in Fig. 6) also had a steep foreshore, a longer inshore with a signifi- 

 cant depression between stations 2 and 20, and a relatively steep off- 

 shore. This development is shown by contour movement plots (Figs. 7, 8, 

 and 9) of the seawardmost contour intercepts for elevations at 0.1-foot- 

 depth increments from +0.2 to -2.1 feet. The heavier lines for -0.2- and 

 -0.8-foot contours distinguish the three profile zones in the figures. 

 In the foreshore and offshore zones the contour lines are close together 

 indicating steeper slopes; in the inshore zone the lines are spaced farther 

 apart indicating flatter slopes. 



(1) Foreshore Zone . Within the first 10 hours the foreshore 

 developed the shape which it maintained throughout the remainder of 

 the experiment (Fig. 10). Between 5 and 125 hours the foreshore re- 

 treated as material eroded from the backshore and the foreshore (upward- 

 sloping lines in Fig. 10); between 125 and 135 hours, the foreshore 

 prograded seaward (downward-sloping lines in Fig. 10). After 135 hours 

 the shoreline position was stable. 



Although the contour lines of the foreshore moved together, the lines 

 were not always parallel, indicating a variation in foreshore slope with 

 time at each range (Figs. 7, 8, and 9). Slope values at the SWL inter- 

 cept (Table 8) were determined by measuring the slope between the survey 

 points on either side of the shoreline. The steepest slope was 0.5 and 

 the flattest slope was 0.02; the average slope of the foreshore (after 

 3 hours) was about 0.19. 



The lateral variation in the slope of the foreshore developed as a 

 result of concentrations of backwash, which created gullies or flatter 

 slopes. The flow of -the wave uprush and backrush for the same wave con- 

 ditions that shaped the foreshore is discussed in Volume II (Chesnutt 

 and Stafford, 1977a). Figure 11 shows the foreshore at 45 hours, with 

 a typical foreshore shape. 



The shoreline (0 contour) movement along the three ranges is compared 

 in Figure 12. The slope of the contour indicates the shoreline reces- 

 sion rate. Because the slope of the backshore was 0.05 (and not flat), 

 the volume rate of erosion was not constant and increased at a rate pro- 

 portional to the square of the shoreline recession rate. No significant 

 lateral variations occurred in the shoreline recession (Fig. 12) . The 

 average rate of shoreline recession between 5 and 125 hours was 0.05 foot 

 per hour. Between 125 and 135 hours the foreshore prograded seaward and 

 then remained stationary. 



(2) Inshore Zone . The movement of all contour intercepts in the 

 inshore zone along the three ranges is shown in Figures 13, 14 and. 15; 

 the movement of selected individual contours along the three ranges is 

 compared in Figure 16. 



Within the first 10 minutes of testing, a longshore bar formed near 

 station +8, between the -0.5- and -0.3-foot contours. By 5 hours 



24 



