breaker characteristics, water temperature, and wave-generated currents 
is analyzed; and (b) profile reflectivity, in which changes in profile 
shape and breaker characteristics are related to the variability of the 
reflection coefficient. Profile development provides an introduction to 
the profile reflectivity discussion. 
1. Profile Development. 
a. Experiment 72B-06. The important changes in the foreshore, in- 
shore, and offshore zones, the median grain size, breaker and current 
conditions, and water temperature during this experiment are summarized 
and tabulated as a function of time in Table 13. 
The profile development discussed previously and condensed in Table 
13 occurred as follows. In the first 10 minutes a longshore bar was 
formed by the plunging breaker in the inshore zone, which remained stable 
in position and varied slightly in crest elevation throughout the experi- 
ment. During the first 10 hours, the foreshore developed an equilibrium 
shape and position and the offshore zone developed a steep slope just 
below the inshore zone. After 10 hours the only profile changes occurred 
in the offshore zone, with erosion from elevations -1.3 to -1.7 feet 
gradually steepening the upper offshore zone and deposition at -2.1 to 
-2.2 feet before 90 hours and at -2.0 to -2.2 feet after 90 hours. The 
profile appeared to be quite close to equilibrium. The sediment became 
coarser in the foreshore and inshore zones and remained about the same 
in the offshore zone. 
The movement of the shoreline with the change in water temperature is 
compared in Figure 42. The shoreline was stable in position even though 
the water temperature dropped several times during the experiment. 
b. Experiment 72B-10. Profile development in this experiment is 
Summarized in Table 14. During the first 10 minutes a longshore bar 
formed in the inshore zone near station 2 by the plunging breaker; at 
station 5 a flat area developed along ranges 1, 3, and 5 and a bar along 
range 9. In the first 5 hours the foreshore developed an equilibrium 
shape, with the shoreline along range 1 farther seaward and along range 
9 farther landward; in the first 10 hours a steep slope formed at the 
upper edge of the offshore zone and a flat area near station 10. Sand 
was also deposited seaward of the -1.8-foot contour, but only along 
range 1. 
From 5 to 10 hours the foreshore was stable, but almost immediately 
after the formation of the bar at station 2 the bar began eroding first 
along range 3, then range 1, and then range 5. The eroded sand was 
deposited in the offshore zone near station 10 all across the tank and 
seaward of the -1.8-foot contour along ranges 1 and 3. A flat area 
began developing near station 5 along range 7 at 65 hours. 
From 70 to 100 hours the foreshore adjusted by eroding along ranges 
1, 3, and 5 so that the shoreline was again normal to the tank walls. 
Ue 
