News and Opinion from Sisters, Oregon

Restoring Sisters Country 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.

Five wells, placed and monitored throughout the wetland just south of Black Butte Ranch, revealed that with the decay in wetland habitat came a concerning drop in groundwater levels.

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.

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.

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.”


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