Levees and berms were originally constructed to control the flow of water, which often sat for extended periods of time, especially after high tide or heavy rains. The standing water killed vegetation, harmed habitat, and promoted mosquitoes. The Marin-Sonoma Mosquito and Vector Control District treated the marshes with approved chemicals. However, accessing the marshes for mosquito management and surveillance disturbed wildlife and plant populations, and degraded habitat.

“We had conflicting missions,” says Giselle Block, wildlife biologist at San Pablo Bay Refuge, “but we came to realize that by improving tidal hydrology and returning the marsh to a more natural state, we could benefit both our missions.” 

The 65-acre Tubbs Marsh enhancement project restored the natural hydrology to an area of tidal marsh that had impaired tidal flows. The project cost $339,000, with funds and in-kind contributions from the Service (a Challenge Cost Share), ConocoPhillips, the San Francisco Foundation, the Marin-Sonoma Mosquito and Vector Control District and Audubon California, which had a longstanding interest in San Pablo Bay as a specially designated Important Bird Area. The project created nine new channels and widened or deepened eight, breached levees at six locations and lowered two levees to marsh elevation. The physical work took three weeks. Planning, raising money and obtaining permits took more than two years. 

Volunteers contributed 500 hours of baseline monitoring on Tubbs Marsh, providing an inventory of birds, vegetation, water quality, sediment, mosquitoes and small mammals – including two endangered species: the California clapper rail and the salt marsh harvest mouse. The inventory will be maintained for at least the next five years.

Come Back in Two Years
As each levee was breached, “the shorebirds responded immediately,” says Block, “but we don’t expect California clapper rails for two years because their habitat takes longer to develop.” The remaining levees will erode naturally now that the original flow of water has been restored. They are being planted with native upland cover like California sagebrush, mudwort and monkey flower. This cover can provide refuge habitat for marsh-dependent species during extreme high tides. Some believe the levee remnants could be a buffer against erosion during extreme tidal events. 

The success of the Tubbs Marsh levee breaches is just the beginning, Block says. The refuge is now collecting baseline data on 500 acres of marsh on Sonoma Creek where once again, past human action has led to poor hydrology. Permitting and fundraising are underway with actual work expected to begin in about three years.
“This was an example of different agencies coming together with different missions and finding common ground,” says Block, with obvious enthusiasm. “The Mosquito Control District is addressing mosquitoes, the refuge improves habitat for endangered species and migratory birds and Audubon California improved an Important Bird Area. Plus, it was an incredible way for people to engage with the environment.”