Unexpected Bathymetry and Habitat Features in Estuarine Environments of Georgia, USA

Surveying the seafloor with new technologies and techniques provides a new generation of higher-resolution imagery of both bathymetry and benthic habitat. Recent surveys using an Edgetech 4600 interferometric sonar have identified previously unknown patterns in these properties in the estuarine and nearshore areas in coastal Georgia, USA. As part of a multi-year mapping effort, four of the seven sounds in coastal Georgia have been mapped: Wassaw Sound, Ossabaw Sound, St. Catherine's Sound and Sapelo Sound. Interferometry, sidescan sonar imagery and bottom sediment character have been combined to identify bathymetric patterns, diverse benthic habitats and to produce comprehensive habitat maps. Although the distribution of habitat types differs within each of these sites, all habitat types are common to all areas, and some general patterns emerge. Each site exhibits regions of mobile sediments, but of critical importance, also exhibits deep scours into semi-indurated materials that create vertical relief and hard substrates. Each project area can be divided into geomorphological features i.e., channels, deep depressions, vertical walls, ridges and flats. Bedforms are commonly visible, particularly in channels and depressions. Sediments are dominated by sand. These data, along with derivatives e.g., slope, rugosity and bathymetric position index, identify potentially important, complex habitat for sessile and mobile organisms. Scarps and ledges (up to 2 m high, up to 1000 m long) are distinctly recognizable in the sidescan imagery and slope analysis. This presentation will describe the procedures for working with shallow water interferometric sonar data and interpretations that can be reached using these tools.