Bay shorelines edged by tidal marshes and wetlands have natural flood protection, are habitats for native plants and animals, and are often locales where people can observe wildlife in close proximity to a metropolis.
Advocates for wetlands along the shores of the nine Bay Area counties are asking voters to approve Measure AA, a $12 annual parcel tax on the ballot in the June 7 primary election. The measure would need a two-thirds majority to pass, and polling shows support from more than 70 percent of those surveyed, San Mateo County Supervisor Dave Pine said.
The measure would make available $25 million annually for 20 years to public agencies to use in restoring Bay Area shorelines, including many former salt ponds, to functioning tidal marshes.
Tidal marshes are seen as a critical to flood protection, an important consideration since sea levels are expected to rise in coming decades in response to greenhouse gas accumulation in the atmosphere. Marshes moderate the impacts of waves on the shore and absorb water like a sponge, trapping it and then slowly releasing it, scientists say.
Restoring the shore
Measure AA would raise $500 million in tax revenues to restore marshes to about 15,000 (out of 35,000) acres of shoreline now in public ownership, Mr. Pine said.
Mr. Pine chairs the seven-member board of the San Francisco Bay Restoration Authority, which put Measure AA on the June ballot. The state Legislature created the nine-county agency in 2008 "for the sole purpose of the collection and distribution of revenues for restoration of wetlands," Mr. Pine said.
Of the $500 million that Measure AA would generate, 50 percent would be allocated to the nine counties organized as four regions named after the four major points on a compass. The other 50 percent would be distributed in grants for the "highest and best" uses, Mr. Pine said.
Using a formula based on population, the West Bay region, San Francisco and San Mateo counties, would receive 11 percent, or $55 million, Mr. Pine said.
Most of Measure AA funding would likely be used as matching funds to leverage as much or more state or federal grant money, he said.
Plans that would likely qualify for Measure AA funding in San Mateo County include the SAFER Bay Project, which focuses on areas of south San Mateo County threatened by rising sea levels, and the Ravenswood Slough adjacent to Bedwell Bayfront Park in Menlo Park.
A map of the slough published in April by the South Bay Salt Pond Restoration Project shows plans for a 295-acre marsh, a 60-acre managed pond and a 270-acre salt flat protected by an improved levee for the nesting of the snowy plover, a threatened species.
Related Measure AA goals include:
■ Restoring beds and meadows of eelgrass, an important species in the lives of crabs and scallops as well as salmon, rockfish and shellfish, according to the National Marine Fisheries Service.
■ Constructing 20 miles of levees for flood protection. All levee work that draws from Measure AA funding must be done in conjunction with wetland restoration.
■ Constructing 25 miles of the Bay (perimeter) Trail -- if the trail work is associated with wetland restoration. A priority would be closing gaps in the trail. Included in the plans is a new trail and observation platform at the Ravenswood Slough.
In a ballot argument against Measure AA, the Silicon Valley Taxpayers Association says the measure is not specific enough in its goals and lacks oversight by a panel of scientists. The measure would create "a whole new bloated and expensive bureaucracy," with overhead costs and expense accounts, the association says.
Asked about these allegations, Mr. Pine said the language of the measure puts a 5 percent ceiling on revenues spent on administrative expenses. Support work for the Restoration Authority tends to be done by employees of the Coastal Commission, which can bill the authority for expenses, he added.
Go to sfbayrestore.org for information in support of Measure AA.
Go to the county Registrar of Voters website for the ballot arguments supporting and opposing Measure AA.
Salt pond to marsh
Converting a salt pond to a marsh is a matter of dismantling the water-flow management system once used by salt companies to channel water into evaporation ponds and collect the resulting salt, said biologist John Bourgeois, the executive project manager of the South Bay Salt Pond Restoration Project.
When tide-driven sea water is allowed to inundate a salt pond, it brings in suspended sediment, Mr. Bourgeois said. Much of that sediment, critical to marsh development, entered the bay in the mid-1800s. Gold Country miners used water cannons to scour soil from the sides of mountains.
The soil, including particles of gold, flowed into rivers where miners could pan for it as the water made its way to the bay. The miners dislodged enough soil to leave the bay shallower and muddier, Mr. Bourgeois said.
As the sediment becomes mud, it attracts birds to feed on the small lifeforms in the mud, and eventually marsh grasses take root, Mr. Bourgeois said. A functioning marsh normally takes 10 or 15 years to establish itself, but since it's a dynamic process, it can be visually interesting to the human observers from the start, he said.
"The bay will deliver a lot of sediment," Mr. Bourgeois said. "The vegetation will start to come in on it's own."
Other species have come to inhabit the salt ponds, so care will be taken to respond to their interests, in particular the snowy plover, a threatened species. Plovers prefer beaches for their nesting sites, but salt flats will do, Mr. Bourgeois said.
Asked about mammals living in the slough, Mr. Bourgeois said he expected a return of the endangered salt marsh harvest mouse and, when the marsh is established, possibly harbor seals.
The marsh at Ravenswood would include an upward sloping habitat transition zone to dry land. A gradual slope dampens wave energy and offers a refuge for the mice during high tides.
Flood control through the use of marshes in San Mateo County is challenging because so much of the shoreline has been developed with infrastructure, a situation that leads to a talk of levees. Salt ponds have levees and they have been serving as flood protection, but they weren't built with that function in mind, Mr. Bourgeois said.
"We have to build real flood protection," he said.
A salt pond levee in the Ravenswood Slough will be made higher and more compacted to add both flood control associated with the new marsh and protection for the snowy plover, he said. This improved levee, unlike salt-pond levees built with the water-logged dredged material, would use tested soil. "We have an entire team of people that (testing soil) is all they do," Mr. Bourgeois said.
Measure AA would be "a huge plus for us to be able to leverage state and federal money," he said.