Filbert Creek Sediment Impact Investigation and Channel Redesign

Filbert Creek passes under SR-524 through a 14-foot wide, three-sided box culvert that was constructed in 2007. Shortly after construction, an upstream section of Filbert Creek that was restored as part of the culvert project failed, causing a large amount of sediment to deposit within and downstream from the culvert, nearly plugging the culvert outlet. WSE, working in partnership with NHC and RH2 Consultants, conducted an investigation to determine the cause of the channel failure and to develop a solution.

Role / Services: WSE completed a thorough inspection of the site, which included collection of sediment data (including laboratory sieve analyses) and discussions with local landowners. A comprehensive evaluation was then undertaken, which included review of as-built plans and photographs, hydrologic and hydraulic modeling, evaluation of sediment transport and deposition, a thorough examination of channel stability, and development of a stable channel design. Findings and recommendations were presented to City staff.

Outcome: The proposed plan calls for the channel to be reconstructed or restored using a stable “roughed rock channel design”. An on-site meeting was held with the City and WDFW to discuss the proposed repairs, all of which were well received.