Aerial photographs taken near the mouth of the Elwha River, from August 2011 (top) and May 2013 (bottom), show the growth of the river mouth as the dams are removed.
The Elwha River
The Elwha River drains the largest basin in Olympic National Park and has huge potential for salmon recovery in the Puget Sound region. For nearly 100 years, the natural flow of the Elwha River was altered by the presence of two dams, the Elwha and the Glines Canyon. These dams interrupted the normal flow of sediment and debris to the shore and prevented anadromous salmon from accessing pristine habitat in the park. From September 2011 to present, the Department of the Interior removed the dams in the largest restoration and dam decommissioning project of its kind. The goal was in restoring connectivity, physical processes, and salmon populations to the river ecosystem. Recovery of the river will be a significant and unprecedented Federal contribution to salmon recovery in the region, but many questions remain about the river's response to dam removal and the recovery process for salmon.
The USGS and our state, federal, tribal, and non-governmental organization partners are using multidisciplinary approaches to examine the ecosystem response to the dam removals. Studies of the physical and biological effects of dam removal are grouped into three general categories: ecosystem responses, flow modification and sediment transport, and cultural resources. We will continue to collect and analyze data related to ecosystem processes of the river and coastal areas after the removal of the dams. Work includes mapping of shelf, nearshore, and beaches; biological communities of the subtidal seafloor near the project area and reference sites; salmon habitat and estuary utilization; monitoring of coastal processes; monitoring of sediment transport and delivery to river and nearshore habitats, and computer modeling of oceanography and sediment dispersal.
For more information, please see the USGS Elwha project page at https://www.usgs.gov/elwha. There you will find detailed descriptions of our multidisciplinary team, the projects that are underway, and links to scientific and outreach products.