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Bathymetry, topography, and sediment grain-size data from the Elwha River delta, Washington

December 5, 2017

Two dams on the Elwha River, Washington State, USA trapped over 20 million cubic meters of sediment, reducing downstream sediment fluxes and contributing to erosion of the river's coastal delta. The removal of the Elwha and Glines Canyon dams between 2011 and 2014 induced massive increases in river sediment supply and provided an unprecedented opportunity to examine the response of a delta system to changes in sediment supply. The U.S. Geological Survey (USGS) developed an integrated research program aimed at understanding the ecosystem responses following dam removal. The research program included repeated surveys of beach topography, nearshore bathymetry, and surface sediment grain size to quantify changes in delta morphology and texture following the dam removals.

This data release currently contains bathymetry and topography data from 13 surveys performed on the Elwha River delta between 2010 and 2016 and will be updated as data from future surveys become available. Sediment grain-size data are available for selected surveys performed after May 2012.

Nearshore bathymetry data were collected using personal watercraft (PWCs), small boats, and a kayak, each equipped with single-beam echosounders and survey-grade global navigation satellite system (GNSS) receivers. Topography data were collected by walking along survey lines with GNSS receivers mounted on backpacks. Positions of the survey platforms were referenced to a GNSS base station placed on a nearby benchmark with known horizontal and vertical coordinates. Surface-sediment grain-size data are derived from physical samples collected using a small ponar, or grab, sampler deployed from a small boat. More detailed information on the survey methodology is provided in the individual data releases and associated metadata.

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