The basic difference between the two facilities was the tank width. 

 One pair of tanks, each 6 feet (1.8 meters) wide, was used for experi- 

 ment 71Y-06; the other pair, each 10 feet (3.0 meters) wide, was used 

 for experiment 71Y-10. The initial test length on the sand side was 93 

 feet (28.3 meters) in experiment 71Y-06 and 54.7 feet (16.7 meters) in 

 experiment 71Y-10 (Table 1). The initial test length was 7 feet greater 

 on the concrete side in both tanks. 



The initial grading of the sand slope in experiment 71Y-06 v.'as on 3 

 May 1971. The first run was on 11 May 1971, the last run was on 8 Decem- 

 ber 1971 after 380 hours, and the data collection was completed 13 Decem- 

 ber 1971. Experiment 71Y-10 began 18 June 1971, stopped on 30 November 

 1971 after 335 hours, and data collection completed 16 December 1971. 

 The dates are important because the experiments were run in outdoor 

 facilities with water temperature varying with ambient air temperature. 

 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 run for 1- , 

 2-, and 5-hour runs. During the first 2 hours when the runs were less 

 than 1 hour long, the same data were collected, with the schedule 

 depending on the length of the run„ 



3. Subexperiment with H^/L^ = 0.002 . 



After 375 hours in experiment 71Y-06, the beach had eroded to the end 

 of the tank. The experiment was continued for an additional 5 hours with 

 a much longer, lower wave, which resulted in accretion on the foreshore. 

 The experimental conditions unique to this subexperiment are given in the 

 Appendix. 



4. Scope . 



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

 ments 71Y-06 and 71Y-10. The original data are available in an unpub- 

 lished laboratory memorandum (No. 2) (Chesnutt and Leffler, 1977) filed 

 in the CERC library (CERTI-LI) . 



Wave reflection, profile evolution, sediment-size distribution, 

 breaker characteristics, and water temperature data are discussed in 

 Section II. Section III discusses (a) profile development, including 

 the interrelation of changes in profile shape, sediment-size distribu- 

 tion, breaker characteristics, and water temperature; and (b) profile 

 reflectivity, including the interrelation of changes in profile shape, 

 breaker characteristics, 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 

 identification and solution of problems facing the laboratory researcher 



II 



