2.e-Marin-County-Multi-Jurisdictional-Local-Hazard-Mitigation-Plan — San Rafael City Council, October 7, 2024 (part 1 of 4)

____________________________________________________________________________________

FOR CITY CLERK ONLY
Council Meeting: _______________________
Disposition: ___________________________
Agenda Item No: 2.e
Meeting Date: October 7, 2024

SAN RAFAEL CITY COUNCIL AGENDA REPORT
Department: Fire, Office of Emergency Services
Prepared by: Quinn Gardner
Deputy Director of Emergency
Management
City Manager Approval: ______________
TOPIC: MARIN COUNTY MULTI-JURISDICTIONAL LOCAL HAZARD MITIGATION PLAN SUBJECT: RESOLUTION ADOPTING THE 2024 MARIN COUNTY MULTI-JURISDICTIONAL LOCAL HAZARD MITIGATION PLAN AND THE CITY OF SAN RAFAEL ANNEX.

RECOMMENDATION:

Adopt a resolution adopting the 2024 Marin County Multi-Jurisdictional Local Hazard Mitigation Plan (MJLHMP) and the City of San Rafael Annex.

BACKGROUND:

What is a Local Hazard Mitigation Plan?
A Local Hazard Mitigation Plan (LHMP) is a living document that assesses regional risks and vulnerabilities and identifies and prioritizes mitigation projects, describing updated strategies for sustaining and building on current mitigation activities to ensure the future safety of lives, preservation of property and protection of the environment during times of disaster. Mitigation planning also improves the ability to recover from a disaster. An annex to an LHMP is a document that provides additional information specific to a jurisdiction, such as a city or special district, which participates in the plan.

Annexes supplement the information in LHMP, which includes federally required elements that apply to the entire planning area. This City of San Rafael Annex (Attachment 3) provides additional information specific to the City, with a focus on providing additional details on the hazard risk assessment and mitigation strategy (i.e., mitigation actions) for the community.

State and Federal Regulations for LHMPs
The Disaster Mitigation Act (DMA) of 2000 (Public Law 106-390) requires local governments to develop and adopt pre-disaster LHMPs to minimize property damage and the risk to public health and safety that might otherwise result from the effects of a natural or human-made disaster.

The Federal Emergency Management Agency (FEMA) requires the plan to be updated every five years to maintain federal hazard mitigation grant eligibility. In addition, California Assembly Bill No. 2140 (AB SAN RAFAEL CITY COUNCIL AGENDA REPORT / Page: 2
2140, 2006) allows cities to be considered for additional state cost-share on eligible public assistance projects by adopting their current, FEMA-approved local hazard mitigation plans (LHMPs) into the Safety Element of their General Plan. This adoption, along with other requirements, makes the City eligible to be considered for up to an additional 6.25% local share to be funded by the state-eligible public assistance projects.

The City of San Rafael’s Planning Efforts
In February 2016, FEMA approved the City’s application for a grant to develop a Local Hazard Mitigation Plan for San Rafael. Previously, the City did not have a FEMA-approved, locally adopted Hazard Mitigation Plan and, thus, was not eligible to apply for any FEMA funding to support City Hazard Mitigation projects. After more than a year of meetings, staff analysis, research, and working with a specialized consultant, on November 17, 2017, the City Council adopted San Rafael’s first Local Hazard Mitigation Plan.

In 2018, the Marin County Sheriff’s Office, which then included the County Office of Emergency Services and County Department of Public Works, spearheaded the development of a countywide Marin County Multi-Jurisdictional Local Hazard Mitigation Plan. The plan included jurisdiction-specific mitigations and countywide mitigation measures that applied to all of Marin County’s twelve (12) cities, towns, and unincorporated areas. This effort was intended to create communitywide resiliency, as large-scale disasters rarely adhere to jurisdictional boundaries, especially in cities and towns in Marin that share natural features, such as waterways and hillsides. San Rafael adopted the Marin County MultiJurisdictional Local Hazard Mitigation Plan in July 2019.

In August 2021, the San Rafael City Council adopted the General Plan 2040, which included a Safety and Resilience Element. The City’s current Safety and Resilience Element of the General Plan includes language and goals relating to hazard mitigation and specifically references the 2019 MJLHMP.

Responding to federal mandates in the Disaster Mitigation Act of 2000 (Public Law 106-390), the 2024 MJLHMP updates the previous plan adopted in 2019.

ANALYSIS:

Mitigation planning allows for improved emergency management and disaster response for all communities we serve. These include targeted assistance to those with access and functional needs, migrant populations, ethnic populations/language accessibility, essential workers, the elderly, and more.

Outreach was conducted with efforts to reach various demographics. This section describes the planning process, organization, and review of the 2024 MJLHMP.

The 2024 MJLHMP Planning Process
In Marin County, jurisdictions collaborate on LHMP updates in a multi-jurisdictional planning effort, reflecting that hazard risks extend beyond jurisdiction borders. Multi-jurisdictional planning efforts have many benefits, including promoting compliance with state and federal disaster mitigation requirements, maintaining eligibility for FEMA mitigation grants, improving communication between jurisdictions, and avoiding duplication of efforts by pooling resources and sharing costs.

The 2024 MJLHMP updates the 2019 MJLHMP. The planning area for the MJLHMP encompasses the entire geographic area of Marin County. The preparation of the 2024 MJLHMP was led by the Marin County Office of Emergency Services, with participation from the Marin County Operational Area and the sixteen (16) cities, towns, and special districts in Marin County. Much like what occurred in 2018, this recent planning effort was intended to advance community-wide resiliency.

SAN RAFAEL CITY COUNCIL AGENDA REPORT / Page: 3
To ensure eligibility for FEMA and the California Governor’s Office of Emergency Services (Cal OES) grants, the MJLHMP development process included the following activities:

1. Identification of potential planning partners. Partners who chose to participate submitted Letters of Intent committing resources to the development effort;

2. Identification and assessment of the risks of natural hazards;

3. Development of actions to mitigate the risks and a plan to implement the actions over the next five years;

4. Public involvement in the development and review of the MJLHMP; and

5. Review and approval of the MJLHMP by Cal OES and FEMA.

As part of the update process, City staff from various departments reviewed previous hazard mitigation plans, pending projects, and newly identified needs. In collaboration with the County of Marin and their consultant, City staff provided input to ensure the plan updates meet the City’s needs for mitigating natural and human-caused disasters.

The Organization of the 2024 MJLHMP
The MJLHMP is organized with a main document (Volume 1) addressing countywide hazards and mitigation actions. Volume 1 (Attachment 2) is accompanied by Volume 2, which contains annexes (i.e., appendices) for each participating jurisdiction. Participating jurisdictions are known as “planning partners” in the document.

The City of San Rafael Community Profile is contained in Volume 2 of the MJLHMP and is provided as Attachment 3 to this report.

Although Volume 1 addresses hazard mitigation on a countywide basis, and Volume 2 considers these same topics for each city, town, and special district, both documents are organized as follows:
• An introduction with an overview of the jurisdiction and a description of the planning process. • A systematic hazard identification and risk assessment of natural and human-caused hazards such as flooding, drought, wildfire, landslides, severe weather, terrorism, cyber threats, pandemics, and the impact of climate change.
• Mitigation strategies and actions to reduce injury, property damage, and community disruption. • A process for adopting, monitoring, and evaluating the plan.

FEMA and Cal OES Review
Jurisdictions must submit their Local Hazard Mitigation Plans to FEMA for approval to be eligible for FEMA funding from the Pre-Disaster Mitigation and Hazard Mitigation Grant programs. In July 2024, FEMA and Cal OES approved the City of San Rafael Annex to the 2024 MJLHMP (Attachment 4). This plan's expiration date will be January 31, 2029. After local adoption, the signed resolution is returned to FEMA for final approval. Final plans are made publicly available via the County Office of Emergency Management website and City sites as needed.

COMMUNITY OUTREACH:

Community outreach was incorporated into the planning and update process. This included a website and public survey, a public comment period, social media campaigns, flyers, and two Town Hall Meetings in San Rafael that were broadcast via Zoom and included translation services. The Town Hall meetings were advertised via press releases and digital communication. Following a presentation, the meetings concluded with question and answer sessions. No members of the public joined in person, and none provided public comment via Zoom. The plan includes full details about the outreach efforts.

SAN RAFAEL CITY COUNCIL AGENDA REPORT / Page: 4
ENVIRONMENTAL DETERMINATION:

The adoption of the 2024 MJLHMP is not a project under California Environmental Quality Act (CEQA) Guidelines Section 15378(a) because it has no potential to result in either a direct physical change in the environment or a reasonably foreseeable indirect physical change in the environment. Instead, the 2024 MJLHMP is a planning study that identifies hazard risk and outlines potential future mitigation actions the County and planning partners may take to reduce hazard risk depending on funding and staffing availability, including projects that are already planned or in progress. Accordingly, even if the adoption of the 2024 MJLHMP were a project, it would be exempt from CEQA under CEQA Guidelines Section 15262 as a planning studies for possible future actions which has no legally binding effect on later activities. Since there would be no potential for a significant effect on the environment, the adoption of the 2024 MJLHMP also qualifies for the common sense exemption as described in CEQA Guidelines Section 15061(b)(3).

FISCAL IMPACT:

Adopting the 2024 MJLHMP and the City of San Rafael Annex has no fiscal impact. However, it maintains the City's eligibility for FEMA mitigation grant funding.

OPTIONS:

The City Council has the following options to consider on this matter:

1. Adopt the provided resolution

2. Adopt resolution with modifications.

3. Direct staff to return with more information.

4. Take no action.

RECOMMENDED ACTION:

Adopt a resolution adopting the 2024 Marin County Multi-Jurisdictional Local Hazard Mitigation Plan (MJLHMP) and the City of San Rafael Annex.

ATTACHMENTS:

1. Resolution

2. Volume 1 of the MJLHMP: Planning Area-Wide Elements

3. Volume 2 of the MJLHMP (Excerpt): City of San Rafael Annex

4. Marin County FEMA Approval Letter, July 2024
RESOLUTION NO.

RESOLUTION OF THE CITY COUNCIL OF THE CITY OF SAN RAFAEL ADOPTING THE 2024 MARIN COUNTY MULTI-JURISDICTIONAL LOCAL HAZARD

MITIGATION PLAN AND THE CITY OF SAN RAFAEL ANNEX
WHEREAS, natural hazards, such as earthquakes, floods, and wildfires, pose a significant threat to the residents and visitors of Marin County and San Rafael; and WHEREAS, disasters start and end at the local level, and it is the inherent responsibility of government to lead hazard mitigation and the reduction of risk and vulnerability to hazards; and WHEREAS, an adopted Local Hazard Mitigation Plan is required as a condition of future funding for mitigation projects under multiple FEMA pre-and post-disaster mitigation grant programs; and
WHEREAS, the City adopted a Local Hazard Mitigation Plan in 2017 through Resolution No. 14418; and
WHEREAS, the San Rafael 2040 General Plan includes a Safety and Resilience Element which expresses the City’s commitment to maintaining an LHMP and minimizing San Rafael’s vulnerabilities and, in accordance with AB 2140, acknowledges the importance of coordinating the most recent LHMP and Safety Element by incorporating the 2017 LHMP and any future amendments to the LHMP by reference, as allowed by California Government Code Section 65302(g); and
WHEREAS, the Marin County 2024 Multi-Jurisdictional Local Hazard Mitigation Plan (MJHMP) amends the 2017 LHMP by fully updating and replacing it; and WHEREAS, the Marin County 2024 Multi-Jurisdictional Local Hazard Mitigation Plan (MJHMP) complies with all requirements set forth under Disaster Mitigation Act (DMA) 2000 and includes information also relevant to the Safety Element. The MJHMP presents environmental hazard analysis, describes important transportation and utility infrastructure at risk from environmental hazards, describes emergency evacuation systems, and mitigation actions to protect Marin County populations and infrastructure from environmental hazards; and WHEREAS, the adoption of the 2024 MJLHMP is not a project under California Environmental Quality Act (CEQA) Guidelines Section 15378(a) because it has no potential to result in either a direct physical change in the environment or a reasonably foreseeable indirect physical change in the environment; and even if the adoption of the 2024 MJLHMP were a project, it would be exempt from CEQA under CEQA Guidelines Section 15262 as a planning studies for possible future actions which has no legally binding effect on later activities, and also under the common sense exemption as described in CEQA Guidelines Section 16061(b)(3) because there would be no potential for a significant effect on the environment; and WHEREAS, adoption by the governing body for the City of San Rafael, demonstrates the jurisdiction’s commitment to fulfilling the mitigation goals and objectives outlined in this Local Hazard Mitigation Plan; and
WHEREAS, adoption of the plan authorizes responsible agencies to carry out their responsibilities under the plan.

NOW, THEREFORE, BE IT RESOLVED that the City Council of the City of San Rafael hereby adopts the 2024 Marin County Multi-Jurisdictional Hazard Mitigation Plan and the City of San Rafael Annex and adopts the updated 2024 MJLHMP by reference into the Safety and Resilience Element of the San Rafael 2040 General Plan.

I, Lindsay Lara, Clerk of the City of San Rafael, hereby certify foregoing resolution was duly and regularly introduced and adopted at a regular meeting on the City Council of said City held on Monday, the 7th day of October 2024, by the following vote to wit:

AYES: COUNCILMEMBERS:

NOES: COUNCILMEMBERS:

ABSENT: COUNCILMEMBERS:
______________________
LINDSAY LARA, City Clerk

COUNTY OF MARI
Cover Photo: The image provided by the Marin County Office of Emergency Management, illustrates the precarious balance of mitigating potential wildfire fuels to ensure a safe evacuation corridor while preserving the exquisite natural beauty unique to Marin County. 2023 Marin County Operational Area
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EXECUTIVE SUMMARY
The Marin County Operational Area (OA) and the sixteen (16) jurisdictions and special districts within the Marin County OA prepared this Multi-Jurisdictional Hazard Mitigation Plan (MJHMP) update to the 2018 Marin County MJHMP to guide County, City, and Special District managers in protecting the people and property within the County from the effects of natural disasters and hazard events. These planned actions will make Marin County and its residents less vulnerable to future hazard events, demonstrates the communities’ commitment to reducing risks from hazards, and serves as a tool to help decision makers direct mitigation activities and resources.

HAZARD MITIGATION
Hazard Mitigation is defined as “any sustained action taken to eliminate or reduce long-term risk to human life, property, and the environment posed by a hazard”.

Hazard mitigation planning is the process of making any sustained plan or course of action taken to reduce or eliminate long-term risk to people and property from both natural hazards and their effects. The planning process includes establishing goals and recommendations for mitigation strategies.

Hazard mitigation may occur during any phase of a threat, emergency, or disaster. Mitigation can and should take place during the preparedness (before), response (during), and recovery (after) phases. The process of hazard mitigation involves evaluating the hazard’s impact and identification and implementation of actions to minimize the impact.

PURPOSE OF THE HAZARD MITIGATION PLAN
Information in this plan will be used to help guide and coordinate mitigation activities and decisions for local land use policy in the future. Proactive mitigation planning will help reduce the cost of disaster response and recovery to communities and their residents by protecting critical community facilities, reducing liability exposure, and minimizing overall community impacts and disruptions. The Marin County OA planning area has been affected by hazards in the past and is thus committed to reducing future impacts from hazard events and becoming eligible for mitigation-related federal funding.

MITIGATION PLAN UPDATE
This 2023 MJHMP is a comprehensive update of the 2018 Marin County Local Hazard Mitigation Plan, which included the unincorporated county, eleven (11) jurisdictions and the North Marin Water District. FEMA approved the 2018 plan on December 27, 2018, and it will expire on December 27, 2023. The current update meets federal requirements for updating hazard mitigation plans on a five-year cycle. It represents the fifth iteration of the Marin County hazard mitigation plan. Fifty-eight planning partners participated in this update, as listed in Tables 2.2 and 2.4.

The Marin County Office of Emergency Management was the lead County Department coordinating this MJHMP update. The Marin County Office of Emergency Management l ~<;>U·N· TY OF
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appointed new leadership in 2023 and the Director, Steven Torrance, made the update to this plan a priority.

The planning area and participating jurisdictions and special districts were defined to consist of the unincorporated county, eleven (11) jurisdictions and five (5) special districts within the geographical boundary of Marin County. All partners to this plan have jurisdictional authority within this planning area. The jurisdictions participating in the 2023 Marin County MJHMP were represented by:

Table 2.1: 2023 MJHMP Participating Jurisdictions
Jurisdiction Representative Title
1 Marin County Hannah Tarling Emergency Management Coordinator 2 Marin County Chris Reilly OEM Project Manager
3 City of Belvedere Irene Borba Director of Planning
4 City of Larkspur Loren Umbertis Public Works Director 5 City of Mill Valley Patrick Kelly Director of Planning and Building 6 City of Novato Dave Jeffries Consultant/JPSC
7 City of San Rafael Quinn Gardner Deputy Emergency Services Coord. 8 City of Sausalito Kevin McGowan Director of Public Works 9 Town of Corte Madera and
Sanitary District #2 RJ Suokko Director of Public Works 10 Town of Fairfax Loren Umbertis Public Works Director 11 Town of Ross Richard Simonitch Public Works Director 12 Town of San Anselmo Sean Condry Public Works & Building Director 13 Town of Tiburon Sam Bonifacio Assistant Planner
14 Bolinas Community Public
Utility District
Jennifer Blackman General Manager
15 Las Gallinas Valley Sanitary
District Dale McDonald Administrative Services Manager
16 North Marin Water District Eric Miller Asst. General Manager 17 Southern Marin Fire District Marshall Nau Fire Marshall/South Marin Fire Dist.

PARTICIPATING JURISDICTION HAZARD ASSESSMENT
Each Marin County OA MJHMP participating jurisdiction and special district reviewed and approved the Top Hazards identified by the Planning Team. Each participating jurisdiction and organization then completed a more complex assessment tool to further develop their hazard assessment and prioritization.

The planning process used the available FEMA tools to evaluate all the possible threats faced.

The primary tool selected was the Hazard Assessment and Prioritization Tool. This matrix allowed the participating jurisdiction or organization to assess their own level of vulnerability and mitigation capability. Each participating Jurisdiction and organization assessed the top hazards for:
• Probability and frequency
• Impact to property, resources, and humans
• Mitigation capacity
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The results of these participating jurisdiction and organization hazard assessment and prioritization are illustrated in the following tables.

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Risk Level Risk Numerical
Score
High Risk 12 - 16
Serious Risk 8 - 11
Moderate Risk 4 - 7
Low Risk 1 - 3

MITIGATION GOALS
The information developed from the risk assessment was used as the primary basis for developing mitigation goals and objectives. Mitigation goals are defined as general guidelines explaining what each jurisdiction wants to achieve in terms of hazard and loss prevention.

Hazard Risk Prioritization
Mitigation Goals & Objectives
Mitigation Project Identification
Mitigation Project Implementation
16 16 16
15 15 15 15
14 13
10 9 9
0 2
4 6
8 10
12 14
16 18
Weighted Rank Percentage Value
Hazard Types
Hazards by Rank
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Goal 1: Minimize risk and vulnerability of the community to the impacts of natural hazards and protect lives and reduce damages and losses to property, economy, and environment in Marin County.
• Minimize economic and resource impacts and promote long-term viability and sustainability of resources throughout Marin County.
• Minimize impact to both existing and future development. • Provide protection for public health.
• Prevent and reduce wildfire risk and related losses.

Goal 2: Provide protection for critical facilities, infrastructure, utilities, and services from hazard impacts.
• Incorporate defensible space and reduce hazard vulnerability. • Develop redundancies in utilities and services.
• Enhance resilience through enhanced construction.

Goal 3: Improve public awareness, education, and preparedness for hazards that threaten our communities.
• Enhance public outreach and participation in the Alert Marin Emergency Notification System.
• Enhance public outreach, education, and preparedness program to include all hazards of concern.
• Increase public knowledge about the risk and vulnerability to identified hazards and their recommended responses to disaster events, including evacuation and sheltering options.
• Provide planning and coordination for "At-Risk" populations. • Provide planning and coordination for companion animals, livestock, and other animal populations.
• Increase community awareness and participation in hazard mitigation projects and activities.

Goal 4: Increase communities' capabilities to be prepared for, respond to, and recover from a disaster event.
• Improve interagency (local, state, federal) emergency coordination, planning, training, and communication to ensure effective community preparedness, response and recovery.
• Enhance collaboration and coordination of disaster-related plans, exercises, and training with local, state, and federal agencies, neighboring communities, private partners, and volunteers.
• Enhance the use of shared resources/Develop a strong mutual aid support system. • Create and maintain a fully functional, interoperable radio and communication system with all regional public safety partners.

Goal 5: Maintain FEMA Eligibility/Position the communities for grant funding. • Review hazard events and ongoing hazard mitigation projects annually. • Assess the need to pursue or adjust hazard mitigation projects after significant hazard events.

Goal 6: Reduce exposure to High Hazard Dams that pose an unacceptable risk to the public. l ~<;>U·N· TY OF
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• Improve alert and warning systems to provide residents downstream of a High Hazard Dam to receive timely warning to evacuation when threatened by potential or imminent dam failure.
• Enhance overall community preparedness to respond and evacuate a potential or imminent dam failure.
• Increase public awareness of the risk posed by High Hazard Dams and the potential for relocation of housing outside a possible inundation zone. • Prioritize High Hazard Dam Mitigation projects and programs.

MITIGATION STRATEGY
The mitigation strategies and activities designed to reduce or eliminate losses resulting from natural hazards are the centerpiece of the mitigation planning process. Through the mitigation actions, participating jurisdictions will become more resilient to disasters.

The 2023 Marin County OA MJHMP was revised to reflect progress in local mitigation efforts.

Mitigation projects were selected for each hazard and for Marin County, the eleven (11) jurisdictions and the five (5) special districts based on the hazard risk assessment. The projects are supported by the mitigation goals and objectives and are ranked using the following criteria:
approximate cost, timeframe of completion, whether the project requires Board of Supervisors regulatory action, and an assumption as to whether or not the project would be subject to CEQA or NEPA requirements. Funding sources are identified for all projects. All projects consider new, future, and existing development.
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1 ACKNOWLEDGEMENTS
The Marin County Office of Emergency Management and Preparative Consulting would like to thank those collaborators and partners who participated in the planning and development of this document.

The official Marin County Operational Area Hazard Mitigation Steering Committee provided the oversight and dedication to this project that was required and without their commitment, this project would not be possible.

As with any working plan, this document represents planning strategies and guidance as understood as of the date of this plan’s release. This plan identifies natural hazards and risks and identifies the hazard mitigation strategy to reduce vulnerability and make the communities of the Marin County Operational Area more disaster resistant and sustainable. l ~<;>U·N· TY OF
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3 LETTER OF PROMULGATION
January 2024
To: Officials and Employees of Marin County
The preservation of life and property is an inherent responsibility of all levels of government.

Whereas disasters may occur in devastating form at any time, Marin County must provide safeguards which will save lives and minimize property damage through mitigation planning and training. Sound mitigation planning carried out by knowledgeable and well-trained personnel can and will minimize losses.

The Marin County Operational Area Multi-Jurisdictional Hazard Mitigation Plan identifies the hazard risks and vulnerabilities for the Marin County Operational Area and identifies mitigation projects and actions to help reduce those risks. It provides for the integration and coordination of planning efforts of Marin County, the Cities of Belvedere, Larkspur, Mill Valley, Novato, San Rafael and Sausalito; the Towns of Corte Madera, Fairfax, Ross, San Anselmo and Tiburon; the Bolinas Community Public Utility District, the Central Marin Fire Department, the Las Gallinas Valley Sanitary District, the North Marin Water District, the Sanitary District Number 2, and the Southern Marin Fire Department.

The content of this plan is based upon guidance approved and provided by the Federal Emergency Management Agency and the California Governor’s Office of Emergency Services.

The intent of the Multi-Jurisdictional Hazard Mitigation Plan is to provide direction on how to mitigate against the threat of disaster through effective mitigation strategies and initiatives.

Once adopted, this plan will be reviewed and tested periodically and revised as necessary to meet changing conditions and requirements.

The Marin County Board of Supervisors gives its full support to this Multi-Jurisdictional Hazard Mitigation Plan and urges all public employees and individuals to mitigate against the threat of disaster before they occur.
_________________________________
Stephanie Moulton-Peters
President, Board of Supervisors
Marin County
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5 TABLE OF CONTENTS
Executive Summary.................................................................................................................. i Acknowledgements ..................................................................................................................1 Letter Of Promulgation.............................................................................................................3 Table of Contents......................................................................................................................5 SECTION 1.0: Introduction .......................................................................................................9

1.1 Hazard Mitigation Principles.................................................................................................... 9

1.2 Purpose..................................................................................................................................... 9

1.3 Scope ...................................................................................................................................... 10

1.4 Legal Authorities..................................................................................................................... 10

1.5 History and Overview............................................................................................................. 11

1.5.1 Demographics.................................................................................................................. 25

1.5.2 Critical Facilities and Infrastructure................................................................................ 31

1.5.3 Natural, Historical, and Cultural Resources.................................................................. 33

1.5.4 National Risk Index and Social Vulnerability................................................................. 55

1.5.5 Social Vulnerability and Risk in Marin County .............................................................. 60

1.5.6 Economics ........................................................................................................................... 66

1.6 Existing Authorities, Policies, Programs, and Resources................................................... 67

1.7 New Items for the 2023 MJHMP........................................................................................... 68

1.7.1 Revision of the Hazard Identification and Risk Assessment ....................................... 70

1.7.2 Climate Change............................................................................................................... 70

1.7.3 Progress on Local Mitigation Efforts.............................................................................. 70

1.8 Plan Organization and Structure........................................................................................... 70 SECTION 2.0: Planning Process ............................................................................................72

2.1 Planning Approach................................................................................................................. 73

2.2 Grant Funding and Consultant Selection ............................................................................. 74

2.3 Establish a Planning Partnership.......................................................................................... 74

2.4 Define the Planning Area and Participating Jurisdictions ................................................... 75

2.5 Steering Committee ............................................................................................................... 76

2.5.1 Steering Committee Planning Process.......................................................................... 78

2.5.2 Steering Committee Tasks ............................................................................................. 79

2.5.3 Steering Committee Future Tasks ................................................................................. 80

2.6 Coordination with stakeholders and agencies ..................................................................... 80 l ~<;>U·N· TY OF
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6 2.7 Review and Incorporation of Existing Plans......................................................................... 87

2.8 Public Engagement................................................................................................................ 92

2.8.1 Website............................................................................................................................... 94

2.8.2 Public Meetings ................................................................................................................. 94

2.8.3 Social media ...................................................................................................................... 96

2.8.4 Press Releases.................................................................................................................. 96

2.8.5 Survey ................................................................................................................................ 97

2.8.6 Public Comment on the Plan............................................................................................ 98 SECTION 3.0: Hazard Identification and Risk Assessment................................................100

3.1 Hazard Identification ............................................................................................................ 100

3.1.1 Disaster Declaration History......................................................................................... 102

3.1.2 Omission of Hazards..................................................................................................... 104

3.2 Hazard Analysis.................................................................................................................... 106

3.2.1 Climate Change............................................................................................................. 111

3.2.2 Participating Jurisdiction Hazard Assessment............................................................ 119

3.3 Hazard Risk Assessment..................................................................................................... 120

3.3.1 Dam Failure ................................................................................................................... 120

3.3.2 Debris Flow.................................................................................................................... 154

3.3.3 Drought........................................................................................................................... 176

3.3.4 Earthquake..................................................................................................................... 185

3.3.5 Flooding.......................................................................................................................... 196

3.3.6 Land Subsidence........................................................................................................... 241

3.3.7 Levee Failure................................................................................................................. 247

3.3.8 Sea Level Rise............................................................................................................... 265

3.3.9 Severe Weather – Extreme Heat................................................................................. 276

3.3.10 Severe Weather – High Wind/Tornado ..................................................................... 281

3.3.11 Tsunami ....................................................................................................................... 290

3.3.12 Wildfire ......................................................................................................................... 322

3.4 Additional Hazards Profiled ................................................................................................. 372

3.4.1 Air Pollution ................................................................................................................ 373

3.4.2 Critical Infrastructure/ Utility Disruption.................................................................... 376

3.4.3 Cyber Threats ............................................................................................................ 378

3.4.4 Oil Spills...................................................................................................................... 383

3.4.5 Pandemic.................................................................................................................... 386 l ~<;>U·N· TY OF
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7 3.4.6 Transportation Systems ............................................................................................ 392 SECTION 4.0: Mitigation Strategy........................................................................................399

4.1 Changes in Development .................................................................................................... 399

4.2 Changes in Priorities............................................................................................................ 401

4.2.1 Vulnerability and Risk Reduction ................................................................................. 401

4.3 Capability Assessment......................................................................................................... 402

4.3.1 Regulatory Capabilities................................................................................................. 402

4.3.2 Administrative and Technical Capabilities................................................................... 408

4.3.3 Fiscal Capabilities ......................................................................................................... 412

4.3.4 Outreach and Partnerships Capabilities...................................................................... 414

4.4 Participation in the National Flood Insurance Program..................................................... 415

4.4.1 Substantially Improved Or Substantially Damaged Properties ................................ 421

4.5 Mitigation Goals.................................................................................................................... 423

4.6 Hazard Mitigation Actions.................................................................................................. 425

4.6.1 Progress in Local Mitigation Efforts ............................................................................. 425

4.6.2 Status of Previous Mitigation Actions .......................................................................... 426

4.6.3 New Mitigation Actions.................................................................................................. 430

4.7 Plan Integration .................................................................................................................... 463

4.8 Future Development Trends............................................................................................... 464 SECTION 5.0: Plan Review, Evaluation, and Implementation............................................468

5.1 Plan Adoption ....................................................................................................................... 468

5.2 Plan Monitoring And Public Engagement........................................................................... 468

5.3 Plan Evaluation..................................................................................................................... 469

5.4 Plan Update .......................................................................................................................... 470 Figures and Tables Index .....................................................................................................471 Acronyms ..............................................................................................................................478 Appendix A: Adoption Letters..............................................................................................483 Appendix B: Documentation of the Planning Process.......................................................513 Appendix C: Public Outreach Survey..................................................................................531 l ~<;>U·N· TY OF
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9 SECTION 1.0: INTRODUCTION
Each year in the United States, natural disasters take the lives of hundreds of people and injure thousands more. Nationwide, taxpayers pay billions of dollars annually to help communities, organizations, businesses, and individuals recover from disasters. These monies only partially reflect the true cost of disasters, because additional expenses to insurance companies and nongovernmental organizations are not reimbursed by tax dollars. Many natural disasters are predictable, and much of the damage caused by these events can be alleviated or even eliminated.

Hazard mitigation is defined by FEMA as “any sustained action taken to reduce or eliminate long-term risk to human life and property from a hazard event.” The results of a three-year, congressionally mandated independent study to assess future savings from mitigation activities provides evidence that mitigation activities are highly cost-effective. On average, each dollar spent on mitigation saves society an average of six dollars in avoided future losses in addition to saving lives and preventing injuries.

This plan was prepared pursuant to the requirements of the Disaster Mitigation Act of 2000 so that the Marin County Operational Area (OA) would be eligible for the Federal Emergency Management Agency’s (FEMA) Pre-Disaster Mitigation and Hazard Mitigation Grant programs as well as to lower flood insurance premiums (in jurisdictions that participate in the National Flood Insurance Program’s Community Rating System).

1.1 HAZARD MITIGATION PRINCIPLES
Hazard mitigation is any sustained action taken to eliminate or reduce long-term risk to human life, property, and the environment posed by a hazard.

The process of hazard mitigation involves evaluating the hazard’s impact and identification and implementation of actions to minimize the impact.

1.2 PURPOSE
Marin County and its participating jurisdictions prepared this Multi-Jurisdictional Hazard Mitigation Plan (MJHMP) update to the 2018 Marin County MJHMP in order to make the Marin County OA and its residents less vulnerable to future hazard events. This plan demonstrates the communities’ commitment to reducing risks from hazards and serves as a tool to help decision makers direct mitigation activities and resources. This plan was also developed to make the Marin County OA eligible for certain federal disaster assistance, specifically, the Federal Emergency Management Agency’s (FEMA) Hazard Mitigation Grant Program (HMGP), l ~<;>U·N· TY OF
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10 Building Resilient Infrastructure and Communities (BRIC) program, and Flood Mitigation Assistance (FMA) program.

1.3 SCOPE
The Marin County OA MJHMP is a multi-jurisdictional plan that geographically covers the Marin County OA, which encompasses the area within Marin County’s jurisdictional boundaries. This area includes the County and its unincorporated communities, the Cities of Belvedere, Larkspur, Mill Valley, Novato, San Rafael and Sausalito; the Towns of Corte Madera, Fairfax, Ross, San Anselmo and Tiburon; the Bolinas Community Public Utility District, the Central Marin Fire Department, the Las Gallinas Valley Sanitary District, the North Marin Water District, the Sanitary District Number 2, and the Southern Marin Fire Department.

This MJHMP was prepared pursuant to the requirements of the Disaster Mitigation Act of 2000 (Public Law 106-390) and the implementing regulations set forth by the Interim Final Rule published in the Federal Register on February 26, 2002, (44 CFR §201.6) and finalized on October 31, 2007. The 2007 amendments also incorporate mitigation planning requirements of the Flood Mitigation Assistance program authorized by the National Flood Insurance Act of 1968. While the Disaster Mitigation Act emphasized the need for mitigation plans and more coordinated mitigation planning and implementation efforts, the regulations established the requirements that local hazard mitigation plans must meet in order for a local jurisdiction to be eligible for certain federal disaster assistance and hazard mitigation funding under the Robert T.

Stafford Disaster Relief and Emergency Act (Public Law 93-288).

Information in this plan will be used to help guide and coordinate mitigation activities and decisions for local land use policy in the future. Proactive mitigation planning will help reduce the cost of disaster response and recovery to communities and their residents by protecting critical community facilities, reducing liability exposure, and minimizing overall community impacts and disruptions. The Marin County OA planning area has been affected by hazards in the past and is thus committed to reducing future impacts from hazard events and becoming eligible for mitigation-related federal funding.

1.4 LEGAL AUTHORITIES
Federal, state and local regulations and policies form the legal framework to implement Marin County’s, and its participating jurisdictions’, hazard mitigation goals and projects.

Federal Laws
• “The Federal Civil Defense Act of 1950”
• Public Law 96-342 “The Improved Civil Defense Act of 1980” • Public Law 91-606 “Disaster Relief Act"
• Public Law 93-288 “The Robert T. Stafford Disaster Relief Act of 1974” • Section 322, Mitigation Planning of the Robert T. Stafford Disaster Relief and Emergency Assistance Act
• Public Law 106-390 enacted by Section 104 of the Disaster Mitigation Act of 2000 (DMA)
• Interim Final Rule for DMA 2002 as published in the February 26,2002, 44 CFR Part 201 l ~<;>U·N· TY OF
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11 State Laws & Plans
California Government Code, Section 3100, Title 1, Division 4, Chapter 4 Defines public employees as disaster service workers. Disaster service workers are subject to such disaster service activities as assigned to them by their superiors or by law. The term "public employees" includes all persons employed by the state or any county, city, city and county, state agency or public district, excluding aliens legally employed. The law applies when:
• A local emergency has been proclaimed.
• A state of emergency has been proclaimed.
• A federal disaster declaration has been made.

This Section provides the basic authorities for conducting emergency operations following a proclamation of Local Emergency, State of Emergency, or State of War Emergency, by the Governor and/or appropriate local authorities, consistent with the provisions of this Act.

The California Emergency Plan - Revised
Promulgated by the Governor, and published in accordance with the Emergency Services Act, the Plan provides overall statewide authorities and responsibilities, and describes the functions and operations of government at all levels during extraordinary emergencies, including wartime.

Section 8568 of the Act states, in part, that "...the State Emergency Plan shall be in effect in each political subdivision of the state, and the governing body of each political subdivision shall take such action as may be necessary to carry out the provisions thereof." Local emergency plans are, therefore, considered to be extensions of the California Emergency Plan.

California Civil Code, Chapter 9, Section 1799.102
This section of the California Civil Code provides for "Good Samaritan Liability" for those providing emergency care at the scene of an emergency. Specifically: "No person, who, in good faith and not for compensation, renders emergency care at the scene of an emergency, shall be liable for any civil damages resulting from any act or omission. The scene of an emergency shall not include emergency departments and other places where medical care is usually offered."
State Hazard Mitigation Plan (SHMP) - 2018
The State Hazard Mitigation Plan (SHMP) identifies policy, establishes goals, and stipulates actions associated with the implementation of enhanced hazard mitigation strategies for California. The SHMP is foundational for local government hazard mitigation planning efforts, and provides inter-organizational guidance and direction based upon established state agency actions and principles.

Operational Area Governmental Authorities & Plans - Local Codes and Ordinances Local government codes, ordinances, and executive policies are identified in Section 4.3.

1.5 HISTORY AND OVERVIEW
The first people to inhabit the area of Marin County thousands of years ago are the indigenous Coast Miwok. The origin of the name “Marin” is unclear, but it is thought to be either named after the Chief of the Licatiut, a Coast Miwok tribe, or after Bahía de Nuestra Señora del Rosario la Marinera Bay between San Pedro Point and San Quentin Point. European colonization of Marin County began in the 1500’s when Sir Francis Drake landed in the area of modern-day Drake’s Bay in 1579. The Spanish eventually made claims to California and established their first settlement in Marin County in 1817. The Settlement of Marin County was incorporated in 1850 as one of the original 27 counties of California.
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12 Marin County is located on northern California’s Pacific coast and is bordered by Sonoma County to the north; the Pacific Ocean to the west; San Pablo Bay and San Francisco Bay to the east, and the City and County of San Francisco to the south. Marin County spans 828 square miles, of which 520 square miles is land and 308 square miles is water. This footprint makes Marin County among the four smallest counties in the State. Within the boundaries of Marin County are 11 municipalities, 20 Census Designated Places, and 8 recognized unincorporated communities. The county seat is the City of San Rafael.

County Government
Marin County is a general law county, whereby the Board of Supervisors is elected by district and principal officers of the County are regulated by statutes that assign their duties. County departments are responsible for providing a wide array of services to the unincorporated areas of Marin County, as well as within municipalities. Departments are managed by elected officials or appointed directors who are responsible for administering local programs and services, in accordance with both applicable state law and county regulations. Many county departments are further sub-divided into divisions, offices, and programs, which provide specific services to the public. The following is a list of Marin County departments:
• Administrator
• Agriculture, Weights and Measures
• Assessor
• Board of Supervisors
• Child Support Services
• County Administrator
• County Counsel
• Community Development
• County Clerk
• Cultural Services
• District Attorney
• Finance
• Elections
• Enhanced Court Collections
• Farm Advisor
• Health and Human Services
• Housing
• Human Resources
• Information Services and Technology
• Library
• Parks
• Probation
• Public Administrator
• Public Defender
• Public Works
• Recorder
• Retirement
• Registrar of Voters
• Sheriff’s Office
• Superior Court
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13 Figure 1.1: Map of Marin County
Source: Marin County OEM
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Cities and Towns
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EMERGENCY

MANAGEMENT
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Point Reyes
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Seashore
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Marin Cities / Towns (shading)

CITY OF BELVEDERE

CITY OF LARKSPUR

CITY OF MILL VALLEY

CITY OF NOVATO

CITY OF SAN RAFAEL
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CITY OF SAUSALITO

TOWN OF CORTE MADERA

TOWN OF FAIRFAX

TOWN OF ROSS

TOWN OF SAN ANSELMO

TOWN OF TIBURON
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San Pablo Bay
Wildlife Area
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Corte Madera
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Mt. Tamalpais
State Park
Mill Valley

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Marin County OEM / Woody Baker-Cohn
email: [email protected]
Date Printed: 08/08/23
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County of Marin, california State Parks, Esri, HERE, Garmin, SafeGraph, FAO, METI/NASA, USGS, Bureau of Land Management, EPA, NPS 2023 Marin County Operational Area
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14 Municipalities
Marin County has six cities and five towns.

City of Belvedere
The City of Belvedere was initially developed by the Belvedere Land Company who built homes and building sites, a water system, roads, and other amenities in the area. The city was officially incorporated on December 21st, 1896 and it’s first post office was opened in 1897.

Early Belvedere had a grocery store, telephone exchange, beauty shop, laundry, boatyard, plumber's shop, coal, wood and ice yard, blacksmith's shop, gas station and a jail. After World War 2, The Belvedere Land Company dredged a lagoon in San Francisco Bay and created additional living areas for Belvedere residents. The city has a total area of 2.4 square miles. It is predominantly hilly and is surrounded on three sides by San Francisco Bay. The City’s population lives in three distinct neighborhoods: Belvedere Island, Belvedere Lagoon and Corinthian Island. Many City residences are considered historically significant.

Belvedere had an estimated population of 2,126 in 2020, with 1,060 housing units in the City.

The median income for a household in the City was $246,500 and the per capita income for the City was $153,697. Approximately 4.4 percent of families and 5.8 percent of the population were below the poverty line (2020 data, U.S. Census Bureau).

Town of Corte Madera
The Town of Corte Madera is named after Corte Madera del Presidio, an 1834 Mexican land grant of the area to Irish immigrant John Reed that also established several communities in Marin County. Spanish for “cut wood”, Corte Madera provided redwood and oak timber for the growth of early San Francisco, including much of the construction at the Presidio. As the timber disappeared, Corte Madera became a farming and ranching community. Corte Madera continued to grow with the formation of the North Pacific Coast Railroad Company in 1872, and a railroad station was constructed by 1875 with freight and commuter service. Development of the town’s harbor allowed for further trade of goods. The town grew around the railroad station with the development of a town square and several neighborhoods. The Adams’ Hotel and Tavern was the Town’s first commercial business when built in 1898 and it served as the Town’s first post office. The town was officially incorporated on June 10th, 1916. Further growth of the town occurred during World War II, when the Marinship Corporation built a shipyard in Sausalito and attracted thousands of ship workers to the area. The town currently has a total area of 3.2 square miles and is situated just south of the South Quentin Peninsula on San Francisco Bay. The terrain consists of hills and marshland where numerous creeks empty into San Francisco Bay.

The Town of Corte Madera had an estimated population of 10,222 in 2020, with 4,174 housing units in the Town. The Town has a total area of 4.406 square miles. The median income for a household in the Town was $183,661 and the per capita income for the Town was $95,257.

Approximately 2.1 percent of families and 4.9 percent of the population were below the poverty line (2020 data, U.S. Census Bureau).

Town of Fairfax
The Town of Fairfax is named after Lord Charles Snowden Fairfax, whose estate in the area served as the site of the last political dual in California in 1861. Charles and Adele Pastori l ~<;>U·N· TY OF
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15 purchased the Fairfax property and built a hotel and restaurant in the 1890’s, attracting visitors who could take the ferry from San Francisco and travel on the newly constructed North Pacific Coast Railroad Company rail line. The first post office was opened in 1910. Fairfax continued to grow with the development of an incline railroad to Manor Hill in 1913, and numerous permanent residences were established. The town was officially incorporated on March 2nd, 1931. Fairfax continued to grow as a “center of grooviness” throughout the 1960’s and 1970’s.

The town currently has a total area of 2.2 square miles and lies inland in the valleys of San Anselmo Creek and its tributary Fairfax Creek. Fairfax is generally hilly and is bordered to the south by the Mount Tamalpais protected watershed.

The Town of Fairfax had an estimated population of 7,441 in 2020, with 3,479 housing units in the Town. The Town has a total area of 2.204 square miles. The median income for a household in the Town is $111,290 and the per capita income for the Town is $59,011.

Approximately 0.3 percent of families and 10.1 percent of the population is below the poverty line (2020 data, U.S. Census Bureau).

City of Larkspur
The City of Larkspur was first developed through an 1834 Mexican land grant to Irish immigrant John Reed that established several communities in Marin County. Much of the area of Larkspur was logged in the 1840’s to supply lumber to San Francisco and the building of Presidio. Two sawmills were built to float logs down Corte Madera Creek to San Francisco Bay. Further growth was spurred by the formation of the North Pacific Coast Railroad Company railroad, with a railroad station being built in Larkspur. C.W. Wright and his American Land and Trust Company purchased much of present-day Larkspur in 1896, subdividing the land and piping in water. Wright’s wife Georgina named the town Larkspur after she mistakenly identified the native lupine as Larkspur. C.W. Wright laid out the town in 1887 and the first post office opened in 1891. Larkspur quickly became a weekend destination for visitors from San Francisco, and a hotel, bathhouse, grocery store, and several retail shops were built. The City of Larkspur was officially incorporated on March 1st, 1908. Larkspur's Downtown Historic District, known also as Old Downtown Larkspur, was listed on the National Register of Historic Places in 1982. The city currently has a total area of 3.2 square miles and lies just inland of San Francisco Bay with hilly terrain on the southwest side.

The City of Larkspur had an estimated population of 13,064 in 2020, with 6,459 housing units in the City. The City has a total area of 3.243 square miles. The median income for a household in the City was $135,260 and the per capita income for the City was $94,909. Approximately 1.5 percent of families and 7.7 percent of the population were below the poverty line (2020 data, U.S. Census Bureau).

City of Mill Valley
The City of Mill Valley was first developed through two land grants: an 1834 Mexican land grant to Irish immigrant John Reed that established several communities in Marin County and an 1838 Mexican land grant to English immigrant William Richardson. A sawmill was built by Richardson in the 1830’s to supply lumber to San Francisco and the building of Presidio, and a dairy ranch was established by Samuel Reading Throckmorton in 1854. Mill Valley continued to l ~<;>U·N· TY OF
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16 grow with the development of the North Pacific Coast Railroad Company and the building of a resort hotel by Dr. John Cushing in the 1880’s. The Tamalpais Land and Water Company took over possession of the land owned by Throckmorton and in 1889 built roads, pedestrian paths and step-systems and the Cascade Dam and Reservoir for water supply. They also set aside land for churches, schools and parks. New residents built houses and the City of Mill Valley was officially incorporated on September 1st, 1900. The post office opened under the name "Eastland" but was changed to "Mill Valley" in 1904. Mill Valley was almost lost to a wildfire in 1929, when 117 homes were destroyed, but a change in winds saved the city. Further growth of the town occurred during World War II, when the Marinship Corporation built a shipyard in Sausalito and attracted thousands of ship workers to the area. Since the mid-1960s, growth in the city has generally remained constant. The city currently has a total area of 4.9 square miles and is located between Mt. Tamalpais on the west and the Golden Gate National Recreational Area on the south. Mill Valley is generally hilly and wooded and is surrounded by hundreds of acres of state, federal, and county park lands. In addition, there are many municipally maintained open-space reserves, parks, and coastal habitats. The Arroyo Corte Madera del Presidio and Cascade Creek flow from the slopes of Mt. Tamalpais through Mill Valley to the San Francisco Bay.

The City of Mill Valley had an estimated population of 14,231 in 2020, with 6,502 housing units in the City. The City has a total area of 4.847 square miles. The median income for a household in the City was $179,529 and the per capita income for the City was $110,356. Approximately

2.4 percent of families and 4.5 percent of the population were below the poverty line (2020 data, U.S. Census Bureau).

City of Novato
The City of Novato is name after Rancho Novato, the first rancho established in the area through a Mexican land grant to Fernando Feliz in 1830. Novato was developed through four additional land grants that established ranchos in the area: Rancho Corte Madera de Novato to John Martin in 1839; Rancho San Jose to Ignacio Pacheco in 1840; Rancho Olómpali to Camilo Ynitia in 1843; and Rancho Nicasio to Pablo de la Guerra and John B.R. Cooper in 1844.

Early pioneers Joseph Sweetser and Francis De Long planted orchards and vineyards in the area in the 1850’s, and the original town grew around Novato Creek. A post office opened in 1856 and a school was built in 1859. With the development of the North Pacific Coast Railroad Company, the center of the town shifted around the newly built railroad station in 1879. Many farmers in Novato lost their land in the Great Depression, but growth accelerated with the building of the 101 freeway. The City of Novato was officially incorporated on January 20, 1960.

The city has an area of 28 square miles and includes ten Marin County Open Space District preserves: Mount Burdell, Rush Creek, Little Mountain, Verissimo Hills, Indian Tree, Deer Island, Indian Valley, Ignacio Valley, Loma Verde, and Pacheco Valle. Novato is located on San Francisco Bay and has extensive farmland and wetlands with hilly terrain on the southwest side.

The City of Novato had an estimated population of 53,225 in 2020, with 21,271 housing units in the City. The City has a total area of 27.440 square miles. The median income for a household in the City was $107,975, and the per capita income for the City was $57,297. Approximately

2.5 percent of families and 7.9 percent of the population were below the poverty line (2020 data, U.S. Census Bureau).
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17 Town of Ross
The Town of Ross was established as part of a Mexican land grant to Juan B.R. Cooper in 1840 known as Ranch Punta de Quentin Canada de San Anselmo. Ross was named in honor of James Ross, who purchased the land from Cooper in 1857. The first post office opened in 1887, and the Town of Ross was officially incorporated on August 21, 1908. The town continued to grow through the 1900’s as residents moved into its shaded canyons and gently sloping hills.

The town has an area of 1.6 square miles and lies inland of San Francisco Bay. Most of Ross is forested with greater open space on its east and west sides.

The Town of Ross had an estimated population of 2,338 in 2020, with 880 housing units in the Town. The Town has a total area of 1.556 square miles. The median income for a household in the Town is $250,000 and the per capita income for the Town is $128,126. Approximately 0 percent of families and 3.5 percent of the population is below the poverty line (2020 data, U.S.

Census Bureau/ 2021 American Community Survey).

Town of San Anselmo
The Town of San Anselmo received its name came from the Punta de Quintin land grant, which marked the valley as the Canada del Anselmo, or Valley of Anselm. The original area of San Anselmo consisted mostly of cattle ranches until the North Pacific Railroad Company formed and built a railroad line through the area in 1874, bringing in visitors from San Francisco. The town began to grow with the building of the San Francisco Theological Seminary in 1892 and the first post office opened in the same year. Summer homes were built in the area by San Francisco residents, and many of these homes became permanent after the 1906 San Francisco Earthquake. The Town of San Anselmo was officially incorporated on April 9th, 1907.

Growth in the town continued until leveling off in the 1960’s. On March 12th, 1974, San Anselmo officially became a town. The town has a total area of 2.7 square miles and lies inland almost completely within the Ross Valley Watershed that flows into San Francisco Bay.

The Town of San Anselmo had an estimated population of 12,830 in 2020, with 5,518 housing units in the Town. The Town has a total area of 2.677 square miles. The median income for a household in the Town is $153,381 and the per capita income for the Town is $ $87,951.

Approximately 0 percent of families and 3.9 percent of the population is below the poverty line (2020 data, U.S. Census Bureau). A large part of southern and western San Anselmo is built on a natural floodplain. San Anselmo's historic raised railroad bed acts as a dike, providing some flood protection to the west-side houses, upstream of the business district.

City of San Rafael
The City of San Rafael is the county seat of Marin County and is named for the Archangel Raphael. Mission San Rafael Archangel was founded in the area of what is now downtown San Rafael in 1817. In its first year, the Mission gained 300 converts. By 1828, there were 1,140 converts. The Mexican government took over the Mission in 1834. Mission San Rafael was abandoned in 1844, eventually deteriorating into ruin. The city continued to grow, however, and was officially incorporated on February 18th, 1874. Further growth of the city occurred when the North Pacific Railroad Company built a rail line through the area in 1879 and when Dominica University of California was built in 1890. The United States Navy operated a San Pablo Bay degaussing range from San Rafael through World War II. The city has a total area of 22.5 l ~<;>U·N· TY OF
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18 square miles and lies along San Francisco Bay. The San Rafael shoreline has been historically filled to a considerable extent to accommodate land development. San Rafael has a wide diversity of natural habitats from forests to marshlands.

The City of San Rafael is the county seat of Marin County. San Rafael had an estimated population of 61,271 in 2020, with 24,502 housing units in the City. The City has a total area of

22.422 square miles. The median income for a household in the City was $104,521 and the per capita income for the City was $61,962. Approximately 5 percent of families and 9.2 percent of the population were below the poverty line (2020 data, U.S. Census Bureau).

City of Sausalito
The City of Sausalito was founded as a place where ships near San Francisco could pick up fresh water in the 1830’s. A mariner named William A. Richardson had arrived in the area and built a rancho in 1925 in the Marin headlands where a freshwater spring was located. Sausalito is named after the Spanish words for “little willow”, for a stand of small willow trees in the town where the fresh water ran down to San Francisco Bay. The town grew throughout the mid1800’s into a small fishing, boat repair and ranching center, inhabited by both fisherman and yacht enthusiasts. The North Pacific Railroad Company developed a southern rail terminus in Sausalito in the 1870’s, providing a link to the Sausalito pier where ferries transported people and goods to and from San Francisco. The first post office was opened in 1870, and the City of Sausalito was incorporated in September 4th, 1893. The neighborhoods of Sausalito continued to grow throughout the early 1900’s, with the development of car ferries to and from San Francisco and the building of the Golden Gate Bridge in 1937. In 1941, the Marin Shipyard Corporation filled in a marshy area north of Sausalito to build the Marin Shipyard, bringing in thousands of ship builders to the area. After World War II, waterfront communities grew out of the abandoned shipyards, contributing to the development of houseboat communities that still exist today. Sausalito maintains its reputation as an art colony and literary enclave. The city has a total area of 2.3 square miles and encompasses both steep, wooded hillside and shoreline tidal flats.

The City of Sausalito had an estimated population of 7,269 in 2020, with 4,425 housing units in the City. The City has a total area of 2.257 square miles. The median income for a household in the City was $140,410 and the per capita income for the City was $111,167. Approximately 0 percent of families and 7.3 percent of the population were below the poverty line (2020 data, U.S. Census Bureau).

Town of Tiburon
The Town of Tiburon is named after the Spanish word for “shark.” The town was first developed through an 1834 Mexican land grant to Irish immigrant John Reed that established several communities in Marin County. The town began to grow in 1884 with the formation of the North Pacific Railroad Company and the first post office opened the same year. The rail line extended from San Rafael to its original southern terminus in Point Tiburon with connection to San Francisco by ferry. Industry including codfish canning, brick making, powder making and train building and repair brought growth to the Tiburon area in the late 1800’s and early 1900’s. The U.S. Navy established a coaling station in Tiburon in 1904. World War II brought additional growth to Tiburon, and the Town of Tiburon was officially incorporated on June 23rd, 1964. The l ~<;>U·N· TY OF
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19 town has a total area of 13.2 square miles, and lies on a peninsula jutting into San Francisco Bay.

The Town of Tiburon had an estimated population of 9,146 in 2020, with 4,047 housing units in the Town. The Town has a total area of 13.182 square miles. The median income for a household in the Town was $192,292 and the per capita income for the Town was $119,477.

Approximately 0 percent of families and 1.3 percent of the population were below the poverty line (2010 data, U.S. Census Bureau).

