Elwha River, Washington

In September 2011, the world’s largest dam removal project began on the Elwha River in Washington. Known for its thriving ecosystems and abundant fish runs, the Elwha has been given a second chance through the removal of Elwha and Glines Canyon dams, and now flows freely from its headwaters to the sea.

The Story

Elwha Dam | Photo by John R McMillan, NOAA
Elwha Dam | Photo by John R McMillan, NOAA

The pristine Elwha River runs 45 miles through lush forests and mountainous landscapes on Washington’s Olympic Peninsula. It originates in the Olympic Mountains of Olympic National Park and flows north until it meets with the Strait of Juan de Fuca at the northern border of the United States.

In the 1900s, both Elwha and Glines Canyon dams were constructed on the Elwha River to support regional growth during the industrial revolution. Prior to their construction, more than 400,000 adult salmon would return to 71 miles of upstream habitat each year to spawn. It was one of few rivers in the Northwest that supported five species of Pacific salmon: chinook, chum, coho, sockeye and pink, plus four species of trout: steelhead, coastal cutthroat, bull and Dolly Varden. After the construction of the two dams, only 4,000 salmon returned to the Elwha to spawn in just five miles of habitat from the mouth of the river to the base of Elwha Dam. These historical runs were culturally and economically significant to many Native American groups, specifically the Elwha Klallam Tribe, who relied on the fish for sustenance.

Elwha Dam before (left) and after (right; taken in March 2012) removal | Photos by National Park Service

The Elwha River system quickly deteriorated in the presence of the dams. In 1995, an Environmental Impact Statement identified the removal of the dams as a preferred alternative to restore native fish runs and the entire river system. In 2000, the U.S. Department of the Interior purchased the dams for $29.5 million.

At 108-foot tall and 450-foot wide, Elwha was the bulkier of the two dams, with thick concrete walls, extensive tubing to divert water, and a massive powerhouse. Glines Canyon Dam was constructed in a tight ravine and towered 210-foot tall and spanned 150-foot wide between the rocky canyon walls.

Former Glines Canyon Dam | Photo by Daimon Eklund
Former Glines Canyon Dam | Photo by Daimon Eklund

The federally-led deconstruction of the dams began in September 2011. Water behind Glines Canyon Dam was lowered using the existing spillway, and then a hydraulic hammer mounted on barges chipped away at the concrete structure creating temporary spillways and allowing the water and sediment that remained in the reservoir to slowly drain and settle out from behind the dam. The powerhouse and other remaining structures were also removed over time.

Similarly to Glines, water behind Elwha Dam was slowly drained using its existing spillways. A temporary structure, acting as a dam, was constructed to divert water into a temporary channel that allowed water to fully drain from behind the dam. The concrete was then chipped away and the powerhouse and other structures, including the temporary dam and channel, were removed allowing the river to be reconnected.

Dam Removal Benefits

  • Opened access to 70 miles of spawning grounds and habitat for migratory and resident fish— Chinook and steelhead counts increased by more than 300 percent within one season after removal and are increasing each year
  • Biodiversity is booming in the ecosystems surrounding the river and on the newly formed river banks
  • Elk, small mammals, birds (e.g., sandpipers and eagles), small mammals (e.g., mice and chipmunks) and otters are frequently spotted swimming, scurrying or soaring in or around the river
  • Wood and sediment that had accumulated behind the dams was liberated, and as it settled out, created newly formed habitat for aquatic and terrestrial species, including 70 acres of estuary habitat at the mouth of the Elwha— this area is harboring a diverse array of ocean dwelling species, such as sardines, anchovies, Dungeness crab, shrimp and more
  • Pride for the Elwha River was restored in local communities— the Elwha Klallam Tribe celebrated the return of historic salmon runs and cultural traditions that were hampered by the dams
  • Boaters and fishers now recreate on the river without the safety risk posed by the dams

lines Canyon Dam before (left) and after (right, taken in May 2013) removal. | Photos by Scott Church (before) and Janis Burger, National Park Service (after)

Extensive monitoring is happening following the completion of these dam removals, and evidence is showing a river coming back to life. The Elwha River watershed has undergone a remarkable transformation as a result of this large-scale dam removal project. This is a great example of how a diverse array of partners and stakeholders can come together to make difficult decisions and smart investments that have major benefits for the environment and local communities.

FOR MORE INFORMATION:
Andy Richtie | U.S. Geological Survey, Pacific Coastal and Marine Science Center | aritchie@usgs.gov