The initial grading of the sand slope in experiment 72B-06 was on 12 
July 1972. The first run was on 20 July 1972, the last run was on 20 
September 1972 after 150 hours, and the data collection was completed 
22 September 1972. Preparation for experiment 72B-10 was begun 14 July 
1972, the first run was on 19 July 1972, the last run was on 21 September 
1972 after 150 hours, and the data collection was completed 26 September 
1972. The major events of each 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 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- 
ments 72B-06 and 72B-10. The original data are available in an unpub-- 
lished laboratory memorandum (No. 6) (Leffler and Chesnutt, 1978) filed 
in the CERC library. 
Wave reflection, profile surveys, sediment-size distribution, breaker 
characteristics, water temperatures, and current observations are dis- 
cussed in the following section. Section III discusses (a) profile 
development, which examines the interrelation of changes in profile 
shape, sediment-size distribution, breaker characteristics, water tem- 
perature, and currents; and (b) profile reflectivity, which examines the 
interrelation of changes in profile shape, breakers, currents, and wave 
reflection. Section IV discusses the results of wave height variability, 
profile equilibrium, and other laboratory effects. 
The conclusions and recommendations (Sec. V) are directed toward the 
problems of the laboratory researcher or engineer in charge of a model 
study. This study demonstrates a laboratory effect only recently identi- 
fied (Madsen, 1974) and points out to the researcher the importance of 
measuring and recording all conditions in a laboratory experiment, even 
those which may appear insignificant at the time. Field engineers should 
be aware of these conclusions and recommendations when discussing and 
analyzing model studies of their projects. 
The data in this study may have other uses. The researcher can use 
these short- and long-term changes in profile shape. After an analysis 
of the scale and laboratory effects, the field engineer may use these 
data to determine generalized profile adjustment rates. 
II. RESULTS 
1. Wave Height Variability. 
a. Incident Wave Heights. Wave height measurements from the con- 
tinuous recording of water surface elevation at the center range, station 
+25 during the first 10 minutes of each experiment are shown in Table 4. 
