IMA was contracted by the owner of this property to stabilize an eroding bank to prevent a channel avulsion on the Lemhi River.  This reach of river has been subject to channel straightening and extensive rip rap installation.  As a result, the project reach experiences abnormally high hydraulic forces and the client had been losing property at a concerning rate.  The river had demonstrated rapid erosion though a healthy stand of cottonwood trees, so conventional bioengineering techniques were not appropriate.  Instead, the bank stabilization design consisted of  a rock barb to deflect flows and an engineered log jam to hold the stream bank.  The Lemhi River contains several endangered and protected fish species.  Construction techniques and timing were critical to adhere to permit constraints.

Pre-construction - rapid bank erosion through a healthy stand of cottonwoods

Pre-construction - rapid bank erosion through a healthy stand of cottonwoods

Design specifications required various diameters/lengths of logs, rootwads, and slash

Design specifications required various diameters/lengths of logs, rootwads, and slash

Construction was completed with the help of the landowner

Construction was completed with the help of the landowner

Post-construction - the engineered log jam stabilizes the bank, absorbs stream energy, and provides cover for fish

Post-construction - the engineered log jam stabilizes the bank, absorbs stream energy, and provides cover for fish