Representative offshore contour 



154. A basic assumption in the formulation of the shoreline change 

 model is that the profile moves parallel to itself. As a consequence, 

 offshore contours move parallel to the shoreline. If this assumption is 

 applied directly in the internal wave model, unrealistic wave transformation 

 can result in regions where the shoreline position changes relatively abrupt- 

 ly, possibly leading to numerical instability. To overcome this limitation, 

 GENESIS has the option of using a smoothed offshore contour in performing the 

 internal wave calculation, as illustrated in Figure 14. In this figure, the 

 shore-parallel contour shown changes radically at the groin. The smoothed 

 contour is expected to better represent the offshore bathymetry. If the 

 smoothed contour option is chosen, the contour is assumed to be representative 

 for all contour lines between the input wave depth and the undiffracted wave 

 breaking depth. The orientation of the representative offshore contour is 

 recalculated on monthly intervals using the shoreline position at that time. 



A 



SHORELINE-PARALLEL 

 OFFSHORE CONTOUR 



SMOOTHED 

 OFFSHORE CONTOUR V 



/, o 



Figure 14. Example of representative contour 



73 



