IMPACTS OF UNDERLYING STRATIGRAPHY, INLET FORMATION, AND GEOMORPHOLOGY ON COASTAL SEDIMENT DYNAMICS: CAPERS INLET QUADRANGLE, SC (USA)

Coastal areas are geologically dynamic, undergoing changes that result from an interplay between underlying and surficial geology and physical factors such as tides and waves. To protect both public and private interests, coastal policy-makers and scientists should have a thorough grasp of the natural processes responsible for influencing the geologic evolution of coastal environments. This study is a USGS-funded EDMAP project that focuses on gaining a better understanding of the geologic framework underlying the barrier islands, inlets, backbarrier environments, and shallow offshore marine areas in the Capers Inlet Quadrangle, South Carolina. Geophysical sidescan sonar and subbottom profiler surveys provide data relating to shallow marine geology and stratigraphy. A number of features, including a large paleochannel adjacent to the mainland and a distinct quaternary boundary offshore, have been identified using data from these surveys. On barrier islands in the study area, ground-penetrating radar (GPR) was used for stratigraphic data collection. Sidescan sonar and subbottom profiler data were incorporated into ArcGIS maps illustrating sediment thickness, geomorphology, and surficial sediment distributions. The geophysical data and resulting maps are used to address questions pertaining to sediment sources as well as possible long and short-term barrier island evolution. Pre-existing knowledge of local geomorphology is also used in combination with stratigraphic data to provide a basis for policy decisions involving issues such as beach erosion and re-nourishment. Sections of the barrier islands in the study area are densely populated, and both residents and coastal managers have a vested interest in understanding how existing geologic features and physical processes may influence the future geologic evolution of the barrier island system. Although populated barrier islands in the study area are considered geologically stable, data allow for a better understanding of how and where future changes may occur. Maps resulting from the project will serve to incorporate geologic data into a visual format that is useful to geologists, policymakers, and members the general public seeking to better understand the processes controlling geomorphology in the area.