Between 100 and 135 hours the foreshore continued to retreat, the 

 inner offshore became a gently sloping region, the outer offshore slope 

 steepness decreased, and Kd continued to drop. 



The movement of the -1.2-foot (36.6 centimeters) contour in Figure 

 9(a) is an indication of some of these profile adjustments and correlates 

 well with Kd variations. The -1.2- foot contour moved seaward at 15 

 hours and K D began rising. After 70 hours the -1.2-foot contour began 

 moving shoreward, as the inner offshore eroded and the outer offshore 

 slope became less steep, and K D began to decrease. 



(2) Experiment 72A-10 . The average K D for three ranges versus 

 time for experiment 72A-10 is shown in Figure 9(b). The K# dropped 

 initially to 0.24 and then began a gradual long-term increase, reaching 



a maximum of 0.37 at 55 hours. Between 60 and 80 hours, K D varied 

 between 0.31 and 0.35. 



During the first 1.5 hours the foreshore developed a steep slope and 

 within the first 10 hours an almost flat shelf developed in the inner 

 offshore region (Table 12). From 1.5 to 25 hours the foreshore prograded 

 0.5 foot (15.2 centimeters), beginning first along the outside ranges. 

 For the first 20 hours sand was deposited in the outer offshore at depths 

 from 1.2 to 1.5 feet; from 20 to 25 hours sand was eroded at depths of 

 1.6 and 1.7 feet (48.8 and 51.8 centimeters), thus forming a slightly 

 steeper slope on the upper part of the outer offshore. During this 

 initial profile development, K D rose sharply. 



After 25 hours the only profile changes were a slight general in- 

 crease in the foreshore slope and a gradual increase in the foreshore 

 berm-crest elevation. The Kd continued to increase, but at a slower 

 rate. The short-term variations in Kd after 35 hours was ±0.03, on 

 the order of the ±0.025 variation in the fixed-bed tank. 



Throughout the experiment the foreshore slope was slightly flatter 

 along the outside ranges and Kd was significantly lower along the 

 outside ranges. 



The movements of the +1.0- , +0.9-, and +0. 8-foot contours in Figure 

 9(b) indicate the gradual increase in the foreshore berm-crest elevation 

 which apparently caused the increase in Kd. The distance between the 

 foreshore and offshore did not vary. 



(3) Summary of the Two Experiments . The average Kd in experi- 

 ment 72A-06 was 0.26 and in experiment 72A-10 was 0.30 (Table 2). The 

 elevation of the top of the submerged offshore slope appeared to be the 

 primary source of long-term Kd variability in experiment 72A-06. The 

 gradually increasing berm-crest elevation appeared to be the source of 

 increasing K D in experiment 72A-10. The development of a steeper slope 

 and higher crest in the foreshore in experiment 72A-10 explains the higher 

 Kd in that experiment. More details on the 3.75-second experiments are 

 in Volume VI. 



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