Application of terrain analysis and geographic information systems to the construction of hydrologic databases: A case study

Spatial data in digital form have become increasingly available in a wide range of different formats. Often, however, the available data are unreliable even in routine applications. This paper illustrates these problems in relation to both digital elevation and stream network data. It presents new techniques within the framework of Geographic Information Systems (GIS) for the Great Miami River Basin of Ohio and Indiana to improve data usability. Inconsistencies in the digital elevation models (DEMs) were reduced by combing the raw 1-degree DEMs with hydrography layers to create a new, hydrologically correct DEM. Relevant topographic characteristics of 34 gaged watersheds could be extracted with improved accuracy from the modified DEM, Discrepancies in the drainage density in the hydrography layers were reduced by extracting the stream network from the DEM, The result is a consistent drainage network that eliminates inconsistencies inherent in the original data across the Indiana-Ohio state line, The database also includes the spatial distribution of land use and land cover, and soil properties. This study shows that computer processing can improve the consistency of commercial data products.