The Elwha River After Dam Removal

CWU Geology graduate student Bryon Free and Geology Professor Lisa Ely are investigating the impacts of the largest dam removal project in U.S. history: The removal of two large dams on the Elwha River in the Olympic National Park in western Washington. The CWU team is documenting the river channel changes and tracking the sediment deposition before, during and after the complete removal of the upstream dam in April, 2013. With the help of Field Engineer Rex Flake from the CWU Cascadia Hazards Institute, they employed a Terrestrial Laser Scanner (TLS) to create detailed topographic surveys of key locations downstream of the dam in August, 2012.

The TLS surveys will be repeated next summer to quantify the effects of this historic dam removal on the river that is now free-flowing for the first time in over 80 years. Six months after the start of the sediment release, the sediment inundation was already far out-pacing previously observed dam removals. Their findings will provide valuable information for the management of other dam removals on similar gravel rivers in the future.

TLS scanning on the Elwha
National Park Service Geologist Andy Ritchie and CWU’s Rex Flake and Bryon Free use the Terrestrial Laser Scanner to survey the reservoir behind the dwindling Glines Canyon Dam on the Elwha River, Washington.

Resurfacing old-growth stumps
Numerous cut stumps of giant old-growth trees, buried in lake sediments, are being exposed as the water level in the reservoir is lowered. These trees were logged just before the downstream dam was closed in 1913 and have been submerged ever since.