USDA and 1987 - - San Luis Obispo -
SBA
declaration
Drought 1988 1/1/1988- - Statewide -
12/31/1988
Drought USDA 1990 1/1990- - - -
7/13/1990
Extreme Cold DR-894 1990 12/19/1990- 2/11/1991 San Luis Obispo County(32 $856,329,675
Weather/ 1/18/1991 other counties)
Freeze
County of San Luis Obispo Local Hazard Mitigation Plan I October
Section 5
Risk Assessment
State Federal
Hazard Type Disaster# Year Proclamation Declaration Location Damage*
Hwy
. . -
Hwy 41 Fire GP 94-02 1994 8/24/1994 -- San Luis Obispo County 12 injuries,
$6,382,235
Burned 48,531
acres,42 homes,
and 61 other
structures
Severe Winter DR-1044 1995 1/6/95- 1/13/1995 San Luis Obispo County 11 deaths,
Storms- Flood 3/14/96 (and 42 other counties) $221,948,347
Severe Winter DR-1046 1995 Proclaimed 1/10/1995 San Luis Obispo County(all 17 deaths,
Storms - Flood counties except Del Norte) $132,040,111
Highway 58 Local 1996 - - San Luis Obispo Burned 106,668
Fire Proclamation acres
of Emergency
Highway - 1997 - - San Luis Obispo Burned 50,000
166/Logan Fire acres
Severe Winter DR-1155 1997 1/2/1997- 1/4/1997 San Luis Obispo County 8 deaths,
Storm- Flood 1/31/1997 (and 47 other counties $194,352,509
Severe Winter DR-1203 1998 Proclaimed 2/9/1998 San Luis Obispo County(42 17 deaths,
Storms- Flood other counties) $385,141,192
Severe Storms- DC 2001-01 2001 3/1/2001 - San Luis Obispo County $2,248,000
Flood (and 2 counties) estimated in
damages
throughout
county.Arroyo
Grande levee
breached on
south side.
Earthquake - DR-1505 2003 12/23/2003 1/13/2004 San Luis Obispo County 2 deaths
San Simeon (and Santa Barbara County) estimated
Earthquake $239,000,000 in
damages,
response and
recovery costs
Parkfield - - 9/2004 - San Luis Obispo Minor damages
Earthquake
Hurricane EM-3248 2005 -- 9/13/2005 Statewide $763,576
Katrina -
Economic
Winter Storms DR-1628 2005 -- 2/3/2006 San Luis Obispo County 1 death;
- Flood - (and 29 counties + $203,050,747
2006 statewide HM)
County of San Luis Obispo Local Hazard Mitigation Plan I October 2019
Section 5
Risk Assessment
State Federal
Hazard Type Disaster# Year Proclamation Declaration Location Damage*
Freeze
. . -
Freeze DR-1689 2007 -- 3/13/2007 San Luis Obispo County $2,700,400
(and 12 other counties)
Winter Storms DR-1952 2010 12/1/2010 1/26/20/11 San Luis Obispo County Most severe
- Flood - (and 12 counties) damages in areas
2011 of South County,
particularly
Oceano area.
$66,318,201
Tsunami DR-1968 2011 3/11/2011 4/18/2011 Statewide -
Freezing 53255 2012 3/1/2012- 6/9/2012 San Luis Obispo County --
Temperature, 4/30/2012 (Sec.Ag
High Winds, (begin to end Approval
Excessive Rain date) date)
Hail Storm, 53320 2012 4/11/2012- 8/3/2012 San Luis Obispo County --
Rain, cold 4/13/2012 (Sec.of Ag
temperatures (begin to end approval
dates) date)
Drought Local 2014 -- -- San Luis Obispo County
Emergency -
2017
Drought 2014 January 17, -- Statewide --
2014—April 7,
2017
Intense - 2015 - - Paso Robles 3.6"of rain in 8
Thunderstorms hours,causing
water and mud
damage to 20-30
homes
Cuesta Fire - 2015 - - Santa Margarita A portion of the
community of
Santa Margarita
was evacuated
Rain and Wind 54003 2016 4/8/2016— 7/27/2016 San Luis Obispo County --
5/6/2016 (Sec.of Ag.
(begin to end approval
dates) date)
County of San Luis Obispo Local Hazard Mitigation Plan I October
Section 5
Risk Assessment
�ffil State Federal
Hazard Type � Disaster# Proclamation Declaration �.
Severe 54164 2016 3/3/2016- 3/31/2017 San Luis Obispo County --
Weather 6/1/2016 (Sec.of Ag
including (begin to end approval
excessive dates) date)
rainfall and
high winds
Excessive rain, 54170 2016 3/1/2016- 4/28/2017 San Luis Obispo County --
high winds, 5/7/2016 (Sec.of Ag
cold (begin to end approval
temperatures, dates) date)
and hail
Chimney Fire FM-5146 2016 8/15/2016 - Nacimiento Lake area 46,344 acres
burned,49
residential type
structures
destroyed, 21
other structures
destroyed,8
damaged. Hearst
Castle was closed
for some time.
Severe Storms- DR-4301 2017 - 2/14/2017 San Luis Obispo County $39,956,354
Flooding and (and 33 other counties)
Mudslides
Severe Storms DR-4305 2017 2/10/2017 3/16/2017 San Luis Obispo County $14,320,716
- Flooding and (and 21 other counties)
Mudslides
Severe Storms DR-4308, GP 2017 3/7/2017 4/1/2017 San Luis Obispo County 8 deaths;
- Flooding and 2017-03 (and 41 counties and 1 $119,834,925
Mudslides tribe) (DR) $331,137
(GP)
Freeze 54350 2018 2/20/2018 7/18/2018 San Luis Obispo County --
(Sec.of Ag
approval
date)
Source:2018 California State Hazard Mitigation Plan,FEMA,USDA
*Damage amount,deaths and inuries reflect totals for all impacted counties
5.1.3 Climate Change Considerations Summary
The County acknowledges that climate change is occurring and has begun to plan for it as seen by the
EnergyWise Plan and ClimateWise Integrated Climate Change Adaptation Planning in San Luis Obispo
County report. County climate change projections include:
Countyof ObispoLocal Hazard Mitigation Plan I October 2019 Page 1
Section 5
Risk Assessment
• An increase in temperature between 2.1 and 3.9 degrees by 2045 and between 4.1 and 7.6 degrees by
2085
• Annual average precipitation decreases up to 4.2 inches or increase up to 1.5 inches by 2045 and
decrease by 4.73 inches or increase by.88 inches by 2085
• 3.3 to 4.6 feet in sea level rise by 2100
• Increase in area of the county burned by wildfire from 3.7%to 6.8-7.3% by 2045 and to 8.1-8.5% by
2085.
• Negative impacts on wildlife due to reduced water supply, rising sea levels, and an increase in wildfire
and flooding events
• Negative impacts on agricultural productivity due to higher temperatures, decrease in water supply
and shifts in seasonal changes
Deteriorating public health due to decrease in water supplies and increase risk of wildfire, which have
detrimental effects on air quality
Decreased supply of fresh water due to higher temperatures and continued population growth
Increased severity of flood events based on climate model projections that predict less frequent
rainfall events, but with greater severity
The important consideration for hazard mitigation is that climate change is exacerbating the hazards
which are already identified and profiled. For example, it can be expected that coastal storm surge will
become more of a threat as sea level rises. Additional specifics associated with the hazards are discussed
in the Climate Change Considerations portion of each hazard profile.
5.1.4 Overview of Hazard Identification and Risk Assessment
Subsection 5.3 contains detailed hazard profiles for the identified hazards. Each hazard profiled includes
the following subsections:
• Hazard/Problem Definition—This section gives a description of the hazard and associated issues
followed by details on the hazard specific to the San Luis Obispo County planning area.
• Geographic Area-This section gives a spatial description of the potential location or areas of San
Luis Obispo County where the hazard expected to impact.
• Extent (Magnitude/Severity)-This section gives a description of the potential strength or
magnitude of the hazard as it pertains to San Luis Obispo County.
• Previous Occurrences—This section contains information on historical incidents, including impacts
where known. Historical incident worksheets were used to capture information from participating
jurisdictions on past occurrences.
• Probability of Future Occurrence—The frequency of past events is used in this section to gauge the
likelihood of future occurrences.Where possible, frequency was calculated based on existing data. It
was determined by dividing the number of events observed by the number of years on record and
multiplying by 100.This gives the percent chance of an event happening in any given year (e.g., three
droughts over a 30-year period equates to a 10 percent chance of a drought in any given year). The
likelihood of future occurrences is categorized into one of the following classifications:
- Highly Likely— Near 100 percent chance of occurrence in next year or happens every year.
- Likely— Between 10 and 100 percent chance of occurrence in next year or has a recurrence
interval of 10 years or less.
County of San Luis Obispo Local October 2019
Section 5
Risk Assessment
- Occasional— Between 1 and 10 percent chance of occurrence in the next year or has a
recurrence interval of 11 to 100 years.
- Unlikely— Less than 1 percent chance of occurrence in next 100 years or has a recurrence
interval of greater than every 100 years.
• Climate Change Considerations -This describes the potential for climate change to affect the
frequency and intensity of the hazard in the future
• Vulnerability- Following the hazard profiles is a vulnerability assessment for each identified hazard.
The assessment was conducted through the study of potential impacts to the following specific
sectors:
- General Property
- People
- Critical Facilities and Infrastructure
- Economy
- Historic, Cultural, and Natural Resources
- Future Development
- Risk Summary - Each vulnerability assessment includes a risk summary of the key issues/problems
based on threat, vulnerability and consequence to the planning area and jurisdictions from the
specific hazard.
Data used to support this assessment included the following:
• County GIS data (hazards, base layers, and assessor's data);
• Statewide GIS datasets to support mitigation planning;
• State of California Hazard Mitigation Plan 2018;
• San Luis Obispo County Hazard Mitigation 2014;
• Jurisdictional Hazard Mitigation Plans;
• Cal FIRE datasets;
• California's Fourth Climate Change Assessment: Central Coast Region Report;
• US Forest Service GIS datasets;
• FEMA's HAZUS-MH GIS-based critical facility inventory data;
• Written descriptions of inventory and risks provided by the jurisdictions;
• Online data sources (cited where applicable);
• Data and information from existing plans and studies; and
• Input from planning team members and staff from the County and local, state, and federal agencies.
5.2 Asset Summary
5.2.1 Assets Exposure
As a starting point for analyzing the Planning Area's vulnerability to identified hazards, the HMPC used a
variety of data to define a baseline against which all disaster impacts could be compared. If a catastrophic
disaster was to occur in the Planning Area, this section describes significant assets exposed or at risk in
the Planning Area. Data used in this baseline assessment included:
• Total assets at risk;
• Critical facility inventory;
• Cultural, historical, and natural resources; and
County of San Luis Obispo Local October 2019
Section 5
Risk Assessment
• Population growth and land use/development trends.
Total Assets at Risk
Parcel data was provided by ParcelQuest, a third-party service working alongside the San Luis Obispo
County Assessor's Office to compile property information. This data provided the baseline for an
inventory of the total exposure of developed properties within the county and helps to ensure that the
updated HMP reflects changes in development. It is important to note that depending on the nature and
type of hazard event or disaster, it is generally the value of the infrastructure or improvements to the
parcels that are of concern or at risk. Generally, the land itself is not a total loss, but may see a reduction
in value. Thus, the parcel analysis excludes land value.
Parcel Exposure and Preparations for Analysis
Building counts and valuations in this plan are based on data from the County Assessor's Office as well as
ParcelQuest.The ParcelQuest GIS layer contains the assessor's information, and for the purpose of parcel
analysis and exposure calculations only parcels with improved values were used, except for exempt or
government properties (which by definition do not include an improvement value and is one limitation
that results in the total improvement values underestimating the actual value). "Improved" parcels have an
improvement value greater than zero. Contents values were also estimated, as a percentage of building
value based on their property type, using FEMA/HAZUS guidelines. Content value estimates are based on
100% of the structure value for commercial and agriculture structures, 150% of the structure value for
industrial structures, and finally 50%for residential structures. Improvement values were added to
contents values to arrive at the total structure values for all properties in the parcel layer. The parcel layer,
originally in the form of polygons, was then converted into points based on the center (or centroid) of a
parcel to approximate building locations. Table 5-4, Table 5-5, and Table 5-6 below summarize the count
and value of improved properties, contents, and total values for the property inventory grouped by
jurisdiction, as well as exposure values by property type, and finally the exposure values by property type
for the unincorporated areas of the County.
Table 5-4 San Luis Obispo County Total Exposure by Jurisdiction
Jurisdiction Improved Value Total Value
Arroyo Grande 61693 $1,608,652,049 $865,870,064 $2,474,522,113
Atascadero 10,298 $2,311,286,428 $1,223,381,289 $3,534,667,717
City of San Luis Obispo 14,083 $4,412,540,270 $2,664,377,282 $7,076,917,552
Grover Beach 41713 $866,176,076 $462,306,623 $1,328,482,699
Morro Bay 5,320 $1,113,527,653 $579,407,494 $1,692,935,147
Paso Robles 10,714 $2,821,913,364 $1,632,765,187 $4,454,678,551
Pismo Beach 4,885 $1,439,073,785 $761,589,312 $2,200,663,097
Unincorporated 46,878 $12,207,641,760 $6,261,161,189 $18,468,802,949
TOTAL 103,584 $26,780,811,385 $14,450,858,440 $41,231,669,825
Source:Wood analysis based on ParcelQuest and San Luis Obispo County Assessor's Office data 2019
County of San Luis ObispoLocal Hazard Mitigation Plan I October 2019 P.. 5-13
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Table 5-5 San Luis Obispo County Total Exposure by Property Type
Property Type Property Count Improved Value Content Value Total Value
Agricultural 623 $503,096,233 $503,096,233 $1,006,192,466
Commercial 3,972 $2,382,146,177 $2,382,146,177 $4,764,292,354
Government/Utilities 2,704 $10,842,823 -- $10,842,823
Other/Exempt/Misc. 3,701 $695,078,084 -- $695,078,084
Residential 73,954 $18,260,098,270 $9,130,049,135 $27,390,147,405
Multi-Family Residential 9,116 $2,265,198,982 $1,132,599,491 $3,397,798,473
Mobile/Manufactured Homes 3,748 $494,287,198 $247,143,599 $741,430,797
Residential:Other 3,414 $1,331,071,111 $665,535,556 $1,996,606,667
Industrial 266 $260,192,166 $390,288,249 $650,480,415
Vacant 2,086 $578,800,341 -- $578,800,341
TOTAL 103,584 $26,780,811,385 $14,450,858,440 $41,231,669,825
Source:Wood analysis based on ParcelQuest and San Luis Obispo County Assessor's Office data 2019
Table 5-6 Total Exposure by Property Type in Unincorporated San Luis Obispo County
Location —F--property Type Property Count Improved Value Content Value Total Value
Agricultural 592 $455,950,949 $455,950,949 $911,901,898
Commercial 799 $382,693,827 $382,693,827 $765,387,654
Government/Utilities 1,932 $7,465,764 -- $7,465,764
Other/Exempt/Misc. 1,904 $234,552,034 -- $234,552,034
Residential 34,081 $9,553,005,276 $4,776,502,638 $14,329,507,914
Unincorporated Multi-Family Residential 1,890 $409,203,080 $204,601,540 $613,804,620
Mobile/Manufactured Homes 3,067 $377,655,433 $188,827,717 $566,483,150
Residential:Other 807 $280,364,775 $140,182,388 $420,547,163
Industrial 85 $74,934,754 $112,402,131 $187,336,885
Vacant 1,721 $431,815,868 -- $431,815,868
TOTAL 46,878 $12,207,641,760 $6,261,161,189 $18,468,802,949
Source:Wood analysis based on ParcelQuest and San Luis Obispo County Assessor's Office data 2019
Critical Facility Inventory
For the purposes of this plan, a critical facility is defined as one that is essential in providing utility or
direction either during the response to an emergency or during the recovery operation.The County of San
Luis Obispo uses the following four categories to describe critical assets:
• Emergency Services— Facilities or centers aimed at providing for the health and welfare of the whole
population (e.g., hospitals, police, fire stations, emergency operations centers, evacuation shelters,
schools).
• Lifeline Utility Systems— Facilities and structures such as potable water treatment plants,
wastewater, oil, natural gas, electric power and communications systems.
• Transportation Systems—These include railways, highways, waterways, airways and city streets to
enable effective movement of services, goods and people.
• High Potential Loss Facilities—These include nuclear power plants, dams, and levees.
County of San Luis Obispo Local Hazard Mitigation Plan I October 2019 Page 5-14
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The specific critical facilities analyzed in this plan are provided in Table 5-7 and Table 5-8 and displayed in
Figure 5-1.A general summary of the critical facilities based on their categories just described is provided
in Table 5-7 below.A portion of the critical facilities data was provided by the San Luis Obispo County
Planning & Building and GIS Departments; supplemental data from the Homeland Infrastructure
Foundation-Level Data (HIFLD) was used to capture additional facilities such as law enforcement facilities
and centers, communications facilities, emergency operations centers, schools, and urgent care facilities
among others. The specific facilities that were provided by the County or its departments came from five
data layers: airports, power plants, water/wastewater treatment plants, California energy commission
substations, and fire facilities. The other types or additional facilities were obtained at the federal level
from the HIFLD dataset. Furthermore, participating jurisdictions identified additional or supplemental
assets on a data collection guide worksheet or in previous LHMPs which may capture more facilities and
additional details not within the main critical facility GIS database. For a list of assets and vulnerabilities
within specific jurisdictions, please refer to the jurisdictional annexes and Appendix E. Vulnerabilities of
specific facilities to specific hazards were analyzed with a GIS overlay analysis where data permitted. The
results are discussed within each hazard's vulnerability section in subsection 5.3 and detailed in Appendix
E.
Table 5-7 Critical Facilities Types by Category
I High
Emergency Services Lifeline Utility Systems Transportation Potential
Systems Loss
Facilities
Colleges/Universities AM Transmission Towers
Day Care Facilities Broadband Radio Service& Educational
Broadband Service Transmitters
Emergency Medical Service Stations Energy Commission Facilities
Fire Stations Cellular Towers
Hospitals Electric Substations
Power
Local Law Enforcement FM Transmission Towers Airports
Plants
Nursing Homes Microwave Service Towers
Private Schools Paging Transmission Towers
Public Schools TV Analog Station Transmitters
Supplemental Colleges TV Digital Transmitters
Urgent Care Water Treatment Facilities
Veterans Affairs Medical Facilities Wastewater Treatment Plants
Source:San Luis Obispo County Planning&Building/GIS;HIFLD.
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Risk Assessment
Figure 5-1 Critical Facilities in San Luis Obispo County
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County of San Luis Obispo Local Hazard Mitigation Plan I October 2019
Section 5
Risk Assessment
Table 5-8 Summary of Critical Facilities in San Luis Obispo County by Jurisdiction
Jurisdiction I Category Critical Facility Type
Day Care Facilities 8
Emergency Medical Service Stations 2
Fire Stations 1
Hospitals 2
Emergency Services Local Law Enforcement 1
Nursing Homes 2
Arroyo Grande Private Schools 4
Public Schools 5
Urgent Care 1
High Potential Loss Facilities Power Plants 1
FM Transmission Towers 1
Lifeline Utility Systems Paging Transmission Towers 1
Energy Commission Facilities 3
Transportation Systems Airports 1
Total 33
Day Care Facilities 13
Emergency Medical Service Stations 2
Fire Stations 3
Hospitals 1
Local Law Enforcement 1
Emergency Services
Nursing Homes 8
Atascadero Private Schools 2
Public Schools 9
Supplemental Colleges 1
Urgent Care 1
High Potential Loss Facilities Power Plants 2
Microwave Service Towers 2
Lifeline Utility Systems TV Analog Station Transmitters 1
Energy Commission Facilities 1
Total 47
Day Care Facilities 2
Emergency Medical Service Stations 1
Fire Stations 1
Emergency Services
Grover Beach Local Law Enforcement 1
Private Schools 1
Public Schools 3
Lifeline Utility Systems Microwave Service Towers 2
Water Treatment Facilities 1
Total 12
Day Care Facilities 4
Emergency Medical Service Stations 2
Fire Stations 2
Emergency Services Local Law Enforcement 1
Morro Bay Nursing Homes 2
Public Schools 2
High Potential Loss Facilities Power Plants 1
Microwave Service Towers 5
Lifeline Utility Systems Wastewater Treatment Plants 1
Energy Commission Facilities 2
Total 22
Colleges/Universities 1
Paso Robles Emergency Services Day Care Facilities 14
Emergency Medical Service Stations 1
County of San Luis Obispo Local Hazard Mitigation Plan I October
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CategoryJurisdiction
Fire Stations 3
Local Law Enforcement 1
Nursing Homes 2
Private Schools 3
Public Schools 12
Supplemental Colleges 1
Urgent Care 1
High Potential Loss Facilities Power Plants 1
AM Transmission Towers 1
FM Transmission Towers 1
Lifeline Utility Systems Microwave Service Towers 12
Water Treatment Facilities 1
Energy Commission Facilities 2
Transportation Systems Airports 1
Total 58
Day Care Facilities 2
Emergency Medical Service Stations 2
Fire Stations 3
Emergency Services Local Law Enforcement 1
Pismo Beach Public Schools 2
Urgent Care 1
Lifeline Utility Systems Microwave Service Towers 6
Wastewater Treatment Plants 1
Transportation Systems Airports 1
Total 19
Colleges/Universities 2
Day Care Facilities 18
Emergency Medical Service Stations 5
Fire Stations 4
Hospitals 3
Emergency Services Local Law Enforcement 2
Nursing Homes 3
Private Schools 5
San Luis Obispo Public Schools 12
Urgent Care 1
Veterans Affairs Medical Facilities 1
AM Transmission Towers 1
FM Transmission Towers 1
Lifeline Utility Systems Microwave Service Towers 52
Wastewater Treatment Plants 1
Energy Commission Facilities 7
Transportation Systems Airports 2
Total 120
Colleges/Universities 2
Day Care Facilities 29
Emergency Medical Service Stations 25
Fire Stations 29
Emergency Services Hospitals 1
Unincorporated Local Law Enforcement 8
Nursing Homes 5
Private Schools 4
Public Schools 40
High Potential Loss Facilities Power Plants 7
Lifeline Utility Systems AM Transmission Towers 5
County of San Luis Obispo Local Hazard Mitigation Plan I October
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Risk Assessment
Jurisdiction Category Critical Facility Type
Broadband Radio Service&Educational Broadband 5
Service Transmitters
Cellular Towers 19
Electric Substations 2
FM Transmission Towers 33
Microwave Service Towers 368
Paging Transmission Towers 6
TV Analog Station Transmitters 15
TV Digital Transmitters 4
Wastewater Treatment Plants 5
Water Treatment Facilities 7
Energy Commission Facilities 8
Transportation Systems Airports 10
Total 637
Grand Total 948
Source:San Luis Obispo County Planning&Building/GIS,Community Service Districts,HIFLD
Cultural, Historical, and Natural Resources
Assessing the County of San Luis Obispo's vulnerability to disaster also involves inventorying the natural,
historical, and cultural assets of the area. This step is important for the following reasons:
• The community may decide that these types of resources warrant a greater degree of protection due
to their unique and irreplaceable nature and contribution to the overall economy.
• In the event of a disaster, an accurate inventory of natural, historical and cultural resources allows for
more prudent care in the disaster's immediate aftermath when the potential for additional impacts is
higher.
• The rules for reconstruction, restoration, rehabilitation, and/or replacement are often different for
these types of designated resources.
• Natural resources can have beneficial functions that reduce the impacts of natural hazards, for
example, wetlands and riparian habitat which help absorb and attenuate floodwaters and thus
support overall mitigation objectives.
Cultural Resources
Historical resources are buildings, structures, objects, places, and areas that are eligible for listing in the
National Register of Historic Places (NRHP), the California Register of Historic Resources (CRHR), or the
County's List of Historic Resources, have an association with important persons, events in history, or
cultural heritage, or have distinctive design or construction method.
San Luis Obispo County has a wealth of historic and prehistoric resources, including sites and buildings
associated with Native Americans, Spanish missionaries, immigrant settlers, and military branches of the
United States. Native American groups have occupied the County dating back at least 10,000 years,
including the Chumash, Salinan, and Yokut tribes. In 1595, the Spanish sailed into San Luis Obispo Bay,
near the large Obispeno village of Sepjato, which thereafter greatly changed the aboriginal way of life. In
1769 Gaspar de Portola and Father Junipero Serra passed through present day San Luis Obispo County
with the objective to secure the port and establish missions along his route, and the Mission San Luis
Obispo de Tolosa was founded near San Luis Obispo Creek. In 1822, California became a Mexican
Territory, and the mission lands gradually became private ranchos via Mexican land grants. After the
County of San Luis Obispo Local October 2019
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Risk Assessment
decline of the mission era in the late 1830s, San Luis Obispo County gradually grew from a remote
outpost into a thriving agricultural and commercial region with an influx of Euro-American land
landholders settling in the area.
For purpose of federal actions, a qualified historic resource is defined as a property listed in or formally
determined eligible for listing in the NRHP before a disaster occurs. The NRHP is part of a national
program to coordinate and support public and private efforts to identify, evaluate, and protect historic
and archeological resources. Properties listed include districts, sites, buildings, structures, and objects that
are significant in American history, architecture, archeology, engineering, and culture. The National
Register is administered by the U.S. Department of the Interior National Park Service. Local and state
agencies may consider a broader definition of qualified historic properties in the review, evaluation, and
treatment of properties damaged during a disaster.
The State of California Office of Historic Preservation can provide technical rehabilitation and preservation
services for historic properties affected by a natural disaster. Depending on the hazard, protection could
range from emergency preparedness, developing a fire safe zone around sites susceptible to wildfires, or
seismically strengthening or structurally reinforcing structures.
State and local registers of historic resources provide designated Historical Landmarks, Points of Historical
Interest, and Historic Buildings. These resources include, but are not limited to:
• The California Register of Historical Resources
• The California Historical Landmarks
• The California Inventory of Historical Resources
• The California Points of Historical Interest
• The City of San Luis Obispo Cultural Heritage Committee
• The History Center of San Luis Obispo has created an inventory of the Historic Buildings of San Luis
Obispo County.
County Historical Resources may be designated on a federal, state, or local level. Local historical resources
may be within the jurisdictions of an Area Plan. Historical resources designated under a regional or local
plan are provided in Table 5-9. Vulnerabilities of specific historic buildings to specific hazards were
analyzed with a GIS overlay analysis where data permitted. The results are discussed within each hazard's
vulnerability section in subsection 5.3.
Table 5-9 San Luis Obispo County Historical Resources and Area Plans
Historical Resource
Rotta Winery 1856 Adelaida Area Plan
Adelaida Cemetery 1891 Adelaida Area Plan
York Mountain Winery 1882 Adelaida Area Plan
San Marcos Cemetery 1889 Adelaida Area Plan
Willow Creek Cemetery 1911 Adelaida Area Plan
Estrella Adobe Church 1878 EI Pomar-Estrella Area Plan
Creston Cemetery -- EI Pomar-Estrella Area Plan
Pozo Saloon 1865 Las Pilitas Area Plan
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Historical Resource Year Area Plan
Santa Margarita de Cortona 1775 Salinas River Area Plan
Mission San Miguel Archangel 1797 Salinas River Area Plan
Bethel Lutheran Church 1887 Salinas River Area Plan
Banning School 1896 San Luis Obispo Area Plan
Hansen Barn -- San Luis Obispo Area Plan
Independence School -- San Luis Obispo Area Plan
Octagon Barn 1900 San Luis Obispo Area Plan
Vasquez-Hollister Adobe 1800 San Luis Obispo Area Plan
Dana Adobe 1839 South County Inland Area Plan
Dana House 1882 South County Inland Area Plan
Pacific Coast Railroad Depot 1881 South County Inland Area Plan
Old St.Joseph's Church 1902 South County Inland Area Plan
Runels Home- Dana Street 1886 South County Inland Area Plan
Hearst Castle 1919 North Coast Area Plan
Van Gordon Archaeological Site -- North Coast Area Plan
Bianchini House 1889 North Coast Area Plan
The Paul Squibb House 1877 North Coast Area Plan
Port San Luis Lighthouse 1890 San Luis Bay Coastal Area Plan
Huasna School 1907 Huasna-Lopez Area Plan
Adelaida School 1917 Adelaida Area Plan
J.F. MacGillivray Residence 1879 Adelaida Area Plan
Geneseo School 1886 EI Pomar-Estrella Area Plan
Creston Community Church 1886 EI Pomar-Estrella Area Plan
Rancho Huasna Sparks Adobe 1850 Huasna-Lopez Area Plan
Tar Springs Ranch -- Huasna-Lopez Area Plan
Porter Ranch House 1890 Huasna-Lopez Area Plan
C.H. Plillips House 1886 Salinas River Area Plan
Rios Caledonia Adobe 1830 Salinas River Area Plan
Marre House 1932 San Luis Bay Area Plan-Inland
Tognazzini General Store 1908 San Luis Obispo Area Plan
Los Osos School House 1872 Estero Area Plan
Captain James Cass House 1872 Estero Area Plan
Los Berros Schoolhouse 1890 South County Inland Area Plan
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Historical Resource Year Area Plan
The Sebastian Store 1860 North Coast Area Plan
Canet Adobe 1840 Estero Area Plan
Lyman House 1895 San Luis Obispo Area Plan
Rinconada School 1880 EI Pomar-Estrella Area Plan
Chandler House(Webster) 1882 EI Pomar-Estrella Area Plan
Linne School 1891 EI Pomar-Estrella Area Plan
Los Berros Adobe Barn 1860 South County Inland Area Plan
Hearst Ranch Headquarters -- North Coast Area Plan
Eight-Mile House 1877 Salinas
-- San Luis Bay Area Plan-Inland
Avila Valley Historic Site 2 -- San Luis Bay Area Plan-Inland
Avila Valley Historic Site 1 -- San Luis Bay Area Plan-Inland
Temple of The People, Halcyon 1903 San Luis Bay Area Plan-Inland
Price Adobe -- San Luis Bay Area Plan-Inland
Captain James Cass House &Adjacent Buildings 1872 Estero Area Plan
Cayucos Pier -- Estero Area Plan
Spooner Residence -- Estero Area Plan
The Bluebird Motel -- North Coast Area Plan
Carroll's Blacksmith Shop -- North Coast Area Plan
Heart's Ease -- North Coast Area Plan
Ian's Restaurant -- North Coast Area Plan
Robin's Restaurant -- North Coast Area Plan
The Squibb House -- North Coast Area Plan
The Brambles Restaurant -- North Coast Area Plan
Rigdon Hall Restaurant -- North Coast Area Plan
The Red House -- North Coast Area Plan
The Bianchini House -- North Coast Area Plan
The Bucket of Blood Saloon -- North Coast Area Plan
Louis Maggetti's House -- North Coast Area Plan
Camozzi's -- North Coast Area Plan
Soto's Market -- North Coast Area Plan
The Leffingwell House -- North Coast Area Plan
The Olallieberry Inn -- North Coast Area Plan
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Historical Resource Year
The Lull House -- North Coast Area Plan
The Old Santa Rosa Chapel -- North Coast Area Plan
The Thorndyke House -- North Coast Area Plan
The First Presbyterian Church -- North Coast Area Plan
The Bank of Cambria -- North Coast Area Plan
Arthur Beale House 1928 North Coast Area Plan
Ah Louis Store 1874 San Luis Obispo Area Plan
Admin\Veterans memorial bldg 1918 Salinas River Area Plan
Coffee T. Rice House 1886 San Luis Bay Area Plan-Coastal
Dallidet Adobe 1859 San Luis Obispo Area Plan
Morro Rock 1769 Estero Area Plan
Mission SLO De Tolosa 1772 San Luis Obispo Area Plan
Ortega-Price Adobes 1840 San Luis Bay Area Plan-Inland
Santa Margarita Asistencia 1775 Salinas River Area Plan
Source:County of San Luis Obispo Office of Planning and Building
Lists of designated historical resources change periodically, and they may not include those currently in
the nomination process and not yet listed.Additionally, as defined by the National Environmental Policy
Act (NEPA), any property over 50 years of age is considered a historic resource and is potentially eligible
for the National Register. Thus, in the event that the property is to be altered, or has been altered, as the
result of a major federal action, the property must be evaluated under the guidelines set forth by NEPA.
Structural mitigation projects are considered alterations for the purpose of this regulation.
Cultural resources defined in California Environmental Quality Act (CEQA) Section 15064.5 as include
prehistoric and historic archaeological resources; historic-period resources (buildings, structures, area,
place, or objects).Archaeological resources reflect past human activity extending from Native American
prehistoric cultures throughout the early 20th century. The artifacts left by previous occupants may be
encountered in small to large residential sites, or special use areas.
Many cultural and historical resources in the County are vulnerable to several hazards due to location and
the nature of their construction. Some of these risks include earthquakes, wildfires, coastal storms, or
adverse weather.
Tribal Cultural Resources
Tribal cultural resources are defined in Public Resources Code (PRC) Section 21074.1 as a site, feature,
place, cultural landscape that is geographically defined in terms of the size and scope of the landscape,
sacred place, or object with cultural value to a California Native American tribe. A Native American tribe is
defined as "a federally recognized California Native American tribe or a non-federally recognized
California Native American tribe that is on the contact list maintained by the Native American Heritage
Commission". Traditional tribal cultural places are defined in PRC Sections 5097.9 and 5097.993 to include
County of San Luis Obispo Local Hazard Mitigation Plan I October 2019 • ge 5-23
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Risk Assessment
sanctified cemeteries, places of worship, religious or ceremonial sites, or sacred shrines, or any historic,
cultural, or sacred site that is listed on or eligible for the CRHR including any historic or prehistoric ruins,
burial grounds, or archaeological site. Cultural and tribal resources are governed primarily by federal,
state, and local laws that regulate potential impacts to such resources. State regulations that were
established to encourage the preservation and protection of traditional tribal cultural resources include:
• Assembly Bill 52 (Public Resources Code [PRC] Section 21080.3.1): mandates early tribal consultation
prior to and during CEQA review to consider tribal cultural values in determination of project impacts
and mitigation.
• Senate Bill 18 (Government Code 655352.3): requires cities and counties to consult with Native
American tribes early during broad land use planning efforts on both public and private lands, prior to
site- and project-specific land use decisions. Consultation is intended to encourage preservation and
protection of traditional tribal cultural places by developing treatment and management plans that
might include incorporating the cultural places into designated open spaces.
• State Executive Order B-10-11 (2011) established the Governor's Tribal Advisor position and
established Administration Policy to encourage State Agencies to communicate and consult with
Californian tribes regarding tribal cultural resources.
Natural Resources
Natural resources issues of the County include those regarding: geology, soils, hydrology, plant and
wildlife ecology, resources laws, and natural resource public policy(County of San Luis Obispo 2019a). San
Luis Obispo County is diverse in natural resources, exemplified by its creeks and rivers that drain inland
mountains in confluence with the Pacific Ocean, coastal dunes and cliffs, oak woodlands, extensive
mountainous landscapes, and grasslands in the Carrizo Plain National Monument. Interfaces of urban
areas and natural landscapes provide accessible walking and hiking trails with sweeping views of the
peaks and valleys of the county's mountain ranges, and the Pacific Ocean. Natural resources within the
county includes several managed areas and protected habitats, including the State Marine Conservation
Areas (SMCA), State Marine Reserves (SMR), State Marine Recreational Management Area (SMRMA), state
parks and beaches, and state game refuges.These areas support ecologically significant habitats where
endangered or threatened species occur, including designated critical habitat and nesting and foraging
sites for migratory bird species.
Natural resources are important to include in benefit/cost analyses for future projects and may be used to
leverage additional funding for mitigation projects that also contribute to community goals for protecting
sensitive natural resources. Inventory and awareness of natural resource assets is vital to meeting
conservation objectives. For example, protecting wetland areas provides sensitive habitat protection as
well as floodwater conveyance and storage, which further enhances public safety. Natural resource maps
can be found in the Planning & Building section of the County of San Luis Obispo web site (County of San
Luis Obispo 2019b).
Natural resources also exhibit varied levels of resiliency to anthropogenic impacts, climate change, and
natural hazards such as flooding, drought, coastal storms or wildfire. Climate change is one of the most
substantial threats to conserving the biodiversity and ecological habitat of the County(OPR 2019). Habitat
resiliency is exemplified in coastal habitat migration to inland areas as a result to sea level rise, and
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Risk Assessment
recovery of burn areas following a wildfire. For example, grassland vegetation burned by wildfire typically
regrows and recovers within five or so years.
Natural and Beneficial Functions
Natural and beneficial functions of a region can describe hydrologically significant, environmentally
sensitive, and ecologically productive areas that perform many natural functions. Floodplains can have
natural and beneficial functions including water storage and conveyance, protection of water quality, and
recharge of groundwater (Walton County 2018).Wetlands function as natural sponges that trap and
slowly release surface water, rain, snowmelt, groundwater and flood waters. Trees, root mats, and other
wetland vegetation also slow the speed of floodwaters and distribute them more slowly over the
floodplain.This combined water storage and braking action lowers flood heights and reduces erosion.
Wetlands within and downstream of urban areas are particularly valuable, counteracting the greatly
increased rate and volume of surface water runoff from pavement and buildings. The holding capacity of
wetlands helps control floods and can help limit impacts to agricultural as well as urban areas. Preserving
and restoring wetlands, together with other water retention, can often provide the level of flood control
otherwise provided by expensive dredge operations and levees.
Natural resources provide scenic value and are vital to recreation in the County. Recreational functions
provided by natural resources include parks and campgrounds, water-oriented sports and activities such
as boating, swimming, and hiking. Wildlife resources in floodplains can be managed for observation, and
recreational hunting and fishing, as coastal floodplains are recognized for their importance to estuarine
and marine fisheries. Coastal beaches, dunes, banks, and tidal flats all play roles in protecting landward
structures from destructive coastal storms and erosion. Other beneficial functions of County natural
resources include diverse habitats for aquatic and terrestrial species, as well as natural crops and timber.
Special Status Species
To further understand natural resources that may be particularly vulnerable to a hazard event, as well as
those that need consideration when implementing mitigation activities, it is important to identify at-risk
species (endangered and threatened species) in the Planning Area. The US Fish and Wildlife Service
maintains a list of federally-listed threatened and endangered species for the country, which can be
queried at the state or even county levels.The California Department of Fish and Wildlife also maintains
species lists and accounts for threatened and endangered species. State and federal laws protect the
habitat of these species through the environmental review process. Species of special concern may
additionally include species that meets the State definition of threatened or endangered but has not been
formally listed, experiences seriously population declines or habitat decline, or has naturally small
populations exhibiting high susceptibility to population decline (Department of Fish and Wildlife 2019).
Table 5-10 summarizes San Luis Obispo County's special status animal species as indicated in the Fish and
Wildlife Service database, within the Environmental Conservation Online System.
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Risk Assessment
Table 5-10 Threatened and Endangered Species in San Luis Obispo Coun
Common Name Scientific Name Group Federal Status State Status(=arroyo None
southwestern)toad Anaxyrus californicus Amphibians Endangered
Bank swallow Riparia Birds None Threatened
Bald eagle Holiaeetus leucocephalus Birds None Endangered
Blunt-nosed leopard lizard Gambelia silus Reptiles Endangered Endangered
Beach spectaclepod Dithyrea maritima Flowering Plants None
Threatened
Buena Vista Lake ornate None
Sorex ornatus relictus Mammals Endangered
shrew
California black rail
Laterallus jamaicensis Birds None Threatened
coturniculus
California ridgway's rail Rallus obsoletus Birds Endangered Endangered
California condor Gymnogyps californianus Birds Endangered Endangered
California jewelflower Caulanthus californicus Flowering Plants Endangered Endangered
California least tern Sterna ontillarum browni Birds Endangered Endangered
California red-legged frog Rana draytond Amphibians Threatened None
California seablite Suaeda californica Flowering Plants Endangered None
California tiger salamander Ambystoma coliforniense Amphibians Threatened Threatened
Chlorogalum purpureum var. Rare
Camatta canyon amole Flowering Plants Threatened
reductum
Chorro Creek bog thistle Cirsium fontinale var. obispoense Flowering Plants Endangered Endangered
Conservancy fairy shrimp Branchinecta conservatio Crustaceans Endangered None
Delta smelt Hypomesus transpacificus Fishes Threatened Endangered
EI Segundo blue butterfly Euphilotes battoides allyni Insects Endangered None
Gambel's watercress Rorippa gambelld Flowering Plants Endangered Threatened
Gaviota Tarplant Deinandra increscens ssp. villosa Flowering Plants Endangered Endangered
Giant garter snake Thamnophis gigas Reptiles Threatened Threatened
Giant kangaroo rat Dipodomys ingens Mammals Endangered Endangered
Arctostaphylos hookeri ssp. Endangered
Hearst's manzanita Flowering Plants None
hearstiorum
Indian Knob mountainbalm Eriodictyon oltissimum Flowering Plants Endangered Endangered
Kern mallow Eremolche kernensis Flowering Plants Endangered None
Kern primrose sphinx moth Euproserpinus euterpe Insects Threatened None
La Graciosa thistle Cirsium loncholepis Flowering Plants Endangered Threatened
Least Bell's vireo Vireo belld pusillus Birds Endangered Endangered
Leatherback sea turtle Dermochelys coriacea Reptiles Endangered None
Longhorn fairy shrimp Branchinecta longiantenna Crustaceans Endangered None
Marbled murrelet Brachyramphus marmoratus Birds Threatened Endangered
Marsh Sandwort Arenaria paludicola Flowering Plants Endangered Endangered
Chorizanthe pungens var. None
Monterey spineflower Flowering Plants Threatened
pungens
Dipodomys heermanni Endangered
Morro Bay kangaroo rat Mammals Endangered
morroensis
Morro manzanita Arctostaphylos morroensis Flowering Plants Threatened None
County of San Luis Obispo Local Hazard Mitigation Plan I October
Section 5
Risk Assessment
Common Name Scientific Name
. -
Morro shoulderband None
Helminthoglypta wa(keriana Snails Endangered
(=Banded dune)snail
Nelson's antelope ground Threatened
Ammospermophilus nelsoni Mammals None
squirrel
Nipomo Mesa lupine Lupinus nipomensis Flowering Plants Endangered Endangered
Olive ridley sea turtle Lepidochelys olivacea Reptiles Threatened None
Pismo clarkia Clarkia speciosa ssp. immaculata Flowering Plants Endangered None
Chlorogalum purpureum var. None
Purple amole Flowering Plants Threatened
purpureum
Cordylonthus maritimus ssp. Endangered
Salt marsh bird's-beak Flowering Plants Endangered
maritimus
San Luis Obispo fountain Endangered
Cirsium fontinale var. obispoense Flowering Plants None
thistle
San Joaquin kit fox Vulpes macrotis mutica Mammals Endangered Threatened
Monolopia (=Lembertia) None
San Joaquin wooly-threads Flowering Plants Endangered
congdonii
Smith's blue butterfly Euphilotes enoptes smithi Insects Endangered None
Southern sea otter Enhydra lutris nereis Mammals Threatened None
Southwestern willow Endangered
Empidonax traillii extimus Birds Endangered
flycatcher
Steelhead -south-central Oncorhynchus mykiss irideus pop. None
California coast DPS g Fishes Threatened
Steelhead -southern Oncorhynchus mykiss irideus pop. None
California coast DPS 10
Fishes Endangered
Surf thistle Cirsium rhothophilum Flowering Plants None Threatened
Spreading navarretia Navarretia fossalis Flowering Plants Threatened None
Swainson's hawk Buteo swainsoni Birds None Threatened
Tidewater goby Eucyclogobius newberryi Fishes Endangered None
Tipton kangaroo rat Dipodomys nitratoides Mammals Endangered Endangered
Vernal pool fairy shrimp Branchinecto lynchi Crustaceans Threatened None
Western snowy plover Charadrius nivosus Birds Threatened None
Yellow-billed Cuckoo Coccyzus americanus Birds Threatened Endangered
Source:US Fish and Wildlife Service—Environmental Conservation Online System,2019
Population, Growth and Development Trends
The County has a population of approximately 280,119 people,with a wide range of income levels and
demographics (US Census Bureau 2017). Over 85% of the County identifies as white, including 22%of
Hispanics.The Countywide median household income in 2017 was estimated to be $67,175 and median
family income was estimated at $83,084. Additionally, US Census Bureau data estimates that 13.8%of the
population is below the federal poverty level and that at least 37.1% of the County's population is
considered low-income relative to State Income Limits. Critical demographic information includes:4.6% of
the civilian labor force over 16 years old is unemployed; 81.5%of the population age 25 and older has at
least a high school degree,with 34.1% having a bachelor's degree or higher (United States Census Bureau
2017); and 40.3% of occupied housing units are renter occupied (U. S. Census Bureau 2010).
