Impact Assessment of Urban Physical Development on Hydrogeomorphological Systems of Tehran Metropolis (Case study:Darband Catchment)

Introduction and Background: The development of urbanization and the transformation of rural areas into cities are accompanied by land use changes and pressure on natural systems. One of the natural systems is the rivers that are affected by human activities in urban areas. The purpose of this study is simulation and estimation of the variations of geohydro-logical parameters including surface runoff, river discharge, permeability and evapotranspiration. his research has been conducted using the semi-distributed SWAT model in the last two decades of the past twenty years (1998) and present (2018) in the catchment area of Darband. In this study, the SUFI2 algorithm was used to calibrate the model. The results of the research show that after optimizing the parameters used in SWAT-CUP, the value of Nash-Sutcliff (NS) and R2 coefficient of year 1998 in the calibration stage is equal to 0.34 and 0.43, respectively, for the validation period, the coefficient value Nash-Sutcliff and the coefficient of determination are respectively 30/0 and 39/0 respectively. Also, the SWAT-CUP model was studied and evaluated in the current situation of Darband-Golad-Dare Basin for 2018. The results of observational and simulated hydrographs are presented and the performance evaluation values of the model are presented below. The value of nisoscatheff (NS) and coefficient of determination (R2) were estimated to be 0.31 and 0.46 during the calibration period, 0.33 and 0.39, respectively, during the validation period. According to the results of the performance evaluation, the model based on Nash-Thaw (NS) coefficient and determination coefficient (R2) shows the ability of the swat model to simulate the runoff of the basin. Similarly, the simulation results show that changes in the range of the study area caused a change in CN values, runoff and evapotranspiration at the user level over a period of 20 years.