Algorithms for using a DEM for mapping catchment areas of stream sediment samples

Abstract

Algorithms are presented which use a digital elevation model (DEM) to create maps of catchment areas of stream sediment sample points, and to locate optimal sample point locations. Drainage flow directions are determined by the popular “D8” algorithm, which assigns the drainage from one point on the DEM grid to one of its eight adjacent neighbors. A new “drainage enforcement” algorithm is presented that insures drainage continuity through flat areas and out of depressions. This algorithm is based on the priority-first-search weighted-graph algorithm. Relatively simple methods for defining internal basins and incorporating digitized stream data are also discussed. All of the selected methods are robust, computationally efficient, and avoid many of the problems associated with other methods. In order to support this claim, the literature is reviewed and comparisons are made between the chosen methods and other methods. A full implementation has been created, and the Pascal source-code and Win95 executable program may be downloaded from the IAMG web site.