Investigating Sediment Transport Off South CarolinaPart of the South Carolina Coastal Erosion Study
Scientists from the U.S. Geological Survey (USGS)'s Coastal and Marine Geology Program in Woods Hole, MA, and Santa Cruz, CA, along with researchers from the University of South Carolina and the Georgia Institute of Technology (Georgia Tech), are conducting an investigation of sediment transport by waves and currents in the coastal waters off South Carolina, in the Myrtle Beach area.
This investigation is part of the USGS' South Carolina Coastal Erosion Study, in which the USGS is collaborating with the National Oceanic and Atmospheric Administration (NOAA)'s Sea Grant Program, the State of South Carolina, and several university partners to examine the causes of severe erosion along the South Carolina coast. (See related article in September 2003 Sound Waves.)
Of particular interest in the recent investigation is a large, shore-oblique sand deposit identified during recent geologic-framework mapping.
The shoal, a potential source of sand for beach-nourishment projects, is approximately 10 km long by 3 km wide and extends to 11-m water depth. It has a relief of about 2 m above the surrounding sea floor, which consists of a thin veneer of Holocene sediment overlying Cretaceous sedimentary rocks.
The sand deposit lies atop an erosional surface cut into the sea floor by landward migration of the shoreline in response to rising sea level in the past. The sand deposit is considered anomalous because its presence cannot be attributed geologically to a tidal inlet, a typical source of sand for such shoals.
Because the sand deposit is in a region with a limited supply of sand, some of the questions researchers are trying to answer are:
The shoal is most likely controlled by tidal and wind-driven currents. To study these and other physical processes in the region, the scientists conducting the recent investigation deployed equipment at eight sites to measure the vertical structure of currents, salinity, temperature, waves, turbulence intensity, suspended-sediment concentration, and bed forms (sand waves).
This field-measurement program will be integrated with a comprehensive numerical-modeling study to predict waves, currents, and sediment transport in the region. The research will identify the oceanographic processes responsible for maintaining the large shore-oblique shoal and will explore possible sediment pathways connecting the shoal to the beach.
in this issue: Seamount Environments off California
Sediment Transport off South Carolina