Last year, the nonprofit urban planning organization SPUR, based South-of-Market, published a 72-page document, Mission Creek Sea Level Rise Adaptation Study. The report emerged from a collaboration among several public and private sector organizations in San Francisco – including the San Francisco Office of Community Investment & Infrastructure and Mission Creek Conservancy – and a Dutch team of flood-control and design specialists from Wageningen University and the Amsterdam-based international consultancy firm, Arcadis.
The report identifies the area surrounding Mission Creek—a river now mostly culverted and infilled, except for a slim remaining channel that empties into the San Francisco Bay just below AT&T Park—as “one of the lowest lying parts” of “a city that is vulnerable to the impacts of sea level rise.”
According to estimations formed by the San Francisco Capital Planning Committee’s Sea Level Rise Committee, Bay waters will ascend 11 inches by 2050, and 36 inches by 2100. Each of the two flood maps included in the Mission Creek Sea Level Rise Adaptation Study envisions a “100-year storm”—a severe rainfall event that has a one percent chance of occurring annually, which would add 41 supplementary inches of water to the midcentury and end-of-century scenarios—and shows how “key assets” in Mission Bay and SoMa, like the Third and Fourth Street bridges and Channel Pump Station, would hold up under projected conditions. It’s speculated that, by 2100, most of the neighborhood will be at risk of inundation.
The report’s second section imagines seven potential solutions to the threat of future flooding around Mission Creek; three focused on preventing overflow from the channel itself and another four intended to protect against a bayside storm surge just below Mission Creek. While the first idea involves constructing a seawall around the Creek’s perimeter, the second visualizes a shorter, movable tidal barrier at the channel’s mouth. The third solution closes off the conduit entirely, reimagining Mission Creek as a dammed Mission Lake.
Along the Mission Bay waterfront the study proposes two different types of levees, as well as the more radical concept of an “elevated Third Street,” which, while sheltering Caltrain and the University of California, San Francisco, would promote a living-with-water philosophy on the neighborhood’s eastern edge, retrofitting existing buildings “with materials and uses that could adapt to potential flooding.” These structures would remain accessible even amid “temporary inundation,” thanks to second-floor pedestrian walkways.
Finally, the report suggests the possibility of creating an entirely new waterfront, given that Mission Bay sits atop infilled wetlands, and the boundary between city and sea is more or less arbitrary, not a fact of nature. Similar infilling could extend San Francisco’s land mass eastward to form a more distant buffer between the Bay and Mission Bay’s vital infrastructure, with an interior lagoon potentially preserving the neighborhood’s present-day waterside character.
The report examined the pros and cons of “holding the line” – the barrier between open water and urban environment – at different points, in terms of expense, safety, and attractiveness. Some approaches would retain Mission Creek’s navigability for its houseboat community; others wouldn’t. The study stresses that it was conceived as a “creative exercise,” with no intention of restricting itself to affordable or easy-to-implement concepts, and no aim to offer “one preferred alternative.” The report’s ideas reflect, however, a wish to “integrate flood protection into the urban fabric” and to avoid “monofunctional infrastructure” that’d “limit our relationship to water.” The levees and lakes envisioned in the study come equipped with ecological and recreational possibilities.
Earlier this year, SPUR held an event at its 654 Mission Street offices to present the study to the public. Laura Tam, Brad Benson, and Peter Wijsman—representatives of SPUR, the Port of San Francisco, and Arcadis, respectively—summarized the report’s contents and answered audience questions. Tam emphasized that there “is no timeline for implementation” and that a “broad public outreach and engagement process” would have to take place before detailed feasibility studies for any particular solution could commence.
Nevertheless, Benson speculated that efforts to improve the most vulnerable points of the Mission Creek shoreline might begin in the next ten to 15 years, while larger projects—like a new waterfront or elevated Third Street—could wait until 2040 or thereabouts. Wijsman noted that cities like New Orleans and New York have demonstrated that “thinking about these solutions now is a lot less costly than doing it once a disaster has occurred.”
The Mission Creek Sea Level Rise Adaptation Study is available for free download at spur.org.