ObispoCounty of San Luis
Section 5
Risk Assessment
Populations in San Luis Obispo County that may face disproportionate risks include the elderly, those
already affected by diseases, outdoor and migrant workers, people living in coastal and inland floodplains,
those living at the wildland-urban interface, the student population, institutionalized individuals
(especially the state hospital), and non-English speaking individuals. Social vulnerability data and
considerations are described in subsection 4.4.1 and further noted in each hazard's Vulnerability: People
section in subsection 5.3.
As part of the planning process, the HMPC analyzed changes in growth and development, both past and
future, and examined these changes in the context of hazard-prone areas, and how the changes in growth
and development affect loss estimates and vulnerability.
Table 5-11 illustrates the moderate pace of population growth in the County of San Luis Obispo dating
back to 2000 and population trends for each incorporated jurisdiction in the county.
Table 5-11 Population Growth for the County of San Luis Obispo from 2000-2017
Municipality 000 Population Growth 2000-2017
Arroyo Grande 15,851 17,252 17,971 13%
Atascadero 26,409 28,310 29,797 13%
Grover Beach 13,067 13,156 13,524 3%
Morro Bay 10,350 10,234 10,568 2%
Paso Robles 24,284 29,793 31,409 29%
Pismo Beach 8,551 7,655 8,060 -6%
City of San Luis Obispo 44,174 45,119 46,997 6%
Countywide 246,681 269,637 280,119 14%
Source:US Census Bureau American FactFinder,2019
Future Population Growth
The California Department of Transportation (Cal Trans) recently published population growth predictions
for the County of San Luis Obispo (Cal Trans, 2018).The report forecasts economic and employment
development using historical evidence from 2012 to 2017 and includes several predictions from 2018 to
2050. According to this report, which seeks to describe the local socioeconomic profile of the county, San
Luis Obispo is expected to continue to grow at a slow rate, averaging 0.4% per year between 2018 and
2023. The majority of the growth will be from migration entering the county. This summary states that, by
2050, the total population could be 298,795.
Development Trends
In order to assess where development is expected to take place (or has recently taken place) across the
county with regards to hazards, new construction permits and entitlements for residential and commercial
properties were obtained, in spatial format, since the last update of this plan (2014 through early 2019).
These permits were then mapped as points and color-coded based on the year in which they were
submitted. Figure 5-2 displays the centroids that were generated from each permit polygon, mapped by
year of submittal to the Office of Planning & Building at the County, while Table 5-12 summarizes the
total building construction permits by year, case type, and work class. The data indicates a dispersal
pattern of development trends with some clusters along the Highway 101 corridor, notably between Paso
Robles and Atascadero and south of Arroyo Grande.
Section 5
Risk Assessment
To further associate these building construction permits with natural hazards in the county and be able to
narrow down potential vulnerable areas to this expected development (hence assessing risk to future
construction of commercial and residential buildings), a spatial overlay analysis was performed that
intersected the centroid points and the hazard layers. With this overlay analysis, summaries similar to
those conducted for parcel and critical facility analyses could be delivered. These assessments are
discussed in more detail in each of the hazard sections, under the Development Trends sections.
County of San Luis Obispo Local October 2019 Page 5-29
Section 5
Risk Assessment
Figure 5-2 Building Construction Permits in San Luis Obispo County from 2014 to Early 2019
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intended for planning purposes only.
Data Source: San Luis Obispo County, N
US Census TIGER Database,CA Open
Data Portal
County of San Luis Obispo Local Hazard Mitigation Plan I October 2019
Section 5
Risk Assessment
Table 5-12 Total Building Construction Permits by Case Type and Work Class
Year Case Type Work Class Count
Conditional Use Permit 29
Land Use
Minor Use Permit 130
2014 PMTC-Commercial Permit 223
New Structure
PMTR- Residential Permit 560
TOTAL 942
Conditional Use Permit 167
Land Use
Minor Use Permit 128
2015 PMTC-Commercial Permit 180
New Structure
PMTR- Residential Permit 514
TOTAL 989
Conditional Use Permit 36
Land Use
Minor Use Permit 117
2016 PMTC-Commercial Permit 151
New Structure
PMTR- Residential Permit 819
TOTAL 1,123
Conditional Use Permit 26
Land Use
Minor Use Permit 146
2017 PMTC-Commercial Permit 186
New Structure
PMTR- Residential Permit 483
TOTAL 841
Conditional Use Permit 78
Land Use
Minor Use Permit 133
2018 PMTC-Commercial Permit 155
New Structure
PMTR- Residential Permit 602
TOTAL 968
Conditional Use Permit 4
Land Use
2019 Minor Use Permit 21
(up to PMTC-Commercial Permit 30
Feb) PMTR- Residential Permit New Structure 85
TOTAL 140
GRAND TOTAL 5,003
Source:San Luis Obispo County Planning&Building
San Luis Obispo County Local Hazard Mitigation Plan I October
Section 5
Risk Assessment
5.3 Hazard Analysis and Risk Assessment
5.3.1 Adverse Weather: General
Adverse weather is generally any destructive weather event, but usually occurs in the San Luis Obispo
County as localized thunderstorms that bring heavy rain and strong winds that occur most often during
the winter and spring months.
For this plan, adverse weather is broken down as follows:
• Thunderstorm/Heavy Rain/Hail/Lighting/Dense Fog/Freeze
• High Wind/Tornado
• Extreme Heat
The proximity to the Pacific Ocean both moderates and exaggerates certain types of adverse weather.
Winter storms impacting coastal portions of the County tend to be more extreme than in the inland
portions. The ocean's influence is also a significant factor in moderating extreme hot and cold
temperatures, hail storms and other cold weather events. These events are rare and short lived, causing
little if any life-threatening situations and only occasional significant damage to property or agricultural
concerns.
The HMPC determined that extreme heat should also be profiled and analyzed within adverse weather for
this 2019 Plan Update. Extreme heat events are projected to increase throughout the state which will have
impacts on people's health, as well as indirect impacts effects such as increased vulnerability and risk to
wildfires and drought.
The National Oceanic and Atmospheric Administration's National Center for Environmental Information
(NCEI) has been tracking adverse weather since 1950. Their Storm Events Database contains data on the
following: all weather events from 1993 to 2017 (except from 6/1993-7/1993); and additional data from
the Storm Prediction Center, which includes tornadoes (1950-1992), thunderstorm winds (1955-1992), and
hail (1955-1992).This database contains 115 storm events that occurred in San Luis Obispo County
between January 1, 1950, and December 31, 2018. The table below summarizes these events.
Table 5-13 NCEI Hazard Event Reports for San Luis Obispo County, 1950-2018*
. . Loss
Excessive Heat/Heat 3 0 0 0 0
Flash Floods 5 0 0 0 0
Floods 10 0 0 0 0
Frost/Freeze 2 0 30,400,000 0 0
Hail 4 0 0 0 0
Heavy Rain 9 5,000,000 0 1 0
High Winds/Thunderstorm Winds 27 4,050,000 0 0 0
Tornado/Funnel Cloud 39 $0 0 3 5
High Surf 4 0 0 0 0
Waterspout 2 0 0 0 0
Wildfire 4 290,000 0 0 0
Winter Weather/Winter Storm 6 0 0 1 2
Totals 115 9,340,000 30,400,000 5 7
Source:National Center for Environmental Information Storm Events Database,www.ncdc.noaa.gov/stormevents/
*Hazards with wide extents have losses which reflect larger zones that extend beyond San Luis Obispo County
Section 5
Risk Assessment
The NCEI table above summarizes adverse weather events that have occurred in San Luis Obispo County
from 1950 to 2018. Only a few of the events actually resulted in state and federal disaster declarations. It
is interesting to note that different data sources capture different events during the same time period, and
often different information specific to the same events. While the HMPC recognizes these inconsistencies,
this data provides value in depicting the County's "big picture" hazard environment.
As previously mentioned, a majority of San Luis Obispo County's state and federal disaster declarations
have been a result of severe winter weather.
The climate of the county is influenced by the effects of the Santa Lucia Range and the Pacific Ocean. The
northern portion of the county where the mountains end at the ocean experience heavier rainfall amounts
compared to the southern portion of the county. Figure 5-3 below, depicts the average annual
precipitation in the county and shows how precipitation differs throughout. Note, the purple lines and text
on the map represent the County's Watershed Groups that are included in the 2018 Integrated Regional
Water Management Plan update.
Due to the size of the county and changes in elevation and climate, weather conditions can vary greatly.
The National Weather Service provides forecasts for three zones within the county: central coast, interior
valley, and mountains and the County Public Works Department has stream and rain gauges in four areas
of the county; North County Coastal Area, North County Inland Area, City of San Luis Obispo Area, and
South County Area.
To give a holistic picture of the various weather conditions the hazard profiles that follow provide
information, where possible, from four weather stations: San Luis Obispo Poly Tech (San Luis Obispo Area,
elevation: 330 feet), Morro Bay Fire Department (North County Coastal Area, elevation: 115 feet), Paso
Robles (North County Inland Area, elevation: 700 feet) and Pismo Beach (South County Area, elevation: 39
feet).
Section 5
Risk Assessment
Figure 5-3 San Luis Obispo County Annual Precipitation, 1971-2000
County of San Luis Obispo
Public Works
Kings County Water Resources
Monterey County Annual Precipitation
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Date Created:328)2019
Source:County of San Luis Obispo Public Works Department,Water Resources
San Luis Obispo County Local Hazard Mitigation Plan I October
Section 5
Risk Assessment
5.3.2 Adverse Weather: Thunderstorm/Heavy Rain/Dense Fog/Freeze
Hazard/Problem Definition
A majority of adverse weather experienced in San Luis Obispo takes place in the winter months as heavy
rain and thunderstorm events sometimes accompanied by high winds, dense fog, hail and freeze events.
High winds and tornado events are profiled in 5.3.3.Approximately 10 percent of the thunderstorms that
occur each year in the United States are classified as severe.A thunderstorm is classified as severe when it
contains one or more of the following phenomena: hail that is three-quarters of an inch or greater, winds
in excess of 50 knots (57.5 mph), or a tornado.
San Luis Obispo's weather is influenced by the Pacific Ocean and routine climate patterns such as EI Nino.
EI Nino is the warm phase of the EI Nino-Southern Oscillation, a pattern found in the tropical Pacific when
there are fluctuations in temperatures between the ocean and atmosphere. During EI Nino, the surface
winds across the entire tropical Pacific are weaker than normal and the ocean surface is at above-average
temperatures in the central and eastern tropical Pacific Ocean (L'Heureux 2014). EI Nino typically develops
over North America during the winter season causing the severe winter storms the County often
experiences.This climate pattern occurs every few years and brings with it above-average rain and snow
across the southern region of United States, especially in California.
Atmospheric rivers, another climate pattern that leads to adverse weather in the County, are responsible
for up to 50 percent of California's precipitation annually and 65 percent seasonally (Arcuni, 2019).An
atmospheric river (AR) is a long, narrow region of the atmosphere, like a river in the sky, that transports
most of the water vapor outside of the tropics. ARs can be 300 miles wide, a mile deep and more than
1,000 miles long and carry an amount of water vapor roughly the same as the average flow of water at the
mouth of Mississippi River(NOAA, 2015).Warm water storms over the Pacific Ocean lead to evaporation
and create a high concentration of moisture in the air. While prevailing winds create the distinctive river
shape, which is often compared "to a fire hose pointed at California" (Arcuni, 2019). When an atmospheric
river reaches land, it releases the water vapor in the form of rain or snow.Atmospheric rivers play an
important role in the global water cycle and are closely tied to both water supply and flooding risk.
Research suggests that atmospheric rivers contributed to the collapse of both Orville Dam spillways in
February 2017 (NASA Global Hydrology Resource Center), as well as the winter flooding in 1861-1862,
which completely inundated Sacramento and is considered the worst flood event in California's history
(Ingram, 2013). When an atmospheric river forms in the tropical regions of the pacific near Hawaii it is
known as a "Pineapple Express".This type of atmospheric river can produce as much as five inches in one
day(NOAA, 2018). In 2018 two Pineapple Express ARs hit California causing significant heavy precipitation
events throughout state.
Hail is formed when water droplets freeze and thaw as they are thrown high into the upper atmosphere
by the violent internal forces of thunderstorms. Hail is sometimes associated with severe storms within the
San Luis Obispo County planning area. Hailstones are usually less than two inches in diameter and can fall
at speeds of 120 miles per hour (mph). Severe hailstorms can be quite destructive, causing damage to
roofs, buildings, automobiles, vegetation, and crops.
Lightning is defined as any and all of the various forms of visible electrical discharge caused by
thunderstorms.Thunderstorms and lightning are usually (but not always) accompanied by rain. Severe
Section 5
Risk Assessment
lighting events in San Luis Obispo County are rare, although they do take place occasionally. Refer to the
Previous Occurrences section below for the narrative on a 2019 adverse weather event.
Intra-cloud lightning is the most common type of discharge. This occurs between oppositely charged
centers within the same cloud. Usually it takes place inside the cloud and looks from the outside of the
cloud like a diffuse brightening that flickers. However, the flash may exit the boundary of the cloud, and a
bright channel, similar to a cloud-to-ground flash, can be visible for many miles.
Cloud-to-ground lightning is the most damaging and dangerous type of lightning, though it is also less
common. Most flashes originate near the lower-negative charge center and deliver negative charge to
earth. However, a large minority of flashes carry positive charge to earth. These positive flashes often
occur during the dissipating stage of a thunderstorm's life. Positive flashes are also more common as a
percentage of total ground strikes during the winter months. This type of lightning is particularly
dangerous for several reasons. It frequently strikes away from the rain core, either ahead or behind the
thunderstorm. It can strike as far as 5 or 10 miles from the storm in areas that most people do not
consider to be a threat (see Figure 5-4). Positive lightning also has a longer duration, so fires are more
easily ignited. And, when positive lightning strikes, it usually carries a high peak electrical current,
potentially resulting in greater damage.
Figure 5-4 Cloud to Ground Lighting
intraclaud flash
#fie blue — �
updraft � `�,
staked
strikes -
Source:National Weather Service Pueblo Office
San Luis Obispo's climate is described as a mild Mediterranean climate; a freeze refers to a particularly
cold spell of weather where the temperature drops below 32 degrees, most typically in the early morning
hours. Usually these cold spells will last only two or three days when the ocean influence will overcome
the cold front and the early morning temperatures will return to the normal 45 to 55-degree range.
Rainfall during these periods may result in snowfall in the higher elevations of the county.
Section 5
Risk Assessment
Dense fog in San Luis Obispo County reduces visibility making driving more dangerous.A fog advisory
issued for San Luis Obispo County in October 2011 warned visibility could be as low as a quarter mile and
reduce suddenly with denser patches. In March 2012 another fog advisory anticipated less than 1/4 of
normal visibility.The National Weather Service issues dense fog advisories when appropriate and suggests
slowing down on the road, using headlights at all times, and leaving plenty of distance from other
vehicles.
Geographic Area
Thunderstorms are generally expansive in size. The entire county is susceptible to any of the effects of a
severe thunderstorm, including hail and heavy rain.As noted at the beginning of the Adverse Weather
profile, the proximity to the Pacific Ocean and the mountain ranges in the county both moderate and
exaggerate certain types of adverse weather depending on where the storm event has occurred.
Extent (Magnitude/Severity)
Extent for adverse weather, particularly severe storms that involve heavy rain and hail can be measured
according to hail by diameter sizes.The National Weather Service (NWS) classifies hail by diameter size,
and corresponding everyday objects to help relay scope and severity to the population. Table 5- 2 below
indicates the hailstone measurements utilized by the NWS.
There is no clear distinction between storms that do and do not produce hailstones. Nearly all severe
thunderstorms probably produce hail aloft, though it may melt before reaching the ground. Multi-cell
thunderstorms produce many hailstones, but not usually the largest hailstones. In the life cycle of the
multi-cell thunderstorm, the mature stage is relatively short so there is not much time for growth of the
hailstone. Supercell thunderstorms have sustained updrafts that support large hail formation by
repeatedly lifting the hailstones into the very cold air at the top of the thunderstorm cloud. In general,
hail 2 inches (5 cm) or larger in diameter is associated with supercells (a little larger than golf ball size
which the NWS considers to be 1.75 inch.). Non-supercell storms are capable of producing golf ball size
hail.
Common problems associated with severe storms include the loss of utilities or immobility. Loss of life is
uncommon but can occur during severe storms. Immobility can occur when roads become impassable
due to dense fog, heavy rains causing flooding, downed trees, or a landslide. Fog specifically poses a risk
to commuters and driving conditions as fog typically forms rapidly in the early morning hours. Fog can
have devastating effects on transportation corridors in the county. Nighttime driving in the fog is
dangerous and multi-car pileups have resulted from drivers using excessive speed for the conditions and
visibility. Loss of utilities, specifically power lines can occur due to downed trees, high winds and heavy
snows. While snow accumulation is unlikely within the San Luis Obispo planning area, high winds and
downed trees are known to result in power outages.
Section 5
Risk Assessment
Table 5-14 Hail Measurements
Average Diameter I . . Obiact
.25 inch Pea
.5 inch Marble/Mothball
.75 inch Dime/Penny
.875 inch Nickel
1.0 inch Quarter
1.5 inch Ping-pong ball
1.75 inch Golf-Ball
2.0 inch Hen Egg
2.5 inch I Tennis Ball
2.75 inch Baseball
3.00 inch I Teacup
4.00 inch Grapefruit
L4.5 inch -Softball
Source:National Weather Service
Lightning is measured by the Lightning Activity Level (LAL) scale, created by the National Weather Service
to define lightning activity into a specific categorical scale. The LAL is a common parameter that is part of
fire weather forecasts nationwide. The San Luis Obispo County is at risk to experience lightning in any of
these categories.The LAL is reproduced in Table 5-15.
Table 5-15 Lightning Activity Level Scale
Lightning Activity Level
LAL 1 No thunderstorms
Isolated thunderstorms. Light rain will occasionally reach the
LAL 2 ground. Lightning is very infrequent, 1 to 5 cloud to ground strikes
in a five-minute period
Widely scattered thunderstorms. Light to moderate rain will reach
LAL 3 the ground. Lightning is infrequent, 6 to 10 cloud to ground strikes
in a five-minute period.
Scattered thunderstorms. Moderate rain is commonly produced.
LAL 4 Lightning is frequent, 11 to 15 cloud to ground strikes in a five-
minute period.
Numerous thunderstorms. Rainfall is moderate to heavy. Lightning
LAL 5 is frequent and intense,greater than 15 cloud to ground strikes in a
five-minute period.
Dry lightning (same as LAL 3 but without rain). This type of
LAL 6 lightning has the potential for extreme fire activity and is normally
highlighted in fire weather forecasts with a Red Flag warning.
Source:National Weather Service
Section 5
Risk Assessment
The heavy precipitation that San Luis Obispo County and all of California experiences is often the result of
an atmospheric river. Atmospheric rivers are categorized by a unit of measurement known as the
Integrated Water Vapor Transport (IVT), which takes into account the amount of water vapor in the
system and the wind that moves it around. For a storm to be classified as an atmospheric river it has to
reach an IVT threshold of 250 units; 1,000 IVT or more is considered to be "extreme" (Arcuni, 2019). In
2019 a system for categorizing the strength and impacts of atmospheric rivers was developed by the
Center for Western Weather and Water Extremes (CW3E), out of the Scripps Institution of Oceanography
at UC San Diego.The newly developed scale ranks ARs into five categorizes from weak to exceptional.
Unlike the Fujita scale for tornadoes that focuses on potential damages, the AR scale accounts for both
storms that may be hazardous and storms that can provide benefits to the local water supply.A category
one AR is considered to be primarily beneficial, generally lasting only 24 hours and produces modest
rainfall.While a category five AR is considered "exceptional" and primarily hazardous, lasting for several
days and associated with heavy rainfall and runoff that may cause significant damages. Table 5-16 below
describes the scale further. The center developed the scale as a tool for officials with an operational need
to assess flooding potential in their jurisdictions before the storms makes landfall.
In both February 2018 and 2019 the West Coast experienced six atmospheric rivers. But as the following
figure from the Center for Western Weather and Water Extremes shows, California experienced vastly
different precipitation totals due to the location of where the atmospheric river made landfall as well as
each atmospheric river's IVT. Using the AR scale developed by CW3E, the ARs in February 2019 were all
considered to be moderate to extreme and concentrated more on California, resulting in heavy
precipitation.
Table 5-16 Atmospheric River Categories
• . Potential Impacts
AR Cat 1:Weak Primarily beneficial. For example, a Feb.2, 2017 AR hit California, lasted 24
hours at the coast,and produced modest rainfall.
AR Cat 2: Moderate Mostly beneficial, but also somewhat hazardous.An atmospheric river on
Nov. 19-20, 2016 hit Northern California, lasted 42 hours at the coast, and
produced several inches of rain that helped replenish low reservoirs after a
drought.
AR Cat 3: Strong Balance of beneficial and hazardous.An atmospheric river on Oct. 14-15,
2016 lasted 36 hours at the coast, produced 5-10 inches of rain that helped
refill reservoirs after a drought, but also caused some rivers to rise to just
below flood stage.
AR Cat 4: Extreme Mostly hazardous, but also beneficial. For example, an atmospheric river on
Jan.8-9, 2017 that persisted for 36 hours produced up to 14 inches of rain
in the Sierra Nevada and caused at least a dozen rivers to reach flood
stage.
AR Cat 5: Exceptional Primarily hazardous. For example,a Dec.29, 1996 to Jan.2, 1997
atmospheric river lasted over 100 hours at the Central California coast.The
associated heavy precipitation and runoff caused more than $1 billion in
damages.
Source: Center for Western Weather and Water Extremes,Scripps Institution of Oceanography at UC San Diego.Scale was developed by F.Martin
Ralph Director of CW3E in collaboration with Jonathan Rutz of NWS
Section 5
Risk Assessment
Figure 5-5 Atmospheric River Strength and Land Distribution, February 2018 vs. February 2019
50'N 50'N
February 2018 �F e6 = _ February 209
475
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Fe4 1 x 425
46"N Fab,17 40p VN y
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1 Weak:YT--2504A kim;r100 1 Weak:lYF=750-500kgm-'s-'
$° o-
30'N 1 Moderate'IYT.itlO 1i01g1 m's' 6p 10 Medcrdtq:FYF=SPo-75P kg rn"'r'
1 Stmhg lVT.75�1000k�m's' {
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+ 2U 4
1 Eelreme,IVS=100b 1254k¢m'�sr 1a 1 Fx"rr&r;1Vr=1t1W1754k9m Jrl Fehl Feh.2
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25"N
145V 140V 135°W 130V 125V 120°W 115°W t 10°W 140V 1350W 130eW 125V 120eW 115°W 110V 105'
Source:Center for Western Weather and Water Extremes,Scripps Institution of Oceanography at UC San Diego
San Luis Obispo County Local Hazard Mitigation Plan I October 2019k
Section 5
Risk Assessment
Previous Occurrences
Heavy rains and adverse storms occur in the San Luis Obispo County primarily during the late fall and
winter but have a chance of occurring in every month of the year.According to information obtained from
the Western Regional Climate Center(WRCC) the majority of precipitation is produced by storms during
January and other winter months. Precipitation during the summer months is in the form of rain showers
and is rare. Snowstorms, and hailstorms occur infrequently in San Luis Obispo County and severe
occurrences of any of these are very rare. Damaging winds often accompany winter storm systems
moving through the area and it is the winds experienced during the winter storms that result in the most
wind-related damage. Refer to 5.3.3 for information related to wind events.
The NCEI records 21 heavy rain, hail and frost/freeze events that have taken place in San Luis Obispo
County in the past 68 years (1950—2018). No dense fog or lightning events have been recorded but does
not mean they do not occur in the county;the HMPC noted in the 2014 plan that the National Weather
Service issued fog advisories in 2011 and 2012.
As shown in the NCEI records heavy rain storms can cause both widespread flooding which can lead to
extensive localized drainage issues. In addition to the flooding that often occurs during these storms,
strong winds, when combined with saturated ground conditions, can down very mature trees. Refer to the
Flood section for more information related to flooding events in the county.
Information from the three representative weather stations introduced in subsection 5.3 Adverse Weather:
General are summarized below and in Figure 5-6 through Figure 5-11
San Luis Obispo Polytech (Period of Record 1893 to 2012)
Information from the closest weather station with the most comprehensive data to represent the City of
San Luis Obispo Area, the San Luis Obispo Polytech Weather Station, is summarized below in Figure 5-6
and Figure 5-7. Average annual precipitation in the interior valley is 22.40 inches per year.The highest
recorded annual precipitation was 48.76 inches in 1969; the highest recorded precipitation for a 24-hour
period is 5.90 inches on January 25, 1969.The lowest recorded annual precipitation was 7.37 inches in
1947.
Section 5
Risk Assessment
Figure 5-6 City of San Luis Obispo Area - Monthly Average Total Precipitation (Period of
Record 1893 -2016)
SAN LUIS OBISPO POLYTECH, CALIFORNIA (047851)
Period of Record : 82/01/1893 to 06/10/2816
C 5
4
G
4
3
2
1
0
Jan Mar May Jul Sep Nov
Feb Apr Jun Aug Oct Dec
Day of Year
4lesterr
Regional
Average Total Monthly Precipitation - climate
Center
Source:Western Regional Climate Center,www.wrcc.dri.edu/
Figure 5-7 City of San Luis Obispo Area - Daily Precipitation Average and Extreme (Period of
Record 1893-2016)
SHN LUIS OBISPO POLYTECH, CALIFORNIA (047851)
Period of Record 82/81/1893 to 86/18/2016
+ 5.5 - - - - - -- E
C 5 E
-4
4.5
C 4 •
O
-tel 3.5
� 3 �
r0 ' —
41 2.5 i
.a 2 +p II
L1 1.5
4i 1
lL 0.5 �I
Jan 1 Mar 1 May 1 Jul 1 Sep 1 Nov 1 Dec 31
Feb 1 Apr 1 Jun 1 Aug 1 Oct 1 Dec 1
Day of Year
Westcrr.
Regional
Extreme Average clirnate
Center
Source:Western Regional Climate Center,www.wrcc.dri.edu/
Section 5
Risk Assessment
North County Coastal Area - Morro Bay Fire Department Weather Station (Period of Record 1959 to
2012)
Information from the closest weather station with the most comprehensive data to represent the North
County Coastal Area of San Luis Obispo, the Morro Bay Fire Department Weather Station, is summarized
below in Figure 5-8 and Figure 5-9. Average annual precipitation in the interior valley is 16.74 inches per
year. The highest recorded annual precipitation was 37.01 inches in 1995; the highest recorded
precipitation for a 24-hour period is 8.82 inches on March 11, 1995. The lowest recorded annual
precipitation was 6.18 inches in 2007.
Figure 5-8 North County Coastal Area - Monthly Average Total Precipitation (Period of Record
1959 -2016)
MORRO BAY FIRE DEPT, CALIFORNIA (045866)
Period of Record : 92/91/1959 to 05/31/2916
.. 4
C 3.5
'H
rr 3
C
� 2.5
2
'a 1.5
� 1
0.5
0 =5 I
Jan filar May Jul Sep Nov
Feb Apr Jun Aug Oct Dec
Day of Year
u.s►.z,.,
Regional
'Wirage Total Monthly Precipitation Climate
Center
Source:Western Regional Climate Center,www.wrcc.dri.edu/
Section 5
Risk Assessment
Figure 5-9 North County Coastal Area - Daily Precipitation Average and Extreme (Period of
Record 1959-2016)
MORRO BHY FIRE DEPT, CRLIFORNIA (045866)
Period of Record ; 02/01/1959 to 05/31/2416
8.5
c $
,.� 7.5
.• 7
6.5
C 6
5.5 — —'
4J 5
rp 4.5
4J 4 `
-4 3.5
12. 3
2.5
1.52
� 1
4.5
Jan I Mar I May I Jul 1 Sep I Nov 1 Dec 31
Feb 1 Apr I Jun I Rug I Oct I Dec 1
Day of Year
Western
Regional
Extreme Average climate
Center
Source:Western Regional Climate Center,www.wrcc.dri.edu/
North County Inland Area - Paso Robles Weather Station (Period of Record 1894 to 2012)
Information from the closest weather station with the most comprehensive data to represent the North
County Inland Area of the county, Paso Robles Weather Station, is summarized below in Figure 5-10 and
Figure 5-11. Average annual precipitation in this region of the county is 15.21 inches per year. The highest
recorded annual precipitation was 29.19 inches in 1941; the highest recorded precipitation for a 24-hour
period is 5.25 inches on December 6, 1966.The lowest recorded annual precipitation was 4.24 inches in
1947.
Section 5
Risk Assessment
Figure 5-10 North County Inland Area - Monthly Average Total Precipitation (Period of Record
1894 -2016)
PHSO ROBLES, CALIFORNIA (046730)
Period of Record 8110111894 to 06/16/2916
c
0
•'� 2
�T
44'W
• 4
CL
U
0
L 9.5
0
Jan Mar May Jul Sep Nett
Feb Alar Jun Aug Oct Dec
[lay of Year
western
Regional
Average Total climate
- – Center
Source:Western Regional Climate Center,www.wrcc.dri.edu/
Figure 5-11 North County Inland Area - Daily Precipitation Average and Extreme (Period of
Record 1894-2016)
PH�.,I] F'OKE� -,. i-HLIFORNIH (046730)
Period of Record 01/01/1894 to 06/1012016
ok
.r- .5 - —
+ 3 _
•� 3.3
-� 7
•v 1.5 � �� — � ij = � j
L Il
0 �. ,•.- � �' � if���w+•Ji i�i ri�h 7•`711 1�1�
.tan 1 Slav-. 1 Maul Jul 1 fief 1 N1-%- i Dec 31
Feb i Hl:�r 1 Jury 1 Aug 1 Oct 1 Dec 1
Day of Year
western
Regional
Extreme Average climate
Ctn+er
Source:Western Regional Climate Center,www.wrcc.dri.edu/
San Luis Obispo County Local Hazard Mitigation Plan I October 2019 • ge 5-45
Section 5
Risk Assessment
South County Area - Pismo Beach Weather Station (Period of Record 1949 to 2016)
Information from the closest weather station with the most comprehensive data to represent the South
County Area of the county, Pismo Beach Weather Station, is summarized below in Figure 5-12 and Figure
5-13. Average annual precipitation in this region of the county is 16.96 inches per year. The highest
recorded annual precipitation was 32.58 inches in 1983; the highest recorded precipitation for a 24-hour
period is 5.16 inches on January 19, 1969.The lowest recorded annual precipitation was 4.49 inches in
1989.
Figure 5-12 South County Area - Monthly Average Total Precipitation (Period of Record 1949 -
2016)
PISMO BEACH, CRLIFORNIH (046943)
Period of Record 07/01/1949 to 06!89/2816
� 3.5
•
C
.pq -
C 2'5
O
2
� 1.S
CL
[s
Rr
[6
p
J ars Nor rlau J u l Sep Nciv
FebApr � Jt�n Aug Oct Dec
Day of Year
Hes�er~n
Regional
Average Total Monthly Precipitation Glsroa+.e
- Centtr
Source:Western Regional Climate Center,www.wrcc.dri.edu/
San Luis Obispo County Local Hazard Mitigation Plan I October
Section 5
Risk Assessment
Figure 5-13 South County Area - Daily Precipitation Average and Extreme (Period of Record
1949-2016)
PI SMB BEACH, F OLI FORM A (046-943)
Period of !Record 07/0111949 to 06/09/2016
4.5E
v 4 _ --
102.5
z
1.5
C6 0.5AYE -
4
Jan 1 Mat 1 Mag 1 Jul Sep 1 Nov 1 Dec 31
Fels 1 Apr 1 Jun 1 Aug 1 Oct 1 Dec i
Day of Year
Iltslerro
Regional
Extr"efile hverage Clim+,e
GenEer
Source:Western Regional Climate Center,www.wrcc.dri.edu/
The following table reports the records collected from the NCEI Storm Events Database for heavy rain, hail
and frost/freeze events. No dense fog events are reported in the database. Table 5-17 is a summary of the
most significant adverse weather events as recorded in the NCEI Storm Events.
Table 5-17 San Luis Obispo County Heavy Rain/Hail/Freeze Events, 1950-2018
Property Crop
Event Type I Date Magnitude Damage Damage Injuries
Heavy Rain
2/20/1996 4-6 in. 0 0 0 0
11/10/1997 0.50-1.50 in. (coastal) 0 0 0 0
3.0 in.(mountains)
1/10/2001 2-5 in.(coastal) 0 0 0 0
5-10 in.(mountains)
2/11/2001 2-8 in. 0 0 0 0
2/24/2001 1-4 in. 0 0 0 0
3/4/2001 2-6 in. (coastal) 0 0 0 0
6-13 in.(mountains)
12/27/2004 2-8 in.(coastal) 0 0 0 0
6-13 in.(mountains)
12/30/2004 1-3 in. (coastal 0 0 1 0
3-6 in. (mountains)
1/7/2005 3-10 in. $5,000,000 0 0 0
Hai
3/6/2001 0.75 in. 0 0 0 0
San Luis Obispo County Local Hazard Mitigation Plan I October
Section 5
Risk Assessment
Property Crop
Event Type Damage Damage
M Magnitude M Injuries
2/23/2005 0.75 in. 0 0 0 0
5/28/2009 0.75 in. 0 0 0 0
3/22/2017 1 in. 0 0 0 0
12/21/1998 - 0 $83,000,000* 0 0
1/13/2007 - 0 $25,000,000 0 0
Totals $5,000,000 $108,000,000 1 0
Source:NCEI Storm Events Database
*Note this recorded crop damage amount is representative of a four-county area
Table 5-18 Past Thunderstorm/Heavy Rain/Dense Fog/Freeze Events, 1950-2018
.. Incident Description 18, Thunderstorms -A thunderstorm caused damage to many of the same areas as winds to nearly
1993 50 mph. Pea-sized hail was reported at Pismo Beach. Power outages due to lightning strikes
were reported in Nipomo and San Luis Obispo. $50,000 in property damage was reported
February 20, Heavy rain in the mountains of San Luis Obispo County led to 4-6 inches of rain and caused
1996 urban and small stream flooding and associated mudslides in the steep terrain and along Hwy
1 and 101.
February 2, 1998 Along with the strong winds (refer to Table 5-5 for information on the wind event), heavy rain
drenched the entire area.On average, rainfall totals ranged from 2 to 8 inches over coastal
areas, up to 12 inches in the mountains.Widespread flooding was reported in all areas (refer
to the past events table in the Flood section).
February 5, 1998 Strong winds,gusting up to 70 mph, knocked down many trees and power lines. Rainfall totals
ranged from 1 to 3 inches over coastal areas, up to 6 inches in the mountains. Numerous
flooding problems were reported across the area. Most highways, including the 1, 101, 126
and 154 were closed due to flooding or mudslides.
December 21-24, Freeze.An unseasonable cold air mass produced a three-night period of sub-freezing
1998 temperatures across Central and Southern California.The California Department of Food and
Agriculture reported over$83 million in crop losses over the four-county area.Crop damage in
San Luis Obispo was reported to be a total of$5.4 million.
1990 to present Very cold Pacific storms brought snow fall to the higher elevations of the county. On rare
(events number occasions, it caused damage to the naturally occurring vegetation.This resulted in an
more than 5) increased fire season threat as the damaged vegetation dried out and augmented the normal
fuel loading.The snow caused rare transportation impacts on Hwy. 101 at Cuesta Grade and
Hwys 41 and 46 at higher elevations.
March 4, 2001 A powerful and slow-moving storm brought heavy rain, strong winds and snow to Central and
Southern California.Across San Luis Obispo and Santa Barbara counties, rainfall totals ranged
from 2 to 6 inches over coastal and valley areas to 6 to 13 inches in the mountains. In San Luis
Obispo County,the heavy rain produced numerous flooding. Refer to the Flood section for
information related to the resulting flood event.
March 6, 2001 A severe thunderstorm produced dime size hail in the community of Santa Margarita.
Section 5
Risk Assessment
�. Incident Description
December 30, A powerful Pacific storm brought more heavy rain, snow and flash flooding to Central and
2004 Southern California.Total rainfall amounts ranged from 1 to 3 inches on the coastal plain to
between 3 and 6 inches in the mountains. Refer to the Flood section for information on the
resulting flooding.
February 23, Nickel size hail was reported in a remote area of San Luis Obispo county.
2005
January 13-15, A very cold arctic storm brought widespread freezing temperatures and some gusty offshore
2007 winds to the area.Across the agricultural areas of San Luis Obispo, Santa Barbara,Ventura and
Los Angeles counties,the freezing overnight temperatures nearly$350 million in crop
damages.Widespread freezing conditions were reported across agricultural areas.Total crop
damages in San Luis Obispo county were estimated to be around $25 million.
May 28, 2009 A severe thunderstorm was reported in San Luis Obispo county near the community of La
Panza.Three quarter inch hail was reported by the local fire station.
April 2011 In mid-April, a bitter cold weather system sent temperatures plunging to the mid-20's,
bringing hail and freezing rain for at least two nights and in some lower elevation areas,three
or four.Thousands of acres of vineyards lost newly emerging grape buds,which experts say
could amount to 50%of the area's 2011 crop. Loss estimates range from 70 to 80 million
dollars.
July 19, 2015 Paso Robles received nearly 3.6 inches of rain in less than 8 hours.The intense rainfall
(remnant of Hurricane Dolores) eroded bare hillsides located outside the City limits and caused
very high volumes of sediment to fill City drainage ways and culverts.20-30 homes were
impacted causing mud and water damage.
March 22, 2017 Several strong thunderstorms developed across the Central Coast of California. In Creston, a
severe thunderstorm developed, producing one-inch hail.
Source:NCEI Storm Events Database,2014 County LHMP,HMPC
In February 2019, San Luis Obispo County experienced severe winter storms that caused heavy rain, hail,
and light snow showers in some areas of the county. The National Weather Service issued a freeze
warning for the County on February 181h, 2019 that lasted until February 22i1, 2019.The County had been
experiencing drought conditions throughout 2018 but received enough rain in the 2019 season to bring it
out of the abnormally dry and drought conditions for the first time in 11 years (San Luis Obispo Tribune,
2019). Refer to the Drought section for more information related to drought conditions in the county. On
February 251h, 2019 Caltrans announced it would be closing portions of Highway 1 along the Central
Coast, in anticipation of a heavy rain event and would not be reopening the highway until the end of that
week after the storm passes to allow for crews to inspect and clean up the highway(San Luis Obispo
Tribune, 2019).
The county continued to experience severe winter storms into March 2019. On March 5th,2019 a severe
thunderstorm, brought heavy rain, thunder and lightning to the South County area.The National Weather
Service's Los Angeles station reported that the region, San Luis Obispo, Santa Barbara, Los Angeles and
Ventura counties, received 4,500 lighting strikes including about 2,500 cloud-to-ground strikes (San Luis
Obispo Tribune, 2019).At one point the NWS recorded 1,489 in one five-minute stretch alone off the
Section 5
Risk Assessment
coast of Central Coast region (Los Angeles Times, 2019). The county and the region are accustomed to
thunderstorms with the occasional lighting strike accompanying the storms, but this amount of lightning
strikes in one thunderstorm event it rare. The storm also caused 300 residents in Grover Beach, 149
residents in rural Arroyo Grande and 70 near See Canyon Road in San Luis Obispo for a total 519 residents
in the county to lose power due to the winter storm. Power was restored by the next morning. The
California Highway Patrol (CHP) reported multiple car accidents and downed trees due to same adverse
weather event.
Probability of Future Occurrences
Highly Likely—Thunderstorms that produce heavy rain with the potential for hail to develop are well-
documented seasonal occurrences that will continue to occur annually in the San Luis Obispo planning
area.
Climate Change Considerations
As average temperatures increase over time, this generally will result in higher extreme temperatures and
more warming in the atmosphere can trigger climate changes, which could result in more frequent
extreme weather events.According to California's Fourth Climate Change Assessment, Central Coast
Region Report (2018), the number of days each year on which the atmospheric rivers bring "extreme"
amounts of rain and snow to the region are expected to increase under the projected climate change for
the state, possibly increasing more than a quarter. Pacific Northwest National Laboratory researchers have
also found that atmospheric rivers will reach the West Coast more frequently (Gao, 2015). Currently, the
West receives rain or snow from these atmospheric rivers between 25 and 40 days each year. By the end
of this century, days on which the atmospheric rivers reach the coast could increase by a third this century,
between 35 and 55 days a year.
According to the climate change analysis completed for the 2014 San Luis Obispo County Integrated
Regional Water Management Plan precipitation is projected to increase in winter months while decreasing
in the spring months, with the greatest change expected to take place in the North County Coastal Area.
Decreases in precipitation in spring months will also have an impact on runoff which may have an impact
on water supply sources, refer to the Drought section for more information on water supply vulnerability;
while the projected increases in precipitation in the spring months will also increase the county's risk to
flooding in some areas, refer to the Flood section for more information in flooding risk and vulnerability.
