boundaries to the left and right, as described in Part V. Notation used in 

 this figure is also described in Part V. 



k-; 



GATED OR PINNED-BEACH 

 BOUNDARY AT CELL WALL 1 



GROIN, 



BREAKWATER TIP, 

 OR END OF SEAWALL 

 AT CELL WALL i 



GATED OR PINNED-BEACH 

 BOUNDARY AT CELL WALL N+1 



DISTANCE ALONGSHORE/GRID CELL NUMBER 

 Figure 19. Example of a coordinate system and grid used by GENESIS 



208. A right-hand coordinate system is drawn with the x-axis (baseline) 

 parallel to the trend of the shoreline and the y-axis perpendicular to it and 

 pointing offshore. It is convenient to place the baseline landward of coastal 

 structures and any expected or historical position of the shoreline so as to 

 deal with only positive -valued shoreline positions, although this need not be 

 the case. The shoreline grid along the x-axis consists of N cells defined 

 by N+1 cell walls. Boundary conditions must be specified at cell walls 1 

 and N+1 . Internally in GENESIS, longshore sand transport rates, positions 

 of structures, and boundary conditions are located at cell walls, and shore- 

 line positions are located in the middle of cells. Cell wall 1 is placed at 

 the location where the left boundary condition is implemented, and the grid 



98 



