SI: This detached breakwater has two diffracting tips, the left tip 

 defining the right boundary of window El and the right tip defining the left 

 boundary of window E2 . The detached breakwater is nontransmissive and, 

 therefore, not itself an energy window. 



S2: The structure S2, a short groin, does not define an energy window 

 since it does not produce diffraction; similarly, it does not define the 

 boundary of a sand transport calculation domain but is merely located inside 

 the transport domain extending from the left boundary of the grid to S3. 



E2 : This window is bounded by diffracting structures SI and S3. Waves 

 entering through this window can reach to the left boundary of the grid but 

 cannot reach the beach segments to the right of S3. Window E2 is thus located 

 inside the same transport domain as window El, the transport domain defined by 

 an open boundary on the left and tip S3 on the right. 



S3 : Because longshore sand transport is produced by breaking waves, 

 only groins extending through the surf zone are considered to influence wave 

 breaking by diffraction. The effect of shorter groins is confined to con- 

 straining the sand transport rate. In this example S3 is considered to be 

 diffracting, and waves entering past one side of the structure cannot propa- 

 gate to the other side. Structure S3 thus defines a boundary of a sand 

 transport calculation domain. 



E3 : Waves entering through this energy window cannot propagate into the 

 area on the left side of structure S3 or to the right of structures S4-S5. 



S4 and S5: In GENESIS the two basic structure elements, the groin and 

 one or more detached breakwaters, can be combined to create T-groins, half-Y 

 groins, spur jetties, or even more complex configurations. Because S4 is 

 connected to a detached breakwater, it must be regarded as being diffracting 

 and, thus, also acts as a boundary of a sand transport calculation domain. 



E4: In this example the structure segment S5 allows wave transmission, 

 and waves arriving at the structure will pass through it but have diminished 

 height. As a result, the structure S5 is also regarded as an energy window. 



E5: Waves entering through this window can reach the right boundary of 

 the grid, but cannot reach the beach segments to the left of S4. 



S6 : If the wave energy entering the project area from the right side of 

 structure S6 can be neglected, the structure can be assumed to be infinitely 



79 



