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Study examines how nearby roads reduce habitat, rearing quality for salmonids

Streams less than 30 meters from roads in the interior Columbia River basin have significantly less wood debris in the stream than those waterways greater than 60 meters from roads, reducing habitat and rearing quality for salmonids in those streams.

River managers have made considerable efforts to improve habitat conditions in streams where young salmon reside, but these efforts are often hindered by “the legacy of past land management decisions,” according to an article published in June in the North American Journal of Fisheries Management.

That legacy includes roads built for logging, recreation, fire suppression and transportation. The impact of this network of existing roads is significant since 29 percent of the total stream mileage in the study zone is within 60 meters of a road and the recovery of in-stream wood may be limited by the presence of these roads.

The study and resulting article looked at the average reduction in in-stream wood at reaches near roads in the interior Columbia River basin and found significant reductions in overall wood frequency (26 percent), volume (42 percent) and pool-forming frequency (37 percent) for reaches within 30 meters of a road. Significant reductions also occurred for stream sites less than 60 meters from a road.

The results of the study lead the authors to conclude that there is a need for road removal and road relocation projects in order to increase wood in streams.

“Road decommissioning, relocation, and improvement projects can have a large impact on improving habitat conditions by reducing road effects on instream wood,” said lead author Christy Meredith, data analyst, PacFish Infish Biological Opinion Effectiveness Monitoring Program, with the U. S. Forest Service.

However, there is a need for additional evaluation of these efforts to determine the types of projects that are most successful, she added. “In the many cases where roads cannot be removed, findings suggest that managers should adjust expectations regarding the amount of wood to expect or to use alternative strategies, such as wood additions.”

“Reductions of In-stream Wood in Streams near Roads in the Interior Columbia River Basin” ( and, was researched and written by Meredith, Brett Roper, National Aquatic Monitoring Program Leader, and Eric Archer, Program Leader, all with the Pacfish Infish Biological Opinion (PIBO) Effectiveness Monitoring Program (EMP) at the U.S. Forest Service in Logan, Utah.

Meredith said this research was funded by the U.S. Forest Service and the Bureau of Land Management.

“Cover provided by in-stream wood contributes to higher densities of fry and juvenile salmonids,” the article says. Wood protects these fish from predation and high flow events, stores and sorts sediment for spawning, shapes channels and creates pools and backwaters.

“Ultimately, reductions in wood have cascading effects on many aspects of salmonid habitat,” including up to a 50 percent reduction of historical “pool frequencies.”

Some of the damaging impacts of high road density, according to the article, are “adverse effects on hydrology and geomorphology, increased habitat fragmentation, increased invasion by exotic species, degraded water quality, and degraded riparian habitat quality.” Much of this is the result of the removal of streamside vegetation, increased erosion and channelization, changes to a stream’s flows and the “alteration of surface and subsurface flow paths.”

The bottom line is that since most in-stream wood comes from a stream’s riparian zone, when a road is nearby there is little available for the stream itself.

The study also found that the amount of wood varies based on climate, land use (grazing for example) and local geomorphic conditions. We “advocate setting different targets regarding how much wood to expect based on these natural conditions,” she said.

“Our findings illustrate that roads can have the same effect on wood in streams as large changes in climate, geomorphology, and management,” the article concludes.

“Road-relocation and improvement projects that minimize the effects of roads on stream conditions are currently a priority within the U. S. Forest Service,” Meredith said. “While there is a focus on removing roads near streams, this is often difficult because of the high public demand and use of these roads.” These trade- offs will be assessed as the Forest Service implements its Travel Management Rule, which designates roads and trails that are open to motor vehicles.

Meredith added that this and other research done by PIBO-EMP complements other efforts in the interior Columbia River basin, including implementation of the Watershed Condition Framework (the U. S. Forest Service’s National Assessment of watershed condition), and will continue to be used in conjunction with “future assessment and prioritization of stream restoration efforts in the interior Columbia River Basin.”

Columbia Basin Bulletin The Columbia Basin Bulletin e-mail newsletter is produced by Intermountain Communications of Bend, Oregon and supported with Bonneville Power Administration fish and wildlife funds through the Northwest Power and Conservation Council's Columbia Basin Fish and Wildlife Program. Articles republished by The Dalles Chronicle with permission.


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