DOI: 10.5066/f76972sc
title: River-channel topography and sediment grain size on the Elwha River, Washington, 2006 to 2017

description: The Elwha River, Washington, USA, was the site of the largest dam-removal project to date, in which two dams were removed between 2011 and 2014. Dam removal was made in stages over about a one-year period for the Elwha Dam (32 m high) and a three-year period for the Glines Canyon Dam (64 m high). This data release presents topographic and sediment grain size data collected by the U.S. Geological Survey (USGS) in the Elwha River channel between 2006 and 2017. These data have been used to inform interpretations of geomorphic and sediment evolution in the Elwha River before, during, and after dam removal, including the response to several flood events (Draut and others, 2011; East and others, 2015; Warrick and others, 2015; Ritchie and others, in review; East and others, in review). We measured topography and bed-sediment grain size in five sites (river reaches) selected for spatially intensive, long-term study, during 20 field surveys between fall 2006 and summer 2017. We refer to these study sites as reaches &quot;1,&quot; &quot;1B,&quot; &quot;2,&quot; &quot;3,&quot; and the &quot;Control Reach&quot; (see map figure). Reach 1, 172 m long, contained 6 channel-perpendicular transects. Reach 1B, 300 m long, contained 5 transects. Reach 2, 110 m long, contained 5 transects within the eastern of two large anabranches. A small side channel (&quot;side channel 5,&quot; or &quot;SC5&quot;) within reach 2 was also surveyed between 2006 and 2008. Reach 3, 112 m long, contained 6 transects. Reach 3 was within the intertidal zone prior to dam removal but experienced only fluvial influence after winter 2012. Our 100-m-long control reach, 1.5 km upstream of the upper end of Lake Mills, was situated at the downstream end of an alluvial section of the Elwha River known as Geyser Valley, within Olympic National Park, where the river gradient is 0.017. Reaches 1, 1B, 2 and 3 were located in the lower watershed, downstream of the site of the lowermost of the two dams (Elwha Dam). The control reach was located upstream from the site of the uppermost dam (Glines Canyon Dam). The control reach was located above any hydraulic influence of the Lake Mills reservoir. In the data files, we use abbreviations R to indicate Reach number, and T to indicate transect number; thus, the abbreviation &quot;R3-T2&quot; indicates Reach 3, Transect 2; &quot;CR-T1&quot; indicates Control Reach, Transect 1; and &quot;R2-SC5-T1&quot; indicates Reach 2, Side Channel 5, Transect 1. References: Draut, A.E., Logan, J.B., and Mastin, M.C., 2011, Channel evolution on the dammed Elwha River, Washington, USA: Geomorphology, v. 127, p. 71-87, https://doi.org/10.1016/j.geomorph.2010.12.008. East, A.E., Pess, G.R., Bountry, J.A., Magirl, C.S., Ritchie, A.C., Logan, J.B., Randle, T.J., Mastin, M.C., Minear, J.T., Duda, J.J., Liermann, M.C., McHenry, M.L., Beechie, T.J., and Shafroth, P.B., 2015, Large-scale dam removal on the Elwha River, Washington, USA: river channel and floodplain geomorphic change: Geomorphology, v. 228, p. 765-786, https://doi.org/10.1016/j.geomorph.2014.08.028. East, A.E., Logan, J.B., Mastin, M.C., Ritchie, A.C., Bountry, J.A., Sankey, J.B., and Magirl, C.S., in review, Geomorphic evolution of a gravel-bed river under sediment-starved vs. sediment-rich conditions: river response to the world&quot;s largest dam removal: Journal of Geophysical Research-Earth Surface. Ritchie, A.C., Warrick, J.A., East, A.E., Magirl, C.S., Stevens, A.W., Bountry, J.A., Randle, T.J., Curran, C.A., Hilldale, R.C., Duda, J.J., Miller, I.M., Pess, G.R., Foley, M.M., McCoy, R., and Ogston, A.S., in review, Morphodynamic evolution following sediment release from the world's largest dam removal: Nature Scientific Reports. Warrick, J.A., Bountry, J.A., East, A.E., Magirl, C.S., Randle, T.J., Gelfenbaum, G., Ritchie, A.C., Pess, G.R., Leung, V., and Duda, J.J., 2015, Large-scale dam removal on the Elwha River, Washington, USA: source-to-sink sediment budget and synthesis: Geomorphology, v. 246, p. 729-750, https://doi.org/10.1016/j.geomorph.2015.01.010.