Void Area elements allow you to free draw an irregular hole in the 2D computational grid. The 2D grid cells overlayed by a Void Area polygon will be inactivated during a simulation. One could employ a Void Area to remove physical barriers, or obstructions such as buildings from the 2D grid altogether. To prevent double accounting, any grid cells corresponding to a significant 1D surface network should be voided. In general, engineering judgement should be used in overlapping a 2D Grid with 1D surface elements such as Catchments, Low Impact Development areas, Ponds, Channels, and Gutters.