Unincorporated Communities
All unincorporated areas of Marin County are under jurisdiction of the County. Unincorporated communities include Bel Marin Keys, California Park, Dogtown, Fallon, Forest Knolls, Greenbrae, Hamlet, Ignacio, Inverness Park, Lagunitas, Los Ranchitos, Lucas Valley, Marconi, Marshall, Olema, Paradise Cay, San Quentin, Tamalpais Valley and Tocaloma. In unincorporated areas, basic services like water, sewer, police and fire protection are provided by the county. The County Service Area (CSA) Law (Government Code §25210.1 et seq.) was created in the 1950’s to provide a means of providing expanded service levels in areas where residents are willing to pay for the extra service. CSAs allow small communities in unincorporated areas to pay for and receive specific services from the county. The CSAs in Marin County include:

County Service Area 1 - Loma Verde
County Service Area 6 - Gallinas Creek
County Service Area 9 - Northbridge
County Service Area 13 - Upper Lucas Valley
County Service Area 14 - Homestead Valley
County Service Area 16 - Greenbrae
County Service Area 17 - Kentfield/Larkspur
County Service Area 18 - Las Gallinas
County Service Area 19 - Los Ranchitos, Country Club, and Santa Venetia County Service Area 20 - Indian Valley
County Service Area 27 - Ross Valley
County Service Area 28 - West Marin
County Service Area 29 - Paradise Cay
County Service Area 31 - Fire Service in Unincorporated Marin County Service Area 33 - Stinson Beach
Special Districts
The following is a list of independent Special Districts in Marin County:

Almonte Sanitary District
Alto Sanitary District
Bel Marin Keys Community Services District
Bolinas Community Public Utility District
Bolinas Fire Protection District
Homestead Valley Sanitary District
Inverness Public Utility District
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20 Kentfield Fire Protection District
Las Gallinas Valley Sanitary District
Marin City Community Services District
Marin Healthcare District
Marin Municipal Water District
Marin Resource Conservation District
Marinwood Community Services District
Muir Beach Community Services District
North Marin Water District
Novato Fire Protection District
Novato Sanitary District
Richardson Bay Sanitary District
Ross Valley Sanitary District
Sausalito-Marin City Sanitary District
Sleepy Hollow Fire Protection District
Sonoma-Marin Area Rail Transit District
Southern Marin Fire Protection District
Stinson Beach Fire Protection District
Stinson Beach Water District
Strawberry Recreation District
Tamalpais Community Service District
Tiburon Fire Protection District
Tiburon Sanitary District No. 5
Tomales Village Community Service District
The following is a list of dependent jurisdictions in Marin County:

Corte Madera Sanitary District No. 2
Marin County Parks Open Space District
San Rafael Sanitation District
San Quentin Village Sewer Maintenance District
Sausalito Marin City Sanitary District
Sewerage Agency of Southern Marin
Murray Park Sewer Maintenance District
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21 Figure 1.2: Fire Protection Districts in Marin County Source: Marin County Community Wildfire Protection Plan l ~ <;>U·N· TY OF
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Central Marin Fire Department
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Kentfield Fire Protection District
Marinwood community Services District
Novato Fire Protection District
Ross Valley Fire Department
San Rafael Fire Department
Southern Marin Fire Protection District
Stinson Beach Fire Protection District
Tiburon Fire Protection District
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Marin County OEM / Woody Baker-Cohn
email: [email protected]
Date Printed : 08/11/23
County of Marin, california State Parks, Esri, HERE, Garmin, SafeGraph, FAO, METI/NASA, USGS, Bureau of Land Management, EPA, NPS 2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
22 Figure 1.3: School Districts in Marin County
Source: Marin County OEM
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Marin County
School Districts
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Marin County OEM / Woody Baker-Cohn
email: [email protected]
Date Printed: 08/08/23
[!an
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County of Marin, (allfomla State Parks, Esrl, HERE, Garmin, SafeGraph, FAO, METI/NASA, USGS, Bureau of Land Management, EPA, NPS 10 2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
23 Protected Areas
The following protected areas are within or contiguous to Marin County:

National Protected Areas
• Golden Gate National Recreation Area
• Marin Islands National Wildlife Refuge
• Muir Woods National Monument
• Point Reyes National Seashore
• San Pablo Bay National Wildlife Refuge
• Greater Farallones National Marine Sanctuary
State Parks
• Angel Island State Park
• China Camp State Park
• Mount Tamalpais State Park
• Olompali State Historic Park
• Samuel P. Taylor State Park
• Tomales Bay State Park
Marine Protected Areas
• Duxbury Reef State Marine Conservation Area
• Estero Americano State Marine Recreational Management Area • Estero de San Antonio State Marine Recreational Management Area • Point Reyes State Marine Reserve & Drakes Estero State Marine Conservation Area Figure 1.4: Muir Woods National Monument
Source: National Park Service
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24 Figure 1.5: Marin County Parks and Public Lands
Source: Marin County
Marin County’s identity is largely shaped by its abundant natural resources and long history of open space preservation efforts to retain its rural character. A variety of factors have strictly limited development in the County over the last 5 years including large swaths of permanently protected federal and state parkland, large acreage of farm and ranch lands permanently protected through conservation easements, and Countywide Plan policies and development codes which restrain growth in sensitive habitat areas and/or flood hazard areas. Similarly future development is limited by these same constraints, as outlined in Section 4.10 Future Development.
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2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
25 1.5.1 DEMOGRAPHICS
Marin County is the 26th most populated county in the state of California. According to the U.S.

Census Bureau, the population of Marin County in July 2021 was 260,206, an increase of

2.99% from the 2010 population of 252,409. The estimated population of Marin County in 2023 is around 265,294.

Figure 1.6: Population of Marin County 1860-2020
Source: U.S. Census Bureau 2020 Survey
Marin County grew rapidly from the 1930’s to the 1970’s, with slower growth from the 1970’s to the 2020’s. Between 1960 and 1970, the population of Marin County grew by 71.48% and has only grown by 21.45% since. Since the last plan update in 2018, the population of Marin County has remained fairly level.

Table 1.1: Marin County Population Changes 1860-2020
Year Population Change Growth Rate
1850 323 N/A N/A
1860 3,334 3,011 932.20%
1870 6,903 3,569 107.05%
1880 11,324 4,421 64.04%
1890 13,072 1,748 15.44%
1900 15,702 2,630 20.12%
1910 25,114 9,412 59.94%
1920 27,342 2,228 8.87%
1930 41,648 14,306 52.32%
1940 52,907 11,259 27.03%
1950 85,619 32,712 61.83%
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POPULATION OF MARIN COUNTY 1860-2020
YEAR
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
26 1960 146,820 61,201 71.48%
1970 206,038 206,038 40.33%
1980 222,568 16,350 8.02%
1990 230,096 7,528 3.38%
2010 252,916 22,313 9.70%
2020 262,321 9,405 3.77%
Table 1.1: Marin County Population Changes 1860-2020
Source: U.S. Census Bureau 2020 Survey
The California Department of Finance shows an overall estimated decrease in the population of Marin County since the last plan update in 2018. Of the total estimated 257,135 residents of Marin County in 2022 based on the 2020 U.S. Census Survey, 190,148 residents live in the incorporated county and 66,987 residents live in the unincorporated county.

Table 1.2: Marin County Estimated Jurisdictional Population Jurisdiction Population 2022
(Estimate) Population 2020 Population 2018 (Estimate)
Percent Change
2018-2022
Marin County 257,135 262,321 262,179 -1.92%
Unincorporated
Marin County
66,987 66,987 68,963 -2.87%
City of Belvedere 2,080 2,126 2,102 -1.04%
City of Larkspur 12,797 13,064 12,396 3.13%
City of Mill Valley 13,850 14,231 14,702 -5.80%
City of Novato 52,441 53,225 54,036 -2.95%
City of San Rafael 60,560 61,271 59,851 1.17%
City of Sausalito 7,072 7,269 7,449 -5.06%
Town of Corte
Madera
10,028 10,222 10,104 -0.75%
Town of Fairfax 7,418 7,605 7,625 -2.71%
Town of Ross 2,301 2,338 2,566 -10.33%
Town of San
Anselmo
12,645 12,830 12,853 -1.62%
Town of Tiburon 8,956 9,146 9,542 -6.14%
Table 1.2: Marin County Estimated Jurisdictional Population Source: California Department of Finance
Population counts of the Marin County unincorporated area were taken in the 2020 and 2010 U.S. Census Surveys.
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27 Table 1.3: Marin County Estimated Jurisdictional Population Community Population 2020 Population 2010 Percent Change 2010-2020
Marin County 262,321 262,179 -1.92%
Unincorporated
Marin County 66,987 68,963 -2.87%
City of Belvedere 2,126 2,102 -1.04%
City of Larkspur 13,064 12,396 3.13%
City of Mill Valley 14,231 14,702 -5.80%
City of Novato 53,225 51,904 -2.95%
City of San Rafael 61,271 59,851 1.17%
City of Sausalito 7,269 7,449 -5.06%
Town of Corte
Madera 10,222 10,104 -0.75%
Town of Fairfax 7,605 7,625 -2.71%
Town of Ross 2,338 2,566 -10.33%
Town of San
Anselmo 12,830 12,853 -1.62%
Town of Tiburon 9,146 9,542 -6.14%
Table 1.3: Marin County Estimated Jurisdictional Population Change 2010-2020 Source: California Department of Finance
The Association Bay Area of Governments (ABAG) projects that the population in the unincorporated County will grow by only 2% in the next two decades. Tam Valley, Kentfield/Greenbrae, and the Marinwood/Lucas Valley communities are the most populous areas within the unincorporated County.

The median age of Marin County residents in 2020 is 47.1, with 45.6 for males and 48.4 for females. The male to female ratio in Marin County as of 2020 is 126,529 males (48.77%) and 132,912 females (51.23%.) There are 207,467 adults in Marin County as of 2020, 57,834 of whom are seniors.

Table 1.4: Marin County Population Age by Gender 2020
Age Population Male Female
Under 5
years
12,014 5,852 6,162
5 to 9 years 13,355 6,703 6,652
10 to 14
years
16,784 8,574 8,210
15 to 19
years
15,122 7,676 7,446
20 to 24
years
11,663 6,009 5,654
25 to 29
years
10,562 5,709 4,853
30 to 34
years
11,896 6,237 5,659
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28 Table 1.4: Marin County Population Age by Gender 2020 Age Population Male Female
35 to 39
years
14,253 7,160 7,093
40 to 44
years
16,191 8,237 7,954
45 to 49
years
20,074 9,925 10,149
50 to 54
years
20,430 10,051 10,379
55 to 59
years
20,887 9,616 11,271
60 to 64
years
18,376 9,071 9,305
65 to 69
years
17,971 8,307 9,664
70 to 74
years
15,424 7,088 8,336
75 to 79
years
10,040 4,689 5,351
80 to 84
years
7,083 3,195 3,888
85 years + 7,316 2,430 4,886
Table 1.4: Marin County Population Age by Gender 2020
Source: U.S. Census Bureau 2020 Survey
By race, Marin County is predominantly white. According to the U.S. Census Bureau, 69.7% of the population is White, 17.1% is Hispanic, 7.1% is Asian, 4.3% is Two or more races, 2.7% is Black or African American, 1.0% is American Indian or Alaska Native, 0.3% is Native Hawaiian or Pacific Islander as of 2022.

Table 1.5: Marin County Population by Race or Ethnicity Race or Ethnicity Percent
White, alone 69.7
Hispanic, Non-white 17.1
Asian, alone 7.1
Two or More Races 4.3
Black or African American, alone 2.7
American Indian or Alaska Native, alone 1.0
Native Hawaiian or Pacific Islander, alone 0.3
Table 1.5: Marin County Population by Race or Ethnicity Source: U.S. Census Bureau 2022 Survey
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29 The average family size in Marin County as of 2022 is 2.97, and the average household size is

2.41 with an approximate home ownership rate of 63.6%. As of 2022, 70.9% of the housing stock was single family structures, 27.3% was multi-family structures, and 1.8% were mobile homes and other types of units. In unincorporated Marin County, the largest proportion of the housing stock was built from 1960 to 1979, with 10,258 units constructed during this period.

Since 2010, 1.2% of the current housing stock was built, which equates to 360 units.

Table 1.6: Marin County Housing Stock
2022 and 2018
Year Total
Units
Single Family Multi-Family Mobile
Detached Attached 2 to 4 5 plus Homes
Marin County
2022 Number 111,879 68,004 11,314 8,524 22,013 1,984
Percent 100.0% 60.8% 10.1% 7.6% 19.7% 1.8%
2018 Number 112,294 68,697 11,318 8,307 21,986 1,986
Percent 100.0% 61.2% 10.1% 7.4% 19.6% 1.8%
California
2022 Number 14,583,998 8,341,577 1,010,851 1,168,669 3,500,674 562,223 Percent 100.0% 57.2% 6.9% 8.0% 24.0% 3.9%
2018 Number 14,157,502 8,160,864 985,926 1,129,761 3,318,946 562,005 Percent 100.0% 57.6% 7.0% 8.0% 23.4% 4.0%
Table 1.6: Marin County Housing Stock
Source: California Department of Finance
Table 1.7: Marin County Jurisdictional Housing Stock
2022 and 2018
Year Total
Units
Single Family Multi-Family Mobile
Detached Attached 2 to 4 5 plus Homes
Unincorporated Marin County
2022
Number 29,293 22,456 1,875 1,443 2,939 580
Percent 100.00% 76.66% 6.40% 6.43% 10.03% 1.98%
2018
Number 29,723 22,833 1,909 1,409 2,993 579
Percent 100.00% 76.82% 6.42% 4.74% 10.07% 1.95%
City of Belvedere
2022
Number 1,062 890 51 84 37 0
Percent 100.00% 83.80% 4.80% 7.91% 3.48% 0.00%
2018
Number 1,048 881 49 81 37 0
Percent 100.00% 84.06% 4.68% 7.73% 3.53% 0.00%
City of Larkspur
2022
Number 6,460 2,653 439 479 2,614 275
Percent 100.00% 41.07% 6.80% 7.41% 40.46% 4.26%
2018
Number 6,479 2,650 427 488 2,625 289
Percent 100.00% 40.90% 6.59% 7.53% 40.52% 4.46%
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30 City of Mill Valley
2022
Number 6,521 4,269 648 380 1,210 14
Percent 100.00% 65.47% 9.94% 5.83% 18.56% 0.21%
2018
Number 6,509 4,296 657 331 1,212 13
Percent 100.00% 66.00% 10.09% 5.09% 18.62% 0.20%
City of Novato
2022
Number 21,337 12,465 3,395 1,362 3,572 543
Percent 100.00% 58.42% 15.91% 6.38% 16.74% 2.54%
2018
Number 21,448 12,581 3,427 1,335 3,557 548
Percent 100.00% 58.66% 15.98% 6.22% 16.58% 2.56%
City of San Rafael
2022
Number 24,631 11,318 2,490 2,174 8,235 413
Percent 100.00% 45.95% 10.11% 8.83% 33.43% 1.68%
2018
Number 24,078 11,123 2,399 2,090 8,059 407
Percent 100.00% 46.20% 9.96% 8.68% 33.47% 1.69%
City of Sausalito
2022
Number 4,435 1,711 802 934 906 82
Percent 100.00% 38.58% 18.08% 21.06% 20.43% 1.85%
2018
Number 4,581 1,776 829 953 938 85
Percent 100.00% 38.77% 18.10% 20.80% 20.48% 1.86%
Town of Corte Madera
2022
Number 4,182 2,468 621 376 717 0
Percent 100.00% 59.01% 14.85% 8.99% 17.14% 0.00%
2018
Number 4,207 2,498 609 373 727 0
Percent 100.00% 59.38% 14.48% 8.87% 17.28% 0.00%
Town of Fairfax
2022
Number 3,486 2,185 338 499 451 13
Percent 100.00% 62.68% 9.70% 14.31% 12.94% 0.37%
2018
Number 3,594 2,281 345 486 469 13
Percent 100.00% 63.47% 9.60% 13.52% 13.05% 0.36%
Town of Ross
2022
Number 882 817 17 23 25 0
Percent 100.00% 92.63% 1.93% 2.61% 2.83% 0.00%
2018
Number 892 831 16 19 26 0
Percent 100.00% 93.16% 1.79% 2.13% 2.91% 0.00%
Town of San Anselmo
2022
Number 5,539 4,177 266 376 683 37
Percent 100.00% 75.41% 4.80% 6.79% 12.33% 0.67%
2018
Number 5,563 4,211 269 356 690 37
Percent 100.00% 75.70% 4.84% 6.40% 12.40% 0.67%
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31 Town of Tiburon
2022
Number 4,051 2,645 386 383 624 14
Percent 100.00% 65.29% 9.53% 9.45% 15.40% 0.35
2018
Number 4,036 2,644 384 370 624 14
Percent 100.00% 65.51% 9.51% 9.17% 15.46% 0.35%
Table 1.7: Marin County Jurisdictional Housing Stock
Source: California Department of Finance

1.5.2 CRITICAL FACILITIES AND INFRASTRUCTURE
A critical facility may be defined as one that is essential in providing utility or direction either during the response to an emergency or during the recovery operation. FEMA uses the following three categories of critical assets (Essential Facilities, High Potential Loss Facilities, and Infrastructure Systems). Essential facilities are those that if damaged would have devastating impacts on disaster response and/or recovery. High potential loss facilities are those that would have a high loss or impact on the community. Infrastructure systems are a third category of critical assets.

Marin County maintains a listing of critical facilities in Marin County and the list is categorized according to FEMA’s critical facility definition. Additionally, each jurisdiction in Marin County lists the critical facilities specific to that jurisdiction. The following are general categories of critical facilities in the Marin County OA:

Critical facilities include, without limitation, public safety, emergency response, emergency medical, designated emergency shelters, communications, public utility plant facilities and equipment, and government operations.
• Public Safety - Police stations, fire and rescue stations, emergency operations centers • Emergency Response - Emergency vehicle and equipment storage and essential governmental work centers for continuity of government operations • Emergency Medical - Hospitals, emergency care, urgent care, ambulance services • Designated Emergency Shelters
• Communications - Main hubs for telephone, main broadcasting equipment for television systems, radio and other emergency warning systems • Public Utility Plant Facilities - including equipment for treatment, generation, storage, pumping and distribution (hubs for water, wastewater, power and gas) • Essential Government Operations - Public records, courts, jails, building permitting and inspection services, government administration and management, maintenance and equipment centers, and public health
• Transportation Lifeline Systems - Airports, helipads, and critical highways, roads, bridges and other transportation infrastructure (Note: Critical highways, roads, etc. will be determined during any hazard-specific evacuation planning and are not identified in this plan)
At risk population facilities include, without limitation, pre-schools, public and private primary and secondary schools, before and after school care centers with 12 or more students, daycare centers with 12 or more children, group homes, and assisted living residential or congregate care facilities with 12 or more residents.
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32 Hazardous materials facilities include, without limitation, any facility that could, if adversely impacted, release of hazardous material(s) in sufficient amounts during a hazard event that would create harm to people, the environment and property.

Transportation
Marin County has an ever-developing transportation system, with most travel concentrated along key highways and arterial streets. There are 5 Highways passing through, terminating, or located wholly in Marin County: Interstate 580, U.S. Route 101, State Route 1, State Route 37, and State Route 131.

Marin County is connected to surrounding communities by bridges. The Golden Gate Bridge is to the south; the Richmond/San Rafael Bridge is to the east; State Route 37 is to the northeast (across filled bay land over San Pablo Bay); and Highway 101 is to the north (which narrows to a 4-lane uncontrolled road that traverses San Antonio Creek). One of the major problems Marin County faces during an emergency is the possibility of being isolated from the surrounding communities and any resources or help. Light rail service recently began supplementing existing transportation options along U.S. Route 101 between Marin and Sonoma Counties.

Utilities
Municipal utilities in Marin County include water (drinking water, stormwater, sanitary sewerage), power (electricity and natural gas), telecommunications, and solid waste. Several water management utilities supply treated water for domestic and fire suppression purposes.

These distribution systems rely largely on the County’s topography for collecting surface water, storing it in reservoirs, and distributing it with gravity-fed systems. As such, the water management utilities are separated by both functional area and geography, but they are working more and more to coordinate within watersheds.

Marin Municipal Water District (MMWD) is the largest water district in Marin, serving central and southern portions of the county east of Mount Tamalpais and Bolinas Ridge. North Marin Water District (NMWD) serves Novato and communities along Tomales Bay including Olema, Point Reyes Station, Inverness, and Dillon Beach. Bolinas and Stinson Beach, two communities in West Marin, have separate water and sanitary districts. To include the Bolinas Community Public Utility District. Inverness Public Utility District is the primary water utility for Inverness Park and the Estero Mutual Water Company serves Dillon Beach. There are 23 agencies providing wastewater services in Marin County, including special districts, municipalities, JPAs and the Federal and State government.

Stormwater utilities such as open channels, catch basins and storm drains are managed by the cities, towns, and the county in unincorporated areas and are coordinated through the Marin County Stormwater Pollution Prevention Program (MCSTOPPP). Additionally, the Marin County Flood Control and Water Conservation District maintains some larger drainage infrastructure where zones have been designated. The District and some cities/towns such as San Rafael, Corte Madera, and Novato operate stormwater pump stations.

Natural gas and electricity distribution occurs through infrastructure owned and maintained by PG&E, a private utility corporation. Natural gas is piped into Marin from the central valley around the North Bay through Solano, Napa, and Sonoma Counties. The main transmission pipelines are underground along Highway 101 and flow south, branching into local distribution lines and private laterals. PG&E also brings power into Marin around the North Bay on overhead l ~<;>U·N· TY OF
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33 transmission lines that emanate from the Ignacio substation in Novato. Additional substations are located along Hwy 101 in Las Gallinas, San Rafael, Greenbrae, and Mill Valley to the South and in Novato, Stafford, Tocaloma, Olema, Bolinas and Woodacre to the North and East.

Telecommunications include telephone service, cable television and wireless services. AT&T maintains infrastructure for providing landlines, while Comcast provides cable television. A variety of cellular and wireless service companies operate in Marin and provide access points in the form of cellular towers, wireless antennas and equipment.

There are six solid waste haulers that operate within Marin County organized geographically and with agreements with cities and towns. All of this garbage, recycling, and greenwaste is brought to one of two processing centers; Redwood Landfill in Novato and Marin Resource Recovery Center in San Rafael.

1.5.3 NATURAL, HISTORICAL, AND CULTURAL RESOURCES
Assessing Marin County’s vulnerability to disaster also involves inventorying the natural, historical, and cultural assets of the area. This step is important for the following reasons:
• The community may decide that these types of resources warrant a greater degree of protection due to their unique and irreplaceable nature and contribution to the overall economy.
• In the event of a disaster, an accurate inventory of natural, historical and cultural resources allows for more prudent care in the disaster’s immediate aftermath when the potential for additional impacts is higher.
• The rules for reconstruction, restoration, rehabilitation, and/or replacement are often different for these types of designated resources.
• Natural resources can have beneficial functions that reduce the impacts of natural hazards.

Natural Resources
Marin County is located along California’s Pacific Coast (between San Francisco and Sonoma), including 72 miles of coastline. The highest point in the county, Mount Tamalpais, is 2,572 feet above sea level. The county has many microclimates with varying weather patterns, but the climate is generally Mediterranean with an average annual temperature of 56.5 degrees Fahrenheit.

The Marin Countywide Plan divides the 606 square miles of land and water that make up Marin County into four distinct environmental regions called corridors. Each corridor is based on specific geographical and environmental characteristics and natural boundaries:
• The Coastal Corridor is adjacent to the Pacific Ocean and is primarily designated for federal parklands, recreational uses, agriculture, and the preservation of existing small coastal communities.
• The Inland Rural Corridor, in the central and northwestern part of the county, is primarily designated for agriculture and compatible uses, and for preservation of existing small communities.
• The City-Centered Corridor, along Highway 101 in the eastern part of the county near San Francisco and San Pablo bays, is primarily designated for urban development and l ~<;>U·N· TY OF
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34 for protection of environmental resources. This corridor is divided into six planning areas generally based on watersheds.
• The Baylands Corridor, encompassing lands along the shoreline of San Francisco, San Pablo, and Richardson bays, provides heightened recognition of the unique environmental characteristics of this area and the need to protect its important resources. The area generally contains marshes, tidelands, and diked lands that were once wetlands or part of the bays, and adjacent, largely undeveloped uplands.

Figure 1.7: Marin County Environmental Corridors
Source: Marin Countywide Plan
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c:J C,>u,ily Bo'°""'IJ'
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2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
35 Within its environmental corridors, Marin County is home to a number of diverse and important natural communities, from coastal marine environments to bay marshlands and mudflats, riparian habitats, and an upland mosaic of forests, woodlands, grasslands, and chaparral.

Figure 1.8: Marin County Habitat Types
Source: Marin Countywide Plan
Since the mid-19th century, grazing, logging, agriculture, road building, and development have markedly altered the natural landscape in Marin County. The continued loss of oak woodland, oak savannah, and other native woodland habitat through their conversion to primarily urban l ~<;>U·N· TY OF
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a
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2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
36 uses resulted in the adoption of the County Native Tree Preservation and Protection Ordinance in 1999. This regulates the removal of native trees and is intended to use local regulations to protect sensitive resources. Sensitive natural communities are natural community types that are considered particularly rare or threatened by the California Natural Diversity Data Base of the California Department of Fish and Game. Sensitive natural community types in Marin include, but are not limited to, coastal and valley freshwater marsh, freshwater seep and spring, riparian forest and woodland, coastal brackish marsh, coastal terrace prairie, central dune scrub, coastal bluff scrub, northern coastal salt marsh, northern maritime chaparral, northern vernal pool, serpentine bunchgrass, valley needlegrass grasslands, old growth redwood and Douglas fir forests, and deciduous woodlands dominated by valley oaks or Oregon white oak.

Marin County’s abundance of natural resources and progressive environmental leadership have supported a long legacy of open space preservation to help protect and restore wetlands and other ecosystems for both habitat and flood control, amongst other co-benefits. The Marin Countywide Plan includes goals, policies, and implementing programs for the acquisition, conservation, and restoration of wetlands, riparian areas, and other habitats.

Watersheds and Wetlands
Marin’s watersheds and wetlands are some of its most valuable assets and can provide protective functions that reduce the magnitude of hazard events. Bounded by ridges, Marin’s watersheds carry water, sediments, nutrients, and more, downstream into large water bodies including the Pacific Ocean, San Francisco Bay, and Tomales Bay. Wetlands can be found in the lower watersheds, with habitat types including fresh-, salt-, and brackish-water marshes which provide food and shelter for a variety of flora and fauna, including special status plants, fish, birds, amphibians, and mammals. These ecosystems can also buffer flood impacts by reducing wave attenuation from storm surge or serve as detention basins during large rainfall events. Sea level rise threats have led to heightened interest in the use of wetlands and other living shorelines such as oyster beds, eelgrass, and sand dunes as adaptation strategies to protect lives and properties while providing habitat, recreation, carbon sequestration, and other co-benefits.

One of the goals of Marin County is to avoid and minimize potential adverse impacts on existing wetlands and to encourage programs for restoration and enhancement of degraded wetlands.

By establishing a Wetland Conservation Area, the County seeks to require that development to avoid wetland areas so that the existing wetlands and upland buffers are preserved and opportunities for enhancement are retained. Maintaining and enhancing wetlands serves to reduce the costs of flood damage, water pollution, and water supply redistribution. Several living shoreline pilot projects are currently underway throughout Marin County to demonstrate their effectiveness.

The Marin County Watershed Program identifies fourteen watersheds throughout the County.

The following pages provide information about watersheds in the unincorporated area of the County.
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37 Figure 1.9: Marin County Wetlands
Source: Marin Countywide Plan
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2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
38 Figure 1.10: Marin County Watersheds
Source: Marin Countywide Plan
Bolinas Lagoon
With a 16.7 mi2 watershed, Bolinas Lagoon consists of mudflats, marshes, tidal channels and a flood shoal island. Other watershed habitats include coastal scrub, Douglas fir, redwood forests, and grasslands as well as small patches of eucalyptus, oak and oak-bay woodland, and pine cypress forest. Noteworthy species include ridgeway and black rails, salt marsh common yellowthroat, California red-legged frog, California brown pelican, American peregrine falcon, l ~<;>U·N· TY OF
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2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
39 Point Reyes mountain beaver, Point Reyes jumping mouse, Coho salmon, steelhead trout, northern spotted owl, black swift, and Marin manzanita.

In 2008 the “Bolinas Lagoon Ecosystem Restoration Project: Recommendations for Restoration and Management” was completed by a working group of community representatives and scientists, with recommended actions including restoring natural sediment transport and ecological functions of the lagoon, identifying and managing non-native species, and protecting water quality. The Marin County Parks’ Bolinas Wye Wetlands Resiliency Project also serves to restore habitat, improve road safety, and adapt to sea level rise in Bolinas Lagoon.

Estero Americano
The County’s northernmost watershed, the 49 mi2 Estero Americano watershed straddles the Marin and Sonoma County boundaries. Americano Creek draining into Bodega Bay, is the watershed’s only tributary, and is ephemeral, generally drying up for 4-6 months between late spring and fall. The Estero Americano contains 301 acres of open water, and 412 acres of wetland habitat with mudflats, seasonal brackish marsh and freshwater marsh. With streamside habitat of grazed pastures with few trees interspersed with dense willow thickets, and coastal oak woodland in the upper watershed, Estero Americano has been identified by the California Department of Fish and Game as among the most significant habitat areas in the State. The watershed’s special status species include the Northwestern pond turtle, steelhead trout, California red-legged frog, Myrtle’s silverspot butterfly, tidewater goby, and tricolored blackbird.

A 1987 enhancement plan led to repair of many of the watershed’s eroded areas, which was undertaken by the Gold Ridge Resource Conservation District (RCD) with funding from the State Coastal Conservancy. In 2007 the RCD developed the Estero Americano Watershed Management Plan.

Gallinas Creek
Located in Eastern Marin, the 5.6 mi
2 watershed has two main drainage areas; the north fork and South Gallinas Slough. The watershed is highly urbanized with fragmented native plant communities. Upper watershed habitats include annual grasslands interspersed with mixed evergreen forest, coastal scrub and small outcroppings of serpentine habitat. Continuous with China Camp State Park is a large tract of oak-bay woodland along the southern watershed boundary. Lower marsh habitats represent some of the largest remaining tidally influenced habitats in the Bay Area with noteworthy special status species including the San Pablo song sparrow, California black rail, salt marsh harvest mouse and the ridgeway rail.

A three-acre tidal marsh restoration effort by the Marin Audubon Society and Marin Community Foundation was completed in 1977. The Friends of Gallinas Creek, San Pablo Watershed Restoration Program Partners, the Bay Institute and Marin County Stormwater Pollution Prevention Program are planning extensive restoration in the upper and lower watershed to improve riparian cover, provide habitat, reduce erosion, and restore wetlands.

Tomales Bay
The Tomales Bay Watershed encompasses the subwatersheds of Lagunitas Creek, Walker Creek, Inverness Creek, and east shore drainages including Millerton Gulch, Grand Canyon, and Tomasini Canyon. Resource rich, nearly 500 species of birds and the most robust l ~<;>U·N· TY OF
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40 population of native coho salmon remaining in the Central Coast region are supported by the Bay. Tomales Bay is a Ramsar Wetland of International Importance with intertidal, subtidal, and benthic habitas, as well as dunes, mud flats, salt marshes and freshwater marshes. Eelgrass beds are also found throughout Tomales Bay, and provide important habitat for fish, birds, and other species, while combatting shoreline erosion by dampening wave energy and storms.

The Tomales Bay Watershed Stewardship Plan was completed in 2003. Restoration projects are underway in the Walker and Lagunitas Creek areas.

Miller Creek
With a watershed covering 12 mi2, Miller creek uniquely has a relatively intact riparian area with very high widths and depths relative to its drainage area. While relatively urbanized, the watershed still supports a small population of steelhead. Its lower marsh habitats include some of the Bay Area’s largest remaining tidally-influenced habitats that support abundant waterfowl.

The watershed is dominated by annual grasslands interspersed with oak-bay woodland and oak savanna in the upper watershed with patches of chaparral. Middle reaches are primarily urbanized. The watershed’s lower reaches east of Highway 101 support saltwater and brackishwater marshes subject to tidal action.

Noteworthy special status species include the San Pablo Song Sparrow, California black rail, saltmarsh harvest mouse, ridgeway rail and steelhead trout.

Novato Creek
As Eastern Marin’s largest watershed, Novato Creek Watershed’s creeks flow eastward through oak and bay forests, grasslands, unincorporated Marin County, and the City of Novato, and into San Pablo Bay near the mouth of the Petaluma River. The basin is 45 mi 2 and its main drainage
is the 17 mi2 Novato Creek, which has 6 major tributaries. Diverse habitat types include saltwater marsh, brackish marsh, freshwater wetlands, oak woodlands, annual grasslands and oak savanna. Special status species include the San Pablo Song Sparrow, California black rail, saltmarsh common yellowthroat, ridgeway rail and Western pond turtle. Salmonids including steelhead and Chinook salmon are also found within the watershed.

Point Reyes National Seashore Creeks
This watershed is comprised of almost 100 mi2 of land and nearly 80 miles of undeveloped coastline, with subwatersheds that drain into Drake’s Estero, Abbotts Lagoon, Estero de Limanotour, the Pacific Ocean, portions of the Bolinas Lagoon and the Tomales Bay. Habitat types include estuaries, mud flats, sandy shores, intertidal communities and a variety of upland habitats. Special-status species include the endemic Mountain Beaver, Point Reyes jumping mouse, California freshwater shrimp, Myrtle’s silverspot, Point Reyes blue butterfly, San Francisco forktail damselfly and steelhead trout.

Richardson Bay
With San Francisco Bay’s second largest eelgrass bed, Richardson Bay supports genetically diverse and extensive intertidal habitat. As an Important Bird Area along the Pacific Flyway, the Bay supports hundreds of thousands of migrating waterbirds during the winter months.

Noteworthy special-status species include the California black rail, San Pablo song sparrow, salt marsh harvest mouse, and Point Reyes bird’s-beak.

Salmonids including steelhead trout are also supported. l ~<;>U·N· TY OF
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41 Ross Valley
Receiving over 50 inches of rain annually, the 28 mi2 Ross Valley watershed is one of Marin County’s wettest areas. With 28 miles of stream channels, the watershed supports a great diversity of habitats including redwood forests, serpentine outcrops, chaparral, oak woodlands, grasslands and tidal wetlands. Special status wildlife include steelhead trout, spotted owls, San Pablo song sparrow, ridgeway and black rails, and salt marsh harvest mouse.

Led by the Marin County Flood Control and Water Conservation District, the Ross Valley Flood Protection & Watershed Program’s objective is to reduce flooding throughout the watershed.

Creek improvements being considered include debris clearance, invasive vegetation removal, creek bank stabilization, and habitat enhancement.

Rush Creek
At the Northern edge of Novato, Rush Creek’s wetland habitats includes coastal saltwater and coastal brackish water marsh habitats. The wetlands provide suitable habitat for San Pablo song sparrow, California black rail, saltmarsh common yellowthroat, California brackishwater snail, and ridgeway rail. Restoration efforts include the Rush Creek and Bahia restoration projects.

San Antonio Creek
Covering around 25% of the Petaluma River watershed, the San Antonio Creek watershed extends from Antonio Mountain and Chileno Valley in the northwest to Petaluma Marsh and the Petaluma River to the southeast. The upper San Antonio Creek watershed is dominated by annual grassland and mixed evergreen forest with patches of oak and bay woodland. The lower watershed includes extensive coastal salt marsh and brackish marsh. Special status species include the California black rail, ridgeway rail, salt marsh common yellowthroat, San Pablo song sparrow, Townsend’s big-eared bat, California red-legged frog, northwestern pond turtle, and salt marsh harvest mouse.

Limited salmonids have also been recorded in the watershed.

The Petaluma River Watershed Enhancement Plan was completed by the Southern Sonoma County RCD in 1999 with information on riparian and fisheries enhancement. In 2008 the Southern Sonoma County RCD completed the San Antonio Creek Watershed Plan in tandem with local landowners and residents.

San Rafael Creek
The 11 mi2 San Rafael watershed is densely developed from its hills to filled wetlands. A small marsh at Pickleweed Park provides habitat for native species, and the watershed’s northern edge include intact woodland, grassland and lagoon areas.

Southern Coastal Creeks
Several smaller watersheds along over 10 miles of southern Marin’s rugged coastlines are protected within National and State Park boundaries. These include Webb Creek, Lone Tree Creek, Cold Stream, Redwood Creek, Alder Creek, Rodeo Lagoon and Tennessee Valley. A variety of habitat types exist amongst these watersheds including seasonal wetlands, riparian woodlands, and freshwater marsh. Special status species include Coho salmon, steelhead trout, l ~<;>U·N· TY OF
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42 California red-legged frog, monarch butterflies, northwestern pond turtle, northern spotted owl and more.

Stemple Creek
Bisected by the Sonoma-Marin County boundary, this 50 mi2 watershed begins just west of Petaluma and empties into the Pacific Ocean through the Estero de San Antonio. Like Estero Americano, the Estero de San Antonio was identified by the California Department of Fish and Game as among the most significant habitat areas in California with densely wooded riparian ravines, saltgrass areas, mudflats, eelgrass beds and freshwater ponds. Special-state species include the California freshwater shrimp, northwestern Pond Turtle, tidewater goby, Myrtle’s silverspot butterfly, and the California red-legged frog.

In 1994 an enhancement plan was completed, leading to local landowner gully stabilization projects to reduce erosion. The Marin and Sonoma County RCDs, along with the Natural Resources Conservation Service have brought funding into the watershed to improve water quality.

Baylands
Baylands are areas between historic high and low tide elevations. The baylands ecosystem in Marin County forms a varied pattern of open water, tidal marshes and mudflats, rocky shoreline, seasonal wetlands, and adjacent uplands. Baylands ecosystems are vital to the health of San Pablo, San Francisco, and Tomales bays and have undergone tremendous change, as historical tidal areas were diked for agricultural use, marshes filled and drained for development, and channels dredged and straightened for navigation. An estimated 82% of the historic tidal marshlands along the edge of the San Francisco Bay–Delta Estuary has been filled or altered.

Marin County seeks to a establish bayland buffer zones between development and remaining or historic tidelands and wetlands in order to enhance the diversity of its baylands ecosystems and reduce the costs of flood damage, water pollution, and habitat degradation.

Grasslands and Forests
Marin County has extensive topographic diversity that supports a variety of vegetation types.

Environmental factors, such as temperature, precipitation, soil type, aspect, slope, and land use history, all help determine the existing vegetation at any given location. In the central and eastern parts of the county, north-facing slopes are usually densely wooded from lower elevations to ridge peaks with a mixture of mostly hardwood tree species such as coast live oak, California bay, Pacific madrone, and other oak species.

Grasslands with a mixture of native and nonnative annual and perennial plant species occur most often in the northern and western parts of the county due to a combination of soil type, lower rainfall, and a long history of ranching. The southern and western slopes tend to have a higher percentage of grasslands.

In the west portion of the county closer to the coast, where precipitation is higher and marine influence is greater, most areas are densely forested with conifer species including Bishop pine, Douglas fir, coast redwood, and associated hardwood species. Chaparral vegetation also occurs in parts of the county, especially on steeper south- and west-facing slopes.

Insect infestations and plant diseases, such as California oak mortality syndrome (Sudden Oak Death), are increasing and threaten to change the structure and overall health of native plant l ~<;>U·N· TY OF
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43 communities in Marin County. Sudden Oak Death has had a major impact on native habitats in Marin since its initial detection in the mid-1990s in Mill Valley, The pathogen believed to be a major cause of Sudden Oak Death, Phytophthora ramorum, is known to affect at least 31 species of plants. Two other plant diseases prevalent in Marin County are pitch canker (which affects conifers such as Bishop pine and other pine species), and madrone twig dieback (which affects Pacific madrones).

Oak woodland and savannah are also threatened by development. The continued loss of oak woodland, oak savannah, and other native woodland habitat through their conversion to primarily urban uses in the County resulted in the adoption of the County Native Tree Preservation and Protection Ordinance in 1999. This regulates the removal of native trees and is intended to use local regulations to protect sensitive resources.

Geology
Marin County is located within the central portion of the Coast Range Physiographic Province of California, composed of a series of northwest-southeast aligned coastal mountain chains dominated by the San Andreas Fault Zone. The geology of Marin County is distinctly different on either San Andreas Fault, with areas east of the fault dominated by the Franciscan Formation and associated mélange and west of the fault by granitic rocks and overlying sedimentary rocks. Areas located east of the San Andreas Fault, have a geology dominated by Cretaceous and Jurassic Age Franciscan Complex bedrock composed of sedimentary and volcanic rocks, serpentine, and sheared mélange. Overlying the bedrock is a layer of colluvium and soil of varying thickness. Slopes underlain by the sheared mélange bedrock tend to have a higher density of deep seated landslides compared to those areas underlain by more competent sandstone. Alluvial sediments made up of unconsolidated sands, gravels, and silts are found along the valley bottoms.
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44 Figure 1.11: Marin County Geologic Units (East of San Andreas Fault) Source: Marin Countywide Plan
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45 Figure 1.12: Marin County Geologic Units (West of San Andreas Fault) Source: Marin Countywide Plan
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2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
46 Mineral Resource Zones are grouped by the State of California into four categories based on geologic factors, with Class 2 (MRZ-2) lands having the greatest importance. Class 2 sites are underlain by demonstrated mineral resources considered important to the region or the state as a whole. All of the Marin County’s mineral resource sites are identified by the State as Class 2, except for Ring Mountain, which is considered a Scientific Resource Zone (and therefore not a production site) due to the presence of rare geologic formations.

Figure 1.13: Marin County Mineral Resource Sites
Source: Marin Countywide Plan
1 ~<;>U·N· TY OF a
~ ARIN ~
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.fi m
•• i I' J J • l I
j Ii . iii!
' ) ll . 11,
fif d 1•1
H " 1!1
dJ'- ~ -Ii! .i ~ i I " Ill
l..i i D I
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
47 Climate
Marin County has many microclimates with varying weather patterns, but the climate is generally Mediterranean with mild and wet winters and hot, dry summers. The average annual temperature is around 56.5 degrees. High temperatures normally range from 49 to 63 degrees in the summer months, which is cooler than most places in California. Low temperatures average around 42 degrees in the winter months, and rarely fall below freezing.

Precipitation generally increases with altitude. The topography in Marin County varies greatly, from sea level to elevations around 2,500 feet on Mount Tamalpais. Marin County averages 39 inches of rain per year, making it wetter than most places in California, though it rarely gets snow.

Figure 1.14 shows average annual precipitation and Figure 1.15 shows average annual temperature over time.

Figure 1.14: Marin County Average Precipitation 1895-2022 Source: National Oceanic Atmospheric Administration
l ~<;>U·N· TY OF
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Marin County, California Precipitation
January-December

80.00 in

70.00 in

60.00 in

50.00 in

40.00 in

30.00 in

20.00 in

10.00 in
2,032.00mm
1,778.00mm
1,524.00 mm

1.270.00mm
1,016.00mm
762.00mm
508.00 mm
254.00mm

0.00in4---~---.-----,---~--~--~--~--~--------~--~---+-o.oomm 1895 1905 1915 1925 1935 1945 1955 1965 1975 1985 1995 2005 2015 2022 2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
48 Figure 1.15: Marin County Average Temperature 1895-2022 Source: National Oceanic Atmospheric Administration
Marin County can experience Northern California Diablo winds in the late summer through early winter. These easterly winds occur as systems of high-pressure form in the Great Basin and flow over the Sierra Nevada Mountains toward the Pacific Ocean. As winds flow over the Sierra Nevada, the winds compress, become warmer, and lower the relative humidity while drying out vegetation. As the winds move through canyons, they pick up speed and create strong gusts which can contribute to large and destructive wildfires.

Figure 1.16: Diablo Wind Patterns
Source: National Oceanic Atmospheric Administration
l ~<;>U·N· TY OF
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Marin County, California Average Temperature
January-December
S9.0°F
ss.o·F

57.0' F
S6.0°F

55.0"F

54.0"F

53.0"F
1895-2022 Trend
(+2.1 "F/Century)
1s.o·c

14.4•c

13.9' C

13.3' C

12.s·c

12.2' C
ll.7' C

52.0"F+----.------..----.-----,----,-----,.-----.------.-----,-----,-----..----,----J-11.1•c 189S 190S 1915 1925 193S 194S 195S 1965 197S 1985 1995 2005 201S 2022 What creates
dangerous winds
The Diab lo winds that were forecast
for Northern California usually come
In the fall, but their behavior is hard
to predict because mountains,
valleys and even cloud formations
can alter their speed and dlrecton.
8 The excessive Q Squeezing through
wind can cause canyons and gaps of
power tines to the coastal mountain
topple and ranges, wind speed is
spark. setting dynamically Increased
fires. to over 40 mph.
~ G
0 High pressure builds
over the Great Basin.

Winds flow In a
clockwise direction ---+--◄
8 Jet stream adds ----1---+-=-~':f!
to downward push
of strong winds UTAH
0 Winds come Into
contact with warm
Central Valley air,
increasing its
temperature.

O High-pressure wind cascades over the Sierra
mountains. The air is compressed. increasing
temperature and reducing humidity.

Central Valley
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
49 Historic and Cultural Resources
Marin County has a large stock of historically significant homes, public buildings, and landmarks. To inventory these resources, the Marin County MJHMP Planning Team collected information from a number of sources. The California Department of Parks and Recreation Office of Historic Preservation (OHP) was the primary source of information. The OHP is responsible for the administration of federally and state mandated historic preservation programs to further the identification, evaluation, registration, and protection of California’s irreplaceable archaeological and historical resources. The OHP administers the National Register of Historic Places, the California Register of Historical Resources, California Historical Landmarks, and the California Points of Historical Interest programs. Each program has different eligibility criteria and procedural requirements. • The National Register of Historic Places is the nation’s official list of cultural resources worthy of preservation. The National Register is part of a national program to coordinate and support public and private efforts to identify, evaluate, and protect historic and archeological resources. Properties listed include districts, sites, buildings, structures, and objects that are significant in American history, architecture, archeology, engineering, and culture. The National Register is administered by the National Park Service, which is part of the U.S. Department of the Interior. • The California Register of Historical Resources program encourages public recognition and protection of resources of architectural, historical, archeological, and cultural significance and identifies historical resources for state and local planning purposes, determines eligibility for state historic preservation grant funding, and affords certain protections under the California Environmental Quality Act. The Register is the authoritative guide to the state’s significant historical and archeological resources. • California Historical Landmarks are sites, buildings, features, or events that are of statewide significance and have anthropological, cultural, military, political, architectural, economic, scientific or technical, religious, experimental, or other value. Landmarks #770 and above are automatically listed in the California Register of Historical Resources.
• California Points of Historical Interest are sites, buildings, features, or events that are of local (city or county) significance and have anthropological, cultural, military, political, architectural, economic, scientific or technical, religious, experimental, or other value.

Points designated after December 1997 and recommended by the State Historical Resources Commission are also listed in the California Register.

It should be noted that as defined by the National Environmental Policy Act (NEPA), any property over 50 years of age is considered a historic resource and is potentially eligible for the National Register. Thus, in the event that the property is to be altered, or has been altered, as the result of a major federal action, the property must be evaluated under the guidelines set forth by NEPA. Structural mitigation projects are considered alterations for the purpose of this regulation.

The Marin County OA has 52 places on the National Register of Historic Places. Notable architects that helped create the Marin County historic places including W.G. Carnes, Frank Lloyd Wright, James A. Shore, William Mercer and Solomon Pierce. Prominent architectural styles found in the Marin County OA are Bungalow/Craftsman, Italianate and Mission/Spanish Revival.
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50 Table 1.8: Historic Sites in Marin County
Name/Landmark
State Plaque
Number
National
Register
(NR)
State
Landmark
California
Register
Date
Listed
(NR)
Jurisdiction
AlexanderAcacia Bridge X 1/5/1984 Larkspur
Angel Island,
U.S. Immigration
Station (529)
X X X 10/14/1971 Tiburon
William G.

Barrett House X 6/17/1980 Sausalito
Boyd House X 12/17/1974 San Rafael
Bradford House X 6/6/1980 San Rafael
Camilo Ynitia
Adobe (210) X X Novato
China Camp
(924) X X X 4/26/1979 San Rafael
The Dipsea Trail X 6/4/2010 Mill Valley/
Stinson Beach
Dixie
Schoolhouse X 12/26/1972 San Rafael
Robert Dollar
Estate X 12/11/1972 San Rafael
Robert Dollar
House X 7/23/1991 San Rafael
Dolliver House X 5/22/1978 Larkspur
Drakes Bay
Historic and
Archeological
District
X 10/16/2012 Point Reyes
Station
Lord Charles
Snowden Fairfax
Home (679)
X X Fairfax
Fashion Shop
and Stephen
Porcella House
X 6/25/1980 Novato
First Sawmill in
Marin County
(207)
X X Mill Valley
Forts Baker,
Barry, and
Cronkhite
X 12/12/1973
Unincorporate
d Marin
County
Golden Gate
Bridge (974) X X
Unincorporate
d Marin
County
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51 Table 1.8: Historic Sites in Marin County
Name/Landmark
State Plaque
Number
National
Register
(NR)
State
Landmark
California
Register
Date
Listed
(NR)
Jurisdiction
Green Brae
Brick Kiln Yard
(917)
X X X 3/24/1978 Larkspur
Griswold House X 9/12/1985 Sausalito
Hamilton Army
Air Field
Discontiguous
Historic District
X 11/20/1998 Novato
Larkspur
Downtown
Historic District
X 10/7/1982 Larkspur
Lighter Wharf
Site (221) X X Bolinas
Lyford's Stone
Tower X 12/2/1976 Tiburon
Benjamin and
Hilarita Lyford
House
X 11/10/2000 Tiburon
Marconi-RCA
Bolinas
Transmitting
Station
X 2/23/2018 Bolinas
Marin Art and
Garden Center X 6/6/2022 Ross
Marin City
Public Housing X 9/18/2017 Marin City
Marin County
Civic Center
(999)
X 7/17/1991 San Rafael
Marinship
Machine Shop X 12/20/2016 Sausalito
Erskine B.

McNear House X 1/11/1982 San Rafael
Miller Creek
School Indian
Mound
X 10/14/1971 San Rafael
Mission San
Rafael Arcangel
(220)
X X San Rafael
Mount
Tamalpais
Mountain
Theater
X 2/2/2015 Mill Valley
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52 Table 1.8: Historic Sites in Marin County
Name/Landmark
State Plaque
Number
National
Register
(NR)
State
Landmark
California
Register
Date
Listed
(NR)
Jurisdiction
Muir Beach
Archeological
Site
X 1/26/1981 Marin City
Muir Woods
National
Monument
X 1/9/2008 Mill Valley
Olema Lime
Kilns (222) X X X 10/8/1976 Olema
Olema Valley
Dairy Ranches
Historic District
X 4/9/2018 Olema
Outdoor Art
Club (922) X X X 11/16/1978 Mill Valley
Pierce Ranch X 12/6/1985 Inverness
Pioneer Paper
Mill (552) X X Lagunitas
Point Bonita
Light Station X 9/3/1991 Sausalito
Point Reyes
Lifeboat Rescue
Station, 1927
X 11/7/1985 Inverness
Point Reyes
Light Station X 9/3/1991 Point Reyes
Point Reyes
Naval Radio
Compass
Station
X 6/29/2018 Inverness
Point Reyes
Peninsula Dairy
Ranches
Historic District
X 10/29/2018 Inverness
RCA Point
Reyes Receiving
Station
X 2/23/2018 Inverness
Rancho
Olompali X 1/12/1973 Novato
Valentine Rey
House X 4/22/1982 Belvedere
St. Hilary's
Mission Church X 2/3/2020 Tiburon
San Francisco
and North
Pacific Railroad
Station HouseDepot
X 8/4/1995 Tiburon
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53 Table 1.8: Historic Sites in Marin County
Name/Landmark
State Plaque
Number
National
Register
(NR)
State
Landmark
California
Register
Date
Listed
(NR)
Jurisdiction
San Rafael
Improvement
Club
X 3/29/1984 San Rafael
Sausalito
Woman's Club X 4/15/1993 Sausalito
St. Vincent’s
School for Boys
(630)
X X San Rafael
Brock Schreiber
Boathouse and
Beach
X 7/7/1978 Inverness
Station KPH
Operating
Station
X 7/24/1989 Marshall
Station KPH,
Marconi
Wireless
Telegraph
Company of
America
X 7/24/1989 Marshall
Steamship

TENNESSEE
Remains
X 4/15/1981 Marin City
Tocaloma
Bridge X 9/14/2018 Tocaloma
Tomales
Presbyterian
Church and
Cemetery
X 8/1/1975 Tomales
West Point Inn X 12/22/2011 Mill Valley
Table 1.8: Historic Sites in Marin County
Source: California Office of Historic Preservation and the National Register of Historic Places l ~<;>U·N· TY OF
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Multi-Jurisdictional Hazard Mitigation Plan
54 Figure 1.17: Historic Sites in Marin County
Source: California Office of Historic Preservation
Lis.1 of properties in Mam on the National or Cali!omia Regl!iter I Tornales Pr~ytenan Clnm::tl an(! Cemet.H)'
2 Flter-ceR.a~ll
J OC.;Je-v. Hoose NDftll Of San frarn:;15,co Bay
&latlan KPH Marecwtl Wlreli:S-6 Telegraph, Company Of A.'T!er,ca 5 S>,t·*:liaMan.s.!"00
6 S:ephE!n Porcetta: Ho0&2 and FalilliOn ShDp
7 6roct; Scme.lla BoathOOlie ana Beacti
8 Hamlltoo Ann-y Alr fie[(! Dl&e00llgoo115 K sill<IC Dlslr1cl 9 Pron.!a ?aper Ml 10 Polm Re-yes NatlOO<f! SeaShtf"e ~ry OISUlct
11 51. V\ncenfS. Sehool Tor 83')'&
12 OIXle SCOOOII006e 13 Polm Re-yes llgflt Statton

1.:: cttna camp
15 Pl:lln1 Re-yes L/Teboa:t ReliCU!: statJCfl 16 Mat1n county CMc Centef 17 o:ema lime- Kltls. 1a Home 01lDfd c11ar1es SrlO"MIE!l'l falr".ax 19 Eturne- B. ~ear H<lus.e 20 Roben Dollar Ho~
21 ~attrord House
22 RctieA Doilar E6tat.e 23 5oyl1 Hoose
\lic::x Tal:rlg Maeht'le Ellllbft
25 San Raiclel lmprovemen CCUO 26 Mlli&IOO s:an Ril'ael Areangel 'Zl Sir Frandsorate-Br1dQ2
28 Sila:Jy La'le B,M._Je 29 Norwood ,',venue Bmlge
JO Gfen:,1'0od ,'.venue 6.Jl~e
31 lagl.Slltas Bfk!ge
32 Gleefl Blae- Br:k:l Yarn
3J se e- or ::.t?.e Ll;lh:eJ Whart' at Bollll3s. .l: Larlilipll" OoM\to"Ml tt'..&Clrtc. Dlstrtct 35 Defflve1J-1ou.se, .36 ~Hat10!!r • Acad.1 Bll~e
37 Mll V"<Cey Nr forc:e Sbtklrl Hl6totk: [1$1Jk:::1 38 OUtdOOf Aft Cl'Ub Jg flrl:il Samii In Mal"II COin)'
.SO Eenjamln. aoo ttllama L)1tlftl Hoose
d.1 Lytord'£ Stone Ta,,,'.et"
d.2 Son franciliOO aml NOOll PacF.lc Rililrt:rall statlOO HOIIE@·Depo( .s.J Vale-rlt!he' Rey HOU5e
4A. Angel ISiand, U.S. lmirtgratroo staUon
d.5 wIuam G. Barren i-1.0Use, casa Mam-on.a HolEf
46 $3'Jsa..,"1Q Central 611Slne61i Hlmirtc CU6trlct 47 Sa:us.a::ta woman'& C.IUb 48 Gr19A'Oliil Houlie
49 Forts. Bal.e.r. 6a1JY and Crontt,tt.e
50 ?cilrl.Bonl'.aUghlS'lillfOO.
.~
,_ -,-, 1·
1 · "'.¾,, "M '""TT .L .J' ; (( \_
..... l ); , .r-rc••.r\':r, , ·~
~- r-- ·, .,, ·~ -1~ ...... '1 ..... if<'·
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l\{.~, ,-,1
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""'\ ' /<J, \ V--•-.....t I •
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1, ',.;, , ' ,' '),--, 1''<. _i, I
>~ :\ :~:_ ,_ :~·-/ ,'_:.,,·_,·;, L>' \ / , ·•.~--..c~·-·•·';- -_ I ' '\ ., -. ,\ ·,~ ,., p-_r. /.,,r-- '\. /'l .,., 1 .- _..-l, ~·· J' .l t '.!...,,..'., 1::.. :-, , /tC"" ' , .... ' Jr-- J , · · • ~-ii -\
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HISTORIC RESO
URC
ES
Legend
c:J """'1ty Boondary
D Cll)'B-
= Hlgh,nys. arw:i Ma;or Roatls
Streams
:Paennlal
-- lntenrtnerll
-- i:;µheme-ral
Water Bodies
D La,,.

