Abstract
A digital model for discretizing three-dimensional terrain into small irregularly shaped polygons or elements based on contour lines and their orthogonals is described. From this subdivision the model estimates a number of topographic attributes for each element including the total upslope contributing area, element area, slope, and aspect. This form of discretization of a catchment produces natural units for problems involving water flow as either a surface or subsurface flow phenomenon. The model therefore has wide potential application for representing the three-dimensionality of natural terrain and water flow processes in the fields of hydrology, sedimentology, and geomorphology. Three example applications are presented and discussed. They are the prediction of zones of surface saturation, the prediction of the distribution of potential daily solar radiation, and the prediction of zones of erosion and deposition in a catchment.