Environmental planners may put Mother Nature to work to help restore the Bay Area’s critical marshes, which gird against sea level rise, while providing habitat for critters and vegetation.
Additional funding for plans to use dredged sediment to improve tidal restoration at sites in Marin County was approved last week by the San Francisco Bay Restoration Authority, which is staffed by the Association of Bay Area Governments‘ San Francisco Estuary Partnership and the State Coastal Conservancy under a Joint Powers Agreement.
Marshes that rest along Bay Area baysides protect communities from storms, flooding, erosion and sea-level rise. Gallinas Creek is an 11-square-mile watershed consisting of north and south forks flowing from the San Rafael hills into San Pablo Bay.
Now, a pair of alternatives will be studied by Marin County Department of Public Works to take sediment from future dredging of Gallinas Creek and use it to improve the quality of its bayfront marshes, including McInnis Marsh.
One of the more innovative approaches utilizes the hydrodynamic “pulse dredging” method, which has a vessel traveling upstream using a trailing water injection nozzle to loosen sediment along the way.
The vessel is deployed during times when the bay is naturally turbid during storm periods or high summer tides. The natural, high energy wave action then transports sediment out of creek channels on ebbtides, building nearby tidal marsh systems, bolstering against sea level rise.
The low cost and low carbon alternative approach provides an additional method for on-site use of dredge material that could result in fewer impacts to fish and other ecologically important species while serving as a model for other projects around the Bay Area.
Each year, the San Francisco Bay Restoration Authority allocates approximately $25 million raised by the June 2016 voter-approved Measure AA parcel tax to shoreline projects that protect, restore, and enhance San Francisco Bay, while connecting communities to the bayshore.
Pulse dredging method. Army Corps of Engineers graphic.
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