wave no longer had sufficient energy to erode the foreshore. Second, 

 because of secondary waves, the velocity distribution at the toe of the 

 profile may have been different in the two experiments since the toe in 

 this experiment was 23 feet closer to the generator than in experiment 

 71Y-06. The effect of secondary waves on profile development was dis- 

 cussed by Hulsbergen (1974) . The difference in velocity distribution at 

 the toe of the profile would have caused a different velocity distribution 

 over the shelf and may be the cause of the trough in the inshore zone. 



V. CONCLUSIONS AND RECOMMENDATIONS 



1 . Conclusions . 



(a) In experiment 72D-06 with a water depth of 2.33 feet (0.71 

 meter), a wave period of 1.90 seconds, and a generator stroke of 0.39 

 foot (11.9 centimeters), the average incident wave height was 0.39 foot. 

 Reflection measurements in the control tanks with a fixed-bed profile 

 varied from 0.04 to 0.07, indicating that the wave generators were opera- 

 ting uniformly and that the measurement error in determining K^ was 

 ±0.015 (Tables 5 and 6) . 



(b) Kn varied from 0.04 to 0.27, and the variation correlated with 

 profile changes. K^ was quite low during the first few hours when the 

 profile had not developed many features on the 0.05 slope. The K/j 

 increased first as the foreshore developed, and later as the inshore 

 zone became a long, flat shelf with a slightly steeper offshore. The 

 mean value of the K^ increased as the offshore steepened. Large fluc- 

 tuations in K^ occurred at times of large shifts in contour position 

 on the inshore shelf ,■ further verifying observations in Volume 111 



that reflection is sensitive to small changes in depth at the shoreward 

 edge of the submerged reflecting surface (Figs. 3 and 21). 



(c) The profile never reached an equilibrium shape, even though the 

 water temperature was relatively constant for the last 80 hours of the 

 experiment (Figs. 7, 8, 9, and 20). 



(d) A comparison of experiment 72D-06 (initial profile slope of 0.05) 

 with experiment 71Y-06 of Volume III (initial slope of 0.10) indicates 

 three primary differences in profile shape: stable foreshore, large 

 trough in inshore, and longer offshore. These differences may have been 

 caused by the different initial slopes (Figs. 7, 8, 9, 13, 14, and 15 

 and Vol. III). 



(e) These two experiments also differed in that experiment 720-06 

 developed typical (for these wave conditions) foreshore and inshore shapes 

 more quickly. This difference is due primarily to the difference in 

 initial slope (Figs. 7, 8, and 9). 



2. Recommendations. 



(a) Experimenters should be cautious in defining equilibrium profile 

 conditions. 



52 



