Development of Flood Inundation Maps and Quantification of Flood Risk in an Urban Catchment of Brahmaputra River

Abstract

Flood inundation mapping (FIM) is required to understand the affects of flooding in a particular area and on important structures such as roadways, railways, streets, buildings and airport. FIM provides important information, like depth and spatial extent of flooded zones, required by the municipal authorities to inform the citizens about the major flood prone areas and adopt appropriate flood management strategies. The present study demonstrates FIM as an effective tool in managing flooding in an urban catchment in northeast India and quantifies the flood risk with respect to different vulnerability parameters. The surface runoff has been estimated by a storm water management model (SWMM) and the drainage network of the study area has been used to find out the inundation pattern for peak rainfall intensities corresponding to different return periods. A flood hazard map has been developed on the basis of the possible flood hazard caused by the 100 year return period flood. The hazard ranks (HR) were developed by the interactive effect of vulnerability parameters such as flood depth and inundated area, land use, affected population, and roads. Based on the hazard ranks, flood risk zones were identified. The study demonstrates the utility of HR for identifying the worst flood-affected area along with the flood depth and durations. The details of this study can be used for planning flood preparedness in the worst affected areas.