PART IV: SHORELINE DATA ANALYSIS 



72. This part of the report presents the first level of analysis of data 

 obtained from digitizing shoreline positions on the accompanying NOS map set. 

 Length of coastline investigated in this study (336 km) prevented adequate 

 display of shoreline change data at a scale suitable to page size format. 

 Therefore, for display purposes, the coastline was subdivided into seven 

 reaches (Figure 21). Reaches one (Tybee Island to St. Helena Sound), two 



(St. Helena Sound to Charleston), and three (Charleston to Bull Bay) corre- 

 spond to Brown's (1977) barrier island geomorphic unit. Reach four is Bull 

 Bay. Reach five (Bull Bay to North Inlet) and six (North Inlet to the North 

 Carolina/South Carolina border) correspond to Brown's cuspate delta and arcu- 

 ate strand geomorphic units respectively. Reach seven covers the remainder of 

 the study area, which lies within the State of North Carolina (North Carolina- 

 South Carolina border to New Inlet) . 



73. Within Part IV of the report, data for each reach are presented in 

 both graphic and tabular format. Average shoreline change and standard devia- 

 tion for the maximum range of years (e.g., 1856 to 1983) and several interven- 

 ing shorter periods (e.g., 1850 to 1929, 1920 to 1965, 1960 to 1983) were 

 calculated and displayed to show spatial and temporal changes in shoreline 

 positions. Header dates presented on temporal graphs in this part of the 

 report are not exact. Exact dates used in the comparison can be found by con- 

 sulting Table 2. Maximum shoreline change during the period of study (the 

 envelope of shoreline change) and the number of surveys and length of survey 

 period used in data analysis are given for each coastal reach. Graphical 

 scales are the same for comparison between reaches. Average shoreline move- 

 ment for every temporal interval of data is presented for each barrier island 

 or mainland beach within each coastal reach. For digitization, the shoreline 

 of each map was divided into straight line segments (Figures 22a and b) . 

 Average maximum movement, average shoreline change, maximum movement, and max- 

 imum deviation are presented for each of these segments in Appendix A. Summa- 

 ries of erosion and accretion are present for each reach, each geomorphic 

 zone, and the entire study area. 



74. Changes at inlets are presented as a separate section. Inlet 

 changes are frequently quite radical and often occur in an alongshore direc- 

 tion rather than onshore or offshore. Methods used here to measure shoreline 



54 



