Sonoma Creek Enhancement Project

Reviving 400-acres of wetland habitat in San Pablo Bay.

Sonoma Creek Marsh Photo: Haymar Lim/Audubon CA

Audubon California, U.S. Fish and Wildlife Service, and Marin Sonoma Mosquito Control District are partnering to  enhance 400 acres of tidal marsh habitat on the San Pablo Bay National Wildlife Refuge along Sonoma Creek in northern San Francisco Bay. The project is part of Audubon’s Coastal Resilience work and this project in particular is the first of its kind to demonstrate how to ensure the marsh and its wildlife will be better adapted to withstand climate change in the future, particularly from sea level rise and storm surges. 

The project will benefit birds such as Ridgway’s Rails, Black Rails, migratory waterbirds, and a number of marsh songbirds, along with the endangered salt marsh harvest mouse and native plants. Fish, such as Coho salmon and steelhead, rely on healthy wetlands as habitat where juvenile fish can feed and grow.

Designated as an Important Bird area, San Pablo Bay and its surrounding wetlands provide critical habitat for the birds of the Pacific Flyway. Birders visiting the refuge can see Brown Pelicans, White-tailed Kites, Golden Eagles, Peregrine Falcons, Common Yellowthroats, and migratory shorebirds including Whimbrels and Willets.

Site History

The Sonoma Creek runs from Sonoma County into the San Pablo Bay on the northernmost end of the greater San Francisco Bay.  More than a hundred years of mining and agricultural operations have greatly limited the ecological function of these wetlands. Open water sediment from hydraulic mining during the Gold Rush caused a rapid buildup of mud flats which were subsequently turned into farmland, and maintained by levees.

In the last three decades, tidal action has reclaimed some of the area, creating stagnant wetlands that built up too fast to form natural channels. These stagnant pools form algal mats and harbor mosquitos. The remaining agricultural land has now become too salty for most agriculture, and some has been sold or abandoned.

Project Goals

The core of the project involves constructing a network of tidal channels within the marsh to drastically improve tidal exchange and nutrient cycling and provide habitat to a myriad of marsh-dependent wildlife species. The channels will also provide spawning and feeding grounds for endangered and commercial fishes.

Improving hydrology will improve water quality by increasing circulation and drastically reducing the amount of pesticides applied to areas  of ponded water that currently facilitate heavy mosquito production.

The project also has a vital climate change adaptation component. Using soil excavated from digging the channels, we created a gently-graded high marsh transition zone along the edge of the marsh and habitat “marsh mounds” within the marsh.  These features will reduce storm surge flooding of adjacent private lands and provide crucial high tide refuges for rails, shorebirds, and small mammals.

This project also helped change Bay Conservation and Development Commission’s (BCDC) restoration policy and permitting process to make it easier for restoration projects to use dredge spoil for beneficial uses in the future. 

Implementation of the project has also provide hands-on educational opportunities for students who would not otherwise experience natural history in the field setting.

Progress Updates

Phase 1 of the Project was constructed in 2015 and involved excavating a large, 4,550-ft long tidal channel through the center of the marsh and using the extracted soils to construct marsh mounds along the channel alignment, as well as a wetland-upland habitat transition “ramp” (or horizontal levee) along the existing perimeter levee. 

Phase 2 of the project was completed October 2020, and added the following enhancement elements:

1. Constructing an additional 1,150 linear ft of the central tidal channel and utilizing the extracted soils to construct a series of marsh mounds along the channel length.

2. Removing a series of rock sills within the central channel, burying the material within pits excavated on the adjacent marsh plain, and using the void spoils to build additional marsh mounds.

3. Enlarging/extending existing tidal marsh channels into persistent open water impoundments on the east side of the central tidal channel to improve tidal exchange and drainage within these areas.

Consultants for this project are Wetlands and Water Resources, Inc. Gillenwater Consulting, LLC, and ESA Associates.  Construction is being carried out by Hanford ARC.

Sonoma Creek Project Biological Monitors

Funding and other support for this project has been provided by:

  • U.S. Fish and Wildlife Service - National Coastal Wetlands Conservation Grant
  • California Wildlife Conservation Board
  • National Fish and Wildlife Foundation
  • California State Coastal Conservancy
  • Environmental Protection Agency (EPA)
  • Marin-Sonoma Mosquito and Vector Control District
  • San Pablo Bay National Wildlife Refuge
  • Point Blue Conservation Science - STRAW program (Students and Teachers Restoring a Watershed)
  • Individual donors and volunteers

Here's the latest on the project

Sonoma Creek Marsh restoration update

We learn all about marsh mounds from restoration manager Courtney Gutman.

Great numbers of shorebirds at our Sonoma Creek restoration site

Audubon California's Courtney Gutman visited our Sonoma Creek restoration site last week, and found that a ton of wintering shorebirds were already enjoying one section of restored habitat. If you look closely, you can see the Northern Harrier that prompted all these birds to go on the wing.

What is a healthy marsh?

Marsh in Baja California and Sonoma Creek Marsh

The above visual answers the question of why we are undertaking a large scale restoration project in San Francisco Bay. On the left is a healthy, functionining marsh in Baja California and on the right is the site of our restoration in Sonoma Creek Marsh, a dead marsh. The difference between a vibrant wetland system and dysfunctional one is dramatic.

Breaking through
Audublog

Breaking through

New channel successfully formed in Sonoma Creek Marsh restoration project. This marks middle point of construction on new Ridgway's Rail habitat.

Digging new channels at Sonoma Creek
Audublog

Digging new channels at Sonoma Creek

Now that we've finished the access road, we're starting the real work of bringing valuable salt marsh habitat back to life.

Herding mice
Audublog

Herding mice

Restoration projects are always full of surprises.

Construction begins at Sonoma Creek
Sonoma Creek Restoration

Construction begins at Sonoma Creek

Our three-year project to enhance habitat at Sonoma Creek gets started with the construction of an access road to the site.

Restoring the Sonoma Creek Marsh
Audublog

Restoring the Sonoma Creek Marsh

Audubon California is nearing the end of a massive restoration of wetland habitat in San Francisco Bay.

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San Francisco Bay
San Francisco Bay

San Francisco Bay

Audubon California is committed to protecting the birds and habitat of the San Francisco Bay.

Read more

Lower Tubbs Island restoration
Seas & Shores

Lower Tubbs Island restoration

Audubon California partnered with the San Pablo Bay National Wildlife Refuge in 2010 to restore vital bird habitat in San Pablo Bay.

Read more

Coasts
Seas & Shores

Coasts

Seabirds and shorebirds need our help.

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How you can help, right now