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Quick summary: This story highlights recent developments related to san francisco, showing how constructive action can lead to meaningful results.
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Last July, a crew gathered along the San Francisco Embarcadero to watch as SF Port personnel detached a series of concrete tiles from the waterfront wall they’d been attached to for three years and hoisted them to the bay’s surface.
Inspired by the successes of living seawalls elsewhere, such as Seattle’s Elliott Bay, the San Francisco Port’s Living Seawall Pilot Project is a collaboration between the West Coast team of the Smithsonian Environmental Research Center (SERC) and the Port of San Francisco.
Much of San Francisco’s modern-day waterline is manmade, offering little natural protection against wave energy, coastal erosion, and flooding. A more natural waterline would have a “sloped, gradual area where you can have robust, intertidal growth and activity,” says the Port’s waterfront resilience program director, Brad Benson. “Hard” structures and steeply dropping manmade shorelines support less biodiversity — which, as Andy Chang, PhD., one of the seawall project’s leading scientists, points out, includes the entire ecosystem: birds, fish, marine mammals and so forth. Even without sloping, a seawall enhanced with habitable and protective areas could promote more biodiversity and help native seaweeds, mollusks and phytoplanktons to resist known invaders such as brown kelp and European green crabs.
San Francisco’s seawall, a three-mile-long concrete behemoth built between 1878 and 1915, has thus far escaped major disrepair. But its advanced age and erosion of the weak soils it sits on increase the urgency for rebuilding it. And sea-level rise is a major concern.
“We’ve had approximately nine inches of sea-level rise over the last century, so during king tide events, we start to see flooding in and around the Ferry building, which is the low point along the Embarcadero,” Benson explains.
“In places where a seawall is a requirement, the options are limited engineering-wise,” notes Chang. “We can add features that make it better habitat, such as adding texture, or shelving or small tidepools … which promotes a greater diversity of species.”
For the tiles, marine biologist-founded concrete company ECOncrete provided a proprietary admixture formulated to lessen the more toxic effects of industrial grade concrete. According to the company’s co-founder, Dr. Ido Sella, at least 70 percent of the world’s marine infrastructure is built of concrete, which has a huge impact on coastal marine life over time. Not only are concrete seawalls (such as San Francisco’s) typically smooth and ecologically “grey,” offering no habitable surfaces for organisms to grow on, but the manufacture of standard industrial concrete is a known source of carbon emissions.
SERC tested three different tiles in three distinct areas of the Bay to see how welcoming they would be to marine life: tiles made of standard concrete, tiles made of ECOncrete but left smooth, and tiles made from ECOncrete but textured in a pattern of ridges and small shelf-like protrusions.
During the years that the tiles were submerged, members of the SERC team regularly visited each site at low tide to photograph and record the variety of marine life they found, test the water salinity and temperature, and collect samples. This was no easy feat: These visits might happen at pre-dawn and after dark, and the sites were often hard to reach. Chang describes the experience as “exhilarating” — albeit cold and wet.
While SERC is still preparing a final report, those seaweed-decorated tiles that recently adorned the Embarcadero demonstrate cause for hope. Not only did the treated textured tiles attract and nurture whole micro-ecologies of seaweeds and shellfish, sea snails and small fish, but many of the organisms that thrived were native to the area. A bonus feature, Chang points out, for “one of the world’s most invaded bays.”
Moreover, the seawall project gives marine biota a chance to help protect their industrialized habitats by acting as buffers against weathering, as part of a carbon sink and as natural water purifiers — integral functions within the greater ecosystem.
Even though the Port is still waiting on the official scientific findings of the pilot project, Benson estimates that almost three miles of the Port’s soon to-be-activated 7.5-mile flood plan will include nature-based engineering solutions, including living seawall features.
“We just want to be able to demonstrate to the San Francisco public that as we make these resilience investments, we’re not only just reducing flood risk and reducing earthquake risks, we’re leaving the waterfront a better place,” he says.
Scrolling images appear courtesy of Arianna Cunha / Port of San Francisco.
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