Morphodynamic evolution following sediment release from the world's largest dam removal.

Autor: Ritchie AC; Pacific Coastal and Marine Science Center, United States Geological Survey, Santa Cruz, CA, USA. aritchie@usgs.gov., Warrick JA; Pacific Coastal and Marine Science Center, United States Geological Survey, Santa Cruz, CA, USA., East AE; Pacific Coastal and Marine Science Center, United States Geological Survey, Santa Cruz, CA, USA., Magirl CS; Arizona Water Science Center, United States Geological Survey, Tucson, AZ, USA., Stevens AW; Pacific Coastal and Marine Science Center, United States Geological Survey, Santa Cruz, CA, USA., Bountry JA; Sedimentation and River Hydraulics Group, Technical Service Center, United States Bureau of Reclamation, Denver, CO, USA., Randle TJ; Sedimentation and River Hydraulics Group, Technical Service Center, United States Bureau of Reclamation, Denver, CO, USA., Curran CA; Washington Water Science Center, United States Geological Survey, Tacoma, WA, USA., Hilldale RC; Sedimentation and River Hydraulics Group, Technical Service Center, United States Bureau of Reclamation, Denver, CO, USA., Duda JJ; Western Fisheries Research Center, United States Geological Survey, Seattle, WA, USA., Gelfenbaum GR; Pacific Coastal and Marine Science Center, United States Geological Survey, Santa Cruz, CA, USA., Miller IM; Washington Sea Grant, Olympic Peninsula Field Office, Port Angeles, WA, USA., Pess GR; Northwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Department of Commerce, Seattle, WA, USA., Foley MM; Pacific Coastal and Marine Science Center, United States Geological Survey, Santa Cruz, CA, USA., McCoy R; Natural Resources Department, Lower Elwha Klallam Tribe, Port Angeles, WA, USA., Ogston AS; School of Oceanography, University of Washington, Seattle, WA, USA.
Jazyk: angličtina
Zdroj: Scientific reports [Sci Rep] 2018 Sep 05; Vol. 8 (1), pp. 13279. Date of Electronic Publication: 2018 Sep 05.
DOI: 10.1038/s41598-018-30817-8
Abstrakt: Sediment pulses can cause widespread, complex changes to rivers and coastal regions. Quantifying landscape response to sediment-supply changes is a long-standing problem in geomorphology, but the unanticipated nature of most sediment pulses rarely allows for detailed measurement of associated landscape processes and evolution. The intentional removal of two large dams on the Elwha River (Washington, USA) exposed ~30 Mt of impounded sediment to fluvial erosion, presenting a unique opportunity to quantify source-to-sink river and coastal responses to a massive sediment-source perturbation. Here we evaluate geomorphic evolution during and after the sediment pulse, presenting a 5-year sediment budget and morphodynamic analysis of the Elwha River and its delta. Approximately 65% of the sediment was eroded, of which only ~10% was deposited in the fluvial system. This restored fluvial supply of sand, gravel, and wood substantially changed the channel morphology. The remaining ~90% of the released sediment was transported to the coast, causing ~60 ha of delta growth. Although metrics of geomorphic change did not follow simple time-coherent paths, many signals peaked 1-2 years after the start of dam removal, indicating combined impulse and step-change disturbance responses.
Databáze: MEDLINE
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