(1) Refl ection from the Foreshore . The foreshore developed a 

 relatively stable shape within the first 10 minutes to 5 hours of each 

 experiment. Since the foreshore shape remained fairly constant through- 

 out each experiment, the reflection coefficient of the foreshore probably 

 remained constant. The height of the wave reflected from the foreshore 

 is assumed to vary directly with the height of the wave incident to the 

 foreshore for each experiment. 



Measuring the reflection from the foreshore alone was difficult, 

 because the distance between the foreshore and the breaker was frequently 

 too short to make an accurate measurement. Fluctuations in the measured 

 Kfl during the first 5 to 10 hours are likely due to fluctuations in the 

 foreshore reflection. 



(2) Reflection as a Result of Wave Breaking . Since surging and 

 collapsing breakers break on the foreshore they do not contribute to the 

 reflection process separately, but rather as part of the foreshore re- 

 flection. Spilling breakers, essentially a crumbling of the wave crest, 

 do not involve any change in direction of the water particles, and thus 

 are not a source of reflection. The plunging breaker propagates energy 

 in both directions as the crest of the wave plunges into the water. How- 

 ever, in most experiments the breaker type changed from plunging to spill- 

 ing as the profile developed, and thus the breaker reflection is assumed 

 to decrease throughout an experiment. 



Measuring the breaker Kn was even more difficult than the foreshore 

 K^>, since the breaker reflection component is always superposed with the 

 foreshore component and in a short distance becomes superposed with the 

 offshore component. Estimates can be made from comparisons of the re- 

 flection from the concrete slope, which had a breaker and no foreshore, 

 and reflections from the early profiles of the movable bed, which had 

 reflection from both the foreshore and the breaker but very little from 

 other parts of the profile. 



(3) Reflection from the Inshore and Offshore Zones . Wave energy 

 is reflected all along the submerged profile, but the reflection does not 

 become significant until the profile slopes become significant. In most 

 experiments, the profile developed into an almost flat shelf between two 

 steep slopes (see Fig. 1). The development of these zones contributed 

 greatly to the reflection variability and hence the temporal wave height 

 variability. Three particular profile changes apparently caused signifi- 

 cant wave height variability: changes in the steepness of the offshore 

 slope, changes in the elevation of the shelf at the top of the offshore 

 slope, and changes in the length of the shelf. 



Increases in the offshore slope steepness increased the reflection; 

 likewise, decreases in the slope steepness decreased the reflection. As 

 the elevation of the shelf and top of the offshore slope increased, the 

 reflection increased; as that elevation decreased, the reflection de- 

 creased. Increases in the length of the flat shelf, which was the dis- 

 tance between the two reflecting slopes, caused the phase difference 



