The land development and increase in urbanization in a watershed affect water quantity and water quality. Especially, uncontrolled urbanization causes flood and poor water quality which results in an increase in peak flow rate and in Total Suspended Solid (TSS) concentration. Low Impact Development (LID) is a Best Management Practice (BMP) and land planning method which may be used to manage storm water runoff in order to reduce flooding as well as simultaneously improve water quality. In this study, the impact of "LID-BMP" on surface runoff and TSS is investigated by employing a calibrated hydrodynamic model for Sazlıdere Watershed which is located in Istanbul, Turkey. For this purpose, a calibrated hydrodynamic model was developed by using Environmental Protection Agency Storm Water Management Model (EPA SWMM). For model calibration and validation, a rain gauge and a flow meter are set into the field and rainfall and flow rate data are obtained. And then, several LID types are selected such as retention basins, vegetative swales and permeable pavement and their influence on peak flow rate and pollutant buildup and washoff for TSS are obtained. Consequently, the possible effects of LID on surface runoff and TSS in Sazlıdere Watershed are observed.