GRAINSIZE ANALYSIS OF SURFICIAL AND SUB-SURFACE PLEISTOCENE SEDIMENTS OF THE OUTER CONTINENTAL SHELF ALONG THE SOUTH EASTERN UNITED STATES

Beach renourishment along shorelines comprising the Southeastern coast of the United States provides one solution to the erosion along these, wave-dominated, tide-dominated, and mixed-energy coastlines. Since 1954, over $350 million dollars have been spent towards renourishment projects along the coast of South Carolina alone (Kana, 2012). This figure does not include the additional expenses related to property loss, property damage, and lost resources (time and infrastructure). In addition to the financial loss, renourishment negatively impacts biological resources, such as turtles and the invertebrates at the base of the food chain for economically important fish species. Demand for new practices may lead to the improvement and sustainability of vulnerable coastal environments, private housing and industry, public access, and economic development in the coastal zone.

In order to improve coastal resilience and sustain coastal environments in the wake of Hurricane Sandy, BOEM and cooperative partners in 13 Atlantic states instituted a collaborative offshore sand-resource investigation along the US East Coast Outer Continental Shelf (OCS). The South Carolina (SC) OCS is the focus of this presentation. For this particular study, 281 sediment samples from 19 offshore vibracores were analyzed with a CILAS laser particle size analyzer. The analyses identify sediment sizes ranging from very fine- grained muds and sands to gravels, and are being used to determine the particle distribution, composition, and depositional history of sediments found along the OCS off SC. Significant effort has been placed on standard operating procedures for removing coarse materials, disaggregating cohesive sediments, and presenting the results of the analysis. CILAS data were processed in excel using Gradistat (Blott and Pye, 2001) and compared to sieve analyses conducted by BOEM subcontractor CB&I. Sieving and laser analysis showed high correlation in results. The results are delivered in varying expository methods including graphs, tables, and statistical outputs, and are used in conjunction with high-resolution chirp subbottom profiles to support ongoing volumetric calculations for viable renourishment quality materials offshore.