PART III: STABILITY AND PERFORMANCE RESULTS 



16. The report herein consolidates findings from all of the data sub- 

 sets identified in Table 2 into general conclusions about the stability and 

 performance characteristics of reef breakwaters. Specific characteristics in- 

 clude the stability of reef breakwaters to irregular wave attack, wave trans- 

 mission over and through the breakwater, wave reflection from the breakwater, 

 and dissipation of wave energy. A mathematical model is developed for each 

 characteristic which provides a simple method to summarize findings from this 

 study and a convenient way to furnish results to potential users. These math- 

 ematical models are intended to work together with the stability model fur- 

 nishing the equilibrium crest height to both transmission and reflection 

 models which together are used to estimate the amount of energy dissipated by 

 the reef. 



Stability to Irregular Wave Attack 



17. The stability of reef breakwaters will be quantified by damage or 

 lack of damage during a test, the most important aspect of which is the reduc- 

 tion in crest height caused by wave attack. This aspect of stability is 

 important because the performance of a reef breakwater will be judged largely 

 on its wave transmission characteristics. Wave transmission is very sensitive 

 to crest height relative to water level. 



Crest height reduction factor 



18. One of the most effective methods to evaluate damage to a reef 



breakwater is to use the ratio of the crest height at the completion of a test 



to the height at the beginning of the test before waves have been run. This 



ratio, h /h' , will be referred to as the crest height reduction factor. For 

 c c 



comparing damage within a subset, h /h' is effective because it inherently 

 accounts for the random variation of one to two centimeters in the constructed 

 crest height from test to test within a subset. Another advantage of the 

 crest height reduction factor is that all stability subsets have the same 

 natural limiting values of 1.0 and 0.0. 



Stability number and 



spectral stability number comparison 



19. Experience with the stability of traditional rubble-mound break- 

 waters to monochromatic waves suggests that one of the most important 



11 



