Geographic Visualization of the 1993 Midwest Flood Water Balance

This report documents the construction of three visualization projects based on hydrologic modeling of the 1993 Midwest flood. The modeling procedures and results have been described in “Water Balance of the 1993 Midwest Flood,” by Mizgalewicz and Maidment (1998). In their report, a water balance was calculated for the Upper Mississippi River basin for all of 1993 using streamflow, precipitation, and evapotranspiration data sets. In both this study, and Mizgalewicz’ and Maidment’s study, the Upper Mississippi River basin (UMRB) includes the Mississippi River basin from the river’s headwaters in Minnesota to Cairo, Illinois, and the Lower Missouri River basin below Gavins Point dam, South Dakota, to St. Louis, Missouri (Figure 1.1). Using a digital elevation model of the study area, the daily flow into and out of the basin was calculated, and a series of 365 maps of basin water storage were created. The basin was subdivided into watershed boundaries as delineated in ArcInfo using a digital elevation model and a coverage of U.S. Geological Survey (USGS) stream gaging stations. The water storage values within these watershed boundaries were then spatially averaged into the standard USGS 8-digit hydrologic unit code (HUC) boundaries, and these maps and data sets were used in the construction of several hydrologic visualization projects. As a follow-up to Mizgalewicz’ and Maidment’s study, the water balance data sets and maps were used to create several map-based, computer-generated scenes that depict the catastrophic flooding that occurred in 1983 in the Upper Mississippi/Lower Missouri River basins. Three primary geographic visualization products have been generated during the course of this research: (1) an area-based map animation of the 1993 basin water storage, (2) a point-based map animation of the 1993 water storage, and (3) a line-based map animation of 1993 basin streamflow.