Anthropogenic influences on shoreline and nearshore evolution in the San Francisco Bay coastal system |
| |
| Authors: | Kate L Dallas Patrick L Barnard |
| |
| Institution: | 1. Dept. of Earth and Planetary Sciences, University of California Santa Cruz, Santa Cruz, CA 95064, USA;2. U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, CA 95060, USA |
| |
| Abstract: | Analysis of four historical bathymetric surveys over a 132-year period has revealed significant changes to the morphology of the San Francisco Bar, an ebb-tidal delta at the mouth of San Francisco Bay estuary. From 1873 to 2005 the San Francisco Bar vertically-eroded an average of 80 cm over a 125 km2 area, which equates to a total volume loss of 100 ± 52 million m3 of fine- to coarse-grained sand. Comparison of the surveys indicates the entire ebb-tidal delta contracted radially, with the crest moving landward an average of 1 km. Long-term erosion of the ebb-tidal delta is hypothesized to be due to a reduction in the tidal prism of San Francisco Bay and a decrease in coastal sediment supply, both as a result of anthropogenic activities. Prior research indicates that the tidal prism of the estuary was reduced by 9% from filling, diking, and sedimentation. Compilation of historical records dating back to 1900 reveals that a minimum of 200 million m3 of sediment has been permanently removed from the San Francisco Bay coastal system through dredging, aggregate mining, and borrow pit mining. Of this total, ∼54 million m3 of sand-sized or coarser sediment was removed from central San Francisco Bay. With grain sizes comparable to the ebb-tidal delta, and its direct connection to the bay mouth, removal of sediments from central San Francisco Bay may limit the sand supply to the delta and open coast beaches. |
| |
| Keywords: | ebb-tidal delta tidal inlet coastal morphology long-term changes man-induced effects USA California San Francisco Bar San Francisco Bay |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
