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