The Elbow Coulee projects are proposed to improve access, rearing habitat, and reduce stranding in two side channels of the Twisp River, located at approximate RM 6.5.  The project includes two components, Elbow Coulee Adaptive Management on the Left Bank, and the Right Elbow Side Channel immediately downstream and across the river.  Together, the proposed actions will restore function and reconnect isolated habitat value in about 1500 lineal feet of side channel.

Historically, the Twisp River meandered through the floodplain portion of these properties, carving new channels through riparian cottonwood galleries and wetlands; recruiting spawning gravels and large wood (LW), and creating the complex habitats that support all life stages of listed fish stocks.  This reach of the Twisp River once contained numerous side channels and flood channels.  Many of these channels are disconnected from the river by push-up levees built in response to the 1972 floods.

The Right Bank Elbow side channel project is an existing groundwater-fed side channel that is isolated from the river by a push-up levee across the inlet.  The lower portion of the existing channel has perennial ground water flow and is connected to the Twisp River for at least a portion of the high flow period each year. Visual observations indicate that this channel supports some level of fish use throughout the year.  Removing the constructed levee will allow fish to enter the side channel from the upstream end, increasing the off-channel habitat available for juvenile spring Chinook and steelhead rearing.

Proposed actions:
1) The Elbow Coulee Adaptive Management component will enlarge a previously constructed levee breach, which established an inlet to a previously isolated side channel in 2008.  This action will increase flushing flows through the side channel by engaging Twisp River when flow is greater than 250 cfs and significantly increasing velocity and volume at elevated flows. This action will reduce stranding of juvenile spring Chinook and steelhead in the upper portion of the side channel and allow the side channel to be more self-sustaining by flushing sediment accumulations annually. The project proposes to enlarge the breech at the inlet of this side channel and re-grade the high portion of the channel to address these limitations.  The project actions will be implemented using a minimally invasive approach relying primarily on hand tools and manual labor.

2) The Right Elbow Side Channel component will breach an existing levee on the Right Bank to reconnect an existing 800-foot long groundwater-fed channel.  The levee breach will create a new inlet to allow an upstream connection at flows greater than 500 cfs.  This action will provide rearing habitat for juvenile spring Chinook, and steelhead. Proposed work in the Right Elbow side channel at Twisp River RM 6.35 includes reconnecting the disconnected groundwater-fed side channel, removing a push up levee that was built across the inlet in response to the 1972 flood and minimal excavation to restore flows to the lower portion of the side channel in place.