By Tiffany Royal Northwest Indian Fisheries Commission
PORT ANGELES — As the Elwha River’s two fish-blocking dams come down, the Lower Elwha Klallam tribe will monitor how a portion of at least 21 million cubic yards of built-up sediment will affect the river’s estuaries at its mouth.
For the past century, sediment has built up behind the 108-foot-tall Elwha and 210-foot-tall Glines Canyon dams.
As the dams are deconstructed the next few years beginning Sept. 17, much of that sediment will come down the river.
“We know a lot of sediment will be deposited within the streambed of the lower river, but we don’t know how much will be deposited in the estuary and how it will change,” said Matt Beirne, the tribe’s environmental coordinator.
Estuaries are important for salmon because they provide a place for salmon to hide from predators and to feed and grow before heading to sea.
The tribe has set up 15 sediment-monitoring locations throughout the 50-acre estuary.
Using a specialized measuring device called a Surface Elevation Table, or SET, the tribe will determine at regular intervals how much sediment is building up throughout the estuary.
The SET uses fiberglass pins to measure the change in height of the deposited sediment.
This technique, developed by USGS researchers, has been applied to estuaries throughout the nation and internationally.
The tribe also has deployed water quality sensors to collect data on water clarity, salinity and temperature in the estuary.
This will show how the sediment-laden water will be distributed in the estuary on tidal, seasonal and annual cycles.
The tribe also will study how increased turbidity and sedimentation in the estuary may affect juvenile salmonids as the dam removal project progresses.
The National Park Service is overseeing the
$27 million dam teardown project, part of a $325 million Elwha River Restoration Project intended to restore the river’s legendary salmon runs.
The Bureau of Reclamation now operates the onetime private dams on the Elwha River.
The dams removal, the largest in the nation so far, will be marked with several days of events Sept. 13-Sept. 18 called “Celebrate Elwha!”
Those events will include a themed poetry reading Sept. 13, the tribe’s hatchery ribbon-cutting Sept. 14, a two-day science symposium beginning Sept. 15 and a lecture by environmentalist and Patagonia outdoor clothing gear company founder Yvon Chouinard on Sept. 16.
On Sept. 17, dignitaries at the beginning of the dams demolition will include Interior Secretary Ken Salazar, National Park Service Director John Jarvis, Sen. Patty Murray and Rep. Norm Dicks, whose congressional district includes Clallam and Jefferson counties.
For more information about events during “Celebrate Elwha!,” visit http://tinyurl.com/3zysae3.
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Tiffany Royal is the Northwest Indian Fisheries Commission information officer.
