due in large measure to trapping of alongshore drift north of 

 the Charleston Harbor jetties. 



Human impact has resulted in rapid erosion along Morris 

 Island, south of the Charleston Harbor jetties, and contrib- 

 uted to wide distribution of erosion in the cuspate delta 

 region. The Santee River had the fourth largest discharge of 

 east coast rivers prior to damming and diversion in 1942. 

 Loss of sediment supply to the coast has contributed to high 

 erosion rates in this area. 



Summarizing shoreline change for the entire study area coast- 

 line shows approximately 51 percent has been stable with 

 ±1 m/year or less change, approximately 31 percent has eroded 

 faster than 1 m/year, and 18 percent has accreted faster than 

 1 m/year over the 130 -year span of survey data. 



Maximum significant wave height correlates well with maximum 

 net shoreline change. Maximum change occurs where maximum 

 significant wave heights are greatest. Maximum significant 

 wave heights are lowest along the arcuate strand and highest 

 near Tybee Island, Charleston, and Cape Romain. 



Nearshore slopes were compared with shoreline changes, but no 

 direct correlations were evident. However, even where near- 

 shore slopes had similar steepness, shoreline changes in the 

 arcuate strand were consistently lowest, suggesting factors 

 other than bathymetry were controlling shoreline movements. 



Coastal stability in the arcuate strand geomorphic zone 

 appears related in part to geology. Throughout this area, 

 pre-Holocene semiconsolidated materials lie at or close to 

 beach and nearshore surfaces. The proximity of these sedi- 

 ments to the surface and their increased resistance to erosion 

 may contribute to the reduced potential for erosion. Stable 

 inlets along this coast have been found by others to be 

 anchored in pre-Holocene sediments. 



147 



