Hazards on the coast are abundant: fires, earthquakes, tsunamis and sea-level rise. A $250,000 grant from the Federal Emergency Management Agency will allow Marin to study these hazards and develop a plan to mitigate their arrival.
Specifically, the grant will be used to assess the integrity of bulkheads in Marshall, to study nature-based and structural strategies for protection against sea-level rise across Tomales Bay, and to evaluate floor elevations of West Marin buildings for flood vulnerability. The grant will also allow the Marin County Fire Department to use light detection and ranging technology, or lidar, to create a property-level fire-threat map, evaluating structures for their defensible space, siding and roof types, and vulnerability.
Ultimately, the research will be put into the 2023 multi-jurisdictional hazard mitigation plan, which is required by law and updated every five years. The plan allows participating jurisdictions to collect more disaster-related FEMA grants; its update is separate from coinciding updates to the Local Coastal Program and the Countywide Plan, but each informs the others.
“It’s about looking at the situation and determining what are the next best steps for dealing with these issues,” county planning manager Jack Liebster said.
In Marshall, bulkheads on private properties—mostly concrete walls—protect Highway 1 and the town’s wastewater system from erosion. The walls were established in the 1800s to support the railroad that ran along the shoreline until 1930; after the railroad ceased operating, a road was laid, and the bayside lots were subdivided. As people built homes, they renovated or constructed bulkheads to support them. The bulkheads, maintained by homeowners, are in various states; in some spots, such as just north of the Marshall Tavern, they have collapsed, leaving the highway’s edge at risk. “Because of the nature of life on the seas, they are always eroding,” said resident George Clyde, a member of the East Shore Planning Group. Even without sea-level rise, many of the bulkheads will need to be repaired or replaced in coming decades; assessing their integrity will help inform strategies around coastal armoring in Marshall.
A separate study by the Community Development Agency will look at how to create a “living shoreline” using natural materials like sand dunes or cobble berms to protect from flooding along Tomales Bay.
The hazard mitigation research could also look at another nature-based strategy: the creation of oyster reefs, which lessen wave severity while providing habitat for native oysters. “I’m talking pie in the sky here,” Mr. Clyde said. “There are a million pages of permits, but these are the ideas of the sort that are being considered for adaption strategies.”
Artificial reefs were tested in 2013 in San Francisco Bay, where volunteers deployed balls made of concrete, sand and crushed oyster shells onto a mudflat. The reef balls, which act as a substrate for oysters, had some 30,000 oysters growing on them by 2016, attracting other organisms and protecting the shoreline from erosion.
Beyond the shoreline, the hazard mitigation plan will be updated with detailed information on two other climate-change threats: fires and floods. With $82,000, the fire department will create and present a map that rates individual parcels based on their wildfire threat and incorporate it into an updated wildfire protection plan. The department will combine lidar mapping collected in 2018 by satellite, vegetation assessments and records about the history and materials of buildings to create the map, expanding on one that was developed for Novato.
“A lot of us already know what the threat and vulnerability is, and what this will do is prove it through modeling and science,” battalion chief Christie Neill said. Finally, public works employees will complete an inventory of the floor elevation of West Marin’s buildings, specifically the height of doorsills, to determine flood risk.