HR: 0800h
AN: H41B-0496    [Abstracts]
TI: Elwha River Delta: Geomorphology of a Mixed-Sediment Beach
AU: * George, D A
EM: dgeorge@usgs.gov
AF: USGS Coastal and Marine Geology, 400 Natural Bridges Dr., Santa Cruz, CA 95060, United States
AU: Warrick, J J
EM: jwarrick@usgs.gov
AF: USGS Coastal and Marine Geology, 400 Natural Bridges Dr., Santa Cruz, CA 95060, United States
AB: The Elwha River drains the Olympic Peninsula of Washington and forms a mixed grain-size delta in the Strait of Juan de Fuca. The Elwha River has been dammed for almost a century, and a pending dam removal project is expected to reconnect upstream sediment sources to the river mouth. Topographic and grain-size mapping of the delta during 1939-2007 is synthesized and the geomorphology and shoreline changes of this system are described. Data sources include historical aerial photographs, airborne LIDAR, semiannual RTK DGPS topographic surveys and grain-size analyses from digital photographs. The delta is divided into three geomorphic regions: west delta, river mouth and east delta. The river mouth is the most complex region due to the river channel movement, side-channels, and bars immediately offshore of the mouth. The east and west delta differ in beach profile and shoreline change rates. The west delta is steep, cuspate and lacks a low-tide terrace. Further, the west delta has exhibited little semi-annual or inter-annual shoreline change. In contrast, the east delta has a steep foreshore, flat low tide terrace that is dominated by cobble, and a consistent trend of erosion during the surveys. These observations can be used to track coastal changes following dam removal on the Elwha River..
DE: 3020 Littoral processes
SC: Hydrology [H]
MN: 2007 Fall Meeting