this island through recent time. Moslow and Colquhoun (1981) examined multi- 

 ple beach ridges and attempted to correlate them with recent sea level rise. 

 They suggest Kiawah originally formed between 6,000 to 8,000 years BP and 

 transgressed landward under rapidly rising sea level until about 4,000 years 

 BP. Since then Kiawah has been episodically prograding seaward because of an 

 excess in sediment supply over sea level rise. 



42. The erosional/accretional nature of South Carolina's barrier 

 islands is intimately connected with tidal inlets and associated ebb- tidal 

 deltas. Nummedal et al . (1977) point out increasing tidal range toward the 

 south because of widening of the continental shelf towards Georgia. The 

 result is a tide -dominated coastline where inlet size is relatively large and 

 inlets are strongly ebb dominant. This in turn leads to seaward- directed sed- 

 iment transport and large ebb -tidal deltas extending far out onto the shelf. 

 These inlets exert a strong influence over erosion and accretion of the bar- 

 riers. As Hubbard et al . (1977) note, only where there is 10 to 15 km between 

 inlets does one get away from their influence. 



43. The large ebb deltas in the vicinity of Kiawah and other barriers 

 have resulted in its bulbous updrift end (Hayes et al. 1975). This is a 

 result of wave refraction over ebb shoals and protection of updrift ends of 

 islands from storm waves (Figure 16) . Wave refraction results in localized 

 alongshore drift reversals toward the north. Large storm waves are attenuated 

 as they break across shoals, thus protecting landward shorelines from storm 

 damage. As a result, sediment accumulates on updrift ends of the barriers. 

 Finley (1976) examined North Inlet, near Winyah Bay, and found that following 

 inlet stabilization, ebb shoals are efficient sediment traps for littoral 

 drift. FitzGerald and Hayes (1980) suggest ebb-tidal delta development could 

 result in sand starvation of downdrift beaches. Measurements of ebb delta 

 volume by Hayes (1977) showed that volume of sand in ebb deltas adjacent to 

 Kiawah Island are 78 percent of the volume of the barrier itself. 



44. Three primary types of shoreline changes were recognized by 

 FitzGerald, Hubbard, and Nummedal (1978) and were associated with three types 

 of inlets found along the South Carolina coast (Figure 17). Stable inlets, in 

 which the ebb channel appears to be anchored in pre-Holocene cohesive sedi- 

 ments, influence shorelines depending on ebb delta size and position. As dis- 

 cussed previously, wave refraction around an ebb shoal causes local drift 

 reversals. Wave shoaling over the delta shelters the barrier from storm waves 



35 



