A geospatial approach to flash flood hazard mapping in the city of Warangal, Telangana, India

Dense urbanization leading to uncontrolled transformations within settlements result in flash flooding with overflowing drains leading to a greater inconvenience for the public and damage to private properties. Hence mapping of flash floods would be useful in identifying the high-risk flood zones for disaster response and urban services, during emergencies with rainfall events of high intensity. This article aims to prepare a flood hazard map of Warangal Municipal Corporation (WMC) in Telangana State, India. WMC is chronically affected due to a rise in water levels resulting in flash floods, with an increase in encroachments. The factors considered in this study are rainfall (curve number), surface slope and surface roughness, type of soil, and distance to main channel, drainage density, and land use cover. To decide the relative weight of the impact of each flood causative factors an Analytical Hierarchical Process (AHP) was used. Accordingly, a composite Flood Hazard Index (FHI) has been derived by using the multiple-criteria decision-making tools by integrating these into a Geographical Information System (GIS). The Soil and Water Assessment Tool (SWAT) in Quantum GIS (QGIS), which is a hydrological model, was used to evaluate the projection of streamflow over the water basin and model parameters were optimized using water balance equations during calibration and validation periods.