PART VI: SUMMARY AND CONCLUSIONS 



Summary 



Optimization . , 



107. Optimization has been demonstrated as a systematic process of max- 

 imizing net tangible economic benefits or of minimizing the total costs (in- 

 cluding economic losses) to the beneficiaries of a public works project. Op- 

 timization of rubble-mound breakwaters addresses the incremental net benefits 

 of these structures which are often major features of a larger coastal devel- 

 opment. Federal laws and policies currently require that incremental net ben- 

 efits be positive for all major features of projects proposed for federal 

 funding. Furthermore, cost sharing policies have placed a substantial burden 

 for financing these projects on local and regional governments. Financeabil- 

 ity of civil works projects is now an important question outside that of posi- 

 tive net benefits. Rubble-mound breakwaters must achieve the maximum benefits 

 for the least cost in order to be affordable as well as economically feasible. 

 Arbitrary conservatism in design of rubble-mound breakwaters is no longer 

 affordable, and coastal engineers must use all the tools and information 

 available to assure the optimum alternative has been proposed. 



Design criteria 



108. Alternatives for rubble-mound breakwaters should be optimized ac- 

 cording to two criteria: functional performance and structural integrity. 

 The functional performance criterion refers to the structure's effectiveness 

 as a wave barrier as measured by its wave transmission characteristics. The 

 structural integrity criterion refers to the structure's ability to survive an 

 extreme storm without significant damage and the rate it suffers damage from 

 storms more extreme (less probable) than the structural design event. 



Analytical design and - ' 



laboratory verification 



109. The analytical tools available to designers of rubble-mound break- 

 waters have been reviewed in some detail. They have all been shown to be the 

 products of a finite set of laboratory experiments, with very little quantita- 

 tive prototype verification. Current research continues to refine the preci- 

 sion of these empirical relations, but this precision is not yet sufficient to 

 warrant construction of rubble-mound breakwaters without verification of 



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