PORT ANGELES, Wash. — Scuba divers from the USGS and the Environmental Protection Agency are exploring and cataloging marine life at the mouth of Washington’s Elwha River. The underwater survey is taking place downstream of the Elwha and Glines Canyon Dams, which are being removed over the next three years starting this September. The primary goal of the dive survey is to learn how underwater plant and animal life react and adapt to the downstream effects of dam removal and provide scientists a more detailed and complete picture of the ecological restoration.
"We are monitoring the affects of dam removal and the release of sediment from the reservoirs on marine life," said Steve Rubin, researcher and lead of the USGS Dive Team, "In the long term, ecologically and commercially important kelp, fish and shellfish resources may benefit from the more natural sediment supply that existed before the dams were built."
The dive teams, in collaboration with the Lower Elwha Klallam Tribe, are establishing and surveying marked transects spread throughout the Elwha River nearshore zone, as well as transect pairs at sites far from the Elwha River mouth. These same strips of seafloor will be monitored during and after dam removal to see how fish, kelp and invertebrate populations respond to changes in deposited and suspended sediments.
More than 19 million cubic meters of sediment, enough to fill 11 football fields the height of the Empire State Building, has accumulated behind the Elwha River dams. As the dams are removed, a portion of this sediment will be carried downstream, changing the structure of the riverbed below the dams. Also affected will be the estuary complex where the river meets the Strait of Juan de Fuca and the nearshore seabed. USGS studies indicate that high concentrations of sediment will create turbid conditions in the river and coastal waters during some seasons for up to five years, a process scientists hope to monitor.
The joint dive operation will expand the focus of downstream sediment impact to include the saltwater environment. "Until now, we’ve focused most of our attention on the effect this project will have on the river, salmon habitat and salmon recovery,” said Sean Sheldrake, EPA Dive Team coordinator in Seattle. ”But with this survey, we will have a more complete and much clearer picture of the effects on the nearshore ocean environment.”
The Elwha River Restoration Project, created by an Act of Congress in 1992, aims at the full restoration of the Elwha River ecosystem and its native anadromous fisheries.