The Allen Lake Outlet Rapid Assessment describes and evaluates the capacity of a low gradient outlet of Allen Lake, near Sammamish, Washington (formerly Mud Lake) to convey flows.

Following reports of local flooding, King County directed a reconnaissance team to assess the condition of this unnamed channel, known as WRIA 08.0111A. The team conducted a site visit September 7, 2010, and observed points on a reach of channel that extends approximately 6,000 feet from NE 8th Street to 244th Avenue NE. During the rain events of December 9-16, 2010, flooding of NE 8th St. east of 244th Ave NE affected access to homes. The roadway was officially closed from December 13 to 16, 2010.

After collecting information during site visits to explore the cause of flooding and evaluate the need for a capital improvement project, the team is recommending a feasibility study that incorporates hydraulic modeling of the channel to evaluate the effectiveness and consequent effects of alternatives. The study will determine the feasibility and preferred alternatives to consider for funding in the capital improvement six-year plan.

The Allen Lake Outlet Rapid Assessment is provided in Adobe Acrobat format for compatibility with a wide variety of browsers and computer systems. For help with Acrobat, please see our Adobe Acrobat help page.

Download here:

• Allen Lake Outlet Rapid Assessment  (7.8 Mb)

For questions about the Rapid Assessment Report, please contact Claire Jonson, Senior Engineer, King County Surface Water Engineering Services.

Related information

• Lake Allen Outlet Project
• Allen Lake
• Stormwater services and information

Related agencies

• Dept. of Natural Resources and Parks
• Water and Land Resources Division