A Unified Multiscale Framework for Flood Hazard and Resilience Assessment: Step Towards Efficient Coastal Flood Management

Abstract Coastal floodplains are highly dynamic environments that remain perpetually vulnerable, with multiple confluences of flood drivers, including interactions among extreme rainfall, river discharge, and storm tides, which are capable of triggering catastrophic flooding. Traditionally, flood hazard and flood resilience are assessed independently from static and dynamic perspectives. This gap is critical in coastal environments, where prolonged waterlogging and delayed drainage often govern impacts more strongly than flood depth alone. The hazard-resilience assessment framework introduced in this work, at multiple administrative scales, provides a practical, application-oriented integrated mapping workflow that integrates a hazard-based perspective of flooding risk to identify critical hotspots in coastal flood-prone catchments within decision-making administrative units. A coupled 1D–2D hydrodynamic flood model is developed to simulate flooding in a multi driver coastal setup, integrating river channel flow (MIKE 11) with floodplain inundation (MIKE 21 FM) to produce high-resolution inundation time-series flood-depth rasters to quantify both flood hazard and flood resilience. These metrics are aggregated to village- and taluka-level administrative units to ensure comparability and to highlight regional contrasts in governance-relevant boundaries. The model demonstrates robust performance, with NSE values ranging from 0.67 to 0.81 during calibration and validation, and achieving a CSI of 0.49 and Hit Rate of 0.79 against satellite-derived inundation extents. Results reveal five distinct levels of hazard and resilience at the village scale, with a clear spatial asymmetry: several regions exhibit prolonged disruption despite moderate inundation levels; high-hazard, low-resilience clusters dominate the riverine and coastal belt, while inland areas generally exhibit lower hazard and higher resilience. Across 50-, 100-, and 200-year multi-driver scenarios, 10%, 19%, and 28% of villages emerge as critical hotspots, highlighting areas that remain undetected under conventional hazard-only assessments. Beyond hazard mapping, the framework enables targeted multi‑scale flood management and provides a scalable approach for coastal resilience, aligning with SDGs.