Historic. Resources
Lann .ark Type Nation.al Register or
State Historical Landmark
""""'"
CIJUreh
h Fe<l«at
h """'
-·
HOOse
Sdloo\ Sdlool
Pllva:eNa.tonal ""'" Na::on.JJ 5ia-:e NilU:lnal Sla.r-! Na~ooal $ia.'2 Naklr\.3I 0!""'~1 - .---=~.--8M'es.
~ '6iftll>-tlrVnOPCP ~(.DIDUIL~llll!PiCIIU
'Ol:.:,oun-,'(Y'M-11.IIOTJIUttaG-.c;QJlu,r,.LI.--
IIK(l:,_ll,l,;l ~ !'nl,.:O.OU:,PIIJUIOlll
+
h
·)> ;;,c--< --<
z~
Cf)
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
55 1.5.4 NATIONAL RISK INDEX AND SOCIAL VULNERABILITY
All communities in the U.S. experience natural hazards, and there is a wide range of environmental, social, and economic factors that influence each community’s risk to natural hazards. The likelihood that a community may experience a natural hazard can vary drastically, as can the associated consequences. Additionally, a community’s risk is influenced by many social, economic, and ecological factors.

A community’s susceptibility to natural hazards varies from location to location. The 18 hazard types evaluated by the National Risk Index were chosen after reviewing FEMA-approved State Hazard Mitigation Plans for all 50 states in early 2016.

Risk Calculation
In the National Risk Index, risk is defined as the potential for negative impacts as a result of a natural hazard. The risk equation behind the National Risk Index includes three components: a natural hazards risk component, a consequence enhancing component, and a consequence reduction component. Expected Annual Loss (EAL) is the natural hazards risk component, measuring the expected loss of building value, population, and/or agriculture value each year due to natural hazards. Social Vulnerability is the consequence enhancing component and analyzes demographic characteristics to measure the susceptibility of social groups to the adverse impacts of natural hazards. Community Resilience is the consequence reduction component and uses demographic characteristics to measure a community’s ability to prepare for, adapt to, withstand, and recover from the effects of natural hazards. The Social Vulnerability and Community Resilience components are combined into one Community Risk Factor (CRF) which is multiplied by the EAL component to calculate risk using Equation 2.

Figure 1.18: Generalized NRI Risk Equation
Source: FEMA National Risk Index Technical Documentation, 2023 Risk Components Overview
The Risk Index score is based on Social Vulnerability, Community Resilience, and Expected Annual Loss, with EAL based on Exposure, Annualized Frequency, and historic loss ratio (HLR) factors, for a total of five risk factors. Each risk factor contributes to either the likelihood or consequence aspect of risk and are classified as one of two risk types: risk based on geographic location, represented by the Community Risk Factor (CRF), or risk based on the nature and historical occurrences of natural hazards, represented by EAL. The five risk factors are summarized in Table 1.9.
1 ~<;>U·N· TY OF a ~ ARIN ~
Equation 2: Generalized National Risk Index Risk Equation Risk = Expected Annual Loss x Community Risk Factor
(
Social Vulnerability ) where Community Risk Factor= f C . R T ommumty esi ience 2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
56 Table 1.9: Risk Components and Factors
Risk Component Risk Factors Risk Factors
Description Risk Contribution Risk Type Assignment
Social
Vulnerability
Social
Vulnerability
Consequence
Enhancer Consequence Geographic Risk
Community
Resilience
Community
Resilience
Consequence
Enhancer Consequence Geographic Risk
EAL Exposure Expected
Consequence Consequence Natural Hazard Risk
EAL Annualized
Frequency
Probability of
Occurrence Likelihood Natural Hazard Risk
EAL HLR Expected
Consequence Consequence Natural Hazard Risk
Table 1.9: NRI Risk Components and Factors
Source: FEMA Na�onal Risk Index Technical Documenta�on, 2023 Social Vulnerability
According to the 2023 National Risk Index Technical Documentation, Social Vulnerability is broadly defined as the susceptibility of social groups to the adverse impacts of natural hazards, including disproportionate death, injury, loss, or disruption of livelihood. Social Vulnerability considers the social, economic, demographic, and housing characteristics of a community that influence its ability to prepare for, respond to, cope with, recover from, and adapt to environmental hazards. As a consequence-enhancing risk factor, the Social Vulnerability score represents the national percentile ranking of social vulnerability for a given county or Census tract in comparison to all other communities at the same level. The higher a county’s or Census tract’s Social Vulnerability is, the higher the risk. Because social vulnerability is unique to a geographic location—specifically, a county or Census tract—it is a geographic risk factor.

Social Vulnerability Source Data
Social Vulnerability source data provider: CDC/ATSDR SVI SVI is a location-specific assessment of social vulnerability that utilizes 16 socioeconomic variables (listed below) deemed to contribute to a community’s reduced ability to prepare for, respond to, and recover from hazards.

1. Below 150% Poverty

2. Unemployed

3. Housing Cost Burden

4. No High School Diploma

5. No Health Insurance

6. Aged 65 & Older

7. Aged 17 & Younger

8. Civilian with a Disability

9. Racial & Ethnic Minority Status

10. Multi-Unit Structures

11. Mobile Homes

12. Crowding

13. No Vehicle

14. Group Quarters

15. Single-Parent Households
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Multi-Jurisdictional Hazard Mitigation Plan
57 16. English Language Proficiency
The dataset was acquired from the CDC/ASTDR website, and users looking for more information should consult CDC/ASTDR.

Social Vulnerability Consideration for Hazard Mitigation Funding The California Governor’s Office of Emergency Services (Cal OES) has initiated the “Prepare California” grant program focused on building community resilience amongst vulnerable individuals living in the areas of the state most susceptible to natural disasters. The Prepare California Initiative is aimed at reducing long-term risks from natural disasters by investing in local capacity building and mitigation projects designed to protect communities.

Prepare California leverages funds approved in Governor Gavin Newsom’s 2021-22 State Budget and is designed to unlock federal matching funds for community mitigation projects that vulnerable communities would otherwise be unable to access. This program is intended for communities that are the most socially vulnerable and at the highest risk for future natural hazard events. The state identified communities by prioritizing California census tracts according to their estimated hazard exposures and social vulnerability.

The National Risk Index is a dataset and online tool to help illustrate the United States communities most at risk for 18 natural hazards: Avalanche, Coastal Flooding, Cold Wave, Drought, Earthquake, Hail, Heat Wave, Hurricane, Ice Storm, Landslide, Lightning, Riverine Flooding, Strong Wind, Tornado, Tsunami, Volcanic Activity, Wildfire, and Winter Weather.

National Risk Index (NRI) hazards align with of eight of the twelve Marin County OA MJHMP Hazards. NRI data is not available for Dam Failure, Land Subsidence, Levee Failure, or Sea Level Rise.

Table 1.10: NRI Hazards and Marin County MJHMP Hazards
NRI Hazards Marin County OA MJHMP Hazards
Earthquake Earthquake
Riverine Flooding Flooding
Coastal Flooding Flooding
Wildfire Wildfire
Landslide Debris Flow
Drought Drought
Heat Wave Severe Weather -Extreme Heat
Tsunami Tsunami
Tornado Severe Weather – Wind, Tornado
Strong Wind Severe Weather – Wind, Tornado
Table 1.10: NRI Hazards and Marin County OA MJHMP Hazards Source: FEMA Na�onal Risk Index 2023
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Multi-Jurisdictional Hazard Mitigation Plan
58 The National Risk Index leverages available source data for Expected Annual Loss (EAL) due to these 18 hazard types, Social Vulnerability, and Community Resilience to develop a baseline relative risk measurement for each United States county and Census tract. These measurements are calculated using average past conditions, but they cannot be used to predict future outcomes for a community. The National Risk Index is intended to fill gaps in available data and analyses to better inform federal, state, local, tribal, and territorial decision makers as they develop risk reduction strategies.

Calculating the Risk Index
Risk Index scores are calculated using an equation that combines scores for Expected Annual Loss due to natural hazards, Social Vulnerability and Community Resilience:

Risk Index = Expected Annual Loss (EAL) × Social Vulnerability ÷ Community Resilience Hazard Type Risk Index
Hazard type Risk Index scores are calculated using data for only a single hazard type, and reflect a community's Expected Annual Loss value, community risk factors, and the adjustment factor used to calculate the risk value. Table 1.10 illustrates the NRI Hazard Type Risk Index for Marin County.

Calculating Expected Annual Loss
Expected Annual Loss scores are calculated using an equation that combines values for exposure, annualized frequency, and historic loss ratios for 18 hazard types:

Expected Annual Loss = Exposure × Annualized Frequency × Historic Loss Ratio Community Risk Factor
The CRF is a scaling factor that incorporates Social Vulnerability and Community Resilience in the National Risk Index to arrive at a distribution of risk values that better reflects the impacts communities experience from natural hazards. By design, the CRF ensures that higher Social Vulnerability and lower Community Resilience, relative to all other communities at the same level (county or Census tract), result in higher Risk Index values for a given level of EAL.

To generate a CRF value for a community, its Social Vulnerability value is divided by its Community Resilience value, and this ratio is mapped to a triangular distribution with minimum

0.5, mode 1, and maximum 2 (see Equation 3).

Table 1.11 illustrates the NRI Hazard Type Risk Index for Marin County. l ~<;>U·N· TY OF
~ ARIN
a
~
Equation 3: CRF Equation
. . ( Social Vulnerability ) Community Risk Factor = f C . R T ommumty esi ience where f(-)-> ,(a= 0.5,b = 2,c = 1)
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
59 Table 1.11: NRI Hazard Type Risk Index for Marin County Hazard Type EAL Value Social
Vulnerability
Community
Resilience CRF Risk Value Score
Earthquake $85,368,321 Relatively
Low Very High 1.02 $86,293,309 98.7
Riverine
Flooding $28,231,043 Relatively Low Very High 1.02 $30,230,864 99 Coastal
Flooding $3,801,318 Relatively Low Very High 1.02 $4,161,749 89.5 Wildfire $2,436,548 Relatively
Low Very High 1.02 $2,205,455 91.8
Landslide $770,102 Relatively
Low Very High 1.02 $736,098 98.3
Drought $780,052 Relatively
Low Very High 1.02 $645,893 89.7
Heat Wave $371,643 Relatively
Low Very High 1.02 $375,597 74.3
Tornado $220,118 Rela�vely
Low Very High 1.02 $213,534 19.4
Tsunami $34,530 Relatively
Low Very High 1.02 $26,783 62.2
Strong Wind $13,888 Relatively
Low Very High 1.02 $13,688 4.4
Table 1.11: NRI Hazard Type Risk Index for Marin County Source: FEMA Na�onal Risk Index 2023
Table 1.12 illustrates the NRI Social Vulnerability & Community Resilience Risk Index for the top 20 highest risk communities within Marin County.

Table 1.12: NRI Highest-Risk Communities in Marin County Rank Community Jurisdiction EAL Value Social
Vulnerability
Community
Resilience CRF Risk Value Score
1 Census tract
06041112202 San Rafael $8,782,817 Relatively High Very High 1.38 $12,103,320 99.66 2 Census tract
06041112100
San Rafael $4,881,418 Relatively
High Very High 1.22 $5,938,596 98.31
3 Census tract
06041106001
San Rafael $3,848,195 Very High Very High 1.4 $5,369,158 97.88 4 Census tract
06041121200
Corte
Madera $4,505,215 Relatively Moderate Very High 1.13 $5,078,528 97.58 5 Census tract
06041103200 Novato $3,649,854 Relatively High Very High 1.37 $5,016,752 97.53 6 Census tract
06041112204 San Rafael $2,686,687 Very High Very High 1.59 $4,274,415 96.57 7 Census tract
06041102203 Novato $2,920,534 Relatively High Very High 1.35 $3,955,365 95.97 8 Census tract
06041106002
County
(Santa
Venetia)
$3,505,637 Relatively
Moderate Very High 1.1 $3,843,988 95.73
9 Census tract
06041119201 Larkspur $2,453,803 Relatively High Very High 1.27 $3,113,358 93.73 10 Census tract
06041119100
County
(Kentfield) $3,547,224 Very Low Very High 0.86 $3,034,275 93.41 11 Census tract
06041110100 San Rafael $2,551,896 Relatively Moderate Very High 1.11 $2,831,154 92.59 l ~<;>U·N· TY OF
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60 12 Census tract
06041117000
San
Anselmo $2,891,493 Relatively Low Very High 0.96 $2,766,643 92.3 13 Census tract
06041120002 Larkspur $2,825,836 Relatively Low Very High 0.95 $2,698,515 91.98 14 Census tract
06041133000 County $2,925,471 Relatively Low Very High 0.93 $2,714,057 92.05 15 Census tract
06041104102 Novato $2,251,767 Relatively High Very High 1.19 $2,685,083 91.89 16 Census tract
06041111001 San Rafael $2,462,117 Relatively Moderate Very High 1.07 $2,629,315 91.59 17 Census tract
06041121100
Corte
Madera $3,328,198 Very Low Very High 0.78 $2,588,404 91.38 18 Census tract
06041101200 Novato $2,847,863 Relatively Low Very High 0.88 $2,518,616 90.98 19 Census tract
06041108202 San Rafael $1,698,202 Very High Very High 1.4 $2,380,050 90.12 20 Census tract
06041104300
County (Bel
Marin Keys) $3,514,869 Very Low Very High 0.65 $2,287,081 89.47 Table 1.12: NRI Highest-Risk Communities in Marin County Source: FEMA Na�onal Risk Index 2023

1.5.5 SOCIAL VULNERABILITY AND RISK IN MARIN COUNTY
Link to Na�onal Risk Index
Social vulnerability is an important factor to consider during all functions of emergency management (mitigation, preparedness, response, recovery). When we work to mitigate hazards, we are alleviating the stress a hazard may put on a community. If a community is considered more socially vulnerable, the residents’ risk of disaster is higher, therefore, to reduce risk, considering the social makeup of a community is critical. Many methodologies exist to aggregate census data into one simple number to represent social vulnerability; this should be seen as macro, supplemental data. It is also important to have input from all sections of a planning area that can truly represent the experiences, needs, and lived risk in a community.

Metrics that create social vulnerability indices are meaningful to planning as they can signify a community’s capacity to mitigate, prepare for, respond to, and recover from the impacts of a disaster. From mitigating your living environment to resist impacts, preparing a backup food source, to understanding alert and warning messages, and having insurance or obtaining government assistance after a disaster, all require time, financial resources, education and language abilities that not all of our community members have the luxury of. This is why looking at social vulnerability metrics is important to understanding where the needs are in Marin.

For a high-level view to assess what communities in Marin are most at risk, the Marin County OA MJHMP chose to use the National Risk Index as it combines Expected Annual Loss (a measurement of expected economic loss), the CDC’s Social Vulnerability Index (2020), and the Community Resilience Index (CRI) to rank census tracts’ risk across the nation. With the three metrics aggregated, we can understand, from a high level, what areas of Marin may be the most holistically impacted by hazards. The most recent version of the National Risk Index was released in 2023, making it one of the most up to date ways to assess hazard impact and social vulnerability. Furthermore, it is the best source for information for macro level assessments. l ~<;>U·N· TY OF
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61 Expected Annual Loss (EAL) is calculated using hazard exposure, annual frequency of a hazard and historic loss. As a whole, EAL is an attempt to represent average yearly economic loss resulting from natural hazards (i.e., losses to buildings, population, and agriculture). The county as whole is ranked as “relatively high” EAL; ranking in the 96-percentile in the nation. Census tracts are also categorized, see Figure 1.24.

Three census tracts in Marin, all in San Rafael, rank “Very High” for EAL. Most of the county is categorized as either “Relatively High” or “Relatively Moderate”, four classify as “Relatively Low”. One is assigned “Very Low” EAL, this is the Marin City census tract; an unincorporated community in southern Marin that has historically been underserved (highlighted with red outline in the following maps). The main contributing factor to this result is the perceived limited economic value and unrecorded economic losses due to disasters in Marin City. The economic impact of disasters in underserved communities has been historically under- or unreported, explaining how a commonly flooded area, such as Marin City, may be reflected as “Very Low” on the EAL. Disruptive flooding in Marin City happens during any significant rain, and this has been happening for over 80 years (KQED, 2022). Lack of reporting may be two-fold; limited connection to government and social capacity of residents to report. Impacts of frequent flooding in Marin City damages residents’ cars and homes, roadways, other structures; it puts people at risk of being swept away in flood water, can expose them to contaminated water; it cuts off residents’ ability to leave for work or errands and return home. All of this damage has direct economic consequences for the residents of Marin City and the County. Despite being classified as “Low Risk” on the EAL, the County of Marin acknowledges the impact disasters have on Marin City.

In Figures 1.19, 1.20, and 1.21 the US Census Tracts are outlined in white, and color coded as indicated on the map legend. The City and Town Jurisdictions are outlined in black while the unincorporated area of Marin City is outlined in blue.
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62 Figure 1.19: Marin County NRI – Expected Annual Loss Source: FEMA Na�onal Risk Index 2023
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0 10 --c=::::J ____ Miles
Marin County OEM / Woody Baker-Cohn
email: [email protected]
Date Printed: 09/13/23
County of Marin, California State Parks, Esri, HERE, Garmin, SafeGraph, FAO, METI/NASA, USGS, Bureau of Land Management, EPA, NPS !Jan
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63 Figure 1.20: Marin County National Risk Index Map
Source: FEMA Na�onal Risk Index 2023
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- Very High
- Relatively High
Relatively Moderate
- Relatively Low
- Very Low
- Insufficient Data
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National Risk Index •
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email: [email protected]
Date Printed: 09/13/23
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County of Marin, California State Parks, Esri, HERE, Garmin, SafeGraph, FAO, METI/NASA, USGS, Bureau of Land Management, EPA, NPS 2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
64 When looking at the CDC’s SVI (see Figure 1.21), we see the most socially vulnerable residents reside in parts of Novato, parts of San Rafael, including in and around the Canal District, the Greenbrae neighborhood of Larkspur, and the unincorporated areas of Marin City and Santa Venetia. This aligns with what the County knows about Marin residents. However, discrepancy lies in the western, more rural area of the county. West Marin is comprised of seven villages, and other populated areas, that are distanced from the centralized resources in the eastern part of the county. At three local elementary school in West Marin (2022-2023 school year), the percentage of students eligible for free and reduced lunch program are, 62%, 41%, and 52%, a reflection of the financial capacity of local families. West Marin is home to many farms that may employ and house underrecognized workers that may not have taken part in a census survey, which is the basis for the SVI is calculation. In the fourth quarter of FY 2021/22 the bus routes traveling to West Marin (Rural Routes) were the only service category to have increased in ridership since pre-COVID (increase 0.1%; Marin Transit, 2022) showing the reliance of West Marin residents on public transportation; however, this data continues to adjust based upon the increase in alternate methods of mass transportation. Considering this, the County of Marin acknowledges that unique social factors in West Marin require different approaches than other parts of the County.

Looking to the community resilience index (CRI) results, the data is only calculated at the county-level and compared across the nation. As a whole, Marin County is considered to have a “very high” ability to prepare for anticipated natural hazards, adapt to changing conditions, and withstand and recover rapidly from disruptions when compared to the rest of the U.S.

Unfortunately, this metric does not give us the distinct experiences of the diverse communities across Marin.

When the Estimated Annual Loss Index (EAL) , Social Vulnerability Index (SVI), and Community Resilience Index are aggregated as one, final results of the National Risk Index show Marin County as a whole to have “Relatively High” risk, this is due to the financial implications a disaster may have on the county. When broken out by census tract, five tracts are in the highest category (“Very High Risk”), this matches generally with the same tracts that are ranked in as higher social vulnerability; parts of Novato, parts of San Rafael, including in and around the Canal District, the Greenbrae neighborhood of Larkspur, and unincorporated areas of Santa Venetia.

However, Marin City is ranked as “Very Low” risk for the National Risk Index. Previous discussion highlighted why the Expected Annual Loss was low, but further discussion is required. As a County, we know Marin City should not be classified as “Very Low” on the NRI.

Marin City residents, for example, only have one way in and out of their community and this road floods frequently, making it unsafe to cross and leave the community for work, school, medical resources. Additionally, there is only one “grocery” store, a Target, in Marin City. Both of these elements contribute to the vulnerability of residents as they may be unable to leave or return home and have limited access to groceries, relying on a single store’s supply chain. At the local elementary school in Marin City, 47% of students are eligible for free and reduced-price meals (2022 – 2023 school year), a reflection of the financial capacity of local families. All this means, we can expect the social and built capacity of Marin City to be limited. l ~<;>U·N· TY OF
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65 Figure 1.21: Marin County CDC Social Vulnerability Index Map Source: FEMA Na�onal Risk Index 2023
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--c:::::::::i---• Miles
Marin County OEM / Woody Baker-Cohn
email: [email protected]
Date Printed: 09/13/23
County of Marin, California State Parks, Esri, HERE, Garmin, SafeGraph, FAO, METJ/NASA, USGS, Bureau of Land Management, EPA, NPS 12 121
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Wildlife Area
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66 The County of Marin has several outreach programs, specifically designed to reach and include traditionally underserved and underrepresented communities, including, Health and Human Services’ Community Response Teams, Office of Equity’s Participatory Budgeting program, and a community-created Race and Equity Plan. To receive feedback on the Marin County OA MJHMP, bilingual outreach was conducted through the Community Response Teams, which are led by local non-profits, representing four zones of Marin County. Local non-profits are selected for grant funding to be the Community Response Team lead. Additionally, County representatives went on the West Marin radio station, KWMR, to reach rural populations.

While decision makers in Marin acknowledge that aggregate hazard and social vulnerability data can be informative for understanding what resources can be most beneficial to what area of the county, it is acknowledged that this data is not considered to be fully representative of Marin’s communities. It is critical to have a diversity of resident voices to represent a community’s needs and experiences. Furthermore, this data does not consider trends and anticipated changes. Climate change continues to increase risk in our communities, with heat, sea level rise, increased flood events, longer droughts, and more powerful wildfires. Additionally, Marin’s population is aging and growing to be less-White which will require the continued development of planning and response approaches to meet the needs of all residents.

1.5.6 ECONOMICS
Marin County has a strong economic base which has changed significantly over the last century. The county’s economy was dominated by agriculture in the early part of its history.

However, in recent years, Marin’s economy has seen increasing job growth in technologyrelated fields such as biotechnology, computer software, and multimedia. With several attractions including beaches and parks in Marin, tourism is important to Marin County’s economy.

The Marin County resident workforce is predominantly white collar. Over 92% of the County’s residents age 25 or older have at least a high school diploma, compared with about 81% statewide; over 54% in this same age group have a bachelor’s degree. These higher-thanaverage educational levels directly correlate with a low poverty rate of 7.5%, compared with

15.3% statewide. The County’s largest employers include the County government, State Corrections Department, Marin General Hospital, Kaiser Permanente, Fireman’s Fund Insurance, Lucas Licensing, Fair Isaac Corporation, and College of Marin. Over half the working population is employed in professional, management, or financial business occupations, but most of these workers are employed outside the County in urban centers such as San Francisco and Oakland. The services, construction, and transportation industries combined employ less than a quarter of the resident population but are major employment sectors within the County. According to the Marin Economic Commission, service industries based in Marin are a major source of employment for residents of surrounding counties who commute to Marin. The agricultural sector also retains a strong cultural and historical presence. l ~<;>U·N· TY OF
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67 Table 1.13: Marin County Civilian Employed Population 16 Years and Over Industry Estimated
Employment
Percent
Civilian employed population 16 years and over 18,676,721 100 Agriculture, forestry, fishing and hunting, and mining 394,881 2.1 Construction 1,235,586 6.6
Manufacturing 1,676,715 9.0
Wholesale trade 501,378 2.7
Retail trade 1,919,513 10.3
Transportation and warehousing, and utilities 1,071,181 5.7 Information 539,683 2.9
Finance and insurance, and real estate and rental and
leasing 1,107,961 5.9
Professional, scientific, and management, and
administrative and waste management services 2,612,859 14.0 Educational services, and health care and social
assistance 3,990,094 21.4
Arts, entertainment, and recreation, and accommodation
and food services 1,835,141 9.8
Other services, except public administration 927,253 5.0 Public administration 864,476 4.6
Table 1.13: Marin County Civilian Employed Population 16 Years and Over Source: US Census Bureau American Community Survey 2021 Estimates

1.6 EXISTING AUTHORITIES, POLICIES, PROGRAMS, AND RESOURCES The jurisdictions represented in this plan are authorized by state law and qualify as separate governments. With the exception of the special districts, the jurisdictions all have a general plan that regulates current and future development through zoning based on described hazards.

State law requires all California Cities and Counties to adopt general plans which include seven mandatory chapters: Land Use, Circulation, Housing, Conservation, Open Space, Noise and Safety. In addition to General Plans, each jurisdiction has an Emergency Action (or Operations) Plan and a Climate Action Plan.

The jurisdictions each have a municipal code of ordinances to establish the minimum requirements to safeguard the public health, safety, and general welfare through structural strength, means of egress facilities, stability, access to persons with disabilities, sanitation, adequate lighting and ventilation and energy conservation, and safety to life and property from fire and other hazards attributed to the built environment; to regulate and control the demolition of all buildings and structures, and for related purposes.

The jurisdictions all have planning departments that review proposed developments and new uses for conformance with policies plans and regulations and are served by law enforcement and fire departments.
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68 Resources vary greatly between jurisdictions according to general funds and staff, which are roughly proportionate to population size and commercial activity. Regardless of size, mitigation actions tend to leverage federal, state, and regional financial resources heavily in the form of matching grants.

With the protection of plans and codes secured through statute, the expansion and improvement of policies and programs are dependent on the allocation of limited financial resources towards staff administration and implementation. An efficient means of improving and expanding programs is through shared resources. The many small jurisdictions in the County often do not have the resources to successfully accomplish the many requirements placed upon them, but through economies of scale they can provide better public service. One example of that is this Multi-Jurisdictional Local Hazard Mitigation Plan, which for most jurisdictions represents a much-needed update. For two of these jurisdictions this will be a new plan. See Section 4.0: Mitigation Strategy for further existing authorities, policies, programs, and resources in Marin County.

1.7 NEW ITEMS FOR THE 2023 MJHMP
The 2018 Marin County OA MJHMP contained a detailed description of the planning process, a risk assessment of identified hazards for the Marin County planning area, and an overall mitigation strategy for reducing risk and vulnerability from these hazards. Since approval of the plan by FEMA, progress has been made by the Marin County OA on implementation of the mitigation strategy. As part of this 2023 MJHMP Update, a thorough review and update of the 2018 plan was conducted to ensure that this update reflects current community conditions and priorities in order to realign the overall mitigation strategy for the next five-year planning period.

This MJHMP update involved a comprehensive review and update of each section of the 2018 plan and includes an assessment of the success of the participating communities in evaluating, monitoring and implementing the mitigation strategy outlined in the initial plan. Only the information and data still valid from the 2018 plan was carried forward as applicable into this MJHMP update.

Table 1.14: Marin County OA MJHMP Participants 2018 and 2023 2018 Plan Participants 2023 Plan Participants
1 Marin County Marin County
2 City of Belvedere City of Belvedere
3 Town of Corte Madera Bolinas Community Public Utility District 4 City of Fairfax Town of Corte Madera
5 City of Larkspur Sanitary District No. 2
6 City of Mill Valley City of Fairfax
7 City of Novato City of Larkspur
8 Town of Ross Las Gallinas Valley Sanitary District
9 City of San Rafael City of Mill Valley
10 Town of San Anselmo North Marin Water District
11 City of Sausalito City of Novato
12 City of Tiburon Town of Ross
13 North Marin Water District Town of San Anselmo
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69 14 Marin County Flood Control and Water
Conservation District City of San Rafael
15 City of Sausalito
16 Southern Marin Fire Department
17 City of Tiburon
Table 1.14: Marin County OA MJHMP Participants 2018 and 2023 Also to be noted, the 2023 MJHMP update identifies key requirements for updating future plans:
• Considers changes in vulnerability due to action implementation; • Documents success stories where mitigation efforts have proven effective; • Documents areas where mitigation actions were not effective; • Documents any new hazards that may arise or were previously overlooked; • Incorporates new data or studies on hazards and risks; • Incorporates new capabilities or changes in capabilities; • Incorporates growth and development-related changes to inventories; and • Incorporates new action recommendations or changes in action prioritization.

These requirements and others as detailed throughout this plan were also addressed during this plan update process.

As part of its 2023 Mitigation Strategy, Marin County and participating jurisdictions recognized that certain data, if available, would enhance the analyses presented in the risk assessment and utilized in the development of the mitigation strategy. New information and analyses contained throughout this plan update includes the following:
• A new assessment of hazards affecting the OA was completed resulting in the inclusion of additional hazards including climate change.
• An entire rework of the risk assessment for each identified hazard, including reworking the hazard profile and adding new hazard event occurrences; redoing the entire vulnerability analysis to add items identified below and updating the vulnerability assessment based on more recent hazard data as well as using the most current parcel and assessor data for the existing built environment.
• An update of the flood hazard analysis utilizing the 2017 DFIRMs to include an updated analysis of the 100-year flood, an analysis of the 500-year flood, and an enhanced analysis of the localized/stormwater flooding problems affecting the planning area. • Development of an updated critical facility definition and a GIS mapping effort of critical facilities for the planning area.
• Greater analysis was performed on the wildfire hazard utilizing CalFire, Fire Severity GIS data and updated CalFire fire hazard severity maps from 2022. • An enhanced vulnerability assessment which added an analysis of populations vulnerable to two priority hazards: flood and wildfire. • An enhanced vulnerability assessment which added an analysis of future development in the planning area and specific to each of the mapped hazards. • Incorporation and analysis of the new 2020 Census data was utilized for this MHHMP update.
• An analysis of the incorporation of the 2023 MJHMP into other planning mechanisms in the Marin County OA was performed.
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70 Also, as required by the FEMA 2008 Local Multi-Hazard Mitigation Planning Guidance, the MJHMP an analysis of each jurisdictions' ongoing and continued compliance with the NFIP.

1.7.1 REVISION OF THE HAZARD IDENTIFICATION AND RISK ASSESSMENT This revised 2023 MJHMP now includes climate change in addition to the natural hazards facing our community. The risk assessment for each identified natural hazard was updated as determined by the Steering Committee. This included a reformulation of the hazard profiles and additions of new hazard occurrences. The vulnerability assessment was updated based on more recent hazard data.

1.7.2 CLIMATE CHANGE
According to the California Natural Resource Agency (CNRA), climate change is already affecting California and is projected to continue to do so well into the foreseeable future.

1.7.3 PROGRESS ON LOCAL MITIGATION EFFORTS
There was success in the implementation of the mitigation actions as defined in the 2018 planning process, so the Steering Committee reassessed the need for those actions, looked at new actions and provided an explanation as to the methodology.

Details of 2018 projects are included in section 4.7 but multiple projects have had success, including completion and ongoing of retrofitting of critical county-owned buildings (project #2), completed construction of a flood basin on Fairfax Creek (project #3), and obtaining a grant to design the McInnis Marsh Restoration Project (project #23). The City of Mill Valley adopted a soft-story wood frame retrofit ordinance, updated the fire code, implemented updated vegetation management requirements, and has emergency generators available for all critical city facilities.

1.8 PLAN ORGANIZATION AND STRUCTURE
The MJHMP has been developed using the latest guidance documents from the FEMA as listed:
• Local Mitigation Plan Review Guide dated October 11, 2011 and is structured similar to their Plan Review Tool.
• Local Mitigation Planning Policy Guide, April 19, 2023 • State Mitigation Planning Key Topics Bulletin: Mitigation Capabilities, November 2022
• State Mitigation Planning Key Topics Bulletin: Mitigation Strategy, October 2022 l ~<;>U·N· TY OF
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71 • State Mitigation Planning Key Topics Bulletins: Planning Process, October 2022 • State Mitigation Planning Key Topics Bulletin: Risk Assessment, October 2022 The Marin County OA Multi-Hazard Mitigation Plan is organized as follows:
• Section 1.0: Introduction
• Section 2.0: Planning Process
• Section 3.0: Hazard Identification and Risk Assessment • Section 4.0 Mitigation Strategy
• Section 5.0: Plan Review, Evaluation, and Implementation • Appendix A: Adoption Letters
• Appendix B: Documentation of the Planning Process
• Appendix C: Public Outreach Survey
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72 SECTION 2.0: PLANNING PROCESS
Local governments have the responsibility to protect the health, safety, and welfare of their community members. Proactive mitigation policies and actions reduce risk and create safer, more disaster-resilient communities. Mitigation is an investment in Marin’s safety and sustainability. Consider the critical importance of mitigation to:
• Reducing the devastating impacts that disasters can have on community members, workers, and businesses in Marin.
• Public safety and preventing loss of life and injury. • Reducing harm to existing and future development.
• Preventing damage to a community’s unique economic, cultural, and environmental assets.
• Minimizing operational downtime and accelerating recovery of communities, government and businesses after disasters.
• Reducing the cost of disaster response and recovery and the exposure to risk for first responders.
• Helping accomplish other community objectives, such as leveraging capital improvements, infrastructure protection, open space preservation, and economic resiliency.

The purpose of mitigation planning is to identify local policies and potential actions that can be implemented over the long term to reduce risk and future losses from hazards. Mitigation policies and actions are identified based on a hazard risk assessment and the participation of a wide range of stakeholders and the public in the planning process. Benefits of mitigation planning include:
• Identifying actions for risk reduction that are agreed upon by stakeholders and the public.
• Focusing resources on the greatest risks and vulnerabilities. • Building partnerships by involving residents and visitors, organizations, and businesses. • Increasing education and awareness of threats and hazards, as well as their risks. • Communicating priorities to State and Federal officials. 44 CFR Requirement §201.6(b): In order to develop a more comprehensive approach to reducing the effects of natural disasters, the planning process shall include:
1) An opportunity for the public to comment on the plan during the drafting stage and prior to plan approval;
2) An opportunity for neighboring communities, local and regional agencies involved in hazard mitigation activities, and agencies that have the authority to regulate development, as well as businesses, academia and other private and non-profit interests to be involved in the planning process; and
3) Review and incorporation, if appropriate, of existing plans, studies, reports, and technical information.
44 CFR Requirement §201.6(c)(1): [The plan shall document] the planning process used to develop the plan, including how it was prepared, who was involved in the process, and how the public was involved.
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73 • Aligning risk reduction with other community objectives.

2.1 PLANNING APPROACH
The initial phase of a planning approach is to identify risk associated with threats and hazards and identify projects to reduce that risk. The Marin Operational Area understands its hazards, vulnerabilities, and risks and is working together and with the public, to develop strategies, policies, and actions necessary to reduce risk and protect residents and visitors. Marin’s hazard mitigation planning process engages the whole community and follows State and Federal planning guidance consistent with the requirements of the Stafford Act and the Federal Code of Federal Regulations (44 CFR Part 201).

The six elements of hazard mitigation planning include:

1. Introduction and Community Overview

2. Planning Process

3. Hazard Identification and Risk Assessment

4. Development of The Mitigation Strategy

5. Plan Review, Evaluation, And Implementation

6. Plan Adoption
This 2023 Marin County OA MJHMP is a comprehensive update of the 2018 Marin County OA MJHMP, which covered County of Marin the Cities of Belvedere, Larkspur, Mill Valley, Novato, San Rafael and Sausalito; the Towns of Corte Madera, Fairfax, Ross, San Anselmo and Tiburon; and the special districts of Bolinas Community Public Utility District, Las Gallinas Valley Sanitary District, North Marin Water District, Sanitary District No. 2, and Southern Marin Fire Protection District. FEMA approved the 2018 plan on December 27, 2018, and the plan is expiring on December 27, 2023. The current update meets federal requirements for updating hazard mitigation plans on a five-year cycle. It represents the third iteration of the Marin County Hazard Mitigation Plan, which was initially developed as a plan in 2013. Eighty-three planning partners have participated in the 2023 update, as listed in Table 2.2 and Table 2.4.

The 2023 Marin County OA MJHMP identifies the process that Marin County will use to develop their roles and responsibilities in hazard mitigation planning. The 2023 Hazard Mitigation Plan is the principal guide for Marin County to identify hazards and mitigation projects that will enhance the resilience of Marin communities from natural disasters.

The planning team used the Federal Emergency Management Agency (FEMA) Local Mitigation Plan Review Guide to ensure the Marin County OA MJHMP includes all necessary components.

The process followed to develop the 2023 Marin County OA MJHMP had the following primary objectives:
• Secure grant funding and select a consultant.
• Establish a planning partnership.
• Define the planning area and jurisdiction.
• Establish a steering committee and planning team.
• Coordinate with stakeholders and agencies.
• Review existing programs.
• Engage the public.
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74 These objectives are discussed in the following sections.

2.2 GRANT FUNDING AND CONSULTANT SELECTION
This planning effort was supplemented by a FEMA Hazard Mitigation Assistance grant in fiscal year 2019. Marin County OEM was the sub-applicant agent for the grant. It covered 75 percent of the cost for development of this plan; the County and planning partners covered the balance through in-kind contributions.

In November 2022, Marin County contracted for consultant services to assist in the update to their 2018 Multi-Jurisdictional Hazard Mitigation Plan. After a comprehensive review process, Preparative Consulting was selected to partner with representatives from Marin County and its participating jurisdictions to complete a comprehensive update of the 2018 Marin County OA MJHMP

2.3 ESTABLISH A PLANNING PARTNERSHIP
As the lead organization, Marin County Fire Department Office of Emergency Management (OEM) established a Steering Committee with representatives from the County, Cities, Towns, and special districts. These participants were engaged to lead the planning process based on the contribution and input from relevant stakeholders and the public. Representatives should have the authority and knowledge to identify and commit resources during the planning process and have subject matter knowledge on local communities, hazards, and risks.

The majority of Marin County is unincorporated sparsely populated rural and protected lands.

Most of the 262,000 county population is consolidated into the Eastern portion of the county.

The County of Marin has a unique populated distribution where the participating planning jurisdictions and district’s planning areas are located in an area of the county with similar climate, similar topography, and are exposed to many of the same hazards. Only three jurisdictions, Larkspur, Ross, and San Anselmo, are not coastal jurisdictions and are not impacted by Tsunami or Sea Level Rise.

The Marin County OA MJHMP Steering Committee and broader Planning Team approached the development of the Marin County OA MJHMP and the associated jurisdictional and district profiles from a coordinated and collaborative planning and public engagement unity of effort.

The Steering Committee felt a unified effort, led by the Marin County OEM, would be the most effective approach for this planning process. This approach allowed the small jurisdictions and districts with limited staffing and resources to take advantage of the combined efforts of the County and other jurisdictions to reach a broader segment of each of their populations and do so in a way to ensure greater equity and inclusion of the public in this planning process.

Extensive and coordinated public outreach was done involving all participating jurisdictions and districts with an eye towards equity, inclusion, openness, accessibility, and ensuring they meet the population where they live, work, or recreate to provide the public convenience of access and ease of participation in this planning process.

Participating jurisdictions worked through multiple sessions and independently on:
• Facilitation of the planning process, including multi-agency collaboration and partnering. • Identification of the primary local stakeholders – formation of the Marin County OA hazard mitigation Planning Team and hazard mitigation Steering Committee. • Review of the 2018 Marin County OA MJHMP.
• Establishment of updated planning goals and objectives. l ~<;>U·N· TY OF
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75 • Establishment of jurisdiction-specific hazard mitigation work groups to facilitate internal planning activities.
• Organization of jurisdiction/agency-specific hazard mitigation Working Groups. • Revision of jurisdictional demographic and organizational data, and reformatting of information presentation.
• Identification and refined assessment of real or potential hazards and threat conditions. • Development of prioritized hazard mitigation strategies and projects, keyed to identified hazards.
• Compliance with the Disaster Mitigation Act requirements as established by federal regulations and following FEMA’s planning guidance.
• Prioritization of equity and engagement of the whole community with a focus on engaging hard-to-reach populations and providing translation and interpretation services in our public outreach and input process.
• Production of the draft and final plan documents; and • Coordination with the California Office of Emergency Services (Cal OES) and FEMA Region IX plan reviews.

2.4 DEFINE THE PLANNING AREA AND PARTICIPATING JURISDICTIONS The planning area and participating jurisdictions and organizations were defined to consist of unincorporated Marin County, the Cities of Belvedere, Larkspur, Mill Valley, Novato, San Rafael and Sausalito; the towns of Corte Madera, Fairfax, Ross, San Anselmo and Tiburon; the Bolinas Public Utility District, the Las Gallinas Valley Sanitary District, the Sanitary District #2, the Southern Marin Fire Protection District, and the North Marin Water District. All participating jurisdictions are within the geographical boundary of Marin County and 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 3, along with a description of planning area characteristics.

This unity of effort approach allowed the Steering Committee to establish a more robust Planning Team representing local, countywide, regional, state, and federal stakeholders servicing the Marin County planning area. These stakeholders were in a unique position to provide informed and specific information and recommendations on hazard mitigation goals and actions, as well as population needs and social vulnerability for each of the jurisdictional and district planning areas. This united effort allowed the planning team to attend fewer meetings than they would have been required to attend if they were required to attend separate meetings for each participating jurisdiction and district. The reduced number of meetings allowed the planning team the opportunity and time to provide more detailed and thoughtful contributions to the planning effort.

Each jurisdiction wishing to join the planning partnership/Steering Committee 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, understanding of expectations, and commitment to adopt the approved Hazard Mitigation plan by their governing body. These expectations are detailed in section 2.5 STEERING COMMITTEE.

The jurisdictions participating in the 2023 Marin County OA MJHMP were represented by:
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76 Table 2.1: 2023 MJHMP Participating Jurisdictions
Jurisdiction Representative Title
1 Marin County Hannah Tarling Emergency Management Coordinator 2 Marin County Chris Reilly OEM Project Manager
3 City of Belvedere Irene Borba Director of Planning
4 City of Larkspur Loren Umbertis Public Works Director 5 City of Mill Valley Patrick Kelly Director of Planning and Building 6 City of Novato Dave Jeffries Consultant/JPSC
7 City of San Rafael Quinn Gardner Deputy Emergency Services Coord. 8 City of Sausalito Kevin McGowan Director of Public Works 9 Town of Corte Madera and
Sanitary District #2 RJ Suokko Director of Public Works 10 Town of Fairfax Loren Umbertis Public Works Director 11 Town of Ross Richard Simonitch Public Works Director 12 Town of San Anselmo Sean Condry Public Works & Building Director 13 Town of Tiburon Sam Bonifacio Assistant Planner
14 Bolinas Community Public
Utility District
Jennifer Blackman General Manager
15 Las Gallinas Valley Sanitary
District Dale McDonald Administrative Services Manager
16 North Marin Water District Eric Miller Asst. General Manager 17 Southern Marin Fire District Marshall Nau Fire Marshall/South Marin Fire Dist.

Table 2.1: 2023 Marin OA MJHMP Participating Jurisdictions

2.5 STEERING COMMITTEE
The Steering Committee led the planning process based on the contribution and input from the whole community stakeholders who identified the community’s concerns, values, and priorities.

Preparative Consulting coordinated and facilitated the 2023 Marin County OA MJHMP update with the assistance of the Marin County Office of Emergency Management and acted as the central point of contact for all partnering jurisdictions and organizations. Preparative Consulting developed the draft plan in conjunction with and at the direction of the hazard mitigation Steering Committee members and served as a liaison between Marin County and the State regarding plan revision.

Table 2.2: 2023 MJHMP Steering Committee Members
No. Agency Point of Contact Title
1 Belvedere Laurie Nilsen Emergency Services Coordinator 2 Belvedere Rebecca Markwick Planning Director
3 Belvedere Samie Malakiman Associate Planner
4 Bolinas Com. PUD Jennifer Blackman General Manager
5 Bolinas Fire Protection Dist Stephen Marcotte Assistant Fire Chief 6 Central Marin Fire District Matt Cobb Battalion Chief/Fire 7 Central Marin Fire District Ezra Colman Battalion Chief/Fire 8 Central Marin Fire District Rubin Martin Fire Chief
9 Corte Madera RJ Suokko Director of Public Works
10 Corte Madera Chris Good Senior Civil Engineer
11 Sanitary District No. 2 RJ Suokko Director of Public Works 12 Fairfax Loren Umbertis Public Works Director
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77 13 Fairfax Mark Lockaby Building Official
14 Larkspur Dan Schwarz City Manager
15 Larkspur Julian Skinner Public Works Director/ City Engineer 16 Larkspur Robert Quinn Public Works Superintendent
17 Las Gallinas Valley
Sanitary District Dale McDonald Administrative Services Mgr. 18 Las Gallinas Valley
Sanitary District Greg Pease Safety Manager
19 Marin County Steven Torrence Director of Emergency Management 20 Marin County Chris Reilly OEM Manager
21 Marin County Woody Baker-Cohn Senior Emergency Management Coordinator
22 Marin County Leslie Lacko Community Development Agency 23 Marin County Hannah Lee Senior Civil Engineer
24 Marin County Felix Meneau Project Mgr./ FCWCD
25 Marin County Julia Elkin Department of Public Works
26 Marin County Beb Skye Department of Public Works
27 Marin County Scott Alber Fire
28 Marin County Lisa Santora Deputy Public Health Officer, Marin Health & Human Services
29 Marin County Kathleen Koblick Marin Health & Human Services 30 Marin County Amber Davis Public Health Preparedness
31 Mill Valley Patrick Kelly Director of Planning & Building Department 32 Mill Valley Ahmed A Aly Engineering Project Manager
33 Mill Valley Jared Barrilleaux Deputy Director of Engineering 34 Mill Valley Daisy Allen Senior Planner
35 Southern Marin Fire District Tom Welch Deputy Chief/South Marin Fire Dist. 36 Southern Marin Fire District Marshall Nau Fire Marshall/South Marin Fire Dist. 37 North Marin Water District Eric Miller Asst. General Manager 38 North Marin Water District Tim Fuette Senior Engineer 39 Novato David Dammuller Engineering Services Mgr.
40 Novato Dave Jeffries Consultant/JPSC
41 Ross Richard Simonitch Public Works Director
42 San Anselmo Sean Condry Public Works & Building Director 43 San Anselmo Erica Freeman Building Official
44 San Anselmo Scott Schneider Asst. PW Director
45 San Rafael Quinn Gardner Deputy Emergency Services Coord. 46 San Rafael Cory Bytof Sustainability
47 San Rafael Joanna Kwok Senior Civil Engineer
48 San Rafael Kate Hagemann Climate Adaptation & Resilience Planner 49 Sausalito Andrew Davidson Senior Engineer/ DPW
50 Sausalito Kevin McGowan Director of Public Works
51 Sausalito Brandon Phipps Planning Director
52 Sausalito Ali Iqbal Assistant Civil Engineer/ Public Works 53 Tiburon Sam Bonifacio Assistant Planner
54 Tiburon Dina Tasini Director of Community Development 55 Tiburon Laurie Nilsen Emergency Services Coordinator Table 2.2: Marin County OA MJHMP Steering Committee Members l ~<;>U·N· TY OF
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78 Table 2.3: Preparative Consulting Planning Team Members No. Agency Point of
Contact
Title
1 Preparative Consulting Paul Bockrath Project Lead/Planner 2 Preparative Consulting Candise
Bockrath Project Manager
3 Preparative Consulting David M. Block Lead Planner
Table 2.3: Marin County OA MJHMP Preparative Consulting Planning Team Members The Steering Committee met and reviewed the mitigation recommendations and strategies identified within this plan. Each participating local jurisdiction established a mechanism for the development and implementation of jurisdictional mitigation projects, as identified within this plan and associated locally specific supporting documents. As deemed necessary and appropriate, participating jurisdictions will organize local mitigation groups to facilitate and administer internal activities.

The Disaster Mitigation Act (DMA) planning regulations and guidance stress that each local government seeking FEMA approval of their mitigation plan must participate in the planning process. The Steering Committee assisted with the planning process in the following ways:
• Attending and participating in the Steering Committee meetings. • Identification of potential mitigation actions.
• Updating the status of mitigation actions from the 2018 Marin County OA MJHMP. • Collecting and providing other requested data (as available). • Making decisions on plan process and content.
• Reviewing and providing comments on plan drafts; including annexes. • Informing the public, local officials, and other interested stakeholders about the planning process and providing opportunity for them to be involved and provide comment.
• Coordinating, and participating in the public input process. • Coordinating the formal adoption of the plan by the governing boards.

2.5.1 STEERING COMMITTEE PLANNING PROCESS
The Steering Committee met monthly to develop the plan. Email notifications were sent out to each Steering Committee member to solicit their participation in the Steering Committee meetings. The meetings were conducted using a Zoom platform videoconferencing. Meeting attendees signed in using the chat feature to record their attendance.

The Steering Committee agreed to make and pass plan-based general policy recommendations by a vote of a simple majority of those members present. The Steering Committee will also seek input on future hazard mitigation programs and strategies from the mitigation planning team by focusing on the following:
• Identify new hazard mitigation strategies to be pursued on a state and regional basis, and review the progress and implementation of those programs already identified. 44 CFR Requirement §201.6(a)(3): Mul�-jurisdic�onal plans may be accepted, as appropriate, as long as each jurisdic�on has par�cipated in the process and has officially adopted the plan. l ~<;>U·N· TY OF
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79 • Review the progress of the Hazard Mitigation program and bring forth community input on new strategies.
• Coordinate with and support the efforts of the Marin County OEM to promote and identify resources and grant money for implementation of recommended hazard mitigation Strategies within local jurisdictions and participating public agencies.

During the planning process, the Steering Committee communicated through videoconferencing, face-to-face meetings, email, telephone conversations, and through the County website. The County website included information for all stakeholders on the MJHMP update process. Hannah Tarling of the Marin County Office of Emergency Management and Preparative Consulting established a Microsoft 365 SharePoint folder which allowed the Steering Committee members and Marin OEM and Preparative Consulting to share planning documents and provide a format for the planning partners to submit completed documents and access other planning related documents and forms. Draft documents were also posted on this platform and the Marin County OES website so that the Steering Committee members and the public could easily access and review them.

2.5.2 STEERING COMMITTEE TASKS
The Steering Committee engaged in research to identify, document, and profile all the hazards that have, and could have, an impact on the planning area. The Steering Committee also conducted a capability assessment to review and document the planning area’s current capabilities to mitigate the risk and vulnerability of each participating jurisdiction to each identified hazard. By collecting information about existing government programs, policies, regulations, ordinances, and emergency plans, the Steering Committee could assess those activities and measures already in place that contribute to mitigating some of the risks and vulnerabilities identified.

Specific tasks were identified for the Steering Committee in order to ensure that project goals for the MJHMP revision were undertaken and completed. The following represents those primary Steering Committee tasks:
• Coordinate tasks and activities with the Marin County OEM to develop all-hazards disaster mitigation plan and oversee the planning process. • Prioritize hazards vs. resources.
• Select highest and best mitigation recommendations and develop those recommendations for further action by Marin County and the Cities/Towns and special districts.
• Review planning drafts, recommendations and updates.
• Develop and implement long and short term goals.
• Integrate the plan with all phases of comprehensive emergency management planning.
• Provide for the implementation of committee decisions. • Encourage, coordinate and provide a methodology for the implementation of public input.
• Provide for the implementation of Steering Committee decisions. l ~<;>U·N· TY OF
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80 2.5.3 STEERING COMMITTEE FUTURE TASKS
Specific future tasks were identified for the Steering Committee in order to ensure that project goals for the MJHMP revision were continued. The following represents those primary Steering Committee future tasks:
• Define the mitigation constraints that the Marin County OA is required to follow in implementing recommendations from the Steering Committee. o Protection of sensitive information
o Apply budget constraints to recommended hazard mitigation strategies o Apply state policy and legal constraints to mitigation strategies brought forward by the Steering Committee.
• Meet on an annual basis to review the work of and contribute to the Steering Committee activities.
• Bring forth the concerns and views of the community to the Steering Committee for consideration in the ongoing hazard mitigation planning process. • Consider utilizing the California Department of Public Health Community Assessment for Public Health Emergency Response (CASPER) to provide public health leaders and emergency managers with a rapid community assessment to determine household-based information about a community following a disaster. • Assist in informing the public and community of the hazard mitigation strategies recommended by the Steering Committee.
• Define the constraints for implementation of prioritized mitigation strategies within the authorities, laws, and regulations of the local entities existing within the Marin County OA.
• Carry out the goals and objectives of the Marin County OA MJHMP. • Support and review the input from meetings of the adjunct members with individuals, agencies and jurisdictions.
• Assure that the public is kept informed of changing strategies and implementation actions periodically.

2.6 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)).

