Drainage basin delineation from vector drainage networks

An automated process for the delineation of drainage basins, using as input only the vector based drainage network, is described which provides an alternative to DEM based methods. The procedure involves an approximation of the line Voronoi diagram for the network using a constrained Delaunay triangulation of the network's Planar Straight Line Graph. The constrained triangulation, which includes all network channels as edges in its resulting triangles, is further sub-divided into a set of facets. A two-stage algorithm is then applied to these facets to assign each facet the identifier of a channel in the input network. The drainage area of each channel is delineated by merging all facets assigned to that channel to form a single polygon. The drainage basin for any point in the network can be determined by tracing the channels upstream from that point and merging the associated drainage polygons. Several examples of the procedure's application are provided on drainage networks of varying size and complexity. While the procedure cannot ultimately match the accuracy of a DEM based basin delineation, it can be used in cases where DEM data is either unavailable or of poor quality.