Staff Report - part 1 — Simi Valley City Council, July 25, 2022 (part 1 of 2)

CITY OF SIMI VALLEY

MEMORANDUM
July 25, 2022
TO: City Council
FROM: Police Department – Office of Emergency Services
SUBJECT:ADOPTION OF A RESOLUTION ACCEPTING ALL OF VOLUME 1 AND THE SIMI VALLEY ANNEX OF VOLUME 2 WITHIN THE VENTURA
COUNTY MULTI-JURISDICTIONAL HAZARD MITIGATION PLAN 2022 AS REQUIRED BY THE DISASTER MITIGATION ACT OF 2000 (P.L. 106-390)

STAFF RECOMMENDATION
It is recommended the City Council adopt the attached Resolution No. 2022-45 (page 5) accepting all of Volume 1 and the Simi Valley Annex of Volume 2 within the Ventura County Multi-Jurisdictional Hazard Mitigation Plan 2022 as required by the Disaster Mitigation Act of 2000 (P.L. 106-390).

BACKGROUND AND OVERVIEW
In May 2021, a coalition of Ventura County planning partners embarked on a planning process to prepare for and lessen the impacts of specified natural hazards.

Responding to federal mandates in the Disaster Mitigation Act of 2000 (Public Law 106-390), the partnership was formed to pool resources and create a uniform hazard mitigation strategy that can be consistently applied to the defined planning area and used to ensure eligibility for specified grant funding sources.

The 25 member planning partnership that completed this plan update process includes:

Consent (9)
The planning area for the Hazard Mitigation Plan (“Plan”) encompasses all of Ventura County. The result of the organizational efforts has been to produce a multi-agency multi- hazard mitigation plan approved by Federal Emergency Management Agency (FEMA) and the California Governor’s Office of Emergency Services (Cal OES).

Mitigation is defined in this context as any sustained action taken to reduce or eliminate long-term risk to life and property from a hazard event. Mitigation planning is the systematic process of learning about the hazards that can affect the community, setting clear goals, identifying appropriate actions, and following through with an effective mitigation strategy. Mitigation encourages long-term reduction of hazard vulnerability and can reduce the enormous cost of disasters to property owners and all levels of government. Mitigation can also protect critical community facilities, reduce exposure to liability, and minimize post-disaster community disruption.

The hazard identification and profiling in the Plan addresses the following natural hazards considered to be of significant importance within the Ventura County planning area:

Dam Failure Inundation Sea Level Rise/Coastal Erosion (SLR) Drought Severe Storms
Earthquake Severe Weather Events (Heat/Freeze Events)
Tsunami Flooding (includes Levee Failures)
Wildfire Landslide & Mass Movements
Ventura County Office of Emergency Services secured funding for developing the Plan and was the lead coordinating agency for this multi-jurisdictional effort. All participating local jurisdictions have been responsible for assisting in the development of the hazard and vulnerability assessments and the mitigation action strategies for their respective jurisdictions and organizations. The Plan presents the accumulated information in a unified framework to ensure a comprehensive and coordinated Plan covering all planning partners within the Ventura County Planning Area. Each jurisdiction has been responsible for the review and approval of their individual sections of the Plan.

The Plan was prepared in accordance with the Cal OES Local Hazard Mitigation Plan and FEMA preparation guidelines. Volume 1 is available for review at the City Clerk’s Office and is available online at https://s29710.pcdn.co/wp- content/uploads/2022/06/2022-06_VenturaHMP_Vol1_Final.pdf. Volume 2 is also available for review at the City Clerk’s Office and is available online at https://s29710.pcdn.co/wp-content/uploads/2022/06/2022- 06_VenturaHMP_Vol2_Final.Reduced.pdf. The City’s Annex is #9 and begins on page 281.

The Plan update process was overseen by a 17-member, stakeholder Steering Committee. The Steering Committee is composed of representative stakeholders from within the planning area and is an established committee that was leveraged for this planning process. In addition, residents were asked to contribute by sharing local knowledge of their individual area’s vulnerability to natural hazards based on past 2 occurrences. Public involvement has been solicited via a multi-media campaign that included public meetings, web-based information, questionnaires, and progress updates via the news media.

FINDINGS AND ALTERNATIVES
Once Cal OES and FEMA have approved the Plan (APA – Approval Pending Adoption), each jurisdiction will need to adopt Volume 1 and respective annex by governing body resolution in order to be eligible to apply for funding sources including grants.

Once the Plan has been approved by Cal OES and FEMA and adopted by all of the jurisdictional partners, the partnership will collectively and individually become eligible to apply for hazard mitigation project funding from the suite of grant programs under FEMA’s Hazard Mitigation Assistance (HMA) program. The City of Simi Valley’s final step in the process is City Council adoption of Volume 1 of the Plan and Simi Valley’s Annex in Volume 2.

Grant funds are made available to local governments and states and can be used to implement the various hazard mitigation measures specified in the respective annexes.

The Hazard Mitigation Plan is considered a living document, such that as awareness of additional hazards develop and new strategies and projects are conceived to offset or prevent loss due to natural hazards, the Plan will be evaluated and revised on an annual basis during the five year Plan timeframe.

As a living document, the Plan information can be integrated and used in conjunction with other emergency and related plans, such as Emergency Operation Plans (EOPs).

The following alternatives are available to the City Council:

1. Adopt Resolution 2022-45 accepting all of Volume 1 and the Simi Valley Annex of Volume 2 within the Ventura County Multi-Jurisdictional Hazard Mitigation Plan 2022;

2. Do not adopt the joint resolution;

3. Provide additional direction to staff.

Staff recommends Alternative No. 1.

SUGGESTED CITY COUNCIL MOTION
I move to adopt Resolution 2022-45 accepting all of Volume 1 and the Simi Valley Annex of Volume 2 within the Ventura County Multi-Jurisdictional Hazard Mitigation Plan 2022. 3 SUMMARY
In May 2021, a coalition of Ventura County planning partners embarked on a planning process to prepare for and lessen the impacts of specified natural hazards. Responding to federal mandates in the Disaster Mitigation Act of 2000 (Public Law 106-390), the partnership was formed to pool resources and create a uniform hazard mitigation strategy that can be consistently applied to the defined planning area and used to ensure eligibility for specified grant funding sources. Therefore, staff recommends that the City Council adopt the resolution accepting all of Volume 1 and the Simi Valley Annex of Volume 2 within the Ventura County Multi-Jurisdictional Hazard Mitigation Plan 2022. ____________________________________
Dave Livingstone, Chief of Police
Prepared by: Eileen Connors, Emergency Services Manager INDEX Page
Resolution No. 2022-45……………………………………………………5
Exhibit 1 – Volume 1 – Ventura County Multi- Jurisdictional Hazard Mitigation Plan……………………………………………………..8
Exhibit 2 - Volume 2 – Ventura County Multi-Jurisdictional Hazard Mitigation Plan Jurisdictional Annexes……………………….49 4 RESOLUTION NO. 2022-45

A RESOLUTION OF THE CITY COUNCIL OF THE CITY OF
SIMI VALLEY ACCEPTING ALL OF VOLUME 1 AND THE
SIMI VALLEY ANNEX OF VOLUME 2 WITHIN THE

VENTURA COUNTY MULTI-JURISDICTIONAL HAZARD
MITIGATION PLAN 2022
WHEREAS, the City is subject to a variety of natural hazards that increase the risk to life, property, environment, and the City’s economy; and WHEREAS, pro-active mitigation of known hazards before a disaster event can reduce or eliminate long-term risk to life and property; and WHEREAS, the City Council is committed to increasing the adaptive capacity and resiliency of the infrastructure, health, housing, economy, government services, education, environment, and land use systems in the City; and
WHEREAS, the federal Disaster Mitigation Act of 2000 (Public Law 106- 390) requires all cities, counties, and special districts to have adopted a Hazard Mitigation Plan to be eligible for funding under multiple Federal Emergency Management Agency (FEMA) pre-and post-disaster grant programs; and WHEREAS, in accordance with FEMA requirements at 44 C.F.R. §201.6, the City of Simi Valley joined the County of Ventura’s collaboration of local governments and special districts to prepare the updated Ventura County Multi- Jurisdictional Hazard Mitigation Plan (HMP), which analyzes the risk of natural hazards affecting the County and specifies potential mitigation measures to address or reduce risk; and
WHEREAS, the HMP partnership includes:

City of Camarillo Channel Islands Beach Community Services District City of Fillmore Conejo Recreation and Park District
City of Moorpark California State University, Channel Islands City of Ojai Pleasant Valley Recreation and Park District City of Oxnard Saticoy Sanitary District
City of Port Hueneme Triunfo Water and Sanitation District City of Santa Paula United Water Conservation District
City of Simi Valley Ventura County Fire Protection District City of Thousand Oaks Ventura County Office of Education City of Ventura Ventura Regional Sanitation District
Ojai Valley Sanitary District Ventura County (Unincorporated Areas) Calleguas Municipal Water DistrictVentura County Public Works Agency-Watershed Casitas Municipal Water DistrictProtection; and
5 WHEREAS, the HMP partnership completed a coordinated, FEMA- prescribed planning process that engaged the public, assessed the risk and vulnerability to the impacts of natural hazards, developed a mitigation strategy consistent with a set of uniform goals and objectives, and created a plan for implementing, evaluating, and revising the strategy over the plan’s 5-year cycle; and
WHEREAS, the HMP partnership invited public comment, and conducted steering committee meetings and other public meetings throughout the process to inform the public and obtain countywide input on the HMP and actions in the plan; and
WHEREAS, the HMP is comprised of two volumes: Volume 1 (Area-Wide Information), and Volume 2 (Jurisdictional Annexes), including the City of Simi Valley’s as Annex #9; and
WHEREAS, the City Council has reviewed the HMP and affirms that its actions will reduce the potential for harm to people and property from future hazard occurrences within our community; and
WHEREAS, the HMP has been reviewed by the California Office of Emergency Services (Cal OES) and the Federal Emergency Management Agency (FEMA), and has been determined to be eligible for final approval pending its adoption by the City Council; and
WHEREAS, the City, as a fully participating jurisdiction of the HMP partnership, is an eligible sub-applicant through the County of Ventura to the State of California under FEMA’s hazard mitigation grant program guidance; and WHEREAS, the City Council finds and determines that adoption demonstrates the jurisdiction’s commitment to fulfilling the mitigation goals and objectives outlined in the HMP as funding allows.

NOW, THEREFORE, THE CITY COUNCIL OF THE CITY OF SIMI VALLEY DOES HEREBY RESOLVE AS FOLLOWS:

SECTION 1. The City Council adopts the Ventura County Multi- Jurisdictional Hazard Mitigation Plan, consisting of Volume 1 in its entirety and the following parts of Volume 2: (1) Introduction; and (2) Part 9, the City of Simi Valley Annex.

SECTION 2. The City will use the HMP to guide pre-and post-disaster hazard mitigation efforts.

SECTION 3. The City will pursue implementation of the identified mitigation actions subject to the limitations of available funding and staff. 6 RES. NO. 2022-45
SECTION 4. The City will coordinate the strategies in the HMP with other planning programs and mechanisms under its jurisdictional authority.

SECTION 5. The City will continue to support ongoing countywide hazard mitigation efforts.

SECTION 6. The City will continue to participate in the regional planning partnership as described by the HMP.

The City Clerk shall certify to the adoption of this resolution and shall cause a certified resolution to be filed in the Office of the City Clerk.

PASSED and ADOPTED this 25thday of July, 2022.

Attest:

Lucy Blanco, City Clerk Keith L. Mashburn, Mayor of the City of Simi Valley, California
Approved as to Form: Approved as to Content:

David L. Caceres, City Attorney Brian Paul Gabler, City Manager Dave Livingstone, Chief of Police
Police Department
7 RES. NO. 2022-45
Multi-JurisdictionalHazard Mitigation Plan
J u n e 2 0 2 2
V e n t u r a C o u n t y
U p d a t e 2 0 2 2
V o l u m e 1 A r e a - w i d e I n f o r m a t i o n 8 9

Ventura County
Multi-Jurisdictional Hazard Mitigation Plan
Update 2022
June 2022

PREPARED FOR PREPARED BY
County of Ventura Tetra Tech
800 South Victoria Avenue
Ventura, CA 93009 1999 Harrison Street
Suite 500
Oakland, CA 94612
Phone: 510.302.6300
Fax: 510.433.0830
tetratech.com

Tetra Tech Project #103s7429
\\tts121fs1\Data\EMCR_Projects\California\VenturaCounty\HMP 2021_103s7429\Plan Development\Plan Documents\2022-06_Final\2022-06_VenturaHMP_Vol1_Final.docx

10 11
Ventura County Multi-Jurisdictional Hazard Mitigation Plan Contents v

CONTENTS
Executive Summary............................................................................................................. xvii Part 1— BACKGROUND AND METHODS

1. Introduction ..................................................................................................................................1-1

1.1 Why Prepare This Plan? ......................................................................................................1-1

1.2 Who Will Benefit from This Plan? .........................................................................................1-2

1.3 Contents of the Plan .............................................................................................................1-3

2. Plan Update—What has Changed? .............................................................................................2-1

2.1 Previous Plans .....................................................................................................................2-1

2.2 Why Update? .......................................................................................................................2-2

2.3 The Updated Plan—What Is Different? ................................................................................2-1

3. Plan Development Methodology ..................................................................................................3-1

3.1 Funding ................................................................................................................................3-1

3.2 Formation of the Core Planning Team .................................................................................3-1

3.3 Establishment of the Planning Partnership ..........................................................................3-1

3.4 Defining the Planning Area ..................................................................................................3-2

3.5 The Steering Committee ......................................................................................................3-3

3.6 Coordination with Stakeholders and Agencies .....................................................................3-4

3.7 Review of Existing Programs ...............................................................................................3-5

3.8 Public Participation ...............................................................................................................3-6

3.9 Plan Development Chronology/Milestones ........................................................................3-12

4. Ventura County Profile .................................................................................................................4-1

4.1 Physical Setting ....................................................................................................................4-1

4.2 Historical Overview ..............................................................................................................4-3

4.3 Population Centers, Transportation, and Government .........................................................4-4

4.4 Development ........................................................................................................................4-4

4.5 Demographics Profile .........................................................................................................4-11

4.6 Economy ............................................................................................................................4-14

5. Hazards of Concern .....................................................................................................................5-1

5.1 Major Past Hazard Events ...................................................................................................5-1

5.2 Hazards Evaluated in 2015 Plan ..........................................................................................5-2

5.3 Identified Hazards for the 2022 Update ...............................................................................5-3

6. Existing Regulations ....................................................................................................................6-1

6.1 Federal and State Agencies, Programs and Regulations ....................................................6-1

6.2 Local Plans, Reports and Codes ..........................................................................................6-6

6.3 Local Capability Assessment ...............................................................................................6-7

6.4 Hazard Mitigation Capabilities for Future Development .......................................................6-9 Part 2— RISK ASSESSMENT

7. Risk Assessment Methodology ....................................................................................................7-1

7.1 Risk Assessment Tools ........................................................................................................7-1

7.2 Risk Assessment Approach .................................................................................................7-2

7.3 Sources of Data Used in Modeling and Exposure analyses ................................................7-3 12 Ventura County Multi-Jurisdictional Hazard Mitigation Plan Contents vi

7.4 Limitations............................................................................................................................7-6

8. Dam Failure .................................................................................................................................8-1

8.1 General Background ............................................................................................................8-1

8.2 Hazard Profile ......................................................................................................................8-3

8.3 Exposure ..............................................................................................................................8-9

8.4 Vulnerability........................................................................................................................8-11

8.5 Scenario .............................................................................................................................8-13

8.6 Issues .................................................................................................................................8-13

9. Drought ........................................................................................................................................9-1

9.1 General Background ............................................................................................................9-1

9.2 Hazard Profile ......................................................................................................................9-5

9.3 Exposure ............................................................................................................................9-11

9.4 Vulnerability........................................................................................................................9-11

9.5 Scenario .............................................................................................................................9-12

9.6 Issues .................................................................................................................................9-13

10. Earthquake ...............................................................................................................................10-1

10.1 General Background ........................................................................................................10-1

10.2 Hazard Profile ..................................................................................................................10-6

10.3 Exposure ........................................................................................................................10-13

10.4 Vulnerability....................................................................................................................10-14

10.5 Scenario .........................................................................................................................10-27

10.6 Issues .............................................................................................................................10-28

11. Flood ........................................................................................................................................11-1

11.1 General Background ........................................................................................................11-1

11.2 Hazard Profile ..................................................................................................................11-7

11.3 Exposure ........................................................................................................................11-22

11.4 Vulnerability....................................................................................................................11-25

11.5 Scenario .........................................................................................................................11-28

11.6 Issues .............................................................................................................................11-29

12. Landslide ..................................................................................................................................12-1

12.1 General Background ........................................................................................................12-1

12.2 Hazard Profile ..................................................................................................................12-2

12.3 Exposure ..........................................................................................................................12-6

12.4 Vulnerability......................................................................................................................12-8

12.5 Scenario .........................................................................................................................12-10

12.6 Issues .............................................................................................................................12-10

13. Sea-Level Rise and Coastal Erosion .......................................................................................13-1

13.1 General Background ........................................................................................................13-1

13.2 Hazard Profile ..................................................................................................................13-2

13.3 Exposure ..........................................................................................................................13-7

13.4 Vulnerability......................................................................................................................13-8

13.5 Scenario ...........................................................................................................................13-9

13.6 Issues ...............................................................................................................................13-9

14. Severe Storms .........................................................................................................................14-1

14.1 General Background ........................................................................................................14-1

14.2 Hazard Profile ..................................................................................................................14-2 13 Ventura County Multi-Jurisdictional Hazard Mitigation Plan Contents vii

14.3 Exposure and Vulnerability ..............................................................................................14-5

14.4 Scenario ...........................................................................................................................14-7

14.5 Issues ...............................................................................................................................14-7

15. Severe Weather .......................................................................................................................15-1

15.1 General Background ........................................................................................................15-1

15.2 Hazard Profile ..................................................................................................................15-4

15.3 Exposure and Vulnerability ..............................................................................................15-8

15.4 Scenario ...........................................................................................................................15-9

15.5 Issues ...............................................................................................................................15-9

16. Tsunami ...................................................................................................................................16-1

16.1 General Background ........................................................................................................16-1

16.2 Hazard Profile ..................................................................................................................16-3

16.3 Exposure ..........................................................................................................................16-6

16.4 Vulnerability......................................................................................................................16-9

16.5 Scenario .........................................................................................................................16-12

16.6 Issues .............................................................................................................................16-12

17. Wildfire .....................................................................................................................................17-1

17.1 General Background ........................................................................................................17-1

17.2 Hazard Profile ..................................................................................................................17-4

17.3 Exposure ..........................................................................................................................17-7

17.4 Vulnerability......................................................................................................................17-9

17.5 Scenario .........................................................................................................................17-11

17.6 Issues .............................................................................................................................17-12

18. Climate Change .......................................................................................................................18-1

18.1 General Background ........................................................................................................18-1

18.2 Impact of Climate Change on Hazards of Concern ..........................................................18-8

19. Other Hazards of Interest .........................................................................................................19-1

19.1 Agricultural and Biological ................................................................................................19-1

19.2 Pandemic .........................................................................................................................19-3

20. Planning Area Risk Ranking ....................................................................................................20-1

20.1 Probability of Occurrence .................................................................................................20-1

20.2 Impact ..............................................................................................................................20-2

20.3 Risk Rating and Ranking ..................................................................................................20-3 Part 3— MITIGATION PLAN

21. Vision Statement, Goals and Objectives ..................................................................................21-1

21.1 Vision STatement .............................................................................................................21-1

21.2 Goals ................................................................................................................................21-1

21.3 Objectives ........................................................................................................................21-2

22. Mitigation Best Practices ..........................................................................................................22-1

22.1 Mitigation Best Practices ..................................................................................................22-1

22.2 Adaptive Capacity ..........................................................................................................22-11

23. Recommended Planning-Area-Wide Actions ...........................................................................23-1

23.1 Recommended Mitigation Actions for All Partners ...........................................................23-1

23.2 Area-Wide Action Plan Prioritization ................................................................................23-1

23.3 Classification of Area-Wide Mitigation Actions .................................................................23-3 14 Ventura County Multi-Jurisdictional Hazard Mitigation Plan Contents viii

24. Plan Adoption and Maintenance ..............................................................................................24-1

24.1 Plan Adoption ...................................................................................................................24-1

24.2 Plan Maintenance Strategy ..............................................................................................24-1 References

Appendices
Appendix A. Public Involvement Materials
Appendix B. Federal and State Agencies, Programs and Regulations Appendix C. Mapping Methods & Data Sources
Appendix D. Detailed Risk Assessment Results
Appendix E. Summary of Peak Discharges for the Planning Area Appendix F. FEMA Approval and Partner Adoption Resolutions Tables
Table ES-1. Countywide Mitigation Initiatives ....................................................................................... xxiii Table 2-1. Key Changes from Previous Hazard Mitigation Plan ............................................................2-1 Table 3-1. Core Planning Team Makeup ...............................................................................................3-1 Table 3-2. Hazard Mitigation Planning Partners ....................................................................................3-2 Table 3-3. Steering Committee Members ..............................................................................................3-3 Table 3-4. Summary of Public Meetings ..............................................................................................3-12 Table 3-5. Plan Development Milestones ............................................................................................3-13 Table 4-1. Normal Precipitation and Temperatures, 2000 – 2020 .........................................................4-2 Table 4-2. Planning Area Building Counts by Occupancy Class ...........................................................4-7 Table 4-3. Estimated Replacement Value of Planning Area Buildings ..................................................4-7 Table 4-4. Critical Facilities by Jurisdiction and Category .....................................................................4-8 Table 4-5. Recent Population by Jurisdiction .......................................................................................4-12 Table 4-6. Comparative Statistics for Renter-Occupied and Owner-Occupied Housing Units ............4-15 Table 4-7. 2021 Principal Employers within Ventura County ...............................................................4-15 Table 5-1. Federal Disaster Declarations for Hazard Events that Affected the Planning Area ..............5-1 Table 5-2. Hazards Addressed in This Hazard Mitigation Plan .............................................................5-3 Table 6-1. Summary of Relevant Federal Agencies, Programs and Regulations ..................................6-1 Table 6-2. Summary of Relevant State Agencies, Programs and Regulations .....................................6-3 Table 7-1. Hazus Model Property and Hazard Data Documentation .....................................................7-5 Table 7-2. Hazus Model Critical Facilities Data Documentation ............................................................7-6 Table 8-1. Ventura County Dams with Potential to Endanger Lives and Property ................................8-4 15 Ventura County Multi-Jurisdictional Hazard Mitigation Plan Contents ix
Table 8-2. Ventura County Dam Inspection Dates ................................................................................8-6 Table 8-3. State of California Downstream Hazard Potential Classification ..........................................8-8 Table 8-4. Exposed Property in Evaluated Dam Failure Inundation Area .............................................8-9 Table 8-5. Estimated Dam Failure Impacts on Population ...................................................................8-11 Table 8-6. Estimated Impact of a Dam Failure in the Planning Area ...................................................8-11 Table 9-1. State Drought Management Program ...................................................................................9-5 Table 10-1. Mercalli Scale and Peak Ground Acceleration Comparison .............................................10-3 Table 10-2. NEHRP Soil Classification System ...................................................................................10-6 Table 10-3. Recent Earthquakes Magnitude 5.0 or Larger Within 100-mile Radius of Planning Area 10-7 Table 10-4. Likely Maximum Magnitudes and Recurrence Intervals ...................................................10-9 Table 10-5. Earthquakes Modeled for Risk Assessment ...................................................................10-15 Table 10-6. Estimated Earthquake Impact on Persons .....................................................................10-15 Table 10-7. Estimated Impact of Earthquake Scenario Events in the Planning Area ........................10-15 Table 10-8. Age of Housing Units in Planning Area ...........................................................................10-21 Table 11-1. Flood Insurance Statistics .................................................................................................11-7 Table 11-2. CRS Status of Participating Jurisdictions .........................................................................11-8 Table 11-3. History of Flood Events ...................................................................................................11-14 Table 11-4. Repetitive Loss Properties in Ventura County ................................................................11-17 Table 11-5. Summary of Peak Discharges in Large Ventura County Drainages ...............................11-19 Table 11-6. Exposed Population in Evaluated Flood Hazard Zones .................................................11-22 Table 11-7. Exposed Property in Evaluated Flood Hazard Zones .....................................................11-23 Table 11-8. Estimated Flood Impacts on Persons and Households ..................................................11-26 Table 11-9. Estimated Impact of a Flood Event in the Planning Area ...............................................11-26 Table 12-1. Landslide Events in the Planning Area .............................................................................12-3 Table 12-2. Exposed Population in Mapped Landslide Hazard Zones ................................................12-6 Table 12-3. Exposed Property in Mapped Landslide Hazard Zones ...................................................12-7 Table 12-4. Loss Estimation for Landslide ...........................................................................................12-9 Table 13-1. History of Coastal Erosion Events ....................................................................................13-3 Table 13-2. Estimated Population Exposure for Sea-Level Rise .........................................................13-7 Table 13-3. Estimated Property Exposure for Sea-Level Rise ............................................................13-7 Table 14-1. Recent Severe Storm Events in the Planning Area ..........................................................14-2 Table 15-1. Beaufort Wind Chart .........................................................................................................15-1 Table 15-2. Operational Enhanced Fujita Scale ..................................................................................15-3 Table 15-3. Recent Severe Weather Events in the Planning Area ......................................................15-4 Table 16-1. Tsunami Events in Ventura County ..................................................................................16-3 Table 16-2. Exposed Property in the Tsunami Inundation Zone ..........................................................16-7 Table 16-3. Estimated Impact of a Tsunami Event in the Planning Area ...........................................16-10 Table 17-1. Federally Declared Wildfire Events in Ventura County .....................................................17-4 Table 17-2. Exposed Population in Mapped Relative Fire Hazard Zones ...........................................17-7 Table 17-3. Exposed Property in Mapped Relative Fire Hazard Zones ...............................................17-8 Table 17-4. Loss Estimates for Fire Hazard Severity Zones .............................................................17-10 Table 19-1. Agricultural and Biological Hazards That Threaten Ventura County ................................19-2 16 Ventura County Multi-Jurisdictional Hazard Mitigation Plan Contents x
Table 19-2. Naturally Spread Diseases Seen in California..................................................................19-4 Table 22-1. Alternatives to Mitigate the Dam Failure Hazard ..............................................................22-2 Table 22-2. Alternatives to Mitigate the Drought Hazard .....................................................................22-3 Table 22-3. Alternatives to Mitigate the Earthquake Hazard ...............................................................22-4 Table 22-4. Alternatives to Mitigate the Flood Hazard .........................................................................22-5 Table 22-5. Alternatives to Mitigate the Landslide Hazard ..................................................................22-6 Table 22-6. Alternatives to Mitigate Sea-Level Rise and Coastal Erosion ...........................................22-7 Table 22-7. Alternatives to Mitigate the Severe Storm and Severe Weather Hazards ........................22-8 Table 22-8. Alternatives to Mitigate the Tsunami Hazard ....................................................................22-9 Table 22-9. Alternatives to Mitigate the Wildfire Hazard ....................................................................22-10 Table-23-1. Action Plan—Countywide Mitigation Initiatives .................................................................23-1 Table 23-2. Mitigation Action Priority ...................................................................................................23-3 Table 23-3. Analysis of Mitigation Actions ...........................................................................................23-4 Table 24-1. Plan Maintenance Matrix ..................................................................................................24-2

Figures
Figure 3-1. Example Page of the Hazard Mitigation Plan Web Site ......................................................3-7 Figure 3-2. Sample Page from Survey Distributed to the Public ............................................................3-8 Figure 3-3. Example Story Map Data Page ...........................................................................................3-9 Figure 3-4. Screenshot from September 16, 2021 Community Emergency Preparedness Workshop 3-10 Figure 4-1. Planning Area ......................................................................................................................4-5 Figure 4-2. Land Use Classifications in the Planning Area ....................................................................4-6 Figure 4-3. Critical Facilities (1 of 2) ......................................................................................................4-9 Figure 4-4. Critical Facilities (2 of 2) ....................................................................................................4-10 Figure 4-5. State of California and Ventura County Population Growth per Decade ...........................4-12 Figure 4-6. Planning Area Age Distribution ..........................................................................................4-13 Figure 4-7. Planning Area Race Distribution ........................................................................................4-14 Figure 4-8. Employment in Ventura County by Industry Sector ...........................................................4-16 Figure 4-9. 10-Year Unemployment Rates for California and Ventura County ....................................4-17 Figure 4-10. Employment in the Planning Area by Type of Work ........................................................4-17 Figure 8-1. Locations of Dams in Ventura County .................................................................................8-5 Figure 8-2. Dam Failure Inundation Area Used for Risk Assessment ...................................................8-7 Figure 8-3. Building Count by Occupancy Class in the Dam Failure Inundation Zone ........................8-10 Figure 8-4. Critical Facilities in Dam Failure Inundation Area ..............................................................8-10 Figure 8-5. Critical Facilities Exposed to and Affected by Mapped Dam Failure Inundation Area .......8-12 Figure 8-6. Average % of Damage to Critical Facilities Caused by Modeled Dam Failure ..................8-12 Figure 9-1. Example Drought Index Maps, Current as of November 18, 2021 ......................................9-3 Figure 9-2. Calleguas MWD’s Lake Bard Reservoir ..............................................................................9-6 Figure 9-3. Casitas MWSD’s Lake Casitas ............................................................................................9-7 Figure 9-4. UWCD’s Freeman Diversion ...............................................................................................9-7 17 Ventura County Multi-Jurisdictional Hazard Mitigation Plan Contents xi
Figure 9-5. Percent of Ventura County Affected by Each USDM Rating, 2000 – 2021 .........................9-9 Figure 10-1. Peak Acceleration (%g) with 2% Probability of Exceedance in 50 Years ........................10-5 Figure 10-2. Local Fault Locations.......................................................................................................10-8 Figure 10-3. NEHRP Soil Class .........................................................................................................10-10 Figure 10-4. Liquefaction Zones ........................................................................................................10-11 Figure 10-5. Peak Ground Acceleration (%g) with 10% Probability of Exceedance in 50 Years .......10-12 Figure 10-6. Building Count by Occupancy Class on NEHRP D or E soils .......................................10-13 Figure 10-7. Critical Facilities on NEHRP D and E Soils ...................................................................10-14 Figure 10-8. Intensity Scale for 100-Year Probabilistic Earthquake Scenario ...................................10-16 Figure 10-9. Intensity Scale for Oak Ridge M7.16 Earthquake Scenario ..........................................10-17 Figure 10-10. Intensity Scale for San Cayetano M7.16 Earthquake Scenario ...................................10-18 Figure 10-11. Intensity Scale for South San Andreas M8.03 Earthquake Scenario ..........................10-19 Figure 10-12. Intensity Scale for Ventura-Pitas Point M7.12 Earthquake Scenario ..........................10-20 Figure 10-13. Critical Facility Damage Potential, 100-Year Probabilistic Earthquake Scenario ........10-22 Figure 10-14. Critical Facility Damage Potential, Oak Ridge M7.16 Earthquake Scenario ...............10-23 Figure 10-15. Critical Facility Damage Potential, San Cayetano M7.16 Earthquake Scenario .........10-23 Figure 10-16. Critical Facility Damage Potential, S San Andreas M8.03 Earthquake Scenario ........10-24 Figure 10-17. Critical Facility Damage Potential, Ventura-Pitas Point M7.12 Earthquake Scenario .10-24 Figure 10-18. Critical Facility Functionality, 100-Year Probabilistic Earthquake Scenario ................10-25 Figure 10-19. Critical Facility Functionality, Oak Ridge M7.16 Earthquake Scenario ........................10-25 Figure 10-20. Critical Facility Functionality, San Cayetano M7.16 Earthquake Scenario ..................10-26 Figure 10-21. Critical Facility Functionality, S San Andreas M8.03 Earthquake Scenario ................10-26 Figure 10-22. Critical Facility Functionality, Ventura-Pitas Point M7.12 Earthquake Scenario ..........10-27 Figure 11-1. Limit of Moderate Wave Action ........................................................................................11-5 Figure 11-2. Floodplains Mapped in the Ventura River Levee Study ................................................11-16 Figure 11-3. Floodplains Mapped in the Santa Clara River Levee Study ..........................................11-17 Figure 11-4. FEMA Flood Hazard Areas ............................................................................................11-18 Figure 11-5. Ventura County Flood Warning System Example .........................................................11-23 Figure 11-6. Building Occupancy Classes in the Mapped Flood Zones ............................................11-24 Figure 11-7. Critical Facilities in 1% Annual Chance Floodplain .......................................................11-24 Figure 11-8. Critical Facilities in 0.2% Annual Chance Floodplain ....................................................11-25 Figure 11-9. Facilities Exposed to and Affected by the 1% and 0.2% Annual Chance Floods ..........11-27 Figure 11-10. Average Damage to Critical Facilities from 1% and 0.2% Annual Chance Floods ......11-27 Figure 12-1. Susceptibility to Deep-Seated Landslides .......................................................................12-4 Figure 12-2. Building Occupancy Classes in the Mapped Landslide Hazard Zones ...........................12-7 Figure 12-3. Critical Facilities in High or Very High Landslide Risk Areas ...........................................12-8 Figure 13-1. Estimated Inundation Area for 25-Centimeter Sea-Level Rise ........................................13-4 Figure 13-2. Estimated Inundation Area for 100-Centimeter Sea-Level Rise ......................................13-5 Figure 13-3. Building Occupancy Classes in 25-cm and 100-cm Sea-Level Rise Exposure Areas ....13-8 Figure 15-1. Santa Ana Winds .............................................................................................................15-2 Figure 15-2. Wind Zones in the United States .....................................................................................15-7 Figure 16-1. Common Sources of Tsunamis .......................................................................................16-1 Figure 16-2. Runup Distance and Height in Relation to the Datum and Shoreline ..............................16-2 Figure 16-3. Tsunami Risk Areas for Ventura County .........................................................................16-4 18 Ventura County Multi-Jurisdictional Hazard Mitigation Plan Contents xii
Figure 16-4. Potential Tsunami Travel Times in the Pacific Ocean, in Hours......................................16-7 Figure 16-5. Structures in the Tsunami Inundation Zone, by Building Occupancy Class ....................16-8 Figure 16-6. Critical Facilities in Tsunami Inundation Area ..................................................................16-8 Figure 16-7. Critical Facilities Exposed to and Affected by Mapped Tsunami Inundation Area ........16-10 Figure 16-8. Average % of Damage to Critical Facilities Caused by Modeled Tsunami ....................16-11 Figure 17-1. CAL FIRE Wildfire Activity Statistics for Ventura County 2011-2019 ..............................17-5 Figure 17-2. Fire Hazard Severity Zones in Ventura County ...............................................................17-6 Figure 17-3. Structures in the Moderate, High or Very High FHSZs, by Occupancy Class .................17-8 Figure 17-4. Critical Facilities in High or Very High Severity Zones ....................................................17-9 Figure 18-1. Global Carbon Dioxide Concentrations Over Time .........................................................18-2 Figure 18-2. Possible Future Sea Levels for Different Greenhouse Gas Pathways ............................18-6 Figure 18-3. Changes in Projected Maximum Temperatures in Ventura County ................................18-7 Figure 19-1. Ventura County COVID-19 Case Rate June – December 20, 2021 ................................19-5 Figure 20-1. Probability Factors for Hazards of Concern .....................................................................20-1 Figure 20-2. Impact Factors for Hazards of Concern ...........................................................................20-3 Figure 20-3. Weighted Impact Factors for Hazards of Concern ..........................................................20-3 Figure 20-4. Total Risk Rating for Hazards of Concern .......................................................................20-4 Figure 20-5. Hazard Risk Ranking .......................................................................................................20-4

19 Ventura County Multi-Jurisdictional Hazard Mitigation Plan Definition of Terms xiii

DEFINITION OF TERMS

0.2 percent-annual-chance flood—the flood that has a

0.2 percent chance of being equaled or exceeded in any
given year; often referred to as the 500-year flood
1 percent-annual-chance flood—the flood that has a
1 percent chance of being equaled or exceeded in any
given year; often referred to as the 100-year flood
AB—Assembly Bill
ADA—Americans with Disabilities Act
asset—any man-made or natural feature that has value,
including people; buildings; infrastructure, such as bridges, roads, sewers, and water systems; lifelines, such as
electricity and communication resources; and
environmental, cultural, or recreational features such as parks, wetlands, and landmarks.
base flood—the flood having a 1% chance of being
equaled or exceeded in any given year, also known as the “100-year” or “1 percent annual chance” flood. The base flood is a statistical concept used to ensure that all
properties subject to the National Flood Insurance
Program (NFIP) are protected to the same degree against flooding.
basin—the area within which all surface water—whether
from rainfall, snowmelt, springs, or other sources—flows to a single water body or watercourse. The boundary of a
river basin is defined by natural topography, such as hills, mountains, and ridges. Basins are also referred to as
“watersheds.”
benefit/cost analysis—a systematic, quantitative method of comparing projected benefits to projected costs of a project or policy. It is used as a measure of cost
effectiveness.
benefit—a net project outcome and is usually defined in monetary terms. Benefits may include direct and indirect effects. For the purposes of benefit/cost analysis of
proposed mitigation measures, benefits are limited to
specific, measurable, risk reduction factors, including reduction in expected property losses (buildings, contents, and functions) and protection of human life.

BLM—Bureau of Land Management
CAL FIRE—California Department of Forestry and Fire
Protection
Cal OES—California Governor’s Office of Emergency
Services
capability assessment—an analysis of a community’s
capacity to address threats associated with hazards. The assessment includes two components: an inventory of an
agency’s mission, programs, and policies, and an analysis of its capacity to carry them out.

CCR—California Code of Regulations
CDBG-DR—Community Development Block Grant
Disaster Recovery grants
CEQA—California Environmental Quality Act
CFR—Code of Federal Regulations
climate action plan—a detailed and strategic framework
for measuring, planning, and reducing greenhouse gas
emissions and related climatic impacts. Climate action
plans, at a minimum, include an inventory of existing
emissions, reduction goals or targets, and analyzed and prioritized reduction actions.
climate change—a change in global or regional climate
patterns, in particular a change apparent from the mid to late 20th century onwards and attributed largely to the increased levels of atmospheric carbon dioxide produced by the use of fossil fuels.

Community Rating System (CRS)—a voluntary program
under the NFIP that rewards participating communities
(provides incentives) for exceeding the minimum
requirements of the NFIP and completing activities that reduce flood hazard risk by providing flood insurance
premium discounts.
critical facilities—facilities and infrastructure that are critical to the health and welfare of the population. These become especially important after any hazard event
occurs.

CWA—Clean Water Act
dam failure—an uncontrolled release of impounded water
due to a partial or complete breach in a dam (or levee) that impacts its integrity.
dam—any artificial barrier or controlling mechanism that can or does impound or divert water.

DART—Disaster Assistance Response Team
debris flow—dense mixtures of water-saturated debris
that move down-valley, looking and behaving much like
flowing concrete. They form when loose masses of
unconsolidated material are saturated, become unstable, and move down slope. The source of water varies but
includes rainfall, melting snow or ice, and glacial outburst floods.

DFIRM—Digital Flood Insurance Rate Map
Disaster Mitigation Act (DMA; Public Law 106-390)—
the latest federal legislation enacted to encourage and promote proactive, pre-disaster planning as a condition of receiving certain federal financial assistance.
drought—the cumulative impacts of long periods of dry
weather. These can include deficiencies in surface and
20 Ventura County Multi-Jurisdictional Hazard Mitigation Plan Definition of Terms xiv
subsurface water supplies and general impacts on health, well-being, and quality of life.

DWR—Department of Water Resources
EAP—emergency action plan
earthquake—the shaking of the ground caused by an
abrupt shift of rock along a fracture in the earth or a contact zone between tectonic plates.
ecosystem services—an ecosystem service is any
positive benefit that wildlife or ecosystems provide to people. The benefits can be direct or indirect—small or large.
epidemic—the spread of an infectious disease beyond a
local population, reaching people in a wider geographical area. Several factors determine whether an outbreak will become an epidemic: the ease with which the disease
spreads from vectors, such as animals, to people, and the ease with which it spreads from person to person.
equity—the absence of avoidable or remediable
differences among groups of people, whether those
groups are defined socially, economically,
demographically, racially, or geographically.

ESA—Endangered Species Act
exposure—the number and dollar value of assets
considered to be at risk during the occurrence of a specific hazard.
extent—the size or location of an area affected by a
hazard. For hazards that do not have a clearly defined
extent, this definition expands to the strength or magnitude (severity) of the hazard. For hazards in this plan that do not have mapping, extent is addressed by the severity
discussion of the hazard profile.
extreme cold—temperatures from winter storms
associated with freezing rain, sleet, snow and strong
winds that may cause hypothermia or frostbite.
extreme heat—temperatures that hover 10 ºF or more
above the average high temperature for a region and last for several days.
federal disaster declaration—declarations for events
that cause more damage than state and local
governments and resources can handle without federal
government assistance. A federal disaster declaration puts into motion long-term federal recovery programs, some of which are matched by state programs, to help disaster
victims, businesses, and public entities.

FEMA—Federal Emergency Management Agency
FERC—Federal Energy Regulatory Commission
FHSZ—Fire Hazard Severity Zone
flash flood—a flood that occurs with little or no warning when water levels rise at an extremely fast rate
Flood Insurance Rate Map (FIRM)—the official map on
which the Federal Emergency Management Agency
delineates the special flood hazard area.

Flood Insurance Study—a report published by the
Federal Insurance and Mitigation Administration for a
community in conjunction with the community’s Flood
Insurance rate Map. The study contains such background
data as the base flood discharges and water surface
elevations that were used to prepare the FIRM. In most
cases, a community FIRM with detailed mapping will have a corresponding flood insurance study.
floodplain—the land area along the sides of a river that becomes inundated with water during a flood.
flood—the inundation of normally dry land resulting from the rising and overflowing of a body of water.

FRA—federal responsibility area
freeboard—the margin of safety added to the base flood
elevation.
frequency—how often a hazard of specific magnitude,
duration, and/or extent is expected to occur on average.

Statistically, a hazard with a 100-year frequency is
expected to occur about once every 100 years on average and has a 1 percent chance of occurring any given year.

Frequency reliability varies depending on the type of
hazard considered.

Fujita tornado damage scale—scale for rating tornado
wind speeds, estimated on the basis of damage sustained.

The scale rates the intensity or severity of tornado events using numeric values from F0 to F5 based on tornado
wind speed and damage. An F0 tornado (wind speed less
than 73 miles per hour (mph)) indicates minimal damage
(such as broken tree limbs), and an F5 tornado (wind
speeds of 261 to 318 mph) indicates severe damage.
g—the acceleration associated with gravity (%g is an
acceleration calculated as a percentage of the
acceleration of gravity)
geographic information system (GIS)—a computer
software application that relates data regarding physical and other features on the earth to a database for mapping and analysis.
goal—a general guideline that explains what is to be
achieved. Goals are usually broad-based, long-term,
policy-type statements and represent global visions. Goals help define the benefits that a plan is trying to achieve.

The success of a hazard mitigation plan is measured by
the degree to which its goals have been met (that is, by the actual benefits in terms of actual hazard mitigation). greenhouse gases—methane, nitrous oxide and other
gases that trap heat and warm the Earth, as a greenhouse traps heat from the sun.
ground shaking—the result of rapid ground acceleration
caused by seismic waves passing beneath buildings,
roads, and other structures.
hazard—a source of potential danger or adverse condition that could harm people and/or cause property damage.
hazardous material—a substance or combination of
substances (biological, chemical, radiological, and/or
21 Ventura County Multi-Jurisdictional Hazard Mitigation Plan AbbreviationsDefinition of Terms xv
physical) that, because of its quantity, concentration, or physical, chemical or infectious characteristics, has the potential to cause harm to humans, animals, or the
environment, either by itself or through interaction with other factors.

Hazus (Hazards U.S.)—a nationally standardized, GIS-
based multi-hazard risk analysis tool developed and
distributed by FEMA
high-hazard dam—a dam that can cause loss of human
life from the failure or improper operation of the dam
IBC—International Building Code
intensity—the measure of the effects of a hazard
inventory—the assets identified in a study region
comprise an inventory. Inventories include assets that
could be lost when a disaster occurs and community
resources are at risk. Assets include people, buildings, transportation, and other valued community resources.

IT—information technology
LiMWA—Limit of Moderate Wave Action
liquefaction—loosely packed, water-logged sediments
losing their strength in response to strong shaking,
causing major damage during earthquakes.
local government—any county, municipality, city, town,
township, public authority, school district, special district, intrastate district, council of governments (regardless of whether the council of governments is incorporated as a nonprofit corporation under State law), regional or
interstate government entity, or agency or instrumentality of a local government; any Indian tribe or authorized tribal organization, or Alaska Native village or organization; and any rural community, unincorporated town or village, or other public entity.

LRA—local responsibility area
magnitude—the measure of the strength of an
earthquake.
mitigation actions—specific actions to achieve goals and objectives that minimize the effects from a disaster and reduce the loss of life and property.
mitigation—a preventive action taken in advance of an
event to reduce or eliminate risk to life or property.
mph—miles per hour
Mw—Moment Magnitude Scale
N/A—not applicable
NASA—National Aeronautics and Space Administration
NCEI—National Centers for Environmental Information
NEHRP—National Earthquake Hazard Reduction Program
NFIP—National Flood Insurance Program
NOAA—National Oceanic and Atmospheric Administration
NWS—National Weather Service
OES—Office of Emergency Services (Ventura County
Sheriff’s)
pandemic—an epidemic of infectious disease that has
spread through human populations across a large region, multiple continents, or worldwide.
peak ground acceleration (PGA)—a measure of the
highest amplitude of ground shaking that accompanies an earthquake, based on a percentage of the force of gravity. ppm—parts per million
preparedness—actions that strengthen the capability of
government, people, and communities to respond to
disasters.
probability of occurrence—a statistical measure or
estimate of the likelihood that a hazard will occur. This probability is generally based on past hazard events in the area and a forecast of events that could occur in the
future. A probability factor based on yearly values of
occurrence is used to estimate probability of occurrence. recurrence interval—the inverse of the probability that a given event will be equaled or exceeded in any given year (sometimes called the return period)
repetitive loss property—any NFIP-insured property
that, since 1978 and regardless of any changes of
ownership during that period, has experienced—Four or
more paid flood losses in excess of $1000.00; or two paid flood losses in excess of $1000.00 within any 10-year
period since 1978; or three or more paid losses that equal or exceed the current value of the insured property.
risk assessment—the process of measuring potential
loss of life, personal injury, economic injury, and property damage resulting from hazards. This process assesses
the vulnerability of people, buildings, and infrastructure to hazards
risk ranking—process to score and rank hazards based
on the probability that they will occur and the impact they will have if they do.
risk—the estimated impact that a hazard would have on
people, services, facilities, and structures in a community.

Risk measures the likelihood of a hazard occurring and
resulting in an adverse condition that causes injury or damage. Risk is often expressed in relative terms such as a high, moderate, or low likelihood of sustaining damage above a particular threshold due to occurrence of a
specific type of hazard. Risk also can be expressed in
terms of potential monetary losses associated with the
intensity of the hazard.
riverine—of or produced by a river. Riverine floodplains have readily identifiable channels.

Robert T. Stafford Act (Robert T. Stafford Disaster
Relief and Emergency Assistance Act, Public Law 100-
107)—the statutory authority for most federal disaster
response activities, especially as they pertain to FEMA and its programs. Signed into law November 23, 1988;
amended by the Disaster Relief Act of 1974 (Public Law
93-288).

SEMS—Standardized Emergency Management System
22 Ventura County Multi-Jurisdictional Hazard Mitigation Plan Definition of Terms xvi
SFHA—special flood hazard area
significant-hazard dam—a dam that can cause
economic loss, environmental damage or disruption of
lifeline facilities, or can impact other concerns, but not necessarily loss of life.
special flood hazard area—the base floodplain
delineated on a Flood Insurance Rate Map. The SFHA is
mapped as a Zone A in riverine situations and zone V in coastal situations. The SFHA may or may not encompass
all of a community’s flood problems
SRA—state responsibility area
stakeholder—business leaders, civic groups, academia,
non-profit organizations, major employers, managers of
critical facilities, farmers, developers, special purpose districts, and others whose actions could impact hazard mitigation.
subsidence—the caving in or sinking of an area of land. surface fault rupture—an offset of the ground surface
when fault rupture extends to the Earth’s surface.
thunderstorm—a storm with lightning and thunder
produced by cumulonimbus clouds. Thunderstorms
usually produce gusty winds, heavy rains, and sometimes hail. Thunderstorms are usually short in duration (seldom more than 2 hours).
tornado—a violently rotating column of air extending
between and in contact with a cloud and the surface of the earth. Tornadoes are often (but not always) visible as
funnel clouds.

USDA—U.S. Department of Agriculture
USDM—U.S. Drought Monitor
USGS—U.S. Geological Survey
vulnerability—an assessment of how susceptible an
asset is to damage, based on its construction, contents, and the economic value of its functions
watershed—an area that drains downgradient from areas
of higher land to areas of lower land to the lowest point.

Zone X—area determined to be outside the 1 percent and

0.2 percent annual chance floodplains.
zoning ordinance—ordinance that designates allowable
land use and intensities for a local jurisdiction.
23 xvii

EXECUTIVE SUMMARY
Ventura County’s hazard mitigation plan update for 2022 defines measures to reduce risks from natural disasters in the Ventura County planning area, which includes unincorporated areas, incorporated cities, and special purpose districts. The plan updates the County’s previous plan, the 2015 Ventura County Multi-Hazard Mitigation Plan. It complies with federal and state hazard mitigation planning requirements to establish eligibility for funding under Federal Emergency Management Agency (FEMA) grant programs for all jurisdictions that participated as planning partners:

City of Camarillo
City of Fillmore
City of Moorpark
City of Ojai
City of Oxnard
City of Port Hueneme
City of San Buenaventura (Ventura)
City of Santa Paula
City of Simi Valley
City of Thousand Oaks
California State University, Channel
Islands
Calleguas Municipal Water District
Casitas Municipal Water District
Channel Islands Beach Community
Services District
Conejo Recreation & Park District
Ojai Valley Sanitary District
Pleasant Valley Recreation & Park District
Saticoy Sanitary District
Triunfo Water & Sanitation District
United Water Conservation District
Ventura County Fire Protection District
Ventura County Office of Education
Ventura County Public Works Agency—
Watershed Protection
Ventura Regional Sanitation District

PLAN DEVELOPMENT APPROACH
Organization
A core planning team consisting of a contract consultant and Ventura County staff was assembled to facilitate this plan update. A planning partnership was formed by engaging eligible local governments and making sure they understood their expectations for compliance under the updated plan. A steering committee was assembled to oversee the plan update, consisting of both governmental and non- governmental stakeholders within the planning area. Coordination with other local, state, and federal agencies involved in hazard mitigation occurred throughout the plan update process. Organization 24 Ventura County Multi-Jurisdictional Hazard Mitigation Plan Definition of Terms xviii
efforts included a review of the County’s 2015 hazard mitigation plan, the California statewide hazard mitigation plan, and existing programs that may support hazard mitigation actions.

Public Outreach
The planning team implemented a multi-media public involvement strategy utilizing the outreach capabilities of the planning partnership that was approved by the Steering Committee. The strategy included virtual public meetings, a community hazard mitigation awareness survey, a project website, and multiple print, web-based, and social media releases. Additionally, the Steering Committee was made up of community-based organizations, non-profit organizations, and other agencies that helped amplify public outreach efforts to their networks.

Plan Document Development
The planning team and Steering Committee assembled a document that is designed to meet federal hazard mitigation planning requirements for all partners. The updated plan contains two volumes.

Volume 1 contains components that apply to all partners and the broader planning area. Volume 2 contains components that are jurisdiction-specific, including each planning partner’s dedicated annex.

Adoption
Once pre-adoption approval has been granted by the California Governor’s Office of Emergency Services and FEMA, each planning partner will individually adopt the updated plan. Each partner has up to one year from FEMA approval to adopt the plan.

RISK ASSESSMENT
Risk assessment is the process of measuring the potential loss of life resulting from natural hazards, as well as personal injury, economic injury, and property damage, in order to determine the vulnerability of people, buildings, and infrastructure. For this update, the risk assessment included the following:

Hazard identification and profiling
Assessment of the impact of hazards on physical, social, and economic assets Identification of particular areas of vulnerability
Estimates of the cost of potential damage
Based on the risk assessment, each hazard of concern was ranked for the risk it poses to the overall planning area using risk ranking criteria provided by the core planning team. These rankings were reviewed and validated by each planning partner through the jurisdictional annex process. Figure ES-1 shows scores and ratings for the entire Ventura County planning area. All planning partners also rated the hazards for their impacts on their own individual planning areas. Figure ES-2 summarizes how the participating planning partners rated each hazard.
25 Executive SummaryDefinition of Terms
xix
Figure ES-1. Countywide Hazard Risk Rating

Figure ES-2. Summary of Risk Rating for Individual Planning Partners Dam Failure
34 Landslide
33 Flooding
18 Earthquake
32 Severe Storms
24 Severe Weather
24 Wildfire
24 Drought
9 Sea Level Rise / Erosion
12 Tsunami
12 0
2 4
6 0 1 2 3 4 5 6 7 8 9 10 11 12Values shown are risk ratings. Larger circles indicate higher rating.

High Risk
Medium
Risk
Low Risk
8 4
10 5
12 0
4 4
0 1011
1 15
18 10
3 21 21
0 9
6 20
0 2 2
9 0 0
12 5
0 0 0 0 1
13 0 0
13 1
0 5
10 15
20 25
Dam Failure Drought Earthquake Flooding Landslide Sea Level Rise /
Erosion
Severe
Storms
Severe
Weather
Tsunami Wildfire
Number of Planning Partners Assigning This Rating to This Hazard Highest Risk Medium Risk Lowest Risk Not Ranked
26 Ventura County Multi-Jurisdictional Hazard Mitigation Plan Definition of Terms xx
The Steering Committee considered the full range of natural hazards that could affect the planning area and then selected those that present the greatest concern for risk assessment in this plan. The process incorporated a review of state and local hazard planning documents as well as information on the frequency of, magnitude of, and costs associated with hazards that have struck the planning area or could do so. Anecdotal information regarding natural hazards and the perceived vulnerability of the planning area’s assets to them was also used. Based on the review, this plan includes risk assessments for the following hazards of concern:

Dam failure
Drought
Earthquake
Flood
Landslide
Sea-level rise and coastal erosion
Severe storms
Severe weather
Tsunami
Wildfire
In addition to the risk assessment of the hazards of concern, this plan provides a qualitative review of “hazards of interest.” The Steering Committee determined that these other hazards, though not required to be evaluated under federal guidelines for hazard mitigation plans, are important to recognize qualitatively in this plan. Hazard profiles, without quantitative risk assessments, are provided for the following hazards of interest:

Agricultural and biological hazards
Pandemic
Climate change is not assessed as an individual hazard, but a profile is provided describing how climate change could affect the hazards of concern assessed in this plan.

MITIGATION GOALS AND OBJECTIVES
The Steering Committee reviewed the 2015 Ventura County Multi-Hazard Mitigation Plan and noted that neither a vision statement nor a list of objectives was part of the previous plan. The following vision statement was selected to guide the Steering Committee and planning partners in selecting the actions contained in this plan update:

The Ventura County Multi-Jurisdictional Hazard Mitigation Plan will establish and promote a comprehensive mitigation strategy and efforts to equitably reduce risk and increase the resiliency of the community and environment from natural hazards. 27 Executive SummaryDefinition of Terms
xxi
Goals
The Steering Committee and planning team established the following 10 goals for the plan update:

Protect life, property, and the environment, and minimize displacement due to natural hazard events.

Effectively communicate natural hazard risks and mitigation strategies to the whole community.

Pursue development and implementation of feasible, cost-effective, and environmentally sound hazard mitigation measures.

Prioritize multi-objective hazard mitigation actions and those that reduce risk to vulnerable communities.

Coordinate with other plans and programs that can support or enhance hazard mitigation.

Enhance the County’s capability and capacity to prepare for, respond to, and recover from the impacts of natural hazards.

Proactively anticipate the risks of future impacts from hazards.

Increase the County’s adaptive capacity to reduce risk from hazard impacts.

Promote proactive, self-sufficient mitigation and response abilities.

Reduce risk to and increase the resilience of critical infrastructure and community lifelines.

The effectiveness of a mitigation strategy is assessed by determining how well these goals are achieved.

Objectives
Each of the selected plan objectives meets multiple goals, serving as a stand-alone measurement of the effectiveness of a mitigation action, rather than as a subset of a goal. The objectives were used to help establish priorities for each action identified in the plan. The plan objectives are as follows:

Utilize the best available data, science, and technology to identify and communicate the risk exposure to hazards to state, regional, and local agencies, as well as the private sector and non-profit groups.

Support efforts to improve the resilience of community lifelines in socially vulnerable communities.

Enhance supply chain diversity and improved resilience by supporting local food and energy production and increased multi-modal transportation.

Research, develop, promote, adopt, and enforce codes and standards to preserve life and property that are affordable and feasible to implement.

Promote and implement measures to mitigate the risk of wildfires, such as greenbelts and fire breaks around communities and along roadways.

Support the protection of vital records, and strengthen or replace buildings, infrastructure, and lifelines to minimize post-disaster disruption and facilitate short-term and long-term recovery.

Improve and expand systems that provide warning and emergency communications to the whole community.
28 Ventura County Multi-Jurisdictional Hazard Mitigation Plan Definition of Terms xxii
Continue developing and strengthening inter-jurisdictional coordination and cooperation in the area of emergency services.

Promote and implement the retrofit or replacement of at-risk structures and lifelines to increase community resilience.

Incentivize mitigation measures for high-risk and repetitive loss areas to address repairs, major alterations, development plans, and practices to increase community resilience.

Reduce repetitive property losses due to hazard impacts through acquisition, retrofitting, design, and updated construction and land use regulations.

Encourage and support leadership within the private sector, non-profit agencies, and community-based organizations to promote and implement local hazard mitigation activities.

Proactively manage and care for natural resources, including grasslands, forests, oak woodlands, riparian forests, stream channels, coastal wetlands, and beaches, to enhance their ability to withstand and recover from natural disasters and minimize public safety risks.

Support hazard mitigation measures that promote and enhance natural processes.

Support hazard mitigation measures, where feasible, that utilize nature-based practices and solutions (e.g., holistic watershed management and green belts) and support and enhance natural processes.

Encourage the creation of financial and regulatory incentives to motivate stakeholders such as homeowners, private sector businesses, and non-profit community organizations to mitigate hazards and risks.

Conduct public outreach activities that increase community awareness and understanding of hazard risk, mitigation options, and preparedness strategies.

