explains 99.5 percent of the variance in C for the 109 tests with N* > 6 . 



s 



28. It was found that when using Equation 8 to predict the relative 

 crest height h /d for values of N* near or below six, illogically high 

 values could result. Higher values are to be expected since Equation 6 was 

 developed for tests where N* > 6 and there was enough rock movement to form 

 an equilibrium reef profile and not for wave conditions where the "as built" 

 reef slope was too stable to be deformed. Since it would be useful to have a 

 stability model which predicts reasonable response crest heights over the 

 entire range of test conditions, another stability equation was developed to 

 predict crest heights for values of N* < 10 . This range provides a con- 

 venient overlap with the range of Equation 8 and allows an equation to be 

 developed which will be simple enough to serve as a rule-of-thumb relation for 

 zero to relatively low damage situations. This equation is given by 



h' 



= exp f-0. 00005 (N*) 3 ' 5 ! (9) 



Equation 9 provides a simple relation which follows the trend of the data 



well, albeit somewhat conservatively in the range N* < 10 as can be seen in 



Figure 11. The small levels of damage predicted by Equation 9 for N* < 6 



represent settlement and consolidation of the reef under wave action and not 



conspicuous stone movement. 



29. Equations 8 and 9 are used together to compute the response crest 



height of the reef over a wide range of wave severity. This approach will be 



referred to as the stability model. The procedure is to use Equation 8 for N* 



s 



> 10 and Equation 9 for N* < 6 . If we let the solution for h /h' in 



/ S \ C C 



Equation 9 be denoted [h /h' ] and the solution for h /h' in Equation 8 be 

 \ c cj l c c 



denoted |h /h'J , then the following equation 

 V / u 



10 - N*\ /h \ /N* - 6 



+ T^ ? CT (10) 



10 - 6 / \h' / \10 - 6/ \h' 



c 



can be used in the transition region 6 < N* < 10 to compute the response 

 crest height h . To judge the effectiveness of this procedure, 



24 



