Green City: The bay-delta connection

Scientists predict that rising sea levels and levee failures could have profound consequences for both ecosystems
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sarah@sfbg.com

GREEN CITY Until recently, politicians and the public tended to view the problems facing the Sacramento–San Joaquin Delta levees as separate from the problems facing the San Francisco Bay. But now that human-made distinction is beginning to blur as scientists predict that rising sea levels and levee failures could have profound consequences for both ecosystems.

As wetlands scientist Philip Williams explained at the State of the Estuary Conference in Oakland last month, if the levees fail, a hole will open that will cause the northern area where the bay meets the delta (roughly from Richmond to Antioch) to fill with salt water and deepen, thereby eroding the delta's valuable tidal marsh habitat.

This doomsday scenario has environmentalists clamoring for an increase in tidal marsh restoration efforts in the southernmost stretches of the bay, which are already home to the South Bay Salt Pond Restoration Project and a broader US Army Corps of Engineers effort to build levees and restore marshlands to protect property from flooding.

As Dr. Letitia Grenier of the San Francisco Estuary Institute said at the SOE conference, people aren't the only ones who need habitat protection. The mosquito-eating Yuma bat, the California clapper rail, the least tern, and the chinook salmon are just a few of the many species that live around, fly across, or swim through the bay and the delta, and their survival depends on a mosaic of interconnected habitats.

Yet no agency has the clear authority to require that marshland marsh be restored, levees built, development prevented, and greenhouse gas emissions reduced.

In a recent report for the San Francisco Bay Conservation and Development Commission, executive director Will Travis notes that while the BCDC, the Bay Area Air Quality Management District, the Metropolitan Transportation Commission, and the Association of Bay Area Governments are working together as part of a Joint Policy Committee, "none of the four agencies has the authority to prohibit development in flood-prone areas [or] require that levees be constructed to protect low-lying areas, and BAAQMD does not have the authority to regulate emissions from vehicles."

Pointing out that the BCDC was created in 1965 to regulate bay fill and thus prevent the bay from becoming smaller, Travis writes that his agency "is neither legally responsible for dealing with this dramatic change of conditions that is making the Bay larger, nor does BCDC have any explicit legal authority to address this problem."

That said, in an Oct. 29 report posted on the BCDC's Web site, Travis announced that his agency "has taken the initiative to formulate a broad outline of a comprehensive strategy for addressing climate change in the Bay region and identified changes that are needed in state law so that BCDC can play a productive role in implementing such a strategy."

This strategy includes mapping flood-prone areas, ceasing planned developments in such areas, identifying property that requires protection, and identifying areas that should be allowed to revert to tidal marsh and other types of natural habitat.

"Another probable impact of climate change is that more precipitation in the Sierra Nevada will fall as rain rather than snow, and the snow pack will melt earlier in the spring," Travis writes. This will in turn reduce the amount of late spring and summer runoff into the delta, allowing salt water to extend farther into the delta than it does now.

Travis predicts that sea level rise and higher flood flows resulting from climate change, as well as earthquake risk, will also increase the probability of catastrophic levee failure.

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