Jeffrey J. Danielson,
UNEP GRID/EROS Data Center
At the U.S. Geological Survey's EROS Data Center, the USGS, the National Aeronautics and Space Administration, the United Nations Environment Program, and others are developing approximately 30 arc second resolution digital elevation models (DEMs). These DEMs are important because they provide the basic data as well as derivative information such as slope, aspect and flow characteristics that are critical in environmental problems for hydrologic, biologic, and geologic studies.
DEM's have been available for many years but only recently have computer speeds, GIS algorithms and appropriate models become available to process DEMs in hydrologic applications (Moore, 1991). Digital delineation of drainage basins from DEM's is a primary example of this newly-evolving capability. Drainage basins are crucial for resource management, ecosystems analysis, and global-change studies. This poster describes drainage basin delineation from a one kilometer DEM on a continental scale for Africa, as part of the on-going project on drainage database design based on DEMs at the EROS Data Center.
A GIS is a tool for collecting, storing, retrieving, transforming, and displaying spatial data (Burrough, 1986). Hydrologic modeling is concerned with the flow of water and its constituents over the land surface and subsurface environment (Maidment, 1993). One important concept in hydrologic modeling is the river basin. The modeling of drainage basins is accomplished most easily with the digital elevation model (Maidment, 1993).
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