The Wetland River basins are one of the critical urban watershed areas due to complex urban activities. The rainfall-runoff process in urban catchment areas is influenced by solid waste dumping, leachate generation from dumping sites, aquatic weeds, sewage generated by municipalities and town panchayats, effluents generated by industries, sand mining along the river bed and encroachment due to urban activities. Considering these complexities, this study aims to predict the stream flow in a river basin concerning a given amount of rainfall using HEC - HMS software models. The sub-basin elements are used to convert rainfall to runoff. A meteorologic model is used to assign the boundary conditions for sub-basins, which include precipitation, short/long wave radiation, and potential evapotranspiration. A time series of flow data is used as input of a model to estimate the average basin rainfall. Calibrate the model and it's required for optimization to be carried out using observed discharge. As a result, considering the three sub-basins and two reach sites, the increase in drainage area is directly proportionate to excess volume, direct run-off volume, and discharge volume, and the reliability of the model is achieved using observed data and predicted data.