and the data collection was completed 18 December 1972. The dates are 

 important because the experiments were run in outdoor facilities with 

 water temperature varying with ambient air temperature. The major events 

 of the experiment and the cumulative time at the end of each run are 

 summarized in Table 2. 



Table 3 gives the data collection schedule within each 5-hour run. 

 During the first 5 hours when the runs varied in length, the same data 

 were collected, with the schedule depending on the length of the run. 



3. Scope . 



This report describes and analyzes the reduced data from LEBS experi- 

 ment 720-06. The original data are available in an unpublished labora- 

 tory memorandum (No. 3) filed in the CERC library (Ghesnutt and Leffler, 

 1977). 



Wave reflection, profile surveys, sediment-size distribution, breaker 

 characteristics, water temperature, and current observations are discussed 

 in Section II. Section III discusses (a) profile development, which ex- 

 amines the interrelation of changes in profile shape, sediment-size dis- 

 tribution, breaker characteristics, water temperature, and currents; and 

 (b) profile reflectivity, which examines the interrelation of changes in 

 profile shape, breaker characteristics, currents, and wave reflection. 

 Section IV summarizes the results of wave height variability, profile 

 equilibrium, and other laboratory effects. 



The conclusions and recommendations (Sec. V) are aimed directly at the 

 problems of the laboratory researcher or engineer in charge of a model 

 study. Field engineers should be aware of these results when analyzing 

 model studies for projects. 



The data in this study (particularly the profiles) may have other uses. 

 The researcher can use these data, after consideration of the laboratory 

 effects, to analyze short- and long-term changes in profile shape. After 

 an analysis of the scale effects, the field engineer may use these data 

 to determine generalized shoreline recession rates. 



II. RESULTS 



1. VJave Height Variability . 



a. Incident Wave Heights . Wave height measurements from the continu- 

 ous recording of water surface elevation along the center range at station 

 +48 during the first 10 minutes for experiment, 72D-06 are shown in Table 4. 

 The wave heights in both tanks varied from 0.32 to 0.44 foot (9.8 to 13.4 

 centimeters) during the first 20 seconds. Ignoring the first group of 

 waves, the range was 0.07 foot (2.1 centimeters) in the movable-bed tank 

 and 0.09 foot (2.7 centimeters) in the fixed-bed tank. The range of wave 

 heights was about the same amount in the two tanks. 



I I 



