Wednesday November 30, 2022
Newswires —
The Lemhi River consisted historically of a large active floodplain containing complex fish and wildlife habitats. The Lewis and Clark expedition noted in their journals an observation of a fish weir constructed by Native Americans that spanned multiple channels, suggesting that the river system contained a network of braided channels. The Lemhi River Valley is well known for its abundant resources that supported, among other things, the fur trade, mining, and agricultural development. With an influx of people, the town of Salmon was established. As the region grew in population, land development expanded throughout the valley. Agricultural demands and associated infrastructure needs (e.g., transportation) resulted in modification of the historic floodplain, leading to straightening and channelization of the Lemhi River. The once active floodplain became isolated from the river, and side channel, riparian, and instream habitats that are important for fish were lost
In recent years, Idaho Department of Fish and Game (IDFG) has worked with landowners in the Lemhi River Valley to return the Lemhi River to a more natural state through a variety of restoration projects. The goal of these projects is to create a diversity of habitat types that are crucial for anadromous and resident fish of all life stages (i.e., fry, parr, presmolt, smolts, and adults). One of the limiting factors for fish in the Lemhi River watershed is overwintering habitat for juvenile fish, particularly for Chinook Salmon. Thus, IDFG biologists began to focus on improving habitat for juvenile fish. In an effort to reduce water velocities and create a variety of good habitat features, biologists prescribed actions that included braided channels, meanders, large woody debris structures, deep pools, and grading to re-establish the floodplain. Many of these projects require a large amount of woody debris to create ideal habitat structures. Some of these structures that use large woody debris include bank roughening to provide bank stabilization and erosion prevention and engineered log jams to create scour pools.