Minimize impacts of hazard events on the economic drivers for the County.

Align the hazard mitigation plan with state mitigation plans; city and county general, community, capital improvement plans; special-purpose district plans; and climate action, resilience, and adaptation plans.

MITIGATION ACTION PLAN
The mitigation actions presented in this update are activities designed to reduce or eliminate losses resulting from natural hazards. The update process resulted in the identification of 300 mitigation actions for implementation by individual planning partners, as presented in Volume 2 of this plan. In addition, the Steering Committee and planning partners identified three countywide actions benefiting the whole partnership, as listed in Table ES-1.
29 Executive SummaryDefinition of Terms
xxiii
Table ES-1. Countywide Mitigation Initiatives
Action Number and Description
Priority for
Implementation
Priority for
Grant Pursuit
CW-1— Continue to maintain a website that will house the multi-jurisdictional hazard mitigation plan and any amendments to it adopted during the next 5-year period to provide the planning partners and the public with ongoing access to the plan and its implementation.

High Low
CW-2— Continue to leverage/support/enhance ongoing, regional public education and awareness programs, such as VCAlert, CERT (Community Emergency Response Team), DART (Disaster Assistance Response Team), TsunamiReady, and StormReady, as methods to educate the public on risk, risk reduction, and community resilience.

High Low
CW-3— Continue to provide a virtual hub for sharing information on hazard mitigation resources on the readyventuracounty.org website that will support mitigation efforts and awareness of grant funding opportunities to the planning partnership.

High Low

IMPLEMENTATION
The Steering Committee developed a plan implementation and maintenance strategy that includes monitoring of the plan’s implementation, progress reporting, a strategy for continued public involvement, and plan integration with other relevant plans and programs.

Full implementation of the recommendations of this plan will require time and resources. The measure of the plan’s success will be its ability to adapt to changing conditions. Ventura County and its planning partners will assume responsibility for adopting the recommendations of this plan and committing resources toward implementation. The framework established by this plan will enable all planning partners to pursue Hazard Mitigation Assistance grant funding for feasible, eligible and cost-effective actions. The planning partnership developed this plan with extensive public input, and public support of the actions identified in this plan will help ensure the plan’s success.

30 31

Ventura County Multi-Jurisdictional Hazard Mitigation Plan Part 1—BACKGROUND AND METHODS

32 33
1-1

1. INTRODUCTION

1.1 WHY PREPARE THIS PLAN?
Hazard mitigation is defined as any action taken to reduce or alleviate the loss of life, personal injury, and property damage that can result from a disaster. Hazard mitigation activities include planning efforts, policy changes, programs, studies, improvement projects, and other steps to reduce the impacts of hazards. These actions may be long- or short-term in nature, and are implemented before, as well as during and after disasters.

1.1.1 Federal Eligibility
Disaster Mitigation Act
The federal Disaster Mitigation Act (DMA) emphasizes planning for disasters before they occur. The DMA requires state and local governments to develop hazard mitigation plans in order to be eligible for certain hazard-related federal grant programs. The grant eligibility requires that the hazard mitigation plan be approved by the Federal Emergency Management Agency (FEMA), formally adopted by the local community, and regularly updated. Regulations developed to fulfill the DMA’s requirements are included in Title 44 of the Code of Federal Regulations (44 CFR).

The DMA encourages cooperation among state and local authorities in pre-disaster planning. The responsibility for hazard mitigation lies with not only with local, state, and federal governments, but also with private property owners and commercial and institutional interests. The enhanced planning network called for by the DMA helps local governments to articulate accurate needs for mitigation, resulting in faster allocation of funding and more cost-effective risk-reduction projects.

The DMA also promotes sustainability in hazard mitigation. To be sustainable, hazard mitigation needs to incorporate sound management of natural resources and address hazards and mitigation in the largest possible social and economic context.

Community Rating System
FEMA’s Community Rating System (CRS) is a voluntary incentive program that encourages community floodplain management activities that go beyond the minimum requirements of FEMA’s National Flood Insurance Program (NFIP). The CRS describes 18 activities that communities can take to reduce or eliminate exposure to floods. To implement these activities, FEMA published the 2013 NFIP CRS Coordinators Manual, which spells out the credit and credit criteria for CRS activities. Some of these activities can be implemented through the adoption of a qualifying hazard mitigation plan. 34 Ventura County Multi-Jurisdictional Hazard Mitigation Plan 1-2

1.1.2 Purposes for Planning
Ventura County prepared a hazard mitigation plan in compliance with the DMA in 2005 and has updated the plan every five years since then, most recently in 2015. The Ventura County Multi- Jurisdictional Hazard Mitigation Plan 2022 update fulfills the ongoing update requirement.

This update identifies resources, information, and strategies for reducing risk from natural hazards.

Elements and strategies in the plan were selected because they meet a program requirement and because they best meet the needs of the County and communities within it. The focus of this plan is on better decision-making to avoid future risk and on activities that will eliminate or reduce current risks.

In preparing this update, the County partnered with local cities and special-purpose districts. Such multi-jurisdictional planning benefits from pooled resources and the elimination of redundant activities.

FEMA encourages multi-jurisdictional planning under its guidance for the DMA. The plan will help guide and coordinate mitigation activities throughout the planning area.

The planning effort identified risks posed by hazards and developed strategies to reduce the impact of hazard events on people and property in Ventura County. The plan was developed to meet the following objectives:

Meet or exceed program requirements specified under the DMA.

Enable Ventura County to continue to qualify for federal grant funding to reduce risk through mitigation.

Create a risk assessment that focuses on Ventura County’s hazards of concern.

Coordinate existing plans and programs so that high-priority mitigation activities are funded and implemented.

Address the Activity 510 Floodplain Management Planning activities of the CRS for the three participating partners:

Ventura County Public Works Agency—Watershed Protection (VCPWA-WP) on behalf of Unincorporated Ventura County, which joined the CRS in 2011 (currently rated at CRS Class 5)
The City of Oxnard, which joined the CRS in 2013 (currently rated at CRS Class 7) The City of Simi Valley, which joined the CRS in 1993 (currently rated at CRS Class 5).

1.2 WHO WILL BENEFIT FROM THIS PLAN?
All residents, visitors, and businesses in Ventura County are the ultimate beneficiaries of this hazard mitigation plan update. The plan identifies strategies and actions to reduce risk for those who live in, work in, and visit the planning area. It provides a viable planning framework for all foreseeable natural hazards. Participation by key stakeholders in developing the plan helped ensure that outcomes will benefit the broadest possible range of communities in the county. The plan’s goals and recommendations can lay the groundwork for development and implementation of local mitigation activities and partnerships.
35 Introduction
1-3

1.3 CONTENTS OF THE PLAN
This plan has been organized into two volumes so that elements that are specific to the individual planning partners can easily be distinguished from those that apply to the whole planning area:

Volume 1—Volume 1 includes all federally required elements that apply to the entire planning area. This includes the description of the planning process, public involvement strategy, goals and objectives, countywide hazard risk assessment, countywide mitigation actions, and a plan maintenance strategy.

Volume 2—Volume 2 includes all federally required jurisdiction-specific elements, in annexes for each participating jurisdiction. It includes a description of the participation requirements confirmed by the core planning team and Steering Committee, as well as instructions and templates that the partners used to complete their individual annexes.

Both volumes include elements required under federal guidelines. The CRS floodplain management planning activities for the participating planning partners are identified in their individual annexes.

Where sections of this plan address specific DMA requirements, the CFR section number in which the requirement is found is cited.

The following appendices provided at the end of Volume 1 include information or explanations to support the main content of the plan:

Appendix A—Public involvement information used in preparation of this update Appendix B—A summary of federal and state programs and regulations relevant to hazard mitigation
Appendix C—A description of data sources and methods used for mapping hazard areas Appendix D—Quantitative risk assessment modeling results by jurisdiction Appendix E—Peak stream flow levels for waterways within Ventura County Appendix F—Plan adoption resolutions from planning partners Each planning partner will adopt Volume 1 in its entirety and at least the following parts of Volume 2:
the introduction, the partner’s jurisdiction-specific annex, and the appendices.

36 37
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2. PLAN UPDATE—WHAT HAS CHANGED?

2.1 PREVIOUS PLANS

2.1.1 2005 Ventura County Hazard Mitigation Plan
The 2005 hazard mitigation plan was prepared by Ventura County and other members of the Local Hazard Mitigation Group—consisting of members of the Inter-Agency Coordination Group, including fire chiefs/officials, emergency managers, safety coordinators, planners, and other officials and staff from 34 local participants including Ventura county, cities, and special districts). Technical support was provided by URS Corporation. The 2005 plan was developed between June 2004 to January 2005. It was adopted by the Ventura County Board of Supervisors on June 7, 2005.

2.1.2 2010 Ventura County Hazard Mitigation Plan
The 2010 Ventura County Hazard Mitigation Plan was a multi-jurisdictional plan covering Ventura County, the Cities of Camarillo, Moorpark, Ojai, Oxnard, Port Hueneme, Santa Paula, Thousand Oaks, and Ventura, eight special purpose districts, and the Ventura County Office of Education. The plan was adopted by the Ventura County Board of Supervisors in December 2010 and was approved by FEMA Region IX in February 2011. The planning process was overseen by a planning committee that was based on the standing Emergency Coordinators’ Council. The plan identified eight goals and identified and prioritized 102 actions to be implemented by the planning partners.

2.1.3 2015 Ventura County Multi-Hazard Mitigation Plan
The 2015 update of the Ventura County Multi-Hazard Mitigation Plan was a multi-jurisdictional plan that covered Ventura County, the Cities of Camarillo, Moorpark, Ojai, Oxnard, Port Hueneme, Santa Paula, Thousand Oaks, and Ventura, eight special purpose districts, and the Ventura County Office of Education. Like the 2010 and 2005 plans before it, the 2015 plan focused on the hazards considered to be the greatest risk to the county based on historical disaster events, future probabilities and degree of vulnerability—including wildfire, earthquake, flood, dam and levee failures, landslide, winter storms, tsunamis, and agriculture/biological events.

The 2015 update process was expanded to address the implications that climate change and drought may have on hazard trends in Ventura County. Additionally, the 2015 process was enhanced to meet FEMA’s Community Rating System Activity 510 planning requirements.

Based on its assessment of the identified hazards, the 2015 Plan recommended 22 mitigation actions for all partners that addressed the following 12 hazards of concern:
38 Ventura County Multi-Jurisdictional Hazard Mitigation Plan 2-2
Agricultural/biological
Climate change
Dam failure/inundation
Drought
Earthquake
Flood
Landslide
Levee failure inundation
Post-fire debris flow
Tsunami
Wildfire
Winter storm
The 18 planning partners identified and prioritized 95 actions to be implemented by individual partners.

The planning process was overseen by a planning committee that included staff from County departments and agencies, representatives for each participating city and special district, and other entities, including the California Governor’s Office of Emergency Services (Cal OES). The committee met two times during the plan update process. The plan was adopted by the Ventura County Board of Supervisors in May 2016 and was approved by FEMA Region IX in August 2016.

2.2 WHY UPDATE?

2.2.1 Federal Eligibility
Under 44 CFR, hazard mitigation plans must present a schedule for monitoring, evaluating, and updating the plan. This provides an opportunity to reevaluate recommendations, monitor the impacts of actions that have been accomplished, and determine if there is a need to change the focus of mitigation strategies. A jurisdiction covered by a plan that has expired is not able to pursue elements of federal funding for which a current hazard mitigation plan is a prerequisite.

2.2.2 Changes in Development
Hazard mitigation plan updates need to reflect any changes in development in the planning area that may have increased or decreased the vulnerability of a jurisdiction to hazards since the last plan was approved (44 CFR Section 201.6(d)(3)). The intent of this requirement is to ensure that the mitigation strategy addresses the risk and vulnerability of existing and potential development, as well as taking into consideration possible future conditions that could affect vulnerability.

The following are significant development and demographic changes in Ventura County since the 2015 hazard mitigation plan update:

As of January 1, 2021, the reported population for Ventura County was 835,459, representing a decrease of 1.7 percent from 2016 (California Department of Finance, 2021) The valuation of the general building stock increased by 21.5 percent (County of Ventura Assessor, 2021)
Based on development permit data provided by the municipal planning partners (see Volume 2), permits were issued for the construction of nearly 20,000 new structures over the past five years. This does not include accessory dwelling units, which are often classified as alterations 39 Plan Update—What has Changed?
2-1
to an existing property rather than new construction. More than 80 percent of this development occurred in the cities of Camarillo, Ojai and Thousand Oaks.

Although the population decreased slightly during the performance period of the 2015 plan, the county experienced an overall increase in general building stock (see Volume 2). This plan update assumes that some of this new development occurred in hazard-prone areas. Because all such new development would have been regulated pursuant to local programs and codes, it is assumed that vulnerability did not increase even if exposure did. Ventura County and its incorporated cities and towns have general plans that govern land-use decisions and policymaking, as well as building codes and flood-management regulations based on state and federal mandates. More detailed information on the types and location of new construction over the last five years is available in the city and County annexes located in Volume 2 of this plan.

2.3 THE UPDATED PLAN—WHAT IS DIFFERENT?
The updated plan differs from the 2015 plan in a variety of ways. Table 2-1 indicates the major changes between the two plans as they relate to 44 CFR requirements for hazard mitigation plans.

Table 2-1. Key Changes from Previous Hazard Mitigation Plan 44 CFR Requirement 2015 Plan Updated Plan
Requirement §201.6(b): In order to
develop a more comprehensive approach
to reducing the effects of natural disasters,
the planning process shall include:

An opportunity for the public to
comment on the plan during the
drafting stage and prior to plan
approval;
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
Review and incorporation, if
appropriate, of existing plans,
studies, reports and technical
information.

The 2015 plan included all of these
components as summarized in Section
3 of the plan. This planning effort
included enhanced coordination with
floodplain management agencies to
meet CRS requirements. The process
was overseen by a designated
planning committee and facilitated
through an oversight hazard mitigation
planning committee. The process
included a public outreach and
stakeholder involvement strategy that
included:

Multi-media releases
Website
Web portal
Engagement with the Emergency
Planning Council
Town hall
Virtual town hall
Brochure
This plan update utilized many of the same mitigation
planning best-management practices but enhanced
them on multiple fronts. The update process was
facilitated by a planning team consisting of key
County staff and a contract consultant, working with
a multidiscipline stakeholder steering committee that
met more frequently than the committee established
for the 2015 effort. The steering committee confirmed
a public engagement strategy that included:

Plan website
Story map
Survey
Public meetings
Social media
Media outreach
This plan update also included enhanced efforts to
coordinate with other agencies and community
stakeholders that could support or enhance the
outcomes of the update effort.
40 Ventura County Multi-Jurisdictional Hazard Mitigation Plan 2-2
44 CFR Requirement 2015 Plan Updated Plan
§201.6(c)(2): The plan shall include a risk
assessment that provides the factualbasis
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.

The 2015 plan included a risk
assessment of 12 hazards of concern:

Agricultural/biological
Climate change
Dam failure inundation
Drought
Earthquake
Flood
Landslide
Levee failure inundation
Post-fire debris flow
Tsunami
Wildfire
Winter storm
Each hazard was profiled with
discussions on nature, history,
location, extent, and probability of
future events. However, the 2015 plan
did not rank the hazards.

Volume 1 Part 2 presents a risk assessment of 10
hazards of concern and risk profiles for two “other
hazards of interest” (agricultural/biological and
pandemic). The identified hazards of concern are as
follows:

Dam failure
Drought
Earthquake
Flood
Landslide
Sea-level rise and coastal erosion
Severe storms
Severe weather
Tsunami
Wildfire
Hazard profiles are standardized for each hazard of
concern, so that there is uniformity in the discussion
of each hazard and the information provided can
support rating of risk for each jurisdiction. All profiled hazards of concern were ranked based on their
quantified impacts.

The “other hazards of interest” profile was added to
address agricultural/biological and pandemic
hazards. These hazards were not ranked, but were
qualitatively assessed to develop a more complete
picture of the hazards facing the planning area.

A climate change chapter was included that
qualitatively profiles the potential impacts of climate change on each hazard of concern.
§201.6(c)(2)(i): [The risk assessment shall
include a] description of the … location
and extent of all natural hazards that can
affect the jurisdiction. The plan shall
include information on previous
occurrences of hazard events and on the
probability of future hazard events.

Each hazard of concern was profiled
with discussions of nature, history,
location, extent and probability of
future events.

Each hazard of concern was profiled in the following
categories:

General Background
Hazard Profile
o Past events
o Location
o Frequency
o Severity
o Warning Time
o Secondary Hazards
Exposure
Vulnerability
Future trends in development
Scenario
Issues
41 Plan Update—What has Changed?
2-3
44 CFR Requirement 2015 Plan Updated Plan
§201.6(c)(2)(ii): [The risk assessment shall
include a] description of the jurisdiction’s
vulnerability to the hazards described in
paragraph (c)(2)(i). This description shall
include an overall summary of each
hazard and its impact on the community
The vulnerability analysis in the 2015
plan is based solely on exposure and
does not estimate loss. The plan does
include an overall summary of each
hazard’s impact based on exposure
but does not determine the value of
that exposure.

For this plan update, this aspect of the plan was
significantly enhanced. Vulnerability was assessed
for all hazards of concern. FEMA’s Hazus risk
assessment platform was used for evaluating dam
failure, earthquake, flood, sea-level rise and tsunami
hazards. The analyses supplemented the data built
into the Hazus program with locally defined city and
county data (Hazus refers to this as a Level 2
analysis). Site-specific data on County-identified
critical facilities were entered into the Hazus model.

Hazus outputs were generated for other hazards by
applying an estimated damage function to an asset
inventory extracted from Hazus. The risk assessment
methodology used is described in Chapter 7 of this
volume.
§201.6(c)(2)(ii): [The risk assessment]
must also address National Flood
Insurance Program insured structures that
have been repetitively damaged floods
Section 5.5 of the plan was dedicated
to FEMA-identified repetitive loss
properties
Section 11.2.7 of Volume 1 of this plan includes a
comprehensive analysis of repetitive loss areas that
includes an inventory of the number and types of
structures in the repetitive loss area. Repetitive loss areas are delineated, causes of repetitive flooding
are cited, and these areas are reflected on maps.

This analysis includes all repetitive loss properties
within the county.
§201.6(c)(2)(ii)(A): The plan should
describe vulnerability in terms of the types
and numbers of existing and future
buildings, infrastructure and critical
facilities located in the identified hazard
area.

The focus of the vulnerability analysis
for the 2015 plan was exposure of
residential structures and identified
critical facilities and infrastructure. The
analysis includes no loss estimation.

The current update used Hazus to model impacts
from dam failure, earthquake, flood, sea-level rise,
and tsunami. A complete inventory of the numbers
and types of buildings exposed (both residential and
non-residential) was generated for each hazard of
concern. Critical facilities were defined for the
planning area, and these facilities were inventoried
by exposure. Each hazard chapter provides a
discussion on future development trends.
§201.6(c)(2)(ii)(B): [The plan should
describe vulnerability in terms of an]
estimate of the potential dollar losses to
vulnerable structures identified in
paragraph (c)(2)(i)(A) and a description of
the methodology used to prepare the
estimate.

The 2015 vulnerability analysis
includes no loss estimation.

Dollar loss estimates were generated for all hazards
of concern. These estimates were generated by
Hazus for dam failure, earthquake, flood, and
tsunami. For the other hazards, loss estimates were
generated by applying a regionally relevant damage
function to the exposed inventory. In all cases, a
damage function was applied to an asset inventory.

The asset inventory was the same for all hazards
and was generated in Hazus.
§201.6(c)(2)(ii)(C): [The plan should
describe vulnerability in terms of] providing
a general description of land uses and
development trends within the community
so that mitigation options can be
considered in future land use decisions.

The 2015 Plan does not describe
vulnerability in terms of land uses and
development trends within the
community so that mitigation options
can be considered in future land use
decisions.

There is a discussion of the overall land use within
the planning area, and a spatial analysis of land use
was performed for hazards with a clearly defined
extent and location. There is a discussion on future
development trends as they pertain to each hazard
of concern. This discussion looks predominantly at
the existing land use and the current regulatory
environment.
42 Ventura County Multi-Jurisdictional Hazard Mitigation Plan 2-4
44 CFR Requirement 2015 Plan Updated Plan
§201.6(c)(3): The plan shall include a
mitigation strategy that provides the
jurisdiction’s blueprint for reducing the
potential losses identified in the risk
assessment, based on existing authorities,
policies, programs and resources, and its
ability to expand on and improve these
existing tools.

The 2015 plan includes two identified
goals, overarching potential mitigation
actions for all local participants, and
jurisdiction-specific actions for each
planning partner.

The plan contains a vision statement, goals,
objectives, and actions. The actions are jurisdiction-
specific and strive to meet multiple objectives. The
objectives are broad but measurable. All objectives
meet multiple goals and stand alone as components
of the plan. Each planning partner was asked to
complete a capability assessment that looks at its
regulatory, technical, and financial capabilities
§201.6(c)(3)(i): [The hazard mitigation
strategy shall include a] description of
mitigation goals to reduce or avoid long-
term vulnerabilities to the identified
hazards.

The 2015 plan identified two goals. A vision statement, 10 goals, and 19 objectives are described in Chapter 21 of this volume. Objectives
were identified that meet multiple goals and were
used to help establish priorities for the action items
identified in the plan. The objectives are the basis for identifying and prioritizing multi-objective actions.
§201.6(c)(3)(ii): [The mitigation strategy
shall include a] section that identifies and
analyzes a comprehensive range of
specific mitigation actions and projects
being considered to reduce the effects of
each hazard, with particular emphasis on
new and existing buildings and
infrastructure.

The 2015 plan prescribes a
methodology for identifying potential
actions from which each planning
partner would draw to prepare an
action plan. For each potential action,
the methodology identifies the hazard
addressed, the mitigation category,
and whether action applies to new or
existing construction.

Volume 1, Chapter 22 includes a catalog of
mitigation best management practices that was
developed through a facilitated process. This catalog
identifies actions that manipulate the hazard, reduce
exposure to the hazard, reduce vulnerability, or
increase mitigation capability. The catalog
segregates actions by scale of implementation. A
table in each planning partner’s action plan analyzes
each action by mitigation type to illustrate the range
of actions selected.
§201.6(c)(3)(ii): [The mitigation strategy]
must also address the jurisdiction’s
participation in the National Flood
Insurance Program, and continued
compliance with the program’s
requirements, as appropriate.

The 2015 Plan addresses the NFIP in
the context of the mapping available
within the planning area. The
addresses the NFIP as a financial
resource available to mitigate the
impacts of the flood hazard, and it
profiles the unincorporated County’s
participation in the NFIP.

The plan addresses the NFIP and the participation
status of all cities within the county. Each municipal
planning partner’s annex in volume 2 of the plan
profiles its NFIP status. All municipal planning
partners that participate in the NFIP identified an
action stating their commitment to maintain
compliance and good standing under the program.
§201.6(c)(3)(iii): [The mitigation strategy
shall describe] how the actions identified
in section (c)(3)(ii) will be prioritized,
implemented and administered by the
local jurisdiction. Prioritization shall include
a special emphasis on the extent to which
benefits are maximized according to a cost
benefit review of the proposed projects
and their associated costs.

The 2015 plan establishes priority
project criteria centered on meeting
FEMA’s Hazard Mitigation Assistance
program requirements. All actions
identified in the 2015 plan are
considered to be “high priority” projects
based on these criteria.

Each recommended action was prioritized using a
qualitative methodology that looked at the objectives
the project will meet, the timeline for completion, how the project will be funded, the impact of the project,
the benefits of the project and the costs of the
project. This prioritization scheme is detailed in the
introduction to Volume 2 of this plan.
§201.6(c)(4)(i): [The plan maintenance
process shall include a] section describing
the method and schedule of monitoring,
evaluating, and updating the mitigation
plan within a five-year cycle.

Section 8 of the 2015 plan includes a
plan maintenance methodology that
meets this requirement
Volume 1, Chapter 24 details a strategy for
monitoring, evaluating, and updating the mitigation
plan within a five-year cycle.
43 Plan Update—What has Changed?
2-5
44 CFR Requirement 2015 Plan Updated Plan
§201.6(c)(4)(ii): [The plan shall include a]
process by which local governments
incorporate the requirements of the
mitigation plan into other planning
mechanisms such as comprehensive or
capital improvement plans, when
appropriate.

Section 8.3 of the 2015 plan includes a
plan maintenance methodology that
meets this requirement
Volume 1, Chapter 24 details recommendations for
incorporating the plan into other planning
mechanisms, such as:

Comprehensive plan
Emergency response plan
Capital improvement programs
Municipal code and standards
Specific current and future plan and program
integration activities are detailed in each participating jurisdiction’s annex in Volume 2.
§201.6(c)(4)(iii): [The plan maintenance
process shall include a] discussion on how
the community will continue public
participation in the plan maintenance
process.

Section 8.4of the 2015 plan includes a
plan maintenance methodology that
meets this requirement.

Volume 1, Chapter 24 details a comprehensive
strategy for continuing public involvement.
§201.6(c)(5): [The local hazard mitigation
plan shall include] documentation that the
plan has been formally adopted by the
governing body of the jurisdiction
requesting approval of the plan (e.g., City
Council, County Commissioner, Tribal
Council).

Adoption documentation and the
FEMA approval letter are provided in
the plan as an appendix.

Volume 1, Appendix F includes all supporting
documentation for adoption of the plan by all
planning partners
44 45
3-1

3. PLAN DEVELOPMENT METHODOLOGY

3.1 FUNDING
Funding for this planning effort was supplemented by a FEMA Hazard Mitigation Assistance grant (DR-4344-341-P). Ventura County Sheriff’s Office of Emergency Services (OES) was the applicant agent for the grant. The grant covered 75 percent of the cost for development of this plan; the County covered the balance through in-kind match funding.

3.2 FORMATION OF THE CORE PLANNING TEAM
The County of Ventura contracted with Tetra Tech, Inc. to assist with development and implementation of the plan (the procurement process complied with 2 CFR A.II.200). The Tetra Tech project manager managed the overall plan development; Tetra Tech’s lead planner was tasked with interacting with the County of Ventura’s grant manager. A core planning team was formed to lead the planning effort, made up of the members shown in Table 3-1.

The core planning team met 14 times during the update process to track plan development milestones and identify meeting content for a steering committee established to help with development of the plan.

Table 3-1. Core Planning Team Makeup
Ventura County
Bonnie Luke, OES, Senior Program Administrator/Grant Manager Ruth Venus, IT Services, GIS Manager Kathy Gibson, OES, Program Administrator Eric Alger, IT Services, GIS Program Analyst Patrick Maynard, OES, Director Richard Paschal, IT Services, GIS Program Analyst Glenn Shephard, VCPWA-WP, Director Ashley Bautista, CEO, Public Information Officer Gerard Kapuscik, VCPWA-WP, Staff Services Manager Jackie Nuñez, CEO, Assistant Public Information Officer Tetra Tech
Rob Flaner, Project Manager Jeana Wiser-Gomez, Public Outreach Lead Cindy Rolli, Lead Project Planner Des Alexander, Planner Carol Baumann, Lead Risk Assessor Megan Brotherton, Planner

3.3 ESTABLISHMENT OF THE PLANNING PARTNERSHIP
In June 2021, a planning partnership was formed to leverage resources and to meet requirements of the federal Disaster Mitigation Act for as many eligible local governments as possible. Ventura County opened this planning effort to all eligible local government and special districts within the planning area. 46 Ventura County Multi-Jurisdictional Hazard Mitigation Plan 3-2
The new partnership expanded the partnership that had been established for the 2010 and 2015 hazard mitigation plan updates.

Each jurisdiction wishing to join the planning partnership was asked to provide a letter of intent to participate that designated a point of contact for the jurisdiction and confirmed the jurisdiction’s commitment to the process and understanding of expectations. The planning partners covered under this plan are listed in Table 3-2.

Table 3-2. Hazard Mitigation Planning Partners
Jurisdiction Point of Contact Title
Cities/County
City of Camarillo Carmen Nichols Assistant City Manager City of Fillmore Keith Gurrola Fire Chief
City of Moorpark Mackenzie Douglass Program Manager
City of Ojai James Vega City Manager
City of Oxnard Scott Brewer Emergency Manger
City of Port Hueneme Scott Matalon Emergency Manager (Police) City of San Buenaventura (Ventura)a Daniel Wall Emergency Manager City of Santa Paula Scott Varner Emergency Manager
City of Simi Valleyb Eileen Connors Emergency Manager
City of Thousand Oaks Grahame Watts Emergency Manager
Ventura County Bonnie Luke Senior Program Administrator Special Purpose Districts
California State University, Channel Islandsb Maggie Tougas Emergency Manager Calleguas Municipal Water District Daniel Cohen Emergency Response Coordinator Casitas Municipal Water District Julia Aranda Engineering Manager Channel Islands Beach Community Services District Peter Martinez General Manager Conejo Recreation & Park Districtb Bill Palermo Park Operations Analyst Ojai Valley Sanitary District Jeff Palmer General Manager Pleasant Valley Recreation & Park Districtb Mary Otten General Manager Saticoy Sanitary Districtb Tim Doyle Engineering Analyst Triunfo Water & Sanitation Districtb Tim Doyle Engineering Program Manager United Water Conservation District Brian Collins Chief Operations Officer Ventura County Fire Protection District Mark Lorenzen Fire Chief Ventura County Office of Education Russ Olsen Director of Risk Management Ventura County Public Works Agency—Watershed Protection Glenn Shephard Director Ventura Regional Sanitation Districtb Tina Rivera Director of Finance a. San Buenaventura is the official name of the city commonly called the City of Ventura. b. New planning partner

3.4 DEFINING THE PLANNING AREA
The planning area was defined to consist of the unincorporated county areas, incorporated cities, and special purpose districts within the geographical boundary of Ventura County. All partners to this plan have jurisdictional authority within this planning area. A map showing the geographic boundary of the defined planning area for this plan update is provided in Chapter 4, along with a description of the planning area characteristics.
47 Plan Development Methodology
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3.5 THE STEERING COMMITTEE
Hazard mitigation planning enhances collaboration among diverse parties who can be affected by hazard losses. A key element of the public engagement strategy for this plan update was the formation of a stakeholder steering committee to oversee all phases of the update. The members of this committee included Ventura County staff, planning partner representatives, and other stakeholders from within the planning area.

For this process, “stakeholder” was defined as any person or public or private entity that owns or operates facilities that would benefit from the mitigation actions of this plan, and/or has an authority or capability to support mitigation actions identified by this plan or be impacted by its recommendations.

Stakeholders were separated into two categories:

Participatory Stakeholders—Stakeholders that actively participated in the planning process as planning partners or members of the Steering Committee.

Coordinating Stakeholders—Stakeholders that were not able to commit to actively participating in the process as a participatory stakeholder but were kept apprised of plan development milestones or were able to provide data that was used in the plan development.

The planning team assembled a list of steering committee candidates representing diverse interests within the planning area. Guidance on the committee’s composition was also obtained from reviewing FEMA’s 2017 recommendations on CRS credit for planning committees. The planning team confirmed a committee of 17 members at the May 19, 2021, kickoff meeting. Table 3-3 lists the Steering Committee members and designated alternates.

Table 3-3. Steering Committee Members
Point of Contact Organization Title Alternate
Ashley Bautista Ventura County Chief Executive Office Public Information Officer Jackie Nuñez Daniel Cohen Calleguas Municipal Water District Emergency Response Coordinator Doug GrahamAmerican Red Cross of Ventura County Volunteer Lead Scott O’Connell Louise LamparaVentura County Coalition of Labor, Agriculture, & Business Executive Director Alyssa Mann The Nature Conservancy Project Director, Disaster Resilience Kat Selm Brian McCarthyCity of Fillmore Senior Planner
Russ Olsen Ventura County Office of Education Director of Risk Management Michelle Kelly Chris Rosa Ventura County Emergency Medical ServicesDeputy Administrator Janelle Hahn Jeff Shea Ventura County Fire Protection District Division Chief Mark Lorenzen Glenn Shephard Ventura County Public Works Agency—Watershed Protection
Director Gerard Kapuscik
John Tolson Simi Valley Chamber of Commerce Director of Membership & Marketing Maggie Tougas California State University Channel Islands Emergency Manager Ventura County Voluntary Organizations Active in DisasterChair Julie Tumamait-
Stenslie
The Barbareño/Ventureño Band of Mission Indians Tribal Chair Frank Arrendondo Lauren UtterbackIndependent Living Resource Center Emergency Preparedness Services Manager
Jamie
Zimmerman
Dave Ward Ventura County Planning Division Planning Director Aaron Engstrom Grahame WattsCity of Thousand Oaks Public Works Emergency Manager Matt Wyatt Ventura County Building and Safety District Manager West County Office Dave Hansen 48 Ventura County Multi-Jurisdictional Hazard Mitigation Plan 3-4
Leadership roles and ground rules were established during the Steering Committee’s initial meeting on May 19, 2021. The Steering Committee then met every one to two months as needed throughout the course of the plan’s development. The core planning team facilitated each Steering Committee meeting, which addressed a set of objectives based on an established work plan. The Steering Committee met six times from May 2021 through February 2022. Agendas were posted to the website prior to each scheduled Steering Committee meeting, and meeting summaries were posted to the hazard mitigation plan website following their approval by the Steering Committee.

3.6 COORDINATION WITH STAKEHOLDERS AND AGENCIES
Opportunities for involvement in the planning process must be provided to neighboring communities, local and regional agencies involved in hazard mitigation, agencies with authority to regulate development, businesses, academia, and other private and nonprofit interests (44 CFR, Section 201.6(b)(2)). The planning team met this requirement as described below.

3.6.1 Notifications About Plan Development Milestones
The following agencies, organizations and entities were invited to participate in the plan development process, including all steering committee meetings, and were kept apprised of plan development milestones:

Aera Energy
American Red Cross of Ventura County
Amgen
Barbareño/Ventureño Band of Mission
Indians
California State University Channel Islands
Calleguas Municipal Water District
Camrosa Water District
Casitas Municipal Water District
Channel Islands Beach Community
Services District
City of Camarillo
City of Fillmore
City of Moorpark
City of Ojai
City of Oxnard
City of Port Hueneme
City of Santa Paula
City of Simi Valley
City of Thousand Oaks
City of Ventura
Conejo Recreation & Park District
Independent Living Resource Center
MICOP (Mixteco/Indigena Community
Organizing Project)
Ojai Valley Sanitary District
Oxnard Chamber of Commerce
Pleasant Valley Recreation and Park
District
Saticoy Sanitary District
Simi Valley Chamber of Commerce
Strickland Mutual Water Company
The Nature Conservancy
Triunfo Water & Sanitation District
United Water Conservation District
Ventura Chamber of Commerce
49 Plan Development Methodology
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Ventura County ACS/ARES
Ventura County Building and Safety
Ventura County Chief Executive Office
Ventura County Coalition of Labor,
Agriculture, and Business
Ventura County Emergency Medical
Services
Ventura County Fire Protection District
Ventura County Health Services Agency
Ventura County Office of Education
Ventura County Planning Division
Ventura County Public Works Agency—
Watershed Protection
Ventura County Sheriff’s OES
Ventura County Voluntary Organizations
Active in Disaster
Ventura Regional Fire Safe Council
Ventura Regional Sanitation District

These entities received meeting announcements, meeting agendas, and meeting minutes by e-mail throughout the plan development process. Some of them supported the effort by attending meetings or providing feedback on issues.

3.6.2 Pre-Adoption Review
All the entities listed above were provided an opportunity to review and comment on this plan during the public comment period, primarily through the hazard mitigation plan website (see Section 3.8.1). All were sent an e-mail message informing them that draft portions of the plan were available for review.

Upon completion of a public comment period, the complete draft plan was sent to the California Governor’s Office of Emergency Services (Cal OES) and FEMA for a pre-adoption review to ensure program compliance.

3.7 REVIEW OF EXISTING PROGRAMS
Hazard mitigation planning must include review and incorporation, as appropriate, of existing plans, studies, reports and technical information (44 CFR, Section 201.6(b)(3)). Chapter 6 of this plan provides a review of laws and ordinances in effect within the planning area that can affect hazard mitigation actions. In addition, the following programs can affect mitigation within the planning area:

California Fire Code
2019 California Building Code
California State Hazard Mitigation Forum
Local capital improvement programs
Local emergency operations plans
Local general plans
Housing elements
Safety elements
Local zoning ordinances
Local coastal program policies
50 Ventura County Multi-Jurisdictional Hazard Mitigation Plan 3-6
Assessments of all planning partners’ regulatory, technical, and financial capabilities to implement hazard mitigation actions are presented in the individual jurisdiction-specific annexes in Volume 2.

Many of these relevant plans, studies and regulations are cited in the capability assessments.

3.8 PUBLIC PARTICIPATION
Broad public participation in the planning process helps ensure that diverse points of view about the planning area’s needs are considered and addressed. The public must have opportunities to comment on disaster mitigation plans during the drafting stages and prior to plan approval (44 CFR, Section 201.6(b)(1)). The Community Rating System (CRS) expands on these requirements by making CRS credits available for optional public involvement activities. The public outreach process for this plan update consisted of a combination of general outreach and information provided during partner meetings and events.

3.8.1 Strategy
As a result of the ongoing COVID-19 pandemic, in-person events were not able to be held during the course of this plan update. Therefore, the strategy for involving the public in this plan update emphasized the following elements:

Identify and involve planning area stakeholders.

Open Steering Committee meetings to members of the public for ongoing input.

Use a survey to evaluate the public’s perception of risk.

Invite public participation and engagement at virtual meetings, including a call-in option for community members to provide input by phone.

Attempt to reach as many planning area residents as possible using multiple media sources, including print, website, and social media.

Publish agendas and minutes for Steering Committee meetings on the website.

In order to engage the broadest segment of the population, all social media posts were posted in both English and Spanish. Additionally, translation into Spanish, Mixteco and American Sign Language was provided during all virtual meetings. Translation services were advertised in meeting announcements and at the beginning of each meeting. Non-English-speaking participants could take advantage of this service by joining a break-out room of the virtual meeting. Recordings of public meetings were posted on the hazard mitigation website.

Stakeholders and the Steering Committee
The inclusion of stakeholders on the Steering Committee (see Section 3.5) served as a significant component of public involvement activities. Stakeholders targeted for this process included the following:

Ventura County and local jurisdiction departments relevant for hazard mitigation planning Members of the academic community
Community member representatives
51 Plan Development Methodology
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Representatives of humanitarian aid and access and functional needs (AFN) support services Tribal representatives
Local special-purpose districts
Local businesses and business interests
Local environmental organizations
Internet
At the beginning of the plan update process in May 2021, the County established a hazard mitigation website (https://www.readyventuracounty.org/local-multijurisdictional-hazards-mitigation-plan-update/) to provide information about the process (see Figure 3-1). The website was used to keep the public informed about milestones and public participation opportunities and to solicit input.

Figure 3-1. Example Page of the Hazard Mitigation Plan Web Site The site’s address was publicized in all press releases, mailings, surveys, and public meetings.

Information on the plan development process, the Steering Committee, the community awareness survey, and drafts of the plan were made available to the public on the site throughout the process. 52 Ventura County Multi-Jurisdictional Hazard Mitigation Plan 3-8
Ventura County intends to keep a website active after the plan is complete to keep the public informed about successful mitigation projects and future plan updates.

Hazard Mitigation Survey
The planning team developed a 27-question community awareness survey with guidance from the Steering Committee (see Figure 3-2). The survey was used to gauge household and individual awareness of natural hazards and community members’ level of knowledge about tools and techniques to assist them in reducing risk and loss from natural hazards.

Figure 3-2. Sample Page from Survey Distributed to the Public The survey was made available on the hazard mitigation plan website in both Spanish and English and was advertised throughout the course of the planning process (June 2021 to September 2021).

Information on the survey was disseminated via an initial press release, the hazard mitigation plan website, social media (Facebook and Twitter), presentations during five publicly held Community Emergency Preparedness Workshops, and emails to emergency management stakeholders and interested parties. Interim results collected through September helped guide the Steering Committee and planning partners in affirming goals and objectives and in developing mitigation strategies. The survey remained active until the end of December 2021 for continued public input.

Story Map
An online “Story Map” was created (using Esri StoryMap software) to communicate the variety and severity of hazards facing Ventura County (see Figure 3-3). During the update process, the Story Map was released to the public and promoted through print and social media, the project website, and during public meetings. It includes risk assessment results for all relevant hazards, an interactive hazard mapping tool, and a report function to produce comprehensive hazard exposure summaries for any given property, block, or defined area. The Story Map expanded the ways in which members of the public could interact with hazard data as the hazard mitigation plan update was underway. 53 Plan Development Methodology
3-9
Figure 3-3. Example Story Map Data Page
After completion of the hazard mitigation plan update, the Ventura County Story Map will continue to support visual and data-based communication about the range of hazards relevant in Ventura County.

New and revised data can be loaded into the platform in the future to compare hazard risk with any other spatial data set.

Public Meetings
Five virtual public meetings—Community Emergency Preparedness Workshops on September 15, 16, 22, and 23 and October 11, 2021—described the hazard mitigation plan update process and provided information on the Story Map and community survey. Guest panelists from different cities were featured at each workshop to speak about local emergency preparedness efforts and current plan updates. The meetings described how participants could learn about hazard mitigation, follow the progress of the plan update, and participate in the plan update process. Each meeting featured a question-and-answer component and was presented in English, Spanish, Mixteco, and American Sign Language. Recordings of each meeting were posted on the website. Figure 3-4 shows an example screen shot from one of these meetings.

Additionally, the Emergency Planning Council meeting held on November 18, 2021 included an update on the status of the hazard mitigation plan update process.

Social Media
The Ventura County Sheriff’s OES social media accounts (Twitter, Facebook, Nixle, and Nextdoor) were used to share information about the hazard mitigation planning process, including the community awareness survey, Community Emergency Preparedness Workshops, and the public comment period. 54 Ventura County Multi-Jurisdictional Hazard Mitigation Plan 3-10
Figure 3-4. Screenshot from September 16, 2021 Community Emergency Preparedness Workshop Print and Other Media Outreach
Press releases were distributed over the course of the plan’s development as key milestones were achieved and before each public meeting. Each press release was supplemented by meeting announcements on the project website. The planning effort received widespread press coverage, including the following:

Announcements of hazard mitigation plan update process and requests for community input:

June 24, 2021—Nixle
June 24, 2021—Citizens Journal
June 2021—City of Thousand Oaks Sustainability Blog
July 1, 2021—City of Thousand Oaks City Scene
July 6, 2021—Ojai Valley News
July 7, 2021—VC Reporter
July 14, 2021—Ojai Valley News
July 19, 2021—The Fillmore Gazette
July 21, 2021—Simi Valley Police Department
July 21, 2021—VC Reporter
July 21, 2021—Simi Valley News
September 2, 2021—City of Moorpark
July 21, 2021—Citizens Journal
July 29, 2021—Simi Valley News announcement of the plan update and community survey 55 Plan Development Methodology
3-11
Announcements of the five virtual Community Emergency Preparedness Workshops that included presentations on the plan update process:

September 8, 2021—Nixle
September 8, 2021—Citizens Journal
September 8, 2021—VC Reporter
September 15, 2021—VC Reporter
HMP Update public service announcement (PSA) video release September 2021—A public service announcement was created to support and inform the public about the hazard mitigation plan update and process. The video is posted on the County’s hazard mitigation website at Hazard Mitigation Plan – Ready Ventura County.

Public Comment
The public outreach process for this plan update consisted of a combination of general outreach and information provided during partner meetings and events. Five virtual public meetings—on September 15, 16, 22, and 23 and October 11, 2021—described the hazard mitigation plan update process and provided information on the Story Map and community survey. The draft plan was made available to the public for comment during a noticed, three-week period in March 2022. The public comment period gave the public an opportunity to comment on the draft plan update prior to its submittal to Cal OES and FEMA. The principle avenue for public comment on the draft plan was the website established for this plan update.

3.8.2 Public Participation Results
Survey Results
From June through December 2021, more than 800 surveys were completed, covering all geographic areas of the County. The survey and detailed results are included in Appendix A; a summary is as follows:
832 surveys were completed.

Surveys were received from all 10 incorporated cities as well as the unincorporated areas of the County.

Respondents ranked wildfire as the hazard of greatest concern, followed by drought, earthquake, severe weather (wind, heat, cold), agricultural/biological hazards, severe storms, sea-level rise and coastal erosion, flood, landslide, tsunami, and dam failure. 84 percent of respondents have experienced or been affected by a wildfire.

Nearly half of the respondents felt that their household was not prepared or only somewhat prepared to deal with a hazard event.

Most respondents (nearly 76 percent) felt that personal experience with one or more natural hazards or disasters provided useful hazard and disaster preparedness to the public, followed by emergency preparedness information from government sources (federal, state, or local) (59 percent).

The concept of incentives to promote hazard mitigation actions on a personal scale was strongly supported, with 67 percent of the respondents supporting a property tax break or incentive and 56 Ventura County Multi-Jurisdictional Hazard Mitigation Plan 3-12
63 percent supporting an insurance premium discount to encourage them to spend money to retrofit their homes.

Survey results were provided to the Steering Committee for use in confirming goals, objectives and county-wide actions for this plan update. Additionally, the survey results were included in the toolkit provided to each planning partner through the jurisdictional annex process described in Volume 2. Each planning partner was able to use the survey results to:

Gauge the public’s perception of risk and identify what citizens are concerned about.

Identify the best ways to communicate with the public.

Determine the level of public support for different mitigation strategies.

Understand the public’s willingness to invest in hazard mitigation.

Meeting Attendance and Participation
Table 3-4 summarizes the attendance at the public meetings. As a result of the COVID-19 pandemic, all meetings were held virtually.

Table 3-4. Summary of Public Meetings
Date Type of Meeting
Number in
Attendance
May 19, 2021 Steering Committee Meeting #1 29
June 9, 2021 Steering Committee Meeting #2 27
July 14, 2021 Steering Committee Meeting #3 24
September 8, 2021 Steering Committee Meeting #4 16
September 15, 2021 Community Emergency Preparedness Workshop 106 September 16, 2021 Community Emergency Preparedness Workshop 90 September 22, 2021 Community Emergency Preparedness Workshop 83 September 23, 2021 Community Emergency Preparedness Workshop 55 October 11, 2021 Community Emergency Preparedness Workshop 30 November 10, 2021 Steering Committee Meeting #5 22
November 18, 2021 Ventura County Emergency Planning Council January 27, 2022 Presentation at the Santa Clara River Watershed Committee’s community organization meeting Unknown February 9, 2022 Steering Committee Meeting #6 20
Total

3.9 PLAN DEVELOPMENT CHRONOLOGY/MILESTONES
Table 3-5 summarizes important milestones in the development of the plan update. 57 Plan Development Methodology
3-13
Table 3-5. Plan Development Milestones
Date Event Description Attendance
2021
1/21 Support Contractor Secured County selects Tetra Tech to facilitate plan update process N/A Feb/
March
COVID-19 COVID- 19 pandemic caused delays in onboarding of project lead and initiation of update process
4/7 Organize Resources Core planning team formed N/A
4/8 Core Planning Team Meeting #1 Core planning team kickoff Planning process overview and schedule
Steering Committee function defined
Planning partner discussion
Data acquisition
Public outreach strategy
Meeting coordination
11 4/13 Core Planning Team Meeting #2 Review of 2015 hazards of concern Steering Committee
Schedule kickoff meeting
11 4/27 Core Planning Team Meeting #3 Steering Committee Hazards of concern
Planning partner kickoff meeting
Public outreach
11 5/5 Project Kickoff Meeting Review work plan
Discuss planning partner expectations
Obtain input on Steering Committee
Risk assessment data needs
Discuss public involvement strategy
34 5/6 Jurisdictional Annex Process
Phase 1
Planning partners begin the jurisdiction annex update process with the team, profile, trends, and previous plan status updates.

N/A
5/11 Core Planning Team Meeting #4 Hazard scenarios
Public outreach
Steering Committee confirmation
Planning partner kickoff meeting review
12 5/13 Public Outreach ReadyVentura County website adapted and expanded for information on 2022 plan update process
N/A
5/19 Steering Committee Meeting #1 Project overview
Role of the Steering Committee
Discuss public outreach strategy
Review of 2015 hazard mitigation plan
29 5/25 Core Planning Team Meeting #5 Hazard scenarios confirmed Draft mission, goals, and objectives
Public outreach—community preparedness survey
14 6/02 Public Outreach Hazard mitigation community awareness survey deployed and kept open through December 31, 2021. https://www.surveymonkey.com/r/G7T7W5R (Survey closed after December 31, 2021)
N/A
6/08 Core Planning Team Meeting #6 Public outreach
Finalized hazards of concern and scenarios
Mission and goals discussion
Define FEMA community lifelines
14 58
Ventura County Multi-Jurisdictional Hazard Mitigation Plan 3-14
Date Event Description Attendance
6/09 Steering Committee Meeting #2 Finalize and confirm Steering Committee guidelines Public outreach strategy
o Website
o Survey
Volume 1 and 2 overview
Vision and goal setting
Hazards of concern accepted and hazard scenarios explained Critical infrastructure / FEMA lifelines definition accepted 27 6/22 Core Planning Team Meeting #7 Public outreach, bilingual survey Mission goals and objectives discussion
13 7/06 Jurisdictional Annex Process
Phase 2 Planning partners continue the jurisdictional annex update process with the capability assessment, integration review, and information sources updates.

N/A
7/14 Steering Committee Meeting #3 Public outreach
o Website
o Survey update
Vision, goals, and objectives accepted
Planning partner update
Story map overview
24 7/20 Core Planning Team Meeting #8 Final mission, goals, and objectives Public outreach
Story map review
Jurisdictional Annex Phase 3 Workshop discussion
9 8/03 Core Planning Team Meeting #9 Public outreach, survey updates Jurisdictional Annex Phase 3 Workshop overview
11 8/31 Core Planning Team Meeting #10 Public outreach update PSA video update
Story map presentation
Planning partner update
Steering Committee meeting preparation
6 9/08 Steering Committee Meeting #4 Public outreach
o Website
o Survey status
o Community meetings
Story map
o PSA video
16 9/14 Core Planning Team Meeting #11 Story map review PSA video status
8 9/15 Public Outreach Community Emergency Preparedness Workshop—Featuring Unincorporated County Areas
106
9/16 Public Outreach Community Emergency Preparedness Workshop—Featuring the City of Oxnard
90 9/22 Jurisdictional annex Workshop -
Municipalities
Workshop for municipal planning partners to assist in completion of Phase 2 of the jurisdictional annex process. Remote technical support provided by Tetra Tech
30 9/22 Public Outreach Community Emergency Preparedness Workshop—Featuring the City of Camarillo
83 9/23 Jurisdictional annex Workshop –
Special Purpose Districts
Workshop for special district planning partners to assist in completion of Phase 2 of the jurisdictional annex process. Remote technical support provided by Tetra Tech
35 9/28 Phase 3 Annex Conference
Call #1
Remote technical support provided to planning partners by Tetra Tech in support of Phase 2 annex completion

59 Plan Development Methodology
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Date Event Description Attendance
9/17 Public Outreach Closure of hazard mitigation survey Tabulation of results

9/23 Public Outreach Community Emergency Preparedness Workshop—Featuring the City of Simi Valley
55 Sept Public Outreach PSA video released in English and Spanish N/A 10/05 Phase 3 Annex Conference
Call #2
Remote technical support provided to planning partners by Tetra Tech in support of Phase 3 annex completion

10/11 Public Outreach Community Emergency Preparedness Workshop—Featuring the City of Santa Paula
30 10/12 Phase 3 Annex Conference
Call #3
Remote technical support provided to planning partners by Tetra Tech in support of Phase 3 annex completion

10/19 Phase 3 Annex Conference
Call #4
Remote technical support provided to planning partners by Tetra Tech in support of Phase 3 annex completion

10/26 Core Planning Team Meeting #12 Planning partner Phase 3 annex status update Countywide initiatives
Plan maintenance strategy
Public meeting to coordinate with the Emergency Planning Council Public comment period discussion
Plan development schedule update

11/10 Steering Committee Meeting #5 Update on planning partner activities Review of proposed county-wide initiatives
Confirmation of plan maintenance strategy
22 11/16 Core Planning Team Meeting #13 Discuss and determine plan maintenance strategy and grant monitoring5 11/18 Public Outreach Emergency Planning Council meeting Status update on the hazard mitigation plan update
not available
2022
1/11 Core Planning Team Meeting #14 Draft plan Volume 1 review Planning partner update
Plan development schedule
5 2/09 Steering Committee Meeting #6 Discuss plan progress Draft plan presentation
Draft plan public comment method
Public comment period
Plan development, submittal and adoption discussion
20 2/08 Core Planning Team Meeting #15 Draft plan Volume 1 internal review update Steering Committee meeting preparation
Public comment press release discussion
Plan development schedule updates
5 3/03 Public Outreach Opening of the 3-week public comment period N/A 3/24 Public Outreach Closure of the 3-week public comment period N/A 4/1 Plan Submittal to Cal OES Submittal of draft plan to Cal OES for review and approval N/A 4/1 Plan Submittal to FEMA Submittal of draft plan to FEMA N/A TBD Approval Pending AdoptionApproval Pending Adoption provided by FEMA N/A TBD Adoption Adoption window for planning partners opens N/A TBD Approval Proof of adoption documentation submitted to FEMA and Cal OESN/A TBD Approval Final approval of the plan by FEMA N/A
60 61
4-1

4. VENTURA COUNTY PROFILE

4.1 PHYSICAL SETTING

4.1.1 Geography and Topography
Ventura County covers 2,208 square miles along southern California’s Pacific coast (1,845 square miles of land and 363 square miles of water). It is bordered by Kern County to the north, Santa Barbara County to the northwest, the Pacific Ocean to the southwest, and Los Angeles County to the east and southeast. National forest makes up 53 percent of Ventura County’s total area. Of the remaining 47 percent (555,953 acres), 59 percent is agricultural and 17.5 percent is urban. Two of California’s eight Channel Islands are also part of the county: Anacapa Island, which is the most visited island in Channel Islands National Park, and San Nicolas Island, which is operated by the U.S. Navy.

The topography in the county is highly variable and includes mountainous areas, rolling hills, a fertile river valley and coastal plain, steep coastal bluffs, and sections of rocky coastline. The northern half of the county is mountainous and sparsely inhabited, and contains some of the most unspoiled, rugged and inaccessible wilderness remaining in southern California. Most of this land lies within the Los Padres National Forest, and includes the Chumash Wilderness in the northernmost portion, adjacent to Kern County, as well as the Sespe Wilderness and portions of the Dick Smith Wilderness and Matilija Wilderness (both of which straddle the line with Santa Barbara County) (California Department of Conservation 2021). This is an area of high topographic relief; eight mountains within this portion of the county exceed 6,000 feet in elevation, and the only major river valley is Lockwood Valley.

Conversely, the southwestern portion of the county consists of a large coastal plain known as the Oxnard Plain. The plain was formed by the deposition of sediments from the Santa Clara River and from the streams of the Calleguas-Conejo drainage system. It has a mean elevation of 50 feet, but the elevation is as much as 150 feet at points south of the Santa Clara River and as much as 300 feet at points north of the river. The part east of the Revolon Slough that centers on Camarillo is called Pleasant Valley. Most of the arable land in the county is found on the coastal plain, as well as the cities of Camarillo, Oxnard, Ventura, and Port Hueneme.

A series of smaller east-west trending hills and mountain ranges make up much of the remainder of the county. The Santa Ynez Mountains, the Topatopa Mountains, and the Piru Mountains constitute the northern boundary of the Oxnard Plain. The Santa Susana Mountains lie alongside the eastern boundary of the county, and the Simi Hills and the Santa Monica Mountains are along the southern border with Los Angeles County. These coastal mountains range in elevation from 50 feet along the coast south of the coastal plain to about 3,100 feet in the Santa Monica Mountains. Inland, the low, long South Mountain and Oak Ridge ranges separate Santa Clara Valley from the Las Posas Valley 62 Ventura County Multi-Jurisdictional Hazard Mitigation Plan 4-2
and Simi Valley. The Camarillo Hills and the Las Posas Hills extend from Camarillo to Simi Valley and separate the Las Posas-Simi area from the Santa Rosa Valley and Tierra Rejada Valley (U.S.

Department of Agriculture 1970).

4.1.2 Watersheds and Surface Waters
Ventura County contains four main watershed zones. The Santa Clara River is by far the largest river, with a drainage area of 1,625 square miles at its mouth. The Ventura River is also a prominent river in the county, with a drainage area of 263 square miles at the Pacific Ocean. Chapter 11 discusses the watershed areas in greater detail. The county also has numerous lakes and reservoirs. The largest dam-created reservoir by volume is Lake Casitas, which holds 254,000 acre-feet of water. It is used primarily for drinking water, irrigation, flood control, and recreation. Lake Piru, another large dam- created reservoir in the county, has a slightly larger surface area than Lake Casitas but is shallower and only holds 83,244 acre-feet of water. Lake Piru is used for recreation, flood control, surface water conservation and groundwater conservation and replenishment.

4.1.3 Climate
Ventura County features a Mediterranean climate characterized by cool, dry summers near the coast and warm, dry summers inland. Winters are typically mild and wet, with the area receiving 95 percent of its annual rainfall from November through April.

Average precipitation is highly variable across the region and varies dramatically with elevation as well as distance from the coast. For example, average annual rainfall ranges from less than 8 inches in the Cuyama Valley in northwestern Ventura County to approximately 38 inches in the Ventura River watershed west of the City of Ojai. Prevailing weather patterns during winter and the orientation of the mountain ranges in the northern half of the county can also combine to produce extremely high- intensity rainfall. Along the coast near Oxnard, Ventura, Simi Valley, and Thousand Oaks, the average rainfall is 14 inches.

Like most of southern California, Ventura County also observes high interannual precipitation variability, where an average rainfall year is the exception rather than the rule.

Table 4-1 summarizes normal climate date from 2000 through 2020 at the National Centers for Environmental Information (NCEI) weather station at the Oxnard Airport.

Table 4-1. Normal Precipitation and Temperatures, 2000 – 2020 Temperature (ºF)
Precipitation (inches) Minimum Average Maximum
Annual 17.6 46.5 58.6 71.3
Winter 10.99 37.7 48.9 60.2
Summer 0.09 55.5 69.3 83.1
Spring 4.29 42.6 54.9 67.1
Autumn 2.16 50.2 61.3 74.6
Weather Station: Oxnard Ventura County Airport
Source: (National Centers for Environmental Information 2021) 63 Ventura County Profile
4-3

4.2 HISTORICAL OVERVIEW
Ventura County was historically inhabited by the Chumash people, who also settled throughout much of Santa Barbara and San Luis Obispo Counties. The Chumash were originally hunters, gatherers, fisherman, and traders, and are known for their rock paintings and basketry.

