seal the gaps between the variable slope, the glass-side walls, and 

 bottom for each slope angle tested to eliminate the effect of leakage 

 around the slope and ensure that the slope was truly impermeable. To 

 develop various slope roughnesses plywood boards with glued-on roughness 

 elements, gravel of diameter d = 0.5, 1, 1.5, and 2 inches (1.25, 2.5, 

 3.8, and 5 centimeters) were attached to the slope. In this manner 

 experiments for various slope roughnesses were readily performed for a 

 given value of the slope angle, tan3s- Photos of the various roughness 

 boards are shown in Figure 18. 



Each experiment for a given value of T, d, and tang^ was performed 

 by running the wavemaker continuously. After approximately 2 minutes, 

 a quasi-steady condition was established in which the wave motion at any 

 point along the flume was periodic with period T equal to that of the 

 wavemaker. When this quasi-steady state was established the free 

 surface variation with time was recorded at 4-inch [10 centimeters) 

 intervals along the flume over a distance of approximately 10 feet 

 (3 meters) of the constant depth region of the flume. The free surface 

 variation was measured by a parallel wire-resistance wave gage and was 

 recorded on a two-channel recorder (Sanborn) . The slope and the 

 instrumentation are shown in Figure 19. From the measurements the 

 incident wave height and the reflection coefficient are determined as 

 discussed in Section 3.b. This procedure was repeated for four values 

 of the incident wave height by changing the wavemaker stroke with 

 everything else being unchanged. 



It was found that a quasi-steady state could be achieved only for 

 wavemaker strokes below a certain value. Therefore, experiments are 

 limited to values of the incident wave heights below approximately 

 2 inches (5 centimeters). This, in turn, means that the incident 

 waves do not break on the slopes tested, thus corresponding to the 

 assumption of nonbreaking waves made in the theoretical analysis. 



From the preceding discussion of the experimental setup and testing 

 procedures it is seen that a total of 48 experimental runs were 

 performed for each value of the slope angle, (four different wave 

 heights times three different wave periods times four different slope 

 roughnesses) . An additional 12 experiments were performed for a 

 smooth slope for each value of the slope angle. For a smooth slope, 

 which corresponds to d ^l 0, the relationship suggested by equation (115) 

 is unrealistic. For a smooth slope a dependency of the wave friction 

 factor on a Reynolds number can be expected. The experimental results 

 for smooth slopes were analyzed without resulting in a useable 

 relationship for f^^. All the data, including the data obtained for 

 smooth slopes, collected in the experimental investigation are presented 

 in Appendix B. 



b. Accurate Determination of Experimental Reflection Coefficients. 

 Since the reflection coefficient obtained from each experimental run is 

 used directly in conjunction with Figure 15 to obtain a corresponding 



61 



