ABSTRACT:In a cooperative demonstration project, NASA and the U.S. Army Corps of Engineers (Corps) compared conventional and Landsat‐derived land‐use data for use in hydrologic models, and the resulting discharge frequency curves were analyzed. When a grid‐based data‐management system was used on a cell‐by‐cell basis (size about 1.1 acres or 0.45 hectare), Landsat classification accuracy was only 64 percent, but, when the grid cells were aggregated into watersheds, the classification accuracy increased to about 95 percent. When both conventional and Landsat land‐use data were input to the HEC‐1 model for generating discharge frequency curves, the differences in calculated discharge were judged insignificant for subbasins as small as 1.0mi2(2.59 km2). For basins larger than 10mi2(25.9km2), use of the Landsat approach is more cost‐effective than use of conventional methods. Digital Landsat data can also be used effectively by local and regional agencies for hydrologic analysis by incorporating the data into grid‐based data‐management systems. The transfer of this new technology is well under way through inclusion in some Corps training courses and through use by both county government personnel an
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