| The hydrologic model has been successfully developed completely within the Geographic Information System (GIS) environment by using ARC Macro Language (AML) within ARC/INFO. This paper discusses the detailed development of the GIS hydrologic model. This study emphasized urban rainfall-runoff. The Soil Conservation Service (SCS) runoff curve number method was used to determine excess rainfall, the unit hydrograph was defined by the SCS triangular unit hydrograph, the convolution method was used to translate the time distribution of the excess rainfall into the runoff hydrograph, and the Muskingum routing method was used to perform the channel routing.; The GIS was used to determine the parameters which are required by the model, including area, runoff curve number, length of stream channel, average slope, and the time of concentration for each subwatershed. Those parameters were then used in the GIS hydrologic model to compute the runoff hydrograph for a watershed.; This study demonstrated the use of the hybrid method in GIS to combine the vector and raster-based coverages in hydrologic modeling. Most of the coverages used in this study are vector-based coverages, such as land use and soil type which are best handled as polygons. Stream channel is line coverage. Only the Digital Elevation Model (DEM) is raster-based coverage to accommodate the elevation data, which is best handled as grid.; The Turtle Creek watershed and the Coombs Creek watershed in Dallas, Texas were used in this study. Turtle Creek watershed was chosen for calibration and verification of the model because of the availability of digital data sources and rainfall-runoff records. Coombs Creek was used to simulate the runoff hydrograph for an ungaged watershed by using the calibrated parameters from the Turtle Creek watershed.; The model was applied to the simulated runoff hydrograph for the Turtle Creek watershed. From the results of the model, the assessment of 6 actual storm events indicated the relatively strong correlation (R{dollar}sp2{dollar} ranged from 0.78 to 0.97) between the observed and the simulated runoff hydrograph when 15 minutes is used as the optimal travel time, K. |
