Restoring large wood in Central Idaho – a preview


By Ashlynn Goody and Cassi Wood 

We are thrilled to announce that The North American Journal of Fisheries Management will soon publish an article co-authored by Cassi Wood, our Central Idaho Project Manager.  Cassi and Jim Gregory, a longtime Trout Unlimited (TU) consultant, recently presented their research at the Annual Meeting of the Idaho Chapter of the American Fisheries Society.   

Cassi Wood & Jim Gregory presenting their research before the Idaho Chapter of the American Fisheries Society.

This study focuses on the Yankee Fork, a river that flows approximately 28 miles from its headwaters in the Salmon River Mountains to its confluence with the Salmon River. The study area is 7.5 miles long, beginning at the confluence with Eightmile Creek and ending at the mouth of Jordan Creek. The Yankee Fork was an easy selection for study; Cassi has been working with partners to restore the Yankee Fork from mining and timber harvest for nearly a decade. 

Unanchored pieces of large wood, placed to mimic an avalanche.

Upon visiting the Yankee Fork in my first week at TU, it’s easy to see why someone would want to dedicate ten years of work to this area. Reconstructing just one mile of the badly damaged river required removal of more than 100,000 cubic yards of dredge tailings; tall rows of piled rock which have confined more than 6 miles of the river to a flume-like channel since the Yankee Fork Gold Dredge finished mining it in 1952. For reference, your average dump truck can only haul 15 cubic yards. That’s over 6,600 dump trucks! It’s hard to imagine how large and impactful these dredge tailings are until you’re standing near one as it hovers a good 10 to 15 feet above you. If the piles of rock that stretch on for miles weren’t enough of an insult, an even larger portion of the watershed was harvested for timber right to the river’s edge to support the mining boom of the late 1800’s. Relocating the dredge piles is regrettably only a portion of the work needed to restore this area. Large wood, now missing from the upper reaches of the river, must be added back in order to create a healthy habitat for fish. Wood in the stream does more than just provide shelter over the heads of our underwater friends; it slows the water they swim in, sorts the gravel they spawn in, and feeds the insects they eat. Without large wood, rivers become sterile and inhospitable for fish.  

A bull trout using wood for cover in the Yankee Fork. 
The Bonanza Project section of the Yankee Fork. Some dredge tailings remain to the left of the re-constructed river. 

The upcoming article will share details of the authors’ research using large wood restoration techniques in the upper Yankee Fork that mimic nature. Their work contrasts with the use of highly engineered log structures, commonplace in the realm of river restoration. Those buried and anchored logs, sometimes even bolted together, are intended for places that cannot risk damage to downstream structures like bridges. But wood that cannot move in concert with the dynamics of an otherwise healthily changing stream can cause more harm than good… and cost a lot of money to construct. Cassi and her partner researchers restored wood to the stream by adding loose trees and logs to the upper Yankee Fork, where risk to downstream structures was low. The project simulated the natural processes of wood recruitment that create healthy rivers. Chiefly, from fallen timber, avalanches, and creek ‘blow-outs’. Next, they evaluated how much of the loose wood in the stream might naturally move over time.  

A map of the project area.

For the study, twenty of the added pieces of large wood were implanted with radio tags and tracked each summer for five years (2015–2019). In 2017, the Yankee Fork experienced a 25-year spring run-off event. The results of the author’s research show that in rivers like the upper Yankee Fork, unanchored large wood moves only very short distances downstream, even during very high flows. The results also show that the total amount of large wood restored to the study area did not decrease over time.  

This research was a huge success; it confirms there are streams where large wood can be restored at a lower cost and in ways that compliment natural rivers, which opens more possibilities for future restoration across the west. This work, part of the collection of restoration projects by Cassi and her partners, is yet another example of TU’s commitment towards ensuring that high quality critical habitat is ready to bring home the numbers of salmon and steelhead that Idaho deserves. 

Tracking tagged wood movement.

TU & partners working to restore large wood in the Yankee Fork.

This research was funded by the US Bureau of Reclamation, the Shoshone-Bannock Tribes, TU, US Fish and Wildlife Service, and the US Forest Service.  TU sincerely appreciates the US Forest Service’s Helitack crew, who installed the helicopter-placed trees, and to Boyd Foster Backhoe Service, who installed the trackhoe-placed trees. Numerous technicians from the Salmon-Challis National Forest assisted with the installation of saw-cut trees, logistics, and assessment. 

We can’t wait to share the full copy of the article with you once it is published and available to the public. 

For specific questions regarding this article, please contact Cassi Wood at

Ashlynn Goody is the Policy and Outreach associate for Trout Unlimited’s Idaho Water and Habitat Program.  Ashlynn works out of TU’s Boise office. Cassi Wood is a Project Manager for Trout Unlimited’s Idaho Water and Habitat Program. Cassi works in the field of Central Idaho’s beautiful landscape. 

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