Board adopts Stinson Beach sea-level rise adaptation study, calls for near-term nature-based measures and coordinated governance

The Marin County Board of Supervisors on Aug. 12 accepted an adaptation study for Stinson Beach that evaluates coastal erosion, storm surge, groundwater and flood risks through mid- and late-century sea-level-rise scenarios and recommends a sequenced “adaptation pathway” of nature-based and structural measures.

Study purpose and scope: Consultant James Jackson of Environmental Science Associates told the board the study refines prior countywide analysis and pilots a pathway approach for a community that faces combined risks to the beach, Bolinas Lagoon and low-lying neighborhoods. “The purpose of this study is first and foremost to protect the community development, habitat and recreational opportunities at Stinson Beach,” Jackson said.

Key findings: The study models multiple hazards — monthly high tides, 100-year storms and shoreline/dune erosion — across a range of sea-level-rise amounts. It estimates storm-related damages rising from millions under current conditions to hundreds of millions with modest sea-level rise. The report’s working figures show roughly $8 million in modeled damages under present conditions for certain extreme events, growing to $500 million at intermediate levels and to $1.3 billion under a 3.3-foot sea-level-rise scenario combined with a 100-year storm (the study caveats that figures exclude certain federal and state assets and the community wastewater facility).

Adaptation pathway and priority actions: The report sets out a phased strategy that combines near-term, lower-impact measures and longer-term structural responses. Near-term priorities include studying and piloting living-shoreline approaches (dune restoration, cobble berms) to buffer wave energy and slow erosion; evaluating and, where necessary, elevating key access roads and Calle Del Arroyo; inspecting and retrofitting aging bulkheads; and advancing a community wastewater-treatment feasibility study. The study also recommends a monitoring program — tracking beach width, flood frequency and groundwater — and staging projects based on hazard thresholds tied to sea-level-rise amounts rather than fixed dates.

Governance and funding: Staff emphasized the adaptation work requires coordination across jurisdictions and agencies — county departments, Caltrans (Shoreline Highway projects), National Park Service, Stinson Beach County Water District and local stakeholders. The report lists existing grant programs and local revenue tools (special assessment districts, climate resilience districts, geologic hazard abatement districts) that could fund adaptations, but it also concludes new long-term revenue mechanisms will likely be necessary.

Public comment and partner input: Representatives from the Seadrift homeowners association, the Environmental Action Committee of West Marin and the Stinson Beach Fire Protection District told supervisors the study is a necessary step. The Environmental Action Committee urged planning for higher sea-level-rise scenarios and for managed retreat discussions; the fire district emphasized emergency-response implications and the need to safeguard both residents and visitors.

Board action: Supervisor Rodoni moved to accept the report; Supervisor Milton Peters seconded and the board adopted the study. Supervisors and staff said the county will pursue governance arrangements, expand monitoring and explore grants and local funding tools while coordinating with Caltrans and federal land managers.

Ending: County staff said the study is a roadmap rather than a final plan and urged continued public engagement. “Local leadership is needed to effectively plan and implement projects in the community in coordination with the county,” Jackson told the board. The study and its appendices are available on the county’s sea-level rise webpage.