HR: 0800h
AN: OS21B-1241    [Abstracts]
TI: The South Carolina Coastal Erosion Study: Wind Wave Energy Dissipation
AU: * Demir, H
EM: huseyin.demir@ce.gatech.edu
AF: Georgia Institute of Technology-Savannah, 210 Technology Circle, Savannah, GA 31407 United States
AU: Work, P A
EM: paul.work@gtsav.gatech.edu
AF: Georgia Institute of Technology-Savannah, 210 Technology Circle, Savannah, GA 31407 United States
AU: Voulgaris, G
EM: gvoulgaris@geol.sc.edu
AF: University of South Carolina, Department of Geological Sciences, Columbia, SC 29208 United States
AB: As part of the South Carolina Coastal Erosion Study (SCCES) wave and current data were collected offshore of Myrtle Beach, SC for 2 months in 2001-02. This field measurement campaign was the second of a three-part experiment series. While the overall objective of the study is to describe the processes governing the circulation, wave propagation and sediment transport along the northern South Carolina coast, this presentation focuses on the wave energy dissipation over a heterogeneous seafloor over a distance of 6 km. The data were collected between November 9, 2001 and January 17, 2002. The instruments were placed along a transect crossing a large sand shoal in an area otherwise largely deprived of sand, at depths of 8 to 12 meters. The four instruments used, in order of decreasing distance from shore, were 600 and1200 KHz RDI ADCP's, a Nortek Aquadopp and a Sontek Argonaut-XR. Bathymetry and bottom characteristics such as depth and thickness of sand layer are available through USGS's coastal relief model and side scan surveys. Wind data are supplied by a large-scale numerical wind model. Its output is compared with wind data collected at Frying Pan Shoals buoy and at an anemometer placed at Spring Maid pier after the experiment. The SWAN wave model (Booij et al. 1999) was used to model the spectral wave transformation from the offshore buoy to the inner stations and to compare the observed wave energy dissipation to the available models. There was no extreme storm event during the deployment period. The maximum significant wave height observed was 1.6 meters at the offshore wave station, and the mean wave height was 0.8 meters. The mean period was between 5 and 7 seconds most of the time. Significant wave energy dissipation (up to 40% decrease in wave energy flux) across 6 km was observed. A shift of the spectral peak and a change in the spectral shape was observed in many events, which were not generally reproduced by the model. Sand and rock bottom characteristics were modeled with different dissipation coefficients. The coefficients were optimized to give the best fit to the data. Since the dissipation process is non-linear, iterative linear regression techniques were employed. The physical meaning of the coefficients and the improvements achieved with varying bottom friction coefficients are discussed.
DE: 4255 Numerical modeling
DE: 4546 Nearshore processes
DE: 4560 Surface waves and tides (1255)
DE: 4594 Instruments and techniques
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting