offshore slope and the foreshore slope as those two zones moved farther 
apart on the developing profile (Figs. 3 and 9). In this experiment the 
top of the offshore zone did not vary significantly in slope or depth 
at the same time that Kp varied (Fig. 27), in contrast to observations 
reported in Volumes II, III, and IV for the longer 1.90-second waves with 
the same wave energy flux. 
: (c) The profile appeared to have almost attained an equilibrium 
shape. This apparent equilibrium was attained for the 1.5-second wave, 
although the 1.90-second wave in the same facility with the same energy 
flux did not approach equilibrium after twice the number of waves had 
been run (see Figs. 7 to 11 and Vol. III). 
(d) Even though this experiment was conducted in a wave tank with 
the direction of wave approach normal to the initial shoreline, the shore- 
line became skewed and a longshore current developed at the base of the 
foreshore. The greater three-dimensional development of the beach in this 
experiment compared with experiment 71Y-10 (Vol. III) is consistent with 
the working hypothesis that the shorter the wavelength relative to a given 
tank width, the greater the likelihood of three-dimensional effects in 
profile shape and profile development (see Figs. 7 to 11 and 14 and Vol. 
LI): 
(e) Measured changes in the median grain-size distribution gave 
results typical of an eroding profile: from ad.) of 0.195 millimeter on 
the initial profile, the mean ds5g everywhere became coarser, so that 
after 140 hours the dsg was 0.25 millimeter on the foreshore, 0.22 milli- 
meter on the inshore, and 0.21 millimeter on the offshore (Table 10). 
2. Recommendations. 
(a) Experimenters should expect three-dimensional effects to become 
significant in otherwise two-dimensional experiments when the wavelength 
decreases to near the tank width. 
(b) Additional research on the interaction of waves reflected from 
two or more segments of the profile is recommended to prove or disprove 
the hypothesis in conclusion (b) above. 
(c) The final profile shape (at 140 hours in Fig. 6) could be used 
aS an approximation to an equilibrium profile for the wave, sediment, and 
slope conditions. 
of 
