In the southern portion of Dhaka, adjacent areas like Shantinagar, Rajarbag, Motijheel, Naya Paltan, Puran Paltan, T&T Colony can be called the busiest economic hub of South Dhaka. The whole region is one the most highly urban flood susceptible regions of Dhaka. These areas get inundated even in the slightest amount of rainfall. This study focuses on designing an adequate drainage system for this economic hub of Dhaka. It is hoped that this research may be helpful to related organizations and experts solving the drainage congestion problem of Dhaka city. In this study, different parameters of each sub-catchments, conduits, junction node, and outlets are calculated through EPA SWMM 5.1. After the model simulation, runoff coefficients of all sub-catchments were obtained. These values are calibrated to match the estimated values from the land use map of the study area (generated from satellite images). The total runoff volume from the model simulation is used to design the minimum cross-section of every conduit which is the prime objective of this study. Flood hazard maps, flood risk maps, and % slope maps were also created using ArcGIS for supporting different causes.