Sensitivity analysis of input variables of SWMM model in estimating urban floods in Azimieh region of Karaj

Urban runoff management models are considered as a useful tool in planning, design and development. One of the most usable models in this field is the SWMM. One of the main problems in studying urban drainage network with these models is the correct choice of parameters. To overcome this problem, the sensitivity analysis method could be used, which shows the relationships between variables included in the model with each other and the priority of their impacts on the model output. The purpose of this study is to determine the sensitivity of affective variables that influence urban flood peak using the SWMM model in Azimiyeh region of Karaj. In order to that, the estimated initial value of the percentage of impervious area, slope, width, curve number, N-Manning for impervious area, depth of depression storage on impervious area, percent of impervious area with no depression storage reduction were decreased and increased to a constant value in the range of acceptable changes and their effect on peak discharge was investigated as a dependent variable. Based on the results, the amount of impervious areas and the percent of impervious area with no depression storage had highest and lowest effect on peak discharge, respectively. 30% increase in the amount of impervious areas, as the most effective parameter, caused peak discharge to be increase 5.09 percent.