The tools of Geographic Information Systems have become increasingly valuable in hydrologic assessments and play an integral role in decision-making processes for flood prediction and mitigation. On the other hand, a quite distinct activity has been the development of GIS-based simulation modeling and visualization systems including realistic landscape visual simulations. Typically GIS, hydrologic simulation models, and virtual reality technology have been utilized as stand alone problem-solving domains. The increasing availability of high performance computation and visualization tools, offers new opportunities to combine sophisticated GIS modeling tools and emerging immersive visualization and decision support environments. This research describes the development of an interactive environment that utilizes the tools of virtual reality and GIS to enhance spatial hydrologic modeling. More specifically this research involves development and application of an interactive virtual modeling environment for spatially explicit hydrologic modeling in support of flood mitigation and flood management decision-making for the Squaw Creek watershed in central Iowa. The environment contains tools to manipulate and display geospatial data, spatial explicit output flow predicted by the Hydrological Engineering Center's Hydrological Modeling System (HEC-HMS) and an immersive virtual environment that uses the Cave Automatic Virtual Environment (CAVE) to increase perception and realism. A component of the study was to develop tools to perform spatial hydrologic modeling in a microcomputer-based three-dimensional virtual environment using a head mounted haptic display. The unique combination of spatially explicit hydrologic models with geospatial and virtual reality visualization tools improves hydrologic analysis of "what-if" land-use and land management options and their hydrological impacts provides an opportunity for rapid assessment of hydrological conditions for improved collaborative environmental decision-making, and enhance the ability of resources planners to navigate and interact with the synthetic landscape environment.