CHARACTERISTICS OF SEDIMENT DELIVERY THROUGH THE TIDAL REACH OF AN ESTUARINE TRIBUTARY OF THE SAN FRANCISCO BAY
Evidence of decreasing sediment delivery to San Francisco Bay (Bay) from its largest tributaries suggests smaller, local tributaries may play increasing roles in sediment delivery to this estuary. However, tidal forcing in the lower reaches of these tributaries can modulate sediment delivery to the estuary. We investigated characteristics of suspended-sediment delivery from Corte Madera Creek, a Bay tributary. Discharge of water and suspended-sediment were observed for three years at two locations along the creek: upstream of tidal influence and at the mouth. Comparison of upstream and mouth gages showed 50% trapping of watershed-sourced suspended-sediments within the tidal reach over this period. At the storm time scale, suspended-sediment trapping varied by storm size. As upstream peak flow increased, large storms exhibited significantly decreased trapping while small storms exhibited nearly constant trapping. Tidal conditions at the mouth during storms were not strong factors in sediment delivery from the creek, suggesting watershed-scale attributes are more important predictors. These results suggest that, for estimating sediment delivery from estuarine tributaries, sediment gages should be near the mouth to account for trapping within the tidal reach.
Downing-Kunz, M. A., United States Geological Survey, USA, email@example.com
Schoellhamer, D. H., United States Geological Survey, USA, firstname.lastname@example.org
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