Wave Crests 



Semi-Infinite 



Detached Breakwater 





/ /' / / / / / / / / / / / / y\ 





K o" 1 - 



\ \ -A -^X^ 08 



0.2 ,V\..- ) Xc?- 6 ! 



\ /N \L 



0.4 



Shadow Region 



Illuminated Region 



Fig. 2. Diffraction behind a semi-infinite breakwater (schematic) 



transported alongshore and into the area behind the structure. In addition, 

 the transmitted waves themselves will tend to transport sand out of the area 

 behind the detached breakwater. Thus, these two mechanisms (reduced transport 

 from diffracted waves and direct transport of sand by transmitted waves) act 

 together to suppress growth of the salient behind the breakwater. 



NUMERICAL MODEL 



GENESIS is a finite -difference numerical model developed to simulate 

 shoreline change produced by wave action (Hanson 1987, 1989; Hanson and Kraus 

 1989). The model calculates shoreline change occurring over a period of 

 months to years and with a length scale varying from one to tens of kilometers 

 (Kraus 1983, 1989). GENESIS simulates shoreline change for a wide variety of 

 user-specified beach and coastal structure configurations (for example, 

 Hanson, Gravens , and Kraus 1988). 



Version 2.0 of GENESIS, presently under testing, allows representation of 

 wave transmission at detached breakwaters. Each breakwater can be assigned a 



44 



