Calibration and Evaluation of the Hydrologic- Hydraulic Model SWMM to Simulate Runoff (Case Study: Gorgan)

This study was done to simulate runoff of Gorgan city using of the hydrologic-hydraulic model SWMM. In this study¡ to calibrate the model¡ four rainfall events¡ were used and the speed of the corresponding runoffs in the chosen sub basin were recorded. In this study¡ NS¡ RMSE and BIAS% were used as model performance indices in the estimating peak discharge and flow volume. Also significant and no significant differences between the observed and simulated values by paired t test were investigated. The model calibration results showed that the simulated peak discharge and flow volume are in good correspondence with the observed values (BIAS%= 11.44¡ RMSE= 0.006 and NS= 0.70) and the calibration results were used for the optimum values of parameters. To evaluate and test model validation¡ two rainfall events¡ were used. That the model performance indices were acceptable in both cases (BIAS%= 8.01¡ RMSE= 0.00043 and NS= 0.69). Furthermore¡ according to paired t test of difference between observed and simulated values in the calibration and validation of the model error (0/01 or 0/05) are not significant. The results of the study indicate that the model has the accuracy required for urban runoff simulation.