By Kate Schimel, Sept. 4, 2017
The Elwha River starts at Dodwell-Rixon Pass, a high crack in Washington’s Olympic Mountains. There, a hiker who crossed would find the Elwha Snowfinger, formed by heavy winter storms and the avalanches that pour off the surrounding mountainsides. Wedged into a steep-walled gully, it forms the upper reaches of the Elwha basin. If the hiker followed this snow down, eventually she’d find a stream, and that stream would widen and become the Elwha River. As she traveled down, as more streams joined its flow, she would find one of those messy rivers that characterize the Pacific Northwest: Wide, braided channels, scattered with logs and boulders, gravel bars strewn with detritus, a sense of a landscape half-finished. Then the river would round a corner and flow out into an area of high gravel banks stretching on for yards, dozens of feet above the water. These are what’s left of Lake Mills, one of two reservoirs that once trapped the Elwha.
On a nippy November day, I look over the remains of Glines Canyon Dam, which formed Lake Mills, with sediment researcher Andy Ritchie. Snow has already begun to collect on the higher slopes; in the path of the wind whistling out of the river canyon, we struggle to talk without chattering teeth. Ritchie is introducing me to one of the largest experiments in ecosystem repair ever undertaken: Beginning in 2011, the federal government removed this dam and one lower down, blasting them away bit by bit over three years. Dozens of researchers from the U.S. Geological Survey and the Lower Elwha Klallam Tribe, University of Washington and the National Park Service, along with universities across the country, have since documented how that removal affected sediment in the water, small mammals, salmon, birds and the ocean the river flows into.
Ritchie’s job was to watch the river’s every move from Lake Mills, past the Elwha Dam site, to the river’s mouth at the Strait of Juan de Fuca in the Pacific Ocean.
“The dam removal dwarfs anything done before,” Ritchie says. A river trapped by a dam is predictable. But undammed rivers carry immense force in the form of sediment, logs and flows that can change course and volume rapidly and violently. He shows me how the freed Elwha dug up part of Lake Mills’ bed and deposited it in front of the dam. Then it carved that new bed into huge stairlike gravel banks, finding its way into old channels but also slashing new ones here and far downstream.
“It was impressive,” Ritchie says. The river’s vigor surprised even the project designers and engineers, moving far more of the lakebed than predicted, devouring swaths of land and choking its own fish with fine sediments.
Read the full article here at HCN.