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Crooked River IDAHO

Historic dredge mining drastically altered river and floodplain habitat throughout Crooked River, near Elk City, Idaho. These changes effect the overall function of the river, valley, and the species that historically thrived here.

In the 1940s, lower Crooked River was dredged mined with a bucket-line Yuba dredge. This type of mining left large tailing piles and ponds throughout the valley and a tortuously meandered river.

The Nez Perce Tribe, Nez Perce Clearwater National Forest, Bonneville Power Administration and other interested agencies partnered in 2011 to develop a strategy to restore Crooked River.

A complete survey of the current conditions, including a hydrologic, hydraulic, sediment, floodplain and wetland analysis was completed in 2012. This survey also documented the existing instream habitat available for salmon and steelhead.

The survey concluded that over 75% of the valley was disconnected from the river channel due to the large tailing piles and ponds.

The altered valley changed the flow patterns in Crooked River and limited areas for salmon and steelhead to spawn and overwinter. Habitat qualities would remain diminished without direct restoration.

A restoration plan was developed to rebuild the river channel and floodplain in the lower two miles of valley over a six year period.

Restoration objectives include developing a floodplain that is accessed each year, creating a river channel with a more natural meander pattern, adding instream habitat complexity, including large woody debris and boulders, and creating off channel habitat for fish and wildlife.

Specific design features, including riffles and bank stabilization are built into the plans and implementation, but the design premise is to allow the river and valley to migrate, live and breathe.

Work began in the lower quarter mile of the valley in 2017. This work included building floodplain and adding instream habitat structures.

Crooked River Option 2 pre-construction.
Option 2- during construction.

Over 10,000 cubic yards of cobble was graded and 17,000 cubic yards of tailing piles were hauled off site and stockpiled. The river channel was not moved during this phase of restoration; instead, 10 large woody debris jams were added to the river to promote pool scour. The river will adjust in size as pools scour and point bars form.

Option 2 - post construction.

Large wood was added to the floodplain to create micro-habitat and slow surface flow over the floodplain during the spring. Over 5,000 plants, including cottonwoods, alders, fir and spruce trees, willows, sedges and rushes were planted. During the spring of 2018, the floodplain was accessed. Flow across the floodplain deposited soil and seeds, scoured backwater alcoves and created habitat for fish and amphibians.

Phase 1 kicked off in 2018, with the development of 22 acres of floodplain and 4,500 feet of new river channel. Over 60 volunteers from various agencies participated in fish salvage efforts prior to restoration activities commencing.

Crews from the Nez Perce Tribe, Nez Perce Clearwater National Forest, Idaho Fish and Game, US Fish and Wildlife, National Marine Fisheries Service, Montana Conservation Corps, and Trout Unlimited worked together to salvage as many fish and aquatic organisms in the channel prior to dewatering.

Video courtesy of BLUEWATER SOLUTIONS, LLC

Phase 1 began by grading tailing piles and filling in the existing channel and ponds. Pockets of vegetation at floodplain grade were preserved where possible.

The floodplain height is designed to flood each year. This will allow for deposition of organic material and seeds to promote vegetation growth. A low floodplain promotes moisture storage and provides off channel habitat for fish during high flows.

Soil was stockpiled, where possible, to spread in future phases to speed recovery of the riparian area. Once the floodplain is complete, the new channel is roughed in.

Over 60,000 cubic yards of material was distributed and another 16,000 cubic yards were imported to create the floodplain.

Trees are salvaged on site and also provided from an adjacent timber sale to create 21 large woody debris structures. These structures provide bank stability and promote pool functions throughout the new river channel.

1,500 feet of side channel was excavated and 10 acres of low areas and ponds were preserved to provide floodplain complexity, wetland areas and additional habitat for fish, birds, and wildlife.

The entire project area will be planted in future phases and the river will be returned to its new channel in the summer of 2021.

Work will continue through 2021 and over 2 miles of the Crooked River Valley will be rehabilitated. This work will restore a more natural hydrologic and hydraulic regime to allow fish habitat to form naturally with the overall goal of increasing abundance and productivity in this watershed.

Stay tuned for updates on this project.

Photo: Hagerty Ryan, USFWS

Created by Jenifer Harris, Project Manager

Department of Fisheries Management, Nez Perce Tribe

Funding for the project provided by Bonneville Power Administration, US Forest Service, and the National Marine Fisheries Service through the Idaho Governor's Office Species of Conservation

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