Oregon biologists are cutting down trees to save rivers
Can felling trees into the Sandy River restore the waterway's ecology and bring back endangered species of salmon and trout?9
Located 60 minutes east of Portland, Sandy River has supported thousands of residents and local businesses for generations. Tributaries of the river, Still Creek and Salmon River, were once popular fly-fishing destinations. But in the second half of the 20th century, all that changed: once abundant salmon and steelhead trout populations collapsed. By the late ’90s, both species of fish were listed under the Endangered Species Act.
The decline can be traced back to a 1964 flood, the most destructive weather event recorded in the region. Authorities, eager to protect local infrastructure from future floods, channeled the waterways and stripped them of natural complexities like wood and rock — both crucial to spawning marine life.
The changes made Sandy River increasingly inhospitable to fish. As a result, today’s fish population is only 20 percent to 40 percent of its historic number. But recent research suggests that removing natural debris from the rivers is also counterproductive for flood mitigation. "Removing the roughness elements actually increases the velocity of the water," says Mark McCollister, director of Habitat Restoration at The Freshwater Trust, "and that causes greater flood risk downstream."
The Freshwater Trust is a not-for-profit organization that devises and implements plans to restore freshwater ecosystems. The organization is currently working in conjunction with the USDA Forest Service and the Bureau of Land Management to restore the Sandy River basin. To restore the rivers to their original status, the team first determines the waterways’ natural rhythm using LIDAR (laser-based, airborne mapping technology) at critical sites. Then, they coordinate efforts to recreate that rhythm, mostly by carefully downing trees into the water to create spawning pools. Over the last three years, McCollister and the team have been working patiently to map, engineer, and reintroduce natural obstacles back into Still Creek, the latest site targeted for restoration.
Planning for the entire region’s rehabilitation took 10 years — half of that time was spent on the Salmon River alone. Salmon and steelhead are returning to their native habitats, but the team’s efforts to restore the basin are ongoing. "Some people come out and say this is the most beautiful stream they’ve ever seen," says Greg Wanner, a supervisory fish biologist with the USDA Forest Service. "But looking from a fish’s eye, you see a river that needs some love."