Runoff Estimation in Urban Watersheds by Analytical Models (Case Study: The Part of District No.22 of Tehran City)

In urban catchment because of developed conditions, the amount of impervious area increases which tends to increase runoff volume, peak discharge rate and decrease of infiltration volume. Most of urban catchments are ungauged and runoff data does not exist, as a result; determining the hydrological response of urban catchments in consideration of complex drainage system is a necessity. For this purpose, storm water management models are considered as useful tools for planning and developing in urban areas. Analytical model is one of the stormwater management tools which formulate the physical rainfall-runoff transformation. In this study, two analytical models are used to predict urban runoff volume. One of models predicts runoff volume on the basis of runoff coefficient and another is formulated in consideration of infiltration parameter. A test catchment located in Tehran city is selected for performing these models. Observed rainfall and runoff data are recorded in this catchment for comparing two approaches. Performance indicators such as Nash-Sutcliffe model efficiency coefficient, root mean square error (RMSE), coefficient of residual mass (CRM), absolute relative error and regression coefficient reveal the precision of two models for urban runoff prediction