When Lewis and Clark traveled up the Missouri River in 1804-06, they reported seeing beaver dams in every tributary. Scientists estimate 250 million ponds dammed by castor canadensis covered the landscape at that time, and sediment trapped by these dams produced much of the rich farm land later utilized by settlers.
Fur trappers, however, immediately followed the Corps of Discovery Expedition. Trapping brigades wiped out beaver populations drainage by drainage. Researchers estimate that by 1900, only 1 percent of North America’s historic beaver population remained.
The carnage continued, as beavers were blamed for flooding property, destroying roadways and harming trees. Last year, federal agents killed more than 23,000 beavers believed to be impacting property.
Now, in an about-face that bodes well for beavers, stream restoration professionals are turning to small wooden impoundments as a way to improve fish habitat and riparian areas across the West. Made of pounded posts and woven willow whips, these beaver dam analogs are considerably cheaper than other restoration techniques.
Even if BDAs don’t attract beavers to an area, they mimic the action of natural beaver dams — slowing stream flow, improving groundwater connectivity to the surrounding area and building up sediment to improve riparian areas. Juvenile fish can swim through gaps in BDAs, and the minimum fish-jumping height for older fish can be achieved by installing multiple BDAs.
Beaver dam analogs can also help reduce stream water temperature, according to Stephen Bennett, an adjunct professor in watershed sciences at Utah State University. BDAs can increase groundwater connectivity through annual spring flooding and by the hydraulic action of the standing water behind the dams.
The temperature underground is about 50 degrees, Bennett said. The log structures also provide some shade, and scouring around BDAs can create deeper pools, but the goal is to improve riparian areas, allowing hardwoods to grow and provide much needed shade.
Support for this new technique does not always extend to government agencies — many officials don’t know how to regulate the structures. Some agencies have cited flood risks in denying permits for BDA projects.
In many cases, streams chosen for BDA projects provide habitat for endangered species, which adds to the bureaucratic hurdles, and installing structures that completely span a stream deemed navigable could trigger an Army Corps of Engineers review. Post-project monitoring might also be required.
The Oregon Department of State Lands attempted to draft new rules to expedite implementation of BDAs, but the process bogged down over statewide versus regional requirements and has been delayed.
Getting the word out on beaver dam analogs was the goal of a workshop held in Grant County July 24-26. Thirty-five stream restoration professionals attended talks at Grant County Regional Airport and field trips to Murderers Creek, Camp Creek and Bear Creek in the Malheur National Forest.
Attendees included people from watershed councils, soil and water conservation districts, federal and state agencies, the Confederated Tribes of Warm Springs and private contractors.
The purpose of the workshop was not just instructing people on how to build beaver dam analogs or persuading them to use the technique, but also to release new information on what’s been accomplished, said Elise Delgado, project manager for the South Fork John Day Watershed Council.
“Not everyone will leave a believer,” she said.
The workshop was sponsored by the John Day Basin Partnership, which represents groups from Prairie City to the Columbia River. Herb Winters, a project manager at the Gilliam Soil and Water Conservation District, sits on the partnership’s steering committee.
“There’s lots of angst about BDAs,” he said.
Winters said he hopes to see the practice used across the basin, employing best management practices and completing quality projects.
“We don’t want failures that will give BDAs a bad name,” he said, calling them a potential game-changer.
Winters said he believes all the group’s partners support BDAs, but they need to take the low-hanging fruit first and take it slow. He noted that many opinions exist on funding sources and permitting, but both state and federal agencies are taking a serious look at this new technology.
The goal should be low-impact construction with no heavy equipment and not to anger people, Winters said. He noted that over time BDAs disappear as sediment builds up behind the structure and vegetation grows over them.
Light on the land
Two BDA projects last year in Grant County took dramatically different approaches. While a project on private land on the South Fork John Day River near Izee was low-tech, with posts pounded in by hand and willows found at the site weaved in between, a Forest Service project on East Fork Beech Creek north of Mt. Vernon utilized heavy equipment, with excavators brought in to drive posts into the stream bed.
Nick Bouwes, a professor at the College of Natural Resources at Utah State University, advised workshop members to be efficient in how they build BDAs because a project might require a lot of them. He said he prefers a messy one, the messier the better — if a post goes in crooked because of rocks, let it be, he said.
Bouwes was a leader in the largest beaver dam analog project in the United States, on Bridge Creek near Mitchell, where a powerful stream had gouged a 6- to 10-foot-deep incision. About 2.5 miles was treated to improve habitat for steelhead starting in 2005.
Bouwes and his team built 121 BDAs from 2009 to 2012. By 2013, beavers had fortified 60 of the BDAs and built 115 new dams. The stream bed gradually filled with sediment and rose back to the top of the trench, and the submerged area tripled.
Monitoring showed Bridge Creek produced nearly three times as much fish as a nearby control stream, and water-temperature spiking eased. The results made Bridge Creek the poster child for BDA projects, drawing international attention and documentary filmmakers.
Camp Creek project
A four-mile section of Camp Creek in the Middle Fork John Day River drainage has seen significant improvement since Malheur National Forest fisheries biologist Dan Armichardy headed up a BDA project there in 2016. The goal was to protect mid-Columbia River steelhead, he said.
There’s no beaver sign now at the three meadows on the project site, but Long Creek rancher Sharon Livingston recalls a large beaver dam at the site when she was a child. The Forest Service blew it up, she said, causing her to wonder why the government has changed its mind about beavers.
The science at the time called for removing beavers, Delgado said. But the science keeps changing. For years, the Forest Service built thousands of check dams across the West to slow stream flow. Made of rocks and intended to be permanent, many failed causing even more damage. The Forest Service also tried log weir dams, but 45 weir dams were removed at the Camp Creek site in 2011.
A five-foot high natural beaver dam exists on Camp Creek about three miles downstream from the project site at Pepper Creek, but the degraded riparian habitat at the project site was not good for fish or cattle. An 8-degree temperature rise had been recorded between the upstream and downstream ends of the 4-mile reach before the project.
The Forest Service installed 70 BDAs and numerous wood jams. About 3,500 cottonwoods and 1,500 willows were planted in the floodplain, but deer and elk ate them and fencing is now needed. Excavators were brought onto the sedge meadows to drive in large wooden posts for the BDAs, but no signs of the heavy equipment were visible to workshop members two years later.
Armichardy noted that the project area was continuously used as a gathering meadow by five permit holders who grazed cattle in the area. All five agreed the meadow is much greener now, he said.
Each spring, runoff will inundate the pasture, killing conifers near the stream bank and promoting growth of hardwoods — food for beavers. Beavers also need cover for protection from coyotes, cougars and wolves. They typically burrow into the stream banks, but Camp Creek is not deep enough yet.
The theory behind beaver dam analogs is “build it and they will come.” This has been proven at other locations, and the Forest Service hopes it will be true for Camp Creek.