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Outreach

Undamming Washington’s Elwha River—Public Lecture on Largest Dam Removal in U.S. History



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The largest dam removal in U.S. history was the subject of a public lecture by U.S. Geological Survey (USGS) research geologist Amy East on February 26, 2015, at the USGS campus in Menlo Park, California. East described changes to the landscape caused by the removal of two large dams—the 32-meter-tall Elwha Dam and the 64-meter-tall Glines Canyon Dam—from the Elwha River in Washington State. This was the largest dam removal ever undertaken, both in terms of the dams’ heights and in terms of how much sediment had accumulated behind them.

USGS research geologist Amy East gave a public lecture on the effects of removing two large dams from the Elwha River in Washington State
Above: USGS research geologist Amy East gave a public lecture in February 2015 at the USGS campus in Menlo Park, California, on the effects of removing two large dams from the Elwha River in Washington State. Screenshot from USGS Evening Public Lecture Series video (click on “Video Archives” in bar at top of page). [larger version]

Staged deconstruction of the two dams began in September 2011 (see “Elwha Dam Removal Begins—Long-Planned Project Will Restore Ecosystem, Salmon Runs,” Sound Waves, Nov./Dec. 2011) and ended in summer 2014. Numerous federal, tribal, state, and academic scientists are collaborating to examine and report the effects of this restoration effort. East is one of many USGS scientists participating in the collaboration. They began gathering baseline data on the Elwha and the coastal area around its mouth on the Strait of Juan de Fuca more than 5 years before dam deconstruction began (for example, see “Studying the Elwha River, Washington, in Preparation for Dam Removal,” Sound Waves, Nov./Dec. 2006), and they will keep studying the river system to understand its physical and biologic changes.

Location of the Elwha River; background images courtesy of Google Earth
Above: Location of the Elwha River. Background images courtesy of Google Earth. [larger version]

After introducing her audience to the history of dams and dam removal in the United States, East focused on the Elwha and, specifically, on the effects of releasing massive amounts of sediment downstream during the first 2 years of dam deconstruction. Approximately 90 percent of this sediment made it to the river mouth, even though there were no floods during that 2-year period; in fact, the river’s water discharge and peak flows were moderate compared with historical gaging records. “This was probably the biggest surprise of the study so far,” she said—that the river could move so much material downstream without floods to push it along.

Additional effects documented by East and her USGS colleagues include a rise of about 1 meter in the elevation of the riverbed, the appearance of new channels, formation of new gravel bars, and a general decrease in bed-sediment grain size—a change that has improved spawning areas for fish. Other USGS scientists have documented significant enlargement of the coastal delta at the river’s mouth.

Survey taken before dam removal in 2007 After dam removal in 2014, the same area had finer grained sediment
Above Left: Before dam removal, Amy East (then Amy Draut) surveys along the Elwha River in March 2007. USGS photograph by Joshua Logan. [larger version]

Above Right: After dam removal, the same area had finer grained sediment in March 2014; surveyor in the distance is James Starr of the USGS Washington Water Science Center. (Note the tall iron I-beam on the left side of both views.) USGS photograph by Joshua Logan. [larger version]

Details about these and many other findings were recently published in the journal Geomorphology in a series of papers about the first 2 years of dam removal (see “Scientific Portrait of the Largest Dam Removal in U.S. History,” this issue). This information about how the physical system has changed provides a basis for biologists to understand changes to habitats.

USGS scientists continue to monitor the river system, and, as East told her audience, “We expect to learn from the Elwha for years to come.”

To watch an archived video of East’s talk, visit the USGS Evening Public Lecture Series website and click on “Video Archives” in the bar at the top of the page.


Related Sound Waves Stories
Elwha Dam Removal Begins—Long-Planned Project Will Restore Ecosystem, Salmon Runs
Nov. / Dec. 2011
Studying the Elwha River, Washington, in Preparation for Dam Removal
Nov. / Dec. 2006
Scientific Portrait of the Largest Dam Removal in U.S. History
Jan. / Feb. 2015

Related Websites
Elwha River Restoration
NPS
USGS Evening Public Lecture Series
USGS

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in this issue:

Research
Virus Calculated as Culprit Killing Sea Stars

Scientific Portrait of the Largest Dam Removal in U.S. History

California Seafloor Mapping Program Reaches Milestone

Future Wave and Wind Effects on Pacific Islands

Fieldwork
California’s Sea Otter Numbers Holding Steady

New USGS Research Vessel in the Great Lakes

Spotlight on Sandy
Five New USGS Oceanographic Datasets Published Online

Outreach
Explore Coastal and Seafloor Images along U.S. Coasts

Getting Out of Harm’s Way—Evacuation from Tsunamis

USGS at the 2014 St. Petersburg Science Festival in Florida

Tribal GIS Training in the Northeast U.S.

Undamming Washington’s Elwha River—Public Lecture

Awards
Geologist Brian Atwater Receives Communications Award

Publications
Frozen Heat—New International Report on Methane Hydrates

Jan. / Feb. Publications

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