The removal of two dams on the Elwha River represented the first large-scale dam removal in history, and has served as a beacon for other river recovery efforts across the globe. Yet, dam removal was just the beginning of the Elwha River restoration; many subsequent and ongoing restoration projects have been carried out in an effort to fully recover fish populations and return the watershed to its pre-dam condition. River restoration projects fall into two major categories: re-vegetation and floodplain connectivity.
Revegetation projects will help restore native plants to the areas around the former dams. The reservoirs created behind the dams flooded about 715 acres of land historically covered with riparian and forest plant communities, which supported numerous ecosystem processes and provided critical habitat for fish and other wildlife. Now that the dams have been removed and reservoirs dewatered, this land is once again available for the river to move freely through, and for plants and animals to thrive.
In addition to preventing access for fish to over 70 miles of upstream habitat, the dams were blocking the downriver transport of trees, branches, root wads, nutrients and sediments. In healthy rivers and streams, large wood accumulates naturally and provides habitat for fish. The removal of large wood from the system began even before dam construction through floodplain logging and clearcutting of the reservoir areas prior to being filled. The depletion of this debris and sediment scouring from the lower Elwha River over time resulted in limited spawning and rearing habitat for salmon and other anadromous fishes. In an effort to restore the ecosystem functions of large woody debris which the lower river was without access to for a century, engineers and biologists constructed and installed log jams as analogs for natural accumulations.
This ongoing recovery story remains a rare opportunity to fully restore an ecosystem where over 97% of the watershed is managed for conservation (Olympic National Park, US Forest Service, LEKT, Project Lands, State lands, NGO lands, and conservation easements on private lands). Since dam removal, over 7,100 pounds of native locally- sourced seeds and 450,000 bareroot plants have been nurtured in the dewatered reservoirs and restored floodplain areas, over 100 engineered logjams have been installed and additional fish barriers such as relict dikes have been corrected to improve connectivity. These ongoing restoration efforts on the mainstem and important tributaries are helping the river continue to heal.
River Features
- Headwaters are 45 miles (72 km) upstream of the river mouth
- The watershed (Elwha River and its tributaries) drains an area of roughly 321 square miles (83,139 hectares)
- Historically home to all five Pacific salmonid species, as well as other anadromous fishes (including bull trout, Eulochon, sea-run cutthroat and Pacific lamprey)
- 4th largest river system in the Olympic National Park (by drainage size)
- 85% of the watershed lies within Olympic National Park
- Watershed contains about 30 miles of tributary streams accessible by salmon
- Elwha Dam was located at river mile 4.9, 105 ft. high & constructed in 1910-12; it was removed in 2011
- Glines Canyon Dam was located at river mile 13.5, 210 ft. high & constructed in 1927; it was removed in 2014
- The former Elwha reservoirs have been planted with 450,000 rooted native trees and shrubs and 7,100 pounds of native and locally-sourced seed
- Invasive plant management adjacent to the former Elwha reservoirs has been occurring since 2008 pre-dam removal, and is ongoing in order to protect the plantings and recovering native plant community
- Total sediment accumulation 24 million cubic yards; 75% of the sediments trapped behind the former dams were released to the Strait of Juan de Fuca within the first three years of dam removal
Learn more about the Elwha River restoration by clicking on the links below: