the movable-bed side is assumed to be about the same as the average K^ 

 values in the fixed-bed tanks; i.e., 0.13 in the 6-foot tank and 0.10 

 in the 10-foot tank. The first measured values of K^ from the movable- 

 bed profile (recorded between 12 and 20 minutes) increased to 0.17 in the 

 6-foot tank and 0.18 in the 10-foot tank. These are significant increases 

 but not as great as inferred in Chesnutt and Galvin (1974). After the 

 initial high values and for the first 10 hours, K^ varied from 0.07 to 

 0.17. For an extended period of time, the K^ was relatively small 

 (K^ < 0.14 for 148 hours in the 6-foot tank and < 0.13 for 210 hours in 

 the 10-foot tank). For the remainder of each experiment, the K^ in- 

 creased in mean value and variability, varying from 0.11 to 0.30 in 

 experiment 71Y-06 and from 0.06 to 0.16 in experiment 71Y-10. 



In general, the reflection coefficient varied from 0.0 3 to 0.30, 

 which is a large variation considering the generated wave conditions 

 were held constant. 



(2) 3.75-Second Wave . During the 5 hours of experiment 71Y-06 

 when the wave period was 3.75 seconds, the Kj^ at cumulative times of 

 375:20, 376:10, and 377:20 was 0.29, 0.36, and 0.27 in the movable-bed 

 tank and 0.34, 0.31, and 0.35 in the fixed-bed tank. Reflection from 

 the movable bed was slightly lower on the average, but the values varied 

 over a greater range. 



2. Profile Surveys . 



a. Interpretation of Contour Movement Plots . The profile surveys 

 (discussed in Vol. I) measured the three space variables of onshore- 

 offshore distance (station), alongshore distance (range), and elevation 

 at fixed times (Table 2) during the experiment. The CONPLT method (see 

 Vol. I) for presenting the data involves fixing the alongshore distance 

 by selecting data from a given range and analyzing the surveys along 

 that range. The surveyed distance-elevation pairs along that range are 

 used to obtain the interpolated position of equally spaced depths; e.g., 

 -0.1, -0.2, and -0.3 on the hypothetical profile in Figure 4(a). These 

 contour positions from each survey are then plotted against time (Fig. 

 4,b). 



A horizontal line in Figure 4(b) represents no change in contour 

 position. An upward-sloping line indicates landward movement of contour 

 position (i.e., erosion); a downward-sloping line indicates deposition. 

 The slope of a line indicates the horizontal rate of erosion or deposi- 

 tion at that elevation. The three x's at time t2 (Fig. 4,b) indicate 

 multiple contour positions at elevation -0.2 which is shown by the inter- 

 section of the dashline with profile tz in Figure 4(a). 



Three types of contour movement plots included in this study are: 



(a) The seawardmost intercepts along one range for specified depths; 



(b) the seawardmost intercepts for one selected depth along all ranges; 

 and (c) all contour intercepts including multiple intercepts along one 



29 



