The main focus of study is to compute the surface runoff and to assess the impact of land use/land cover changes (LU/LCC) with the help of hydrological model (SWAT) in Subarnarekha River Basin (SRB) over a period of 1999–2014. For runoff simulation, two different loss models were employed like SCS-CN (Soil Conservation Services – Curve Number) model and Green-Ampt model (GA). Drainage map, elevation map, land use/land cover map, slope map, and soil map of the watershed are prepared using remote sensing and GIS approaches as input data to the model. Simulation has been done at six observing stations located at Adityapur, Jamshedpur, Ghatsila, Jamsholaghat, Fekoghat, and Rajghat. During this period, runoff is found to increase by 6.06% due to decrease in infiltration rate. The comparison between the observed and estimated data shows the Nash–Sutcliffe efficiency (NSE) values are 0.91 and 0.90, and coefficient of determination (R²) values are 0.89 and 0.88 for SCS-CN and GA methods, respectively. Thus, SCS model is found to do well than GA model in Subarnarekha River Basin. This type of study would be beneficial for the watershed development at that particular watershed.