1942. This should have led to erosion of the adjacent coastline since dis- 

 charge and sediment supply were reduced at the river mouth by 90 percent. 

 Instead, downdrift of the river mouth, South Island shows accretion. One pos- 

 sible explanation for these two anomalies is that with damming and diversion, 

 reduced discharge at the mouth of the Santee may have allowed ebb -tidal sedi- 

 ments to migrate onshore to nourish downdrift beaches. The Santee was the 

 fourth largest river on the east coast prior to 1942. Its large discharge 

 probably moved large amounts of sediment onto the inner continental shelf. 

 With a severe reduction in the freshwater input to the ebb flow, nearshore 

 portions of the ebb delta may have migrated onshore under the influence of 

 flood currents and/or waves . 



99. Despite accretion immediately adjacent to Winyah Bay jetties, the 

 majority of reach 5 can be classified as eroding over the long term (Fig- 

 ure 42). Approximately 54.5 percent of reach 5 showed erosion in excess of 



1 m/year, undoubtedly related to reduction in sediment supply from the Santee 

 River. This is surpassed only by erosion in reach 1. Accreting (24.1 per- 

 cent) and stable (21.4 percent) transects are approximately equal along this 

 shoreline . 

 Coastal reach 6 



100. The arcuate strand geomorphic zone (Brown 1977), defined here as 

 reach 6, has been primarily a stable shoreline (Figure 43). Unlike reaches 1, 

 2, 3, and 5, most of this shoreline has shown less than ±1 m/year of shoreline 

 change over the period of record. Only downdrift of Murrells Inlet does an 

 area exceed 2.5 m/year. 



101. Standard deviations of average net rate of change are small 

 throughout most of this reach, suggesting that shoreline change rates have not 

 varied considerably (Figure 43) . Maximum variability (±14 m/year) occurs 

 immediately downdrift of Murrells Inlet. Most of the coastline has less than 

 ±2.5 m/year of variability over 130 years of data. This variability tends to 

 increase in the vicinity of those few inlets that punctuate this shoreline. 

 Only at inlets does the standard deviation exceed ±5 m/year. 



102. Maximum net movement is greatest in the vicinity of Murrells Inlet 

 (over 500 m) and other inlets (Figure 44) . Most of reach 6 has experienced 

 less than 100 m of net change over the span of data. The magnitude of maximum 

 net changes is small compared with changes occurring in the barrier island 

 geomorphic zone , reaches 1 , 2 , and 3 . 



87 



