AUTOMATED RECOGNITION OF VALLEY LINES AND DRAINAGE NETWORKS FROM GRID DIGITAL ELEVATION MODELS - A REVIEW AND A NEW METHOD

The literature on valley and drainage line recognition from grid digital elevation models (DEMs) is reviewed. Two problems preventing the successful delineation of fully connected drainage networks of single-line width are identified: (a) the positioning of the ends of drainage networks, and (b) the assignment of drainage directions to a DEM, in particular the assignment of drainage directions across flat areas and at closed depressions in the DEM ('pits'). A new method for drainage network delineation is suggested which incorporates an alternative method for drainage direction assignment over a DEM. This method is found to produce realistic directions, and performs well on two complex DEMs.