Mary Shelley missed her calling. Reanimating dead stream tissue is just as hard as making a monster out of spare parts. When you think about it that’s what BDAs are really. A good article about them should have at least 4 of those parts. (1) A description of the benefits they are trying to replace (and their benefactor), (2) an explanation of how it all used to work originally, (3) the necessary Igors and volunteer believer labor to pull it off and (4) a hope that beavers will come back and take over the work. Let’s be honest. The wish for beavers to COME BACK is the only part that makes it NOT a Frankenstein story.
If the first and last parts aren’t included in the article you should run as far as you can in the opposite direction because what you’re actually watching is a horror film. But this one from Oregon is pretty close to being a role model. Every stream should be so lucky.
Restoring Sisters County Wetlands
Mike Riehle stands knee-deep in life returning.
“Not long ago this whole area was dry,” he says, gesturing over weeds and decaying willows. “We’re hoping these efforts will fix that.”
That area, the Lower Black Butte Swamp, is a 50-acre parcel that was once parched land, and is now by design — flooded with water.
The gradual decline in this regional ecosystem was set in motion by the void left from one of nature’s finest eco-engineers — the beaver. Beyond its iconic status as Oregon’s state symbol, these mammals have a unique talent: fabricating natural dams that disperse water into the surrounding environment. Their constructs are a vital resource, irrigating surrounding vegetation and cultivating habitat for wildlife to thrive in.
In 2011, the last known beaver disappeared from the swamp. Without their dams, Indian Ford Creek, running through the wetland, narrowed and the surrounding ecosystem lost its lifeline as water levels dropped. Willows died, their silvery corpses now dotting the undergrowth, grass sedges collapsed, and noxious dry-climate weeds, such as the common mullein and tansy ragwort, colonized the landscape. As the biology of the swamp changed so did the presence of wildlife. The former wetland became a dry wetland, absent its bio-diversity. The remaining water source was the perennial flow of Indian Ford Creek along a single, narrow channel.
Now THAT is what sets the stage for a good BDA article. We used to have this splendid resource that now we don’t anymore and so we want to fix it. I’d love to see a similar article about Alhambra Creek now that our beavers are gone. It’s a miserable trickle compared to what it once was. We all know it.
And that. THAT is the kicker. Good job guys. The stage is set.
Riehle, the fisheries biologist for the Sisters Ranger District, says the concern turned to worry, and in January of 2022 the District drafted plans to find a solution. Their solution was simple: construct a series of BDAs (Beaver Dam Analogue), or man-made dams, to restore the native habitat, and replenish the underlying water table as nature once did. In June, natural materials were collected, and in September physical work began on the Lower Black Butte Swamp Restoration Project.
A LIDAR image, taken in 2011, was utilized to 3D map the terrain, and sketch a plan for reestablishing the native path of the creek, identifying key points to construct the dams. Using one-foot contour lines they would methodically restore the swamp’s natural flow.
Despite modern technology, constructing a beaver dam by hand requires basic hand tools and the realization that nature’s architects know something humans don’t.
“Beavers are great engineers but they haven’t exactly shared their formula with us,” Riehle says.
Every word of this article is perfectly written to emulate – not REPLACE- the good work done by beavers. Remember that Oregon still allows trapping on public lands. This article is quietly giving reminders why that needs to change.
Sisters Ranger District Hydrologist Jamie Sheahan Alonso, echoed his sentiment.
“No one on our core team has ever done this before,” she said.
The concept of BDAs isn’t new, but the art of constructing and implementing them, and their desired impact on the local ecology, is a study in progress.
A total of 26 BDAs were constructed along a 2,500-foot stretch of Indian Ford Creek, requiring considerable resources and crews in a process once designated to a handful of beavers. Prior to building, members of the Youth Conservation Corps snorkeled, collecting and relocating 310 fresh water mussels from the construction zone.
To build a man-made dam involves strength and the ability to shape nature’s fabric. Lodgepole pines are embedded into the creek bed three feet deep, and across the width of the creek. Cottonwood branches are then handwoven along the length and depth of the poles to the bottom of the creek, then consecutively stacked to create a water break. Clumps of sod and grass sedges are hand-placed at the bottom of the weave to prevent water from seeping under and uprooting the poles. Juniper branches are inserted perpendicularly into the weave, stretching upstream and downstream to reduce the water turbulence, further securing the integrity of the design and preventing poles from being uprooted by the current.
Lots of people with lots of tools and technology can barely accomplish what beavers were doing without any government funding or equipment. You got that, right?
As teams stack branches, the weave increases in depth, and sod is reapplied, acting as a mortar sealing the branches into place.
Once dams are set in place, the effects are immediate: Creek water levels rise multiple feet within minutes and begin seeping horizontally into the dry plain. The intended effect on the water table is quickly observed too.
“After our first three dams were built, we noticed a six-foot rise in the water table within the 24 hours,” Riehle said.
Upstream, the formerly dry and arid landscape now sits under a foot of water as a result of only a handful of dams. That water will eventually soak into the earth, says Sheahan Alonso. And with that comes a reinvigorated landscape that will someday turn green again.
The challenging manual labor was done by the Heart of Oregon Corps, who provided over 20 personnel for the project, and employees of the Sisters Ranger District. An excavator was also hired to set poles into the creek bed and dig up sod for the dams.
John Deluka, the Sisters Ranger District wildlife biologist, stood waist-deep in the effects of his freshly constructed BDA, weaving another cottonwood branch into place while ruminating on its rising benefits.
“This ecology is suffering and I hope this project will bring back the beavers and other wildlife that once thrived here,” he said.
Deluka noted that 115 bird species have been recorded in the swamp alone and more than a dozen animals, including elk, roam the terrain.
“I expect those numbers to increase after this project, and I hope to hear a symphony of frogs when this place recovers,” he said.
Wildlife is a key attribute to restoring the biological habitat, but that wildlife is only a glimpse of the bigger ecological picture, he said.
The Lower Black Butte Swamp is a small part of a larger ecosystem that directly affects the climate. Scientific studies show that three percent of the earth’s surface is wetlands, similar to the Black Butte Swamp. And one third of CO2 and methane is absorbed into its soil, which is then naturally converted into oxygen. Restoring the “wet” to a wetland reactivates that function.
Deluka says with the return of healthy habitat, the land and those within it can only thrive.
And in the Black Butte Lower Swamp, those restorative effects are beginning to take shape. Much of the wetland is now wet again. Riehle says the noxious weeds will die off with the overabundance of water, and the sedges, willows, and other native habitat will start to recover in time. He ultimately hopes the water table will continue to rise and nature will find its way back, and hopefully beavers will reinhabit the area.
“Water is life,” said Deluka. “And we’re just trying to restore that.”
HOPEFULLY BEAVERS WILL FIND THEIR WAY BACK. HOPEFULLY. It occurs to me with your last quote about restoring life that BDA’s are kind of like the Frankenstein of the ecological world. You are basically reanimating dead tissue and to be honest the creature you end up with is nothing like the beaver dam you are replacing. But it’s more alive than it used to be and I guess that’s the point.
We need more beavers and fewer Frankensteins.
