AN ALTERNATIVE DELINEATION OF BASINS METHOD USING DEMS. PRELIMINARY ALGORITHMS

摘要

The initial motivation of this work was to have roughly identified the basin prior to perform the conventional process (via TauDEM or ArcHydro Tools) in all the cells of a Digital Elevation Model (DEM), promoting savings of processing time and data memory when doing the actual conventional process. The delineation of a basin using a DEM starts assigning a flow direction to each cell of a grid of flow directions; then, a process ending with the identification of watersheds is followed. Finally, if only the basin is needed, all watersheds are dissolved into it. In this work it is presented a different approach that in essence begins from the exit cell of the basin and proceeds upstream until all cells that contribute their flows to the exit cell are found. Two approaches are tested, one that considers that a cell flows to the previous cell if it has the same or greater elevation than the previous one, and the other that considers that a cell flows to the previous cell if it has its steepest descent directed to the previous cell. Both algorithms were implemented in a plug-in created for MapWindowGIS version 4.X. To compare the results of the proposed algorithms with those obtained with the TauDEM tools a dataset of four basins was selected. The corresponding DEM grids were obtained from the Mexican Continuum of Elevations of Institute) Nacional de Estadistica y Geografia (INEGI). Both algorithms tend to delineate basins larger than they should be; but the second one produces significant smaller basins than the first one, making it useful for preliminary delineations.