Restoration of the Elwha River Ecosystem

Large-scale dam removal on the Elwha River, Washington, USA: River channel and floodplain geomorphic change

“…The dams were built to supply hydropower to a timber and paper mill operation; neither reservoir provided significant flood control or water supply benefits. The two reservoirs inundated more than 9 km of former riverine habitat, reducing accessible habitat for anadromous salmonid fish by 90% (U.S. Department of Interior, 1996a); Lake Aldwell and Lake Mills also trapped sediment and wood, reduced transport of organic material, and increased downstream water temperatures in late summer and early fall because of heat storage in the reservoirs (Wunderlich et al, 1994). Most dam operations after 1975 were largely run-of-the-river hydrology (Johnson, 1994;U.S.…”

Large-scale dam removal on the Elwha River, Washington, USA: Erosion of reservoir sediment

“…This 32-m-high concrete gravity dam had 30 m of head and formed Lake Aldwell, which had a storage capacity of 10 million m 3 at the time of removal. Built without fish passage structures, the dam significantly impacted formerly productive salmon populations by restricting their distribution to the lowermost portion of the watershed in habitat that continued to decline in quality and quantity from the effects of the upstream dams (Wunderlich et al, 1994;Duda et al, 2008;Pess et al, 2008). Glines Canyon Dam was completed in 1927, 21 km upstream from the river mouth (Fig.…”

Beach morphology and change along the mixed grain-size delta of the dammed Elwha River, Washington

“…1a). Two dams were constructed on the river for hydroelectric power generation, Elwha Dam completed in 1913 and Glines Canyon Dam in 1927, which trap over 90% of the watershed drainage area (Wunderlich et al, 1994;Duda et al, 2008). The dams effectively eliminated sediment from moving from the upper river to the river mouth; estimates are that 13.5 million m 3 of sediment was stored in the reservoir deltas as of 1995.…”