step 7 — estimate economic losses 



with the breakwater for each alternative 



98. The climate of transmitted waves behind the breakwater can now be 

 approximated as a cumulative probability distribution F(H^) given a set of 

 H^(H.) points from Step 6 and the cumulative distribution of incident waves 

 F(H;) from Step 1. The loss function estimated in Step 2 can be used to es- 

 timate the expected annual economic losses E{$L'/yr} for each alternative by 



) = x/$L(H^)^dH^ - . (33) 



"BWL0SS2," a computer program, has been developed to perform these computa- 

 tions. It has been documented in a CETN*, and it is included in Appendix C of 

 this report. 



Step 8 — estimate expected annual 

 breakwater damages for each alternative 



99. The methods discussed in Part III can be applied to relate a damage 



function %D{H/H.) to each alternative. The incident wave climate defined 



by F(H) from Step 1 can in turn be applied to estimate the expected annual 



damages E{$D/yr} given representative unit repair prices $/vol and the 



volume of the armor layer Vol by adapting Equation 18 as follows: 



100. This quantity is useful for comparative purposes, but it does not relati 

 directly to a programmed cash flow for repairs. It is better that Equation 18 

 be applied to each alternative in its unmodified form to predict the expected 

 annual %D in order to make some Judgment if and when a repair project should 

 be scheduled. The average time to reach a threshold level of unacceptable 

 damage %D* can be estimated by simply dividing that value by E{7oD/yr} . The 

 return period of %D* could also be estimated by solving for H(7»D*) in the 

 damage function (Equation 14) and applying Equation 21 to determine the asso- 

 ciated return for that particular storm intensity. A computer program titled 



* US Army Engineer Waterways Experiment Station, Coastal Engineering Research 

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

 Waves Transmitted by a Breakwater— Computer Program BWL0SS2 (_MACE-l6)," 

 Coastal Engineering Technical Note, Vicksburg, Miss. 



65 



