HR: 0800h
AN: H51D-0399    [Abstracts]
TI: Bedform Morphology Under Significant Wave-Tidal Current Interaction at the Mouth of a Major Tidal Inlet, San Francisco, California
AU: * Barnard, P L
EM: pbarnard@usgs.gov
AF: United States Geological Survey, 400 Natural Bridges Dr., Santa Cruz, CA 95060 United States
AU: Hanes, D M
EM: dhanes@usgs.gov
AF: United States Geological Survey, 400 Natural Bridges Dr., Santa Cruz, CA 95060 United States
AB: The mouth of San Francisco Bay is an extremely dynamic tidal inlet environment, where wave heights commonly exceed 5 m during the winter. During peak flow, tidal currents approach 3 m/s at the Golden Gate, which carries a tidal prism of 2 billion cubic meters. Flow structure varies markedly spatially and temporally due to the complex interaction of wind, waves and tides. The dominant patterns of this interaction are expressed in the bedform morphology of the tidal inlet, which in turn is an expression of the dominant sediment-transport pathways. Identifying pathways of sediment transport is essential information for coastal managers in this region who direct dredging operations and seek the most efficient means of mitigating erosion on adjacent Ocean Beach. A multibeam sonar survey was recently completed that mapped in high resolution, for the first time, the seafloor morphology at the mouth of San Francisco Bay. Highlights of the data set include one of the largest sand-wave fields on record (n= 40, max wavelength= 220 m, max amplitude= 5 m, max depth= 106 m) and an extremely diverse array of bedform morphologies, scales and orientations around the inlet mouth. Hydrodynamic and wave modeling suggest complex flow structures around the inlet mouth and offshore of adjacent Ocean Beach that are well correlated with observed bedform morphologies. The processes that control the morphology of the adjacent beach are intimately related to the processes that control sediment transport about the ebb tidal delta at the mouth of San Francisco Bay. The link between the ebb tidal delta and the adjacent beach is well represented by the bedform morphology.
DE: 1862 Sediment transport (4558)
DE: 3045 Seafloor morphology, geology, and geophysics
DE: 4255 Numerical modeling (0545, 0560)
DE: 4512 Currents
DE: 4560 Surface waves and tides (1222)
SC: Hydrology [H]
MN: Fall Meeting 2005