Spanish explorers began arriving in the area in the mid-1500s, although active occupation did not effectively occur until more than 200 years later. The Spanish encouraged settlement of the area with large land grants called ranchos. The Catholic church established the Mission San Buenaventura in 1782 in what is now the City of San Buenaventura (commonly called the City of Ventura).

The County of Ventura was established on January 1, 1873, when it separated from Santa Barbara County, just 23 years after California’s statehood was attained. At this time, the area remained largely rural, consisting of a population of less than 5,000 individuals that engaged predominantly in ranching and the cultivation of grain crops.

During the early 1900s, increased demand from new markets in the burgeoning Los Angeles area led to a significant expansion and diversification of agriculture in Ventura. Together with the discovery of vast oil reserves in the area, this resulted in an influx of immigrants, wealth, and substantial improvements to transportation infrastructure in the region.

A second, intense population boom (>5% annually) occurred beginning in the 1940s with the construction of Port Hueneme and the establishment of a military base at Point Mugu, which brought numerous professionals and ancillary industries to the region. Ventura County, and the Oxnard area in particular, benefited from the hiring of more than 10,000 civilian workers and 21,000 military personnel, thus providing jobs for local residents and reviving the economy following the Depression of the 1930s.

By 1950, the population of the county had increased to over 114,000, more than double its population in 1930.

The East County saw a large growth in population starting in the mid-20th century with people moving from the San Fernando Valley in Los Angeles to the Conejo and Simi Valleys. Many working-class people migrated to these areas during the 1960s and 1970s out of East and Central Los Angeles.

Making the U.S. 101 a full freeway in the 1960s, and the expansions that followed, helped make commuting to Los Angeles easier and opened the way for development westward. The communities that saw the most substantial development were Calabasas, Hidden Hills, Agoura Hills, Westlake Village, Thousand Oaks, and Newbury Park. The East County area of Simi Valley saw its already considerable population of nearly 60,000 inhabitants in 1970 grow to over 100,000 over the following two decades.

Development moved farther out the U.S. 101 corridor and sent population rising in West County cities as well. The largest population growth there was in Camarillo, Oxnard, and Ventura. Development in the East County and along the U.S. 101 corridor is rare today, because most of these cities are master- planned cities, such as Thousand Oaks and Simi Valley, and are approaching buildout. Although the area still has plenty of open space and land, almost all of it is mandated to never be developed as part of the master plan of each city.
64 Ventura County Multi-Jurisdictional Hazard Mitigation Plan 4-4

4.3 POPULATION CENTERS, TRANSPORTATION, AND GOVERNMENT
The major population centers in Ventura County today are in the southern part of the county, within the incorporated cities of Camarillo, Fillmore, Moorpark, Ojai, Oxnard, Port Hueneme, Santa Paula, Simi Valley, Thousand Oaks, and San Buenaventura (Ventura). Unincorporated communities of note include La Conchita, Lake Sherwood, Meiners Oaks, Oak Park, Oak View, Santa Rosa Valley, El Rio, and Saticoy. The City of Ventura, located along the northwestern coast of the county, is the county seat.

The nearby City of Oxnard is the most populous city. Both these cities are located on the Oxnard Plain, a large alluvial fan formed by deposition from the Santa Clara River. The planning area is shown in Figure 4-1. The risk analysis for this hazard mitigation plan assessed risk both countywide and for each planning partner’s jurisdictional area.

U.S. Highway 101 is the main highway in the county, running east to west through the southern half of the county, and connecting the cities of Thousand Oaks, Camarillo, Oxnard, and Ventura. U.S.

Highway 126 runs east to west along the Santa Clara River Valley, through the cities of Fillmore, Santa Paula, and Ventura, before joining with U.S. Highway 101. Highway 1 follows the coastline along the county’s southern boundary. Other major roadways include State Highways 33, 34, 118, and 150.

Airports in the county include Camarillo Airport, Oxnard Airport, Santa Paula Airport, and Naval Base Ventura County. Both Camarillo and Oxnard airports are operated by the Ventura County Department of Airports. Santa Paula airport is a privately owned, public-use airport. Naval Base Ventura County is operated by the U.S. Navy. The National Railroad Passenger Corporation (Amtrak) and Metrolink trains carry passengers on track extending from Simi Valley to Oxnard. Amtrak service continues to Ventura and along the coastline/Highway 101 to Santa Barbara County.

The Ventura County Board of Supervisors sits as the governing board of Ventura County and of various special jurisdictions such as the Sonoma County Water Agency, the Ventura County Air Pollution Control District, the Agricultural Preservation and Open Space District, County Sanitation Districts, and the Community Development Commission. The Board is composed of five supervisors elected from supervisorial districts for four-year terms. The boundaries of these districts are included on Figure 4-1.

4.4 DEVELOPMENT

4.4.1 Land Use
The Ventura County 2040 General Plan and its land use maps govern the types of land uses and development that may occur in different areas of the unincorporated county. The focus of current land use policies is to preserve agricultural, rural, and open space lands while directing growth to cities and unincorporated communities. Figure 4-2 shows the distribution of current land uses in the unincorporated county.

4.4.2 Building Count, Occupancy Class and Estimated Replacement Value Table 4-2 presents planning area building counts by occupancy class; these are broad use classes assigned in the Hazus model. Table 4-3 summarizes estimated replacement value for building structures and contents combined, based on County assessor data. 65 Fillmore
Moorpark
Simi Valley
Santa Paula
Oxnard
Ojai
Port
Hueneme
Camarillo
San
Buenaventura
Thousand Oaks
Lake Piru
Lake
Casitas
11833
34 118126
150
1 1
23 126
23 33
33 34
1 150
232
33 23
101
Figure 4-1. Planning Area
Data Sources: Ventura Co.,
Esri
County Boundary
Cities
Major Roads
0 6 3 Miles
66 Ventura County Multi-Jurisdictional Hazard Mitigation Plan 4-6
Figure 4-2. Land Use Classifications in the Planning Area Source: Ventura County 2020
67 Ventura County Profile
4-7
Table 4-2. Planning Area Building Counts by Occupancy Class Number of Buildings
AgriculturalCommercialEducationGovernmentIndustrial ReligionResidential Total Camarillo 24 736 215 280 832 85 19,657 21,829
Fillmore 7 328 85 69 39 17 4,310 4,855
Moorpark 101 410 183 63 153 18 9,769 10,697
Ojai 23 345 56 48 54 87 2,918 3,531
Oxnard 92 3,117 654 429 961 150 40,471 45,874
Port Hueneme 0 299 57 430 26 18 5,583 6,413
San Buenaventura 72 2,933 381 250 788 192 30,694 35,310 Santa Paula 55 833 119 50 190 69 7,211 8,527
Simi Valley 56 1,210 434 53 301 108 35,640 37,802
Thousand Oaks 7 1,442 325 171 286 218 36,348 38,797
Unincorporated 11,027 3,172 494 745 523 493 32,568 49,022 Total 11,464 14,825 3,003 2,588 4,153 1,455 225,169 262,657 Table 4-3. Estimated Replacement Value of Planning Area Buildings

Estimated Total Replacement Value
(Structure and Contents)
Estimated Total Replacement Value
(Structure and Contents)
Camarillo $17,707,287,595 San Buenaventura $23,838,143,638 Fillmore $2,467,839,895 Santa Paula $4,571,072,937
Moorpark $8,222,512,567 Simi Valley $24,328,139,279
Ojai $2,340,202,613 Thousand Oaks $30,560,756,798
Oxnard $32,903,823,044 Unincorporated $29,161,232,550
Port Hueneme $4,655,956,714 Total $180,756,967,629
Source: Ventura County tax parcel data

4.4.3 Critical Facilities
Critical facilities are those that are essential to the health and welfare of the population. These become especially important after a hazard event. Also included are facilities that hold significant amounts of hazardous materials with a potential to impact public welfare during a hazard event. The risk assessment for each hazard in this plan discusses potential impacts on critical facilities. This plan update uses the following definition of critical facilities:

A structure, facility, or other improvement that, because of its function, service area, or uniqueness, provides service that enables the continuous operation of critical business and government functions, and is critical to human health and safety, or economic security.

The planning team and Steering Committee recommended that this plan update include a definition of critical facilities that aligns with FEMA’s “community lifelines” concept. This will position the County for future funding under FEMA grant programs and initiatives. The FEMA-defined lifeline categories are as follows:

Safety and Security—Law enforcement/security, search and rescue, fire services, government service, responder safety, and imminent hazard mitigation 68 Ventura County Multi-Jurisdictional Hazard Mitigation Plan 4-8
Food, Water and Shelter—Evacuations, schools, food/potable water, shelter, durable goods, water infrastructure and agriculture
Health and Medical—Medical care (hospitals), patient movement, public health, fatality management, health care and supply chain
Energy—Power (grid), temporary power and fuel
Communications—Infrastructure, alerts, warnings, messages, 911 and dispatch, responder communications and financial services
Transportation—Highway/roadway, mass transit, railway, aviation, maritime and pipeline Hazardous Materials—Facilities, hazardous debris, pollutants, and contaminants Table 4-4 provides a summary of the critical facilities in the planning area by category and jurisdiction.

General locations of identified critical facilities are shown on Figure 4-3 and Figure 4-4. The County and its planning partners consider this information to be subject to change as new information about critical facilities becomes available during the performance period for this plan. Due to the sensitivity of this information, a detailed list of facilities is not provided; however, all critical facilities were analyzed in Hazus to help rank risk and identify mitigation actions. The risk assessment for each hazard discusses critical facilities with regard to that hazard.

Table 4-4. Critical Facilities by Jurisdiction and Category Number of Facilities Present
Communications Energy
Food, Water,
Shelter
Hazardous
Material
Health &
Medical
Safety &
Security Transportation Total
Camarillo 20 5 34 14 1 35 32 141
Fillmore 3 1 4 1 0 10 3 22
Moorpark 5 1 7 9 0 19 11 52
Ojai 6 1 14 0 1 13 2 37
Oxnard 24 33 11 23 2 59 36 188
Port Hueneme 7 2 1 2 0 7 8 27
San Buenaventura 34 10 6 6 3 54 63 176
Santa Paula 5 1 3 3 1 15 20 48
Simi Valley 19 4 4 13 1 51 71 163
Thousand Oaks 53 7 20 13 1 55 54 203
Unincorporated 74 46 106 9 0 73 223 531
Total 250 111 210 93 10 391 523 1,588

4.4.4 Development Trends
An understanding of population and development trends can assist in planning for future development and ensuring that appropriate mitigation, planning, and preparedness measures are in place to protect human health and community infrastructure. The Disaster Mitigation Act requires that communities consider land use trends, which can alter the need for, and priority of, mitigation options over time.

Land use and development trends significantly affect exposure and vulnerability to various hazards. For example, significant development in a hazard area increases the building stock and population exposed to that hazard.
69 Fillmore
Moorpark
Simi Valley
Santa Paula
Oxnard
Ojai
Port
Hueneme
Camarillo
San
Buenaventura
Thousand Oaks
Lake Piru
Lake
Casitas
11833
34 118126
150
1 1
23 126
23 33
33 34
1 150
232
33 23
101
Figure 4-3. Critical Facilities (1 of 2)
Data Sources: Ventura Co., VCFD,
Casitas MWD, Calleguas MWD,
City of Camarillo, CA Energy
Commission, Cal Trans, EPA,
HIFLD, Esri
Health and Medical
Food, Water, Shelter
Safety and Security
County Boundary
Cities
Major Roads
0 6 3 Miles
70 Fillmore
Moorpark
Simi Valley
Santa Paula
Oxnard
Ojai
Port
Hueneme
Camarillo
San
Buenaventura
Thousand Oaks
Lake Piru
Lake
Casitas
11833
34 118126
150
1 1
23 126
23 33
33 34
1 150
232
33 23
101
Figure 4-. Critical Facilities (2 of 2)
Data Sources: Ventura Co., VCFD,
Casitas MWD, Calleguas MWD,
City of Camarillo, CA Energy
Commission, Cal Trans, EPA,
HIFLD, Esri
Communications
Energy
Hazardous Material
Transportation
County Boundary
Cities
Major Roads
0 6 3 Miles
71 Ventura County Profile
4-11
Projected Future Trends
The Regional Housing Needs Assessment (RHNA) is mandated by state law as part of the periodic process of updating local general plan housing elements. RHNA quantifies the need for housing within each jurisdiction during specified planning periods. The Southern California Association of Governments is in the process of developing its sixth cycle RHNA allocation plan, which will cover the planning period October 2021 through October 2029 (Southern California Association of Governments 2021a). Ventura County’s 2021-2029 allocation is 24,452 housing units (Southern California Association of Governments 2021b).

Planning Framework
Ventura County and all incorporated cities included in this hazard mitigation plan have general plans, adopted under state law, to ensure that their governing bodies take actions that the community has determined to be the most orderly, beneficial, and supportive of the community vision. All partners have committed to link their general plans to this hazard mitigation plan. This will create an opportunity for wise land use decisions as future growth impacts hazard areas.

The County of Ventura has land use regulatory authority over most unincorporated land in the county.

The County lacks land use authority within the city limits of incorporated cities and in unincorporated areas that are owned and managed by the state or federal government (e.g., state parks, national parks, Bureau of Land Management areas, and tribal lands), except for portions of state parks and other state land in the coastal zone. Under state law, the County has land use authority over land owned and managed by special districts in the unincorporated area (e.g., school districts, cemetery districts, water districts), subject to limited exceptions (Ventura County 2020).

All city and county planning partners have specific capabilities to manage growth in a way that limits increased risk associated with hazards. Details on these capabilities for each hazard assessed in this plan are provided in Section 6.4. Each of these planning partners reviewed their general plans under the capability assessments performed for this effort, as presented in Volume 2 of the hazard mitigation plan. Deficiencies identified by these reviews can be identified as mitigation actions to increase the capability to deal with future trends in development.

4.5 DEMOGRAPHICS PROFILE

4.5.1 Population Counts
Information about population is a critical part of planning because it directly relates to land needs such as housing, industry, stores, public facilities and services, and transportation. Population changes are useful socio-economic indicators. A growing population generally indicates a growing economy, while a decreasing population may signify economic decline. Due to delays associated with the COVID-19 pandemic, some 2020 census information was not yet available at the time of this plan update. The Census Bureau changed the 2020 American Community Survey release schedule. 72 Ventura County Multi-Jurisdictional Hazard Mitigation Plan 4-12
Current and Historical Population
Table 4-5 shows the population of the County and its incorporated cities from 1990 to 2020. Oxnard and Thousand Oaks are the largest cities in Ventura County, together accounting for 39.4 percent of the planning area’s population in 2010 and 39.5 percent in 2020. Unincorporated areas accounted for

11.5 percent of the planning area’s population in 2010 and about 11.3 percent in 2020.

Table 4-5. Recent Population by Jurisdiction
Population
1990 2000 2010 2020
Camarillo 52,297 57,084 65,201 69,964
Fillmore 11,992 13,643 15,002 15,558
Moorpark 25,494 31,415 34,421 36,264
Ojai 7,613 7,862 7,461 7,450
Oxnard 142,560 170,358 197,899 205,950
Port Hueneme 20,322 21,845 21,723 23,707
Ventura 92,557 100,916 106,433 105,878
Santa Paula 25,062 28,598 29,321 30,386
Simi Valley 100,218 111,351 124,237 124,953
Thousand Oaks 104,381 117,005 126,683 126,384
Unincorporated 86,500 93,120 94,937 94,725
Total 669,016 753,197 823,318 841,219
Source: California Department of Finance, 2021
Overall decrease in population of the unincorporated areas was 0.2 percent from 2010 to 2020; the City of Oxnard grew 3.9 percent during the same timeframe, and the population of the City of Thousand Oaks decreased 0.2 percent. Figure 4-5 shows the planning area’s 10-year population growth rates from 1970 to 2020 compared to those of the state.

Figure 4-5. State of California and Ventura County Population Growth per Decade Source: California Department of Finance, 2021
0%
5%
10%
15%
20%
25%
30%
35%
40%
45%
1970 - 1980 1980 - 1990 1990 - 2000 2000 - 2010 2010 - 2020 % 10-Year Change in Population
California
Ventura County
73 Ventura County Profile
4-13
Projected Future Population
According to projections by the California Department of Finance, Ventura County’s population is expected to increase to 885,628 by 2040. This represents about a 5 percent increase from the 2020 population of 841,219.

4.5.2 Age Distribution
The overall age distribution for the County is shown in Figure 4-6. Based on U.S. Census 2019 data estimates, 15.9 percent of the planning area’s population is 65 or older, compared with the state average of 14.8 percent. It is also estimated that 18.4 percent of the population is 14 or younger, which varies slightly from the state’s average of 18.7 percent.

Figure 4-6. Planning Area Age Distribution
Source: U.S. Census—American Community Survey 5-Year Estimates 47,323
46,665
61,801
57,549
55,414
113,309
104,866
109,967
58,672
53,817
78,541
40,324
17,758
0 20,000 40,000 60,000 80,000 100,000 120,000
Under 5 years
5 to 9 years
10 to 14 years
15 to 19 years
20 to 24 years
25 to 34 years
35 to 44 years
45 to 54 years
55 to 59 years
60 to 64 years
65 to 74 years
75 to 84 years
85 years and over
Number of People
Age
74 Ventura County Multi-Jurisdictional Hazard Mitigation Plan 4-14

4.5.3 Race, Ethnicity and Language
According to the U.S. Census, the racial composition of the planning area is predominantly white, at 56 percent. The largest minority populations are Asian at 7.5 percent, and some other race at 5.1 percent.

Figure 4-7 shows the racial distribution in the planning area. Based on the U.S. Census ethnicity definitions, Ventura County consists of 43.2 percent of individuals of Hispanic or Latino ethnicity (of any race). The planning area has a 21.6 percent foreign-born population. Other than English, the most spoken language in the planning area is Spanish. The Census estimates 53.6 percent of the residents speak English “less than very well.”
Figure 4-7. Planning Area Race Distribution

4.5.4 Persons with Disabilities or with Access and Functional Needs According to the 2018 Census estimates, persons with disabilities or with access and functional needs make up 10.8 percent of the total civilian non-institutionalized population of Ventura County. According to U.S. Census data, 32.1 percent of the over-65 population have disabilities of some kind.

4.6 ECONOMY

4.6.1 Income
Based on 2019 Census data, per capita income in the County of Ventura was $40,293 and the median household income was $92,236. The Department of Housing and Urban Development estimated a 2021 median family income for Oxnard-Thousand Oaks-Ventura of $94,340.

The Census estimates that 7.9 percent of all families in the planning area and 7.2 percent of the over- 65 population have incomes below the poverty level. Children under the age of 18 account for 11.3 percent of individuals who are below the poverty line.

White

80.3%
Black or African
American

1.8%
American Indian and
Alaska Native

0.7%
Asian

7.5%
Some Other Race

5.1%
Two or More Races

4.6%
75 Ventura County Profile
4-15

4.6.2 Homeownership and Renter-Occupied Housing
According to 2019 American Community Survey estimates, there are 268,524 occupied housing units in Ventura County. Table 4-6 compares general demographic statistics for renter-occupied and owner- occupied housing units.

Table 4-6. Comparative Statistics for Renter-Occupied and Owner-Occupied Housing Units Renter-Occupied Housing Units Owner-Occupied Housing Units Occupied Housing Units
Number 100,014 168,510
% of Total 37.2 62.8
Age of Residents
< 35 26,463 8,547
55 and older 30,084 105,535
Time Living at Current Residence
Moved in in 2017 or Later 41,142 21,887

4.6.3 Industry, Businesses, and Institutions
Table 4-7 identifies the principal employers in Ventura County in 2019 as provided by the American Community Survey. Figure 4-8 shows the breakdown of employment in the planning area by industry sector. The County’s economy is strongly based in the education/health services sector and the professional/scientific/management sector. Information and wholesale trade make up the smallest sectors of the local economy.

Table 4-7. 2021 Principal Employers within Ventura County Employer Employer Type
Adventist Health Simi Valley Hospitals
Amgen Inc Biological Specimens-Manufacturers
Baxter Healthcare Medical Manufacturers
Community Memorial Health System Health Care Management County of Ventura Government
Haas Automation Inc Machinery-Manufacturers
Harbor Freight Tools Tools-New & Used
Los Robles Hospital Hospitals
Moorpark College Education
Nancy Reagan Breast Center Diagnostic Imaging Centers
National Guard Government
Ojai Valley Inn Hotels & Hospitality
Oxnard College Education
Pentair Aquatic Systems Retail
Port Hueneme Military
Procter & Gamble Manufacturing
Rancho Simi Recreation Park District Public Administration 76 Ventura County Multi-Jurisdictional Hazard Mitigation Plan 4-16
Employer Employer Type
Sheriff’s Department Government
City of Simi Valley Government
City of Simi Valley City Manager Government
St. John’s Regional Medical Center Hospitals
U.S. Department of the Navy Military
Ventura County Medical Center Hospital
Ventura County Office of Education School District
Figure 4-8. Employment in Ventura County by Industry Sector

4.6.4 Employment Trends and Commuting
Ventura County’s local employment base has remained nearly the same since 2010. In 2019, the estimated total number of employed Ventura County residents was 422,172, an increase of only 0.58 percent from 2010. Of the working-age population who make up the labor force, 52.1 percent are men and 47.9 percent are women.

Figure 4-9 compares unemployment rates for the State of California and Ventura County from 2010 through 2019. The 2019 Ventura County unemployment rate was the lowest in 10 years at 2.6 percent.

The rate peaked at 7.3 percent in 2011 and declined overall through 2019. In each year from 2010 through 2019, the County unemployment rate was lower than that of the state.

Figure 4-10 shows U.S. Census data for the most common occupations for the employed population of Ventura County. This includes wage and salary jobs, and jobs held by business owners and self- employed persons. The total job count does not include unpaid volunteers or family workers, or private household workers.

Agriculture,
forestry, fishing
and hunting, and
mining
Construction

5.9%
Manufacturing

9.8%
Wholesale

2.9%
Retail

10.4%
Transportation

3.6%
Information

2.4%
Finance

7.3%
Professional

12.1%
Education

19.8%
Arts and
Entertainment

9.7%
Other Services

5.6%
Public
Administration

5.1%
77 Ventura County Profile
4-17
The 2019 U.S. Census Bureau data shows 78.4 percent of the County’s population work and live in Ventura County; 21.6 percent commute to other places. In 2019, 34.4 percent of Ventura County commuters spent more than 30 minutes to travel to work.

Figure 4-9. 10-Year Unemployment Rates for California and Ventura County

Figure 4-10. Employment in the Planning Area by Type of Work

0%
2%
4%
6%
8%
10%
12%
14%
2010 2011 2012 2013 2014 2015 2016 2017 2018 2019
Unemployement Rate
State of California
Ventura County
Management,
Business, Science
and Arts
37%
Service
19%
Sales & Office
22%
Natural Resources,
Construction and
Maintenance
12%
Production,
Transportation, and
Material Moving
10%
78 79
5-1

5. HAZARDS OF CONCERN
Defining the hazards that present the greatest risk to the planning area is the first step in assessing overall risk to the community. The planning team and Steering Committee reviewed available information to determine what types of hazards may affect the planning area, how often they can occur, and their potential severity.

5.1 MAJOR PAST HAZARD EVENTS
Federal disaster declarations are typically issued for hazard events that cause more damage than state and local governments can handle without assistance from the federal government, although no specific dollar loss threshold has been established for these declarations. A federal disaster declaration puts federal recovery programs into motion to help disaster victims, businesses, and public entities.

Some of the programs are matched by state programs. Federal disaster, emergency, or fire management assistance declarations were issued for 46 events since 1954 in the planning area. These events are listed in Table 5-1.

Table 5-1. Federal Disaster Declarations for Hazard Events that Affected the Planning Area Type of Event
Disaster
Declaration # Date
Flooda DR-15 02/05/1954
Flooda DR-47 12/23/1955
Firea DR-65 12/29/1956
Flooda DR-82 4/4/1958
Flooda DR-122 3/6/1962
Severe Storma DR-138 10/24/1962
Flooda DR-145 2/25/1963
Heavy Rains, Flooding DR-211 December 7, 1965
Severe Storms, Flooding DR-253 January 26, 1969
Forest, Brush Fires DR-295 September 29, 1970
Severe Storms, High Tides, Flooding DR-364 February 8, 1973 Coastal Storms, Mudslides, Flooding DR-547 February 15, 1978 Severe Storms, Mudslides, Flooding DR-615 January 8, 1980 Coastal Storms, Floods, Slides, Tornadoes DR-677 January 21 – March 30, 1983 Grass, Wildlands, Forest Fires DR-739 June 26 – July 19, 1985 Severe Storms, High Tides, Flooding DR-812 January 17 – 22, 1988 Severe Freeze DR-894 December 19, 1990 – January 3, 1991 Snow Storm, Heavy Rain, High Winds, Flooding, Mudslide DR-935 February 10 – 19, 1992 80 Ventura County Multi-Jurisdictional Hazard Mitigation Plan 5-2
Type of Event
Disaster
Declaration # Date
Severe Storm, Winter Storm, Mud & Landslides, Flooding DR-979 January 5 – March 20, 1993 Fires, Mud & Landslides, Soil Erosion, Flooding DR-1005 October 26 – April 22, 1994 Northridge Earthquake DR-1008 January 17 – November 30,1994 Severe Winter Storms, Flooding, Landslides, Mud Flows DR-1044 January 3 – February, 1995 Severe Winter Storms, Flooding, Landslides, Mud Flows DR-1046 February 13 – April 19, 1995 Severe Fires EM-3120 October 21 – 31, 1996
Severe Winter Storms and Flooding DR-1203 February 2 – April 30, 1998 Severe Storms, Tornadoes, High Winds and Flooding DR-1267 December 20 – 28, 1998 Wildfires, Flooding, Mudflow and Debris Flow DR-1498 October 21, 2003 – March 31, 2003 Severe Storms, Flooding, Debris Flows, and Mudslides DR-1577 December 27, 2004 – January 11, 2005 Severe Storms, Flooding, Landslides, and Mud and Debris Flows DR-1585 February 16 – 23, 2005 Hurricane Katrina Evacuation EM-3248 August 29 – October 1, 2005 Topanga Fire FM-2583 September 28 – October 10, 2005
School Fire FM-2586 November 18 – 23, 2005
Day Fire FM-2677 September 25 – 30, 2006
Shekell Fire FM-2681 December 3 – 6, 2006
Severe Freeze DR-1689 January 11 – 17, 2007
Wildfires, Flooding, Mudflows, and Debris Flows DR-1731 October 21 – March 31, 2008 Guiberson Fire FM-2839 September 22 – 29, 2009
Springs Fire FM-5024 May 2 – 11, 2013
Thomas Fire FM-5224 December 4, 2017
Wildfires, Flooding, Mudflows, and Debris Flows DR-4353 December 4, 2017- January 31, 2018 Wildfires DR-4407 November 8 – 25, 2018
Saddleridge Fire FM-5293 October 10, 2019
Getty Fire FM-5297 October 28, 2019
Easy Fire FM-5298 October 30, 2019
Maria Fire FM-5302 November 1, 2019
COVID-19 Pandemic DR-4482 January 20, 2020 and continuing a. FEMA did not begin distinguishing declarations by county until 1964. Declarations prior to then are statewide, not county-specific.

Source: FEMA 2021
Review of these events helps identify hazards of concern and targets for risk reduction activities.

However, many natural hazard events do not trigger federal disaster declaration protocol but have significant impacts on their communities (e.g. landslides that result in road closures). These events are also important to consider in identifying hazards of concern and establishing their recurrence intervals.

5.2 HAZARDS EVALUATED IN 2015 PLAN
The planning team also reviewed information on hazards from the previous plan update conducted in 2015. That plan addressed the following 12 hazards of concern:

Agricultural / biological
Climate change
Dam failure/inundation
Drought
Earthquake
Flood
81 Hazards of Concern
5-3
Landslide
Levee failure inundation
Post-fire debris flows
Tsunami
Wildfire
Winter storm

5.3 IDENTIFIED HAZARDS FOR THE 2022 UPDATE
The Steering Committee considered the full range of natural hazards that could affect the planning area and then selected those that present the greatest concern for risk assessment in this plan. The process incorporated a review of state and local hazard planning documents as well as information on the frequency of, magnitude of, and costs associated with hazards that have struck the planning area or could do so. Anecdotal information regarding natural hazards and the perceived vulnerability of the planning area’s assets to them was also used.

Based on the review, this plan includes risk assessments for the hazards of concern listed in Table 5-2.

Climate change is not assessed as an individual hazard, but a profile is provided describing how climate change could affect the hazards of concern assessed in this plan.

Table 5-2. Hazards Addressed in This Hazard Mitigation Plan Hazards of Concern Hazards of Interest
Dam failure inundation
Drought
Earthquake
Flooding (includes levee failures)
Landslide & mass movements
Sea-level rise and coastal erosion
Severe storms
Severe weather (heat/freeze events)
Tsunami
Wildfire
Agricultural biological incidents
Pandemic
Note: Hazards are listed in alphabetical order in this table and in the risk assessment portion of this plan; the order presented does not indicate the hazards’ relative severity or risk.

In addition to the risk assessment of the hazards of concern, this plan provides a qualitative review of the “hazards of interest” listed in Table 5-2. The Steering Committee determined that these other hazards, though not required to be evaluated under federal guidelines for hazard mitigation plans, are important to recognize qualitatively in this plan. Hazard profiles, without quantitative risk assessments, are provided for these hazards of interest.

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6. EXISTING REGULATIONS
Existing regulations, agencies and programs at the federal, state, and local level can support or impact hazard mitigation actions identified in this plan. Hazard mitigation plans are required to include a review and incorporation, if appropriate, of existing plans, studies, reports, and technical information as part of the planning process (44 CFR, Section 201.6(b)(3)). Information presented in this section can be used to review local capabilities to implement the action plan this hazard mitigation plan presents. Individual review by each planning partner of existing local plans, studies, reports, and technical information is presented in the annexes in Volume 2.

6.1 FEDERAL AND STATE AGENCIES, PROGRAMS AND REGULATIONS State and federal regulations and programs that need to be considered in hazard mitigation are constantly evolving. For this plan, a review was performed to determined which regulations and programs are currently most relevant to hazard mitigation planning. The findings are summarized in Table 6-1 and Table 6-2. Short descriptions of each program are provided in Appendix B.

Table 6-1. Summary of Relevant Federal Agencies, Programs and Regulations Agency, Program or
Regulation
Hazard Mitigation
Area Affected Relevance
Americans with Disabilities ActAction Plan
Implementation
FEMA hazard mitigation project grant applications require full compliance with applicable federal acts.

Bureau of Land Management Wildfire Hazard The Bureau funds and coordinates wildfire management programs and structural fire management and prevention on BLM lands.

Civil Rights Act of 1964 Action Plan
Implementation
FEMA hazard mitigation project grant applications require full compliance with applicable federal acts.

Clean Water Act Action Plan
Implementation
FEMA hazard mitigation project grant applications require full compliance with applicable federal acts.

Community Development
Block Grant Disaster
Resilience Program
Action Plan Funding This is a potential alternative source of funding for actions identified in this plan.

Community Rating System Flood Hazard This voluntary program encourages floodplain management activities that exceed the minimum National Flood Insurance Program requirements.

Disaster Mitigation Act Hazard Mitigation
Planning
This is the current federal legislation addressing hazard mitigation planning.

Emergency Relief for Federally
Owned Roads Program
Action Plan Funding This is a possible funding source for actions identified in this plan. 84 Ventura County Multi-Jurisdictional Hazard Mitigation Plan 6-2
Agency, Program or
Regulation
Hazard Mitigation
Area Affected Relevance
Emergency Watershed
Program
Action Plan Funding This is a possible funding source for actions identified in this plan.

Endangered Species ActAction Plan
Implementation
FEMA hazard mitigation project grant applications require full compliance with applicable federal acts.

Federal Energy Regulatory
Commission Dam Safety
Program
Dam Failure Hazard This program cooperates with a large number of federal and state agencies to ensure and promote dam safety.

Federal Wildfire Management
Policy and Healthy Forests
Restoration Act
Wildfire Hazard These documents mandate community-based collaboration to reduce risks from wildfire.

National Dam Safety Act Dam Failure Hazard This act requires a periodic engineering analysis of most dams in the country National Environmental Policy
Act
Action Plan
Implementation
FEMA hazard mitigation project grant applications require full compliance with applicable federal acts.

National Fire Plan Wildfire Hazard This plan calls for joint risk reduction planning and implementation by federal, state and local agencies.

National Flood Insurance
Program
Flood Hazard This program makes federally backed flood insurance available to homeowners, renters, and business owners in exchange for communities enacting floodplain regulations
National Incident Management
System
Action Plan
Development
Adoption of this system for government, nongovernmental organizations, and the private sector to work together to manage incidents involving hazards is a prerequisite for federal preparedness grants and awards National Landslide
Preparedness Act
Risk Assessment of
Landslide Hazard
This act authorized a national landslide hazards reduction program and a 3D elevation program, providing tools and data to assess the landside hazard.

Presidential Executive Order
11988 (Floodplain
Management)
Flood Hazard This order requires federal agencies to avoid long and short-term adverse impacts associated with modification of floodplains
Presidential Executive Order
11990 (Protection of Wetlands)
Action Plan
Implementation
FEMA hazard mitigation project grant applications require full compliance with applicable presidential executive orders.

Rural Development Program Action Plan
Implementation
The program provides project financing and technical assistance to help rural communities provide the infrastructure needed by rural businesses, community facilities, and households.

U.S. Army Corps of Engineers
Dam Safety Program
Dam Failure Hazard This program is responsible for safety inspections of dams that meet size and storage limitations specified in the National Dam Safety Act.

U.S. Army Corps of Engineers
Flood Hazard Management
Flood Hazard, Action
Plan Implementation,
Action Plan Funding
The Corps of Engineers offers multiple funding and technical assistance programs available for flood hazard mitigation actions
U.S. Bureau of Reclamation
Safety Evaluation of Existing
Dams Program
Dam Failure Hazard The program emphasizes site evaluations to identify potential safety deficiencies on Interior Department dams and analyses to expedite corrective action decisions.

U.S. Fire Administration Wildfire Hazard This agency provides leadership, advocacy, coordination, and support for fire agencies and organizations.

U.S. Fish and Wildlife ServiceWildfire Hazard This service’s fire management strategy employs prescribed fire throughout the National Wildlife Refuge System to maintain ecological communities. 85 Existing Regulations
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Table 6-2. Summary of Relevant State Agencies, Programs and Regulations Agency, Program or Regulation
Hazard
Mitigation
Area Affected Relevance
AB 9: Fire safety: Wildfires: Fire Adapted
Communities
Wildfire Hazard Establishes the Regional Forest and Fire Capacity Program to support regional leadership to build local and regional capacity and develop, prioritize, and implement strategies and projects that create fire adapted communities and landscapes by improving watershed health, forest health, community wildfire preparedness, and fire resilience.

AB 32: The California Global Warming
Solutions Act
Action Plan
Development
This act establishes a state goal of reducing greenhouse gas emissions to 1990 levels by 2020
AB 38: Fire safety: Low-Cost Retrofits:

Regional Capacity Review: Wildfire
Mitigation
Wildfire Hazard Directs the California Natural Resources Agency to review the regional capacity of each county that contains a very high fire hazard severity zone and establishes a comprehensive wildfire mitigation and assistance program.

AB 70: Flood Liability Flood Hazard A city or county may be required to partially compensate for property damage caused by a flood if it unreasonably approves new development in areas protected by a state flood control project
AB 162: Flood Planning Flood Hazard Cities and counties must address flood-related matters in the land use, conservation, and safety and housing elements of their general plans.

AB 267: California Environmental Quality
Act: Exemption: Prescribed Fire,
Thinning, and Fuel Reduction Projects.

Wildfire Hazard Extends to January 1, 2026, the exemption from requirements of the California Environmental Quality Act for prescribed fire, thinning, or fuel reduction projects on federal lands to reduce the risk of high-severity wildfire that had been reviewed under the National Environmental Policy Act.

AB 380: Forestry: Priority Fuel Reduction
Projects
Wildfire Hazard Requires the Department of Forestry and Fire Protection to identify priority fuel reduction projects annually and exempts the identified priority fuel reduction projects from certain legal requirements.

AB 431: Forestry: Timber Harvesting
Plans: Defensible Space: Exemptions
Wildfire Hazard Extends to January 1, 2026, the exemption from a requirement to complete a timber harvest plan for maintaining defensible space between 150 feet and 300 feet from a habitable structure.

AB 497: Forestry and Fire Protection:

Local Assistance Grant Program: Fire
Prevention Activities: Street and Road
Vegetation Management
Wildfire Hazard Appropriates funds for local assistance grants for fire prevention activities with priority for projects that that manage vegetation along streets and roads to prevent the ignition of wildfire.

AB 575: Civil Liability: Prescribed
Burning Activities: Gross Negligence
Wildfire Hazard Provides that a private entity engaging in a prescribed burning activity that is supervised by a person certified as burn boss is liable for damages to a third party only if the prescribed burning activity was carried out in a grossly negligent manner.

AB 642: Wildfires Wildfire Hazard This bill is an omnibus fire prevention bill that makes various changes to support cultural and prescribed fire, including the creation of a Cultural Burning Liaison at the Department of Forestry and Fire Protection, and requires a proposal for creating a prescribed fire training center.

AB 747: General Plans—Safety Element Hazard
Mitigation
Planning
The safety elements of cities’ and counties’ general plans must address evacuation routes and include any new information on flood and fire hazards and climate adaptation and resiliency strategies.

AB 800: Wildfires: local general plans:
safety elements: fire hazard severity
zones.

Wildfire Hazard This Bill has provisions for wildfire hazard mapping and applications for that mapping in the Safety elements General plans within the state. 86 Ventura County Multi-Jurisdictional Hazard Mitigation Plan 6-4
Agency, Program or Regulation
Hazard
Mitigation
Area Affected Relevance
AB 1255: Fire prevention: Department of
Forestry and Fire Protection: Grant
Programs
Wildfire Hazard Requires the Natural Resources Agency to develop a guidance document that describes goals, approaches, opportunities, and best practices in each region of the state for ecologically appropriate, habitat-specific fire risk reduction. Requires consultation with counties related to the Department of Forestry and Fire Protection’s local fire prevention grant program.

AB 1295: Residential development
Agreements: Very High-Risk Fire Areas
Wildfire Hazard Prohibits the legislative body of a city or county from entering into a residential development agreement for property in a very high fire risk area as designated by a local agency or a fire hazard severity zone classified by the director of CAL FIRE.

AB 1439: Property Insurance Discounts Wildfire Hazard Requires residential or commercial property insurance policies to include a discount if a local government where the insured property is located funds a local wildfire protection or mitigation program.

AB 1500: Safe Drinking Water, Wildfire
Prevention, Drought Preparation, Flood
Protection, Extreme Heat Mitigation, and
Workforce Development Bond Act of
2022.

Drought,
Flood, Extreme
Heat and
Wildfire
Hazards
If approved by the voters, would authorize the issuance of bonds to finance projects for safe drinking water, wildfire prevention, drought preparation, flood protection, extreme heat mitigation, and workforce development programs.

AB 2140: General Plans—Safety Element Hazard
Mitigation
Planning
This bill enables state and federal disaster assistance and mitigation funding to communities with compliant hazard mitigation plans.

AB 2800: Climate Change—Infrastructure
Planning
Action Plan
Development
This act requires state agencies to take into account the impacts of climate change when developing state infrastructure.

Alquist-Priolo Earthquake Fault Zoning
Act
Earthquake
Hazard
This act restricts construction of buildings used for human occupancy on the surface trace of active faults.

Board of Forestry and Fire Protection
Fire Safe Regulations
Wildfire Hazard The Fire Safe Regulations set the floor for fire safety standards for perimeters and access to residential, commercial, and industrial building construction.

California Coastal Management Program Flood,
Landslide,
Tsunami and
Wildfire
Hazards
This program requires coastal communities to prepare coastal plans and requires that new development minimize risks to life and property in areas of high geologic, flood, and fire hazard.

California Department of Forestry and
Fire Protection (CAL FIRE)
Wildfire Hazard CAL FIRE has responsibility for wildfires in areas that are not under the jurisdiction of the Forest Service or a local fire organization.

California Department of Parks and
Recreation
Wildfire Hazard State Parks Resources Management Division has wildfire protection resources available to suppress fires on State Park lands.

California Department of Water
Resources
Flood Hazard This state department is the state coordinating agency for floodplain management.

California Division of Safety of Dams Dam Failure
Hazard
This division monitors the dam safety program at the state level and maintains a working list of dams in the state.

California Environmental Quality Act Action Plan
Implementation
This act establishes a protocol of analysis and public disclosure of the potential environmental impacts of development projects. Any project action identified in this plan will seek full California Environmental Quality Act compliance upon implementation.

California Fire Alliance Wildfire Hazard The alliance works with communities at risk from wildfires to facilitate the development of community fire loss mitigation plans.

California Fire Plan Wildfire Hazard This plan’s goal is to reduce costs and losses from wildfire through pre-fire management and through successful initial response.
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Agency, Program or Regulation
Hazard
Mitigation
Area Affected Relevance
California Fire Safe Council Wildfire Hazard This council facilitates the distribution of National Fire Plan grants for wildfire risk reduction and education.

California Fire Service and Rescue
Emergency Mutual Aid Plan
Wildfire Hazard This plan provides guidance and procedures for agencies developing emergency operations plans, as well as training and technical support.

California General Planning Law Hazard
Mitigation
Planning
This law requires every county and city to adopt a comprehensive long- range plan for community development, and related laws call for integration of hazard mitigation plans with general plans.

California Multi-Hazard Mitigation Plan Hazard
Mitigation
Planning
Local hazard mitigation plans must be consistent with their state’s hazard mitigation plan.

California Residential Mitigation Program Earthquake
Hazard
This program helps homeowners with seismic retrofits to lessen the potential for damage to their houses during an earthquake.

California State Building Code Action Plan
Implementation
Local communities must adopt and enforce building codes, which include measures to improve buildings’ ability to withstand hazard events.

Disadvantaged and Low-Income
Communities Investments
Action Plan
Funding
This is a potential source of funding for actions located in disadvantaged or low-income communities.

Division of the State Architect’s AB 300
List of Seismically At-Risk Schools
Earthquake
Hazard, Action
Plan
Development
The Division of the State Architect recommends that local school districts conduct detailed seismic evaluations of seismically at-risk schools identified in the inventory that was required by AB 300.

Governor’s Executive Order S-13-08
(Climate Impacts)
Action Plan
Implementation
This order includes guidance on planning for sea-level rise in designated coastal and floodplain areas for new projects.

Office of the State Fire Marshal Wildfire Hazard This office has a wide variety of fire safety and training responsibilities.

Senate Bill 12: Local government:
planning and zoning: wildfires.

Wildfire Hazard Requires the safety element to be reviewed and updated as necessary to include a comprehensive retrofit strategy to reduce the risk of property loss and damage during wildfires. Requires the planning agency to submit the adopted strategy to the Office of Planning and Research for inclusion into a central clearinghouse.

Senate Bill 92: Public Resources Portion
of Biennial Budget Bill
Dam Failure
Hazard
This bill requires dams (except for low-risk dams) to have emergency action plans that are updated every 10 years and inundation maps updated every 10 years, or sooner if specific circumstances change.

Senate Bill 97: Guidelines for
Greenhouse Gas Emissions
Action Plan
Implementation
This bill establishes that greenhouse gas emissions and the effects of greenhouse gas emissions are appropriate subjects for California Environmental Quality Act analysis.

Senate Bill 99: General Plans: Safety
Element: Emergency Evacuation Routes
Action Plan
Implementation
This bill requires the safety element must include information to identify residential developments in hazard areas that do not have at least two emergency evacuation routes.

Senate Bill 182: Local Government:

Planning and Zoning: Wildfires
Wildfire Hazard This bill made a number of changes to state law regarding planning for and permitting development in areas designated as very high fire risk areas.

Senate Bill 379: General Plans: Safety
Element—Climate Adaptation
Action Plan
Implementation
This bill requires cities and counties to include climate adaptation and resiliency strategies in the safety element of their general plans.

Senate Bill 1000: General Plan
Amendments—Safety and Environmental
Justice Elements
Action Plan
Implementation
Under this bill, review and revision of general plan safety elements are required to address only flooding and fires (not climate adaptation and resilience), and environmental justice is required to be included in general plans.
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Agency, Program or Regulation
Hazard
Mitigation
Area Affected Relevance
Senate Bill 1035: Fire, Flood, and
Adaptation Safety Element Updates
Action Plan
Implementation
Clarifies that revisions to the Safety Element to address fire hazards, flood hazards, and climate adaptation and resilience strategies all must occur upon each revision to a Housing Element or Local Hazard Mitigation Program.

Senate Bill 1241: General Plans: Safety
Element—Fire Hazard Impacts
Wildfire Hazard This bill requires cities and counties to make findings regarding available fire protection and suppression services before approving a tentative map or parcel map.

Standardized Emergency Management
System
Action Plan
Implementation
Local governments must use this system to be eligible for state funding of response-related personnel costs.

Western Governors Association Ten-
Year Comprehensive Strategy
Wildfire Hazard This strategy implementation plan prepared by federal and Western state agencies outlines measures to restore fire-adapted ecosystems and reduce hazardous fuels.

6.2 LOCAL PLANS, REPORTS AND CODES
Plans, reports, and other technical information were identified and provided directly by participating jurisdictions and stakeholders or were identified through independent research by the planning consultant. These documents were reviewed to identify the following:

Existing jurisdictional capabilities.

Needs and opportunities to develop or enhance capabilities, which may be identified within the local mitigation strategies.

Mitigation-related goals or objectives considered during the development of the overall goals and objectives.

Proposed, in-progress, or potential mitigation projects, actions and initiatives to be incorporated into the updated jurisdictional mitigation strategies.

The following local regulations, codes, ordinances, and plans were reviewed in order to develop complementary and mutually supportive goals, objectives, and mitigation strategies that are consistent across local and regional planning and regulatory mechanisms:

General plans (land use, housing, safety, and open space elements) Building codes
Zoning and subdivision ordinances
NFIP flood damage prevention ordinances
Stormwater management plans
Emergency management and response plans
Land use and open space plans
Climate action plans
Community wildfire protection plans
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6.3 LOCAL CAPABILITY ASSESSMENT
All participating jurisdictions compiled an inventory and analysis of existing authorities and capabilities called a “capability assessment.” A capability assessment creates an inventory of a jurisdiction’s mission, programs, and policies, and evaluates its capacity to carry them out. This assessment identifies potential gaps in the jurisdiction’s capabilities.

The planning partnership views all core jurisdictional capabilities as fully adaptable to meet a jurisdiction’s needs. Every code can be amended, and every plan can be updated. Such adaptability is itself considered to be an overarching capability. If the capability assessment identified an opportunity to add a missing core capability or expand an existing one, then doing so has been selected as an action in the jurisdiction’s action plan, which is included in the individual annexes presented in Volume 2 of this plan.

Capability assessments for each planning partner are presented in the jurisdictional annexes in Volume

2. The sections below describe the specific capabilities evaluated under the assessment.

6.3.1 Planning and Regulatory Capabilities
Jurisdictions have the ability to develop policies and programs and to implement rules and regulations to protect and serve residents. Local policies are typically identified in a variety of community plans, implemented via a local ordinance, and enforced through a governmental body.

Jurisdictions regulate land use through the adoption and enforcement of zoning, subdivision, and land development ordinances, building codes, building permit ordinances, floodplain, and stormwater management ordinances. When effectively prepared and administered, these regulations can lead to hazard mitigation.

6.3.2 Fiscal Capabilities
Assessing a jurisdiction’s fiscal capability provides an understanding of the ability to fulfill the financial needs associated with hazard mitigation projects. This assessment identifies both outside resources, such as grant-funding eligibility, and local jurisdictional authority to generate internal financial capability, such as through impact fees.

6.3.3 Administrative and Technical Capabilities
Planning, regulatory, and fiscal capabilities provide the backbone for successfully developing a mitigation strategy; however, without appropriate personnel, the strategy may not be implemented.

Administrative and technical capabilities focus on the availability of personnel resources responsible for implementing all the facets of hazard mitigation. These resources include technical experts, such as engineers and scientists, as well as personnel with capabilities that may be found in multiple departments, such as grant writers.
90 Ventura County Multi-Jurisdictional Hazard Mitigation Plan 6-8

6.3.4 NFIP Compliance
Flooding is the costliest natural hazard in the United States and, with the promulgation of recent federal regulation, homeowners throughout the country are experiencing increasingly high flood insurance premiums. Community participation in the NFIP opens up opportunity for additional grant funding associated specifically with flooding issues. Assessment of the jurisdiction’s current NFIP status and compliance provides planners with a greater understanding of the local flood management program, opportunities for improvement, and available grant funding opportunities.

6.3.5 Public Outreach Capability
Regular engagement with the public on issues regarding hazard mitigation provides an opportunity to directly interface with community members. Assessing this outreach and education capability illustrates the connection between the government and community members, which opens a two-way dialogue that can result in a more resilient community based on education and public engagement.

6.3.6 Community Classifications
Other programs, such as the Community Rating System, Storm/Tsunami Ready, and Firewise USA, can enhance a jurisdiction’s ability to mitigate, prepare for, and respond to natural hazards. These programs indicate a jurisdiction’s desire to go beyond minimum requirements set forth by local, state, and federal regulations in order to create a more resilient community. These programs complement each other by focusing on communication, mitigation, and community preparedness to save lives and minimize the impact of natural hazards on a community.

6.3.7 Development and Permitting Capability
Identifying previous and future development trends is achieved through a comprehensive review of permitting since completion of the previous plan and in anticipation of future development. Tracking previous and future growth in potential hazard areas provides an overview of increased exposure to a hazard within a community.

6.3.8 Adaptive Capacity
An adaptive capacity assessment evaluates a jurisdiction’s ability to anticipate impacts from future conditions. By looking at public support, technical adaptive capacity, and other factors, jurisdictions identify their core capability for resilience against issues such as sea-level rise. The adaptive capacity assessment provides jurisdictions with an opportunity to identify areas for improvement by ranking their capacity high, medium, or low.

6.3.9 Integration Opportunity
The assessment looked for opportunities to integrate this mitigation plan with the planning and regulatory capabilities identified. Capabilities were identified as integration opportunities if they can support or enhance the actions identified in this plan or be supported or enhanced by components of this plan. Planning partners considered actions to implement this integration as described in their jurisdictional annexes.
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6.3.10 Expansion of Existing Capabilities
Local hazard mitigation plans are required to document each jurisdiction’s ability to expand on and improve existing policies and programs. For this plan update, all planning partners reviewed their existing capabilities through the jurisdictional annex process (see Volume 2) and developed mitigation actions to address identified gaps in their capabilities or to expand on or improve existing capabilities.

In the analysis to assign each mitigation action to a defined category (see Section 23.3), these actions are classified as “community capacity building” actions, which are defined as follows:

Actions that increase or enhance local capabilities to adjust to potential damage, to take advantage of opportunities, or to respond to consequences. Includes staff training, memorandums of understanding, development of plans and studies, and monitoring programs.

Of 275 actions identified by the jurisdictions adopting this plan, 105 were identified as community capacity building actions that will expand on or improve the capabilities of the planning partnership.

6.4 HAZARD MITIGATION CAPABILITIES FOR FUTURE DEVELOPMENT The identification of hazards of concern and the areas that they affect allows local communities to review expected future development to assess whether it would be at risk from those identified hazards.

Avoiding such future risk is a core element of local hazard mitigation. Through the capability assessment described in Section 6.3, all planning partners identified their ability to address risks to future development posed by identified planning area hazards of concern. The planning partners’ general plans and other planning activities provide guidance related to hazard mitigation and future development as follows:

Dam failure—Dam failure is currently addressed as a stand-alone hazard in the safety elements of many municipal partners’ general plans. Flood-related policies in the general plans will help to reduce the risk associated with dam failure for all future development in the planning area. Municipalities participating in this plan have established comprehensive policies regarding sound land use in identified dam failure inundation hazard areas. Most of the areas vulnerable to severe impacts from dam failure intersect the mapped flood hazard areas. However, there are structures on the perimeter of the dam failure inundation outside of the regulated floodplain that are not subject to floodplain management codes and standards. These structures would be considered to be more vulnerable than those constructed with floodplain codes and standards.

Drought—Each municipal planning partner in this effort has a general plan with policies directing land use and dealing with issues of water supply and the protection of water resources.

These plans provide the capability at the local municipal level to protect future development from the impacts of drought. In addition, water providers in the planning area have plans and programs in place to balance competing needs for water resources within the planning area.

Earthquake—Ventura County and participating cities strictly enforce all seismic building codes and design standards to prevent loss of life and property caused by earthquake. Municipal planning partners are encouraged to establish general plans with policies directing land use and dealing with issues of seismic safety. These plans provide the capability at the municipal level to protect future development from the impacts of earthquakes. Public education, cooperation with the development community, and individual preparedness are essential as the planning area welcomes thousands of new residents and hundreds of new businesses to each year. 92 Ventura County Multi-Jurisdictional Hazard Mitigation Plan 6-10
Flood—All municipal planning partners have general plans that address frequently flooded areas in their safety elements. Additionally, all municipal planning partners are participants in the NFIP and have adopted flood damage prevention ordinances in response to its requirements. With 20 percent of communities and the County participating in the CRS program, there is incentive to adopt consistent, appropriate, higher regulatory standards in communities with the highest degree of flood risk. All municipal planning partners have committed to maintain their good standing under the NFIP through initiatives identified in this hazard mitigation plan.

Communities participating or considering participation in the CRS program will be able to refine this commitment using CRS programs and templates as a guide.

Landslide—The State of California has adopted the International Building Code (IBC) by reference in its California Building Standards Code. The IBC includes provisions for geotechnical analyses in steep slope areas that have soil types considered susceptible to landslide hazards. These provisions assure that new construction is built to standards that reduce the vulnerability to landslide risk.

Sea-Level Rise and Coastal Erosion—Sea-level rise and coastal erosion are addressed as part of climate change adaptation and resilience in the general plans of Ventura County and coastal cities. By coordinating their general plans with climate change adaptation strategies, cities and the County will be better able to make wise land use decisions as future growth impacts coastal areas affected by sea-level rise and coastal erosion.

Severe Storms—Impacts from winter storms and thunderstorms can be addressed through proactive planning and utilization of best available information in making land use decisions.

Severe storms are not currently addressed as a stand-alone hazard in the safety elements of municipal partners’ general plans, but programs such as building code enforcement, public information, and early warning will help Ventura County manage the likely impacts of severe storm events as the County expands and grows.

Severe Weather—The most common severe weather events that impact the planning area are damaging winds, extreme temperatures, and heavy rain. Many of the impacts associated with severe weather hazards, including wind events, can be addressed through proactive planning and utilization of best available information in making land use decisions. Severe weather is not currently addressed as a stand-alone hazard in the safety elements of municipal partners’ general plans, but programs such as building code enforcement, public information, and early warning will help Ventura County manage the likely impacts of severe weather as the County expands and grows.

Tsunami—The tsunami inundation maps provided by the California Department of Conservation offer jurisdictions a way to guide development away from tsunami-prone areas. By coordinating their general plans, cities and the County will be better able to make wise land use decisions as future growth impacts tsunami hazard areas.

Wildfire—The expansion of development into high wildfire hazard areas can be managed with strong land use and building codes. The planning area is well equipped with these tools, and this planning process asked each planning partner to assess its capabilities with regards to the tools. As Ventura County experiences future growth, it is anticipated that the exposure to this hazard will remain as assessed or even decrease over time due to these capabilities.

Other hazards of interest—Agricultural and biological as well as pandemic hazards primarily result in ecological, recreational, economic, and vital impacts, but are not considered in the future development and land use decisions of municipal partners’ general plans. 93 Ventura County Multi-Jurisdictional Hazard Mitigation Plan Part 2—RISK ASSESSMENT

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7. RISK ASSESSMENT METHODOLOGY
This plan evaluated risks associated with each identified hazard of concern for individual incorporated cities and for the unincorporated portion of Ventura County. The following steps were used to assess risk for each hazard:

Identify and profile the hazard—The following information is given for each hazard:

A summary of past events that have impacted the planning area Geographic areas most affected by the hazard
Event frequency estimates
Severity descriptions
Warning time likely to be available for response.

Determine exposure to the hazard—Exposure was assessed by overlaying hazard maps with an inventory of structures, facilities, and systems to decide which of them would be exposed to each hazard.

Assess the vulnerability of exposed facilities—Vulnerability of exposed structures and infrastructure was evaluated by estimating potential impacts on people and damage to property and the environment in the event of a hazard incident.

For each hazard, one of the following assessment approaches was used, depending on the nature of information available for the hazard:

Quantitative assessment—Performed when numerical data is available to define risk.

Available hazard data may include financial impact, probability, or the number of injuries and deaths.

Qualitative assessment—Uses words to describe and categorize the likelihood and consequences of a risk when numerical data is unavailable. In this type of analysis, defined terms (words) can represent a range of possibilities.

7.1 RISK ASSESSMENT TOOLS

7.1.1 Mapping
National, state, and county databases were reviewed to locate available spatially based data relevant to this planning effort. Maps were produced using geographic information system (GIS) software to show the spatial extent and location of hazards when such datasets were available. These maps are included in the hazard profile chapters of this document and the jurisdiction-specific annexes in Volume 2.

Details regarding the data sources and methodologies employed in these mapping efforts is located in Appendix C.
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7.1.2 Modeling
Overview
FEMA developed the GIS-based program Hazards U.S. (Hazus) to identify areas that face high risk from earthquakes, hurricanes, floods, and tsunamis by estimating losses. Hazus provides a wide range of inventory data, such as demographics, building stock, critical facilities, transportation and utility infrastructure, and multiple models to estimate potential losses from natural disasters. The program maps and calculates hazard data and damage and economic loss estimates for buildings and infrastructure. Its advantages include the following:

Provides a consistent methodology for assessing risk across geographic and political entities.

Provides a way to save data so that it can readily be updated as population, inventory, and other factors change and as mitigation planning efforts evolve.

Facilitates the review of mitigation plans because it helps to ensure that FEMA methodologies are incorporated.

Supports grant applications by calculating benefits using FEMA definitions and terminology.

Produces hazard data and loss estimates that can be used in communication with local stakeholders.

Is administered by the local government and can be used to manage and update a hazard mitigation plan throughout its implementation.

Levels of Detail for Evaluation
Hazus provides default data for inventory, vulnerability, and hazards; this default data can be supplemented with local data to provide a more refined analysis. The model can carry out three levels of analysis, depending on the format and level of detail of information about the planning area:

Level 1—All of the information needed to produce an estimate of losses is included in the software’s default data. This data is derived from national databases and describes in general terms the characteristic parameters of the planning area.

