80 breakwater segments have recently been constructed on the Danish North Sea 

 coast (Laustrup 1988). Shore-parallel structures for shore protection have 

 also been used in Spain (Berenguer and Enriquez 1988) and Singapore (Silvester 

 and Ho 1972; Chew, Wong, and Chin 1974) and are being evaluated for a major 

 coast protection scheme in Negombo, Sri Lanka (Danish Hydraulic Institute 

 1988) . The documented performance of these structures in Japan and Israel 

 demonstrates that this type of shore protection is both effective and versa- 

 tile, successfully performing in low to moderate wave energy environments with 

 sediment ranging from fine sand to pebbles. 



5. A primary reason breakwaters have been under-utilized in the United 

 States is the lack of functional design guidance. Techniques to predict beach 

 response in the project area and on adjacent shores as a function of struc- 

 tural and site parameters may be unreliable, unproven, cost- and time- 

 intensive, or not readily available to the project designer. Other factors 

 limiting the use of breakwaters in the United States include the high cost of 

 water-based construction (used in most cases for detached breakwaters) and an 

 inability to predict and compensate for structure -related phenomena such as 

 adjacent beach erosion, rip currents, scour at the structure base, and the 

 effects of structural settlement on project performance. 



6. The purpose of this report is to present and evaluate the various 

 empirical breakwater design methods available to the project engineer. In 

 Part II, the major categories of design techniques available are briefly 

 presented, and empirical design relationships available in the literature are 

 discussed with a common definition of terms. The methods described in Part II 

 are evaluated in Part III using data available from several US projects. In 

 Part IV, the empirical design techniques demonstrated to predict prototype 

 response to detached breakwater systems are recommended for use by field 

 engineers. Variables used throughout the report are defined in Appendix A. 



