generator and the generator motion caused a varying average incident 

 wave height. Transverse, cross, and secondary waves also contributed 

 to the spatial variability of the incident wave height. 



(b) The reflection coefficient variation ranged from moderate to 

 significant in the movable-bed tanks, ranging from 0.02 to 0.12 in ex- 

 periment 72C-10 and from 0.04 to 0.27 in experiment 72D-06. In the 

 fixed-bed tanks, which is an indication of the measurement accuracy 



in the movable-bed tanks, K^ ranged from 0.01 to 0.02 in experiment 

 72C-10 and from 0.02 to 0.09 in experiment 72B-10. 



(c) Waves are reflected by the runup on the foreshore, a plunging- 

 type breaker, and any segment of the submerged profile where the depth 

 change is significant. Variations in the steepness and top elevation 

 of any submerged slope can cause significant variations in K^. The 

 distance between two reflecting zones can affect the phase difference 

 between waves reflected from the two zones and thus affect the K^ 

 measurement seaward of the profile. The important source of K^ vari- 

 ability in any one experiment did not appear to be a function of the 

 wave period. The steepness of the submerged slope was an important 

 source of variability in all experiments except 72A-10, and the increas- 

 ing foreshore berm elevation was the primary source of variability in 

 only experiment 72A-10. Variations in the elevations of the top of the 

 submerged slope caused significant K^ variability in experiments 71Y-06, 

 72D-06, and 72A-06. The increasing distance between the foreshore and 

 submerged slopes caused some K^ variability in all experiments with the 

 1.90-second wave and was the primary source in experiment 72C-10 with the 

 1.50-second wave. As the shelf length varied in each experiment, the K^ 

 varied correspondingly. 



(d) The average K„ from profiles which developed from an initial 

 0.10 slope increased with increasing wavelength (or wave period). 



(e) The average K ff of the 1.90-second wave increased, rather than 

 decreased, as the initial profile steepness decreased. 



(f) Reflection coefficient variation was less than 0.05 during the 

 last 25 hours of the three experiments which appeared to be at or very 

 near equilibrium, but this does not conclusively prove that K„ varia- 

 bility is eliminated on an equilibrium profile. 



(g) In all experiments except 72C-10 the K„ tended to increase 

 during the experiment indicating that the profile adjustment tended 

 toward reflecting, rather than absorbing, energy. 



(h) Incident wave height, Hj, measurements in the fixed-bed tanks 

 were indicative of the measurement errors in the movable-bed tank. Hj 

 range in the fixed-bed tanks was as little as 0.03 foot in five experi- 

 ments, and as much as 0.07 foot in experiment 72A-06. 



(i) The effect of varying re-reflection on the incident wave height 

 in each experiment was calculated by subtracting the range of heights in 



121 



