was considerable data scatter at higher average significant wave heights and 

 larger shoreline movements. The trend between maximum shoreline change and 

 maximum significant wave height is clear (Figure 56) . Shoreline movement 

 increases with increasing maximum height. Figure 4 shows that maximum signif- 

 icant wave height is greatest along the barrier island and cuspate delta geo- 

 morphic zones and least along the arcuate strand. Likewise, spatial 

 distribution of erosion is greater in the barrier island and cuspate delta 

 zones than in the arcuate strand (Figure 52) . 



173. Figures 54 through 56 suggest that shoreline change along South 

 Carolina's coast is dependent on incidence of large waves at the shoreline. 

 This in turn suggests that long-term erosional history of the coast may depend 

 heavily on storm frequency and magnitude. Data presented by Simpson and Miles 

 (1971) suggest a decreasing probability of tropical storm occurrence from 

 south to north in the study area. It is difficult to attribute shoreline ero- 

 sion or accretion at every segment to presence or absence of large waves since 

 other factors influence effectiveness of waves in changing the shoreline. 

 Orientation of the coast relative to direction of wave approach, nearshore 

 slope, and sediment composition of beach and nearshore are factors that can 

 greatly modify effects of waves on shoreline change. 



174. In addition to wave height, wave period (T) was examined relative 

 to average and maximum shoreline movements. Occurrence of waves with periods 

 greater than 4, 7, 8, and 11 sec were compared with shoreline change data. No 

 relationship was apparent between average shoreline change and any wave period 

 data. Data points were widely scattered (e.g. Figure 57). Comparisons of 

 maximum shoreline movement and wave period do not show any trends except at 

 periods greater than 11 sec (Figure 58). Three distinct groups are evident 

 related to percentage of time that waves of T > 11 sec occur. Within each 

 group, there appears to be no correlation between maximum movement and T > 



11 sec . Examination of the three groups shows a division based on shoreline 

 orientation. The four east-west trending WIS segments west of Cape Fear 

 receive fewest T > 11 sec waves. These four WIS segments roughly coincided 

 with reaches 6 and 7, which have the most stable shorelines (Figure 52). 

 Northeast- southwest trending barriers form the middle grouping. The segment 

 of coast receiving most T > 11 sec waves is north- south trending zones north 

 of Cape Romain and near Tybee Island. This corresponds with reaches 5 and 1 

 respectively, which have the largest amount of erosion of all reaches 



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