West Coast
Part of a wooden walkway to the beach is missing after storms at Stinson Beach on Tuesday, Jan. 17, 2023. (Alan Dep/Marin Independent Journal)

CA - Stinson Beach to begin study of sea-level rise defenses

As sea level rise threatens to inundate hundreds of homes, cut off roads and swallow the sands of Stinson Beach, Marin planners and town residents are preparing a new defense plan in an effort to save the popular coastal destination.

Bordered by both the Pacific Ocean and Bolinas Lagoon, the town of about 500 residents is in the vanguard of Marin communities most vulnerable to rising ocean waters.

Residents such as Jeff Loomans, who has owned a home in the town for 13 years, said the future their community faces is driven home by recent incidents such as the January winter storms that battered homes, broke pilings, flooded roads and washed away tons of sand.

“I would say sea level rise is already here. It’s not something that is just coming,” said Loomans, who also serves on the Stinson Beach Village Association’s sea level rise committee.

Marin County planners recently completed a six-month effort to update its sea-level rise projections that were first developed in 2016.

The results show that the beach often seen crowded with visitors from throughout the Bay Area on warm summer days could become inundated by the mid- to late century. More than 600 homes would face permanent flooding by the end of the century.

Access roads such as Calle Del Arroyo and Highway 1 would face increased storm flooding with as little as 1 to 2 feet of sea level rise, which the study projects would occur between 2040-2050. Nearby sensitive habitats such as wetlands in Bolinas Lagoon would be drowned by the end of the century.

Isaac Pearlman, a senior planner leading the new Stinson Beach effort, said the newly published flooding projections include updated data and other research that was not available when the county published its initial projections in 2016.

“That’s almost eight years,” he said. “I think the science has progressed a lot around sea level rise.”

The projections now incorporate state sea-level rise projections developed in 2018 by the California Ocean Protection Council. One of the more notable changes is that the study now incorporates recent federal projections on how sea level rise interacts with groundwater.

A UC Berkeley and San Francisco Estuary Institute report published this year found flooding issues in Marin would be exacerbated as saltwater intrudes into the groundwater table, pushing the less dense freshwater to the surface. Pearlman said these findings are especially important for Stinson Beach, given that residents rely on underground septic systems and utility lines buried underground.

The county plans to hold an online public hearing at bit.ly/3NUXTNu at 5:30 p.m. May 18 to present the updated projections.

A separate 2018 report by the county identified potential options to adapt the community to rising ocean waters, including restoring dunes, elevating roads and homes, building sea walls, boardwalking entire neighborhoods and building a new community sewage system. The report did not analyze the costs and benefits of each option.

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