Wetlands: Flood control in plans for Bay salt ponds

By Dan Stober
Monday, September 26, 2005

The levees that shape the salt evaporation ponds that make up much of the south end of San Francisco Bay were never intended to be flood control devices, but that's what they've become.

That fact of life leaves state and federal experts guiding an unprecedented effort to convert 16,000 acres of saltwater ponds back to freshwater wetlands with an extra burden: flood control must be a part of the project.

``We're not just opening the levees in a lot of places to let bay water come in willy-nilly,'' said Steve Ritchie, director of the South Bay Salt Pond Restoration Project.

``We're going to have to beef up a levee line somewhere,'' probably along the shore, Ritchie said.

But the wetlands themselves will also help control flooding. They form a ``large, spongy buffer'' that slows and stores storm water,'' said Josh Collins, a hydrology expert with the San Francisco Estuary Institute. ``Louisiana wishes it still had its wetlands.''

Storm-driven waves can slosh around in the shallow water of wetlands, dissipating their energy in the vegetation and mud before reaching shore, said Ann Draper of the Santa Clara Valley Water District.

But that's years away, when the ponds are dismantled. In the meantime, there are concerns about the maintenance of the low-tech levees, which were created by piling mud on top of mud. Once Cargill sold the ponds to state and federal agencies in 2003, maintenance responsibility was transferred to the U.S. Fish and Wildlife Service and the California Department of Fish and Game.

``It's not one of their missions, and they have a very low budget for that,'' said Yvonne LeTellier, the project leader for a U.S. Army Corps of Engineers study of South Bay levees.

-- Dan Stober

Contact Dan Stober at dstober@mercurynews.com or (650) 688-7536.