A Model For The Growth And Development Of Wave-Dominated Deltas Fed By Small Mountainous Rivers: Insights From The Elwha River Delta, Washington

Details

• Journal Title:
  Sedimentology
• Personal Author:
  Zurbuchen, Julie ; Simms, Alexander R. ; Warrick, Jonathan A. ; Miller, Ian M. ; Ritchie, Andrew
• NOAA Program & Office:
  Sea Grant ; OAR (Oceanic and Atmospheric Research)
• Sea Grant Program:
  WASHU (Washington Sea Grant)
• Description:
  Observations from ground-penetrating radar, sediment cores, elevation surveys and aerial imagery are used to understand the development of the Elwha River delta in north-western Washington, USA, which prograded as a result of two dam removals in late 2011. Swash-bar, foreshore and swale depositional elements are recognized within ground-penetrating radar profiles and sediment cores. A model for the growth and development of small mountainous river wave-dominated deltas is proposed based on observation of both the fluvial and deltaic settings. If enough sediment is available in the fluvial system, mouth-bars form after higher than average river discharge events, creating a large platform seaward of the subaqueous delta plain. Swash-bars form concurrently or within a month of mouth-bar deposition as a result of wave action. Fair-weather waves drive swash-bar migration landward and in the direction of littoral drift. The signature of swash-bar welding to the shoreline is landward-dipping reflections, as a result of overwash processes and slipface migration. However, most swash-bars are eroded by the river mouth, as only 10 of the 37 swash-bars that formed between August 2011 and July 2016 survived within the Elwha River delta. The swash-bars that do survive either amalgamate onto the shoreline or an earlier deposited swash-bar, forming a single larger barrier at the delta front. In asymmetrical deltas, the signature of swash-bar welding is more likely to be preserved on the downdrift side of the delta, where formation is more likely and accommodation behind newer swash-bars preserves older deposits. On small mountainous river deltas, welded swash-bars may be more indicative of a large sediment pulse to the system, rather than large hydrological events.
• Keywords:
  Geology Sediments Ground-penetrating radar
• Source:
  Sedimentology 67(5): 2310-2331
• DOI:
  https://doi.org/10.1111/sed.12702
• Sea Grant Document Number:
  WASHU-R-20-001
• Document Type:
  Journal Article
• Place as Subject:
  Elwha River Watershed (Wash.)
• Rights Information:
  CC BY
• Compliance:
  Library
• Main Document Checksum:
  urn:sha256:56a092d9ece8f1496c55d2d194bbe994f84866e4e72d9bc785076e2e87b558c5
• Download URL:
  https://repository.library.noaa.gov/view/noaa/37501/noaa_37501_DS1.pdf
• File Type:
  [PDF - 3.04 MB ]