2005 Salt Lake City Annual Meeting (October 16–19, 2005)

Paper No. 5
Presentation Time: 9:00 AM


WARRICK, Jonathan A., Coastal and Marine Geology, USGS, USGS Pacific Science Center, 400 Natural Bridges Dr, Santa Cruz, CA 95060, GELFENBAUM, Guy, U. S. Geol Survey, 345 Middlefield Road, MS999, Menlo Park, CA 94025, JOHANNESSEN, Jim, Coastal Geologic Services, Inc, Bellingham, WA 98225 98225, BEIRNE, Matt, Lower Elwha Klallam Tribe, Port Angeles, WA 98363, YOUNG, Robert, Department of Geosciences, Western Carolina University, Cullowhee, NC 27823 and WINTER, Brian, Olympic National Park, Port Angeles, WA 98362, jwarrick@usgs.gov

Dams on the Elwha River of the Olympic Peninsula have reduced sediment transport in the river for almost a century. Following dam removal, which is slated to begin in 2008, over 14 million cubic meters of mixed grain-size sediments will be exposed in the former reservoirs, a portion of which will erode and transport to the Strait of Juan de Fuca. Increased supply of sediment to the strait, may end, or perhaps reverse, the current trend of erosion along the river delta and adjacent shoreline. Here we describe the history of shoreline evolution along the Elwha River delta and detail monitoring plans to track nearshore changes following dam removal. Historic data document a general trend of erosion along the delta resulting in a net loss of approx. 65,000 sq. meters of land between 1926 and 1995, although variability in erosion rates is observed over both space and time. Continued monitoring of the shoreface is planned by both U.S. Geological Survey (USGS) and Lower Elwha Klallam Tribe (LEKT) scientists. USGS scientists have also implemented a research program that includes beach and nearshore mapping, process (wave and current) monitoring, and numerical modeling of sediment dispersal. Here we will present preliminary results of this work including high-resolution seabed maps of bathymetry and sediment type and changes in the nearshore bathymetry and beach topography from semi-annual mapping using RTK GPS technologies.