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Line in the Sand: How Can We Protect a Shoreline from the Ravages of the Future?

June 17, 2015
by Timothy Lesle

When San Francisco’s Great Highway opened in 1929, some 50,000 people celebrated the coastal stretch of pavement with a parade and a 1,014-piece band. A magazine article from the time boasted of “a wonderfully constructed Esplanade of enduring concrete, which will render for all time the beach safe from the destructive effects of the ocean’s activities.”

“For all time” may have been overly optimistic. While the O’Shaughnessy seawall has so far stood the test, Ocean Beach, the three-and-a-half-mile stretch of shoreline on San Francisco’s western littoral, is continually threatened by wave action and storms, which wash away sand and erode bluffs—a problem that will be exacerbated by global warming. With sea levels at the Golden Gate expected to rise by as much as 4.5 feet this century, the challenge of safeguarding coastal infrastructure all around the Bay will grow significantly. (As reference, consider that even a 16-inch sea level rise could inundate runways and access roads at Oakland and San Francisco International Airports.)

Indeed, the scope of the problem is such that concerned parties have debated whether the proper response—at Ocean Beach and elsewhere—is to defend or surrender. That is, should we further “armor” our shorelines with concrete and rock, sacrificing natural habitats and landscapes for the sake of infrastructure? Or would it be better to simply abandon low-lying areas, remove man-made structures, and stage what planners call “managed retreat”?

Benjamin Grant of the San Francisco Planning and Urban Research Association, or SPUR, says the problem requires compromise. “When it’s public interest versus public interest, there’s no either-or. You have to find a way forward.”

Grant is the manager of SPUR’s Ocean Beach Master Plan, an ambitious project initiated in 2010 to address the area’s future. Published in 2012, SPUR’s vision attempts to forge a middle path, with a plan that strives to preserve the beach’s role as a natural and recreational area, while also protecting vital infrastructure like the Lake Merced Tunnel, which carries storm runoff and sewage to a nearby treatment plant and is at risk of rupture due to accelerating erosion at the beach’s south end.

Under the proposed plan the tunnel will be protected as long as possible by a new structure. Sand dredged from the Golden Gate shipping channel will be used to replenish the beach and native dunes will be restored. The Great Highway will be retired along its southern reach, where erosion is expected to worsen due to sea-level rise, replaced by a new coastal trail, and car traffic will be diverted inland, re-routed past the San Francisco Zoo.

Bob Battalio, who like Grant is a Cal alum, and a coastal engineer with the firm Environmental Science Associates, contributed to the plan. He characterizes it as a balanced solution and a move “away from hard armoring and holding the line and more into soft sand placement and trying to maintain the infrastructure and property that a lot of people are really invested in.”

UC Berkeley landscape architecture professor Kristina Hill says such measures as actively managing sand will be important and necessary for the rest of the Bay as well. “The good news is we’re going to get a lot more beaches on the Bay,” she says. “The bad news is we have to build them all and make them work ourselves.”

Such adaptations won’t come cheap. The projected cost of the Ocean Beach Project alone is $350 million. A long-term project to turn salt ponds in the South Bay into tidal wetlands, which will yield flood-protection benefits, could cost hundreds of millions more.  Hill worries that if too many communities wait too long to initiate this kind of work, it may result in a credit crunch as everyone tries to borrow at the same time. 

Batallio is similarly concerned. “The question is whether we will procrastinate and dither until our coast and communities are degraded and the costs are maximized, or whether we can get ahead of sea-level rise within the next twenty to thirty years.”  In that sense, the Ocean Beach Master Plan is remarkable for having created a blueprint for going forward now, while there’s still time.

Grant is now finishing up final implementation studies, after which the plan will be sent to the relevant government agencies to mull over, and hopefully, to act upon.

There probably won’t be a parade this time, but perhaps there should be.

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