"BWLOSSl" has been documented in a CETN*, and a sample is provided in Appen- 

 dix A of this report. 



Step 3 — formulate en- 

 semble of alternatives 



89. This step is highly subjective and will control the scope of the 

 overall optimization effort since it determines the number of individual al- 

 ternative breakwater configurations that must be investigated. The applica- 

 tion of practical judgment can reduce this number, but too few alternatives or 

 a conservative bias could also preclude identification of an optimum plan. A 

 proposed method of organizing an ensemble of alternatives is illustrated in 

 Table 7. 



Table 7 



Selection of Alternative Design Criteria for Return 



Periods of Storms Causing the Stated Conditions 



Func 



jtional Pel 



:'formance 





x7, H^. > 



H» 





< 10 







20 







30 







40 







50 





Structural Integrity 



<30, 40, 50, 60, 70, 80, 90, 100 



<30, 40, 50, 60, 70, 80, 90, 100 



<30, 40, 50, 60, 70, 80, 90, 100 



<30, 40, 50, 60, 70, 80, 90, 100 



<30, 40, 50, 60, 70, 80, 90, 100 



90. Table 7 lists a comprehensive set of potential functional and 

 structural design criteria combinations which may be abbreviated by carefully 

 considered subjective judgments. The first column in Table 7, "functional 

 performance," refers to an exceedance value X/J of transmitted wave heights 

 H^ greater than some critical wave height H* . H* might conveniently be 

 taken as the H, value applied in the loss function of Step 2, but this is 

 not necessary. This column includes a range of functional performance design 

 criteria which could be addressed in terms of wave transmission. A wave 

 height of 1 m, for example, might be a threshold value for damage to vessels 



* US Army Engineer Waterways Experiment Station, Coastal Engineering Research 

 Center, in preparation," Estimation of Expected Annual Economic Losses Due 

 to Wave Attack— Computer Program BWLOSSl (MACE-15)," Coastal Engineering 

 Technical Note, Vicksburg, Miss. 



60 



