The average incident wave heights in the movable-bed tanks from the 

 two experiments are shown in Table 6. These heights were determined as 

 part o£ the automated method for determining K^ (see Vol. I). The 

 range of wave heights was 0.09 foot (2.7 centimeters) in both experiments. 

 The difference in range of variation between fixed- and movable-bed tanks 

 is due to the changing shape and position of the profile, causing a vary- 

 ing re- reflection from the wave generator. The re-reflected wave super- 

 posing with the generated wave created an incident wave which varied in 

 time. Thus, the variation due to re-reflection was 0.06 foot (1.8 centi- 

 meters) in experiment 71Y-10 and 0.05 foot (1.5 centimeters) in experi- 

 ment 71Y-06. 



(2) 5.75-Second Wave . Table 7 shows the wave height measure- 

 ments from the continuous recording of water surface elevation during 

 the first 10 minutes of waves with the 3.75-second wave period. A well- 

 developed profile was created by 375 hours of 1.90-second waves. Wave 

 heights varied from 0.09 to 0.15 foot (2.7 to 4.6 centimeters) in the 

 movable-bed tank and from 0.09 to 0.16 foot (2.7 to 4.9 centimeters) 

 in the fixed-bed tank. The average wave height was 0.12 foot in both 

 movable- and fixed-bed tanks. 



The average incident wave height for runs with cumulative times of 

 375:40, 376:30, and 378:00 were 0.15, 0.15, and 0.16 foot in the fixed- 

 bed tank and 0.16, 0.14, and 0.14 foot (4.9, 4.3, and 4.3 centimeters) 

 in the movable-bed tank, respectively (i.e., the incident wave height 

 variations were small). 



b. Wave Reflection . The reflection coefficient data determined by 

 the manual method in experiments 71Y-06 and 71Y-10, are given in Table 

 8. Kfl data determined by the automated method and a comparison of the 

 two methods are included in the Appendix. 



(1) 1.90-Second Wave . The variation in K^ from the concrete 

 slope in experiments 71Y-06 and 71Y-10 is shown in Figure 1. The K^ 

 varied from 0.10 to 0„16 in experiment 71Y-06 and from 0.09 to 0.12 in 

 experiment 71Y-10. In both fixed-bed tanks, the K^ increased during 

 the early part of the tests and then gradually decreased. The explana- 

 tion is not apparent. The reason for a higher Kp in the narrower tank 

 is unknown. The variation in K^ in the fixed-bed tank indicates the 

 total of the measurement error in determining K^ from the changing 

 movable-bed profile. The average K^ in the fixed-bed tanks was 0.13 

 in experiment 71Y-06 and 0.10 in experiment 71Y-10. Chesnutt and Galvin 

 (1974) gave average K^ values between 0.03 and 0.0 7 for these experi- 

 ments; however, those values were determined by the automated method 

 which gives values lower by 0.04 to 0o05 (see App.). 



The variation in K/? from the movable-bed profile in experiments 

 71Y-06 and 71Y-10 is shown in Figures 2 and 3. The two experiments show 

 the same pattern of variation. The Kj^ during the first 10 minutes on 



