This research addresses the intricate challenges posed by floods in low-lying coastal cities, focusing on the case of Chennai. Urbanization, climate change, and a surge in flood events underscore the critical need for comprehensive flood inundation mapping and modelling. The study introduces a semi-automated mathematical model utilizing Sentinel 1A microwave images to map combined pluvial and fluvial flood scenarios, with a specific focus on the 2015 and 2021 floods in Chennai. Flood inundation depth, a crucial parameter for assessing vulnerability and flood risk, is estimated using high-resolution digital elevation models and interpolation techniques. The research explores the advantages and disadvantages of employing simple interpolation techniques, acknowledging the computational challenges of traditional hydraulic models.

The study innovatively explores the calibration and validation of hydraulic models using pluvial and fluvial inundation maps from microwave imagery, for reducing the uncertainties in simulation results. The calibrated model can be tested for structural flood management practices, providing insights for mitigating future pluvial and fluvial flooding. In conclusion, this study contributes to understanding historical flood footprints, estimating water depths, and providing a robust foundation for enhancing flood inundation mapping practices in anticipation of future events.