Linking human impacts within an estuary to ebb-tidal delta evolution
San Francisco Bay, California, USA is among the most anthropogenically altered estuaries in the entire United States, but the impact on sediment transport to the coastal ocean has not been quantified. Analysis of four historic bathymetric surveys has revealed large changes to the morphology of the San Francisco Bar, an ebb-tidal delta at the mouth of the San Francisco Bay. From 1873 to 2005 the bar eroded an average of 80 cm, which equates to a total volume loss of 100 + 65 x 106 m3 of sediment. Comparison of the surveys indicates the entire ebb delta has contracted radially while its crest has moved landward an average of 1 km. Compilation of historic records reveals that 130 x 106 m3 of sediment has been permanently removed from the San Francisco Bay and adjacent coastal ocean. Constriction of the bar is hypothesized to be from a decrease in sediment supply from San Francisco Bay, a reduction in the tidal prism of the estuary, and/or a reduction in the input of hydraulic mining debris. Changes to the morphology of the San Francisco Bar have likely altered wave refraction and focusing patterns on adjacent beaches and may be a factor in persistent beach erosion occurring in the area.
Citation Information
Publication Year | 2009 |
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Title | Linking human impacts within an estuary to ebb-tidal delta evolution |
Authors | Kate L. Dallas, Patrick L. Barnard |
Publication Type | Article |
Publication Subtype | Journal Article |
Series Title | Journal of Coastal Research |
Index ID | 70148354 |
Record Source | USGS Publications Warehouse |
USGS Organization | Pacific Coastal and Marine Science Center |