Sea Level Rise

Marin County has more than 110 miles of bay and ocean shoreline, making it one of the California communities most vulnerable to the impacts of sea level rise. Marin’s communities, transportation corridors, public infrastructure, natural resources, and economic assets face significant risks from coastal flooding, king tides, and storm surge. These impacts cross jurisdictional boundaries, affecting incorporated cities/towns, special districts and utilities, federal and state assets, and involves navigating complex regulatory agencies.

Preparing for sea level rise is a long-term effort. It includes understanding future flood risks, planning and designing multi-jurisdictional adaptation projects, securing funding, coordinating with regulatory agencies, and implementing projects that protect communities while preserving Marin's natural and cultural resources.

Marin's bayside shoreline includes eight incorporated shoreline cities and towns, more than 30 special districts, numerous transportation and utility providers, and multiple state and federal regulatory agencies responsible for planning, permitting, funding, and project implementation. In contrast to the bayside, Marin's Pacific coastline is entirely unincorporated and is subject to a distinct regulatory framework under the California Coastal Act and the California Coastal Commission. Marin's Pacific coastline also includes federal national parklands.

While the County maintains jurisdiction only within unincorporated areas, the Office of the County Executive's Climate Office serves as a countywide resource to support sea level rise adaptation planning and coordination. Working with cities and towns, special districts, Tribal governments, community organizations, regional partners, and regulatory agencies, the Climate Office helps convene partners, support regional planning efforts, and strengthen coordination across jurisdictional boundaries. In doing so, the County helps align planning and implementation efforts while respecting the authority and decision-making responsibilities of individual jurisdictions.

The County has been engaged in sea level rise planning and climate adaptation efforts for more than a decade. Key past initiatives have included:

• Collaborative Sea Level Rise Marin Adaptation Response Team (C-SMART) in West Marin
• Marin Shoreline Sea Level Rise Vulnerability Assessment (2017), identified risks and impacts along the entire bay shoreline in collaboration with shoreline cities and towns
• BayWAVE (Bay Waterfront Adaptation Vulnerability Evaluation) along the bay shoreline, a monthly multijurisdictional group that came from the 2017
  Vulnerability Assessment and continues to convene to share updates
• Resilient by Design Bay Area Challenge, exploring innovative, multi-benefit resilience concepts
• Transportation Authority of Marin’s Countywide Transportation Plan 2050, which included a countywide assessment of transportation infrastructure vulnerabilities and adaptation needs associated with sea level rise

In 2024, the Marin County Civil Grand Jury recommended that the County evaluate options for a countywide approach to sea level rise adaptation and governance. At the same time, new state requirements, including Senate Bill 272, established a framework for Regional Shoreline Adaptation Plans (RSAPs) – further highlighted the need for coordinated planning across jurisdictions.

In 2024, the County of Marin commissioned the Countywide Sea Level Rise Adaptation Organizational Structure and Decision-making Process Study to evaluate how local governments, special districts, community organizations, and regional partners in Marin could work together more effectively to prepare for sea level rise.

Following a competitive Request for Proposals process, the County selected AECOM to conduct the study. The study sought to examine opportunities to strengthen countywide coordination, improve access to funding, support implementation of adaptation projects, and identify organizational approaches that could help Marin address increasingly complex sea level rise challenges.

Between 2024 and 2025, the consultant team conducted an extensive review of plans and stakeholder engagement effort. The study included:

• Review of previous countywide and regional adaptation plans
• Case studies of collaborative governance models from California and across the United States
• Formation of a countywide Steering Committee
• Participation in BayWAVE meetings
• Interviews with local governments, special districts, community organizations, technical experts, and regional partners
• Focus groups representing bayside, coastal, transportation, environmental, and community interests
• Public and stakeholder surveys
• Community presentations and outreach events throughout Marin County

Final recommendations of the study were completed in 2026 following establishment of the County's new Climate Office. The study found that Marin has a strong foundation of sea level rise planning and technical expertise, but implementation is constrained by fragmented coordination, limited staffing capacity, complex regulatory processes, and competition for funding. Stakeholders broadly supported increased collaboration focused on grant strategy, technical assistance, regulatory coordination, community engagement, and project delivery.

Rather than recommending the creation of a new formal governance entity, the study recommended strengthened voluntary collaboration, building trust through shared projects and initiatives, and demonstrating the value of coordination -- before considering more formal governance structures.

While the study was underway, in 2025 the County reorganized its Climate, Sustainability and Sea Level Rise functions within the Office of the County Executive, creating a dedicated Climate Office with a Chief Climate Officer and staff focused on sea level rise adaptation.

The County also began engagement with Marin Community Foundation (MCF) and the climate-focused consulting group Coastal Quest in early 2026, through MCF’s Building Resilient Communities initiative. Coastal Quest conducted a parallel assessment for MCF in 2025 focused on opportunities for broader countywide climate collaboration and resilience planning for a multi-hazard approach.

Reports and supporting documents

Board of Supervisors Staff Report (July 14, 2026)

1. County Staff Memo: Summary of AECOM and Coastal Quest initiatives
2. County Staff presentation to Board of Supervisors
3. AECOM Findings Report: Countywide Sea Level Rise Adaptation Organizational Structure and Decision-making Process
4. AECOM Memo: Collaborative Governance Research Findings
5. Coastal Quest Memo: Multi-hazard collaborative approach