PART VI: SUMMARY AND CONCLUSIONS 



89. Detached breakwaters, especially segmented ones, are a viable and 

 cost-effective alternative for many shoreline erosion and beach stabilization 

 problems. However, no means presently exists for quantitatively predicting 

 beach response to these structures. The functional design of a detached 

 breakwater is, not unlike other coastal engineering design problems, an empir- 

 ical process. Review of the literature and examination of existing breakwater 

 projects provide substantial insight and some qualitative design guidance. 



The natural parameters which are most important are those which affect wave 

 diffraction (wave length, height, direction, and the gap width-to-wavelength 

 ratio for segmented breakwaters), natural beach slope, water-level range, na- 

 tive sediment size, and available supply of sediment. The techniques avail- 

 able for controlling beach response include: (a) variation of the ratio of 

 breakwater length to distance offshore, (b) location of the structure with 

 respect to the breaker line, (c) orientation of the structure with respect to 

 the original shoreline and the predominant wave direction, and (d) the degree 

 of wave transmission by overtopping, permeability, or by segmenting the break- 

 water. Other topics which should be considered when designing detached 

 breakwaters include ecology, safety, navigational aspects, aesthetics, and 

 currents through breakwater gaps. 



90. A three-phase approach is recommended for the functional design of 

 detached breakwaters. First, based on the material presented in this report, 

 one or more initial designs should be developed and the shoreline response 

 under various conditions predicted. Physical and/or numerical model tests 

 should then be performed to find and improve upon the best plan. Finally, 

 field tests could then be conducted to arrive at a final configuration. 



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