County works to reduce Lake Sammamish flooding

 

In response to concerns about seasonal flooding expressed by residents living on the shores of Lake Sammamish, King County will remove brush and trim trees that slow the flow of water from the lake into the Sammamish River.

In addition to mowing more frequently and cutting back willows on both banks of the slough between the lake and the river, the county may be able to remove silt and debris that have accumulated there over decades.

Mark Isaacson, director of the county’s Water and Land Resources Division, presented the action plan for the Sammamish Slough to the Bellevue City Council on June 21. Shoreline property owners have complained about recent flooding damaging their land and docks.

Widespread flooding was actually a regular occurrence in the Sammamish River valley until 1964, when the U.S. Army Corps of Engineers completed a project to deepen and straighten the meandering waterway, which flows north from the lake through Redmond to Kenmore, where it empties into Lake Washington.

To ensure the water level in Lake Sammamish doesn’t drop too much during the summer, a shallow, concrete weir or sill was built in the slough to stem the flow as part of the Army Corps project.

The county will monitor the lake level to confirm that mowing and willow removal reduce flooding. Isaacson told the council the county is also looking into removing the debris downstream from the weir next fall with money from the King County Flood Control District.

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