parameters described in the previous sections. This design is evaluated 

 relative to the project's objectives, predicted beach response, and potential 

 effects on adjacent shorelines; modifications are then made to the initial design 

 and the project is reevaluated. Initial design should start by considering 

 incident wave energy flux to determine the extent of wave energy reduction 

 necessary to develop the desired beach planform. 



Tools for design evaluation 



Design techniques or evaluation tools for detached breakwaters can be 

 classified into three categories: physical and numerical models, empirical 

 methods, and prototype assessment (Rosati 1990). Numerical and physical 

 models, when calibrated and verified at a particular project site, can 

 effectively simulate coastal response to a particular breakwater design. 

 Modeling, particularly numerical, is recommended prior to the implementation 

 of the breakwater project. The use of numerical and physical modeling as 

 tools in functional breakwater design is discussed in Chapter 3, Tools for 

 Prediction of Morphologic Response. Models, however, can be more 

 expensive and time-consuming than required for feasibility-level studies. 

 Empirical "desktop" methods provide quick techniques for qualitatively 

 evaluating beach response to a particular project design (Rosati 1990). The 

 use of these simplified, inexpensive methods is desirable in the feasibility 

 stage of project design; in the design of more extensive laboratory, numerical 

 model and field testing; and as a check for detailed evaluation results. 



Dally and Pope (1986) suggest a three-phase breakwater design process: 

 first, a desktop study employing various empirical relationships to relate 

 proposed structural and site parameters to shoreline response and identify 

 design alternatives; second, a physical or numerical model study to assess and 

 refine alternatives; and finally, if feasible, a prototype test to verify and adjust 

 the preliminary design. 



Prototype breakwater database 



A database of detached breakwater projects in the United States and several 

 other countries is maintained by CERC. The database contains information 

 such as type of breakwater, dates of construction, project dimensions, and 

 other site data. A brief narrative description of the project's performance is 

 also included. Because limited design guidance exists, experience from 

 prototype sites such as those contained in the database may prove valuable for 

 the design of a new breakwater project. 



Chapter 2 Functional Design Guidance 



37 