Early in the planning process, the Steering Committee determined that data collection, risk assessment analyses, mitigation strategy development, and plan approval would be greatly 44 CFR Requirement 201.6(b): An open public involvement process is essen�al to the development of an effec�ve plan. In order to develop a more comprehensive approach to reducing the effects of natural disasters, the planning process shall include: (2) An opportunity for neighboring communi�es, local and regional agencies involved in hazard mi�ga�on ac�vi�es, 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. (3) Review and incorpora�on, if appropriate, of exis�ng plans, studies, reports, and technical informa�on. l ~<;>U·N· TY OF
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81 enhanced by inviting other local, state and federal agencies and organizations to participate in the process. Based on their involvement in hazard mitigation planning, their landowner status in the County, and/or their interest as a neighboring jurisdiction, representatives from the following groups were invited to participate on the Planning Team:

Table 2.4: Marin County OA MJHMP Planning Team Members
No. Agency Point of Contact Title
Special Districts & Partner Agencies
1 Bolinas Fire Protection District Stephen Marcotte Assistant Fire Chief 2 County of Sonoma Jeffrey DuVall Deputy Director, County of Sonoma OEM
3 County of Marin Disability Access
Program Laney Davidson Disability Access Manager/ ADA Coordinator 4 County of Marin Disability Access
Program Peter Mendoza Disability Access Manager/ ADA Coordinator 5 Emergency Medical Services Chris Le Baudour EMS Authority 6 Fire Departments Jason Weber Fire Chief
7 Golden Gate Bridge, Highway &
Transportation District Daniel Rodriguez Security, Emergency Management Specialist 8 Golden Gate Bridge, Highway &
Transportation District Dennis Mulligan General Manager & CEO, 9 Marin City Climate Resilience and
Health Justice Terrie Green Executive Director
10 Marin Center for Independent
Living Peter Mendoza Director of Advocacy and Special Projects 11 Marin City Community Services
District Juanita Edwards Interim General Manager
12 Marin County Community
Development Agency Leslie Lacko Community Development Agency 13 Marin County Flood Control &
Water Conservation District Garry Lion Advisory Board Member 14 Marin County Office of Education Michael Grant Director, Marin County Office of Education
15 Marin County Parks Max Korten General Manager and
Director
16 PG&E Mark Van Gorder Government Affairs, North
Bay
17 PG&E Ron Karlen PG&E Public Safety
Specialist
18 Sonoma Marin Area Rail Transit
(SMART) Jennifer McGill Chief of Police
19 Transportation Authority of Marin
(TAM) Anne Richmond Executive Director
20 Willow Creek School Itoco Garcia Superintendent
State Agencies
21 Cal OES - ESC Sarah Finnigan Cal OES, Sr. Emergency
Services Coordinator
22 Cal OES, Division of Safety of
Dams Danielle Jessup Coordinator/ Dam Safety Planning Division 23 California Department of Public
Health Svetlana Smorodinsky Disaster Epidemiologist/ Environmental & l ~<;>U·N· TY OF
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82 Table 2.4: Marin County OA MJHMP Planning Team Members No. Agency Point of Contact Title
Occupational Emergency
Preparedness Team
24 California Department of Public
Health Patrice Chamberlain
Health Program Specialist
II / Environmental &
Occupational Emergency
Preparedness Team
25 California Department of Water
Resources Julia Ekstrom, PhD
Supervisor, Urban Unit
Water Use Efficiency
Branch
26 Caltrans Trang Hoang Senior Transportation Engr/
Office of Advance Planning
27 Caltrans Markus Lansdowne Caltrans D4 Emergency
Coordinator
Federal Agencies
27 Army Corps of Engineers Jessica Ludy
Flood Risk Management,
Equity, and Environmental
Justice
28 National Park Service Stephen Kasierski OneTam
29 US Coast Guard LT Tony Solares Sector SF Waterways
Safety Branch
30 US Coast Guard MST1 Brandon M. Ward Emergency Management Specialist
31 US Coast Guard LT William K. Harris USCG SEC San Francisco Table 2.4: Marin County OA MJHMP Planning Team Members
Coordination with key agencies, organizations, and advisory groups throughout the planning process allowed the Planning Team to review common problems, develop policies and mitigation strategies, as well as identifying any conflicts or inconsistencies with regional mitigation policies, plans, programs and regulations. For example, in conjunction with the kick off meetings, several key stakeholder/agency conversations were held at the beginning of the project to solicit input and to identify and obtain data at the beginning of the project. This included initial discussions with: Cal OES, DWR, Marin County Flood Control & Water Conservation District and Marin County Fire Agencies. Coordination with these key agencies continued throughout the project. Representatives from Cal OES attended most of the Planning Team meetings where they helped present, answered questions and provided input and support on the MJHMP process and plan requirements and provided details as requested on other related programs, such as FEMA grant programs. Through their attendance at Planning Team meetings, these key stakeholders and agencies provided ongoing information and data as requested to support the overall plan development process.

These key agencies, organizations, and advisory groups received meeting announcements, agendas, and minutes by e-mail throughout the plan update process. They supported the effort by attending meetings or providing feedback on issues. All the agencies were provided with an opportunity to comment on this plan update and were provided with a copy of the plan to review and offer edits and revisions. They were also provided access to the Marin County OEM hazard mitigation plan website to review all planning documents and hazard mapping tools.

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83 Emergency Services (Cal OES) and FEMA Region IX for a pre-adoption review to ensure program compliance.

In addition, through the public meetings conducted at the beginning of the planning process, members of the planning team, the public, and other key stakeholders were invited to participate in the planning process through public outreach activities.

The Steering Committee used technical data, reports, and studies from the following agencies and groups:
• California Governor’s Office of Emergency Services
• California Department of Forestry and Fire Protection • California Department of Finance
• California Department of Fish and Game
• California Department of Forestry and Fire Protection • California Department of Water
• California Geological Survey
• California Register of Historic Places
• Federal Emergency Management Agency
• National Oceanic and Atmospheric Association
• National Performance of Dams Program
• National Register of Historic Places
• National Resource Conservation Service
• National Weather Service
• United States Army Corps of Engineers
• United States Bureau of Land Management
• United States Department of Agriculture
• United States Drought Impact Reporter
• United States Farm Service Agency
• United States Forestry Service
• United States Geological Survey
• Western Regional Climate Center
Several opportunities were provided for the groups listed above to participate in the planning process. At the beginning of the planning process, invitations were extended to these groups to actively participate on the Planning Team. Participants from these groups assisted in the process by providing data directly as requested in worksheets or through data contained on their websites or as maintained by their offices. Further as part of the public outreach process, all groups were invited to attend the public meetings and to review and comment on the plan prior to submittal to Cal OES and FEMA.

The following planning meetings were held with the planning team:
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84 Table 2.5: Marin County OA MJHMP Planning Meetings
No. Date Attendees Meeting Planning Meeting Objectives
1 10/26/22 Steering
Committee
Project Overview
Meeting
• Plan Overview – Steps and
Timeline
• Planning Process
• Steering Committee Role
2 11/9/22 Steering
Committee
Steering
Committee
Kickoff Meeting
• Hazard Mitigation and
Emergency Management
Overview
• Plan Overview – Steps and
Timeline
• Community Overview
• Planning Process
• Hazard Identification and Risk
Assessment
• Stakeholders and Planning Team
Identification
3 12/6/22
Steering
Committee,
Planning
Team
Planning Team
Kickoff Meeting
• Hazard Mitigation and
Emergency Management
Overview
• Plan Overview – Steps and
Timeline
• Community Overview
• Planning Process
• Hazard Identification and Risk
Assessment
4 02/07/23 Steering
Committee
Steering
Committee
Hazard Profile
Meeting
• Jurisdictional Letter of
Commitment
• Identify Planning Team Members
• Hazard Risk Ranking
Worksheets
• Jurisdictional Profiles
• Jurisdictional/ District Capability
Assessment
• 2018 Hazard Mitigation Project
Status Update
5 03/07/23
Steering
Committee/
Planning
Team
Planning Team
Public Outreach
Strategy Meeting
• Planning Goals and Objectives
• Hazard Risk Ranking
Worksheets
• Jurisdictional Profiles
• Jurisdictional/ District Capability
Assessment
• 2018 Hazard Mitigation Project
Status Update
• Public Outreach Strategy
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85 Table 2.5: Marin County OA MJHMP Planning Meetings
No. Date Attendees Meeting Planning Meeting Objectives
6 04/04/23 Steering
Committee
Steering
Committee
Meeting
• HMGP (DR-4683) Funding
Timeline
• Public Outreach
• Planning Goals and Objectives
• Jurisdictional Hazard
Vulnerability Maps
• Jurisdictional Profiles
• Jurisdictional/ District Capability
Assessment
• 2018 Hazard Mitigation Project
Status Update
7 04/13/23
General
Public,
Steering
Committee,
Planning
Team
Public Outreach
Town Hall
Meeting #1
(In-person and
virtual on Zoom)
Thursday, 6:00
pm to 7:30 pm
Marin County
BOS Chambers
• Meeting translated live in
Spanish with 29 language
subtitle capability for virtual
participants.
• Meeting also interpreted in
American Sign Language
• Meeting recorded and posted on
Hazard Mitigation website.
• Hazard Mitigation and
Emergency Management
Overview
• Planning Process
• Hazard Identification and Risk
Assessment
• Planning Goals and Objectives
• Hazard Mitigation Projects
• Community Input
8 04/29/23
General
Public,
Steering
Committee,
Planning
Team
Public Outreach
Town Hall
Meeting #2
(In-person and
virtual on Zoom)
Saturday, 10:00
am to 11:30 am
Marin County
Health and
Wellness Center
• Meeting translated live in
Spanish with 29 language
subtitle capability for virtual
participants.
• Meeting also interpreted in
American Sign Language
• Meeting recorded and posted on
Hazard Mitigation website.
• Hazard Mitigation and
Emergency Management
Overview
• Planning Process
• Hazard Identification and Risk
Assessment
• Planning Goals and Objectives
• Hazard Mitigation Projects
• Community Input
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86 Table 2.5: Marin County OA MJHMP Planning Meetings
No. Date Attendees Meeting Planning Meeting Objectives
9 05/31/23 Steering
Committee
Steering
Committee
Hazard Ranking
Meeting
• HMGP (DR-4683) Funding
Timeline
• Public Outreach Status
• Jurisdictional Hazard
Vulnerability Maps
• OEM Overview of Hazard Maps
and Marin Maps
• Marin Co. MJHMP Risk
Assessment Tool Overview
• 2018 Hazard Mitigation Project
Status Update
• Hazard Working Groups
10 06/27/23
Steering
Committee,
Planning
Team
Marin County
Planning Team
Meeting
• HMGP (DR-4683) & BRIC Grant
Funding Timeline
• Public Outreach Status
• Jurisdictional Hazard Risk
Assessment Tool
• OEM Overview of Hazard Maps
and Marin Maps
• Marin County Hazards over the
Last 5-Years
• 2018 Hazard Mitigation Project
Status Update
• 2023 Hazard Mitigation
Projects/Capital Improvement
Projects
• Hazard Working Groups
11 07/01/23-
09/01/23
Steering
Committee
Members
Steering
Committee
Members Plan
Development
Sessions
• Individual phone or conference
calls with planning jurisdictions
and districts to answer specific
questions and assist them in
developing their profile annex.
12 11/27/23
Steering
Committee,
Planning
Team
Marin County
Final Planning
Team Meeting
• Presentation and review of the
Draft Marin County OA MJHMP
and Jurisdictional/District
Annexes
13 11/28/23
General
Public
Public Outreach
Presentation on
Marin County
Office of
Emergency
Management
Website
• Presentation and review of the
Draft Marin County OA MJHMP
and Jurisdictional/District
Annexes.
• Opportunity for public comment
and questions and answers.

Table 2.5: Marin County OA MJHMP Planning Meetings
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87 2.7 REVIEW AND INCORPORATION OF EXISTING PLANS
Planning efforts are supportive of each other. Information from the Marin OA MJHMP is incorporated into and used to support the City, County, and Town General Plans, Emergency Operations Plans, and continuity plans. Many of these planning efforts incorporate all Marin County jurisdictions and Special Districts. The development of this plan incorporated information from the following existing plans, studies, reports, and initiatives as well as other relevant data from neighboring communities and other jurisdictions:

All Jurisdictions (Marin County OA)
• Association of Bay Area Governments (ABAG) 2010 multi- jurisdictional Local Hazard Mitigation Plan for the San Francisco Bay Area, 2010 Update of 2005 Plan • Marin Map- online mapping tool includes hazard data, assets, zoning, current FEMA flood maps www.marinmap.org
• FEMA data via Flood Insurance Studies, BureauNet
• Marin County - Community Wildfire Protection Plan(CWPP) www.firesafemarin.org/cwpp • Marin Community Wildfire Protection Plan, 2020.
• Marin Shoreline Sea Level Rise Vulnerability Assessment • DSOD dam safety information
• ABAG earthquake: https://abag.ca.gov/our-work/resilience/data-research/earthquake • 2018 State of California Hazard Mitigation Plan
• Marin Stormwater Resource Plan 2017
• The Scoop on Marin County Sewer Systems: Part I 2013/2014 Marin County Civil Grand Jury
• U.S. Census Bureau 2010 Census
• The studies detail flood depths and base flood elevations. Used in development of risk assessments and mitigation actions
• Marin Municipal Water District Urban Water Management Plan 2015 (approved June 7, 2016)
• Countywide Watershed Stewardship Plan
• Plan Bay Area 2040
• Sonoma County Water Agency Local Hazard Mitigation Plan • CAL FIRE & Marin County Fire Department Strategic Fire Plans • International Urban-Wildland Interface Code 2003
• Community Exposure to Tsunami Hazards in California report & National Geodetic Data Center database of tsunami occurrences
• Cliff and Erosion Technical Background Report, 2003 prepared for Marin County Local Coastal Program update
• Landslide Inventory, California Department of Conservation • California Building, Plumbing and Mechanical Codes
Unincorporated Marin County
Marin County’s 2023 MJHMP will be referenced in the 2023 County of Marin General Plan:

Safety Element and Housing Element 2023 Update.
• 2007 Marin Countywide Plan
• Local Coastal Program
City of Belvedere
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88 Belvedere’s 2023 General Plan Environmental Hazards Element has thorough treatment of environmental hazards and references the City’s participation in the 2018 Marin County MJHMP and development of the 2023 update. The City’s 2011 Local Hazard Mitigation Plan (LHMP) was contained its Flood Mitigation Plan.
• 2023 General Plan
• Flood Mitigation Plan
• Capital Improvement Plan
• Emergency Operations Plan (EOP)
• Traffic Safety Study
Town of Corte Madera
Corte Madera’s General Plan was updated in 2023. The General Plan calls for implementation of a Hazard Plan. The Town’s Capital Improvement Plan and building and municipal codes have been updated since 2011 and incorporate portions of the Marin County OA MJHMP Corte Madera Community Profile.
• Capital Improvement Plan (CIP)
• General Plan Safety Element
• Housing Element
City of Larkspur
Larkspur is in process of updating its General Plan, which was last updated in 2023. The updated plan will comply with the Disaster Management Act 2000 by including a Safety Element that references this Hazard Mitigation Plan. The following documents are examples of the City’s continuing progress implementing mitigation measures.
• General Plan Safety Element
• Comprehensive Emergency Management Plan
City of Mill Valley
Mill Valley’s participation in the 2018 Marin County MJHMP was approved in 2019 and it has been incorporated it into other mechanisms such as the City’s General Plan (MV2040, adopted 2014) which calls for maintenance, updates, and implementation of the All Hazard Mitigation Plan.
• 2023 General Plan Update ‘2040 General Plan’ including Climate Action Plan & Housing Element
• General Fund and Capital Improvement Plan
• Sewerage Agency of Southern Marin (SASM) Master Plan
• City of Mill Valley Emergency Operations Plan
• City of Mill Valley Bicycle and Pedestrian Master Plan Update 2017 City of Novato
Novato participated in the 2018 Marin County MJHMP and is currently updating its General Plan. The current draft Safety and Health strategy #7a is to “Periodically update the City’s Emergency Operations Plan and Local Hazard Mitigation Plan to coordinate with emergency plans of other governmental agencies and respond to changing conditions”. The new general plan also refers to the previous hazard mitigation plan for additional information on certain hazards such as wildfire.
• 2035 General Plan
• Existing Conditions Report, April 2014
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89 • 2008 City Flood Mitigation Plan
• Emergency Preparedness Plan
• Emergency Operations Plan
• Stafford Dam Emergency Action Planning and Risk Awareness in 2015 • Identified Site Emergency Planning Application, (ISEPA) • Novato Elected/Appointed Official Guide to Disaster Operations 2017 • City of Novato Local Drainage Master Plan
• City of Novato Repetitive Loss Plan
City of San Rafael
The City’s “General Plan 2040” updated in 2021 calls for preparation and adoption of an LHMP.

Since then, the City has prepared and adopted an LHMP.

City of San Rafael 2040 General Plan
• City of San Rafael 2040 General Plan Background Report • City of San Rafael Climate Change Action Plan
• City of San Rafael Community Emergency Preparedness Plan • City of San Rafael Greenhouse Gas Reduction Strategy Report • Climate Adaptation – Sea Level Rise, San Rafael CA. White Paper • Marin Bay Shoreline Sea Level Rise Vulnerability Assessment City of Sausalito
Sausalito participated in the 2018 Marin County MJHMP that it incorporated into other mechanisms.
• 2021 General Plan
• 2021 General Plan, including Climate Action Plan & Hazards & Public Safety Element Town of Fairfax
The Town’s 2012 General Plan and 2011 ABAG Hazard Mitigation Plan Annex were developed concurrently, so the General Plan Advisory Committee (GPAC) reviewed, refined, and incorporated selected mitigation strategies into the final draft 2021 General Plan Safety Element. The Safety Element states that it “is intended to complement and support not only the other General Plan Elements, but also other Town plans and documents, such as the Emergency Operations Plan (EOP), the Local Hazard Mitigation Plan (LHMP), and the Flood Mitigation Plan (FMP).
• 2021 General Plan Safety Element
• Capital Improvement Plan (CIP)
• Emergency Response Plan
• Community Preparedness Plan
Town of Ross
Ross’s General Plan was completed and adopted in 2007, before its participation in the 2018 Marin County MJHMP. The 2018 Marin County MJHMP has been incorporated into other planning mechanisms.
• Town of Ross General Plan 2007 – 2025
• 2023 General Plan – Housing Element
• 2018 Marin County MJHMP
• Ross Valley Sanitary District Strategic Plan
• Ross Valley Sewer System Replacement Master Plan 2007 l ~<;>U·N· TY OF
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90 • Ross Valley Sanitary District response to Grand Jury Report Dated June 16, 2011:
"Ross Valley Sanitary District: Not Again!"
Town of San Anselmo
San Anselmo’s participated in the 2018 Marin County MJHMP, and has incorporated it into other planning mechanisms such as the General Plan, which was adopted in 2019. 2011 Climate Action Plan
• 2011 Capital Improvement Plan Study for Flood Damage Reduction and Creek Management in Flood Zone 9/Ross Valley
• Town of San Anselmo 2019 General Plan
• 2023 General Plan – Housing Element
• 2008 Flood Mitigation Plan
• Town of San Anselmo Municipal Code
• 7-year Capital Improvement Plan 2015
• Corte Madera Creek 2010 Flood Control Study Baseline Report Available through US Army Corps of Engineers and Ross Valley Flood Control Program website Town of Tiburon
Tiburon’s “General Plan 2040” from 2023 calls for the adoption of an LHMP to comply with DMA 2000. Since then the Town has adopted the ABAG LMHP Annex in 2012. • 2023 General Plan Update ‘2040 General Plan’ including Climate Action Plan & Hazards & Public Safety Element
• Capital Improvement Plan
• Emergency Operations Plan
• General Plan Safety Element
North Marin Water District
• 2017 Stafford Dam Emergency Action Plan
• 2015 Master Plan Update for the Oceana Marin Wastewater System, NMWD Job File 8 4046.00
• 2018 Novato Water System Master Plan Update, NMWD Job File 1 7039.02 Coordination with other community planning efforts is also paramount to the success of this plan. Hazard mitigation planning involves identifying existing policies, tools, and actions that will reduce a community’s risk and vulnerability to hazards. Marin County uses a variety of comprehensive planning mechanisms, such as general plans and ordinances, to guide growth and development. Integrating existing planning efforts and mitigation policies and action strategies into this plan establishes a credible and comprehensive plan that ties into and supports other community programs. The development of this plan incorporated information from the following existing plans, studies, reports, and initiatives as well as other relevant data from neighboring communities and other jurisdictions:
• California Drought Contingency Plan.
• California Volcanoes and Volcanics. U.S. Geological Survey, Cascades Volcano Observatory.
• Central Valley Flood Control Project.
• Cities/Counties Ranked by Size, Numeric, and Percent Change. State of California Department of Finance. 2014.
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91 • Community Rating System. Federal Emergency Management Agency National Flood Insurance Program.
• Contingency Plan for Excessive Heat Emergencies – A Supporting Document to the State Emergency Plan, April 2010.
• Developing the Mitigation Plan: Identifying Mitigation Actions and Implementation Strategies. Federal Emergency Management Agency. FEMA 386-3. 2003. • Ebbets Pass Special Plan. 1988.
• Enhanced Fujita Scale. National Oceanic and Atmospheric Administration Storm Prediction Center. 2007.
• Future Eruptions in California's Long Valley Area—What’s Likely? U.S. Geological Survey. Fact Sheet 073-97. 1997.
• Getting Started: Building Support for Mitigation Planning. Federal Emergency Management Agency. FEMA 386-1. 2002.
• Hazard Mitigation Planning and Hazard Mitigation Grant Program. Federal Register.

Interim Final Rule. February 26, 2002.
• HAZUS-MH 2.1. Federal Emergency Management Agency. 2012. • Integrating Manmade Hazards into Mitigation Planning. Federal Emergency Management Agency. FEMA 386-7. 2003.
• Introduction to Hazard Mitigation. Federal Emergency Management Agency. FEMA IS393.A. 2006. • Multi-Hazard Identification and Risk Assessment. Federal Emergency Management Agency. 1997.
• Natural Hazard Mitigation Saves: An Independent Study to Assess the Future Savings from Mitigation Activities. National Institute of Building Science Multi-Hazard Mitigation Council. 2005.
• Probabilistic Seismic Hazard Assessment for the State of California. California Geological Survey. Open-File Report 96-08. 1996.
• Robert T. Stafford Disaster Relief and Emergency Act. Public Law 93-288, as amended, 42 U.S.C. 5121-5207. June 2007.
• Saddle Creek Special Plan. 2008.
• Spatial Hazard Events and Losses Database for the United States. University of South Carolina Hazards Research Lab.
• State of California Multi-Hazard Mitigation Plan. California Emergency Management Agency. 2013.
• Understanding Your Risks: Identifying Hazards and Estimating Losses. Federal Emergency Management Agency. FEMA 386-2. 2001.

Data from these plans and ordinances were incorporated into the risk assessment and hazard vulnerability sections of the plan. Where the data from the existing studies and reports is used in this plan update, the source document is referenced throughout this plan update. The data was also used in determining the capability of the community in being able to implement certain mitigation strategies.

A key example of coordinating with other planning efforts is the coordination of this MJHMP with local-CWPPs. This is critical for two important reasons. First, wildfires do not stop at corporate or jurisdictional boundaries and evaluating fire risk issues on a regional basis provides a comprehensive approach to understanding and addressing identified wildfire risk and vulnerability. Second, a successful mitigation strategy requires that these planning efforts be coordinated.
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92 Many other local, state, and federal documents were reviewed and considered, as appropriate, during the collection of data which include the hazard identification, vulnerability assessment, and capability assessment.

2.8 PUBLIC ENGAGEMENT
The Public Outreach efforts mirrored the Planning Team approach with a unified effort, led by the County OEM, involving all participating jurisdictions and districts. Extensive and coordinated public outreach was done involving all participating jurisdictions and districts with an eye towards equity, inclusion, openness, accessibility, and ensuring we meet the population where they live, work, or recreate to provide convenience of access and ease of participation in this planning process.

Early discussions with the Marin County OEM established the initial plan for public engagement to ensure a meaningful and inclusive public process with a focus on equity and accessible to the whole community. Public outreach for this plan update began at the beginning of the plan development process with an informational press release to inform the community of the purpose of the hazard mitigation planning process for the Marin County planning area and to invite the public to participate in the process.

Public involvement activities for this plan update included press releases; website postings; a community survey; stakeholder and public meetings; tabling at local events: and the collection of public and stakeholder comments on the draft plan which was posted on the County website.

Information provided to the public included an overview of the mitigation status and successes resulting from implementation of the 2018 plan as well as information on the processes, new risk assessment data, and proposed mitigation strategies for the plan update.

The County of Marin has several outreach programs, specifically designed to reach and include traditionally underserved and underrepresented communities, including, Health and Human Services’ Community Response Teams, Office of Equity’s Participatory Budgeting program, and a community-created Race and Equity Plan. To receive feedback on the Marin County OA MJHMP, bilingual outreach was conducted through the Community Response Teams, which are led by local non-profits, representing four zones of Marin County. Local non-profits are selected for grant funding to be the Community Response Team lead. Additionally, County representatives went on the West Marin radio station, KWMR, to reach rural populations.

Equity and Whole Community Approach
The Marin County OEM and the Steering Committee prioritized equity and engagement of the whole community in the development of the Marin County Multijurisdictional Hazard Mitigation Plan. As a means to reach as many members of the community as possible, Marin County OEM required that services be universally designed and delivered from the beginning to allow for the greatest level of engagement and feedback possible. Elements of the equity approach included:
44 CFR Requirement 201.6(b): An open public involvement process is essen�al to the development of an effec�ve plan. In order to develop a more comprehensive approach to reducing the effects of natural disasters, the planning process shall include: (1) An opportunity for the public to comment on the plan during the dra�ing stage and prior to plan approval. l ~<;>U·N· TY OF
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93 • Providing multiple means for public engagement via hybrid meetings (in-person meetings with a virtual attendance and comment option). • All presentations were accompanied by American Sign Language (ASL), ClosedCaptioning, and Spanish Interpretation • Presentations were reviewed by accessibility professionals prior to broadcasting to ensure the documents were able to be read by screen-readers. • All presentations were available on-line and recorded for persons who may not have been able to attend the live presentations.

Engaging hard-to-reach populations
This effort was to ensure the greatest equity and access to the public to enable participation in the process. The Marin County OEM outreach strategy is to “meet people where they are.” The Town hall meetings were conducted at different familiar locations within the county where people could easily access them and were conducted on both a weekday and weekend, and in the evening and during the daytime. The meetings were offered in-person with a virtual broadcast using Zoom videoconferencing and streamed live on the Marin County OEM Facebook account. After the meetings, Marin County OEM uploaded the recorded meetings to their website to allow the public on demand access to the meetings.

Translation and Interpretation Services
The survey and outreach materials were provided in both English and Spanish to improve accessibility among populations with limited English proficiency. The website uses Google Translate for accessibility in multiple languages. Interpretation services were offered for both town hall meetings. Each town hall meeting included, live Spanish translation and subtitles, live American Sign Language/ Certified Deaf Interpreter (ASL/CDI) interpretation, the ability for the Zoom videoconferencing attendee to activate subtitles in 28 different languages, and vision accessible PowerPoint slides.

Three stakeholder and public meetings were held, two at the beginning of the plan development process and one prior to finalizing the updated plan. Where appropriate, stakeholder and public comments and recommendations were incorporated into the final plan, including the sections that address mitigation goals and strategies. Specifically, public comments were obtained during the plan development process and prior to plan finalization.

All press releases and website postings are on file with the Marin County OEM. Public meetings were advertised in a variety of ways to maximize outreach efforts to both targeted groups and to the public at large. Advertisement mechanisms for these meetings and for involvement in the overall MJHMP development process include:
• Development and publishing of an MJHMP public outreach article • Providing press releases to local newspapers and radio stations • Posting meeting announcements on the local County MJHMP website • Email to established email lists
• Personal phone calls
The public outreach activities were conducted with participation from and on behalf of all jurisdictions participating in this plan.
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94 The Steering Committee has made the commitment to periodically bring this plan before the public through public meetings and community posting so that community members may make input as strategies and implementation actions change. Public meetings will continue to be held twice a year. Public meetings will continue to be stand-alone meetings but may also follow a council meeting or other official government meeting. The public will continue to be invited to public meetings via social media messaging, newspaper invitations, and through the website for each jurisdiction participating in the plan. Each jurisdiction is responsible for assuring that their community members are informed when deemed appropriate by the Steering Committee.

2.8.1 WEBSITE
At the beginning of the plan update process, Marin County OEM established a hazard mitigation website ( https://emergency.marincounty.org/pages/lhmp) to keep the public posted on plan development milestones and to solicit relevant input. The website also provided information on signing up for Alert Marin, provided detailed information about the hazard mitigation process and plan development, provided a URL and QR code link to the survey in both English and Spanish, and provided information about upcoming town hall meetings. (See Figure 2.1) The site’s address was publicized in all press releases, surveys and public town hall meetings. Each planning partner also established a link on their own agency website.

Information on the plan development process, the Steering Committee, a link to the Hazard Mitigation survey, and drafts of the plan were made available to the public on the site. Marin County intends to keep a website active after the plan’s completion to keep the public informed about successful mitigation projects and future plan updates.

Figure 2.1: Marin County OEM MJHMP Website
Source: Marin County OEM

2.8.2 PUBLIC MEETINGS
Two separate Marin County OA MJHMP Public Town Hall Meeting were conducted at different locations within the County, on different days of the week and during different times of the day. This effort was to ensure the greatest equity and access by the public to enable l ~<;>U·N· TY OF
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__ J. ~ •RIN Emergencv. Portal Get Alerted Stay Informed Weather Prepare COVID-19 More· ~ 0 Marin County Multi-Jurisdictional Hazard Mitigation
Update
The various communities and service providers within
Marin County are working together to update our Marin
County Multi-Jurisdictional Hazard Mitigation Plan . As part of this update process, we are asking for
community insight and input.
https1/t-me<gency.manncountyorg/pages/alerts
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
95 participation in the process. The Marin County OEM outreach strategy is to “meet people where they are”. Each Town Hall Meeting included, live Spanish translation and subtitles, Live American Sign Language (ASL/CDI) interpretation, the ability for the Zoom videoconferencing attendee to activate subtitles in 28 different languages, and vision accessible PowerPoint slide.

The first Town Hall Meeting was conducted on Thursday, April 13, 2023, from 6:00 pm to 7:30 pm, at the Marin County Board of Supervisors Chambers, Marin County Civic Center, 3501 Civic Center Drive, Room #330 San Rafael, CA 94903. The in-person meeting was also broadcast virtually using Zoom videoconferencing and streamed live on Marin County OEM Facebook account. Each of the jurisdictions participating in the MJHMP released a Press Release on their respective websites announcing the Public Town Hall Meeting and providing the date, time, and URL link to the Zoom Meeting for the public to log in and attend the Zoom Meeting. Marin County OEM also posted a notice for the Public Town Hall Meeting on their Facebook account. At the conclusion of the presentation, a question and answer session was held to answer questions from the attendees.

The second Town Hall Meeting was conducted on Saturday, April 29, 2023, from 10:00 am to 11:30 am, at the Marin County Health and Wellness Center, 3240 Kerner Ave. Rooms #109 and #110 San Rafael, CA. 94903. The meeting followed the same format as the first and hosted the same access level of equity and accessibility.

The Marin County MJHMP Public Town Hall Meeting was recorded and downloaded from Zoom and made available to all of the jurisdictions and districts to place on their websites and local Access TV for the public to view.

Meeting participants were also invited to complete the Hazard Mitigation Survey and were provided the URL link to the Survey Monkey website to complete the survey.

Figure 2.2: Marin County OA MJHMP Town Hall Meeting
Source: Preparative Consulting
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96 Figure 2.3: Collecting community feedback on the MJHMP Source: Marin County OEM

2.8.3 SOCIAL MEDIA
Marin County and its participating jurisdictions utilized several forms of social media to reach residents and customers. Information about the Hazard Mitigation Planning process was communicated to the public via Facebook, Twitter, and local access TV. Residents and customers were invited to complete the Hazard Mitigation Plan survey which was accessible via an attached URL or QR Code and provide feedback on potential hazard mitigation projects or programs.

The results of the survey were provided to each of the planning partners and used to support the jurisdictional annex process. Each planning partner was able to use the survey results to help identify actions as follows:
• Gauge the public’s perception of risk and identify what community members 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.

During this planning process, completed surveys were submitted. The complete survey can be found in Appendix C of this plan.

2.8.4 PRESS RELEASES
Press releases were distributed over the course of the plan’s development as key milestones were achieved and prior to each Marin County OA MJHMP Public Town Hall Meeting. All press releases were made available to the community in both English and Spanish. l ~<;>U·N· TY OF
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97 Figure 2.4: Hazard Mitigation Plan Public Outreach Press Release Source: Marin County OEM

2.8.5 SURVEY
A hazard mitigation plan survey (see Figure 2.5) was developed by the Steering Committee and made available to the public in both English and Spanish. The survey was used to gauge household preparedness for natural hazards and the level of knowledge of tools and techniques that assist in reducing risk and loss from natural hazards. This survey was designed to help identify areas vulnerable to one or more natural hazards. The answers to its 10 questions helped guide the Steering Committee in defining our hazards, and selecting goals, objectives, and mitigation strategies. The survey was made available on the hazard mitigation plan website, advertised in press releases, and at town hall meetings. Finally, the survey and the process of public input was advertised throughout the course of the planning process. The survey was made available to the public on March 13, 2023, and closed on June 12, 2023. At the conclusion of the planning process 293 surveys were completed by the public.

Public Comments Considered by the Planning Team
The Planning Team used the following information gathered from the Public Outreach Survey to inform decisions regarding hazard mitigation strategies, actions, and priorities. • Climate Change, Wildfire, and Drought were the top hazards of concern for the public. • Text messages, mail, and the County website were the preferred methods for receiving hazard mitigation information.
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The var10u, oormiunlHes <within Marin CO!..flly are YQklng 1ogelher IO UIP03'le \:=I Mar111 Ccxn,fy"s Mui~ Haz.Vd Millgatlorl Pian. As part or this ~,.,.. .. oommunltypl,tfmlng procen, we iJre asl&'Q torccmmunltylnf)ut to ensuret~t the prooo,ed ~ 1>oject,, .... ...-i .... ,. oJJoned""" , .. comnu,11)'$ e'1stt11g ~ 1iU1d e-xpec:Ul\lOn$.
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.As pr'qt!Cls or ptOgramS lo reduce or mitigate the Impact ol ttiose natural l'laZards on the com~. To be ellrJlb+e tor loc::ill Hazan:! MIUgaflon PrQ/e(:I: IUncJln9 we mustrirstconsldcrl'IOWttw::st- l\acut-ill ha.tar~"11pact U5and !twntiXPIOrehOWwe can ?(otecl agalnsl tnem. Wf! ~I II IS lrl'.,ortan1 to~ lhil!! wt'IOlc tOrlTrUJnlly [ntht$t!:ltoi'l
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The County wm also addle,, new and eme,glng ltlreats W!tt;ln lnls document SUCh as cwna10 t.hangO ;,nt:1 ~ air quat1ry; ~ . ine prln'laly na1ura1 naza,cts being assessed are:

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2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
98 • 48% of respondents expressed that they were “Very Much” concerned and 31% were “Moderately” concerned that a natural disaster could impact their home or place of residence.
• 85% of respondents own their own home.
• 99% of respondents have access to the internet.

Figure 2.5: Hazard Mitigation Plan Survey
Source: Preparative Consulting

2.8.6 PUBLIC COMMENT ON THE PLAN
To solicit public feedback on the draft plan, Marin OEM engaged in a multi-faceted approach intended to reach as many Marin residents as possible, including members of the community who are under-served and under-represented. All members of the community had the opportunity to provide initial comments on the plan during a two-week period from Public Outreach Survey
h�ps://www.surveymonkey.com/r/MarincountyMJHMP
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Mar1n County Multi-Jurisdictional Hazard Mitigation Plan Survey Public Outreach Survey
Encuesta del Plan Local de Mitigad6n. de Riesgos MultiJurlsdlcclonal de'l Condado de Marin en Espaflol https://www.surveymonkey.com/r/MarinCountyMJHMPEspanol
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
99 Wednesday, December 4, 2023, to Wednesday, December 18, 2023. Although the initial comment period was listed as two weeks, the public could submit comments indefinitely via the County’s website to support the County’s continuous improvement efforts. The base plan, as well as city, town and special district annexes, were available for download on emergency.marincounty.org (include photos). The website additionally asked for feedback in a survey in English and Spanish (include photos), the survey was designed to establish where that person lives or works, their top hazards of concern, elicit feedback on the plan and offer a place for them to share projects to reduce risk in their community. The survey collected responses from the community in English and in Spanish.

The website and survey were shared through traditional and social media (photos) The Marin Independent Journal (Marin IJ) used the press release to write an article (hopefully; include photos). Social media accounts were updated four times with an initial ask, two reminders, and a closing announcement. The Marin OEM Public Information Officer coordinated with the Marin County Public Information Officers (MAPIO) working group to distribute information to partner jurisdictions (city, town, and special districts) to share this information on their social media sites and with the communities in the area.

To reach those who may not be engaged digitally, the planning team worked with Marin County Community Response Teams, (CRTs are a collaboration of non-profit organizations supporting underrepresented communities in four zones) to conduct outreach with half-sheet flyers in English and Spanish to share in the 4 CRT zones (southern Marin, north Marin, west Marin, San Rafael). These half sheets were also shared county-wide at libraries, including in areas not covered by CRTs, like at the Fairfax library. CRTs are designed to reach Marin’s traditionally underserved and underrepresented communities, so by conducting outreach through this method, we were able to inform residents who may not have been engaged otherwise, including residents in Marin City, West Marin, and the Canal District of San Rafael.

The 14-day public comment period gave the public an opportunity to comment on the draft plan update prior to the plan’s submittal to Cal OES. Comments received on the draft plan are available upon request. All comments were reviewed by the planning team and incorporated into the draft plan as appropriate.

Public Comments Considered by the Planning Team
The Marin County OEM posted the draft Hazard Mitigation Plan and hazard mitigation actions on their website and solicited public comments on the content. The Planning Team gathered public comments and information on the Marin County OEM website regarding proposed and current Hazard Mitigation Actions. The Planning Team used the comments and suggestions to inform decisions regarding hazard mitigation strategies, actions, and priorities. Most comments included ideas for hazard mitigation projects and comments on the effectiveness of current mitigation projects. These comments were used to revised the proposed hazard mitigation actions which resulted in the final list of hazard mitigation actions listed in 4.9 Hazard Mitigation Actions.
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SECTION 3.0: HAZARD IDENTIFICATION AND RISK

ASSESSMENT
The Marin County Operational Area (OA) is at risk from a variety of hazards. Many of these hazards, could result in a disastrous impact on the county.

Although an attempt has been made to identify all major hazards and their respective impacts within Marin County, it must be highlighted that we live in a time of new and emerging threats.

To the extent to which there are certain natural events which are inevitable and necessary for the environment to remain in balance (e.g., earthquakes, wildfires, and flooding), the County of Marin recognizes that no natural hazard is solely natural, and the risk assessments identified within this plan are linked to human influences from local and global human actions or inaction.

Risk to natural hazards is a combination of hazard, vulnerability, and capability. The risk assessment process identifies and profiles relevant hazards and assesses the exposure of lives, property, and infrastructure to these hazards. The goal of the risk assessment is to estimate the potential losses in Marin County from a hazard event. This process also allows communities in Marin County to better understand their potential risk to human-influenced, natural hazards and provides a framework for developing and prioritizing mitigation actions to reduce risks from future hazards in Marin County.

3.1 HAZARD IDENTIFICATION
The process of identifying hazards that do or could potentially affect Marin County at various levels was the first step in assessing overall risk. Recognizing the potential required an analysis of known, suspected, and emerging hazards existing within or directly affecting Marin County.

Some of the following questions were used during the analysis:
• What are the known hazards?
• What are the suspected hazards?
• What are the potential, new, or emerging hazards?
• What are the elements of the hazard?
• What are the conditions associated with the occurrence of a hazardous event? • What factors are required for an event to turn hazardous? The Steering Committee reviewed data from the following sources on hazards affecting the county: the Federal and State Disaster Declaration History, the State of California Hazard Mitigation Plan (2018), the Safety Element of the participating jurisdictions, and the 2018 Marin County OA MJHMP. Additional documents are noted in the reference section of this document. 44 CFR Requirement §201.6(c)(2)(i) [The risk assessment shall include a] descrip�on of the type, loca�on and extent of all natural hazards that can affect the jurisdic�on. The plan shall include informa�on on previous occurrences of hazard events and on the probability of future hazard events. l ~<;>U·N· TY OF
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The Steering Committee came to agreement on significant hazards to the Marin County OA.

The following natural hazards are detailed in this section and are profiled for each jurisdiction participating in the Marin County OA MJHMP:

Table 3.1: Marin County OA MJHMP Hazard Identification and Comparison 2023 Hazards Climate
Profile
2018
Hazards Comment
Climate Change Yes Climate Change –
not included
The impact of climate change
profiled and discussed in all
applicable hazards.

Coastal Erosion Now profiled under debris
flows/landslide.

Dam Failure Earthquake Now profiled as a separate hazard.

Debris Flow Yes Severe Storm
and Wildfire Now profiled as a separate hazard.

Drought Yes Wildfire Now profiled as a separate hazard.

Earthquake Earthquake Continued as a hazard.

Flood Yes Severe Storm Now profiled as a separate hazard.

Land Subsidence Yes Severe Storm Now profiled as a separate hazard.

Levee Failure Yes Severe Storm Now profiled as a separate hazard.

Liquefaction Now profiled under Earthquake.

Sea Level Rise Yes Sea Level Rise
– Severe Storms
Sea Level Rise now profiled as a
separate hazard.

Severe Weather –
Extreme Heat Yes Wildfire Now profiled under Severe Weather.

Severe Weather –
High Wind/Tornado Yes Severe Storm Continued as a hazard under Severe Weather.

Tsunami Yes Tsunami/Seiche Continued as a hazard
Wildfire Yes Wildfire Continued as a hazard
Table 3.1: Marin County OA MJHMP Hazard Identification and Comparison Table 3.2 below lists additional hazards of interest that were identified by the Steering Committee as having some potential to impact the planning area but are not hazards eligible for Hazard Mitigation Grant Funding. These hazards have been briefly profiled to illustrate their potential impact on the County of Marin. No formal risk assessment of these hazards was performed. However, all planning partners for this plan should be aware of these hazards and should take steps to reduce the risks they present whenever it is practical to do so. l ~<;>U·N· TY OF
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Table 3.2: Marin County OA MJHMP Other Hazards Profiled Critical Infrastructure/ Utility Disruption
Cyber Threats
Oil Spills
Pandemic
Air Pollution
Transportation Systems
Table 3.2: Marin County OA MJHMP Other Hazards Profiled

3.1.1 DISASTER DECLARATION HISTORY
One method to identify hazards is to look at the events that have triggered federal and/or state disaster declarations that included Marin County. The following table lists the disaster declarations where Marin County was designated federal and/or state disaster declarations since the 2018 MJHMP update.

Table 3.3 shows the number of state and federal declared disasters in Marin County in relation to the rest of California from 1950-2023.

Table 3.3: State and Federal Declared Disasters in Marin County Location Event Type(s) Year State/Federal # Damage Est.* Tomales Tornado 1996 $205,000
Southern Marin Flash Flood 1998 $2,000,000
Corte Madera Heavy Rain 2002 $200,000
Coastal Marin Coastal Flood 2005/
2006 $340,000
Countywide Flood 2005/
2006 $219,000,000
Interior Valleys Debris Flow 2006 $45,900,000
Coastal Marin Strong Wind 2006 $500,000
Interior Valleys Frost/Freeze 2007 $3,000,000
Corte Madera Flash Flood 2008 $50,000
Interior Valleys and
Mountains Strong Wind 2009 $140,000
Countywide (Santa
Venetia) Flood/Wind 2009 $260,000
Interior Valleys Strong Wind 2009 $85,000
Coastal Marin Coastal Flood, Strong
Wind, Flood 2010 $770,000
Countywide (Larkspur) Heavy Rain/ Strong
Wind 2010 $100,000
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Countywide Strong Wind 2010 $85,000
Coastal Marin Strong Wind/Storm
Surge 2011 $325,000
Interior Valleys Strong Wind 2011 $50,000
Interior Valleys Strong Wind 2011 $200,000
Interior Valleys Strong Wind 2012 $60,000
Interior Valleys and
Coast Strong Wind 2012 $501,500
Interior Valleys Strong Wind 2012 $150,000
Interior Valleys Strong Wind 2012 $50,100
Countywide Flood/Strong Wind 2012 $210,100
Mountains Strong Wind 2013 $80,000
Countywide (Greenbrae,
Novato, Marin City,
Tamalpais Valley, Olema)
Flash Flood/Debris
Flow 2014 $6,001,000
Interior Valleys/Coast Strong Wind 2014 $115,600
Interior Valleys and
Mountains Strong Wind 2015 $23,500
Mill Valley AFS Heavy Rain 2015 No data
Interior Valleys Coastal Flood 2016 No data
Interior Valleys Strong Wind 2016 No data
Alto Flash Flood 2016 No data
Countywide Severe Winter Storms,
Flooding, Landslides 2017 Fed 3381 No data
Countywide Severe Winter Storms,
Flooding, Landslides 2017 Fed 4301 No data
Countywide Severe Winter Storms,
Flooding, Landslides 2017 Fed 4302 No data
San Rafael and Corte
Madera Flood 2017 Local No data
Kentfield Flash Flood 2017 Local No data
Tomales Flood 2017 Local No data
Corte Madera Flood 2017 Local No data
Ignacio, Burdell, Marin
City, Mountains
Strong Wind, Flash
Flood, Flood 2017 Local No data
Interior Valleys Strong Wind 2017 Local No data
Mountains Strong Wind 2017 Local No data
Mountains and Coast Strong Wind 2017 Local No data
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Interior Valleys and
Mountains Strong Wind 2017 Local No data
Greenbrae and
Mountains Strong Wind, Flood 2017 Local No data
Interior Valleys and
Coast Strong Wind 2017 Local No data
Corte Madera Flood 2018 Local No data
Countywide Public Safety Power
Shutoff (PSPS) 2019 Local
Countywide Severe Winter Storms,
Flooding, Landslides 2019 Fed 4431
Countywide Severe Winter Storms,
Flooding, Landslides 2019 Fed 4434
Countywide COVID-19 2020 Fed 4482
Woodward Valley Trail
and the Coast Trail
(Woodward Fire)
Lightning, Wildfire 2020 Local
Pt Reyes
Coastal Oil Spill
(American Challenger
ship wreck)
2021 Local
Countywide Drought 2021 Local
Countywide Extreme Heat Event 2021 Local
Countywide
Atmospheric River,
Severe Winter Storms,
Flooding
2021 CDAA 2022-02
Countywide Severe Winter Storms,
Flooding, Landslides 2022 Fed DR-4683
Countywide
Severe Winter Storms,
High Winds, Flooding,
Landslides
2022 Fed DR-4699
Countywide Severe Winter Storms,
Flooding, Landslides
2022-
2023
CDAA 2023-01
CDAA 2023-02
Countywide Severe Winter Storms,
Flooding, Landslides 2023 CDAA 2023-03
* Damage estimates may be initial damage estimates for the Local Proclamations and do not necessarily represent the final damage estimates.

Table 3.3: State and Federal Declared Disasters in Marin County

3.1.2 OMISSION OF HAZARDS
Several natural hazards were omitted from further analysis for all participating jurisdictions due to either their low probability of occurrence or minimal impact:
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Avalanche: An avalanche is a rapid flow of snow down a hill or mountainside. The Marin County OA rarely gets snow and not in significant enough quantities to cause an avalanche.

Fog: Fog is a collection of water droplets or ice crystals suspended in the air at or near the Earth’s surface. While the Marin County OA experiences severe and dense fog, Marin County does not consider it to be a significant enough threat for profiling in the 2023 Marin County OA MJHMP.

Haboob: A haboob is a type of intense dust storm carried on an atmospheric gravity current known as a weather front. Haboobs occur primarily in arid regions including parts of Arizona, New Mexico, and Texas. The Marin County OA does not have arid land and does not experience haboobs.

Severe Weather – Hail/Ice/Snow: Hail is pellets of frozen rain that fall in showers from cumulonimbus clouds while snow is atmospheric water vapor frozen into ice crystals and falling in light white flakes. There have been minor occurrences of hail, ice, and snow in Marin County, but none that have had significant impacts. A significant event is not expected to occur in the Marin County OA due to its mild winter temperatures and climate.

Severe Weather – Freeze/Extreme Cold: Freeze and extreme cold are defined as a period in which temperatures fall below the freezing point of 32 degrees Fahrenheit or 0 degrees Celsius.

The Marin County OA rarely experiences freezing temperatures or extreme cold due to its mild winter temperatures and climate.

Space Weather: Space weather includes conditions and events on the sun, in solar wind, in near-Earth space, and in Earth’s upper atmosphere that can affect space-borne and groundbased technological systems. Space weather also includes asteroids, comets, and meteors.

There have been no space weather events in Marin County. While a solar flare has the potential to disrupt communications and while an impact from a space object could cause significant loss of life and destruction, the unknown results of these events limit the County’s ability to truly profile and assess this hazard.

Tropical Storm/Hurricane: A tropical storm is a tropical cyclone with winds of 39-73 miles per hour while a hurricane is a tropical cyclone with winds of 74 miles per hour or greater. Though tropical cyclones have passed over Southern California, none have reached Marin County due to its northern latitude and climate. Whereas climate change may include the likelihood of a Tropical Storm and Hurricane reaching the Bay Area, the Marin Operational Area will view these hazards as a severe storm, strong winds, and/ or flooding events, which are profiled within the document.

Volcano: A volcano is a mountain that opens downward to a reservoir of molten rock below the surface of the earth. While there are volcanoes in the Cascade Range to the north of Marin County that could potentially impact the Marin County OA with ash fall upon eruption, the Marin County OA does not consider volcanoes to be significant enough for profiling in the 2023 Marin County OA MJHMP.
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3.2 HAZARD ANALYSIS
The Hazard Identification and Risk Assessment (HIRA) provides the factual basis for activities proposed in the mitigation strategy that will reduce losses from identified hazards. The HIRA makes a clear connection between the community’s vulnerability and the hazard mitigation actions. According to Section 44 of the Code of Federal Regulations, The MJHMP must include a definition and description of the natural hazards that can affect the jurisdiction(s) in the planning area, as well as several additional required elements for natural hazards:

Location and Previous Occurrences
Location means the geographic areas in the planning area that are affected by each hazard.

This information is shown in narrative form and/or in maps. The MJHMP also includes the history of previous hazard events for each of the identified hazards.

Impacts
Impact means the consequence or effect of the hazard on the community and its assets.

Assets are determined by the community and include, for example, people, structures, facilities, systems, capabilities, and/or activities that have value to the community.

Extent
Extent describes the potential severity of a disaster and any secondary events caused by the hazard in the operational area. Extent is classified by the following:
• Catastrophic: More than 50 percent of the operational area affected • Critical: Between 25-50 percent of the operational area affected • Limited: 10-25 percent of the operational area affected • Negligible: Less than 10 percent of the operational area affected Probability
Probability notes the frequency of past events and is used to gauge the likelihood of future occurrences. Based on historical data, the probability of future occurrences is categorized into 44 CFR Requirement §201.6(c)(2)(ii) [The risk assessment shall include a] descrip�on of the jurisdic�on’s vulnerability to the hazards described in paragraph (c)(2)(i) of this sec�on. This descrip�on shall include an overall summary of each hazard and its impact on the community. All plans approved a�er October 1, 2008 must also address NFIP insured structures that have been repe��vely damaged by floods. The plan should describe vulnerability in terms of:
(A) The types and numbers of exis�ng and future buildings, infrastructure, and cri�cal facili�es located in the iden�fied hazard areas;
(B) An es�mate of the poten�al dollar losses to vulnerable structures iden�fied in … this sec�on and a descrip�on of the methodology used to prepare the es�mate. (C) Providing a general descrip�on of land uses and development trends within the community so that mi�ga�on op�ons can be considered in future land use decisions. §201.6(c)(2)(iii) For mul�‐jurisdic�onal plans, the risk assessment sec�on must assess each jurisdic�on’s risks where they vary from the risks facing the en�re planning area. l ~<;>U·N· TY OF
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one of the following classifications:
• Highly Likely: Near 100 percent chance of occurrence next year or happens every year • Likely: Between 10 percent and 100 percent chance of occurrence in the next year or has a recurrence interval of 10 years or less
• Occasional: Between 1 percent and 10 percent chance of occurrence in the next year or has a recurrence interval of 11 to 50 years
• Unlikely: Less than 1 percent chance of occurrence in next 50 years or has a recurrence interval of greater than every 50 years
The probability, or chance of occurrence, was calculated where possible based on existing data.

Probability was determined by dividing the number of events observed by the number of years and multiplying by 100. This gives the percent chance of the event happening in any given year.

An example would be three droughts occurring over a 30-year period, which suggests a 10 percent chance of that hazard occurring in any given year.

Vulnerability
The vulnerability assessment further defines and quantifies populations, buildings, critical facilities, and other community assets at risk to natural hazards. The vulnerability assessment for this plan followed the methodology described in the FEMA 386-2, Understanding Your Risks – Identifying Hazards and Estimating Losses.

The vulnerability assessment was conducted based on the best available data and the significance of the hazard. Data to support the vulnerability assessment was collected from the following sources:
• County and jurisdictional GIS data (hazards, base layers, and other government data) through MarinMap
• Statewide GIS datasets compiled by CalOES to support mitigation planning • Written descriptions of assets and risks provided by participating jurisdictions • Existing plans and reports
• Personal interviews with jurisdictional representatives and other stakeholders The vulnerability assessment describes the assets at risk in Marin County, including the total exposure of people and property; critical facilities and infrastructure; natural, cultural, and historic resources; and economic assets.

During the Kickoff Meeting with the MJHMP Planning Team and the Steering Committee, the group was provided with a Hazard Risk Ranking Worksheet to complete. The members were asked to provide their opinion on the types of hazards that may impact Marin County. These hazards will be included in the Hazard Identification and Risk Assessment portion of the MJHMP and considered in the Mitigation Strategy portion of the MJHMP. They were asked to consider a hazard from the perspective of the worst-case scenario. Members were provided a list of hazards from the 2018 MJHMP and additional hazards they presented for consideration.

The list of hazards was consolidated to group similar hazards and focused on only natural hazards, per FEMA’s guidance for local hazard mitigation planning. Members were asked to choose the most likely hazards within the County.
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The results of the assessment from the Planning Team and Steering Committee assessment were presented to the Steering Committee to validate. The Steering Committee came to agreement on the following significant hazards to Marin County and its participating jurisdictions. These significant natural hazards are detailed and ranked in this section:

Table 3.4: Marin County Hazard Risk Assessment
Hazard
Probability/
Likelihood of
Future Events
Geographic
Extent
Magnitude/
Severity
Climate
Change
Influence
Significance Risk
Score
Dam Failure Unlikely Negligible Extreme Low Medium 9.00 Debris Flow,
Erosion, Landslide,
Post-Fire Debris
Flow
Occasional Extensive Severe Medium Medium 13.00
Drought Highly Likely Extensive Moderate High High 16.00 Earthquake Highly Likely Extensive Extreme None High 15.00 Flooding Highly Likely Limited Severe High Medium 14.00 Land Subsidence
(Sinkhole) Occasional Limited Moderate Medium Medium 10.00 Levee Failure Unlikely Negligible Moderate Medium High 9.00 Sea Level Rise Highly Likely Limited Extreme High High 16.00 Severe Weather –
Extreme Heat Highly Likely Extensive Moderate High Medium 15.00 Severe Weather –
Wind, Tornado Highly Likely Extensive Moderate High Medium 15.00 Tsunami Highly Likely Limited Extreme Medium High 15.00 Wildfire Highly Likely Significant Severe High High 16.00 Table 3.4: Marin County Hazard Risk Assessment
Once the Steering Committee determined the hazards to be profiled, they were asked to assess the vulnerability and risk to their jurisdictions or districts posed by these hazards. To inform this assessment the Steering Committee completed a detailed list of their critical facilities, critical infrastructure, and high potential loss facilities in their jurisdiction or district. This information was inputted into the County of Marin Office of Emergency Management GIS mapping program and plotted on a map of their jurisdiction or district. Each hazard profiled was then separately overlayed onto the map of the jurisdiction or district to show the impact the hazard may have on the critical facilities, critical infrastructure, and high potential loss facilities.

