Sonoma Creek Marsh Enhancement
August 2015
Designated as an Important Bird Area, San Pablo Bay and its fringing wetlands provide critical decreasing habitat for the birds of the Pacific Flyway. The Sonoma Creek Enhancement Project will provide long-term enhancement and conservation of an impounded San Pablo Bay tidal wetland by improving the hydrological and ecological function of the 400 acre Sonoma Creek Marsh.
The San Pablo Bay National Wildlife Refuge, Audubon California at Richardson Bay and the Marin-Sonoma Mosquito & Vector Control District are partnering together to enhance tidal exchange and drainage within the fringing tidal marsh along the western bank of Sonoma Creek, at its confluence with San Pablo Bay.
The marsh routinely ponds water following spring tides and storm events when high waters inundate the entire marsh and become trapped in a large topographic basin in the marsh interior and between a series of relic levee berms along the western boundary of the marsh. The ponded water in these problem areas leads to high mosquito production rates and reduced vigor of marsh vegetation. These conditions, in turn, reduce habitat functions for the federally endangered salt marsh harvest mouse and California clapper rail, as well as other marsh-dependent species, not to mention support a population of pests most people tend not to like.
In order to improve tidal exchange and drainage to the central basin of the marsh a new, approximately 5,000-foot long, 30 to 50-foot wide (4.20 ac) by 7-foot deep channel is being constructed. When completed it will extend into the marsh interior and connect to San Pablo Bay via lower Sonoma Creek. Lateral channels, totaling approximately 2,450 linear feet (0.55 acres) also will be established to connect the relic berm area of the marsh to this channel.
Other components of the planned enhancement include:
- constructing close to 2 acres of marsh mounds in the central basin to provide habitat heterogeneity and high tide refuge habitat for marsh wildlife,
- creating approximately 10 acres of marsh/upland transitional habitat,
- increasing drainage channels by 650 feet,
- enhancing 3,200 feet of existing drainage channels, and
- constructing 3 acres of high marsh lifts in the relic berm area.
Read this article about how the project is already benefitting birds: Sonoma Creek tidal marsh works like a charm during king tide event
Work on this project has been ongoing since September 2012 and was completed in December 2015.
Sonoma Creek Enhancement Project [434 KB PDF]