The Fourth Climate Change Assessment for the Central Coast region projects an increase of 3 to 10 inches
across the five counties in the central coast.
Vulnerability:Thunderstorm/Heavy Rain/Dense Fog/Freeze
General Property
The San Luis Obispo County Planning Area experiences a rainy season in the winter months through early
spring.These winter storms can include significant precipitation as well as high winds, and hail. The
primary effect of these storms has not resulted in significant injury or damages to people and property, or
the losses are typically covered by insurance. It is the secondary hazards caused by weather, such as
floods, that have had the greatest impact on the County. Damage and disaster declarations related to
adverse weather have occurred and will continue to occur in the future. Heavy rain and thunderstorms are
the most frequent type of severe weather occurrences in the County. Utility outages, downing of trees,
San Luis Obispo County Local • 0
Section 5
Risk Assessment
debris blocking streets and damage to property can be a direct result of these storm events. Given the
nature of these types of storms, the entire County is potentially at risk.
People
Exposure is the greatest danger to people from severe thunderstorms. People can be hit by lightning,
pelted by hail, and caught in rising waters. Serious injury and loss of human life is rarely associated with
hailstorms.
Reduced visibility is the greatest risk to people when heavy fog is prevalent. Particularly when fog is
dense, it can be hazardous to drivers, mariners and aviators and contributes to numerous accidents each
year. To reduce injury and harm, people should avoid driving when dense fog is prevalent, if possible. If
driving is pertinent, emergency services advise driving with lights on low beam, avoiding stopping on
highways, and avoiding crossing traffic lanes.
Aspects of the population who rely on constant, uninterrupted electrical supplies may have a greater,
indirect vulnerability to lightning.As a group, the elderly or disabled, especially those with home health
care services relying on rely heavily on an uninterrupted source of electricity. Resident populations in
nursing homes, residential facilities, or other special needs housing may also be vulnerable if electrical
outages are prolonged. If they do not have a back-up power source, rural residents and agricultural
operations reliant on electricity for heating, cooling, and water supplies are also especially vulnerable to
power outages.
Social Vulnerability
Outdoor laborers are particularly at risk to thunderstorms and the association hazards of precipitation,
hail and the increased risk of being struck by lightning. Based on the SoVI data presented and discussed
in subsection 4.4.1, the communities located in north county San Luis Obispo such as Paso Robles, San
Miguel and Atascadero and in south county such as Oceano and Nipomo, where many agricultural
activities take place are also among the areas of the county with the highest ranking overall social
vulnerability.
Critical Facilities and Infrastructure
Because of the unpredictability of severe thunderstorm and a tornado event strength and path, most
critical infrastructure that is above ground is equally exposed to the storm's impacts. Due to the random
nature of these hazards, a more specific risk assessment was not conducted for this plan.
Economy
Economic impact of a severe thunderstorm is typically short term. Lightning can cause power outages and
fires. Hail can destroy exposed property; an example is car lots, where entire inventories can be damaged.
Generally, long-term economic impacts center more around hazards that cascade from a severe
thunderstorm, including wildfires ignited by lightning, and flooding (refer to the Flood section).
In general, all adverse weather poses a risk to agriculture economy in the county. Table 5-19 below
describes the crops losses related to adverse weather events and associated indemnity amounts or loss
payments from the United States Department of Agriculture (USDA), Risk Management Agency in the past
three years. Heat, frost/freeze, and high wind/excess wind events have been the cause of the majority of
crop losses related to weather since 2015. Overall, in the past three years there have been 200 adverse
Section 5
Risk Assessment
weather events that have led to crop losses in the county, totaling in over $20 million in loss payments
due to adverse weather.
Table 5-19 San Luis Obispo County Crop Losses and Loss Payments, 2015-2018
Cause of Loss Number Indemnity Amounts
of Events (loss payments)
Frost/Freeze 45 $6,713,314
Cold Winter 5 $43,037
Excess Moisture/Cold Wet Weather 47 $6,457,335
Hail 3 $36,272
Heat 64 $3,569,208
Wind/Excess Wind 33 $3,133,818
Other 3 $51,683
Totals 200 $20,004,667
Source:USDA Risk Management Agency,https://www.rma.usda.gov/summary0fBusiness/CauseOfLoss
Historic, Cultural, and Natural Resources
Severe thunderstorms are a natural environmental process. Environmental impacts include the sparking of
potentially destructive wildfires by lightning and localized flattening of plants by hail. As a natural process,
the impacts of most severe thunderstorms by themselves are part of the overall natural cycle and do not
cause long-term consequential damage.
Future Development
New critical facilities, such as communication towers should be built to withstand heavy rain, wind, and
hail damage. Future development projects should consider adverse weather hazards at the planning,
engineering and architectural design stage with the goal of reducing vulnerability. Stormwater master
planning and site review should account for buildings to withstand adverse weather events considered for
all new development. Thus, development trends in the County are not expected to increase overall
vulnerability to the hazard but all development will be affected by adverse weather and storm events and
population growth will increase potential exposure to hazards such as thunderstorms and dense fog.
Risk Summary- Thunderstorm/Heavy Rain/Dense Fog/Freeze
• The overall impact to the community from severe weather events associated with heavy rain,
thunderstorms, hail, and fog could include:
• San Luis Obispo County has experienced 21 hail, heavy rain, and frost/freeze events in past 68 years
• Average annual precipitation ranges from 22.4 inches to 15.2 inches depending on the area of the
County
• Since 2015 over $20 million in loss payments from USDA related to crop losses from adverse weather
events have been paid.
• Related hazards: Flood, Wildfire, Landslide and Debris Flow, Coastal Storm/Coastal Erosion/Sea Level
Rise, Agriculture/Pest Infestation/Plant Disease/Tree Mortality
Section 5
Risk Assessment
Table 5-20 Hazard Risk Summary- Thunderstorm/Heavy Rain/Dense Fog/Freeze
OverallJurisdiction I Geographic Area Probability of Magnitude/
OccurrenceFuture Severity Significance
San Luis Obispo County Significant Likely Negligible Medium
City of Arroyo Grande Significant Likely Limited Low
City of Atascadero Significant Likely Limited Low
City of Grover Beach Significant Likely Limited Low
City of Morro Bay Extensive Highly Likely Limited High
City of Paso Robles Significant Highly Likely Limited High
City of Pismo Beach Significant Likely Limited Low
City of San Luis Obispo Extensive Likely Limited Medium
Avila Beach CSD Significant Occasional Negligible Medium
Ground Squirrel Hollow CSD Limited Likely Negligible Medium
Heritage Ranch CSD Extensive Highly Likely Critical High
Los Osos CSD Significant Likely Limited Medium
Nipomo CSD Limited Likely Negligible Low
San Miguel CSD Extensive Likely Catastrophic High
San Simeon CSD Likely Significant Limited Low
Templeton CSD Significant Highly Likely Limited High
Cayucos Sanitary District Extensive I Likely Critical I High
Port San Luis Harbor District Extensive ` Highly Likely Limited I Medium
San Luis Obispo FCWCD Significant Highly Likely Negligible Low
South San Luis Obispo Significant Likely Limited Low
Sanitary District
San Luis Obispo County Local Hazard Mitigation Plan I October
Section 5
Risk Assessment
5.3.3 Adverse Weather: High Wind/Tornado
Hazard/Problem Description
High winds, often accompanying severe thunderstorms, can cause significant property and crop damage,
threaten public safety, and have adverse economic impacts from business closures and power loss.
Windstorms in San Luis Obispo County are typically straight-line winds. Straight-line winds are generally
any thunderstorm wind that is not associated with rotation (i.e., is not a tornado). It is these winds, which
can exceed 100 mph, that represent the most common type of severe weather and are responsible for
most wind damage related to thunderstorms. These winds can overturn mobile homes, tear roofs off
houses, topple trees, snap power lines, shatter windows, and sandblast paint from cars. Other associated
hazards include utility outages, arcing power lines, debris blocking streets, dust storms, and an occasional
structure fire.
Tornadoes are another severe weather hazard that can affect the San Luis Obispo County planning area.
Tornadoes form when cool, dry air sits on top of warm, moist air.Tornadoes are rotating columns of air
marked by a funnel-shaped downward extension of a cumulonimbus cloud whirling at destructive speeds
of up to 300 mph, usually accompanying a thunderstorm. Tornadoes are the most powerful storms that
exist.They can have the same pressure differential that fuels 300-mile-wide hurricanes across a path only
300-yards wide or less. Figure 5-14 illustrates the potential impact and damage from a tornado.
Figure 5-14 Potential Impact and Damage from a Tornado
Figure 2-2 Potential impact of a tornado potential Impact and Damage
From a Tornado
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Prior to February 1, 2007, tornado intensity was measured by the Fujita (F) scale. This scale was revised
and is now the Enhanced Fujita scale. Both scales are sets of wind estimates (not measurements) based on
damage. The new scale provides more damage indicators (28) and associated degrees of damage,
allowing for more detailed analysis and better correlation between damage and wind speed. It is also
more precise because it takes into account the materials affected and the construction of structures
San Luis Obispo County Local Hazard Mitigation Plan I October 2019 Page
Section 5
Risk Assessment
damaged by a tornado. Table 5-21 shows the wind speeds associated with the original Fujita scale ratings
and the damage that could result at different levels of intensity. Table 5-22 shows the wind speeds
associated with the Enhanced Fujita Scale ratings. The Enhanced Fujita Scale's damage indicators and
degrees of damage can be found online at www.spc.noaa.gov/efscale/ef-scale.html.
Table 5-21 Original Fujita Scale
Fujita Scale
Fujita (F) Wind Estimate
Scale (mph) Typical Damage
FO < 73 Light damage. Some damage to chimneys; branches broken
off trees;shallow-rooted trees pushed over;sign boards
damaged.
F1 73-112 Moderate damage. Peels surface off roofs; mobile homes
pushed off foundations or overturned; moving autos blown off
roads.
F2 113-157 Considerable damage. Roofs torn off frame houses; mobile
homes demolished; boxcars overturned; large trees snapped
or uprooted; light-object missiles generated;cars lifted off
ground.
F3 158-206 Severe damage. Roofs and some walls torn off well-
constructed houses;trains overturned; most trees in forest
uprooted; heavy cars lifted off the ground and thrown.
F4 207-260 Devastating damage.Well-constructed houses leveled;
structures with weak foundations blown away some distance,-
cars
istance;cars thrown, and large missiles generated.
F5 261-318 Incredible damage. Strong frame houses leveled off
foundations and swept away;automobile-sized missiles fly
through the air in excess of 100 meters (109 yards);trees
debarked; incredible phenomena will occur.
Source:National Oceanic and Atmospheric Administration Storm Prediction Center,www.spc.noaa.gov/faq/tornado/f-scale.html
Table 5-22 Enhanced Fujita Scale
Enhanced
Enhanced Fujita Scale
Fujita (EF) Wind Estimate
Scale (mph) Potential Damage
Minor damage. Peels surface off some roofs;some damage to
gutters or siding; branches broken off trees;shallow-rooted
EFO 65-85 trees pushed over.Confirmed tornadoes with no reported
damage (i.e.,those that remain in open fields)are always
rated EFO.
Moderate damage. Roofs severely stripped; mobile homes
EF1 86-110 overturned or badly damaged; loss of exterior doors;
windows and other glass broken.
Considerable damage. Roofs torn off from well-constructed
EF2 111-135 houses;foundations of frame homes shifted; mobile homes
completely destroyed; large trees snapped or uprooted; light-
object missiles generated;cars lifted off ground.
Section 5
Risk Assessment
Enhanced
Enhanced Fujita Scale
Fujita (EF) Wind Estimate
Scale (mph) Potential Damage
Severe damage. Entire stories of well-constructed houses
destroyed;severe damage to large buildings such as
EF3 136-165 shopping malls;trains overturned;trees debarked; heavy cars
lifted off the ground and thrown;structures with weak
foundations are badly damaged.
Devastating damage.Well-constructed and whole frame
EF4 166-200 houses completely leveled;cars and other large objects
thrown,and small missiles generated.
Incredible damage.Strong-framed,well-built houses leveled
off foundations are swept away;steel-reinforced concrete
EF5 Over 200 structures are critically damaged;tall buildings collapse or
have severe structural deformations;some cars,trucks,and
train cars can be thrown approximately 1 mile(1.6 km).
Source:National Oceanic and Atmospheric Administration Storm
Prediction Center,www.spc.noaa.goy/faq/tornado/ef-scale.html
Table 5-23 below outlines the Beaufort scale,which describes the damaging effects of wind speed.
Table 5-23 Beaufort Wind Scale
DescriptionWind Speed
0 Calm;smoke rises vertically
1-4 Light air;direction of wind shown by smoke but not by wind vanes
4-7 Light breeze;wind felt on face; leaves rustle;ordinary wind vane moved by wind
8-12 Gentle breeze; leaves and small twigs in constant motion;wind extends light flag
13-18 Moderate breeze; raises dust and loose paper,small branches are moved
19-24 Fresh breeze;small trees in leaf begin to sway;crested wavelets form on inland water
25-31 Strong breeze; large branches in motion;telephone wires whistle;umbrellas used with
difficulty
32-38 Moderate gale whole trees in motion;inconvenience in walking against wind
39-46 Fresh gale breaks twigs off trees;generally, impedes progress
47-54 Strong gale slight structural damage occurs;chimney pots and slates removed
55-63 Whole gale trees uprooted; considerable structural damage occurs
64-72 Storm very rarely experienced;accompanied by widespread damage
73+ Hurricane devastation occurs
Source:NWS
San Luis Obispo County Local Hazard Mitigation Plan I October
Section 5
Risk Assessment
High winds and tornadoes can cause damage to property and loss of life. While most tornado damage is
caused by violent winds, most injuries and deaths result from flying debris. Property damage can include
damage to buildings, fallen trees and power lines, broken gas lines, broken sewer and water mains, and
the outbreak of fires.Agricultural crops and industries may also be damaged or destroyed.Access roads
and streets may be blocked by debris, delaying necessary emergency response.
Geographic Area
Wind and tornadoes have the potential to happen anywhere in the County. The resulting damage from
wind and tornado events may be most severe in the downtown areas of incorporate communities where
there are more large trees, infrastructure, and higher density development.
Extent
Based on NCEI records between 1950 and 2018 there have been a combined 31 high wind/thunderstorm
winds (27 events) and four tornado/funnel cloud events in San Luis Obispo County which has resulted in a
total of$4,050,000 in property damage. The most damaging event took place on January 2, 2006 and was
a 56-mph wind event that resulted in $4,000,000 in property damages. Overall, high wind event impacts
would likely be limited, with a majority of impacts being related to property damages caused my downed
trees as well as power outages.
In the past 68 years all the tornado events that have taken place in San Luis Obispo County have been FO
tornadoes. However, it should be noted that, although unlikely, larger tornadoes could occur. Should the
County be hit by an EF-3 or higher tornado, it can be extrapolated that because of its relative size and the
potential size and length of a tornado's path a significant portion of the County could be impacted,
resulting in property and crop damage and loss of life.
Tornado impacts to the County would likely be negligible, with less than 10 percent of the planning area
affected by events in the EFO-2 range, though stronger tornadoes are possible. The impact to quality of
life or critical facilities and functions in the affected area would depend on where the tornado occurred.
Injuries or deaths are possible due to wind thrown trees or property damage caused by wind events.
Overall, impacts from high wind and tornado events would likely be negligible, with less than 10 percent
of property severely damaged and shutdown of facilities due to loss of power for 24 hours or less.
Previous Occurrences
During the rainy season, the San Luis Obispo planning area is prone to relatively strong thunderstorms,
sometimes accompanied by high winds and tornadoes. While tornadoes do occur occasionally, most
often they are of FO intensity.The NCEI Storm Events Database does not record any F1, F2, or F3 events
that have occurred in the planning area in the past. Documented incidents of high wind/thunderstorm
winds and tornado/funnel cloud events in San Luis Obispo from the NCEI Database are listed in the
following tables. Table 5-25 Past High Wind and Tornado Events contains incident descriptions for
significant historic events.
Section 5
Risk Assessment
Table 5-24 San Luis Obis o County High Wind Events
� . Magnitude (mph) Property Damage
February 18, 1993 - $50,000
November 26, 1997 62 0
February 2, 1998 78 0
February 5, 1998 61 0
February 7, 1998 61 0
February 19, 1998 50 0
April 3, 1999 55 0
February 11, 2000 52 0
December 17,2000 48 0
January 10,2001 55 0
March 4,2001 65 0
November 24,2001 55 0
December 7,2001 52 0
December 19,2002 55 0
February 25, 2004 47 0
January 7, 2005 58 0
January 2,2006 56 $4,000,000
December 7,2007 51 0
January 4,2008 65 0
January 27,2008 54 0
February 23,2008 65 0
October 13,2009 68 0
December 13, 2009 50 0
January 18,2010 52 0
January 20,2010 52 0
December 11,2014 50 0
Total $4,050,00
Source:NCEI Storm Events Database*NOTE no reports of crop damages,deaths or injuries were recorded
San Luis Obispo County Local Hazard Mitigation Plan I October
Section 5
Risk Assessment
Table 5-25 Past High Wind and Tornado Events
.. Incident Description 26, A line of severe thunderstorms rumbled across San Luis Obispo and Santa Barbara counties.
1997 The storms produced winds gusting up to 71 mph and heavy rain.
February 2, 1998 Hearst Castle, in San Luis Obispo county, reported winds gusting to 90 mph. Elsewhere,winds
gusting in excess of 70 mph were reported. Hundreds of trees and power lines were blown
down, resulting in numerous power outages.Along with the strong winds, heavy rain drenched
the entire area. (refer to Table 5-4 for details on the rain event).
February 19, Strong thunderstorms moving across San Luis Obispo county produced strong winds in the
1998 Templeton area.A spotter reported winds gusting to 58 mph.
May 5, 1998 A small tornado developed over the City of San Luis Obispo.The tornado knocked out power
to several hundred homes.Also,four homes were damaged, including a home struck by a
fallen cypress tree. (FO)
February 11, A powerful cold front brought strong winds and heavy snow to parts of Central and Southern
2000 California. In Morro Bay, southeast winds, gusting to 60 mph ahead of the front, knocked
down numerous trees and power lines.
December 17, Gusty offshore winds buffeted coastal sections of San Luis Obispo county. In the City of San
2000 Luis Obispo,the winds blew out the windows in an unoccupied mobile home,as well as
destroyed part of a car port. In Nipomo, a weather spotter reported sustained winds of 35 mph
with gusts to 55 mph.Also,the strong winds produced widespread power outages.
January 10, 2001 A strong thunderstorm produced damaging winds in northern San Luis Obispo County.Across
southern sections of Atascadero,trees were uprooted as well as damage to fences and decks.
March 4, 2001 Across Central and Southern California, strong southeasterly winds accompanied the storm.
Widespread winds between 30 and 50 MPH with stronger gusts were reported from the
coastal areas to the mountains. (Refer to Table 5-4 for more details on the heavy rain and
flooding that accompanied this event)
November 24, A strong cold front moved though San Luis Obispo County, producing strong and gusty winds.
2001 Weather spotters and the Morro Bay Fire Department reported sustained winds between 35
and 45 mph with gusts as high as 62 mph. Numerous small trees and power lines were blown
down between Morro Bay and Atascadero.
December 7, Gusty northeast winds knocked down power lines and small trees in the community of Morro
2001 Bay.Wind speeds were estimated between 25 and 35 mph with local gusts as high as 60 mph.
February 2, 2004 A waterspout,which developed offshore of Oceano Dunes, came onshore as a weak tornado.
The weak tornado hit a park ranger in his truck. Fortunately,the park ranger was not injured,
and his truck sustained no reportable damage.
January 2, 2006 Strong west to northwest winds, gusting to 65 MPH,affected the community of Cambria in
San Luis Obispo County. In total, 84 homes sustained damage with 31 homes sustaining major
damage. Estimates of property damage were around $4 million.
January 4, 2008 In early January,a powerful Pacific storm brought strong winds, heavy rainfall,flash flooding
and winter storm conditions to Central and Southern California.The strongest winds were
reported across San Luis Obispo and Santa Barbara counties as well as all mountain areas.The
winds knocked down trees and power lines, producing numerous power outages.An
automated sensor in Atascadero reported sustained winds of 43 mph.A weather spotter in
Morro Bay reported a southeasterly wind gust of 75 mph.
January 27, 2008 An observer at Hearst Castle reported southeast winds gusting to 62 mph.The last of several
January storms brought high winds and heavy snow to sections of Central and Southern
Section 5
Risk Assessment
�. Incident Description
California.Across San Luis Obispo and Santa Barbara counties, strong southeasterly winds
gusting to 65 mph knocked down trees and power lines across the area.
February 23, An automated sensor at Atascadero reported southeast winds gusting to 59 mph.An
2008 automated sensor at Point Arguello reported southeast winds gusting to 63 mph. In the
nearby community of Cambria, numerous trees and power lines were knocked down by the
winds.Strong southeast winds gusting to 75 mph were reported in the mountains of San Luis
Obispo county.A powerful cold front moved across Central and Southern California in late
February.Although the front did not produce significant rainfall, it did bring strong and gusty
southeasterly winds to the area.Wind gusts as high as 75 to 86 mph were reported in some
areas.The strongest and most widespread winds occurred across the Central Coast as well as
the mountains. Numerous trees and power lines were knocked down.
October 13, 2009 From October 12th through October 14th,the first significant storm of the season moved
through Southern California.The storm brought heavy rainfall and very gusty southerly winds
to the area. Rainfall totals were very impressive, generally ranging between 1 and 3 inches over
coastal areas to between 4 and 10 inches in the mountains.Some isolated areas received
rainfall amounts over 10 inches over San Luis Obispo and Santa Barbara counties.This storm
brought very strong and gusty southerly winds to the area with warning-level winds reported
in many areas.
December 13, A trained weather spotter reported a wind gust of 58 MPH associated with a severe
2009 thunderstorm.A powerful winter storm brought heavy rain,flash flooding, gusty winds and
severe thunderstorms to Central and Southern California. Rainfall amounts for this storm
ranged from 1 to 3 inches over coastal areas to between 3 and 6 inches in the mountain and
foothill areas.With such heavy rainfall,there were several reports of flash flooding along with
mud and debris flows near the Station Fire burn area. In San Luis Obispo County, a severe
thunderstorm producing very strong winds.
January 18, 2010 Strong and gusty south winds associated with an approaching winter storm affected the coast
of San Luis Obispo County.A weather spotter in Grover Beach reported south winds gusting to
60 MPH.A series of powerful winter storms affected Central and Southern California between
the 18th and 22nd of January.As this series of storms moved across the area,they brought
heavy rain,flash flooding,gusty winds, heavy snow and even severe weather to the area.
January 20, 2010 Strong and gusty south winds associated with an approaching winter storm affected the
interior valleys of San Luis Obispo county.The Carrizo RAWS sensor reported south winds
gusting to 60 MPH while the ASOS at Paso Robles reported sustained south winds of 40 MPH.
A trained spotter in the Grover Beach area reported a thunderstorm wind gust of 58 MPH.
February 13— 14, February 2019 brought heavy rain and high wind throughout the County.These events
2019 resulted in downed power lines and trees.The National Weather Service issued a wind
advisory which lasted from February 13th— 14th.On February 13th, 2019, high winds lead to
2,000 PG&E customers to lose power and downed power lines in Arroyo Grande causes roads
to be closed.The Atascadero Fire Department reported a 50-foot pine tree fell on two single-
story multi-family residences leading to eight people being displaced but none were injured.
The fallen tree led to $400,000 in property damage due to a broken water line(San Luis
Obispo Tribune, 2019).
Source:NCEI Storm Events Database,2014 San Luis Obispo LHMP
The following figures spatially depict the past high wind and tornado events that described in the table
above and that have occurred in San Luis Obispo County since 1950.
Section 5
Risk Assessment
Figure 5-15 San Luis Obispo County Wind Events 1955 -2017
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Reservo,: Monterey Kings Tulare
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,
Map compiled 2/2019; 0 10 20 40 Miles N
intended for planning purposes only.
Data Source, San Luis Obispo County, /11V
US Census TIGER Database,CA Open
Data Portal,NOAA Storm Database
San Luis Obispo County Local Hazard Mitigation Plan I October
Section 5
Risk Assessment
Figure 5-16 San Luis Obispo County Tornado Events 1950 -2017
Seitz Antz1�%.
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Map compiled 212019; 0 10 20 40 Miles N
intended for planning purposes only.
Data Source: San Luis Obispo County, '!1V
US Census TIGER Database,CA Open
Data Portal,NOAA Storm Database
San Luis Obispo County Local Hazard Mitigation Plan I October
Section 5
Risk Assessment
Likelihood of Future Occurrences
Likely—Thirty-one high wind and tornado events have occurred in San Luis Obispo County over 68 years
of record keeping, which equates to one high wind or tornado event every 2.2 years, on average, and a 46
percent chance of a high wind or tornado event occurring in any given year. Historical wind activity within
the planning area indicates that the area will likely continue to experience high wind during thunderstorm
events with a potential of the formation of funnel clouds and low intensity tornadoes during adverse
weather conditions. The actual risk to the County is dependent on the nature and location of any given
thunderstorm or tornado event.
Climate Change Considerations
There presently is not enough data or research to quantify the magnitude of change that climate change
may have related to tornado frequency and intensity. NASA's Earth Observatory has conducted studies
which aim to understand the interaction between climate change and tornadoes. Based on these studies
meteorologists are unsure why some thunderstorms generate tornadoes and others don't, beyond
knowing that they require a certain type of wind shear. Tornadoes spawn from approximately one percent
of thunderstorms, usually supercell thunderstorms that are in a wind shear environment that promotes
rotation. Some studies show a potential for a decrease in wind shear in mid-latitude areas. Because of
uncertainty with the influence of climate change on tornadoes, future updates to the mitigation plan
should include the latest research on how the tornado hazard frequency and severity could change. The
level of significance of this hazard should be revisited over time.
Vulnerability to Severe Weather: High Wind and Tornadoes
Property
General damages are both direct (what the wind event physically destroys) and indirect, which focuses on
additional costs, damages and losses attributed to secondary hazards spawned by the event, or due to the
damages caused by the wind event. Depending on the magnitude of the wind events as well as the size of
the tornado and its path, a tornado is capable of damaging and eventually destroying almost anything.
Construction practices and building codes can help maximize the resistance of the structures to damage.
Secondary impacts of damage caused by wind events often result from damage to infrastructure. Downed
power and communications transmission lines, coupled with disruptions to transportation, create
difficulties in reporting and responding to emergencies.These indirect impacts of a wind event put
tremendous strain on a community. In the immediate aftermath, the focus is on emergency services.
Downed trees caused by a wind event are a common occurrence in the county (refer to Table 5-25).
Falling trees can cause significant damage to property and put people at risk. Due to multiple years of
drought in the county, combined with tree disease and pests, (refer to the Drought section and the
section on Agricultural Pest Infestation, Plant Disease, Marine Invasive Species and Tree Mortality), many
trees in the area have been impacted making them more susceptible to blow-down during wind events.
GIS was used to estimate the potential for wind damage from fallen trees, assuming that tree mortality
areas will be most susceptible.Tree mortality composes just over 13% of the county in area and are found
to intersect with a total of 35,780 properties across the county, based on the property centroids defined
for all the hazards' parcel analyses. The western half of county is most impacted by tree mortality, with the
areas most affected being North County Inland and South County Areas. The following table summarizes
Section 5
Risk Assessment
the number of properties in each jurisdiction found within tree mortality high hazard zones (both Tier 1
and 2) based on GIS overlay analysis. Refer to each jurisdictions annex for more details on the types of
properties within tree mortality high hazard zones.Additional analysis related to critical facilities and tree
mortality high hazard zones is discussed further below.
Table 5-26 Properties Within Tree Mortality High Hazard Zones, by Type and Jurisdiction
Jurisdiction
• . .
Arroyo Grande 3,253 $825,279,845
Atascadero 57 $14,895,750
City of San Luis Obispo 11 $2,804,138
Grover Beach 4,713 $866,176,076
Paso Robles 10,306 $2,556,604,120
Pismo Beach 4,293 $1,290,261,821
Unincorporated 13,147 $3,508,212,028
TOTAL 35,780 $9,064,233,778
Source:CalFire FRAP,2019;Wood GIS analysis
People
Community members are the most vulnerable to high wind and tornado events. The availability of
sheltered locations such as basements, buildings constructed using tornado-resistant materials and
methods, and public storm shelters, all reduce the exposure of the population. However, there are also
segments of the population that are especially exposed to the indirect impacts of high winds and
tornadoes, particularly the loss of electrical power. These populations include the elderly or disabled,
especially those with medical needs and treatments dependent on electricity. Nursing homes, community-
based residential facilities, and other special needs housing facilities are also vulnerable if electrical
outages are prolonged, since backup power generally operates only minimal functions for a short period
of time.
Social Vulnerability
Communities that are vulnerable to the impacts of a high wind or tornado event are the same areas of the
county with the highest-ranking vulnerable household compositions and overall high ranking of social
vulnerability such as Paso Robles and Grover Beach. Based on the SoVI data presented in and discussed in
subsection 4.4.1, mitigation efforts to address vulnerability to high wind and tornado should be focused
on the communities with the highest social vulnerability rankings.
Critical Facilities and Transportation Infrastructure
Public gathering places including (but not limited to) schools, community centers, shelters, nursing homes
and churches, may have increased impacts at certain times of day if struck by a tornado. Other critical and
essential facilities, transportation and utility lifelines, and high potential loss facilities such as power plants
could also be significantly affected by powerful wind or tornado events, particularly in areas impacted by
tree mortality. In the following two tables summarizing critical facilities, GIS overlay analysis was
performed to find which of these facilities fall within the high tree mortality areas. Table 5-15 summarizes
the facilities found in tree mortality hazard zones by type, while Table 5-16 summarizes the total facilities
in these tree mortality areas byjurisdiction.According to this analysis, most critical facilities found at risk
are in the unincorporated portions of county, with 47 in Paso Robles and 13 or fewer in Pismo Beach,
Section 5
Risk Assessment
Grover Beach, and Arroyo Grande. The three most common facility types at risk are microwave service
towers, public schools, and day care facilities. Most of the critical facilities are found in Tier 2 tree mortality
areas (190), though 5 facilities are in Tier 1 tree mortality areas.
Table 5-27 Critical Facilities Within Tree Mortality Hazard Zones, by Facility Type
Critical Facility Type Critical Facility Count
Airports 3
AM Transmission Towers 1
Cellular Towers 4
Colleges/Universities 1
Day Care Facilities 21
Emergency Medical Service Stations 12
Energy Commission Facilities 4
Fire Stations 12
FM Transmission Towers 11
Hospitals 1
Local Law Enforcement 5
Microwave Service Towers 68
Nursing Homes 5
Paging Transmission Towers 1
Power Plant 1
Private Schools 7
Public Schools 26
TV Analog Station Transmitters 3
Urgent Care 3
Water Treatment Facilities 3
Wastewater Treatment Plants 3
Airports 3
TOTAL 195
Source:CalFire FRAP,2019;HIFLD,San Luis Obispo Planning&Building/GIS Dept.,San Luis Obispo County Community Services Districts;Wood GIS
analysis
Table 5-28 Critical Facilities Within Tree Mortality Hazard Zones, by Jurisdiction
G Critical Facility Count
Arroyo Grande 10
Grover Beach 12
Paso Robles 47
Pismo Beach 13
Unincorporated 113
TOTAL 195
Source:CalFire FRAP,2019;HIFLD,San Luis Obispo Planning&Building/GIS Dept.,San Luis Obispo County Community Services Districts;Wood GIs
analysis
Historic, Cultural, and Natural Resources
High winds and tornadoes can cause massive damage to the natural environment, uprooting trees and
other debris. This is part of a natural process, however, and the environment will return to its original state
in time. GIS was used to estimate the potential for wind damage to historic properties from fallen trees,
San Luis Obispo County Local Hazard Mitigation Plan I October
Section 5
Risk Assessment
assuming that tree mortality areas will be most susceptible. The analysis indicates that a total of thirty-
three (33) historic properties in San Luis Obispo County are located in high hazard tree mortality zone, five
(5) are located in a Tier 1 zone and twenty-eight (28) are located in a Tier 2 hazard zone. Details on the
specific properties at risk are found in Appendix E.
Economy
Winds typically don't have long-term impacts on the economy, although wind does have an impact on the
agriculture economy in the county. As shown in Table 5-19, wind events have been a leading cause of
crop loss in the past three years (2015-2018), resulting in over $3 million in loss payments from the USDA.
Both winds and tornadoes may impact exposed critical infrastructure such as power lines; depending on
the impact and the function, this could cause a short-term economic disruption. The most common
problems associated with tornadoes and high winds are loss of utilities. Downed power lines can cause
power outages, leaving large parts of the county isolated, and without electricity, water, and
communication. Damage may also limit timely emergency response and the number of evacuation routes.
Downed electrical lines following a storm can also increase the potential for lethal electrical shock.
Damaging winds can also cause wildfires, refer to the Wildfire section for more information on the
county's vulnerability to wildfires.
Future Development
As the County continues increase in population, the number of people and housing developments
exposed to the hazard increases.Adherence to current building codes, coupled with proper education on
building techniques and the use of sturdy building materials, attached foundations, and other structural
techniques may minimize the property vulnerabilities. Public shelters at parks and open spaces may help
reduce the impacts of tornadoes and high wind events on the recreational populations exposed to storms.
Risk Summary—High Wind and Tornadoes
The overall impact to the community from tornadoes and wind due to severe storms could include:
• San Luis Obispo has experienced 31 wind events in the past 68 years;
• Most damaging wind event occurred on 1/2/2006 and resulted in $4,000,000 in property damages;
• Over $3 million in crop indemnities have been paid due to crop loss from excessive wind;
• Related hazards:Wildfire, Coastal Storm/Coastal Erosion/Sea Level Rise, Agriculture/Pest
Infestation/Plant Disease/Tree Mortality
Section 5
Risk Assessment
Table 5-29 Hazard Risk Summary-High Wind and Tornadoes
OverallGeographic Probability of Magnitude/
OccurrenceJurisdiction Area Future Severity Significance
San Luis Obispo County Significant Likely Negligible Low
City of Arroyo Grande Significant Likely Negligible Low
City of Atascadero Extensive Likely Limited Low
City of Grover Beach Significant Likely Negligible Low
City of Morro Bay Significant Highly Likely Limited Medium
City of Paso Robles Significant Highly Likely Limited High
City of Pismo Beach Significant Likely Limited Low
City of San Luis Obispo Extensive Occasional Limited Medium
Avila Beach CSD Significant Occasional Negligible Medium
Ground Squirrel Hollow CSD Limited Likely Negligible Medium
Heritage Ranch CSD Extensive Highly Likely Critical High
Los Osos CSD Significant Likely Limited Medium
Nipomo CSD Limited Likely Negligible Low
San Miguel CSD Extensive Likely Catastrophic High
San Simeon CSD Significant Likely Limited Low
Templeton CSD Significant Highly Likely Limited High
Cayucos Sanitary District Extensive Likely Critical High
Port San Luis Harbor District Extensive Highly Likely Limited Medium
San Luis Obispo FCWCD Limited Highly Likely Negligible Low
South San Luis Obispo Sanitary District Significant Likely Negligible Low
San Luis Obispo County Local Hazard Mitigation Plan I October
Section 5
Risk Assessment
5.3.4 Adverse Weather: Extreme Heat
Hazard/Problem Definition
Extreme heat events can have severe impacts on human health and mortality, natural ecosystems, the
agriculture sector and other economic sectors.According to information provided by FEMA, extreme heat
is defined as temperatures that hover 10 degrees or more above the average high temperature for the
region and last for several weeks. Heat kills by taxing the human body beyond its abilities, usually from
heat stroke. In a normal year, about 175 Americans succumb to the demands of summer heat. According
to the National Weather Service (NWS), among natural hazards, only the cold of winter—not lightning,
hurricanes, tornadoes, floods, or earthquakes—takes a greater toll. As a comparison, in the 40-year period
from 1936 through 1975, nearly 20,000 people were killed in the United States by the effects of heat and
solar radiation. In the heat wave of 1980, more than 1,250 people died.The 2018 California State Hazard
Mitigation Plan (SHMP) notes the 2006 heat wave lead to 650 deaths in a 13-day period (Cal OES 2018)
and in the past 15 years heat waves have claimed more lives in California than all other declared disaster
events combined (California Climate Adaptation Strategy 2018).
Heat disorders generally have to do with a reduction or collapse of the body's ability to shed heat by
circulatory changes and sweating or a chemical (salt) imbalance caused by too much sweating. When heat
gain exceeds the level the body can remove, or when the body cannot compensate for fluids and salt lost
through perspiration, the temperature of the body's inner core begins to rise, and heat-related illness may
develop. The elderly, small children, individuals who work outside, patients with chronic medical
conditions, those on prescription medication therapy, and people with weight and alcohol problems are
particularly susceptible to heat reactions, especially during heat waves in areas where moderate climate
usually prevails. Figure 5-17 illustrates the relationship of temperature and humidity to heat disorders.
Figure 5-17 National Weather Service Heat Index
NWS Heat Index Temperature (°F)
80 82 84 86 88 90 92 94 96 98 100 102 104 106 108 110
40 80 81 83 85 88 91 94 97 101 105 109 114 119 124
45 80 82 84 87 89 93 96 100 104 109 114 119 124
50 81 83 85 88 91 95 99 103 108 113 118 124
>, 55 81 84 86 89 93 97 101 106 112 117 124
T5 60 82 84 88 91 95 100 105 110 116 123
E 65 82 85 89 93 98 103 108 114 121
= 70 83 86 90 95 100 105 112 119
75 84 88 92 97 103 109 116 124
e 80 84 89 94 100 106 113 121
85 85 90 96 102 110 117
90 86 91 98 105 113 122
95 86 93 100 108 117
1100187 95 143 112 t21
Likelihood of Heat Disorders with Prolonged Exposure or Strenuous Activity
❑ Caution ❑ Extreme Caution ® Danger Extreme Danger
Source:National Weather Service Note:Since heat index values were devised for shady,light wind conditions,exposure to full sunshine can increase
heat index values by up to 157.Also,strong winds,particularly with very hot,dry air,can be extremely hazardous.
Section 5
Risk Assessment
Geographic Area
All of San Luis Obispo County is at risk of extreme heat events, although different areas of the county may
be more at risk than others. Coastal communities on average have lower temperatures compared to
communities in the inland areas of the county and may be less at risk to extreme temperatures although
potentially less acclimatized to high temperatures if they occur. The North County inland area has the
potential for the highest extreme heat days.
Extent (Magnitude/Severity)
The NWS has in place a system to initiate alert procedures (advisories, watches, and warnings) when high
temperatures are expected to have a significant impact on public safety.The expected severity of the heat
determines which type of alert is issued.The "California OES Contingency Plan for Excessive Heat
Emergencies" (2014) indicates that through the use of historical weather and mortality data, the NWS and
the California Department of Public Health (CDPH) have identified five major types of climate regions
within California to account for climate differences among regions in order to recognize what constitutes
an excessive heat event in each of the regions. When temperatures spike for two or more consecutive
days without an adequate drop in nighttime temperature to cool the outdoor and indoor environments,
there is a significant increase in the risk to vulnerable populations.
Overall, extreme heat impacts would likely be limited in the planning area, with the inland portions of the
planning area being most affected. Extreme heat will have an impact on vulnerable populations as well as
impact the agricultural sector if the event occurs during certain times of the year.
Previous Occurrences
Information from the four representative weather stations introduced in subsection 5.3.1 Adverse
Weather: General is summarized below and in Figure 5-18 through Figure 5-21
City of San Luis Obispo Area - San Luis Obispo Polytech (Period of Record 1893 to 2012)
The monthly average maximum temperatures in the warmest months (June through October) range from
the low-70s to the mid-70s. Monthly average minimum temperatures from November through May range
from the low to high 40s.The highest recorded daily extreme was 112°F on September 14, 1971.
Section 5
Risk Assessment
Figure 5-18 San Luis Obispo Poly Tech Daily Temperature Averages and Extremes (Period of
Record 1893 -2016)
SAN LUIS OBISPO POLYTECH, CALIFORNIA (047851)
Period of Record 02/01/1893 to 06/16/2916
120
110
rr 100
Li 90
ti.+
80
as
L 70
60
L 50
d f0
CL
30
20
10
Jan 1 filar 1 May 1 Jul 1 Sep 1 Nov 1 Dec 31
Feb 1 Apr 1 Jun 1 Aug 1 Oct 1 Dec 1
Day of Year
Western
Regional
Extreme Max Ave Max Aug Min Extreme Min climate
cenaew
Source:Western Regional Climate Center,www.wrcc.dri.edu/
North County Coastal Area - Morro Bay Fire Department Weather Station (Period of Record 1959 to
2012)
The monthly average maximum temperatures in the warmest months (July through November) range
from the mid-60s to the high-60s. Monthly average minimum temperatures from November through June
range from the low- to mid-60s.The highest recorded daily extreme was 102°F on September 8, 1984.
Section 5
Risk Assessment
Figure 5-19 North County Coastal Area - Daily Temperature Averages and Extremes (Period of
Record 1959 -2016)
MORRO BRY FIRE DEPT , EHLIFORNIH (045866)
Period of ReoDrd 02/01/1959 to 05/31/201.6
110
100
L 70
L `o
C 40
� 3A
-
Jan 1 Mar 1 May 1 Jul 1 Sep 1 Nov 1 Dec 31
Feb 1 Apr 1 Jori 1 Aug S Oct 1 Dec 1
Day of Year
ges�ern
R�gianai
Extreme Max Ave Max —Ave Min Extreme Min ciirrats
CeM
Source:Western Regional Climate Center,www.wrcc.dri.edu/
North County Inland Area - Paso Robles Weather Station (Period of Record 1894 to 2012)
The monthly average maximum temperatures in the warmest months (May through October) range from
the high-70s to the low-90s. Monthly average minimum temperatures from October through April range
from the low-30s to low-40s. The highest recorded daily extreme was 117°F on August 13, 1933.
ObispoSan Luis
Section 5
Risk Assessment
Figure 5-20 North County Inland Area - Daily Temperature Averages and Extremes (Period of
Record 1894 -2016)
PASO ROBLES, CALIFORNIA (046730)
Period of Record 81/01/1894 to 06/19/2816
120
110
100
ILL 90
..
80
as
70
0 60
50
CU 40
CL 30 ,.
y 20 .--
H 10
0
Jan i Mar 1 May i Jul i Sep i Nov i Dec 31
Feb 1 Apr 1 Jun i Aug i Oct 1 Dec i
Day of Year
Western
Regional
Extr~ Man[ Ave Max Ave Min Ext"Me Min climate
Center
Source:Western Regional Climate Center,www.wrcc.dri.edu/
South County Area—Pismo Beach Weather Station (Period of Record 1949 to 2016)
The monthly average maximum temperatures in the warmest months (May through October) range from
the high-60s to the low-70s. Monthly average minimum temperatures from October through April range
from the high-40s to low-50s.The highest recorded daily extreme was 108°F on August 28, 1962.
