Twisp Horseshoe Floodplain Restoration

The Horseshoe Floodplain Restoration project (Twisp River 11.1-12.1) was completed in October 2022. This project took place on a 3,500 foot long segment of the Twisp River and included the installation of 10 mainstem large wood jams. These jams addressed the top priority ecological concerns in the Lower Twisp River Assessment unit in the Methow Subbasin by increasing instream structural complexity, reconnecting side channels, increasing floodplain connectivity and by restoring habitat forming processes that will benefit Upper Columbia spring Chinook and Upper Columbia steelhead in the long term. The project involved the strategic placement of engineered large wood jams using heavy lift helicopters and heavy tracked excavators. The installation of six of these structures also included pool excavation on the upstream end. All 10 wood structures immediately provided cover habitat and the six excavated pools immediately provided deeper pools better connected to groundwater thermal refuge. Overtime, three of the apex wood structures will serve to increase floodplain inundation to areas of the floodplain with existing groundwater fed pools.

Emulate and restart geomorphological processes driving wood and gravel recruitment and retention to improve spawning and rearing conditions for spring Chinook and steelhead in the Twisp River. Additionally, to reestablish large wood structures to increase channel roughness and hydraulic complexity to restore peripheral and transitional habitat necessary for rearing spring Chinook and steelhead in the Twisp River.