EXAMINING TEMPORAL AND SPATIAL VARIABILITY OF BEACH EROSION ALONG THE GRAND STRAND, SC

Increasing erosional pressures on coastal systems due to rising sea level and the unnatural vulnerability of societal oceanfront infrastructure require a better understanding of the mechanisms of natural and anthropogenic induced alterations. This is especially important in sediment-starved coastal systems where the effects from geologic framework may exert a disproportionate influence. Studies into coastal geologic framework and erosional patterns are comprehensive and well documented, yet detailed analysis of their temporal and spatial connection in South Carolina is limited.

The Grand Strand region of South Carolina has a comprehensive set of geophysical data, such as seismic, sonar, and a rich suite of RTK-DGPS surveys of a shoreline contour (MHW; 0.625 m) collected monthly since 2007 to consider shoreline variability over 52 km of coastline. Calculation of various statistical parameters using the USGS Digital Shoreline Analysis System v4.2 software, including end point rate (EPR), linear regression rate (LRR) and shoreline change envelope (SCE), provides quantitative assessment of shoreline behavior. Spectral analysis is utilized to define patterns in spatial variability.

Preliminary results discern the significance of anthropogenic influences, namely beach renourishment projects, on rates of shoreline erosion and accretion. These initial results demonstrate the defining influence of framework in locations of known historical inlets and increased shoreline position variability. Aside from a section of shoreline exhibiting distinctly higher net shoreline movement from the mean, the amount of shoreline change generally increases in the southerly direction from North Myrtle Beach into Arcadian Shores (SCE mean increasing from 27.2 m to 40.26 m), while similar patterns are not reflected in southern regions of the Grand Strand. Additional spectral analysis shows significant alongshore variability on the order of 1-1.6 km for the northern portion of the Grand Strand, with a smaller spatial variability of 0.6-0.8 km dominating the southern regions. Continued efforts will focus on differentiating the influence of framework and other drivers including storm influence and bar presence on the variabilities in shoreline behavior.