Extracting hydrologic information from spatial data for HMS modeling

A methodology is presented for extracting topographic, topologic, and hydrologic information, from the digital spatial data of a hydrologic system, for hydrologic modeling with HMS. Methods for stream and watershed delineation from digital elevation models are presented. After vectorizing the raster-based stream segments and watersheds, navigation fields are added to their tables to support topologic analysis based entirely on the information stored in the tables of the spatial datasets. Algorithms for calculation of stream segment and watershed hydrologic parameters are also discussed. These parameters are curve number, area, and lag-time for the watersheds, and routing model and travel time for the stream segments. Once the hydrologic parameters and topology are defined, a basin model that summarizes all the information and which can be used as input for HMS is created. Using this methodology, the determination of the spatial parameters for HMS is an automatic process that accelerates the setting up of a hydrologic model and leads to reproducible results.