Monitoring of a Nearshore Disposal Mound at Silver Strand State Parkby Christopher J. Andrassy, USACOE, Los Angeles, United States,
Abstract: The migration of an underwater disposal berm constructed in December 1988 approximately six miles south of the entrance to San Diego Bay is investigated. The berm was composed of medium sized sand and had an initial volume of approximately 148,000 cy, all of which was removed from the outer portion of the entrance. Seven profile lines were surveyed at regular intervals, extending from the beach berm to the -40 foot MLLW contour. Wave data were collected with a bottom-mounted puv type gage for four months after construction. The berm flattened out and migrated shoreward from construction to around May 1989. From May to November 1989, significant accretion occurred between +10 and 0 ft MLLW. Between November 1989 and February 1990 the relative volume of material within the surveyed area had returned to levels comparable to those of the post-construction condition. Between February and November 1990 significant accretion had again occurred between +10 and 0 ft MLLW concurrent with a reduction of approximately 84% in the relative volume within the area containing the original disposal berm. The evidence from the hydrographic surveys suggests that the disposal berm has contributed both directly and indirectly to the accretion in the nearshore while being slowly dissipated over nearly two years from within the immediate littoral zone which was surveyed.
Subject Headings: Berms | Nearshore | Parks | Underwater surveys | Littoral drift | Hydrographic surveys | Construction management | Bays | Littoral zones | North America | California | United States | San Diego
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