Level 2—More accurate estimates of losses require more detailed information about the planning area. To produce Level 2 estimates of losses, detailed information is required about local geology, hydrology, hydraulics and building inventory, as well as data about utilities and critical facilities. This information is needed in a GIS format.

Level 3—This level of analysis generates the most accurate estimate of losses. It requires detailed engineering and geotechnical information to customize it for the planning area.

7.2 RISK ASSESSMENT APPROACH

7.2.1 Hazard Profile Development
Hazard profiles were developed through web-based research and review of previously developed reports and plans, including community general plans and state and local hazard mitigation plans.

Frequency and severity indicators include past events and the expert opinions of geologists, emergency management specialists, and others.
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7.2.2 Exposure and Vulnerability
Flood, Dam Failure, Earthquake, and Tsunami
Community exposure and vulnerability to the following hazards were evaluated using Hazus:

Dam Failure, Flood, and Tsunami—A Level 2 (user-defined) analysis was performed for general building stock and for critical facilities. Current mapping for the planning area was used to delineate hazard areas for flood, dam failure, and tsunami and estimate potential losses. To estimate damage that would result from these inundation-based hazards, Hazus uses pre- defined relationships between water depth at a structure and resulting damage, with damage given as a percent of total replacement value. Curves defining these relationships have been developed for damage to structures and for damage to typical contents within a structure. By inputting inundation depth data and known property replacement cost values, dollar-value estimates of damage were generated.

Earthquake—A Level 2 analysis was performed to assess earthquake exposure and vulnerability for four scenario events and one probabilistic event:

A Magnitude-7.16 event on the Oak Ridge Fault with an epicenter 4.5 miles northwest of Moorpark.

A Magnitude-7.16 event on the San Cayetano Fault with an epicenter 10 miles north- northwest of Fillmore.

A Magnitude-8.03 event on the San Andreas Fault with an epicenter 27.5 miles north- northeast of Fillmore.

A Magnitude-7.12 event on the Ventura-Pitas Point Fault with an epicenter 2.5 miles north of San Buenaventura.

The standard Hazus 100-year probabilistic event.

Landslide, Sea-Level Rise & Coastal Erosion, Severe Storms, Severe Weather, and Wildfire
Historical datasets were not adequate to model future losses for these hazards of concern. However, areas and inventory susceptible to some of the hazards of concern were mapped by other means to evaluate exposure. A qualitative analysis was conducted for other hazards using the best available data and professional judgment.

Drought
The risk assessment methodologies used for this update focus on damage to structures. Because drought does not impact structures, the risk assessment for this hazard was more limited and qualitative than the assessment for the other hazards of concern.

7.3 SOURCES OF DATA USED IN MODELING AND EXPOSURE ANALYSES

7.3.1 Building and Cost Data
Replacement cost is the cost to replace an entire structure with one of equal quality and utility.

Replacement cost is based on industry-standard cost-estimation models published in the 2021 edition of RS Means Square Foot Costs. It is calculated using the RS Means square foot cost for a structure, 98 Ventura County Multi-Jurisdictional Hazard Mitigation Plan 7-4
which is based on the Hazus occupancy class (i.e., multi-family residential or commercial retail trade), multiplied by the square footage of the structure. The construction class and number of stories for single-family residential structures also factor into determining the square foot costs.

Replacement cost values and detailed structure information derived from parcel and building footprints data were loaded into Hazus. When available, an updated inventory was used in place of the Hazus defaults for critical facilities and infrastructure.

7.3.2 Hazus Data Inputs
The following hazard datasets were used for the Hazus Level 2 analysis conducted for the risk assessment:

Flood—The effective Digital Flood Insurance Rate Map (DFIRM) for the planning area was used to delineate flood hazard areas and estimate potential losses from the FEMA 1-percent- annual chance and 0.2-percent-annual-chance (100- and 500-year) flood events. Using the DFIRM floodplain boundaries and base flood elevation information, and the USGS’s 1-meter digital elevation model data, flood depth grids were generated and integrated into the Hazus model.

Dam Failure—Dam failure inundation area boundaries and depth grids data for were provided by the California Department of Water Resources the following dams: Arundell Barranca, Bouquet Canyon, Castaic, Lake Eleanor, Lake Sherwood, Lang Creek Detention Basin, Las Llajas, Matilija, Pyramid, Runkle, Santa Felicia, Senior Canyon, Sinaloa Lake, Stewart Canyon Debris Basin, Sycamore Canyon, Westlake Reservoir, and Wood Ranch. The individual dam depth grids were combined, and the combined depth grid was integrated into the Hazus model.

Where dam inundation areas overlapped the maximum depth was used.

Tsunami— California Geological Survey tsunami inundation zone data and NOAA’s 5-meter digital elevation model data were used to develop an inundation depth grid that was integrated into the Hazus model.

Earthquake—Earthquake ShakeMaps and probabilistic data prepared by USGS were used for the analysis of this hazard. A National Earthquake Hazard Reduction Program soils map from the California Department of Conservation was integrated into the Hazus model, as were liquefaction zones and susceptibility to deep-seated landslide data from the California Geological Survey.

7.3.3 Other Local Hazard Data
Locally relevant information on hazards was gathered from a variety of sources. Data sources for specific hazards were as follows:

Drought— No GIS format drought hazard area datasets were identified for Ventura County.

Landslide—The California Geological Survey provided data on susceptibility to deep-seated landslides. Areas categorized as very high and high susceptibility (Categories X, XI, VIII, and VII) were used in the exposure analysis.

Sea-Level Rise and Coastal Erosion—Sea-level rise data were provided by USGS’s Our Coast, Our Future tool. Sea-level rises of 25 cm (no storm) and 100 cm (no storm) were used for the exposure analysis. The 25-cm scenario was chosen as the level nearest to the “high” 99 Risk Assessment Methodology
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projection of 8 inches (20 cm) of sea-level rise by 2030 used by the VC Resilient Project. The 100-cm scenario was chosen as the interval nearest to the State of California Sea-Level Rise Guidance (2018 Update) of 3.5 feet (106 cm) by 2050.

Severe Storms—No GIS format severe storm area datasets were identified for Ventura County.

Severe Weather—No GIS format severe weather area datasets were identified for Ventura County.

Wildfire—Fire severity zone data for local and state responsibility areas were acquired from California Department of Forestry and Fire Protection (CAL FIRE). Very high and high fire severity zones were used in the exposure analysis.

7.3.4 Data Source Summary
Table 7-1 and Table 7-2summarizes the data sources used for the risk assessment for this plan.

Table 7-1. Hazus Model Property and Hazard Data Documentation Data Source Date Format
Property parcel data including building information (use code, square footage, year built)
Ventura County 2021 Digital (GIS)
Building footprints Ventura County 2018 Digital (GIS)
Building replacement (square foot) costs RS Means 2021 Digital (pdf) Dam breach inundation maps (inundation boundaries and
depth grids)
California Department of Water Resources 2018-20 Digital (GIS) ShakeMaps—Oak Ridge (Onshore) M7.16; San Cayetano
M7.16; S. San Andreas (PK+CH+CC+BB+NM+SM+NSB+SSB)
M8.03; Ventura-Pitas Point M7.12
USGS 2017 Digital (GIS)
NEHRP soils (VsMapV3_Geology) California Department of Conservation 2015 Digital (GIS) Seismic Hazard Zone Maps for Liquefaction California Geological Survey 2017 Digital (GIS) Digital Flood Insurance Rate Map (DFIRM) – Ventura County effective 1/29/2021 with latest LOMR effective date 6/18/2021 FEMA 2021 Digital (GIS)
Susceptibility to deep-seated landslides California Geological Survey 2011 Digital (GIS) Sea-level rise data (USGS Coastal Storm Modeling System v3.0, Phase 2)
Our Coast Our Future (OCOF) 2018 Digital (GIS)
Tsunami Inundation Map for Emergency Planning California Emergency Management Agency, California Geological Survey, and University of
Southern California – Tsunami Research Center
2009 Digital (GIS)
Very High Fire Hazard Severity Zones in Local Responsibility Areas
California Department of Forestry and Fire
Protection
2007 Digital (GIS)
Fire Hazard Severity Zones for State Responsibility Areas California Department of Forestry and Fire Protection
2007 Digital (GIS)
USGS 1-meter LiDAR digital elevation model U.S. Geological Survey 2018 Digital (GIS) NOAA Coastal Services Center Coastal Inundation Digital Elevation Model (5-meter resolution)
National Oceanic and Atmospheric
Administration
2012 Digital (GIS)
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Table 7-2. Hazus Model Critical Facilities Data Documentation Data Source Date Format
Sheriff stations Ventura County Provided 2021 Digital (GIS) Fire stations Ventura County Provided 2021Digital (GIS) Schools Ventura County Provided 2021 Digital (GIS)
Wastewater treatment plants Ventura County Provided 2021Digital (GIS) Sewer lift stations Ventura County Provided 2021 Digital (GIS) Recycled water pumps Ventura County Provided 2021Digital (GIS) Red Cross shelters Ventura County Provided 2021 Digital (GIS) Hospitals Ventura County Provided 2021Digital (GIS)
Fire district facilities Ventura County Fire Protection District Provided 2021 Digital (GIS) Potable water system facilities Casitas Municipal Water District Provided 2021Digital (GIS) Potable water system facilities Calleguas Municipal Water District Provided 2021 Digital (GIS) Potable water system facilities City of Camarillo Provided 2021Digital (GIS) California jurisdictional dams California Department of Water Resources Downloaded 2020 Digital (GIS) Wastewater treatment facilities California State Water Resources Control BoardDownloaded 2020Digital (GIS) Power plants California Energy Commission Downloaded 2020 Digital (text) Electric substations California Energy Commission Downloaded 2020 Digital (GIS) Natural gas stations California Energy Commission Downloaded 2018 Digital (GIS) California rail stations California Department of TransportationDownloaded 2020 Digital (GIS) Public airports California Department of Transportation Downloaded 2020 Digital (GIS) Military airports California Department of TransportationDownloaded 2020 Digital (GIS) Ports California Department of Transportation Downloaded 2020 Digital (GIS) Local highway bridges California Department of TransportationDownloaded 2020 Digital (GIS) State highway bridges California Department of Transportation Downloaded 2020 Digital (GIS) Local Emergency Operations Centers Homeland Infrastructure Foundation-Level Data Downloaded 2020 Digital (GIS) Veterans Health Administration Medical Facilities Homeland Infrastructure Foundation-Level Data Downloaded 2020 Digital (GIS) Cellular towers Homeland Infrastructure Foundation-Level Data Downloaded 2022 Digital (GIS) FM transmission towers Homeland Infrastructure Foundation-Level Data Downloaded 2020 Digital (GIS) AM transmission towers Homeland Infrastructure Foundation-Level DataDownloaded 2022Digital (GIS) TV analog station transmitters Homeland Infrastructure Foundation-Level Data Downloaded 2022 Digital (GIS) FDIC insured banks Homeland Infrastructure Foundation-Level Data Downloaded 2022 Digital (GIS) Toxic Release Inventory (TRI) facilities extracted
from EPA Facility Registry Service (FRS): Facility
Interests Dataset
U.S. Environmental Protection Agency Downloaded 2020 Digital (GIS) Critical facilities identified in the planning partner
annexes for the Ventura County Multi-Jurisdictional
Hazard Mitigation Plan
Planning partners (California State University
Channel Islands, Calleguas Municipal Water
District, Ojai Valley Sanitary District, Saticoy
Sanitary District, United Water Conservation
District, Ventura County)
2021 Digital (text)

7.4 LIMITATIONS
Loss estimates, exposure assessments and hazard-specific vulnerability evaluations rely on the best available data and methodologies. Uncertainties are inherent in any loss estimation methodology and 101
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arise in part from incomplete scientific knowledge concerning natural hazards and their effects on the built environment. Uncertainties also result from the following:

Approximations and simplifications necessary to conduct a study Incomplete or outdated inventory, demographic or economic parameter data The unique nature, geographic extent, and severity of each hazard Mitigation measures already employed
The amount of advance notice residents have to prepare for a specific hazard event.

These factors can affect loss estimates by a factor of two or more. Therefore, potential exposure and loss estimates are approximate and should be used only to understand relative risk. Over the long term, the planning partners will collect additional data to assist in estimating potential losses associated with other hazards.

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8. DAM FAILURE

8.1 GENERAL BACKGROUND

8.1.1 Definition and Classification of Dams
A dam is an artificial barrier that can store water, wastewater, or liquid-borne materials for many reasons—flood control, human water supply, irrigation, livestock water supply, energy generation, containment of mine tailings, recreation, or pollution control. Many dams fulfill a combination of these functions. They are an important resource in the United States. In California, dams are regulated by the State of California Division of Safety of Dams. Additional regulatory oversight of dams is cited in Chapter 6 and described in Appendix B.

The California Water Code (Division 3) defines a dam as any artificial barrier, together with appurtenant works, that does or may impound or divert water, and that either:

Is 25 feet or more in height from the natural bed of the stream or watercourse at the downstream toe of the barrier (or from the lowest elevation of the outside limit of the barrier if it is not across a stream channel or watercourse) to the maximum possible water storage elevation; or
Has an impounding capacity of 50 acre-feet or more.

Dams can be classified according to their purpose, the construction material or methods used, their slope or cross-section, the way they resist the force of the water pressure, or the means used for controlling seepage. Materials used to construct dams include earth, rock, tailings from mining or milling, concrete, masonry, steel, timber, plastic, rubber, and combinations of these.

8.1.2 Causes of Dam Failure
A dam failure can damage ecosystems and communities downstream. Partial or full failure can occur as a result of one or a combination of the following reasons (Federal Emergency Management Agency 2016):

Overtopping caused by floods that exceed the dam capacity (inadequate spillway capacity) Prolonged periods of rainfall and flooding
Deliberate acts of sabotage (terrorism)
Structural failure of materials used in dam construction Movement and/or failure of the foundation supporting the dam 104
Ventura County Multi-Jurisdictional Hazard Mitigation Plan 8-2
Settlement and cracking of concrete or embankment dams
Piping and internal erosion of soil in embankment dams
Inadequate or negligent operation, maintenance, and upkeep Failure of upstream dams on the same waterway
Earthquake (liquefaction/landslides).

Many dam failures in the United States have been secondary results of other disasters. The most common causes are earthquakes, landslides, extreme storms, equipment malfunction, structural damage, foundation failures, and sabotage. Poor construction, lack of maintenance and repair, and deficient operational procedures are preventable or correctable by a program of regular inspections.

Terrorism and vandalism are serious concerns that all operators of public facilities must plan for; these threats are under continuous review by public safety agencies.

8.1.3 Planning Requirements
State of California
All dams whose inundation areas may impact the planning area have emergency action plans (EAPs) on file. The EAPs must include the following (Cal OES 2021):

Emergency notification flow charts
Information on a four-step response process
Description of agencies’ roles and actions in response to an emergency incident Description of actions to be taken in advance of an emergency Inundation maps
Additional information such as revision records and distribution lists.

After the EAPs are approved by the state, the law requires dam owners to send the approved EAPs to relevant stakeholders. Local public agencies can then adopt emergency procedures that incorporate the information in the EAP in a manner that conforms to local needs and includes methods and procedures for alerting and warning the public and other response and preparedness related items (Cal OES 2021).

Federal Energy Regulatory Commission
Dams that fall under the jurisdiction of the Federal Energy Regulatory Commission (FERC) also have specified planning requirements. FERC cooperates with a large number of federal and state agencies to ensure and promote dam safety and, more recently, homeland security. FERC requires licensees to prepare emergency action plans and conducts training sessions on how to develop and test these plans. The plans are designed to serve as an early warning system if there is a potential for, or a sudden release of water from, a dam failure or accident to the dam. The plans include operational procedures that may be used, such as reducing reservoir levels and reducing downstream flows and procedures for notifying affected residents and agencies responsible for emergency management. 105
Dam Failure
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These plans are frequently updated and tested to ensure that in emergency situations everyone knows what to do, thus saving lives and minimizing property damage.

8.1.4 Secondary Hazards
Dam failure can cause secondary hazards of landslides, bank erosion, and downstream habitat destruction. It may worsen the severity of a drought by releasing water that might have been used as a potable water source.

8.2 HAZARD PROFILE

8.2.1 Past Events
There is no record of a failure of any dam located in Ventura County. However, the failure of one dam in another county had catastrophic effects in Ventura County. The St. Francis Dam in the San Francisquitos Canyon in Los Angeles County (within the Santa Clara River watershed) was constructed to provide 38,000 acre-feet of storage for water from the Los Angeles–Owens River Aqueduct. The midnight collapse of the dam in March 1928 occurred after the newly constructed concrete-arch dam was completely filled for the first time. The resulting flood swept through the Santa Clara Valley in Ventura County toward the Pacific Ocean, about 54 miles away. At its peak, the wall of water was reported to be 78 feet high; by the time it hit Santa Paula, 42 miles south of the dam, the water was estimated to be 25 feet deep. Almost everything in its path was destroyed, including structures, railways, bridges, livestock, and orchards. By the time the flood subsided, parts of Ventura County lay under 70 feet of mud and debris. Nearly 500 people were killed, and damage estimates exceeded $20 million. The communities of Piru, Fillmore, Santa Paula, Bardsdale, Saticoy, Montalvo, and El Rio sustained extensive life and property loss from the flood (Ventura County 2015).

According to the 2013 State of California Multi-Hazard Mitigation Plan, there have been nine failures of federally regulated dams in the state since 1950. Overtopping caused two of the nine dam failures in the state, and the others were caused by seepage or leaks. The state’s most recent dam emergency occurred in February 2017 when the Oroville Dam in Butte County was on the verge of overflow. The dam’s concrete spillway was damaged by erosion and a massive hole developed. The auxiliary spillway was used to prevent overtopping of the dam, and it experienced erosion problems also. Evacuation orders were issued in advance of a potential large uncontrolled release of water from Lake Oroville, but such a release did not occur.

After this incident, state officials ordered that flood-control spillways be reinspected on 93 California dams with potential geologic, structural or performance issues that could jeopardize their ability to safely pass a flood event. The 2017-2018 Ventura County Grand Jury investigated the condition of more than 20 dams in or adjoining Ventura County. The Grand Jury found that 14 of these dams (10 in Ventura County and 4 in Los Angeles County) could cause significant loss of life and property if they failed. Four of these dams, all under the jurisdiction of the State of California Division of Safety of Dams (DSOD), are identified as having existing or potential deficiencies (Ventura County 2018). 106
Ventura County Multi-Jurisdictional Hazard Mitigation Plan 8-4

8.2.2 Location
List of High-Hazard Dams
There are 10 state regulated dams in Ventura County, and 4 state regulated dams outside the County whose failure could lead to inundation in Ventura County. In particular, if dams in the Santa Clara River watershed in Los Angeles County fail, the resulting flood would affect the Santa Clara River corridor, which includes Fillmore, Santa Paula, Oxnard, and Port Hueneme, as demonstrated by the 1928 event (Ventura County 2015). Table 8-1 lists the dams that constitute failure hazards for Ventura County.

Their locations are shown on Figure 8-1. The National Inventory of Dams (NID) provides the most recent inspection dates for these dams, as shown in Table 8-2.

Table 8-1. Ventura County Dams with Potential to Endanger Lives and Property Name
National
ID#
Hazard
Potential Owner
Year
Built Dam Type
Crest
Length
(feet)
Height
(feet)
Storage
Capacity
(acre-feet)
Condition
Assessment
Arundell Barranca CA01412 Extremely High VCPWA-WPa 1996 Earthen Embankment 368 57 155 Satisfactory Casitas CA10139 High Federal 1959 Earthen Embankment N/A 334 283,727 N/A Ferro Debris
Basin
CA01299 Significant VCPWA-WPa 1986 Earthen Embankment 265 45 24 Satisfactory Lake Eleanor CA00737 High COSCAb 1881 Constant Radius Arch140 37 104 Satisfactory Lake Sherwood CA00736 Extremely High SDCc 1904 Constant Radius Arch 350 45 2,600 Satisfactory Lang Creek
Detention Basin
CA01368 Extremely High VCPWA-WPa 2004Earthen Embankment 345 67 263 Satisfactory Las Llajas CA01217 Extremely High VCPWA-WPa 1981 Earthen Embankment 580 96 1,250 Satisfactory Matilija CA00312 Extremely High VCPWA-WPa 1949 Variable Radius Arch 620 163 1,800 Poor Runkle CA00313 Extremely High VCPWA-WPa 1949 Earthen Embankment 250 41 100 Satisfactory Santa Felicia CA00805 Extremely High UWCDd 1955 Earthen Embankment 1,275 213 100,000 Fair Senior CanyonCA01019 High SCMWCe 1964 Earthen Embankment 970 76 72 Satisfactory Silt Pond CA01589 High Brett Jones N/A Earthen Embankment N/A 80 20 N/A Sinaloa Lake CA01018 High SLOAf 1925Earthen Embankment800 30 205 Satisfactory Stewart CanyonCA01159 Extremely High VCPWA-WPa 1963 Earthen Embankment 1,263 34 890 Satisfactory Sycamore Canyon CA01266 Extremely High VCPWA-WPa 1981 Earthen Embankment 1,520 40 890 Satisfactory Wood Ranch CA00850 Extremely High CMWDg 1965 Earthen Embankment 1,020 146 11,000 Satisfactory a. Ventura County Public Works Agency—Watershed Protection b. Conejo Open Space Conservation Agency
c. Sherwood Development Company
d. United Water Conservation District
e. Senior Canyon Mutual Water Company
f. Sinaloa Lake Owners Associates, Inc.
g. Calleguas Municipal Water District
Sources: California Department of Water Resources Division of Safety of Dams, 2020; U.S. Army Corp of Engineers National Inventory of Dams, 2021
107
Fillmore
Moorpark
Simi Valley
Santa Paula
Oxnard
Ojai
Port
Hueneme
Camarillo
San
Buenaventura
Thousand Oaks
Lake Piru
Lake
Casitas
11833
34 118126
150
1 1
23 126
23 33
33 34
1 150
232
33 23
101
Figure 8-1. Locations of Dams in Ventura County
Data Sources: Ventura Co.,
CA DWR, Esri
California Jurisdictional Dams
County Boundary
Cities
Major Roads
0 6 3 Miles
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Ventura County Multi-Jurisdictional Hazard Mitigation Plan 8-6
Table 8-2. Ventura County Dam Inspection Dates
Dam Inspection Date Dam Inspection Date
Arundell Barranca 2/13/2018 Runkle 2/14/2018
Casitas N/A Santa Felicia 5/10/2017
Ferro Debris Basin 2/13/2018 Senior Canyon 5/24/2018
Lake Eleanor 5/25/2018 Silt Pond N/A
Lake Sherwood 5/24/2018 Sinaloa Lake 5/23/2018
Lang Creek Detention Basin 2/14/2018 Stewart Canyon 2/13/2018 Las Llajas 2/14/2018 Sycamore Canyon 2/14/2018
Matilija 2/13/2018 Wood Ranch 5/23/2018
The Ventura County Public Works Agency—Watershed Protection (VCPWA-WP) owns and operates the Matilija Dam, which received a “Poor” rating by the DSOD. The DSOD rating was based on concerns as to the ability of the dam—specifically the wing walls—to withstand a 7.5 magnitude earthquake. While the analysis did not appear to indicate complete failure, it indicated a likelihood of significant weakening. There are roughly 8 million cubic yards of debris behind Matilija Dam, and a big storm could push huge amounts of mud and water over the top, overwhelming bridges, culverts and roads below (Ventura County 2018). The VCPWA-WP is working to complete the feasibility analyses, design engineering, CEQA, and implementation of a project to remove the Matilija Dam.

The United Water Conservation District owns and operates Santa Felicia Dam on Lake Piru. The District is currently designing improvements to the existing outlet and spillway. The dam’s “Fair” rating is primarily due to deficiencies in the dam’s outlet that could result in damage should a maximum credible earthquake occur before the District completes the planned upgrades (Ventura County 2018).

Inundation Mapping
A key element for EAPs required for dams in California is a map defining the potential downstream inundation should the dam fail. For this risk assessment, dam failure inundation areas for which inundation mapping was available were combined into a single inundation area. These included all extremely high and high hazard dams where dam breach inundation area data is available. The combined dam failure inundation area is shown in Figure 8-2. Simultaneous failure of all dams is highly unlikely, but the assessment provides information adequate for planning purposes.

8.2.3 Frequency
Dam failure events are infrequent and usually coincide with or follow events such as earthquakes, landslides and excessive rainfall and snowmelt. Only one recorded failure has occurred on a dam that impacted the planning area, so no estimate of frequency or probability of future occurrence can be developed based on the historical record. Although the 2017 Oroville event raised public concern about dam failure, the probability of such failures remains low in today’s regulatory environment. 109
Fillmore
Moorpark
Simi Valley
Santa Paula
Oxnard
Ojai
Port
Hueneme
Camarillo
San
Buenaventura
Thousand Oaks
Lake Piru
Lake
Casitas
11833
34 118126
150
1 1
23 126
23 33
33 34
1 150
232
33 23
101
Figure 8-2. Dam Failure Inundation Area Used for Risk Assessment Data Sources: Ventura Co.,
CA DWR, Esri
Combined Dams Inundation Area
County Boundary
Cities
Major Roads
0 6 3 Miles
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Ventura County Multi-Jurisdictional Hazard Mitigation Plan 8-8
All dams face a “residual risk” of failure, which represents the risk that conditions may exceed those for which the dam was designed. For example, dams may be designed to withstand a probable maximum precipitation, defined as “the maximum depth of precipitation at a location for a given duration that is meteorologically possible” (Sarkar and Maity 2020). The chance of occurrence of a precipitation event of a greater magnitude than that represents residual risk for such dams. This in turn represents a theoretical probability of future occurrence for a dam failure event, though the probability of an event exceeding the assumed maximum is not generally calculated as part of dam design.

8.2.4 Severity
California’s Division of Safety of Dams has developed a hazard potential classification system for state- jurisdiction dams, as shown on Table 8-3. This system is modified from federal guidelines, which recommend three-tier classification. The California system adds a fourth hazard classification of “extremely high.” Dams classified as extremely high hazard are expected to cause considerable loss of human life or would result in an inundation area with a population of 1,000 or more. (California Division of Safety of Dams 2021) Dams within state jurisdiction listed in Table 8-1 are classified in this system.

Table 8-3. State of California Downstream Hazard Potential Classification Hazard Category Direct Loss of Life Economic, Environmental, and Lifeline Losses Low None expected Low and principally limited to dam owner’s property Significant None expected Yes
High Probable (one or more expected) Yes, but not necessary for this classification Extremely High Considerable Yes, major impacts to critical infrastructure or property Source: California Division of Safety of Dams, 2021

8.2.5 Warning Time
Advance Warning of Failure
Warning time for dam failure varies depending on the cause of the failure. Events of extreme precipitation or massive snowmelt can be predicted in advance, so evacuations can be planned with sufficient time. In the event of a structural failure due to earthquake, there may be no or limited warning time. The USGS Earthquake Hazards Program has several dam-safety related earthquake programs, including dam-specific earthquake monitoring programs in California to help monitor safety concerns following seismic events.

Time for Failure to Occur
The process of the dam failure affects warning time. Earthen dams do not tend to fail completely or instantaneously. Once a breach is initiated, discharging water erodes the breach until either the reservoir water is depleted or the breach resists further erosion. Concrete gravity dams also tend to have a partial breach as one or more monolith sections are forced apart by escaping water. The time of breach formation ranges from a few minutes to a few hours. 111
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Time After Failure Before Downstream Areas Are Affected Flood waters from a failure of the Wood Ranch dam at Bard Reservoir would reach the City of Camarillo in approximately 1 hour and 40 minutes. The natural drainage would enter Camarillo along the Las Posas Arroyo through Somis (City of Camarillo 2007). The number of people to be alerted and evacuated can vary widely. There may be few people along the river in winter, when only permanent residents are apt to be present; but there may be many more people in summer, with the presence of recreational visitors.

Another factor that must be considered is the initial flow in the river when the failure occurs. The initial flow is normally very low on all the rivers from May through October. During the winter, the initial flow is much higher and at times may even be equal to or greater than flood stage. This wide variation in initial flow has a significant impact on the areas that must be evacuated.

8.3 EXPOSURE
Exposure to the dam failure hazard was assessed by overlaying the mapped combined inundation area in Figure 8-2 with planning area features including general building stock and critical facilities. Detailed results by jurisdiction are included in Appendix D; countywide summaries are provided below.

8.3.1 Population
The estimated total population living in the evaluated dam failure inundation zone is 267,136 (31.7 percent of the total planning area population).

8.3.2 Property
Table 8-4 summarizes the estimated property exposure in the evaluated dam failure inundation area.

Figure 8-3 shows the Hazus-defined occupancy class of all buildings in the combined dam failure inundation area. These occupancy classes provide an indication of land use within the mapped hazard area. Some land uses are more vulnerable to dam failure inundation, such as single-family homes, while others are less vulnerable, such as agricultural land or parks.

Table 8-4. Exposed Property in Evaluated Dam Failure Inundation Area Acres of Inundation Area 254,761
Number of Buildings Exposed 72,448
Value of Exposed Structures $28,821,842,548
Value of Exposed Contents $22,630,155,206
Total Exposed Property Value $51,451,998,753
Total Exposed Value as % of Planning Area Total 28.5%
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Figure 8-3. Building Count by Occupancy Class in the Dam Failure Inundation Zone

8.3.3 Critical Facilities
Figure 8-4 shows critical facilities located in the dam failure inundation zone by facility type. The total count of critical facilities in the dam failure inundation zone (406) represents 26 percent of the planning area total of 1,588. A breakdown by municipality is provided in Appendix D.

Figure 8-4. Critical Facilities in Dam Failure Inundation Area

Residential
61,269
85%
Commercial
5,268
7%
Industrial
1,697
2%
Agriculture
1,896
3%
Religion
263
0%
Government
1,241
2%
Education
814
1%
54 41
48 48
2 91
130
0 30
60 90
120
150Number of Facilties in Hazard Area
Communication
Energy
Food, Water, Shelter
Hazardous Materials
Medical and Health
Safety and Security
Transportation

21.6%

36.9%

22.9%

51.6%

20.0%23.3%24.9%
0%
20%
40%
60%
80%
100%Facilties in Hazard Area as % of Planning Area Total Communication
Energy
Food, Water, Shelter
Hazardous Materials
Medical and Health
Safety and Security
Transportation
113
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8.3.4 Environment
All natural features in the dam failure inundation zone are at risk from the dam failure hazard.

8.4 VULNERABILITY
The vulnerability of people, property, and critical facilities was evaluated for the combined dam failure inundation area. Appendix D shows results by jurisdiction; countywide summaries are provided below.

8.4.1 Population
Vulnerable populations are all populations downstream from dam failures that are incapable of escaping the area before floodwaters arrive. This population includes the elderly and young who may be unable to get themselves out of the inundation area. The vulnerable population also includes those who would not have adequate warning from a television, radio emergency warning system, siren, or cell phone alert. Impacts on persons and households for the combined dam failure inundation area are estimated through the Level 2 Hazus analysis. Table 8-5 summarizes the results.

Table 8-5. Estimated Dam Failure Impacts on Population
Number of Persons Displaced 207,158
Number of Residents Requiring Short-Term Shelter 14,254

8.4.2 Property
Properties closest to the dam failure inundation zone would experience the largest, most destructive surge of water. Low-lying areas are also vulnerable since they are where the dam waters would collect.

Properties in the dam failure inundation zone that are built to National Flood Insurance Program (NFIP) minimum construction standards may have some level of protection against dam failure inundation, depending on the velocity and elevation of the inundation waters. These properties also are more likely to have flood insurance. Table 8-6 summarizes the loss estimates for dam failure.

Table 8-6. Estimated Impact of a Dam Failure in the Planning Area Number of Buildings Impacted 63,936
Estimated Loss, Structures $6,795,872,395
Estimated Loss, Contents $8,126,268,419
Estimated Loss, Total $14,922,140,815
Total Loss as % of Total Replacement Value 8.3%

8.4.3 Critical Facilities
Significant facilities predicted by Hazus to be affected by the modeled dam failure include the following:
10 wastewater treatment facilities
36 hazardous material sites
1 hospital
18 fire stations or battalion headquarters
60 schools
120 road bridges
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Hazus was used to estimate the number of critical facilities affected by dam failure and the resulting percent of damage to the building and contents. Figure 8-5 compares the predicted number of affected facilities to the number of exposed facilities. Between 50 and 96 percent of exposed facilities are predicted to experience some damage, depending on the category.

Figure 8-5. Critical Facilities Exposed to and Affected by Mapped Dam Failure Inundation Area

Figure 8-6 shows the estimated damage to critical facilities for the modeled dam failure. Depending on critical facility category, the average amount of damage to structures, measured as a percentage of total value, ranges from 2.3 to 30.0 percent of total value, and average damage to contents ranges from

29.4 to 84.1 percent.

Figure 8-6. Average % of Damage to Critical Facilities Caused by Modeled Dam Failure 54 41 41 48
2 90
130
50 39
30 36
1 80
125
0 50
100
150
Communications Energy Food, Water &
Shelter
Hazardous
Material
Health & Medical Safety & Security Transportation
Number of Faciliities Exposed or Affected
Exposed Facilities
Affected Facilities

23.0 18.9

30.0 18.4

11.9 14.5

2.3 84.1

36.3 52.9

31.0 48.2 52.1

29.4 0
20 40
60 80
100
Communications Energy Food, Water &
Shelter
Hazardous
Material
Health & Medical Safety & Security Transportation
Average Damage as % of Total Value
Damage to Structure
Damage to Contents
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Typical vulnerabilities of these facilities include the following:

Transportation routes are vulnerable to dam failure inundation and have the potential to be wiped out, creating isolation issues and significant disruption to travel. Those that are most vulnerable are those that are already in poor condition and would not be able to withstand a large water surge.

Utilities such as overhead power lines, cable and phone lines in the inundation zone could also be vulnerable. If phone lines were lost, significant communication issues may occur in the planning area due to limited cell phone reception in many areas.

In addition, emergency response would be hindered due to the loss of transportation routes as well as some protective-function facilities in the safety and security category located in the inundation zone. Recovery time to restore many critical functions after an event may be lengthy.

8.4.4 Environment
The environment would be vulnerable to a number of risks in the event of dam failure. The inundation could introduce foreign elements into local waterways, resulting in destruction of downstream habitat and detrimental effects on many species of animals, especially endangered species such as the tidewater goby.

8.5 SCENARIO
An earthquake in the region could lead to liquefaction of soils around a dam, without warning during any time of the day. A human-caused incident such as a terrorist attack also could trigger a catastrophic failure of a dam that would impact the planning area. Failure of a high hazard dam in the County would likely result in losses of life, roadways, structures, and property, and exert severe impacts on the local economy. While the possibility of failure is remote, results would be devastating.

The worst-case scenario would involve failure of the Santa Felicia Dam. In addition to severe property damage and potential injuries or loss of life, loss of water from Lake Piru could lead to reduction in available water used to replenish underground basins in the County. Coupled with the ongoing drought throughout the state and already low water supply availability, this damage could lead to significant water shortages.

8.6 ISSUES
The most significant issues associated with dam failure involve properties and populations within inundation zones. Flooding as a result of a dam failure would significantly impact these areas. Warning time for dam failure plausibly would be limited. Moreover, dam failure is frequently associated with other natural hazard events such as earthquakes, landslides, or severe weather, which limits predictability of dam failure and compounds the hazard. Important issues associated with dam failure hazards are as follows:

A significant number of the structures located in the dam failure inundation zone are located outside of special flood hazard areas, meaning that they are not constructed to withstand floodwaters and are less likely to be covered by flood insurance. Even structures that have been 116
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designed with flood hazards in mind may not be able to withstand the height and velocity of flow from a dam failure event.

Addressing security concerns and the need to inform the public of the risk associated with dam failure is a challenge for public officials.

California law requires that a property’s location in a dam failure inundation be disclosed to a buyer if the seller or the seller’s agent has knowledge of the property’s location within the hazard area or if the local jurisdiction has compiled a list of parcels that are in the inundation area and has posted at the offices of the county recorder, county assessor, and county planning agency a notice that identifies the location of the list. This information is only available by request from county planning.

Dam failure inundation areas are often not considered special flood hazard areas under the National Flood Insurance Program, so flood insurance coverage in these areas is not common.

Dam infrastructure may require repair and improvement to withstand climate change impacts, such as changing in the timing and intensity of rain events.

Federally regulated dams have an adequate level of oversight and sophistication in the development of emergency action plans for public notification in the unlikely event of failure.

However, the protocol for notification of downstream residents of imminent failure needs to be tied to local emergency response planning.

In the event of a dam failure that interrupted land line phone service, significant issues with communication could occur.

Limited financial resources for dam maintenance during economic downturns result in decreased attention to dam structure operational integrity, because available funding is often directed to more urgent needs. This could increase potential for maintenance failures.

Mapping for federally regulated dams is already required and available; however, mapping for non-federally regulated dams that estimates inundation depths is needed to better assess risks associated with failure of these dams.

Although mapping is required for federally regulated dams, development downstream of dams and upgrades to older dams may have altered inundation areas; however, these inundation maps may not have been updated for significant periods of time. Encouraging property owners of dams to update EAPs and inundation maps will ensure availability of the most accurate data to assist emergency planners and local officials.

Most dam failure mapping required at federal levels requires determination of the probable maximum flood. While the probable maximum flood represents a worst-case scenario, it is generally the event with the lowest probability of occurrence. Mapping of dam failure scenarios for non-federal-regulated dams that are less extreme than the probable maximum flood, but have a higher probability of occurrence, can be valuable to emergency managers and community officials downstream of these facilities. This type of mapping can illustrate areas potentially impacted by more frequent events to support emergency response and preparedness actions.

The concept of residual risk associated with structural flood control projects should be considered in the design of capital projects and the application of land use regulations.

There may be dams located in the planning area that do not meet regulatory thresholds for jurisdiction under State of California or federal programs. 117
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9. DROUGHT

9.1 GENERAL BACKGROUND
Drought is a significant decrease in water supply relative to what is typical in a given location. It is a normal phase in the climate cycle of most regions, originating from a deficiency of precipitation over an extended period of time, usually a season or more. This leads to a water shortage for some activity, group or environmental sector. Drought can be characterized based on various impacts or measurements:

Meteorological measurements such as rainfall deficit compared to normal or expected rainfall Agricultural impacts due to reduced rainfall and water supply (e.g., crop loss, herd culling, etc.) Hydrological measurements of stream flows, groundwater, and reservoir levels relative to normal conditions
Direct and indirect socio-economic impacts on society and the economy (e.g., increased unemployment due to failure of an industry because of drought).

Drought is a normal phase in the climatic cycle of most geographical regions. If the weather pattern that causes a drought lasts a short time (a few weeks or a couple of months), the drought is considered short-term. If the weather pattern becomes entrenched and the precipitation deficits last for several months or years, the drought is considered to be long-term. It is possible for a region to experience a long-term circulation pattern that produces drought, and to have short-term changes in this long-term pattern that result in short-term wet spells. Likewise, it is possible for a long-term wet circulation pattern to be interrupted by short-term weather spells that result in short-term drought.

9.1.1 Monitoring and Categorizing Drought
National Oceanic and Atmospheric Administration Drought Indices The National Oceanic and Atmospheric Administration (NOAA) has developed several indices to measure drought impacts and severity and to map their extent and locations:

The Crop Moisture Index measures short-term drought weekly to assess impacts on agriculture.

The Palmer Z Index measures short-term drought on a monthly scale.

The Palmer Drought Severity Index is based on long-term weather patterns. The intensity of drought in a given month is dependent on current weather plus the cumulative patterns of 118
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previous months. Weather patterns can change quickly, and the Palmer Drought Severity Index can respond fairly rapidly.

The Palmer Hydrological Drought Index quantifies hydrological effects (reservoir levels, groundwater levels, etc.), which take longer to develop and last longer. This index responds more slowly to changing conditions than the Palmer Drought Index.

The Standardized Precipitation Index considers only precipitation. A value of zero indicates the median precipitation amount; the index is negative for drought and positive for wet conditions. The Standardized Precipitation Index is computed for time scales ranging from one month to 24 months.

Figure 9-1 shows examples of these indices as of mid-November 2021.

U.S. Drought Monitor
The U.S. Drought Monitor (USDM) is a map that is updated weekly to show the location and intensity of drought across the country. The USDM uses a five-category system (National Integrated Drought Information System 2021):

D0—Abnormally Dry
Short-term dryness slowing planting, growth of crops
Some lingering water deficits
Pastures or crops not fully recovered
D1—Moderate Drought
Some damage to crops, pastures
Some water shortages developing
Voluntary water-use restrictions requested
D2—Severe Drought
Crop or pasture loss likely
Water shortages common
Water restrictions imposed
D3—Extreme Drought
Major crop/pasture losses
Widespread water shortages or restrictions
D4—Exceptional Drought
Exceptional and widespread crop/pasture losses
Shortages of water creating water emergencies
The USDM categories show experts’ assessments of conditions related to drought. These experts check variables including temperature, soil moisture, water levels in streams and lakes, snow cover, and meltwater runoff. They also check whether areas are showing drought impacts such as water shortages and business interruptions. Associated statistics show what proportion of various geographic areas are in each category of dryness or drought, and how many people are affected. U.S. Drought Monitor data go back to 2000.

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Figure 9-1. Example Drought Index Maps, Current as of November 18, 2021

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9.1.2 Drought Impacts
Drought can have a widespread impact on the environment and the economy, although it typically does not result in loss of life or damage to structures, as do other natural disasters. The National Drought Mitigation Center uses three categories to describe likely drought impacts:

Economic Impacts—These impacts of drought cost people (or businesses) money. Farmers’ crops are destroyed; low water supply necessitates spending on irrigation or drilling of new wells; water-related businesses (such as sales of boats and fishing equipment) may experience reduced revenue.

Environmental Impacts—Plants and animals depend on water. When a drought occurs, their food supply can shrink, and their habitat can be damaged.

Social Impacts—Social impacts include public safety, health, conflicts between people when there is not enough water to go around, and changes in lifestyle.

The demand that society places on water systems and supplies—such as expanding populations, irrigation, and environmental needs—contributes to drought impacts. Drought can lead to difficult decisions regarding the allocation of water, as well as stringent water use restrictions, water quality problems, and inadequate water supplies for fire suppression. There are also issues such as growing conflicts between agricultural uses of surface water and in-stream uses, surface water and groundwater interrelationships, and the effects of growing water demand on uses of water.

Vulnerability of an activity to drought depends on its water demand and the water supplies available to meet the demand. The impacts of drought vary between sectors of the community in both timing and severity:

Water supply—The water supply sector encompasses urban and rural drinking water systems that are affected when a drought depletes ground water supplies due to reduced recharge from rainfall.

Agriculture and commerce—The agriculture and commerce sector includes the reduction of crop yield and livestock sizes due to insufficient water supply for crop irrigation and maintenance of ground cover for grazing.

Environment, public health, and safety—The environmental, public health, and safety sector focuses on wildfires that are both detrimental to the forest ecosystem and hazardous to the public. It also includes the impact of desiccating streams, such as the reduction of in-stream habitats for native species.

Drought generally does not affect groundwater sources as quickly as surface water supplies, but groundwater supplies generally take longer to recover. Reduced precipitation during a drought means that groundwater supplies are not replenished at a normal rate. This can lead to a reduction in groundwater levels and problems such as reduced pumping capacity or wells going dry. Droughts can affect groundwater storage as reserves are drawn down in anticipation of drought impacts. Such conjunctive use assists in drought resilience, but it can take years to replenish the water that was stored. Shallow wells are more susceptible than deep wells. Reduced replenishment of groundwater affects streams. Much of the flow in streams comes from groundwater, especially during the summer when there is less precipitation and after snowmelt ends. Reduced groundwater levels mean that even less water will enter streams when stream flows are lowest. 121
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9.1.3 Defined Drought Stages in California
During critically dry years, the California State Water Resources Control Board can mandate water entitlements on water right holders to address statewide water shortages. Table 9-1 shows the state drought management program stages mandated to water right holders.

Table 9-1. State Drought Management Program
Drought Stage State Mandated Customer Demand Reduction Rate Impacts Stage 0 or 1 <10% Normal rates
Stage 2 10 to 15% Normal rates; Drought surcharge
Stage 3 15 to 20% Normal rates; Drought surcharge
Stage 4 >20% Normal rates, Drought surcharge

9.1.4 Secondary Hazards
The secondary impact most commonly associated with drought is wildfire. A prolonged lack of precipitation dries out vegetation, which becomes increasingly susceptible to ignition as the duration of the drought extends. In addition, lack of sufficient water resources can stress trees and other vegetation, making them more vulnerable to infestation from pests, which in turn, can make them more vulnerable to ignition.

9.2 HAZARD PROFILE

9.2.1 Planning Area Water Supply and Drought Response
Water Supply Strategy
Groundwater provides about 67 percent of the locally utilized water in Ventura County (Ventura County Public Works Agency 2020). Additionally, more than 100,000 acre-feet of potable water is imported annually from the Metropolitan Water District of Southern California. The remainder of local water comes from surface and recycled water sources.

Calleguas Municipal Water District (MWD), Casitas MWD, and United Water Conservation District (UWCD) are the main water providers for much of Ventura County, allowing other jurisdictions, water districts, and private utilities to coordinate in order to ensure continual water supply necessary to maintain health, safety, and economic well being of residents, businesses, and community organizations. These three water districts have developed long-term water supply strategies for customers in Ventura County:

Calleguas MWD is active in regional water planning, conservation, watershed protection and development of reclaimed water.

Casitas MWD is actively engaged in managing existing local water resources and planning for water security.

UWCD offers unique approaches to regional watershed management, responsibly conserving and enhancing resources, and protecting the environment while meeting water demands. 122
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Water supply strategies recognize that drought year shortfalls could be significant. Dry years could result in cutbacks of up to 20 percent, but 10 to 15 percent is the more consistent standard. Calleguas MWD and Casitas MWD maintain Urban Water Management Plans that outline the following:

Water source reliability over a 20-year timeframe
Water shortage contingency plans
Drought risk assessment
While the three districts are the primary water service agencies in the County, they are not the only option for residents and businesses. Some water purveyors and residents in the County have wells on their property. The last available report shows 4,016 active water wells in Ventura County (Ventura County Watershed Protection District 2015).

Water Supply Infrastructure
Calleguas MWD receives water from the Metropolitan Water District of Southern California brought south by the State Water Project. Calleguas MWD built a pipeline network to bring water into Ventura County, including the Santa Susana Tunnel that connects to Metropolitan’s system in Los Angeles County. Lake Bard reservoir (Figure 9-2) was built to store water for peak summer and emergency demand. Las Posas Aquifer Storage and Recovery Well Field is also used to store water that is not immediately distributed to purveyors. The stored water is treated before entering the Calleguas MWD system.

Figure 9-2. Calleguas MWD’s Lake Bard Reservoir
Source: Calleguas MWD
Only 17 percent of the Casitas MWD’s water comes from groundwater; 83 percent comes from Lake Casitas (Figure 9-3). The lake fills primarily from the natural flow of local creeks and the Robles Diversion. The diversion is a large canal that brings water about 7 miles from the Ventura River. This diversion accounts for about one-third of the lake’s water each year. 123
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Figure 9-3. Casitas MWSD’s Lake Casitas
Source: Casitas MWD
UWCD built the Freeman Diversion (Figure 9-4) to redirect water from the Santa Clara River to spreading basins for groundwater recharge. The Santa Felicia Dam and Lake Piru Reservoir recharge downstream groundwater basins through conservation releases when downstream basins are at their seasonal lows. The Pumping Trough Pipeline delivers surface water from the Santa Clara River and deep wells to agricultural users.

Figure 9-4. UWCD’s Freeman Diversion
Source: The Fillmore Gazette
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Defined Drought Levels
Ventura County does not have a defined drought level. County and regional drought response is determined case by case, and response priorities are typically based on imminence of potential water shortages. Drought stages defined by the California State Water Resources Control Board (see Table 9-1) can serve as a reference for County and stakeholder agencies when determining need for response.

Calleguas MWD adopted a resolution on August 18, 2021, declaring a Stage 2 water shortage and calling for enhanced water use efficiency efforts. For Casitas MWD, drought conditions remain in effect since the Board of Directors declared Stage 3 water supply conditions on April 27, 2016. The primary source of water for UWCD is managed by the Fox Canyon Groundwater Management Authority, which sets allocations for each water pumper and imposes water shortage contingency plan levels. Significant penalties are levied on purveyors if they take delivery of water in excess of their allocations.

9.2.2 Past Events
California Department of Water Resources hydrologic data from the early 1900s shows multi-year droughts from 1912 to 1913, 1918 to 1920, 1922 to 1924, and 1929 to 1934, 1959 to 1961 (California Department of Water Resources 2003). The following sections describe more-recent prolonged droughts that have impacted the planning area.
2020 Ongoing Drought
The 2020-21 water year was the second driest year on record, with a near record low storage in California’s largest reservoirs. August 2021 was the driest and hottest August on record since reporting began. The executive proclamation of drought emergency includes Ventura County. Executive orders include water conservation and a ban on wasteful water practices. 2012 to 2017 Drought
The period from 2012 to 2014 ranked as the driest three consecutive years for statewide precipitation.

Calendar year 2014 set new records for statewide average temperatures and for record-low water allocations from the State Water Project and the federal Central Valley Project. Calendar year 2013 set minimum annual precipitation records for many communities. Detailed executive orders and regulations addressed water conservation and management. The statewide drought emergency was lifted in April 2017.
2007 to 2009 Drought
The state proclaimed a statewide drought emergency on June 4, 2008 after spring 2008 was the driest spring on record, with low snowmelt runoff. On February 27, 2009, the state proclaimed a state of emergency for the entire state as severe drought continued. The largest court-ordered water restriction in state history (at the time) was imposed.
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1987 to 1992 Drought
California received precipitation well below average levels for four consecutive years. While the Central Coast was most affected, Southern California counties were also affected. In 1991, the State Water Project sharply decreased deliveries to water suppliers. By February 1991, all 58 counties in California were experiencing drought. Urban areas as well as agricultural areas were impacted. 1976 to 1977 Drought
California had a severe drought due to lack of rainfall during the winters of 1976 and 1977. 1977 was the driest period on record in California at that time, with the previous winter recorded as the fourth driest in California’s hydrological history at that time. The cumulative impact led to widespread water shortages and severe water conservation measures statewide. Over $2.6 billion in crop damage was recorded in 31 counties. FEMA declared a drought emergency (Declaration 3023-EM) on January 20, 1977.

9.2.3 Location
Drought is a regional phenomenon that has the potential to impact the entire planning area. A drought affects all aspects of the environment and the community simultaneously and has the potential to directly or indirectly impact every person in the planning area as well as adversely affect the local economy.

9.2.4 Frequency
Drought has a high probability of occurrence in the planning area. From January 2000 to November 2021, some part of Ventura County experienced a USDM rating of D1 or higher in 604 out of 1,142 weeks— more than half the time (see Figure 9-5). The planning area has also been included in USDA drought disaster declarations in eight of the past nine years (U.S. Department of Agriculture 2021a).

Historical drought data for the planning area indicate there have been four significant multi-year droughts in the last 45 years (1976 to 2021), amounting to a severe drought every 10 to 11 years on average.

Figure 9-5. Percent of Ventura County Affected by Each USDM Rating, 2000 – 2021 126
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Source: U.S. Drought Monitor, 2021

9.2.5 Severity
The severity of any given drought depends on the degree of moisture deficiency, the duration, and the size and location of the affected area. The longer the duration of the drought and the larger the area impacted, the more severe the potential impacts.

U.S. Drought Monitor Ratings
Ventura County has a history of severe droughts. As shown in Figure 9-5, at least part of the county has experienced extreme (D3) or exceptional (D4) droughts more than once since 2000.

Drought Impact Reporter
The National Drought Mitigation Center developed the Drought Impact Reporter in response to the need for a national drought impact database for the United States. Information comes from a variety of sources: on-line, drought-related news stories and scientific publications, members of the public who visit the website and submit a drought-related impact for their region, members of the media, and staff of government agencies. The database is being populated beginning with the most recent impacts and working backward in time.

The Drought Impact Reporter indicates 1,316 impacts from drought that specifically affected Ventura County from January 2011 through November 15, 2021 (National Drought Mitigation Center 2021).

Most (70.2 percent) are based on media reports. The rest are from the Community Collaborative Rain, Hail & Snow Network. The following are the reported numbers of impacts by category (some incidents are assigned to more than one impact category):

Agriculture—323
Business and Industry—107
Energy—15
Fire—195
Plants and Wildlife—361
Relief, Response, and Restrictions—601
Society and Public Health—340
Tourism and Recreation—137
Water Supply and Quality—769

9.2.6 Warning Time
Predicting drought depends on the ability to forecast precipitation and temperature. Scientists at this time do not know how to predict drought more than a month in advance for most locations. Only generalized warning can take place due to the numerous variables that scientists have not pieced together well enough to make accurate and precise predictions. 127
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Determination of when drought begins is based on impacts on water users and assessments of available water supply, including water stored in reservoirs or groundwater basins. Different water agencies have different criteria for defining drought. Some issue drought watch or drought warning announcements.

9.3 EXPOSURE
All people, property and environments in the planning area would be exposed to some degree to the impacts of moderate to extreme drought conditions.

9.4 VULNERABILITY

9.4.1 Population
The entire population of the County is vulnerable to drought events. Drought can affect people’s health and safety, including health problems related to low water flows, poor water quality, or dust. Droughts can also lead to loss of human life (National Centers for Environmental Information 2021). Other possible impacts include recreational risks; effects on air quality; diminished living conditions related to energy, air quality, and hygiene; compromised food and nutrition; and increased incidence of illness and disease (Centers for Disease Control and Prevention 2020).

9.4.2 Property
No structures will be directly affected by drought conditions, though some structures may become vulnerable to wildfires, which are more likely following years of drought. Droughts can have significant impacts on other types of property such as landscaped areas and economically important natural resources. Drought causes the most significant economic impacts on industries that use water or depend on water for their business, most notably agriculture and related sectors (forestry, fisheries, and waterborne activities), power plants, and oil refineries. In addition to losses in yields in crop and livestock production, drought is associated with increased insect infestations, plant diseases, and wind erosion. Drought can lead to other losses because so many sectors are affected - losses that include reduced income for farmers and reduced business for retailers and others who provide goods and services to farmers. This leads to unemployment, increased credit risk for financial institutions, capital shortfalls, and loss of tax revenue. Prices for food, energy, and other products may also increase as supplies decrease.

9.4.3 Critical Facilities
Critical facilities as defined for this plan will continue to be operational during a drought. Critical facility features such as landscaping may not be maintained due to limited water resources, but the risk to critical facility core functions is low.
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9.4.4 Environment
Groundwater and Streams
Drought generally does not affect groundwater sources as quickly as surface water supplies, but groundwater supplies generally take longer to recover. Reduced precipitation during a drought means that groundwater supplies are not replenished at a normal rate. This can lead to a reduction in groundwater levels and problems such as reduced pumping capacity or wells going dry. Shallow wells are more susceptible than deep wells. Reduced replenishment of groundwater affects streams. Much of the flow in streams comes from groundwater, especially during the summer when there is less precipitation and after snowmelt ends. Reduced groundwater levels mean that even less water will enter streams when stream flows are lowest. Where stream flows are reduced, development that relies on surface water may seek to establish new groundwater wells, which could further increase groundwater depletion.

Other Potential Losses
Environmental losses from drought are associated with damage to plants, animals, wildlife habitat, and air and water quality; forest and range fires; degradation of landscape quality; loss of biodiversity; and soil erosion. Some of the effects are short-term and conditions quickly return to normal following the end of the drought. Other environmental effects linger for some time or may even become permanent.

Although environmental losses are difficult to quantify, growing public awareness and concern for environmental quality has forced public officials to focus greater attention and resources on these effects. The following are potential impacts of drought:

Wildlife habitat may be degraded through the loss of wetlands, lakes and vegetation. The degradation of landscape quality, including increased soil erosion, may lead to a more permanent loss of biological productivity.

Drought conditions greatly increase the likelihood of wildfires, a major threat to agricultural resources.

Water shortages and severe drought conditions would have a significant impact on Native American tribes’ way of life in fishing and farming subsistence.

Scenic resources in the County are vulnerable to the increased likelihood of wildfires associated with droughts.

Drying up of recreational reservoirs could reduce tourist values.

Any shortage of water supply can have significant economic impacts.

9.5 SCENARIO
A multi-year drought that impacts the entire west or the State of California, similar to the 2012 to 2017 drought, is the worst-case scenario for the planning area. The 2012-2017 drought and the wildfires and floods that followed it caused extensive damage to natural systems. If another severe multi-year drought occurs before these systems have a chance to recover, it could exacerbate the stress already placed on existing planning area water resources.
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9.6 ISSUES
The planning team has identified the following drought-related issues:

Alternative water supplies need to be identified and developed, as well as alternative strategies to allocate and distribute existing water sources.

Alternative techniques (groundwater recharge, water recycle, local capture and reuse, desalination, and transfer) could stabilize and offset snowpack water supply shortfalls that may affect imported water.

There is a need for local or regional drought-level indicators to correspond with water conservation measures.

Drought in the county could increase and expand fire-prone areas and adversely affect the agricultural economy.

If tension increases over surface water, additional draw-downs to groundwater supplies may occur.

More studies need to be done regarding overall county water usage and how it relates to the economy to prepare for a worst-case scenario drought.

Planning must address the degree of future development in drought-prone areas.

Drought frequencies and durations may increase due to climate change.

Water conservation should be promoted to a greater extent, even during non-drought periods.

Frequent or prolonged droughts may limit the County’s and residents’ ability to successfully recover from or prepare for more occurrences.

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10. EARTHQUAKE

10.1 GENERAL BACKGROUND
An earthquake is the vibration of the earth’s surface following a release of energy in the earth’s crust.

This energy can be generated by a sudden dislocation of the crust or by a volcanic eruption. Most destructive quakes are caused by dislocations of the crust. The crust may first bend and then, when the stress exceeds the strength of the rocks, break and snap to a new position. In the process of breaking, vibrations called “seismic waves” are generated. These waves travel outward from the source of the earthquake at varying speeds.

10.1.1 Earthquake Location
The location of an earthquake is commonly described by its focal depth and the geographic position of its epicenter. The focal depth of an earthquake is the depth from the Earth’s surface to the region where an earthquake’s energy originates (the focus or hypocenter). The epicenter of an earthquake is the point on the Earth’s surface directly above the hypocenter.

10.1.2 Earthquake Geology
Tectonic Plates
The Earth’s crust, which is the rigid outermost shell of the planet, is broken into seven or eight major tectonic plates (depending on how they are defined) and many minor plates. Where the plates meet, they move in one of three ways along their mutual boundary: convergent (two plates moving together), divergent (two plates moving apart), or transform (two plates moving parallel to one another).

