Hydrologic modeling utilizing ArcView (GIS): Application of the HEC-GeoHMS utility package

ESRI's geographical information system (GIS) software package ArcView is a multifaceted program capable of being used for hydrologic modeling. Using spatial relationships derived from digital elevations models (DEM's), the user can determine hydrologic parameters such as watershed/sub-basin areas, reach length, and average watershed slope. Additionally, landuse maps can be overlaid on the DEM to determine forested, rural, and urbanized areas. The NRCS STATSGO or SURGO soils maps can be used in conjunction with the landuse maps to determine runoff curve numbers.

The Hydrologic Engineering Center has developed a utility package known as HEC-GeoHMS that works implicitly within ArcView. The program allows the user to gather and organize data within a GIS database. The data then can be imported directly into the HEC-HMS program for hydrologic analysis of a watershed. Parameters that can be obtained directly from the Arcview/HEC-GeoHMS package include watershed or sub-basin areas, longest hydraulic lengths, lengths from the centroid of a basin to its outlet, and overall watershed slope. These parameters are used in the various unit hydrograph theories that are in the HMS program, such as the Clark instantaneous unit hydrograph, the Snyder synthetic unit hydrograph, and the NRCS dimensionless unit graph.

Data acquisitions from several watersheds using the ArcView and HEC-GeoHMS packages have been obtained by the authors. The results were analyzed and compared to specifications supplied by USGS and NRCS documentations. All results compared favorably with discrepancies of less than 2 % observed. 7 pp., 3 references.