THE TRANSECT RIVER CHANNEL: SONAR AND SCUBA EXPLORATION OF AN ANCIENT RIVER

In 2004, leg 02 of the College of Charleston Transect Program sailed aboard the R/V Savannah and identified an area within the continental shelf off Charleston, SC that contained remarkable hard-ground features. The original feature identified in 2004 is known as the Harris Meander. It is an ancient mid-shelf meandering stream channel incised within the hardground, with approximately 1.5 m relief in 20 m water depth. Repeated surveys during legs 03 and 04 in 2004 and 2005, and another November 2006 auxiliary multibeam survey cruise aboard the NOAA Ship Nancy Foster vastly expanded our knowledge of the mid-shelf region. Undergraduate researchers have cleaned, processed, and visualized the multiple Klein sidescan and Simrad multibeam sonar surveys with Caris HIPS/SIPS Professional v6. The surveys were groundtruthed with Smith-MacIntyre sediment grabs, video data collected from ROV and SCUBA dives, and rock and sediment samples also collected via SCUBA. The Harris Meander is one of more than twenty meanders mapped as part of a continuous meandering channel system that trends roughly in a shore-normal orientation, referred to as the Transect River Channel. The feature's geomorphological attributes will be studied, and additional characterization from bathymetrically correlated backscatter data and mineralogical identification of the recovered rock samples will be presented. Spring, 2007 investigations of this site may include additional SCUBA dives to collect more samples and sub-bottom profiler seismic data evaluation with the goal of studying the age, context, and depositional history of the environment that created it.