Another important consideration in favor of addressing these longer return 

 periods is the uncertainty of the future funding capacity of local sponsors 

 for repair efforts. 



93. The final choice of alternatives should contain a minimum of 

 15-20 pairs of functional performance and structural integrity criteria pairs. 

 A single pair of these criteria will define each alternative breakwater con- 

 figuration throughout the optimization process. Consistency in application of 

 these criteria in analytical design efforts is critical to maximizing the re- 

 liability of the procedure. Mew alternatives should not be added without car- 

 rying the new ones through the entire procedure. 



Step 4-identify apparent optimum com- 

 bination of armor size and type, slope, 

 and crest elevation for each alternative 



94. Each pair of design criteria will have several combinations of 

 features that will provide the same performance and stability. An acceptable 

 method of choosing an apparent cost-effective combination for each plan is to 

 consider a standard parameterized cross section, as illustrated in Figure 17. 

 The Hudson formula (Equation 1), the relation of armor thickness and crest 

 width to armor weight (Equation 9), and the wave transmission relations (Equa- 

 tions 26 through 29) can then be used to approximate all the dimensions of 

 this standard cross section for a range of armor type and slope combinations. 

 The relative advantages of armor unit hydraulic stability and of runup dissi- 

 pation are both measured by this approach. The relative cost per unit length 

 of breakwater trunk for each slope and unit type combination can also be esti- 

 mated by incorporating representative unit prices for each armor type and 

 size. 



95. This method does not deal with the variation of reserve stability 

 between armor types which would involve a substantial amount of extra input 

 and computational effort. The question of reserve stability is addressed 

 later in this proposed procedure, but at this stage it is neglected as a 

 time-saving measure. "BWCOMP," an interactive computer program, has been 

 developed to estimate the volume and first cost per unit trunk length of the 

 parameterized cross section of Figure 17, given the two design criteria (as 

 incident H^ and T^ values and an H* maximum transmitted height) 



along with the other information discussed above. The program is documented 

 in Appendix B of this report and in a CETN (WES, CERC 1984b). 



62 



