Boaters, endangered salmon and out-flowing water from Lake Sammamish share “The Slough” to the Sammamish River at Marymoor Park.

Over the last decade, this 1960s Corps of Engineers flood control project has been altered. Though King County agreed to “operate” the project, infrequent maintenance, an illegal rock dam and sediment build-up now block flow.

The Corps of Engineers designed the outlet channel at Marymoor to handle a “once-in-a-decade” storm. Key to passing this flow downstream was a channel clear of obstructions.  When constructed, King County agreed to maintain it to this standard each year. But fast growing willows were planted in the channel and maintenance was reduced to once every four years. Unfortunately, the willows created superb habitat for bass. (Bass love to eat young salmon.) And cuttings from periodic vegetation maintenance were left behind resulting in sediment build-up.

The Corps of Engineers recognized impending problems in 2008 and notified the county that the Sammamish flood control project was being decertified, making it ineligible for federal support. Even earlier than 2008, public records show the corps advised the county it should inform lake residents their properties and improvements would be impacted.

Unfortunately, their prediction came true, as many who’ve lost docks, bulkheads, and landscaping would attest — losses that easily have reached millions of dollars.

At resident urging last year, the county returned to annual vegetation trimming. However, some county officials are advocating delaying removal of the sediment and debris, offering instead a long-term, costly solution that would rebuild this section of the river.

Common sense calls for clearing today’s debris and blockage problems. Then we should take a comprehensive look at cost-effective solutions that balance water flow, water quality and the needs of salmon and recreational users.

Lakeside jurisdictions, lake residents and the Corps of Engineers must be involved. Otherwise this federally funded project is a non-navigable, impeded floodway that has negatively impacted salmon and threatens greater and greater damages each year.

Dr. Martin Nizlek is a retired civil engineer, a board member of the Washington Sensible Shorelines Association, past president of the West Lake Sammamish Association and a Bellevue resident of 20 years.