Sunday, November 06, 2011

Tidal wetland sediment accretion might keep up with sea level rise in one location. Maybe.

I attended our annual Santa Clara County Creeks Conference last Saturday, with an even better than usual program that included a panel on tidal wetlands restoration in South San Francisco Bay, where we're bringing back 16,000 acres of tidal wetlands from former saltponds (will post a video link when it's online).

The restoration has barely begun, but the land that sank after being separated from tidal flows has gained sediment rapidly, something that's necessary to create a complex environment of open water, partially submerged, and emergent tidal environments. While it's slowed more after the first few years that individual ponds have been opened to the the tides, they're still adding sediment, two inches annually, far more than the worst projections for sea level rise.

So, good for us. Except that California is a geologically young area with lots of gradients, erosion, and sediment flow. Our particular part of San Francisco Bay might also disproportionately benefit from the "backwash" of sediment from the rest of the Bay.

Our tidal wetlands can keep up where they are, for now, but whether that will work in other places is less clear.  Still, it's one small piece of good news that demonstrates the value of restoring tidal wetlands, which have been lost to a far greater extent in the US than even freshwater wetlands have.