This study employs coupled hydrological and hydraulic modelling to assess flood resilience in the Adayar, Kosasthalaiyar, Araniar, and Cooum River Basins, which face a significant flooding due to heavy precipitation. These events pose serious threats to the community’s vulnerability. Flood management strategies include structural measures, such as levees, and non-structural approaches, like land-use planning and advanced warning systems. A key aspect of flood management is understanding the return period, which evaluates the probability or interval between floods of similar magnitude. The Intensity–Duration–Frequency (IDF) relationship, derived from historical storm events for different return periods, is crucial for estimating rainfall intensity in hydrological modelling. This integrated approach gathers extensive data on rainfall patterns, river morphology, land use, and infrastructure to improve model calibration and validation for more accurate basin representation. In this study, IDF analysis was statistically carried out for the basins, showing reasonable accuracy and compliance with empirical distribution functions. Additionally, two-dimensional unsteady flow hydraulics enabled the rapid production of floodplain maps for various return period events using a Digital Elevation Model (DEM) at the mesoscale level, providing effective modelling with HEC-RAS. The research also tests existing flood management strategies through flood simulations and highlights the need for improved performance to enhance risk mitigation.