developed the flat inshore shelf and had surpassed experiment 71Y-10 in 

 the progradation of the offshore zone. The comparison of the final pro- 

 files for the two experiments in Figure 23 indicates that the experiments 

 had roughly the same shape, but that in experiment 71Y-06 the foreshore 

 had eroded farther landward and the offshore had prograded farther sea- 

 ward. 



(3) Comparison of the Four Experiments . The final profiles in 

 the experiments with the 1.90-second waves are compared in Figure 24, 

 showing that the profile shape was similar in all four experiments, but 

 that the longer the experiment, the farther landward the foreshore and 

 the farther seaward the offshore. The K^ variability increased with 

 time during each test (Figs. 3 to 6) . This indicates that if an equi- 

 librium slope can be attained for the 1.90-second period on an initial 

 0.10 sand slope, it is probably shaped like these four profiles with an 

 even longer inshore zone. 



c. 2.35-Second Wave . The profile in experiment 72B-06 adjusted 

 slowly to the waves and appeared to be near equilibrium at the end of 

 the experiment (150 hours) (Fig. 25); the profile in experiment 72B-10 

 adjusted more rapidly and did not appear to be near equilibrium at the 

 end of the experiment (150 hours) (Fig. 26). 



The differences in rate of profile adjustment and the differences in 

 the shape of the offshore zone between the two experiments are shown in 

 Figure 27. These differences may have been caused by differences in 

 tank width and initial test length or by the transverse wave which was 

 only generated in experiment 72B-10. 



d. 3.75-Second Wave . Two experiments were conducted with a 3.75- 

 second wave. Although the profile in the narrower tank (experiment 

 72A-06) did not appear close to equilibrium, the profile in the wider 

 tank (experiment 72A-10) did, as shown by comparing Figures 28 and 29. 

 The development and disintegration of circulation cells between antinodes 

 of the standing wave envelope evidently prevented the profile from reach- 

 ing equilibrium in experiment 72A-06 (discussed in Vol. VI). The absence 

 of any horizontal contours in Figure 28 (narrower tank) shows this lack 

 of equilibrium. However, in the wider tank, nearly all contours are 

 horizontal after only 25 hours (Fig. 29) . 



Figure 30 compares the center profiles from the two experiments at 

 25, 50, and 80 hours, indicating that throughout the experiments the 

 profile shapes were quite different in the two tanks, probably as a 

 result of the circulation pattern in experiment 72A-06. Profile changes 

 during the final 55 hours of experiment 72A-06 are shown in Figure 31. 

 The offshore zone changed to a more gently sloping region. 



e. Comparison of the Profiles . Although the profile in experiment 

 71Y-06 was not at equilibrium, it appears to well represent the shape 



of profile adjustment for a 1.90-second wave. The profile in experiment 

 72C-10 (1.50-second wave) was close to equilibrium and is assumed to be 



64 