Section 5
Risk Assessment
Figure 5-21 South County Area - Daily Temperature Averages and Extremes (Period of Record
1949 -2016)
PISMO BEACH, CALIFORNIA (046943)
Period of Record 87/0111949 to 06/09/2016
110
100
.t %
LL
&0
L 70
i.nFr
�?
so
0 50
CL 4fl
30
Jan 1 Feb 1 fpr 1 :Ian 1 Mar 1 May 1 Jul 1 Aug 1 Sep 1 Oct 1 Nov 1 Dec 1 Dec 31
Day of Year
Nis!-erin
Regional
Extreme Max Ave Ptax Ave Min Extreme 11in climte
ceoter
Source:Western Regional Climate Center,www.wrcc.dri.edu/
Events of Note
According to information obtained from the NCEI Storm Events Database, in the past 68 years (1950-
December 2018) there have been 3 heat and excessive heat events in San Luis Obispo County. The
following significant events that have occurred within San Luis Obispo County are highlighted below:
July 22, 2006 - The combination of high pressure aloft and above-normal relative humidity resulted in an
extended period of excessive heat across San Luis Obispo, Santa Barbara, Ventura and Los Angeles
counties. At times, heat index values ranged from 100°F to 119°F.
According to the Central Coast Region Report of California's Fourth Climate Change Assessment, during
the 2006 California heat wave the state experienced an overall excess number of emergency room (ER)
visits and hospitalizations. The Central Coast region (San Luis Obispo, Santa Barbara, Monterey, San
Benito, and Santa Cruz) contributed far more to both ER visits (28 percent) and hospitalizations (47
percent) than what would have been expected (18 percent) based on overall state populations. The report
attributes the high number of ER visits and hospitalizations on the regions typically cooler climate and
residents lack of acclimatization to the extreme heat.
September 3, 2007 -The combination of above normal temperatures and relative humidity produced
excessive heat conditions across the mountains and valley of San Luis Obispo county. Heat index values
between 1057 and 1127 were reported. The heat wave which started at the end of August continued
into the first few days of September. The combination of above normal temperatures and relative
humidity continued to produce excessive heat conditions across sections of Southern California.
Section 5
Risk Assessment
June 20, 2008 - The combination of strong high pressure centered over Arizona and weak offshore flow
generated extreme heat conditions across Central and Southern California. Across many sections of the
area, afternoon temperatures climbed to between 100 and 114 degrees which set numerous high
temperature records.The extreme heat resulted in several power outages due to excessive electrical use.
The automated sensor at Paso Robles reported a high temperature of 107 with a heat index of 105
degrees.
Probability of Future Occurrences
Occasional—Temperature extremes are likely to continue to occur annually in the San Luis Obispo
County planning area.
Climate Change Considerations
According to the Central Coast Region Report of California's Fourth Climate Change Assessment report,
both average high and average minimum temperatures are expected to increase, with the greatest
increases in the inland regions of the Central Coast. Due to the rising temperatures heat waves are likely
to become more frequent, which will have direct impacts on human health in terms of heat related illness.
San Luis Obispo's large farming and viticulture production which employs 1,OOOs of outdoor laborers will
be vulnerable to the rising temperatures and most at risk for heat related illnesses. Residents on the
coastal regions of County will also be vulnerable to rising temperatures, as many of the homes of the
coast do not have air conditioning units as there was less of a need in the past and may be less prepared
compared to the inland region of the county to adapt to extreme heat events.
Cascading impacts include increased stress on water quantity and quality, degraded air quality, and
increased potential for more severe or catastrophic natural events such as heavy rain, droughts, and
wildfire. Another cascading impact includes increased duration and intensity of wildfires with warmer
temperatures. According to the 2013 document, "Preparing California for the Extreme Heat", Cal-Adapt
projects that throughout California urban and rural population centers will experience an average of 40 to
53 extreme heat days by 2050 and an average of 40 days by 2099; compared to a historical average of 4
per year(CalAdapt 2013).
Extreme heat has also been shown to accelerate wear and tear on the natural gas system and electrical
infrastructure (California Natural Resources Agency 2018a). Projected increases in summer demand
associated with rising temperatures may increase risks to energy infrastructure and may exceed the
capacity of existing substations and distribution line infrastructure and systems.
Vulnerability: Extreme Heat
General Property
Recent research indicates that the impact of extreme heat, particularly on populations, has been
historically under-represented. The risks of extreme heat are often profiled as part of larger hazards, such
drought or wildfire. However, as temperature variances may occur outside of larger hazards or outside of
the expected seasons but still incur large costs, it is important to examine them as stand-alone hazards.
Extreme heat may overload demands for electricity to run air conditioners in homes and businesses
during prolonged periods of exposure and presents health concerns to individuals outside in the
temperatures. While extreme heat rarely damages buildings, it can cause infrastructure damage to roads.
Section 5
Risk Assessment
People
Traditionally, the very young and very old are considered at higher risk to the effects of extreme heat, but
any populations outdoors during periods of extreme temperatures are exposed, including otherwise
young and healthy adults and homeless populations. While everyone is vulnerable to extreme heat
incidents, some populations are more vulnerable than others. Extreme heat poses the greatest danger for
San Luis Obispo's thousands of outdoor laborers who support the County's agriculture economy who are
exposed to extreme temperatures and at higher risk of heat related illnesses than other populations of the
county. Climate change projections of rising temperatures in the region also pose a risk to the County's
coastal population who is more accustomed to cooler temperatures. and therefore, may have never
needed air conditioning in their homes. This could result in some populations being unprepared for an
extreme heat event.
The elderly, children, people in poor physical health, and the homeless are also vulnerable to exposure.
Arguably, the young-and-otherwise-healthy demographic may also experience a higher vulnerability of
exposure, due to the increased likelihood that they will be out in temperatures of extreme heat, whether
due to commuting for work or school, conducting property maintenance such as lawn care, or for
recreational reasons.
Social Vulnerability
The North County inland area has the potential for the highest extreme heat days. Based on the SoVI data
presented and discussed in subsection 4.4.1, within this region, the communities of Paso Robles San
Miguel, and Shandon have the highest social vulnerability.
Critical Facilities and Infrastructure
Extreme heat can affect road infrastructure, damaging and buckling road surfaces. Other direct impacts
to critical infrastructure includes power line sagging and power surges. Critical infrastructure that relies
on public utility systems that could be overloaded may result in impacts during extreme heat events. Peak
demand exceeding the local utility's capacity for supply can lead to blackout or brownout conditions. The
loss of utilities or power outages during extreme heat events could also result in adverse secondary
impacts to sensitive populations. Electrical power outages may impact response capabilities or care
capabilities for hospitals and clinics.
Economy
Extreme heat impacts on the economy may be more indirect compared to other hazards. San Luis Obispo
has a large agriculture economy. As noted previously outdoor laborers who are exposed to extreme heat
and at a high risk of heat related illnesses, and a long-term heat event could cause work interruptions.
Crops are also impacted by heat events and could have an impact on the overall economy in the county.
According to the USDA RMA Indemnity Report, since 2015 there have been 65 heat events that have
resulted in $3,569,208 in crop losses in the county.
Section 5
Risk Assessment
Historic, Cultural, and Natural Resources
Extreme heat may cause temporary drought-like conditions. For example, several weeks of extreme heat
increases evapotranspiration and reduces moisture content in vegetation, leading to higher wildfire
vulnerability for that time period even if the rest of the season is relatively moist.
Future Development
Since structures are not usually directly impacted by severe temperature fluctuations, continued
development is less impacted by this hazard than others in the plan. However, pre-emptive measures
such as construction of green buildings that require less energy to heat and cool, use of good insulation
on pipes and electric wirings, and smart construction of walkways, parking structures, and pedestrian
zones that minimize exposure to severe temperatures may help increase the overall durability of the
buildings and the community to the variations. Continued development also implies continued
population growth, which raises the number of individuals potentially exposed to variations. Public
education efforts should continue to help the population understand the risks and vulnerabilities of
outdoor activities, property maintenance, and regular exposures during periods of extreme heat.
Risk Summary—Extreme Heat
• There have been three notable extreme heat events in past 68 years in San Luis Obispo County;
• The inland area of the eastern County is more likely to experience an extreme heat event
• Coastal areas are potentially vulnerable to extreme heat due to lack of acclimatization to high
temperatures and less air conditioning;
• Highest recorded temperature for the San Luis Obispo Area is 112°F on Sep. 14, 1971
• Highest recorded temperatures for North County Coastal Area is 1027 on Sept. 14, 1984
• Highest recorded temperatures for Inland Area is 1177 on Aug. 13, 1933
• High recorded temperatures for South County Area is 1087 on Aug. 28, 1962;
• Extreme heat can have considerable impacts on human health, the natural environment and the
economy;
• The County's agriculture economy is at risk of extreme heat from outdoor laborers being vulnerable
to heat illnesses as well as crop losses due to heat;
• The very young, the very old, people with poor physical health and the homeless are more susceptible
to the impacts of extreme temperatures;
• Climate change is projected to increase temperatures in the Central Coast region of the State.
• Related hazards: Drought, Land Subsidence, Wildfire, Agriculture/Pest Infestation/Plant Disease/Tree
Mortality,
Section 5
Risk Assessment
Table 5-30 Hazard Risk Summary—Extreme Heat
OverallJurisdiction Geographic Area Probability of Magnitude/
OccurrenceFuture Severity Significance
San Luis Obispo Extensive Occasional Negligible Low
County
City of Arroyo Grande Extensive Occasional Negligible Low
City of Atascadero Extensive Occasional Negligible Low
City of Grover Beach Extensive Occasional Negligible Low
City of Morro Bay Significant Highly Likely Limited Medium
City of Paso Robles Extensive Highly Likely Limited High
City of Pismo Beach Significant Likely Limited Low
City of San Luis Obispo Extensive Occasional Negligible Low
Avila Beach CSD Significant Occasional Negligible Medium
Ground Squirrel Hollow Limited Likely Negligible Medium
CSD
Heritage Ranch CSD Extensive Highly Likely Critical High
Los Osos CSD Significant Likely Limited Medium
Nipomo CSD Limited Likely Negligible Low
San Miguel CSD Extensive Likely Catastrophic High
San Simeon CSD Significant Likely Limited Low
Templeton CSD Significant Highly Likely Limited High
Cayucos Sanitary Extensive Likely Critical High
District
Port San Luis Harbor Extensive Highly Likely Limited Medium
District
San Luis Obispo Extensive Occasional Negligible Low
FCWCD
South San Luis Obispo Extensive Occasional Negligible Low
Sanitary District
Section 5
Risk Assessment
5.3.5 Agricultural Pest Infestation, Plant Disease, Marine Invasive Species and Tree
Mortality
Hazard/Problem Definition
Agricultural pests and pathogens (insects, fungi, bacteria, viruses and invasive plants) cause injury or
destruction to crops or livestock. From exotic fruit flies to noxious weeds, California's agriculture can be
impacted by a wide variety of invasive pests.These pests pose significant threats to the state's agricultural
crops, economy, food supply and native habitat. The number of invasive pests and pathogens newly
detected in California and the rest of the United States has increased at alarming rates in recent years, and
that trend is projected to continue into the future.
Invasive species are not just contained to dry land. Marine invasive species can take over enclosed water
ecosystems, disrupting delicate ecological structure and displacing entire native species. Marine invasive
species can also foul pipes of hydroelectrical facilities, water works, and other industrial facilities, impairing
facility functions.
A specific concern of the county is tree vulnerability and mortality. Over 100 million trees have died and
more continue to die due to many years of drought that have weakened trees, and left millions of acres of
forestland highly susceptible to insect attacks. The drought stress is exacerbated in forests with too many
trees competing for limited resources, especially water. Forest pests (insects and diseases) annually
destroy ten times the volume of timber lost to due to forest fires. Native bark beetles took hold in
Southern California forests and caused unprecedented tree mortality. Pitch Canker disease has attacked
Monterey Pines along the central coast. Sudden Oak Death has been found in 14 counties in California
and has killed thousands of oaks. Tree losses due to drought stresses and bark beetle attacks are
expected to increase until precipitation levels return to normal or above normal for one to multiple years.
Geographic Area
Agricultural pests usually occur in rural areas used for the growing of crops, though tree mortality can
affect urban and rural forested areas; marine invasive species usually occur in contained aquamarine
areas, including rivers, creeks, ponds and lakes. In San Luis Obispo County, agriculture lands are
interspersed across the county but largely focused in the North County region. Figure 5-22 shows land
use across the county; agricultural lands are shown in light green.
Section 5
Risk Assessment
Figure 5-22 San Luis Obispo—County Land Use
L' �- .s '. v •• aa• u:: e• yea
V
- 0 5 le 29
LUSS OBISPO COUNTY
RURAL LA0 USE CATEGORY MAP
w:J^' North•County Planning Area u
Goasta!Zone 1
Leaexo
.- 7
Coanal Zma Buntlary
`" � � OPlann?tA Aaa BoanOdy
`��WY. Q aiainng$aOArya evuneary
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�.L Gmm•iaa Resl
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{ -j�m°tia srv�
- Ga o Plaaaing Area �\
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Soutli County Planning Area
' a J
- -• - a ental Pupa
asaenn•swroa
ae—fi.isnyia Femur
%r.
During discussions with the HMPC, it was noted that while most agricultural pests occur in rural areas, the
initial introduction of those pests is often due to human/vehicle movement and occurs in more urbanized
areas. Often, especially in the case of insect pests, the species will first become established in a residential
or urban area, and then move into croplands.
Marine invasive species are a threat to marine areas with a relatively enclosed, self-contained ecosystem.
Figure 5-22 shows main bodies of water and waterways in the county; specific points of interest include
Nacimiento Reservoir, Soda Lake, Twitchell Reservoir, Santa Margarita Lake and Whale Rock Reservoir.
The Dam Incident section has more information on reservoirs and other bodies of water.
Tree Mortality: Tree mortality was identified as an additional drought impact of significance to the
county during the 2019 update. Tree mortality is a cascading impact which also affects (or worsens) other
hazards such as wildfire, agricultural and biological hazards, and wind. In recent years, due to the multi-
year drought throughout the planning area and state-wide, a vast number of trees have been (and
continue to be) impacted within San Luis Obispo County foothill and mountain communities and beyond.
Standing dead trees could fall and pose a risk to people, buildings, power lines, roads and other
infrastructure. In addition, drought-impacted trees become susceptible to diseases and insect infestations
(bark beetle) further adding to the risk of tree mortality and related potential impacts.
California established the California Tree Mortality Task Force in October 2015. As part of the work of the
Task Force, areas of tree mortality were identified and mapped to show areas that pose the greatest
potential to harm people and/or property. These areas, known as High Hazard Zones, are the areas
prioritized for tree removal, and are separated into Tiers. Tier I High Hazard Zones are areas where
San Luis Obispo County LocalOctober 2019 • ge 5-79
Section 5
Risk Assessment
mortality and the asset to be protected (utilities, roads, recreation sites etc.) directly coincide with
mortality identified by the USFS. Tier 2 HHZ is based on watersheds and are intended to focus on
ecosystem health and identify watersheds where there is both the greatest amount of ecological assets to
be protected, as well as the greatest threat.
Figure 5-23 shows High Hazard Zones in the county, as well as areas of tree mortality and community
boundaries. Paso Robles, Atascadero, Pismo Beach, Arroyo Grande, Grover Beach and the unincorporated
county are all impacted by Tier 2 High Hazard Zones; Tier I High Hazard Zones are found in the
unincorporated county, as well as Atascadero.
Figure 5-23 San Luis Obispo—Tree Mortality and High Hazard Zones
Montes � \ .
!te<erroir. Y Kings Tulare
41
i •
q, 01
46
?'s x,2•.- - '- tYr Kern
s��!_• - Paso Robles
46
as 41
escrror
41
Atascader
Morro Bay
01 58
SanLuis - '-�e,uire .w�0
PACIFIC OCEAN t -Obi,po
- _ F,•
101 z _ .-�r•:f, ..
-� Pismo Beach 4,du larks
Tree Mortality Grover Beach Arroyo Grande
-Tier 1 High Hazard Zones 2018 - L
tot. f
Tier 2 High Hazard Zones 2018 �`• ,�-.
1
-r 188 7irililri'l1 Nr.r, ,,..
—Vlhterways i,
Lakes _ r
Santa Barbara
Railroads •S < -!•----1
—Highway
Freeway ' Ventura
i�Counties _ ne
Map compiled 212019; 0 10 20 40 Miles N
intended for planning purposes only. I I I 1�
Data Source:San Luis Obispo County, N
US Census TIGER Database.CA Open
Data Portal,Cali FRAP
Extent (Magnitude/Severity)
2017 San Luis Obispo County annual crop statistics released by the San Luis Obispo County Department
of Agriculture/Weights and Measures show that agricultural assets in the county have a gross valuation of
$924,698,000. The top twenty value crops based on county data shown in the following table.
Fi ure 5-24 San Luis Obispo County—2017 Top Twenty Value Crops
. . Value
Wine Grapes(All) $267,662,000
Strawberries $228,169,000
Cattle and Calves $42,241,000
Broccoli $42,996,000
San Luis Obispo County Local Hazard Mitigation Plan I October 2019 • ge :•
Section 5
Risk Assessment
Crop Value
Vegetable Transplants $33,119,000
Avocados $27,295,000
Cut Flowers $27,165,000
Cauliflower $23,253,000
Head Lettuce $17,477,000
Lemons $16,016,000
Leaf Lettuce $11,161,000
Outdoor Ornamentals $9,320,000
Celery $8,405,000
Rangeland Grazed $8,096,000
Grain Hay $2,447,000
Alfalfa Hay $2,421,000
Barley $1,761,000
English Walnuts $1,264,000
Squash $1,027,000
Peas $532,000
Source: San Luis Obispo County Department of Agriculture/Weights and Measures
Different pests can impact different crops in different ways;while there is no scale to define the extent of
an infestation, a pest could have a major economic impact on the value of infested crops.
According to Cal-IPC, invasive plants cost California $82 million every year in control, monitoring and
outreach; estimated actual impacts can reach into the billions.
Previous Occurrences
San Luis Obispo County has a demonstrated vulnerability to pest infestation including the Vine Mealybug,
Glassy-winged sharpshooter and Pine Pitch Canker.
Vine Mealybug: The Vine Mealybug (VMB), Plonococcus ficus, is an exotic pest in California that was first
found in San Luis Obispo County in 1991. It causes an enormous amount of damage, is very difficult and
costly to treat, and can lead to total crop loss without the diligent use of insecticide treatment.Although it
has only been found on grapes so far in California, alternate hosts include avocados, citrus and other
crops. It is currently seen in most grape growing counties of California including vineyards in San Luis
Obispo, Santa Barbara and Monterey counties.
The Vine Mealybug has 5 to 7 generations per year, enabling populations to grow very rapidly. Unlike
other mealybugs, all life stages of the VMB can be present year-round on a vine. During winter months,
eggs, crawlers, nymphs, and adults are found under bark, within developing buds, and on roots.
Prevention: The female VMB can easily be transported through contaminated nursery stock, equipment,
personnel as well as birds and other wildlife. Vineyard managers need to employ strict biosecurity and
sanitation in the vineyard. Best Management Practices (BMP) in the vineyard and at the wineries that
process the grapes can reduce the spread of VMB. Monitoring vineyards for the presence of VMB by
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Risk Assessment
detection trapping is essential to the early detection and successful treatment of the pest. It is unlikely
that VMB will be eradicated from most vineyards.With early detection and vigilant treatment VMB
populations can be kept in check.
Glassy-winged sharpshooter (GWSS):The Glassy-winged sharpshooter(Homa(odisca coagu(ata) is an
insect that poses a significant hazard to California agriculture.When feeding, it can transmit Pierce's
disease, caused by the bacterium, Xylella fastidiosa, to grapevines, and other diseases to almond trees,
alfalfa, citrus and oleanders. First detected in California in 1994, this insect has spread throughout
Southern California and into the southern San Joaquin Valley. The first major infestation in California
occurred in 1999 in Temecula, where more than 300 acres of vineyards were destroyed.
Figure 5-25 Glassy-winged Sharpshooter
,r r
M
The Glassy-winged sharpshooter is considered a serious threat to San Luis Obispo County's multimillion-
dollar wine industry because it spreads bacteria that cause a lethal disease to grape plants. It is also a
nuisance to homeowners because it deposits a sticky residue on plant.
Localized infestations have been found in San Luis Obispo County, although these are believed to be
eradicated. A single glassy-winged sharpshooter was found in a trap in July 2017; additional inspection
and survey found no additional sharpshooters in the area, and no signs of an established breeding
population were detected.
Prevention: The San Luis Obispo County Agricultural Commissioner's Office (SLOCACO) is in partnership
with the California Department of Food and Agriculture (CDFA), the United States Department of
Agriculture, the University of California, and other county Agricultural Commissioner's offices to
collaborate with the Pierce's Disease Control Program (PDCP). The PDCP works to minimize the statewide
impact of Pierce's Disease and the Glassy-winged sharpshooter. The strategy is to slow or stop the spread
of GWSS while both short and long-term solutions to Pierce's disease are developed.
This strategy relies on the following five elements:
• Containing the Spread
• Statewide Survey and Detection
• Rapid Response
• Outreach
• Research
The bulk of the SLOCACO's efforts have been in excluding the sharpshooter from San Luis Obispo County
and implementing a detection program most heavily weighted in nursery and urban settings. The
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Risk Assessment
exclusion efforts for the program consist mainly of inspecting incoming plant shipments from infested
portions of the state bound for wholesale and retail nurseries throughout San Luis Obispo County.
The detection efforts for the program consist mainly of deploying insect traps in nursery and urban
residential areas. Monitoring of the traps is performed every two weeks along with periodic relocation of
the traps.
Pine Pitch Canker:A condition that is threatening the health of the Monterey pine trees in the Cambria
area is the Pine Pitch Canker (Fusarium subglutinans pini). This disease, native to Mexico and the
southeastern United States, was first found in California in 1986. Since then, it has been found in 16
counties, and is spread by insects, the use of contaminated tools, and the transport of infected wood. The
Pine Pitch Canker is considered to be a significant threat to the continued survival of the Monterey Pine
ecosystem. Large native stands of the trees are now only found in the Ano Nuevo, Monterey, and Cambria
areas. If a tree becomes infected with the Pine Pitch Canker, the disease can spread quickly, and can result
in the rapid death of the tree. If an infected or dead tree is not properly removed, it not only becomes a
threat to spread the disease, but can also result in a safety threat, as a large dead tree is a fire hazard as
well as presenting the potential to become uprooted and to fall during a storm.This pathogen is also a
serious concern to the commercial nursery industry.
Prevention: Preventative measures consist of pest detection, exclusion and eradication in production
nursery settings, and informing the public and nursery industry about the dangers of moving infected
plant material out of infested areas.
Light Brown Apple Moth:The Light Brown Apple Moth (Epiphyas postvittana), is native to Australia and
is found in New Zealand, the United Kingdom and Hawaii. The range of host plants is broad with more
than two-thousand plant species known to be susceptible to attack by this pest, and more than 250 crops.
It threatens California's environment—including cypress and oak trees—by destroying, stunting or
deforming young seedlings and damaging new growth in the forest canopy. The moth also feeds on host
plants and damages or spoils the appearance of ornamental plants, citrus, grapes, and deciduous fruit
tree crops. In 2010, nine coastal California counties were under quarantine for the presence of this pest.
State and federal agriculture officials are currently developing sterile insect technology to combat the
infestation. In 2015, light brown apple moths were identified in the city of San Luis Obispo for the first
time.
Prevention: Preventative measures consist of pest detection, exclusion and eradication.
Figure 5-26 Light Brown Apple Moth
y � p
in/i L
San Luis Obispo County Local Hazard Mitigation Plan I October 2019 Page 5-83
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Risk Assessment
During the review process, a Hazard Mitigation Planning Committee member representing the San Luis
Obispo County Department of Agriculture noted that as of 2019, the Light Brown Apple Moth is
established across most of coastal California, and that efforts are underway to de-classify this species as
an official rated pest insect. While the Light Brown Apple Moth remains in the 2019 Hazard Mitigation
Plan, future versions may remove this pest from consideration.
Asian Citrus Psyllid/Citrus Greening Disease (Huanglongbing): The Asian citrus psyllid (ACP) is a pest
that acts as a carrier or vector spreading "huanglongbing", a devastating disease of citrus trees. This
bacterial disease is transmitted to health trees by the psyllid after it feeds on infected plant tissue.
ACP was first identified in San Luis Obispo County in March 2014 in Arroyo Grande. In response to the
identification, the San Luis Obispo Agriculture Department implemented a quarantine in a five-mile radius
from the site. The quarantine required growers and nursery owners to use pesticides to eradicate any
ACP before moving fruit or trees out of the area. Numbers of the ACP identified in San Luis Obispo
County have been steadily on the rise; according to the California Department of Agriculture, more than
100 invasive insects were found in southern San Luis Obispo County (specifically in the Nipomo area) in
2018; this was triple the number found in 2017. The County has a proactive detection program, with
approximately 2,000 traps set up around the county, mostly in the South County.
Symptoms and Impact: ACP damages plants directly through its feeding activities; new shoot growth
that is heavily infested by psyllids does not expand and develop normally and is more susceptible to
breaking off. While direct damage is serious, there is even greater concern that the psyllid is an efficient
vector of the bacterium that causes the economically devastating disease citrus greening, or
huanglongbing.
Prevention: The California Department of Food and Agriculture tracks the presence of pests and disease
and establishes quarantines to help protect California citrus trees.
Invasive Shot Hole Borer/Goldspotted Oak Borer: The goldspotted oak borer (GSOB) is an invasive
pest contributing to the ongoing oak tree mortality; it is a concern for both native oaks and oak
woodlands. The invasive shothole borer are potential pests for agriculture, native trees and urban forests.
The insects can attack over 110 tree species, including sycamore, cottonwood, alder, willows and
boxelders.
As of March 2019, these insects have not been located anywhere in San Luis Obispo County, but have
been found in surrounding areas. The University of California Cooperative Extension notes isolated areas
of infestation in Riverside, Orange and Los Angeles counties.
Symptoms and Impact: Widespread tree mortality caused by borer beetles can have severe implications
and impacts to the environment and human safety, including tree death and increased wildfire danger.
Prevention: Most of the prevention activities undertaken by the county revolve around public
information and awareness. Many wood-boring pests are spread by the transport of infested wood
material. According to the University of California Agriculture and Natural Resources, researchers believe
that the goldspotted oak borer may have traveled to California from Arizona on infested firewood.
Refraining from moving firewood, proper disposal of infested material and proper pruning are
recommended to prevent the spread of these pests.
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Risk Assessment
Sudden Oak Death:A disease of oak trees and more than one hundred other plant species, Phytophthoro
ramorum (or Sudden Oak Death), has been found throughout much of coastal California, and was
identified in San Luis Obispo County for the first time in 2016 in Bay Laurel Trees. This disease has killed
over a million trees in Coastal California forests and has the potential for broad ecological changes to
natural areas, including significantly increasing the risk of wildfire.
Figure 5-27 Sudden Oak Death
4
V
This pathogen is also a serious concern to the commercial nursery industry.
Symptoms and Impact: On oaks and tanoak, cankers are formed on the stems. Cankered trees may
survive for one to several years, but once crown dieback begins, leaves often turn from green to pale
yellow to brown within a few weeks.
Figure 5-28 Bleeding Ooze from a Canker on an Oak
! .0 Y` .
"gyp
Black or reddish ooze often bleeds from the cankers, staining the bark, as well as killing the mosses that
grow on it. Bleeding ooze may be difficult to see if it has dried or has been washed off by rain. Necrotic
bark tissues surrounded by black zone lines are present under affected bark. Because these symptoms can
also be caused by other Phytophthora species, laboratory tests must be done to confirm pathogen
identity. Infected coast live oaks sometimes gradually lose their leaves and fade out slowly. If bleeding
oaks and leaf spots on bay laurel or other symptomatic hosts are adjacent to one another, the presence of
Phytophthora romorum is likely.
San Luis Obispo County Local Hazard Mitigation Plan I October 2019 Page 5-85
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Risk Assessment
Prevention: Preventative measures consist of pest detection, exclusion and eradication in production
nursery settings, and informing the public and the nursery industry about the dangers of moving infected
plant material out of infested areas.
Quagga/Zebra Mussels: Quagga/Zebra mussels are non-native freshwater mussels from eastern Europe
that clog waterways, undermine healthy lake ecosystems, ruin boat engine cooling systems, and
financially burden water resources agencies. Prolific breeders, these mussels can overrun a lake causing
hundreds of thousands of dollars'worth of damage annually. Rapid reproduction can negatively disrupt
an ecosystem in a short amount of time. Once these mussels are introduced into a waterway, there is no
way to fully eradicate the species.
Figure 5-29 Quagga/Zebra Mussels
1. _3
According to the daily USGS Nonindigenous Aquatic Species Database, no reported Quagga/Zebra
mussels have been found in waterways in the county as of January 28, 2019, though occurrences have
been reported both north and south of the county.
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Risk Assessment
Figure 5-30 Zebra and Quagga Mussels Sightings Distribution Map
Zebra and Quagga Mussel Sightings Distribution
Dreissena polymorpha and D-rostriformis bugensis
■
■
r
Quagga
Zebra MUSSO
Mas&el
■
■ ■
■
�r
■
r ■
■
■Zebra mussel occurrencesA
4 :]Quagga mussel occurrences
AL Zebra or Quagga mussel occurrences .
''3 Both species occurrences _
■ZebralQuagga mussels eradicated
Mep produced by the U.S.Gea'ogkal Survey l-I ZebralCQuagga mussels failed
Nonmdgg us Rquakc Species Database.January 28 2019 _
Source: USGS;San Luis Obispo County general area noted by red square
Prevention: California has passed the Dreissenid Mussel Prevention Program, which requires vulnerability
assessments on uninfested reservoirs and development of programs to prevent the introduction of the
mussels, including public information, monitoring and management of recreational activities. San Luis
Obispo County currently engages in a public information campaign to spread information regarding this
invasive species.
Probability of Future Occurrences
While probability of future occurrence is usually calculated based on past experience, different pests have
different recidivism rates across the county. Based on past experience, pests and invasive species will
continue to present a constant threat to the county and its jurisdictions.
Climate Change Considerations
California's Fourth Climate Change Assessment (2018) notes that"climate change impacts terrestrial
ecosystems and wildlife in multiple ways, including invasion by exotic species, prevalence of wildlife
disease, and loss of native habitats." Changing climate conditions can impact viable living areas of species
and cause migration; changing habitat temperatures can make previously undesirable habitats welcoming
for new species and lengthen habitable seasons.
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Risk Assessment
Vulnerability
General Property
Grapes (glassy winged sharpshooter, vine mealybug), trees (pine pitch canker, light brown apple moth,
sudden oak death) and reservoirs and waterways (zebra mussels) are all at risk from invasive species and
pests. An infestation of agriculture pests could impact crop yields, potential destroying whole fields.
Zebra mussels can cause damage to water-based property, including boat engines.
Between 2015 and 2018, the RMA paid no indemnities due to damage from insects, and $22,900 in
indemnities due to damage from crop disease.
People
A widespread infestation of animals/livestock and crops could impact the economic base of the county
and its communities. According to the USDA 2012 Census of Agriculture, San Luis Obispo 2,666 farms, -
4% change from the previous census in 2007. Jobs could be negatively impacted during an agriculture
emergency;jobs tangentially tied to the agriculture industry could also be affected.
Disease can exacerbate the impacts from other hazards, and an example of this is adverse weather; dead
branches can be broken by high winds, and there are reports of these branches falling and causing harm
to people.
Social Vulnerability
Based on the SoVI data presented and discussed in subsection 4.4.1, the communities located in north
county San Luis Obispo where much of the grape production activities take place in the county are also
ranked as having the highest overall social vulnerability, including San Miguel and Paso Robles. These
communities as well as those working in the agricultural sector in south county, would likely be impacted
by the effects of agricultural hazards compared to coastal areas of the county.
Critical Facilities and Infrastructure
The major pest/invasive species identified in this section with the potential to impact critical infrastructure
is the quagga/zebra mussel. In large concentrations, zebra mussels can accumulate in waterways,
clogging pipes and damaging equipment used for drinking water and irrigation. As discussed previously,
dead trees can exacerbate the impacts of other hazards; more information on this hazard can be found in
the Vulnerability section of the Adverse Weather section. Additionally, dead trees can accelerate the
spread of wildfire, adding to the vulnerability of infrastructure; analysis of wildfire risk in relation to parcels
is located in the Adverse Weather section as well.
Economy
According to the University of California's Center for Invasive Species Research, it has been estimated in
California alone that invasive pests cost the state at least $3 billion per year. Nationally, it is estimated
that invasive species cost the USA $138 billion per year. Economic impacts include both prevention,
response and recovery costs.
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Risk Assessment
Historic, Cultural, and Natural Resources
Invasive species typically harm native species through predation, habitat degradation and competition for
shared resources;they can muscle native species out of natural habitats and are a leading cause of
population decline and extinction in animals.
Tree mortality raises the wildfire threat in healthy forests, increasing the vulnerability, strength, speed and
destruction of fires in the area.
Future Development
Most likely, good development practices in the future would not have an impact on the planning area's
vulnerability to agricultural pests, plant diseases, marine invasive species or tree mortality.
Risk Summary
• The overall significance is Medium
• San Luis Obispo is vulnerable to a variety of plant diseases, infestations and invasive species; not all
pests identified in this section
• Rapid detection, response, efforts are essential to stop the spread of agricultural pests, plant diseases
and marine invasive species
• Infestations, pests and invasive species could cost millions in response and recovery
• There are public programs in place regarding prevention, response and eradication to pests and
infestations
• Risk Management Agency (RMA) crop indemnities for insect and disease damages have been
relatively low compared to total crop value
• Infestations, pests and diseases can worsen impacts from other hazards including wind and drought,
and can cascade into other hazards including infrastructure failure and wildfire
• Related hazards:Adverse Weather, Drought, Wildfire
Figure 5-31 Risk Summary by Jurisdiction
Jurisdiction Geographic Area Probability of Magnitude/ Overall
Future Severity(Extent) Significance
Occurrence I
San Luis Obispo Limited Highly Likely Negligible Medium
County
City of Arroyo Grande Limited Highly Likely Negligible Medium
City of Atascadero Limited Highly Likely Negligible Medium
City of Grover Beach Limited Highly Likely Negligible Medium
City of Morro Bay Limited Unlikely Negligible Low
City of Paso Robles Limited Limited Unlikely Low
City of Pismo Beach Limited Unlikely Negligible Low
City of San Luis Obispo Limited Highly Likely Negligible Medium
Avila Beach CSD Limited Unlikely Negligible Low
Ground Squirrel Hollow Limited Unlikely Negligible Low
CSD
Heritage Ranch CSD Limited Unlikely Negligible Low
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Risk Assessment
OverallJurisdiction Geographic Area Probability of Magnitude/
OccurrenceFuture Severity(Extent) Significance
Los Osos CSD N/A
Nipomo CSD Limited Unlikely Negligible Low
San Miguel CSD Significant Occasional Limited Medium
San Simeon CSD Significant Likely Limited Low
Templeton CSD N/A
Cayucos Sanitary Limited Unlikely Negligible Low
District
Port San Luis Harbor Extensive Unlikely Negligible Low
District
San Luis Obispo Limited Highly Likely Negligible Low
FCWCD
South San Luis Obispo Limited Highly Likely Negligible Medium
Sanitary District
San Luis Obispo County Local Hazard Mitigation Plan I• •0
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Risk Assessment
5.3.6 Biological Agents (Naturally Occurring)
Hazard/Problem Definition
Public health associated hazards may be naturally occurring or the result of malevolent acts such as
terrorism. The Hazard Mitigation Planning Committee determined in 2013 that this plan should focus on
naturally occurring hazards such as pandemic flu and flood and waterborne illnesses;the 2019 update
follows this precedent. Terrorism and other homeland security concerns are addressed separately by the
county's Office of Emergency Services.
The following diseases caused by naturally occurring biological agents possess epidemic potential for San
Luis Obispo County.
Influenza (Pandemic)
Influenza viruses have for centuries threatened the health of humans and animals worldwide by causing a
contagious respiratory illness with mild to severe severity. Annual influenza epidemics create a significant
public health burden with the highest risk of complications occurring in the elderly, children under the
age of 2, and individuals with prior medical conditions. This virus' diversity and propensity for mutation
has prevented the development of both a universal vaccine and highly effective antiviral drugs. Ongoing
concern exists over the potential emergence of a new strain of influenza with the ability to infect and be
passed between humans. Because humans won't have immunity to this novel virus, a worldwide epidemic
(pandemic) could result as recently occurred.
Three human influenza pandemics have occurred in the 20th century each resulting in illness in
approximately 30 percent of the world population and death in up to 2 percent of those infected. The
1918 Spanish Influenza (H1 N1) pandemic occurred towards the end of World War I. More people died
during the flu pandemic than were killed during the entire war.The influenza death toll was an estimated
50-100 million worldwide. In the United States, about 675,000 died. The 1957 Asian Influenza (1-121\12)
pandemic killed 1-2 million worldwide and caused approximately 70,000 deaths in the United States. The
third pandemic, the Hong Kong Influenza (1-131\12), occurred in 1968-69 and killed an estimated one million
people worldwide.
More recently, a novel influenza virus emerged, the 2009 H1N1, which spread worldwide and caused the
first flu pandemic in over 4 decades. In the U.S., the Centers for Disease Control and Prevention (CDC)
believed H1 N1 may have been responsible for up to 17,000 deaths as of May 2010. According to the
California Department of Public Health, 2018 was an especially strong flu season in the Golden State.
San Luis Obispo County is proactive in prevention and education efforts every flu season, ensuring
residents are informed of the dangers of the flu and encouraging flu shots and other prophylactic
measures.
Prevention: Preventing transmission of influenza virus and other infectious agents within healthcare
settings requires a multi-faceted approach. Spread of influenza virus can occur among patients, healthcare
personnel, and visitors. Additionally, healthcare personnel may acquire influenza from persons in their
household or community.
Prevention strategies include:
0 Administration of influenza vaccine
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Risk Assessment
• Implementation of respiratory hygiene and cough etiquette
• Appropriate management of ill healthcare personnel
• Adherence to infection control precautions for all patient-care activities and aerosol-generating
procedures
• Implementing environmental and engineering infection control measures.
General public prevention measures include:
• Educating the public on cough etiquette and basic personal hygiene
• Immunization with available influenza vaccine
Once an epidemic has been identified, the County of San Luis Obispo County Public Health Department
will respond in the following manner:
1. Investigate the epidemic to determine its etiology, level of severity, mode of transmission, and
persons affected and at risk.
2. Determine and institute control measures to prevent further spread.
3. Communicate control measures to the public and healthcare professionals.
The San Luis Obispo Community Health Assessment, published in July 2018 notes that nationally, an
estimated 200,000+ people are hospitalized each year due to flu-related complications. The report notes
that from 2014-2016, less than half(41%) of people in the county received their annual flu shot— lower
than the state overall in the same period. Between 2000 and 2010, an average of 43 deaths per year
occurred in the county with a primary cause of influenza or pneumonia. Influenza/pneumonia was the 91h
leading cause of death in the county between 2005 and 2013.
Novel Infections (SARS et al)
Novel infections, particularly those of viral origin, pose a tremendous risk to public health because the
general public has no immunity from prior infections or vaccination, and because a vaccine is not readily
available. For influenza viruses, it takes at least six months to produce large quantities of vaccine. For
other viral pathogens such as HIV, a vaccine that protects individuals against HIV infection has been the
goal of many research programs for the past two decades, yet only in the past few years has a vaccine
reached the clinical trial stage.
Vaccines, which are believed to work by activating the body's ability to produce antibodies, eliminated or
curtailed smallpox, polio and other feared viral diseases.
One novel virus that took the world by surprise was the appearance of the Severe Acute Respiratory
Syndrome (SARS) virus in China at the end of 2002. Within months, this coronavirus spread
internationally, with the help of air travel, resulting in 8,098 cases in 26 countries with 774 deaths
occurring.
Prevention: Preventative measures consist of preparedness planning to enable the rapid detection,
investigation and detainment of unexplained clusters of illness or death. Isolation of persons with
unexplained potentially infectious disease may be indicated.
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Risk Assessment
Food and Waterborne Illness
Food and waterborne illnesses are major global health problems resulting in over 2 million deaths per
year. In the United States alone, an estimate 76 million cases of foodborne disease occurs annually
resulting in 325,000 hospitalizations and 5,000 deaths.
The following biological agents have been historical threats to the food and water supply in this county.
• Staphylococcus aureus
• Salmonella species
• E. coli 0157: H7
• Campylobacter species
• Amebiasis
• Hepatitis A
• Shigella species
Food-borne outbreaks are identified by the presence of illness shortly following a meal. Illness can occur
within a few hours and up to several weeks. Symptoms range from mild to severe:
• Upset stomach
• Abdominal cramps
• Vomiting
• Diarrhea
• Fever
• Dehydration
Intrinsic problems in food or water production, processing, storage, distribution, or preparation can all
result in contamination of the food supply. Because food production and distribution practices are
constantly changing, new unforeseen problems will continue to emerge. The need for ongoing
monitoring and control efforts is essential.
Prevention: Preventative measures are based on the principles of: avoiding food contamination,
destroying contaminants, and preventing further spread. Specifically, these include:
• Education of food handlers about sanitation, food and personal hygiene, kitchen cleanliness,
temperature control, thorough cooking of animal related food products and hand washing before,
during and after food preparation.
• Reducing food-handling time from initial preparation to service to be no more than 4 hours at
ambient temperature.
• Teaching food handlers, the importance of keeping wounds covered and not working with nasal or
eye infections, boils, abscesses or other purulent skin lesions.
• Exclude individuals with diarrhea from food handling and from care of hospitalized patients, the
elderly and children.
• Education of farmers on the importance of sanitary work practices and safe food preparation and
transportation.
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Risk Assessment
Antibiotic Resistant Microorganisms (e.g. MRSA, MDR and XDR-TB)
MRSA: Methicillin-resistant Staphylococcus Aureus (MRSA) is a bacterium that is resistant to certain
antibiotics called beta-lactams. These antibiotics include methicillin and other more common antibiotics
such as oxacillin, penicillin, and amoxicillin. In the community, most MRSA infections are skin infections.
More severe or potentially life-threatening MRSA infections occur most frequently among patients in
healthcare settings.While 25%to 30% of people are colonized in the nose with staphylococcus, less than
2%are colonized with MRSA.
MRSA Community Transmission: MRSA infections, as with all Staphylococcus, are usually spread by having
contact with someone's skin infection or personal items they have used, like towels, bandages, or razors
that touched their infected skin. These infections are most likely to be spread in places where people are
in close contact with others—for instance, schools and locker rooms where athletes might share razors or
towels.
