CALCULATING CATCHMENT-AREA WITH DIVERGENT FLOW BASED ON A REGULAR GRID

A new procedure is described for determining the catchment areas for all cells in a regular elevation grid, a problem of fundamental importance in analyzing drainage patterns, mineral deposition, erosion, and pollution in streams and groundwater. The new procedure allows for divergent flow, which arises in most natural terrain on hill slopes. Failure to allow for this can introduce serious artifacts in the calculations. The procedure is demonstrated on analytic surfaces that give poor results if divergent flow is ignored, and is applied to natural terrain. Also discussed is the problem of clearing sinks or pits in the elevation model and flat spots.