Seminar: Emily Eidam, UW School of Oceanography
March 1 @ 3:30 pm - 4:30 pm
Presenter Affiliation: University of Washington School of Oceanography
Presenter Discipline: Marine Sediment Transport
Seminar Title: Sedimentary processes contributing to delta evolution: Insights from the Elwha and Mekong dispersal systems
Summary: Submarine deltas are the endpoints for many large and small rivers worldwide. Deltaic sediments serve as repositories for nutrients, natural resources, and stratigraphic histories of land-surface changes, but the processes by which they evolve are complex. The sediment transport community is continually working to improve in situ observations and models of how waves, currents, and episodic processes like gravity flows deliver, re-work, and remove sediment in these environments, on time scales of seconds to millennia. The small Elwha River Delta, WA has served as an excellent natural laboratory for studying how massive influxes of fluvial sediment are processed in the coastal ocean and converted to deltaic deposits, thanks to a recent dam removal project. Transport processes are presented in a source-to-sink framework, from estimates of particle clearance in the buoyant surface plume to boundary-layer gravity flows, export by asymmetric tidal currents, and evolution of a new—but surprisingly small—muddy deposit. In this type of system, tidal currents limit the growth of sediment deposits. In contrast, for larger systems like the Mekong Delta, sediment fluxes overwhelm the transport capacity, and seasonal interaction of tidal currents and river discharge may facilitate sediment retention near the river mouth.