Factors that have been associated with the spread of MRSA skin infections include: close skin-to-skin
contact, openings in the skin such as cuts or abrasions, contaminated items and surfaces, crowded living
conditions, and poor hygiene. People may be more at risk in locations where these factors are common,
including: athletic facilities, dormitories, military barracks, households, correctional facilities, and daycare
centers.
Prevention: Preventative measures consist of good hygiene practices, using Standard Precautions in
healthcare settings and patient education.
MDR and XDR Tuberculosis:Tuberculosis (TB) is a disease caused by the infectious bacterium
Mycobacterium tuberculosis. It is responsible for 1.7 million deaths globally each year(230,000 are HIV
associated cases). Person to person transmission of TB occurs when droplet nuclei are inhaled (typically
occurs after sustained or recurrent exposure to an infected patient from coughing, sneezing, talking,
singing or spitting). The aerosolized particles (bacilli) are inhaled into the lungs and subsequently
ingested by alveolar macrophages initiating a new infection. The treatment regimen for infected patients
involves multiple drug therapy for a minimum of 6 months. If not properly treated, TB can be fatal.
Outbreaks of multidrug-resistant TB (MDR-TB) defined as exhibiting resistance to at least isoniazid and
rifampicin, have occurred primarily in settings where HIV-infected persons congregate such as hospitals,
prisons, drug treatment clinics and HIV residences. These outbreaks have been associated with high
fatality rates. Transmission of M.tuberculosis to healthcare workers and other patients also occurred.
Recently, extensively resistant TB (XDR-TB) has emerged. This is defined as MDR-TB plus resistance to any
fluoroquinolone and any of the three injectable drugs (amikacin, capreomycin and kanamyin). Outbreaks
have primarily occurred in situations where the use of second-line TB drugs has been used and poorly
managed. A 2005-2006 outbreak in South Africa resulted in a 98%fatality rate and a median survival rate
of 16 days from the date of XDR-TB diagnosis.
Prevention: Preventative measures include: 1) Promptly identifying and treating infectious patients, 2)
Active case finding for secondary cases of TB amongst contacts with subsequent treatment, 2) Public
education, 3) Reducing overcrowding, and 4) Providing outreach services for direct supervision of patient
therapy.
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Risk Assessment
Vector-Borne Diseases
One area of particular concern for the County of San Luis Obispo is the limited surveillance for vector
borne diseases such as West Nile Virus. Surveillance efforts throughout California have been extensive,
including human and horse case detection, and WNV testing of mosquitoes, sentinel chicken flocks, and
dead birds. Because San Luis Obispo County is one of the few remaining counties in California without a
Vector Control District, the risk of vector borne diseases increases.
Environmental Hazard
Valley Fever (coccidioidomycosis):Valley Fever is an illness caused by breathing in a fungus which lives
naturally in the soil in San Luis Obispo County. When the soil is disturbed— by wind, construction, or
everyday activities such as biking or gardening — people can breathe in the spores from this fungus and
develop Valley Fever.
Most people who become infected with Valley Fever(60%) do not experience any symptoms and do not
need treatment. Around 30%-40% of people develop flu-like symptoms such as severe fatigue, cough,
fever, heavy sweating at night, loss of appetite, muscle and joint aches, and sometimes a rash. A small
percentage experience a much more serious form of the disease in which the infection spreads
throughout the body. People who experience this serious form of Valley Fever are at risk of dying from
complications of the disease and may need to take medication for the rest of their lives. Valley Fever is
more common among older adults, though anyone of any age can contract it. Several groups of people
are at higher risk for developing the severe forms of Valley Fever, including African Americans, Filipinos,
women in the third trimester of pregnancy, and people with weak immune systems.
According to the County of San Luis Obispo Public Health Department, Valley Fever appears to be on the
rise in recent years, with 2017 bringing the highest number of recorded cases on record to California. A
March 2013 Morbidity and Mortality Weekly Report published by the Centers for Disease Control and
Prevention (CDC) and referenced in the 2018 California State Hazard Mitigation Plan notes that more than
20,000 cases of Valley Fever are reported each year in the United States, but many more cases likely go
undiagnosed. Some researchers estimate that each year the fungus infects more than 150,000 people,
many of whom are sick without knowing the cause or have symptoms so mild they are not recognized.
Prevention: Persons can limit their risk of Valley Fever by taking steps to avoid breathing dirt and dust in
the air, avoiding dusty areas, dampening soil to prevent it from drifting in the air, staying inside and
sealing windows during dust storms, and closing car windows and setting air conditioners to recirculate
while driving on dust-filled roads.
Mosquito-Borne Illness: Mosquito-borne viruses belong to a group of viruses commonly referred to as
arboviruses. Although 12 mosquito-borne viruses are known to occur in California, only West Nile Virus,
Western Equine Encephalomyelitis (WEE) virus and St. Louis encephalitis (SLE) virus are significant causes
of human disease. West Nile continues to seriously affect the health of humans, horses, and wild birds
throughout the state. As of 2019, San Luis Obispo County does not provide mosquito abatement services.
Zika virus has been found in California, but according to the California Department of Public Health, Zika
infections in the state have mainly been reported in people who were infected while traveling in areas
outside of California with ongoing Zika transmission. As of 2019, there are no records of local
transmission of Zika anywhere in California.
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Risk Assessment
Prevention: The CDC recommends insect repellant, covering exposed skin and making sure mosquitoes
stay outdoors as methods of preventing insect bites and disease transmission.
Lyme Disease: Lyme disease is transmitted by the western black-legged tick. Lyme disease was first
described in North America in the 1970s. Though the tick has been reported in 56 of the 58 counties in
California, the highest incidence of the disease occurs in the northwest coastal counties and northern
Sierra Nevada counties with western-facing slopes. According to the California Department of Public
Health, San Luis Obispo County is in an area where the western black-legged tick is commonly found;
however, Lyme disease cases are not common or go unreported.
Prevention: Risk factors for Lyme disease include spending time in wooded or grassy areas, having
exposed skin and not removing ticks promptly and properly. Prevention techniques include covering up,
using insect repellents, checking clothing, yourself, children and pets for ticks, and removing a tick as soon
as possible with tweezers.
Geographic Area
Disease outbreaks usually occur in densely populated areas, where person to person proximity provides
ample opportunity for transmission of illnesses. Places of work and business, schools and high-
population public spaces are of particular concern when the threat of transmissible illness occurs.
Vector-borne illness are concentrated around the vector they are transmitted by: the risk of Lyme disease
is highest in wooded areas, and mosquito-borne illnesses are most prevalent around standing water. Due
to its prevalence in the soil across the county, Valley Fever is of concern throughout the planning area.
Extent (Magnitude/Severity)
The diseases with the potential to have the most impact is novel influenza and pandemic flu, which has
the potential for high morbidity(infected) and mortality(fatality) rates. This could include treatment and
hospitalization of hundreds or more depending on the severity of the outbreak.
Previous Occurrences
The Community Health Assessment published in July 2018 provides historical disease counts in San Luis
Obispo County between 2010 and 2017.
West Nile Virus: The Community Health Assessment notes that statewide, cases of West Nile virus rose
from 442 in 2016 to 516 in 2017; while the last reported case of the virus in the county occurred in 2016,
West Nile continues to be present in the county, as testing of dead birds has confirmed.
Lyme Disease: There were 11 reported cases of confirmed Lyme disease among San Luis Obispo
residents from 2006-2015, or an incidence rate of 0.4 per 100,000 population.
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Risk Assessment
Valley Fever: The following figure notes Valley Fever cases in San Luis Obispo County from 2010-2017.
vofi y r`evo case.S, _S011 LUIS OWSPO COW)ty, Z(J i!
368
257
225
135
142
82
5
33
2010 2011 2012 2013 2014 2095 2016 2017
5ourcv County of Saa Cies obispo Pubf c Health Depnrtmeol
According to the CDC, while the reasons for the increased incidence in Valley Fever in 2016 are not
known, climatic and environmental factors favorable to Valley Fever proliferation and airborne release
might have contributed, including rainfall after several years of drought and soil disturbance resulting
from construction. The UC Davis Valley Fever Center attributes the increase in cases to drought
conditions and firefighting equipment stirring up fungus in the soil.
Foodborne Illnesses: In San Luis Obispo County in 2017, reported cases of foodborne illness included 72
cases of campylobacter, 16 cases of E. coli, no cases of listeria, 29 cases of salmonella, and 8 cases of
shigella. While it is possibly the most common cause of gastrointestinal disease, data is not available for
norovirus as health care providers are not required to report it to the Public Health Department.
Antibiotic Resistant Microorganisms: The CDC reported in 2016 that for the first time, researchers have
identified a person in the United States carrying a bacteria resistant to antibiotics of last resort, an
alarming development that could mean the "end of the road"for antibiotics.
Probability of Future Occurrences
The potential exists within the entire county and in all regions of the U.S. for an outbreak of an infectious
disease to occur that would dramatically affect the health and safety of the general public and the
economy of the affected area, state and possibly nation. The County of San Luis Obispo Public Health
Department has been proactive in its infection control surveillance efforts and in its emergency
preparedness planning activities.
The San Luis Obispo County Community Health Assessment notes annual recurrence in cases of Valley
Fever and Lyme Disease between 2010 and 2017, or a 100% annual recurrence rate. For Lyme Disease,
the Assessment notes cases in 2011-2017 (none reported in 2010), or an 87.5% chance of recurrence per
year. Foodborne illnesses are an annual occurrence in the county.
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Risk Assessment
No known cases of Zika Virus transmission have been recorded in the county or the State of California,
though once case of travel related Zika was reported in the county in 2016;this constitutes a 0%
recurrence interval.
The Community Health Assessment notes that nationally, it is estimated that 5%to 20% of the population
is infected with influenza, though rates of infection vary among age groups. The Assessment also notes
that between 2000 and 2010, an average of 43 deaths per year occurred in San Luis Obispo County with a
primary cause of influenza or pneumonia.
The greatest ongoing concern national health agencies have is the potential emergence of a novel
influenza virus as recently occurred with the 2009 H 1 N 1 pandemic. For the past several years, federal,
state and local governments have been actively engaged in pandemic influenza preparedness planning
efforts. The County of San Luis Obispo Public Health Department has an up-to-date Pandemic Influenza
Plan and Medical Countermeasure Plan. While influenza is an unpredictable virus, these preparedness
measures will facilitate prevention, early detection and treatment when the next pandemic does strike.
Globally, an average of three pandemic influenza outbreaks have occurred per century over the past 300
years.
Climate Change Considerations
Climate change will likely affect vector-borne disease transmission patterns. Changes in temperature and
precipitation can influence seasonality, distribution, and prevalence of vector-borne diseases. A changing
climate may also create conditions favorable for the establishment of invasive mosquito vectors in San
Luis Obispo County, and dry conditions have the potential to exacerbate prevalence of Valley Fever.
Vulnerability
General Property
Historically, naturally occurring biological agents and vector-borne illnesses do not have a direct impact
on general property.
People
The health of the general public is the main impact from naturally occurring biological agents. Each
disease has its own morbidity and mortality rates, as well as various rates and vectors for transmissibility.
Specific impacts of diseases profiled in this section are included in the Hazard/Problem Definition section.
As a worst case scenario, the most notable pandemic influenza outbreak was the 1918 Spanish Flu that
was responsible for 20 million to 40 million deaths throughout the world. In 2009, a pandemic of H1 N1
influenza, popularly referred to as the swine flu, resulted in many hospitalizations and deaths.
Social Vulnerability
The areas of the county that have the highest overall social vulnerability, based on the SoVI data
discussed and presented in subsection 4.4.1, will also be the most vulnerable to the effects of naturally
occurring biological agents and pandemics. Outreach and public education efforts related to these
hazards should be focused on the communities that are among the highest social vulnerability in the
county.
Critical Facilities and Infrastructure
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Risk Assessment
While biological agents and vector-borne illnesses would not have direct structural impacts on critical
facilities and infrastructure, the potential exists for impacts to critical facility and infrastructure operation.
A widespread disease and any associated social distancing could cause absenteeism at the workplace.
Disease and illness could also cause pressure on the county's public health system, with an outsized
number of patients seeking treatment and the potential for a diminished number of health care workers
to meet the demand.
Economy
Disease mainly has an impact on economic drivers, including commerce. The risk of disease exposure
may cause consumers to avoid brick and mortar establishments, though e-commerce may not be as
affected. Social distancing put in place to limit exposure to and spread of disease may also impact
workplace efficiency, as people stay home and away from public places. Additionally, tourism may be
impacted in affected areas.
Historic, Cultural, and Natural Resources
By and large, impacts from naturally occurring biological agents are focused on people; biological agents
would not have an adverse impact to historic, cultural or natural resources.
Future Development
No impacts to future development are expected from this hazard.
Risk Summary
• San Luis Obispo County and its population is vulnerable to a variety of different naturally occurring
diseases
• Ongoing Public Health surveillance and emergency preparedness planning activities are geared
towards minimizing the likelihood and reducing the severity of such an occurrence
• While the greatest impacts in the county from disease occur to populations, secondary impacts
include reduced workplace efficiency and effects on the tourist trade
• Past and recent history dictates that the most likely microorganism to be involved in a local epidemic
or global pandemic is the influenza virus; antibiotic-resistant microbes are also a grave concern
• Due to an increasingly global marketplace for food products, occurrence of significant foodborne
outbreaks is also on the rise
• The continued absence of a Vector Control District within San Luis Obispo County delays the
detection of vector borne disease such as plague, tularemia and West Nile Virus
• Vector-borne illnesses can especially be impacted by environmental factors, including drought
• Due to the multiple biological agents referenced in this section, defining a single significance and
probability rating for this hazard is difficult; scores in the Hazard Risk Summary table below are based
on an outbreak of novel pandemic influenza, likely the worse-case scenario in the county. An overall
significance of Medium is assigned to account for the lower probability of this event.
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Risk Assessment
Table 5-31 Biological Agents Hazard Risk Summary
OverallJurisdiction Geographic Area Probability of Magnitude/
OccurrenceFuture Severity Significance
San Luis Obispo Extensive Occasional Critical Medium
County
City of Arroyo Grande Extensive Occasional Critical Medium
City of Atascadero Extensive Occasional Critical Medium
City of Grover Beach Extensive Occasional Critical Medium
City of Morro Bay Limited Unlikely Negligible Low
City of Paso Robles Limited Limited Unlikely Low
City of Pismo Beach Limited Likely Limited Medium
City of San Luis Obispo Extensive Occasional Critical Medium
Avila Beach CSD Limited Unlikely Negligible Low
Ground Squirrel Hollow Limited Unlikely Negligible Low
CSD
Heritage Ranch CSD Limited Unlikely Negligible Low
Los Osos CSD N/A
Nipomo CSD Limited Occasional Negligible Low
San Miguel CSD Significant Occasional Critical Medium
San Simeon CSD Significant Unlikely Negligible Low
Templeton CSD Limited Unlikely Negligible Low
Cayucos Sanitary Limited Unlikely Negligible Low
District
Port San Luis Harbor Extensive Unlikely Catastrophic Low
District
San Luis Obispo Extensive Occasional Critical Low
FCWCD
South San Luis Obispo Limited Unlikely Negligible Low
Sanitary District
San Luis Obispo County Local Hazard Mitigation Plan I• 00
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Risk Assessment
5.3.7 Coastal Storm/Coastal Erosion/Sea Level Rise
Hazard/Problem Definition
Coastal Storm: Coastal storms are characterized by offshore storm systems that make landfall, bringing
high winds, rain, and storm surges to the coastline (USGS 2018).They originate from the combination of
low-pressure systems offshore that circulate counterclockwise with high-pressure systems that blow in
one direction over a long period of time, which creates a phenomenon of rising water, resulting in
massive waves beyond the normal movement of tides. Coastal storms may have hurricane-force winds
and cause damage similar to that of a hurricane; however, they are not classified as such because they do
not originate in the tropics. The destructiveness of a coastal storm depends on the duration, wind speeds,
and tidal factors, with particularly severe potential for damage where strong storm-generated waves
coincide with high tides or King Tides (exceptionally high tides that occur once or twice a year). Such
storms can exacerbate beach and cliff erosion and increase risks of bluff failure or flooding in low-lying
areas. They have the greatest impact on the coastline and coastal communities in the form of beach and
cliff erosion which can expose bluff top structures or facilities to bluff failure or landslides, and flooding of
low-lying communities due to storm surges and wave energy. During such events, property and
infrastructure in unprotected low-lying areas can be damaged by wave attack or flooding, and evacuation
routes can become inaccessible.When coastal storms coincide with high tides, as well as during EI Nino
years, coastal erosion and flooding hazards substantially increase (Russell &Griggs 2012).
Figure 5-32 Coastal Storm Damage at Pismo Beach, 1982/83 EI Nino
Coastal storms can severely damage coastal development and substantially erode the shoreline,especially when they coincide with EI Nino years;the
1982/83 EI Nino-related storms destroyed coastal structures at Pismo Beach,damaging the Pier,RV park,access trail,and seawall;incurring an
estimated replacement cost of over$5.5 million in Pismo Beach alone(in 2019 dollars)(Dean et al.1984).
Photo credit:Lance Nix
Coastal Erosion: Coastal erosion refers to the natural geological process resulting in loss of sand,
sediment, vegetation, or soil on beaches, dunes, bluffs, or cliffs along the coast caused by the wave attack,
winds, tides, coastal storms, and the gradual movement of tectonic plates. Coastal erosion takes place
gradually over decades to thousands of years, or may occur rapidly, as with landslides or severe storms.
Coastal erosion processes are highly complex and depend on a number of factors such as geologic
formation, groundwater seepage, and exposure to wave energy. The 100 miles of San Luis Obispo County
coastline are variable in terms of geologic composition and exposure to high tides, wave energy and
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Risk Assessment
related erosion. Sections of the coast exhibit a variety of backshore landforms including wide sand and
cobble beaches backed by cliffs, sandy beaches backed by sand dunes, secluded and undeveloped pocket
beaches, rocky intertidal areas, rocky bluffs, and loosely consolidated bluffs. Due to these various
backshore types along the shoreline, erosion characteristics also vary significantly.
Driven by rising sea levels, large storms, flooding, and powerful ocean waves, erosion wears away the
beaches and bluffs along shorelines. Beach and dune erosion occur through high wave run-up during
high tides and increased wave energy that carry sand away from the shoreline. Beach and dune erosion
may occur gradually over time as beaches naturally accrete and erode, resulting in mild changes in the
shoreline and volume of sand present on the beach (Hapke et. al 2006). Energetic coastal storms and
particularly strong EI Nino events potentially result in the abrupt loss of large quantities of sediment and
increased landward retreat of the shoreline.
Coastal bluff erosion also occurs in the form of irreversible landward retreat of coastal bluffs and cliffs
(Griggs 2003). Historical bluff erosion has been episodic in nature with rates that vary throughout San Luis
Obispo County due to the composition of coastline bluff rock formations and vulnerability to wave
interaction with the cliffs. Rising tides, currents, and waves directed at the base of the bluff cause the
erosion of relatively non-resistant rock. As a bluff erodes, the top edge moves landward. This is a natural
process that becomes a hazard as it threatens structures or other developed property, infrastructure, as
well as recreational trails and public coastal access. The retreat of the bluffs threatens waterfront
residences, businesses, and public facilities, eventually rendering them uninhabitable or unusable.
Human alteration of the shoreline can influence long and short-term erosion rates. One of the major
causes of beach erosion is the construction of dams and other structures along creeks and rivers that trap
sediment and prevent it from reaching the ocean. This deprives the shoreline of the material that would
replenish beach sand supplies. Coastal structures such as groins,jetties, seawalls, and breakwaters can
also alter littoral drift. Beach groins and breakwaters, for example, can trap littoral sand and build beaches
over a limited area; but by doing so, they reduce the amount of sand that flows to down-current beaches.
This can result in a rapid loss of beach sand in down-current beaches. Seawalls are often used to protect
seacliffs from eroding wave action. These structures, however, can reflect wave energy to strip protective
beach sand at an accelerated rate. This may ultimately result in increased seacliff erosion rates, particularly
at sections of coastline adjacent to the seawall.
Sea Level Rise: Sea level rise is defined as the relative average rise in mean sea level. Global sea level rise
refers to the long-term gradual increase of sea levels driven by the expansion of ocean waters as they
warm, the addition of freshwater to the ocean from melting land-based ice sheets and glaciers, and
extractions from groundwater. Regional and local factors such as tectonics and ocean and atmospheric
circulation patterns result in relative sea level rise rates that can be higher or lower than the global
average. Sea level rise also contributes to increased coastal flooding and more frequent and severe tidal
inundation. This can exacerbate existing coastal hazards from severe storms, as well as accelerate coastal
beach and bluff erosion. Unlike coastal flooding caused by coastal storms,tidal inundation when combined
with sea level rise would occur with predictable high tides and with some regularity. Existing low-lying coastal
areas are expected to be semi-permanently or permanently inundated resulting from unabated global climate
change and resulting sea level rise. Sea level rise is anticipated to contribute to increased coastal hazards
including coastal storms and coastal erosion (County of San Luis Obispo 2019a).
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Risk Assessment
Geographic Area
The entire 100-mile coastline of San Luis Obispo County and existing urban development and natural
resources are potentially exposed to a range of coastal hazards, including coastal storms and coastal
erosion. Such hazards are projected to become more severe when combined with sea level rise (County of
San Luis Obispo 2019a). The creeks and rivers that drain inland mountains in confluence with the Pacific
Ocean result in an ecologically diverse range of low-lying habitats including bays, inlets, and coastal
wetlands.Additionally, bluffs and dunes line much of the County's coast, including the cities of Grover
Beach, Pismo Beach, and Morro Bay. The coastline also includes five large unincorporated communities
served by Community Services Districts (CSD): Avila Beach, Los Osos, Cambria, Oceano, and San Simeon;
and extensive rural areas (County of San Luis Obispo 2019b).These areas contain a number of popular
recreational beaches such as Pismo Beach, Morro Bay, Cayucos and Moonstone, along with visitor-serving
uses, developed and undeveloped coastal bluffs and trails, two harbors (Morro Bay and Port San Luis), and
a large dune field ranging from the Pismo Dunes through the Guadalupe Dunes. Low-lying portions of
Highway 1, an officially designated State Scenic Highway, which has been damaged by past bluff erosion,
also extend along the coastline. Designated State Parks in the San Luis Obispo Coast District include
Cayucos State Beach, Estero Bluffs State Park, Los Osos Oaks State Reserve, Montana de Oro State Park,
Morro Bay State Park, Hearst San Simeon State Park, and W.R. Hearst Memorial State Beach (Department
of Parks and Recreation 2019). A summary of hazard potential byjurisdiction or urban area within the
county are provided in Table 5-32 below.
Table 5-32 Hazard Potential of Jurisdictions and Urban Areas within the San Luis Obispo
County Coast
Jurisdiction or Urban Area Primary Characteristics and Vulnerabilities
City of Grover Beach Sandy beaches backed by low sand dunes covered with dense
vegetation
• Commercial, residential (i.e. mobile homes) and recreational (golf
course) development
• Active erosion of beaches and dunes, impacts to low-lying coastal
recreational uses, commercial and residential structures
City of Morro Bay Wide sandy beaches and large sand dunes backed by residential and
commercial development on higher elevated terraces
• Includes low-lying development, lagoons,trails, and saltwater marsh
• Active erosion of beaches and dunes, low-lying areas susceptible to
projected sea level rise
• Erosion and landward retreat of bluffs
City of Pismo Beach
• Topography varies from sandy beaches and sand dunes to cliffs and
bluffs ranging from 10 to 100 feet in height
• Commercial and residential development close to the shoreline
• Parks on top of bluffs include Dinosaur Caves Park with trails and a
playground;Chumash Park; Monarch Butterfly Grove
• Erosion of beaches and dunes; erosion and landward retreat of bluffs
threaten residential, commercial, and recreational development
• Development close to the shoreline vulnerable to coastal hazards and
sea level rise
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Risk Assessment
Jurisdiction or Urban Area Primary Characteristics and Vulnerabilities
Avila Beach CSD Southerly-facing wide sandy beach backed by development including
Avila Beach Park,commercial and residential development, and
overnight accommodation
• Avila Beach beaches and recreational Pier protected from northerly
swells by the Point San Luis Breakwater
• Erosion of the sandy beach threatens low-lying commercial, residential,
and recreational development
Los Osos CSD Sand dunes and scenic bluffs of the Los Osos Oaks State Natural
Reserve
• Active erosion of sand dunes and bluffs
• Low-lying development in downtown Los Osos threatened by projected
sea level rise,and inundation from coastal storms and flooding
San Simeon CSD
• Low cliffs and rolling coastal hills of the Hearst San Simeon State Park'
• Supports low-lying areas of Highway 1 with little to no coastal
development
• Erosion of low cliffs, coastal bluff retreat
Cayucos
• Varies from narrow sandy beaches backed by undeveloped bluffs and
sea cliffs;to wider sandy beaches backed by relatively low-lying coastal
development
• Erosion of bluffs and sea cliffs, active erosion of narrow sandy beaches
• Sea level rise and coastal hazards threaten low-lying commercial and
residential development
Port San Luis Harbor District Port San Luis Pier, Boat Yard,and RV Campground backed by 100-foot
high cliffs which descend eastward to lower elevations
• Southerly-facing beach protected from northerly swells by the Port San
Luis breakwater
• Erosion of 30 to 100-foot high cliffs,coastal bluff retreat
• Sea level rise and coastal storms threaten Port San Luis Pier, Boat Yard,
and campgrounds
Cambria
• Rocky shoreline with some areas of narrow beaches backed by low cliffs
approximately 20-50 feet high
• Bluff top residential development and pubic open space such as the
Fiscalini Ranch Preserve
• Bluff retreat,active erosion of sandy beaches
• Projected sea level rise and accelerated bluff erosion threaten bluff top
residential development
Oceano
• Wide sandy beaches backed by low active dunes, residential
development and campgrounds
• Popular for beach and dunes for off road vehicle use
• Active erosion of sandy beaches and dunes
Coastal Storms, Coastal Erosion, and Sea Level Rise by Area
The reported rates of erosion presented in the following sections approximate future coastal erosion rates
and vulnerability due to difficulties in obtaining accurate erosion data.
San Luis Obispo County: The San Luis Obispo County coastline has the potential to be significantly
impacted by coastal storms. Bluff erosion resulting in landward retreat of the seacliffs and beach erosion
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Risk Assessment
may result in landward retreat of the shoreline and impacts to coastal development and infrastructure.
Low-lying areas often located by coastal streams or estuaries are vulnerable to inundation, wave run-up
and flooding associated with projected sea level rise. California's Fourth Climate Change Assessment
notes that periodic EI Nino events exert a dominant control on coastal hazards across the region, driven
by seasonally-elevated water levels as high as 30 cm (11.8 inches) above average, and, on average, 30
percent larger winter wave energy in California (Langridge et al. 2018). Past EI Ninos, including the
extreme 1982-83 and 1997-98 events, caused significant erosion along the Central Coast due to the
elevated winter waves and water levels, but impacts were more acute along the southern ends of littoral
cells due to the more southerly wave approaches driving sand to the north (Langridge et al. 2018).
Further, the large EI Nino event of 2015-16, one of the three largest in the historical record, resulted in
winter wave energy that was over 25 percent larger than a typical winter along the Central Coast and
caused substantial acceleration of beach erosion (State of California 2018).
City of Grover Beach: Grover Beach is fronted by sandy beaches backed by low active dunes that are
covered with dense vegetation, backed by a golf course, a mobile home park and Highway 1. The sandy
beaches provide structures with moderate protection from storm waves. Timber beach access ramps were
damaged, however, during the winter storms of 1983. The Grover Beach shoreline is classified as a
"moderate risk"with respect to possible coastal damage incurred by storm waves.
City of Morro Bay:The Morro Bay coast is fronted by large sand dunes from Atascadero State Beach and
continuing south through much of Montana de Oro State Park that provide protection for developments
located on terrace materials behind the sand dunes. Due to the construction of the Morro Bay Harbor
Breakwater and the presence of Morro Rock, the littoral drift north of Morro Bay is interrupted and the
coast has extended seaward.The beach has widened about 250 feet near San Jacinto Avenue and almost
500 feet in front of Morro Bay High School in the past 50 years. This sandbar protects development in this
region.The bay is protected by the sandspit south of Morro Rock that provides a barrier to wave attack
that would otherwise impact the developed areas along the Embarcadero. Portions of Morro Bay are low-
lying and are classified as a "high risk"with respect to possible future coastal flooding associated with sea
level rise.
City of Pismo Beach: Cliffs and bluffs ranging in height from ten to one hundred feet exist along
approximately five miles of the northwest portion of the city shoreline,with the southern areas of the city
around the Pismo Beach Pier being low-lying. Bluff erosion rates in Pismo Beach vary from an average of
2 inches per year where bedrock is present to up to 12 inches per year in areas with limited bedrock (City
of Pismo Beach 2002). Past studies have found that more than 60 homes are within the bluff retreat
hazard zone and may be subject to damage or destruction by 2100,without accounting for accelerated
bluff retreat associated with sea level rise (City of Pismo Beach 2002). Portions of Pismo Beach are either
low-lying or are located atop eroding coastal bluffs and are classified as a "moderate risk"with respect to
possible future coastal flooding or accelerated bluff retreat associated with sea level rise.
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Risk Assessment
Figure 5-33 Bluff Erosion and Overlying Development at Dinosaur Caves Park in Pismo Beach,
January 2010
7.
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Residential structures situated adjacent to coastal bluff cliffs are vulnerable to the impacts of coastal storms and actively eroding bluffs.Irreversible bluff
erosion exacerbated by future sea level rise has the potential to damage communities such as those in Pismo Beach(January 2010).Source:San Luis
Obispo Tribune 2010.
Avila Beach:Avila Beach is a southerly-facing sandy beach backed by areas of low-lying coastal
development in the north along San Luis Creek including commercial and residential uses, hotels and
Avila Beach Park, as well as homes atop a 10-35 foot high low coastal bluff.Although most of Avila Beach
is protected by 10 to 20-foot-high seawalls, low-lying areas to the north including Avila Park, and coastal
access parking are potentially exposed to wave run-up and flooding. Avila Beach is partially sheltered
from northerly swells by the Point San Luis Breakwater but is vulnerable to coastal storms originating from
the southwest. The 1983 EI Nino event severely damaged the recreational pier at Avila Beach. Low-lying
areas of Avila Beach are classified as a "moderate risk"with respect to possible future coastal flooding
associated with sea level rise.
Los Osos-Baywood Park:The community of Los Osos-Baywood Park is located a hillside and low-lying
areas of the shoreline of Morro Bay. The sand dunes of Morro Bay State Park sandspit and Park currently
protect the community of Los Osos from potential wave hazards, although dozens of homes along the
shoreline of Morro Bay are constructed just above sea level. The low-lying shoreline areas of this
community along Morro Bay may have low to moderate risk with respect to future coastal flooding from
sea level rise over the long term. It is unknown if sea level rise could eventually erode or lead to breaches
in the sand dunes along Morro sandspit or to what extent such a breach could affect coastal flooding in
Los Osos-Baywood Park.
San Simeon: San Simeon is fronted by a narrow sandy beach backed by low coastal bluffs that support
several bluff top homes and a hotel with minimal setbacks and the town's wastewater treatment plant,
which is protected by a low rock revetment. These bluff top uses are currently exposed to moderate risk
and may be threatened in the near term if bluff retreat rates accelerate with sea level rise. Such threats
would be considered medium or high with projected sea level rise and potential accelerated bluff retreat.
Cayucos:The shoreline in Cayucos generally supports narrow beaches backed by low cliffs approximately
20 feet-high as well as a low-lying downtown area by Cayucos Creek, much of which is protected by low
rock revetments and a low seawall. Over 100 residences with minimal setbacks from the edge of the bluff
are potentially exposed to coastal erosion hazards, although a number are protected by rock revetments
or seawalls. In the winter month the sandy beach often erodes, and waves strike directly against the
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Risk Assessment
bluffs.The Cayucos shoreline faces south such that its beaches are partially protected from northerly
swells. Wave action in this area is still significant. The seacliffs are comprised of Franciscan melanges,
characterized by blocks of rocks often surrounded by small zones of sheared or crushed rock that tend to
erode easily. Some zones contain more erosion resistant rock blocks that have been exposed as the
weaker blocks have eroded away. During the intense storm waves of 1983, these resistant blocks were
breached at some spots.As a result, the bluff receded as much as 20 feet (San Luis Obispo County 1999).
Figure 5-34 Low-lying Residential Development Fronted by Sandy Beaches in Cayucos
Cayucos shoreline residential development is typically fronted by a wide sandy beach that protects development from coastal storms and sea level rise;
however,the beach provides limited protection from potentially severe coastal storms and associated wave run-up and flooding.
Rates of erosion are highly variable along this coastline and range from 6 to 10 inches per year.
Emergency rip-rap and numerous seawalls were constructed in response to the storm waves of 1983 (San
Luis Obispo County 1999).
Downtown Cayucos is another area of concern. Built upon the unconsolidated sediment deposited from
the Cayucos creek, this area is susceptible to shoreline erosion.
During rainy months when the ground becomes wet, the low permeability of the clays tends to perch or
elevate the groundwater table. Consequently, the saturated soils cause increased erosion due to slope
instability and slumping of the seacliff face.Therefore, much of Cayucos is either low-lying around the
downtown or includes bluff top homes with minimal setbacks and is therefore classified as "moderate to
high risk"with respect to both existing coastal hazards and possible future coastal flooding and
accelerated bluff retreat associated with sea level rise.
Port San Luis: Port San Luis and the coastline surrounding San Luis Bay is well-protected from the
dominant northwesterly swells by the 2,300-foot long Port San Luis breakwater, though little protection is
offered from southerly swells.The Port San Luis area is backed by 100-foot high cliffs that descend
eastward into approximately 30-foot high cliffs. A rock revetment protects Avila Beach Drive from Port
San Luis toward Avila Beach from storm waves and bluff erosion.
Section 5
Risk Assessment
Historic storms have shown that both Port San Luis and Avila Beach are susceptible to coastal damage
resulting from storm waves, especially those generated from southerly swells.Winter storm waves during
1983 EI Nino-related coastal storms, for example, damaged the concrete seawall that runs parallel to Front
Street. This region is classified with a "moderate risk"with respect to possible coastal damage incurred by
storm waves.
Cambria: Cambria is characterized by rocky intertidal shoreline and narrow beaches backed by low cliffs
approximately 20 to 40 feet high.This section of coastline is subject to moderate to heavy wave action,
mostly from northerly swells.The coast in the area is comprised of a rock unit called the Cambrian slab
that is a local, colloquial name for the Cretaceous-age sandstones that form the resistant rock headlands
in the area. Since this type, of sandstone is fairly resistant to erosion, seacliff retreat rates in Cambria are
relatively low when considering the wave energy imposed on this area. However, while some coastal bluff
top homes are protected by rock revetments, dozens of homes along the coastal bluff tops have minimal
setbacks and are currently threatened by erosion by wave action and current sea cliff erosion rates of two-
to three- inches per year.
Figure 5-35 Low Coastal Bluffs and Residential Development in Cambria
s - EWE
Ile-
The San Luis Obispo coastline is diverse in geologic composition and subject to variable coastal hazard impacts.Urban development adjacent to coastal
bluffs are highly vulnerable to irreversible bluff erosion,such as those in Cambria in close proximity to the shoreline(pictured above).
All developed coastal areas of Cambria are in high hazard zones (USACE 2016). Much of the shoreline of
Cambria includes bluff top homes with minimal setbacks and scattered rock revetments is therefore
classified as "moderate to high risk"which would increase with respect to possible future accelerated bluff
retreat associated with sea level rise.
Shell Beach:The coastline from Fossil Point proceeding eastward to Shell Beach is characterized by
offshore rocks and sea stacks backed by 30-to 100-foot eroding cliffs. Seacliff retreat rates range from 4
to 7 inches per year for the Shell Beach coastline; catastrophic rock fall is an important agent of erosion in
this area. Although many homes located adjacent to the coastline of Shell Beach are protected by
seawalls, bulkheads, sandbags, and rip rap, this stretch of coastline is characterized as "high risk"with
respect to possible erosion.
Section 5
Risk Assessment
Oceano: Oceano is generally fronted by wide sandy beaches backed by low active dunes. These dunes
provide protection for structures located nearby; however, they are subject to erosion during storm surges
at extreme high tides. Although these sand dunes protect dwellings from storm waves, the winter storms
of 1983 damaged structures and destroyed timber ramps that provided vehicular beach access. Therefore,
this region is characterized with a "moderate risk" and a "high risk" region adjacent to the Arroyo Grande
Creek mouth with respect to coastal erosion.
South County:The coastline from Oceano southward to the San Luis Obispo/Santa Barbara County line is
described as "sandy beaches backed by active dunes with sparse vegetative cover, high intermediate old
dunes with vegetative cover, marshes, and lakes" (San Luis Obispo County 1999). Although the dune face
is wave-cut and experiences frequent slides, this region is classified with a "moderate risk"with respect to
coastal erosion.
Extent (Magnitude/Severity)
All low-lying coastal areas within San Luis Obispo County including beaches are exposed to coastal storm
hazards that would be subject to inundation with projected sea level rise. Increased frequency, severity,
and duration of high tide and storm events related to climate change may also result in more frequent
and severe storm events along the coast.
Coastal Storm: Coastal storms can cause high winds and strong storm surges that would affect low-lying
"vulnerable" coastal resources and infrastructure located in urban areas such as Morro Bay. For wind
hazards, the extent of wind speeds can range from tropical depressions (less that 35 kts), tropical storms
(35-65 kts) to hurricane force winds are 65kt or greater. Low-lying areas susceptible to wave run-up and
coastal flooding due to coastal storms are often protected by seawalls or revetments. These protective
structures may be breached during a severe coastal storm, however, such as those associated with EI Nino
years and/or a 100-year coastal storm event. Wave runup elevations are used in coastal flood studies to
determine flood hazard areas for sites along the open coast that are subject to direct assault by deep-
water waves. Runup elevations range with location and local beach slope. Wave runup elevations for the
1% annual chance coastal storm range from 11 to 24 feet above Mean Sea Level depending on location;
the 0.2 % annual chance wave runup elevations range from 17 to 30 feet, but generally are around 22 feet
above Mean Sea Level. Actual depth of inundation would vary, depending on the ground elevation at a
particular site. Areas with ground elevations 3 feet or more below the 1% annual chance wave runup
elevation are subject to velocity hazard, shown as the VE zone on FEMA flood hazard maps. More details
on specific sites can be referenced in the County's 2012 Flood Insurance Study (FEMA 2012).
Coastal development on coastal bluffs and cliffs that are not susceptible to direct wave run-up and
flooding are vulnerable to coastal storms and the resultant bluff erosion. All coastal development in
proximity to the shoreline is threatened by landward retreat of the shoreline due to beach and bluff
erosion, which are exacerbated by coastal storm events.
Coastal Erosion: Coastal erosion threats include both dune erosion and bluff erosion, and can result from
storms, sea level rise, strong wave action, and human activities. Unlike coastal storms, cliff erosion can
result in permanent and significant alterations of coastal geology that can expose landward development
and resources to additional coastal threats. Large sections of the county coastline, especially those with
rocky headlands or sea cliffs, are not vulnerable to flooding, but are highly susceptible to erosion
(Heberger et. al 2009). Areas vulnerable to impacts of coastal beach erosion within the county include
low-lying areas fronted by sandy beaches and dunes, including sand dunes at Pismo State Beach, Oceano,
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Risk Assessment
and Los Osos. Impacts of coastal bluff erosion affect development above or adjacent to coastal cliffs and
bluffs, including bluff top residential development in Cambria, Shell Beach, Pismo Beach, and the cliffs at
the Point San Luis Lighthouse. Erosion extent can range from gradual wearing away of coastal land at
inches per year to more significant, catastrophic events that can result in bluff failures involving several
hundred cubic yards of material.
Sea Level Rise: Low-lying coastal areas such as those in Morro Bay, Oceano, Cayucos and portions of
Avila Beach are more susceptible to wave run-up and flooding in combination with sea level rise than
structures atop coastal cliffs; however, such bluff top structures may be threatened by accelerated bluff
erosion induced by projected sea level rise. Projected sea level rise in Morro Bay may increase threats to
low-lying habitats or development relative to current sea level conditions). Further, as noted above, sea
level rise may lead to accelerated coastal bluffs retreat and erosion that may exacerbate threats to
communities located along the cliffs and close to the coast such as Pismo Beach, Shell Beach, Avila Beach,
Morro Bay and Cambria. Projected sea level rise may exacerbate saltwater intrusion into coastal aquifers
potentially affecting water supply of some communities. Sea level rise may also exacerbate the frequency
and depth of inundation of coastal marshland, leading to its conversion to open water or mudflat habitat.
This in turn can increase the concentrations of brackish water that can compromise coastal marshland
habitat integrity.
Specific to sea level rise, the extent of anticipated rise for the purposes of this plan is modeled for three
different scenarios generally ranging from 1 ft, 3 ft, and 10 ft;this is described in more detail in the
Vulnerability subsection; maps showing potential inundation from the three sea level rise scenarios are
included in the jurisdictional annexes for Avila Beach, Cambria, Cayucos, Grover Beach, Los Oso, Morro
Bay, Oceano, Pismo Beach, San Simeon and South San Luis Obispo County Sanitation District.
Previous Occurrences
Coastal Storm: Increased coastal erosion and flooding from intense storm activity along the California
coast occurred during major EI Nino events of 1982/83 and 1997/98 (Bromierski 2003). High tides and
severe storm waves during the EI Nino storm in March 1983 damaged the concrete seawall in Port San
Luis as well as development within the community of Avila Beach (the wide sandy beach eroded and was
not sufficient to protect urban development from severe storm waves). Housing developments in this area
experienced landslide activity as well as cracking of foundations and roads. The Union Oil Pier at Avila
Beach was also severely damaged, as well as the Avila Beach Pier(Figure 5- 36) (San Luis Obispo County
1999). Historic storms have resulted in substantial damage to coastal regions and demonstrated
susceptibility of the coastline to swells originating in both the northwest and southwest.
San Luis ObispoCounty Local . Mitigation Plan I October 2019 Page I
Section 5
Risk Assessment
Fi ure 5- 36 Union Oil Pier in Avila Beach Collapses Following Severe 1983 Storm
ITT
u _
A severe coastal storm in March 1983 brought high winds and powerful surf that damaged coastal pier and infrastructure including sections of Highway
1 and destroyed the wooden Union Oil Pier in Avila Beach.Source:San Luis Obispo Tribune 2018.
EI Nino-related storms cause increased damage to the coastline with heavy rainfall, energetic wave
conditions, and accelerated dune and bluff erosion. Such storms are also correlated with increased
coastal flooding magnitudes (Andrews et al. 2004).Wave height, sea level, and precipitation, which are the
primary external forcing parameters in seacliff erosion, further increase with storm intensity. Significant
cliff erosion and storm damage occurred along the central coast of California during the 1982/1983,
1997/1998 and 2015/16 EI Nino winters (Table 5-33) (Storlazzi &Griggs 2000). Further data on previous
storm occurrences and related impacts to the county are provided in subsection 5.3.1,Adverse Weather.
