Hamilton/Bel Marin Keys Wetlands Restoration Project

The restoration of tidal and seasonal wetlands on the former Hamilton Army Airfield and the adjacent North Antenna Field (NAF) and Bel Marin Keys Unit V (BMKV) properties is a joint project between the US Army Corps of Engineers, San Francisco District, and the California State Coastal Conservancy. The Conservancy is the non-federal sponsor and landowner (with the exception of the NAF which is owned by the State Lands Commission). The U.S. Congress authorized the Hamilton Wetland Restoration Project (including the NAF) in 1999 and the addition of the BMKV property to the project in 2007. The combined project site comprises approximately 2,600 acres, located 25 miles north of San Francisco, along San Pablo Bay, in and adjacent to the City of Novato, Marin County, California. When complete, the project will be a mosaic of seasonal and tidal wetlands, providing public access to sections of the Bay Trail and habitat for birds and wildlife.

More information on the restoration of Bel Marin Keys Unit V can be found on the Coastal Conservancy’s website here.

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We restore tidal marshes

Between 1800 and the late 1990s, about 80% of the tidal marshes in the San Francisco Bay estuary were lost due to diking and filling. These tidal marshes provide many ecosystem services which benefit not only nature, but our society. Here’s how tidal marshes benefit you:

Flood Protection: Improved protection against floods and sea-level rise

Flooding in the Bay Area often occurs where runoff from major storm events collides with a rising high tide. The marshes around the fringes of the bay store water at these collision points, absorbing it like giant sponges, then releasing it during low tides. Tidal marshes also serve as “horizontal levees” by absorbing the energy of storm waves, thereby reducing the potential for bay waters to flood low-lying areas along the bay during storm events and rising sea levels. Tidal marshes form by trapping sediment until the sediment builds up to an elevation that allows vegetation to grow. At that point, marshes gain elevation in two ways: (1) additional sedimentation, and (2) accumulation of organic matter (such as roots and rhizomes of plants) below the surface of the sediment. Historically, marshes were able to keep pace with sea- level rise by migrating inland to higher elevations. The ability of marshes to keep up with sea-level rise is dependent on sediment availability, the presence and type of vegetation and its organic root zone building capacity, the rate that sea levels rises, and the topography and connectivity of adjacent uplands.

Healthier Ecosystem: Improved water and air quality and fisheries

A marsh acts as a natural filter and improves water quality by trapping and filtering nutrients, sediment and pollutants transported by runoff. This prevents these pollutants from ever reaching the bay and adversely affecting its marine life. The San Francisco Bay Estuary was once teeming with salmon, crab and oysters. The fishing industry thrived, and harvests from the Bay not only fed the region, but much of the west coast as well. Tidal marsh was an essential component to the health of the fishing industry in the San Francisco Bay. With the closure of the herring fishery in 2009, commercial fishing and shell fishing is now prohibited. Restoring our marshes will undoubtedly improve the health of the fisheries in the Bay. Additionally, tidal marsh can serve to purify the air and reduce a major cause of climate change, carbon dioxide. Marshes tend to be “carbon sinks” because of the amount of carbon dioxide absorbed through photosynthesis by the prolific wetland vegetation. These sinks are especially important in highly urbanized areas, like the San Francisco Bay Area, where carbon dioxide levels are elevated.

Recreational and Educational Opportunities

Restoring tidal marsh also provides recreational opportunities for people to experience the natural world, such as hiking, biking, kayaking, and bird watching. The San Francisco Bay Area is one of the most densely populated metropolitan areas in the United States, and we are fortunate to have such large areas close by that have not been developed. With proper planning and funding, tidal restoration projects present a unique opportunity to provide recreational areas for its residents that are, at times, right outside their front door. In a similar respect, public access to the marsh provides an educational opportunity to learn about our natural environment and how plants, animals and humans can coexist.

Sustainability: Reduced levee building and maintenance

Most levees along the San Francisco Bay are aging and poorly constructed as they were built with technology and methods from the turn of the 19th century. Further complicating the matter is subsidence. As the land sinks, the water on the tidal side places more pressure on the levees, requiring them to be widened & strengthened to keep from failing. Without constant maintenance, failures are inevitable. Tidal restorations reduce the need for levees and are designed to restore the natural processes and let the site evolve as it needs given the specific conditions of the site. This approach effectively provides a long-term solution to reduce maintenance costs into the future.

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We reuse dredged sediment

Approximately 3-6 million cubic yards of sediment must be dredged to maintain safe navigation in and around San Francisco Bay each year. These sediments (“dredged spoils” or “dredged material”); from federal navigation channels, ports, refineries, marinas, etc.; have generally been placed at designated open-water disposal sites within the Bay and in the ocean. A great alternative to disposal is to “beneficially reuse” dredged sediment. One of the first projects to incorporate beneficial reuse was the restoration of the 348-acre Sonoma Baylands, just north of Bel Marin Keys. At both the Sonoma Baylands and the Hamilton airfield, the Army Corps and the Conservancy worked together to raise the elevation of subsided lands to create tidal marsh. Maximizing beneficial reuse of dredged sediment is one of the goals of the Long Term Management Strategy for Dredged Material in San Francisco Bay (LTMS), a joint initiative of federal and state government that is involved in dredging and dredged material disposal.

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Our Partners

In addition to the partnership between the U.S. Army Corps of Engineers and the State Coastal Conservancy, the project has greatly benefited from the assistance and cooperation of many partners, including:

At Point Blue, our mission is to advance the conservation of birds, other wildlife, and ecosystems through science, partnerships, and outreach.

San Francisco Bay Conservation and Development Commission protects and enhances San Francisco Bay and encourages the Bay's responsible and productive use for this and future generations.

The Marin/Sonoma Mosquito and Vector Control District is committed to protecting the health and welfare of the communities we serve from mosquitoes and vector-borne disease

San Pablo Bay National Wildlife Refuge (US Fish and Wildlife Service) – Diverse Species Benefiting From Restored Marshlands

City of Novato Parks, Recreation and Community Services Department

City of Novato Public Works Department

Marin County Flood Control and Water Conservation District – Reducing the risk of flooding for the protection of life and property while utilizing sustainable practices

Ducks Unlimited – Banding Together for Waterfowl

San Francisco Bay Joint Venture – A partnership working to protect, restore and enhance wetlands for the benefit of wildlife and people in the Bay Area

San Francisco Bay Trail Project – A planned 500-mile walking and cycling path around the entire San Francisco Bay running through all nine Bay Area counties, 47 cities, and across seven toll bridges

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