A new scientific tool has boosted the Quileute Tribe’s ability to monitor river restoration projects.
Environmental DNA (eDNA) can detect species in an ecosystem by collecting the genetic samples organisms leave behind. The tribe is using this data to prepare for and monitor the success of an upcoming restoration project.
This project aims to restore flows through an oxbow—a U-shaped bend in the river—that was cut off decades ago from the Quillayute River’s mainstem. A flood caused the main channel of the river to move away from the oxbow in 1967.
Anthropogenic impacts over the next few decades resulted in complete disconnection of the oxbow channel and the surrounding 100 acres of floodplain. That disconnection has increased the flood risk for the tribal village of La Push, as floods moving downstream have one less “safety valve” to disperse into the floodplain before they reach the village.
“When you can’t release pressure from a high flow event, it means you have bigger, more intense flows. You have more erosion. You have risks such as those to La Push,” said Caroline Walls, habitat program manager for the tribe.
The tribe has long planned to restore the oxbow. Once permits are approved, the tribe could begin to reconnect the oxbow in early summer 2026 by excavating channels between the main channel and the oxbow. They will add engineered logjams, then revegetate the site in 2027. The plan is to reconnect 2 miles of salmon habitat and 100 acres of floodplain.
“It’s a huge opportunity for us to add salmon habitat and flood control,” Walls said.
The project will reconnect the river’s main channel with the oxbow, which is now a series of disconnected ponds. Collecting eDNA has helped the tribe better understand species currently using the ponds.
This data can be used to monitor post-restoration changes in species and population sizes found in the ecosystem. While other survey techniques would be difficult in the oxbow ponds, due to their size, composition and water chemistry, collecting eDNA provides a full picture of the ecosystem’s composition, providing insight into salmon distribution, invasive species and overall ecological function.
For example, data revealed that after the oxbow was temporarily reconnected with the mainstem after a 50-year flood in 2021, coho, pink and steelhead took refuge in the ponds.
“We likely had successful spawning in the oxbow, particularly with pinks.” Walls said, because eDNA from pink salmon was found in the oxbow ponds months after the flood, long after the adults that moved in would have died.
“We’ve got evidence of great rearing habitat when the salmon are able to access the ponds,” Walls said. “The picture eDNA gives us is that this is suitable habitat for salmon. It’s really compelling. It helps tell us we’re on the right track.”
Sierra Hemmig (left), a riparian biologist with the Quileute Tribe, helps as tribal staffers and partners get ready to collect eDNA samples in 2025. Photo and story: Trevor Pyle.