Table 5-33 Recorded EI Nino related coastal storms and flooding in coastal communities within
the County of San Luis Obispo
DamageStorm Event(Year) Primary Area(s) affected Extent of
Heavy rainfall increased coastal flooding and accelerated
EI Nino,Winter 1982/83 Entire County Coastline dune and cliff erosion.Classified as one of the three
strongest EI Nino storms since 19502.
High intensity storm which brought 6-8 inches of rain;
March 1983 Avila Beach, Port San Luis high energy surf over a 7-day period destroyed the Union
Oil Pier in Avila Beach and seawall in Port San Luis'
High intensity storm that impacted the coastline with high
EI Nino,Winter 1997/98 Entire County Coastline energy wave conditions, substantial rainfall,and
accelerated beach and bluff erosion Classified as one of
the three strongest EI Nino storms since 19502.
High wind, rainfall,and energetic waves that accelerated
EI Nino,Winter 2015/2016 Entire County Coastline beach and bluff erosion.Classified as one of the three
strongest EI Nino storms since 19502.
Source:(County of San Luis Obispo Public Works Department 2019)
Source:(Jan Null 2019;World Meteorological Organization 2019)
Coastal Erosion: Coastal erosion within San Luis Obispo County has primarily occurred during periods of
intense wave action coinciding with high tides and coastal storms. Local annual beach erosion rates from
ObispoSan Luis
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Risk Assessment
1942 to 2002 (Hapke et. al 2006) range from three inches to over one foot (Table 5-34) (San Luis Obispo
County 1999; USACE 2016). Beach erosion of up to 3 feet per year has occurred in areas including
Cayucos, Morro Strand State Beach, Morro Bay State Park, Montana de Oro State Park, Shell Beach, Pismo
Beach, and Oceano Dunes. Historical rates may not accurately predict future erosion; however, as
substantial erosion can occur during individual severe storms that are expected to be exacerbated by
climate change and associated sea level rise. This can result in bluff and cliff collapse (Griggs 2003). Major
historical erosion events coincide with heavy storm years including: Piedras Blancas in 2001, the general
county coastline in 2010, and Shell Beach and Montana de Oro in 2017 (Protsman 2018). Reliable
estimates of retreat are difficult to obtain because the historical record and the quality of the information
is limited relative to ongoing coastal processes (City of Pismo Beach 2002).
Dune erosion can either be short term where large coastal storm events and severe wave attack result in
loss of sand or cliff failure, or long term with the gradual erosion of the shoreline over time due to
onshore winds and high tides. Dune-backed shorelines may also change over time as dunes expand and
recede (Hapke, 2006). Specific locations within the County experience differing rates of shoreline change.
Long-term shoreline change in the northern section of the county has historically been approximately 0.1
meters (0.32 feet/3.84 inches) of erosion per year, and short-term change averaged 0.7 meters (2.30 feet
/27.6 inches) of erosion per year. Short-term shoreline changes averaged 3.4 meters (11.5 feet/ 138
inches) of erosion per year in the short-term but was relatively stable in the long-term.
Pismo Beach is an example of an area vulnerable to cliff erosion, where low bluffs consist of relatively
weak sedimentary rock susceptible to wave erosion and undercutting of the cliff.The City of Pismo Beach
conducted a Bluff Erosion Study in order to quantify historic erosion rates and evaluate impacts to coastal
resources and development. Bluff retreat typically occurs episodically with several feet to several tens of
feet of the bluff top eroded during a single season or storm event, while the bluff top in adjacent areas
may remain unchanged.This bluff study estimates an approximate average retreat of 4 inches per year
over the last 50 years. Retreat rates of only 2 inches per year were observed at relatively resistant south-
facing bluffs. Retreat rate of 6 to 12 inches per year, however, were observed in areas with higher
instability where there has been sea cave collapse (City of Pismo Beach 2002). Rapid bluff collapse that
contributes to higher bluff erosion rates are difficult to predict and projected to increase with sea level
rise. For example, an approximate 100-foot section of the Pismo Beach bluff collapsed following the
winter storm season in March 2011, a much more rapid erosion rate than those reflected in historical
records (Figure 5-37). The historic bluff retreat rates determined in this study did not consider increasing
wave energy and sea level rise. Existing rates of annual erosion may only approximate future coastal
erosion rates and associated hazard vulnerability.
Table 5-34 Historic Rates of Erosion at Specific Sections of the Coastline
Historic Erosion' Shoreline Characteristics
Rate(inches/year)
Narrow beaches backed by low cliffs approximately
Cambria 2-3 20 feet high with urban development and public
parkland
Cayucos 6-10 Wider beaches backed by low cliffs approximately 20
feet high
Morro Bay +602 Large sand dunes backed by elevated terraces along
a bay protected by a sandspit
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Risk Assessment
Los Osos 4-6 Large sand dunes backed by developed areas
Sandy beach backed by cliffs up to 100 feet high,
Port San Luis Not Available protected from northwesterly swells by the Port San
Luis Breakwater
Pirates Cove 4-7 Offshore rocks and sea stacks backed by eroding
cliffs approximately 30-100 feet high
Sandy beaches backed by low active dunes covered
Grover Beach Not Available with vegetation, a golf course, and residential
development
Oceano Not Available Wide sandy beaches backed by low active dunes
Sandy beaches backed by active dunes with sparse
South County Not Available vegetative cover, high intermediate established
dunes with vegetative cover, marshes and lakes.
s 2-12 (Average of 4 Relatively steep bluffs approximately 20 to 110 feet
Pismo Bluffs inches/year) high fronted by narrow and steep beaches formed
by bluff erosion.
I Historic rates of erosion describe the approximated change in shoreline position and/or bluff retreat calculated over the period from 1942 to 2002,
and vary depending on geologic composition and exposure to wave energy(Hapke et.al 2006).
z Due to the construction of the Morro Bay Harbor Breakwater and the presence of Morro Rock,the littoral drift north of Morro Bay has been
interrupted and the coast has extended seaward with increased beach width(San Luis Obispo County 1999).
3 Historical erosion rates of the Pismo Bluffs are based on evaluation of approximately S miles of coastline between Harloe Avenue and The Bluffs Drive
in Pismo Beach(City of Pismo Beach 2002).
Figure 5-37 Bluff Erosion at Pismo Beach, March 2011
IV
r • it"ASI "J'191F,�;.'��1/.
7 7
An approximate 100-foot section of cliff collapsed in Pismo Beach due to erosion of the bluff following winter storms in March 2011,demonstrating the
severe impacts of coastal hazards on weak bluff sediments.Source:San Luis Obispo Tribune 2011
Hard shoreline protective structures (i.e. seawalls, revetments) are implemented in some areas to slow
erosion; however, such structures become less effective during severe storms and high tide events. The
efficacy of existing protection devices and natural barriers such as typically stable serpentine rock is
expected to decrease with projected sea level rise. Substantial beach erosion and cliff collapse resulting
from severe storms has occurred along the bluffs adjacent to Pacific Avenue and Studio Drive in Cayucos.
Extensive blocks of sheared serpentine that normally serve to slow erosion were breached by intense
Section 5
Risk Assessment
storm waves during a coastal storm event in March 1983. The bluff receded as much as 20 feet, causing
severe beach and bluff erosion along the coast and irreparably damaged to coastal infrastructure (San
Luis Obispo County 1999).
Severe coastal erosion also occurred at low-lying portions of Highway 1 near Piedras Blancas; from just
north of the Piedras Blancas Lighthouse to the Arroyo de la Cruz Bridge. The temporary rock revetment
armoring the road was not sufficient to protect the road from coastal storm and flood damage, and
coastal erosion compromised the safety and structural integrity of the Highway. Approximately 2.8 miles
of Highway 1 was relocated up to 475 feet landward in order to prevent coastal bluff erosion from
adversely affecting future operation of the highway for the next 100 years (Figure 5-38) (Caltrans 2010).
Figure 5-38 Vulnerable Portions of Highway 1 and Realignment near Piedras Blancas
r-�
A
y
Low-lying portions of Highway 1 near are threatened by severe coastal erosion due to wave damage and insufficient protection from hard structures
(pictured left).In response,an approximate 2.8 mile-long segment of Highway 1 near Piedras Blancas was realigned 475 feet inland to protect the
roadway from future erosion(new roadway completed in 2017,pictured right)(Caltrans 2010).
Photo Source:San Luis Obispo Tribune 2014(left);AP Photo/Dania)Dreifuss(right)
Sea Level Rise: Sea levels are rising at different rates in different regions of the California Coast due to
local differences in tectonic uplift/subsidence and other factors such as nearshore bathymetry. Typically,
the highest sea level readings along California's coastline occur during periods of heavy rain that coincide
with high tides, causing coastal flooding, coastal bluff erosion, and cliff collapses such as those
experienced during the 1982/83 and 1997/98 EI Nino events.
The Port San Luis Tide Gauge located on the Hartford Pier reports the local sea level rise rate at
approximately 0.93 (+/-0.38) millimeters per year (mm/year) since 1948 (NOAA 2017) (Figure 5-39).This
rate compares to the global average annual rate of 3.2mm/year (Griggs et. al. 2017) and near the mouth
of San Francisco Bay that has recorded approximately 7 inches in sea level rise variation over the past 100
years. The monthly sea level tide gauge record at Port San Luis was at its lowest recorded level (-0.2
meters or -0.66 feet) in the 1940s and reached its highest measured monthly average in the late 1990s at
approximately 0.2 meters (0.66 feet). The growth trend is projected to increase in future years (NOAA
2017).
Section 5
Risk Assessment
Figure 5-39 Tide Record and Sea Level Rise Trend from Port San Luis Tide Gauge (NOAA Station
9412110)
9412110 Port San Luis,California 0.93+i- 0.38 min iyr
0.60
—Linear Relative Sea Level Trend
0.45-- —Lipper 95%Confidence Interval - _ _ - _ - _ - _ - - - - y - - - - - - - - - - - - - _ _ _
—Lower 95%Confidence Interval
„
_Monthly mean sea level with the i
0.30 average seasonal cycle removed - - ----J ------ - - - - - - - - - - - - - -
0.15' - - - - - - - - - - - - - - - - - - - - -- - - - -- ---- - - - - - - - - - - - - - - -
0.00
- - - - - - - -0.00
-0.15 — — — — ——— — — —— — — — — — — — — — — — —— — — — — — — — — — — — — — — — — — — -
-0.30f` — — — — - - - - - — — — — — - - - - - — — — — ---- - - — - - - — - - - - - - - — - - - - - - -
-0.45 ———---
-6.60
1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 2020
Source:(NOAA 20191b)
Probability of Future Occurrences
Coastal Storm: Highly Likely. Coastal storms typically occur every winter season between the months of
November and March. Coastal storms vary in frequency and severity and will be exacerbated by rising sea
levels and future increase in variation in climate. The Federal Emergency Management Agency(FEMA)
estimates and maps future coastal storms based on the 1-percent probability of an extreme storm
occurring during any given year (FEMA 2019). Thus, extreme coastal storms occur less frequently.
Increasing trends in coastal storm frequency and severity based on climate-related variables have also
been identified by studies of cyclone frequency and wave height (see subsection 5.1.3 Climate Change
Considerations of the base plan). The future occurrence of coastal storms is projected to increase;
however, the projected frequency and intensity is difficult to quantify with current climate science and
coastal storm modeling.
Coastal Erosion: Highly Likely.Average rates of historic beach and cliff erosion and shoreline retreat and
are expected to continue and accelerate, but future erosion rates are difficult to project due to variable
coastal processes and uncertainty in sea level rise projections. Increased frequency of coastal storms and
wave run-up due to sea level rise increases the irreversible bluff erosion and cliff collapse that may occur.
Dunes and cliffs will exhibit differential responses to rising sea levels. The Pacific Institute models
projected rates of coastal dune and cliff erosion in its "Erosion hazard with a 1.4-meter(4.6 foot) sea level
rise, 2100" dataset, which represents the areas vulnerable to erosion with a sea level rise of 1.4 meters (4.6
feet) by 2100.This data is utilized in a larger study: The Impacts of Sea-Level Rise on the California Coast,
which quantifies the projected impacts of coastal dune and bluff erosion (Heberger et. al 2009). This study
projects a total dune and cliff erosion of 2.9 square miles (80.8 million square feet) with 1.4 meters (4.6
feet) of sea level rise by 2100. Projected rates of average and maximum dune and cliff retreat inform the
severity of future erosion and impact on existing coastal development in close proximity to the shoreline
(Table 5-35). These values project the total amount of erosion and average landward retreat of the county
by 2100, and do not consider short-term responses of sandy beaches, dunes, and cliffs as a result of
coastal storms (e.g., cliff failure due to severe wave attack). Dune and cliff erosion rates vary significantly
Section 5
Risk Assessment
throughout due to geological composition and the physical forces acting on the coastline;therefore,
actual erosion and shoreline retreat distance will not be uniform throughout the county. Further, areas
protected by hard structures such as seawalls (i.e. Avila Beach) will also experience lesser impacts of cliff
erosion than unaltered natural coastlines.
Actual future rates of erosion are relative to future coastal processes and difficult to project with certainty.
Projected rates of erosion are naturally varied and will likely accelerate by 2100; thus, most erosion will
occur towards the end of the century (Heberger et. al 2009).
Table 5-35 Coastal Erosion Projections with 1.4 meter (4.6 foot) Sea Level Rise by 2100
ObispoSan Luis
Distance 2 Distance
Dune Erosion 1.4 square miles 150 meters/492 feet 330 meters/1083 feet
Cliff Erosion 1.5 square miles 78 meters/256 feet 280 meters/918 feet
Total Erosion Area refers to the total area of dunes or cliff loss due to erosion projected to occur by 2100.
'Retreat Distance refers to the landward retreat of dunes or cliffs as a result of coastal erosion projected to occur by 2100.
Source:(Heberger et.al 2009).
Sea Level Rise: Likely. Scientific understanding of sea level rise is advancing at a rapid pace; projections of
future sea level rise continue to change as new studies become available. Future climate change is
projected to particularly affect sea levels as the glaciers, polar ice packs, and ice sheets retreat. The
predicted sea level rise over the course of this century varies widely. Since 1992, trends in sea level rise
have been monitored by satellites and recorded by tide gauges. Given the variables involved, it is not yet
possible to determine the actual rate of sea level increase. The Ocean Protection Council (OPC) suggests
that sea level rise along the coast of California could occur on the order of 0.5-1.0 foot by 2030, 1.0-2.6
feet by 2050, and 3.1-10 feet by 2100 (Table 5-36). These sea level rise scenarios are based on various
projections of global greenhouse gas (GHG) emissions. The probabilities take into account uncertainties
related to each of these scenarios. In addition, Rising Seas in California:An Update on Sea-Level Rise
Science identifies an extreme sea level rise scenario (H++) that projects 10 feet of sea level rise by 2100
based on an accelerated rate of Arctic and Antarctic ice sheet loss (Griggs et. al. 2017). The H++ scenario
assumes a trajectory of high GHG emissions and an accelerated rate of Arctic and Antarctic ice sheet loss.
Note that there is a high level of uncertainty associated with the H++ scenario (as well as all SLR
projections and projected timing) and given the emerging nature of SLR science, these estimates are
intended to be used as a guide only and are subject to refinement over time. If this extreme sea level rise
scenario were to occur, the modeled elevations of sea level rise and associated hazards could be
experienced substantially sooner than the projected horizon year.
Table 5-36 Sea Level Rise Projections
Projected Horizon Year 67% Probability SLR 0.5% Probability SLR H++ Extreme SLR Scenario
Time meets or exceeds meets or ei (no probability assigned)
2030 0.5 ft 0.7 ft 1.0 ft
2050 1.0 ft 1.8 ft 2.6 ft
2100 2.1-3.1 ft 5.4-6.7 ft 9.9.ft
Note:Probabilities based on projections by the OPC for both low and high GHG emissions scenarios(Griggs et.al.2017).
Section 5
Risk Assessment
Climate Change Considerations
As ocean temperatures warm as a result of climate change, the water in the ocean expands and occupies
more volume, resulting in a rise in sea levels. In addition, global sea levels rise from the additional volume
of water added to the oceans from the melting of mountain glaciers and ice sheets on land. The rate at
which sea levels will rise is largely dependent on the melting of the ice, which changes the land cover from
a reflective ice surface to open ocean water; the ocean continues to absorb more of the sun's energy and
subsequently increases the rate of ice melt.The uncertainties associated with the rate at which ice melt
occurs is largely responsible for the wide variation in sea level rise projections in the latter half of this
century(i.e., between 2050 and 2100) and can explain the H++ scenario.
The time scales for sea level rise are related to complex interactions between the atmosphere and the
oceans, delays in stabilizing GHG levels in the atmosphere, and the dissolution of those gases into the
ocean. The Intergovernmental Panel on Climate Change (IPCC) has published scientific evidence that
demonstrates that sea levels will be rising for the next several thousand years due to the GHGs that have
already been released into the atmosphere. Much of the scientific advancement in recent years has been
in understanding the contribution and rate of ice melt to global sea levels. It has also revealed the
potential for extreme sea level rise resulting from rapid acceleration of ice melt as noted above under the
RCP 8.5 and H++ scenarios. In general, the higher the GHG emissions, the higher the temperature, the
more rapid the ice melt, and the higher the rate of sea level rise.
A study conducted to examine the variability of coastal storms in California using historical records of
storms and tide gauge data in San Francisco identified an increasing trend in the frequency and intensity
of coastal storms over the last 50 years (Bromierski et. al 2003). Increasing trends in climate-related
variables have also been identified by studies of cyclone frequency (Graham & Diaz 2001) and wave
height (Allan & Komar 2000);these have been substantially affected in the last two decades by increased
coastal storm frequency and intensity. Continuation of these trends would have serious consequences
for structures and ecosystems along the West Coast. The projected frequency and intensity of future
coastal storms, however, is difficult to confidently quantify (Bromierski et. al 2003).
Vulnerability
The assessment of vulnerabilities to coastal storms, coastal erosion, and sea level rise within San Luis
Obispo County relies on the best available science and modeling and methodology from a range of
sources including FEMA and OPC planning guidance. Data was derived from several sources, including
NOAA sea level rise viewer and previous studies that quantify historic rates of coastal erosion and
frequency/severity of coastal storms and provide evidence for future trends (NOAA 2019b; USGS 2018).
This assessment is further guided by FEMA's Local Mitigation Planning Handbook(2013), which provides
strategies to describe and quantify hazards risk in the context of individual jurisdictions.
Sea level rise modeling and adaptation is an evolving field. The sea level rise projections used in studies
previous to this Plan to identify vulnerabilities do not reflect the most recent update of California sea level
rise guidance, as provided in the California OPC 2018 State of California Sea-Level Rise Guidance Update
(OPC 2018).The NOAA Sea Level Rise and Coastal Flooding Impacts online tool uses a "bathtub" model
comparing water elevations to ground elevation contours but may not fully account for hydrodynamics
such as King Tides, storm surges or wave run-up, often key elements in coastal flooding. Spatial data
layers within the CSMW WebMapper developed by the Pacific Institute (2009) also estimate areas that will
be affected by future sea level rise; however, the data layers also use the "bathtub" model and do not
Section 5
Risk Assessment
reflect the most recent sea level rise projections, which are substantially higher than those used within the
Pacific Institute model. The CSMW WebMapper layers that identify areas vulnerable to bluff erosion and
dune erosion hazards represent all dunes and bluffs as susceptible to sea level rise induced erosion with a
55-inch (4.6-foot) rise in sea level by 2100 (USACE 2016).The Pacific Institute spatial data layers provide
projections for coastal bluff and cliff erosion in total area of erosion (square miles) and shoreline retreat
(linear meters/feet) with sea level rise of 1.4 meters (4.6 feet) by 2100. Historic and projected rates of
erosion inform future vulnerability of coastal development; however, erosion future rates are relative to
variable coastal hazards and are difficult to quantify.
A San Luis Obispo California Polytechnic State University graduate study titled A Sea Level Rise
Vulnerability Assessment and Adaptation Strategies for the County of San Luis Obispo completed to inform
future updates of the Safety Element of the County's General Plan analyzed the potential impacts of
coastal hazards and sea level rise to identify vulnerabilities along the coast (Protsman 2018). This study
provides site-specific erosion rates and detailed maps of site-specific shoreline change and coastal
hazards that utilizes USGS and Pacific Institute data (Protsman 2018; USGS 2018). USGS data provides
information on coastal change hazards during storms, beach morphology during extreme storms, short-
term and long-term shoreline change rates, a coastal vulnerability index, and probabilities of coastal
shoreline retreat on a regional scale. USGS has a more localized and accurate model called the Coastal
Storms Modeling System (COSMOS), and this model had not yet been applied to San Luis Obispo County
until mid-2019. As this modeling represents more current sea level rise science it was integrated into this
HMP before it was finalized. This was also done to reflect the most recent update of California sea level
rise guidance, as provided in the California OPC 2018 State of California Sea-Level Rise Guidance Update
(OPC 2018).
The California Coastal Commission (CCC) requires sea level rise analysis and bluff retreat studies for new
coastal development permits,which provide site-specific research on historic and projected rates of sea
level rise and bluff erosion. Individual jurisdictions, such as the city of Pismo Beach, have also conducted
sea level rise and bluff erosion studies to evaluate vulnerability and establish policies for reviewing
proposed coastal development. Sea level rise studies and adaptation reports conducted for smaller
jurisdictions include site-specific coastal modeling including the Morro Bay Sea Level Rise Adaptation
Strategy Report(Moffat & Nichol 2018).
Genera(Property
Public and private property vulnerable to coastal storms, coastal erosion, and sea level rise generally
include low-lying coastal structures and those built close to the edge of eroding bluffs.Vulnerable private
development primarily includes residential and commercial buildings in cities and unincorporated
communities, as well as agricultural buildings in rural areas. Parcels located in close proximity to the
coastline include agriculture and residential structures, commercial structures, industrial structures,
agriculture and residential parcels, commercial parcels, and industrial parcels. (County of San Luis Obispo
2018; Protsman 2018).A property risk assessment conducted by Protsman (2018) determined that the
buildings and parcels with the highest vulnerability are located within the central and northern regions of
the coast due to health, safety, and displacement concerns of damaged or destroyed structures and
parcels (Protsman 2018).
Coastal hazard impacts on coastal property are dependent on several factors including the elevation and
composition of the shoreline (i.e. wide sandy beach versus a rocky intertidal beach fronting coastal bluffs).
Section 5
Risk Assessment
For example, structures built adjacent to eroding bluffs are vulnerable to bluff erosion and coastal storms.
Public and private property susceptible coastal storms and projected sea level rise may be protected
through shoreline adaptation measures including hard structures such as seawalls or rock revetments or
softer approaches such as beach nourishment that slow the landward retreat of the shoreline (USACE
2016). Natural features such as dune fields and coastal cliffs exist over much of the county coastline that
are subject to irreversible beach and bluff erosion. However, less than 5 percent of the San Luis Obispo
County coastline is estimated to be protected from coastal hazards with hard structures such as
revetments or seawalls as of 2016 (USACE 2016).
Figure 5-40 Residential and Commercial Coastal Development in Morro Bay
k..
f?,,1`.�Ef - 111 11 muwe 111T►. —
?w ei u • ••••11 ..111 1 ICE mxd[ u 1
s�
Low-lying commercial and residential coastal development in Morro Bay is has little protection from coastal flooding and sea level rise;however,the
strand and dunes across the bay provide some protection from strong offshore swells.Photo Source:San Luis Obispo Tribune 2014.
As an estimate of potential losses to coastal flooding a GIS analysis of exposure within FEMA coastal flood
zones (VE) was completed. The GIS analysis takes into account improved values of properties and
estimated content values. Approximately 64 properties worth $3 million is currently exposed, including
both improved and content value within Morro Bay, Pismo Beach, and unincorporated areas based on the
intersection of improved parcel centers with VE flood hazard areas (Table 5-37). Note that the type of
properties with the greatest exposure include a number of government/utilities and exempt properties
that do not have valuations in the assessor's data, thus the property values are likely under-represented.
The loss estimate assumes 50% of the structure and content exposure value due to the potential for
deeper flooding and wave effects associated with the VE zones.The unincorporated areas, such as low-
lying areas in Cayucos, are exposed to the highest total value and greatest loss estimate due to potential
coastal flooding (Table 5-38). While this analysis generally shows relatively low risk to existing
development, the risk could increase over time with sea level rise.
San Luis ObispoCounty Local . Mitigation Plan I October 2019 •.. 5-119
-
Section 5
Risk Assessment
Table 5-37 Coastal Flooding Hazard Exposure—General Property Summary by Jurisdiction
Jurisdiction Property Coun Improved Value Content Value Total Value Loss Estimate Population
MORRO BAY 11 $5,724 $0 $5,724 $2,862 -
PISMO BEACH 10 N/A N/A N/A N/A -
Unincorporated 43 $2,016,245 $1,008,123 $3,024,368 $1,512,184 8
TOTAL 64 $2,021,969 $1,008,123 $3,030,092 $1,515,046 8
Source:Parcel analysis by Wood.
Table 5-38 Coastal Flooding Hazard Exposure by Property Type
Property Type Property Count Improved Value Content Value Total Value Loss Estimate Population
Government/Utilities 48 -- -- N/A N/A --
Other/Exempt/Misc 10 -- -- N/A N/A --
Residential 1 $968,412 $484,206 $1,452,618 $726,309 3
Multi-Family Residential 1 $972,774 $486,387 $1,459,161 $729,581 3
Residential:Other 1 $75,059 $37,530 $112,589 $56,294 3
Vacant 3 $5,724 -- $5,724 $2,862 --
TOTAL 64 $2,021,969 $1,008,123 $3,030,092 $1,515,046 8
Source:Parcel analysis by Wood.
San Luis Obispo County Local Hazard Mitigation Plan I October 2019 Page 5-120
Section 5
Risk Assessment
Sea Level Rise Impact Analysis
A geographic information systems (GIS) overlay analysis was performed to determine parcels and critical
facilities that may be affected by sea level rise. The GIS analysis method is the same in nature as that used
with other hazard layers, which are used in an intersection process to determine whether a critical facility,
shown as a point, or a developed parcel polygon, which is then converted to a centroid point to be more
easily represented, either falls in or outside of each hazard area.
For this particular overlay analysis two sets of sea level rise inundation data were used, based upon
currently available (August 2019) modeling representative of the best available science.The U.S.
Geological Survey Coastal Storm Modeling System Version 3.1 (USGS COSMOS 3.1) data provides detailed
projections of tidal inundation and coastal flood hazards between Golden Gate Bridge in San Francisco
Bay and Point Conception in Santa Barbara County. Projections show the modeled flood extents under
both existing conditions, and ten (10) possible future sea level rise scenarios ranging from 25 cm to 500
cm. COSMOS 3.1 is based on global climate models (GCMs) developed by the Intergovernmental Panel on
Climate Change and considers region-specific factors such as oceanographic conditions, backshore types
(beach, bluff or estuarine), long-term changes in the shoreline, river and stream drainages, wind patterns,
and seasonal changes. The model identifies areas along the coast where significant flooding may occur
under both a non-storm scenario and storm scenarios.
With COSMOS 3.1 data, for each modeled increase in sea level elevation, there is a minimum, average and
maximum range of uncertainty that is modeled. The maximum uncertainty scenario was used for the
purposes of this analysis, which effectively models a worst-case scenario for each given SLR scenario.
The SLR analysis includes three ranges of sea level rise across two scenarios, one with 100-year flooding
and one without. Sea level rise scenarios selected for analysis are based on projections for San Luis
Obispo provided by the Ocean Protection Council State of California Sea -Level Rise Guidance (OPC 2018)
under a worst case, or extreme risk aversion scenario (H++ scenario within Table 5-36 above). The H++
scenario was selected for analysis as the intent is to identify infrastructure and critical facilities that could
be irreversibly damaged by sea level rise, or would be significantly costly to repair, and would have
considerable impacts to public safety, health, or environmental resources. The first phase of analysis
models property and critical facility exposure to an average maximum tidal inundation at these
increments:
• Area extent of maximum tidal inundation with 25cm (approximately 1.0 ft) increase in sea level rise
• Area extent of maximum tidal inundation with 75cm (approximately 2.6 ft) increase in sea level rise
• Area extent of maximum tidal inundation with 300cm (approximately 9.9 ft) increase in sea level rise
These hazard zones show the projected maximum extent of what will be regularly flooded by tidal
movements under the three sea level rise elevations.
The second scenario of analysis uses the same sea level rise elevations previously described but models
the area extent of inundation associated with a 100-year coastal flood event (or 1% annual chance coastal
flood including waves). The addition of the flooding worsens the extent of the overall inundation and
represents how coastal and estuarine flooding will be exacerbated by sea level rise in the future.
Section 5
Risk Assessment
• Area extent of flooding from 100-year coastal flood event with 25cm (approximately 1.0 ft) increase in
sea level rise
• Area extent of flooding from 100-year coastal flood event with 75cm (approximately 2.6 ft) increase in
sea level rise
• Area extent of flooding from 100-year coastal flood event with 300cm SLR (approximately 9.9 ft)
increase in sea level rise
An exposure analysis was performed to identify the counts of improved properties, values of those
properties, and critical facilities located within the six scenarios. The number of parcels and critical facilities
were aggregated by parcel type and community (whether incorporated or instead a Community Services
District or Special District) or critical facility type and category. Improved value totals were calculated by
summing up all the improved values of the parcels of each type and in each community, as summarized in
the following tables.As a clarification, improved values are the values of the developments, or
improvements, not land value. The analysis does not predict damage loss, as property and content values
may change in the future, and it is assumed that some property will eventually be relocated or removed
prior to permanent inundation.The analysis does not account for undeveloped parcels that might be
permanently inundated by sea level rise in the future. Note that the inundation events become
progressively more extensive with the addition of the deeper sea level rise levels, thus property that is
inundated in the 25cm and 75cm scenarios is also inundated in the 300cm scenario and are totaled as
such.
The following results are aggregated into three main categories: incorporated jurisdictions, community
service districts, and special districts.A total of six tables are provided, two for each category, that depict
the count of exposed parcels and values of improvements on those parcels for the three sea level rise
scenarios, both with and without the 100-year flood (Note: SLR stands for Sea Level Rise).
Table 5-39 Number of Parcels Inundated by Sea Level Rise, with and without a 1%Annual
Chance Coastal Flood— Incorporated Jurisdictions
25-cm 75-cm 75-cm SLR 300-cm
cm
Parcel Type SUR SLR W/1% SLR w/
_L Flood 1%Flood
Commercial 6 6
Government/Utilities 4 7
Other/Exempt/Misc. 4 9
Grover Beach Residential 2 15
Multi-Family Residential 3 9
Mobile/Manufactured Homes 1
Industrial 1 3
TOTAL 0 0 20 0 0 50
Commercial - 12 - - 50
Government/Utilities 1 1 19 1 12
Morro Bay Other/Exempt/Misc. 6 1 3 19
Residential 1 12 9
Residential:Other - 3 1 1 76
Vacant 1 1 3 1 4
TOTAL 2 3 55 3 7 124
Commercial 9 2 4 9
Government/Utilities 1 1 12 4 5 13
Pismo Beach Other/Exempt/Misc. 1 18 1 6 22
Residential 1 2 37 2 9 41
Multi-Family Residential 93 6 104
Mobile/Manufactured Homes 3 2 3
Section 5
Risk Assessment
25-cm 75-cm00
Location Parcel Type SLR SLRM25-cm 75-cm SLR 4
Flood ...
Residential:Other -- -- 7 -- 13
TOTAL 2 4 179 9 32 205
Agricultural -- -- 4 3 3 4
Commercial -- 2 46 4 15 59
Government/Utilities 1 2 35 8 16 48
Other/Exempt/Misc. -- -- 43 2 16 59
Unincorporated Residential 14 434 30 92 563
Multi-Family Residential 1 110 3 18 163
Mobile/Manufactured Homes -- -- 2 -- -- 2
Residential:Other 1 1 39 3 14 47
Vacant -- -- 21 1 13 25
TOTAL 2 20 734 54 187 970
Source:USGS CoSMoS v3.1(2019),San Luis Obispo Assessor's Office/GIS,ParcelQuest 2018,Wood Parcel Analysis.
Table 5-40 Improved Values of Properties Inundated by Sea Level Rise with and without a 1%
Annual Chance Coastal Flood - In orated Jurisdictions
Location Parcel Type
Commercial $834,388 $834,388
Government/Utilities* -
Other/Exem pt/M isc.* $3,181,722 $3,883,627
Grover Beach Residential $198,637 $1,675,517
Multi-Family Residential $971,575 $3,466,989
Mobile/Manufactured Homes -- $305,343
Industrial $62,392 $107,956
TOTAL $0 $0 $5,248,714 $0 $0 $10,273,820
Commercial -- -- $4,441,799 -- $800,000 $4,441,799
Government/Utilities* -
Other/Exempt/Misc.* -- $74,906 -- -- $74,906
Morro Bay Residential $42,463 $3,930,417 $42,463 $42,463 $30,817,911
Residential:Other -- -- $7,707,961 -- $4,072,244 $9,981,210
Vacant $5,724 $5,724 $3,312,145 $5,724 $5,724 $3,337,145
TOTAL $5,724 $48,187 $19,467,228 $48,187 $4,920,431 $48,652,971
Commercial -- -- $3,931,762 $255,000 $330,726 $3,931,762
Government/Utilities* -- I -- -- -- --
Other/Exempt/Misc.* -- $2,214,828 $3,727,316 $2,214,828 $2,349,497 $3,727,316
Pismo Beach Residential $174,047 $176,839 $6,468,297 $176,839 $3,056,157 $6,933,545
Multi-Family Residential -- -- $22,908,703 -- $1,255,367 $24,617,998
Mobile/Manufactured Homes $17,059,909 $16,215,406 $17,059,909
Residential:Other $13,124,415 $17,033,080
TOTAL $174,047 $2,391,667 $67,220,402 $2,646,667 $23,207,153 $73,303,610
Agricultural -- -- $286,564 $120,863 $120,863 $286,564
Commercial $546,320 $11,955,715 $981,159 $3,759,287 $16,209,339
Government/Utilities* $8,491,063 $26,751,762 $8,491,063 $8,552,857 $26,921,391
Other/Exempt/Misc.* $13,477,246 $645,000 $5,987,495 $19,278,257
Unincorporated Residential $2,323,098 $83,336,297 $4,859,099 $21,089,501 $110,892,058
Multi-Family Residential $125,465 $15,885,589 $693,107 $5,211,282 $30,108,820
Mobile/Manufactured Homes -- -- $343,452 -- I -- 1 $343,452
Residential:Other $75,059 $75,059 $16,669,622 $2,084,548 $10,138,380 $34,731,855
Vacant -- -- $3,616,752 $10,404 $2,958,652 $6,135,235
TOTAL $75,059 $11,561,005 $172,322,999 $17,885,243 $57,818,317 $244,906,971
*Values may be underestimated as some values not available in parcel data due to being exempt from tax assessment.
Source:USGS CoSMoS v3.1(2019),San Luis Obispo Assessor's Office/GIS,ParcelQuest 2018,Wood Parcel Analysis.
San Luis Obispo County Local Hazard Mitigation Plan I October
Section 5
Risk Assessment
Table 5-41 Number of Parcels Inundated by Sea Level Rise with and without a 1% Annual
Chance Coastal Flood—Community Service Districts
Parcel Type Zb-cm rMon-cm 300-cm SLR Z!)-CM�,L& 75-cm SLR 300-cm SLP1
Commercial 10 -- F67
Government/Utilities 7 1 Other/Exempt/Mist. 13 1Avila Beach Residential 14 Multi-Family Residential 19 1Residential:Other 10 1Vacant -- -- 13 -- 1TOTAL 0 0 86 1 7Commercial -- 2 12 3 Government/Utilities -- 1 --Other/Exempt/Misc. -- 1 1
Residential 14 222 28 71 294
Los Osos
Multi-Family Residential - 4 -- - 10
Mobile/Manufactured Homes -- - 1 -- - 1
Residential:Other 1 1 3 3 3 3
Vacant -- - 2 1 2 2
TOTAL 1 17 246 36 83 327
Agricultural -- - 1 -- - 1
Commercial 9 13
Government/Utilities 10 10
Other/Exempt/Misc. 17 20
Oceano Residential 145 162
Multi-Family Residential 71 76
Mobile/Manufactured Homes 1 1
Residential:Other 20 24
Vacant -- - 2 -- - 2
TOTAL 0 0 276 0 0 309
Government/Utilities -- - - 1 1 1
San Simeon Multi-Family Residential -- - 21
Other/Exempt/Misc. -- - - 3
TOTAL 0 0 0 1 1 1 25
Government/Utilities -- -- -- -- -- 4
Cambria Other/Exempt/Misc. 1 1 1 1 1 1
Residential -- -- 7 -- -- 30
TOTAL 1 1 8 1 1 1 35
Source:USGS CoSMoS v3.1(2019),San Luis Obispo Assessor's Office/GIS,ParcelQuest 2018,Wood Parcel Analysis.
San Luis Obispo County Local Hazard Mitigation Plan I October 2019 Page 5-124
Section 5
Risk Assessment
Table 5-42 Value of Improved Values of Properties Inundated by Sea Level Rise and 1% Annual
Chance Coastal Flood—Community Service Districts
Location Parcel Type 25-cm 75-cm 25-cm SUR w/ 75-cm SLR
SLR SLR = 1%Flood W/1%Flood w/1%Flood
Commercial $4,744,109 $2,427,671 $6,267,359
Government/Utilities* $61,794 $61,794 $61,794
Other/Exempt/Misc.* $5,342,495 $5,342,495 $7,605,508
Avila Beach Residential $5,286,138 $4,001,139 $5,394,363
Multi-Family Residential $5,157,029 $4,518,175 $8,464,474
Residential:Other $7,193,724 $7,193,724 $22,050,689
Vacant $3,248,427 $2,937,427 $5,744,835
TOTAL $0 $0 $31,033,716 $0 $26,482,425 $55,589,022
Commercial -- $546,320 $2,243,469 $744,960 $883,510 $2,544,092
Government/Utilities* -- -- -- --
Other/Exempt/Misc.* $420,000 $420,000 $420,000 $420,000
Residential $2,323,098 $41,957,596 $4,462,878 $12,338,675 $55,511,993
Los Osos Multi-Family Residential $1,264,339 $3,120,843
Mobile/Manufactured Homes $62,149 $62,149
Residential:Other $75,059 $75,059 $2,084,548 $2,084,548 $2,084,548 $2,084,548
Vacant -- -- $21,225 $10,404 $21,225 $21,225
TOTAL $75,059 $2,944,477 $48,053,326 $7,722,790 $15,747,958 $63,764,850
Agricultural -- $165,701 $165,701
Commercial $1,558,192 $2,094,953
Government/Utilities* $0 $0
Other/Exempt/Misc.* $2,891,663 $3,045,326
Oceano Residential $23,372,714 $26,784,979
Multi-Family Residential $6,749,991 $8,992,923
Mobile/Manufactured Homes $281,303 $281,303
Residential:Other $2,792,785 $4,238,793
Vacant -- $242,315 $242,315
TOTAL $0 $0 $38,054,664 $0 $0 $45,846,293
Government/Utilities -- -- -- -- $0
San Simeon Multi-Family Residential $4,274,750
Other/Exempt/Misc. $0
TOTAL $0 $0 $0 $0 $0 $4,274,750
Government/Utilities* -- -- --
Cambria Other/Exempt/Misc.* -- --
Residential -- $2,255,769 -- $10,685,000
TOTAL I $0 1 $0 1 $2,255,769 $0 $0 $10,685,000
*Values may be underestimated as some values not available in parcel data due to being exempt from tax assessment.
Source:USGS CoSMoS v3.1(2019),San Luis Obispo Assessor's Office/GIS 2018,ParcelQuest,Wood Parcel Analysis.
San Luis Obispo County Local Hazard Mitigation Plan I October
Section 5
Risk Assessment
Table 5-43 Number of Parcels Inundated by Sea Level Rise with and without 1% Annual Chance
Coastal Flood -Special Districts
Location Parcel Type 25-cm 7S-cm 300-cm SLR 25-cm SLR w/ 75-cm SLR 300-cm SLR
Commercial 15 1 2 19
Government/Utilities 11 1 4 6 14
Other/Exempt/Misc. 10 1 3 12
Cayucos Sanitation District Residential - 46 2 12 83
Multi-Family Residential 1 16 3 3 28
Residential:Other - 6 1 8
Vacant - 3 - 3
TOTAL 0 1 107 11 27 167
Port San Luis Harbor District Government/Utilities 1 2 5 2 4 5
Other/Exempt/Misc. 1 1
TOTAL 1 2 6 2 4 6
Agricultural 1 - 1
Commercial 15 19
Government/Utilities 13 16
Other/Exempt/Misc. 21 29
South San Luis Obispo Residential 147 177
County Sanitation** Multi-Family Residential 74 85
Mobile/Manufactured Homes 1 2
Residential:Other 20 24
Industrial 1 3
Vacant 2 2
TOTAL 0 0 295 0 0 358
Source:USGS CoSMoS v3.1(2019),San Luis Obispo Assessor's Office/GIS,ParcelQuest 2018,Wood Parcel Analysis.
Table 5-44 Improved Values of Properties Inundated by Sea Level Rise with and without a 1%
Annual Chance Coastal Flood -Special Districts
Location Parcel Type 25-cm 75-cm 300-cm SLR 25-cm SLR 75-cm SLR 300-cm SLR
Commercial $3,409,945 $236,199 $448,106 $5,302,935
Government/Utilities* $0 $169,629
Other/Exempt/Misc.* $4,823,088 $225,000 $225,000 $6,418,638
Cayucos Sanitation District Residential $11,574,166 $396,221 $4,749,687 $21,631,681
Multi-Family Residential $125,465 $2,714,230 $693,107 $693,107 $5,255,830
Residential:Other $4,598,565 $860,108 $5,444,156
Vacant $104,355 $104,355
TOTAL $0 $125,465 $27,224,349 $1,550,527 $6,976,008 $44,327,224
Port San Luis Harbor District Government/Utilities* $8,491,063 $26,689,968 $8,491,063 $8,491,063 $26,689,968
Other/Exempt/Misc.*
TOTAL $0 $8,491,063 $26,689,968 $8,491,063 $8,491,063 $26,689,968
Agricultural $165,701 $165,701
Commercial $2,392,580 $2,929,341
Government/Utilities* $0 $0
Other/Exempt/Misc.* $6,073,385 $6,928,953
South San Luis Obispo Residential $23,571,351 $28,460,496
County Sanitation** Multi-Family Residential $7,721,566 $12,459,912
Mobile/Manufactured Homes $281,303 $586,646
Residential:Other $2,792,785 $4,238,793
Industrial $62,392 $107,956
Vacant $242,315 $242,315
TOTAL $0 $0 $43,303,378 $0 $0 $56,120,113
*Values may be underestimated as some values not available in parcel data due to being exempt from tax assessment.
