Decoding Design

SF is ground zero for redesigning, rethinking coastal zones

Posting in Cities

What does smart growth mean for beaches hammered by erosion, exacerbated by climate change? In San Francisco, city planners, engineers and a network of agencies are struggling to find out.

Intense winter rain storms in early 2010 left the southern lanes of the Great Highway, a 3.5-mile road that runs along San Francisco's Ocean Beach, full of sand and closed for much of the year.  When the road construction was completed in 1929, it was seen as a key artery to connect the city with Marin County to the north and southern reaches of the city's peninsula. Today, the highway has become a key focus in an escalating erosion problem that the city has been band-aiding for years.

The coast has been eroding for tens of thousands of years, but the pace of erosion is accelerating as the global climate warms. Sea level rises of 14 inches are expected by 2050. City planners, coastal engineers and a network of agencies are struggling to find the best, smartest ways to adapt to changes to the city's coast.

It's not going to be cheap. The San Francisco Planning and Urban Research (SPUR) Association has drafted a Master Plan that would include reducing the width of the Great Highway, redirecting traffic inland, restoring the beach's dunes that have been eroded away, and linking the beach with nearby Golden Gate Park. The raft of changes would cost around $343 million, reports the San Francisco Chronicle. But here's the kicker: no one knows how long adaptations like these will hold.

The Army Corps of Engineers has a cheaper plan: restore the beach using the tons of sand it regularly pumps up from the Bay in order to ensure safe depths in the shipping lane under the Golden Gate Bridge. It would cost around $10 million, but it would be far from a permanent solution and just one major storm could erase its benefits.

What's concerning planners and engineers is much more than vehicular access or a shrinking beach. The city's wastewater and storm water infrastructure, in particular a seaside treatment plant and a 14-foot-wide underground pipe that prevents storm water overflow into the ocean, are at stake. One proposed solution to protecting the infrastructure is to continue to fortify the beach with boulders or build new retaining walls. But some research shows this isn't a long term solution because the hard surfaces force wave energy to ricochet and that leads to more erosion, reports the New York Times. Plus, it will shrink or eliminate the sandy beach, which is a major draw for residents and tourists alike.

One study estimates that if nothing is done, it will be a $650 million problem.

Cities all over the country are intently watching to see how San Francisco will address its coastal erosion. It's not just about how the city will or will not make physical changes to the beach or use technology to adapt to or combat erosion, but also how the many agencies and stakeholders involved with the decision-making will work together. Or not.

[Via: San Francisco Chronicle, New York Times]

Image: Ocean Beach, Flickr / jamalfanaian

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Mary Catherine O'Connor

Contributing Writer

Mary Catherine O'Connor has written for Outside, Fast Company, Wired.com, Smithsonian.com, Entrepreneur, Earth2Tech.com, Earth Island Journal and The Magazine. She is based in San Francisco. Follow her on Twitter. Disclosure