ECOSYSTEM RESPONSE DURING REMOVAL OF THE ELWHA RIVER DAMS
George R. Pess, Ph.D.
Supervisory Research Fishery Biologist
NOAA – NMFS – NFWSC
2725 Montlake Blvd East
Seattle WA, 98112
george.pess@noaa.gov
Abstract Annual General Meeting of the WA/BC Chapter of the AFS
Vancouver WA
March 25-27, 2014
The removal of the Elwha River dams on the Olympic Peninsula of Washington State is a unique
opportunity to examine ecosystem recovery on a watershed scale. Over the last century, the two
dams blocked the upstream movement of anadromous fish to over 90% of the watershed, and
restricted the downstream movement of sediment, wood, and other organic materials to the lower
river and estuary. Populations of all five Pacific salmon species and steelhead in the Elwha are
critically low, habitat complexity decreased in the middle and lower river, and downstream
coastal habitats sediment starved.
Simultaneous deconstruction of the two dams began in September 2011 and is expected to take 3
years to complete. During and after that time, researchers are examining dam removal effects in
three geographic regions: the former reservoirs, across the river floodplain, and in the nearshore
environment. Short-term (< 3 years post dam removal) monitoring is focused on the downstream
transport of approximately 13 million cubic meters of fine sediments accumulated in the
reservoir deltas, associated peaks in river and estuary turbidity levels, and re-vegetation of the
reservoir themselves. Longer-term effects of dam removal (> 5 years) to be evaluated are the
delivery of gravels and cobbles to the lower river and nearshore, the re-establishment of a natural
wood delivery regime, the re-colonization of the upper watershed by anadromous fish, and the
associated effects on aquatic and riparian foodwebs.
The recent removal of the Elwha dam has also given us an opportunity to explore linkages
among changes in ecosystem attributes, salmonid populations, and sediment supply. Sampling of
each of these elements before and during dam removal, as well as in nearby reference rivers has
given us insights into functional relationships among salmonid populations, life history
strategies, and resultant ecosystem dynamics. This talk will provide an overview of the Elwha
restoration project, and highlight recent changes observed in this first year and a half of dam
removal.
BIOGRAPHY:
George Pess has worked in fisheries since 1989. His primary research interest during that time
has been the examination of natural and land-use effects on salmon habitat and salmon
production. George has conducted research on historic and current land use impacts on salmon
habitat and production, the influence of wood in forested stream channels, and how landscape
characteristics and land use affect salmon abundance. George's main current research projects
include the ecosystem response to the removal of the Elwha River dams, and differences in
salmonid recolonization associated with population and aquatic habitat dynamics. George has a
B.A. in Economics and Environmental Science (Bowdoin College 1987), an M.S. in Forest
Science (Yale University 1992), and a Ph.D. in Aquatic and Fishery Sciences (University of
Washington, 2009). George enjoys spending time with his wife Susan and their two children
Samantha and Olivia, as well as fly-fishing, hiking, and reading.