feasible, a prototype test can be conducted to verify and adjust the preliminary 

 design. 



Structural design guidance for detached breakwaters involves assessment of 

 structural stability and anticipated performance characteristics for critical and 

 average wave and water level conditions. The use of low-crested breakwaters 

 for beach and wetland stabilization projects has increased since they can be 

 more cost-effective than conventional multilayered navigation breakwaters. 

 Recent guidance to assess structural stability and performance characteristics 

 of low-crested breakwaters is presented in this report. 



Additional Research Needs 



Continued research relative to detached breakwaters should explore 

 improved techniques to predict beach response and methods to optimize 

 breakwater design. Primary reasons for the limited use of detached 

 breakwaters in the United States are the lack of functional design guidance and 

 high construction costs. Further development of comprehensive criteria is 

 needed for breakwater design in the feasibility, continuing authority, and 

 reconnaissance phases. Current techniques to predict shoreline response and 

 downdrift impacts as a function of structural and site parameters can be 

 insufficient, costly, time-consuming, and not readily available to the designer. 

 Continuing efforts at CERC are completing the development of functional 

 design criteria, in the form of nomographs, based on site and structural 

 parameters (Rosati, Gravens, and Chasten 1992). Additional research is also 

 needed in predicting wave transmission characteristics of detached breakwaters 

 and the resulting influence of transmitted wave energy on beach planform and 

 wetland development. Continued research addressing breakwaters as beach 

 fill stabilization and wetland development structures would be beneficial. 

 Increased benefits from the use of breakwaters in these manners may help 

 justify their costs of construction and encourage breakwater applications in 

 more areas of the United States. 



114 



Chapter 6 Summary and Conclusions 



