AUTOMATED EXTRACTION OF DRAINAGE NETWORK AND WATERSHED DATA FROM DIGITAL ELEVATION MODELS

This paper discusses a computer program which extracts a number of wat ershed and drainage network properties directly from digital elevation models (DEM) to assist in the rapid parameterization of hydrologic ru noff models. The program integrates new and established algorithms to address problems inherent in the analysis low-relief terrain from rast er DEMs similar to those distributed by the U.S. Geological Survey for 7.5-minute quadrangles. The program delineates the drainage network f rom a DEM, and determines the Strahler order, total and direct drainag e area, length, slope, and upstream and downstream coordinates of each channel link. It also identifies the subwatershed of each channel sou rce and of the left and right bank of each channel link, and assigns a unique number to each network node. The node numbers are used to asso ciate each subwatershed with the channel link to which it drains, and can be used to control flow routing in cascade hydrologic models. Prog ram output includes tabular data and raster maps of the drainage netwo rk and subwatersheds. The raster maps are intended for import to a Geo graphical Information System where they can be registered to other dat a layers and used as templates to extract additional network and subwa tershed information.