CATALDO, Idaho – On the banks of the Coeur d’Alene River, Jo Christensen turned a willow branch over in her hands, pointing out dozens of nodules that will sprout roots next spring.
“Willows have an ability to send out crazy amounts of roots,” said Christensen, a restoration biologist for the Forest Service. “People figured out really early on that they were good at grabbing soil and holding it.”
Since ancient times, people have exploited the shrub’s prolific root structure, planting willows along streambanks for erosion control. Christensen and other scientists still use willows in projects. From Alaska to Colorado, she’s incorporated willow plantings in shoreline restoration work.
Her latest project involves 500 feet of unraveling streambank along the Coeur d’Alene River at the Kahnderosa RV Park and Campground in Cataldo. It’s a pilot project, financed by the Coeur d’Alene Trust and the U.S. Environmental Protection Agency, to show other property owners how low-cost willows can solve erosion problems and reduce people’s exposure to heavy metals. Money in the trust is dedicated to cleaning up historic mining pollution.
On Monday, slate-colored water rushed past the RV park, which borders the Trail of the Coeur d’Alenes rails-to-trails project. For years, the river has been clawing at the bank.
The erosion exposed pockets of heavy metals, a legacy of upstream mining activity in Idaho’s Silver Valley. Some soil samples had lead levels of 10,000 parts per million, well above EPA’s cleanup threshold of 700 parts per million.
“People were tromping down these banks to get to the river,” said Ed Moreen, an EPA project manager. “The biggest potential exposure to metals is ingesting or inhaling lead dust.”
The solution is a 4-foot-high berm that Christensen refers to as a soil “burrito.”
“There’s a food analogy for most restoration work,” she said.
Large rocks form the base of the berm. Willow branches are stacked between the “burrito,” rolls of jute fabric that are packed with rocks and dirt. Eventually, the fabric will disintegrate, but the tenacious willow roots will hold the berm in place.
The Kahnderosa’s guests can still get to the river from two paths, and the contaminated hillside will be covered with a screen of willows.
“They’re calling it a burrito; I call it a beaver dam,” said Wade Kahn, who owns the RV park with his wife, Sheri.
In addition to protecting guests who access the river, the berm should halt the loss of valuable waterfront acreage from erosion, he said.
The construction work will cost about $250,000. Moreen thinks that landowners will be able to adapt the concept for smaller projects, with the ability to do some of the work themselves.
People flock to the beaches and flood plains along the Coeur d’Alene River for recreation, but bare soils are places where they encounter metals, Moreen said.
“We are seeing tremendous growth in recreation,” he said. “This technology is one of the ways we can reduce exposure.”
A similar project at the Medimont boat launch also improved fish habitat and water quality, said Christensen, the restoration biologist. When the river’s current hits the berm, the water slows down. Sediment gets trapped by the overhanging willows. Smaller fish hang out by the berm, where they’re less likely to get swept downstream.
“We’re harnessing the natural power of willows,” Christensen said. “Plants can do the job.”
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