MULTIBEAM EXPLORATION OF THE TRIFECTA TERRAIN ON THE MID-CONTINENTAL SHELF OFF CHARLESTON, SC

A multibeam survey was conducted off Charleston, SC in the mid-shelf region at a depth of 20-25 m, to examine a paleo-river channel previously investigated during the College of Charleston's 2004 Transect Program. This study took place November 9-11, 2006 on the NOAA Ship Nancy Foster. A segment of the Transect River Channel, identified as the Trifecta Terrain, contains several geomorphological features, including a set of moderately incised meanders, evidence of current flow structures, and a relatively large, smooth sand bar adjacent to the system. Comprehensive bathymetric information was gathered using multibeam sonar. Hardground and soft-substrate analyses can be gleaned from the sonar backscatter, ground-truthed by several surface sediment grab samples that will provide information on grain size and composition. Similar shelf studies have been conducted at Gray's Reef National Marine Sanctuary. The goals of this study are to determine relative distributions of hardground and soft-substrate, and to ascertain if any previously unknown features or anomalies exist. Ultimately, we will determine which sites should be revisited for further investigation and what technologies are necessary.