The removal of the Elwha dams was the largest dam removal project in U.S. history. More than 20 million tons of sediment were released–about a decade’s worth of accumulation–significantly altering the river channel and floodplain. Woody debris that had been held behind the dams was dispersed along the river’s length downstream of the former reservoirs.
Now, salmon are again spawning in pristine river habitats of the Olympic National Park, and sediment is again flowing down the river and to the eroding shoreline. The river continues to change a decade after the last dam was removed.
Check out this 10-year retrospective from the USGS.