Pacific Northwest Research Station

North American beavers were once so plentiful in the Scott River Basin of northern California that the area was referred to as “Beaver Valley” by the first Euroamerican fur trappers who travelled there in the early 1830s. But heavy trapping of the fur-bearing rodent—one historical record reports 1,800 beavers trapped by a single man in one month in 1836 along the two forks of the Scott River—ultimately caused the species to rapidly decline in number. As beavers departed the landscape, so, too, did their trademark dams, which played a critical role in shaping the hydrology of the Scott River and its tributaries. Beaver removal, along with activities like mining, deforestation, road construction, and agriculture, have had major impacts on the Scott River Valley watershed over the past 150 years.

Fast forward more than a century, and the Scott River basin and beavers are, once again, intertwined. In 2014, the Scott River Watershed Council, an independent nonprofit organization, launched an initiative to reintroduce the benefits of beaver dams to the basin by building “beaver dam analogues,” also known as BDAs. These structures, which are made of wooden posts woven with vegetation and sediment, are strategically placed in streams to mimic the effects of natural beaver dams. The streams included in the project flow through private lands and are important habitat for federal Endangered Species Act-listed southern Oregon/northern California coast coho salmon. The council installed the BDAs with the goals of improving instream habitat for salmon, raising groundwater levels, and reducing stream channel incision.

To date, 20 BDA structures have been installed at six sites and the council has plans for more. Beavers have been active, or have taken over maintenance, at all of the sites, and agency personnel and landowners feel that beaver populations in the Scott Valley are increasing in number.

“Most of the private landowners involved in this project are ranchers who also grow hay and who have largely positive views of beavers and beaver dams, so long as they do not interfere with irrigation infrastructure,” said Susan Charnley, a Pacific Northwest Research Station research social scientist and author of a case study on the project. “Monitoring data and interviews with stakeholders indicate that BDAs are starting to achieve their goals and are benefitting both landowners and fish.”

The case study report includes a detailed description of the pioneering restoration project – the first of its kind in California – and the experiences of partners and stakeholders involved in it – as well as a discussion of the lessons learned.

Although this watershed restoration project was the first in California, results are showing promise, and other California groups are starting to use this restoration technique. The project offers important lessons for undertaking beaver-related restoration on private lands across the west.

Read the case study online at https://www.fs.usda.gov/treesearch/pubs/57456.