Land Sculpture: Creating a Marsh

by Ann Thomas

Walkers and cyclists on the multiuse path through the Corte Madera marshes are being treated to a view of the creation of a new tidal wetland, and of an improved trail system using dredge spoils from the 1950s. The project is on a four-acre portion of 72 acres east of Hwy 101 purchased by the Golden Gate Bridge, Highway and Transportation District in the 1970s as mitigation for habitat loss and damage caused by the district’s construction of the Larkspur Ferry Terminal.

The restoration, northeast of The Village shopping mall, is bordered on three sides by the California Department of Fish and Wildlife’s Corte Madera Ecological Reserve, and on the west side by a strip of land owned by the Sonoma Marin Area Rail Transit, a popular walkway through the marsh system.

Work began in October and is scheduled for completion by January 31 of 2021, to be followed by a four-month maintenance period. Some social trails, along with portions of berms that were constructed to contain dredge spoils, are being removed and parts of the area have been temporarily closed to the public.

The four-acre restoration is an obligation imposed on the transit district in return for permits it received in 1988 for dredge disposal and in 1996 for modifications in ferry use. In the intervening years the project site has been colonized by nonnative vegetation, becoming a haven for pampas grass and the homeless while restoration work was deferred.

To meet the permit requirements, the project is designed to provide tidal marsh habitat suitable for federally listed species including Ridgway’s rail and the salt marsh harvest mouse. Components include mudflats, low marsh, high marsh, and a transition zone with vegetative refugia suitable for these endangered species and other wildlife that use the marsh. The upland refugia would be fenced off from pedestrians and dogs that use the 25-foot-wide fenced public zone. The project also includes relocation of about a quarter-acre of seasonal wetlands within the project boundaries.

While work is proceeding on the restoration, 14 acres of the district’s property have been enclosed by orange fencing to keep the public safe. In late October through December visitors had daily views of bulldozers, water trucks, excavators and dump trucks excavating approximately 28,000 cubic yards of material to be reused onsite. Heavy equipment removed invasive vegetation and reshaped the four-acre project site, opening a new tidal channel on December 10 to the wetland site; excavated material was placed next to the wetland for upland habitat. Following this, 17,000 native plants are being installed, and the surrounding 10 acres hydroseeded with native seed.

Once the project is completed, visitors will be able to hike around the restored marsh on a new berm that will create a loop similar to the existing trail. Benches, trash cans, and interpretive signs are planned along the reconfigured loop trail that will be open to the public when construction is complete.

Tidal waters are being welcomed back to an area of former marsh, east of Hwy 101. Photo courtesy of GGBHTD