After 85 hours the seaward movement of the -0.7-foot contour in Fig- 

 ure 3 corresponds to the steepening of the upper part of the offshore 

 slope and that roughly corresponds to the increase in K^ after 95 

 hours. The large fluctuation in K^ did not result from any apparent 

 profile change, but the general relationship between the -0.7-foot con- 

 tour and K^ did exist. 



(2) Experiment 70X-10 . K^> versus time for experiment 70X-10 is 

 shown in Figure 4. During the first 20 hours, K^> varied from 0.07 to 

 0.12, and between 21 and 89 hours, K^ ranged between and 0.08. From 

 89 to 174 hours, K^, increased from 0.04 to 0.14 with a maximum of 0.15 

 at 139 hours. After 174 hours, K ff decreased, to as low as 0.06 at 204 

 hours . 



The higher Kp values during the first 20 hours occurred while the 

 foreshore developed and eroded landward, a longshore bar developed, and 

 the bar and the plunging breaker moved landward (Table 5) . Between 21 

 and 89 hours, while K^ was lower but gradually increasing, the fore- 

 shore and the bar moved landward, then the foreshore stabilized and the 

 bar eroded. During the same time the breaker moved seaward and changed 

 to plunging (at 70 hours), and the offshore slope slightly steepened and 

 prograded seaward. The distance between the 0- and -1.5- foot contours 

 increased 2.2 feet (67.1 centimeters), enough for a 180° change in phase 

 difference between the two reflected wave components. 



The gradually increasing K^> after 21 hours followed the general 

 seaward movement of the -0.7-foot contour (Fig. 4), but individual K^> 

 fluctuations were not directly relatable to the movement of this or 

 other contours. The increase in both K^> and K^> variability between 

 89 and 174 hours occurred while the foreshore was stable, the breaker 

 was spilling (no reflection), and the offshore was gradually steepening. 



(3) Experiment 71Y-06 . Kff versus time for experiment 71Y-06 is 

 shown in Figure 5. During the first 10 hours, K„ varied from 0.01 to 

 0.10. Then, for 115 hours the K^ remained relatively low, ranging from 

 0.01 to 0.07 with most of the values near 0.05. For the remainder of the 

 experiment, K^ increased in mean value and in variability, varying from 

 0.05 to 0.22. 



The higher K^> values during the first 10 hours occurred while the 

 foreshore zone and longshore bar were developing and retreating landward 

 (Table 6). Between 10 and 125 hours, when K^ was low and fairly con- 

 stant, the foreshore zone and longshore bar were retreating landward and 

 the offshore zone was prograding seaward but did not steepen. After 125 

 hours, when K„ was increasing and becoming more variable, the foreshore 

 zone continued^ to erode, the onshore zone developed into a flat shelf 

 with the depth over the shelf varying between 0.7 and 0.8 feet, and the 

 offshore zone became steeper and continued to prograde seaward. 



Some variations in K^> were related to the movement of the -0.7-foot 

 contour (Fig. 5). The general seaward movement of the -0.7-foot contour 



24 