The Steering Committee was provided a hazard vulnerability and risk assessment tool to assess and score each hazard based on five categories: Probability/ Likelihood of Future Events, Geographic Extent, Magnitude/ Severity, Climate Change Influence, and Significance.

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jurisdiction or special district was asked to consider their exposure to each hazard. If their jurisdiction or district is not vulnerable to sea level rise then they might assess their vulnerability to that hazard as "None." For hazards that they are vulnerable to they were asked to assess them using the extent, likelihood, and severity categories discussed above.

Probability/ Likelihood of Future Events
• Unlikely: Occurs in intervals greater than 100 years - Less than 1% probability of occurrence in the next year or a recurrence interval greater than 100 years. • Occasional: Occurring every 11 to 100 years - 1-10% probability of occurrence in the next year or a recurrence interval of 11 to 100 years.
• Likely: Occurring every 1 to 10 years - 10-90% probability of occurrence in the next year or recurrence interval of 1 to 10 years.
• Highly Likely: Occurring almost every year - 90-100% probability of occurrence in the next year or a recurrence interval of less than 1 year.

Geographic Extent
• Negligible: Less than 10% of the planning area
• Limited: 10-25% of the planning area
• Significant: 25-75% of planning area
• Extensive: 75-100% of planning area
Magnitude/ Severity
• Weak: Limited classification on scientific scale, slow speed of onset or short duration of event, resulting in little to no damage.
• Moderate: Moderate classification on scientific scale, moderate speed of onset or moderate duration of event, resulting in some damage and loss of services for days. • Severe: Severe classification on scientific scale, fast speed of onset or long duration of event, resulting in devastating damage and loss of services for weeks or months. • Extreme: Extreme classification on scientific scale, immediate onset or extended duration of event, resulting in catastrophic damage and uninhabitable conditions.

Table 3.5: Hazard Magnitude and Severity Scale
Hazard Scale/Index Weak Moderate Severe Extreme
Drought Palmer Drought
Severity Index +1.99 to -1.99 -2.00 to -2.99 -3.00 to -3.99 -4.00 and below Earthquake Modified
Mercalli I to IV V to VII VIII IX to XII
Richter
Magnitude 2,3 4,5 6 7,8
Hurricane Wind
Saffir-Simpson
Hurricane
Wind Scale
1 2 3 4,5
Tornado Fujita Tornado
Damage Scale FO F1, F2 F3 F4, F5
Table 3.5: Hazard Magnitude and Severity Scale
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Climate Change Influence
• Low: Minimal potential impact
• Medium: Moderate potential impact
• High: Widespread potential impact
Significance
• Low: Minimal potential impact - Two or more criteria fall in lower classifications, or the event has a minimal impact on the planning area. This rating is sometimes used for hazards with a minimal or unknown record of occurrences or for hazards with minimal mitigation potential.
• Medium: Moderate potential impact - The criteria fall mostly in the middle ranges of classifications and the event’s impacts on the planning area are noticeable but not devastating. This rating is sometimes used for hazards with a high extent rating but very low probability rating.
• High: Widespread potential impact - The criteria consistently fall in the high classifications and the event is likely/highly likely to occur with.

Each jurisdiction and district completed the Hazard Vulnerability and Risk Assessment Tool, and their individual results are recorded in their Jurisdictional or District Profile. The following Table

3.4 illustrates the results of the Marin County Risk Assessment.

Table 3.6: Marin County OA Hazard Risk Assessment –
Top Hazards Scored
Hazard Ranking Score

1. Drought 16

2. Sea Level Rise 16

3. Wildfire 16

4. Earthquake 15

5. Severe Weather – Extreme Heat 15

6. Severe Weather – Wind, Tornado 15

7. Tsunami 15

8. Flooding 14

9. Debris Flow, Erosion, Landslide, Post-Fire
Debris Flow 13

10. Land Subsidence (Sinkhole) 10

11. Dam Failure 9

12. Levee Failure 9
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Risk Level Risk Numerical Score
High Risk 12 - 16
Serious Risk 8 - 11
Moderate Risk 4 - 7
Low Risk 1 - 3
Figure 3.1: Marin County Risk Assessment – Top Hazards Graphed

3.2.1 CLIMATE CHANGE
The County of Marin and associated jurisdictions profiled jointly recognize that the earth’s climate is forcibly being augmented due to humans’ reliance on fossil fuels and non-natural resources which pose negative impacts on the earth’s climate. Reliance on fossil fuels and nonnatural products results in the climate shifting to include unseasonable temperatures, more frequent and intense storms, prolonged heat and cold events, and a greater reliance on technological advancements to maintain the wellbeing of community members and balance of the environment. The forced adaptation to climatic shifts is necessary for the County and jurisdictions to understand and include with these assessments.

Locally to Marin, drought and rain events have already had devastating impacts to critical infrastructure, agriculture, and water resources; and globally, unseasonable temperatures have been identified as the cause for enhanced wildfires, severe droughts, ice sheets and glaciers disappearing, and persons emigrating from their countries due to a lack of sustainable, local resources. Melting land ice contributes additional water to the oceans and as ocean temperatures rise the water expands, both of which contribute to increase rates of sea level rise.

Marin is bordered on the west by the Pacific Ocean and on the east by San Francisco Bay, making it particularly vulnerable to flooding and erosion caused by sea level rise. 16 16 16
15 15 15 15
14 13
10 9 9
0 2
4 6
8 10
12 14
16 18
Weighted Rank Percentage Value
Hazard Types
Hazards by Rank
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The cause of current climate change is largely human activity, burning fossil fuels, natural gas, oil, and coal. Burning these materials releases greenhouse gases into Earth’s atmosphere.

Greenhouse gases trap heat from the sun’s rays inside the atmosphere causing Earth’s average temperature to rise. This rise in the planet's temperature was formerly called, “global warming”, but climate change has shown to include both intense heat and cold shifts. The warming of the planet impacts local and regional climates. Throughout Earth's history, climate has continually changed; however, when occurring naturally, this is a slower process that has taken place over hundreds and thousands of years. The human influenced climate change that is happening now is occurring at an abnormally faster rate with devastating results.

GLOBAL OBSERVED AND PROJECTED CLIMATE CHANGE IMPACTS AND RISKS The Intergovernmental Panel on Climate Change (IPCC) assesses the impacts of climate change, looking at ecosystems, biodiversity, and human communities at global and regional levels. The IPCC also reviews vulnerabilities and the capacities and limits of the natural world and human societies to adapt to climate change. In their Sixth Assessment Report from 20221 ,
the following observations were made:
• Human-induced climate change, including more frequent and intense extreme events, has caused widespread adverse impacts and related losses and damages to nature and people, beyond natural climate variability.
• Global warming, reaching 1.5°C in the near-term, would cause unavoidable increases in multiple climate hazards and present multiple risks to ecosystems and humans. • Beyond 2040 and depending on the level of global warming, climate change will lead to numerous risks to natural and human systems.
• The magnitude and rate of climate change and associated risks depend strongly on near-term mitigation and adaptation actions, and projected adverse impacts and related losses and damages escalate with every increment of global warming. • Multiple climate hazards will occur simultaneously, and multiple climatic and non-climatic risks will interact, resulting in compounding overall risk and risks cascading across sectors and regions.

A 2020 study by the National Aeronautics and Space Administration (NASA) 2 confirmed that climate models are getting future warming projects right, finding the following:
• If global warming transiently exceeds 1.5°C in the coming decades or later, then many human and natural systems will face additional severe risks. • An estimated 60% of today’s methane emissions are the result of human activities. The largest sources of methane are agriculture, fossil fuels, and decomposition of landfill waste.
1 Intergovernmental Panel on Climate Change, Headline Statements from the Summary for Policymakers, 2022. https://www.ipcc.ch/report/ar6/wg2/resources/spm-headline-statements/ 2 Study Confirms Climate Models are Getting Future Warming Projections Right, 2020. https://climate.nasa.gov/news/2943/study-confirms-climate-models-are-getting-future-warming-projectionsright/ l ~<;>U·N· TY OF
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• The concentration of methane in the atmosphere has more than doubled over the past 200 years. Scientists estimate that this increase is responsible for 20 to 30% of climate warming since the Industrial Revolution (which began in 1750). • According to the most recent National Climate Assessment, droughts in the Southwest and heat waves (periods of abnormally hot weather lasting days to weeks) are projected to become more intense, and cold waves less intense and less frequent. • The last eight years have been the hottest years on record for the globe.

Figure 3.2: NASA Global Temperature Change CO2 Gas
Source: NASA Global Climate Change, 2022
Figure 3.3: NASA Global Temperature Change 1884 to 2022 Source: NASA Global Climate Change, 2022
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ATMOSPHERIC METHANE CONCENTRATIONS
SINCE 1984
Data source Data frorn NOAA, measured from a global
networK of a,r sampling sites
c
g
:ZS 1soo ------,------+-----"7'1-""'-----+- m

0. ~ "' 1750 ---~--~ - ,:e_-+-----~------+-
£',
I
Ll 1100 -----,,.c...,-------+--------,-------+--
1650
19M 2000 2010 ?020
YfcAR
TIME SERIES: 1884 TO 2022
Data source: NASNGISS
Credit: NASA's Scientific Visualization Studio
420
400
c
~ 380 E

11. "1 360 t:
!
6 340 [J
320
\ !160 19 70
YEAR
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Drought
• The 22-year-long megadrought in southwestern US was the driest the territory had experienced in at least 1,200 years and was expected to persist.

Sea Level Rise
• Global sea levels are rising as a result of human-caused global warming, with recent rates being unprecedented over the past 2,500-plus years. • U.S. sea levels are projected to rise 1 to 6.6 Feet by 2100. (Note: Global sea levels have risen about 8 inches (0.2 meters) since reliable record-keeping began in 1880. By 2100, scientists project that it will rise at least another foot (0.3 meters), but possibly as high as

6.6 feet (2 meters) in a high-emissions scenario.)
• Sea ice cover in the Arctic Ocean is expected to continue decreasing, and the Arctic Ocean will very likely become essentially “ice-free” in late summer seasons if current projections hold. This change is expected to occur before mid-century. • An indicator of changes to the projected sea level rise is the Arctic Sea ice minimum over time. Arctic Sea ice to this extent both affects and is affected by global climate change.

Figure 3.4: NASA Global Temperature Change Sea Level
Source: NASA Global Climate Change, 2022
Wildfire
• Warming temperatures have extended and intensified wildfire season in the West, where long-term drought in the region has heightened the risk of fires. 1 ~<;>U·N· TY OF a ~ ARIN ~
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Data source: Satellfte sea level observations.

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• Scientists estimate that human-caused climate change has already doubled the area of forest burned in recent decades. By around 2050, the amount of land consumed by wildfires in Western states is projected to further increase by two to six times. • Even in traditionally rainy regions like the Southeast, wildfires are projected to increase by about 30%.

Flooding (Precipitation)
• Climate change is having an uneven effect on precipitation (rain and snow) in the United States, with some locations experiencing increased precipitation and flooding, while others suffer from drought.
• On average, 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 U.S. suggest that the recent trend toward increased heavy precipitation events will continue. This means that while it may rain less frequently in some regions (such as the Southwest), when it does rain, heavy downpours will be more common.

Extreme Cold
• The length of the frost-free season, and the corresponding growing season, has been increasing since the 1980s, with the largest increases occurring in the western United States.

Climate change can also have numerous general impacts on human health (see Figure 3.5).

Figure 3.5: Human Health Impacts from Climate Change
Source: U.S. Center for Disease Control and Prevention

INDICATORS OF CLIMATE CHANGE IN CALIFORNIA
According to the California Natural Resource Agency (CNRA), climate change is already affecting California and is projected to continue to do so well into the foreseeable future.

Current and projected changes include increased temperatures, sea level rise, a reduced winter snowpack, altered precipitation patterns, and more frequent storm events. Over the long term, reducing greenhouse gases can help make these changes less severe, but the changes cannot be avoided entirely. Unavoidable climate impacts result in a variety of secondary consequences including detrimental impacts on human health and safety, economic continuity, ecosystem l ~ <;>U·N· TY OF
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Environmental Degradation
Forced migration, civil conflict, mental
health impacts, los.:s of jobs and income
Extreme Heat
Hei;lt; elated illness i;ind death,
cardiovascular failure
Severe Weather
Injuries, fatalities, loss of homes,
mental health impacts
Water & Food Supply Impacts
Malnutrition, dianheal disegse
Degraded Living Conditions
& Social Inequities
Exacerbation of existing social and health
inequitill:!s and vulnerabilities
Changes In Vector Ecology
Malaria, dengue, encephalitis,
hantavirus, Rrft: Valley fever, Lyme
diseasl:!, c:hikungunya, West Nile virus
Air Pollution &
Increasing Allergens
Asthma, cardiovascular disease,
respiratory allergies
W.W QualQ:y Impacts

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integrity and provision of basic services. Climate change is being profiled in the 2023 Marin County Hazard Mitigation Plan as a standalone hazard while addressing each of the other natural hazards. Marin County is considering climate change issues when identifying future mitigation actions.

California is experiencing a climate crisis that is increasingly taking a toll on the health and wellbeing of its people and on its unique and diverse ecosystems. Every Californian has suffered from the effects of record high temperatures, dry winters, prolonged drought, and proliferating wildfires in recent years. California’s biodiversity is threatened as alterations to habitat conditions brought about by a changing climate are occurring at a pace that could overwhelm the ability of plant and animal species to adapt.

The California Office of Environmental Health Hazard Assessment (OEHHA) found the following indicators of climate change in California in a 2022 report3 :
• Since 1895, annual average air temperatures in California have increased by about 2.5 degrees Fahrenheit (°F). Warming occurred at a faster rate beginning in the 1980s. • Recent years have been especially warm: Eight of the ten warmest years on record occurred between 2012 and 2022; 2014 was the warmest year on record. • Of all the Western states, California endured the hottest temperatures for the longest time, driving the average statewide temperature to the second warmest over the past 128 years.
• Extreme heat ranks among the deadliest of all climate-driven hazards in California, with physical, social, political, and economic factors effecting the capacity of individuals, workers, and communities to adapt, and with the most severe impacts often on communities who experience the greatest social and health inequities. • Glaciers have essentially disappeared from the Trinity Alps in Northern California • In 2020, wildfire smoke plumes were present in each county for at least 46 days. • The 2022 fire season saw more fires than the previous fire season along with continued extreme drought and heat conditions.
• The drought, begun in 2019, was the third statewide drought declared in California since 2000.
• This drought has been marked by extreme swings; the state received record-breaking amounts of precipitation in October and December 2021 that were offset by the driest January, February, and March 2022 dating back more than 100 years. The year 2023 opened with California simultaneously managing both drought and flood emergencies. • A series of storms in late December 2022 and early January 2023 broke rural levees, disrupted power, flooded roads, downed trees, and eroded coastal land. • Sea level rise accelerates coastal erosion, worsens coastal flooding during large storms and peak tidal events, and impacts important infrastructure positioned along our state’s 1,100-mile coast.
• The western drought which impacted all of California and the western United States was nearly lifted due to unseasonably heavy rains in late 2022 and early 2023. 3 2022 Report: Indicators of Climate Change in California. https://oehha.ca.gov/climate-change/epic-2022 l ~<;>U·N· TY OF
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The graph below shows the relative change, in millimeters, in sea levels at Crescent City (1933-2020), San Francisco (1900-2020), and La Jolla (1925-2020) as a result of climate change:

Figure 3.6: Annual Mean Sea Level Trends
Source: 2022 Report: Indicators of Climate Change in California | OEHHA The impact of climate change in California varies across the state due to diversity in biophysical setting, climate, and jurisdictional characteristics. The California Adaptation Planning Guide organized the state into climate impact regions based on county boundaries in combination with projected climate impacts, existing environmental settings, socioeconomic factors, and regional designations and organizations (see Figure 3.7).
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- 100
- 150
-200
1900 1910 1920 1930 1940 1950 1960 1970
Chart: OEHHA Climate Change Indicators of California 2022 • Source: NOAA · Get the data · Download image • Created with Datawrapper 1980 1990 2000 2010 2020
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Figure 3.7: California Climate Impact Regions
Source: California Adaptiation Planning Guide

CLIMATE CHANGE IN THE MARIN COUNTY OPERATIONAL AREA
Climate change is already having significant impacts across California and the Marin County OA. Temperatures are warming, heat waves are more frequent, seas are rising and precipitation has become increasingly variable. Climate change will continue to alter Marin County OA ecosystems as a result of rising temperatures, changes in precipitation, and sea level rise, which will increase the severity and occurrence of natural hazards across the Marin County OA well into the future. Coastal cooling processes that keep temperatures down, such as fog, will continue to decrease. Rising temperatures will exacerbate drought conditions and raise the potential for significant wildfires and associated smoke as vegetation becomes drier and tree mortality increases. Forested woodlands that play a major role in carbon reduction will gradually transition into chaparral and shrublands. There will be more extreme storms and l ~ <;>U·N· TY OF
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weather events, including expanded heat waves and increased rain events with changes in precipitation, placing increased strain on levees and dams across the Marin County OA.

Significant rain events will lead to an increase in flooding and the potential for severe landslides.

Shoreline communities will become inundated with sea level rise, storm surge, high tide events, and potential tsunamis. Marshlands and wetlands that act as natural storm barriers will disappear as they transition into open water.

Notable impacts from climate change that are already evident in the Marin County OA and surrounding region as identified in a 2020 Marin County Civil Grand Jury Report include:
• From 1895-2018, the average temperature in Marin County increased by 2.3 degrees Fahrenheit.
• Over the past century, sea level rise in the San Francisco Bay Area rose by eight inches and has accelerated rapidly since 2011.
• The threat of wildfires in 2019 was so severe that Pacific Gas and Electric shut off electric power to the County for multiple days.

Climate change will continue to affect homes, businesses, infrastructure, utilities, transportation systems and agriculture across the Marin County OA. The risk to socially vulnerable populations will increase as they feel the immediate impacts of climate change more significantly and are less able to adapt to climate changes and recover from its impacts.

The Marin County OA has adopted numerous planning initiatives and mitigation measures to help combat the effects of climate change across the OA. The Marin Climate Energy Partnership (MCEP), which is a partnership program including numerous Marin County jurisdictions, the County of Marin, and regional agencies, adopted a model Climate Action Plan (CAP) that is intended to support countywide strategic efforts and is currently being used to update or establish climate action plans for additional jurisdictions within Marin County. The adopted Climate Action Plan serves as the adopted plan for the unincorporated County, which was completed in 2020. The MCEP also collects data and reports on progress in meeting each County jurisdictions’ individual greenhouse gas emission targets. In October 2022, the County published the Greenhouse Gas Inventory for Unincorporated Community Emissions for the Year 2020. Marin County OA jurisdictions have already met their greenhouse reduction goals for 2020 and are about halfway to meeting the statewide goal to reduce emissions 40% below 1990 levels by the year 2030. Marin County also formed a Sea Level Marin Adaptation Response Team in 2018 and had a Sea Level Rise Vulnerability Assessment and associated Adaptation Report completed for the County and each of its jurisdictions in 2017 as part of their Bay Waterfront Adaptation and Vulnerability Evaluation. Additional Marin County OA climate change mitigation programs and initiatives include Marin Clean Energy, Electrify Marin, the Marin Solar Project, the Marin Energy Watch Partnership, Resilient Neighborhoods, and Drawdown: Marin.

3.2.2 PARTICIPATING JURISDICTION HAZARD ASSESSMENT
Each Marin County OA MJHMP participating jurisdiction and organization reviewed and approved the Top Hazards identified by the Planning Team. Each participating jurisdiction and organization then completed a more complex assessment tool to further develop their hazard assessment and prioritization. The completed Hazard Risk Assessment Tables are located in the Section 2.0: Hazard Identification and Risk Assessment of the Jurisdictional or Special District Annex Profile.
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The planning process used the available FEMA tools to evaluate all the possible threats faced.

The primary tool selected was the Hazard Risk Assessment and Prioritization Tool. This matrix allowed the participating jurisdiction or organization to assess their own level of vulnerability and mitigation capability. Each participating Jurisdiction and organization assessed the top hazards for:
• Probability/Likelihood of future events or frequency
• Geographic Extent
• Impact to property, resources, and humans
• Magnitude/Severity
• Significance
• Climate Change Influence
• Mitigation capacity
Through the threat analysis process, the most probable, frequent and devastating threats to Marin County were identified. Other threats not identified in this plan, that could potentially affect Marin County, are identified and addressed in other plans such as the County Emergency Operations Plan, functional annexes, operational response plans, and various policies and procedures.

3.3 HAZARD RISK ASSESSMENT

3.3.1 DAM FAILURE
Dams are manmade structures built for a variety of uses including flood protection, power generation, agriculture, water supply, and recreation. When dams are constructed for flood protection, they are usually engineered to withstand a flood with a computed risk of occurrence.

For example, a dam may be designed to contain a flood at a location on a stream that has a certain probability of occurring in any one year. If prolonged periods of rainfall and flooding occur that exceed the design requirements, that structure may be overtopped and fail.

Overtopping is the primary cause of earthen dam failure in the United States.

Dam failure is the uncontrolled release of impounded water from behind a dam. Flooding, earthquakes, blockages, landslides, lack of maintenance, improper operation, poor construction, vandalism, and terrorism can all cause a dam to fail. Dam failure causes downstream flooding that can affect life and property. Dam failures can result from any one or a combination of the following causes:
• Earthquake
• Inadequate spillway capacity resulting in excess overtopping flows • Internal erosion caused by embankment or foundation leakage, or piping or rodent activity
• Improper design
• Improper maintenance
• Negligent operation
• Failure of upstream dams on the same waterway
Water released by a failed dam generates tremendous energy and can cause a flood that is catastrophic to life and property. A catastrophic dam failure could challenge local response l ~<;>U·N· TY OF
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capabilities and require evacuations to save lives. Impacts to life safety will depend on the warning time and the resources available to notify and evacuate the public. Major loss of life could result as well as potentially catastrophic effects to roads, bridges, healthcare facilities, schools, homes, and hazardous materials storage facilities. Electric generating facilities and transmission lines could also be damaged and affect life support systems in communities outside the immediate hazard area. Associated water supply, water quality and health concerns could also be an issue. Factors that influence the potential severity of a full or partial dam failure are the amount of water impounded; the density, type, and value of development and infrastructure located downstream; and the speed of failure.

In general, there are three types of dams: concrete arch or hydraulic fill, earth and rockfill, and concrete gravity. Each type of dam has different failure characteristics. A concrete arch or hydraulic fill dam can fail almost instantaneously, where the flood wave builds up rapidly to a peak then gradually declines. An earth-rockfill dam fails gradually due to erosion of the breach, where a flood wave will build gradually to a peak and then decline until the reservoir is empty. A concrete gravity dam can fail instantaneously or gradually with a corresponding buildup and decline of the flood wave.

The California Department of Water Resources (DWR) Division of Safety of Dams (DSOD) has jurisdiction over impoundments that meet certain capacity and height criteria. Embankments that are less than six feet high and impoundments that can store less than 15 acre-feet are nonjurisdictional. Additionally, dams that are less than 25 feet high can impound up to 50 acre-feet without being jurisdictional. The Cal DWR DSOD assigns hazard ratings to large dams within the State. The following two factors are considered when assigning hazard ratings: existing land use and land use controls (zoning) downstream of the dam. Dams are classified in three categories that identify the potential hazard to life and property:
• High hazard indicates that a failure would most probably result in the loss of life. • Significant hazard indicates that a failure could result in appreciable property damage.
• Low hazard indicates that failure would result in only minimal property damage and loss of life is unlikely.

Since 1929, the state has supervised all non-federal dams in California to prevent failure for the purpose of safeguarding life and protecting property. Supervision is carried out through the state’s Dam Safety Program under the jurisdiction of DWR. The legislation requiring state supervision was passed in response to the St. Francis Dam failure and concerns about the potential risks to the general populace from a number of water storage dams. The law requires:

Examination and approval or repair of dams completed prior to August 14, 1929, the effective date of the statute.

Approval of plans and specifications for and supervision of construction of new dams and the enlargement, alteration, repair, or removal of existing dams.

Supervision of maintenance and operation of all dams under the state’s jurisdiction.

The 1963 failure of the Baldwin Hills Dam in Southern California led the Legislature to amend the California Water Code to include within state jurisdiction both new and existing off-stream storage facilities.
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Dams and reservoirs subject to state supervision are defined in California Water Code §6002 through §6004, with exemptions defined in §6004 and §6025. In administering the Dam Safety Program, DWR must comply with the provisions of the California Environmental Quality Act (CEQA). As such, all formal dam approval and revocation actions must be preceded by appropriate environmental documentation.

In 1972, Congress moved to reduce the hazards from the 28,000 non-federal dams in the country by passing Public Law 92-367, the National Dam Inspection Act. With the passage of this law, Congress authorized the U.S. Army Corps of Engineers (USACE) to inventory dams located in the United States. The action was spurred by two disastrous earthen dam failures during the year, in West Virginia and South Dakota, that caused a total of 300 deaths.

The Water Resources Development Act of 1986 (P.L 99-662) authorized USACE to maintain and periodically publish an updated National Inventory of Dams (NID). The Water Resources Development Act of 1996 (P.L. 104-303), Section 215, re-authorized periodic updates of the NID by USACE.

Location and Previous Occurrences
Reservoirs for water supply and the dams that impound them are integral parts of the municipal infrastructure in Marin County. Unlike most other counties in California, Marin does not import or export water through the Central Valley State and Federal water projects. The Marin Municipal Water District (MMWD) and the North Marin Municipal Water District (NMWD) operate and maintain eight major dams for municipal water supplies within their jurisdictions (see Table 3.7) MMWD dams include Alpine Dam, Bon Tempe Dam, Lagunitas Dam, Phoenix Dam, Peters Dam (Kent Lake), Nicasio Dam, and Soulajule Dam. NMWD maintains and operates one dam at Stafford Lake on Novato Creek for its smaller service area. None of these reservoirs generate hydroelectricity nor are they actively managed for downstream flood control.

The California Water Code entrusts dam safety regulatory power to the California Department of Water Resources (DWR), Division of Safety of Dams (DSOD). Dams greater than 6-feet in height and impounding 50 acre feet or more of water, and dams greater than 25-feet in height and impounding more than 15 acre-feet of water are subject to DSOD jurisdiction. According to the California water code, owners of regulated dams are responsible for emergency preparedness with regard to potential loss of life or property. All regulated dams are inspected by DSOD annually. MMWD inspection reports are available on their website. As of 2017 DSOD classifies the public safety risk of all jurisdictional dams.

Dam locations of high, significant, and low hazard dams that may affect the Marin County OA are shown in Figure 3.10.
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Table 3.7 shows dams in Marin County that could impact the OA.

Table 3.7: Hazard Ranked Dams in Marin County with Potential to Impact to the OA Dam Name/
Dam Number
Hazard
Class Latitude Longitude Nearest City/ Distance
Population
At Risk
Capacity
(acrefeet)
Dam
Height Dam Owner
Alpine
33-0 High 37.94 -122.64 Stinson Beach,
CA 2.76 miles 10 - 100 8,892 143 Marin Municipal Water District Big Rock
Ranch 437-0 High 38.05 -122.63 > 1,000 91 45 Lucasfilm, LTD Bon Tempe
33-6 High 37.96 -122.61 Fairfax, CA

2.49 miles
100 –
1,000 4,300 98 Marin Municipal Water District
Lagunitas
33-2 Significant 37.95 -122.60 Kentfield, CA 2.14 miles 100 –
1,000 341 48 Marin Municipal Water District
Novato Creek/
Stafford Lake
88-0
Extremely
High 38.12 -122.64 Novato, CA 3.76 miles 10 - 100 140 76 North Marin County Water District Peters
33-7 High 38.00 -122.70 Lagunitas, CA

1.00 miles 0 32,900 320 Marin Municipal Water District
Phoenix Lake
33-3 High 37.96 -122.58 Kentfield, CA

1.01 miles 10 - 100 612 90 Marin Municipal Water District Seeger
33-8 High 38.08 -122.76 1 - 10 22,400 115 Marin Municipal Water District
Soulajule
33-9 High 38.15 -122.78 Inverness, CA 5.26 miles 1 - 10 10,700 122 Marin Municipal Water District
Vonsen
430-0 High 38.18 -122.68 Sheep Ranch 6
miles 10 - 100 70 35 Private Property
Table 3.7: Hazard Ranked Dams in Marin County with Potential to Impact to the OA Source: California Department of Water Resources, Division of Safety of Dams I ~'?U ..N. TY OF
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Figure 3.8: Dams in and around the Marin County OA
Source: Cal OES, Department of Water Resources, DSOD, 11/27/23 Figure 3.9 illustrates the Dam Failure risk to Marin County. l ~<;>U·N· TY OF
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Figure 3.9: Marin County Dam Inundation Susceptibility to Critical Facilities Source: Marin County OEM
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email: [email protected]
Date Printed: 11/20/23
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California has had about 45 failures of non-federal dams. The failures occurred for a variety of reasons, the most common being overtopping. Other reasons include specific shortcomings in the dams themselves or an inadequate assessment of surrounding geomorphologic characteristics.

California’s first notable dam failure was in 1883 in Sierra County, while the most recent failure occurred in 1965. The most catastrophic event was the failure of William Mulholland’s infamous St. Francis Dam, which failed in 1928 and killed an estimated 450 people, only slightly fewer than the 1906 San Francisco earthquake. The actual number of dead from the St. Francis Dam failure was likely substantially higher. San Francisquito Canyon, which was flooded in the event, was home to hundreds of transients and illegal immigrants who were never accounted for in the death totals.

In February 2017 California witnessed the failure of the spillway and emergency spillway at Lake Oroville leading to the evacuation of 188,000 people from the downstream inundation area. Situations like this, overtopping and erosion of a dam’s face as a result of flows exceeding the capacity of spillway is another mechanism of dam failure, however reservoir inflows in the Marin County OA do not have to accommodate the volatility of melting snowpack that occurs in the Sierra Nevada foothills.

There is no record of a failure of any regulated dam located in the Marin County OA.

Impacts
Areas of Marin County could be significantly impacted by a failure of any one of its high hazard dams. Inundation maps are based on a hypothetical failure of a dam or critical appurtenant structure and the information depicted on the maps is approximate.

Phoenix Lake Dam
Failure of the Phoenix Lake Dam with Phoenix Lake at full capacity could flood about five miles along Ross Creek down to the Town of Ross, part of San Anselmo where Ross Creek meets Corte Madera Creek, along Corte Madera Creek to unincorporated Kentfield, through the edge of Larkspur and Corte Madera and out into San Pablo Bay. Inundation maps and a discussion of vulnerability for San Anselmo, Ross, Larkspur and Corte Madera can be found in their respective Annexes.
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Figure 3.10: Phoenix Lake Dam Inundation Area
Source: Cal OES, Department of Water Resources, DSOD, 11/27/23 In the unlikely event of a dam failure associated with Phoenix Lake Dam, floodwaters could reach the commercial center of Kentwood in approximately half an hour, inundating it up to five feet in some areas. Sections of critical infrastructure, including Sir Francis Drake Boulevard and several medical facilities could flood as a result of this dam failure. Dozens of homes and apartment complexes, numerous commercial buildings and community facilities, the Kent Middle School, part of the College of Marin-Kentfield Campus including the College of Marin Police Department station, and the Marin County Sherriff’s Office Kentfield Substation could all experience flooding.

Phoenix Lake Dam
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Figure 3.11: Phoenix Lake Dam Inundation Area – Kentfield North Source: California Department of Water Resources
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Figure 3.12: Phoenix Lake Dam Inundation Area – Kentfield South Source: California Department of Water Resources
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Novato Creek/Stafford Lake Dam
Failure of the Novato Creek Dam with Stafford Lake at full capacity would affect an area that extends approximately five miles down Novato Creek through parts of the unincorporated County and the City of Novato to San Pablo Bay at Bel Marin Keys. Inundation maps and a discussion of vulnerability for Novato can be found in Annex I.

Figure 3.13: Novato Creek/ Stafford Lake Dam Inundation Area Source: Cal OES, Department of Water Resources, DSOD, 11/27/23 Parts of Ohair Park adjacent to the dam and along Novato Creek could be immediately inundated with up to ten feet of water. After passing through Novato, floodwaters could reach the Novato RV Park in approximately two hours and some businesses and the Novato Fire Protection District Station 62 along Atherton Avenue in the Green Point area in approximately ten to fifteen hours, inundating them in over ten feet of water. Floodwaters could reach Bel Marin Keys in ten to fifteen hours. While most homes in Bel Marin Keys should be protected from floodwaters, some homes could be flooded up to several feet. Parts of Bel Marin Keys Boulevard could become flooded in several feet of water, possibly turning Bel Marin Keys into an island temporarily. A PG&E substation at Hamilton Wetlands along with the Bel Marin Gardens Hospital could be inundated with several feet of water.

Novato Creek/ Stafford Lake Dam
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Figure 3.14: Novato Creek Dam Inundation Area – Green Point and Bel Marin Keys Source: California Department of Water Resources
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Bon Tempe Dam
Failure of the Bon Tempe Dam with Kent Lake at full capacity could result in flooding in unincorporated areas of West Marin County, stretching about 10 miles from the reservoir down to Point Reyes Station at Highway 1 and into Tomales Bay.

Figure 3.15: Bon Tempe Dam Inundation Area
Source: Cal OES, Department of Water Resources, DSOD, 11/27/23 On its path, floodwaters could extend up San Geromino Creek in approximately one hour, flooding dozens of homes and buildings along the creek in Lagunitas and Forest Knolls in a depth up to fifty feet in some areas. Floodwaters from the creek could extend into the western edges of San Geronimo in approximately one and half hours, impacting several shelters, the San Geronimo Valley Community the San Geronimo Valley School, and the Lagunitas School with a depth of several feet.

Bon Tempe Dam
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Figure 3.16: Bon Tempe Dam Inundation Area – Lagunitas-Forest Knolls-San Geronimo Area Source: California Department of Water Resources
Further down Lagunitas Creek, water could flood parts of Samuel P. Taylor State Park including camping areas. Water could flood around five miles of Sir Francis Drake Boulevard along Lagunitas Creek and several dozen buildings along the road including the PG&E substation at Tocaloma. Floodwaters could extend down Platform Bridge Road towards Point Reyes Petaluma Road at a depth up to fifty feet in some areas. Eventually the inundation area could reach Point Reyes Station, with floodwaters extending into the southern end of the community around Highway 1 in the commercial core at a depth of several feet including the Marin County Point Reyes Fire Station, The Marin County Sherrif’s Office Point Reyes Substation and the West Marin Elementary School. Floodwaters could reach up to thirty feet in some areas surrounding Point Reyes Station. Floodwaters could eventually reach Tomales Bay in approximately six hours, impacting the Tomales Bay estuary with an influx of fresh water. The unincorporated community of Inverness could experience a surge from Tomales Bay, with flooding up to several feet in residences, marinas, hotels, and other facilities along Sir Francis Drake Boulevard including the main commercial area. Inundation from Tomales Bay could also impact some homes and businesses on the east side of the Bay, including up Walker Creek and around Nick’s Cove, Marshall, and Marconi in up to ten feet of water. l ~<;>U·N· TY OF
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Figure 3.17: Bon Tempe Dam Inundation Area – Point Reyes Station Area South Source: California Department of Water Resources
Figure 3.18: Bon Tempe Dam Inundation Area – Point Reyes Station Area North and Inverness Source: California Department of Water Resources
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Peters Dam
Failure of the Peters Dam with Kent Lake at full capacity could result in flooding in unincorporated areas of West Marin County with similar impacts as a failure of the Bon Tempe Dam but to a different extent.

Figure 3.19: Peters Dam Inundation Area
Source: Cal OES, Department of Water Resources, DSOD, 11/27/23 While floodwaters could extend up San Geronimo Creek in approximately half an hour and flood dozens of homes in Lagunitas and Forest Knolls in a depth up to twenty feet in some areas, the floodwaters are not expected to reach San Geronimo.

Peters Dam
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Figure 3.20: Peters Dam Inundation Area – Lagunitas-Forest Knolls Area Source: California Department of Water Resources
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Water could flood parts of Samuel P. Taylor State Park including camping areas. Water could flood around five miles of Sir Francis Drake Boulevard along Lagunitas Creek and several dozen buildings along the road to a depth of several feet. Floodwaters could extend down Platform Bridge Road towards Point Reyes Petaluma Road. Eventually the inundation area could reach Point Reyes Station at approximately one hour after dam failure. Floodwaters could extend at a depth of several feet into the southern end of the community around Highway 1 and up to thirty feet in surrounding areas but would not reach as far as with a failure of the Bon Tempe Dam. Numerous homes and businesses in the commercial core of Point Reyes Station could still be flooded. Floodwaters could eventually reach Tomales Bay in approximately an hour and a half, impacting the Tomales Bay estuary with an influx of fresh water. The unincorporated community of Inverness could experience a surge from Tomales Bay, with flooding up to several feet in residences, marinas, hotels, and other facilities along Sir Francis Drake Boulevard including the main commercial area. Inundation from Tomales Bay could also impact some homes and businesses on the east side of the Bay, including up Walker Creek and around Nick’s Cove, Marshall, and Marconi in several feet of water.

Figure 3.21: Peters Dam Inundation Area – Point Reyes Station Area Source: California Department of Water Resources
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Alpine Dam
Failure of the Alpine Dam with Alpine Lake at full capacity could result in flooding in unincorporated areas of West Marin County along a similar path as a failure of the Bon Tempe and Peters Dam but to a lesser extent.

Figure 3.22: Alpine Dam Inundation Area
Source: Cal OES, Department of Water Resources, DSOD, 11/27/23 Water would not extend as far out along Lagunitas Creek and would not extend up San Geronimo Creek into Lagunitas and Forest Knolls. While a failure of the dam could still flood around five miles of Sir Francis Drake Boulevard and several dozen buildings along that road including the PG&E substation at Tocaloma, the inundation area skirts the edge of Point Reyes Station where there is less of a risk for flooding of homes and facilities than with a failure of the Bon Tempe Dam or the Peters Dam. Floodwaters could reach the Point Reyes Station area around Highway 1 in approximately four hours with a depth up to ten feet in some areas.

Floodwaters could eventually reach Tomales Bay in approximately six hours, impacting the Alpine Dam
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Tomales Bay estuary with an influx of fresh water. Floodwaters are not expected to reach the community of Inverness or have any major flooding to residents and businesses along the east side of Tomales Bay.

Figure 3.23: Alpine Dam Inundation Area – Point Reyes Station Source: California Department of Water Resources
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Lagunitas Dam
Failure of the Lagunitas Dam with Lake Lagunitas at full capacity could result in flooding in unincorporated areas of West Marin County along a similar path as a failure of the Bon Tempe, Peters, and Alpine Dams but to a much lesser extent. Water would stay mostly confined to Lagunitas Creek before it reached Tomales Bay in approximately 32 hours and no major flooding impacts would be expected.

Figure 3.24: Lagunitas Dam Inundation Area
Source: Cal OES, Department of Water Resources, DSOD, 11/27/23 Lagunitas Dam
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Seeger Dam
Failure of the Seeger Dam with Nicasio Reservoir at full capacity could send water several miles down Novato Creek to Lagunitas Creek and could result in flooding in unincorporated areas of West Marin County.

Figure 3.25: Seeger Dam Inundation Area
Source: Cal OES, Department of Water Resources, DSOD, 11/27/23 Floodwaters could extend down Lagunitas Creek and Point Reyes Petaluma Road, eventually reaching the commercial core of Point Reyes Station at approximately one hour after dam failure. Floodwaters could extend to a depth of several feet into the southeastern end of the community inundating numerous homes and businesses and could extend to a depth up to thirty feet in surrounding area. Floodwaters could travel down Sir Francis Drake Boulevard, inundating it in several feet of water, before eventually reaching Tomales Bay in approximately 45 minutes. The Tomales Bay estuary would be inundated with an influx of fresh water. The unincorporated community of Inverness could experience flooding of a few feet in residences, marinas, hotels, and other facilities along Sir Francis Drake Boulevard including in the main commercial area.

Seeger Dam
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Figure 3.26: Seeger Dam Inundation Area – Point Reyes Station East Source: California Department of Water Resources
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Figure 3.27: Seeger Dam Inundation Area – Point Reyes Station West Source: California Department of Water Resources
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Floodwaters could also extend up Lagunitas Creek and Platform Bridge Road to Sir Francis Drake Boulevard at approximately half an hour and extend as far south as the edge of Samuel P. Taylor State Park before becoming contained in the creek. Both roadways could flood in several places with up to fifty feet of water. Several dozen buildings along both roads including the PG&E substation at Tocaloma could be inundated with several feet of water.

Big Rock Ranch Dam
Failure of the Big Rock Ranch Dam with Big Rock Ranch Lake at full capacity could send water several miles down Nicasio Creek.

Figure 3.28: Big Rock Ranch Dam Inundation Area
Source: Cal OES, Department of Water Resources, DSOD, 11/27/23 Water could flood sections of Lucas Valley Road in up to five feet of water in some places and could flood several homes in several feet of water. Floodwaters could eventually reach Nicasio Valley Road in approximately eighty minutes and then be contained in the creek without impacting the community of Nicasio.
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Figure 3.29: Big Rock Ranch Dam Inundation Area East
Source: California Department of Water Resources
Dam Name: Big Rock Ranch
DSOD No.: 437.000
NID No.: CA01457
Dam Owner: Skywalker Properties Ltd. LLC
County: Marin
Failure Scenario: Sunny Day Breach
Projection: NAD 83 California Teale Albers (US Feet)
Horizontal Datum: NAD83, GRS 1980 Spheroid
Vertical Datum: NAVD88
Floodihg Illa! ii oonflned within a et·u,111W1&I btJI not•~ wllh., the lnuMatlon bt11.11.iary Mil')' uintinue beytind the ln~l!IUi:s, bOul'ldllry.

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Structure
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Value (foot)
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Breach Analysis
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Sunny Day Breach Scenario
Flood Depth and Arrival Time
Marin County, CA
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Figure 3.30: Big Rock Ranch Dam Inundation Area West
Source: California Department of Water Resources
Dam Name: Big Rock Ranch
DSOD No.: 437.000
NID No.: CA01457
Dam Owner: Skywalker Properties Ltd. LLC
County: Marin
Failure Scenario: Sunny Day Breach Projection: NAD 83 California Teale Albers (US Feet) Horizontal Datum: NAD83, GRS 1980 Spheroid
Vertical Datum: NAVD88
Floodrlg that i!I; canfil'H!!d within a du11'1'!el blA nots~ ~In lh1!' ll'All'ldallon bounda,y may conUrnJe bey'OOd the lntmallM boondaty. 0 500 1,000
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Value (featl
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Exhibit 2-2
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Flood Depth and Arrival Time
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Soulajule Dam
Failure of the Big Rock Ranch Dam with Soulajule Reservoir at full capacity could send water several miles down Walker Creek in a mostly rural area of western Marin County.

Figure 3.31: Soulajule Dam Inundation Area
Source: Cal OES, Department of Water Resources, DSOD, 11/27/23 Marshall Petaluma Road could become inundated with up to forty feet of water where it runs along Walker Creek and part of Salmon Creek, with several buildings along the road to the east and west of the intersection of Arroya Sausal Road becoming inundated with several feet of water. Parts of the Marin County Office of Education at Walker Creek Ranch and the Walker Creek Ranch itself could be inundated with up to twenty feet of water in approximately half an hour after dam failure.

Soulajule Dam
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Figure 3.32: Soulajule Dam Inundation Area around Soulajule Dam Source: California Department of Water Resources
Floodwaters along Walker Creek could eventually reach Highway 1 south of Tomales in approximately three hours, inundating the roadway with several feet of water before emptying into Tomales Bay in approximately three and half hours. There are a few residences and other buildings along Walker Creek and Highway 1 that could be impacted by floodwaters several feet deep.
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Figure 3.33: Soulajule Dam Inundation Area – Walker Creek at Highway 1 Source: California Department of Water Resources
Figure 3.34: Soulajule Dam Inundation Area – Walker Creek at Highway 1 and Tomales Bay Source: California Department of Water Resources
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Vonsen Dam
Failure of the Vonsen Dam could inundate several homes around the dam and along San Antonio Creek for several hundred feet with up to a foot of water before floodwaters are contained within the creek.

Figure 3.35: Vonsen Dam Inundation Area
Source: Cal OES, Department of Water Resources, DSOD, 11/27/23 Vonsen Dam
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Figure 3.36: Vosen Dam Inundation Area
Source: California Department of Water Resources
Extent and Probability
According to the 1988 Town of Ross General Plan Safety Element, “in 1974, a seismic stability analysis of Phoenix Lake Dam was conducted for the Marin Municipal Water District. The purpose of this study was to assess the risk of seismically induced flooding associated with failure of Phoenix Lake Dam. The earth dam was constructed just prior to the 1906 earthquake, which created a landslide on the inside portion of the dam embankment. The slope stability analysis conducted in 1974 concluded that the dam spillway could settle from 4 – 6 feet during an earthquake with a Richter magnitude of 8.5 generated along the San Andreas fault. The 1906 San Francisco earthquake had a Richter magnitude of 8.3…In response to this assessment, the Marin Municipal Water District has widened the spillway by 5 to 6 feet and has lowered the spillway by 6 feet. Accordingly, these improvements to the dam have reduced the flood risk to one flood in 30,000 years.”
According to MMWD, “the dam has been modified several times in the last 100 years including increased height of fill, outlet works changes, an embankment buttress fill in the 1960s and a new spillway, designed for a spillway design flood with a recurrence interval of once in 10,000 years or so, and an increase in freeboard in the mid-1980s.” The Town of Ross’s 2017 Local Hazard Mitigation Plan states “the dam is inspected yearly by the California Division of Safety of Dams and has been rated by that agency as acceptable for continued operation. Their rating for the facility is 3C, there is a potential for damage should the dam fail but that the dam is in good condition for its age. l ~<;>U·N· TY OF
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SUNNY DAY BREACH INUNDATION MAP - VONSEN DAM
CA State Dam No. 430
NID No. CA 00592
Simulation Date March 28, 2021
Map Preparation Date July 28, 2021
Failure Scenerio - Sunny Day Failure

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“MMWD has a comprehensive Dam Safety Program to ensure all of the MMWD dams and spillways are safe and functioning properly. This program includes three main components:
monitoring, routine inspections and maintenance, and emergency preparedness and response planning. The district also works closely with state and federal regulators and local emergency response partners to ensure public safety. MMWD produced a February 13, 2017 inspection report documenting the current conditions.
“The Phoenix Lake Dam is over 100 years old. According to ABAG, when a dam in known to have a failure potential, the water level is reduced to allow for partial collapse without loss of water as required by the State Division of Safety of Dams and by safety protocols established by dam owners. Thus, the probability of failure resulting in damage from the inundation is low.” According to the City of Novato’s 2011 Local Hazard Mitigation Plan, a seismic stability analysis prepared for the North Marin Water District by Woodward-Clyde Consultants in 1992 confirmed the Stafford Dam was designed to withstand a magnitude 8.25 Richter earthquake on the San Andreas Fault, with a design epicenter located 10 miles from the dam.

Table 3.8: Marin County OA Hazard Risk Assessment – Dam Failure Jurisdiction
Probability/
Likelihood
of Future
Events
Geographic
Extent
Magnitude/
Severity
Climate
Change
Influence
Significance Risk
Score
Marin County Unlikely Negligible Extreme Low Medium 9.00 City of
Belvedere Unlikely Negligible Extreme High High 12.00
Town of
Corte Madera Unlikely Negligible Weak None None 3.00
Town of
Fairfax None None None None None 0.00
City of
Larkspur Unlikely Limited Severe Low Low 8.00
City of
Mill Valley None None None None None 0.00
City of
Novato Unlikely Significant Severe Low Low 9.00
Town of
Ross Unlikely Limited Severe Low Medium 9.00
Town of
San Anselmo Unlikely Negligible Weak Low Low 5.00
City of
San Rafael None None None None None 0.00
City of
Sausalito None None None None None 0.00
Town of
Tiburon Unlikely Negligible Extreme None Medium 8.00
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Bolinas
Public Utility
District
Unlikely Limited Extreme Medium Medium 11.00
Las Gallinas
Valley
Sanitary
District
None None None None None 0.00
North Marin
Water
District
Unlikely Extensive Extreme High High 15.00
Southern
Marin Fire
District
None None None None None 0.00
Table 3.8: Marin County OA Hazard Risk Assessment – Dam Failure Source: Profiled Jurisdictions and Districts
Vulnerability
Because of the catastrophic nature of the threat of dam inundation, dams tend to be built conservatively and the actual likelihood of either dam overflow or dam failure are extremely low.

The Phoenix Lake and Novato Creek Dams in particular are expected to withstand an earthquake at least magnitude 8.2 on the San Andreas Fault, which is a rare magnitude to encounter. Earthquakes of a magnitude 8.0 or greater are expected once every 494 years in California according to USGS.

The areas of unincorporated Marin County most vulnerable to the threat of a dam failure are those areas most like to be impacted by one. Several incorporated jurisdictions in the Marin County OA would be affected by a failure of either the Phoenix Lake or Novato Creek Dams, and their vulnerability assessments can be found in their respective Annexes.

The community of Point Reyes Station and the surrounding area lies in the inundation path of several dams including the Bon Tempe, Peters, Alpine, Lagunitas, and Seeger Dams. Major roadways, including Highway 1, Sir Francis Drake Boulevard, Platform Bridge Road and Point Reyes Road are particularly vulnerable to a failure of any one of these dams which would limit access to the communities of Point Reyes Station and Inverness from the south. Residences, businesses, critical facilities, and other buildings around the Point Reyes and Inverness areas and along the eastern and western shores of Tomales Bay that are not built to withstand the depth and velocity of floodwaters from a dam failure would be most vulnerable, including older buildings and those that are not elevated. A failure of the PG&E substation at Tocaloma could cause power outages throughout the area. Older docking facilities along Tomales Bay are particularly vulnerable to a surge in Tomales Bay as a result of a dam failure.

The communities of Lagunitas and Forest Knolls and to a lesser extend the community of San Geronimo are also susceptible to a failure of the Bon Tempe and Peters Dams. With flooding of Sir Francis Drake Boulevard, these communities would effectively be cut off from the west.

Residences, businesses, schools, and other buildings in these communities that are not elevated to withstand the depth of floodwaters are most susceptible.

The community of Kentwood is vulnerable to a failure of the Phoenix Lake Dam, particularly the areas closest to Corte Madera Creek. Residences, businesses, commercial facilities, and critical facilities around the College of Marin Kentfield Campus that are not elevated to withstand floodwaters are particularly susceptible.
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Areas of Green Point would be most susceptible to a failure of the Novato Creek Dam, as most of Bel Marin Keys should avoid major flooding. Buildings that are not elevated and those that are not as able to withstand the velocity of floodwaters from a dam failure, such as mobile home parks, would be most susceptible.

Climate Change and Future Development Considerations
Most dams in the United States are aging and are at significant risk from increased storm events as a result of climate change. The average dam age in the United States is 60 years, and more than 8,000 dams in the United States including the Phoenix Lake Dam are over 90 years old. More than 200 U.S. dams have failed in bad weather since 2000. As the climate warms, rain events are predicted to become more intense. An increase in rainfall and runoff as a result of climate change will increase the potential for higher water levels in reservoirs across the Marin County OA, placing increased stress on its dams and increasing the potential for a dam failure. As development increases in the populated areas of the Marin County OA downstream of its dams, particularly in the inundation area of the Phoenix Lake Dam, the potential for significant impacts to residents and infrastructure will only increase.

3.3.2 DEBRIS FLOW
For the purposes of the Marin County OA MJHMP, debris flows are classified as landslides (including rockslides) and mud flows.

A landside is the breaking away and gravity-driven downward movement of hill slope materials, which can travel at speeds ranging from fractions of an inch per year to tens of miles per hour depending on the slope steepness and water content of the rock/soil mass. Landslides range from the size of an automobile to a mile or more in length and width and, due to their sheer weight and speed, can cause serious damage and loss of life. The rate of a landslide is affected by the type and extent of vegetation, slope angle, degree of water saturation, strength of the rocks, and the mass and thickness of the deposit. Some of the natural causes of this instability are earthquakes, weak materials, stream and coastal erosion, and heavy rainfall. In addition, certain human activities tend to make the earth materials less stable and increase the chance of ground failure. These activities include extensive irrigation, poor drainage or groundwater withdrawal, removal of stabilizing vegetation and over-steepening of slopes by undercutting them or overloading them with artificial fill. These activities can cause slope failure, which normally produce landslides.

Landslide material types are often broadly categorized as either rock or soil, or a combination of the two for complex movements. Rock refers to hard or firm bedrock that was intact and in place prior to slope movement. Soil, either residual or transported material, means unconsolidated particles. The distinction between rock and soil is most often based on interpretation of geomorphic characteristics within landslide deposits but can also be inferred from geologic characteristics of the parent material described on maps or in the field. Landslide movements are also based on the geomorphic expression of the landslide deposit and source area, and are categorized as falls, topples, spreads, slides, or flows. Falls are masses of soil or rock that dislodge from steep slopes and free fall. Topples move by the forward pivoting of a mass around an axis below the displaced mass. Lateral spreads move by horizontal extension and shear or tensile fractures. Slides displace masses of material along one or more discrete planes and can either be rotational or transitional. Flows mobilize as a deforming, viscous mass without a discrete failure plane.

Natural conditions that contribute to landslide include the following:
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• Degree of slope
• Water (heavy rain, river flows, or wave action)
• Unconsolidated soil or soft rock and sediments
• Lack of vegetation (no stabilizing root structure)
• Previous wildfires and other forest disturbances
• Earthquake
In addition, many human activities tend to make the earth materials less stable and, thus, increase the chance of ground movement. Human activities contribute to soil instability through grading of steep slopes or overloading them with artificial fill, by extensive irrigation, construction of impermeable surfaces, excessive groundwater withdrawal, and removal of stabilizing vegetation.

Another hazard related to landslide and erosion is the fall of a detached mass of rock from a cliff or down a very steep slope (rockfall). Weathering and decomposition of geological materials produce conditions favorable to rockfalls. Other causes include ice wedging, root growth, or ground shaking (earthquake). Destructive landslides and rockfalls usually occur very suddenly with little or no warning time and are short in duration.

Landslides can cause high mortality and injuries from rapidly flowing water and debris. The most common cause of death in a landslide is trauma or suffocation by entrapment. Broken power, water, gas or sewage pipes can also result in injury or illness in the population affected, such as water-borne diseases, electrocution or lacerations from falling debris. People affected by landslides can also have short- and long-term mental health effects due to loss of family, property, livestock or crops. Landslides can also greatly impact the health system and essential services, such as water, electricity or communication lines.

