Shoreline Movements: Tybee Island, Georgia, to Cape Fear, North Carolina, 1851-1983

The history of shoreline change along the Coast of South Carolina is examined. Maps depicting the entire shoreline at various points in time were prepared by the Oceanic and Atmospheric Administration, National Ocean Service, and the South Carolina Division of Research and Statistical Services. These maps were used by Staff of the US Army Engineer Waterways Experiment Station, Coastal Engineering Research Center, to analyze changes in shoreline position over the past 150 years. The shoreline maps were digitized at an along-the-coast interval of 50 m. Cross shore transects were established at each location to facilitate examination of shoreline position changes. Shoreline position was compared both spatially and temporally to determine net and average rate of change. Data are summarized in this report for each transect, defined segments of shoreline, each barrier island or mainland beach, and defined geomorphic regions. The technique allows quantification of shoreline change in an onshore offshore direction. Pronounced alongshore changes, such as often occurs at inlets or capes, were examined using manual techniques to measure areal changes. Results are presented for the entire Atlantic coast from Tybee Island, Georgia to Cape Fear, North Carolina, in both graphic and tabular format. Erosion and accretion were variable spatially and temporally throughout the period of record. Results show that long-term erosion (>I m/year) predominated throughout the region of coast fronted by barrier islands. Mainland beaches, such as those along the "Grand Strand" were relatively stable. In both regions, erosion rates were most variable and greatest in the vicinity of inlets. 4. A variety of factors were compared with the shoreline change data to determine the cause for measured patterns of erosion and accretion. Proximity to inlets was a major cause for variable erosion present along the barrier island coastline. Lack of inlets could also be a major reason for stability of "Grand Strand" beaches, along with the shallow depth to less erodible pre-Holocene sediments. Human impacts in the coastal zone had localized measurable effects on erosion/accretion patterns. Maximum wave height also correlated well with erosion, suggesting that susceptibility to storms was an important factor in determining shoreline stability. Other factors, such as nearshore bathymetry and shoreline orientation showed little effect on shoreline changes.