**Note that South SLO Sanitation District encompasses the Cities of Grover Beach and Arroyo Grande as well as the majority of the Oceano CSD.As
such,the totals for the Sanitation District may be duplicative when compared to the other cities'and the CSD's totals.
Source:USGS CoSMoS v3.1(2019),San Luis Obispo Assessor's Office/GIS,ParcelQuest 2018,Wood Parcel Analysis.
San Luis Obispo County Local Hazard Mitigation Plan I October
Section 5
Risk Assessment
The results of the parcel analysis are projected estimates based on available data and modeling results,
which are subject to change based on the actual rate of sea level rise and the frequency and duration of
coastal storms. Sea level rise alone is not anticipated to be the primary cause of damage, but rather, sea
level rise exacerbates existing coastal hazards, including damage caused by severe storms and the
frequency, duration, and extent of tidal flooding. Further, this analysis assumes no adaptation nor
mitigation strategies are in place; implementation of future mitigation strategies may minimize these
impacts.
The parcel analysis indicates the greatest vulnerability from sea level rise is within the unincorporated
areas of the County and incorporated areas of Pismo Beach and Morro Bay.The results do not show any
property at risk within Grover Beach, which is largely set-back further and has less coastal development.
Both Morro Bay and Pismo Beach have relatively low vulnerability to the 25cm and 75cm tidal inundation
scenarios, but vulnerability increases significantly with a 300cm scenario. Combined with a 300cm and
100-year coastal flood scenario, the property at risk nearly doubles for Morro Bay.
The unincorporated areas of the County have the most overall vulnerability in terms of counts and values
of improved parcels. The majority of these vulnerable areas are located in the community service districts
of Los Osos, Oceano, Avila Beach, Cayucos and Cambria.
Regarding the community service districts (CSD), Los Osos, Oceano, and Avila Beach have the greatest
number of improved parcels potentially vulnerable to sea level rise. All three communities have
significant counts of developed parcels in the 300cm inundation level, both with and without the 100-year
flood.
In terms of improved parcel impacts the Port San Luis Harbor District, South San Luis Obispo County
Sanitation District and Cayucos Sanitation District is more vulnerable to the 300cm inundation level, with
relatively minor impacts to the smaller levels of inundation. Note that the South San Luis Obispo County
Sanitation District has overlap with Oceano and the Grover Beach. The values of property at risk for the
Port San Luis Harbor District include two piers, with values provided by the District. There is potential for
other property and infrastructure in the District to be at risk that is not accounted for due to limitations in
the asset database.
People
Some populations are more vulnerable to coastal erosion, coastal flooding, and sea level rise impacts due
to having certain sensitivities, an increased likelihood of exposure, or a lower adaptive capacity (Public
Health Institute Center for Climate Change and Health 2016). Demographic characteristics including
health conditions that affect physical ability and health, or socioeconomic factors that amplify risk factors
for poor health conditions, may affect the abilities of individuals or households to prepare for, respond to,
and recover from coastal hazards (EPA 2017). Specific attributes may create additional stresses on
individuals and communities resulting in reduced resiliency in the event of a coastal hazard event. Many
of these factors may also be exacerbated by the specific, localized nature of flooding, erosion, and other
impacts associated with sea level rise.
Social Vulnerability
Coastal areas with a high social vulnerability index inform which communities are more susceptible to
adverse impacts of coastal storms, flooding, and sea level rise. Based on the SoVI data presented and
Section 5
Risk Assessment
discussed in subsection 4.4.1, populations along the coastline that are most socially vulnerable to coastal
hazards are identified as Grover Beach, Oceano, and San Simeon.
A San Luis Obispo California Polytechnic State University graduate study titled A Geospatial Assessment of
Social Vulnerability to Sea-Level Rise in Coastal San Luis Obispo County was also referenced as another
source for a preliminary assessment of social vulnerability exposure (Carpentier 2017). This study focused
on the unincorporated areas only, and suggests higher social vulnerability in San Simeon, Cambria, and
Avila Beach.
Based on 2000 U.S. Census Bureau data and coastal floodplain modeling, the estimated population of the
county vulnerable to a 1-percent-annual-chance extreme coastal flood event is approximately 670 people
(Heberger et. al 2009). A 1.4-meter(4.6-foot) increase in sea level rise is projected to increase the number
of people in the county vulnerable to a 100-year coastal flood event to approximately 1,300, resulting in a
98% increase in the affected population. Of these, 85% identify as white, including white Hispanics, and
13% identify as a minority race. Additionally, approximately 45% of this vulnerable group is considered
low-income (<$30,000/year) (CEC 2012). An additional 1,100 people are vulnerable to erosion-related risk
along the coast as a result of 1.4 meter(4.6-foot) sea level rise.
Critical Facilities and Infrastructure
Critical facilities that are vulnerable to coastal hazards and sea level rise may include public transportation,
wastewater treatment and water supply infrastructure, schools, law enforcement facilities, and community
centers. Essential education facilities such as the Morro Bay High School and Coast Union High School
may be subject to coastal storms and flooding exacerbated by future sea level rise. Coastal erosion also
threatens the structural foundation of schools built close to the shoreline such as Shell Beach Elementary
School. Law Enforcement Facilities that are in close proximity to the shoreline such as in Pismo Beach and
Oceano are also vulnerable to coastal storms and flooding. Additional vulnerable facilities include the
Cambria wastewater treatment plant and municipal wells in Santa Rosa and San Simeon Creeks, the
Children's Center and the Avila Beach Community Center, each of which is located within a low-lying area
subject to potential inundation during a coastal storm.
Regional and local-serving public and utility infrastructure vulnerable to coastal hazards and sea level rise
include roads, bridges, railroad lines and crossings,wastewater treatment plants, culverts, water lines,
communication line and towers, stormwater outlets, bike lanes, bike facilities, airports, and fiber optic
lines. Utility infrastructure containing hazardous materials that are vulnerable to coastal hazards and sea
level rise include hazardous material facilities, the Diablo Canyon Nuclear Power Plant, underground tanks,
and Regional Water Quality Control Board clean-up sites (Protsman 2018). Facilities that are impacted by
coastal hazards could also result in a release of hazardous materials or deteriorating water or air quality,
as well as disruption to key public and utility services to the wider community. Such vulnerable facilities
include:
• The Diablo Canyon Power Plant
• San Simeon Wastewater Treatment Plant
• Cayucos Sanitary District
• Cambria Community Services District Municipal Water Wells
• Cambria Community Services District Wastewater Treatment Plant
• Oceano Wastewater Treatment Plant
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Risk Assessment
• City of Morro Bay Wastewater Treatment Plant
• Oceano County Airport
Low-lying transportation infrastructure is vulnerable to the impacts of coastal hazards, including roads in
Cayucos, Avila Beach, portions of the Southern Pacific Railroad, and sections of Highway 1 and Highway
101 (Caltrans 2018a). Highway 1 was found to be potentially vulnerable to inundation, flooding, and bluff
erosion hazards as a result of sea level rise (Figure 5-41), as existing shore protection is either absent or
easily overwhelmed by overtopping waves (Moffat & Nichol 2018). Approximately 2.8 miles of Highway 1
at Piedras Blancas north of San Simeon was recently relocated inland due to past and future threatened
damage from coastal bluff erosion.
Figure 5-41 Low-lying Portions of Highway 1 in San Luis Obispo County
Currently,low-lying sections of Highway 1 in San Luis Obispo County are vulnerable to coastal hazards such as erosion and inundation from coastal
storms and sea level rise;a segment.Source:(Caltrans 2018b)
Wastewater treatment plants for coastal communities located in low-lying areas along coastal streams
may be vulnerable to coastal hazards and projected sea level rise. For example, while the Cambria
Community Services District and Oceano wastewater treatment plants are both located more than 1,500
feet from the shoreline, their location in low-lying coastal stream valleys may make them vulnerable to the
combination of fluvial flooding and tidal inundation associated with projected sea level rise. In addition,
coastal community municipal wells, such as CCSD wells along San Simeon and Santa Rosa Creeks are
located near the coast and may be vulnerable to sea level rise-related inundation or possible future salt
water intrusion. Hazardous materials facilities such as underground gas tanks and known hazardous
cleanup sites equate to higher potential losses because damage to such structures may implicate leaked
chemicals that pose impacts to health and safety(Protsman 2018).
Sea Level Rise Analysis on Critical Facilities
Exposure of 11 critical facilities to sea level rise is noted in the following tables; all of these with the
exception of one are not at risk until the 300cm level of inundation. Wastewater treatment plants
potentially at risk include the Morro Bay/Cayucos WWTP, San Simeon WWTP, and South San Luis Obispo
County WWTP; San Simeon's WWTP is most vulnerable and at risk to 100-year coastal flooding with the
25cm SLR scenario. Table 5-45 summarizes the critical facilities based on sea level rise inundation type
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Risk Assessment
and location, while Table 5-46 includes additional details on these facilities (facility name, address, type of
facility, and category of the facility).
Table 5-45 Critical Facilities in Sea Level Rise Areas by Facility Category and Location
Total Tota I I Total
Total Total Total Facilities— Facilities— Facilities—
Facility Facility Category Facilities— Facilities— Facilities— SLR of SLR of 75cm SLR of
Location SLR of SLR of SLR of 25cm+ 00
00 00 00
flood flood flood
Emergency Services -- , -- 1 -- -- 1
High Potential Loss - 1 - 1
Morro Bay Facilities
Lifeline Utility
5
Systems
TOTAL 0 0 7 0 0 7
San Simeon Lifeline Utility -- -- -- 1 1 1
Systems
TOTAL 0 0 0 1 1 1
Ca ucos I -- -- -- 1 -- -- 1
TOTAL 0 0 1 0 1 0 1
South San Luis
Obispo Lifeline Utility
Sanitation -- -- 1 -- -- 1
District and Systems
Oceano
Oceano Transportation 1 1
Systems
TOTAL 0 0 2 0 0 2
GRAND TOTAL 0 0 10 1 1 11
Source:USGS CoSMoS v3.1,San Luis Obispo Planning&Building/GIS,HIFLD,SLO County Community Service Districts and Special Districts,Wood
Parcel Analysis.
San Luis Obispo County Local Hazard Mitigation Plan I October
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Risk Assessment
Table 5-46 Critical Facilities in Sea Level Rise Areas by Facility Category and Location
Morro Bay/Cayucos 160 Atascadero Wastewater Treatment
Wastewater Treatment Road Lifeline Utility Systems Plant
Plant
Microwave Service Morro Bay Power Lifeline Utility Systems Microwave Service
Tower Plant Towers
Microwave Service Not Available Lifeline Utility Systems Microwave Service
Tower Towers
Morro Bay
Microwave Service Not Available Lifeline Utility Systems Microwave Service
Tower Towers
Morro Bay Electrical PG&E Lifeline Utility Systems Energy Commission
Substations Substations
Morro Bay Power Plant Dynegy, Inc. High Potential Loss Power Plants
Facilities
Morro Bay High School 235 Atascadero Rd Emergency Services Public Schools
Cayucos Fire Protection
Cayucos District 201 Cayucos Drive Emergency Services Fire Stations
San Simeon San Simeon Wastewater 9245 Balboa Ave Lifeline Utility Systems Wastewater Treatment
Treatment Plant Plant
South San Luis South San Luis Obispo Wastewater Treatment
Obispo Sanitation Sd Wastewater 1600 Aloha PI Lifeline Utility Systems Plant
District and Oceano Treatment Plant
Oceano Oceano County Airport Oceano Transportation Systems Airport
Source:USGS CoSMoS v3.1,San Luis Obispo Planning&Building/GIS,HIFLD,SLO County Community Service Districts and Special Districts,Wood
Parcel Analysis.
Economy
The major economic industries in San Luis Obispo County by employment include tourism, retail, service
industries, government, and agriculture (Moser, Ekstrom 2012). Developed areas of the San Luis Obispo
coast that are important to tourism include Cambria/Moonstone Beach, Cayucos, Morro Bay, Port San
Luis/Avila Beach, and Pismo Beach (USACE 2016). Although the most popular beaches are located in the
southern part of the county, beach tourism is important throughout the county (USACE 2016). However,
projected climate change and sea level rise could cause an overall reduction of economic value in beach
visitation. Some beaches may potentially lose attendance and associated earnings due to loss of beach
resulting from beach erosion, while others may experience increased attendance and beach-related
earnings as beaches elsewhere become less usable for recreation (Moser and Ekstrom 2012). Vertical and
lateral beach access points may also be affected by coastal erosion and inundation due to sea level rise,
which would prevent residents and visitors from accessing the beach and may increase the risk of injuries
(Protsman 2018).
Beach tourism is important to the county' economy and generates significant revenue as many visitors
rent hotels or other accommodations, dine out or shop at area stores.Visitor-serving areas such as those
in Oceano, Cambria, and Avila Beach include local businesses and hotels that benefit the local economy
(Protsman 2018). These businesses depend on tourism, and cities and communities within San Luis
Obispo benefit from sales tax revenues. Disruption of these areas due to impacts of coastal hazards and
projected sea level rise could decrease economic activity and affect the local economy.
Future coastal beach and bluff erosion in the county may also negatively impact coastal businesses and
households and decrease coastal real estate opportunities. Coastal bluff failure due to coastal erosion can
create hazardous conditions due to roadway collapse, undermined home foundations and damage to
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Risk Assessment
utilities (Russell &Griggs 2012). Natural resources with recreational and economic value may also be
adversely affected.The county supports some of the largest dune habitats in the State including Morro
Bay State Park, Oceano Dunes Natural Preserve, and the Guadalupe-Nipomo Dunes, which are vulnerable
to damages from coastal storms and erosion. As this vulnerability increases over time, damages may
impact the economy of the area and impact viable coastal land uses. Coastal storms can also cause
erosion impacts and severe flooding and inundation of economically important infrastructure such as
harbors and buildings related to commercial and recreational fisheries (Moser and Ekstrom 2012).
Historic, Cultural, and Natural Resources
Historic resources along the coast include designated historic sites and points, county-designated
Sensitive Resource Areas and Archeological Resource Areas, county and State Parks, and other important
habitat resource areas (Protsman 2018). Historic resources close to the coastline include museums such as
the Morro Bay Maritime Museum, Museum of Natural History, and the Oceano Depot Museum. Historic
resources also include coastal features such as recreational piers in Cayucos, Pismo, Avila and the Point
San Luis Lighthouse, and the restored historic warehouse at the foot of Harford Pier in Port San Luis
Harbor(Port San Luis Harbor District 2007). Cayucos Pier is considered a historic property in the VE
coastal 100-year flood zone.
One of the most visually prominent historic natural landmarks immediately vulnerable to coastal hazards
and sea level rise is Morro Rock. Morro Rock stands approximately 576 feet tall and was created from a
volcanic plug. The area is a significant cultural and religious monument, as it was once the site of
Chumash sacred rituals (City of Morro Bay 2018). Morro Rock is a protected State Historic Landmark
(#821) that also provides nesting habitat for peregrine falcons, a previously endangered and currently fully
protected species (Department of Fish and Wildlife 2019).
Figure-.5-42.. Morro Bay and Morro Rock
140,
l
A.
Y
4
Morro Rock is a historical,cultural,and natural landmark at the mouth of Morro Bay that also provides nesting habitat for Peregrine Falcons.Photo
Source:Morrobay.org 2019
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Risk Assessment
The county's coastline includes a variety of natural habitats including sandy beaches, subtidal soft-bottom,
rocky tide pools, offshore reefs, bays, estuaries, and harbors (USACE 2016). These include several
managed areas and protected habitats, including the State Marine Conservation Areas (SMCA), State
Marine Reserves (SMR), State Marine Recreational Management Area (SMRMA), state parks and beaches,
and state game refuges.These areas support ecologically significant habitats where endangered or
threatened species occur, including designated critical habitat and nesting and foraging sites for
shorebirds. State parks and beaches within the San Luis Obispo County coastline include Cayucos State
Beach, Estero Bluffs State Park, Los Osos Oaks State Reserve, Montana de Oro State Park, Morro Bay State
Park, Morro Strand State Beach, Harmony Headlands State Park, Hearst San Simeon State Park, and the
W.R. Hearst Memorial State Beach (Department of Parks and Recreation 2019).
Figure 5-43 Estero Bluffs State Park, Cayucos
n-
a f
1
. V
, n
The Estero Bluffs State Park has a variety of natural resources including intertidal areas,native grasslands,wetlands,low bluffs,and coastal terraces with
hiking trails and 3 miles of beach,which is vulnerable to coastal hazards(Department of Parks and Recreation 2019).
The combined influence of sea level rise and coastal hazards may result in a migration of habitat inland
and to higher elevations, or a transition to a different habitat type.With this consideration, there may be
development or other impediments to inland migration that may result in the net loss of habitat. For
example, accelerated erosion of the Oceano Dunes may cause this habitat may migrate inland. If a
freshwater wetland is exposed to rising tides, it will transition to a saline estuarine wetland. The faster the
climate changes, the more difficult it will be for animal species to migrate and for floral habitats to re-
establish elsewhere. Nevertheless, some of the more resilient species may adapt in place.
Future Development
Land use and development along the county's shoreline is governed by the California Coastal Act.
Regulations under the Coastal Act are typically administered by the county and local cities through
adopted Local Coastal Plans, overseen by the California Coastal Commission (California Coastal
Commission 2019; County of San Luis Obispo 2018).The California Coastal Commission mandates that a
site-specific sea level rise analysis and bluff retreat study are performed to obtain a coastal development
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Risk Assessment
permit for new development. Planning for proposed bluff-top development must assess the average
long-term beach and bluff retreat rate, erosion rate due to various sea level rise scenarios, and erosion
potential from 100-year storms and other extreme events. Bluff retreat studies must establish a
"development setback"that creates a buffer behind which development would be protected from bluff
erosion for a minimum of 75 years.
The county and each incorporated city's certified Local Coastal Plans govern land use planning and
development permitting. The county's General Plan, including the Framework for Planning- Coastal Zone
guides development in unincorporated areas. The Estero Area Plan, North Coast Area Plan, San Luis Bay
Coastal Area Plan, Port San Luis Harbor District Port Master Plan, and the South County Coastal Area Plan
provide area specific guidance (County of San Luis Obispo 2019c). Each city also as a certified Local
Coastal Plan which governs land use and permitting with the coastal areas of the cities.
Risk Summary
Coastal storms are a recurring hazard for San Luis Obispo County that impact the entire coastline. Wave
run-up erodes the coastline at varying rates depending upon geological composition. Development
located in proximity to the shoreline is most vulnerable to coastal hazards and sea level rise; however,
impacts are variable. Residential development is most susceptible to damage from coastal bluff erosion
due to cliff collapse and shoreline retreat. Low-lying development and infrastructure fronted by sandy
beaches however, are most vulnerable to dune erosion and impacts of sea level rise.
Coastal Storms:
• Coastal storms impact the entire coastline, causing beach and bluff erosion and coastal flooding of
low-lying areas.
• Proximity of structures to the coastline increases vulnerability to the effects of coastal storms, coastal
erosion, and sea level rise.
Coastal Erosion:
• The County of San Luis Obispo coastline's geologic composition and exposure to wave energy is quite
varied. Sections of the coast range from rocky coastline to sandy beaches backed by cliffs, to sandy
beaches backed by sand dunes. These differing characteristics affect erosion characteristics as well.
• Short-term coastal erosion (e.g., cliff failure) occurs episodically, mainly during periods of intense
wave action that coincides with high tides and coastal storms.
• Annual rates of coastal erosion range from about three inches a year to more than one foot a year
depending on coastline composition and exposure to coastal hazards.
• Some of the potentially most vulnerable structures in the county are bluff top homes and business
that are exposed to bluff erosion in the communities of San Simeon, Cayucos, Cambria and Pismo
Beach. Public streets that border the coastal bluffs can also be subject of erosion damage.
• Portions of communities are low-lying which can expose public facilities such as wastewater
treatments plans to costal flood hazards.
• Both bluff erosion and coastal flooding are exacerbated during major EI Nino events such as the
2015-2016 EI Nino event.
• Coastal storm flooding hazards are limited throughout much of the county, while those from bluff
erosion range from moderate to significant for bluff top homes and facilities.
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Risk Assessment
Sea Level Rise:
• Future projected sea level rise may affect potential hazards in the county and is projected based on
the best available science and modeling.
• Rising sea levels alone are not anticipated to be the primary cause of vulnerabilities and potential
damages to resources, property and infrastructure within San Luis Obispo County.
• Impacts may instead be caused by existing severe storm coastal process-related hazards increasing in
frequency and duration as a result of sea level rise.
• If sea levels continue to rise at higher projected rates, episodic coastal erosion and coastal flooding
impacts that already occur during large storm wave events could become more frequent, as
predictable high tides may regularly inundate public beaches and low-lying coastal infrastructure.
• Effects on people and housing: Historically, there has been little or no loss of life or injury in San Luis
Obispo County due to coastal storms. The primary impacts have been economic in nature.
• Effects on commercial and industrial structures:As beaches erode, the amount of recreational beach
available to the public is substantially reduced. Changes in beach geometry can alter the wave
characteristics of a particular site. Beach erosion results in the loss of sand from coastal areas.This
hazard can accelerate the rate of erosion of coastal bluffs and can also contribute to increased wave-
related damage to coastal structures.
• Effects on infrastructure: Erosion of beach sand removes the natural barrier that protects landforms
and structures from the potentially destructive wave action.The end result can be the direct
destruction of roads, homes, and other structures by waves whose force is no longer dissipated by
wide beaches.
• Related Hazards:Adverse Weather, Flooding
Table 5-47 Coastal Storm/Coastal Erosion/Sea Level Rise Hazard Risk Summary
Jurisdiction Geographic -T-Probability of Future Magnitude/ Overall
Extent Occurrence Severity Significance
San Luis Obispo County Limited Likely Limited Medium
City of Arroyo Grande N/A I N/A N/A N/A
City of Atascadero N/A I N/A N/A N/A
City of Grover Beach Limited I Occasional Limited Low
City of Morro Bay I Extensive I Likely Critical High
City of Paso Robles I N/A N/A N/A N/A
City of Pismo Beach I Significant Occasional Limited Medium
City of San Luis Obispo N/A I N/A N/A N/A
Avila Beach CSD Significant Likely Limited Medium
Ground Squirrel Hollow CSD N/A
Heritage Ranch CSD N/A
Los Osos CSD Significant I Likely Limited Low
Nipomo CSD N/A
San Miguel CSD N/A
San Simeon CSD Significant Likely Limited Low
Section 5
Risk Assessment
Jurisdiction Geographic Probability of Future Magnitude/ TOverall
OccurrenceExtent Sigr
Templeton CSD N/A
a
Cayucos Sanitary District Significant Likely Limited Medium
Port San Luis Harbor District Significant Highly Likely Limited High
San Luis Obispo FCWCD Limited Likely Limited Medium
South San Luis Obispo Sanitation N/A
District
San Luis Obispo County Local Hazard Mitigation Plan I October
Section 5
Risk Assessment
5.3.8 Dam Incidents
Hazard/Problem Description
Dams are manmade structures built for a variety of uses, including flood protection, power generation,
agriculture, water supply, and recreation.When dams are constructed for flood protection, they usually
are engineered to withstand a flood with a computed risk of occurrence. For example, a dam may be
designed to contain a flood at a location on a stream that has a certain probability of occurring in any one
year. If prolonged periods of rainfall and flooding occur that exceed the design requirements, that
structure may be overtopped and fail. Overtopping is the primary cause of earthen dam failure in the
United States. Dam failures can also result from any one or a combination of the following causes:
• Earthquake
• Inadequate spillway capacity resulting in excess overtopping flows
• Internal erosion caused by embankment or foundation leakage or piping or rodent activity
• Improper design
• Improper maintenance
• Negligent operation
• Failure of upstream dams on the same waterway
Water released by a failed dam generates tremendous energy and can cause a flood that is catastrophic
to life and property. A catastrophic dam failure could challenge local response capabilities and require
evacuations to save lives. Impacts to life safety will depend on the warning time and the resources
available to notify and evacuate the public. Major loss of life could result as well as potentially
catastrophic effects to roads, bridges, and homes. Associated water quality and health concerns could also
be issues. Factors that influence the potential severity of a full or partial dam failure are the amount of
water impounded;the density, type, and value of development and infrastructure located downstream;
and the speed of failure.
Controlled release or spillway flooding: inadequate spillway capacity often results in excess overtopping
flows, though the potential for flooding as a result of discharge from dam outlet structures or spillways
could be expected during excessive rain events. However, controlled releases of water from dams is a
measure that can prevent or minimize spillway flooding or structure failure, by regulating capacity in a
managed way. Even controlled releases can lead to unwanted or unpredicted flooding, depending on
environmental and weather conditions, or even human error.
In general, there are three types of dams: concrete arch or hydraulic fill, earth-rockfill, and concrete
gravity. Each type of dam has different failure characteristics. A concrete arch or hydraulic fill dam can fail
almost instantaneously: the flood wave builds up rapidly to a peak then gradually declines.An earth-
rockfill dam fails gradually due to erosion of the breach: a flood wave will build gradually to a peak and
then decline until the reservoir is empty.And, a concrete gravity dam can fail instantaneously or gradually
with a corresponding buildup and decline of the flood wave.
Geographic Area
According to the California Department of Water Resources'Jurisdictional Dams as well as the National
Inventory of Dams databases there are dams in the County constructed for flood control, irrigation
storage, recreation, and stock watering purposes.The combined state and federal dataset identifies 15
Section 5
Risk Assessment
dams, located in or upstream of the County of San Luis Obispo. Of these dams, ten are considered high
hazard,three as significant hazards, one as a low hazard, and one as undetermined hazard. The San
Antonio Dam is located just north of San Luis Obispo County, within Monterey County,while Twitchell is
on the boundary between Santa Barbara and San Luis Obispo Counties; however, they pose a threat to
San Luis Obispo County since they are on drainages that flow into the County. Table 5-48 details the high
and significant hazard dams affecting the County of San Luis Obispo. The majority of these dams are in
the Salinas and Central Coastal watersheds, with one being located in the Cuyama watershed, all in the
central and west portions of the county. Both incorporated and unincorporated areas are at risk of
damage from flooding in the event of a dam failure, however,Atascadero, the City of San Luis Obispo,
and the central portions of the unincorporated county are at greater risk due to being more largely urban
or more directly downstream/below the dams on the valley floor. Besides the 13 high or significant hazard
dams noted below, the Las Tablas Creek dam is rated as a low hazard structure, with 180 acre-feet of
storage capacity and 37 feet in height, while the Klau Dam is undetermined hazard rating-wise, only
having a 50 acre-feet of storage capacity and being 45 feet in height.
Table 5-48 County of San Luis Obispo Dams of Concern Characteristics
Dam Storage
Hazard Dam Name Drainage Downstream Dam Height Capacity
Rating Community Type (in (Acre- Plan?
Feet) Feet)
High Atascadero Tr Atascadero Creek Atascadero Earth 18 250 No
Park
High Chorro Chorro Creek Camp San Luis Earth 77 90 No
Creek Obispo
Significant Eagle Ranch Hale Creek Atascadero Earth 55 300 No
Significant Hartzell Santa Rita Creek Atascadero Earth 50 300 Yes
High Lopez Arroyo Grande Creek Arroyo Grande Earth 166 52,500 No
High Nacimiento Nacimiento River Bradley Earth 255 470,000 Yes
High Righetti W Corral De Piedra Edna Earth 83 735 No
High Salinas Dam Salinas River Santa Margarita Concrete 135 43,200 Yes
High San Antonio San Antonio River Bradley Earth 202 350,000 No
Significant San Marcos San Marcos Creek Paso Robles Earth 42 325 Yes
High Terminal Tr Arroyo Grande Arroyo Grande Earth 53 844 No
High Twitchell Cuyama River Santa Maria Earth 241 398,120 Yes
High Whale Rock Old Creek Cayucos Earth 193 40,662 Yes
Source:National Inventory of Dams,2018;California Department of Water Resources—Jurisdictional Sized Dams,2018
Note:1 acre-foot=325,851 gallons
Figure 5-44 illustrates the locations of identified dams of concern within the County, including their major
drainages, while Figure 5-45 displays the dam inundation areas for eight of the ten high hazard dams in
the county.
San Luis Obispo County Local Hazard Mitigation Plan I October 2019
Section 5
Risk Assessment
Figure 5-44 Dams of Concern to San Luis Obispo County
SanAnionio Reservoir
Kings
Monterey 'G, r
� � Tulare
�- >�6
SAN AN,
i-�41J W
NACIMIENTO Es"
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41 �p r.
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Morro Bay" CHORRO 01 I
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A RIGHETTI
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Counties
Map compiled 212019; a 10 20 40 Miles N
intended for planning purposes only. I
Data Source: San Luis Obispo County, N
US Census TIGER Database,CA Open
Data Portal,CA DWR,NID 2018
San Luis Obispo County Local Hazard Mitigation Plan I October
Section 5
Risk Assessment
Figure 5-45 Dam Inundation Areas in San Luis Obispo County
Monterey { Kings Tulare
-101 1
z
---------------SAN ANTONIO- t
4 A I" -
r, NACIMIENTO 46
V� A
I"'-- LAS TABLAS CREEK !� Prrr;e:rark
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41 �. c
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41
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PACIFIC OCEAN HORRO '101 I
SALINAS -
j�s $8
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} RIGHETTI - i- -----�
+� LOPEZ T'keen ral", _ r
Dam Hazard Category i"=_. Counties Pismo
L---j <_ Beach. st,m L.k, i------
♦ High -Cares TERMINALGroveI
Significant Dam Inundation Extent Beach Arroyo Grande
Beach i
Low Lopez Dam X101 j f,,:
f 1 f ti r --
- Undetermined Nacimiento Dam
Waterways -Righetti Dam !1 > A.TWITCHELL
Lakes _Salinas Dam 1 Santa Barbara \��� -j
I Railroads �San Antonio Dam i -----I
Highway -Terminal Dam
Freeway Twitchell Reservoir Ventura
Whale Rock Reservoir
Map compiled 512019; o 10 20 4o Miles N
intended for planning purposes only. I I I A
Data Source- San Luis Obispo County,
US Census TIGER Database,CA Open
Data Portal,NID 2018,CA D1NR
San Luis Obispo County Local Hazard Mitigation Plan I October
Section 5
Risk Assessment
Extent (Magnitude/Severity)
Standard practice among federal and state dam safety offices is to classify a dam according to the
potential impact a dam failure (breach) or mis-operation (unscheduled release) would have on
downstream areas. The hazard potential classification system categorizes dams based on the probable
loss of human life and the impacts on economic, environmental and lifeline facilities. Dams are classified
in three categories that identify the potential hazard to life and property:
• High hazard indicates that a failure would most probably result in the loss of life;
• Significant hazard indicates that a failure could result in appreciable property damage;
• Low hazard indicates that failure would result in only minimal property damage and loss of life is
unlikely.
• Undetermined hazard dams have not been rated or their hazard rating is not known
Since the County has several High and Significant hazard dams, there is potential for loss of life and
property damage. Both unincorporated and incorporated areas of the County are identified on dam
failure inundation maps included in the County's Dam and Levee Failure Evacuation Plan, last updated on
February of 2016, and also displayed in Figure 5-45.The inundation areas for each of the dams are
generally downstream and include large rural and urban areas on the valley floor below the dams.
Adjacent jurisdictions could also be affected by a dam failure in San Luis Obispo County. These include,
depending on the dam involved and to a limited extent, the Counties of Monterey and Santa Barbara.
The extent of impacts depends on the nature of failure and location of the dam. The largest populations
potentially at risk would be in Arroyo Grande, Grover Beach, Pismo Beach, Paso Robles, and Atascadero.
Unincorporated areas across the county, particularly running through the Salinas River, east of the
Nacimiento Reservoir, and west of the Twitchell Reservoir, would also be impacted were a dam to fail and
flood downstream.
Past Occurrences
There is no history of dam failure affecting the county, but there have been recurring issues with flooding
due to high flows released below dams in the area.
Events in 1969, 2006, 2011, 2017, Nacimiento Area/Heritage Ranch Community Service District(HRCSD) -
Heavy rains on several occasions have led to flooding, which led to filling of the Nacimiento Reservoir to
capacity. High flow releases from the dam by Monterey County Water Resources Agency (MCWRA) was
necessary to relieve pressure on the dam. HRCSD's only potable water system is a fourth of a mile
downstream from the dam and has been destroyed once and damaged at least two other times by these
high flow releases.The high release in 1969 caused very significant damage to downstream property prior
to construction of HRCSD facilities. Destruction of HRCSD Gallery Wells (water system intake facilities) did
take place in the 2011 event, and damage of the same on at least two other occasions (2006 and 2017).
The District noted costs associated with replacement and repair of infrastructure, additional water
treatment necessary to compensate for loss of treatment efficiency due to temporary intake facilities
during reconstruction, damage from scour and removal of gallery well filter media during at least two
other high flow events (HRCSD 2019 HMP Update Workbook). The replacement value of the water
treatment and distribution system is $18.1 million.
Section 5
Risk Assessment
Probability of Future Occurrences
Unlikely—The County remains at risk to dam failures from numerous dams under a variety of ownership
and control and of varying ages and conditions. However, based on historical experience and HMPC input,
dam failure is unlikely in the area. Nevertheless, given the number of dams of concern in the County the
potential exists for future dam failures in San Luis Obispo County, but the likelihood of this is low.
Uncontrolled or controlled release flooding as well as spillway flooding below dams due to excessive rain
or runoff are more likely to occur than failures.
Climate Change Considerations
The potential for climate change to affect the likelihood of dam failure is not fully understood at this point
in time. With a potential for more extreme precipitation events a result of climate change, this could
result in large inflows to reservoirs. However, this could be offset by generally lower reservoir levels if
storage water resources become more limited or stretched in the future due to climate change, drought
and/or population growth.
Vulnerability
A dam incident can range from a small, uncontrolled release to a catastrophic failure.Vulnerability to dam
failures is confined to the areas and populations subject to inundation downstream of the facility.
Secondary losses would include loss of the multi-use functions of the dam itself and associated revenues
that accompany those functions.
The Central Coast Tribune News for the County of San Luis Obispo yielded the following information
(summarized in Figure 5-46) on potential dam failures and how they would affect nearby communities,
based on dam inundation data from the San Luis Obispo County Office of Emergency Services (Tribune
Staff, 2017). However, parcel analysis was carried out with the latest datasets from the county as well as
assessor's office improvement values and ParcelQuest provided spatial layers, to overlay each dam
inundation layer with the parcels to arrive at total parcels exposed, loss estimates, and populations at risk.
The dam inundation areas by high hazard dam in the county are displayed in Figure 5-45 and the results
of the parcel analysis explained in more detail in the sections below.
Section 5
Risk Assessment
Figure 5-46 Dam Inundation Impacts to Downstream Communities in San Luis Obispo County
MONTEREY COUNT'(
�� �•.,�� SAN LUIS OU15PO COUNTY
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n
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People living in the populated areas 6u•d•t•pe yenta" 1
downstream from Lopez Lake and Marla
Whale Rock Reservoir face the biggest `
risks of damage ifa dam failed. BARBARA
COUNT4 orcutt mapslrieg5:o7[iy RE
NACIMIENTO DAM•Lake Nacimiento
Earth-filled dam,377,900 acre-feet capacity. roads Flooded may include Las PiIitas Road;
Most flooding would flow north along the Highways 41,46.58.101,Indian Valley Road;
Salinas River in Monterey County;some water North River Road near Paso Robles;and Main
would flow south toward San Miguel,During a Street in Templeton,
major flood,Highway 101 would Flood from
Camp Roberts through San Ardo. LOPEZ DAM•Lopez Lake
Earth-filled dam,49,000 acre feet capacity.
WHALE ROCK DAM•Whale Rock Reservoir In a dam failure,water would flow west
Earth-filled dam,4a600 acre feet capacity.In follow Ing Arroyo Grande Creek and could
a dam failure,water would Flow southwest along flood about 3,000 feet—or more than half a
Old Creek,about 1,000 feet on each side of the mile—on each side of the creek's center line.
creek's center line,reaching 13th Street and About 10,000 to 12,000 people could be
Ocean Avenue in Cayucos.About 1,500 people affected in Arroyo Grande,Grover Beach,
would be affected,as would the Cayucos Water Halcyon,Oceano and Pismo Beach.
Treatment Plant.Highway 1 may flood. Floodwaters could reach Huasna Road in 30
minutes and Highway 101 in 40 minutes.
SALINAS DAM a Santa Margarita Lake
Concrete dam,23,000 acre feet capacity.In a TWITCHELL DAM•Twitchell Reservoir
dam failure,water would Flaw north along the Earth-filled dans,240,100 acre feet capacity.
Salinas River about 300 to 500 feet on each In a dam and levee Failure,most flooding
side of the centerline of the river and into would occur in Santa Barbara County.About
fingers in low-lying areas up to Atascadero. 100 to 160 people could be affected in the
Significant water rise is not expected.About Oso Raco area.Major roads Flooded could
1,000 to 2,000 people could be affected.Major include Highway 1 near the SLD County line.
SOURCE:San Luis Obispo County Office of Emergency Services BE TH ANDERSON banderson@the[nbu nenem c
MONICA VAUG HAN.—jhan@tfietnb�nen—c
San Luis ObispoCounty Local • Mitigation Plan I October 2019 Page 5-143
Section 5
Risk Assessment
General Property
In general, communities located below a high or significant hazard dam and along a waterway are
potentially exposed to the impacts of a dam failure. For reference, high hazard dams threaten lives and
property, significant hazard dams threaten property only. Inundation maps that identify anticipated
flooded areas (which may not coincide with known floodplains) are produced for all high hazard dams
and are contained in the Emergency Action Plan (EAP) required for each dam. A GIS layer that contained
inundation maps for eight of the ten high hazard dams that affect the County was analyzed to quantify
risk across the planning area.Table 5-49, Table 5-50 and Table 5-51 summarize the estimated losses
calculated from tallying up the parcels' improved and content values (more details on the parcel analysis
methodology under the Asset Summary section). The loss estimate percentage used for dam failure
inundation is 50% of a parcel's total value.
Figure 5-47 displays the parcels found to overlay with the dam inundation layer. According to the analysis
of the dams with a potential to impact the planning area the Lopez Dam has the greatest potential
downstream impacts coupled with a relatively short time to evacuate downstream areas. The Whale Rock,
Salinas, and Twitchell dams also pose significant threats should a failure occur. Some jurisdictions are
more at risk to dam failure than others. The cities of Arroyo Grande, Grover Beach, portions of the
unincorporated areas are the most vulnerable.Atascadero, Pismo Beach, and Paso Robles also have a high
hazard dams located upstream of them.The failure of any of these dams would cause downstream
flooding and would likely result in loss of life and property. The potential magnitude of a dam failure
depends on the time of year and the base flow of the river when the failure occurs. During the winter
months, when the river flows are higher, the impact to the area would be much greater and evacuation
times even shorter.
Section 5
Risk Assessment
Figure 5-47 Parcels Within Dam Inundation Areas in San Luis Obispo County
N
A41
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Reservoir
46
Paso Robles
41
46
4
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a1 Atascadero
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San Luis s
Obispo
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iy 101
Pismo Beach
Parcels Within Dam Inundation Areas Railroads
• Parcels -- - Highway
Dam Inundation Extent Grover Arroyo Grande
Freeway Beach
Lopez Dam I
Lakes
Nacimiento Dam • 101
Waterways1
- Righetti Dam t
a Cities �• _••1 \1
- •
Salinas Dam --- Counties i •• P
l '•�• •
- Terminal Dam • .• ~'•►r• •w►•• _
Twitchell Reservoir i �•r �• • i;;_;;;•,,;,;-
Whale Rock Reservoir
Map compiled 3/2019; a 10 20 Miles N
intended for planning purposes only. I I
Data Source: San Luis Obispo County,
LIS Census TIGER Database,CA Open
Data Portal,ParcelQuest
Section 5
Risk Assessment
Table 5-49 Dam Inundation Estimated Losses by Jurisdiction and Dam
Jurisdiction Dam Parcel Improved Value Content Total Value Loss Estimate
Count Value 7
Arroyo Grande Lopez 3,565 $681,052,289 $356,141,266 $1,037,193,555 $518,596,777 8,273
Atascadero Salinas 181 $28,803,852 $16,315,428 $45,119,280 $22,559,640 399
Grover Beach Lopez 2,392 $417,358,957 $217,731,586 $635,090,543 $317,545,272 5,319
Paso Robles Salinas 68 $34,219,768 $22,658,110 $56,877,878 $28,438,939 58
Pismo Beach Lopez 66 $33,076,320 $15,020,878 $48,097,198 $24,048,599 113
Lopez 2,333 $362,698,180 $181,512,103 $544,210,283 $272,105,141 5,125
Nacimiento 7 $144,774 $69,426 $214,200 $107,100 3
Righetti 16 $12,694,743 $6,339,437 $19,034,180 $9,517,090 38
Unincorporated Salinas 116 $19,560,321 $9,493,807 $29,054,128 $14,527,064 201
Terminal 11 $2,336,587 $1,157,154 $3,493,741 $1,746,870 20
Twitchell 224 $37,806,448 $22,799,265 $60,605,713 $30,302,856 183
Whale Rock 643 $129,036,238 $64,260,893 $193,297,131 $96,648,565 1,556
Lopez 3,565 $681,052,289 $356,141,266 $1,037,193,555 $518,596,777 8,273
TOTAL 9,622 $1,758,788,477 $913,499,350 $2,672,287,827 $1,336,143,914 21,287
Source:San Luis Obispo County Planning and Building Dept.,Assessor's Office,ParcelQuest,Wood Plc Parcel Analysis
Table 5-50 Dam Inundation Estimated Losses by Property Type
Property T�pe 11111111111,T1�.M Improved Value Content Value Loss Estimate Population
Agricultural 101 $14,469,017 $14,469,017 $28,938,034 $14,469,017 -
Commercial 314 $105,608,490 $105,608,490 $211,216,980 $105,608,490 -
Government/Utilities 227 $75,984 - $75,984 $37,992 -
Other/Exempt/Misc. 379 $60,173,041 - $60,173,041 $30,086,521 --
Residential 6,627 $1,145,400,771 $572,700,386 $1,718,101,157 $859,050,578 16,634
Multi-Family Residential 999 $223,706,043 $111,853,022 $335,559,065 $167,779,532 2,507
Mobile/Manufactured 55 $33,945,009 $16,972,505 $50,917,514 $25,458,757 138
Homes
Residential:Other 800 $150,192,292 $75,096,146 $225,288,438 $112,644,219 2,008
Industrial 27 $11,199,857 $16,799,786 $27,999,643 $13,999,821 --
Vacant 93 $14,017,973 -- $14,017,973 $7,008,987 --
TOTAL 91622 $1,758,788,477 $913,499,350 $2,672,287,827 $1,336,143,914 21,287
Source:San Luis Obispo County Planning and Building Dept.,Assessor's Office,ParcelQuest,Wood Plc Parcel Analysis
Table 5-51 Dam Inundation Estimated Losses by Dam
Dam Parcel Count Improved Value Content Value Total Value Loss Estimate Population
Lopez 8,356 $1,494,185,746 $770,405,832 $2,264,591,578 $1,132,295,789 18,830
Nacimiento 7 $144,774 $69,426 $214,200 $107,100 3
Righetti 16 $12,694,743 $6,339,437 $19,034,180 $9,517,090 38
Salinas 365 $82,583,941 $48,467,345 $131,051,286 $65,525,643 658
Terminal 11 $2,336,587 $1,157,154 $3,493,741 $1,746,870 20
Twitchell 224 $37,806,448 $22,799,265 $60,605,713 $30,302,856 183
Whale Rock 643 $129,036,238 $64,260,893 $193,297,131 $96,648,565 1,556
TOTAL 9,622 $1,758,788,477 $913,499,350 $2,672,287,827 $1,336,143,914 21,287
Source:San Luis Obispo County Planning and Building Dept.,Assessor's Office,ParcelQuest,Wood Plc Parcel Analysis
San Luis Obispo County Local Hazard Mitigation Plan I October
Section 5
Risk Assessment
Dam failure flooding would vary by community depending on which dam fails and the nature and extent
of the dam failure and associated flooding. Based on the risk assessment, it is apparent that a major dam
failure could have a devastating impact on the planning area. Dam failure flooding presents a threat to life
and property, including buildings, their contents, and their use. Large flood events can affect crops and
livestock as well as lifeline utilities (e.g., water, sewerage, and power), transportation,jobs, tourism, the
environment, and the local and regional economies.
