Simulation of rainfall-runoff for basins in the Rolla, Missouri, area

Important rainfall-runoff characteristics for basins in the Rolla, Missouri, area were determined to be overland flow, interception storage, interception losses, evaporation, and infiltration. Using these characteristics, the U.S. Environmental Protection Agency's Stormwater Management Model (SWMM) was configured for basins in the study area. The data network for the model calibration consisted of four continuous rainfall gages and three continuous streamflow gages. The model was calibrated, using observed data from three runoff events, by minimizing objective functions representing peak discharge, volume of runoff, and time to peak discharge from the beginning of simulation. The absolute mean percentage difference between the simulated and observed data for peak discharge, volume of runoff, and time to peak discharge are 9.47, 10.8, and 19.6 percent. A sensitivity analysis of SWMM parameters was performed on a simplified drainage basin. The output of runoff (volume, peak, and timing) in SWMM was determined to be most sensitive to subarea width, percentage impervious area, saturated hydraulic conductivity, and initial moisture deficit. The volume of runoff was affected by percentage impervious area, saturated hydraulic conductivity, and initial moisture deficit. The peak flow rate was affected by subcatchment width and percentage impervious area, whereas the time to peak was affected by subcatchment width. The model also was determined to be sensitive to the time step in the streamflow routing part.