Earthquakes, volcanic activity, mountain-building, and oceanic trench formation occur along these plate boundaries. Subduction is a geological process that takes place at convergent boundaries of tectonic plate, in which one plate moves under another. Regions where this process occurs are known as subduction zones, and they have the potential to generate highly damaging earthquakes.

California is seismically active because of movement of the North American Plate, east of the San Andreas Fault, and the Pacific Plate to the west, which includes the state’s coastal communities. The transform (parallel) movement of these tectonic plates against one another creates stresses that build as the rocks are gradually deformed. The rock deformation, or strain, is stored in the rocks as elastic strain energy. When the strength of the rock is exceeded, rupture occurs along a fault. The rocks on opposite sides of the fault slide past each other as they spring back into a relaxed position. The strain energy is released partly as heat and partly as elastic waves called seismic waves. The passage of these seismic waves produces the ground shaking in earthquakes. 132
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Faults
Geologists have found that earthquakes reoccur along faults, which are zones of weakness in the earth’s crust. When a fault experiences an earthquake, there is no guarantee that all the stress has been relieved. Another earthquake can still occur. In fact, relieving stress along one part of a fault may increase it in another part.

Faults are more likely to have future earthquakes on them if they have more rapid rates of movement, have had recent earthquakes along them, experience greater total displacements, and are aligned so that movement can relieve the accumulating tectonic stresses. Geologists classify faults by their relative hazards. “Active” faults, which represent the highest hazard, are those that have ruptured to the ground surface during the Holocene period (about the last 11,000 years). “Potentially active” faults are those that displaced layers of rock from the Quaternary period (the last 1,800,000 years) (California Department of Conservation 2019a).

Determining if a fault is “active” or “potentially active” depends on geologic evidence, which may not be available for every fault. The majority of the seismic hazards are on well-known active faults. However, inactive faults, where no displacements have been recorded, also have the potential to reactivate or experience displacement along a branch sometime in the future. An example of a fault zone that has been reactivated is the Foothills Fault Zone. The zone was considered inactive until evidence of an earthquake (approximately 1.6 million years ago) was found near Spenceville, California. Then, in 1975, an earthquake occurred on another branch of the zone near Oroville, California (now known as the Cleveland Hills Fault). The State Division of Mines and Geology indicates that increased earthquake activity throughout California may cause tectonic movement along currently inactive fault systems.

10.1.3 Earthquake-Related Hazards
According to the U.S. Geological Survey (USGS) Earthquake Hazards Program, an earthquake hazard is anything associated with an earthquake that may affect resident’s normal activities. This includes the following:

Surface Faulting—Displacement that reaches the earth’s surface during slip along a fault.

Commonly occurs with shallow earthquakes, those with an epicenter less than 20 kilometers.

Ground Motion (shaking)—The movement of the earth’s surface from earthquakes or explosions. Ground motion or shaking is produced by waves that are generated by sudden slip on a fault or sudden pressure at the explosive source and travel through the earth and along its surface.

Landslide—A movement of surface material down a slope.

Liquefaction—A process by which water-saturated sediment temporarily loses strength and acts as a fluid. Earthquake shaking can cause this effect.

Tectonic Deformation—A change in the original shape of a material due to stress and strain.

Tsunami—A sea wave of local or distant origin that results from large-scale seafloor displacements associated with large earthquakes, major submarine slides, or violent underwater volcanic eruptions.
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10.1.4 Earthquake Classifications
Earthquakes are typically classified in one of two ways: By the amount of energy released, measured as magnitude; or by the impact on people and structures, measured as intensity.

Magnitude
An earthquake’s magnitude is a measure of energy released at the earthquake source. It is commonly expressed by ratings on the moment magnitude scale (MW). Most people have heard about the Richter scale, but the moment magnitude scale is a more accurate measure of magnitude (U.S. Geological Survey 2021c). It is based on the product of the distance a fault moved and the force required to move it. The scale is as follows:

Great— MW> 8
Major— MW = 7.0 – 7.9
Strong— MW= 6.0 – 6.9
Moderate— MW= 5.0 – 5.9
Light— MW = 4.0 – 4.9
Minor— MW = 3.0 – 3.9
Micro— MW < 3
Intensity
The most commonly used intensity scale is the modified Mercalli intensity scale. Table 10-1 lists perceived shaking and damage potential for structures using this scale. The scale is represented visually using shake maps, which show the expected ground shaking produced by an earthquake with a specified magnitude and epicenter. An earthquake has only one magnitude and one epicenter, but it produces a range of ground shaking at sites throughout the region, depending on the distance from the earthquake, the rock and soil conditions at sites, and variations in the propagation of seismic waves from the earthquake due to complexities in the structure of the earth’s crust. A shake map shows the variation of ground shaking in a region immediately following significant earthquakes (for technical information about shake maps see (U.S. Geological Survey 2021e)).

Table 10-1. Mercalli Scale and Peak Ground Acceleration Comparison Modified Potential Structure Damage Estimated PGAa
Mercalli Scale Perceived Shaking Resistant BuildingsVulnerable Buildings (%g) I Not Felt None None <0.17%
II-III Weak None None 0.17% - 1.4%
IV Light None None 1.4% - 3.9%
V Moderate Very Light Light 3.9% - 9.2%
VI Strong Light Moderate 9.2% - 18%
VII Very Strong Moderate Moderate/Heavy 18% - 34%
VIII Severe Moderate/Heavy Heavy 34% - 65%
IX Violent Heavy Very Heavy 65% - 124%
X – XII Extreme Very Heavy Very Heavy >124%
a. PGA = peak ground acceleration. Measured in percent of g, where g is the acceleration of gravity Sources: (U.S. Geological Survey 2021b); (U.S. Geological Survey 2011) 134
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10.1.5 Ground Motion
Earthquake hazard assessment is based on expected ground motion. During an earthquake when the ground is shaking, it also experiences acceleration. The peak acceleration is the largest increase in velocity recorded by a particular station during an earthquake. Estimates are developed of the annual probability that certain ground motion accelerations will be exceeded; the annual probabilities can then be summed over a time period of interest.

The most commonly mapped ground motion parameters are horizontal and vertical peak ground accelerations (PGA) for a given soil type. PGA is a measure of how hard the earth shakes, or accelerates, in a given geographic area. Instruments called accelerographs record levels of ground motion due to earthquakes at stations throughout a region. PGA is measured in g (the acceleration due to gravity) or expressed as a percent acceleration force of gravity (%g). These readings are recorded by state and federal agencies that monitor and predict seismic activity.

Maps of PGA values form the basis of seismic zone maps that are included in building codes such as the International Building Code. Building codes that include seismic provisions specify the horizontal force due to lateral acceleration that a building should be able to withstand during an earthquake. PGA values are directly related to these lateral forces that could damage “short period structures” (e.g. single-family dwellings). Longer period response components determine the lateral forces that damage larger structures with longer natural periods (apartment buildings, factories, high-rises, bridges).

Table 10-1 lists damage potential and perceived shaking by PGA factors, compared to the Mercalli scale.

10.1.6 Earthquake Mapping Programs
ShakeMaps
The USGS Earthquake Hazards Program produces maps called ShakeMaps that map ground motion and shaking intensity following significant earthquakes. ShakeMaps focus on the ground shaking caused by the earthquake, rather than on characteristics of the earthquake source, such as magnitude and epicenter. An earthquake has only one magnitude and one epicenter, but it produces a range of ground shaking at sites throughout the region, depending on the distance from the earthquake, the rock and soil conditions at sites, and variations in the propagation of seismic waves from the earthquake due to complexities in the structure of the earth’s crust.

A ShakeMap shows the extent and variation of ground shaking immediately across the surrounding region following significant earthquakes. Such mapping is derived from peak ground motion amplitudes recorded on seismic sensors, with interpolation where data are lacking based on estimated amplitudes.

Color-coded instrumental intensity maps are derived from empirical relations between peak ground motions and Modified Mercalli intensity. In addition to the maps of recorded events, the USGS creates the following:

Scenario ShakeMaps of hypothetical earthquakes of an assumed magnitude on known faults Probabilistic ShakeMaps, based on predicted shaking from all possible earthquakes over a 10,000-year period. In a probabilistic map, information from millions of scenario maps are combined to make a forecast for the future. The maps indicate the ground motion at any given 135
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point that has a given probability of being exceeded in a given timeframe, such as a 100-year (1-percent-annual chance) event.

National Seismic Hazard Map
National maps of earthquake shaking hazards provide information for creating and updating seismic design requirements for building codes, insurance rate structures, earthquake loss studies, retrofit priorities and land use planning. After thorough review of the studies, professional organizations of engineers update the seismic-risk maps and seismic design requirements contained in building codes (Brown, et al. 1998). The USGS updated the National Seismic Hazard Maps in 2018. New seismic, geologic, and geodetic information on earthquake rates and associated ground shaking were incorporated into these revised maps. The 2018 map, shown in Figure 10-1, represents the best available data as determined by the USGS.

Figure 10-1. Peak Acceleration (%g) with 2% Probability of Exceedance in 50 Years Source: USGS, 2018
Alquist-Priolo Zone Maps
Alquist-Priolo zone maps generated by the State of California show regulatory zones for potential surface fault rupture where fault lines intersect with future development and populated areas. The purpose of these maps is to assist in geologic investigation before construction to ensure that new structures are not located on an active fault. Alquist-Priolo maps were referenced, but not specifically used, in the assessment of risk for this plan. They are available online at:
http://maps.conservation.ca.gov/cgs/informationwarehouse/index.html?map=regulatorymaps. 136
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10.1.7 Liquefaction and Soil Types
Soil liquefaction occurs when water-saturated sands, silts or gravelly soils are shaken so violently that the individual grains lose contact with one another and float freely in the water, making the ground like a pudding. Building and road foundations lose load-bearing strength and may sink into what was previously solid ground. Unless properly secured, hazardous materials can be released, causing damage to the environment and people.

A program called the National Earthquake Hazard Reduction Program (NEHRP) creates maps based on soil characteristics to help identify locations subject to liquefaction. NEHRP soil types define the locations that will be significantly impacted by an earthquake. Table 10-2 summarizes NEHRP soil classifications. NEHRP Soils B and C typically can sustain ground shaking without much effect, dependent on the earthquake magnitude. The areas that are commonly most affected by ground shaking have NEHRP Soils D, E and F (Southern California Earthquake Center 2018). In general, these areas are also most susceptible to liquefaction. The areas that are most commonly affected by ground shaking have NEHRP Soils D, E and F.

Table 10-2. NEHRP Soil Classification System
NEHRP Soil
Type Description
Mean Shear Velocity to
30 m (m/s)
A Hard Rock 1,500
B Firm to Hard Rock 760-1,500
C Dense Soil/Soft Rock 360-760
D Stiff Soil 180-360
E Soft Clays < 180
F Special Study Soils (liquefiable soils, sensitive clays, organic soils, soft clays >36 m thick)

10.1.8 Secondary Hazards
Earthquakes can cause disastrous landslides. River valleys are vulnerable to slope failure, often as a result of loss of cohesion in clay-rich soils. Earthen dams and levees are highly susceptible to seismic events, and the impacts of their eventual failures can be considered secondary risk exposure to earthquakes. Depending on the location, earthquakes can also trigger tsunamis. Additionally, fires can result from gas lines or power lines that are broken or downed during the earthquake. It may be difficult to control a fire, particularly if the water lines feeding fire hydrants are also broken.

10.2 HAZARD PROFILE

10.2.1 Past Events
Although no large (M 5.0>) earthquakes have occurred recently within Ventura County’s boundaries, a number of relatively large earthquakes in other areas have caused damage within the county. These earthquakes occurred in 1925 (Santa Barbara), 1927 (Point Arguello), 1933 (Long Beach), 1941 (Santa Barbara), 1952 (Tehachapi), 1971 (San Fernando), and 1994 (Northridge). Additionally, damaging earthquakes occurred in the County in 1950 (north of Ojai), 1957 (Hueneme), 1963 (Camarillo), and 1973 (Point Mugu). The three most recent events are as follows (Ventura County 2015):
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San Fernando, M 6.5, February 9, 1971—This event was caused by oblique-slip reverse faulting in the San Fernando fault zone. The earthquake caused the destruction of freeway interchanges, houses, and buildings and severe damage to three hospitals in the San Fernando Valley. The earthquake claimed 65 lives. Although the epicenter was within 25 miles of Ventura County, damage sustained within the County was minor.

Point Mugu, M 5.3, February 21, 1973—The Point Mugu earthquake was responsible for at least five injuries and more than $1 million damage in the Point Mugu–Oxnard area, though damage was confined mainly to the vicinity of the epicenter. Large boulders fell down onto State Route 1 at Point Mugu, partially blocking the road. More than 7,000 customers lost electricity for several hours. Most reported damage was to windows, ceilings, plaster, chimneys, and shelved goods, though structural damage and broken pipes were also reported. Although much less powerful than the San Fernando earthquake of 1971, the Point Mugu earthquake was similar in focal mechanism.

Northridge, M 6.7, January 17, 1994—This blind thrust earthquake occurred along the Northridge thrust fault. It was the strongest earthquake instrumentally recorded in an urban setting in North America and caused parking structures, apartments, office buildings, and sections of freeways to collapse. Approximately 25,000 dwellings were rendered uninhabitable.

Total damage exceeded $44 billion. The incident resulted in 51 deaths.

Table 10-3 lists recent earthquakes with a magnitude of 5.0 or greater within a 100-mile radius of Ventura County.

Table 10-3. Recent Earthquakes Magnitude 5.0 or Larger Within 100-mile Radius of Planning Area Date Magnitude Epicenter Location
April 5, 2018 5.3 29km SW of Santa Cruz Island
March 29, 2014 5.1 2km NW of Brea Springs
July 29, 2008 5.4 5km S of Chino Hills, California
Source: USGS

10.2.2 Location
Fault Locations
As in most of southern and coastal California, the potential for earthquake damage exists throughout Ventura County because of the number of active faults within and near the county. These faults are shown on the California Geological Society Fault Activity Map of California. Descriptions of the active faults are provided below. The locations of the active and potentially active faults are shown on Figure 10-2.

Significant faults are as follows (Ventura County 2015):

Malibu Coast fault system—The Malibu Coast fault system includes the Malibu Coast, Santa Monica, and Hollywood faults. The system begins in the Hollywood area, extends along the southern base of the Santa Monica Mountains, and passes offshore a few miles west of Point Dume. The 1973 Point Mugu earthquake, described in the previous section, is believed to have originated on this fault system.
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Figure 10-2. Local Fault Locations
Source: (U.S. Geolgoical Survey 2021a)
Oak Ridge fault system—The Oak Ridge fault system is a steep (65 degrees) southerly dipping reverse fault that extends from the Santa Susana Mountains westward along the southerly side of the Santa Clara River Valley and into the Oxnard Plain. The system is more than 50 miles long on the mainland and may extend an equal or greater distance offshore.

Several recorded earthquake epicenters on land and offshore may have been associated with the Oak Ridge fault system. Portions of the system are zoned by the state as active.

Pine Mountain thrust fault and Big Pine fault—These two large faults occur in the mountainous portion of Ventura County north of the Santa Ynez fault; the faults are located 9 and 16 miles north of the City of Ojai, respectively. The Pine Mountain thrust fault is reported to have ruptured the ground surface for a distance of 30 miles along its length during the northern Ventura County earthquakes of November 1852.

San Andreas fault—San Andreas is the longest and most significant fault in California.

Because of clearly established historical earthquake activity, this fault has been designated as active by the State of California. The last major earthquake on this fault near Ventura County was the Fort Tejon earthquake of 1857, which was estimated at M 8.0 and would have caused considerable damage if there had been structures in the southern part of the county. There is a 59 percent chance that an M 6.7 quake or larger will occur on this fault within the next 30 years. 139
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San Cayetano–Red Mountain–Santa Susana fault system—This fault system consists of a major series of north-dipping reverse faults that extend over 150 miles from Santa Barbara County into Los Angeles County. Within this system, the San Cayetano fault is the greatest hazard to Ventura County; it is a major, north-dipping reverse fault that extends for 25 miles along the northern portion of the Ventura Basin. The San Fernando earthquake of 1971, described in the previous section, was caused by activity along this fault.

Simi–Santa Rosa fault system—This fault system extends from the Santa Susana Mountains westward along the northern margin of the Simi and Tierra Rejada valleys and along the southern slope and crest of the Las Posas Hills to their westerly termination.

Ventura-Pitas Point fault—The western half of this fault is known as the Pitas Point fault, and the eastern half is known as the Ventura fault. The Pitas Point fault extends offshore into the Pacific Ocean and is roughly 14 miles long. The Ventura fault extends into the communities of Ventura and Sea Cliff and runs roughly parallel to portions of U.S. 101 and State Route 126.

The fault is roughly 12 miles long. The Ventura-Pitas Point fault is a left-reverse fault.

NEHRP Soil Type and Liquefaction Mapping
Figure 10-3 shows NEHRP soil classifications in Ventura County. Figure 10-4 shows areas in that have moderate, high or very high susceptibility to liquefaction.

10.2.3 Frequency and Severity
The California Department of Conservation probabilistic ground shaking maps, based on current information about fault zones, show the PGA that has a certain probability of being exceeded in a 50- year period. Figure 10-5 shows the expected peak horizontal ground accelerations for a probability of 10 percent. Ventura County is in a high-risk area, with a peak PGA exceeding 60 percent of gravity near the northern border of the County (California Department of Conservation 2019b). Ongoing field and laboratory studies suggest the likely maximum magnitudes and recurrence intervals for the major local faults shown in Table 10-4.

Table 10-4. Likely Maximum Magnitudes and Recurrence Intervals Fault Likely Maximum Magnitude Recurrence Interval
Malibu Coast fault system M 6.7 2,908 years
Oak Ridge fault system M 6.9 299 years
Red Mountain fault system M 6.8 507 years
San Andreas fault M 8.0 300 years
San Cayetano fault system M 6.8 150 years
Santa Susana fault system M 6.6 138 years
Simi–Santa Rosa fault system M 6.7 933 years
Ventura-Pitas Point fault system M 6.9 not available
Source: (U.S. Geolgoical Survey 2021a)
140
Fillmore
Moorpark
Simi Valley
Santa Paula
Oxnard
Ojai
Port
Hueneme
Camarillo
San
Buenaventura
Thousand Oaks
11833
34 118126
150
1 1
23 126
23 33
33 34
1 150
232
33 23
101
Figure 10-3. NEHRP Soil Class
Data Sources: Ventura Co.,
CGS, Esri
C (Dense soil/soft rock)
D (Stiff soil)
E (Soft clay)
Water
County Boundary
Cities
Major Roads
0 6 3 Miles
141
Fillmore
Moorpark
Simi Valley
Santa Paula
Oxnard
Ojai
Port
Hueneme
Camarillo
San
Buenaventura
Thousand Oaks
Lake Piru
Lake
Casitas
11833
34 118126
150
1 1
23 126
23 33
33 34
1 150
232
33 23
101
Figure 10-4. Liquefaction Zones
Data Sources: Ventura Co.,
CGS, Esri
Liquefaction Zones
County Boundary
Cities
Major Roads
0 6 3 Miles
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Ventura County Multi-Jurisdictional Hazard Mitigation Plan 10-12
Figure 10-5. Peak Ground Acceleration (%g) with 10% Probability of Exceedance in 50 Years

10.2.4 Warning Time
There is no current reliable way to predict the day or month that an earthquake will occur at any given location. Research is being done with warning systems that detect the lower energy compressional waves (P waves) that precede the secondary waves (S waves) experienced as an earthquake.

Earthquake early warning systems may provide a few seconds’ or a few minutes’ notice that a major earthquake is about to occur. The warning time is very short, but it could allow for someone to get under a desk, pause hazardous or high-risk work, or initiate protective automated systems in structures or critical infrastructure.
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New technology is being developed for early warnings. For example, MyShake is a global smartphone seismic network for early warning that can keep users informed about earthquakes. It monitors for earthquakes using data from smartphone sensors. More information about the MyShake technology and the USGS ShakeAlertproject is available online at https://myshake.berkeley.edu/about-us.html.

10.3 EXPOSURE

10.3.1 Population
The entire population of the planning area (843,843) is potentially exposed to direct damage from earthquakes or indirect impacts such as business interruption, road closures, and loss of function of utilities. There are estimated to be 588,376 people in the planning area living on NEHRP D or E soils, which make buildings more susceptible to damage from earthquakes. This is about 70 percent of the total population.

10.3.2 Property
According to County Assessor records, there are 262,657 buildings in the planning area. Most of the buildings (86 percent) are residential. All buildings are considered to be exposed to the earthquake hazard. There are estimated to be 178,000 buildings in the planning area (68 percent of the total) on NEHRP D or E soils, which make buildings more susceptible to damage from earthquakes. Figure 10-6 shows the Hazus-defined occupancy class of all buildings on these soil types.

Figure 10-6. Building Count by Occupancy Class on NEHRP D or E soils Residential
149,797
84%
Commercial
11,705
7%
Industrial
3,686
2%
Agriculture
7,180
4%
Religion
967
1%
Government
2,269
1%
Education
2,375
1%
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10.3.3 Critical Facilities
Since the entire planning area has exposure to the earthquake hazard, all critical facilities components are considered to be exposed. The breakdown of the numbers and types of facilities is presented in Table 4-4.

Critical facilities constructed on NEHRP Type D and E soils are particularly at risk from seismic events.

Figure 10-7 shows the exposure of critical facilities built on these soils in the planning area, by type of facility. The total count of critical facilities on NEHRP Type D and E soils (1,150) represents 74 percent of the planning area total of 1,588. A breakdown by municipality is provided in Appendix D.

Figure 10-7. Critical Facilities on NEHRP D and E Soils

10.3.4 Environment
The entire planning area is exposed to the earthquake hazard, including all natural resources, habitat, and wildlife.

10.4 VULNERABILITY
Earthquake vulnerability data for the risk assessment was generated using a Hazus Level 2 (user- defined) analysis for the for the events listed in Table 10-5. The analysis results are summarized in the sections below. Detailed information, broken down by municipality, can be found in Appendix D.

10.4.1 Population
Hazus estimated impacts on persons and households in the planning area for the evaluated earthquake scenarios as summarized in Table 10-6.
151
74 127
79 7
281
452
0 100
200
300
400
500Number of Facilties in Hazard Area
Communication
Energy
Food, Water, Shelter
Hazardous Materials
Medical and Health
Safety and Security
Transportation

60.4%

66.7%

60.5%

84.9%

70.0%71.9%

86.4%
0%
20%
40%
60%
80%
100%Facilties in Hazard Area as % of Planning Area Total Communication
Energy
Food, Water, Shelter
Hazardous Materials
Medical and Health
Safety and Security
Transportation
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Table 10-5. Earthquakes Modeled for Risk Assessment
Event Magnitude Focal Depth Epicenter Location PGA
100-Year Probabilistic N/A N/A N/A Figure 10-8
Oak Ridge Scenario 7.16 8.0 miles 34.314°N 118.960°W Figure 10-9 San Cayetano Scenario 7.16 6.3 miles 34.539°N 118.953°W Figure 10-10 S San Andreas Scenario 8.03 4.1 miles 38.399°N 123.110°W Figure 10-11 Ventura-Pitas Point Scenario7.12 6.2 miles 34.322°N 119.281°W Figure 10-12 Table 10-6. Estimated Earthquake Impact on Persons
Displaced Households Persons Requiring Short-Term Shelter Scenario Number % of Total Number % of Total
100-Year Probabilistic 205 0.07% 147 0.02%
Oak Ridge Scenario 160 0.06% 127 0.02%
San Cayetano Scenario 14 0.01% 11 0.00%
S San Andreas Scenario 0 0% 0 0%
Ventura-Pitas Point Scenario 112 0.04% 79 0.01%

10.4.2 Property
Loss Potential
Table 10-7 summarizes Hazus estimates of earthquake damage in the planning area for the evaluated scenarios. The debris estimate includes only structural debris; it does not include additional debris that may accumulate, such as from trees. These estimates do not include losses that would occur from any local tsunamis or fires stemming from an earthquake.

Table 10-7. Estimated Impact of Earthquake Scenario Events in the Planning Area Structure Debris Structure + Contents Damage
Earthquake Scenario Event x 1,000 Tons Truckloads Value % of Total Value 100-Year Probabilistic Earthquake 503.31 20,132 $7,983,590,943 4.4% Oak Ridge Scenario 3,418.21 136,728 $21,516,138,914 11.9% San Cayetano Scenario 613.21 24,528 $7,794,984,008 4.3% S San Andreas Scenario 153.94 6,158 $2,004,237,540 1.1% Ventura-Pitas Point Scenario 2,078.98 83,159 $14,556,417,724 8.1% 146
Fillmore
Moorpark
Simi Valley
Santa Paula
Oxnard
Ojai
Port
Hueneme
Camarillo
San
Buenaventura
Thousand Oaks
11833
34 118126
150
1 1
23 126
23 33
33 34
1 150
232
33 23
101
Figure 10-. 100-Year Probabilistic Earthquake Scenario
Data Sources: Ventura Co.,
USGS, Esri
Mercalli Intensity Scale
VII (Very Strong/Moderate)
County Boundary
Cities
Major Roads
0 6 3 Miles
Intensity scale described as:
(perceived shaking / potential damage)
147
Fillmore
Moorpark
Simi Valley
Santa Paula
Oxnard
Ojai
Port
Hueneme
Camarillo
San
Buenaventura
Thousand Oaks
11833
34 118126
150
1 1
23 126
23 33
33 34
1 150
232
33 23
101
Figure 10-. Oak Ridge M7.16 Earthquake Scenario
Data Sources: Ventura Co.,
USGS, Esri
Mercalli Intensity Scale
V (Moderate/Very Light)
VI (Strong/Light)
VII (Very Strong/Moderate)
VIII (Severe/Moderate-Heavy)
County Boundary
Cities
Major Roads
0 6 3 Miles
Intensity scale described as:
(perceived shaking / potential damage)
148
Fillmore
Moorpark
Simi Valley
Santa Paula
Oxnard
Ojai
Port
Hueneme
Camarillo
San
Buenaventura
Thousand Oaks
11833
34 118126
150
1 1
23 126
23 33
33 34
1 150
232
33 23
101
Figure 10-. San Cayetano M7.16 Earthquake Scenario
Data Sources: Ventura Co.,
USGS, Esri
Mercalli Intensity Scale
V (Moderate/Very Light)
VI (Strong/Light)
VII (Very Strong/Moderate)
VIII (Severe/Moderate-Heavy)
County Boundary
Cities
Major Roads
0 6 3 Miles
Intensity scale described as:
(perceived shaking / potential damage)
149
Fillmore
Moorpark
Simi Valley
Santa Paula
Oxnard
Ojai
Port
Hueneme
Camarillo
San
Buenaventura
Thousand Oaks
11833
34 118126
150
1 1
23 126
23 33
33 34
1 150
232
33 23
101
Figure 10-1. South San Andreas M8.03 Earthquake Scenario Data Sources: Ventura Co.,
USGS, Esri
Mercalli Intensity Scale
V (Moderate/Very Light)
VI (Strong/Light)
VII (Very Strong/Moderate)
VIII (Severe/Moderate-Heavy)
County Boundary
Cities
Major Roads
0 6 3 Miles
Intensity scale described as:
(perceived shaking / potential damage)
150
Fillmore
Moorpark
Simi Valley
Santa Paula
Oxnard
Ojai
Port
Hueneme
Camarillo
San
Buenaventura
Thousand Oaks
11833
34 118126
150
1 1
23 126
23 33
33 34
1 150
232
33 23
101
Figure 10-1 Ventura-Pitas Point M7.12 Earthquake Scenario Data Sources: Ventura Co.,
USGS, Esri
Mercalli Intensity Scale
V (Moderate/Very Light)
VI (Strong/Light)
VII (Very Strong/Moderate)
VIII (Severe/Moderate-Heavy)
County Boundary
Cities
Major Roads
0 6 3 Miles
Intensity scale described as:
(perceived shaking / potential damage)
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Building Age
Table 10-8 identifies significant milestones in building and seismic code requirements that directly affect the structural integrity of development. Using U.S. Census estimates of housing stock age, estimates were developed of the number of housing units constructed before each of these dates. Almost 18 percent of the planning area’s housing units were constructed after the Uniform Building Code was amended in 1994 to include seismic safety provisions. Housing units built before 1939 when there were no building permits, inspections, or seismic standards, account for 3.6 percent. Many of the housing units in the planning area are detached, single-family residences of wood construction, which generally perform well during earthquake events.

Table 10-8. Age of Housing Units in Planning Area
Time Period
Number of Current Planning Area
Housing Units Built in Period
% of Total Housing
Units Significance of Time Frame
Pre-1939 10,455 3.6 Before 1933, there were no explicit earthquake requirements in building codes. State law did not require local governments to have building officials or issue
building permits.
1940-1959 36,544 12.7 In 1940, the first strong motion recording was made. 1960-1979 123,979 42.9 In 1960, the Structural Engineers Association of California published guidelines on recommended earthquake
provisions. In 1975, significant improvements were made to lateral force requirements.
1980-1999 81,631 28.2 In 1994, the Uniform Building Code was amended to include provisions for seismic safety.
2000-present 36,287 12.6 Seismic code is currently enforced.

Total 288,896 100%
Note: Number and percent estimates are approximation as housing unit age information does not correspond directly with the time periods indicated. In addition, there are significant margins of error associated with the Census estimates.

Source: 2019 American Community Survey, Ventura County, California

10.4.3 Critical Facilities
The following are significant critical facilities that Hazus predicts would have at least a 50 percent change of at least moderate damage for the Oak Ridge scenario earthquake:
1 water reclamation plant
18 wastewater treatment facilities
92 hazardous material sites
7 hospitals
65 fire stations or battalion headquarters
6 sheriff stations
271 schools
4 port facilities
1 airports
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Ventura County Multi-Jurisdictional Hazard Mitigation Plan 10-22
Level of Damage
Hazus classifies the vulnerability of critical facilities to earthquake as no damage, slight damage, moderate damage, extensive damage, or complete damage. Hazus was used to assign a category to each critical facility in the planning area for the assessed earthquake scenarios. Figure 10-13 through Figure 10-17 show the results for the evaluated events as the average estimated probability for all facilities in each category.

Time to Return to Functionality
Hazus estimates the time to restore critical facilities to fully functional use. Results are presented as probability of being functional at specified time increments: 1, 3, 7, 14, 30 and 90 days after the event.

For example, Hazus may estimate that a facility has 5 percent chance of being fully functional at Day 3, and a 95-percent chance of being fully functional at Day 90. The analysis of critical facilities in the planning area was performed for the assessed earthquake scenarios. Figure 10-18 through Figure 10-22 show the results as the average estimated probability for all facilities in each category.

Figure 10-13. Critical Facility Damage Potential, 100-Year Probabilistic Earthquake Scenario 0%
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Figure 10-14. Critical Facility Damage Potential, Oak Ridge M7.16 Earthquake Scenario Figure 10-15. Critical Facility Damage Potential, San Cayetano M7.16 Earthquake Scenario 0%
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Ventura County Multi-Jurisdictional Hazard Mitigation Plan 10-24
Figure 10-16. Critical Facility Damage Potential, S San Andreas M8.03 Earthquake Scenario Figure 10-17. Critical Facility Damage Potential, Ventura-Pitas Point M7.12 Earthquake Scenario 0%
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Figure 10-18. Critical Facility Functionality, 100-Year Probabilistic Earthquake Scenario Figure 10-19. Critical Facility Functionality, Oak Ridge M7.16 Earthquake Scenario 0 10
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Ventura County Multi-Jurisdictional Hazard Mitigation Plan 10-26
Figure 10-20. Critical Facility Functionality, San Cayetano M7.16 Earthquake Scenario Figure 10-21. Critical Facility Functionality, S San Andreas M8.03 Earthquake Scenario 0 10
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at Day 1 at Day 3 at Day 7 at Day 14 at Day 30 at Day 90 Probability of Being Fully functional on Day Shown, Average of All Facilities in Category (%) Safety and Security
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Figure 10-22. Critical Facility Functionality, Ventura-Pitas Point M7.12 Earthquake Scenario

10.4.4 Environment
Environmental problems as a result of an earthquake can be numerous. Secondary hazards will likely have some of the most damaging effects on the environment. Earthquake-induced landslides can significantly damage surrounding habitat. It is also possible for streams to be rerouted after an earthquake. Rerouting can change the water quality, possibly damaging habitat and feeding areas.

Streams fed by groundwater wells can dry up because of changes in underlying geology.

10.5 SCENARIO
Based on history and geology, the planning area will be frequently impacted by earthquakes. The worst-case scenario is a higher-magnitude event (7.5 or higher) with an epicenter within 50 miles of the county. Earthquakes of this magnitude or higher could lead to massive structural failure of property on soils prone to liquefaction. Building and road foundations would lose load-bearing strength. Injuries could occur from debris, such as parapets and chimneys that could topple or be shaken loose and fall on those walking or driving below. Levees and revetments built on these poor soils would likely fail, representing a loss of critical infrastructure. An earthquake event of this magnitude located off the coast could cause a significant local tsunami that would further damage structures and jeopardize lives. An earthquake may also cause minor landslides along unstable slopes, which put at risk major roads and highways that act as sole evacuation routes. This would be even more likely if the earthquake occurred during the winter or early spring.
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Ventura County Multi-Jurisdictional Hazard Mitigation Plan 10-28

10.6 ISSUES
Important issues associated with an earthquake include the following:

More information is needed on the exposure and performance of soft-story construction within the planning area.

Based on the modeling of critical facility performance performed for this plan, a high number of facilities in the planning area are expected to suffer complete or extensive damage from scenario events. These facilities are prime targets for structural retrofits.

Critical facility owners should be encouraged to create or enhance Continuity of Operations Plans using the information on risk and vulnerability contained in this plan.

Geotechnical standards should be established that take into account the probable impacts from earthquakes in the design and construction of new or enhanced facilities.

There are a large number of earthen dams within the planning area. Dam failure warning and evacuation plans and procedures should be reviewed and updated to reflect the dams’ risk potential associated with earthquake activity in the region. The County levees should also be included in any assessments for earthquake risk.

Earthquakes could trigger other natural hazard events such as dam failures, flooding, fire, and landslides, which could severely damage the County.

A worst-case scenario would be the occurrence of a large seismic event during a flood or high- water event. Levees would fail at multiple locations, increasing the impacts of the individual events.

Residents are expected to be self-sufficient up to 3 days after a major earthquake without government response agencies, utilities, private-sector services, and infrastructure components.

Education programs are currently in place to facilitate development of individual, family, neighborhood, and business earthquake preparedness. Government alone can never make this region fully prepared. It takes individuals, families, and communities working in concert with one another to truly be prepared for disaster.

After a major seismic event, Ventura County is likely to experience disruptions in the flow of goods and services resulting from the destruction of major transportation infrastructure across the broader region.

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11-1

11. FLOOD

11.1 GENERAL BACKGROUND

11.1.1 Types of Flooding in the Planning Area
Riverine Floods
Riverine flooding is overbank flooding of rivers and streams. Natural processes of riverine flooding add sediment and nutrients to fertile floodplain areas. Flooding in large river systems typically results from large-scale weather systems that generate prolonged rainfall over a wide geographic area, causing flooding in hundreds of smaller streams, which then drain into the major rivers. Two types of flood hazards are generally associated with riverine flooding:

Inundation—Inundation occurs when floodwater is present and debris flows through an area not normally covered by water. These events cause minor to severe damage, depending on velocity and depth of flows, duration of the flood event, quantity of logs and other debris carried by the flows, and amount and type of development and personal property along the floodwater’s path.

Channel Migration—Erosion of banks and soils worn away by flowing water, combined with sediment deposition, causes migration or lateral movement of a river channel across a floodplain. A channel can also abruptly change location (termed “avulsion”); a shift in channel location over a large distance can occur within as short a time as one flood event.

The frequency and severity of flooding for river systems are based on discharge probability. The discharge probability is the probability that a certain river discharge (flow) level will be equaled or exceeded in a given year. Flood studies use historical records to determine the probability of occurrence for different discharge levels and storm surge levels. These measurements reflect statistical averages only; it is possible for multiple floods with a low probability of occurrence (such as a 1- percent-annual-chance flood) to occur in a short time period. For riverine flooding, the same flood event can have flows at different points on a river that correspond to different probabilities of occurrence.

Shallow area flooding is a special type of riverine flooding. FEMA defines shallow flood hazards as areas inundated by the 1-percent-annual-chance flood with flood depths of only 1 to 3 feet. These areas are generally flooded by low-velocity sheet flows of water.

Stormwater Runoff Floods
Stormwater flooding is a result of local drainage issues and high groundwater levels. Locally, heavy rain, especially during high lunar tide events, may induce flooding within areas other than delineated 160
Ventura County Multi-Jurisdictional Hazard Mitigation Plan 11-2
floodplains or along recognizable channels due to presence of storm system outfalls inadequate to provide gravity drainage into the adjacent body of water. If local conditions cannot accommodate intense precipitation through a combination of infiltration and surface runoff, water may accumulate and cause flooding problems. Flooding issues of this nature generally occur within areas with flat gradients, and generally increase with urbanization, which speeds accumulation of floodwaters because of impervious areas. Shallow street flooding can occur unless channels have been improved to account for increased flows.

Urban drainage flooding is caused by increased water runoff due to urban development and drainage systems. Drainage systems are designed to remove surface water from developed areas as quickly as possible to prevent localized flooding on streets and within other urban areas. These systems utilize a closed conveyance system that channels water away from an urban area to surrounding streams, and bypasses natural processes of water filtration through the ground, containment, and evaporation of excess water. Because drainage systems reduce the amount of time surface water takes to reach surrounding streams, flooding in those streams can occur more quickly and reach greater depths than prior to development within that area.

Flash Floods
The National Weather Service defined a flash flood as follows (National Weather Service 2009a):
“a rapid and extreme flow of high water into a normally dry area, or a rapid water level rise in a stream or creek above a predetermined flood level, beginning within 6 hours of the causative event (e.g., intense rainfall, dam failure). However, the actual time threshold may vary in different parts of the country. Ongoing flooding can intensify to flash flooding in cases where intense rainfall results in a rapid surge of rising flood waters” Flash floods can tear out trees, undermine buildings and bridges, and scour new channels. In urban areas, flash flooding is an increasingly serious problem due to removal of vegetation and replacement of ground cover with impermeable surfaces such as roads, driveways, and parking lots. The greatest risk from flash floods is occurrence with little to no warning. Major factors in predicting potential damage are intensity and duration of rainfall, and steepness of watershed and streams.

Coastal Floods
Coastal floods are usually caused by coastal storms that, when combined with normal tides, push water toward the shore. This is commonly referred to as storm surge. The result can be waves that extend further inland, causing damage to development that would not normally be subject to wave action.

Coastal floodplains are adjacent to the ocean and other tidally influenced areas. The floodplains may be broad or narrow, depending on local topography and natural flood defenses such as dune systems or tidal wetlands.

Levee-Failure Floods
Levees can help reduce the risk of flooding, but they do not eliminate the risk. Levees deteriorate over time and must be maintained to retain their effectiveness. A levee failure can occur when a levee is damaged, experiences surface or foundation erosion, or is overtopped by floodwaters or storm surge 161
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that are higher than the lowest crest of the levee system. When levees fail or are overtopped, the results can be catastrophic. The resulting damage can be greater than if the levee had not been built.

11.1.2 FEMA Regulatory Flood Zones
The extent of flooding associated with a 1-percent annual probability of occurrence (also called the base flood) is used as a regulatory boundary by many agencies. Also referred to as the special flood hazard area (SFHA), this boundary is a convenient tool for assessing vulnerability and risk in flood- prone communities. Many communities have maps that show the extent and likely depth of flooding for the base flood. Corresponding water-surface elevations describe the elevation of water that will result from a given discharge level, which is one of the most important factors used in estimating flood damage.

Mapped Flood Zones
FEMA defines flood hazard areas as areas expected to be inundated by a flood of a given magnitude.

These areas are determined via statistical analyses of records of river flow, storm tides, and rainfall; information obtained through consultation with the community; floodplain topographic surveys; and hydrologic and hydraulic analyses. Flood hazard areas are delineated on DFIRMs (Digital Flood Insurance Rate Maps), which provide the following information:

Locations of specific properties in relation to special flood hazard areas Base flood elevations (1-percent-annual-chance) at specific sites Magnitudes of flood in specific areas
Undeveloped coastal barriers where flood insurance is not available Regulatory floodways and floodplain boundaries (1-percent and 0.2-percent-annual-chance floodplains).

Land covered by floodwaters of the base flood is the special flood hazard area on a DFIRM—an area where NFIP floodplain management regulations must be enforced, and where mandatory purchase of flood insurance applies. This regulatory boundary is a convenient tool for assessing vulnerability and risk in flood-prone communities, because many communities have maps showing the extent of the base flood and likely depths that will occur.

The base flood elevation (the water elevation of a flood that has a 1-percent chance of occurring in any given year) is one of the most important factors in estimating potential damage from flooding. A structure within a 1-percent-annual-chance floodplain has a 26-percent chance of undergoing flood damage during the term of a 30-year mortgage. The 1-percent-annual-chance flood is used by the NFIP as the basis for insurance requirements nationwide. DFIRMs also depict 0.2-percent-annual- chance flood designations.

DFIRMs and other flood hazard information can be used to identify the expected spatial extent of flooding from a 1 percent and 0.2 percent-annual-chance event. They depict the following SFHAs and other areas:

Zone A (Also known as Unnumbered A-zones)—SFHAs where no base flood elevations or depths are shown because detailed hydraulic analyses have not been performed. 162
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Zones A1-30 and AE—SFHAs that are subject to inundation by the base flood, determined using detailed hydraulic analysis. Base flood elevations are shown within these zones.

Zone AH—SFHAs that are subject to shallow flooding, usually in the form of a pond, with an average depth ranging from 1 to 3 feet. Base flood elevations derived from detailed analyses are shown at selected intervals within these zones.

Zone AO—SFHAs subject to inundation by types of shallow flooding where average depths are between 1 and 3 feet. These are normally areas prone to shallow sheet flow flooding on sloping terrain.

Zone AR—Areas with a temporarily increased flood risk due to the building or restoration of flood control system (such as a levee or a dam). Mandatory flood insurance purchase requirements apply, but rates do not exceed the rates for unnumbered A zones if the structure is built or restored in compliance with Zone AR floodplain management regulations.

Zone A99—Areas with a 1 percent annual chance of flooding that will be protected by a federal flood control system where construction has reached specified legal requirements. No depths or base flood elevations are shown within these zones.

Zone B and X (shaded)—Zones where the land elevation as been determined to be above the base flood elevation, but below the 500-year flood elevation. These zones are not SFHAs.

Zones C and X (unshaded)—Zones where the land elevation has been determined to be above both the base flood elevation and the 500-year flood elevation. These zones are not SFHAs.

Floodways
The FEMA designated floodway is the channel of a water course and portion of the adjacent floodplain that is needed to convey the base flood without increasing flood levels by more than a specified amount (typically, 1 foot). A floodway may be designated within the SFHA where the deepest, highest velocity flow is expected and any infrastructure will be at risk. Floodways should be kept free of obstructions and development to allow floodwaters to move downstream unobstructed. Any development in a floodway is subject to severe damage and high risks for occupants and emergency responders.

Unmapped Flood Areas
Flood damage may occur outside of SFHAs. FEMA typically does not designate SFHAs for areas subject to flooding from local drainage problems, particularly in urban areas; drainage basins of less than 1 square mile in area; or hillside areas subject to runoff, erosion, and mudflow. FEMA does not map flooding along the length of all streams or in areas that are undeveloped.

Coastal Flood Hazard Zones
Coastal floods are characterized by inundation of normally dry lands by ocean waters, often caused by storm surge associated with severe storms, tsunamis, or extreme high tide events that result in shallow flooding of low lying coastal areas. Storm surge floods typically result in coastal erosion, salinization of freshwater sources, and contamination of water supplies. These floods are also responsible for significant agricultural losses, loss of life, and damage to public and private structures and infrastructure. DFIRMS depict two coastal flood hazard zones:
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Zone VE, where the flood elevation includes wave heights equal to or greater than 3 feet.

Zone AE, where flood elevation includes wave heights less than 3 feet.

Wave heights as low as 1.5 feet can cause significant damage to structures built without consideration of coastal hazards. Newer DFIRMs for coastal areas include a line showing the limit of moderate wave action (LiMWA), the inland limit of the area expected to receive 1.5-foot or greater breaking waves during the 1- percent annual-chance flood event (Figure 11-1). The area between Zone VE and the LiMWA is subject to flood hazards associated with floating debris and high-velocity flow that can erode and scour building foundations and, in extreme cases, cause foundation failure. Addition of LiMWA area to DFIRMs alerts property owners that their properties may be affected by 1.5-foot or higher breaking waves, and may therefore be at significant risk during a 1-percent-annual-chance flood event (Federal Emergency Management Agency 2020).

Figure 11-1. Limit of Moderate Wave Action
Source: Journal of Marine Science and Engineering 2020

11.1.3 Floodplains
A floodplain is the area adjacent to a river, creek, lake or the ocean that becomes inundated during a flood. Riverine floodplains may be broad, as when a river crosses an extensive flat landscape, or narrow, as when a river is confined in a canyon.

When floodwaters recede after a flood event, they leave behind layers of rock and mud. These gradually build up to create a new floor of the floodplain. Floodplains generally contain unconsolidated sediments (accumulations of sand, gravel, loam, silt, and/or clay), often extending below the bed of the stream. These sediments provide a natural filtering system, with water percolating back into the ground and replenishing groundwater. These are often important aquifers, the water drawn from them being filtered compared to the water in the stream. Fertile, flat reclaimed floodplain lands are commonly used for agriculture, commerce and residential development.
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Connections between a river and its floodplain are most apparent during and after major flood events.

These areas form a complex physical and biological system that not only supports a variety of natural resources but also provides natural flood and erosion control. When a river is separated from its floodplain with levees and other flood control facilities, natural, built-in benefits can be lost, altered, or significantly reduced.

Floodplain Ecosystems and Beneficial Functions
Floodplains can support ecosystems that are rich in plant and animal species. A floodplain can contain 100 or even 1,000 times as many species as a river. Wetting of the floodplain soil releases an immediate surge of nutrients: those left over from the last flood, and those that result from the rapid decomposition of organic matter that has accumulated since then. Microscopic organisms thrive, and larger species enter a rapid breeding cycle. Opportunistic feeders (particularly birds) move in to take advantage. The production of nutrients peaks and falls away quickly, but the surge of new growth endures for some time. This makes floodplains valuable for agriculture. Species growing in floodplains are markedly different from those that grow outside floodplains. For instance, riparian trees (trees that grow in floodplains) tend to be very tolerant of root disturbance and very quick-growing compared to non-riparian trees.

Floodplains have many natural beneficial functions, and disruption of them can have long-term consequences for entire regions. Some well-known, water-related functions of floodplains (noted by FEMA) include:

Natural flood and erosion control
Provide flood storage and
conveyance
Reduce flood velocities
Reduce flood peaks
Reduce sedimentation
Surface water quality maintenance
Filter nutrients and impurities from runoff
Process organic wastes
Moderate temperatures of water
Provide groundwater recharge
Promote infiltration and aquifer recharge
Reduce frequency and duration of low surface
flows
Areas in the floodplain that typically provide these natural functions are wetlands, riparian areas, sensitive areas, and habitats for rare and endangered species.

Effects of Human Activities
Because they border water bodies, floodplains have historically been popular sites to establish settlements. Human activities tend to concentrate in floodplains for a number of reasons: water is readily available; riverine floodplain land is fertile and suitable for farming; transportation by water is easily accessible; land is flatter and easier to develop; and there is value placed in ocean views. But human activity in floodplains frequently interferes with the natural function of floodplains. It can affect the distribution and timing of drainage, thereby increasing flood problems. Human development can create local flooding problems by altering or confining drainage channels or causing erosion of natural flood protection systems such as dunes. Flood potential can be increased in several ways: reducing a stream’s capacity to contain flows; increasing flow rates or velocities downstream; and allowing waves 165
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to extend further inland. Human activities can interface effectively with a floodplain as long as steps are taken to mitigate the activities’ adverse impacts on floodplain functions.

11.1.4 Secondary Hazards
The most problematic secondary hazard for riverine flooding is bank erosion, in some cases more harmful than actual flooding. This is especially true in the upper courses of rivers with steep gradients, where floodwaters may pass quickly and without much damage, but scour banks, edging properties closer to the floodplain or causing them to fall in. Flooding is also responsible for hazards such as landslides when high flows over-saturate soils on steep slopes, causing them to fail. Hazardous materials spills are also a secondary hazard of flooding if storage tanks rupture and spill into streams, rivers, or storm sewers.

11.2 HAZARD PROFILE

11.2.1 Federal Flood Program Participation
National Flood Insurance Program (NFIP)
The first flood maps of the planning area became available in 1974 and 1975. Properties constructed after adoption of a FIRM or DFIRM are considered less vulnerable to flooding because they were constructed after adoption of regulations and codes to decrease vulnerability. Properties built before adoption of a FIRM or DFIRM are more vulnerable to flooding because either they do not meet code or are within hazardous areas.

Table 11-1 lists flood insurance statistics for planning-area municipalities that participate in the NFIP.

Nearly 6,300 policies are in force, providing more than $1.7 million in insurance. According to FEMA statistics, 1,174 flood insurance claims were paid between January 1, 1978, and March 31, 2021, for a total of $13,243,730, an average of $11,281 per claim.

Table 11-1. Flood Insurance Statistics

Date of
Entry
# of Flood Insurance
Policies, as of 3/31/2021
Insurance in
Force
Total Annual
Premiums
Claims,
1/1/1978 to
3/31/2021
Value of Claims Paid,
1/1/1978 to 3/31/2021
Camarillo 9/29/1986 664 $203,471,400 $534,728 21 $1,135,612 Fillmore 10/17/1978 74 $22,517,800 $34,315 37 $226,509
Moorpark 9/29/1986 117 $39,692,000 $114,239 2 $33,576
Ojai 10/17/1978 79 $25,299,000 $41,007 43 $223,301
Oxnard 3/1/1979 497 $166,210,700 $323,235 71 $244,574
Port Hueneme 9/24/1984 57 $17,732,000 $37,235 7 $846
Santa Paula 4/15/1980 1,021 $306,954,400 $604,233 63 $134,387 Simi Valley 9/27/1991 1,624 $425,325,500 $1,337,947 82 $116,840 Thousand Oaks 9/29/1978 336 $109,948,800 $253,564 62 $341,390 Ventura 9/29/1986 471 $161.828,500 $374,421 62 $660,191 Unincorporated 10/31/1985 1,346 $395,320,600 $1,327,849 724 $10,126,504 Total 6,286 $1,712,472,200 $4,982,773 1,174 $13,243,730 166
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To be eligible to participate in the NFIP, a local government must possess the authority to adopt codes and standards to regulate development in the Special Flood Hazard Area. The special purpose district planning partners do not possess these authorities and are therefore not listed in this section.

Additionally, their jurisdictional annexes in Volume 2 do not address federal hazard mitigation planning requirements related to the NFIP.

Community Rating System
Ventura County and the Cities of Oxnard and Simi Valley currently participate in the CRS program.

Table 11-2 summarizes the CRS status of each. Many of the mitigation actions identified in this plan are creditable activities under the CRS program. Therefore, successful implementation of this plan offers potential to enhance the CRS classification.

Table 11-2. CRS Status of Participating Jurisdictions
Current CRS Premium Discount
Jurisdiction NFIP Community # CRS Entry Date Classification SFHA Non-SFHA Oxnard 060417 5/1/2013 7 15 5
Simi Valley 060421 10/1/1993 5 25 10
Ventura County 060413 10/1/2011 5 25 10

11.2.2 Ventura County Public Works Agency—Watershed Protection Ventura County Public Works Agency—Watershed Protection (VCPWA-WP), formerly known as the Ventura County Flood Control District, was formed on September 12, 1944, by an act of the California State Legislature. It is a dependent county special district (governed by a city or county council or board or its appointees). The Ventura County Board of Supervisors governs VCPWA-WP, and it is administratively housed in the Ventura County Public Works Agency. Its mission is to protect life, property, and community infrastructure from flood events, improve water resources management, and enhance the health and natural function of watersheds in Ventura County. The goals of VCPWA-WP include the following:

Comprehensive, long range watershed planning
Collaboration with watershed stakeholders
Administration of adopted regulations, policies, and resolutions Responsible and accountable use of public resources
Excellence in public service

11.2.3 Ventura County Watershed Zones
The sections below describe watershed zones in Ventura County that VCPWA-WP uses for planning.

Zone 1 Ventura River
The watershed of the Ventura River and its tributaries, covering the west-center portion of Ventura County, is the major watershed in Flood Zone 1. Significant tributaries to the Ventura River are Matilija Creek, North Fork Matilija Creek, Coyote Creek, Senior Canyon, Reeves Creek, Thacher Creek, Lion 167
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Canyon, Coyote Creek, San Antonio Creek, and Cañada Larga. The Ventura River watershed covers 223 square miles—a little less than half of it within the Los Padres National Forest. The Ventura River discharges directly to the Pacific Ocean and serves as the western boundary of the City of San Buenaventura (Ventura).

Zone 2 Santa Clara River
The major river in Flood Zone 2 is the Santa Clara River with a watershed area of 1,634 square miles.

Most streams in Zone 2 are tributaries to the Santa Clara River with eventual drainage to the Pacific Ocean. The only exceptions are minor water courses in coastal watershed areas of the Cities of Oxnard, San Buenaventura, and Port Hueneme that drain directly to the Pacific Ocean. The largest of these direct-coastal drainages is the Arundell Barranca, which collects and channels runoff from Lake and Sexton Canyons in the City of San Buenaventura foothill areas before discharging into Ventura Harbor.

Zone 3 Calleguas Creek
The major river in Flood Zone 3 is Calleguas Creek with a watershed area of 341 square miles. All stream flows in Zone 3 eventually end up in Mugu Lagoon before entering the Pacific Ocean. Major tributaries to Calleguas Creek are Revolon Slough (drains a portion of Flood Zone 2), Conejo Creek, Arroyo Santa Rosa, Arroyo Conejo, Arroyo Las Posas/Arroyo Simi, Happy Camp Canyon, Lang Creek, and Tapo Canyon. Virtually the entire watershed is within Ventura County, with dozens of smaller creeks.

Zone 4 South and North
Ventura County Flood Zone 4 covers 225,000 acres in three unconnected areas:

The southeast area (Zone 4 South) includes 61,000 acres of coastal drainages for tributaries to Malibu Canyon (or Malibu Creek), areas surrounding Lake Sherwood, Potrero Creek, Westlake Village, and the coastal streams of Deer Canyon and Big and Little Sycamore Creeks, draining the northern tip of the Santa Monica Mountains directly into the Pacific Ocean.

The northwest area (see Zone 4 North) is primarily the watershed of the Cuyama River, which covers about 150,000 acres within Ventura County.

The remaining 14,000 acres in the relatively undeveloped northeast corner of the county (Zone 4 Northeast) drains outside the County to the north and then to the east. This area includes Frazier Mountain Creek and Mill Canyon Creek, which are tributaries to Cuddy Creek in Kern County. Cuddy Creek follows the San Andreas Fault trace before terminating in the enclosed runoff basin called Castac Lake.

Coastal Creeks
The following areas near the coastline drain directly to the Pacific Ocean (Ventura County Public Works Agency 2020b):

North Coast—At the Santa Barbara-Ventura County Line and south of it, several coastal creeks drain the face of the Santa Ynez Mountains. This area is referred to as the North Coast of Ventura County (sometimes also called the Rincon coast). It includes the principal stream of 168
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Rincon Creek, as well as Las Sauces Creek, Madranio Canyon, Javon Canyon, Padre Juan Canyon, and Line Canyon. The southern boundary is at the northern banks of the Ventura River.

Mid Coast—The Mid Coast (sometimes also called the Oxnard Plain Coastal Area) includes minor stream courses between the Ventura River and Calleguas Creek-Mugu Rock. This stretch of coastline is dominated by urban runoff carrying high pollutant concentrations from residential and industrial activities.

South Coast—Runoff channels and stream courses between Mugu Rock and the Ventura-Los Angeles County Line are referred to as South Coast streams. These include La Jolla Canyon, Big Sycamore Canyon, Little Sycamore Canyon, and Deer Creek Canyon—all of which drain to the western extent of the Santa Monica Mountains. The next drainage to the south—Arroyo Sequit-Triunfo Canyon Creek—is just past the county line and thus under Los Angeles County control.

11.2.4 Principal Flooding Sources and Floodplains
Upland Flooding
The mountainous terrain of northern Ventura County and the hills in the central and eastern parts of the county give rise to numerous annual streams, many draining into steep canyons. These streams are subject to floods of relatively short duration, often following high-intensity rainfall. Such floods may occur with little warning and carry large quantities of sediment and debris. Communities adjacent to the upland areas, such as Fillmore, Ojai, Piru, and Santa Paula, are subject to this hazard. Many of the watersheds in question contain dams or basins designed to attenuate flow and trap debris, reducing the effects on downstream communities.

Broad Floodplains
The watersheds of the Santa Clara River (watershed area of 1,650 square miles), the Ventura River (watershed area of 226 square miles), and Calleguas Creek (watershed area of 325 square miles) drain to the broad coastal plain in the southern part of Ventura County. This plain is subject to inundation during longer intervals of rain, typically as the result of a series of winter storms. These floods typically have longer duration and may be forecast with more warning time. Because of its sediment load, the Santa Clara River has migrated across the valley floor during significant floods. Numerous levees have been built in the Santa Clara River Valley to protect agricultural lands along the river. The levees are typically not sufficient to withstand severe flood events.

Coastal Flooding
The County’s 43-mile coastline is subject to tidal flooding, storm surge, and wave action, all of which usually occur during winter storms. Severe wave action is generally confined to narrow areas immediately adjacent to the tidal zone, including Sea Cliff Colony, Oxnard Shores, Silver Strand Beach, and several sections of U.S. 101 from Rincon Point to Emma Wood State Park. The effects of coastal flooding can be severe. In addition to wave action, beach and bluff erosion can cause significant damage to coast-side homes and infrastructure. Coastal flooding may also occur as the result of tsunamis caused by earthquakes or undersea landslides.
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Winter coastal storms can cause minor coastal erosion along the shores of Ventura County. Coastal erosion is a natural process that occurs particularly in winter, when coastal storms wear away land by the action of waves and tides. Material deposited on beaches during the mild summer and fall months gets redistributed by the waves. According to City of San Buenaventura engineers, most of the sand is pulled just off coast and then comes back to shore over time. Although most receding sand stays fairly close to shore, some is driven south by currents until it reaches Hueneme Canyon, a large deep-water depression near the Port of Hueneme.

