VARIATION & CONTROLS OF BEACH MORPHOLOGY ALONG THE COAST OF SOUTH CAROLINA

Regional analysis of beach profile data from the whole coast of South Carolina (SC) is carried out as part of Phase II of the SC/GA Coastal Erosion Study. The analysis aims at 1) identifying mean profile shapes along the South Carolina coast; 2) examining their spatial variability; 3) relating identified variability in profile shape with controlling factors (i.e., shoreline orientation, wave climate, tidal inlets, sediment grain size, etc.); and 4) determine the applicability of statistical models in defining beach morphological characteristics of the South Carolina coastline. Mean beach profiles and secondary morphology for each barrier island or stretch of beach along the coast of SC are defined using empirical orthogonal functions. The applicability of several widely used beach profile statistical models was examined for SC. A new double exponential model developed herein (h=B1*(1-e^(-k1x))+B2*(1-e^(-k2x))) was found to provide the best and most consistent representations of mean profile shapes. Based on trends in mean profile shapes, secondary morphology, and longshore variability of parameters defining beach profile characteristics the coast was divided into eight morphologically different regions (Region 1 to 8). Large tidal inlets and estuaries dominate the southern study region, and these play an extremely important role in shaping adjoining barrier islands and beaches. Profile shape appears to be dictated by proximity to tidal inlets and the amount of sediment provided by shoal bypassing. Barrier islands dominantly influenced by large estuaries (e.g., Hilton Head Island, Hunting Island) exhibited different mean profiles than barrier islands influenced by tidal inlets (e.g., Kiawah Island, Isle of Palms). The latter exhibited well-barred, low-sloped sediment-rich beach profiles (Region 3), while those surrounded by estuaries were generally steeper and showed general erosive trends (Region 1, 2). Portions of the northern study region (Regions 4, 5 and 8) appear to be influenced by small tidal inlets. Profiles within Regions 6 and 7, comprised by the 'Grand Strand' (Myrtle Beach and North Myrtle Beach), lack natural sediment input (by tidal inlets), and appear to depend on the reworking of existing sediments by waves and swashes.