By Pacific Coastal and Marine Science Center
July 31, 2023
From 2011-2014, a team of federal, state, tribal, academic, and community partners worked to remove two large dams on the Elwha River in Washington State that had blocked salmon and sediment passage for almost 100 years.
This was the largest dam removal project in U.S. history. More than 20 million tons of sediment were released–several decades' worth of accumulation–which significantly altered the river channel and floodplain. Woody debris that had been held behind the dams was dispersed along the river’s length downstream of the former reservoirs.
Now, salmon are once again spawning in pristine river habitats of the Olympic National Park, and sediment is once again flowing down the river and to the eroding shoreline. A decade after the last dam was removed, the river continues to change.
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Elwha River ScienceScape: Understanding Ecosystem Recovery Following Large-Scale Dam Removal
The Elwha River – located on the Olympic Peninsula in Washington - is home to an iconic dam removal and ecosystem restoration project. The Elwha offers a unique setting to explore the ecosystem level effects of dam removal and river restoration because of its prominence, such as large sediment volume, several salmon populations, and pristine wilderness.
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USGS science supporting the Elwha River Restoration Project
The Elwha River Restoration Project has reconnected the water, salmon, and sediment of a pristine river and coast of the Olympic Peninsula of Washington.
Elwha River Restoration Project
From 2011 to 2014, the Nation’s largest dam removal project to date took place in Washington State, allowing the Elwha River to once again flow unimpeded from its origin in the Olympic Mountains to the Strait of Juan de Fuca. Nearly 100 years of sediment (30 million tons) had accumulated behind two dams, and about two-thirds of that (20 million tons) was released, dramatically affecting the river...
Elwha River Sediment Monitoring
The Issue: The Elwha River Restoration Project is the largest single restoration action planned for the Puget Sound region in the foreseeable future and is a high priority for the Puget Sound Partnership. Beginning in 2011, two large dams on the Elwha River in Clallam County, Washington, will be removed by the National Park Service over about two and a half years. During removal, sediment...
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Elwha River ScienceScape: Understanding Ecosystem Recovery Following Large-Scale Dam Removal
The Elwha River – located on the Olympic Peninsula in Washington - is home to an iconic dam removal and ecosystem restoration project. The Elwha offers a unique setting to explore the ecosystem level effects of dam removal and river restoration because of its prominence, such as large sediment volume, several salmon populations, and pristine wilderness.
Landscape Response to Disturbance
This project characterizes and measures sediment-related effects of landscape disturbances (such as major storms, drought, or wildfire) and river management. We focus primarily on the U.S. west coast, and our work relates to natural hazards and resource management.
USGS science supporting the Elwha River Restoration Project
The Elwha River Restoration Project has reconnected the water, salmon, and sediment of a pristine river and coast of the Olympic Peninsula of Washington.
Elwha River Restoration Project
From 2011 to 2014, the Nation’s largest dam removal project to date took place in Washington State, allowing the Elwha River to once again flow unimpeded from its origin in the Olympic Mountains to the Strait of Juan de Fuca. Nearly 100 years of sediment (30 million tons) had accumulated behind two dams, and about two-thirds of that (20 million tons) was released, dramatically affecting the river...
Elwha River Sediment Monitoring
The Issue: The Elwha River Restoration Project is the largest single restoration action planned for the Puget Sound region in the foreseeable future and is a high priority for the Puget Sound Partnership. Beginning in 2011, two large dams on the Elwha River in Clallam County, Washington, will be removed by the National Park Service over about two and a half years. During removal, sediment...