The main objective of this study is to analyze and calculate the hydrological benefit of providing onsite detention pond for sub catchment Mahiminside Mithi River watershed. The Mithi River watershed is one of the most developed regions in India with the rapid urbanization which serves as an excellent case study site for proving the benefit of detention pond. SWMM 5.1 software has been used to simulate the model and to evaluate the result. The detention pond was found very effective to reduce the peak of flood and to postpone its time of occurrence. The size of detention pond with varying configuration of weirs/orifice plays vital role in flood management. The result obtained shows that (1) the onsite detention of rainwater can reduce the peak flood and can increase its time to occurrences; (2) peak flow is approximately reduced by 52% and its time of occurrence increase by 180 minutes, respectively; (3) analysis of results shows that successive events of rainfall can exaggerate the flood. In conclusion, detention pond with other best management practices will be very useful. The study suggested that more attention must be given for flood mitigation and water resources management in planning future urban development in the region.