Upfront: Rising up

The effect of surging tides on Bolinas Lagoon restoration

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Could sea level rise be a good thing for Bolinas Lagoon?

by Peter Seidman

Could sea level rise be a good thing for Bolinas Lagoon? A climactic irony has led to altering previous assumptions about restoring the lagoon.

The irony may prove to be a boon, especially to surfers and other wave-riders at what is arguably the best surf spot in Marin. Other spots may have bigger, more powerful waves, but Bolinas is home to the best longboard and paddleboard venue in the North Bay. For decades, Bolinas has been a family-friendly surf destination for Marin surfers and other water aficionados. It also attracts wave-riders from the rest of the Bay Area—most notably the East Bay.

That popularity triggered a “sign war” in which local surfers continually took down the street sign at what’s called the “Bolinas Wye.” Although the spelling sometimes changes, the importance of that sign to motorists coming from the south and looking for the Bolinas turnoff from Highway One is a big deal. Pass the turnoff without noticing the road to Bolinas and motorists are on their way to points north if they miss the main turnoff just past the Wye. Street crews would erect new signs, but locals would tear them down in an exercise of defiant localism.

It’s been a long time since Bolinas could be called a secret spot. It’s in all of the surf destination literature for the North Bay. On hot summer weekends, crowds deluge the town, and parking becomes a premium. But on chilly mornings, old-time surfers who remember catching waves at Bolinas with eight people out instead of 80 can still get a taste of ocean solitude.

Bolinas offers two distinct surf breaks. “The Patch” is rock reef off the northern section of shoreline. The paddle out can be taxing for beginners. But right in front of the central beach, the waves are made for family play. The southern end of the Bolinas wave emporium is in front of and on either side of the entrance to Bolinas Lagoon.

Tidal action moves water into and out of the lagoon, carrying sediment and gravel that create sandbars, perfect for wave-riding setups and most perfect for summer south swells.

The prospect of the lagoon silting up and transforming to a marsh and then to a grassland was a motivating factor in developing a plan to preserve open water in the lagoon, or at least as open as possible. The push for action came not from surfers, though. It came from environmentalists—and from homeowners. People who spent millions for a house in Seadrift (a private, gated community) with direct access to the lagoon, didn’t relish the body of water transforming. A coalition of disparate stakeholders coalesced to look for possible plans.

The idea of possibly restoring lost tidal flow to the lagoon floated around quietly until 1996, when the Marin County Department of Parks and Open Space agreed with locals and lagoon lovers that the lagoon’s tidal prism was decreasing.

Then the Army Corps of Engineers put a public-service finger in the wind to check whether national public support might exist for remedial action at the lagoon. The Army Corps did what it does best and outlined a plan for a major offensive to secure the tidal prism. The solution stunned locals: Bring in a dredge and suck mud out of the lagoon. Some estimates put the amount of dredging at an astonishing 1.5 million cubic yards.

The stunner to those who love and revere the lagoon were the ecological consequences that such a massive dredging project would trigger. Environmentalists pointed out that dredging the bottom of the lagoon would kill important marine life. And the effects of dredging on the seals using the lagoon to raise their young seemed obvious and negative. A huge dredging project also could have a negative impact on the migratory bird population. It didn’t take too long for the county to put the brakes on the Army Corps.

The strong reaction seemed reasonable. In 1998, the Ramsar Convention recognized the importance of the ecological significance of the 1,100-acre lagoon by designating it as a wetland of international significance, the first designation of its kind for an area on the critical Pacific Flyway. (The Ramsar Convention on Wetlands, signed in 1971, is, in its own words, “an intergovernmental treaty” that created a framework to conserve wetlands.)

Rather than take a sledgehammer approach, locals and other lagoon lovers favored a plan that seeks to take a number of smaller actions over a long time period while watching the effects of the remedial actions. That way the actions will do no harm. And while the smaller actions are underway, circumstances could change and necessitate a change in long-term strategy.

That’s exactly what’s happening.

Coastal ecologist and botanist Peter R. Baye told the Bolinas Lagoon Restoration Design Review Group that sea level rise now has replaced the risk of losing tidal prism because of sedimentation. “The 19th Century historical sediment legacy is relatively unimportant; it was overcompensated by the 1906 earthquake subsidence event,” which dropped the floor of the lagoon, which is a consequence of the San Andreas Fault. “Short-term tidal sedimentation may be conspicuous, but in the long-term (e.g., by mid-21st Century or sooner), high lagoon sedimentation rates will be needed to keep pace with accelerated rates of sea level rise.”

Rather than being a threat, sedimentation now is an ally to maintaining a healthy lagoon.

Earlier this year, county officials approved spending $300,000 to develop a plan to enhance and
rrptect the marshland on the north end of the lagoon, at the Bolinas Wye—where locals once staged their nonviolent protests by tearing down the street sign. One of the options includes removing the turn-off road from the south, according to Mary Jane Schramm, spokesperson for the Greater Farallones National Marine Sanctuary. It and the Corps of Engineers, the Golden Gate National Recreation Area, the Point Reyes National Seashore, Marin County parks and the support of local Stinson Beach, Seadrift and Bolinas communities, are participating in the planning and execution of a number of restoration projects.

But it’s sea level rise that will keep the entrance to the lagoon open to tidal prism. To meet the challenge that will come with surging tides and storms, according to Baye, “Accommodation space (room for the lagoon to migrate into lowlands of stream and fault valleys) is a primary concern for long-term health and stability” of the lagoon … . This realignment of the lagoon’s margins is inevitable, and will require reconfiguration of roads, other infrastructure and existing land uses, forced by increased flooding frequency and rising groundwater linked to sea level.”

Buttressing and armoring the shoreline to protect homes is a losing proposition, according to Baye and other experts. But homeowners understandably beg to differ. The scientists caution that armoring shorelines merely moves erosion and sedimentation problems down a shoreline. As part of an initial look at the lagoon, research showed that erosion from the Bolinas bluffs, exacerbated by material shed into the ocean during the 1906 earthquake, accounts for a great deal of the material now in the lagoon, and that process continues. About 80 percent of the sediment in the lagoon comes from the ocean. The other 20 percent comes from local watershed and road runoff. One of the restoration projects involves reducing road runoff.

Schramm says that among the several restoration projects, one now underway focuses on restoring Kent Island, which formed in the north end of the lagoon. The project may not have called attention to itself, and people may not have noticed, but it and other projects have been progressing quietly and steadily. Removing non-native plant species is a high priority in the restoration project. The Marin County Open Space District is the lead agency for the Kent Island project.

Another project involves battling an infestation of green crabs on Seadrift. An eradication program reduced their number from around 89,000 in 2009 to 8,000 in 2012. But, says Schramm, funding dried up in 2013, and as of 2014, there were an astonishing 400,000 green crabs estimated just in Seadrift. Why the population exploded remains a mystery.

The Greater Farallones Marine Sanctuary includes the lagoon. The sanctuary, an expanded Farallones Marine Sanctuary, came into formal being just a few weeks ago. It now stretches all the way to Mendocino.

The numerous lagoon restoration projects continue, but in the end it may be Mother Nature who plays the biggest role in restoring Bolinas Lagoon—for wildlife, for surfers and for other wave-riders, by raising the level of the Pacific Ocean and sending winter storm water to Bolinas.

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