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Data in support of 5-year sediment budget and morphodynamic analysis of Elwha River following dam removals

February 8, 2018

Two large dams were removed from the Elwha River in Washington, starting in 2011 and ending in 2014. The Elwha and the Glines Canyon dams were located approximately 7 km and 20 km upstream, respectively, from the Elwha River's mouth on the Strait of Juan de Fuca. The dams trapped over 20 million cubic meters of sediment. Dam removal changed the river's sediment budget and water flow, which affected the river's morphology. This data release presents digital elevation models (DEMs), orthomosaic images, dam height measurements, sediment measurements and river streamgage data that were collected by the U.S. Geological Survey (USGS) and U.S. Bureau of Reclamation (USBR) to support studies on morphodynamic and sediment budget responses of the Elwha River to the removal of the dams. The DEMs were created using a synthesis of lidar and structure-from-motion (SfM) photogrammetry to study elevation changes in the river channel. Photographs from the SfM photogrammetry surveys were also used to create orthomosaic images of the middle and lower reaches of the Elwha River. These mosaics stitched together thousands of images to create a single orthorectified image which allowed scientists to study how the river's path changed in response to differing sediment and water volume conditions after the removal of the dams. Because of the large scale of the dam removals, their deconstruction took multiple years. This gradual removal is reflected in the dam heights data, where dams' heights above the river bed were measured numerous times during the study. Streamgage measurements recorded changes in the river's surface water level and were collected with a water logger deployed downstream of the Elwha Dam's location. The river's sedimentology was measured in terms of the suspended sediment in the river, the bedload (or sediment transported along the riverbed), and the upstream sediment contribution. Table 1. List of authors, their agency, and the data they collected. Author Agency Data Andrew C. Ritchie USGS1 Orthomosaics, DEMs, streamgage Christopher A. Curran USGS Upstream sediment, suspended sediment, bedload, daily sediment Christopher S. Magirl USGS Upstream sediment, suspended sediment, bedload, daily sediment Jennifer A. Bountry USBR2 Upstream sediment, dam elevations, streamgage Robert C. Hilldale USBR Bedload, daily sediment Timothy J. Randle USBR Upstream sediment, dam elevations, streamgage Jefferey J. Duda USGS Suspended sediment 1. U.S. Geological Survey 2. U.S. Bureau of Reclamation For more information on the USGS's science in support of the Elwha River Restoration Project, please visit https://walrus.wr.usgs.gov/elwha/