Landslide susceptibly can be characterized by looking at both slope class and rock strength.

Landslide susceptibility classes express the generalization that on very low slopes, landslide susceptibility is low even in weak rock, and that landslide susceptibility increases with slope and in weaker rocks. Very high landslide susceptibility includes very steep slopes in hard rocks and moderate to very steep slopes in weak rocks. Figure 3.39 shows landslide susceptibility classes. l ~<;>U·N· TY OF
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Figure 3.37: Landslide Susceptibility Classes
Source: USGS
A mud flow is a general term for a mass-movement landform and process characterized by a flowing mass of fine-grained earth material with a high degree of fluidity. Heavy rainfall, snowmelt, or high levels of groundwater flowing through cracked bedrock may trigger a movement of soil or sediments. Floods and debris flows may also occur when strong rains on hill or mountain slopes cause extensive erosion and/or what is known as "channel scour".

Some broad mud flows are rather viscous and therefore slow; others begin very quickly and continue like an avalanche. Mud flows are composed of at least 50% silt and clay-sized materials and up to 30% water.

The point where a muddy material begins to flow depends on its grain size and the water content. Fine grainy material or soil has a smaller friction angle than a coarse sediment or a debris flow, but falling rock pieces can trigger a material flow, too. When a mud flow occurs it is given four named areas, the 'main scarp', in bigger mud flows the 'upper and lower shelves', and the 'toe'. See Figure 3.40 for the typical areas of a mud flow, with shelves (right) and without (left). The main scarp will be the original area of incidence, the toe is the last affected area(s). The upper and lower shelves are located wherever there is a large dip (due to mountain or natural drop) in the mud flow's path. A mud flow can have many shelves. 1 ~ <;>U·N· TY OF a ~ ARIN ~

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Figure 3.38: Mud Flow Areas
Source: Washington Department of Natural Resources
If large enough, mud flows can devastate villages and country-sides. Mud flows are common in mountain areas prone to wildfire, where they have destroyed many homes built on hillsides without sufficient support after fires destroy vegetation holding the land. The area most generally recognized as being at risk of a dangerous mud flow are:
• Areas where wildfires or human modification of the land have destroyed vegetation. • Areas where landslides have occurred before.
• Steep slopes and areas at the bottom of slopes or canyons. • Slopes that have been altered for construction of buildings and roads. • Channels along streams and rivers.
• Areas where surface runoff is directed.

Location and Previous Occurrences
Landslides are a part of natural geologic processes and have impacted both private and public property in various areas throughout Marin County since development began. Much of the Marin County OA was developed in the early 20th century prior to the implementation of grading requirements and road design standards. During this time, many of the roads in the Marin County OA were benched or cut into steep hillsides without sufficient compaction of the roadbed. Furthermore, the use of earth retaining structures was not common in roadway construction and/or retaining structures were built using wood materials that have since deteriorated. Figure 3.39 shows landslide susceptibility across the Marin County OA. l ~<;>U·N· TY OF
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Figure 3.39: Landslide Susceptibility in the Marin County OA Source: USGS
7/2412023, 1 :33:52 PM
Landslide
Susceptiblity
Classes
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Figure 3.40: Marin County Landslide Susceptibility for Critical Facilities Map Source: Marin County OEM
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Legend
• Dams Fire Stations
• Military and Civil Hospitals and Medical
Defense Installations Facilities
Communication Police/ Sheriff Stations Facilities
Schools Electric Power Facilities
Wastewater Facilities Landslide
Water Supply Facilities Susceptibility
Airports Class
Emergency Operations
Centers Ill
Marin County
Landslide
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VI
-VII .,.,..... ... ,
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0 2~~',,--s
e omc101
. . : EMERGENCY

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---' 10
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San Pablo Bay
Wildlife Area
Marin County OEM / Woody Baker-Cohn
email: [email protected] LJan
Date Printed: 10/ 30/23 N
County of Marin, California State Parks, Esri, HERE, Garmin, SafeGraph, Geo Technologies, Inc, METI/NASA, USGS, Bureau of Land Management, EPA, NPS, USDA, DOC/CGS, County of Marin, California State Parks, Esri, HERE, Garmin, SafeGraph, FAO, METI/ NASA, USGS, Bureau of Land Management, EPA, NPS 2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
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Several unincorporated communities in Marin County have high to extreme landslide susceptibility, which are shown below.

Figure 3.41 shows landslide susceptibility in Lagunitas, Forest Knolls, San Geronimo and Woodacre.

Figure 3.41: Landslide Susceptibility – Lagunitas, Forest Knolls, San Geronimo and Woodacre Source: Marin County, 11/27/23
Figure 3.42 shows landslide susceptibility in Nicasio and Tocoloma.

Figure 3.42: Landslide Susceptibility – Nicasio and Tocoloma Source: Marin County, 11/27/23
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Figure 3.43 shows landslide susceptibility in Olema and Point Reyes Station.

Figure 3.43: Landslide Susceptibility – Olema and Point Reyes Station Source: Marin County, 11/27/23
Figure 3.44 shows landslide susceptibility in Inverness.

Figure 3.44: Landslide Susceptibility – Inverness
Source: Marin County, 11/27/23
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Figure 3.45 shows landslide susceptibility in Dillon Beach and Tomales.

Figure 3.45: Landslide Susceptibility – Dillon Beach and Tomales Source: Marin County, 11/27/23
Figure 3.46 shows landslide susceptibility in Dogtown, Bolinas and Stinson Beach.

Figure 3.46: Landslide Susceptibility – Dogtown, Bolinas and Stinson Beach Source: Marin County, 11/27/23
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Figure 3.47 shows landslide susceptibility in the unincorporated area of Southern Marin County.

Figure 3.47: Landslide Susceptibility – Southern Marin County Source: Marin County
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Marin County / Southern Marin
Landslide •

DIHCIDI

EMERGENCY
• MANAGEMENT
Military and Civil
Defense Installations
Electric Power Facflities
Wastewater Facilities
Emergency Operations
Centers
County of Marin, Califor~i~ S

USDA, DOC/ CGS
Fire Stations
Hospitals and Medical
Facilities
Police / Sheriff Stations
Schools
Landslide
Susceptibility
Class
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M / Woody Baker-Cohn
_:[email protected]
ted : 10/ 30/23 ~ N _ USGS, Bureau of Land Management, EPA, NPS, 2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
164
Figure 3.48 shows landslide susceptibility in the unincorporated area of west central Marin County.

Figure 3.48: Landslide Susceptibility – West Central Marin County Source: Marin County
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Landslide
Hospitals and Medical III
Facilities v
Police/ Sheriff Stations - VI
Electric Power Facilities Schools • vn
- VIII Water Supply Facilities Landslide
Susceptibility - IX
• x
Fire Stations Class
County of Marin, California State Parks, Es ,, . . , ... .._,_,,.

USDA, DOC/CGS
•
0IIICI0I

EMERGENCY
• MANAGEMENT
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Figure 3.49 shows landslide susceptibility in the unincorporated area west of Novato.

Figure 3.49: Landslide Susceptibility – Novato West
Source: Marin County OEM
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Communication
Electric Power Facilities
Wastewater Facilities
Emergency Operations
Centers
Marin County / Novato West
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facilities V
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Schools - Vil
Landslide • vm
• ix Susceptibility • x
Class
•
omc101

EMERGENCY
• MANAGEMENT
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Figure 3.50 shows landslide susceptibility in the unincorporated area of west central Marin.

Figure 3.50: Landslide Susceptibility – West Central Marin County Source: Marin County OEM
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a
~
Marin County / W Central
Landslide
Hospitals and Medical
Facilities
Police/ Sheriff Stations
Electric Power Facilities Schools
Water Supply Facilities Landslide
~~n~!:ncy Operations Susceptibility
Class
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- VI
• vn
• vm
• ix
• x
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EMERGENCY
• MANAGEMENT
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Figure 3.51 shows landslide susceptibility in unincorporated area of North Novato.

Figure 3.51: Landslide Susceptibility – North Novato
Source: Marin County OEM
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Marin County / Novato North
Landslide
Landslide
Susceptibility
Electric Power Facilities Class
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V
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- VII
• vm
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EMERGENCY - MANAGEMENT
/
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The California Geological Survey has an interactive landslide inventory map available on their website that shows records associated with past landslide events in Marin County.

Figure 3.52: Landslide Inventory in the Marin County OA Source: California Geological Survey, 11/27/23
The inventory shows extensive areas of prior landslides around the county particularly in developed areas. Affected areas notably include many landslides near Bolinas Lagoon, Inverness and Bolinas (Point Reyes Station) ridges on the west coast; throughout Ross Valley including Sleepy Hollow, Fairfax and San Anselmo; San Rafael just outside downtown at Lincoln, Lock Lomond affecting many residences, San Quentin potentially affecting a wastewater treatment plant, and Bret Harte potentially affecting Highway 101; Santa Venetia affecting N. San Pedro Rd; Novato at Little Mountain and Mount Burdell affecting major roads such as Center Road, San Marin Drive and Novato Blvd and their nearby residential areas; Paradise Cay and Reed residential areas near Tiburon; and Mill Valley at Homestead Valley.

Smaller scale, and/or more isolated slides occur throughout the county where there are slopes.

These are typically of concern if there are roads or structures affected.

A massive mudslide occurred in Marin County during a storm from January 3-5, 1982, weakening foundation of the Golden Gate Bridge. The bridge had to be closed for several days, cutting off the one road linking Marin County to San Francisco and stranding residents. Another landslide blocked Highway 101, closing it completely. The Point Reyes and Inverness areas were especially hard hit. The unincorporated community of Inverness was isolated for several days when numerous slides covered the road into town. The storm caused huge amounts of water to rush down canyons, scouring them as rocks, mud, trees and massive trunks hit roads and houses on their way downward. Inverness and Inverness Park were inundated in rocks and mud.
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Ami [: 38.168 -121.799 Degrees
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Figure 3.53: Damage in Inverness from the January 1982 Storm Source: Jack Mason Museum of West Marin History
Twelve houses in Inverness were destroyed or damaged by mudslides, mostly in the Alder Creek Canyon area and the Vallejo Avenue area of Inverness Park. Over 300,000 cubic yards of mud was removed from public property in Inverness. The Inverness water system was destroyed when a main pipe ruptured and reservoirs were damaged.

Figure 3.54: January 1982 Highway 101 Mudslide in Marin County Source: San Francisco Chronicle
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From January to March of 1995, a series of winter storms caused several mudslides in Marin County, blocking roads and damaging residential and public property.

Marin County sustained significant damage as a result of the Winter and Spring storms of 2006 (DR-1628 and DR-1646) which resulted in hundreds of locations in Marin County where damage occurred; many of those being landslides, rock fall, or other infrastructure damage related to slope instability.

In 2011, a $1.5M emergency slide repair was constructed at the intersection of Terrace Avenue and Overlook Drive on the Bolinas Mesa to repair recent drastic settlement (up to 8-feet) such that access for emergency vehicles and resident egress could be maintained. As much as 20,000 cubic yards of material was excavated and re-compacted in lifts with earth reinforcing fabric to affect the repair.

In 2014, several debris flows impacted Marin County. On February 28th, a mudslide blocked part of Highway 1 at Panoramic. On December 11th, a mudslide occurred along Tennessee Valley Road, causing $1 million in property damage. Another landslide under sixty feet of Highway 1 near Muir Beach on the same day resulted in a full closure of the road, causing $1 million in damages.

Severe damage occurred during the January and February Winter storms of 2017 (DR-4305 and DR-4308) resulting in over 100 locations in Marin County where damage occurred.

Landslides occurred along Highway 101 and several local roads.

Figure 3.55: February 2017 Landslide on Lucas Valley Road Source: Marin County
Significant damage in Marin County occurred during the January and February Winter storms of 2019 (DR-4431 and DR-4344), where a series of atmospheric rivers caused separate mudslides on Sir Francis Drake Boulevard in Lagunitas and on Highway 101 in Waldo (shutting down the road southbound).
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On March 22, 2023, a mudslide severely damaged and buckled a 100-foot stretch of road on Redwood Boulevard adjacent to Highway 101 and just west of the Marin County Airport, forcing the closure of Olompali State Historic Park. The mudslide uncovered one of two PG&E gas lines but it remained intact.

Figure 3.56: March 2023 Mudslide in Marin County
Source: San Francisco Chronicle
Impacts
Marin County is largely undeveloped and has a widespread natural environment where creeks and rivers adjoin both private and public infrastructure. During times of intense rainfall, creeks tend to rise and the resulting high flows can erode roadway supporting earthen embankments leading to landslides and sometimes property damage. Historic development in the Marin County OA tends to be concentrated in small areas, with many homes located along creeks and on steep hillsides potentially impacted by precipitation-induced landslides. Thousands of existing structures have the potential to be impacted by landslides, including over ten thousand single family homes, in addition to multi-family, commercial structures, and structures on a few industrial parcels. Notably, hundreds of miles of roads are potentially impacted by landslides which can lead to their short-term closure during and after intense storm events and some power utility facilities could also be affected. Infrastructure, such as natural gas pipelines and water or wastewater infrastructure, can break or malfunction if the soil supporting them fails.

This can lead to disruptions in energy delivery and water or wastewater services. Landslides, mudslides, and debris flows can move fast enough to damage or destroy homes or other structures in their path, block roadways (including evacuation routes), and injure or kill people caught in them. For most jurisdictions in the Marin County OA, at least 10% of its homes and roadways can potentially be impacted by landslides. Landslides and debris flows could also have ecological impacts for numerous waterbodies in Marin County, including Tomales Bay and the Bolinas Lagoon.

Extent and Probability
Slope instability throughout much of the Marin County OA is related to many factors, including, but not limited to; type(s) of soil involved and various geologic factors (presence of faults or other weakened soil planes), steepness of the slope and surrounding topography, intensity and duration of rainfall, presence of underground springs or groundwater, adequacy of surface water management, and proper erosion protection. While landslides occur in any given year, the frequency and number of landslides has been observed to be directly proportionate to the frequency and duration of rainfall events. A landslide and/or a debris flow could occur in any l ~<;>U·N· TY OF
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unincorporated community of Marin County and throughout much of the Marin County OA due to its overall moderate to high landslide susceptibility.

Landslides are less likely to occur during the fall months (October-November) when the ground is sufficiently dry and can absorb the moderate rain events typically observed during this time of year. Landslides are more often observed between December and May when rain events are usually more intense and/or frequent. Under these circumstances, the ground has been saturated, becomes heavier, and the presence of water within the soil increases the pore pressure thereby reducing the friction between soil particles – which leads to sliding. Proper drainage management to maintain existing sufficient drainage patterns (on both private and public lands) is essential to limiting potential future landslide events. In the Marin County OA, renewed and potentially widespread landslide activity will most likely occur during or after future periods of prolonged or intense rainfall.

The extent of typical landslides in the Marin County OA, including in the unincorporated area, as estimated from previous occurrences, is on the order of 500 cubic yards of material displaced from an area 100 feet long and 30 feet deep. According to County engineering staff, Marin County seems to have bad slide years during heavy storms every five years. During these years, the County repairs a half dozen slides or more, so there might be a dozen bad slides across the County including incorporated areas. According to NOAA, the 5-year recurrence interval precipitation amount is 4 inches of rain in 12 hours, 5.8 inches of rain in 24 hours, or 7.6 inches of rain in 2 days.

Table 3.9: Marin County OA Hazard Risk Assessment – Debris Flows Jurisdiction
Probability/
Likelihood
of Future
Events
Geographic
Extent
Magnitude/
Severity
Climate
Change
Influence
Significance Risk
Score
Marin County Occasional Extensive Severe Medium Medium 13.00 City of
Belvedere Occasional Extensive Severe Medium Medium 13.00 Town of
Corte Madera Likely Limited Severe Low Medium 11.00
Town of
Fairfax Likely Limited Moderate Medium Low 10.00
City of
Larkspur Likely Limited Severe Medium Medium 12.00
City of
Mill Valley Likely Significant Moderate Medium High 13.00 City of
Novato Likely Negligible Weak Low Low 7.00
Town of
Ross Occasional Significant Moderate Medium Medium 11.00 Town of
San Anselmo Likely Limited Moderate Medium Medium 11.00 l ~<;>U·N· TY OF
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City of
San Rafael
Highly
Likely Significant Moderate Medium Medium 13.00
City of
Sausalito Likely Significant Severe Medium High 14.00
Town of
Tiburon Occasional Extensive Severe Medium Medium 13.00 Bolinas
Public Utility
District
Highly
Likely Limited Moderate High High 14.00
Las Gallinas
Valley
Sanitary
District
Occasional Negligible Weak Low Low 6.00
North Marin
Water
District
Occasional Significant Moderate High Medium 12.00
Southern
Marin Fire
District
Likely Significant Moderate Low Low 10.00
Table 3.9: Marin County OA Hazard Risk Assessment – Debris Flow Source: Profiled Jurisdictions and Districts
Vulnerability
Landslides due to storms are a relatively frequent occurrence in many populated areas of the Marin County OA, including in the unincorporated area, making it quite vulnerable to landslides.

Areas with slopes greater than 50 percent have extreme susceptibility to landslide. Areas of particular concern are those that include high elevations and steep ravines and gulches associated with river and stream channels. Numerous major roads in unincorporated Marin County, including Sir Francis Drake Boulevard, Point Reyes Petaluma Road, Marshall Petaluma Road, Nicasio Valley Road, Lucas Valley Road, Highway 1 and Highway 101 all run through areas of steep slopes where a landslide could occur. A major closure of any of these roads could cut off access to communities, particularly in western Marin County, and limit access to emergency vehicles. Many of these major roads and communities along them, such as Lucas Valley, Marinwood, Lagunitas, Forest Knolls, San Geronimo, Woodacre, Olema and Point Reyes Station, lie along creeks that could impact them with debris flows.

Areas located at the base of creek alluvial fans have extreme susceptibility to mud flows, including after major fires where loose soil and ash can become deposited. Areas of particular concern are those where the widespread and lateral movement of mud and debris can occur.

Areas where mud and debris can be channeled, including downslope roads and waterways, are also susceptible to mud flows. Overgrowth of vegetation in creeks and changes to natural drainage due to development can inhibit the flow of water and muddy debris, causing it to spill over creek banks and create overflow channels onto roadbeds and into adjacent communities in a debris flow or flooding event. A major wildfire and/or rain soaking event in any area of unincorporated Marin County could threaten creek-side communities with a debris flow. In addition, the Bolinas Lagoon and Highway 1 running along the east side of it lie at a natural alluvial fan of the Mount Tamalpais Watershed and could be susceptible to mud and debris from a wildfire around Mount Tamalpais. The Stinson Beach area is particularly vulnerable to any debris flows and subsequent flooding in the Bolinas Lagoon. l ~<;>U·N· TY OF
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Critical infrastructure and facilities that are built into steep slopes, including water access delivery and communication systems, are all susceptible to landslides. Populations serviced by this infrastructure and/or that live in extreme landslide susceptibility zones are subsequently susceptible as well. Numerous communication facilities and other critical infrastructure lie in areas of western Marin County where there is high landslide susceptibility. The Marin County OA is hilly and mountainous overall and the distribution of the landslide hazard is varied across the county as indicated in figure 3.40. The combination of factors that cause landslides, including geology, vegetation, local drainage, and local grading make slope a poor proxy of landslide risk. However, parcels with an average slope above 20 percent are considered hillside lots and risks of slides are present on slopes of 30 percent and above. Slopes as high as 60 or 65 percent are common on hillsides throughout the county.

Numerous unincorporated communities in the Marin County OA have susceptibility to a debris flow: Lagunitas, Forest Knolls, San Geronimo and Woodacre all lie along San Geronimo Creek and a stretch of Sir Francis Drake Boulevard with high to moderate landslide susceptibility and could be vulnerable to debris flows. Numerous residences, businesses, schools and community centers lie in this area.

Outlying areas of Nicasio, particularly on the west side of Nicaso Valley Road, where there are multiple residences, have high to moderate susceptibility to landslides. Tocoloma lies along a section of Lagunitas Creek and could be susceptible to debris flow. The Tocoloma PG&E substation lies adjacent to the creek.

Several residences and businesses in Olema lie along Olema Creek and could be susceptible to debris flow. Point Reyes Station lies along Lagunitas Creek, though most of the buildings around the downtown core are not adjacent to the creek. There are residences and businesses in the outlying areas south of Point Reyes Station that could be susceptible to a debris flow in Lagunitas Creek. The hilly northern area of Point Reyes Station where there are residences is more susceptible to landslide.

Parts of Inverness are particularly susceptible to a landslide, including the southern end where there are numerous residences, a school, and the Inverness Fire Department. Areas of Seahaven where there are numerous residences are also particularly susceptible to a landslide.

Large sections of Point Reyes National Seashore where there are residences, historic ranches, and other structures lie in areas of high landslide susceptibility.

Sections of the east shore of Tomales Bay along Highway 1, including north of Bivalve, from Marconi to Marshall, and from the area of Clarke Road north to Walker Creek are susceptible to a landslide. There are numerous residences and businesses along the shore, including in Marshall and at Marconi Conference Center State Historic Park (which is a critical facility), that lie in areas of high landslide susceptibility. While most of Tomales is in an area of moderate landslide susceptibility, the area is hilly and there are numerous residences, businesses, community facilities, schools, and emergency facilities susceptible to landslide. Areas of Dillon Beach where there are numerous residences have a high landslide susceptibility, particularly on the northern outlying areas of the community.

Areas in and around Bolinas where there are numerous homes, schools, and community facilities have a high landslide susceptibility. The Woodrat Water Treatment Plant and associated facilities along with the Bolinas PG&E substation north of Bolinas lie in areas of moderate to high landslide susceptibility. The community of Dogtown, where there are numerous residences, lies in areas of moderate to high landslide susceptibility. There are also numerous creeks that run through Dogtown that could impact it with debris flows. Parts of l ~<;>U·N· TY OF
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Stinson Beach, particularly northeast of Highway 1 in the foothills. where there are numerous residences, the Stinson Beach Community Center and the Stinson Beach Fire Station, lie in areas of moderate to high landslide susceptibility.

Most all of Muir Beach and the surrounding area, where there are numerous residences, the Muir Beach Community Center and the Muir Beach Fire Station, lie in an area of high landslide susceptibility. Much of Tamalpais Valley and the outskirts of Marin City lie in an area of high landslide susceptibility. There are hundreds of residences along with several schools, community centers and emergency facilities that lie in this area, including on the northern end of Marin City. While Alto has low landslide susceptibility, most of Strawberry down to Harbor Point lies in an area of moderate to high landslide susceptibility. Parts of Paradise Cay and most of the east side of the Tiburon Peninsula also have high landslide susceptibility. There are hundreds of residences and several schools and community centers in these areas, as well as the Southern Marin Fire Protection District Station #9.

Areas of Kentfield, particularly in the foothills of Mount Tamalpais and on the northeast side of Sir Francis Drake Boulevard down into Greenbrae, and most of California City have moderate to high landslide susceptibility. There are hundreds of residences in this area. Most critical facilities in Kentwood do not lie in areas of landslide susceptibility but are located along Corte Madera Creek and could be susceptible to debris flows that originate along the flanks of Mount Tamalpais. The northern end of San Quentin is in an area of moderate to high landslide susceptibility, and parts of San Quentin State Prison are vulnerable to a landslide.

Residences on the outskirts of Lucas Valley, Marinwood, and Sleepy Hollow that lie in the foothills have a moderate to high susceptibility to landslides, as do residences in most of Los Ranchitos and in the area of Marinwood and Saint Vincent around Highway 101. Several health care facilities and schools also lie in this fringe. Areas of Lucas Valley and Marinwood along Miller Creek may be particularly susceptible to a debris flow in the creek. Numerous residences and a school lie in this area. Areas of Santa Venitia around the San Pedro Mountain Open Space Preserve have moderate to high susceptibility to landslides. There are dozens of homes in this area. Most critical facilities in Santa Venitia lie outside areas of landslide susceptibility.

The western side of the Green Point-Black Point area has high landslide susceptibility while the eastern side is more moderately susceptible with pockets of high susceptibility. The entire area is primarily residential and hundreds of homes along with a school have some vulnerability to a landslide. There are residential areas in the unincorporated County west of Novato in the foothills with hundreds of homes that have moderate to high susceptibility of a landslide and could be vulnerable to a debris flow from any of the creeks that originate in the mountains.

Landslides, mudslides, and debris flows can move fast enough to damage or destroy homes or other structures in their path, block roadways (including evacuation routes), and injure or kill people caught in them. Marin County OA populations that are most vulnerable to the effects of landslides, debris flows, and post-fire debris flows include:
• Low-income households
• Households in poverty
• Renters
• Persons living in mobile homes
• Persons living on single access roads
• Persons without access to transportation or telecommunications • Outdoor workers
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• Houseless population
• Persons with disabilities
The most vulnerable populations are those that may be unable to evacuate due to limited mobility, lack of access to a vehicle, or language barriers that may prevent awareness of emergency notifications. Those living on single-access roadways in the hilly areas of the County or those living in less resilient housing may lose access to their homes if roadways or the structures are damaged or destroyed by a landslide. Development on hillsides in places like Mill Valley was done in the 1920s and 1930s, long before landslides were factored into design and construction regulations.

Climate Change and Future Development Considerations
Extreme storm events and more frequent wildfires as a result of climate change have the potential to increase the amount and severity of landslides, including disastrous debris flows.

Climate change is leading to more volatile precipitation patterns around the world with very dry stretches punctuated by storms that drop large amounts of rain in a short amount of time.

Landslides in wetter regions of California, including the Marin County OA, move on average faster and farther downhill during rainy periods compared to drought years, according to a 2022 study by the American Geophysical Union (AGU), showing the increased potential for landslides in the Marin County OA in rainy years. As development increases in the numerous canyons and around the many open spaces of the Marin County OA, the potential for significant impacts from a landslide and/or mudflow increases. Future development should take into account the movement of mud and debris in waterways after a major rain event. Adequate space adjacent to susceptible waterways should be maintained free of development to allow for the passage of mud and debris, and catchment basins should be built in these areas to help capture any excess mud and debris.

3.3.3 DROUGHT
A drought is a deficiency in precipitation over an extended period, usually a season or more, resulting in a water shortage causing adverse impacts on vegetation, animals, and/or people. It is a normal recurrent feature of climate that occurs in virtually all climate zones, from very wet to very dry. Drought is a temporary aberration from normal climatic conditions and can thus vary significantly from one region to another. Droughts occur slowly, over a multi-year period, and it is often not obvious or easy to quantify when a drought begins and ends. Drought is a complex issue involving many factors—it occurs when a normal amount of moisture is not available to satisfy an area’s usual water-consuming activities.

There are several types of drought which can often be defined regionally based on their effects:
• Meteorological drought is usually defined by a period of below average water supply, based on the degree of dryness (in comparison to normal or average) and the duration of the dry period. Drought onset generally occurs with a meteorological drought.
• Agricultural drought occurs when there is an inadequate water supply to meet the needs of the state’s crops and other agricultural operations such as livestock.

Agricultural drought links various characteristics of meteorological (or hydrological) drought to agricultural impacts, focusing on precipitation shortages, soil water deficits, reduced ground water or reservoir levels needed for irrigation. l ~<;>U·N· TY OF
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• Hydrological drought is defined as deficiencies in surface and subsurface water supplies. It is generally measured as stream flow, snowpack, and as lake, reservoir, and groundwater levels. Hydrological drought usually occurs following periods of extended precipitation shortfalls.
• Socioeconomic drought occurs when a drought impacts health, well-being, and quality of life, or when a drought starts to have an adverse economic impact on a region.

Location and Previous Occurrences
Historically, California has experienced multiple severe droughts. According to the California Department of Water Resources (DWR), droughts exceeding three years are relatively rare in Northern California, the source of much of the State’s developed water supply. The 1929-34 drought established the criteria commonly used in designing storage capacity and yield of large Northern California reservoirs. The driest single year of California’s measured hydrologic record was 2013. A drought emergency was declared for the state in 2014, and lifted in 2017 after a series of strong winter storms.

The U.S. Drought Monitor provides a general summary of current drought conditions. See Figure

3.57 for drought conditions in 2023, Figure 3.58 for drought conditions in 2020 and Figure 3.59 for drought conditions in 2016.

Figure 3.57: U.S. Drought Monitor for California (2023) Source: USDA
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U.S. Drought Monitor
California
October 31, 2023
(Released Thursday, Nov. 2, 2023)
Valid 8 a.m. EDT
Drought Conditions (Percent Area)
None 00-04 01-04 02-04
Current £14~ 066 0,00 0Jl0 000 000
Last Week
J0-2,4,2023
£,4,32 5,68 0.00 0,00 0.00 0.00
3MonthsAgo 74.43 25,57 1>52 000 000 0.00 Of.(}1.201:

Stlrtof
Calendar Year 0,00 10000 97,93 7114 2710 0,00 01.0:J.2023 Start of
Water Year 94,01 599 0,07 0.00 0,00 0,00 09-$2023
One Vear Ago
U,Qf"'Q22. 0,00 10000 ~ 77 9, ss 4306 16.57
~
c::::JNone D2 Severe Drought
D DO Abnormally Dry - D3 Extreme Drought
c:J 01 Moderale Drought - D4 Excepttonal Droughl
The Drou{fnl Momror foouses on broad-scale cond/11011s Local condiflons may vary. Fo, mO/tJ ,ntormatlon on the Qbughl Momlor. go lo hNps l/droughlmonrtor;unl.BdiJIAIJoul,aspX Author:

Brian Fuchs
National Drought Mitigation Center
USDA
-
droughtmonitor.unl.edu
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Figure 3.58: U.S. Drought Monitor for California (2020) Source: USDA
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U.S. Drought Monitor
California
July 28, 2020
(Released Thursday, Jul. 30, 2020)
Valid 8 a.m. EDT
lntensitv:

LJ None
LJ DO Abnormally Dry
D D1 Moderate Drought
D D2 Severe Drought
- D3 Extreme Drought
- D4 ExcepUonal Drought
The Drought Monitor focuses on broad-scale
condiUons. Local conditions may vary. For more
information on the Drought Monitor, go to
https:1/droughtmonitor. unl.edu/About. aspx
Author:

Richard Heim

NCEI/NOM
~SDA (., @ {.
droughtmonitor.unl.edu
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Figure 3.59: U.S. Drought Monitor for California (2016) Source: USDA
Figure 3.60: Water Supply Conditions in California 2005-2018 Source: 2018 State of California Hazard Mitigation Plan l ~<;>U·N· TY OF
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U.S. Drought Monitor
California
February 1 Statewide conditions
Department of Water Resources
California Cooperative Snow Surveys
March 15, 2016
(Re/oased Thursday, Mar. 17, 2016)
Valid 8 a.m. EDT
Droug//1 ConditiOns (Percent Area)
None- C0-0• 01-04 02-04 ... ~. Current 0.4:l 99.57 g3.za 7.l.64 55.31 J.H4 Last Week 0.43 93.57 97.49 83 16 60.86 38.40 J.MCIH

31.1ontnsAQo 0.14 W.86 S7.:J.3 !!0.63 69.09 44.84 fM l.•:wu St!Wtol Cetend er 't e...,r 0,00 100 00 97,33 87,55 69,07 44,84 f2,,2j,-2Qf:5 Start or 'WiterYeM 0.14 ro.B6 Sl.33 92.36 71.08 46.00
M:?/.:tlfS
One Year Ago
3"1'?',~i:HS 0.16 93.B• 98. 11 93.44 67.46 l9.92
Intensity:

O0l'bnorrn YD l'I 1111 O3E xtrem-eDroug t
01 .U.odcr11te DrougM 1111 04 Exo::ption,ail Orcn.rr.iH - 02Smro Dn>u "11
n w DIOtsg!'lt UOtli!O( (OCUS9-S on lYOOd-~are CO:ldi!jon-5'. t..ocalcond4JOM may 11&.ry See accom.oan.Ylna text w mma,y torfOtGCas:J. star9ft1iel'tt!S.

Author:

Richard Heim

NCEIINOAA
http :fldroughtmonltor.unl.edu/
2so~-------------------------------------
215
200+------------------------------------1
150 (ll
(ll
~
~
0 ~ a;
a.
so
2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 = Snowpack = Preciptation Runoff to Date --Reservoir Storage 2023 Marin County Operational Area
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A drought emergency for the State of California was issued on January 17, 2014. This declaration came on the heels of a report that stated that California had the least amount of rainfall in its 163-year history. Drought conditions worsened through 2014 and into 2015. On April 1, 2015, following the lowest snowpack ever recorded, actions were announced by the State that would save water, increase enforcement to prevent wasteful water use, streamline the State’s drought response, and invest in new technologies to make California more drought resilient. The State Water Resources Control Board was directed to implement mandatory water reductions in cities and towns across California to reduce water usage by 25 percent.

This savings amounted to approximately 1.5 million acre-feet of water through the end of 2015.

In July 2021, the State of California added Marin County to its list of counties falling under its state of emergency regarding deepening drought conditions and record-breaking high temperatures statewide. After hearing details about local dry conditions and water supplies, the Marin County Board of Supervisors voted unanimously on May 18, 2021 to declare a local emergency and acknowledge the imminent threat of disaster. The declaration acknowledged the extent and impacts of the drought in Marin, which is severely affecting dairies and ranchers in West Marin. It also made the County eligible for California Disaster Assistance and other forms of state funding and resources. The local declaration cleared the way for state authorities to aid response and recovery efforts available to the County, water suppliers, farmers, impacted businesses and residents. In August 2021, with reservoir levels at historic lows, both MMWD and NMWD declared a water shortage emergency and adopted mandatory water use restrictions, with respective reduction goals of 40 percent and 20 percent. In October 2021, the Governor of California signed a proclamation extending the drought emergency statewide. In March 2023 the Governor eased drought restrictions and ended the drought emergency.

All areas of the Marin County OA could experience drought, including vegetated areas where drier conditions could lead to an increase in wildfires and tree mortality.

Impacts
Drought impacts are wide-reaching and may be economic, environmental, and/or societal. The most significant impacts associated with drought in the planning area are those related to water intensive activities such as agriculture, wildfire protection, municipal usage, commerce, tourism, recreation, and wildlife preservation. During a drought, allocations go down, which results in reduced water availability. Voluntary conservation measures are typically implemented during extended droughts. A reduction of electric power generation and water quality deterioration are also potential problems. Drought conditions can also cause soil to compact and not absorb water well, potentially making an area more susceptible to flooding.

Drought can have secondary impacts. For example, drought is a major determinant of wildfire hazard, in that it creates greater propensity for fire starts and larger, more prolonged conflagrations fueled by excessively dry vegetation, along with reduced water supply for firefighting purposes. Drought is also an economic hazard. Significant economic impacts on California’s agriculture industry can occur as a result of short‐ and long‐term drought conditions; these include hardships to farmers, farm workers, packers, and shippers of agricultural products. Health and property impacts, such as water contamination (especially private wells), economic losses to individuals, physical and mental health impacts may also occur. In some cases, droughts can also cause significant increases in food prices to the consumer due to shortages, causing possible food insecurity or dietary changes, which may lead to poorer health outcomes. Drought can also result in lack of water and subsequent feed available to grazing l ~<;>U·N· TY OF
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livestock, potentially leading to risk of livestock death and resulting in losses to the State’s and Marin County’s agricultural economy.

Based on historical information, the occurrence of drought in California, including the Marin County OA, is cyclical, driven by weather patterns. Drought has occurred in the past and will occur in the future. Periods of actual drought with adverse impacts can vary in duration, and the period between droughts is often extended. Although an area may be under an extended dry period, determining when it becomes a drought is based on impacts to individual water users.

Figure 3.61: Drought Impacts
Source: National Drought Mitigation Center
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Natural Climate Valiability
Precipitation deficiency
(amount, intensity, timing)
Reduced infiltration, runoff
deep percolation, and
ground water recharge
High temp., high winds, low
relative humidity, greater
sunshine, less cloud cover
Increased evaporation
and transpiration
Soil water deficiency
Plant water stress, reduced
biomass and yield
i6
u ·-o,_ ... o- _o,
o=
'-0 o ...
~Q
:E
------- -----------------·------------- Reduced streamflow, inflow to reservoirs, lakes, and ponds;
reduced weti ands,
wildlife habitat
] ... ·er;,
o_
oo
......
~ - - - - - - - - - _'--_ _ - _ - _ - _- _- _ - _ ....,...._ - _- _ - _ - _ - _ - _----' _ - - - - - - - - - - - :c - Economic Im acts social Im acts Environmental Im acts
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Drought also has a significant impact on tree mortality. Figures 3.64 shows the impact of tree mortality in Marin County in 2022.

Figure 3.62: 2022 Locations of Tree Mortality in the Marin County OA Source: CALFIRE
Extent and Probability
Scientists expect that climate change will lead to more frequent and more intense droughts statewide. Overall, precipitation levels are expected to stay similar, and may even increase in some places. However, the state’s current data say that there will be more years with extreme levels of precipitation, both high and low, as a result of climate change. This is expected to cause more droughts that last longer and are more intense, compared to historical norms.

Higher air temperatures are expected to increase evaporation, causing more water loss from lakes and reservoirs and decreasing soil moisture to greater depths. 1 ~<;>U·N· TY OF a
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y
181.) I'll
P~talumcf
0 1:577,791
3 s4Mi1 Francisco.

H
p
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Table 3.10: Marin County OA Hazard Risk Assessment – Drought Jurisdiction
Probability/
Likelihood
of Future
Events
Geographic
Extent
Magnitude/
Severity
Climate
Change
Influence
Significance Risk
Score
Marin County Highly
Likely Extensive Moderate High High 16.00
City of
Belvedere
Highly
Likely Extensive Moderate High High 16.00
Town of
Corte Madera Likely Extensive Weak High Medium 13.00
Town of
Fairfax Occasional Extensive Weak Medium Low 10.00
City of
Larkspur Occasional Extensive Moderate High Medium 13.00 City of
Mill Valley Likely Extensive Weak High Medium 13.00
City of
Novato Likely Extensive Weak High Medium 13.00
Town of
Ross Likely Extensive Moderate Medium High 14.00
Town of
San Anselmo Likely Extensive Extreme High High 17.00
City of
San Rafael Likely Extensive Moderate High Medium 14.00
City of
Sausalito Unlikely Negligible None Low Low 4.00
Town of
Tiburon
Highly
Likely Extensive Moderate High High 16.00
Bolinas
Public Utility
District
Highly
Likely Extensive Severe High High 17.00
Las Gallinas
Valley
Sanitary
District
Likely Limited None High Medium 10.00
North Marin
Water
District
Occasional Extensive Severe High Medium 14.00
Southern
Marin Fire
District
Likely Significant Severe High Medium 14.00
Table 3.10: Marin County OA Hazard Risk Assessment – Drought Source: Profiled Jurisdictions and Districts
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Vulnerability
The vulnerability of the Marin County OA to drought is countywide, but impacts may vary by area and include reduction in water supply, agricultural losses, and an increase in dry fuels.

During drought, declines in surface water flows can be detrimental to water supplies for agriculture and cities, hydropower production, navigation, recreation, and natural ecosystems, particularly habitat for aquatic and riparian species. Communities in the Marin County OA, may experience water shortages during drought conditions which lead to mandatory water use restrictions and possibly the importation of water. During drought events, the flow of water in creeks and streams is reduced, creating more slow-moving or standing water. This can concentrate sediment and toxins in the low water levels, causing harm to plants and animals.

Many fish species also rely on specific water temperatures and stream flow speeds, especially for spawning and egg incubation, and changes to stream velocity as a result of drought conditions can affect reproduction. Droughts can also indirectly lead to more wildfires, and the stress caused by water shortages can weaken plants, making them more susceptible to pests and diseases. As drought persists, longer-term impacts can emerge, such as land subsidence, seawater intrusion, and damage to ecosystems. During prolonged or severe drought, County residents would be impacted by water use restrictions and changes to water supply.

Climate Change and Future Development Considerations
Climate change increases the odds of worsening drought. Warmer temperatures enhance evaporation, which reduces surface water and dries out soils and vegetation. This makes periods with low precipitation in the summer drier than they would be in cooler conditions.

Climate also alters the timing of water availability as warmer winter temperatures cause less precipitation to fall. During droughts, communities in the Marin County OA may have limited access to water for household use, including drinking, cooking, cleaning, and watering plants, as well as for agriculture, transportation, and power generation. Drought may lead to higher water costs, rationing, or even the decimation of important water sources like wells in the Marin County OA. As more people move into the Marin County OA, additional strain will be placed on the OA’s water supply. Drought can affect livestock and crops in the Marin County OA, impacting its economy. Drought can increase the occurrence and severity of wildfires and tree mortality in the Marin County OA. Impacts to residents and infrastructure from wildfire as a result of drought will increase as more development occurs in the mountainous areas of the Marin County OA where wildfires are more likely to occur. Drought also increases the amount of carbon dioxide in the atmosphere, including by decreasing land productivity, which reduces the amount of vegetation storing carbon dioxide. In addition, increases in drought-related wildfire and soil erosion can release carbon dioxide sequestered in trees and plants back into the atmosphere. This will only worsen climate change for the Marin County OA into the future.

When considering future development, the Marin County OA can help prepare for both future droughts and climate change by practicing and promoting water conservation and enhancing water efficiency throughout landscapes, city plans, and water infrastructure. The Marin County OA can also identify alternative water supplies, create drought emergency plans, and encourage farmers to plant drought-resistant crops.
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3.3.4 EARTHQUAKE
Earthquakes are sudden rolling or shaking events caused by movement under the earth’s surface. Earthquakes happen along cracks in the earth's surface, called fault lines, and can be felt over large areas, although they usually last less than one minute.

The amount of energy released during an earthquake is usually expressed as a magnitude and is currently measured by seismologists on the Moment Magnitude (Mw Scale). The Mw Scale was developed to succeed the previously used Richter Scale and is measured on a scale of zero to ten with increasing values reflecting increasing intensity.

The other commonly used measure of earthquake severity is intensity, which is an expression of the amount of shaking at any given location on the ground service. Intensity is most commonly measured on the Modified Mercalli Intensity (MMI) Scale (see Figure 3.63).

Figure 3.63: Modified Mercalli Intensity Scale
Figure 3.64 gives intensities (measured on the MMI scale) that are typically observed at locations near the epicenter or earthquakes of different magnitudes. l ~<;>U·N· TY OF
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Intensity Shaking
Not felt
Weak
Ill Weak
IV Light
V Moderate
VI Strong
VII Very
strong
Severe
Violent
a
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Description/Damage
Not felt except by a very few under especially favorable conditions.

Felt only by a few persons at rest,especially on upper floors of buildings.

Felt quite noticeably by persons indoors, especially on upper floors of buildings. Many people do not recognize it as an earthquake.

Standing motor cars may rock slightly. Vibrations similar to the passing of a truck. Duration estimated.

Felt indoors by many, outdoors by few during the day. At night, some awakened. Dishes, windows, doors disturbed; walls make cracking sound. Sensation like heavy truck stri king building. Standing motor cars roc ked noticeably.

Felt by nearly everyone; many awakened. Some dishes, windows broken. Unstable objects overturned. Pendulum clocks may stop.

Felt by all, many frightened. Some heavy furniture moved; a few instances of fallen plaster. Damage slight.

Damage negligible in buildings of good design and construction; sl ight to moderate in well-built ordinary structu res; considera ble damage in poorly built or badly designed structures; some chimneys broken.

Damage slight in specially designed structures; considerable damage in ordinary substantial buildings with partial collapse. Damage great in poorly built structures. Fall of chimneys, factory stacks, columns, monuments, walls. Heavy furniture overturned.

Damage considerable in specially designed structures; well-designed frame structures thrown out of plumb. Damage great in substantial buildings, with partial collapse. Buildings shifted off foundations.

Some well-built wooden structures destroyed; most masonry and frame structures destroyed with foundations. Rails bent. 2023 Marin County Operational Area
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Figure 3.64: Mercalli Scale vs. Magnitude
The extent of ground shaking also depends in large part on how soft the underlying soil is. Soft soils amplify ground shaking (see Figure 3.65). This was observed during the 1989 Loma Prieta Earthquake when the most significant damages experienced in San Francisco were in the Marina District, which was built on fill.

Figure 3.65: Soil Types
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Soil Vs>
type 1500
A m/ sec
1500
Soil
type m/ sec >
Vs> 750
B
m/sec
750
Soil m/ sec>
Type Vs>350
C m/ sec
350
Soil
Type m/ sec>
Vs> 200
D m/ sec
Soil 200
Type m/ sec>
E Vs
a
~
Richter
Magnitude Scale

1.0-2.9

3.0-3.9

4.0 -4.9

5.0-5.9

6.0-6.9
7 .0 or higher
Typical Maximum
Modified Mercalli
Intensity Scale
I
TI-Ill
.._
IV-V
I VJ-Vil

VII- IX --
VIII or higher
Includes unweathered intrusive igneous rock. Occurs infrequently in the bay area. We consider it with type B (both A and Bare represented by the color blue on the map). Soil types A and B do not contribute greatly to shaking amplification.

Includes volcanics, most Mesozoic bedrock, and some Franciscan bedrock. (M esozoic rocks are between 245 and 64 million years old. The Fra nciscan Complex is a Mesozoic unit that is common in the Bay Area.) Includes some Quaternary (less than 1.8 million years old) sands, sandstones and mudstones, some Upper Tertiary (1.8 to 24 million years old) sandstones, mudstones and limestone, some Lower Tertiary (24 to 64 million years old) mud stones and sandstones, and Franciscan melange and serpentinite.

Includes some Quaternary muds, sands, gravels, silts and mud. Significant amplification of shaking by these soils is generally expected.

Includes water-satu rated mud and artificial fill. The strongest amplification of shaking due is expected for this soil type.
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An earthquake fault is defined as “a fracture or fracture zone in the earth’s crust along which there has been displacement of the sides relative to one another.” For the purpose of planning there are two types of faults, active and inactive. Active faults have experienced displacement in historic time, suggesting that future displacement may be expected. Inactive faults show no evidence of movement in recent geologic time, suggesting that these faults are dormant.

Two types of fault movement represent possible hazards to structures in the immediate vicinity of the fault: fault creep and sudden fault displacement. Fault creep, a slow movement of one side of a fault relative to the other, can cause cracking and buckling of sidewalks and foundations even without perceptible ground shaking. Sudden fault displacement occurs during an earthquake event and may result in the collapse of buildings or other structures that are found along the fault zone when fault displacement exceeds an inch or two. The only protection against damage caused directly by fault displacement is to prohibit construction in the fault zone.

Location and Previous Occurrences
The potential for earthquake damage exists throughout Marin County because of a combination of the number of active faults within and near the County and the presence of soils vulnerable to liquefaction. These faults are shown on the California Geological Survey (CGS) Fault Activity Map of California (see Figure 3.68. Fault Activity Map below). Descriptions of the most significant active faults to Marin are provided below.

San Andreas fault: The San Andreas Fault traverses Marin County running north and south in the western quarter of the county. It enters Marin on the Pacific Coast near Bolinas, follows the path of Highway 1 and Tomales Bay, exiting Marin at sea just west of Dillon Beach. Hayward fault: the eastern, more heavily populated part of Marin is less than ten miles from the northern section of the Hayward fault. Rodgers Creek fault: The northern part of Marin is less than ten miles from the Rodgers Creek fault. See Figure 3.66 for a map of earthquake faults and probability of shaking across the Marin County OA.

Earthquake Shake Intensity
The colors on Figures 3.66 and 3.67 represent the level of ground shaking intensity of a potential future earthquake. The result is expressed as the level of ground shaking (expressed as a percentage of gravity) that on average occurs every 500 years.

This map shows the expected relative intensity of ground shaking and damage in California from anticipated future earthquakes. The shaking potential is calculated as the level of ground motion that has a 2% chance of being exceeded in 50 years, which is the same as the level of ground-shaking with about a 2500 year average repeat time. The relatively long-period (1.0 second) earthquake shaking is shown here. Long period-shaking affects tall, relatively flexible buildings, but also correlates well with overall earthquake damage.

Earthquake Shaking Potential Maps for California depict expected intermediate period (1s or 1hz) ground motions with 2% exceedance probability in 50 years. l ~<;>U·N· TY OF
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Figure 3.66: Earthquake Faults and Probability of Shaking in the Marin County OA Sources: Marin County OEM, USGS
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/
\
\
I
(
\
i
I
I
I
/
/
/
a
~
Marin County / Full County
Earthquake

DIIICUII

EMERGENCY

MANAGEMENT
San Pablo Bay
Wildlife Area
Legend
Earthquake

1.95 1.85

1.15 1.05
0 1.45

1.35 - 1.25
- 0.95

0.85 0.75

0.65 0.55

0.45 0.35
Marin County OEM / Woody Baker-Cohn
email: [email protected] Ii
Date Printed: 09/22/23
County of Marin, california State Parks, Esri, HERE, Garmin, SafeGraph, Geo Technologies, Inc, METI/NASA, USGS, Bureau of Land Management, EPA, NPS, USDA, County of Marin, (alifornia State Parks, Esri, HERE, Garmin, SafeGraph, FAO, METI/NASA, USGS, Bureau of Land Management, EPA, NPS N
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Figure 3.67: Marin County Earthquake Shaking Potential and Critical Facilities Source: Marin County OEM
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/
I
/
I
I
(
• Dams
• Military and Qvil
Defense Installations
COl'r'lmunic.atior'l
Facil~ies
Elecbic Power Facllltles
Legend
Fire Stations
Hospitals and Medical
Facilities
Police / Sheriff Stations
Schools
Wastewater facilities EarthquakeShaking
Water Supply Facilities 0.45
o.ss AirportS 0.65 Emergency Operations 0.75 Centers

0.85 Marin County
Earthquake
10 1
- 0.95
- I.OS
- I.IS
- 1.25
- 1.35
- 1.45

1.55 1.65

1.75 0
DfllctOI

EMERGENCY

MANAGEMENT
10 Miles
12 21
37 San Pablo Bay
Wildlife Area

1.85 1.95
Marin County OEM / Woody Baker-Cohn
email: [email protected]
Date Printed: 11/01/23 N
County of Marin, california State Parks, Esri, HERE, Garmin, SafeGraph, Geo Technologies, Inc, METI/NASA, USGS, Bureau of Land Management, EPA, NPS, USDA, County of Marin, califomia State Parks, Esri, HERE, Garmin, SafeGraph, FAO, METI/ NASA, USGS, Bureau of Land Management, EPA, NPS 2023 Marin County Operational Area
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There are faults that do not traverse the Marin County OA that may cause shaking effects to occur inside the County.

According to the Association of Bay Area Governments Resilience Program, “the San Andreas Fault was the source of the magnitude of 7.8 earthquake in 1906. Marin was sparsely inhabited at that time and experienced relatively moderate property loss and only two deaths. The epicenter was just two miles west of San Francisco and West Marin experienced some pronounced earthquake effects. This included a horizontal earth displacement of 21 feet near the head of Tomales Bay.

On October 17, 1989, a magnitude 7.1 earthquake occurred on the San Andreas Fault, the largest earthquake to occur in the San Francisco Bay Area since 1906. This earthquake was named the Loma Prieta Earthquake due to its calculated epicenter. The impact of the Loma Prieta Earthquake was most apparent in the northeast area of Santa Cruz. If the fault rupture location were closer, a strong shaking such as this could have caused severe damage within Marin County, including damage to life-line routes. The Loma Prieta Earthquake was not “the big one,” which is a common reference to an event with a magnitude of 8 or larger (such as the 1906 San Francisco quake).

Impacts
Ground shaking is the primary earthquake hazard. Many factors affect the survivability of structures and systems from earthquake-caused ground motions. These factors include proximity to the fault, direction of rupture, epicenter location and depth, magnitude, local geologic and soils conditions, types and quality of construction, building configurations and heights, and comparable factors that relate to utility, transportation, and other network systems.

Ground motions become structurally damaging when average peak accelerations reach 10 to 15 percent of gravity, average peak velocities reach 8 to 12 centimeters per second, and when the Modified Mercalli Intensity Scale is about VII (18-34 percent peak ground acceleration), which is considered to be very strong (general alarm; walls crack; plaster falls).

Earthquakes can result in liquefaction. Liquefaction is a process whereby soil is temporarily transformed to a fluid form during intense and prolonged ground shaking. Areas most prone to liquefaction are those that are water saturated (e.g., where the water table is less than 30 feet below the surface) and consist of relatively uniform sands that are loose to medium density. In addition to necessary soil conditions, the ground acceleration and duration of the earthquake must be of sufficient energy to induce liquefaction.

Liquefaction during major earthquakes has caused severe damage to structures on level ground as a result of settling, tilting, or floating. Such damage occurred in San Francisco on bay-filled areas during the 1989 Loma Prieta earthquake, even though the epicenter was several miles away. If liquefaction occurs in or under a sloping soil mass, the entire mass may flow toward a lower elevation. Of particular concern in terms of developed and newly developing areas are fill areas that have been poorly compacted.

Earthquakes can cause settlement. Settlement can occur in poorly consolidated soils during ground shaking. During settlement, the soil materials are physically rearranged by the shaking to result in a less stable alignment of the individual minerals. Settlement of sufficient magnitude to cause significant structural damage is normally associated with rapidly deposited alluvial soils or improperly founded or poorly compacted fill. These areas are known to undergo extensive settling with the addition of irrigation water, but evidence due to ground shaking is not available. l ~<;>U·N· TY OF
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Earthquakes can also cause seiches, landslides, and dam failures. A seiche is a periodic oscillation of a body of water resulting from seismic shaking or other factors that could cause flooding. Earthquakes may cause landslides, particularly during the wet season, in areas of high water or saturated soils. Earthquake impact on life, property, and environment may include cascading impacts of lifelines loss (water, electricity), loss of housing, injuries and mortality, surge in healthcare facilities, and disruption to EMS services.

Most structures in the Marin County OA, including in the unincorporated area, were built before 1970, when major seismic design changes were made to the building code and are particularly vulnerable to earthquakes and liquefaction. Wood framed homes, however, are light and flexible and can often survive earthquakes with minimal damage as long as the foundations are properly retrofitted (bolted and braced). The County of Marin and its political subdivisions have adopted California Building, Plumbing, Electrical and Mechanical Codes whereby no building or structure is erected, constructed, enlarged, improved, removed, or converted without a permit. Adherence to these codes currently allows the county to gather data on retrofitting and current building code compliance. It is important to note that these data continue to have limitations for assessing overall vulnerability in the county for all structures.

The majority of the Marin County OA’s single-family buildings with foundations to bedrock will perform well in a shake. Modern multi-story buildings with foundations to bedrock should not be subject to collapse, although some serious damage may occur. However, many heavier developed areas of the Marin County OA are built on soft alluvial soils or filled-in water ways.

Due to liquefaction, these soils will significantly increase the shaking effects and will account for the majority of damaged and destroyed structures, regardless of their proximity to the fault line.

