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Exciting and dramatic changes have taken place in the Elwha
River in the last two years with the removal of two dams. The Glines Canyon Dam
(1927) and the Elwha Dam (1910) were removed to restore the watershed’s ecology
unblocking passage for migratory salmon. Salmon have already begun to find
their way up the newly freed river. Since the time of their building many
things have changed about our understanding of river system ecology causing an ever-increasing
movement to remove them. The Elwha River
dam removal project is currently the largest one in history.
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With the major elements of the actual dams dismantled in
2011 and 2013, focus is now being placed on the removal and movement of the
sediment formerly built up and housed behind the dam structure. Hydrologists,
ecologists and biologists watch with fascination. Project planning though began
nearly a decade ago. Considerations included sediment removal and movement,
reservoir and bank erosion, water temperatures, plant and aquatic animal
repopulation, oceanic conditions and human impact.
Two reservoirs once poised behind the dams have now been
drained. These reservoirs had held back waters creating a warmer freshwater
climate throughout the watershed affecting the natural environment for fish and
plants.
The complexion of the new river includes a newly restored
sand and gravel bed with braided reaches important for salmon. Additionally, free
moving water is cooler accommodating the needs of aquatic life indigenous to
the area. The sand and silt has moved to the delta creating a more prominent
Elwha drift cell, starved for the last century. The release of the silt and
clay has caused much anticipated turbity and nearshore sedimentation.
Ongoing field studies monitor the topography as nearly a
century of the sediment finds its way into new areas of the landscape. Oceanic
changes are also evident at the river enters into the Puget Sound. Sediment
enters the ocean as a buoyant surface plume, settles to the seabed where it is
picked up in the oceanic tidal cycle.
The United States currently has about 84,000 dams. By 2020,
70 percent of them will be more than 50 years old. Decisions are currently
being made as to their continued benefit and viability. Many are at risk for failure setting in
motion plans to repair, remove or replace them. Additionally many of the oldest
ones never were licensed because they were built before standards were
established. To date more than 500 dams have been removed, with many more to
go. Monitoring the progress and effects of the Elwha River restoration will
benefit other systems whose future is also at stake.
Read more about the freeing of the Elwha River at the Washington
Post, Yale
Environment 360 and the Coastal Watershed
Institute.
Jumping
Salmon photo via Shutterstock.
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