Duwamish Estuary Subwatershed
Duwamish Estuary Subwatershed Facts
Human population: 61,086 (2009 estimate)
Primary land uses: industrial (43%), residential (39%)
Mean annual discharge: tidally influenced reach with more than 2,000 cubic feet per second of freshwater
Salmon species currently present:
Chinook, coho, chum, pink, sockeye, steelhead, coastal cutthroat trout, bull trout
Why is the Duwamish Estuary Important to Salmon?
The Duwamish estuary plays a key role in the life history of salmon. Young fish migrate from freshwater streams and the river higher in the watershed to the estuary. In the estuary, they feed and their bodies adapt to salt water. Estuary habitat is particularly important for Chinook salmon, which are listed as "threatened" under the federal Endangered Species Act.
Subwatershed Salmon Habitat Overview
The Duwamish River is that portion of the Green River downstream of the historic confluence with the Black River. It consists of the river between River Mile 0 and River Mile 11. The entire stretch of the river is influenced by tides.
The map at right shows the Duwamish Estuary subwatershed. View a map showing this subwatershed in relation to the rest of the watershed.The Duwamish used to be a larger and longer river. Prior to 1916, it was defined at its upper point by the joining of the Black River and the White River at what is today Fort Dent Park in Tukwila. The Black River drained Lake Washington and also was fed by the Cedar River. The White River flowed from the slopes of Mt. Rainier and met the Green River in modern-day Auburn. From the junction of the Black and the White, the Duwamish meandered 15 miles to reach Elliott Bay, where it spread out in large estuary characterized by mud flats, marshes, and swamps. Since the area the Duwamish then drained was three times larger than it is today -- about 1600 square miles versus 500 square miles -- the river carried much more water, sediment, and large woody debris into Elliott Bay than it does now.
In the last 150 years, the Duwamish has been transformed more than any other part of the watershed. Over 97% of the historic estuarine mudflats, marshes, and forested streamside swamps have been eliminated by channel straightening, draining, dredging, and filling. All of the tidal swamps bordering the Duwamish were filled by 1940. The straightening of the river and filling in of the winding channel reduced its length by four miles. The remaining shortened channel suffers from polluted sediments along with on-going contamination due to stormwater discharges. So severe is the contamination that the lower five miles of the estuary has been declared a federal "Superfund" site, a designation given to the most contaminated sites in the country.
Currently all salmon species migrate, rear, and acclimate in this transitional area between river and marine waters. Juvenile Chinook and chum salmon are most dependent on this type of habitat. Small numbers of char (bull trout/Dolly Varden char) have been documented as using this reach.
There are numerous small and medium sized tributary streams that drain into the Duwamish. All have experienced significant development that in turn has made many of them inaccessible and inhospitable for salmon. Many of these stream basins have high levels of impervious surfaces (pavement, roofs) that have degraded and altered the historic hydrologic regime. Stream flows are too high when it rains and too low when it doesn't. Most of the small patches of remaining marginal habitat are disconnected and heavily impacted by stormwater-associated flows and poor water quality. Functional riparian areas have been eliminated or fragmented to a few undeveloped areas often in the high gradient reaches associated where the creeks cascade down the valley walls. The potential salmonid production of these creeks is expected to continue to be limited due to current land use practices.
Where the Fish Are in the Duwamish Estuary Subwatershed
Fish distribution maps show where anadromous salmon and trout have been found or should be present.
Problems on the Mainstem Duwamish
- Urban and industrial land use practices that have:
- Dredged, channelized, and filled 97 percent of the estuarine mudflats, marshes, and forested riparian swamps that formerly characterized the estuary;
- Simplified the remaining channel and severely reduced riparian function; and
- Polluted the remnant, shortened channel with stormwater and wastewater effluent.
Problems on Tributary Streams
- Development that is:
- Creating fish passage barriers;
- Leaving small patches of disconnected marginal habitat;
- Altering hydrology and channel stability due to stormwater-associated flows; and
- Reducing water quality.
