The Impact of Urban Development and Land Use Changes on Runoff Production in Abshouran Watershed

Physical development of cities and expansion of its dimensions is one of the important forms of land use change that has many environmental, economic and social consequences. Changes in the natural pattern of drainage systems in urban and suburban areas, unprincipled use, development Impermeable surfaces are a major cause of urban flooding. The purpose of this study is to estimate the changes in discharge and runoff volume leading to the city as a result of increasing impermeable levels and urban development. In this regard, land use changes related to Abshouran watershed in three time periods have been tracked using Landsat images. EPA SWMM model was used to investigate changes in runoff peak flow. After calibrating the SWMM model based on the observed rainfall-runoff events, the calibration and validation results confirmed the conformity of the model simulations. Fitting of land use changes and corresponding floods during the study period shows that the area of urban areas in 2018 and 2001 compared to 1991 has increased by 189.68 and 60.79 percent, respectively. With increasing the percentage of urban impermeable surfaces, peak discharge and runoff volume for rainfall with a 20 year return period in 2018 compared to 1991, 198.82 and 188.04, respectively, and compared to 2001, 72.34 and 94.85 percent, respectively. Increased.