Project goals included stabilizing an eroding river bank, reducing the flooding frequency at a home-site, and creating juvenile overwinter habitat for Steelhead and Chinook salmon.  IMA performed an extensive survey of the property and merged this survey data with available LiDAR data. Ground water monitoring wells were installed with automated data loggers to monitor fluctuations in ground water levels.  Site topography, historic flow data, and groundwater data was used to model the existing hydraulic conditions and design a project that would address project goals.  IMA’s design included a bioengineered bank stabilization design to address an unstable bank, and a grading plan to construct a backwater channel to provide juvenile salmonid habitat.  The backwater channel also functions to funnel flood flows away from the adjacent homesite and back into the main stem river. The channel was designed to carry 150 cfs, or the equivalent of the 5-yr flood, back to the river.  A complete construction ready plan set was delivered to the client that included grading, revegetation, and construction sequence specifications.  IMA was on-site during construction to provide management and oversight. 

Before - Unstable, eroding bank

Before - Unstable, eroding bank

After - The bank is stabilized with multiple layers of plantings and erosion control fabric

After - The bank is stabilized with multiple layers of plantings and erosion control fabric

Surveying the area before the new backwater channel was constructed

Surveying the area before the new backwater channel was constructed

Installing groundwater monitoring wells prior to design completion

Installing groundwater monitoring wells prior to design completion