Elwha River Restoration Research

A scientist stands on a tree stump on the bank of the Elwha River.
Monitoring sediment erosion during dam removal.

NPS photo


Elwha River Restoration is a National Park Service project that includes the removal of two large dams on the Elwha River, restoration of the Elwha watershed, its native anadromous fish, and the natural downstream transport of sediment and woody debris. Dam removal began September 19, 2011 and concluded in the summer of 2014.

The Elwha project, including dam removal, restoration efforts, and protection measures, is serving as a “living laboratory” for monitoring large-scale ecosystem recovery and investigating particular ecosystem processes and components.The project provides a rare opportunity for scientists to learn what happens when a dam is removed and salmon return to a wild, protected river. Among the researchers are fish and marine biologists, botonists, entomologists, geologists, ornithologists, and students.

Scientific monitoring and analysis for the project is led by the U.S. Geological Survey (USGS), in coordination with the Olympic National Park, Lower Elwha Klallam Tribe, the Bureau of Reclamation, Washington Department of Fish and Wildlife, U.S. Fish and Wildlife Service, the Environmental Protection Agency, the National Oceanic and Atmospheric Administration, and other local and state entities.

River Dam Removal – Rebirth of a River
This four-page USGS Fact Sheet describes the river restoration project and USGS science and monitoring.
Areas of Study
A scientist stands on a stump along a riverbank holding a piece of equipment.
A scientist measures sediment topography.

NPS photo

Elwha River
The Elwha River basin covers over 300 square miles (833 square kilometers), transporting freshwater and sediment from the Olympic Mountains to the Strait of Juan de Fuca. Prior to dam removal, most of the river's natural sediment flow was trapped in reservoirs behind the dams. As the dams came down, over 100 years of accumulated sediment was released downstream, causing elevated water turbidity, changes to the channel shape, and modifications to river habitats. Efforts to track the effects of dam removal on the river include monitoring and analyses of river water and sediment discharge, channel morphology, floodplain vegetation, and river geochemistry and nutrients.

Learn more about ongoing river studies at the USGS website.

Salmon with a radio tag on its dorsal fin.
Radio tagging is one method scientists are using to monitor salmon distribution in the Elwha River.

NPS Photo/R. McKenna

The Elwha River was once one of the most productive salmon streams in the Pacific Northwest, home to all five species of Pacific salmon, as well as at least eleven other fish species.When the Elwha and Glines Canyon dams were constructed on the river in the early 1900s, salmon migration into Olympic National Park was blocked and their habitat was reduced to five miles (8 km) of river downstream of Elwha Dam.

Removal of the dams has restored access to over 70 miles of mainstem and tributary habitat. Using research methods such as snorkel surveys, radio telemetry and sonar imagery, biologist are monitoring how salmon are recolonizing the river.

A river otter eating a fish.
Salmon is an important food resource for many riverine animals, including river otters.

Photo by Ken & Mary Campbell (c)

Other Wildlife
Throughout their life cycle, salmon nourish over 130 species of insects, birds, fish, and mammals. Despite a general appreciation that salmon are key to sustaining many species of wildlife in the riverine environment, few studies have described the effects of salmon on wildlife diversity, abundance, or distribution patterns. This is largely because there have been so few opportunities for large scale experimentation and long-term studies.

Removal of the dams on Elwha River offers an opportunity to investigate these salmon-wildlife interactions. Prior to dam removal, the USGS, National Park Service, and Lower Elwha Klallam Tribe conducted baseline studies of wildlife distribution and species diversity patterns. These studies are providing a comparative baseline to evaluate the long-term effects of dam removal and watershed restoration on wildlife resources in the Elwha River ecosystem.

Learn more about wildlife research.

View of the Elwha River estuary.
Elwha River estuary.

NPS photo

Elwha River Estuary
The Elwha River estuary is the primary location where freshwater from the Elwha River mixes with the coastal waters of the Strait of Juan de Fuca. This habitat provides an important refuge for juvenile salmon and other wildlife. Studies of the estuary have are carried out in collaboration with the Lower Elwha Klallam Tribe, which owns and manages most of the estuarine complex. These studies include investigations of the estuary's hydrology, sedimentation, ecology, and vegetation.

Learn more about Elwha River estuary research on the USGS website.

Aerial view of the mouth of the Elwha River.
Sediment flows into the Strait of Juan de Fuca.

Photo by Tom Roorda (c)

Coastal Habitat
Damming of the Elwha River dramatically altered sediment flow to the coast. This reduction of sediment transport coincided with rapid erosion of the shoreline of the Elwha River delta. Removal of the dams has resulted in the release of millions of cubic yards of sand and silt to the nearshore waters of the Strait of Juan de Fuca. To better assess the restorative impacts of these renewed supplies of sediment on coastal ecosystems and habitats, the USGS is conducting inventories using scuba surveys and sonar technologies.

Learn more about coastal research on the USGS website.

Last updated: August 9, 2016

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