Bay mud could help wetlands survive sea level rise, new study shows

"We desperately now, in the face of sea level rise, need wetlands to protect our shoreline."

ByDan Ashley and Tim Didion KGO logo
Wednesday, April 14, 2021
Study: Bay mud could help wetlands survive sea level rise
An environmental group says sediment could help strengthen Bay Area wetlands with rising sea levels.

SAN FRANCISCO (KGO) -- It's a growing threat that sneaks in with the tide. Sea levels here in the Bay Area are expected to rise by a foot or more over the next several decades, potentially overwhelming levees and seawalls around the Bay.

But now an environmental group says one of the most powerful weapons we have to fight back, is being literally, thrown away.

"There are these giant machines that go out and basically dredge out the channels, so the big ships can come into Oakland and Stockton and other parts of our estuary. So all of that material could be reused," explains Letitia Grenier of the San Francisco Estuary Institute.

Grenier's talking about the tons of sediment that are dredged out of the Bay every year and barged out sea, or dumped in deep water. Instead, the group argues that sediment could be the perfect solution to bolster the wetlands that surround the Bay.

First, it helps to understand that the wetlands play a critical role in absorbing the surges in Bay tides. But to survive, they need to literally rise along with the sea level.

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"What you want over time is for all that shoreline protection that the wetlands are providing to be building up naturally, really at no cost to you if they have enough sediment," says Grenier.

But researchers say, changes in places like the Sacramento-San Joaquin Delta and the Sierra watershed have modified the flows of sediment that act as a kind of adjustable flooring for wetlands. Now, in a new report, they're encouraging State and Federal officials, along with the Army Corp of engineers, to beginning using Bay sediment to make up the difference.

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We desperately now, in the face of sea level rise, need wetlands to protect our shoreline," says the Grenier's colleague Warner Chabot.

The Federal government already spends tens of millions of dollars a year dredging the Bay's shipping channels and has historically focused on the most cost effective disposal options. But the new report argues that cost increases could be off-set by lessening storm damage and the need for major levee building.

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"We have literally billions of dollars in vulnerable communities, and shoreline infrastructure assets from airports, freeways, water treatment plants, that are now suddenly at risk," Chabot argues.

They say sediment has already been used successfully in smaller, targeted restoration projects. And by broadening the strategy, they believe we could potentially turn an expensive waste product, into a valuable tool to protect San Francisco Bay. While the threat might seem slow moving to some, some models suggest that the California coast could face more than a seven foot rise in sea levels by the end of the century.

The study is available from the San Francisco Estuary Institute.