Hydrological modeling for the regional stormwater management plan: An application and intercomparison of event based runoff generation in an urban catchment using empirical, lumped vs. physical, distributed parameter modeling

Hydrologic modeling for the characterization of two Regional Stormwater Management Plans is performed using both a lumped parameter, empirical model and a fully distributed, physical model. Both urban/suburban watersheds located in the Northeast United States contain impaired waters, impervious surfaces ranging from 15 to 25% of total land area and are officially un-gauged. Event based models performed on storms that range from 0.5 to 1.25 inches total depth were modeled to compare the resultant simulation hydrographs of the HEC-HMS model to the MIKE-SHE model. The results of the calibrated model predictions compared well with the observed stream flow in the lumped parameter model, but were less accurate in simulating soil infiltration parameters and impervious surfaces in the fully distributed model. Sensitivity analysis of the lumped parameter model indicated that the empirical parameter representing infiltration and runoff had the greatest effect on the accuracy of the event hydrograph. The parameter that most affected accurate simulation of the overland flow in the fully distributed, physical model was the land roughness coefficient, Manning M. When the impervious surfaces and unsaturated zone were included in the fully distributed model, the hydraulic conductivity became the principal element of calibration.