Unmapped Flood Hazard Areas
Unmapped flood hazard areas include numerous small channels. Agricultural drainage ditches and urban drains cover much of the flatter parts and urban areas of Ventura County. Flooding in these areas is due to high-intensity rainfall over a very short period. The flooding is usually shallow and mainly affects roadways and other low-lying areas. The Hollywood Beach and Silver Strand residential coastal communities have historically experienced localized flooding conditions, primarily due to inadequate storm drainage infrastructure and topography. These residential coastal communities (largely built out) are not currently mapped by FEMA in the Zone VE coastal high hazard SFHA. They have historically been mapped by FEMA as a Zone B and most recently under the DFIRMs as a Zone X-Shaded (500-year floodplain).

11.2.5 Natural and Beneficial Floodplain Functions
The county’s floodplains drain into five major wetlands as described in the sections below. A wetland is an area of land whose soil is saturated with moisture either permanently or seasonally. Such areas may also be covered partially or completely by shallow pools of water. Wetlands include swamps, marshes, and bogs; the water found in wetlands can be saltwater, freshwater, or a mixture of both.

McGrath Lake Wetlands
Located on the western city limits of Oxnard, the McGrath Lake wetlands extend south from the Santa Clara River. A small lake within the wetlands helps to attract more than 200 species of birds. The Santa Clara Estuary Natural Preserve on the northern boundary of McGrath Lake Park offers a refuge for birds and habitat for burrowing animals. In April 2010, the Nature Conservancy, the State of California, and the U.S. Fish and Wildlife Service purchased 141 acres of prime riparian habitat, agriculture fields, and floodplains within the McGrath Lake Wetlands to become part of the Santa Clara River Parkway.

The parkway was established to protect and restore the river’s floodplain and functions, and to provide recreational opportunities such as hiking and bird watching.

Mugu Lagoon
The Mugu Lagoon consists of 1,474 acres of wetlands on the Point Mugu Naval Base, 8 miles southeast of the City of Oxnard. Calleguas Creek flows into the lagoon. In addition, there is a tidal connection through an inlet in the barrier beach. High concentrations of banned pesticides are found in lagoon’s sediment. The Navy has undertaken several wetland restoration projects since the mid-1990s, restoring several acres of tidal mudflats, sandflats, channels, ponds, salt marsh, and sand islands. A number of special-status species inhabit the lagoon.
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Ormond Beach Wetlands
The Ormond Beach wetlands, located in the City of Oxnard between the Port of Hueneme and the Point Mugu Naval Base, support many rare plants and hundreds of species of migratory birds. A secondary metal smelter, operating at Ormond Beach from 1965 to 2004, created such a large amount toxic pollution that the site is now a U.S. Environmental Protection Agency Superfund site. A once- through-cooling natural gas power plant, scheduled to be decommissioned in 2023, also is located within the wetlands. The California State Coastal Conservancy, the City of Oxnard, and The Nature Conservancy are spearheading efforts to permanently protect habitat and expand and restore the wetlands. As of late 2020, these groups had acquired 650 acres of the wetlands (ESA 2021).

Santa Clara River Estuary
The 49-acre Santa Clara River
Estuary is at the mouth of the Santa
Clara River and the Pacific Ocean
near the City of San Buenaventura.

The river drains a 1,600-square-mile
watershed. The estuary provides
habitat to many listed species such
as the southern California steelhead
trout. The recovery plan for southern
California steelhead identified the
Santa Clara River as one of the
highest priority sites for recovery
actions. In 2015, with funding
provided by state and federal wildlife
agencies, the Wishtoyo Chumash
Foundation drafted a habitat
restoration and enhancement
feasibility study for the Santa Clara
River Estuary. The purpose of the
study was to assess the feasibility of
expanding and enhancing estuarine
habitat for steelhead and other
native and protected species by
restoring and by providing lagoon,
side channel, contiguous wetland,
and additional upland riparian
habitat, or a combination of each.

Ventura River Estuary
The 110-acre Ventura River Estuary, directly west of the City of San Buenaventura, drains a 226- square-mile watershed. The estuary is home to several special-status species. In 1996, the Ventura River Estuary Enhancement Plan was implemented to restore and enhance the estuary. The plan Treatment Plant Discharge to the Santa Clara River Estuary The City of San Buenaventura’s sewage treatment plant discharges up to 9 million gallons per day of tertiary treated wastewater into the Santa Clara River Estuary. This discharge—one of the last remaining estuary discharges in California—is in conflict with the State Water Resources Control Board’s Water Quality Control Policy for the Enclosed Bays and Estuaries of California (Resolution No. 74-43, 1974), which mandates that the discharge of municipal and industrial wastewaters to enclosed bays and estuaries be phased out. Exceptions to this policy are limited to circumstances in which a regional water quality control board finds that the treated wastewater enhances the quality of receiving waters.

The City of San Buenaventura has been granted an exception since 1977 on the basis that the treatment plant’s discharge enhanced fish and wildlife habitat and non-contact water recreation. However, more recent information about the relationship of the discharge to the ecological function of the estuary is lacking.

Issues associated with the discharge include impacts of nutrient-rich water in the estuary and the artificial hydrology created by the volume of water. With this discharge, the lagoon fills up and breaches more frequently than it would under natural conditions. In 2008, the Los Angeles Regional Water Quality Control Board required the City of San Buenaventura, as a condition to continue the current discharge practice, to perform three studies to evaluate environmental solutions.

The Santa Clara River Estuary Scientific Review Panel convened in 2017 to determine how much, if any, discharge from the Ventura Water Reclamation Facility is needed to protect and sustain the native and endangered species known to use the Santa Clara River Estuary, and how much discharge could be eliminated to protect these species and sustain additional priority beneficial uses.

The panel recommended a 90 percent diversion from the current discharge volumes (Santa Clara River Estuary Scientific Review Panel 2018). In 2019 Ventura City Council approved a $200 million wastewater treatment plant to increase drinking water resources and reduce the treated wastewater released into the Santa Clara River estuary. The city plans to reduce its estuary discharge to less than 500,000 gallons per day by 2030 (Tuser 2019).
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outlines riparian restoration along the river, its floodplain, and the surrounding dunes; re-creation of habitat types; habitat protective fencing; and trail soil stabilization.

11.2.6 Past Events
Major Historical Floods
Damaging floods in Ventura County were reported as early as the middle of the 1800s. A 1945 report by the Ventura County Flood Control District described floods that caused extensive damage in 1862, 1867, 1884, 1911, 1914, 1938, 1941, 1943, and 1944.

The largest and most damaging natural floods recorded in the Santa Clara and Ventura watersheds occurred in January and February of 1969. The January flood was a result of the highest monthly precipitation total ever recorded in Ventura County at that time. The February flood was a result of intense rainfall similar in magnitude to the rainfall that caused the record-breaking flood in January. The combined effects of the 1969 floods were disastrous: 13 people lost their lives, and property damage was estimated at $60 million (1969 dollars). Homes in Casitas Springs, Live Oak Acres, and Fillmore were flooded, and 3,000 residents in Santa Paula and several families in Fillmore were evacuated twice. A break in the Santa Clara River levee threatened the City of Oxnard. Agricultural land, primarily citrus groves, was seriously damaged or destroyed. All over the county, transportation facilities, including roads, bridges, and railroad tracks, were damaged. The Fillmore, Oak View, and Ventura sewage treatment plants were severely damaged and dumped raw sewage into the Santa Clara and Ventura Rivers. The untreated sewage polluted the rivers and the beaches at their outlets into the ocean. Sewer trunk lines broke along the Ventura River and San Antonio Creek. Suspended sediment concentrations and discharge in many streams greatly exceeded any previously measured levels in the flood-affected areas (Ventura County 2015).

In 1980, Calleguas Creek breached its levee in the Oxnard Plain, and flooding and sediment deposition caused $9 million (in 1980 dollars) in damage to the Point Mugu Naval Base. Floodwaters covered about 1,500 acres of farmland. The peak discharge was 9,310 cubic feet per second at the Madera Road Bridge in Simi Valley.

In 1983, a federal disaster was declared because of storm damage. Repairs to flood-control facilities have been estimated to cost $15 million (in 1983 dollars). Improved channels in Moorpark and Simi Valley suffered severe damage from erosion during this event, and Calleguas Creek experienced record flooding. Damage to other public and private facilities has been estimated at $39 million, with little more than half of that total due to damage to agricultural lands.

Recent Floods
Table 11-3 lists major flood events to affect Ventura County since 2000. 172
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Table 11-3. History of Flood Events
Date Event Type Locations Deaths or Injuries Property Damage June 2, 2019 Flash Flood Wheeler Springs 0 N/A
May 29, 2019 Flash Flood Wheeler Springs 0 N/A
March 22-23, 2018 Flash Flood Seacliff 0 N/A
March 22-23, 2018 Flash Flood Haines 0 N/A
February 17, 2017 Flash Flood Dulah 0 N/A
February 17, 2017 Flash Flood Newbury Park 4 N/A
February 17, 2017 Flash Flood Somis 0 N/A
March 7, 2016 Flash Flood Dulah 0 N/A
January 6, 2016 Flash Flood Dulah 0 N/A
January 6, 2016 Flash Flood Piru 0 N/A
January 5, 2016 Flash Flood Dulah 0 N/A
July 30, 2015 Flash Flood Wheeler Springs 0 N/A
June 12, 2015 Flash Flood Wheeler Springs 0 N/A
March 1, 2015 Flash Flood Point Mugu 0 N/A
December 12, 2014 Flash Flood Santa Susana 0 N/A
December 12, 2014 Flash Flood Camarillo 0 Ten homes severely damaged July 22, 2013 Flash Flood Gorman 0 N/A
September 13, 2011 Flash Flood Wheeler Springs 0 N/A
July 5, 2011 Flash Flood Wheeler Springs 0 N/A
July 4, 2011 Flash Flood Lockwood Valley 0 N/A
October 2, 2010 Flash Flood Wheeler Springs 0 Vehicle damaged January 20, 2010 Flash Flood Moorpark 1 N/A
July 13-14, 2008 Flash Flood Wheeler Springs 0 N/A
January 25, 2008 Flash Flood Moorpark 0 N/A
January 4, 2008 Flash Flood Santa Paula 0 N/A
January 4, 2008 Flash Flood Fillmore 0 N/A
October 14, 2006 Flash Flood Piru 0 N/A
July 24, 2006 Flash Flood Ventura Countya 0 N/A
July 23, 2005 Flash Flood Ventura Countya 0 N/A
February 20-21, 2005Flood, Flash Flood Ventura Countya 0 $8 million February 18, 2005 Flash Flood Ventura Countya 0 N/A
January 9-10, 2005 Flash Flood Ventura Countya 0 N/A
January 21, 2005 Coastal Flood Ventura Countya 0 N/A
January 3, 2005 Flash Flood Ventura Countya 0 N/A
February 25-26, 2004 Flash Flood Simi Valley 0 N/A
March 15, 2003 Flood Ventura Countya 0 N/A
December 17, 2002 Flood Ventura County Coasta 0 N/A
November 30, 2002 Flash Flood Santa Paula 0 N/A
December 20, 2001 Flood City of San Buenaventurab 0 N/A November 24, 2001 Flood City of San Buenaventurab 0 N/A November 12, 2001 Flood City of San Buenaventurab 0 N/A November 12, 2001 Flood El Rio 0 N/A
November 12, 2001 Flood Newbury Park 0 N/A
September 3, 2001 Flash Flood Ventura Countya 0 N/A
July 7, 2001 Flash Flood Ventura Countya 0 N/A
March 5, 2001 Flood Ventura Countya 0 N/A
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Date Event Type Locations Deaths or Injuries Property Damage January 11-12, 2001 Flood Ventura County Coasta 0 N/A
August 1, 2000 Flash Flood Ventura Countya 0 N/A
April 17, 2000 Flood Ventura Countya 0 N/A
February 20-21, 2000 Flood Ventura Countya 0 N/A
February 20, 2000 Flash Flood Ojai 0 N/A
a. Multiple locations are associated with this event.
b. The City of San Buenaventura is commonly called the City of Ventura.

Source: NCEI Storm Events Database 2021

11.2.7 Location
Levee-Protected Areas
Sixty-eight miles of levees are located throughout Ventura County. Two of these levees have undergone detailed economic analysis studies: the 2.65-mile-long Ventura River Levee (VR-1) and the

4.72-mile-long Santa Clara River Levee (SCR-1). Figure 11-2 and Figure 11-3 show the flood hazard areas defined in the levee studies, which were used in the risk assessment scenario of this plan. For consistency with the FEMA data, the 1 percent-annual chance and 0.2 percent-annual chance flood hazard areas of the levee studies were used (indicated on the figures as 100-year and 500-year floods).

Mapped Flood Zones
Flooding in Ventura County has been documented by gage records, high water marks, damage surveys, and personal accounts. This documentation was the basis for the January 2021 Flood Insurance Study that is incorporated in the current effective DFIRMs. The DFIRMs are the most detailed and consistent data source available for determining flood extent. Data from the January 2021 Flood Insurance Study was used in this risk assessment to map extents and locations of the 1 percent- annual chance and 0.2 percent-annual chance flood hazard areas, as shown on Figure 11-4.

Repetitive Loss
A repetitive loss property is an NFIP-insured property that has experienced repeated flood damage. A repetitive loss area is the portion of a floodplain holding structures that FEMA has identified as repetitive loss properties. Identifying repetitive loss areas helps to identify structures that are at risk but are not on FEMA’s list of repetitive loss structures. FEMA-sponsored programs, such as the CRS, require participating communities to identify repetitive loss areas. Repetitive loss properties in Ventura County are listed in Table 11-4.
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Figure 11-2. Floodplains Mapped in the Ventura River Levee Study 175
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Figure 11-3. Floodplains Mapped in the Santa Clara River Levee Study Table 11-4. Repetitive Loss Properties in Ventura County Jurisdictiona
Repetitive Loss
Properties
Properties That Have
Been Mitigated
Number of
Corrections
Corrected Number of
Repetitive Loss Properties
City of Camarillo 0 * * *
City of Fillmore 0 * * *
City of Moorpark 0 * * *
City of Ojai 0 * * *
City of Oxnard 7 * * *
City of Port Hueneme 0 * * *
City of San Buenaventura 4 * * *
City of Santa Paula 3 * * *
City of Simi Valley 0 * * *
City of Thousand Oaks 5 * * *
Ventura County Unincorporated Areas 63 * * *
Totals 82 * * *
a. Special purpose district planning partners to this plan have no identified repetitive loss properties because districts are not eligible participants in the NFIP.
* Data not available to support this planning effort due to FEMA’s Privacy Act policies and the time associated with processing the requisite Information Sharing Access Agreement (ISAA).

Source: September 9, 2021, FEMA Report of Repetitive Losses 176
Fillmore
Moorpark
Simi Valley
Santa Paula
Oxnard
Ojai
Port
Hueneme
Camarillo
San
Buenaventura
Thousand Oaks
11833
34 118126
150
1 1
23 126
23 33
33 34
1 150
232
33 23
101
Figure 11-4. FEMA Flood Hazard Areas
Data Sources: Ventura Co.,
FEMA, Esri
1% Annual Chance Flood (100-Year)

0.2% Annual Chance Flood (500-Year)
County Boundary
Cities
Major Roads
0 6 3 Miles
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11.2.8 Frequency
Recurrence intervals and average annual numbers of flood events in Ventura County were calculated as follows based on events from 2000 to 2021 recorded in the NCEI Storm Events Database:

Coastal floods have a 4.6 percent chance of occurring in any given year Flash floods have a 173 percent chance
Other floods have a 54.6 percent chance of occurrence
Total estimated percent chance of occurrence for any type of flood in a given year is 232 percent, meaning that flooding will likely continue to be an annual hazard.

The NCEI database lists 51 significant flooding events in Ventura County from 2000 to 2021, most of which have been flash floods. Smaller floods may occur more frequently and be categorized in the database under a different hazard event type, typically severe weather or severe storms.

11.2.9 Severity
The principal factors affecting flood damage are flood depth and velocity. The deeper and faster flood flows become, the more damage they can cause. Shallow flooding with high velocities can cause as much damage as deep flooding with slow velocity—especially when a channel migrates over a broad floodplain, redirecting high velocity flows and transporting debris and sediment. Flood severity is often evaluated by examining peak discharges. Peak flows used by FEMA to map floodplains within the planning area are listed in Appendix E. A summary list of only the sources with drainage areas of 20 square miles or greater is provided in Table 11-5.

Table 11-5. Summary of Peak Discharges in Large Ventura County Drainages Drainage Area Discharge (cubic feet/second)
Source/Location (square miles) 10-Percent 2-Percent1-Percent 0.2- Percent Arroyo Las Posas
Upstream of confluence of Peach Hill Wash 117.4 8,260 17,120 22,090 36,520 Downstream of confluence of Long Canyon Creek 143.4 9,390 19,460 25,100 41,500 Arroyo Simi
Downstream of confluence with Happy Camp Canyon Creek113.20 8,300 17,200 22,190 36,670 Downstream of Alamos Canyon 88.70 5,670 13,060 17,460 31,200 Downstream of North Simi Canyon 69.50 5,600 12,890 17,240 30,810 Upstream of Bus Canyon Drain 61.50 5,110 11,950 15,900 28,580 Upstream of Tapo Canyon Channel 32.30 4,440 10,220 13,670 24,420 Downstream of Meier Canyon 30.90 4,460 10,270 13,730 24,540 Calleguas Creek
At Highway 1b 262.00 12,230 28,140 37,630 67,240
Downstream of confluence of Conejo Creek 248.30 16,000 30,610 38,460 61,030 Upstream of Conejo Creek & Lewis Drain 168.70 10,390 21,520 27,770 45,900 At Seminary Road 164.90 10,350 21,450 27,680 45,760
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Ventura County Multi-Jurisdictional Hazard Mitigation Plan 11-20
Drainage Area Discharge (cubic feet/second)
Source/Location (square miles) 10-Percent 2-Percent1-Percent 0.2- Percent Conejo Creek
At confluence with Calleguas Creek 77.60 9,300 17,800 22,300 35,500 At Highway 101 bridge 71.90 9,560 18,300 22,000 36,500
Downstream of confluence of Arroyo Conejo 60.00 9,660 18,500 23,200 36,900 Coyote Creek
Upstream of confluence with Ventura River 41.10 680 1,980 3,410 4,830 Approximately 570 feet downstream of Casitas Dam Spillway 40.10 671 1,953 3,363 4,766 At Casitas Dam Spillway 38.50 120 370 2,590 3,750
Piru Creek
At confluence with Santa Clara River 441 2,500 33,000 41,000 60,000 Revolon Slough
Downstream of Camarillo Hills Drain 38.70 2,500 7,100 10,000 20,000 At Highway 101 30.00 2,200 6,200 8,700 16,500
San Antonio Creek
At confluence with Ventura Rivera 51.1 9,960 24,715 32,679 51,450 Approximately 410 feet upstream of North Ventura Avenue 49.7 9,930 26,946 37,893 73,689 Upstream of confluence of San Antonio Creek Tributary 46.5 10,430 28,300 39,800 77,690 Upstream of confluence with Lion Canyon Creek 33.8 7,760 21,050 29,600 57,780 Downstream of Stewart Canyon Creek 31.3 8,590 23,320 32,800 64,030 Upstream of confluence of Steward Canyon Creek 26.5 7,620 20,690 29,100 56,800 Downstream of confluence of Thacher Creek 25.4 7,490 20,330 28,600 55,830 Santa Clara River
At mouth 1,625 41,000 116,000 161,000 270,000
At Willard Bridge 1,534 41,000 116,000 161,000 270,000
Upstream of confluence of Santa Paula Creek 1,505 40,000 113,000 157,000 265,000 Downstream of confluence of Sespe Creek 1,500 40,000 113,000 157,000 265,000 Upstream of confluence of Sespe Creek 1,182 23,000 66,000 92,000 160,000 Downstream of confluence of Hopper Creek 1,174 40,000 113,000 157,000 265,000 Downstream of confluence of Piru Creek 1,100 40,000 113,000 157,000 265,000 At Ventura County/Los Angeles County boundary 644 15,000 43,000 60,000 104,000 Santa Paula Creek
At stream gauging station 40 6,800 18,000 26,000 48,000 Sespe Creek
Approximately 4,000 feet downstream of Highway 126263 33,000 72,000 92,000 145,000 Approximately 5,000 feet upstream of Southern Pacific
Railroad
259 29,000 62,000 80,000 131,000
Tapo Canyon Channel
At confluence with Arroyo Simi 20.70 * * 8,500 *
Ventura River
At Pacific Oceanb 226 34,000 67,000 78,000 103,000
At Shell Chemical Plant 223 41,300 67,900 78,900 105,500 Approximately 0.6 mile upstream of confluence of Canada Larga
191 36,583 59,999 70,055 93,593
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Drainage Area Discharge (cubic feet/second)
Source/Location (square miles) 10-Percent 2-Percent1-Percent 0.2- Percent At Casitas Vista Road 188 36,400 59,700 69,700 93,100
Approximately 1,400 feet upstream of Casitas Vista Road 148 35,529 57,135 67,239 90,127 Approximately 1,000 feet downstream of confluence of San Antonio Creek
144 35,000 56,600 66,600 89,000
Approximately 300 feet upstream of confluence of San
Antonio Creek

92.8 16,449 25,493 29,104 37,856
At Baldwin Road 83.0 16,000 24,800 28,300 36,700
Approximately 1,120 feet upstream of Camino Cielo 72.4 15,000 24,000 27,100 35,200 Upstream of confluence of North Fork Matilija Creek56.4 12,500 18,800 21,600 27,900 Note: All locations are at mouth unless otherwise noted. Locations do not include jurisdictional boundaries. * Data not available
a. Decrease due to overbank losses upstream
b. Discharges are larger than those downstream due to updated hydrology (San Antonio Creek & Ventura River) Source: Ventura County FIS 06111CV002E, FEMA January 29, 2021

11.2.10 Warning Time
Potential warning time available to a community for response to a flooding threat depends on the time between the first measurable rainfall and the first occurrence of flooding. The time needed to recognize a flood threat reduces potential warning time for a community. Because of the sequential pattern of weather conditions needed to cause serious flooding, occurrence of a flood without warning is unusual.

Warning times for floods can be between 24 and 48 hours. Flash flooding can be less predictable, but populations in potential hazard areas can be warned in advance of flash flooding danger.

National Weather Service Watches and Warnings
The National Weather Service (NWS) issues watches and warnings when forecasts indicate rivers may approach bank-full levels. Flood extent or severity categories used by NWS include minor flooding, moderate flooding, and major flooding, based on property damage and public threat:

Minor Flooding—Minimal or no property damage, but possibly some public threat or inconvenience.

Moderate Flooding—Some inundation of structures and roads near streams. Some necessary evacuations of people and/or transfer of property to higher elevations.

Major Flooding—Extensive inundation of structures and roads. Significant evacuations of people and/or transfer of property to higher elevations (National Weather Service 2009b).

When a watch is issued, the public should prepare for the possibility of a flood. When a warning is issued, the public is advised to stay tuned to a local radio station for further information and be prepared to take quick action if needed. A warning means a flood is imminent, generally within 12 hours, or is occurring. Local media broadcast NWS warnings. Alerts are also sent via Twitter, Everbridge, and email and posted to the VCPWA-WP website. 180
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Ventura County ALERT System
VCPWA-WP operates 90 self-reporting rain gages and 30 self-reporting stream gages. VCPWA-WP also receives telemetered data from 65 additional rain gages and 23 stream gages operated by other agencies. The real-time rain gage data are fed into watershed hydrologic models to predict flow hydrographs and stream levels at stream gage stations installed at strategic locations throughout the County.

The Automated Local Evaluation in Real-Time (ALERT) network is the essential component of the flood warning system. Ventura County implemented a flood warning system for Sespe Creek after a flood in 1978 that caused significant damage in Fillmore. Six rain gages were installed in 1979 in the Sespe Creek and Santa Paula Creek watersheds. All six of these gages remain in operation today.

In response to the 1980 Calleguas Creek flood and with some funding provided by the US Navy, a nine-gage system was installed in the Calleguas Creek watershed. Three are still in their original locations.

The 1980s saw improvement in the technology which included both hardware and software. ALERT transmitters were connected to stream gages so water levels could be monitored in real-time, just like rainfall. Computer software also improved, allowing for display of rainfall and stream flow in graphs and maps. The ALERT network continued to grow with the addition of gages in the Ventura River watershed in response to the 1985 Wheeler Fire. This was the first time that all three of Ventura County watersheds were covered by the ALERT system (Ventura County Public Works Agency 2020a).

Figure 11-5 shows an example of the local flood warning system.

11.3 EXPOSURE
A quantitative assessment of exposure to the flood hazard was conducted using the flood mapping shown in Figure 11-4 and the asset inventory developed for this plan. Detailed results by municipality are provided in Appendix D; results for the total planning area are presented below.

11.3.1 Population
Table 11-6 summarizes the estimated population living in the evaluated flood hazard areas.

Table 11-6. Exposed Population in Evaluated Flood Hazard Zones 1% Annual Chance Flood Zone0.2% Annual Chance Flood Zone Population Exposed 33,202 180,772
% of Total Planning Area Population 3.9% 21.4%

11.3.2 Property
Table 11-7 summarizes the estimated property exposure in the evaluated flood hazard areas.

Figure 11-6 shows the occupancy class defined by Hazus for all buildings in the mapped floodplains.

These occupancy classes provide an indication of land use within the mapped hazard area. Some land uses are more vulnerable to flood risks, such as single-family homes, while others are less vulnerable, such as agricultural land or parks.
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Figure 11-5. Ventura County Flood Warning System Example

Table 11-7.Exposed Property in Evaluated Flood Hazard Zones 1% Annual Chance Flood Zone 0.2% Annual Chance Flood Zone Acres of inundation area 68,046 102,019
Number of Buildings Exposed 12,547 54,978
Value of Exposed Structures $5,265,874,679 $23,232,737,392 Value of Exposed Contents $4,681,379,253 $19,502,977,592 Total Exposed Property Value $9,947,253,933 $42,735,714,984 Total Exposed Value as % of Planning Area Total 5.5% 23.6% 182
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Figure 11-6. Building Occupancy Classes in the Mapped Flood Zones

11.3.3 Critical Facilities
Figure 11-7 and Figure 11-8 show critical facilities located in the 1 percent-annual-chance and

0.2 percent-annual-chance floodplains, respectively, by facility type.

Figure 11-7. Critical Facilities in 1% Annual Chance Floodplain

Residential
9,183
73%
Commercial
1,091
9%Industrial
537
4%
Religion
62 1%
Agriculture
1,427
11%
Government
94 1%
Education
153
1%
1% ANNUAL CHANCE FLOOD
Residential
44,784
82%
Commercial
3,737
7%
Industrial
1,942
4%
Religion
220
0%
Agriculture
2,372
4%
Government
1,240
2%
Education
683
1%

0.2% ANNUAL CHANCE FLOOD
23 5
22 11
0 13
159
0 50
100
150
200
250Number of Facilties in Hazard Area
Communication
Energy
Food, Water, Shelter
Hazardous Materials
Medical and Health
Safety and Security
Transportation

9.2%

4.5%

10.5%11.8%

0.0% 3.3%

30.4%
0%
20%
40%
60%
80%
100%Facilties in Hazard Area as % of Planning Area Total Communication
Energy
Food, Water, Shelter
Hazardous Materials
Medical and Health
Safety and Security
Transportation
183
Flood
11-25
Figure 11-8. Critical Facilities in 0.2% Annual Chance Floodplain

A breakdown by municipality is provided in Appendix D. Critical facilities exposed to the flood hazard represent the following percentages of all critical facilities in the planning area:
15 percent (233 facilities) of all critical facilities are in the 1 percent-annual-chance flood hazard area.
30 percent (466 facilities) of all critical facilities are in the 0.2 percent-annual-chance flood hazard area.

11.3.4 Environment
Because floodplain management measures place restrictions on development in areas affected by flooding, floodplains often have a higher portion of area that is undeveloped open space or natural area. These undeveloped areas represent environment exposed to the flood hazard.

11.4 VULNERABILITY
The results of the vulnerability assessment indicate estimated damage for the 1-percent, and

0.2-percent-annual-chance flood hazards. Detailed results by jurisdiction are included in Appendix D; countywide summaries are provided below.

11.4.1 Population
Flood impacts on persons and households were estimated for each event through the Level 2 Hazus analysis. Table 11-8 summarizes the results.
52 31
61 37
0 82
213
0 50
100
150
200
250Number of Facilties in Hazard Area
Communication
Energy
Food, Water, Shelter
Hazardous Materials
Medical and Health
Safety and Security
Transportation

20.8%

27.9%29.0%

39.8%

0.0%

21.0%

40.7%
0%
20%
40%
60%
80%
100%Facilties in Hazard Area as % of Planning Area Total Communication
Energy
Food, Water, Shelter
Hazardous Materials
Medical and Health
Safety and Security
Transportation
184
Ventura County Multi-Jurisdictional Hazard Mitigation Plan 11-26
Table 11-8. Estimated Flood Impacts on Persons and Households Number of Persons DisplacedNumber of Persons Requiring Short-Term Shelter 1% Annual Chance Flood Zone 10,829 785

0.2% Annual Chance Flood Zone 117,102 8,221

11.4.2 Property
Table 11-9 summarizes Hazus estimates of flood damage in the planning area. The debris estimate includes only structural debris and building finishes; it does not include additional debris that may result from a flood event, such as from trees, sediment, building contents, bridges, or utility lines.

Table 11-9. Estimated Impact of a Flood Event in the Planning Area Damage Type 1% Annual Chance Flood Zone 0.2% Annual Chance Flood Zone Structure Debris (Tons) 96,710 396,325
Buildings Impacted 7,885 27,662
Total Value (Structure + Contents) Damaged $743,893,665 $5,725,626,424 Damage as % of Total Replacement Value 0.4% 3.2%

11.4.3 Critical Facilities
Significant facilities predicted by Hazus to be affected by the 1 percent-annual-chance flood include the following:
1 water reclamation plant
11 hazardous material sites
1 airport
11 schools
2 fire stations
105 road bridges
Estimated Damage
Hazus was used to estimate the number of critical facilities affected by flooding and the resulting percent of damage to the building and contents. Figure 11-9 compares the predicted number of affected facilities to the number of exposed facilities, for the 1 percent and 0.2 percent-annual chance flood events. Results for the 1 percent-annual-chance-event are as follows:

All exposed facilities in the hazardous materials and safety/security categories are predicted to experience some damage
For all other categories with exposure, between 30 and 70 percent of exposed facilities are predicted to experience some damage
Figure 11-10 shows the estimated damage to critical facilities for both modeled flood events. For the 1 percent-annual-chance-event, the average amount of damage to structures, measured as a percentage of total value, ranges from 1.4 to 17.1 percent of total value and average damage to contents ranges from 11.6 to 47.1 percent, depending on critical facility category. 185
Flood
11-27
Figure 11-9. Facilities Exposed to and Affected by the 1% and 0.2% Annual Chance Floods Figure 11-10. Average Damage to Critical Facilities from 1% and 0.2% Annual Chance Floods 23 52
5 31 22
55 11
37 0 0
13 78
159
213
7 35
3 23
10 40
11 29
0 0
13 48
106
151
0 50
100
150
200
250
1% Ann.

Chance

0.2%
Ann.

Chance
1% Ann.

Chance

0.2%
Ann.

Chance
1% Ann.

Chance

0.2%
Ann.

Chance
1% Ann.

Chance

0.2%
Ann.

Chance
1% Ann.

Chance

0.2%
Ann.

Chance
1% Ann.

Chance

0.2%
Ann.

Chance
1% Ann.

Chance

0.2%
Ann.

Chance
Communications Energy Food, Water &
Shelter
Hazardous
Material
Health & Medical Safety & Security Transportation
Number of Faciliities Exposed or Affected
Exposed Facilities
Affected Facilities

9.7 12.0

17.1 18.6

10.1 15.7

7.9 14.4

5.7 9.3

1.4 2.6

47.1 64.9

29.2 40.5

25.0 24.9

11.6 26.1 27.4

43.5 23.0

10.8 0
20 40
60 80
100
1% Ann.

Chance

0.2%
Ann.

Chance
1% Ann.

Chance

0.2%
Ann.

Chance
1% Ann.

Chance

0.2%
Ann.

Chance
1% Ann.

Chance

0.2%
Ann.

Chance
1% Ann.

Chance

0.2%
Ann.

Chance
1% Ann.

Chance

0.2%
Ann.

Chance
1% Ann.

Chance

0.2%
Ann.

Chance
Communications Energy Food, Water &
Shelter
Hazardous
Material
Health & Medical Safety & Security Transportation
Average Damage as % of Total Value
Damage to Structure
Damage to Contents
186
Ventura County Multi-Jurisdictional Hazard Mitigation Plan 11-28
Impacts on Hazardous Materials
During a flood event, containers holding hazardous materials can rupture and leak into the surrounding area. These facilities could release chemicals that cause cancer or other human health effects, significant adverse acute human health effects, or significant adverse environmental effects.

Impacts on Utilities and Infrastructure
Roads that are blocked or damaged can isolate residents and can prevent access throughout the planning area, including for emergency service providers needing to get to vulnerable populations or to make repairs. Bridges washed out or blocked by floods or debris also can cause isolation. Underground utilities can be damaged. Levees can fail or be overtopped, inundating the land that they protect.

Floodwaters can back up drainage systems, causing localized flooding. Culverts can be blocked by debris from flood events, also causing localized urban flooding. Floodwaters can get into drinking water supplies, causing contamination. Sewer systems can be backed up, causing wastewater to spill into homes, neighborhoods, rivers, and streams.

11.4.4 Environment
Flooding can impact the environment in negative ways. Migrating fish can wash into roads or over dikes into flooded fields, with no possibility of escape. Pollution from roads, such as oil, and hazardous materials can wash into rivers and streams. During floods, these can settle onto normally dry soils, polluting them for agricultural uses. Human development, such as bridge abutments, levees, or logjams from timber harvesting, can increase stream bank erosion, causing rivers and streams to migrate into non-natural courses.

Many species of mammals, birds, reptiles, amphibians, and fish live in the planning area in plant communities that are dependent upon streams, wetlands, and floodplains. Wildlife and fish are impacted when plant communities are eliminated or fundamentally altered to reduce habitat. Since water supply is a major limiting factor for many animals, riparian communities are of special importance.

Loss estimation platforms such as Hazus are not currently equipped to measure environmental impacts of flood hazards. The best gauge of vulnerability of the environment would be a review of damage from past flood events. Loss data that segregates damage to the environment was not available at the time of this plan. Capturing this data from future events could be beneficial in measuring the vulnerability of the environment for future updates.

11.5 SCENARIO
The major river systems in Ventura County flood at irregular intervals, but generally in response to a succession of intense winter rainstorms. Storm patterns of warm, moist air usually occur between early November and late March. A series of such storms can cause severe flooding in Ventura County. The worst-case scenario is a series of storms that flood numerous drainage basins in a short time. This would overwhelm local response and floodplain management departments. Major roads would be blocked, preventing access for many residents and critical functions. High river flows could cause rivers to scour, possibly washing out roads and creating more isolation problems. In the case of multi-basin flooding, the county would not be able to make repairs quickly enough to restore critical facilities. 187
Flood
11-29

11.6 ISSUES
The planning team has identified the following flood-related issues relevant to the planning area:

Accuracy of existing flood hazard mapping by FEMA regarding true flood risk within the planning area is questionable. This is most prevalent within areas protected by levees not accredited by the FEMA mapping process.

Extent of flood protection currently provided by flood control facilities (dams, dikes, and levees) is not known due to lack of established national policy on flood protection standards.

The levee system within the planning area is not consistently adequate to mitigate effects of a 1 percent-annual-chance flood.

Risk associated with the flood hazard overlaps risks associated with other hazards such as earthquakes, landslides, and coastal erosion. This provides opportunity to seek mitigation alternatives with multiple objectives that can reduce risks from multiple hazards.

Land-use practices are not consistent with the scope of regulatory floodplain management within the planning area.

How climate change will affect flood conditions in Ventura County is uncertain.

More information is needed regarding flood risk to support the concept of risk-based analysis of capital projects.

To determine cost-effectiveness of future mitigation projects, sustained effort is necessary to gather damage reports and historical damage data such as high-water marks on structures.

Ongoing flood hazard mitigation will require funding from multiple sources.

A coordinated hazard mitigation effort is necessary among jurisdictions affected by flood hazards within the County.

Floodplain residents must continue to seek and receive information about flood preparedness and resources available during and after floods.

The concept of residual risk should be considered in design of future capital flood control projects and should be communicated to residents living in the floodplain.

Promotion of flood insurance as a means of protecting private property owners from economic impacts of frequent flood events should continue.

Existing floodplain-compatible uses such as agricultural and open space must be maintained.

Pressure is constant to convert these existing uses to more intense uses within the planning area during times of moderate to high growth.

The economy affects a jurisdiction’s ability to manage its floodplains. Budget cuts and personnel losses can strain resources needed to support floodplain management.

188
189
12-1

12. LANDSLIDE

12.1 GENERAL BACKGROUND
A landslide is a mass of rock, earth or debris moving down a slope. Landslides may be minor or large and can move at slow to very high speeds. Mudslides are rivers of rock, earth, organic matter, and other soil materials saturated with water. They develop in the soil overlying bedrock on sloping surfaces when water rapidly accumulates in the ground, such as during heavy rainfall or rapid snowmelt.

Landslides in hillside terrain can pose serious hazard to downslope property and structures. They can disrupt roadways and other infrastructure lifelines, destroy private property, and cause flooding, bank erosion, and rapid channel migration. A slide can move rapidly down slopes or through channels and can strike with little or no warning. It can travel miles from its source, growing as it descends, picking up trees, boulders, cars, and anything else in its path. Although slides behave as fluids, they convey many times the hydraulic force of water due to the mass of material they carry.

In spite of their destructive potential, landslides can serve beneficial functions to the natural environment. They supply sediment and large wood to the channel network and can contribute to complexity and dynamic channel behavior critical for aquatic and riparian ecological diversity.

12.1.1 Landslide Causes
Slides are caused by a combination of geological and climate conditions and the influence of urbanization. They can be initiated by storms, earthquakes, fires, volcanic eruptions, or human modification of the land. Vulnerable natural conditions are affected by human development and the infrastructure that supports it. In some cases, irrigation increases the landslide potential. The following factors can contribute to slide formation:

Change in slope of the terrain
Increased load on the land
Shocks and vibrations
Change in water content
Groundwater movement
Frost action
Weathering of rocks
Removing or changing the type of vegetation covering slopes. 190
Ventura County Multi-Jurisdictional Hazard Mitigation Plan 12-2
While small landslides are frequently a result of human activity, the largest landslides are often naturally occurring phenomena with little or no human contribution. The sites of large landslides are typically areas of previous landslide movement that are periodically reactivated by significant precipitation or seismic events.

12.1.2 Landslide Risk Areas
Landslides are typically a function of soil type and steepness of slope. Soil type is a key indicator for landslide potential and is used by geologist and geotechnical engineers to determine soil stability for construction standards. In general, landslide hazard areas are where the land has characteristics that contribute to the risk of the downhill movement of material, such as the following:

A slope greater than 33 percent
Post-wildfire areas
A history of landslide activity or movement during the last 10,000 years Stream or wave activity, which has caused erosion, undercut a bank or cut into a bank to cause the surrounding land to be unstable
The presence or potential for snow avalanches
The presence of an alluvial fan, indicating vulnerability to the flow of debris or sediments The presence of impermeable soils, such as silt or clay, mixed with granular soils, such as sand or gravel.

The best predictor of where slides might occur is the location of past movements. Past landslides can be recognized by their distinctive topographic shapes, which can remain in place for thousands of years. Most landslides recognizable in this fashion range from a few acres to several square miles.

Most show no evidence of recent movement and are not currently active. A small proportion of them may become active in any given year, with movements concentrated within all or part of the landslide masses or around their edges. The recognition of ancient dormant landslide sites is important in the identification of areas susceptible to flows and slides because they can be reactivated by earthquakes or by exceptionally wet weather. Also, because they consist of broken materials and frequently involve disruption of groundwater flow, these dormant sites are vulnerable to construction-triggered sliding.

12.1.3 Secondary Hazards
Landslides that block rivers or streams can contribute to flooding.

12.2 HAZARD PROFILE

12.2.1 Past Events
Table 12-1 lists known landslide events that affected Ventura County between 1995 and 2021. 191
Landslide
12-3
Table 12-1. Landslide Events in the Planning Area
Date Event Type
FEMA Declaration
Number Location
March 8, 2016 Mudslide N/A Solimar
Losses/Impacts: Near the Solimar burn area, heavy rain produced a mud and debris flow across Highway 101.

December 2014 Landslide, Mudslide N/A Camarillo Springs Losses/Impacts: Heavy rains destabilized the wildfire char area above Camarillo Springs. 13 homes were damaged and considered uninhabitable.

February 16 – 23, 2005Severe Storms, Flooding, Landslides, and Mud and Debris Flows
DR-1585 Ventura County
Losses/Impacts: Seven Southern California counties were included in the declaration.

Winter 2005 Landslide, Debris Flow, Severe Storm N/A West of Santa Paula Losses/Impacts: A large landslide that transformed into a debris flow and smaller landslides was triggered by strong winter storms January 10, 2005 Landslide N/A La Conchita
Losses/Impacts: The landslide occurred at the end of a 15-day period that produced record and near-record amounts of rainfall in many areas of southern California. It consisted of a remobilization of a portion of the 1995 landslide deposit. It destroyed 13 homes and severely damaged 23 others. Ten people died.

Dec. 27, 2004 – Jan. 11, 2005 Severe Storms, Flooding, Debris Flows, and Mudslides DR-1577 Ventura County Losses/Impacts: Eight Southern California counties were included in the declaration.

March 4, 1995 Landslides, Debris Flow, Severe Storm N/A La Conchita Losses/Impacts: After seasonal rainfall approximately twice the normal amount, the hill behind La Conchita failed, destroying or severely damaging nine homes. Several days later, debris flows from a canyon to the northwest damaged five additional homes.

February 13 – April 19, 1995Severe Winter Storms, Flooding, Landslides, Mud Flows DR-1046 Ventura County Losses/Impacts: All California counties except Del Norte were included in this declaration. More than 100 stations recorded their greatest ever 1-day rainfall total.

Jan. 3 – Feb. 10, 1995 Severe Winter Storms, Flooding, Landslides, Mud Flows DR-1044 Ventura County Losses/Impacts: 42 California counties were included in this declaration.

Source: USGS 2005, TWC 2015, FEMA 2021
The bluff above La Conchita, which is underlain by two rock formations separated by the Red Mountain fault, has been associated with a variety of landslide activity. Historical accounts date back to 1865.

More recently, two small slides occurred in 1988 and 1991, followed by large movements in 1995 and 2005. The 1995 landslide, which occurred one month after the heaviest rainfall of an extraordinarily wet year, was considered to be a deep, slow-moving landslide. This landslide destroyed nine houses. The January 2005 event was a shallow and highly fluid remobilization of the same material that carried a thick layer of dry, viscous material. This landslide, which occurred at the peak of an extremely wet two- week period, killed 10 people and destroyed 13 homes. Approximately 400,000 tons of debris cascaded down the slope behind the La Conchita housing development.

12.2.2 Location
In 2011, the California Geological Survey conducted a statewide analysis using a combination of regional rock strength and slope data to create classes of susceptibility to deep-seated landslides. The analysis assumed, in general, that susceptibility to deep-seated landslides is low on very low slopes in all rock materials and increases with slope and in weak rocks. The analysis also factored in locations of past landslides. Figure 12-1 shows deep-seated landslide susceptibility classes (none, low, moderate, high, and very high).
192
Fillmore
Moorpark
Simi Valley
Santa Paula
Oxnard
Ojai
Port
Hueneme
Camarillo
San
Buenaventura
Thousand Oaks
Lake Piru
Lake
Casitas
11833
34 118126
150
1 1
23 126
23 33
33 34
1 150
232
33 23
101
Figure 12-1. Susceptibility to Deep-Seated Landslides
Data Sources: Ventura Co.,
CGS, Esri
low
moderate
high
very high
County Boundary
Cities
Major Roads
0 6 3 Miles
193
Landslide
12-5
Landslides have occurred in areas along the Rincon Fault and on hillsides south of the Santa Clara River and east of the Ventura River. The most damaging recent landslides in Ventura County occurred in the coastal community of La Conchita, just southeast of the Santa Barbara county line. La Conchita has been the site of multiple non-earthquake-induced landslides. The community was built on ground that had been graded by the Southern Pacific Railroad after a 1909 landslide slid into the railroad tracks. The land was intended to be a buffer zone between the retreating and eroding cliff and the Pacific Ocean, but it was subdivided into residential lots in 1924.

12.2.3 Frequency
Mass movements are often triggered by other natural hazards such as earthquakes, heavy rain, floods or wildfires, so their frequency is often related to the frequency of the precipitating hazards. In Ventura County, landslides typically occur during and after severe storms, so the potential for landslides largely coincides with the potential for sequential severe storms that saturate steep, vulnerable soils. Most weather-induced landslides in the county occur in the winter after the water table has risen. Landslides that result from earthquakes can occur at any time.

The probability of a landslide event occurring in the County in any given year is high. Table 12-1 lists nine landslide events in the County between 1995 and 2021. Federal disaster declarations were issued for four of these—an average of one such major event every six years.

12.2.4 Severity
Landslides destroy property and infrastructure and can claim human lives. They have the potential of destabilizing the foundation of structures, which may result in monetary loss for residents. Slope failures in the United States result in an average of 25 to 50 lives lost per year (U.S. Geological Survey 2020). Over the past 26 years, 10 lives have been lost in Ventura County from slope failures. Slides can pose a serious hazard to properties on or below hillsides. They can block access to roads, which can isolate residents and businesses and delay commercial, public, and private transportation. This can result in economic losses for businesses. Trees or utility poles on slopes can be knocked over, resulting in possible losses to power and communication lines. Landslides also can damage rivers or streams, potentially harming water quality, fisheries, and spawning habitat.

12.2.5 Warning Time
Landslides can occur suddenly or slowly. The velocity of slide may range from a slow creep of inches per year to many feet per second, depending on slope angle, material, and water content. Generally accepted warning signs for landslide activity include the following:

Springs, seeps, or saturated ground in areas that have not typically been wet before New cracks or unusual bulges in the ground, street pavements, or sidewalks Soil moving away from foundations
Ancillary structures such as decks and patios tilting or moving relative to the main house Tilting or cracking of concrete floors and foundations
Broken water lines and other underground utilities
194
Ventura County Multi-Jurisdictional Hazard Mitigation Plan 12-6
Leaning telephone poles, trees, retaining walls or fences Offset fence lines
Sunken or down-dropped road beds
Rapid increase in creek water levels, possibly accompanied by increased turbidity (soil content) Sudden decrease in creek water levels though rain is still falling or just recently stopped Sticking doors and windows and visible open spaces indicating frames out of plumb A faint rumbling sound that increases in volume as the landslide nears Unusual sounds, such as trees cracking or boulders knocking together.

Some methods used to monitor landslides can provide an idea of the type of slide and the amount of time prior to failure. Assessing the geology, vegetation, and amount of predicted precipitation for an area can help in predictions of what areas are at risk during general time periods. Currently, there is no practical warning system for individual landslides, however. The standard operating procedure is to monitor situations on a case-by-case basis and respond after an event has occurred.

12.3 EXPOSURE
A quantitative assessment of exposure to the mass movement/landslide hazard was conducted using the landslide hazard mapping and the asset inventory developed for this plan, with an emphasis on the zones with the highest degree of susceptibility (Zones V through X). Detailed results by jurisdiction are provided in Appendix D. Results for the whole planning area are presented in the sections below.

12.3.1 Population
Population exposure was estimated by calculating the number of buildings in each hazard area as a percent of total planning area buildings, and then applying this percentage to the estimated planning area population. Table 12-2 summarizes the estimated countywide population living in the mapped landslide risk areas.

Table 12-2.Exposed Population in Mapped Landslide Hazard Zones

12.3.2 Property
Table 12-3 summarizes the estimated property exposure in the evaluated landslide hazard areas.

Figure 12-2 shows the occupancy class defined by Hazus for all buildings in the mapped landslide hazard areas. These occupancy classes provide an indication of land use within the mapped hazard area. Some land uses are more vulnerable to landslides, such as single-family homes, while others are less vulnerable, such as agricultural land or parks.
195
Landslide
12-7
Table 12-3. Exposed Property in Mapped Landslide Hazard Zones

Moderate Landslide
Risk (Susceptibility
Categories V and VI)
High Landslide Risk
(Susceptibility
Categories VII, VIII, IX)
Very High Landslide Risk
(Susceptibility Category X;
Includes existing landslides)
Number of Buildings Exposed 11,850 52,054 4,743
Value of Exposed Structures $4,978,606,389 $20,201,170,128 $1,802,233,448 Value of Exposed Contents $2,924,877,062 $12,899,948,351 $1,122,397,897 Total Exposed Property Value $7,903,483,451 $33,101,118,479 $2,924,631,346 Total Exposed Value as % of Planning Area Total4.4% 18.3% 1.6% Figure 12-2. Building Occupancy Classes in the Mapped Landslide Hazard Zones

Residenti
al
10,489…
Commercia
l
393…
Industri
al
26 0%
Agricultur
e
793…Religion
48 0%
Governme
nt
28…
Educatio
n
73…

MODERATE LANDSLIDE RISK
Residential
44,625
86%
Commercial
2,142
4%
Industrial
293
0%
Agriculture
3,989
8%
Religion
394
1%
Government
285
0%
Education
326
1%

HIGH LANDSLIDE RISK
Residential
3,664
77%
Commercial
219
5%
Industrial
7 0%
Agriculture
752
16%
Religion
51 1%
Government
39 1%
Education
11 0%

VERY HIGH LANDSLIDE RISK
196
Ventura County Multi-Jurisdictional Hazard Mitigation Plan 12-8

12.3.3 Critical Facilities
Figure 12-3 shows critical facilities located in the high or very high landslide risk areas, by facility type.

The total count of critical facilities in these risk areas (341) represents 22 percent of the planning area total of 1,588. A breakdown by municipality is provided in Appendix D.

Figure 12-3. Critical Facilities in High or Very High Landslide Risk Areas

12.3.4 Environment
All natural areas within the high susceptibility zones for landslide are considered to be exposed to the hazard.

12.4 VULNERABILITY
Vulnerability estimates for the landslide hazard are described qualitatively. No loss estimation of these facilities was performed because damage functions have not been established for the landslide hazard.

12.4.1 Population
All people exposed the landslide hazard are potentially vulnerable to landslide impacts. Populations with access and functional needs as well as elderly populations and the very young are more vulnerable to the landslide hazards as they may not be able to evacuate quickly enough to avoid the impacts of a landslide.
38 27
74 9
1 64
140
0 30
60 90
120
150Number of Facilties in Hazard Area
Communication
Energy
Food, Water, Shelter
Hazardous Materials
Medical and Health
Safety and Security
Transportation

15.2%

24.3%

35.2%

9.7% 10.0%

16.4%

26.8%
0%
20%
40%
60%
80%
100%Facilties in Hazard Area as % of Planning Area Total Communication
Energy
Food, Water, Shelter
Hazardous Materials
Medical and Health
Safety and Security
Transportation
197
Landslide
12-9

12.4.2 Property
Estimates of potential losses associated with landslides were developed representing 10 percent, 30 percent, and 50 percent of the replacement value of structures exposed to the landslide hazard. This allows emergency managers to assess potential economic impact based on assumptions about the percent of damage to the general building stock. Damage in excess of 50 percent is considered to be substantial by most building codes and typically requires total reconstruction of the structure.

Table 12-4 shows potential losses in the areas with the highest degree of landslide susceptibility.

Table 12-4. Loss Estimation for Landslide

Exposed Value
(Structure Only) Loss Value
Loss as % of Total Planning Area
Replacement Value
Moderate Landslide Susceptibility Zone
Loss = 1% of Exposed Value
$4,978,606,389
$49,786,064 0.03%
Loss = 10% of Exposed Value $497,860,639 0.28%
Loss = 30% of Exposed Value $1,493,581,917 0.83%
Loss = 50% of Exposed Value $2,489,303,195 1.38%
High Landslide Susceptibility Zone
Loss = 1% of Exposed Value
$20,201,170,128
$202,011,701 0.11%
Loss = 10% of Exposed Value $2,020,117,013 1.12%
Loss = 30% of Exposed Value $6,060,351,038 3.35%
Loss = 50% of Exposed Value $10,100,585,064 5.59%
Very High Landslide Susceptibility Zone
Loss = 1% of Exposed Value
$1,802,233,448
$18,022,334 0.01%
Loss = 10% of Exposed Value $180,223,345 0.10%
Loss = 30% of Exposed Value $540,670,034 0.30%
Loss = 50% of Exposed Value $901,116,724 0.50%

12.4.3 Critical Facilities
There are 341 critical facilities exposed to the landslide hazard to some degree. An in-depth analysis of mitigation measures taken by these facilities should be completed to evaluate whether they could withstand impacts of a landslide. No loss estimates were developed as a result of the lack of established damage functions for the landslide hazard.

12.4.4 Environment
Environmental problems as a result of landslides can be numerous. A landslide alters the landscape. In addition to changes in topography, vegetation and wildlife habitats may be damaged or destroyed, and soil and sediment runoff will accumulate downslope, potentially blocking waterways and roadways and impairing the quality of streams and other water bodies. Landslides that fall into streams may significantly impact fish and wildlife habitat, as well as affecting water quality. Hillsides that provide wildlife habitat can be lost for prolonged periods of time due to landslides. 198
Ventura County Multi-Jurisdictional Hazard Mitigation Plan 12-10

12.5 SCENARIO
Major landslides in Ventura County typically occur as a result of soil conditions affected by severe storms, wildfires, groundwater, or human development. The worst-case scenario for landslide hazards in the planning area would generally correspond to a severe storm with heavy rain that caused flooding in an area that had been burned by wildfire. Landslides are more likely during the late winter when the water table is high. After heavy rains from November to December, soils become saturated with water.

As water seeps downward through upper soils that may consist of permeable sands and gravels and as it accumulates on impermeable silt, it will weaken and destabilize the slope. A short intense storm could cause saturated soil to move, resulting in landslides. As rains continue, the groundwater table rises, adding to the weakening of the slope. Gravity, poor drainage, a rising groundwater table, and poor soil exacerbate hazardous conditions.

Landslides are becoming a greater concern as development moves outside of city centers and into areas with less developed infrastructure. Most landslides would be isolated events affecting specific areas. It is probable that private and public property, including infrastructure, would be affected.

Landslides could affect bridges that pass over landslide-prone ravines and knock out rail service through the County. Road obstructions caused by landslides would create isolation problems for residents and businesses in sparsely developed areas. Property owners exposed to steep slopes may suffer damage to property or structures. Landslides carrying vegetation such as shrubs and trees may cause a break in utility lines, cutting off power and communications to residents.

Continued heavy rains and flooding would complicate the problem further. As emergency response resources are applied to problems with flooding, it is possible they will be unavailable to assist with landslides across Ventura County.

12.6 ISSUES
Important issues associated with landslides in the planning area include the following:

The data and science regarding mapping and assessing landslide hazards are constantly evolving. As new data and science become available, assessments of landslide risk should be re-evaluated.

The impact of climate change on landslides is uncertain. If climate change affects atmospheric conditions, the exposure to landslide risks in Ventura County could increase.

There are existing homes in landslide risk areas throughout the County. The degree of vulnerability of these structures depends on the codes and standards applied in constructing the structures.

Future development could lead to more homes in landslide risk areas.

Landslides may cause negative environmental consequences, including water quality degradation.

The risk associated with the landslide hazard overlaps the risk associated with other hazards, including earthquake, flooding, and wildfire. The County has an opportunity to seek mitigation alternatives with multiple objectives that can reduce risk for multiple hazards.

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13. SEA-LEVEL RISE AND COASTAL EROSION

13.1 GENERAL BACKGROUND

13.1.1 Coastal Erosion
Coastal erosion occurs when strong wave action, coastal floods, and local sea-level rise wear away rocks, soil, and sand along a coastline. This is compounded during severe storm events. In the United States, coastal erosion causes roughly $500 million in property loss each year. Coastal erosion affects all shorelines, but erosion rates and potential impacts are highly localized (U.S. Climate Resilience Toolkit 2021). Coastal erosion can exacerbate high surf or tsunami/run-up incidents along coast flood zones subject to wave action. Coastal erosion includes:

Beach erosion, when sand is carried away from a beach and deposited farther from shore Dune erosion, when sand or sediment not normally affected by wave action is carried away from land and deposited farther from shore
Low air pressure during a storm causes an immediate rise in sea level above predicted tides, referred to as storm surge. It also increases wind activity, generating erosive waves on top of the already high sea level. This combination of factors can cause widespread damage in coastal areas. Sandy beaches and dunes are at risk from inundation and erosion related to sea-level rise and climate change-induced storms (The Nature Conservancy 2021a).

The following human activities may increase coastal erosion:

Shoreline hardening such as building seawalls, which may protect land directly behind the structure but can accelerate coastal erosion on the waterward side of the structure due to scouring.

Dune leveling for development, which removes the natural protection from high waves and sea- level rise.

Canalization to control flash flooding, which may trap sand in coastal channel mouths.

Accumulated sand may be removed offsite, leaving a deficiency in the immediate beach area.

Salt mining

13.1.2 Sea-Level Rise
Sea-level rise will increase the risk of erosion and the adverse impacts of storm surge and high waves.

Short-term variations in sea level occur daily as a result of waves, tides, or specific flood events. Long- term variations in sea level occur over various time scales, from monthly to yearly, and may be 200
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repeatable cycles, gradual trends, or intermittent differences. Seasonal weather patterns, changes in coastal and ocean circulation, anthropogenic influences, vertical land motion, and other factors may influence changes in the sea level over time. When sea level trends are estimated, a minimum of 30 years of data are used to account for long-term sea level variations and reduce errors in computing sea level trends based on the monthly mean sea level (National Oceanic and Atmospheric Administration 2021).

The two major causes of sea-level rise are thermal expansion caused by the warming of the oceans and loss of land-based ice (glaciers and polar ice caps) through increased melting. A steady increase in global atmospheric temperature creates an expansion of saltwater molecules, increasing ocean volume. The melting of glaciers and continental ice masses contributes significant amounts of freshwater to the earth’s oceans. Ice-mass loss has caused twice as much sea-level rise since 1900 as has thermal expansion. The acceleration in sea-level rise since the 1970s has resulted from the combination of thermal ocean expansion and increased ice-mass loss from Greenland (Frederikse, et al. 2020).

