A(t ) - A(t ,) 

 S i - (t. - t. ,)! (1) 



1 1-1 



where i varies from 2 to n , and n equals number of surveys. This shore- 

 line change rate is the average shore-normal movement landward (-) or seaward 

 (+) of the shoreline. This approach was used to quantify changes in both the 

 ocean and sound shoreline between survey dates. 



72. A straight-line shoreline length £ was used because the average 

 shore-normal rate of change in shoreline position was desired. Generally, the 

 ocean and sound shoreline orientation, a (Figure 27), did not vary at any 

 site by more than a degree during the study period. This indicates that shore- 

 line changes within 1-minute increments were mostly shore-normal; i.e., the 

 coastline in the interval did not pivot a great deal. Therefore, the length 



£ between latitude or longitude boundaries 1 minute apart remained almost 

 constant. The use of the straight-line distance £ rather than the actual 

 shoreline distance was preferred on the sound side because (a) that shore was 

 often very irregular and (b) one objective of the study was to compare ocean 

 and sound shoreline changes. The sound shoreline change must, therefore, be 

 viewed as the average rate of shore-normal movement based on changes in plan 

 area and including nearshore islands. The straight-line shoreline length £ 

 is thus a fairly constant, easily measured, and reasonable scaling factor to 

 transform changes in area to shore-normal shoreline changes. 



73. Areas, as shown in Figure 27, were digitized at NOS for each 

 1-minute increment. In the sound, islands immediately off the coast were in- 

 cluded in the area computations because they had often been part of the coast 

 at an earlier time; the islands were included only when they were clearly near 

 the barrier island and when the sound beyond the island was open and wide. 



74. The least-squares shoreline change rate Sp is the slope of the 

 best fit line to a plot of shoreline positions A./£ (Equation 1) versus time 

 of each of the surveys in that 1-minute shoreline reach, or 



A. - A 



£ (t, - t) -i 



S„ = ^ , (2) 



£ n _ 2 



n=l 



57 