Additional information on the quality of habitat along the Duwamish River and use by salmonids is available in the following reports:
- 2005 Juvenile Chinook Duwamish River Studies (May 2006) (Adobe Acrobat 4.5 MB)
- Lower Green River Baseline Habitat Survey Report (January 2004) - includes the Duwamish from River Mile 5.7 (just south of Turning Basin #3) to River Mile 11.2 (Fort Dent Park)
- Lower Duwamish Inventory Report (May 2004)(Adobe Acrobat 6.1 MB) - includes the Duwamish from Elliott Bay to River Mile 5.7 (just south of Turning Basin #3)
Habitat historically found in the Duwamish Estuary Subwatershed (Adobe Acrobat 1.5 MB) has been researched to inform decisions about future restoration.
Water quality information on the Duwamish is available in two reports:
More recent water quality data are available at the King County stream monitoring page.
Project Solutions to These ProblemsProjects funded by the Salmon Recovery Funding Board and other grantors are listed here. The projects listed below are only a few of the various projects of governments and volunteer groups in this subwatershed.
- North Wind's Weir (Site 1) on the Duwamish in Tukwila
- Habitat Inventory and Utilization Assessment of the Lower Green, Duwamish, and Nearshore Subwatersheds
- Duwamish Gardens Acquisition and Restoration in Tukwila
- Riverton Flap Gate Removal in Tukwila
Information on the status of individual projects also is tracked on the state's Lead Entity Habitat Work Schedule.
Local Governments in the Duwamish Estuary Subwatershed
Follow the external links to learn more about these communities and what they are doing to improve habitat for salmon.
Other Organizations/Efforts in the Duwamish Estuary Subwatershed
Lower Duwamish Superfund Site - U.S. Environmental Protection Agency
The lower (northern) five miles of the Duwamish have been listed as a "Superfund" site under federal law. This is because of high levels of pollutants in the sediments of the river. These pollutants pose a risk to human health and aquatic creatures such as fish. The U.S. Environmental Protection Agency and the Washington State Department of Ecology are in charge of cleanup of the site. This web page lists a variety of both technical and reader-friendly documents to help explain the problems and the process that EPA and Ecology are using to figure out how to solve them.
Lower Duwamish Waterway Source Control Investigation - Washington State Department of Ecology
The state Department of Ecology is leading the efforts to control sources of sediment pollution in the Lower Duwamish Waterway in cooperation with the City of Seattle, the Port of Seattle, King County, the City of Tukwila, and the U.S. Environmental Protection Agency. Source control is the process of finding and controlling releases of pollution to waterway sediments to prepare for cleanup and prevent sediment recontamination.
Duwamish River Cleanup Coalition
The Duwamish River Cleanup Coalition is an alliance of community, environmental, and small business groups affected by on-going pollution and cleanup plans for the Duwamish River under the federal "Superfund" law. The Coalition helps people learn about and get involved in decisions regarding cleanup. Activities include tours of the river.
Lower Duwamish Waterway Group
The Lower Duwamish Waterway Group (LDWG) is a public-private partnership working together to address environmental concerns and issues in the Lower Duwamish. Its primary focus is cleanup up polluted sediments in the river as part of the federal "Superfund" listing of the Lower Duwamish. The four LDWG partners are City of Seattle, Port of Seattle, King County, and the Boeing Company.
King County Duwamish Waterway Programs
King County is working on a variety of programs to clean up and help restore the Duwamish. This page lists some of the recent clean up accomplishments by King County, the City of Seattle, Port of Seattle, and other partners. A related page on Duwamish community events lists opportunities to learn about and help the river.
