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Investigating Sediment Transport Off South Carolina—Part of the South Carolina Coastal Erosion Study

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Deployment of oceanographic equipment off the research vessel Dan Moore
Deployment of oceanographic equipment off the research vessel Dan Moore.

Steve Ruane, John Warner, Jonathan Borden, George Voulgaris, Ben Gutierrez, Duncan Smith, Marinna Martini, and Stephanie Obley
Field-deployment personnel onboard the research vessel Dan Moore, owned and operated by Cape Fear Community College in Wilmington, NC. From left to right: Steve Ruane (USGS), John Warner (USGS), Jonathan Borden (USGS), George Voulgaris (University of South Carolina [USC]), Ben Gutierrez (USC), Duncan Smith (USC), Marinna Martini (USGS), and Stephanie Obley (USC). Not shown are Dan Hanes (USGS), Paul Work (Georgia Tech [GT]), and Kevin Haas (GT).

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:

  • Where does the sand come from?
  • Is the shoal in a steady state, or is it eroding? accumulating?

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.

Map of the inner continental shelf of Long Bay, South Carolina South Carolina continental shelf: Map of the inner continental shelf of Long Bay, South Carolina. Land is in color, the sea floor is in gray tones produced from sidescan-sonar data—a measure of sound energy reflected, or backscattered, from the sea floor. Ground-truth data, such as sediment samples and video footage, indicate that the dark (low backscatter) areas are generally smooth or rippled surfaces composed of mostly fine and medium sand and mud. Light (high backscatter) areas represent more rugged surfaces, consisting of larger scale bedforms or hardgrounds composed of coarse sand, shell hash, gravel, and exposed rock. The arrow points to the shore-oblique sand shoal (elongate black area) being studied in the recent investigation. The sidescan-sonar data were collected between October 1999 and May 2002 and will be published in a USGS Open-File Report by Wayne Baldwin and others. Land images were provided by the South Carolina Department of Natural Resources.

Related Sound Waves Stories
Imaging Remnants of Ancient Landscapes Beneath South Carolina Beaches
September 2003

Related Web Sites
Coastal Processes Sediment Dynamics Lab
University of South Carolina
Coastal Engineering Academic Programs
Georgia Tech Savannah
Regional Coastal Studies: South Carolina
U.S. Geological Survey (USGS)

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in this issue: Fieldwork Seamount Environments off California

Sediment Transport off South Carolina

Sea Floor off Massachusetts

Research cover story:
Snowy Plover Population Recovery

Ecological Repercussions of Mosquito Control

Outreach St. Petersburg Open House

Pink Sunsets Caused by African Dust

GIS Day: University of South Florida

GIS Day: Woods Hole

Students Visit Woods Hole Scientists

Great American Teach-In: Tampa Bay

Meetings Sustainable Beaches Summit

Mid-Atlantic Offshore Sand Resources

Awards Regional Science Excellence Award

AAPG Award for Presentation Excellence

Staff & Center News Birthday Surprise

Parke Snavely Passes Away

Parke Snavely: The Journey of the Model A

Parke Snavely: Tribute by Terry Bruns

Parke Snavely: Tribute by David Scholl

Publications New Map of Hawai'i Sea Floor

USGS Coral Photograph on GSA Bulletin Cover

Dec. / Jan. Publications List

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Updated December 02, 2016 @ 12:09 PM (THF)