There are two types of sea level: global and relative. Global sea level refers to the average sea level worldwide. Global sea level has been rising over the past century, and the rate has increased in recent decades. In 2014, global sea level was 2.6 inches above the 1993 average—the highest annual average change in the satellite record (1993 to present). Sea level continues to rise at a rate of about one-eighth of an inch per year (National Oceanic and Atmospheric Administration 2021).

Local sea level refers to the height of water measured along the coast relative to a specific point on land. The heights of both the land and water are changing, so the land-water interface can vary spatially and temporally and must be defined over time. Measurements at any given tide station include the effects of both global sea-level rise and vertical land motion (subsidence, glacial rebound, or large- scale tectonic motion). Water level measurements at tide stations are referenced to stable vertical points on the land, and a known relationship is established. Changes in local sea level over time are typically the most critical sea level trend for coastal applications such as coastal mapping, marine boundary delineation, coastal zone management, coastal engineering, and sustainable habitat restoration (National Oceanic and Atmospheric Administration 2021).

13.1.3 Secondary Hazards
Loss of beaches due to erosion and sea-level rise can have negative impacts on ecosystems, native species, cultural and historical sites, recreation, subsistence practices, and tourism.

13.2 HAZARD PROFILE

13.2.1 Past Events
Coastal Erosion
Known coastal erosion events affecting Ventura County between 1980 and 2021 are identified in Table 13-1.
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Table 13-1. History of Coastal Erosion Events
Date Event Type FEMA Declaration Number Location
January 2021 Coastal Erosion N/A Surfer’s Point, City of San Buenaventura Losses/Impacts: The 2021 damage was more than anticipated, as relatively calm conditions were predicted with “La Niña” conditions dominating the Pacific Ocean. However, an anomalous storm track developed producing a series of large swell events during the entire month of January, some coinciding with the year’s highest tides. Erosion undermined the bike path and several parking spaces.

February 2014 Coastal Erosion N/A Port Hueneme
Losses/Impacts: 14 feet of sand washed away during the month of February February 27, 2010 Tsunami, Coastal Erosion N/A Ventura Harbor Losses/Impacts: Tsunami waves in excess of 3 feet affected the coastal areas of Ventura County. At Ventura Harbor, the tsunami damaged at least 21 docks, displaced several buoys, and produced some significant beach erosion.

Sources: KABC 2014, venturariver.org 2021, NOAA 2021
The beaches south of Channel Islands Harbor are subject to continual erosion. Every two years, the harbor is dredged to remove sand that has accumulated from beach erosion and sand migration. The sand is used to replenish eroded sand at Port Hueneme Beach (U.S. Army Corps of Engineers 2021).

The City of San Buenaventura has had ongoing erosion at Surfer’s Point, a popular surfing spot adjacent to the mouth of the Ventura River. A California State Park bike path along the shoreline and an adjacent county fairground parking lot have also experienced frequent damage from erosion. To protect the point, the City placed boulders in the 1980s above the mean high tide line. The project ended up exacerbating erosion further down the coast and the fairground parking lot and bike path have continued to erode into the ocean; in some places more than 60 feet of land have been lost (Georgetown Climate Center 2011). The Surfers’ Point Managed Shoreline Retreat Project has since pulled existing structures inland to make room for natural beach processes. Though the situation has improved, rising sea levels will continue to threaten the beach (U.S. Climate Resilince Toolkit 2021).

Sea-Level Rise
The average annual mean sea level recorded by NOAA at the Los Angeles station for 1950 was 2.5955 feet. By 2020, the elevation had risen to 2.9724 feet. This represents a sea-level rise of more than 4.5 inches in 70 years (National Oceanic and Atmospheric Administration 2021).

13.2.2 Location
Ninety-three percent of Ventura County’s shoreline consists of sandy beaches. Sea-level rise and coastal erosion are likely to affect all coastal areas of the county. The North Coast beaches are highly vulnerable to erosion and wave damage. Dredging operations in Santa Barbara Harbor alter sand transport down coast. Without adequate replacement sand, high tides and waves erode the beaches.

The Central Coast is subject to erosion during periods of high tides and wave action. Major erosion occurs on the South Coast during winter, including nearly 2 feet of annual erosion at Sycamore Beach (Ventura County 2020). The Our Coast Our Future sea-level rise data was used in the risk assessment for this hazard mitigation plan. The data indicate sea-level rise inundation areas for a sea-level rise of 25 centimeters and 100 centimeters. The mapped inundation areas for these two scenarios (25-cm SLR and 100-cm SLR) are shown on Figure 13-1 and Figure 13-2. 202
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Figure 13-1. Estimated Inundation Area for 25-Centimeter Sea Level Rise Data Sources: Ventura Co.,
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Figure 13-. Estimated Inundation Area for 100-Centimeter Sea Level Rise Data Sources: Ventura Co.,
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13.2.3 Frequency
Coastal erosion results from storms and flooding, which typically occur in California in winter (November to April). Storm severity and frequency are influenced by climate patterns, most prominently the El Niño Southern Oscillation. Every two to seven years, the Southern Oscillation alternates between two phases—La Niña and El Niño. El Niño years generally result in persistently low air pressure, greater rainfall, and high winds. The water levels reached during these large, short-term events have exceeded mean sea levels projected for 2100, so understanding their additive effects is crucial for coastal planning. Individual erosion events are not regularly reported; however, according to the Ventura County General Plan 2040, many coastal areas experience annual beach erosion including:

Faria Beach Park: 1.3 feet per year
Emma Wood State Beach: 0.6 feet per year
Point Mugu State Park, Sycamore Beach: 1.9 feet per year Point Mugu State Park, Solromar Beach: 0.9 feet per year Sea-level rise is an ongoing phenomenon that will likely impact the frequency and severity of coastal storms. As sea-level rises, flooding from storms will become more frequent and potentially more hazardous.

13.2.4 Severity
Coastal erosion can destroy property and infrastructure and cause loss of human life. Erosion has the potential to destabilize the foundation of structures, which may result in monetary loss for residents.

The collapse of coastal cliffs can be deadly, although it is unknown if any deaths have occurred in Ventura County as a result of coastal erosion.

The severity of sea-level rise to Ventura County will become greater over the next 30 to 80 years. The severity could be exacerbated by the following conditions:

Daily tidal inundation—As sea-level rises, the amount of land and infrastructure subjected to daily inundation by high tides—also known as increases in mean higher high water—will increase. This would result in increased permanent future inundation of low-lying areas.

Annual high tide inundation (King Tides)—King Tides are abnormally high, predictable astronomical tides that occur about twice per year. they are the highest tides that occur each year during the winter and summer when the Earth, moon and sun are aligned. Winter King Tides may be amplified by stormy weather, making them even more significant. King Tides result in temporary inundation associated with nuisance flooding, such as inundation of low-lying roads, boardwalks, and waterfront promenades.

Extreme high tide inundation (storm surge)—When Pacific Ocean storms coincide with high tides, storm surge can elevate ocean levels and produce extreme high tides. Extreme high tides can cause severe inundation of low-lying roads, boardwalks, and promenades. They can exacerbate coastal and riverine flooding, cause upstream flooding, and interfere with stormwater outfalls.
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13.2.5 Warning Time
Sea-level rise is not a hazard that requires near-term advance warning to support response and recovery operations. Programs such as the NOAA sea-level rise program are keeping an active watch on the sea-level rise phenomena to keep communities informed of its progression. This stream of information will feed programs to help the County to be prepared for and mitigate the long-term impacts from sea-level rise.

The timing of individual erosion events cannot be predicted, however general forecasting can be made about high surf conditions, which often result in advanced beach erosion. High surf warnings and high surf advisories are issued by the National Weather Service.

13.3 EXPOSURE
An analysis was performed using the 25-cm SLR and 100-cm SLR sea-level rise scenarios to estimate the potential exposure of resources within the planning area. Appendix D presents detailed exposure results for each coastal city in the planning area. County-wide summary results are presented in the sections below. Exposure analysis is not available for coastal erosion due to a lack of data, and storm events were not combined with the sea-level rise analysis. If erosion, large wave events, and storms were included, the exposure metrics and vulnerability results for population, property, and critical facilities would be substantially higher.

13.3.1 Population
The planning team overlaid the sea-level rise projection data on the population and asset data developed for the hazard risk assessment for this plan. Results for the total planning area are presented in Table 13-2.

Table 13-2. Estimated Population Exposure for Sea-Level Rise 25-cm SLR Scenario 100-cm SLR Scenario
Population Exposed 39 563
% of Total Planning Area Population 0.002% 0.07%

13.3.2 Property
Results for property exposed to the sea-level rise hazard for the total planning area are presented in Table 13-3. Current land use distribution in the areas affected by sea-level rise, as represented by building occupancy class, is shown in Figure 13-3.

Table 13-3. Estimated Property Exposure for Sea-Level Rise 25-cm SLR Scenario 100-cm SLR Scenario
Number of Buildings Exposed 10 249
Value of Exposed Structures $15,774,103 $140,841,021
Value of Exposed Contents $14,460,807 $121,450,187
Total Exposed Property Value $30,234,909 $262,291,208
Total Exposed Value as % of Planning Area Total 0.02% 0.15% 206
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Figure 13-3. Building Occupancy Classes in 25-cm and 100-cm Sea-Level Rise Exposure Areas

13.3.3 Critical Facilities
Hazus analysis identified only one critical facility within the mapped 25-cm sea-level rise inundation zone (a transportation facility) and only six within the mapped 100-cm sea-level rise inundation zone (four transportation facilities, one hazardous materials facility, and one food/water/shelter facility). A breakdown by municipality is provided in Appendix D.

13.3.4 Environment
All county beaches and other critical coastal habitats, including wetlands, are vulnerable to the effects of sea-level rise and coastal erosion. A study by the State Coastal Conservancy and The Nature Conservancy found that 44 percent of estuarine marsh in Ventura County is vulnerable to loss with 5 feet of sea-level rise (Heady, et al. 2018).

13.4 VULNERABILITY
No quantitative vulnerability analysis was performed for the sea-level rise and coastal erosion hazard.

The following potential impacts were identified:

Storm drainage systems may experience backups as a result of higher level of daily tidal flooding, especially if outfalls are located within sea-level rise inundation areas.

Important coastal habitat may be lost as sea-level rise permanently inundates areas, or it may be damaged due to extreme tide and storm surge events.

Saltwater intrusion into freshwater resources may occur, further altering habitat and ecosystems. Protective ecosystem services may be lost as land area and wetlands are permanently inundated.

Residents of homes exposed to coastal erosion are vulnerable to this hazard.

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Sea-level rise will have an impact on Ventura Countys coastal ecosystems. Aquatic ecosystems located in creeks, streams, and estuaries along the coast, many containing a range of sensitive species of plants and animals, will need to adapt to changes in water quality from saltwater intrusion/incursion further upstream. The beneficial services that coastal ecosystems provide, such as flood protection, water filtration, and support for fisheries, will be threatened as rising sea levels expose beach, dune, estuarine, and freshwater habitats. Natural resources, such as cobble, sand, and dunes that have been overlooked for coastal planning will be increasingly necessary to hold and maintain the Countys beaches for sea-level rise adaptation (Ventura County 2020).

Erosion and associated secondary hazards will likely have some of the most damaging effects on the environment. Coastal habitats are critical to the natural environment, society, and economy, and their loss has compounding effects on the vulnerability of the community at large.

13.5 SCENARIO
The worst-case scenario would be high wave events from winter storms coinciding with high tide.

During a scenario of this magnitude, individuals and properties alike are potentially impacted by high surf, coastal flooding and erosion. The impacts of such an event will become greater with time if sea- level rise continues.

13.6 ISSUES
The following issues have been identified related to the sea-level rise and coastal erosion hazard:

Potential Impacts from Sea-Level RiseRising sea levels are very likely to have significant impacts on the frequency and severity of coastal erosion. Areas not typically exposed to erosion events may become exposed, increasing vulnerability to this hazard of concern.

Future Development Impact StudiesErosion events are particularly destructive when natural processes are unable to replenish beaches due to development, causing erosion to impact infrastructure. Building on eroding coasts increases vulnerability to shoreline hazards.

Local jurisdictions need to ensure that future development does not contribute to coastal erosion.

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14. SEVERE STORMS

14.1 GENERAL BACKGROUND
The severe storms hazard for this plan refers specifically to winter storms and thunderstorms with the potential to cause damage, serious social disruption, or loss of human life. Other severe weather hazards are addressed in Chapter 15.

14.1.1 Winter Storms
California’s southern coast features a Mediterranean climate, in which summers are hot and dry and winters are cool and damp. A dominating factor in the weather of California is the semi-permanent high- pressure area of the North Pacific Ocean, sometimes called the Pacific High. This pressure center moves northward in summer, holding storm tracks well to the north. As a result, California receives little or no precipitation during that period. The intensity of the Pacific High decreases in winter and it moves farther south, permitting storms to move into and across the state and producing high winds, widespread rain at low elevations, and snow at high elevations.

Occasionally the state’s circulation pattern permits a series of storm centers to move into California from the southwest. This type of storm pattern is responsible for occasional heavy rains that can cause serious winter flooding. Winter storms may occur during the rainy season from mid-autumn to mid- spring. In addition to high winds and flooding, winter storms may bring extended periods of freezing temperatures to the county.

14.1.2 Thunderstorms
NOAA classifies a thunderstorm as a storm with lightning and thunder produced by cumulonimbus clouds, usually producing gusty winds, heavy rain, and sometimes hail. Thunderstorms are usually short in duration (seldom more than two hours), but they may deliver enough rainfall to cause urban or flash flooding. In addition to the hazards associated with heavy rainfall, thunderstorms present hazards associated with lightning and hail:

Lightning is an electrical discharge that results from the buildup of positive and negative charges within a thunderstorm. When the buildup becomes strong enough, lightning appears as a bolt.

This flash of light usually occurs within the clouds or between the clouds and the ground. A bolt of lightning instantaneously reaches temperatures approaching 50,000 ºF. The rapid heating and cooling of air near the lightning causes thunder.
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Hail occurs when updrafts in thunderstorms carry raindrops up into cold areas where they freeze. Eventually, the hailstones encounter downdraft air and fall to the ground. Hailstones can begin to melt and then re-freeze together, forming large and irregularly shaped hail.

14.1.3 El Niño Effects on Severe Storms
El Niño is a natural climatic event that impacts the frequency and intensity of severe storms. It is characterized by a warming of the ocean surface in the central and eastern tropical Pacific Ocean. Low- level surface winds, which normally blow from east to west along the equator, instead weaken or, in some cases, start blowing the other direction. El Niño recurs irregularly, from once every two years to once a decade. El Niño events can disrupt normal weather patterns in the United States and globally (U.S. Geological Survey 2021d). The most recent strong El Niño events were as follows:

The 1997–1998 El Niño event gained national recognition for its contribution to hurricanes, floods, landslides, droughts, and fires that killed substantial numbers of people and caused billions of dollars in damage. Australia, Indonesia, and the Americas were particularly impacted.

The 2015–2016 El Niño event affected California, since the state was already dealing at that time with the impacts of a long-term drought (Lee, et al. 2017).

14.1.4 Secondary Hazards
Major flooding can result from heavy rain (see Chapter 11 for more information on flooding). Rain falling on saturated soils on slopes or on areas recently burned by wildfire may lead to landslides (see Chapter 12 for more information on landslides). Lightning during thunderstorms presents a risk of starting a wildfire (see Chapter 17 for more information on wildfires). Storms can also increase the frequency of erosion along coastal cliffs (see Chapter 13 for more information on coastal erosion).

14.2 HAZARD PROFILE

14.2.1 Past Events
Ventura County was included in the federal disaster declarations for freezing/severe winter storms that occurred in December 1990-January 1991, December 1998, and January 2007. The 1998 freeze was particularly damaging to citrus crops. According to the NCEI Storm Events Database, 26 winter storms and thunderstorms causing snow and ice have occurred in Ventura County over the last 10 years.

Some of the thunderstorms also caused hail. Two hailstorms were recorded in Ventura County in 2010, with hail of up to 1.5 inches in diameter reported. Table 14-1 summarizes recent severe storm events in Ventura County as recorded in the Storm Events Database.

Table 14-1. Recent Severe Storm Events in the Planning Area Date Type Deaths or Injuries Property Damage
January 27-29, 2021 Winter Storm 0 0
Snowfall totals around 12 inches were reported at 5,000 feet. The snow combined with southerly winds, gusting to 70 mph, to generate hazardous winter weather conditions.

January 25, 2021 Winter Storm 0 0
Winter storm conditions impacted the mountains of Ventura County. Snowfall totals between 3 and 6 inches and southerly wind, gusting up to 65 mph, combined to produce hazardous winter weather conditions. 211
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Date Type Deaths or Injuries Property Damage
December 28, 2020 Winter Storm 0 0
Above 5,000 feet, 6 to 12 inches of snowfall was reported. Additionally, southerly winds, gusting up to 45 mph, were reported.

March 16, 2020 Winter Storm 0 0
At around 5,000 feet, snowfall totals of 4 to 8 inches were reported with likely heavier amounts above 7,000 feet. Additionally, southerly winds, gusting to 50 mph, were observed.

December 26, 2019 Winter Storm/Thunderstorm 0 0
Snowfall totals ranged from 18 to 24 inches above 5,000 feet to 6 to 18 inches between 3,500 and 5,000 feet. Strong winds with gusts to 55 mph were reported. The winter storm conditions resulted in road closures, including Highway 33. Thunderstorms generated a waterspout over the coastal waters and a very weak tornado over Ventura Harbor.

November 28-29, 2019 Winter Storm 0 0
Snow levels dropped to between 2,000 and 3,000 feet. Snowfall totals ranged between 12 and 24 inches above 5,000 feet with 6 to 12 inches down to around 3,000 feet. Additionally, gusty winds in excess of 50 mph were reported. These winter storm conditions resulted in significant travel issues, including closure of parts of Highway 33.

January 9, 2018 Winter Storm 0 0
At around 7,000-foot elevation, 6 to 8 inches of snowfall was reported along with southerly winds, gusting to 50 mph.

February 18, 2017 Winter Storm 0 0
In the mountains, 8 to 16 inches of snow accumulated. Additionally, southerly winds gusting to 70 mph were reported.

March 7-8, 2016 Winter Storm/Thunderstorm 0 0
In the mountains, 5 to 10 inches of snow accumulated while winds gusted to 67 mph. Near the Solimar burn area, heavy rain produced a mud and debris flow across Highway 101. Elsewhere, strong thunderstorm gusts knocked down several trees.

January 31, 2016 Winter Storm/Thunderstorm 0 0
Above 6,000 feet, between 6 and 12 inches of snow was reported. Some severe thunderstorms developed with strong thunderstorm winds (in excess of 60 mph) reported.

January 6, 2016 Thunderstorm 0 0
A severe thunderstorm moved across the community of Fillmore, generating damaging wind gusts up to 60 mph. The thunderstorm winds knocked down a large tree across Highway 126.

January 5-6, 2016 Winter Storm 0 0
Above 7,000 feet, Mount Pinos reported 12 to 18 inches of snowfall while locations around 5,000 feet reported 4 to 8 inches of snowfall.

Along with the snow, south winds gusting between 45 and 60 mph were reported.

March 1, 2014 Winter Storm/Thunderstorm 0 0
Snowfall amounts between 6 and 12 inches were reported above 6,000 feet along with southerly winds gusting to near 90 mph. This winter storm generated intense showers that produced flash flooding and debris flows as well as severe thunderstorms.

February 20, 2013 Winter Storm 0 0
Along with northwest winds gusting in excess of 50 mph, snowfall amounts between 6 and 12 inches were observed, with the highest totals reported at Mount Pinos.

January 10, 2013 Winter Storm 0 0
A band of heavy snowfall, combined with gusty north winds, brought critical winter storm conditions to the mountains of Ventura County.

In 30 minutes, 2 to 3 inches of snowfall was reported across the Interstate 5 corridor near the Grapevine. This snowfall, combined with winds gusting in excess of 50 mph, shut down Interstate 5 for several hours, stranding hundreds of vehicles.

March 25-26, 2012 Winter Storm 0 0
Above 5,000 feet, significant snowfall occurred. Some reports include: Mount Pinos (12 inches), Pine Mountain Club (8 inches), and Frazier Park (10 inches). The heavy snowfall combined with gusty south winds in excess of 60 mph to produce dangerous winter storm conditions.

March 17-18, 2012 Winter Storm 0 0
Above 6,000 feet, significant snowfall (12 to 20 inches) was reported. Along with the heavy snowfall, gusty south winds in excess of 65 mph were reported.
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Date Type Deaths or Injuries Property Damage
September 13, 2011 Lightning/Thunderstorm 3 0
At the Lockwood Valley Fire Station, three firefighters were injured when lightning struck within 50 feet of the station. All three firefighters reported disorientation and ringing in the ears.

March 20-21, 2011 Winter Storm 0 0
Elevations above 4,500 feet received 1 to 4 feet of snow that, combined with gusty southerly winds, produced hazardous conditions.

February 26, 2011 Winter Storm 0 0
Above 6,000 feet, snowfall totals ranged between 12 and 24 inches. Below 6,000 feet, snowfall amounts ranged between 3 and 8 inches.

Along with the heavy snowfall, southerly winds gusting between 40 and 50 mph produced very hazardous winter storm conditions.

February 19-20, 2011 Winter Storm/Thunderstorm 0 0
Snowfall between 12 and 24 inches was reported above 6,000 feet; 3 to 8 inches was reported between 3,500 and 6,000 feet. Strong winds with gusts between 60 and 70 mph were reported. Cold and unstable air generated some strong thunderstorms across the area.

January 3, 2011 Winter Storm 0 0
Snowfall totals generally ranged between 4 and 8 inches. Southeast winds gusting between 45 and 55 mph accompanied the snowfall, producing reduced visibilities in blowing snow.

December 30, 2010 Winter Storm 0 0
Significant winter storm conditions developed across the mountains of Ventura County. Dangerous winter storm conditions were reported across the Interstate 5 corridor with a snow and gusty winds. Snowfall totals ranged between 3 and 7 inches. Northerly winds gusting in excess of 60 mph generated near zero visibilities in blowing snow and wind chills below 0 ºF. Interstate 5 was shut down.

December 22, 2010 Winter Storm 0 0
High elevation areas received over 12 inches of snowfall. Along with the snowfall, southeasterly winds gusted between 45 and 55 mph and produced dangerous winter storm conditions.

October 19, 2010 Thunderstorm/Hail 0 0
A trained weather spotter reported one-inch hail in association with a severe thunderstorm.

April 12, 2010 Winter Storm 0 0
Cuddy Valley reported 4 to 8 inches of snowfall. Along with the snowfall, strong southerly winds developed with gusts to 61 mph reported.

February 9-10, 2010 Winter Storm 0 0
Over 10 inches of snowfall was reported above 6,000 feet with southerly winds gusting as high as 60 mph.

January 21, 2010 Thunderstorm/Hail 0 0
A trained spotter in the Agoura Hills area reported large hail with a diameter of 1.50 inches.

January 20-21, 2010 Winter Storm 0 0
Cuddy Valley received 15 inches of snowfall while Mount Pinos reported between 12 and 18 inches of snowfall. Along with the heavy snowfall, strong and gusty southerly winds were reported across the mountains.

Source: NOAA 2021

14.2.2 Location
The entire county is susceptible to severe storms. Only higher elevation areas (typically at or above 4,000 feet) experience snowfall; lower elevation areas experience heavy rains. Thunderstorms affect relatively small, localized areas, rather than large regions like severe winter storms.

14.2.3 Frequency
Predicting the frequency of severe storm events in a constantly changing climate is a difficult task.

Based on reports of past occurrences since 2010, Ventura County experiences at least two winter storms and one thunderstorm annually (Table 14-1). The planning area can expect to experience exposure to and adverse impacts from both winter storms and thunderstorms at least annually. 213
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14.2.4 Severity
The most common problems associated with severe storms are immobility and loss of utilities. Fatalities are uncommon, but can occur. Roads may become impassable due to snowfall, flooding, downed trees, or mudflows and landslides. Power lines may be downed due to high winds, and services such as water or phone may not be able to operate without power. Lightning can cause severe damage and injury. Physical damage to homes and facilities can be caused by wind or flooding.

Heavy rain can have significant impacts, including crop damage, soil erosion, and increased risk of flood. Stormwater runoff from heavy rains can also impair water quality by washing pollutants into local waterways (U.S. Environmental Protection Agency 2021). Soil erosion, particularly in areas affected by wildfire and along the coast, is a significant concern.

Lightning severity is typically based on both property damage and life safety (injuries and fatalities). The relationship of lighting to wildfire ignitions increases the significance of this hazard. There are no recorded instances of lightning appearing alone (without a storm) in Ventura County, and any lightning damage is likely to be compounded by other storm damage.

14.2.5 Warning Time
Meteorologists can often predict the likelihood of a severe storm event. This can give several days of warning time. However, meteorologists cannot predict the exact time of onset or severity of the storm.

Some storms may come on more quickly and have only a few hours of warning time. The Los Angeles/Oxnard Weather Forecast Office of the NWS monitors weather stations and issues watches and warnings to alert government agencies and the public of possible or impending weather events when appropriate. The watches and warnings are broadcast over NOAA weather radio, posted on the NWS website, and forwarded to the local media for retransmission using the Emergency Alert System.

14.3 EXPOSURE AND VULNERABILITY
All people and property and the entire environment of the planning area are exposed to some degree to the severe storm hazard.

14.3.1 Population
Thunderstorm-related deaths and injuries in the planning area are most likely to result from accompanying wind and flood events. There are no recorded fatalities from lightning within the planning area. Winter storm-related deaths and injuries are most likely to result from dangerous road conditions and accompanying wind, landslide and flood events.

The most common impacts on people associated with severe storm events are immobility and loss of utilities. All populations in the planning area are exposed to severe storm events, and some are especially vulnerable. The most vulnerable populations are generally those who lack adequate shelter during severe weather events, who are reliant on sustained sources of power in order to survive, and who live in isolated areas with limited ingress and egress options. Power outages can be life threatening to those dependent on electricity for life support. Populations living at higher elevations with 214
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large stands of trees or power lines may be more susceptible to wind damage and black out, while populations in low-lying areas are at risk for possible flooding.

14.3.2 Property
All property is vulnerable during severe weather events, but properties in poor condition or in particularly vulnerable locations may risk the most damage. The most common impacts of specific weather event types on property are as follows:

Thunderstorms—Damage from thunderstorms in the planning area is most likely to be related to secondary hazards accompanying the event, such as flooding, landslides, or damaging winds. If lightning directly strikes a building, it may cause substantial damage and may even set the structure on fire.

Winter storms—Damage from winter storms in the planning area is most likely to be related to secondary hazards accompanying the event, such as freezing, flooding, landslides or damaging winds. Freezing events can also cause pipes to burst in buildings leading to structural flooding.

No modeling is available for quantitative loss estimations for the severe weather hazard. Instead, loss estimates were developed representing 10 percent, 30 percent, and 50 percent of the replacement value of exposed structures:

Loss of 10 percent of planning area replacement value—$18,075,696,763 Loss of 30 percent of planning area replacement value—$54,227,090,289 Loss of 50 percent of planning area replacement value—$90,378,483,815

14.3.3 Critical Facilities
All critical facilities are vulnerable during severe weather events, especially those that lack backup power generation capabilities. When facilities supplying power to planning area land-line telephone systems are frequently disrupted, significant issues arise with communication in the planning area. In addition, some facilities are particularly vulnerable to specific types of severe weather events:

Thunderstorm—Facilities located in areas prone to localized or major flooding are vulnerable.

Transportation systems are vulnerable to disruption from secondary hazards such as flooding or landslides.

Winter storms—Facilities located in areas prone to freezing and snow accumulation are vulnerable. Transportation systems are vulnerable to disruption from secondary hazards such as road closures, flooding, or landslides.

14.3.4 Environment
The environment is highly vulnerable to severe storm events. Natural habitats such as streams and trees exposed to the elements during a severe storm risk major damage. Prolonged rains can saturate soils and lead to slope failure. Flood events caused by severe storms can produce river channel migration or damage riparian habitat. Storm surges can erode beachfront bluffs and redistribute sediment loads.
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14.4 SCENARIO
Impacts of severe storms can be significant, particularly when secondary hazards of flood and landslide occur. A worst-case event would involve thunderstorms with prolonged high winds. Such an event would have both short-term and longer-term effects. Initially, schools and roads would be closed due to power outages caused by high winds and downed tree obstructions. In more rural areas, some subdivisions could experience limited ingress and egress. Prolonged rain could produce flooding, overtopped culverts with ponded water on roads, and landslides on steep slopes. Significant erosion and landslides along the coast may occur, further increasing the vulnerability of residents living right on the edge of coastal cliffs. Flooding and landslides could obstruct roads and bridges, isolating residents.

Fog after the storm, resulting from the heavy moisture still in the area, could increase traffic accidents as visibility worsens.

14.5 ISSUES
Severe local storms are probably the most common widespread hazard. They affect large numbers of people in the planning area when they occur. Severe storms can quickly overwhelm city and county resources. Residents should be prepared for these types of storms: family plans should be developed, disaster kits should be put in homes, workplaces, schools, and cars, and every family member should be taught how to shut off household utilities. Initiating early dismissal from schools and business is an effective mitigation measure and should be encouraged.

Severe storms cannot be prevented, but measures can be taken to mitigate the effects. Critical infrastructure and utilities can be hardened to prevent damage during an event. The secondary effect of flooding can be addressed through decreasing runoff and water velocity. Important issues associated with severe storms in the Ventura County planning area include the following:

Redundancy of power supply throughout the planning area must be evaluated to better understand what areas may be vulnerable.

Although primarily thought of as an urban area, the County has a larger physical land mass containing rural communities and must also consider the needs of these residents (as well as their possible isolation during storm events).

Public education on dealing with the impacts of severe storms needs to continue to be provided so that residents can be better informed and prepared for severe storm events.

Debris management (downed trees, etc.) must be addressed, because debris can impact the severity of severe storm events, it requires coordination efforts, and may require additional funding.

The effects of climate change may result in an increase of heavy rain or more intense storm events and will likely lead to changes in overall precipitation amounts.

Older building stock in the planning area is built to low code standards or none at all. These structures could be highly vulnerable to severe winter weather effects.

Urban forest management programs should be evaluated to help reduce impacts from tree- related damage.

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15. SEVERE WEATHER

15.1 GENERAL BACKGROUND
Severe weather refers to any dangerous meteorological phenomena with the potential to cause damage, serious social disruption, or loss of human life. It includes thunderstorms, downbursts, tornadoes, waterspouts, snowstorms, ice storms, and dust storms, among other events. The most common severe weather events that impact the planning area are severe storms (as described in Chapter 14), damaging winds (including straight-line winds and tornadoes), and extreme temperatures (heat and cold). The frequency and intensity of severe weather events can be affected by El Niño conditions, as described in Section 14.1.3.

15.1.1 Damaging Winds
Straight-Line Winds
Straight-line wind is a general term used to describe winds that have no rotation (i.e., are not tornadoes). Damaging straight-line winds are those that exceed 50 to 60 mph. The Beaufort wind chart (Table 15-1) provides terminology and a description of potential impacts at different levels.

Table 15-1. Beaufort Wind Chart
Beaufort
Number
Range
(mph) TerminologyDescription
0 0 Calm Calm. Smoke rises vertically.
1 1-3 Light air Wind motion visible in smoke.
2 4-7 Light breeze Wind felt on exposed skin. Leaves rustle. 3 8-12 Gentle breeze Leaves and smaller twigs in constant motion. 4 13-18 Moderate breeze Dust and loose paper are raised. Small branches begin to move. 5 19-24 Fresh breeze Smaller trees sway
6 25-31 Strong breeze Large branches in motion. Whistling heard in overhead wires. Umbrella use is difficult. 7 32-38 Near gale Whole trees in motion. Some difficulty when walking into the wind. 8 39-46 Gale Twigs broken from trees. Cars veer on road. 9 47-54 Sever gale Light structure damage.
10 55-63 Storm Trees uprooted. Considerable structural damage. 11 64-73 Violent stormWidespread structural damage.
12 74-95 Hurricane Considerable and widespread damage to structures.

Source: NWS, n.d.
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Santa Ana Winds
In Southern California, strong, dry, gusty downslope winds known as Santa Ana winds form when air from a region of high pressure over the desert region of the southwestern U.S. flows westward toward low pressure areas off the California coast. As the wind flows over the Sierra Nevada and Santa Ana mountains, it drops from high elevation to sea level. The air becomes compressed and heats up as it sinks, and its relative humidity drops. Gaps in mountains form wind tunnels that strengthen these winds as they pour warm air east to west through the canyons (Figure 15-1). These winds play a major role in increasing wildfire risk in the Ventura region because of the dryness of the winds and the speed with which they can cause a fire to spread, complicating containment efforts.

Figure 15-1. Santa Ana Winds
Santa Ana winds may occur year-round, but are most common during the cooler months, typically from September through March. A Santa Ana wind event can yield sustained winds of 40 miles per hours; isolated wind gusts of over 80 miles per hour have been recorded. Most Santa Ana wind events peak for a 12- to 24-hour period but can persist for a few days.

Public Safety Power Shutoff Events
High winds can uproot trees, blow branches onto power lines or create sparks if power lines contact one another. When this occurs in combination with extreme heat and low humidity that dry out vegetation, it poses increased risks of wildfire. In 2012, the California Public Utilities Commission ruled that California Public Utilities Code gives electric utilities authority to shut off electric power to protect public safety by reducing the potential to ignite wildfires (California Public Utilities Commission 2021).

Such shutoffs are referred to as public safety power shutoff events. Given the long, connected nature of power supply systems, a shutoff event targeted to a small at-risk area can affect a larger area outside the risk zone. The duration of a shutoff is tied directly to the severe weather that triggers it; the shutoff typically ends within 24 hours after the severe weather has passed (Pacific Gas & Electric n.d.). 219
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Tornadoes
Although uncommon in the Ventura County area, a tornado is potentially the most dangerous of storms on a local scale (National Weather Service 2009b). Tornadoes are formed by the turbulent mixing of layers of air with contrasting temperature, moisture, density, and wind flow. Most of California’s documented tornadoes have taken place primarily in winter or spring. Since 1950, NOAA has tracked six tornadoes touching down in Ventura County. All six were classified as F0, using the Fujita Tornado Damage Scale shown in Table 15-2.

Table 15-2. Operational Enhanced Fujita Scale
Enhanced Fujita Number Wind, Damage
F0 (weak) 40-72 mph, light damage
F1 (weak) 73-112 mph, moderate damage
F2 (strong) 113-157 mph, considerable damage
F3 (strong) 158-206 mph, severe damage
F4 (violent) 207-260 mph, devastating damage
F5 (violent) 261-318 mph (rare), incredible damage
Source: (National Weather Service 2009b)

15.1.2 Extreme Temperatures
Extreme Heat
Extreme heat is defined as temperatures that hover 10 ºF or more above the average high temperatures for a region for several days or weeks. Extreme heat events can lead to an increase in heat-related illnesses and deaths, cause drought, and impact water supplies. Such events do not typically impact buildings; however, losses may be associated with the urban heat island effect and overheating of heating, ventilation, and air conditioning systems.

Extreme heat is the primary weather-related cause of death in the United States. Excessive heat claims over 100 lives each year in this country. In a 30-year record of weather fatalities across the nation (1990-2019), excessive heat claimed more lives each year than floods, lightning, tornadoes, and hurricanes (Erdman 2021). According to the California Climate Adaptation Strategy, heat waves have claimed more lives in California than all other declared disaster events combined. Despite this history, in a span of 60 years, only four heat emergencies (August 14, 2020; September 2, 2020; June 16, 2021; July 9, 2021) were proclaimed in California at the state level and none were proclaimed at a federal level. Heat waves do not strike victims immediately, but their cumulative effects slowly cause harm to vulnerable populations. Older adults, children, and sick or overweight individuals are at greater risk from extreme heat.

Extreme Cold
In areas that typically have mild winter weather, extreme cold is defined as near freezing temperatures.

Frost or freeze warnings are issued when temperatures below freezing are expected. Whenever temperatures drop below normal and as wind speed increases, heat can leave the body more rapidly.

These conditions are dangerous to those without shelter, those who are stranded, and those who live in 220
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homes that have no heat or are poorly insulated. Extreme cold can cause hypothermia and frostbite if a person is exposed for a long period of time.

In addition to direct risks to people, extreme cold can cause freezing rain, which can leave a coating of ice on roads and walkways. Rain that turns to ice pellets before reaching the ground, referred to as sleet, may become slippery.

15.1.3 Secondary Hazards
Strong Santa Ana winds can quickly cause or spread wildfires (see Chapter 17 for more information on wildfires). Erosion along coastal cliffs can be affected when high winds associated with winter storms increase the intensity of the surf (see Chapter 13 for more information on coastal erosion). Extreme heat can exacerbate drought conditions (see Chapter 9 for more information on drought).

15.2 HAZARD PROFILE

15.2.1 Past Events
Table 15-3 summarizes recent severe weather events in Ventura County as recorded in the NCEI Storm Events Database. Of 136 high wind events recorded, only those recorded at 70 knots or greater or that had a death, injury, or reported property damage are listed in this table. Ventura County was included in federal disaster declarations for extreme cold/freezing events that occurred in December 1990-January 1991, December 1998, and January 2007. The 1998 freeze was particularly damaging to citrus crops.

Table 15-3. Recent Severe Weather Events in the Planning Area Date Event Typea Deaths or Injuries Property Damage
January 19, 2021 High Wind 0 Gusty winds produced numerous reports of downed small trees and branches.

Very strong and gusty Santa Ana winds impacted many areas of Ventura and Los Angeles counties. Winds gusting up to 99 mph were reported across many areas.

November 26, 2020 High Wind 0 0
Strong Santa Ana winds impacted the mountains of Ventura County. Sycamore Canyon reported wind gusts between 67 and 86 mph.

December 25, 2019 Tornado 0 Only very minor damage was reported.

A strong thunderstorm generated a weak tornado over Ventura Harbor (in Ventura County).

December 6, 2017 High Wind 0 0
Across the interior valleys of Ventura County, northeast wind gusts up to 85 mph were reported. This event coincided with Thomas Fire.

December 25, 2014 High Wind 0 0
Strong north winds developed near the Interstate 5 corridor. Wind gusts in excess of 80 mph were reported at the higher elevations.

April 7, 2013 High Wind 0 0
Strong northerly winds developed across the mountains of Ventura County. Gusts between 65 and 85 mph were reported in some areas.

February 24, 2013 High Wind 0 0
Strong Santa Ana winds developed across Ventura County. Wind gusts in excess of 70 mph were reported.

October 25, 2012 High Wind 0 0
Strong and gusty north to northeast winds were reported across the mountains of Ventura County. The strongest wind gusts occurred near the Interstate 5 corridor with gusts near 80 mph reported. 221
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Date Event Typea Deaths or Injuries Property Damage
May 29, 2010 High Wind 0 0
Gusty northwest to north winds developed across the mountains of Ventura County through the Interstate 5 corridor. Sustained winds between 40 and 48 mph were reported along with wind gusts between 66 and 87 mph.

January 21, 2010 Tornado 0 Several homes, a car and a farm outbuilding were damaged.

A small EF-0 tornado touched down in the City of San Buenaventura.

January 13, 2010 High Wind 0 0
Strong and gusty north winds affected the mountains of Ventura County especially near the Interstate 5 corridor. Wind gusts between 60 and 83 mph affected the area.

October 27, 2009 High Wind 0 0
Very strong and gusty winds were reported across the mountains of Ventura County through the Interstate 5 corridor. Wind gusts between 60 and 80 mph were reported.

May 6, 2009 High Wind 0 0
Strong north winds were reported through the Interstate 5 corridor. Sustained winds between 40 and 50 mph with gusts as high as 85 mph were reported.

October 13, 2008 High Wind 0 0
Gusty northeast winds to 84 mph were reported across eastern sections of the Ventura County mountains.

June 20-21, 2008 Excessive Heat 0 0
An automated sensor at Newbury Park reported a high temperature of 108 ºF with a heat index of 106 ºF.

January 24, 2008 Tornado 0 Tore the roof off a building, knocked over several trash cans.

A weak tornado moved onshore across Point Mugu Naval Air Station.

August 31-September 1, 2007Excessive Heat 0 0
The combination of above normal temperatures and relative humidity produced excessive heat across the interior valleys of Ventura County. Heat index values between 105 and 112 ºF were reported.

April 12, 2007 High Wind 0 0
RAWS observations across the mountains measured very strong and gusty winds. At Whitaker Peak RAWS a peak northwest wind gust of 86 mph was reported. Other sensors, including Sandberg and Warm Springs, indicated sustained winds and gust that met warning criteria.

January 13-15, 2007 Frost/Freeze 0 0
Widespread freezing conditions were reported across agricultural areas of Ventura County. Total crop damage in Ventura County was estimated to be around $280 million.

July 22-26, 2006 Heat 0 0
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 to 119 ºF.

July 15, 2006 Heat 0 0
The combination of strong high pressure aloft and high relative humidity produced excessive heat conditions across the mountains of Ventura County. Heat index values ranged from 100 to 105 ºF in the mountains.

January 10, 2005 Tornado 0 0
A California Highway Patrol officer reported a weak tornado in the community of El Rio.

October 27, 2004 Funnel Cloud 0 0
An early-season storm brought rain, snow, and funnel clouds to Central and Southern California. Across Ventura and Santa Barbara counties, two funnel clouds were reported.

February 24, 2003 Funnel Cloud 0 0
A weather observer at the Point Mugu Naval Base reported a funnel cloud offshore of the base.

February 9, 2002 High Wind 1 Strong winds knocked down power lines and overturned a wooden bus stop structure in Moorpark.

Strong and gusty Santa Ana winds developed across the interior valleys of Ventura County. Reports from spotters indicated northeast winds gusting between 50 and 70 mph. In Simi Valley, a man was killed when a 45-foot tree was knocked down and pinned him.

Sources: NOAA 2021
a. This list represents only high wind events recorded at 70 knots or greater, or that had a death, injury, or reported property damage. 222
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The NCEI Storm Events Database lists 19 wildfire events in Ventura County from 2000 through 2021, and all but two of those events are directly attributed to wind events or occurred within one or two days of high wind events recorded in the database (National Centers for Environmental Information 2022).

15.2.2 Location
The entire county is susceptible to damage from wind. Wind events are most damaging to areas that are heavily wooded. The State of California has a low risk for serious tornados compared to other parts of the country (Croswell 1995). Tornadoes are usually localized and have historically formed in the southwest portion of Ventura County during the winter.

All of Ventura County is subject to extreme temperatures. The mountains are more likely to experience extreme cold. Extreme heat impacts may be exacerbated in inland areas more prone to urban heat island effects, such as Thousand Oaks and Simi Valley, than coastal regions (Oakley, et al. 2019).

15.2.3 Frequency
Based on reports since 2000, Ventura County experiences an average of two damaging wind events each year and an extreme temperature event every two years (Table 15-3). The planning area can expect to experience exposure to and adverse impacts from severe weather events at least annually, including damaging wind events every year and extreme temperature events biennially.

15.2.4 Severity
Damaging Winds
Windstorms can be a frequent problem in the planning area and have been known to cause damage to utilities. The predicted wind speed given in wind warnings issued by the National Weather Service is for a one-minute average; gusts may be 25 to 30 percent higher. Lower wind speeds typical in the lower valleys are still high enough to knock down trees and power lines and cause other property damage.

Higher elevations in the County can experience much higher winds under more varied conditions.

According to the FEMA Winds Zones of the United States map (Figure 15-2), Ventura County is in Wind Zone I, where wind speeds can reach up to 130 mph. The map indicates the strength of windstorms in the United States, and the general location of the most wind activity (Federal Emergency Management Agency 2021).

Tornadoes are potentially highly dangerous. If a major tornado were to strike within the populated areas of the County, damage could be widespread. Because the County has never experienced a tornado more severe than an F0, however, such severity is unlikely.

Extreme Temperatures
The record high temperature in the county (120 ºF) was set in Fillmore and Oak View in September 2020. The record low (25 ºF) was set in December 1998.
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Figure 15-2. Wind Zones in the United States
Source: FEMA 2021

15.2.5 Warning Time
Meteorologists can often predict the likelihood of a severe weather event. This can give several days of warning time. However, meteorologists cannot predict the exact time of onset or severity of the storm.

Some weather events may come on more quickly and have only a few hours of warning time. The Los Angeles/Oxnard Weather Forecast Office of the NWS monitors weather stations and issues watches and warnings when appropriate to alert government agencies and the public of possible or impending weather events. The watches and warnings are broadcast over NOAA weather radio, posted on the NWS website, and are forwarded to the local media for retransmission using the Emergency Alert System.
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15.3 EXPOSURE AND VULNERABILITY

15.3.1 Population
All people in the planning area are exposed to some degree to the severe weather hazard. The most common problems associated with severe weather events are immobility and loss of utilities.

Vulnerable populations are the elderly, low income or linguistically isolated populations, people with life- threatening illnesses, and residents living in areas that are isolated from major roads. Power outages can be life threatening to those dependent on electricity for life support. Populations living at higher elevations with large stands of trees or power lines may be more susceptible to wind damage and black out. The most common impacts of specific weather event types on people are as follows:

Windstorms—Damaging winds can cause injuries and fatalities in a number of ways. Downed trees may fall on homes or cars, killing or injuring those inside. Objects that are not secured can be picked up in wind events and become projectiles.

Tornado—Structures that collapse or blow over during tornadoes may kill or injure those inside.

Excessive heat—Heat exhaustion or heat stroke can cause illness or death. Toddlers are especially vulnerable if left or trapped in a parked vehicle. Seniors in residences without air conditioning are at more risk of heat illness and death during excessive heat waves.

Extreme cold— Extreme cold can cause hypothermia and frostbite, especially among the population that does not have adequate shelter.

15.3.2 Property
All property in the planning area is exposed to some degree to the severe weather hazard. Properties in poor condition or in particularly vulnerable locations may risk the most damage. The most common impacts of specific weather event types on property are as follows:

Windstorm—Mobile homes can be seriously damaged by wind gusts over 80 mph, even if they are anchored (National Severe Storms Laboratory 2018). Properties at higher elevations or on ridges may be more prone to wind damage. Falling trees can result in significant damage to structures.

Tornado—A major tornado could cause widespread damage to property in the planning area, but such an event is unlikely.

Excessive heat—Periods of high heat do not typically pose risks to structures, but when power fails during high heat events, air conditioning systems also fail and result in secondary shutdowns of heat-sensitive electronic or networking systems housed in those structures.

Extreme cold—Infrastructure and building systems can be damaged by extreme cold when pipes freeze. Roofs can be damaged by ice buildup.

No modeling is available for quantitative loss estimations for the severe weather hazard. Instead, loss estimates were developed representing 1 percent, 3 percent, and 5 percent of the replacement value of exposed structures:

Loss of 10 percent of planning area replacement value—$18,075,696,763 Loss of 30 percent of planning area replacement value—$54,227,090,289 225
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Loss of 50 percent of planning area replacement value—$90,378,483,815

15.3.3 Critical Facilities
All critical facilities are exposed to some degree to the severe weather hazard. Those that lack backup power generation capabilities are especially vulnerable. When facilities supplying power to planning area land line telephone systems are disrupted, significant issues arise with communication. Some facilities are particularly vulnerable to specific types of severe weather events:

Windstorms—Facilities located near trees or power lines that are likely to fall are vulnerable.

Roads and other transportation infrastructure could be blocked by downed trees or other debris.

Tornado—Critical facilities in the direct path of a tornado are particularly vulnerable.

Excessive heat—Transportation systems can be impacted if extreme heat causes roads or railways to buckle.

Extreme cold—Facilities that lack backup power are more likely to be impacted during extreme cold events. Pipes freeze more quickly in unheated buildings.

15.3.4 Environment
The entire environment of the planning area is exposed to some degree to the severe weather hazard.

High winds can cause extensive damage to forested areas. Storm surges increased by high winds can erode beachfront bluffs and redistribute sediment loads. Periods of prolonged heat can increase pest and disease pressure on crops and increase the effects of drought.

15.4 SCENARIO
A worst-case severe weather event would involve prolonged high winds accompanied by thunderstorms. Initially, schools and roads would be closed due to power outages caused by high winds and downed tree obstructions. In more rural areas, some subdivisions could experience limited ingress and egress. If these events coincided with extreme heat or cold, the impacts on the population would be even greater.

15.5 ISSUES
Severe weather cannot be prevented, but measures can be taken to mitigate the effects. Critical infrastructure and utilities can be hardened to prevent damage during an event. Important issues associated with severe weather in the Ventura County planning area include the following:

Redundancy of power supply throughout the planning area must be evaluated to better understand what areas may be vulnerable.

Public education on dealing with the impacts of severe weather needs to continue to be provided so that residents can be better informed and prepared for severe weather events.

Debris management (downed trees, etc.) must be addressed, because debris can impact the severity of severe weather events, requires coordination efforts, and may require additional funding.
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Climate change may result in more intense weather events and will likely lead to increased temperatures.

Older building stock in the planning area is built to low code standards or none at all. These structures could be highly vulnerable to severe wind.

Urban forest management programs should be evaluated to help reduce impacts from forest- related wind damages.

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16. TSUNAMI

16.1 GENERAL BACKGROUND
A tsunami is a series of high-energy waves that radiate outward like pond ripples from an area where a generating event occurs, arriving at shorelines over an extended period. Tsunamis can be induced by earthquakes, landslides, and submarine volcanic explosions (see Figure 16-1). Tsunamis are typically classified as local or distant, depending on the location of their source in comparison to where waves occur:

The waves nearest to the generating source represent a local tsunami. Such events have minimal warning time, leaving few options except to run to high ground after a strong, prolonged local earthquake. Damage from the tsunami adds to damage from the triggering earthquake due to ground shaking, surface faulting, liquefaction, and landslides.

The waves far from the generating source represent a distant tsunami. Distant tsunamis may travel for hours before striking a coastline, giving a community a chance to implement evacuation plans if a warning is received.

Figure 16-1. Common Sources of Tsunamis

In the open ocean, a tsunami may be only a few inches or feet high, but it can travel with speeds approaching 600 miles per hour. As a tsunami enters the shoaling waters near a coastline, its speed diminishes, its wavelength decreases, and its height increases greatly. At the shoreline, tsunamis may take the form of a fast-rising tide, a cresting wave, or a bore (a large, turbulent wall-like wave). The bore phenomenon resembles a step-like change in the water level that advances rapidly (from 10 to 60 miles per hour). The first wave is usually followed by several larger and more destructive waves. 228
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16.1.1 Factors Affecting Tsunami Impact
The configuration of the coastline, the shape of the ocean floor, and the characteristics of advancing waves play important roles in the destructiveness of the waves. Bays, sounds, inlets, rivers, streams, offshore canyons, islands, and flood control channels may alter the level of damage. Offshore canyons can focus tsunami wave energy, and islands can filter the energy. A tsunami wave entering a flood control channel could reach a mile or more inland, especially if it enters at high tide. The orientation of the coastline determines whether the waves strike head-on or are refracted from other parts of the coastline. A wave may be small at one point and much larger at others. The inundation area for a tsunami event is often described as runup as illustrated in Figure 16-2.

Figure 16-2. Runup Distance and Height in Relation to the Datum and Shoreline Source: UNESCO, Retrieved from Different Directions: Tsunami, n.d.

16.1.2 Secondary Hazards
The secondary hazards most directly associated with tsunamis are flooding and coastal erosion, which are likely results of tsunami events.
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16.2 HAZARD PROFILE

16.2.1 Past Events
More than 80 tsunamis have been recorded or observed in California, according to state records; however, many of these events were small and led to little or no damage. All tsunamis from the past century have been distant, not local. That is, they have all resulted from earthquakes far across the Pacific basin (as opposed to earthquakes near the American coastline). Ventura County has been affected by major statewide tsunamis as well as more local minor tsunamis. Table 16-1 lists known tsunami events that have struck the County or one of its jurisdictions since 1812.

Table 16-1. Tsunami Events in Ventura County
Date Description
March 11, 2011 A 7.1 magnitude earthquake in Japan caused a run-up within Ventura Harbor. A federal disaster declaration was issued (DR-1968).

February 27, 2010 An 8.8 magnitude earthquake in Chile caused a 3-foot run-up in Ventura, as well as damage to 21 docks in Ventura Harbor.

September 29, 2009An 8.2 magnitude earthquake in Samoa moved buoys within Ventura Harbor.

March 28, 1964 A 9.2 magnitude earthquake in Alaska caused the tide in Ventura to drop 8 feet and large swells were reported in Oxnard.

May 24, 1960 A 9.5 magnitude earthquake in Chile created a 4.4-foot run-up in Port Hueneme causing damage to docks and ships.

March 9, 1957 An 8.3 magnitude earthquake along the Aleutian Islands caused an approximate 2-foot run-up 6 hours after the first wave hit in Port Hueneme.

November 4, 1952 An 8.2 magnitude earthquake in Kamchatka caused a 2.3-foot run-up in Port Hueneme.

April 1, 1946 An 8.8 magnitude earthquake along the Aleutian Islands caused sand to sweep over the railroad tracks near Ormond Beach and minor ship berthing problems in Port Hueneme.

December 21, 1812 A 7.1 magnitude earthquake centered in the Santa Barbara or Ventura area caused a 6.5-foot run-up and damage to San Miguelito Chapel.

Source: Ventura County 2021

16.2.2 Location
The California Department of Conservation maintains detailed tsunami inundation maps for Ventura County and other parts of the state. These maps are generated through computer modeling of the areas most likely to be affected by a tsunami event and serve as an important preparedness tool. The tsunami hazard areas identified in the mapping are based on a suite of tsunami sources, both local and distant, and do not, therefore, represent risk from a single-source event. Tsunami risk areas are shown in Figure 16-3.

16.2.3 Frequency
Generally, four or five tsunamis occur every year in the Pacific Basin, and those that are most damaging are generated in the Pacific waters off South America rather than in the northern Pacific.

Based on risk factors for the County and past occurrences, it is highly likely that tsunamis will continue to strike the coastline in Ventura County. Tsunami probabilities are tied to earthquake and other geologic events; however, not all earthquakes or submarine landslides will trigger a tsunami. 230
Fillmore
Moorpark
Simi Valley
Santa Paula
Oxnard
Ojai
Port
Hueneme
Camarillo
San
Buenaventura
Thousand Oaks
Lake Piru
Lake
Casitas
11833
34 118126
150
1 1
23 126
23 33
33 34
1 150
232
33 23
101
Figure 16-3. Tsunami Risk Areas for Ventura County
Data Sources: Ventura Co.,
CGS, Esri
Tsunami Inundation Zones
County Boundary
Cities
Major Roads
0 6 3 Miles
231
Tsunami
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16.2.4 Severity
A tsunami’s size and speed, as well as the coastal area’s form and depth, affect the impact of the tsunami. At some locations, the advancing turbulent wave front will be the most destructive part of the tsunami wave. In other situations, the greatest damage will be caused by the outflow of water back to the sea between crests, sweeping away items on the surface and undermining roads, buildings, bulkheads, and other structures. This outflow action can carry enormous amounts of highly damaging debris, resulting in further destruction. Ships and boats, unless moved away from shore, may be forced against breakwaters, wharves, and other craft, or be washed ashore and left grounded after the withdrawal of the seawater (National Tsunami Warning Center 2021).

16.2.5 Warning Time
Visible Indications
Tsunamis are difficult to detect in the open ocean; with waves generally less than 3 feet high. The first visible indication of an approaching tsunami may be either a rise or drop in water surface levels (National Tsunami Warning Center 2021):

A drop in water level (draw down) can be caused by the trough preceding the advancing, large inbound wave crest. Rapid draw down can create strong currents in harbor inlets and channels that can severely damage coastal structures due to erosive scour around piers and pilings. As the water’s surface drops, piers can be damaged by boats or ships straining at or breaking their mooring lines. The vessels can overturn or sink due to strong currents, collisions with other objects, or impact with the harbor bottom.

The advancing tsunami may initially arrive as a strong surge increasing the sea level. This can be similar to the rising tide, but the tsunami surge rises faster and does not stop at the shoreline. Even if the wave height appears to be small, 3 to 6 feet for example, the strength of the accompanying surge can be deadly. Waist-high surges can cause strong currents that float cars, small structures, other debris, and hazardous materials. Boats and debris are often carried inland by the surge and left stranded when the water recedes.

Warning System
The tsunami warning system for the Pacific Ocean evolved from a program initiated in 1946. It is a cooperative effort involving 26 countries along with numerous seismic stations, water level stations and information distribution centers. The National Weather Service operates two regional information distribution centers: The Pacific Tsunami Warning Center in Ewa Beach, Hawaii; and the National Tsunami Warning Center covering the California coast in Palmer, Alaska. The warning centers issue tsunami watches, warnings, and advisories. A watch is issued when a large earthquake has occurred far away from the region and the threat is still being determined.

A warning is issued when damaging tsunami waves inundating dry land are expected. An advisory is issued when tsunami waves less than 1 meter high and dangerous strong currents will occur in harbors. The warning system is activated when a Pacific basin earthquake of magnitude 6.5 occurs or an earthquake is widely felt along the North American coast. When this occurs, the following sequence of actions occurs:

Data is interpolated to determine epicenter and magnitude of the event. 232
Ventura County Multi-Jurisdictional Hazard Mitigation Plan 16-6
If the earthquake is of the right type, depth, magnitude, and is far away from California coast, a TSUNAMI WATCH is typically issued for the California coastline.

A TSUNAMI WATCH is upgraded to a TSUNAMI WARNING if tsunami wave heights are forecast to be 1 meter or larger. A TSUNAMI ADVISORY is issued if tsunami wave heights are forecast to be 0.3 meters to less than 1 meter.

Tsunami travel times are calculated, and the warning is transmitted to disseminating agencies who relay it to the public.

The National Tsunami Warning Center will cancel/expire watches, warnings, or advisories if tide gauges and buoys indicate no significant tsunami was generated or if tsunami waves no longer meet the criteria for at least 3 hours.

This system is not considered to be effective for communities close to the tsunami source, because the first wave would arrive before the data can be processed and analyzed, and communications systems may be impacted by the precipitating event. In this case, strong ground shaking would provide the first warning of a potential tsunami and evacuations should begin immediately.

Estimated Travel Times
The NOAA National Center for Environmental Information website provides maps that show estimated travel times to coastal locations for various tsunami-generating events. Figure 16-4 shows one example of the travel time for a tsunami generated in Aburatsu, Japan to reach the planning area— approximately 13 hours.

16.3 EXPOSURE
Exposure and vulnerability estimates are based on tsunami inundation maps. The value of exposed buildings in the tsunami inundation zone was generated by overlaying the inundation areas on the general building stock. The population living in tsunami hazard zones was estimated using the percent of buildings within the tsunami inundation areas and applying this percent to the estimated planning area population. Detailed results by jurisdiction are included in Appendix D; results for the total planning area are presented below.