Port of Seattle
The Port of Seattle manages large areas of the waterfront on Elliott Bay and the Duwamish. The natural areas of these properties are managed to provide fish and wildlife habitat as well as public access to water. In addition, piers and other shoreline facilities are designed and operated to minimize harmful impacts to salmon and other aquatic resources. In 2008, the Port developed a Habitat Restoration Plan for the Lower Duwamish.
City of Seattle Restore
Our Waters Initiative
This City of Seattle effort is a partnership with the community to protect and restore the Duwamish as well as streams, lakes, and marine shorelines.
People For Puget Sound
People for Puget Sound is a non-profit citizens group dedicated to educating and involving people in protecting and restoring the land and waters of Puget Sound and the Northwest Straits. It regularly organizes volunteer restoration efforts at several sites in the Duwamish and relies on citizen monitors to help evaluate the success of Duwamish restoration efforts.
Puget Soundkeeper Alliance
Puget Soundkeeper Alliance was created in 1984 as a coalition of citizens and organizations concerned about the health of Puget Sound. It periodically cruises the Duwamish to detect illegal pollution.
ECOSS (Environmental Coalition of South Seattle)
ECOSS is a non-profit agency that helps residents and business with hazardous waste disposal, recycling, and other environmental issues. It is currently planning to restore salmon habitat along the Duwamish River in South Park.
Learn more about the original inhabitants and stewards of the Duwamish at the Tribe's web site.
The Nature Consortium is a very active environmental education, urban forest restoration, and arts organization in West Seattle. The focus of their restoration work is the West Duwamish Greenbelt.
Duwamish- John Beal YouTube Video
This 13-minute video profiles John Beal, who worked tireless to restore the Duwamish until his death in 2006. The video explains the importance of the Duwamish and shows views of the river from the air and by boat.
King Conservation District
Since 1949, the KCD has been helping the people of King County manage their natural resources by educating landowners, schools groups, scientists, consultants and agencies in recognizing problem situations and avoiding the creation of them. KCD also provides technical assistance in solving problems.
Green/Duwamish Ecosystem Restoration Project
The US Army Corps of Engineers, in partnership with King County, the cities of the watershed, the Muckleshoot and Suquamish Tribes, state agencies, and local interests have developed the Green/Duwamish Ecosystem Restoration Project to restore the ecosystem of the watershed. Several projects are in the Duwamish subwatershed.
Elliott Bay/Duwamish Restoration Panel
The Elliott Bay/Duwamish Restoration Panel was established to implement the sediment cleanup, habitat restoration/development, and pollution source control provisions of a court settlement involving the federal government, King County, and the City of Seattle. The Panel has paid for a number of significant habitat restoration/creation projects in the Duwamish. The web site includes many photographs of restoration sites.
Information Resources for the Duwamish Estuary Subwatershed
Reconnaissance Assessment Report on the Green/Duwamish and Central Puget Sound Watershed
Comprehensive information on salmon habitat as of 2000. Includes detailed information on on salmon populations, conditions in specific subwatersheds and stream basins, and maps showing salmon habitat.
Lower Green River Baseline Habitat Survey Report
Detailed information, maps, and photos of Duwamish River mainstem habitat conditions from River Mile 5.7 (just south of Turning Basin #3) to River Mile 11.2 (Fort Dent Park). Also available upon request are Geographic Information System (GIS) layers with these data. Published January 2004.
Urban Blueprint for Salmon - City of Seattle
Information about how Chinook salmon use the Duwamish and other parts of Seattle.
Green River Watershed Page - King County
Information about the Green/Duwamish River watershed.
Environmental Information Page for WRIA 9 - Washington State Department of Ecology
Includes downloadable publications, maps, and water quality information for Green/Duwamish and Central Puget Sound Watershed (WRIA 9). Most information is related to the Green/Duwamish portion of WRIA 9.
Surf Your Watershed - U.S. Environmental Protection Agency
Site contains links to various U.S. EPA documents related to environmental conditions in the Green/Duwamish watershed. There are links for environmental parameters such as air quality and hazardous waste in addition to water quality.