King County Flood Control District home page
The King County Flood Control District is a special purpose government created to provide funding and policy oversight for flood protection projects and programs in King County.
Investments by River Basin
Cedar / Issaquah / Sammamish River Basin
Green River Basin
Snoqualmie / S.F. Skykomish River Basin
White River Basin

Cedar/Issaquah/Sammamish River Basin

The King County Flood Control District invests resources in the Cedar/IIssaquah/Sammamish River Basin to protect public safety, the regional economy and critical infrastructure. For the purposes of the Flood District's budgeting and planning, the Cedar River Basin includes Cedar River, Issaquah Creek, and the Sammamish River.

King County Flood Control District Investments
Cedar River
Issaquah Creek
Sammamish River
King County Flood Control District Investments

Cedar River Basin (including Issaquah Creek and Sammamish River)

2016 Capital Budget: ($504,580)

2015 Capital Budget: $9,236,644 

2014 Capital Budget: $4,165,254

2013 Capital Budget: $3,547,995

2012 Capital Budget: $10,065,634

2011 Capital Budget: $4,073,839

2010 Capital Budget: $4,663,624

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Cedar River

The Cedar River flows 45 miles from its headwaters in the Cascade Range to its mouth at Lake Washington, ultimately draining to Puget Sound. Divided by several dams, the upper and lower river areas differ distinctly in character and management.

The City of Seattle owns and manages a 90,000 acre protected area along the upper river known as the Cedar River Watershed. The Cedar River Watershed provides drinking water for 1.4 million people in the greater Seattle area and hydroelectric power generation. Residences, commercial businesses, and industrial facilities are located along the lower part of the watershed, downstream of Landsburg. More than 60,000 people, live in and around this area, in the communities of Maple Valley, Ravensdale, and Renton. As the river enters Renton, one finds parks, single- and multi-family residential development, commercial development, and portions of the downtown business core.

During the winter flood season, shifting floodwaters can inundate, erode or shift areas of low-lying floodplain, channel banks, and active gravel bars. Steep landslide prone hillsides flank the Cedar River creating additional risks. Landslides can deposit a significant amount of material in the river, blocking a portion of the mainstem channel, backing up the river, and even rerouting its course, as was the case in February 2001 as a result of the Nisqually earthquake.

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Issaquah Creek

Issaquah Creek headwaters originate from the steep slopes of Cougar, Squak, Tiger and Taylor mountains. The basin encompasses about 61 square miles and includes Holder, Carey, Fifteen-mile, and McDonald creeks as tributaries to Issaquah Creek. More than 75 percent of the basin is forested, with the remainder in wetlands and pastures. Over 40 percent of the land is in public ownership with Washington Department of Natural Resources, Washington State Parks, King County Parks, and City of Issaquah Parks. Less than 10 percent of the basin is comprised of urban and cleared areas, but this urbanized area is located in and around the floodplains of Issaquah and Tibbetts Creeks near Lake Sammamish.

Flooding is widespread and recurrent in the lower Issaquah Creek basin. Much of the City of Issaquah is built on the floodplains of Issaquah and Tibbetts Creeks, and many homes and businesses in the city are flooded when the streams overflow their banks. Floods in 1986 and 1990 caused extensive property damage and threatened to undermine several houses.

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Sammamish River

The Sammamish River flows 14 miles from Lake Sammamish to its mouth in Lake Washington. Major tributaries include Bear, Little Bear, North and Swamp Creeks. The entire river is part of a flood control project completed by the US Army Corps of Engineers in 1966 that channelized, dredged, and straightened the previously meandering channel network. King County now provides long-term maintenance.

The majority of the Sammamish River basin lies within incorporated areas including Kenmore, Bothell, Woodinville, and Redmond. A wide variety of land uses are found along the river, which was once almost exclusively agricultural. In and around city cores, land uses include moderate-density residential, business districts, and some light industrial uses.

Major river flooding is infrequent since the river was deepened and straightened. However, ongoing development has reduced flood storage areas and increased runoff volumes and peak flows. The largest flood event for the present day channel occurred in 1997, when the Sammamish River Trail overtopped near NE 124th Street and several properties along Lake Sammamish experienced overtopping or damage.

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Flood Warning & Preparation

For assistance during a flood event call 206-296-4535/ 800-768-7932. If it is an emergency, call 911.

The King County Flood Warning Program warns residents and agencies of impending floodwaters on major rivers so they can take action and prepare themselves before serious flooding occurs. Once a flood warning is issued, residents should prepare for flooding.

- Learn how to prepare for a flood and what to do during and after a flood

-Learn more about what you can do

-Explore additional resources