Some of the difference may have been due to the gages in the fixed- 
bed tanks being 7 feet farther from the profile (see Fig. A-1 in the 
App.) and thus the gages may have been at different positions between 
nodes and antinodes. For example, on the envelopes recorded beginning 
at 20 minutes (10 minutes after the data given in Table 1) in experiment 
72A-06, an antinode is at station 25 in the fixed-bed tank and a node in 
_the movable-bed tank (Fig. 1). 
Table 5 shows the average incident wave heights in both tanks from 
the two experiments. These heights were determined by the automated 
method for determining the reflection coefficient, Kp (see Vol. I). 
The range of variation in the fixed-bed tank was 0.07 foot (2.1 centi- 
meters) in experiment 72A-06 and 0.04 foot (1.2 centimeters) in experi- 
ment 72A-10. This variation was probably caused by generator operation 
variation, measurement errors, and all errors not caused by a changing 
profile. 
The range of wave heights in the movable-bed tank was 0.10 foot 
in experiment 72A-06 and 0.11 foot (3.3 centimeters) in experiment 
72A-10. The difference in range of variation between the two tanks 
was due to the changing shape and position of the profile which caused 
a varying re-reflection from the wave generator. The re-reflected 
wave superposing with the generated wave created an incident wave which 
varied in time. Thus, a measure of the variation due to re-reflection 
is the difference in range of heights on fixed and movable beds: 
0.03 foot (0.9 centimeter} in experiment 72A-06 and 0.07 foot in experi- 
ment 72A-10. 
b. Wave Reflection. The reflection coefficient, Kp, from experi- 
ments 72A-06 and 72A-10 as determined by the manual and automated 
methods, is given in Table 6. The two methods are described in Volume I. 
A plot of Kp versus time for the fixed-bed tanks of both experiments 
is shown in Figure 2. In experiment 72A-06 the range of Kp was only 
0.02 with no long-term trends; in experiment 72A-10 the mean Kp was 
lower and the range of Kp was 0.05, with a decrease in Kp to the 
minimum near the beginning of the experiment, followed by a long-term 
rise to the maximum. This variation was not seen in the incident wave 
height data in Table 5. An explanation for the variation in Kp in the 
fixed-bed tank of experiment 72A-10 is not apparent. As with the inci- 
dent wave heights, the range of Kp variation in the fixed-bed tanks is 
a measure of all the errors and variations not due to the changing pro- 
file in the movable-bed tanks. Thus, the accuracy of the reflection 
measurement in the movable-bed tanks is about +0.01 in experiment 72A-06 
and +0.025 in experiment 72A-10. 
A plot of Kp versus time in the movable-bed tanks for three ranges 
in experiment 72A-10 and the center range in experiment 72A-06, compares 
the data reduced by the two methods (Fig.3). The same temporal variation 
in Kg occurred in both tanks. A scatter plot of Kp values for the 
manual method versus the automated method for those wave records reduced 
by both methods is shown in Figure 4. This indicates that the manual 
15 
