along the five ranges during the first 10, hours of experiment 72A-10). 
The steepness of the beach varied across the tank, as indicated by the 
close spacing (steep slope) along ranges 3, 5, and 7 and wider spacing 
(flatter slopes) along ranges 1 and 9. 
After the initial development (about 5 hours), most of the foreshore 
zone was at equilibrium in position along ranges 3, 5, and 7 (Figs. 16, 
17, and 18). Along ranges 1 and 9 (Figs. 15 and 19) the position 
fluctuated, particularly along range 9. The slope at the SWL intercept 
along each range is given in Table 7. The slopes increased, in general, 
with time, and were steepest along the centet ranges and flattest along 
the outside ranges, with the average slope at 80 hours, varying from 
0.209 along range 3 to 0.171 along range 9. The berm crest marking the 
maximum foreshore elevation reached +1.0 foot between 30 and 70 hours, 
earlier at ranges 1 and 3 and later at the other ranges, as indicated 
by the seaward movement of the: +1.0-foot contour in Figures 15 to 19. 
The movements of the shoreline (0 contour) along the five ranges of 
experiment 72A-10 are compared in Figure 23. The shoreline advanced 
approximately 0.5 foot seaward during the experiment, beginning first 
along the outside ranges. Although seaward movements occurred between 
0 and 25 hours and fluctuations between 30 and 50 hours, the shoreline 
was relatively stable, compared to the long-term trend in the 6-foot 
tank for the same wave conditions (Fig. 23, experiment 72A-06). 
(2) Offshore Zone. Within the first 5 to 10 hours the offshore 
zone in each experiment developed into a nearly flat shelf (inner region) 
and a steep slope (outer region). 
(a) Inner Region (Experiment 72A-06). The movements of all 
contour intercepts in the offshore zone along the three ranges for 
experiment 72A-06 are shown in Figures 25, 26, and 27. The movements of 
selected individual contours along the three ranges are compared in 
Figure 28. 
In this experiment the -1.2-foot contour is the boundary between the 
inner and outer regions. As the foreshore formed, the area just below 
the foreshore (-1.0 to -1.2 feet) also eroded and the material deposited 
at depths from 1.3 to 1.5 feet during the first 10 hours, forming the 
nearly flat shelf. Between 10 and 15 hours, sand deposited on the shelf, 
moving the -1.2-foot contour seaward. 
For the next 55 hours «(until 70 hours) the shelf continued to grow 
in both directions; the depth over the shelf varied from -1.0 to -1.3 
feet, as shown by the widening of the distance between the -0.9- and 
-1.2-foot contours and the multiple intercepts for all depths of -1.0 
to -1.3 feet in Figures 24, 25, and 26. The multiple intercepts indicate 
that the shelf developed into a bar and trough, with the crest of'the bar 
at about station +15 and the bottom of the trough between stations +10 
and +12. 
46 
