As seas rise, county mulls whether to guard or retreat from coast

11/19/2015

Every seat was filled at a public meeting about coping with sea level rise in West Marin, held at the Stinson Beach Community Center last Saturday. About 175 people came to learn about a host of measures that fall into three categories: protect, accommodate and retreat.

The meeting—held just weeks after the county released a lengthy draft report on the risks faced by coastal West Marin due to sea-level rise—was the next step in a county program, called C-SMART, which is studying sea-level rise in West Marin and deciding how to respond.

Some potential response measures—particularly removing infrastructure like roads and homes—are likely to ignite heated discussion in the coming months, as the county prepares an amendment to its Local Coastal Program about how to regulate development in areas prone to coastal hazards like sea-level rise. The Board of Supervisors is expected to vote on the amendment in April so that the California Coastal Commission can consider it next fall.  

Supervisor Steve Kinsey, who is also a coastal commissioner, commented on looming challenges on Tuesday during a presentation to supervisors on sea-level rise. “I found it somewhat interesting that the coastal commission staff at the workshop on Saturday focused on planned retreat exclusively,” he said. “I think this is a challenge that we’re going to face. There are going to be parts of our community where it makes sense to retreat…But I don’t think it can be, by any means, our primary tool.”

Adaptations will be further evaluated, and some will be included in an action plan being developed by the county, which should be released this spring, according to Jack Liebster, lead planner for the sea-level rise project. Results of an ongoing community survey about adaptation will inform, but not determine, the action plan. 

Options discussed at Saturday’s meeting and proposed in the survey include dune construction, coastal armoring, oyster reefs, “living” horizontal levees, permitting houseboats, elevating buildings, elevating roads and promoting “self-funded assessment districts” that can pay for local solutions. Relocating or removing roads, buildings, septic systems and other infrastructure close to the coast is also being considered.

Estimates for how much the sea will rise by 2100 vary from 40 to 80 inches, Mr. Liebster said. But, he added, now is the time to plan. 

“We’re dealing with uncertainty, and we have to find a way to move forward in the face of that uncertainty,” he said.

No solution is a total panacea. Armoring, such as seawalls, and traditional levees can stop flooding but can also be disruptive to the ecology, said Peter Wisjman, vice-president of the design and engineering firm Arcatis, based in San Francisco. “It [also] disconnects the community from the water. One of the reasons that you’re living here is the connection to the water.” 

State agencies and environmentalists also often discourage armoring. 

“Building more and more walls doesn’t seem like the answer,” said Davis resident Lars Anderson, who has owned a home in Inverness for a couple decades, after the meeting.

More nature-based solutions, like sand dunes or habitat restoration, could be more amenable to environmental regulators. But though they can protect property by curbing wave impacts, they do not stop rising waters or always prevent flooding. Sand dunes, also known as “beach nourishment,” can combat erosion. But this is only feasible at bigger beaches, like Stinson; narrow beaches along Tomales Bay or in Bolinas probably don’t have room for them.

So-called “living” horizontal levees mix the idea of traditional earthen levees that hold back water with restored marsh or wetlands that can absorb water, so that the protective structures can be lower.

Perhaps the option most likely to alarm homeowners is what government agencies call “managed retreat,” or removing shoreline infrastructure entirely.

That could mean rerouting Highway 1—a solution that the coastal commission has already approved in part of San Luis Obispo. It could also include moving or demolishing buildings near the shore.

Mr. Liebster suggested that the county could evaluate and perhaps rezone lands further inland in Marin and exchange them for private coastal land—or perhaps even exchange coastal land for federal park land, though he acknowledged that the idea would “require acts of Congress and drive some people up the wall.”

Leaving the shoreline is a troubling thought for many. One Stinson resident stood up after the presentations and said people in the town are worried—not just about sea-level rise but also about recent flood zone development restrictions in Stinson. “We want to have standards for development. We don’t want zero development,” he said. 

Options like dune construction could help in the shorter term, said Coastal Commission planner Shannon Fiala, who presented on managed retreat. But in the long run, retreat—which would need to be handled in a “sensitive” way, she added—would give the oceans more room to move in. 

Observing the king tides on Nov. 24, 25 and 26 is a good way to see what conditions could soon be like regularly, Mr. Liebster said. “It’s a way of looking into the future,” he said.

 

The community survey on adaptation strategies is available at marincounty.org/depts/cd/divisions/planning/sea-level-rise/adaptation-poll or local libraries. Submit responses by Jan. 17 to marinslr@marincounty.org or a local library, or mail to Marin County Community Development Agency c/o Jack Liebster, 3501 Civic Center Drive, Suite 308, San Rafael CA 94903. To comment on the Vulnerability Assessment, visit marincounty.org/depts/cd/divisions/planning/sea-level-rise/draft-vulnerability-assessment. Comments due Dec. 14.