Liquefaction occurs when ground shaking causes loose, saturated soil to lose strength and act as a viscous fluid. When liquefaction occurs, it can result in the sidelong movement of large masses of soil, loss of strength in the soil supporting structures causing structures to collapse, and/or consolidation due to soil settlement decreasing soil surface elevations. The county’s topography includes large areas of steep slopes, adding to the vulnerability of earthquake induced disasters with the additional danger of debris flow (landslides). Bluff erosion along the coastal areas also poses unique threats to coastal structures and roads during times of earthquake.

Extent and Probability
An earthquake could occur and affect any area of the Marin County OA, including the unincorporated area. The ABAG Resilience Program analysis shows risk of liquefaction in Corte Madera, Larkspur, Bel Marin Keys, Novato, Ross Valley along creeks (Ross, San Anselmo, Fairfax), San Geronimo, San Rafael, Santa Venetia, communities around Richardson Bay (Belvedere, Marin City, Mill Valley, Sausalito, Strawberry, Tam Valley, Tiburon), Stinson Beach, Tomales Bay-side communities, and the county-owned Gnoss Field Airport.

According to a September 24, 2016 article in the Marin Independent Journal, “The Working Group on California Earthquake Probabilities has updated its earthquake forecast and determined there is a 72 percent probability - up from 63 percent - of at least one earthquake of magnitude 6.7 or greater striking somewhere in the Bay Area before 2043.” The Association of Bay Area Governments (ABAG) Resilience Program projects a 52% chance of a 6.7 or greater earthquake on one of the faults affecting Marin between now and 2036 (21% at San Andreas fault and 31% on Hayward/Rodgers Creek). Supporting this article’s assertions is the Uniform California Earthquake Rupture Forecast, Version 3 (UCERF3), which provides authoritative estimates of the magnitude, location, and time-averaged frequency of potentially damaging l ~<;>U·N· TY OF
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earthquakes in California (see Figure 3.68). Uniform California Earthquake Rupture Forecast primary achievements have been to relax fault segmentation assumptions and to include multifault ruptures, both limitations of the previous model (UCERF2).

Figure 3.68: Uniform California Earthquake Rupture Forecast Version 3 Source: USGS
The September 24, 2016 article goes on to say “Marin sits smack dab (sic) in the middle of two major faults. To the east is the Rodgers Creek-Hayward fault just a few miles from Marin’s shores through San Pablo Bay, which the U.S. Geological Survey estimates has a 33 percent likelihood of a 6.7-magnitude quake or greater in the next 30 years — the highest probability of any Bay Area fault to slip. But movement on those faults could be worse than originally thought.” The Rodgers Creek-Hayward fault, thought to be two separate faults, actually may be linked and have the potential to cause more damage than previously determined, according to USGS research.
“The Rodgers Creek Fault runs from Sonoma County into San Pablo Bay near Marin’s shore.

The Hayward Fault runs through the western part of Alameda County into San Pablo Bay east of San Rafael and Novato. They were thought to be offset by about two miles under San Pablo Bay. But underwater exploration done in 2014 seems to link them. More study will occur to confirm those initial findings.”
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1/1000 1/100 1110
30--year M ~6-7 likelihood
(percent)
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Uniform California Earthquake Rupture Forecast (Version 3) 100
Ttvee+dimensional perspective view of the likelihood
that each region of California will experience a
magnitude 6.7 or larger earthquake in the next
30 years (6.7 matches the magnitude of
the 1 994 Northridge earthquake. and
30 years is the typic<II duration
of a homeowner mortgage).
faults are shown by the rectangles outlined in black. The entire cofored area represents greater California,and the white line across the middle defines northern versus southern C,alifornia. Results do not include earthquakes on the Cascadia Subduction Zone, a 750-mile offshore fault that extends about 1 SO miles into California from Oregon and Washington to the north. 2023 Marin County Operational Area
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Table 3.11: Marin County OA Hazard Risk Assessment - Earthquake Jurisdiction
Probability/
Likelihood
of Future
Events
Geographic
Extent
Magnitude/
Severity
Climate
Change
Influence
Significance Risk
Score
Marin County Highly
Likely Extensive Extreme None High 15.00
City of
Belvedere
Highly
Likely Extensive Extreme None High 15.00
Town of
Corte Madera Occasional Extensive Severe None High 12.00 Town of
Fairfax
Highly
Likely Extensive Extreme None High 15.00
City of
Larkspur Occasional Extensive Extreme None High 13.00
City of
Mill Valley Occasional Extensive Extreme Low Medium 13.00 City of
Novato Occasional Extensive Extreme None Medium 12.00
Town of
Ross Likely Significant Severe None Medium 11.00
Town of
San Anselmo Occasional Extensive Extreme High High 16.00 City of
San Rafael Occasional Significant Severe None Medium 10.00 City of
Sausalito Occasional Limited Moderate Low Low 8.00
Town of
Tiburon
Highly
Likely Extensive Extreme None High 15.00
Bolinas
Public Utility
District
Occasional Extensive Severe None High 13.00
Las Gallinas
Valley
Sanitary
District
Occasional Extensive Extreme None Medium 12.00
North Marin
Water
District
Occasional Extensive Extreme Low Medium 13.00
Southern
Marin Fire
District
Occasional Extensive Extreme None High 13.00
Table 3.11: Marin County OA Hazard Risk Assessment – Earthquake Source: Profiled Jurisdictions and Districts
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Vulnerability
The areas most vulnerable to earthquake in the Marin County OA, including the unincorporated area, are on bay mud and current and former marshlands. Many of these areas have been artificially filled over the last century. Other areas with some risk of liquefaction include those along creeks due to fluvial and alluvial deposits. Unfortunately, much of Marin’s residential areas and infrastructure are located on former marshes and along creeks. Tens of thousands of acres of residential areas, along with roads, airports, military facilities, retail centers, schools, hospitals, prisons, jails, government administration centers, convention centers, recreation areas, croplands/pasture are in areas vulnerable to liquefaction in the Marin County OA.

For all three faults mentioned above that run through the Marin County OA, many areas of the most severe vulnerability to earthquake coincide with the heavily populated Highway 101 corridor on the eastern side of the county. Numerous unincorporated communities with large populations and buildings lie in this area. According to the ABAG Resilience Program, a 7.8 magnitude earthquake on the San Andreas fault would leave 3,100 homes in the Marin County OA uninhabitable, displace 6,200 households, and result in total building damage of $1,260 billion dollars. Because many people in the region do not have earthquake insurance, many homeowners will not be able to afford to rebuild their homes.

In addition to damaging buildings, a 7.8 magnitude San Andreas earthquake could close 77 roads in Marin due to faulting, liquefaction, debris flow/ landslide, shaking damage to bridges and interchanges, threat of building collapse, structural damage to highway and rail structures, small hazardous material releases, water and gas pipe leaks, and other miscellaneous reasons for closure.

Figure 3.69 shows the social vulnerability of Marin County populations to earthquake in relation to the rest of California.
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Figure 3.69: Population/Social Vulnerability to an Earthquake in California Source: 2018 State of California Hazard Mitigation Plan 1 ~<;>U·N· TY OF a ~ ARIN ~
0 25 SO 100 MRes
cal Poly - San Luis Obispo
City and Reeional Pi nning
June 2018
Popu lation/Soc1:a II Vulnerability
with Earthquake Hazard
R,eliative Vulnerability
High
Low
Grid cell size approximate, y
•one square kilometer.

Cells with population < 75
are not mapped.
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Climate Change and Future Development Considerations
There is no direct link between climate change and seismic activity that could impact the Marin County OA, so climate change is not expected to cause any changes to the frequency or intensity of seismic shaking. According to a 2018 study by the Institute of Physics (IOP), climate change could result in “isostatic rebounds,” or a sudden upward movement of the crust because of reduced downward weight caused by glaciers. As glaciers are known to melt when overall global temperatures increase, climate change could indirectly lead to an increase in seismicity in the Marin County OA. Climate change could also impact earthquakes felt in the Marin County OA as droughts can further deteriorate existing fault lines and pumping groundwater can put further pressure on the earth’s crust. Future development in the populated areas of Marin County OA where seismic shaking and subsidence are more prevalent could exacerbate the impacts of an earthquake.

3.3.5 FLOODING
Flooding is the rising and overflowing of a body of water onto normally dry land. Floods are among the costliest natural disasters in terms of human hardship and economic loss nationwide.

The area adjacent to a channel is the floodplain. Floodplains are illustrated on inundation maps, which show areas of potential flooding and water depths. In its common usage, the floodplain most often refers to that area that is inundated by the 100-year flood, the flood that has a one percent chance in any given year of being equaled or exceeded. The 100-year flood is the national minimum standard to which communities regulate their floodplains through the National Flood Insurance Program. The 200-year flood is one that has 0.5% chance of being equaled or exceeded each year. The 500-year flood is the flood that has a 0.2 percent chance of being equaled or exceeded in any given year. The potential for flooding can change and increase through various land use changes and changes to land surface, which result in a change to the floodplain. A change in environment can create localized flooding problems inside and outside of natural floodplains by altering or confining natural drainage channels. These changes are most often created by human activity such as construction of bridges or channels. In areas where flow contains high sediment load, such as Easkoot Creek in Stinson Beach (due to an active landslide upstream), the flow carrying capacity of the channel may be reduced dramatically during a single flood event. Coastal floodplains may also change over time as waves and currents alter the coastline (especially wetlands) and sea levels rise.

Flooding can occur in several ways:

Riverine flooding – Riverine flooding, defined as when a watercourse exceeds its “bank-full” capacity, generally occurs as a result of prolonged rainfall, or rainfall that is combined with snowmelt and/or already saturated soils from previous rain events. This type of flood occurs in river systems whose tributaries may drain large geographic areas and include one or more independent river basins. The onset and duration of riverine floods may vary from a few hours to many days and is often characterized by high peak flows combined with a large volume of runoff. Factors that directly affect the amount of flood runoff include precipitation amount, intensity and distribution, the amount of soil moisture, seasonal variation in vegetation, snow depth, and water-resistance of the surface due to urbanization. In the Marin County OA, riverine flooding can occur anytime from November through April and is largely caused by heavy and continued rains, sometimes combined with snowmelt, increased outflows from upstream dams, and heavy flow from tributary streams. These intense storms can overwhelm the local waterways as well as the integrity of flood control structures. Flooding is more severe when l ~<;>U·N· TY OF
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antecedent rainfall has resulted in saturated ground conditions. The warning time associated with slow rise riverine floods assists in life and property protection.

Flash flooding – Flash flooding describes localized floods of great volume and short duration.

This type of flood usually results from a heavy rainfall on a relatively small drainage area.

Precipitation of this sort usually occurs in the winter and spring. Flash floods often require immediate evacuation within the hour and thus early threat identification and warning is critical for saving lives.

Localized/Stormwater flooding – Localized flooding problems are often caused by flash flooding, severe weather, or an unusual amount of rainfall. Flooding from these intense weather events usually occurs in areas experiencing an increase in runoff from impervious surfaces associated with development and urbanization as well as inadequate storm drainage systems.

Tidal flooding – Tidal flooding develops when high tides exceed either the top of bank elevation of tidal sloughs and channels, or the crest of bay levees. An especially high tide event that occurs during alignment of the gravitational pull between the sun and the moon, causes tidal water levels to rise to higher-than normal levels. King tides are normal, predictable events that occur semi-annually during winter months. Typically storms in which high tides coincide with peak stormwater flow are the most damaging.

The area is also at risk of flooding resulting from levee failures and dam failures. Dam failure flooding is discussed separately in the Dam Failure Section of this document; levee failure flooding is discussed separately in the Levee Failure Section of this document. Regardless of the type of flood, the cause is often the result of severe weather and excessive rainfall, either in the flood area or upstream reach.

A weather pattern called the “Atmospheric River” contributes to the flooding potential of the area. An Atmospheric River brings warm air and rain to the West. A relatively common weather pattern brings southwest winds to the Pacific Northwest or California, along with warm, moist air. The moisture sometimes produces many days of heavy rain, which can cause extensive flooding. The warm air also can melt the snowpack in the mountains, which further aggravates the flooding potential. In the colder parts of the year, the warm air can be cooled enough to produce heavy, upslope snow as it rises into the higher elevations of the Sierra Nevada or Cascades. Forecasters and others on the West Coast often used to refer to this warm, moist air as the “Pineapple Express” because it comes from around Hawaii where pineapples are grown.

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Figure 3.70: Diagram of an Atmospheric River Event
Source: NOAA
The Marin County OA is susceptible to various types of flood events. In coastal areas, flooding may occur when strong winds or tides result in a surge of seawater into areas that are above the normal high tide line. Other types of flooding in Marin include isolated ponding and stormwater overflow. Isolated ponding is when pools form on the ground and can occur in any area that doesn’t drain effectively – for example, in a natural depression in the landscape.

Stormwater overflow is when storm drains back up. Stormwater drainage systems quickly convey rainwater through underground pipes to creeks and the Bay. When the stormdrains are obstructed or broken or when the water bodies to which they lead to are already full, water backs up onto the streets. Although stormwater overflow and isolated ponding also occur throughout the County, the effects are typically not widespread or significantly damaging.

Location and Previous Occurrences
Figure 3.71 shows the Federal Emergency Management Agency (FEMA) flood hazard zones in the Marin County OA, using the Flood Insurance Rate Maps (FIRMs) for Marin County. l ~ <;>U·N· TY OF
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The science behind atmospheric rivers
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Figure 3.71: FIRM Zones in the Marin County OA
Source: FEMA
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Special Flood Hazard Areas
Flood Zone
A
AE
III AH
Ill Ao
111111 V
lll vE
N
A
0 10
----======:::JMiles
5 Data Source: Marin Map, 2018
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Major county watersheds where significant numbers of structures are at risk from riverine flooding include Coyote Creek, Arroyo Corte Madera del Presidio, East and West Creek watersheds, Corte Madera Creek, Novato and Rush Creeks, Miller Creek, Easkoot Creek (Stinson Beach), Gallinas Creek. Additionally, many locations along Richardson Bay, Tomales Bay, lower Las Gallinas Creek, the San Rafael Canal, East San Rafael and Novato shores, and the outer Pacific coastline are vulnerable to coastal flooding.

In many cases, where there is a significant history of flooding there is a Marin County Flood Control & Water Conservation District “Flood Zone” established. There are 8 County Flood Zones located in the following areas as described in Table 3.11 .

Table 3.11: The 100-year, 200-year and 500-year floodplains in the Marin County OA Zone No. Name Location
1 Novato Northern Marin: Most of City of Novato and some surrounding areas within the Novato Creek watershed.
3 Richardson Bay
Southern Marin: Marin City watershed, Coyote Creek
watershed (includes Tamalpais Valley and Almonte); Arroyo Corte Madera del Presidio watershed and Ryan Creek
watershed (both include much of the City of Mill Valley), and a watershed including Sutton Manor/Alto/part of Strawberry. 4 Bel Aire
Southern Marin: East and West Creek watersheds which
run through the Bel Aire neighborhood of the Town of
Tiburon and part of (unincorporated) Strawberry.
5 Stinson Beach West Marin: Part of the lower Easkoot Creek watershed at Stinson Beach
6 San Rafael
Meadows
Central Marin: A part of the Las Gallinas Creek
watershed in the City of San Rafael across from the
County Civic Center.
7 Santa Venetia Central Marin: The unincorporated community of Santa Venetia along Las Gallinas Creek.
9 Ross Valley
Central Marin: The Corte Madera Creek watershed, including the towns of Fairfax, San Anselmo, Ross, and Larkspur, as well as unincorporated parts of San Anselmo, Fairfax,
Kentfield and Greenbrae.
10 Inverness West Marin: Inverness, along the west shore of Tomales Bay and the East flank of Inverness Ridge.

Figure 3.72: The 100-year, 200-year and 500-year floodplains in the Marin County OA. l ~<;>U·N· TY OF
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Figure 3.73: 100, 200, 500-Year Floodplains in the Marin County OA Source: Marin OEM
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Legend
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Military and Ovil
Defense Installations
Communication
Facilities
Electric Power Facilities
Wastewater Facilities
Marin County
Flooding
•
•
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Emergency Operations
Centers
Fire Stations
Hospitals and Medical
Facilities
Police / Sheriff Stations
Schools
Petaluma
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MANAGEMENT
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Springs El Verano
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Airports 500 Year Flood Plain
100 Year Flood Plain
Marin County OEM / Woody Baker-Cohn
email: [email protected]
Date Printed: 10/30/23
County of Marin, callfornia State Parks, Esri, HERE, Garmin, SafeGraph, Geo Technologies, Inc, METI/NASA, USGS, Bureau of Land Management, EPA, NPS, USDA, County of Marin, califomia State Parks, Esri, HERE, Garmin, SafeGraph, FAO, METI/NASA, USGS, Bureau of Land Management, EPA, NPS 2023 Marin County Operational Area
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Several unincorporated communities in Marin County lie in a special flood hazard area (the 100- year floodplain), which are shown below along with the 500-year floodplain, where applicable.

Figure 3.74 shows the 100-year floodplain in the Lagunitas area.

Figure 3.74: 100-Year Floodplain – Lagunitas
Source: Marin County, 11/27/23
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Figure 3.75 shows the 100-year floodplain in the Forest Knolls are.

Figure 3.75: 100-Year Floodplain – Forest Knolls Area
Source: Marin County, 11/27/23
Figure 3.76 shows the 100-year floodplain in the San Geronimo area.

Figure 3.76: 100-Year Floodplain – San Geronimo Area
Source: Marin County, 11/27/23
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Figure 3.77 shows the 100-year floodplain in the Woodacre area.

Figure 3.77: 100-Year Floodplain – Woodacre Area
Source: Marin County, 11/27/23
Figure 3.78 shows the 100-year floodplain in Tocoloma.

Figure 3.78: 100-Year Floodplain – Tocoloma
Source: Marin County, 11/27/23
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Figure 3.79 shows the 100-year floodplain in Nicasio.

Figure 3.79: 100-Year Floodplain – Nicasio
Source: Marin County, 11/27/23
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Figure 3.80 shows the 100-year floodplain outside of Nicasio to the east.

Figure 3.80: 100-Year Floodplain –Nicasio East
Source: Marin County, 11/27/23
Figure 3.81 shows the 100-year floodplain in Olema.

Figure 3.81: 100-Year Floodplain –Olema
Source: Marin County, 11/27/23
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Figure 3.82 shows the 100-year floodplain in Point Reyes Station and the area immediately south.

Figure 3.82: 100-Year Floodplain – Point Reyes Station Area - South Source: Marin County, 11/27/23
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Figure 3.83 shows the 100-year floodplain in the northern end of Point Reyes Station.

Figure 3.83: 100-Year Floodplain – Point Reyes Station Area - North Source: Marin County, 11/27/23
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Figure 3.84 shows the 100-year floodplain in the Inverness Park area.

Figure 3.84: 100-Year Floodplain – Inverness Park Area
Source: Marin County, 11/27/23
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Figure 3.85 shows the 100-year floodplain in the area south of Inverness.

Figure 3.85: 100-Year Floodplain – Inverness South
Source: Marin County, 11/27/23
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Figure 3.86 shows the 100-year floodplain in Inverness.

Figure 3.86: 100-Year Floodplain – Inverness
Source: Marin County, 11/27/23
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Figure 3.87 shows the 100-year floodplain in Reynolds/Marconi area.

Figure 3.87: 100-Year Floodplain – Reynolds and Marconi Area Source: Marin County, 11/27/23
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Figure 3.88 shows the 100-year floodplain in the Marshall area.

Figure 3.88: 100-Year Floodplain – Marshall Area
Source: Marin County, 11/27/23
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Figure 3.89 shows the 100-year floodplain in the Tomales area.

Figure 3.89: 100-Year Floodplain – Tomales Area
Source: Marin County, 11/27/23
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Figure 3.90 shows the 100-year floodplain in the area north of Bolinas.

Figure 3.90: 100-Year Floodplain – Bolinas North
Source: Marin County, 11/27/23
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Figure 3.91 shows the 100-year floodplain (blue) and the 500-year floodplain (brown) in Bolinas and the area west of Stinson Beach.

Figure 3.91: 100-Year and 500-Year Floodplain – Bolinas and Stinson Beach West Source: Marin County, 11/27/23
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Figure 3.92 shows the 100-year floodplain (blue) and the 500-year floodplain (brown) in Stinson Beach.

Figure 3.92: 100-Year and 500-Year Floodplain – Stinson Beach Source: Marin County, 11/27/23
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Figure 3.93 shows the 100-year floodplain in Muir Beach.

Figure 3.93: 100-Year and 500-Year Floodplain – Muir Beach Source: Marin County, 11/27/23
Figure 3.94 shows the 100-year floodplain (blue) and the 500-year floodplain (brown) in the Tamalpais Valley Area.

Figure 3.94: 100-Year and 500-Year Floodplain – Tamalpais Valley Area Source: Marin County, 11/27/23
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Figure 3.95 shows the 100-year floodplain in Alto and Strawberry.

Figure 3.95: 100-Year and 500-Year Floodplain – Alto and Strawberry Source: Marin County, 11/27/23
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Figure 3.96 shows the 100-year floodplain (blue) and the 500-year floodplain (brown) in Kentfield and Greenbrae.

Figure 3.96: 100-Year and 500-Year Floodplain – Kentfield and Greenbrae Source: Marin County, 11/27/23
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Figure 3.97 shows the 100-year floodplain in California City.

Figure 3.97: 100-Year Floodplain – Marin City
Source: Marin County, 11/27/23
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Figure 3.98 shows the 100-year floodplain in Lucas Valley and Marinwood.

Figure 3.98: 100-Year Floodplain – Lucas Valley and Marinwood Source: Marin County, 11/27/23
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Figure 3.99 shows the 100-year floodplain in Saint Vincent.

Figure 3.99: 100-Year Floodplain – Saint Vincent
Source: Marin County, 11/27/23
Figure 3.100 shows the 100-year and 500-year floodplain in the Santa Venetia area.

Figure 3.100: 100-Year and 500-Year Floodplain – Santa Venetia Area Source: Marin County, 11/27/23
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Figure 3.101 shows the 100-year floodplain (blue) and the 500-year floodplain (brown) in the San Pedro Hill area.

Figure 3.101: 100-Year and 500-Year Floodplain – San Pedro Hill Area Source: Marin County, 11/27/23
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Figure 3.102 shows the 100 and 500-year floodplains in Novato with critical facilities including the Marin County Landfill and the Marin County Airport.

Figure 3.102: Novato Flooding - Marin County Landfill and Marin County airport Source: Marin County
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Figure 3.103 shows the100- and 500-year floodplain in San Rafael Area.

Figure 3.103: Flooding in San Rafael Area
Source: Marin County OEM
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Figure 3.104 shows the 100-year floodplain in Bel Marin Keys.

Figure 3.104: 100-Year Floodplain – Bel Marin Keys
Source: Marin County OEM
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Figure 3.105 shows the 100-year floodplain in Bolinas.

Figure 3.105: Stinson - Bolinas Area Flooding
Source: Marin County OEM
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Figure 3.106 shows flood control zones in the Marin County OA.

Figure 3.106: Flood Control Zones in the Marin County OA Source: Marin County
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Novato Creek in the northern part of the county historically caused damage to large numbers of homes, particularly in the 1960’s, until the Novato Flood Control Project was completed in eight construction phases starting in the 1980’s and continuing through 2006. Novato still experiences some damage during significant winter storms despite the completed Novato Creek Flood Control project. Power outages are also a frequent problem for one of the major pump stations in the area.

Although the current Corte Madera Creek Flood Control project is partially complete (Unit 4 in the Town of Ross is yet to be constructed), flooding will still occur for storms greater than about a 5-year recurrence flood event. Potentially all nine southerly and some centrally located communities of the Marin County OA on this creek are impacted by high tides and heavy rains in above average winter storms. The north-east part of the county, densely populated around the floodplain zones, is threatened every winter and still experiences some damage during winter storms despite the completed Novato Creek Flood Control project.

Since the middle of the last century, the winter/spring storms of 1950, 1955*, 1958*, 1963, 1964*, 1965, 1969*, 1970*, 1973*, 1978, 1980, 1982*, 1983*, 1986*, 1995*, 1996, 1997*, 1998*, 2002, 2005/2006*, 2006*, 2008, 2014, 2017, 2019 and 2023 caused significant damage across the Marin County OA.
*Major Federal Disasters declared for flood.

Flooding in December 1964 and January 1965 had widespread impacts across the Marin County OA. Floods were generally moderate to high. Precipitation was heavy in the San Rafael-Kentfield area. From December 19th-23rd, precipitation was 8.49 inches at Kentfield.

From January 2nd-7th, precipitation at Kentfield was 7.45 inches. The flow in Corte Madera Creek was moderate but the stream flows and overflows of drains caused some local flooding in areas that are subject to frequent flooding in Kentfield. Flood flows in the Walker Creek basin in the northwestern part of Marin County exceeded previous maximum flows.

A major winter storm originating over the Pacific Ocean moved through Marin County in early January 1982. The maximum rainfall from an area of high rainfall in southern Marin County was about 16 inches. The center of this storm was near Kentfield. Large areas of southern and western Marin County had total storm rainfall exceeding 10 inches. Numerous towns were under water, homes and businesses were destroyed, and many roads were damaged across the Marin County OA. The Inverness area was especially hit hard with floodwaters and debris flows. l ~<;>U·N· TY OF
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Figure 3.107: Damage in Inverness from 1982 Storm
Source: Jack Mason Museum of West Marin History
The New Year’s Eve 2005-2006 flood caused widespread damage in the Marin County OA.

Easkoot Creek in Stinson Beach overflowed its banks. At least $219 million in damage was reported in the Marin County OA due to this storm. Over a thousand homes, apartments and businesses across the OA were damaged or destroyed. The Marin City exit off of Highway 101 was inundated with water and water covered all but one lane of southbound 101, creating a giant traffic jam. Western Marin County was scattered with downed trees, flooded roadways and mudslides.

In 2014, Marin County sustained an estimated $13,321,134 in damage from flooding, mudslides, winds, high tides and other storm damage from a December 10th-11th downpour.

There was an estimated $9,324,134 in damage to public property and $3,997,000 in private damages includes 34 homes, 11 businesses and two outbuildings.

In 2017, a powerful February storm thrashed Marin County. Kentfield received 6.3 inches of rain in a 24-hour period. Other rainfall totals for the period included 2.3 inches in Point Reyes.

The College of Marin closed its Kentfield campus because of the storm, and nine school districts canceled classes. Eleven private schools were closed. Pacific Gas and Electric Co. reported thousands of power outages in Marin, including in Kentfield and Lagunitas. Olema Road was closed at Westbrae Drive because of mud, flooding and debris, and flooding was reported on Sir Francis Drake Boulevard at the Bon Air Shopping Center in Greenbrae. In the San Geronimo Valley, flooding closed Sir Francis Drake Boulevard at West Cintura Avenue in Lagunitas. The National Park Service closed Muir Woods National Monument because of the weather. The Lagunitas School District and the Laguna Joint School canceled classes, while the BolinasStinson Union School District closed the Stinson Beach campus and held classes at the Bolinas campus.

In 2019, a storm on February 13th brought heavy rains to Marin County, saturating the ground and exacerbating high tides. County-maintained roads washed out and creeks overflowed their banks, endangering public infrastructure. Flooding occurred in Marin City and was particularly severe in areas of rural Marin. Highway 1 was impassable south of Tomales Petaluma Road and Sir Francis Drake Boulevard was only passable with high-clearance vehicles at Mount l ~<;>U·N· TY OF
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Vision Road in Inverness. Rainfall totals for the storm included 4.3 inches on Mount Tamalpais and 4.16 inches in Kentfield.

Figure 3.108: Flooding in Marin City – 2019 Storm
Source: Marin Independent Journal
In 2023, a storm on January 9th battered Marin county with rain and wind. Rainfall totaled 0.91 inches in Dillon Beach, 1.14 inches in Point Reyes Station, 1.69 inches in Kentfield, 3.04 inches in Woodacre and 2.04 inches on the middle peak of Mount Tamalpais. The Lagunitas School District, Shoreline Unified School District and two elementary schools in the Ross Valley School District stayed closed. More than 4,700 PG&E customers across the Marin County OA had no power at one point.

Impacts
Floods can cause substantial damage to structures, landscapes, and utilities as well as life safety issues throughout the Marin County OA, including in the unincorporated area.

Floodwaters can transport large objects downstream, which can damage or remove stationary structures. Ground saturation can result in instability, collapse, or other damage. Objects can also be buried or destroyed through sediment deposition. Floodwaters can also break utilities lines and interrupt services. Standing water can cause damage to crops, roads, foundations, and electrical circuits. Certain health hazards are also common to flood events. Standing water can also cause septic tank failure and well contamination. Standing water and wet structures can become breeding grounds for microorganisms such as bacteria, mold, and viruses. This can cause disease, trigger allergic reactions, and damage materials long after the flood. When floodwaters contain sewage or decaying animal carcasses, infections become a concern. Direct impacts, such as drowning, can be limited with adequate warning and public education about what to do during floods. Where flooding occurs in populated areas, warning and evacuation will be of critical importance to reduce life and safety impacts from any type of flooding.

Certain health hazards are also common to flood events. While such problems are often not reported, three general types of health hazards accompany floods. The first comes from the water itself. Floodwaters carry anything that was on the ground that the upstream runoff picked up, including dirt, oil, animal waste, and lawn, farm and industrial chemicals. Pastures and areas where cattle and hogs are kept or their wastes are stored can contribute polluted waters to the receiving streams.
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Floodwaters also saturate the ground, which leads to infiltration into sanitary sewer lines. When wastewater treatment plants are flooded, there is nowhere for the sewage to flow. Infiltration and lack of treatment can lead to overloaded sewer lines that can back up into low-lying areas and homes. Even when it is diluted by flood waters, raw sewage can be a breeding ground for bacteria such as e. coli and other disease-causing agents. Floodwaters may scour stream banks, edging properties closer to the floodplain or causing structures to collapse into floodwaters. Flooding is also responsible for hazards such as landslides when high flows oversaturate 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 drains.

The second type of health problem arises after most of the water has gone. Stagnant pools can become breeding grounds for mosquitoes, and wet areas of a building that have not been properly cleaned breed mold and mildew. A building that is not thoroughly cleaned becomes a health hazard, especially for small children and the elderly.

Another health hazard occurs when heating ducts in a forced air system are not properly cleaned after inundation. When the furnace or air conditioner is turned on, the sediments left in the ducts are circulated throughout the building and breathed in by the occupants. If a water system loses pressure, a boil order may be issued to protect people and animals from contaminated water.

The third problem is the long-term psychological impact of having been through a flood and seeing one’s home damaged and irreplaceable keepsakes destroyed. The cost and labor needed to repair a flood-damaged home puts a severe strain on people, especially the unprepared and uninsured. There is also a long-term problem for those who know that their homes can be flooded again. The resulting stress on floodplain residents takes its toll in the form of aggravated physical and mental health problems.

Additional growth in or around the Marin County OA could contribute to increased flooding in the county. Many historic and cultural resources are located in the mapped flood zones.

The impact of damage resulting from the flooding hazard, as mentioned, can be extremely variable. Nevertheless, most damage results from rising water that inundates residences and buildings, damage to infrastructure and critical facilities, and loss of ingress and egress by the population in the affected areas and the inability of the jurisdictions emergency response capabilities. Damage from flooding can range from minimal, where the damage to an individual home can be on the order of a few thousand dollars to the complete loss of a building or loss of life from the inability to evacuate from the rising floodwaters.

The diversity and dispersion of the Marin County OA’s flood hazards, in addition to the tendency for floods to be flashy in nature, make response to emergencies more difficult and increase the need for planning and community awareness in areas of increased flood risk. While property damage to structures within 100-year flood zones is a major concern, damage to roads, utilities, and other supporting infrastructure located in these zones can potentially impact areas of the community outside of the flood zones as well.

Arroyo Corte Madera del Presidio is at risk of overtopping due to less than a 5-year flow. On average Corte Madera Creek and Easkoot Creek are at risk of overflowing their banks due to 5- 10 year flow events. Novato Creek overflows in some locations due to 10-year flow. Coyote l ~<;>U·N· TY OF
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Creek and Gallinas Creek are more vulnerable to overtopping due to tidal elevations and may be able to carry 100-year riverine flows at low tides.

Extent and Probability
In areas such as Marin County that do not have extended periods of below-freezing temperatures or significant snowfall, floods usually occur during the season of highest precipitation or during heavy rainfalls after prolonged dry periods. Marin County is dry during the late spring, summer, and early fall and receives most of its rain during the winter months. The rainfall season extends from November through April, with most rainfall occurring during this period. Due to varying microclimates within the County, rainfall measured in water year 2016- 2017 where there are Marin County Flood Control & Water Conservation District-owned gages ranged inland from as low as 47 inches in Novato to over 82 inches in Kentfield. Along the coast, rainfall ranged from 36 inches at Oceana Marin to 45 inches at Point Reyes Station.

In should be noted winter 2016-2017 was an unusually wet year. An average of 56 inches of rain falls each year at the summit of Mount Tamalpais, at 2,572 feet elevation. The rain collects in several channels, flowing down steep slopes and onto broad, flat valleys, many of which are populated. The valleys usually only receive on average 32 inches of rain per year, thus flows from the uplands contribute greatly to flows on the valley floor. During most rainfall events, waterways remain within their channels or underground pipes until they reach a bay or the ocean.

The Marin County OA has several major 100-year and 500-year floodplains which are mapped by FEMA in the most recent Flood Insurance Rate Maps (FIRM), several of which were recently updated in 2016 and 2017 (see above). While they may look small relative to the size of the County as a whole, the bulk of the floodplains are located in some of the County’s most heavily populated areas along the eastern shoreline: notably portions of Novato, San Rafael, and Mill Valley. These floodplains vary in size, probability and severity of inundation, underlying causes (riverine, tidal, etc.), and potential impacts to the communities in them. The areas of most concern are located in what is designated by FEMA as a 100-year flood zone or Special Flood Hazard Area (SFHA). What is currently considered a 100-year flood may occur more often due to climate change. Due to the increased probabilities of flooding (1% chance in any given year), these properties face high insurance premiums and major restrictions on further development.

Along the Pacific Ocean there are a number of homes in Stinson Beach which are mapped as being in a VE zone. A VE zone is a 100-year flood zone where tsunamis or other forms of wave action threaten low lying coastal areas.

For some of the developments along the San Francisco Bay, such as Santa Venetia and Tamalpais Valley, the main issues concern poor drainage due to flat terrain and/or differential settlement, low elevation relative to the tides, and the reliance on a system of pumps and levees to keep floodwaters from inundating homes. Runoff collecting in this area can be especially difficult to remove during high tides.

Other more inland areas, such as areas along Corte Madera Creek and its tributaries, have higher elevations yet still contain properties located in 100-year flood zones. This is mainly due to threats caused by local creeks which have a tendency to overflow their banks when rainfall reaches critical levels. Properties along Novato Creek and its tributaries face similar threats.

The main stems of these creeks and many of their tributaries are constrained by development on the banks.

When flooding occurs in the Marin County OA, depths are commonly on the order of 0-2 feet in streets and sidewalks. This level occurs when storm drains are overwhelmed and/or during king l ~<;>U·N· TY OF
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tides. Flood depths on the order of 2- 4 feet have occurred in recent memory and represent significant flood events that caused damage to structures and property. 1982 was the most extreme flood of record along Corte Madera Creek in Central Marin County and probably had some inundations depths as high as 5 feet. In 2016 the FEMA San Francisco Bay Coastal Study became effective and raised the static Base Flood Elevation of the Bay to an elevation of 10-feet NAVD88. This level of flooding has not been observed but is feasible in any given year.

If this level of tidal flooding was to occur along the bay shoreline there would be inundation depths as much as 6-8 feet in neighborhoods such as Santa Venetia.

On the Marin County OA’s outer coast V zones have BFEs of up to 22 feet according to FIRMs updated August 2017. In the unincorporated community of Stinson Beach this corresponds to a maximum inundation depth of 8-10 feet. Although some houses were destroyed by wave action and storm surge during the 1982 event, nothing approaching this level of inundation has occurred in recorded history here.

The other index for extent is the speed of onset of flooding or the rainfall-runoff lag time, which doesn’t apply to tidal flooding. The riverine flooding comes directly from rainfall runoff of adjacent uplands in the County’s series of relatively small, short watersheds. While antecedent moisture is a big factor, this flash flooding is typically short duration and directly associated with the magnitude of the passing storm system. These storms, often in the form of atmospheric rivers coming off the Pacific Ocean, can last anywhere from a few hours to a day or two. The speed of onset of flooding ranges from minutes to about 2 hours after the precipitation exceeds the drainage capacity.
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Table 3.12: Marin County OA Hazard Risk Assessment – Flooding Jurisdiction
Probability/
Likelihood
of Future
Events
Geographic
Extent
Magnitude/
Severity
Climate
Change
Influence
Significance Risk
Score
Marin County Highly
Likely Limited Severe High Medium 14.00
City of
Belvedere
Highly
Likely Limited Severe High Medium 14.00
Town of
Corte Madera Likely Significant Severe High High 15.00
Town of
Fairfax Occasional Limited Moderate Medium Medium 10.00 City of
Larkspur Occasional Limited Severe High Medium 12.00
City of
Mill Valley Occasional Extensive Severe Medium Medium 13.00 City of
Novato Likely Negligible Weak Medium Low 8.00
Town of
Ross
Highly
Likely Significant Severe High High 16.00
Town of
San Anselmo Occasional Limited Moderate Medium Medium 10.00 City of
San Rafael
Highly
Likely Significant Severe High High 16.00
City of
Sausalito Likely Significant Moderate High Medium 13.00 Town of
Tiburon
Highly
Likely Limited Severe High Medium 14.00
Bolinas
Public Utility
District
Likely Limited Moderate High Medium 12.00
Las Gallinas
Valley
Sanitary
District
Likely Significant Moderate Medium High 13.00
North Marin
Water
District
Occasional Significant Severe High Medium 13.00
Southern
Marin Fire
District
Likely Limited Moderate Medium Medium 11.00
Table 3.12: Marin County OA Hazard Risk Assessment – Flooding Source: Profiled Jurisdictions and Districts
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Vulnerability
Prior to development, the Marin County OA’s flat lowlands flooded frequently. When rain fell on the Marin County OA, it infiltrated into the ground and moved slowly toward creek channels. The ground acted like a sponge, storing water and releasing it slowly. While water moved underground, it was naturally cleansed by physical and biological processes. Annual floods brought life-giving water to parched floodplains, nourishing them with fresh sediment. They recharged aquifers and allowed fish to swim over normally dry land that was rich with food.

Tides flooded biologically rich marshes along the bay perimeter twice a day. When humans began to develop the land, they created conflicts between what was built and the natural tendency of creeks to flood. Much of the development in the Marin County OA was built in floodprone areas which put it at risk of inundation. Roads, parking lots, roofs, and other impervious surfaces prevent water from infiltrating the ground. Instead, the water moves quickly across the landscape into pipes and creeks further increasing flood risk downstream. Homes, commercial areas, schools, hospitals, police and fire stations, roads and highways, sanitary sewers and waterlines, sewage treatment plants, pump stations are all located in floodplains in the Marin County OA.

All of Marin County OA’s watersheds are small and largely prone to flash flooding. Flash floods are particularly dangerous. The National Weather Service (NWS) defines a flash flood as one in which the peak flow travels the length of a watershed within a 6-hour period. These floods arise when storms produce a high volume of rainfall in a short period over a watershed where runoff collects quickly. They often affect populated areas of the Marin County OA’s cities and towns.

They often strike with little warning and are accompanied by high velocity flow.

All incorporated cities and towns in the Marin County OA have flood risk – and are in fact participants in the National Flood Insurance Program. Even those that are not in a Marin County Flood Control & Water Conservation District “Flood Zone,” have robust maintenance and capital improvement programs that help manage and mitigate flood risk. These cities without District Flood Zones include most of San Rafael and Tiburon, and all of Corte Madera, Sausalito, and Belvedere. Additionally, San Anselmo, Ross, Larkspur, Fairfax, Mill Valley and Novato have flood mitigation programs that operate largely independently of the Flood District, although extensive coordination of activities and collaboration with the Flood District is facilitated through the Marin County Watershed Program (part of the County Department of Public Works). Every city and town, and many unincorporated communities in Marin contain FEMA Special Flood Hazard Areas (SFHA), meaning they lie in the 100-year floodplain and have at least a 1% chance of flooding in a given year. They all participate in the National Flood Insurance Program and many of the structures in the SFHA carry FEMA flood insurance or private flood insurance.

Flood risk to the Marin County OA’s incorporated cities and towns are discussed in their respective Annexes. Most unincorporated communities in the Marin County OA have some level of flood risk, as discussed below:

Lagunitas, Forest Knolls, San Geronimo and Woodacre all lie along San Geronimo Creek.

Dozens of homes lie in the 100-year floodplain of the creek and could be susceptible to flooding.

Sir Francis Drake Boulevard could be susceptible to flooding where it is crossed by Lagunitas Creek and San Geronimo Creek at the south end of Lagunitas. Several road bridges on the south side of San Geronimo Creek that connect residential communities to Sir Francis Drake Boulevard could be susceptible to flooding that could cut off ingress and egress to the area.

Numerous residences and businesses in Nicasio and along Lucas Valley Road to the west of Nicasio lie in the 100-year floodplain and could be susceptible to flooding. Nicasio Valley Road could flood in several places on both sides of Nicasio. Numerous buildings in Tocoloma, including the Tocoloma PG&E substation, lie in the 100-year floodplain. Sir Francis Drake l ~<;>U·N· TY OF
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Boulevard could also be susceptible to flooding where Lagunitas Creek crosses it at Platform Bridge Road.

Much of Olema west of Highway 1 and along Olema Creek is in the 100-year floodplain. There are numerous residences and businesses in this area, including the Olema Campground. The southern end of Point Reyes Station is particularly susceptible to flooding, including the area where Highway 1 intersects with Sir Francis Drake Boulevard. There are numerous homes and businesses in this area, along with the CalTrans Point Reyes Maintenance Station that lie in the 100-year floodplain. Flooding along Highway 1 and Sir Francis Drake Boulevard from either Lagunitas Creek or Tomales Bay could affect ingress and egress to Point Reyes Station, Inverness and Point Reyes National Seashore. Several buildings in the south and west sides of Point Reyes Station and at the U.S. Coast Guard Station lie in the 100-year floodplain and could be susceptible to flooding. Highway 1 and several homes north of Point Reyes Station also lie in the 100-year floodplain and could be susceptible to flooding.

Several homes, businesses and sections of Sir Francis Drake Boulevard from Inverness Park to Inverness lie in the 100-year floodplain and could be susceptible to flooding from either Tomales Bay or inland canyons.

Sections of the east shore of Tomales Bay along Highway 1, including around Reynolds and Marconi, lie in the 100-year flood plain and are susceptible to flooding. Most of the residences and businesses in Marshall lie in the 100-year floodplain and could be susceptible to flooding from Tomales Bay. While most of Tomales is outside the 100-year floodplain, the area south of it has numerous residences and businesses along Keys Creek and Walker Creek that are in the 100-year floodplain and could be susceptible to flooding.

An area north of Bolinas along Pine Gulch Creek and the Bolinas lagoon lie in the 100-year floodplain. Numerous residences, the Bolinas-Stinson Elementary School, and a section of Olema Bolinas Road are in this area and could be susceptible to flooding. While most of Bolinas lies outside the 100-year floodplain, there are numerous residences along Bolinas Lagoon and Bolinas Bay that are in the 100-year floodplain and could be susceptible to flooding. Most of the residences in Stinson Beach along Dipsea Road and Seadrift Road in Stinson Beach lie in the 500-year floodplain, though several lie in an area of the 100-year floodplain and could be particularly susceptible to coastal flooding. Most of the residences closer to Stinson Beach along Cale del Arroyo lie in the 100-year floodplain and could be susceptible to flooding, with some that could be particularly susceptible to coastal flooding. Some homes, the Stinson Beach Fire Station 32, and the Stinson County Water District Office lie in the 500-year plain in this area and could also be susceptible to flooding. Numerous residences and businesses in and around the southern core of Stinson Beach lie in the 500 and 100-year floodplain and could be susceptible to flooding.

The east side of Muir Beach along Railroad Creek lies in the 100-year floodplain. Numerous residences and a section of Highway 1 could be susceptible to flooding in this area. Flooding of Highway 1 could affect ingress and egress north towards Stinson Beach.

Most of the Tamalpais Junction area of Tamalpais Valley along Coyote Creek and the creek along Tennessee Valley Road lies in the 100-year floodplain, with a smaller section lying in the 500-year floodplain. Numerous residences lie in the 500-year floodplain and could be susceptible to either creek flooding or flooding from Richardson Bay. Hundreds of residences, a church, the Tamalpais Valley Community Center, part of the Tamalpais Valley Elementary School, a large shopping center with numerous businesses, the CalTrans Manzanita Station, sections of Highway 1, a section of Highway 101 and the Commodore Center Heliport all lie in l ~<;>U·N· TY OF
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the 100-year floodplain and could be susceptible to flooding. Most of the Strawberry and Alto areas lie outside the 100 and 500-year floodplain, though dozens of residences, several apartment complexes, numerous commercial buildings and part of the Strawberry Point Middle School lie in the 100-year floodplain and could be susceptible to flooding. A small area north of Keil Cove on the Tiburon Peninsula where there are several homes also lies in the 100- yearfloodplain and could be susceptible to flooding.

A large part of Kentfield lying along Corte Madera Creek is in the 100-year floodplain. Dozens of homes, numerous businesses and shopping centers, the Adeline E. Kent Middle School, parts of the College of Marin and the Kentfield Hospital, and sections of major thoroughfares including Sir Francis Drake Boulevard and College Avenue lie in this area and could be susceptible to flooding. Most of the College of Marin (including the College of Marin Police Department), part of the Kentfield Hospital and the Marin Health Medical Center, all of Marin Catholic High School and Anthony G. Bacich Elementary School, the Kentfield Fire Station #17, several medical facilities, dozens of homes, numerous businesses and a large section of Sir Francis Drake Boulevard in the Kentfield area lie in the 500-year floodplain and could be susceptible to flooding. There are dozens of homes in the Greenbrae area that lie in the 500- year floodplain and could be susceptible to flooding. A section of California City on the north side near Anderson Drive and the railroad tracks lie in the 100-year floodplain and there are several homes here along with the Montessori School of Central Marin that could be susceptible to flooding.

The 100-year floodplain in Lucas Valley and Marinwood is mostly confined to Miller Creek and while most buildings and infrastructure are not in the 100-year floodplain, part of it runs along the edge of Lucas Valley Elementary School, the Miller Creek Middle School and the Marin County Juvenile Complex that could all be susceptible to flooding. There are several bridges, including on Lucas Valley Road and Highway 101, along with several homes in Marinwood that lie in the 100-year floodplain and could be susceptible to flooding. Part of the Saint Vincent School in Saint Vincent is also in the 100-year floodplain and could be susceptible to flooding.

The northwestern corner of Santa Venitia along the San Venetia Open Space Preserve lies in the 100-year floodplain, and there are several hundred homes along with a few pump stations and critical care facilities in this area that could be susceptible to flooding. Sections of San Pedro Boulevard and areas of San Pedro Point, including part of the McNear Brickyard, lie in the 100-year floodplain and could be susceptible to flooding. Several homes in the unincorporated County along San Pedro Boulevard near San Rafael lie in either the 100-year or 500-year floodplain and could be susceptible to flooding.

Part of the County Redwood Landfill and all of the Marin County airport, including the access road, lie in the 100-year floodplain and could be susceptible to flooding. This area is mostly marshland that could experience coastal flooding. Most of the Green Point-Black Point area lies outside the 100-year floodplain though there are several homes in the Black Point area near marshland that lie in the 100-year floodplain and could be susceptible to flooding.

Numerous homes in Bel Marin Keys and sections of Bel Marin Keys Boulevard lie in the 100- year floodplain and could be susceptible to flooding. A flooding event could affect ingress and egress to Bel Marin Keys.

San Antonio Creek forms part of the boundary between Marin and Sonoma Counties from the area around Chileno Valley Road east to the Petaluma River and there are several homes along it that lie in the 100-year floodplain and that could be susceptible to flooding. There are also l ~<;>U·N· TY OF
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several road bridges that cross the creek in the 100-year floodplain and that could be susceptible to flooding.

Figure 3.109 shows the social vulnerability of the Marin County OA’s population to flooding in relation to the rest of California.

Figure 3.109: Population/Social Vulnerability to Flooding in California Source: 2018 State of California Hazard Mitigation Plan l ~<;>U·N· TY OF
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0 25 50 100 Miles
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City and Regional Planning
June 2018
Population/Social Vulnerability
with Flood Hazard
Relative Vulnerability
High
Low
Grid cell size approximately
one square kilometer.

Cells with population <75
are not mapped.
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Climate Change and Future Development Considerations
Climate change is expected to affect California's precipitation patterns, which are likely to influence future flood events. A 2017 study found that the number of very intense precipitation days in California is projected to more than double by the end of the century, increasing 117 percent, making it likely that flood events will become more frequent in the Marin County OA.

Climate change is expected to alter rainfall patterns in Northern California, including the Marin County OA. As the climate warms, rain events are predicted to become more intense. The Marin County OA will likely experience more rain inundation events that lead to flooding and increase the potential threat of dam and levee failure, tree mortality, and other potential hazards. Sea level rise as a result of climate change will exacerbate the impacts of tidal flooding in the lowland areas of the Marin County OA. Future development in these areas will expose more people and infrastructure to the effects of flooding in the Marin County OA.

Development in marshland of the Marin County OA would expose additional people and infrastructure to flooding as marshlands act as a natural buffer to storm surge.

3.3.6 LAND SUBSIDENCE
Land subsidence is a gradual settling or sudden sinking of the Earth's surface owing to subsurface movement of earth materials. The principal causes are aquifer-system compaction, drainage of organic soils through groundwater pumping, underground mining, hydrocompaction, natural compaction, sinkholes, and thawing permafrost. More than 80 percent of the identified subsidence in the United States is a consequence of underground water exploitation. The increasing development of land and water resources threatens to exacerbate existing land-subsidence problems and initiate new ones.

Sinkholes can form in three primary ways. Dissolution sinkholes form when dissolution of the limestone or dolomite is most intensive where the water first contacts the rock surface.

Aggressive dissolution also occurs where flow is focused in preexisting openings in the rock, such as along joints, fractures, and bedding planes, and in the zone of water-table fluctuation where groundwater is in contact with the atmosphere. See Figure 3.110 for a picture and description of how dissolution sinkholes form.

Figure 3.110: Dissolution Sinkhole Formation
Source: USGS
Cover-subsidence sinkholes tend to develop gradually where the covering sediments are permeable and contain sand. In areas where cover material is thicker, or sediments contain more clay, cover-subsidence sinkholes are relatively uncommon, are smaller, and may go 1 ~<;>U·N· TY OF a ~ ARIN ~
Thin overburden Rain
---1 r- --,---
Rainfall and surface water percolate through
joints in the limestone. Dissolved carbonate
rock is carried away from the surface and a
small depression gradually forms.

On exposed carbonate surfaces. a depression
may focus surface drainage, accelerating the
dissolution process. Debris carried into the
developing sinkhole may plug the outflow,
ponding water and creating wetlands.
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undetected for long periods. See Figure 3.111 for a picture and description of how coversubsidence sinkholes form.

Figure 3.111: Cover-Subsidence Sinkhole Formation
Source: USGS
Cover-collapse sinkholes may develop abruptly over a period of hours and cause catastrophic damages. They occur where the covering sediments contain a significant amount of clay. Over time, surface drainage, erosion, and deposition of sediment transform the steep-walled sinkhole into a shallower bowl-shaped depression. See Figure 3.112 for a picture and description of how cover-collapse sinkholes form.

Figure 3.112: Cover-Collapse Sinkhole Formation
Source: USGS
New sinkholes have been correlated to land-use practices, especially from groundwater pumping and from construction and development practices that cause land subsidence.

Sinkholes can also form when natural water-drainage patterns are changed and new waterdiversion systems are developed. Some sinkholes form when the land surface is changed, such as when industrial and runoff-storage ponds are created. The substantial weight of the new material can trigger an underground collapse of supporting material, thus causing a sinkhole.

The overburden sediments that cover buried cavities in the aquifer systems are delicately balanced by groundwater fluid pressure. The water below ground helps to keep the surface soil in place. Groundwater pumping for urban water supply and for irrigation can produce new sinkholes in sinkhole-prone areas. If pumping results in a lowering of groundwater levels, then underground structural failure, and thus, sinkholes, can occur. 1 ~ <;>U·N· TY OF a ~ ARIN ~
Granular sediments spall
into secondary openings
in the underlying carbonate
rocks.
:o vero~en' •.

A column of overlying sediments settles into the
vacated spaces (a process
termed "piping").

Sediments spall into a cavity. As spalling continues, the cohesive covering sediments form a structural
arch.

Gverei:irden - - - - - - - - -
,most1¥,d<¥)- ~- - - - - - - - y·----. ."I_.·•,,,,-,,~ _,..-~ Dissolution and infilling continue, forming a noticable depression in the land
surface.

The cavity migrates upward by progressive roof
collapse.

The slow downward erosion
eventually forms small surface depressions I inch to
several feet in depth and
diameter.

The cavity eventually
breaches the ground surface, creating sudden and
dramatic sinkholes.
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Location and Previous Occurrences
Collapsible soils with the potential for subsidence (i.e., vertical displacement of the ground surface over a locality or region) are more present in the low-lying flatland deposits along the Marin County OA’s valley basins and bays, including in the unincorporated area. In the low-lying exposed areas in nearly every community, except Kentfield, subsidence is an ongoing issue.

Roadways throughout the Marin County OA along the shoreline, notably US Highway 101, and roads in lower Paradise Cay, already experience subsidence. See Figure 3.113 for a map of land subsidence and uplift in California and the Marin County OA from 2007-2018. Areas of increased subsidence occur along San Francisco Bay with an area of uplift on both sides of the northern end of Tomales Bay.

Figure 3.113: Land Subsidence in California 2007-2018 with Marin County Cutout l ~<;>U·N· TY OF
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Source: NASA
Figure 3.114 shows the areas of the United States where certain rock types that are susceptible to dissolution in water occur. In these areas the formation of underground cavities can form, and sinkholes can happen. These rock types are evaporites (salt, gypsum, and anhydrite) and carbonates (limestone and dolomite).

Figure 3.114: U.S. Rock types Susceptible to Water Dissolution Source: USGS
Impacts
Land subsidence has the potential to damage drinking water wells and infrastructure throughout the Marin County OA, including in the unincorporated area. Loss of drinking water for rural communities can cause health problems as well as significant financial impacts with the redrilling and testing of wells and providing alternate potable water sources for community members. Prolonged drought can exacerbate the impacts from land subsidence. As the water table is drawn down, land can sink even further and damage underground aquifers. Critical infrastructure such as highways, sewer lines, and gas lines can also become undermined due to land subsidence and sinkholes, becoming a threat to public safety and resulting in the devotion of significant financial resources to fix any damages. Sinkholes can form in parking lots, or directly under houses and other structures, potentially causing loss of life and significant damage.

