Investigating the effectiveness of the SWMM model in simulating and evaluating the capacity of Kalat Naderi urban channels for the passage of flood flows

Urban development and industrialization, combined with the lack of proper drainage systems and the disorder of canals and channels, have had adverse effects on urban areas, leading to flooding of roads and inundation. This research, conducted in a region of Kalat city, aimed to analyze these issues. First, the physical characteristics of the area—such as area size, slope, equivalent width, percentage of impervious surfaces, and other parameters—were estimated. After determining the average water flow velocity, the concentration time of the study area was calculated based on the length of the largest waterway.Using rainfall parameters such as intensity-duration-frequency (IDF) and the temporal and spatial distribution of rainfall, the SWMM (Storm Water Management Model) was simulated, sensitivity-analyzed, and evaluated for different return periods. Sensitivity analysis revealed that among the eight parameters analyzed, the percentage of impervious surfaces had the greatest effect on peak flow rate.To calibrate and evaluate the model, five measured events were analyzed. Three events were used for calibration, where criteria such as Nash-Sutcliffe Efficiency (NS), Root Mean Square Error (RMSE), BIAS%, and Kling-Gupta Efficiency (KGE) were employed to assess performance. The calibration results indicated good agreement between simulated and observed runoff, with NS values greater than 0.5 for all three events.For model evaluation, two additional events were analyzed using the same criteria. The RMSE values for the calibration simulations were 0.01, 0.003, and 0.01 cubic meters per second, respectively, while the RMSE values for the evaluation simulations were 0.04 and 0.04 cubic meters per second. These results demonstrate the model's acceptable performance.The findings indicate a strong agreement between simulated and observed runoff, proving that the SWMM model has the required accuracy for urban runoff simulation. Thus, this model can be effectively used for urban runoff management plans and drainage network design. Additionally, it was determined that the upstream watershed of the study area, characterized by good permeability and a small size, supports channels with suitable dimensions for return periods ranging from 2 to 50 years.