Table 3. Comparison of measured and predicted reflection coefficients 

 (h = 16 inches (0.41 meter). 





Incident 





R 



R 



Wave Period 



Wave Height in 



R 



Predicted 



Predicted 



[in seconds) 



centimeters 



Measured 



[eq. 127) 



(eq. 126) 



2.0 



1.86 



0.49 



0.50 





2.0 



2.65 



0.47 



0.48 



0.46 



2.0 



3.50 



0.45 



0.46 





2.0 



4.05 



0.43 



0.45 





1.8 



1.74 



0.47 



0.47 





1.8 



2.47 



0.45 



0.46 



0.43 



1.8 



3.10 



0.43 



0.44 





1.8 



3.63 



0.42 



0.42 





slope. This is a surprisingly large energy dissipation, particularly 

 when it is realized that the incident waves showed no sign of breaking 

 on the slope. This considerable energy dissipation is therefore due 

 mainly to bottom friction. 



The procedure enables one to determine the wave runup in addition 

 to the reflection coefficient. The determination of the wave runup, 

 |a|, is an integral part of the procedure itself. Figure 16 is used 

 both in establishing values of f from the experimental values of R, 

 and in solving the empirical relationship (eq. 127) for the slope 

 friction angle, 4). Thus, although not explicitly appearing in the final 

 result, the procedure for the prediction of reflection coefficients of 

 rough slopes relies implicitly on the runup prediction afforded by 

 Figure 16. Therefore, it would be somewhat disturbing if the runup 

 predicted by Figure 16 was drastically different from the runup occurring 

 in the experiments. For this reason a simple observation was made of 

 the runup in the experiments used in establishing the empirical 

 relationships for f^, and the observed runup was compared with the runup 

 predicted from Figure 16. This comparison, involving the 96 experiments 

 listed in Appendix B, shows a mean value of R^ (predicted) /R,j (observed) 

 to be 1.15 with a standard deviation of 0.28. This agreement is not 

 sufficient for the runup predictions afforded by Figure 16 to be used 

 in actual design, but it does show that its use as part of the procedure 



73 



