HR: 14:55h
AN: OS33D-06    [Abstracts]
TI: Observations of onshore sediment transport in water depths of 10-20 m off Long Island, NY
AU: * Flood, R D
EM: roger.flood@sunysb.edu
AB: A high-resolution multibeam echosounder has been used as part of investigations of sediment transport, benthic habitat and coastal infrastructure in a number of estuarine and inner shelf settings. High-resolution multibeam topographic data provides important information on the nature and distribution of sedimentary bed forms while co-registered backscatter at 300 kHz provides insights into sediment type and the presence of smaller bed forms. A number of studies have been conducted on the inner continental shelf off Long Island, New York to characterize surf-clam habitat and the present-day structure of artificial reefs. These studies, which range in depth from to over 20 m, often show the existence of asymmetric sand waves and other features caused by sediment movement (especially scour depressions and backscatter anomalies) which indicate onshore sediment transport. Repeat surveys show that sand waves can migrate onshore as much 15 m over a 6-month period, although migration is likely to be episodic, occurring primarily during storms or other events. This high-resolution bathymetric data shows the sand waves are not uniformly distributed across the sea bed, but are often concentrated on the flanks of elongate topographic depressions. This onshore sediment movement appears to be occurring along the length of Long Island, although there are regional variations in the water depth in which they are observed. This observed transport may represent a portion of the onshore sediment transport thought to exist in this area.
DE: 3000 MARINE GEOLOGY AND GEOPHYSICS
DE: 3022 Marine sediments--processes and transport
DE: 3045 Seafloor morphology and bottom photography
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting