Friday, June 10, 2011

Logjams for Salmon and Bull Trout in the Skokomish River

The Skokomish River is the largest source of fresh water for Hood Canal, a 70-mile natural fjord-like side basin of Puget Sound. It is also the most frequently flooded river in Washington State. The Skokomish River is home to four species of salmon and trout that are listed as threatened under the Endangered Species Act. After years of intense logging, road building and development in the watershed, strong partnerships have formed to turn the tide of worsening conditions and restore the river.

The U.S. Fish and Wildlife Service (FWS) provided funds to the Skokomish Tribe to complete one of the largest logjam projects in the Pacific Northwest. Through the support of many partners throughout Hood Canal, 30 massive man-made logjams were placed along 1 mile of the mainstem South Fork Skokomish River last summer. These structures were installed to stabilize streambanks, restore stream function, and improve aquatic habitat in a reach that had been cleared for a proposed reservoir in the 1950s. The goal of the project is to improve fish habitat by increasing pools and habitat complexity--large pools create microhabitats where fish can hide and stay cool. 

Logjam construction             (Photo: Skokomish Tribe)
 To create the logjams, over 2,000 second-growth trees were uprooted at upland sites and transported to the stream by helicopter. The trees averaged 100 feet long and were embedded far into the streambanks using excavators. Smaller trees and log sections were then carefully wedged in to create a very complex and dense logjam. Planting of trees along banks and within the floodplains has also begun and will continue in following years.

The structures were placed strategically in a section of the South Fork Skokomish that had few natural logjams. This area, approximately 11-14 miles upstream from where the Skokomish empties into Hood Canal, was heavily logged in the 1950's and 1960's in preparation for a dam that was never built. The lack of streamside structure allowed the river to subsequently grow wider and shallower, causing the water temperature to rise. The addition of these logjams should cause the water to carve out a deeper, more natural channel, result in cooler temperatures, and help retain spawning gravels for the fish to use. In addition, vegetation is likely to grow along the edges of the logjams, eventually shading the river and providing natural structure.

Fortunately, the logjams held up well to last winter’s storms and flooding. Few components of a small number of the jams were lost, while several of the structures even managed to collect additional logs that were floating downstream. As of April 2011, deep pools had already formed downstream of the logjams, creating places for fish to rest, find refuge, and feed. With these habitat improvements, the upper reaches of the Skokomish River should be able to support larger runs of threatened steelhead and bull trout. Additional benefits will accrue for federally-listed summer/fall and spring Chinook salmon, coho salmon, rainbow and cutthroat trout, and lampreys.

Before construction              (Photo: Skokomish Tribe)

After construction                (Photo: Skokomish Tribe)
The Skokomish Tribe sponsored this project. Partners included the U.S. Forest Service, TEAMS Enterprise, FWS, Hood Canal Coordinating Council, and the Skokomish Watershed Action Team. The Skokomish Tribe acquired $729,000 in Washington Salmon Recovery Funding Board and FWS grant funding for this project. The Forest Service contributed $525,000, which includes the value of the trees, planning and construction costs.

More logjams are needed downstream of the project area and construction will begin as soon as funding and approval is acquired.