Imagine that many downtown buildings in Bolinas are regularly inundated by tides, as are hundreds of homes in low-lying areas of Stinson Beach. Agate and Brighton Beaches have disappeared. Twenty miles of Highway 1 are awash in water. Businesses and homes along the East Shore of Tomales Bay are regularly inundated. Large portions of marshes around the bay are gone, and its beaches are also shrinking.
Climate change could realistically lead to these troubling scenarios and more, according to a 300-plus-page analysis of the effects of rising sea levels on West Marin’s coastal villages in the next 85 years. The report, released last week, was based in large part on computer models from the United States Geological Survey, as well as input from meetings in West Marin’s towns over the past year. It is the most recent phase of an ongoing county project called Collaborating on Sea-Level: Marin Adaptation Response Team, or C-SMART.
The project—funded by the county, the California Coastal Commission and the California Ocean Protection Council—will inform a looming update to the county’s Local Coastal Program, which governs development in the coastal zone, including what rules should guide development in areas prone to hazards like earthquakes or flooding. The next phase of the project, which begins later this month with a community meeting, will focus on soliciting input on possible adaptations. That could theoretically include raising roads or incentivizing people to move to higher ground.
Despite the stark analysis, county senior planner Jack Liebster, the manager for the project, said he did not want to raise the prospect of inevitable calamity.
“It’s very important not to catastrophize here,” he said. “We need to look at what the potential effects are, and we have to have a sober respect for what could happen. But at the same time, we have a strong confidence that we can do a great deal to manage those impacts if we work together diligently, cooperatively and with a good deal of smarts.”
Over the next 15 years, the report predicts sea level will rise 10 inches. By 2100, the county’s best-case scenario estimates a rise of roughly 40 inches; the worst-case scenario, based on more recent research, is 80 inches—more than six feet. Even if greenhouses gas emissions are curbed, “hundreds of years could pass before sea level stabilizes or drops,” the report says. And as the sea creeps higher, flooding during major storms will worsen.
The highly specific report details which areas and what assets in six West Marin communities—Muir Beach, Stinson Beach, Bolinas, Point Reyes Station, Inverness and Tomales Bay’s East Shore—are vulnerable to sea-level rise and associated impacts. It identifies potential risks to particular businesses, organizations or facilities such as libraries, community centers, stores and post offices.
The findings are sobering: by 2100, one in five buildings in the coastal zone could be affected by worsening flooding and rising seas as well as bluff erosion; in total, about 1,100 buildings could be directly affected, mostly in Stinson, downtown Bolinas and the shores of Tomales Bay.
About half of 956 residentially-zoned parcels found to be vulnerable are located in Stinson Beach. In the worst-case scenario, 60 percent of buildings in Stinson would be exposed to high tide or storm flooding. In particular, the narrow, low-lying streets near the shore are at risk of inundation, or exposure to daily high tides. Even now storms can cut off emergency routes so that no one can get in or out except by kayak, said Seadrift resident Jeff Loomans, who lives about 100 feet from Bolinas Lagoon and who is part of a C-SMART stakeholder advisory group.
“We’re very concerned about impacts to Highway 1 and Calle del Arroyo. Those are major evacuation routes for hundreds of people,” Loomans said. “It’s nerve-wracking.”
While the number of buildings directly affected by rising waters would be less in other communities, a greater percentage of some smaller towns would be affected. For example, in Marshall every commercial building—including Tony’s Restaurant, Hog Island Oyster Company, Tomales Bay Oyster Company and others—could be exposed to very high daily tides by 2100, along with 90 percent of homes.
Within the next 15 years, a dozen or so parcels in downtown Bolinas may be vulnerable—five to occasional flooding, and eight to daily tidal inundation. By 2100, 98 parcels could be affected, with most facing high daily tides.
In Point Reyes Station and Inverness, the number of exposed buildings is much fewer. But by 2050, portions of Sir Francis Drake—the only road in and out of Inverness—could begin to face tidal flooding, though it would get much worse by 2100, as could portions of Highway 1 on the coast, including the Green Bridge.
A total of roughly 20 miles of road around coastal Marin could be affected by tides or storms exacerbated by sea-level rise. Olema-Bolinas Road, Calle del Arroyo, Highway 1 and Sir Francis Drake Boulevard would be affected the most.
“At worst,” the analysis says, “some roadways will become completely inundated most hours of the day or eroded beyond repair.”
Predicted impacts extend beyond roads and buildings. Infrastructure such as septic systems, wells and water lines near the coast could face saltwater intrusion. Additionally, though a small percentage of Marin’s agricultural landscape, roughly 450 acres of agricultural lands could be affected by worsening storms and sea levels, about 400 near Dillon Beach and a few dozen acres around the East Shore and Point Reyes Station.
Beaches and wetlands could shrink or disappear, trapped between rising water and immovable inland boundaries such as bluffs, roads and other development. Their loss would not only affect the cultural life of the coast, but would erode habitat of wildlife including seals, sea lions, birds and other creatures.
Brighton and Agate Beach in Bolinas are particularly vulnerable. Agate Beach is now 22 meters wide; by 2030, it could be down to nine meters. By 2050 it could be only three meters. By 2100 it could be gone.
The county will hold a meeting on Nov. 14 from 10 a.m. to 2 p.m. at the Stinson Beach Community Center to discuss adaptation strategies for sea-level rise.