Settling Velocities of Fine Sediments in San Francisco Estuary Margins
Abstract
In San Francisco Bay, suspended sediment can transport contaminants and nutrients, limit light availability for primary production, and accumulate in or erode mudflats and tidal wetlands. To predict sediment dynamics and transport, models must include sediment settling velocities. However, fall velocities are still predicted mostly empirically and they are challenging to observe in-situ, thus they remain parameterized in models with high uncertainty. Previous work in San Francisco Bay found that settling velocities ranged between 0.5 and 10 mm/s. However, this work was conducted along the "backbone" of the bay, and may not apply throughout San Francisco Bay's extensive shoals, mudflats, and intertidal regions. We measured settling velocities at margin regions around San Francisco Bay to assess the potential for spatial and temporal variability in settling velocity and sediment dynamics. Results from a 24 hour field experiment in a channel slough of South San Francisco Bay suggest that sediment in margin regions may be slower settling (0.3-0.4 mm/s) than sediments in the bay center, consistent with results from San Mateo shoals. At a tidal creek in Stege Marsh, in central San Francisco Bay, a basin-scale seiche at a 20 minute period dominates near-bed currents. We compare settling velocities from this seiche-influenced location with settling velocities from Alviso Slough and Arrowhead Marsh, in San Leandro Bay. An improved understanding of sediment characteristics, settling velocities, forcing energetics, and spatial variability throughout the edges of San Francisco Bay will help us develop more accurate and predictive models of sediment transport.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFMEP33A0970A
- Keywords:
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- 1815 Erosion;
- HYDROLOGYDE: 1862 Sediment transport;
- HYDROLOGY