Urban Drainage and Stormwater Management Using GIS and SWMM Software in Tenali Municipality, Guntur District, Andhra Pradesh, India

Rapid urbanization has significantly altered natural hydrological processes in many Indian towns, resulting in frequent urban flooding during monsoon rainfall events. The expansion of impervious surfaces reduces infiltration and increases surface runoff, often overwhelming existing stormwater drainage systems that were designed based on outdated rainfall and population projections. Tenali Municipality, located in Guntur District of Andhra Pradesh, experiences recurrent waterlogging and flooding during moderate to heavy rainfall events due to inadequate drainage infrastructure and improper system planning. In the present study, the urban stormwater drainage system of Tenali Municipality was analysed using an integrated approach combining Geographic Information System (GIS) techniques and the United States Environmental Protection Agency Stormwater Management Model (EPA-SWMM). Spatial data required for the study were extracted using Google Earth Pro and processed in ArcGIS to delineate drainage networks, catchment areas, and land use characteristics. A detailed SWMM model was developed by defining sub-catchments, junctions, conduits, outfalls, and rainfall inputs, and simulations were carried out at 15-minute time intervals to evaluate system performance under high-intensity rainfall conditions. The simulation results indicate that several drainage conduits experience surcharge conditions, leading to localized flooding in low-lying areas. Insufficient conduit capacity, inadequate slopes, and downstream flow obstructions were identified as major contributors to flooding. Flood-prone locations were spatially mapped using GIS to clearly visualize vulnerable zones within the municipality. The study demonstrates that the integrated use of GIS and SWMM is an effective tool for diagnosing deficiencies in urban drainage systems and provides valuable insights for improving stormwater management strategies. The findings can assist municipal authorities in planning infrastructure upgrades and mitigating urban flood risks in Tenali and similar mediumsized towns in India.