People
Persons located underneath or downstream of a dam are at risk of a dam failure, though the level of risk
can be tempered by topography (specifically where populations are located within the inundation path of
a dam), amount of water in the reservoir and time of day of the breach. Injuries and fatalities can occur
from debris, bodily injury and drowning. Once a dam has breached, standing water presents all the same
hazards to people as floodwater from other sources. People in the inundation area may need to be
evacuated, cared for, and possibly permanently relocated. Impacts could include thousands of evacuations
and likely hundreds of casualties, depending on the dam involved. Specific population impacts are noted
in Table 5-49, Table 5-50, and Table 5-51, and total people at risk were calculated by multiplying the
average number of persons per household in the county of San Luis Obispo (2.51) times the number of
residential parcels where dam inundation occurs.An incident at the Lopez dam would potentially put the
most people at risk, followed by the Whale Rock and Salinas dams.
Social Vulnerability
The inundation paths of the Lopez and Salinas dams not only put the most people at risk, they will also
potentially impact the communities of Grover Beach (Lopez dam) and Paso Robles (Salinas dam). Both
communities are among the areas with the highest ranking of overall social vulnerability in the county
based on the SoVI data presented and discussed in subsection 4.4.1. Public outreach and education on
dam incidents as well as ensuring alert and warning systems are working properly should be focused in
these areas.
Critical Facilities
A total dam failure can cause catastrophic impacts to areas downstream of the water body, including
critical infrastructure. Any critical asset located under the dam in an inundation area would be susceptible
to the impacts of a dam failure. Of particular risk would be roads and bridges that could be vulnerable to
washouts, further complicating response and recovery by cutting off impacted areas. Risk to specific
facilities could be considered sensitive information additional details can be found within the San Luis
Obispo County's Dam and Levee Failure Evacuation Plan, updated as of February 2016.
Table 5-52 summarizes the number and types of critical facilities found to be at risk of dam failure
incidents from the Lopez and Nacimiento Lake Dams, given no other dams' inundation extents cross the
path of key facilities or structures in the county. These results were found by performing overlay analysis
of the critical facilities and the dam inundation layers in GIS. Most of these facilities at risk (13) are found
in Arroyo Grande, with another 13 in the unincorporated portions of the county and 8 in Grover Beach.
Overall, a total of 34 critical facilities are found within dam inundation zones across the county.
Note that 33 of the 34 critical facilities found in dam inundation areas fall under the Lopez Dam extents,
while only 1 (a water treatment facility in the Heritage Ranch Community Services District, in the
unincorporated portion of the County, falls under the Nacimiento Lake Dam inundation extent).
Section 5
Risk Assessment
Table 5-52 Critical Facilities in the Lopez Dam and Nacimiento Lake Dam Inundation Areas, by
Type of Facility and Dam Name
Jurisdiction Critical Facility Type
Day Care Facilities 3
Emergency Medical Service Stations 1
Fire Stations 1
ARROYO GRANDE Hospitals 2
Nursing Homes 2
Private Schools 1
Public Schools 3
TOTAL 13
Day Care Facilities 2
Microwave Service Towers 2
GROVER BEACH Private Schools 1
Public Schools 2
Water Treatment Facilities 1
TOTAL 8
Day Care Facilities 4
Emergency Medical Service Stations 1
Fire Stations 1
Local Law Enforcement 1
UNINCORPORATED Public Schools 1
Wastewater Treatment Plant 1
Airport 1
Energy Commission Facilities 1
Water Treatment Facilities (1 in Lopez Dam area and 1 in Nacimiento 2
Lake Dam area)
TOTAL 13
GRAND TOTAL 34
Source:San Luis Obispo County Planning&Building Department,HIFLD,San Luis Obispo County Community Services Districts,Wood GIS analysis
Economy
Extensive and long-lasting economic impacts could result from a major dam failure including the long-
term loss of water in a reservoir after a failure event.A major dam failure and loss of water from the
associate reservoir could include direct business and industry damages and indirect disruption of the local
economy.
Historic, Cultural, and Natural Resources
Dam failure effects on the environment would be similar to those caused by flooding from other causes.
Water could erode stream channels and topsoil and cover the environment with debris. For the most part
the environment is resilient and would be able to rebound from whatever damages occurred, though this
process could take years. However, historic and cultural resources could be affected just as housing or
critical infrastructures would, were a dam to fail and cause downstream inundation that could further
Section 5
Risk Assessment
erode surfaces or cause scouring of structural foundations. GIS analysis indicates the following 3 historic
properties are potentially at risk to dam inundation.
Table 5-53 Historic and Cultural Properties in Dam Inundation Areas, San Luis Obispo County
Dam Causing Inundation
Southern Pacific Railroad Depott1903
- San Luis Bay Area Plan-Inland Lopez
Coffee T. Rice House 86 San Luis Bay Area Plan-Coastal Lopez
Temple of The People, Halcyon San Luis Bay Area Plan-Inland Lopez
Source:County of San Luis Obispo Planning and Building Dept.,2019
Future Development
Areas slated for future development should take into consideration potential impacts from dam failure
risk upstream and should attempt to overlay the existing dam inundation maps with proposed future
development. In the case of a dam failure, inundation would likely follow some existing FEMA mapped
floodplains, which contains development restrictions for areas in the 1% annual chance floodplain, but it
could exceed those floodplains and affect areas that are not regulated for flood hazards.Also of note is
that development below a low or undetermined hazard dam could increase its hazard rating, though
there is only one low hazard and one undetermined hazard dam in the County (while the majority are
high or significant hazard dams). Finally, added development could compromise dams and reservoir
resources if populations depend on them for critical needs such as potable water during or after a dam
failure event. For example, the Nacimiento Reservoir is the only source of potable water within the
Heritage Ranch Community Services District, and were this reservoir and dam to fail, the growing
residential population would be potentially affected by dam inundation, resource damages, and lack of
necessary potable water.
For this plan, a GIS overlay analysis of building construction permits for residential and commercial
properties was additionally performed across the county, pulling from permits submitted from 2014 to
early 2019. This assessment provides a general idea of how many future properties (a total of 333) may be
constructed, or may have upgrades done, within dam inundation areas (see Table 5-54). More detail on
the specific types of permits granted, particularly the kind of work class and case type for each permit
group, can be found under the Asset Summary section of this plan.
Table 5-54 Building Permits Submitted in Dam Inundation Areas from 2014-2019
TotalWork Class Type
Conditional Use Permit 24
Land Use
Minor Use Permit 106
PMTC -Commercial Permit 43
New Structure
PMTR- Residential Permit 160
TOTAL 333
Source:San Luis Obispo County Planning&Building Department,Wood GIS analysis
Section 5
Risk Assessment
Risk Summary
The overall significance of dam inundation in San Luis Obispo County is Medium.
• Based on historical evidence dam failures can happen and flood downstream communities in the
county, though not frequently.
• Effects on property:Countywide there are 9,622 parcels at risk, worth $2.67 million, with a loss estimate
of$1.33 million. The Unincorporated areas account for 35% of the total structures at risk, and about
32% of the total estimated losses.The Lopez dam puts the most parcels at risk of dam inundation,
with 8,356 county-wide (most in Arroyo Grande), followed by the Salinas and Whale Rock dams.
However, besides Arroyo Grande, the most parcels at risk of various high hazard dam failures are
Grover Beach and the unincorporated areas of the county. Residential structures make up the most
parcels at risk of flooding from dam failures (including multi-family residential, other residential
parcels, and mobile/manufactured homed), followed by exempt/miscellaneous/government/utilities
parcels and commercial parcels.
• Effects on people: People are vulnerable to dam failure in San Luis Obispo County. An estimated
21,287 people might be displaced from their homes based the location of their residences along the
inundation areas.
• Effects on critical facilities and infrastructure: GIS analysis yielded that 33 critical facilities are found
within the Lopez Dam's inundation area, with 1 additional falling in the Nacimiento Lake Dam
inundation area (within the Heritage Ranch Community Services District) for a total of 34 critical
facilities at risk of this hazard.A total of 13 of those in Arroyo Grande, 13 in the unincorporated areas
of the county, and 8 facilities in Grover Beach.
• Effects on economy: Dam inundation can disrupt transportation corridors, affecting the economy by
impeding or reducing flows of goods, people, and resources.
• Related Hazards:adverse weather, flooding, earthquake/liquefaction, tsunami/seiches, land
subsidence, landslide, drought.
Table 5-55 Dam Inundation Risk Summary by Jurisdiction
OverallProbability of Magnitude/
OccurrenceJurisdiction Geographic Area Future Severity(Extent) Significance
San Luis Obispo
Limited Occasional Critical Medium
County
City of Arroyo Grande Extensive Unlikely Catastrophic Medium
City of Atascadero Limited Unlikely Limited Low
City of Grover Beach Extensive Unlikely Catastrophic Medium
City of Morro Bay Limited Unlikely Negligible Low
City of Paso Robles Significant Occasional Limited Low
City of Pismo Beach Limited Occasional Critical Medium
City of San Luis Obispo N/A
Avila Beach CSD Limited Unlikely Limited Low
Ground Squirrel Hollow Limited Unlikely Limited Low
CSD
Heritage Ranch CSD Extensive Likely Catastrophic High
San Luis ObispoCounty Local . Mitigation Plan October 2019 • •- t
do 0
Section 5
Risk Assessment
Probability of Magnitude/ Overall
Jurisdiction Geographic Area Future Severity(Extent) Significance
Occurrence
Los Osos CSD N/A
Nipomo CSD Limited Unlikely Limited Low
San Miguel CSD Limited Unlikely Negligible Medium
San Simeon CSD N/A
Templeton CSD Significant Occasional Limited Low
Cayucos Sanitary Limited Unlikely Limited Low
District
Port San Luis Harbor
Limited Unlikely Negligible Low
District
San Luis Obispo
Limited Occasional Critical Medium
FCWCD
South San Luis Obispo
Extensive Unlikely Catastrophic Medium
Sanitary District
Section 5
Risk Assessment
5.3.9 Drought and Water Shortage
Hazard/Problem Description
Drought is a gradual phenomenon. Although droughts are sometimes characterized as emergencies, they
differ from typical emergency events. Most natural disasters, such as floods or forest fires, occur relatively
rapidly and afford little time for preparing for disaster response. Droughts occur slowly, over a multi-year
period, and it is often not obvious or easy to quantify when a drought begins and ends.
Drought is a complex issue involving many factors—it occurs when a normal amount of moisture is not
available to satisfy an area's usual water-consuming activities. Drought can often be defined regionally
based on its effects:
• Meteorological drought is defined by a period of substantially diminished precipitation duration
and/or intensity. The commonly used definition of meteorological drought is an interval of time,
generally on the order of months or years, during which the actual moisture supply at a given place
consistently falls below the climatically appropriate moisture supply.
• Agricultural drought occurs when there is inadequate soil moisture to meet the needs of a particular
crop at a particular time.Agricultural drought usually occurs after or during meteorological drought,
but before hydrological drought and can affect livestock and other dry-land agricultural operations.
• Hydrological drought refers to deficiencies in surface and subsurface water supplies. It is measured
as stream flow, snow pack, and as lake, reservoir, and groundwater levels. There is usually a delay
between lack of rain or snow and less measurable water in streams, lakes, and reservoirs.Therefore,
hydrological measurements tend to lag behind other drought indicators.
• Socio-economic drought occurs when physical water shortages start to affect the health, well-being,
and quality of life of the people, or when the drought starts to affect the supply and demand of an
economic product.
The California Department of Water Resources (DWR) says the following about drought:
"One dry year does not normally constitute a drought in California. California's extensive system of
water supply infrastructure—its reservoirs, groundwater basins, and inter-regional conveyance
facilities—mitigates the effect of short-term dry periods for most water users. Defining when a
drought begins is a function of drought impacts to water users. Hydrologic conditions constituting a
drought for water users in one location may not constitute a drought for water users elsewhere, or for
water users having a different water supply. Individual water suppliers may use criteria such as
rainfall/runoff, amount of water in storage, or expected supply from a water wholesaler to define their
water supply conditions."
The drought issue in California is further compounded by water-rights.Water is a commodity possessed
under a variety of legal doctrines. The prioritization of water rights between farming and federally
protected fish habitats in California is part of this issue.
Drought impacts are wide-reaching and may be economic, environmental, and/or societal. The most
significant impacts associated with drought in the planning area are those related to water intensive
activities such as agriculture, wildfire protection, municipal usage, commerce, tourism, recreation, and
wildlife preservation. Also, during a drought, allocations go down, which results in reduced water
availability.Voluntary water conservation measures are typically implemented during extended droughts.
A reduction of electric power generation and water quality deterioration are also potential problems.
Section 5
Risk Assessment
Drought conditions can also cause soil to compact and not absorb water well, potentially making an area
more susceptible to flooding.
Geographic Area
Drought is a regional hazard, and at its worst can affect the entire state of California with varying levels of
dryness and drought activity(as will be covered in more detail under the sections to follow). It is safe to
assume that unless the drought event is at its very beginning or very end, if any area of the County of San
Luis Obispo is affected by any level of drought, the other areas of the county are experiencing varying
effects as well. The San Luis Obispo Integrated Regional Water Management Plan (2014) organized the
County into sixteen Water Planning Areas), "intended to recognize important hydrogeologic units or water
management areas throughout the County" (IRWM, 2014). As this plan was being written the County's
Integrated Regional Water Management Plan was also in the process of being updated. The update to the
IRWMP revised to the number of Water Planning Areas to six and aligned them with the USGS watershed
boundary datasets, refer to Figure 5-48 below.
The major water supply for all of the Water Planning Areas (WPA) come from groundwater sources and
minor supplies from surface water sources such as the Salinas and Estrella Rivers. During periods of
drought there is an increased demand for groundwater resources. This being the case, in addition to
groundwater sources most of the WPAs also receive water supplies from other sources such as, the State
Water Project, Nacimiento Water Project and Reservoirs (Whale Rock, Chorro, Lopez Lake, Salina). Some
communities have gone beyond groundwater and surface water supplies and have developed recycled
water programs (City of San Luis Obispo and City of Pismo Beach) for the purposes of irrigating
landscaping or control dust on construction sites. The City of Morro Bay has also implemented a
desalination project. Drought impacts are an issue for all of the Water Planning Areas.
Sustainable Groundwater Management Act of 2014
Then Central Coast region and all of California have been experiencing significant drought and water
shortages since 2011. Only recently as of February 2019 did the County and the majority of the state
come out of drought. In January 2014 the Governor declared an emergency proclamation due to multiple
years of drought.The proclamation called on citizens to reduce water use by 20 percent;with a
subsequent executive order in April 2015 that directed urban water agencies to reduce water use by 25
percent (Ken Topping, 2016). In September 2014, the Governor signed a three-bill package (California
Senate Bills 1168 and 1319, and Assembly Bill 1739), known as the Sustainable Groundwater Management
Act of 2014 (SGMA). The SGMA provides for the establishment of local Groundwater Sustainability
Agencies (GSAs) to manage groundwater sustainability within the groundwater subbasins defined by the
California Department of Water Resources (DWR).
The DWR prioritized all groundwater basins in the state designating High and Medium priority basins.
High or medium priority basins are subject to critical conditions of overdraft are required to submit a
Groundwater Sustainability Plan (GSP) by January 31, 2020.The purpose of the GSP to ensure a
sustainable yield of groundwater, without causing undesirable results. The deadline to submit a GSP for
high or medium priority basin not subject to critical conditions of overdraft is January 31,2022. Failure to
comply with that requirement could result in the State asserting its power to manage local groundwater
resources. The State has identified the following five high and medium priority groundwater basins within
San Luis Obispo County:
Section 5
Risk Assessment
1. Paso Robles (Priority Pending) 4. San Luis Obispo (Edna) Valley(High)
2. Santa Maria (Priority Pending) 5. Cuyama Valley (High)
3. Los Osos (Priority Pending) 6. Atascadero (Very Low)
Section 5
Risk Assessment
Figure 5-48 San Luis Obispo County Water Planning Areas
County of San Luis Obispo
Public Works
Kings County Water Resources
Water Planning
Monterey County.
Cholame Areas and
\\
l\ alley r Groundwater Basins
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val - Groundwater Basins
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horro WPA 1 San Seri Cambria
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5 L• is Olspo ++. Area
Valley Lon az RI.—VI1 Carrizo Plain
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Arroyo Grande Regional Mier Management(IRWM)
Pismo Beach 0� Plan Update
Grover Beach Arroyo Grande ria ��r heP,ryn n my a,ernrg;n m
Valley
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Date Created:3/28;2019
Source: San Luis Obispo Public Works,Water Resources Division
Section 5
Risk Assessment
Extent (Magnitude/Severity)
The U.S. Drought Monitor is an accepted and widely used site for obtaining and summarizing drought
information, as it integrates data from several other sources including the Palmer Drought Index, Soil
Moisture Models, U.S. Geological Survey Weekly Stream Flows, Standardized Precipitation Index, and the
Satellite Vegetation Health Index. It includes drought intensity categories for measuring dry conditions
across counties, states, and regions of the U.S., so that drought can be quantified. These categories range
from "abnormally dry"to "exceptional drought." The following figures provide "snapshots in time" of the
drought conditions in California as of March 2019, February 2019, and August 2015 (during the period of
the last multi-year drought in San Luis Obispo County and the state, from 2012- 2017). The snapshots
selected are instrumental in depicting both the historic and potential change in drought's geographic
range and severity in the County(circled in blue). Due to severe winter storms that brought heavy rains in
February and March 2019, the County for the first time since 2011 is no longer experiencing dryness or
drought (San Luis Obispo Tribune 2019).
Note: The Drought Monitor maps integrate data from several sources including the Palmer Drought Index,
Soil Moisture Models, U.S. Geological Survey Weekly Stream flows, Standardized Precipitation Index, and
Satellite Vegetation Health Index.
Figure 5-49 U.S. Drought Monitor for California: March 7, 2019
U.S. Drought Monitor March 5, 2019
California (Released Valid a.m.ST ''2019)
Drought Con di fron s(Aercent A real
None DO-D4 D1-D4 D2-04 �•
Current 89.84 10.16 0.60 0.00 0.00 0.00
Last Week 87 17 12.83 233 0.00 0.00 0.00
02-2620]9
3 MonthsAgo 777 9223 79.69 18.34 3.78 0.00
12-04.03
Starto I
Calendaryear 7.77 92.23 75.17 14.12 210 0.00
25,9
Start
Start of
Nffier Year 12.18 87.82 47.97 22.82 494 0.00
0325-2078
Gne YearAgo 048 91.52 47.87 22.40 0.43 0.00
0206,013
Irz[ensi
DO Abno rmally Dry -D3Extreme Drought
D1 Moderate Drought D4 Exceptional Drought
D2 Severe Drought
The Drought Monitor focuses on broad-scale conditions.
Local conditions may vary.See accompanying text summary
For Forecast statements.
Author:
Eric Luebehusen
IJ.S.Department of Agriculture
USD
1�� NO
.
http:iidroughtmonitor.un1.edu/
San Luis Obispo County Local Hazard Mitigation Plan October 2019 Page 5-156
• 0 0
Section 5
Risk Assessment
Figure 5-50 U.S. Drought Monitor for California: February 5, 2019
U.S. Drought Monitor February 5, 2019
California
(Released Idu75a.m.EST 2019)
Drought Conditfons(PercentArea)
None DO-D4 D1-D4 D2-D4 DMIMIMEM
current 34.37 65.63 10.55 1.89 0.00 0.00
Last Vikek 23.93 76.07 23.66 1.89 0.00 0.DO
01-2a201s
3Months Ago 0.00 100.00 51.92 18.35 239 0.00
11-06-2018
Start Of
CalendarYear 7.77 92.23 75.17 14.12 210 0.00
07-01-2019
Start of
V&ter Year 12.1 B 87.82 47.97 22.82 4.94 0.00
0SL2&2018
One Year Ago 18.27 81.73 45.60 6.39 0.00 0.00
oz-0s-tors
Intensity-
DO Abnormally Dry -D3 Extreme Drought
D1 Moderate Drought D4 Exceptional Drought
_D2 Severe Drought
The Drought Monitor focuses on broad-scale conditions.
Local conditions may vary.See accompanying text summery
for forecast statements.
Author:
Ric nard Tinker
CP Cl N OAAlN W S1N C EP
USDA A
wi•.� � �,.:
http:lldroughtmo nitor.0 ni.edul
San Luis Obispo County Local Hazard Mitigation Plan I October
Section 5
Risk Assessment
Figure 5-51 U.S. Drought Monitor for California:August 4, 2015
U.S. Drought Monitor August 4, 20'15
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Past Occurrences
Historically, California has experienced multiple severe droughts. California's most recent multi-year
drought occurred from 2012-2017 as previously mentioned, but the driest single year of California's
measured hydrologic record was 1977.
The following multi-year droughts were identified as having significant impacts on the planning area:
1929– 1934–This statewide drought established the criteria commonly used in designing storage
capacity and yield for large Northern California reservoirs, and is hence one of the first major historic
droughts noted in California.
• 1975-1977— From November 1975 through November 1977, California experienced one of its most
severe droughts.Although people in many areas of the state are accustomed to very little
precipitation during the growing season (April to October), they expect it in the winter. In 1976 and
1977, the winters brought only one-half and one-third of normal precipitation, respectively. Most
surface storage reservoirs were substantially drained in 1976, leading to widespread water shortages
when 1977 turned out to be even drier. Thirty-one counties were affected, resulting in $2.67 billion in
crop damage.
Section 5
Risk Assessment
• 1987-1992—San Luis Obispo County also suffered adverse effects resulting from this statewide
drought, when low precipitation and runoff levels hit the Central Coast the hardest, adversely
affecting about 30% of the state's population, much of the dry-farmed agriculture, and over 40
percent of the irrigated agriculture. Fish and wildfire suffered as well, as did the recreation and
hydroelectric production sectors. Forestry losses and fires were very high.
• 2007–2009–California proclaimed a statewide drought in 2009, and unprecedented restrictions
were placed on water diversions to protect fish species, exacerbating drought impacts for water users.
The greatest impacts of this multi-year drought were suffered on the western side of the San Joaquin
Valley, on agricultural communities where drought effects were coupled with the economic recession.
Emergency response actions were necessary with regards to social services.
• 2012–2017– Drought produced severe impacts to water wells throughout the planning area, with a
high number of wells running dry. Land subsidence due to increased groundwater pumping also
occurred in areas of the San Joaquin Valley close to the Central Coast counties. Crop damage was
widespread as well. Water allotments were drastically reduced in many towns and water agencies,
with extremely high costs for procuring water. In addition,job loss occurred with many families
requiring food supply assistance, and water supply assistance provided to home owners with dry
wells. According to a report released by UC Davis Center for Watershed Sciences, the 2014 California
drought cost the state's agriculture industry about $1 billion in lost revenue, with a total statewide
economic cost of the drought calculated to be $2.2 billion.The 2014 drought, the report says, is
responsible for the greatest water loss ever seen in California agriculture - about one third less than
normal. The report calls the groundwater situation in California "a slow-moving train wreck." (Source:
https:Hstatesummaries.ncics.org/ca). On March 11, 2014 the San Luis Obispo County Board of
Supervisors proclaimed a local emergency which lasted for three years until the Board adopted a
resolution on May 23, 2017 to end the local emergency.As noted above, the Governor proclaimed a
State of Emergency due to drought conditions and the related wide-ranging impacts. The Governor's
proclaimed State of Emergency due to drought covered a similar period, from January 17, 2014 to
April 7, 2017. For the County of San Luis Obispo there were 13 disaster declarations from 2012-2017,
though total associated financial losses across the various economic sectors is not available for all
these recent drought-related declarations.
The following table summarizes both state and federal proclamations related to drought affecting the
County of San Luis Obispo.
Table 5-56 Summary of Secretarial and Governor Disaster Declarations for Drought in San Luis
Obispo County
Hazard Type Disaster# Year State Federal
Proclamation �.
Declaration
Drought - 1976 2/1976, 3/1976, Not declared $2,664,000,000
7/1976
Drought EM-3023 1977 -- 1/20/1977 --
2/21/2012- 7/12/2012
Drought- Fast Track 53268 2012 5/14/2012 --
(Sec.approval)
(begin to end)
Drought S3379 2012 1/1/2012 9/5/2012 --
Drought S3452 2012 -- 12/19/2012 --
Section 5
Risk Assessment
Hazard Type ®® State Federal
Proclamation Declaration
�.
Drought(FAST TRACK)
Wind, Fire, Excessive 53491 2013 1/1/2013 2/27/2013 --
heat, insects
Drought(FAST TRACK)
Wind, Fire, Excessive 53497 2013 1/15/2013 3/13/2013 --
heat, insects
Drought(FAST TRACK)
Wind, Fire, Excessive S3504 2013 2/12/2013 4/10/2013 --
heat, insects
Drought(FAST TRACK)
Wind, Fire, Excessive S3542 2013 4/23/2013 6/19/2013 --
heat, insects
Drought(FAST TRACK)
Wind, Fire, Excessive 53626 2014 1/1/2014 1/15/2014 --
heat, insects
Drought S3743 2014 41/1/2014 9/17/2014
Local --
March 11,
Drought 2014- May -- -- --
Emergency 23, 2017
Drought(Fast Track) 53784 J2015 1/1/2015 2/4/2015 --
Excessive Heat; insects
Drought 53943 2015 1/2/2015 12/23/2015 --
Drought(FAST TRACK)
Wind, Fire, Excessive 53952 2016 1/1/2016 2/17/2016 --
heat, insects
Drought- Fast Track 54144 2017 1/1/2017 2/23/2017 --
Drought—Fast Track 54467 2018-2019 10/1/2018 1 3/6/2019 --
Source: USDA Secretarial Disaster Declarations,2019;FEMA Disaster Declarations,2019,HMPC.
Figure 5-52 graphically displays the amount of drought-related reported impacts to San Luis Obispo
County (United States Drought Impact Reporter 2019). While it is difficult to extract the specific impacts
affecting the planning area, a total of 124 reports were submitted at the County level between January 1,
1990 and February 11, 2019. It is assumed that these drought related impacts for areas across the County
are likely to have also affected the jurisdictions and communities at some point or to some extent. Based
on the summary of negative effects to the county since 1990 the categories of water supply/quality as
well as relief/response/restrictions have had the most reports, followed by the agriculture sector and
society/public health. Other sectors such as "plants and wildlife" have also suffered the effects of drought
but to smaller extents.
Section 5
Risk Assessment
Figure 5-52 Drought Impact Reporter Summary of Impacts at the County Level in San Luis
Obispo County, 1990-Febuary 2019
NATIONAL DROUGHT MITIGATION CENTER
DFoujht Impact Reporter
Impacts
veno
Opacity _
Impacts
59-112
113-165
• �. ss r;ory. —166-21E
—219-271
—272-324
Las Vegas
-Reports
-Drought Declarations
osa
CE-By-&&My Time Period
Lbs
-tze�aw,et zra>u4
—_ - — .. _- cLstomixe ■
lel Impacts I San Luis Obispo County,CA
01-01-1990-02-11-2019 x Start:
County Impacts 124 End:
Ca"or 02-11-2019
Agriculture 31
Business&Industry 12
Energy 4 Location
Fire 11
Plants&Wildlife 29 State: califomia ■
Relief,Response&Restrictions 53 County:I San Luis Obisp(■
Society&Public Health 31
Q Tourism&Recreation 7
Water Supply&Quality 62 t Categories
Report Source
Media 102 /Report Types
I�1
i User 2
IR OtherAgency 5
{r CoCcRaHS 1 ` r
Legacy 16
Irnpacts List Al I-States View
fi.
Source:National Drought Mitigation Center-Drought Impact Reporter,2019
Probability of Future of Drought Occurrences
Likely—Historical drought data for the County planning area and the Central Coast region indicate there
have been five significant multi-year droughts in the last 90 years. This equates to a multi-year drought
every 18 years on average, or a 5.5 percent chance of a drought in any given year. Based on this data,
droughts will likely affect the planning area. Given the historical occurrence of severe drought impacts
throughout San Luis Obispo County and across the state (summarized in the Past Occurrences section of
this section), the HMPC understands that drought will continue to pose a high degree of risk to the entire
planning area, potentially impacting crops, livestock, water resources, the natural environment at large,
buildings and infrastructure (from cascading or compound hazards), and local economies.
San Luis Obispo County Local Hazard Mitigation Plan I October 2019
Section 5
Risk Assessment
In addition, although drought affects the entire planning equally, the potential impacts may be variable
and specific to each jurisdiction, depending on contextual factors such as the degree of assets and
activities historically impacted by drought within each jurisdiction, such as the agricultural and parks and
tourism industries.
Climate Change Considerations
Scientific studies prepared for various California climate assessments and adaptations strategies show that
drought conditions in California are likely to become more frequent and persistent over the next century
due to climate change. Temperatures are warming, heat waves are more frequent, and precipitation has
become increasingly variable (California Natural Resources Agency 2018). Water resources are also
already experiencing the following stresses: population growth, poor water quality, groundwater
overdraft, and aging water infrastructure.
According to California's Climate Adaptation Strategy, also referred to as "Safeguarding California Plan:
2018 Update", climate change is likely to significantly diminish California's future water supply. As a result
the state must change its water management, as climate change will create greater competition for
limited water supplies (California Natural Resources Agency 2018a).The recent drought conditions over
the past decade underscore the need to examine water supply and distribution management,
conservation, and use policies. California and the Central Coast region have experienced a succession of
dry spells and with warmer temperatures and periodic droughts that frequently contribute to water
shortages in the region.
Climate change projections of extreme prolonged droughts will exacerabte the Central Coast's existing
water supply challenges (Fourth Climate Change Assessment, 2018). In an average year, approximately 40
percent of the state's total water supply comes from groundwater, and during a dry year this increases to
more than half of the state's water supply, with groundwater acting as a critical buffer against the impacts
of drought and climate change (California Natural Resources Agency 2018).
Table 5-57 Summary of Climate Change Impacts on Water Resources
Type .
Resource Impact Description Level Direct Sea level is rising and will likely impact coastal areas
Prolonged dry seasons can lead to decreases in soil
Soil Moisture Direct moisture;drier vegetation
Longer and more intense fire season with increased
Vegetation Indirect extent of area burned
Increases in water temperature; potential effects on
Stream Conditions Direct fish
Increases in temperature will lead to decreases in
Snowpack Indirect snowpack
Warmer temperatures are likely to lead to a shift in
peak runoff from spring to winter and a likely
Runoff Direct decrease in summer baseflow
Decreased summer flows resulting from earlier
snowmelt and a shift in peak runoff could affect
Hydropower Indirect hydropower generation during summer months
Section 5
Risk Assessment
Type of
Resource Impact Description
Warmer winter temperatures will result in a greater
percentage of precipitation falling as rain rather than
Precipitation Direct as snow
Reduction in snowpack and extended periods of
drought are likely to increase dependency on
Groundwater Indirect groundwater
Source:http://frap.fire.ca.gov/data/assessment2010/pdfs/3.lwater.pdf p.140
Vulnerability to Drought (High)
The historical and potential impacts of drought on property include crop loss, injury and death of
livestock and pets, and damage to infrastructure and other buildings resulting from the secondary or
cascading drought impacts such as land subsidence, soil erosion, and flash flooding.As a related drought
impact,tree mortality has resulted in potentially vulnerable critical infrastructure property as these trees
become more susceptible to falling with time and could affect properties in the county. For the following
vulnerability categories crop losses, potential health issues related to drought, tree mortality, and other
such issues tied to secondary and cascading impacts will be discussed.
General Property
Based on the USDA's Risk Management Agency Crop Indemnity Reports, which were collected for the
years 2015-2018, crop losses due to drought were reported in every year except 2017 across the county.
Table 5-58 summarizes the agricultural losses experienced across the county communities.A total of
$870,473 was indemnified for 11,169 acres of affected crops covering 30 policies,just in the last few years
(since the last County hazard mitigation plan from 2014).
Table 5-58 Risk Mana ement A enc Cro Indemnity Reports, 2015-2018
Month of Loss Policies Net
Year .
Indemnity
.
Name Indemnified
Amount Loss Ratio
Acres
Wheat March 1 22 $ 1,541 4.05%
September 1 22 $ 1,541 4.05%
May 1 40 $ 15,582 1.86%
Walnuts April 1 32 $20,186 8.90%
July 1 104 $36,851 3.14%
October 1 14 $63,113 17.57%
Grapes September 1 12 $37,250 13.81%
2015 May 1 12 $29,745 10.23%
April 1 331 $ 5,672 6.48%
February 1 691 $ 17,188 1.69%
March 1 84 $2,816 1.41%
Barley September 1 84 $2,816 1.41%
January 3 4,561 $323,541 2.23%
January 2 715 $47,569 2.11%
December 1 671 $ 16,682 1.69%
San Luis Obispo County Local Hazard Mitigation Plan I October
Section 5
Risk Assessment
Net
Year Crop Month of Loss Policies Determined Indemnity Loss Ratio
Name Indemnified Amount
Acres
April 1 29 $259 0.30%
Walnuts August 1 32 $ 13,360 5.70%
2016 February 1 104 $43,307 4.14%
Grapes June 1 8 $4,933 2.45%
November 3 2,513 $ 146,165 2.16%
2018 Barley January 1 389 $9,424 4.58%
January 4 698 $30,932 2.04%
TOTAL 30 11,169 $870,473
Source:USDA RMA Crop Indemnity Reports,2019
In addition to crop losses, tree mortality hazards from drought, which composejust over 13% of the
county in area, are found to intersect with a total of 39,540 properties across the county, based on the
property centroids defined for all the hazards' parcel analyses. Refer to the Adverse Weather: High Wind
and Tornados section for a summary of the analysis.
People
According to this California Department of Finance (DOF) the 2018 County population was 280,118
people. The County's population is projected to continue to increase by 0.4 percent annually through
2023 (Caltrans 2018).This projected population growth would add additional strain to the surface and
already depleted groundwater supplies.
The historical and potential impacts of drought on populations include agricultural sector job loss,
secondary economic losses to local businesses and public recreational resources, increased cost to local
and state government for large-scale water acquisition and delivery, and water rationing and water wells
running dry for individuals and families.As drought is often accompanied by prolonged periods of
extreme heat, negative health impacts such as dehydration can also occur, where children and elderly are
most susceptible. Air quality often declines in times of drought which can affect those with respiratory
ailments.
Social Vulnerability
The areas of the county with the highest overall social vulnerability, based on the SoVI data presented and
discussed in subsection 4.4.1, such as the City of Paso Robles and the City of San Luis Obispo are also
located within groundwater basins identified by the State Department of Water Resources as potential
priority basins due the depletion of groundwater resources. Both the City of Paso Robles and the City of
San Luis Obispo have formed Groundwater Sustainability Agencies (GSA) to develop and implement of
groundwater sustainability plans (GSP) to ensure sustainable management of the groundwater resources
within their basin for current and future populations.
Critical Facilities
Drought impacts to critical facilities include water shortfalls for facility operations and critical functions,
and potential structural destabilization and damage resulting from land subsidence. Refer to the section
on Subsidence for more information.
Section 5
Risk Assessment
Economy
Drought impacts to the local or regional economy can be difficult to quantify but can be extensive and
long-lasting depending on the circumstances during, and after a severe drought event. If water resources
are limited, effects would be more severe for industries that rely on large amounts of water and any
prolonged drought would intensify these impacts. Sectors critical to the economy such as commerce,
distribution, agriculture, tourism, related environmental resources, municipal and industrial water supply,
key city assets, energy generation, and even socioeconomic aspects can be affected due to lack of, or
even reduced quality of water resources.
Drought directly impacts rangeland for livestock in the County as was witnessed during the 2014 drought
which had a significant impact on the ranching and agriculture economy. Between 2010 and 2014, roughly
75 percent of the cattle in San Luis Obispo County were sold or taken out of state to escape the drought
conditions the County had been experiencing (LA Times 2015).The heavy reliance upon groundwater to
irrigate rangeland for livestock makes this sector of the local economy especially vulnerable to future
drought events.
Historic, Cultural, and Natural Resources
The historical and potential impacts of drought on the natural environment are widespread throughout
public and private lands within the County, including tree mortality, impacts to all flora and fauna, and
destabilization (erosion, subsidence) of land along streams and rivers, and within watersheds.
One of the core issues shaping the impact of drought in San Luis Obispo County and throughout
California is water supply and demand. Several factors play into the issue including groundwater basins,
surface water run-off, public and agricultural demand, and surface water storage watersheds.As such, an
analysis was conducted through the 2010 Forest and Rangeland Assessment to identify threats and assets
in order to select Priority Landscapes (PL) where water supply would benefit from forest management
designed to protect or enhance water resources, the key effort which, in part, both defines and mitigates
the severity of drought risk and vulnerabilities.
Given that the extent of the drought hazard is, in part, determined by the extent of groundwater over-
pumping in San Luis Obispo County, it should also be pointed out that such over-pumping is part of a
broader context of water supply and demand trends with related impacts to agriculture and the secondary
hazard impacts from land subsidence resulting from groundwater withdrawal.The Paso Robles
Groundwater Basin has experienced serious declines over the years due to groundwater pumping with the
largest water use sector being agricultural uses (Paso Robles GSA, 2018). Refer to the Subsidence section
for more information on the impacts on groundwater withdrawal.
Tree mortality was identified as an additional drought impact of significance to the County during the
2019 update. Tree mortality is a cascading impact which also affects (or worsens) other hazards such as
wildfire, agricultural and biological hazards, and wind. In addition, drought-impacted trees become
susceptible to diseases and insect infestations (bark beetle) further adding to the risk of tree mortality and
related potential impacts. A die of blue oak trees which are considered some of the most drought-tolerant
trees caused alarm throughout the County during the multiyear drought from 2012-2015. Researchers
stated the reasoning behind the oak tree mortality was due to the roots of the trees were no longer able
to reach the aquifers due to severe groundwater depletion (Weiser 2017).
Section 5
Risk Assessment
The location, extent, and probability of occurrence for tree mortality can be viewed as sub-set to the
drought hazard (though tree mortality issues are also discussed under other hazards sections such as
Agricultural Pest Infestation and Plant Disease; Wildfires;Adverse Weather/Wind). Those areas of the
natural environment susceptible to drought comprise a larger area, since tree mortality is related to other
sub-factors specific to the species impacted such as tree age and soil composition. Refer to the Adverse
Weather: High Wind and Tornado section for analysis on tree mortality in the county.
Future Development
With the County's population projected to continue to grow while climate change projections are showing
an increased duration an intensity of drought events for the Central Coast region, it will be important for
each new development application to be reviewed with existing and future water supplies in mind.
Because future development encompasses all forms of property, buildings, infrastructure, critical facilities
and all related populations and their functions, drought impacts to future development align with the
historical and potential impacts to populations, property, natural environment, and critical facilities
discussed (above).
Risk Summary
Due to the widespread impacts it can have, drought is considered a High significance hazard.
There have been five multi-year droughts in the past 90 years. Most recent drought lasted from 2012
to 2017 and resulted in a declared state of emergency.
15 Disaster Declarations due to drought have been made in the last 41 years.
124 reports of impacts related to drought were made within San Luis Obispo between, 1990 and
February 11, 2019.
• Between 2015-2018 a total of$870,473 crop indemnity claims was paid due to crop losses for a total
of 11,169 acres due to drought impacts.
• Significant impacts associated with past multiyear droughts have included 75% of livestock to be sold
or moved out of state (2012-2015); Oak trees thought to be drought resilient were no longer able to
reach aquifers and began to die off.
• Climate change projections show that extreme prolonged drought is likely to continue and will
exacerbate existing water supply challenges.
• Related Hazards: Extreme Heat, Wildfire, Subsidence, Agricultural Pest Infestation and Disease
Table 5-59 Drought and Water Shortage Hazard Risk Summary
Probability of Magnitude/ Overall
Jurisdiction Geographic Area Future Severity(Extent) Significance
Occurrence
San Luis Obispo Extensive Likely Critical High
County
City of Arroyo Grande Significant Likely Limited Medium
City of Atascadero Extensive Likely Limited Medium
City of Grover Beach Extensive Likely Limited High
City of Morro Bay Limited Occasional Negligible Low
City of Paso Robles Extensive Likely Limited High
City of Pismo Beach Extensive Likely Negligible Medium
Section 5
Risk Assessment
OverallProbability of Magnitude/
OccurrenceJurisdiction Geographic Area Future Severity(Extent) Significance
City of San Luis Obispo Extensive Likely Limited Medium
Avila Beach CSD Extensive Likely Critical High
Ground Squirrel Limited Occasional Negligible Low
Hollow CSD
Heritage Ranch CSD Extensive Highly Likely Critical High
Los Osos CSD Significant Likely Limited Medium
Nipomo CSD Significant Likely Limited High
San Miguel CSD Extensive Likely Catastrophic High
San Simeon CSD Significant Likely Limited Medium
Templeton CSD Extensive Likely Limited High
Cayucos Sanitary Limited Occasional Negligible Low
District
Port San Luis Harbor Extensive Likely Limited Low
District
San Luis Obispo Extensive Likely Critical High
FCWCD
South San Luis Obispo Significant Likely Limited Low
Sanitary District
San Luis Obispo County Local Hazard Mitigation Plan I October