Extent and Probability
Many shoreline properties in the Marin County OA, including in the unincorporated area, are built on fill and mud, and underlying soils will become more saturated under sea level rise conditions and, consequently, vulnerable to increasing rates of subsidence. Subsidence is already a factor for many roads and will likely worsen as the ground becomes saturated with bay or coastal waters further inland. Utilities infrastructure located along the shoreline on fill and mud and in the bay itself, which already experiences the effects of subsidence, will be subject to increased levels of subsidence in the future.
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~ Evaporite rocks-salt and gypsum
D Karst from evaporite rock
D Karst from carbonate rock
(modified from Davies and Legrand, 1972
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Table 3.13: Marin County OA Hazard Risk Assessment – Land Subsidence Jurisdiction
Probability/
Likelihood
of Future
Events
Geographic
Extent
Magnitude/
Severity
Climate
Change
Influence
Significance Risk
Score
Marin County Occasional Limited Moderate Medium Medium 10.00 City of
Belvedere Occasional Limited Moderate Medium Medium 10.00 Town of
Corte Madera Likely Negligible Weak Low Low 7.00
Town of
Fairfax Occasional Negligible Weak Low Low 6.00
City of
Larkspur Occasional Limited Moderate Medium Medium 10.00 City of
Mill Valley Likely Negligible Moderate Low Low 8.00
City of
Novato Likely Negligible Weak Low Low 7.00
Town of
Ross Unlikely Limited Weak Low Low 6.00
Town of
San Anselmo Unlikely Negligible Moderate Low Low 6.00
City of
San Rafael
Highly
Likely Significant Weak Low Medium 11.00
City of
Sausalito Likely Limited Moderate Medium Medium 11.00
Town of
Tiburon Occasional Limited Moderate Medium Medium 10.00 Bolinas
Public Utility
District
Likely Limited Moderate Medium Medium 11.00
Las Gallinas
Valley
Sanitary
District
Occasional Negligible Weak Low Low 6.00
North Marin
Water
District
Occasional Negligible Moderate Medium None 7.00
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Southern
Marin Fire
District
Unlikely Negligible Severe None Low 6.00
Table 3.13: Marin County OA Hazard Risk Assessment – Land Subsidence Source: Profiled Jurisdictions and Districts
Vulnerability
Land subsidence can severely impact public facilities and infrastructure as well as private development in areas where it occurs through the damage or compete failure of underground utilities, damaged building or utility infrastructure foundations, damaged roadways, etc.

Vulnerable substations; electrical transmission towers and lines; underground natural gas water supply, and sanitary sewer pipelines; pump stations; hazardous facilities, including those with underground storage tanks (e.g., gas stations); and other facilities and infrastructure along the shoreline would be compromised by subsidence. Subsidence can lead to damage to healthcare facilities, private wells, and general drinking water quality. Subsidence can place pressure on underground utility pipelines when roadways begin to sink around the pipes, causing them to bend. Electrical transmission towers, including land-based towers east of Bel Marin Keys and South of Novato over to the Sonoma County border and in the bay off the shores of Corte Madera and Mill Valley, are subject to increased rates of subsidence, which can impact the mounting platforms that support the towers. Landfills are often subjected to subsidence because they are typically located where marshes once existed, and because buried materials settle over time. Jetties, which are structures built into the water to protect a harbor or shore, are also prone to subsidence.

Transportation facilities along the OA’s coastline are vulnerable to subsidence. Increased subsidence could warp the buildings and runways at Marin County Airport in North Novato and San Rafael Airport. Parking and access areas along Richardson Bay, including those in Waldo Point Harbor, are also prone to continuous subsidence. As discussed above, roadways and highways along the shoreline also suffer from subsidence.

Important cultural resources, including archaeological sites at or near the edge of the bay may be vulnerable to subsidence. Vulnerable sites include permanent settlements represented by shell mounds or middens associated with marshes and other locations at or near the edge of the bay where shellfish/marine resources were available.

The areas of the Marin County OA most vulnerable to land subsidence are those underlain with the younger Holocene unconsolidated alluvial and colluvial sediments, and even more so the younger bay muds. In general, Marin County unincorporated community shoreline properties, especially those in Southern Marin on fill in the low-lying areas east of US Highway 101, are the most exposed and vulnerable to subsidence. Almonte, Belvedere, Santa Venetia, Paradise Cay and Bel Marin Keys were built on bay fill and mud, and already experience subsidence. This impacts buildings, roads, and utility infrastructure. These areas could anticipate increased rates of subsidence as bay waters saturate the soil from below.

Land subsidence is an ongoing issue in the low-lying exposed areas of nearly every unincorporated Bayshore community, except for Kentfield, and sea level rise associated with climate change would only exacerbate existing subsidence impacts. 1 ~<;>U·N· TY OF a
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Climate Change and Future Development Considerations
Climate change could indirectly influence land subsidence as more severe and prolonged periods of drought may encourage more groundwater withdrawals. In coastal areas like the Marin County OA, land subsidence leads to higher sea levels and increased flood risk. The rate of land subsidence could increase across the Marin County OA as a result of climate change.

The impacts of land subsidence on infrastructure, including roads and underground utilities, in the Marin County OA could increase with future development in the lowland populated areas where land subsidence is more likely to occur.

3.3.7 LEVEE FAILURE
Levee failure is the overtopping, breach or collapse of the levee. Levees can fail in the event of an earthquake, internal erosion, poor engineering/construction or landslides, but levees most commonly fail as a result of significant rainfall or very high tides. During a period of heavy rainfall, the water on the water-body side of the levee can build up and either flow over the top (“overtopping”) or put pressure on the structure causing quickening seepage and subsequent erosion of the earth. The overflow of water washes away the top portion of the levee, creating deep grooves. Eventually the levee weakens, resulting in a breach or collapse of the levee wall and the release of uncontrollable amounts of water. Figure 3.115 shows a levee and the multiple ways it can fail.

Figure 3.115: Levee Failure Mechanisms
Source: University of California
Location and Previous Occurrences
Several Marin County OA communities, such as Tamalpais Valley, Santa Venetia, Corte Madera, Belvedere, and parts of Strawberry, Novato, and Ross Valley are protected by levees. l ~<;>U·N· TY OF
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Anat.omy of a levee
2, Internal Erosion/Piping

5. Wave lmpa<U

8. Piping •Of substratum
I a. Overtopping 1 b. Overtopping/Jetting

3. Surface Erosion

4. Sliding

6. Structural Impacts

7. Liquefaction

9. Tree damage 10. Slope fa I lure
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Levees are typically earthen embankments designed to contain, control, or divert the flow of water to provide some level of protection from flooding. No levee system provides full protection from all flooding events to the people and structures located behind it. Some level of flood risk exists in the levee-affected areas. Except for one levee system in Novato-Hamilton, none of the County’s levees are FEMA-accredited. Many were built many decades ago (non-engineered) by farmers or developers and material may have been added over the years. l ~<;>U·N· TY OF
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Figure 3.116: Marin County Levee System
Source: Marin County OEM
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The Coyote Creek Left Bank Levee System (COYL) is a federally authorized and non-federally operated and maintained project and is located in the County of Marin on the west shore of Richardson Bay, an arm on the western side of San Francisco Bay where the Coyote Creek drains approximately 2,200 acres of the eastern slopes of the Marin Peninsula. The COYL is

0.96 miles long with a maximum height of four feet. The COYL is one of the two flood protection systems of the Coyote Creek flood control project and is situated along the left bank of the creek when looking downstream. The other system is along the right bank of Coyote Creek. There is only one segment within the COYL. The subject levee system is located along the left bank of Coyote Creek and is approximately 1.5 miles long. The purpose of the levee is to provide flood protection to the community of Tamalpais Valley, California. The channel improvement project for Coyote Creek, located in the County of Marin, California, was authorized by the Chief of Engineers on January 15, 1963, under the provisions of Section 205 of the Flood Control Act of 1948, as amended by the Flood Control Act of 1962. The COYL was completed in February 1965. Improvements to
the project to address
the local subsidence
were completed in
1977. The public
sponsor of the COYL is
the Marin County
Department of Public
Works.

The other Coyote
Creek Levee system is
an additional smaller
levee that was
constructed on the right
bank in 1965. It is 0.22
miles long with a
maximum height of four
feet. The levee from
the Highway 1 bridge to
the downstream end is
no longer maintained.

Figures 3.17 - 3.19
show the levees and
Levee inundation in the
Tamalpais Valley
Figure 3.117: Levees in Tamalpais Valley
Source: U.S. Army Corps of Engineers, 11/27/23
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Figure 3.118: Levees in Strawberry
Source: U.S. Army Corps of Engineers, 11/27/23
The horseshow shaped levee at the Sewerage Agency of Southern Marin (SASM) shown in Figure 3.121, according to the Mill Valley Department of Public Works, the levee at the SASM is above the high tide water mark and is not technically a levee but rather a berm to hold extra water storage at the side. It is not acting as a flood wall. The City of Mill Valley has no risk of levee failure.
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Figure 3.119: Tam Junction Levees
Source: Marin County OEM
Sewerage Agency of Southern
Marin (SASM) berm.
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One levee system exists in Kentfield and is located along Corte Madera Creek. The Corte Madera Creek Left Bank Levee is 0.7 miles long with an undocumented height. Figure 3.120 shows the Corte Madera Creek Left Bank Levee in Kentfield.

Figure 3.120: Levee in Kentfield
Source: U.S. Army Corps of Engineers, 11/27/23
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Figure 3.121 shows the Greenbrae Levee system:

Figure 3.121: Greenbrae Levee System
Source: Marin County OEM
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The McNears sea wall runs along Point San Pedro Road from roughly Marine Drive to the McNear Brickyard and is located along San Pablo Bay. The McNears sea wall is approximately

1.4 miles long with an undocumented height. Figure 3.122 shows the sea wall.

Figure 3.122: McNears Sea Wall in the San Pedro Hill Area Source: U.S. Army Corps of Engineers, 11/27/23
One levee system exists in Santa Venetia and is located along the South Fork of Galinas Creek.

The Santa Venetia Levee is 1.45 miles long with an undocumented height. Figure 3.123 shows the Santa Venetia Levee in Santa Venetia.
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Figure 3.123: Santa Venetia Levee in Santa Venetia
Source: U.S. Army Corps of Engineers, 11/27/23
Three levee systems exist in St. Vincent. Two of them, Marin County Levee 33 and Marin County Levee 24, are located along the north bank of Miller Creek. Marin County Levee 33 is

0.25 miles long with an undocumented height and Marin County Levee 24 is 0.2 miles long with an undocumented height. The third levee is the Las Galinas Valley Sanitary District Levee which extends along the north and east bank of Miller Creek before diverging north to the Hamilton Wetlands and west to Long Point. It is 3.63 miles long with an undocumented height.

Figure 3.124 shows the three levees in St. Vincent.
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Figure 3.124: Marin Levee 33, Marin County Levees 33 and 24 and the Las Gallinas Valley Sanitary District Levee in St. Vincent
Source: U.S. Army Corps of Engineers, 11/27/23
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Figure 3.125: Santa Venetia Levee System
Source: Marin County OEM
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Hospitals and Medical
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Several levee systems exist around Bel Marin Keys and the Black Point area, but their failure does not present a risk to the communities.

Figure 3.126: Bel Marin Keys Levee System
Source: Marin County OEM
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Electric Power Facilities
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Two levee systems are located around the Marin County Airport. The State Fish and Game Levee surrounds the Airport property and neighboring wetlands on three sides to the north, south, and east. The Gnoss Airport Levee consists of two sections that intersect the airport property. One section is 2.59 miles long with an undocumented height and the other section is

0.43 miles long with an undocumented height. Figure 3.127 shows the levee systems around the Marin County Airport.

Figure 3.127: Levees Around the Marin County Airport
Source: U.S. Army Corps of Engineers, 11/27/23
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Figure 3.128: Novato North Levee System
Source: Marin County OEM
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In 1982 a levee in Santa Venetia was breached by tidal elevations and flooded the neighborhood with 2-3 feet of water.

Over a million dollars-worth of levee damage on Novato Creek occurred in 2014 and 2017 and a heavy burden on stormwater pumping systems caused additional damage to pumping system components.

Impacts
Levee failure flooding would vary depending on which structure fails and the nature and extent of the failure and associated flooding. This flooding presents a threat to life and property, including buildings, their contents, and their use. Large flood events can affect lifeline utilities (e.g., water, sewerage, and power), transportation, jobs, tourism, the environment, agricultural industry, and the local and regional economies.

The overall impact to the community from levee breach or failure includes:
• Injury and loss of life;
• Commercial and residential structural damage;
• Disruption of and damage to public infrastructure;
• Health hazards associated with mold and mildew;
• Damage to roads/bridges resulting in loss of mobility; • Significant economic impact (jobs, sales, tax revenue) to the community; • Negative impact on commercial and residential property values; • Long dewatering periods;
• Significant disruption to students and teachers as temporary facilities and relocations would likely be needed.
•
Extent and Probability
The probability of future levee failures in the Marin County OA is largely unknown but may result from a large winter storm or seismic event.
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Table 3.14: Marin County OA Hazard Risk Assessment – Levee Failure Jurisdiction
Probability/
Likelihood
of Future
Events
Geographic
Extent
Magnitude/
Severity
Climate
Change
Influence
Significance Risk
Score
Marin County Unlikely Negligible Moderate Medium High 9.00 City of
Belvedere Occasional Limited Moderate Medium Medium 10.00 Town of
Corte Madera Unlikely Limited Severe High Medium 11.00
Town of
Fairfax None None None None None 0.00
City of
Larkspur Unlikely Negligible Moderate Medium Low 7.00
City of
Mill Valley None None None None None 0.00
City of
Novato Occasional Negligible Weak Medium Low 7.00
Town of
Ross None None None None None 0.00
Town of
San Anselmo None None None None None 0.00
City of
San Rafael Unlikely Significant Severe High High 13.00
City of
Sausalito Occasional Negligible Weak Low Low 6.00
Town of
Tiburon Unlikely Negligible None None High 5.00
Bolinas
Public Utility
District
Unlikely Limited Extreme High Medium 12.00
Las Gallinas
Valley
Sanitary
District
Unlikely Significant Severe High High 13.00
North Marin
Water
District
Unlikely Significant Extreme High Medium 13.00
Southern
Marin Fire
District
None None None None None 0.00
Table 3.14: Marin County OA Hazard Risk Assessment – Levee Failure Source: Profiled Jurisdictions and Districts
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Vulnerability
The areas of the Marin County OA most vulnerable to levee failure are those with levees that could fail. Several unincorporated communities in Marin County are susceptible to levee failure:

A small area of Tamalpais Valley is protected from the Coyote Creek Levees (COYL) and could be susceptible to a levee failure. This area includes dozens of homes along with several commercial buildings and a section of Highway 1. Approximately 206 people and 105 buildings are at risk from a failure of the COYL levee, with a property value risk of around $59.4 million.

Approximately 557 people and 265 buildings are at risk from the levee on the southern bank of Coyote Creek, with a property value risk of around $156 million. The risk is considered to be low LSAC 4 (Levee Safety Action Classification) for both levees prior to overtopping and overtopping breach scenarios. The levee has an overtopping recurrence of 1/100 USACE with low life safety risk. Seepage has not been documented since the construction of a seepage barrier in 2005 (the levee was loaded 75% in 2008). Some uncertainty exists in the condition of culvert penetrations. Areas of oversteepened slope and erosion at the waterside levee toe are also moderate concerns. No loss of life is anticipated, and economic damages are anticipated to be low.

Two small areas of Strawberry are protected by levees and could be susceptible to levee failure.

The area protected by the Seminary Marsh Levee consists of several businesses adjacent to Highway 101. Approximately 325 people and 13 buildings are at risk from a failure of the Seminary Marsh Levee, with a property value risk of $20.9 million. The area protected by the Strawberry Marsh Levee consists of several homes and Strawberry Elementary School.

Approximately 488 people and 36 buildings are at risk from a failure of the Strawberry Marsh Levee, with a property value risk of around $17.2 million.

Part of the southern end of Kentfield is protected from Corte Madera Creek by the Corte Madera Creek Left Bank Levee and could be susceptible to a levee failure. This area includes a few dozen homes and the Marin General Hospital. Approximately 260 people and 104 buildings are at risk from a failure of the Corte Madera Creek Left Bank Levee, with a property value risk of around $40.3 million. The Levee was assessed in 2021 and the risk was determined to be low.

Numerous homes along with San Pedro Point Road and the McNears Brickyard are susceptible to a failure of the McNears sea wall. Approximately 604 people and 242 buildings in the unincorporated area and the City of San Rafael are at risk from a failure of the sea wall, with a total property value risk of around $169 million.

Part of the northern area of Santa Venetia is protected from the South Fork of Galinas Creek by the Santa Venetia Levee. There are several hundred homes in this area along with numerous pump stations and several medical facilities that could be susceptible to a levee failure.

Approximately 1,901 people and 676 buildings are at risk from a failure of the Santa Venetia Levee, with a property value risk of around $323 million.

The area of St. Vincent, which includes the St. Vincent School and the Las Galinas Valley Treatment Plant, is protected from Miller Creek and San Pablo Bay from Marin County Levee 33, Marin County Levee 24 and the Las Gallinas Valley Sanitary District Levee and could be susceptible to a levee failure. Approximately 8 buildings are at risk from a failure of both Marin County Levee 33 and Marin County Levee 24. Approximately 19 people and 9 buildings are at l ~<;>U·N· TY OF
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risk from a failure of the Las Gallinas Valley Sanitary District levee, with a property value risk of around $9.47 million.

The Marin County Airport is protected by the State Fish and Game Levee and the Gnoss Levees, and airport facilities along with the access road could be susceptible to a levee failure.

The qualitative risk of the levees around the Airport is unknown.

Climate Change and Future Development Considerations
Climate change is expected to lead to an increase in the frequency and severity of major storm events, which can place added strain on levee systems. An increase in rainfall and runoff as a result of climate change will increase the potential for higher water levels in leveed areas across the Marin County OA, increasing the potential for a levee failure. Rising seas will lead to increased stress on the levees around the Marin County OA shoreline, particular during a major tidal event and potential tsunami. As development increases in the populated areas of the Marin County OA protected by its levees, particularly in coastal areas, the potential for significant impacts to residents and infrastructure will only increase.

3.3.8 SEA LEVEL RISE
Climate change is the distinct change in measures of weather patterns over a long period of time, ranging from decades to millions of years. More specifically, it may be a change in average weather conditions such as temperature, rainfall, snow, ocean and atmospheric circulation, or in the distribution of weather around the average. While the Earth’s climate has cycled over its 4.5-billion-year age, these natural cycles have taken place gradually over millennia, and the Holocene, the most recent epoch in which human civilization developed, has been characterized by a highly stable climate until recently.

The Marin County OA MJHMP is concerned with human-induced climate change that has been rapidly warming the Earth at rates unprecedented in the last 1,000 years. Since industrialization began, the burning of fossil fuels (coal, oil, and natural gas) at escalating quantities has released vast amounts of carbon dioxide and other greenhouse gases responsible for trapping heat in the atmosphere, increasing the average temperature of the Earth. Secondary impacts include changes in precipitation patterns, the global water cycle, melting glaciers and ice caps, and rising sea levels. According to the Intergovernmental Panel on Climate Change (IPCC), climate change will “increase the likelihood of severe, pervasive and irreversible impacts for people and ecosystems” if unchecked.

Through changes to oceanic and atmospheric circulation cycles and increasing heat, climate change affects weather systems around the world. Climate change increases the likelihood and exacerbates the severity of extreme weather – more frequent or intense storms, floods, droughts, and heat waves. Consequences for human society include loss of life and injury, damaged infrastructure, long-term health effects, loss of agricultural crops, disrupted transport and freight, and more. Climate change is not a discrete event but a long-term hazard, the effects of which communities are already experiencing.

Climate change adaptation is a key priority of the State of California. The 2013 State of California Multi- Hazard Mitigation Plan stated that climate change is already affecting California. The State has also seen increased average temperatures, more extreme hot days, l ~<;>U·N· TY OF
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fewer cold nights, a lengthening of the growing season, shifts in the water cycle with less winter precipitation falling as snow, and earlier runoff of both snowmelt and rainwater in the year. In addition to changes in average temperatures, sea level, and precipitation patterns, the intensity of extreme weather events is also changing.

Rising sea levels are considered a secondary effect of climate change due to warming ocean temperatures and melting glacial ice sheets into the ocean. The California coast has already seen a rise in sea level of four to eight inches over the 20th century due to climate change. Sea level rise impacts can be exacerbated during coastal storms, which often bring increased tidal elevations called “storm surge.” The large waves associated with such storm surges can cause flooding in low-lying areas, erosion of coastal wetlands, saltwater contamination of drinking water, disruption of septic system operations, impacts on roads and bridges, and increased stress on levees. In addition, rising sea levels result in coastal erosion as shoreline sediment is re-deposited back into the ocean. Evidence shows that winter storms have increased in frequency and intensity since 1948 in the North Pacific, increasing regional wave heights and water levels during storm events.

According to the 2017 “Rising Seas in California, An Update on Sea-Level Rise Science” report Marin County may experience impacts from Sea Level Rise over defined periods of time, to include long-term changes (second half of this century and beyond), and short- to mid-term projections (within the next two or three decades).
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Figure 3.129: Marin County Sea Level Rise Susceptibility to Critical Facilities Source: Marin County OEM
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Location and Previous Occurrences
Past flooding, wildfire, levee failure, and drought disasters have been exacerbated by climate change in frequency of occurrence and intensity. Unlike earthquakes and floods that occur over a finite time period, climate change may be experienced as a compounding, long term hazard, the effects of which some communities may already be experiencing.

The 2018 State of California Multi-Hazard Mitigation Plan states that climate change is already affecting California. Sea levels have risen by as much as seven inches along the California coast over the last century, increasing erosion and pressure on the state’s infrastructure, water supplies, and natural resources. The State has also seen increased average temperatures, more extreme hot days, fewer cold nights, a lengthening of the growing season, shifts in the water cycle with less winter precipitation falling as snow, and both snowmelt and rainwater running off sooner in the year. In addition to changes in average temperatures, sea level, and precipitation patterns, the intensity of extreme weather events is also changing. This data suggests that the effects of climate change have been occurring in the Marin County area. See Figure 3.130 for the historic and future change in average July temperatures across California.

Figure 3.130: Average July Temperatures in California
Source: California Climate Adaptation Strategy
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40 38
36 34
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50 60 70 80 90 100 110
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Impacts
During the next few decades, scenarios project average temperature to rise between 1°F and

2.3°F in California. As such, temperatures across the Marin County OA, including in the unincorporated area, would be expected to rise, leading to increase in drought conditions that could lead to forest devastation and wildfires, and an increase in major flooding and associated debris flow events. These extreme weather events can cause additional injuries and fatalities and can cause worsened damage or destruction to homes and critical facilities and infrastructure across the County. Socioeconomic disruption can also occur across the County as a result of climate change.

Dealing with flooding from rain and upstream runoff is already complicated. Sea level rise will make it even more complicated by increasing the frequency and duration of flooding. When water temperature increases, warm water expands and takes up more space than colder water.

As the planet warms, the water in the ocean warms, expands, and elevates sea levels. The changing climate has also melted parts of the ice caps at the North and South Poles. As this ice melts and flows into the ocean, it increases the amount of water in the ocean and raises sea levels even more. Sea levels in San Francisco Bay have risen seven inches over the past century. Predictions of future sea level rise vary from 12 inches by 2030 to 60 inches by 2100.

The Bay Conservation and Development Commission (BCDC) recommends using 36 inches of sea level rise for planning purposes. Rising sea levels increase the upstream extent of tidal flooding, worsen creek overflow due to backwater effects of elevated high tides, and create larger, stronger waves which erode the shoreline and destroy sensitive marshes. Coastal flooding will have a large impact on cities and habitat.

A 36-inch increase in sea levels will greatly impact people’s lives throughout the Marin County OA, including in the unincorporated area. Daily high tides will inundate major thoroughfares, schools, retirement communities, private homes, shopping areas, bike paths, and stormwater detention ponds. Valuable marsh and mudflat habitat will be permanently flooded. Infrastructure will need to be armored, abandoned, or relocated. Shorelines will be eroded by increased wave erosion, threatening even more infrastructure. With sea level rise it is projected that more land along Marin’s coastline and bayside will be permanently inundated or subject to more regular flooding, while the frequency and intensity of storm events are anticipated to increase with climate change. Greater riparian flooding may also occur with sea level rise and future storm events, though modeling is necessary to better understand the extent of such hazards. As previously discussed best available sea level rise and future flood models indicate that by 2100 around 7,000 acres, 9,000 parcels, 10,000 buildings and 120 miles of roads throughout Marin County may be exposed to flooding due to future sea level rise and 100-year storm events. l ~<;>U·N· TY OF
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Extent and Probability
Table 3.15: Marin County OA Hazard Risk Assessment - Sea Level Rise Jurisdiction
Probability/
Likelihood
of Future
Events
Geographic
Extent
Magnitude/
Severity
Climate
Change
Influence
Significance Risk
Score
Marin County Highly
Likely Limited Extreme High High 16.00
City of
Belvedere
Highly
Likely Limited Extreme High High 16.00
Town of
Corte Madera Occasional Significant Weak High Medium 11.00 Town of
Fairfax None None None None None 0.00
City of
Larkspur
Highly
Likely Limited Extreme High High 16.00
City of
Mill Valley
Highly
Likely Limited Weak High Medium 12.00
City of Novato Occasional Limited Moderate High Medium 11.00 Town of Ross None None None None None 0.00
Town of
San Anselmo None None None None None 0.00
City of
San Rafael
Highly
Likely Significant Moderate High High 15.00
City of
Sausalito Likely Significant Severe High Medium 14.00
Town of
Tiburon
Highly
Likely Limited Extreme High High 16.00
Bolinas Public
Utility District Likely Extensive Severe High High 18.00 Las Gallinas
Valley
Sanitary
District
Likely Significant Moderate High High 14.00
North Marin
Water District Occasional Significant Moderate High Medium 12.00 Southern
Marin Fire
District
Likely Significant Extreme Medium Low 13.00
Table 3.15: Marin County OA Hazard Risk Assessment - Sea Level Rise Source: Profiled Jurisdictions and Districts
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Vulnerability
All residents in the Marin County OA, including in the unincorporated area, are susceptible to climate change, with effects being more prevalent in those with pre-existing health conditions and the elderly. Communities most vulnerable to the impacts of sea level rise in unincorporated Marin County include Muir Beach, Stinson Beach, Bolinas, Inverness, Pt. Reyes Station, East Shore, and Dillon Beach.

Coping with a changing climate presents opportunities for local health departments and partners in Marin County to consider policies, actions, and infrastructure design that will not just protect the public from climate change threats, but also establish health equity, resiliency, and sustainability. A critical step for building resilience is to improve capacity of communities to prepare, respond, and recover from climate-related health risks.

The most vulnerable assets in Marin County OA’s unincorporated communities in the near-term are Shoreline Highway through Almonte, Waldo Point Harbor houseboats and facilities, Greenbrae homes and facilities, and Paradise Cay homes and marina. The elevated homes on Greenbrae Boardwalk and floating homes in Waldo Point Harbor may be more adaptable in the near term than homes with solid foundations. In the medium-term, portions of Bel Marin Keys could face impacts, as would Santa Venetia homes, Tamalpais Valley homes, and the Greenwood Cove, Strawberry Circle, Strawberry Village Shopping Center, homes along Seminary Drive in Strawberry, and Kentfield creek side homes. In the long-term, Black Point and North Novato could anticipate damaging impacts. In the medium-term timeframe, regular high tide tidal flooding could adversely impact the same locations tidally flooded in the nearterm, though more severely. Storm surge flooding could be 10 inches with a 100-year storm surge, and extend further inland beyond the marshy areas of Mill Valley, Strawberry, San Rafael, St. Vincent’s, and North Novato. In the long-term (second half of this century and beyond), regular tidal flooding could adversely impact the same locations impacted in the nearand medium-terms (within the next two or three decades) and significant portions of what would have previously only flooded from the 100-year storm surge. The additional areas that would tidally flood at 60 inches of sea level rise are:
• Tamalpais Valley
• Mill Valley from the Richardson’s Bay shoreline up to and beyond Camino Alto between Miller and East Blithedale Avenues
• Mill Valley and Strawberry fronting US Highway 101 between Seminary Drive and Tiburon Boulevard
• Santa Venetia north of N. San Pedro Boulevard
• Cove Neighborhood, Tiburon
• Belvedere Lagoon neighborhood
• Paradise Cay
• Mariner Cove, Marina Village, Madera Gardens, and major retail centers lining US Highway 101
• Riviera Circle, Creekside, and Heatherwood neighborhoods, Larkspur • Interstate 580 and westward towards Andersen Drive in San Rafael and the community of California Park
• Marin Lagoon and Peacock Gap neighborhoods, San Rafael • Bel Marin Keys northern and southern lagoon areas
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• Hamilton, Vintage Oaks, and pockets of development east of US Highway 101 at Rowland Boulevard and State Route 37 in Novato, and
• North Novato at US Highway 101 and Binford Road.

Bayside areas that could anticipate increased storm surge flooding are:
• Sausalito west of Bridgeway
• Marin City neighborhood
• Mill Valley east of East Blithedale Avenue at Alto Shopping Center • Las Gallinas and North San Pedro Boulevard, east of US Highway 101, San Rafael • Bayside Acres
• Country Club
• Kentfield
In their current conditions, the most vulnerable coastal Marin County OA infrastructure, in order of onset and flood depth, includes
Near term (ten years):
• Beaches, underground on-site wastewater treatment systems (OWTS), buildings, and streets in Stinson Beach west of Shoreline Highway
• Shoreline Highway between Stinson Beach and Bolinas, at Green Bridge over Lagunitas Creek in Pt. Reyes Station, the Walker Creek crossing in Marshall, and bridges on Middle Road and Valley Ford Lincoln School Road
• Beaches and beach front and downtown buildings and streets in Bolinas • Septic systems, beaches, marshes, and buildings along the eastern and western shores of Tomales Bay
• The water distribution pipe underneath Shoreline Highway and Sir Francis Drake • Boulevard serving many Inverness residents
• Intertidal rocky lands in Muir Beach and Duxbury Reef in Bolinas • Fire service facilities and tsunami evacuation routes in Stinson Beach • Recreational facilities at Dillon Beach Resort and Lawson’s Landing • Blufftop buildings in Muir Beach, Bolinas, and Dillon Beach may be vulnerable to accelerated erosion
Medium Term (thirty years):
• Olema-Bolinas Road, which is the only road to Downtown Bolinas • Additional buildings and streets in downtown Bolinas, including the historic district • Bolinas Public Utilities District lift station at the end of Wharf Road • Shoreline Highway in Pt. Reyes Station and East Shore, and Sir Francis Drake Blvd. in Inverness
• Along the east shore of Tomales Bay, homes on piers over the water are particularly vulnerable
Long Term (seventy years):
• Shoreline Highway along the East Shore
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• Buildings in Inverness west of Sir Francis Drake Blvd • Downtown Bolinas up to Brighton Road, including the market, library, community center, gas station, museum, and other valued places
Along the bay shoreline, in the near-term timeframe, tidal flooding at 10 inches of sea level rise could reach 5,000 acres, 1,300 parcels, and 700 buildings, potentially impacting tens of thousands of residents, employees, and visitors. With an additional 100-year storm surge, the previously impacted acres, parcels, and buildings could face tidal and storm surge flooding. An additional 3,000 acres, 2,500 parcels, and 3,800 buildings could anticipate storm surge flooding across the Marin County OA. Eight miles of road could expect tidal flooding. Smaller public and private and marinas and boat launches along the bay in Strawberry, Bel Marin Keys, and Black Point could be flooded out and unusable. Storm surges can be powerful enough to damage and sink boats, including those belonging to the Southern Marin Fire Protection. Most concerning, however, is the potential inability of emergency professionals and vehicles to access people in or through flooded areas.

In this medium-term timeframe, tidal flooding at 20 inches of sea level rise could reach nearly 7,000 acres, 3,000 parcels, and 2,000 buildings in the Marin County OA, potentially impacting even more residents, employees, and visitors than in the near-term. With an additional 100-year storm surge, the previously impacted acres, parcels, and buildings could face tidal and storm surge flooding, and an additional 7,000 acres, 2,200 parcels, and 3,600 buildings in the Marin County OA could anticipate storm surge flooding. Most levees south of Novato are not designed to withstand this level of flooding and could be overtopped.

Eighteen miles of roadway, ten more miles than in the near-term, could expect tidal flooding.

Many of the impacted roads are the same as those impacted in the near-term, though much greater lengths could anticipate tidal flooding and flooding depths would increase. Storm surge flooding could reach a total of 44 additional miles of roadway. Water travel could experience similar outcomes as in the near-term, though the highest high tides and storms surges would cause even more damage than weathered twenty years earlier.

Pipelines under vulnerable roads, and lateral pipes to vulnerable properties, would become squeezed between rising groundwater and the confining roadway. This could cause pipes to bend and break and could even damage roadways. In the medium-term, impacts to the North Marin Water District service area would impact water service in Bel Marin Keys and unincorporated area around Novato. Vulnerable substations, electrical transmission towers and lines, and underground natural gas pipelines along the shoreline would be compromised by flooding and subsidence. Disruptions or failures in this network could also have far reaching impacts in transportation, sanitary service, stormwater management facilities, food storage, communications, and general public safety.

In the long-term timeframe, tidal flooding at 60 inches of sea level rise could reach nearly 7,000 acres, 8,000 parcels, and 9,000 buildings in the Marin County OA, potentially impacting hundreds of thousands of residents, employees, and visitors. In the long-term scenario, storm surge flooding could occur on nearly 13,500 acres hosting 12,600 parcels with 12,000 buildings in the Marin County OA, potentially impacting 200,000 residents, thousands of employees, and several million visitors.
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One-hundred miles of public and private roadways in the Marin County OA could be vulnerable to tidal exposure. Roads could degrade more quickly, or if flood waters are deep enough, become impassable. Lane miles could be more than double this figure. An additional 30 miles of roadway could be vulnerable at 60 inches of sea level rise and a 100-year storm surge.

Moreover, several park and rides, several hundred bus stops, and bus transit and SMART rail routes could flood. Breakdowns in the transportation network would have major impacts on the economy and daily life functions. In addition, significant safety hazards could cause injury or loss of life. Flooding at the Sewerage Agency of Southern Marin (SASM) and Novato Sanitary Wastewater Treatment Plants is a significant vulnerability that could arise, potentially disrupting hundreds of thousands of people.

By this time, much of the low-lying shoreline sanitary sewer and stormwater infrastructure could be flooded out. By the end of the century, sea level rise could have direct impacts to the Novato Atherton Avenue Fire Station. A few emergency shelters in Southern Marin communities could be vulnerable to tidal flooding, and several more could expect storm surge flooding and may not be available when needed most.

Beaches, estuaries, marshes, wetlands, and intertidal areas on the Marin County OA coast, including in the unincorporated area, are vulnerable to sea level rise and storms. Nearly all beaches except Dillon Beach and the federal portion of Stinson Beach, could be lost entirely in the long-term. Roughly 9,000 acres in the estuaries of Tomales Bay, Bolinas Lagoon, and Esteros Americano and San Antonio, 1,800 acres of wetlands and marshlands could be impacted to varying degrees across all of the scenarios in all of the communities. Sea level rise may push coastal habitats inland where possible, flooding tidal areas more frequently and inundating new inland areas with saltwater. The North Central California Coast and Ocean Vulnerability Assessment identified the five most vulnerable species to sea level rise as the Western snowy plover, black oystercatcher, black rail, California mussel, and red abalone.

On the bayside, the marshlands that buffer the shoreline communities from high tides and storm surges could begin to experience transitions in habitat, especially those in the Southern Marin County OA where they are typically bordered by urban development. Consequently, the waters here would get deeper and flood out the existing habitat, shifting high marsh to low marsh, low marsh to mud flat, and mud flats to open water. Without adequate light of shallow water, eelgrass beds would shrink. Collectively, these habitat shifts could have significant impacts on vulnerable species such as the salt marsh harvest mouse, Ridgway’s Rail, or the long-fin smelt.

A twenty-inch increase in sea level in the medium-term would continue to shrink the Southern Marin County OA, Tiburon Peninsula, and Pt. San Pedro marsh and tidal habitats.

Southern Marin County OA marshes may no longer exist by the end of the century, destroying the habitat of several shoreline birds and mammals. Northern Marin marshes would become increasingly tidally influenced, with tide water reaching US Highway 101 in Bel Marin Keys and North Novato up the Petaluma River. Typically freshwater marshes west of US Highway 101, for example, Sutton Marsh, could also expect damaging salinity impacts. Tidal marsh lands may increase in Northern Marin if they are not prevented from migrating inland. Approximately 1,358 acres on 30 agricultural parcels could be vulnerable to sea level rise and storm conditions.

Another 3,000 acres are public agency lands near Bel Marin Keys, Hamilton Field, and the Novato Sanitary District that are leased for agricultural use. Higher high tides could push brackish conditions inland, reducing grazing, manure spreading, and cultivation area. l ~<;>U·N· TY OF
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Loss of or compromised emergency services could be more devastating to communities with higher populations that fall into certain demographic categories. Communities with higher populations that fall into these categories include Marin City and the canal neighborhoods in the unincorporated area around the City of San Rafael. Marin County OA populations that are most vulnerable to the effects of sea level rise include:
• Low-income households
• Households in poverty
Climate Change and Future Development Considerations
The two major causes of global sea level rise are thermal expansion of warming oceans and the melting of land-based glaciers and polar ice caps. Climate change is affecting natural and built systems around the world, including the California coast. In the past century, average global temperature has increased about 1.4°F, and average global sea level has increased 7 to 8 inches. Sea level rise in the San Francisco Bay Area is projected to increase by eight inches MHW in 2050 and could reach 4.5 to eight feet by 2021 if greenhouse gas emissions aren’t reduced4
.

Figure 3.131: Projections of Sea Level Rise in the San Francisco Bay Area, 2000-2100 Source: 2019–2020 Marin County Civil Grand Jury, Climate Change: How Will Marin Adapt? While the Marin County OA shoreline already experiences regular erosion, flooding, and significant storm events, sea level rise will exacerbate these natural processes, leading to significant social, environmental, and economic impacts. The third National Climate Assessment cites strong evidence that the cost of doing nothing exceeds the costs associated with adapting to sea level rise by 4 to 10 times. Sea level rise will continue to affect the Marin County OA with increased tidal flooding and storm surge during severe weather events, and future along the Marin County OA shoreline will only amplify these impacts. Sea level can also lead to increased land subsidence and the potential of levee failure. The impacts of a tsunami would also be magnified with rising seas. Future development in the coastal areas of Marin County will put more people and property at risk from flooding as a result of sea level rise. Roads and utility infrastructure across the Marin County OA will continue to become inundated. 4 2017 Marin Shoreline Sea Level Rise Vulnerability Assessment. https://www.marincounty.org/- /media/files/departments/cd/planning/slr/baywave/vulnerability-assessmentfinal/final_allpages_bvbconsulting_reduced.pdf?la=en l ~ <;>U·N· TY OF
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Sea-Level Rise if Greenhouse Gas
Emissions Remain High
2000 2010 2020 2030 2040 2050 2060 2070 2080 2090
(Year)
Sea-Level Rise if Greenhouse Gas
Emissions Are Moderated
2000 2010 2020 2030 2040 2050 2060 2070 2080 2090
(Year)
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3.3.9 SEVERE WEATHER – EXTREME HEAT
Extreme heat is defined as temperatures that hover 10 degrees or more above the average high temperature for the region and last for several weeks. A heat wave is an extended period of extreme heat, often with high humidity. When relative humidity is factored in, the temperature can feel much hotter as reflected in the Heat Index (see Figure 3.132):

Figure 3.132: Heat Index
Source: NOAA
Heat kills by taxing the human body beyond its abilities. In a normal year, about 1,300 Americans succumb to the demands of summer heat. Heat is the leading weather-related cause of mortalities in the US. In 2006, California reported a high of 204 heat related deaths, with 98 reported in 2017 and 93 deaths reported in 2018.

Location and Previous Occurrences
Extreme heat has the potential to impact all areas of the Marin County OA, though more predominantly in the lower elevations further away from the coast. In the unincorporated area this includes the Tamalpais Valley, Kentwood, Lucas Valley-Marinwood and Santa Venetia areas. Communities along the Pacific Ocean and Tomales Bay including Muir Beach, Stinson Beach, Bolinas, Inverness and Point Reyes Station tend to have cooler temperatures due to the ocean and bay breezes.

In the 40-year period from 1936 through 1975, nearly 20,000 people were killed in the United States by the effects of heat and solar radiation. In the heat wave of 1980, more than 1,250 people died. According to the 2018 California State Hazard Mitigation Plan, the worst single heat wave event in California occurred in Southern California in 1955, when an eight-day heat wave resulted in 946 deaths.

Impacts
Heat waves do not strike victims immediately, but rather their cumulative effects slowly take the lives of vulnerable populations. Heat waves do not cause damage or elicit the immediate 1 ~<;>U·N· TY OF a ~ ARIN ~
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Heat lnd·ex
Temperature (OF)
80 82 84 86 88 90 94
40 80 81 83 85 88 91 9
45 80 82 84 87 89 93 1
l 50 81 83 85 88 91 95
~ 55 81 84 86 89 93 97 1
-0 60 82 84 88 91 95 100 .E 65 82 8E, 89 93 98 103 :::i :c 70 83 86 90 95 100 00 a, 75 84 88 92 97 10$ 109' ::,, :g 80 84 89 94 100 ., G)
Cl:'. 85 85 90 96
90 86 91 98
95 86 93 100
100 87 95 103 1
Likelihood ol Heat O is orders w ith Prolonged E x1rns ure or Streuou s Activity O c .. ution 0 E;,.1 re me c .. 1.11,on Oanger ■ Eictreme Ooinger 2023 Marin County Operational Area
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response of floods, fires, earthquakes, or other more “typical” disaster scenarios. While heat waves are obviously less dramatic, they are potentially more deadly. Heat emergencies are often slower to develop, taking several days of continuous, oppressive heat before a significant or quantifiable impact is seen. Heat waves do not strike victims immediately, but rather their cumulative effects slowly take the lives of vulnerable populations. Sickness can occur if someone has been in extreme heat for too long, or has over-exercised for his or her age or physical condition. Extreme heat can be more dangerous for older people, the very young, and people who are sick or overweight. See Figure 3.133 for a description of possible heat disorders by heat index level.

Figure 3.133: Heat Disorders by Heat Index Level
Source: National Weather Service (NWS)
Rural buildings without electricity, some mobile homes, or older homes that have not been retrofitted for AC, can become susceptible to extreme heat effects. The OA may open cooling centers as a result of heat or prolonged period of hot temperatures. When combined with low humidity, extreme heat can contribute to the start and spread of wildfires.

The NWS will issue a Heat Advisory, Watch, or Warning when the Heat Index is expected to have a significant impact on public safety. The expected severity of the heat determines whether advisories or warnings are issued. A common guideline for the issuance of excessive heat alerts is when the maximum daytime high is expected to equal or exceed 105°F and a nighttime minimum high of 80°F or above is expected for two or more consecutive days. The NWS office in Sacramento can issue the following heat-related advisory as conditions warrant.

Heat Advisory means that temperatures of at least 100°F or Heat Index values of at least 105°F are expected. Consider postponing or rescheduling any strenuous outdoor activities. If you must be outside, be sure to drink plenty of water and take frequent breaks in the shade. The young and elderly and those with medical conditions should use extra caution outdoors.

Excessive Heat Watch means that Heat Index values are expected to reach or exceed 110°F and not fall below 75°F for at least a 48 hour period. Plan to suspend all major daytime outdoor activities if a warning is issued. If you do not have air conditioning, locate the nearest cooling shelter or discuss staying with nearby family or friends who have A/C.

Excessive Heat Warning means that Heat Index values are expected to reach or exceed 110°F and not fall below 75°F for at least a 48-hour period, beginning in the next 24 hours. A warning may also be issued for extended periods with afternoon heat index values of 105°F-110°F. Refrain from outdoor activities of any nature during the warmest time of the day. Drink plenty of water and 1 ~ <;>U·N· TY OF a ~ ARIN ~
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..
130°F or Extreme
higher Danger
105°- Danger 129° F
goo- Extreme
105° F Caution
80° - 90°F Caution
I Possible heat disorders for people in high risk groups Heatstroke risk extremely high with continued exposure.

Sunstroke, Heat Cramps and Heat Exhaustion likely, Heatstroke possible with prolonged exposure and/or physical activity.

Sunstroke, Heat Cramps and Heat Exhaustion possible with prolonged exposure and/or physical activity.

Fatigue possible with prolonged exposure and/or physical activity. 2023 Marin County Operational Area
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take frequent breaks if you must be outside. Stay indoors in an air-conditioned building as much as possible. Check on elderly family members if they are living alone.

Extent and Probability
The frequency, intensity, and duration of extreme heat events and heat waves are expected to rise as a result of climate change, with an increased number of extreme heat days and nights, increased temperatures over extreme heat days and greater duration of extreme heat events.

By the end of the century, most of the region will average six heat waves a year, with the average longest heat wave lasting ten days. Extreme heat events will also extend seasonally into spring and fall.

Table 3.16: Marin County OA Hazard Risk Assessment – Severe Weather, Extreme Heat
Jurisdiction
Probability/
Likelihood
of Future
Events
Geographic
Extent
Magnitude/
Severity
Climate
Change
Influence
Significance Risk
Score
Marin County Highly
Likely Extensive Moderate High Medium 15.00
City of
Belvedere
Highly
Likely Extensive Moderate High Medium 15.00
Town of
Corte Madera Likely Extensive Weak Medium Low 11.00
Town of
Fairfax Unlikely Significant Weak Medium Low 8.00
City of
Larkspur Likely Extensive Moderate High Medium 14.00
City of
Mill Valley Likely Extensive Moderate Medium Medium 13.00 City of
Novato Likely Extensive Weak Medium Medium 12.00
Town of
Ross Likely Significant Moderate Medium Medium 12.00
Town of
San Anselmo Likely Extensive Extreme High High 17.00
City of
San Rafael Likely Extensive Moderate High Low 13.00
City of
Sausalito Unlikely Negligible Weak Low Low 5.00
Town of
Tiburon
Highly
Likely Extensive Moderate High Medium 15.00
Bolinas
Public Utility
District
Unlikely Extensive Weak Low Low 8.00
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Las Gallinas
Valley
Sanitary
District
Highly
Likely Negligible Weak High Low 10.00
North Marin
Water
District
Likely Extensive Weak Medium Medium 12.00
Southern
Marin Fire
District
Likely Significant Moderate High High 14.00
Table 3.16: Marin County OA Hazard Risk Assessment – Severe Weather, Extreme Heat Source: Profiled Jurisdictions and Districts
Vulnerability
Extreme heat can affect a range of key infrastructure from energy systems, water and wastewater treatment systems, the operation of government buildings, and public transit. While higher summer temperatures increase electricity demand for cooling, at the same time, they also can lower the ability of transmission lines to carry power, possibly leading to electricity reliability issues during heat waves. Increased temperatures also impact the efficiency of solar power infrastructure by increasing the surface temperature of solar panels, which reduces the voltage that panels can generate and thereby lowers efficiency. Although warmer winters will reduce the need for heating, modeling suggests that total U.S. energy use will increase in a warmer future. Extreme heat can also increase the risk of other types of disasters and exacerbate the urban heat island effect. Heat can exacerbate drought, and hot dry conditions can in turn create wildfire conditions. In cities, buildings, roads and infrastructure can be heated to 50 to 90 degrees hotter than the air while natural surfaces remain closer to air temperatures.

The heat island effect is most intense during the day, but the slow release of heat from the infrastructure overnight (or an atmospheric heat island) can keep cities much hotter than surrounding areas. People who are required to work outside during extreme heat are especially vulnerable to the effects of extreme heat. In California , between 2000-2017, 15,996 workers experienced heat related illness (Risk factors for occupational heat-related illness among California workers, 2000-2017 - PubMed (nih.gov). Animals, including livestock, poultry, and domestic pets are susceptible to extreme heat. For example, dogs and cats are in danger of heat stroke in temperatures of 110°F. The heat wave of 2006 resulted in more than 25,000 cattle, 700,000 fowl, and 15 reported heat-related pet deaths in California. Heat wave impacts on livestock and poultry can lead to financial losses in agriculture.

High temperature can be felt throughout the Marin County OA, though the lower elevations of the County are more vulnerable to higher temperatures than the higher elevations. People who live in the more urban areas of the County can be at greater risk to heat because concrete and asphalt store heat for longer and release it throughout the night. High temperatures can cause brownouts and increase the susceptibility of people to the effects of heat. Though crops in the Marin County OA are adaptable to heat, they can become vulnerable to prolonged periods of high temperatures.

Northern Marin County (roughly north of Point Reyes, Nicasio, and Lucas Valley-Marinwood to the northern County line) is likely to see greater increases in annual average maximum temperatures due to climate change at a faster rate than southern portions of the County. While l ~<;>U·N· TY OF
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climate change induced extreme heat events will impact County residents in the future, extreme heat effects will be less severe in the County relative to other areas of the state, including the Central Valley, that already experience higher temperatures and more extreme heat events. In terms of overall level of impact to County residents and infrastructure, extreme heat due to climate change will be less of a concern compared to flooding, sea level rise, wildfire, and landslides, debris flows, and post-fire debris flows in most cases. However, extreme heat will have a relatively greater impact on certain populations. Marin County OA populations most vulnerable to the effects of extreme heat include:
• Low-income households
• Households in poverty
• Persons without access to transportation or telecommunications • Low-resources racial or ethnic minorities
• Outdoor workers
• Healthcare workers, first responders, and protective service occupations • Houseless population
• Children
• Persons with disabilities
• Persons with chronic health problems
• Senior community members
In extreme temperatures, air quality is also affected. Hot and sunny days can increase ozone levels, which in turn affects Nitrogen Oxides Control levels. In addition, greater use of heating and cooling of indoor spaces requires more electricity and, depending on the electricity source, can emit more of other types of pollution, including particulates. These increases in ozone and particulate matter can pose serious risks to people, particularly the same vulnerable groups directly impacted by heat mentioned above.

Climate Change and Future Development Considerations
The primary effect of climate change is warmer average temperatures. The annual average daily high temperatures in California are expected to rise by 2.7°F by 2040, 5.8°F by 2070, and

8.8°F by 2100 compared to observed and modeled historical conditions5 . At the current rate,
annual average temperatures in the Marin County region and Bay Area will likely increase by approximately 4.4 degrees by 2050 and 7.2 degree by the end of the century unless significant efforts are made to reduce greenhouse emotions according to California’s latest climate change assessment.
5 California Adaptation Planning Guide
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Figure 3.134: Annual Average Temperatures in the San Francisco Bay Area, 2000-2100 Source: California Climate Change Assessment (Fourth Edition) As climate change accelerates in the 21st century, it is anticipated that extreme heat events will become more frequent and intense across the Marin County OA. There will be increased residential and business needs for cooling and addressing heat-related issues. Heat waves also tax the energy grid. Future development in the Marin County OA could exacerbate the impacts from heat related events, particularly in electricity provision and water delivery.

Increased temperatures will also lead to an increase in the occurrence and severity of wildfires across the Marin County OA as conditions become hotter and drier. Future development near the many open spaces around Marin Couty could expose more people and infrastructure to the threat of a major wildfire as a result of increasing temperatures.

3.3.10 SEVERE WEATHER – HIGH WIND/TORNADO
High Wind
High wind is defined as a one-minute average of surface winds 40 miles per hour or greater lasting for one hour or longer, or winds gusting to 58 miles per hour or greater regardless of duration that are either expected or observed over land. These winds may occur as part of a seasonal climate pattern or in relation to other severe weather events such as thunderstorms.

The Beaufort scale is an empirical measure that relates wind speed to observed conditions on land and is a common measure of wind intensity (see Figure 3.135). l ~<;>U·N· TY OF
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a
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-.. 82
t
QI 80 .._
::,
~ 78 QI
C.

E 76
2l
;;'; 74
E
~ 72
~
~ 70 IO
iii
::, 68 C
C
<t 66
a) Annual time series
Historical • observed
Historical - modeled range
RCP4.S average
RCP8.5 average
RCP4.S range
RCP8.5 range
1960 1980 2000 2020 2040 2060 2080 2100
f 82
~ 80 ::,
~ 78 Q)
C.

E 76
2l
~ 74
E
~ 72
~
~ 70 re
ro
::, 68 C
C
<t 66
bl Time period summaries
Historical· observed AVG/MIN/MAX
Historical· modeled AVG/MIN/MAX
RCP4.S AVG/MIN/MAX
RCP8.5 AVG/MIN/MAX
tt=
MIN
1976-2005 2006-2039 2040-2069 2070-2100
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Figure 3.135: Beaufort Wind Scale
Source: NOAA
Windstorms in the Marin County OA are typically straight-line winds. Straight-line winds are generally any thunderstorm wind that is not associated with rotation (i.e., is not a tornado). It is these winds, which can exceed 100 mph, which represent the most common type of severe weather and are responsible for most wind damage related to thunderstorms.

Location and Previous Occurrences
The entire Marin County OA, including the unincorporated area, is susceptible to storms and damage from wind. The coastal and mountainous areas are particularly susceptible to wind, although wind has caused damages throughout the county. High winds often occur with the onset of atmospheric river events. Figure 3.136 shows wind zones for the United States. The l ~<;>U·N· TY OF
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Beaufort
number
0 1
2 3
4 s
6 1
8 g
10 Oesaiptlon
calm
Ught air
Ugh breeze
Gentle breeze
Moderate breeze
Fre!;h breeze
51rong breeze
High wind, Moderate
gale, ear gale
Gale, Fr!'!~h gale
Strong gale
Storm, Whole gale
Violent storm
Hurricane
Wind speed Land conditions
kt$
<1
1-2
3 - 6
7- 10
11 - lS
16-20
21-26
27 - 33
m/h
<1 Clllm. Smo):~ rise-s ver lea Iv.
1-5 Wind mo on vislbl~ ins oke.
6 - ll Wind ell one posed skin. wves rustle.
2- lS Lc:a~cs end sm~ ller twie, in conH~nt mo1 iot1
20 - 28 Ous:t and loose paper rai:.ed. Sma11 branches bee in to move. 29-38 Branch!!S of a moder<!! e sire mo e. Sm<!! I •~ be11ln to s ~v. 3 ~_ 49 Laree branches in motion. Vh istlin1: lm1rd in overhead wires. Umbrella use hernme5 diffi cu lt. Emp~ plast.lc garbage can5 tip over. 50 _ 61
Wkoletree5 ln motion. Effo • ne~ed to ,,.,tk a11a ln!.t the wind. Swayln1 of skvscrapers mav be fel e:spe<la llv by people on ul)pet oors. 61 _ 74 Some twies broken from tree:s. e&rs veer on road. Proeress on foot is serlously lmpedtd.

Some branches break off tree:i;, and sonie sma ll rees blowo er. 41 - 47 75 - 88 COn.structlon/ empor11ry ~TiM nd l>Drrlc d~ blo "011«. D11m11ee toclr.::u~ ten!5 and canopies.
48-55 89 _ 1
02 rees are broken o or uprooted, sapllngs bent and de ormed. Poorly attached esphelt shl"£1ti end st11na1" in poor condi ion peel o·f roofs.

San Rafael City CouncilOctober 7, 2024

San Rafael City Council
October 7, 2024