change cannot adequately handle this type of data; therefore, measurements 

 were made separately at each inlet to show associated alongshore and aerial 

 changes . 



Changes in Shoreline Position 

 Coastal reach 1 



75. Average shoreline movement within coastal reach 1 (Tybee Island to 

 St. Helena Sound), between 1852/59 and 1982/83, was quite variable, ranging 

 from just over 10 m of accretion/year to 8 m/year of erosion (Figure 23) . 

 Overall, erosion dominated accretion in spatial distribution along this shore- 

 line. Substantial accretion (defined here as greater than 1 m/year) occurred 

 along a small segment of Tybee Island, the south end of Hilton Head Island, 

 Bay Point Island, the southern and northern ends of Fripp Island, and the 

 extreme northern terminus of Hunting Island. A small percentage of shoreline 

 showed little net change (less than ±1 m/year) over the time span. The 

 remainder of shoreline was strongly erosional. 



76. Rate of shoreline change is quite variable spatially along the 

 entire reach (Figure 23) . Standard deviation is an indicator of variability 

 of shoreline position changes. It is evident from this graph that magnitude 

 of variability increases dramatically in the vicinity of inlets. It can be 

 observed in the plot of standard deviation along the coast that every occur- 

 rence of a standard deviation in excess of 5 m/year is adjacent to an inlet. 

 This agrees with conclusions reached by authors previously discussed, that 

 shoreline position is most dynamic in the vicinity of inlets. 



77. Maximum shoreline movement, the difference between the two most 

 divergent shoreline positions regardless of temporal position, is quite large 

 in this coastal reach (Figure 24) . Range of shoreline movement is from 

 approximately 50 m at Hilton Head to almost 1,400 m at Hunting Island over the 

 period of record. In all cases where maximum shoreline movement has exceeded 

 500 m, it has been in the vicinity of inlets. Average shoreline movements 

 summarized by barrier island for each interval of survey data are presented in 

 Table 4. 



78. Changes in average rate of shoreline movement are presented in Fig- 

 ure 25. Average shoreline movements are presented in three distinct time 

 groups to observe temporal changes. Prior to the 1920's, the shoreline was 

 strongly erosional. This same trend is visible right up to the last survey 



57 



