over the widest range, between 0.04 and 0.15. Between 10 and 150 hours, 

 K^> fluctuated (maximum 5-hour fluctuation of 0.06) about an increasing 

 mean, reaching peak values at 125 and 140 hours. 



The major profile adjustments in Figure 8(a) and Table 9 were the 

 development of an equilibrium foreshore and longshore bar and steepening 

 of the offshore zone just below the inshore zone. These adjustments 

 occurred during the first 10 hours when K^> was fluctuating greatly. 

 Between 10 and 150 hours, when K^> was gradually increasing, the only 

 profile changes were the gradual steepening of the upper part of the 

 offshore zone and the seaward movement of the offshore bar (crest eleva- 

 tion of -2.1 to -2.0 feet or 64.0 to 61.0 centimeters). The steepening 

 of the upper offshore most likely caused the increases in K^>. 



(2) Experiment 72B-10 . The K^> versus time for experiment 

 72B-10 is shown in Figure 8(b). During the first 10 hours, K„ in- 

 creased from 0.13 to 0.18, and then between 15 and 35 hours, K^> varied 

 only between 0.12 and 0.13. At 40 to 90 hours, K^> was higher, fluctuat- 

 ing about a mean of 0.16. Between 90 and 100 hours, K^> increased from 

 0.16 to 0.24 and then fluctuated about a mean of 0.21 for the remainder 

 of the experiment. 



The increasing K^> during the first 10 hours coincides with the 

 development of most of the profile features: the steep foreshore zone, 

 the flat inshore zone, and the flat region near station 10 in the off- 

 shore zone (Fig. 8,b and Table 10). There was little profile change 

 between 15 and 35 hours when the K^> was low and almost constant. At 

 40 to 90 hours the elevation of the flat region near station 10 gradually 

 increased while the K^ was higher and more variable. Between 90 and 

 100 hours, when K^ increased by 0.08, a longshore bar was forming be- 

 tween ranges 1 and 5. The high values of Kn at the end of the experi- 

 ment (after 100 hours) occurred while slopes near stations 20 and 14 were 

 steepening. 



(3) Summary of the Two Experiments . These experiments with the 

 2.35-second wave are compared in Volume VII. The average K^ in experi- 

 ment 72B-06 was 0.08 and in experiment 72B-10 was 0.17 (Table 2). The 

 gradual steepening of segments of the offshore zone appeared to be the 

 primary source of long-term K^ variability in these two experiments. 

 The development of a more convex offshore region with several steep 

 sections in experiment 72B-10 and a more concave offshore region with 

 only one steep section in experiment 72B-06 possibly explains the lower 

 K# values in experiment 72B-06. The distance between the foreshore and 

 offshore zones changed very little, so that the K^> variability was not 

 a result of phase-difference changes between reflected wave components. 



e. Reflection of the 3.75-Second Wave . 



(1) Experiment 72A-06 . The K^ versus time for experiment 

 72A-06 is shown in Figure 9(a) . The Kn dropped from an initial value 



36 



