values of £ (including the plane slope data) and overpredicts K r at 

 higher | -values . The Battjes equation predicts increasing reflection as 

 the surf similarity parameter increases, whereas the data show little depen- 

 dence on £ . Neither the equation of Miche nor that of Battjes predicts K r 

 well for barred profiles over the range of £ -values . These equations were 

 developed for plane slopes and, as Figure 31 illustrates, are not valid if the 

 bottom topography is irregular. 



129. Reflection coefficients from the experiment were compared with 

 Equation 11 (Ahrens 1987), shown in Figure 32, but no strong correlation was 

 found with the reef reflection parameter P . Equation 11 predicts K r 

 better than Equations 8 (Miche 1951) and 10 (Battjes 1975), but does not 

 exhibit a constant trend. The Ahrens equation does have the desirable 

 property of remaining bounded, as opposed to Equations 8 and 10. 



Kr 



0.6 



0.5 



0.4 



0.3 



0.2 



0.1 



0.0 



/? 





(cleg 



) 





5 



+ 



10 



* 



15 



D 



20 



X 



30 







40 



10 



Figure 32 . Measured wave reflection and predicted 

 values of Ahrens (1987) as a function of P 



130. An empirical equation was developed to predict K r . Reflection 

 coefficients from tests with and without bars were plotted as a function of 

 Pi (Figure 33) , which shows a weakly increasing dependence of K r on /3 X . 

 The visually fit curve represents: 



K r = 0.132 + O.llQtan/?! 

 83 



(77) 



