Predicting Floodplain Vegetation Response to Dam Removal on the Elwha River

The Elwha River


The removal of two dams on the Elwha River, scheduled for 2012, will be the largest dam removal project ever undertaken in the United States. Dam removal is expected to restore what was once one of the most productive salmon streams in Washington state, opening access to more than 70 miles of protected habitat within Olympic National Park.

One concern is the potential for invasive plants to outcompete native species and dominate the newly created floodplain habitats once the reservoirs are drained and the river channel is reestablished. In collaboration with our partners at Eastern Washington University (EWU), the U.S. Geological Survey (USGS) and the National Park Service (NPS), we are conducting a series of greenhouse experiments to characterize the growth of native and invasive plants on sediments dredged from the bottom of the reservoirs. Information gained from these experiments will guide restoration efforts following dam removal to help maintain the integrity of floodplain ecosystems.

Greenhouse Experiment

Jamie Michel & Jim Helfield


  • Jamie Michel, WWU
  • Jim Helfield, WWU
  • Rebecca Brown, EWU
  • Pat Shafroth, USGS
  • Jerry Freilich, NPS
  • Josh Chenoweth, NPS
  • Steve Acker, NPS


  • National Park Service
  • Gravity Environmental, Ltd.
  • Western Washington University

Lake Mills Sediment

July 2009