a. 1.50-Second Wave . The profile in the one experiment (72C-10) 

 conducted with a wave period of 1.50 seconds appeared to be near equi- 

 librium, as indicated by horizontal contours in the foreshore zone and 

 most of the inshore zone in Figure 15. Erosion of the foreshore was con- 

 tinuing but slowing along the range 1 side of the tank and some erosion 

 was occurring in parts of the inshore zone. Deposition continued in the 

 offshore zone, but at a slower rate. The breaker type and position had 

 stabilized and the K^> and its variability had decreased to small values. 

 If this experiment had been continued, presumably it would have soon 

 reached equilibrium. The final profile is shown in Figure 16. 



b. 1.90-Second Wave . Four experiments were conducted with a wave 

 period of 1.90 seconds and an initial slope of 0.10. 



(1) Experiments 70X-06 and 70X-10 . These experiments had a 

 7-foot longer initial test length than the other experiments in their 

 respective tanks. Because the shoreline was stabilized by the renourish- 

 ment of the backshore after 54 and 62 hours in experiments 70X-06 and 

 70X-10, the final profile shapes for those experiments may not have been 

 characteristic of profiles for the 1.90-second wave. The final profiles 

 could not have been at equilibrium because sand was still being eroded 

 from the backshore when the experiments were stopped (see Table 10 in 

 Vol. II). However, the nearly horizontal contour lines near the end of 

 the experiment in the offshore in Figure 17 indicate that parts of the 

 profile in experiment 70X-06 may have been approaching equilibrium. It 

 is difficult to determine from Figure 18 if the profile in experiment 

 70X-10 was approaching equilibrium. Several of the offshore contours 

 had stopped moving in the seaward direction and had begun to move in the 

 shoreward direction, indicating the possible approach to some dynamic 

 equilibrium, but the lateral variations in the shape and development of 

 the profiles (see Vol. II and Section IV, 5 in this volume) made it diffi- 

 cult to determine equilibrium. 



Figure 19 compares the center profiles from the two experiments at 

 50, 100, and 175 hours, indicating that the profiles at 50 and 100 hours 

 were nearly the same, but that at 175 hours the profile in experiment 

 70X-10 had built farther seaward while maintaining a similar shape. The 

 profile development after 175 hours in experiment 70X-10 is shown in 

 Figure 20. 



(2) Experiments 71Y-06 and 71Y-10 . These experiments had a 

 shorter initial test length than the two experiments discussed above. 

 There is no indication that either experiment 71Y-06 or 71Y-10 was near 

 equilibrium at the end of the experiments, as shown in Figures 12 and 21; 

 both experiments showed slow, steady development throughout. 



Figure 22 compares the center profiles from the two experiments at 

 100, 200, and 300 hours, indicating that at 100 hours the profiles had 

 nearly the same shape; at 200 hours the profile in experiment 71Y-10 had 

 already developed a flat inshore shelf while the profile in experiment 

 71Y-6 had not, and at 300 hours the profile in experiment 71Y-06 had 



55 



