Improvement of the Stormwater Drainage System in the Maligaon Railway Colony, Guwahati, Assam: A Case Study

Urban flooding and water-logging have become recurring problems in Guwahati, Assam, India, primarily due to rapid and unplanned urbanization, high monsoonal rainfall, and degradation of natural drainage systems. The Maligaon Railway Colony, one of the most flood-prone areas of the city, frequently experiences surface inundation caused by inadequate stormwater conveyance, encroachment on natural drains, and runoff from the surrounding Kamakhya and Gotanagar hills. This study evaluates the performance of the existing stormwater drainage system of the Maligaon Railway Colony and proposes improvement measures to mitigate flooding. A detailed assessment was carried out using topographic data and hydraulic modeling in SWMM to simulate rainfall–runoff processes and drainage network behaviour under peak rainfall conditions. Initial simulations identified critical deficiencies in the existing system, particularly poor connectivity among several drainage nodes on the northern side of the railway line, leading to localized flooding. These issues were addressed through network modification and re-simulation. Two improvement scenarios were analysed, a proposed drainage system without wetland interaction and a system incorporating wetland storage effects linked to Deepor Beel. Simulation results indicate that, in the absence of wetland influence, the proposed outfall system conveys peak discharges of approximately 34 m³/s during a 2-hour rainfall event with a 5-year return period. When wetland storage is considered, the peak outflow is reduced to about 20 m³/s, demonstrating a substantial attenuation of flood peaks. The findings highlight the importance of preserving and integrating wetlands into urban drainage planning. The study provides practical design recommendations for improving drainage efficiency, reducing flood risk, and promoting sustainable stormwater management in the Maligaon Railway Colony.