16.3.1 Population
The estimated total population living in the evaluated tsunami inundation zone is 27,626 (3.3 percent of the total planning area population). People recreating along beaches, low-lying coastal areas, tidal flats, and stream deltas that empty into ocean-going waters also would be exposed.

16.3.2 Property
Table 16-2 summarizes the estimated property exposure in the evaluated tsunami inundation areas.

Figure 16-5 shows the Hazus-defined occupancy class of all buildings in the tsunami inundation areas.

These occupancy classes provide an indication of land use within the mapped hazard area. Some land uses are more vulnerable to inundation, such as single-family homes, while others are less vulnerable, such as agricultural land or parks.
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Figure 16-4. Potential Tsunami Travel Times in the Pacific Ocean, in Hours Source: National Centers for Environmental Information, 2021 Table 16-2. Exposed Property in the Tsunami Inundation Zone Acres of Inundation Area 4,690
Number of Buildings Exposed 7,300
Value of Exposed Structures $2,703,527,102
Value of Exposed Contents $1,659,832,511
Total Exposed Property Value $4,363,359,613
Total Exposed Value as % of Planning Area Total 2.4%
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Ventura County Multi-Jurisdictional Hazard Mitigation Plan 16-8
Figure 16-5. Structures in the Tsunami Inundation Zone, by Building Occupancy Class

16.3.3 Critical Facilities
Figure 16-6 shows critical facilities located in the tsunami inundation zone by facility type. The total count of critical facilities in the tsunami inundation zone (22) represents 1.4 percent of the planning area total of 1,588.

Figure 16-6. Critical Facilities in Tsunami Inundation Area

Residential
6,725
92%
Commercial
274
4%
Industrial
4 0%
Agriculture
18 0%
Religion
0 0%Government
263
4%
Education
16 0%
4 1
13 0 0
3 7
0 4
8 12
16 20Number of Facilties in Hazard Area
Communication
Energy
Food, Water, Shelter
Hazardous Materials
Medical and Health
Safety and Security
Transportation

1.6% 0.9%

6.2%

0.0% 0.0%0.8% 1.3%
0%
20%
40%
60%
80%
100%Facilties in Hazard Area as % of Planning Area Total Communication
Energy
Food, Water, Shelter
Hazardous Materials
Medical and Health
Safety and Security
Transportation
235
Tsunami
16-9

16.3.4 Environment
All waterways and beaches would be exposed to the effects of a tsunami; inundation of water and introduction of foreign debris could be hazardous to the environment. All wildlife inhabiting the area also is exposed.

16.4 VULNERABILITY
The vulnerability of people, property, and critical facilities was evaluated for the mapped tsunami inundation areas. Appendix D shows results by jurisdiction; countywide summaries are provided below.

16.4.1 Population
The populations most vulnerable to the tsunami hazard are the elderly, disabled, and very young who reside or recreate near beaches, low-lying coastal areas, tidal flats, and stream or river deltas that empty into ocean-going waters. Visitors recreating in or around inundation areas also would be vulnerable, as they may not be as familiar as residents with appropriate responses to a tsunami or ways to reach higher ground.

Impacts on persons and households in the mapped tsunami inundation area were estimated through the Level 2 Hazus analysis. Countywide results are as follows:

Number of Displaced Population = 21,957
Number of Residents Requiring Short-Term Shelter= 1,584

16.4.2 Property
Property Impacted
The impact of tsunami waves and the scouring associated with debris that may be carried in the water could be damaging to all structures along beaches, low-lying coastal areas, tidal flats, and river deltas.

The most vulnerable are those in the front line of tsunami impact and those that are structurally unsound. The Hazus analysis indicated that 17.8 percent of the exposed structures (1,297 structures) would be impacted by the modeled scenario event.

Damage Estimates
Table 16-3 summarizes Hazus estimates of tsunami damage in the planning area. The estimated damage value is associated with the tsunami wave only; it does not include additional damage that may occur as a result of debris battering structures as the tsunami wave rushes in and out of the inundation area or fires caused by an earthquake and tsunami event. The debris estimate includes only structural debris and building finishes; it does not include additional debris that may result from a tsunami event, such as from boats, trees, sediment, building contents, bridges, or utility lines. Structures that were built to current floodplain regulations in the tsunami inundation area may have some level of protection, particularly if they were built to withstand wave action. 236
Ventura County Multi-Jurisdictional Hazard Mitigation Plan 16-10
Table 16-3. Estimated Impact of a Tsunami Event in the Planning Area Structure Debris (tons) 1,755,480
Buildings Impacted 1,297
Structure Value Damaged $125,195,566
Content Value Damaged $198,643,647
Total Value Damaged 4323,839,203
Damage as % of Total Value 0.2%

16.4.3 Critical Facilities
Significant facilities predicted by Hazus to be affected by the modeled tsunami event include one fire station, one school, and five road bridges
Damage Estimates
Hazus was used to estimate the number of critical facilities affected by tsunami and the resulting percent of damage to the building and contents. Figure 16-7 compares the predicted number of affected facilities to the number of exposed facilities. Figure 16-8 shows the estimated damage to critical facilities from a tsunami event. Depending on critical facility category, the average amount of damage to structures, measured as a percentage of total value, ranges from 1.3 to 13.0 percent of total value, and average damage to contents ranges from 0 to 47.4 percent.

Figure 16-7. Critical Facilities Exposed to and Affected by Mapped Tsunami Inundation Area 4 1
7 0 0
3 7
2 1 1
0 0
2 5
0 2
4 6
8 10
Communications Energy Food, Water &
Shelter
Hazardous
Material
Health & Medical Safety & Security Transportation
Number of Faciliities Exposed or Affected
Exposed Facilities
Affected Facilities
237
Tsunami
16-11
Figure 16-8. Average % of Damage to Critical Facilities Caused by Modeled Tsunami

Vulnerable Infrastructure
In addition to the vulnerable critical facilities identified by the Hazus analysis, the following infrastructure is also generally vulnerable to damage:

Water Proximate Infrastructure—Breakwaters and piers collapse, sometimes because of scouring actions that sweep away their foundation material and sometimes because of the sheer impact of the tsunami waves.

Flood Control Systems—Floodwaters can back up drainage systems, causing localized flooding. Culverts can be blocked by debris from tsunami events, also causing localized urban flooding.

Utility Systems—Floodwaters can get into drinking water supplies, causing contamination.

Sewer systems can be backed up, causing waste to spill into homes, neighborhoods, rivers, and streams. Tsunami waves can knock down power lines and radio/cellular communication towers.

Power generation facilities can be severely impacted by wave action and by inundation from floodwater.

16.4.4 Environment
Environmental impacts on local waterways and wildlife would be most significant in areas closest to the point of impact. Areas near gas stations, industrial areas and facilities storing hazardous materials are vulnerable. The vulnerability of aquatic habit and associated ecosystems in low-lying areas close to the coastline is high. Tsunami waves can carry destructive debris and pollutants that can have devastating impacts on all facets of the environment. A tsunami event has the potential to alter the shoreline, depending on the force of the run-up.

10.2 6.2

13.0 0.0 0.0 2.0 1.3

47.4 0.0 0.0 0.0 0.0

8.8 0.00
20 40
60 80
100
Communications Energy Food, Water &
Shelter
Hazardous
Material
Health & Medical Safety & Security Transportation
Average Damage as % of Total Value
Damage to Structure
Damage to Contents
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Ventura County Multi-Jurisdictional Hazard Mitigation Plan 16-12
Most environmental and ecological impacts from tsunamis derive from direct damage from the waves, which can physically remove vegetation and wildlife, increase sediment load, and smother vegetation that is not physically carried away. Other environmental impacts from tsunamis include chemical changes from saltwater intruding into freshwater sources; eutrophication (enrichment) of water from increased runoff; and decomposition of vegetation, wildlife, rotting property (boats or buildings) and unrecovered remains. Non-biodegradable waste, such as plastics, can lead to a buildup in marine debris, and toxic wastes, if inadequately stored, may be released into the environment. Lastly, exotic wildlife may be introduced or may escape into the local ecosystem.

16.5 SCENARIO
The presentation Tsunami Hazards and Preparedness in Ventura County shows that local tsunamis may cause serious impact. A worst-case-scenario for the Ventura coastline would be a nearshore tsunami caused by a significant off-shore seismic event. While history has shown that these type events are not likely, should one occur, damage for this type of event would exceed what is estimated in the risk assessment for this hazard mitigation plan.

16.6 ISSUES
The planning team has identified the following issues related to the tsunami hazard for the planning area:

Hazard Identification—To truly measure and evaluate the probable impacts of tsunamis on planning, hazard mapping based on probabilistic scenarios must continue to be updated regularly. The science and technology in this field are emerging. Accurate probabilistic tsunami mapping will need to be a key component for tsunami hazard mitigation programs to be effective.

Building Code Revisions—Present building codes and guidelines may not adequately address the impacts of tsunamis on structures. Planning partners, in the cities of Ventura, Oxnard, and Port Hueneme, should review their building code for requirements for tsunami-resistant construction standards in vulnerable areas.

Enhancement of Current Capabilities—As tsunami warning technologies evolve, the tsunami warning capability within the planning area will need to be enhanced to provide the highest degree of warning.

Vulnerable Populations Planning—Special attention will need to be focused on the vulnerable communities in the tsunami zone and on hazard mitigation through public education, outreach, and warning capabilities. This issue may be especially important for visitors to Ventura County.

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17-1

17. WILDFIRE

17.1 GENERAL BACKGROUND
A wildfire is any uncontrolled fire on undeveloped land that requires fire suppression. Although wildfires can occur naturally and are important to many ecosystem processes, most are started by human activity.

17.1.1 CAL FIRE Wildfire Mapping
Fire Hazard Severity Zones
CAL FIRE has modeled and mapped wildfire hazard zones
using a computer model that designates moderate, high or very high fire hazard severity zones (FHSZ). FHSZ ratings are derived from a combination of fire frequency (how often an area burns) and expected fire behavior under severe weather conditions. CAL FIRE’s model derives fire frequency from 50 years of fire history data. Fire behavior is based on factors such as the following (CAL FIRE 2021):

Fuel—Fuel may include living and dead vegetation on
the ground, along the surface as brush and small trees, and above the ground in tree canopies. Lighter fuels
such as Arundo donax and other grasses, leaves, and
needles quickly expel moisture and burn rapidly, while
heavier fuels such as tree branches, logs and trunks
take longer to warm and ignite. Trees killed or
defoliated by forest insects and diseases are more
susceptible to wildfire.

Weather—Relevant weather conditions include temperature, relative humidity, wind speed and direction, cloud cover, precipitation amount and duration, and the stability of the atmosphere.

When the temperature is high, relative humidity is low, wind speed is increasing and coming from the east (offshore flow), and there has been little or no precipitation, so vegetation is dry, conditions are very favorable for extensive and severe wildfires. These conditions occur more frequently inland where temperatures are higher and fog is less prevalent.

Terrain—Topography includes slope and elevation. The topography of a region influences the amount and moisture of fuel; the impact of weather conditions such as temperature and wind;

FIRE HAZARD SEVERITY AS

DETERMINED BY CAL FIRE
CAL FIRE classifies areas of the state as
having a moderate, high, or very high fire
hazard, based on how a fire would behave
in a given area and the probability of
flames and embers threatening buildings.

For wildland areas, the FHSZ model uses
burn probability and expected fire behavior
based on weather, fuel (the vegetation in
the area), and terrain. For urban areas,
hazard levels are based on vegetation
density, distance from wildlands, and the
levels assigned to surrounding zones.

Each area gets a score for flame length,
embers, and the likelihood of the area
burning. Scores of smaller areas are then
averaged over larger zones that
encompass them.
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Ventura County Multi-Jurisdictional Hazard Mitigation Plan 17-2
potential barriers to fire spread, such as highways and lakes; and elevation and slope of landforms (fire spreads more easily uphill than downhill).

The model also is based on frequency of fire weather, ignition patterns, and expected rate-of spread. It accounts for flying ember production, which is the principal driver of the wildfire hazard in densely developed areas. A related concern in built-out areas is the relative density of vegetative fuels that can serve as sites for new spot fires within the urban core and spread to adjacent structures. The model refines the zones to characterize fire exposure mechanisms that cause ignitions to structures.

Significant land-use changes need to be accounted for through periodic model updates.

Wildfire Protection Responsibility Areas
Hundreds of agencies have fire protection responsibility for wildland and wildland/urban interface fires in California. Local, state, tribal, and federal organizations have primary legal (and financial) responsibility for wildfire protection. In many instances, two fire organizations have dual primary responsibility on the same parcel of land —one for wildfire protection, and the other for structural or “improvement” fire protection. According to the 2018 California State Hazard Mitigation Plan, this layering of responsibility and resulting dual policies, rules, practices, and legal ordinances can cause conflict or confusion. To address wildfire jurisdictional responsibilities, the California state legislature in 1981 adopted PublicResource Code Section 4291.5 and Health and Safety Code Section 13108.5 establishing the following responsibility areas:

Federal Responsibility Areas (FRAs)—FRAs are fire-prone wildland areas that are owned or managed by a federal agency such as the U.S. Forest Service, National Park Service, Bureau of Land Management, U.S. Fish and Wildlife Service, or U.S. Department of Defense.

Primary financial and rule-making jurisdictional authority rests with the federal land agency. In many instances, FRAs are interspersed with private land ownership or leases. Fireprotection for developed private property is usually not the responsibility of the federal land management agency; structural protection responsibility is that of a local government agency.

State Responsibility Areas (SRAs)—SRAs are lands in California where CAL FIRE has legal and financial responsibility for wildfire protection and where CAL FIRE administers fire hazard classifications and building standard regulations. SRAs are defined as lands that meet the following criteria:

Are county unincorporated areas
Are not federally owned
Have wildland vegetation cover rather than agricultural or ornamental plants Have watershed or range/forage value
Have housing densities not exceeding three units per acre.

Where SRAs contain built environment or development, the responsibility for fire protection of those improvements (non-wildland) is that of a local government agency.

Local Responsibility Areas (LRAs)—LRAs include land in cities, cultivated agriculture lands, and non-flammable areas in unincorporated areas, and lands that do not meet the criteria for SRA or FRA. LRA fire protection is typically provided by city fire departments, fire protection districts, and counties, or by CAL FIRE under contract to local governments. LRAs may include flammable vegetation and wildland/urban interface areas where the financial and jurisdictional responsibility for improvement and wildfire protection is that of a local government agency.
241
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17.1.2 State Codes and Policies for Mitigating the Fire Hazard Urbanization tends to alter the natural fire regime and can lead to expansion of urbanized areas into wildland areas. State and local policies and regulations require landowners to carry out activities such as maintaining defensible space and reducing vulnerability to damage or loss from wildfire. The most important policies and regulations related to residential wildfire safety in California are as follows:

General Plan Safety Element Review: Government Code 65302.5—The Board of Forestry and Fire Protection (BOF) must provide recommendations to a local jurisdiction’s general plan safety element at the time that the general plan is being amended. BOF recommendations include goals and policies that provide for contemporary fire-prevention standards for the jurisdiction. This is not a direct and binding fire-prevention requirement for individuals.

Sprinkler Systems: California Residential Code, Chapter 3, Section R313—All new dwellings, dwelling units, and one- and two-family townhomes must be equipped with an automatic fire-sprinkler system that can protect the entirety of the dwelling. Dwellings and homes constructed prior to January 1, 2011, that do not have a sprinkler system may be retrofitted, but it is not required.

Fire Safety Standards: California Public Resources Code 4290 and 14 California Code of Regulations (CCR) 1270—These regulations govern roads, driveway width, clearance, turnarounds, signing, and water related to fire safety throughout California. Public Resources Code 4290 is typically enacted through regulation at the county level, as described below.

Wildland-Urban Interface Building Standards: California Government Code 51189—The Office of the State Fire Marshal is required to create building standards for wildfire resistance.

Construction of buildings in the wildland-urban interface must use fire-resistant materials to save life and property. As of 2011, the standards relevant to fire-safe construction for all new structures in the SRA are the California Building Code, Chapter 7A (for commercial construction) and the California Residential Code, Chapter 3, Section R327 (for residential construction).

State Responsibility Area: Public Resources Code 4102, 4125-4229 and 14 CCR 1220— These statutes and regulations establish the locations where CAL FIRE has the financial responsibility for preventing and suppressing fires. These designations define financial arrangements for fire protection services and establish the locations where fire safe and defensible space laws or regulations apply.

Hazardous Fire Areas: Public Resources Code 4251-4255 and 14 CCR 1200—These laws and regulations allow petitioners to the BOF or CAL FIRE to establish hazardous fire areas, providing for area closures and other restrictions for fire prevention.

Defensible Vegetation Clearing Around Structures: Public Resources Code 4291/14 CCR 1299— Public Resources Code 4291 regulates fuel management around a property. It states that a person who owns or controls a building or structure in or adjoining to forest, brush, or grass covered lands shall follow certain guidelines outlined in the code. At least 100 feet of defensible space is required. The owner of the property is liable for making these changes to protect habitable structures. The 100 feet is separated into two zones, with the closer zone, 30 feet out from the structure, being managed more intensively. 242
Ventura County Multi-Jurisdictional Hazard Mitigation Plan 17-4

17.1.3 Secondary Hazards
Wildfires can generate a range of secondary effects, which in some cases may cause more widespread and prolonged damage than the fire itself. Wildfires strip slopes of vegetation, exposing them to greater amounts of runoff. This in turn can weaken soils and cause failures on slopes. Major landslides can occur several years after a wildfire. Most wildfires burn hot and for long durations that can bake soils, especially those high in clay content, thus increasing the imperviousness of the ground. This increases the runoff generated by storm events, thus increasing the chance of flooding.

17.2 HAZARD PROFILE

17.2.1 Past Events
Ventura County has a prolific fire history, including 11 events since 2000 that have triggered federal disaster declarations, as listed in Table 17-1. Most of these fires coincided with strong Santa Ana wind events.

Table 17-1. Federally Declared Wildfire Events in Ventura County Date Started FEMA Declaration # Description
October 31, 2019 FM-5302 Maria Fire 9,999 acres burned, 4 structures destroyed October 30, 2019 FM-5298 Easy Fire 2,375 acres burned, 1 structure damaged, 1 structure destroyed November 8, 2018 DR-4407 Woolsey Fire 96,949 acres, 1,643 structures destroyed, 3 fatalities December 4, 2017 FM-5224
DR-4353 Thomas Firea281,893 acres burned, 280 structures damaged, 1,063 structures destroyed, 2 fatalities
May 2, 2013 FM-5024 Springs Fire 24,251 acres burned, 12 structures damaged, 10 structures destroyed September 22, 2009 FM-2839 Guiberson Fire 17,500 acres burned December 3, 2006 FM-2681 Shekell Fire 13,600 acres burned, 7 structures burned September 4, 2006 FM-2677 Day Fire 162,702 acres burned November 17, 2005 FM-2586 School Fire 3,891 acres burned September 28, 2005 FM-2583 Topanga Fire 24, 175 acres burned, 6 structures burned October 25, 2003 DR-1498 Simi Fire 107,560 acres burned, 48 structures lost Source: FEMA 2021, CAL FIRE 2021
a. Statistics include Ventura and Santa Barbara Counties CAL FIRE maintains statistics on historical wildfire activity through its annual reporting (Redbooks).

Wildfire statistics include state and county information, cause and size, acres burned, and dollar damage, among other details. Figure 17-1 shows the wildfire activity for Ventura County between 2011 and 2019, the most recent annual report available. CAL FIRE has Redbooks available for every year back through 1942.
243
Wildfire
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Figure 17-1. CAL FIRE Wildfire Activity Statistics for Ventura County 2011-2019

17.2.2 Location
Figure 17-2 shows the moderate, high, and very high FHSZs for Ventura County. These maps are the basis for the wildfire risk assessment.

17.2.3 Frequency
The wildfire season in coastal Southern California displays a distinct seasonality. Unlike the rest of western North America, which is mainly susceptible to wildfires during the summer, Southern California’s fire season historically peaks in the fall. This is the result of two factors: the long dry summer defining the local Mediterranean climate regime; and the dry, gusty downslope Santa Ana winds, whose season starts in the fall when vegetation is at its driest.

Based on its history of past events, Ventura County has a high chance of a wildfire in any given year.

The most common causes of wildfires, based on recent past events, will be “undetermined,” miscellaneous, equipment use, playing with fire, and arson.

17.2.4 Severity
The Thomas Fire in 2017 had greater impact on Ventura County than any other wildfire to date. This fire started near Santa Paula and spread quickly, aided by strong Santa Ana winds. It burned for 38 days, covering 282,000 acres in Ventura and Santa Barbara counties and destroying or damaging more than 1,300 structures. Two people lost their lives. The agriculture industry in Ventura County suffered losses of at least $171 million.
0 10
20 30
40 50
60 70
80Number of Fires
Reported Cause
2011-13
2014-16
2017-19
244
Fillmore
Moorpark
Simi Valley
Santa Paula
Oxnard
Ojai
Port
Hueneme
Camarillo
San
Buenaventura
Thousand Oaks
Lake Piru
Lake
Casitas
11833
34 118126
150
1 1
23 126
23 33
33 34
1 150
232
33 23
101
Figure 17-2. Wildfire Hazard Severity Zones in Ventura County Data Sources: Ventura Co.,
CAL FIRE, Esri
Moderate
High
Very High
County Boundary
Cities
Major Roads
0 6 3 Miles
245
Wildfire
17-7
In CAL FIRE’s July 2021 list of the deadliest, largest, and most destructive wildfires that have occurred in the state, the Thomas Fire ranks as the 8th largest and 15th most destructive. The 2018 Woolsey Fire ranks as the 8th most destructive. Both these fires were exacerbated by strong Santa Ana wind conditions. Although no Ventura County fires are listed among the top 20 deadliest events, four of the deadliest fires recorded were in neighboring Los Angeles County.

17.2.5 Warning Time
Whether intentionally or accidentally, most wildfires are caused by humans. There is no way to predict when one might break out. Dry seasons, prolonged droughts, and Santa Ana wind events are factors that greatly increase fire likelihood. Severe weather can be predicted, so special attention can be paid during weather events that may increase wildfire risk. Since fireworks often cause brush fires, extra diligence also is warranted around holidays, such as Fourth of July, when the use of fireworks is highest.

If a fire does break out and spread rapidly, residents may need to evacuate within days or hours.

According to the U.S. Forest Service, a fire’s peak burning period generally is between 10 a.m. and sundown. Once a fire has started, fire alerting is reasonably rapid in most cases. The rapid spread of cellular and two-way radio communications in recent years has further contributed to significant improvements in warning time.

17.3 EXPOSURE
A quantitative assessment of exposure to the wildfire hazard was conducted using the hazard mapping shown in Figure 17-2 and the asset inventory developed for this plan. Detailed results by municipality are provided in Appendix D; results for the total planning area are presented below.

17.3.1 Population
Population exposure was estimated by calculating the number of buildings in each hazard area as a percent of total planning area buildings and applying this percentage to the planning area population.

Table 17-2 summarizes the estimated countywide population living in the mapped risk areas. In addition to populations who reside in risk areas where fires may occur, visitors, hikers and campers may be exposed to wildfires. The entire population of the planning area has the potential to be exposed to smoke from nearby wildfires.

Table 17-2. Exposed Population in Mapped Relative Fire Hazard Zones Moderate FHSZ High FHSZ Very High FHSZ
Population Exposed 6,101 4,188 175,759
% of Total Planning Area Population 0.7% 0.5% 20.8%

17.3.2 Property
Table 17-3 summarizes the estimated countywide property exposure in the mapped wildfire risk areas.

Figure 17-3 shows the occupancy class for all buildings in the mapped fire hazard areas. These 246
Ventura County Multi-Jurisdictional Hazard Mitigation Plan 17-8
occupancy classes provide an indication of land use within the mapped hazard area. Some land uses are more vulnerable to fire, such as single-family homes, while others are less vulnerable, such as agricultural land or parks.

Table 17-3. Exposed Property in Mapped Relative Fire Hazard Zones Moderate FHSZ High FHSZ Very High FHSZ
Number of Buildings Exposed 4,648 2,872 58,678
Value of Exposed Structures $1,444,900,462 $955,204,682 $24,250,894,229 Value of Exposed Contents $1,099,162,715 $725,563,443 $15,324,915,299 Total Exposed Property Value $2,544,063,177 $1,680,768,126 $39,575,809,528 Total Exposed Value as % of Planning Area Total 1.4% 0.9% 21.9% Figure 17-3. Structures in the Moderate, High or Very High FHSZs, by Occupancy Class

Residential
2,089
45%
Commercial
281
6%
Industrial
12 0%
Agriculture
2,133
46%
Religion
59 1%
Government
64 2%
Education
10 0%

MODERATE FHSZ
Residential
1,451
50%
Commercial
178
6% Industrial
0 0%
Agriculture
1,141
40%Religion
28 1%
Government
56 2%
Education
18 1%

HIGH FHSZ
Residential
51,856
88%
Commercial
2,274
4%Industrial
491
1%
Agriculture
2,922
5%
Religion
421
1%
Government
243
0%
Education
471
1%

VERY HIGH FHSZ
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17.3.3 Critical Facilities
Figure 17-4 shows critical facilities located in the high or very high fire hazard severity zones, by facility type. The total count of critical facilities in these risk areas (386) represents 25 percent of the planning area total of 1,588. A breakdown by municipality is provided in Appendix D.

Figure 17-4. Critical Facilities in High or Very High Severity Zones

17.3.4 Environment
All natural resources and habitats in mapped fire hazard severity zones are exposed to the risk of wildfire.

17.4 VULNERABILITY

17.4.1 Population
All people exposed to the wildfire hazard are potentially vulnerable to wildfire impacts. Persons with access and functional needs, the elderly and very young may be especially vulnerable to a wildfire if there is not adequate warning time for them to evacuate if needed. In addition, people outside the mapped risk areas are susceptible to health hazards associated with smoke and air pollution from wildfires, especially sensitive populations including children, the elderly, and those with respiratory and cardiovascular diseases. In addition, wildfires threaten the health and safety of those fighting the fires.

17.4.2 Property
All property exposed to the wildfire hazard is vulnerable. Structures that were not constructed to standards designed to protect a building from a wildfire may be especially vulnerable. As of 2008, 72 36
79 14
2 69
131
0 30
60 90
120
150Number of Facilties in Hazard Area
Communication
Energy
Food, Water, Shelter
Hazardous Materials
Medical and Health
Safety and Security
Transportation

28.8%32.4%

37.6%

15.1%

20.0%17.6%

25.0%
0%
20%
40%
60%
80%
100%Facilties in Hazard Area as % of Planning Area Total Communication
Energy
Food, Water, Shelter
Hazardous Materials
Medical and Health
Safety and Security
Transportation
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California State Building code requires minimum standards be met for new buildings in fire hazard severity zones. According the 2019 American Community Survey estimates, most of the housing in the planning area—96.8 percent—was built prior to this code requirement. It is unknown how many of these structures are located in fire hazard zones.

Estimates were developed to indicate the loss that would occur if wildfire damage were equal to 1, 10, 30 or 50 percent of the exposed property value, as summarized in Table 17-4. Damage in excess of 50 percent is considered to be substantial by most building codes and typically requires total reconstruction of the structure.

Table 17-4. Loss Estimates for Fire Hazard Severity Zones Exposed Value Loss Value Loss as % of Total Planning Area Replacement Value Moderate FHSZ
Loss = 1% of Exposed Value
$2,544,063,177
$25,440,632 0.01%
Loss = 10% of Exposed Value $254,406,318 0.14%
Loss = 30% of Exposed Value $763,218,953 0.42%
Loss = 50% of Exposed Value $1,272,031,589 0.70%
High FHSZ
Loss = 1% of Exposed Value
$1,680,768,126
$16,807,681 0.01%
Loss = 10% of Exposed Value $168,076,813 0.09%
Loss = 30% of Exposed Value $504,230,438 0.27%
Loss = 50% of Exposed Value $840,384,063 0.45%
Very FHSZ
Loss = 1% of Exposed Value
$39,575,809,528
$395,758,095 0.22%
Loss = 10% of Exposed Value $3,957,580,953 2.19%
Loss = 30% of Exposed Value $11,872,742,858 6.57%
Loss = 50% of Exposed Value $19,787,904,764 10.95%

17.4.3 Critical Facilities
Currently there are 14 hazardous material containment sites identified in wildfire risk zones. During a wildfire event, containers with these materials could rupture because of the excessive heat and act as fuel for the fire, causing rapid spreading and escalating the fire to unmanageable levels. In addition, they could leak into surrounding areas, saturating soils and seeping into surface waters, and have a disastrous effect on the environment.

In the event of wildfire, there would likely be little damage to most infrastructure. Most roads would not be damaged except in the worst scenarios, although roads and bridges can be blocked by debris or fire-related conditions and become impassable. Power poles are the most at risk to wildfire because most are made of wood and susceptible to burning. In the event of a wildfire, pipelines could provide a source of fuel and lead to a catastrophic explosion.
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17.4.4 Environment
Fire is a natural and critical ecosystem process in most terrestrial ecosystems, affecting the types, structure, and spatial extent of native vegetation. However, in some circumstances it can also cause severe environmental impacts, such as the following:

Soil Erosion—The protective covering provided by foliage and dead organic matter is removed, leaving the soil fully exposed to wind and water erosion. Accelerated soil erosion occurs, causing landslides and threatening aquatic habitats.

Reduced Agricultural Resources—Wildfire can have disastrous consequences on agricultural resources, removing them from production and necessitating lengthy restoration programs.

Spread of Invasive Plant Species—Non-native plant species, such as Arundo donax, frequently invade burned areas. When weeds become established, they can dominate the plant cover over broad landscapes, and become difficult and costly to control.

Disease and Insect Infestations—Unless diseased or insect-infested trees are swiftly removed, infestations and disease can spread to healthy forests and private lands. Timely active management actions are needed to remove diseased or infested trees.

Destroyed Endangered Species Habitat—Wildfire can have negative consequences for endangered species by degrading their habitat.

Soil Sterilization—Some wildfires burn so hot that they can sterilize the soil. Topsoil exposed to extreme heat can become water repellant, and soil nutrients may be lost.

Damaged Fisheries—Fisheries can suffer from increased water temperatures, sedimentation, and changes in water quality.

Damaged Cultural and Historical Resources—The destruction of cultural and historic resources may occur, scenic vistas can be damaged, and access to recreational areas can be reduced.

17.5 SCENARIO
With Ventura County’s Mediterranean climate, high moisture levels during the winter rainy season can significantly increase the growth of plants, followed by that vegetation becoming dried during the long, hot summers, decreasing plant moisture content and increasing the ratio of dead fuel to living fuel. As a result, fire susceptibility increases dramatically, particularly in late summer and early autumn.

The worst conditions for local wildfires also depend on how long it has been since the last fire. For several years after a fire has occurred, easily flammable herbaceous species predominate and increase the likelihood of new fires. When woody species become re-established, they contribute to a lower overall level of fire susceptibility for approximately 10 years. However, after this period, the slow aging plant community becomes ever more likely to burn because of increased levels of dead plant material and lowered plant moisture levels.

Santa Ana winds contribute to the likeliness of wildfires in Ventura County, bringing extremely dry air and high wind speeds that further desiccate plant communities during the period of the year when the constituent species have very low moisture content. The effect of these winds on existing fires is particularly dangerous; the winds can greatly increase the rate at which fires spread. 250
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A worst-case scenario would include an active fire season throughout the American west, spreading resources thin. Firefighting teams would be exhausted or unavailable. Many federal assets would be responding to other fires that started earlier in the season.

To further complicate the problem, heavy rains could follow, causing flooding and landslides in areas where vegetation has been removed by the fire.

17.6 ISSUES
The major issues for wildfire are the following:

Public education and outreach to people living in or near the fire hazard zones should include information about and assistance with mitigation actions such as defensible space and advance identification of evacuation routes and safe zones.

Wildfires could cause landslides as a secondary natural hazard.

Wildfire preparedness and response planning should emphasize being alert to any predictions of Santa Ana winds, which are significant contributors to wildfire in Ventura County.

Climate change could exacerbate the wildfire hazard.

Future growth into interface areas should continue to be managed.

Area fire districts need to continue to train on wildland-urban interface events.

Vegetation management activities—This issue would include enhancement through expansion of thetarget areas as well as additional resources.

Regional consistency of higher building code standards such as residential sprinkler requirements and prohibitive combustible roof standards.

Firefighters in remote and rural areas are faced with limited water supply and lack of hydrant taps.

Expand certifications and qualifications for fire department personnel.

Ensure that all firefighters are trained in basic wildfire behavior, basic fire weather, and that all company officers and chief level officers are trained to the wildland command and strike team leader level.

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18. CLIMATE CHANGE

18.1 GENERAL BACKGROUND

18.1.1 What is Climate Change?
“Climate change” refers to alterations in the long-term patterns of temperature, precipitation, humidity, wind and seasons that play a fundamental role in shaping natural ecosystems and the human economies and cultures that depend on them. These shifts may result from natural processes (e.g., cyclical ocean patterns like El Niño, La Niña and the Pacific Decadal Oscillation, volcanic activity, changes in the sun’s energy output, variations in Earth’s orbit), but they can also be driven by human activity. Many of the changes observed in Earth’s climate since the early 20th century have been attributed to human activity.

The well-established worldwide warming trend of recent decades and its related impacts are caused by increasing concentrations of carbon dioxide and other greenhouse gases in the earth’s atmosphere.

Greenhouse gases are gases that trap heat in the atmosphere, resulting in a warming effect. Carbon dioxide is the most commonly known greenhouse gas; however, methane, nitrous oxide and fluorinated gases also contribute to warming. Emissions of these gases come from a variety of sources, such as the combustion of fossil fuels, agricultural production, and changes in land use. According to the National Aeronautics and Space Administration (NASA), carbon dioxide concentrations measured about 280 parts per million (ppm) before the industrial era began in the late 1700s and have risen dramatically since then, surpassing 400 ppm in 2013 for the first time in recorded history (see Figure 18-1).

18.1.2 How Climate Change Affects Hazard Mitigation
Climate change will affect the people, property, economy, and ecosystems of the planning area in a variety of ways. Consequences of climate change include increased periods of prolonged drought, potential for heat-related illnesses, detrimental impacts on agricultural productivity, and increased flood vulnerability. The most important effect for the development of this hazard mitigation plan is that climate change will have a measurable impact on the occurrence and severity of many natural hazards.

An essential aspect of hazard mitigation is predicting the likelihood of future hazard events. Typically, predictions are based on statistical projections from records of past events. This approach assumes that the likelihood of hazard events remains essentially unchanged over time. Thus, averages based on the past frequencies of, for example, floods are used to estimate future frequencies: if a river has flooded an average of once every 5 years for the past 100 years, then it can be expected to continue to flood an average of once every 5 years.
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Figure 18-1. Global Carbon Dioxide Concentrations Over Time Source: NASA 2021
For hazards that are affected by climate conditions though, the assumption that future behavior will be equivalent to past behavior is not valid. For example, flooding is generally associated with precipitation frequency and quantity. However, the frequency of flooding will not remain constant if broad precipitation patterns change over time. Specifically, as hydrology changes, storms currently considered to be the 100-year flood might strike more often, leaving many communities at greater risk.

The risks of landslide, severe storms, severe weather, and wildfire are all affected by climate patterns as well. For this reason, an understanding of climate change is pertinent to efforts to mitigate natural hazards. Information about how climate patterns are changing provides insight on the reliability of future hazard projections used in mitigation analysis.

18.1.3 Current Indicators of Climate Change
Global Indicators
The major scientific agencies of the United States—including NASA and the National Oceanic and Atmospheric Administration (NOAA)—have presented evidence that climate change is occurring. NASA summarizes key evidence as follows (National Aeronautics and Space Administration 2021):

Global Temperature Rise—The planet’s average surface temperature has risen about 2.12 ºF since the late 19th century, a change driven largely by increased carbon dioxide emissions into 253
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the atmosphere and other human activities. Most of the warming occurred in the past 40 years, with the seven most recent years being the warmest. The years 2016 and 2020 are tied for the warmest year on record. The ocean has absorbed much of this increased heat, with the top 100 meters (about 328 feet) of ocean showing warming of more than 0.6 ºF since 1969. Earth stores 90 percent of its extra energy in the ocean.

Shrinking Ice Sheets—The Greenland and Antarctic ice sheets have decreased in mass. Data from NASA’s Gravity Recovery and Climate Experiment show Greenland lost an average of 279 billion tons of ice per year between 1993 and 2019, while Antarctica lost about 148 billion tons of ice per year.

Glacial Retreat—Glaciers are retreating almost everywhere around the world—including in the Alps, Himalayas, Andes, Rockies, Alaska and Africa.

Decreased Snow Cover—Satellite observations reveal that the amount of spring snow cover in the Northern Hemisphere has decreased over the past five decades and that the snow is melting earlier
Sea-Level Rise—Global sea levels rose about 8 inches in the last century. The rate in the last two decades is nearly double that of the last century and is accelerating slightly every year.

Declining Arctic Sea Ice—Both the extent and thickness of Arctic sea ice has declined rapidly over the last several decades
Extreme Events—The number of record high temperature events in the United States has been increasing, while the number of record low temperature events has been decreasing, since 1950. The U.S. has also witnessed an increasing number of intense rainfall events.

Ocean Acidification—Since the beginning of the Industrial Revolution, the acidity of surface ocean waters has increased by about 30 percent. The amount of carbon dioxide absorbed by the upper layer of the oceans is increasing to about 7 to 10 billion metric tons per year.

California Indicators
Monitoring and research efforts across California have generated data that describe changes already underway in the state. Notable examples across the state include the following (California Office of Environmental Health Hazard Assessment 2018):

Dissolved oxygen in coastal waters is declining throughout the south coast survey region Since 1950, the northern Sierra Nevada showed an overall snowpack decline of 7.4 inches.

Unusually warm waters occurred in the Pacific Ocean in 2014-2015, leading to widespread impacts on marine life. This marine heat wave first appeared as a large area of exceptionally high sea surface temperatures in the Gulf of Alaska in November 2013 and later extended along the entire west coast of North America.

The surface area of seven Sierra Nevada glaciers has decreased dramatically since the beginning of the 20th century. In 2014, the size of these glaciers ranged from 14 to 52 percent of their 1903 area.

Sea level has risen by about 7 inches since 1900 at San Francisco and by about 6 inches since 1924 at La Jolla.

Since 1906, the fraction of annual snowmelt runoff that flows into the Sacramento River between April and July has decreased by about 9 percent. 254
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Compared to the 1930s, forests across much of California today have lower densities of large trees, and higher densities of small trees. Water stress, which increases in a warming climate, poses a greater risk to large trees than to small trees.

Annual tree mortality in California forests increased in 2014, and steep increases in mortality followed in subsequent years; the highest number, 62 million tree deaths, was recorded in 2016.

Future droughts may be hotter, as warm temperatures coincide with periodic dry years; 2016 and 2020 were the warmest years on record.

Heat-related deaths and illnesses in California increased dramatically in 2006 following a record-breaking heat wave. At least 140 deaths occurred between July 15 and August 1. Deaths related to this heat wave were largely attributed to elevated nighttime temperatures.

The number of acres burned by wildfires statewide has been increasing since 1950. Large fires affecting 1,000 acres or more account for most of the area burned each year.

18.1.4 Projected Future Impacts
Climate change projections contain inherent uncertainty, largely derived from the fact that they depend on future greenhouse gas emission scenarios. Generally, the uncertainty in greenhouse gas emissions is addressed by the presentation of differing scenarios: low-emissions or high-emissions scenarios. In low-emissions scenarios, greenhouse gas emissions are reduced substantially from current levels. In high-emissions scenarios, greenhouse gas emissions generally increase or continue at current levels.

Uncertainty in outcomes is generally addressed by averaging a variety of model outcomes. Despite this uncertainty, climate change projections present valuable information to help guide decision-making for possible future conditions.

Global and National Projections
The Intergovernmental Panel on Climate Change, which includes more than 1,300 scientists from the United States and other countries, project that Earth’s average temperatures will raise 2.5 to 10 ºF over the next century (National Aeronautics and Space Administration 2021). The Third and Fourth National Climate Assessment Reports indicate the following:

Change Will Continue Through This Century and Beyond—Global climate is projected to continue to change over this century and beyond. The magnitude of climate change beyond the next few decades depends primarily on the amount of heat-trapping gases emitted globally, and how sensitive the Earth’s climate is to those emissions.

Temperatures Will Continue to Rise—Because human-induced warming is superimposed on a naturally varying climate, the temperature rise has not been, and will not be, uniform or smooth across the country or over time.

Frost-Free Season and Growing Season will Lengthen—The length of the frost-free season and the corresponding growing season has been increasing nationally since the 1980s, with the largest increases occurring in the western United States, affecting ecosystems and agriculture.

Across the United States, the growing season is projected to continue to lengthen.

In a future in which heat-trapping gas emissions continue to grow, increases of a month or more in the lengths of the frost-free and growing seasons are projected across most of the United States by the end of the century, with slightly smaller increases in the northern Great Plains.

The largest increases in the frost-free season (more than eight weeks) are projected for the 255
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western United States, particularly in high elevation and coastal areas. The increases will be smaller if heat-trapping gas emissions are reduced.

Changes in Precipitation Patterns—Average U.S. precipitation has increased since 1900, but some areas have had increases greater than the national average, and some areas have had decreases. More winter and spring precipitation is projected for the northern United States, and less for the Southwest, over this century.

Projections of future climate over the United States suggest that the recent trend toward increased heavy precipitation events will continue. This trend is projected to occur even in regions where total precipitation is expected to decrease, such as the Southwest.

More Droughts and Heat Waves—Droughts in the Southwest and heat waves everywhere are projected to become more intense, and cold waves less intense everywhere. Summer temperatures are projected to continue rising, and a reduction of soil moisture, which exacerbates heat waves, is projected for much of the western and central United States in summer. By the end of this century, what have been once-in-20-year extreme heat days (one- day events) are projected to occur every two or three years over most of the nation.

Hurricanes Will Become Stronger and More Intense—The intensity, frequency, and duration of North Atlantic hurricanes, as well as the frequency of the strongest (Category 4 and 5) hurricanes, have all increased since the early 1980s. The relative contributions of human and natural causes to these increases are still uncertain. Hurricane-associated storm intensity and rainfall rates are projected to increase as the climate continues to warm.

Arctic Likely to Become Ice-Free in Summer—The Arctic Ocean is currently expected to become essentially ice free in summer before 2050.

Sea Level Will Rise 1 to 8 feet by 2100—Global sea level has risen by about 8 inches since reliable record keeping began in 1880. It is projected to rise another 1 to 8 feet by 2100. This is the result of added water from melting land ice and the expansion of seawater as it warms.

In the next several decades, storm surges and high tides could combine with sea-level rise and land subsidence, resulting in increased flooding in many regions. Sea-level rise will continue past 2100 because the oceans take a very long time to respond to warmer conditions at the Earth’s surface. Ocean waters will therefore continue to warm and sea level will continue to rise for many centuries at rates equal to or higher than those of the current century. Figure 18-2 shows the projected rate of global sea-level rise under different greenhouse gas scenarios (National Oceanic and Atmospheric Administration 2021).

Projections for California
According to California’s Fourth Climate Change Assessment, the state can expect the following climate change impacts (State of California 2021):

By 2100, the average annual maximum daily temperature is projected to increase by 5.6 to 8.8 ºF
By 2100, the water supply from snowpack is projected to decline by two-thirds By 2050, a study estimates California’s agricultural production could face climate-related water shortages of up to 16 percent in certain regions
By 2100, the frequency of extreme wildfires will increase, and the average area burned statewide would increase by 77 percent
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Figure 18-2. Possible Future Sea Levels for Different Greenhouse Gas Pathways

Source: NOAA, 2021
By 2100, 13 to 67 percent of Southern California beaches may completely erode due to sea- level rise
By 2100, the miles of highways susceptible to coastal flooding in a 100-year storm event will triple
By 2050, heat waves in cities could cause 2 to 3 times more heat-related deaths Projections for Ventura County
The 2019 report, Projected Changes in Ventura County Climate, lists the following local projections (Oakley, et al. 2019):

Changes in temperature—Both annual average temperatures and the frequency of extreme temperatures will increase across Ventura County. Inland areas are likely to see an increase of at least 3 to 5 ºF. Coastal areas are likely to see an increase of at least 2 to 3 ºF. Figure 18-3 shows the projected maximum temperature changes from the average temperature for 1950 – 2005, to the average temperature for 2021 – 2040. Increases in maximum temperatures and overnight minimum temperatures as well as frequency of extreme temperatures will likely have negative impacts on human health and ecosystems, disproportionately affecting disadvantaged communities and impacting species extent and abundance.

Changes in Precipitation—Precipitation is likely to intensify, meaning that the same amount of precipitation will fall in fewer days. Projections suggest a 7 percent decrease in winter precipitation days, an 11 percent decrease in spring precipitation days, and a 20 percent decrease in fall precipitation days with little overall projected change in seasonal precipitation totals. Changes in precipitation characteristics (intensification and concentration into winter season) may have implications for groundwater recharge and how surface water is conveyed, captured, and stored. There may be increased potential for post-fire flash flooding and/or debris flows due to more frequent short-duration, high intensity rainfall. 257
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Figure 18-3. Changes in Projected Maximum Temperatures in Ventura County

Changes in evaporative demand—The greatest changes are likely in inland terrain, particularly in the headwaters of the Santa Clara River (Los Angeles County). Seasonally, the greatest total evaporation changes in demand will be in the spring, followed by summer and fall, with modest changes during the winter. The fall season demonstrates the largest percentage increases in evaporative demand over the largest area while the greatest percentage increases during spring and summer occur in the Topatopa Mountains. Increased evaporative demand may affect what crops can be grown economically, alter ecosystem function, and increase drought susceptibility.

18.1.5 Responses to Climate Change
Communities and governments worldwide are working to address, evaluate and prepare for climate changes that are likely to impact communities in coming decades. Generally, climate change discussions encompass two separate but inter-related considerations: mitigation and adaptation.

The term “mitigation” has multiple meanings across disciplines. Mitigation in emergency management, as generally addressed in this hazard mitigation plan, is typically defined as the effort to reduce loss of life and property by lessening the impact of disasters. Mitigation in climate change discussions is defined as a human intervention to reduce impacts on the climate system. It includes strategies to reduce greenhouse gas sources and emissions and enhance greenhouse gas sinks. In this chapter, mitigation is used as defined by the climate change community. In the other chapters of this plan, mitigation is primarily used in an emergency management context.

Adaptation refers to adjustments in natural or human systems in response to the actual or anticipated effects of climate change and associated impacts. These adjustments may moderate harm or exploit beneficial opportunities. Mitigation and adaptation are related, as the world’s ability to reduce greenhouse gas emissions will affect the degree of adaptation that will be necessary. Some initiatives 258
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and actions can both reduce greenhouse gas emissions and support adaptation to likely future conditions.

Societies across the world are facing the need to adapt to changing conditions associated with natural disasters and climate change. Farmers are altering crops and agricultural methods to deal with changing rainfall and rising temperature; architects and engineers are redesigning buildings; planners are looking at managing water supplies to deal with droughts or flooding.

Adaptive capacity goes beyond human systems, as some ecosystems are able to adapt to change and to buffer surrounding areas from the impacts of change. Forests can bind soils and hold large volumes of water during times of plenty, releasing it through the year; floodplains can absorb vast volumes of water during peak flows; coastal ecosystems can hold out against storms, attenuating waves and reducing erosion. Other ecosystem services—such as food provision, timber, materials, medicines, and recreation—can provide a buffer to societies in the face of changing conditions. Ecosystem-based adaptation is the use of biodiversity and ecosystem services as part of an overall strategy to help people adapt to the adverse effects of climate change. This includes the sustainable management, conservation and restoration of specific ecosystems that provide key services.

Assessment of the current efforts and adaptive capacity of the planning partners participating in this hazard mitigation plan are included in the jurisdiction-specific annexes in Volume 2.

18.2 IMPACT OF CLIMATE CHANGE ON HAZARDS OF CONCERN

18.2.1 Dam Failure
On average, changes in California’s annual precipitation levels are not expected to be dramatic; however, small changes may have significant impacts for water resource systems, including dams.

Dams are designed partly based on assumptions about a river’s flow behavior, expressed as hydrographs. Changes in weather patterns can have significant effects on the hydrograph used for the design of a dam. If the hygrograph changes, it is conceivable that the dam can lose some or all of its designed margin of safety, also known as freeboard.

If freeboard is reduced, dam operators may be forced to release increased volumes earlier in a storm cycle in order to maintain the required margins of safety. Such early releases of increased volumes can increase flood potential downstream. According to the California Department of Water Resources, flood flows on many California rivers have been record-setting since the 1950s. This means that water infrastructure, such as dams, have been forced to manage flows for which they were not designed. The California Division of Dam Safety has indicated that climate change may result in the need for increased safety precautions to address higher winter runoff, frequent fluctuations of water levels, and increased potential for sedimentation and debris accumulation from changing erosion patterns and increases in wildfires. According to the Division, climate change also will impact the ability of dam operators to estimate extreme flood events (California Department of Water Resources 2021b).

A strategy called Forecast Informed Reservoir Operations (FIRO) is being developed and tested in California as a way to inform decisions to retain or release water by allowing flexibility in operation policies and rules with enhanced monitoring and improved weather and water forecasts (Center for Western Weather and Water Extremes 2021).
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Dams are constructed with safety features known as “spillways.” Spillways are put in place on dams as a safety measure in the event of the reservoir filling too quickly. Spillway overflow events, often referred to as “design failures,” result in increased discharges downstream and increased flooding potential.

Although climate change will not increase the probability of catastrophic dam failure, it may increase the probability of design failures.

The following summarizes changes in exposure and vulnerability to the dam failure hazard resulting from climate change:

Population—Population exposure and vulnerability to the dam failure hazard are unlikely to change as a result of climate change.

Property—Property exposure and vulnerability to the dam failure hazard are unlikely to change as a result of climate change.

Critical facilities—The exposure and vulnerability of critical facilities are unlikely to change as result of climate change. Dam owners and operators are sensitive to the risk and may need to alter maintenance and operations to account for changes in the hydrograph and increased sedimentation.

Environment—The exposure and vulnerability of the environment to dam and levee failure are unlikely to change as a result of climate change. Ecosystem services may be used to mitigate some factors that could increase the risk of design failures, such as increasing the natural water storage capacity in watersheds above dams.

18.2.2 Drought
The long-term effects of climate change on regional water resources are unknown, but global water resources are already experiencing the following stresses without climate change:

Growing populations
Increased competition for available water
Poor water quality
Environmental claims
Uncertain reserved water rights
Groundwater overdraft
Aging urban water infrastructure.

With a warmer climate, droughts could become more frequent, more severe, and longer-lasting.

According to the National Climate Assessment, “higher surface temperatures brought about by global warming increase the potential for drought. Evaporation and the higher rate at which plants lose moisture through their leaves both increase with temperature. Unless higher evapotranspiration rates are matched by increases in precipitation, environments will tend to dry, promoting drought conditions” (U.S. Climate Resilience Toolkit 2021).

Because changes in precipitation patterns are still uncertain, the potential impacts and likelihood of drought are uncertain. DWR has noted impacts of climate change on statewide water resources by charting changes in snowpack, sea level, and river flow. As temperatures rise and more precipitation 260
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comes in the form of rain instead of snow, these changes will likely continue or grow even more significant. DWR estimates that the Sierra Nevada snowpack, which provides a large amount of the water supply for other parts of the state, will experience a 48- to 65-percent loss by the end of the century compared to the historical April 1 average (California Department of Water Resources 2021a).

Projections for the planning area show a significant decline in projected snow water equivalent in April snowpack. Increasing temperatures may also increase net evaporation from reservoirs, which would reduce water availability for ecosystems and human use (Mount, Escriva-Bou and Sencan 2021).

By addressing current stresses on water supplies and by building a flexible, robust program, the County will be able to more adeptly respond to changing conditions and to survive dry years.

The following summarizes changes in exposure and vulnerability to the drought hazard resulting from climate change:

Population—Population exposure and vulnerability to drought are unlikely to increase as a result of climate change. While greater numbers of people may need to engage in behavior change, such as water saving efforts, significant life or health impacts are unlikely.

Property—Property exposure and vulnerability may increase as a result of increased drought resulting from climate change, although this would most likely occur in non-structural property such as crops and landscaping. It is unlikely that structure exposure and vulnerability would increase as a direct result of drought, although secondary impacts of drought, such as wildfire, may increase and threaten structures.

Critical facilities—Critical facility exposure and vulnerability are unlikely to increase as a result of increased drought resulting from climate change; however, critical facility operators may be sensitive to changes and need to alter standard management practices and actively manage resources, particularly in water-related service sectors Environment—The vulnerability of the environment may increase as a result of increased drought resulting from climate change. Prolonged or more frequent drought resulting from climate change may stress ecosystems in the region, which include many special-status species.

18.2.3 Earthquake
The impacts of global climate change on earthquake probability are unknown, although scientists have identified tiny earthquakes triggered by the change of fault stress loads from rain and snow. Similarly, long-term drought can result in a significant change in the stress load on earth’s crust.

Pumping of groundwater from underground aquifers by humans, which is exacerbated during times of drought, has also been shown to impact patterns of stress loads by “unweighting” Earth’s crust. A 2014 study looked at the effects of groundwater extraction in California’s Central Valley on seismicity on the adjacent San Andreas Fault. The researchers found that such extractions can promote lateral changes in stress to the two sides of the San Andreas, which move horizontally against each other along the boundary of two major tectonic plates. This could potentially cause them to unclamp and slip, resulting in an earthquake (National Aeronautics and Space Administration 2019).

Because impacts on the earthquake hazard are not well understood, increases in exposure and vulnerability of local resources are not able to be determined. 261
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18.2.4 Flood
Use of historical hydrologic data has long been the standard of practice for designing and operating water supply and flood protection projects. For example, historical data are used for flood forecasting models and to forecast snowmelt runoff for water supply. This method of forecasting assumes that the climate of the future will be similar to that of the period of historical record. However, the hydrologic record cannot be used to predict changes in frequency and severity of extreme climate events such as floods. Scientists project greater storm intensity with climate change, resulting in more direct runoff and flooding. High frequency flood events in particular will likely increase with a changing climate. What is currently considered a 1-percent-annual-chance also may strike more often, leaving many communities at greater risk. Going forward, model calibration must happen more frequently, new forecast-based tools must be developed, and a standard of practice that explicitly considers climate change must be adopted.

Climate change is already impacting water resources, and resource managers have observed the following:

Historical hydrologic patterns can no longer be solely relied upon to forecast the water future.

Precipitation and runoff patterns are changing, increasing the uncertainty for water supply and quality, flood management and ecosystem functions.

Extreme climatic events will become more frequent, necessitating improvement in flood protection, drought preparedness and emergency response.

The amount of snow is critical for water supply and environmental needs, but so is the timing of snowmelt runoff into rivers and streams. Rising snowlines caused by climate change will allow more mountain areas to contribute to peak storm runoff. Changes in watershed vegetation and soil moisture conditions will likewise change runoff and recharge patterns. As stream flows and velocities change, erosion patterns will also change, altering channel shapes and depths, possibly increasing sedimentation behind dams, and affecting habitat and water quality. With potential increases in the frequency and intensity of wildfires due to climate change, there is potential for more floods following fire, which increase sediment loads and water quality impacts.

The following summarizes changes in exposure and vulnerability to the flood hazard resulting from climate change:

Population and Property—Population and property exposure and vulnerability may increase as a result of climate change impacts on the flood hazard. Runoff patterns may change, resulting in flooding in areas where it has not previously occurred.

Critical facilities—Critical facility exposure and vulnerability may increase as a result of climate change impacts on the flood hazard. Runoff patterns may change, resulting in risk to facilities that have not historically been at risk from flooding. Changes in the management and design of flood protection critical facilities may be needed as additional stress is placed on these systems.

Planners will need to factor a new level of safety into the design, operation, and regulation of flood protection facilities such as dams, bypass channels and levees, as well as the design of local sewers and storm drains.

Environment—The exposure and vulnerability of the environment may increase as a result of climate change impacts on the flood hazard. Changes in the timing and frequency of flood 262
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events may have broader ecosystem impacts that alter the ability of already stressed species to survive.

18.2.5 Landslide
Climate change may impact storm patterns, increasing the probability of more frequent, intense storms with varying duration. Increase in global temperature is likely to affect the snowpack and its ability to hold and store water. Warming temperatures also could increase the occurrence and duration of droughts, which would increase the probability of wildfire, reducing the vegetation that helps to support steep slopes. Each these factors would increase the probability of landslides.

The following summarizes changes in exposure and vulnerability to the landslide hazard resulting from climate change:

Population and Property—Population and property exposure and vulnerability would be unlikely to increase because of climate change impacts on the landslide hazard. These events may occur more frequently, but the extent and location should be contained within mapped hazard areas or recently burned areas.

Critical facilities—Critical facility exposure and vulnerability would be unlikely to increase due to climate change impacts on the landslide hazard; however, critical facility owners and operators may experience more frequent disruption to service provision resulting from landslide hazards. For example, transportation systems may experience more frequent delays if movements blocking these systems occur more frequently.

Environment—Exposure and vulnerability of the environment would be unlikely to increase because of climate change, but more frequent movements in river systems may impact water quality and have negative impacts on stressed species.

18.2.6 Sea-Level Rise and Coastal Erosion
Coastal areas are sensitive to sea-level rise, changes in precipitation and the frequency and intensity of storms, and warmer ocean temperatures. According to NASA, warmer temperatures may lead to an increase in the intensity of storms, leading to weather events that can have increase impacts on coastal erosion. A study on increased storm wave heights from climate change indicated that coastal erosion and flooding may occur twice as fast from sea-level rise alone and up to four times as fast as a doubling of the frequency of major El Niño events. Should all these potential events from climate change occur simultaneously, there could be up to an order of magnitude increase in coastal erosion compared to current rates (National Aeronautics and Space Administration 2010).

Climate change-related sea-level rise could exacerbate sea water intrusion issues under the agricultural lands of the Oxnard coastal plain, which were first observed in the 1930s and became a serious problem in the 1950s. This could result in diminishing returns or even render existing, valuable crop lands completely unusable.

18.2.7 Severe Storms
Climate change presents a challenge for risk management associated with severe storms. The science for linking the severity of specific severe storm events to climate change is still evolving; however, a 263
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number or trends provide some indication of how climate change may be impacting these events.

According to the Fourth National Climate Change Assessment, heavy rainfall events are becoming more severe (U.S. Global Change Research Program 2018). Climate change impacts on other severe storm events such as thunderstorms are still not well understood. The following summarizes changes in exposure and vulnerability to the severe weather hazard resulting from climate change:

Simi Valley City CouncilJuly 25, 2022

Simi Valley City Council
July 25, 2022