Assessment of Coastal Compound Flooding using an Integrated Coupled Modelling and Remote Sensing Approach

This study presents an integrated compound flood modelling framework for the analysis of Cyclone FANI (2019), which caused extensive inundation in the coastal regions of Odisha, India. By coupling storm surge dynamics from the ADCIRC finite element model with inland riverine flooding using the HEC-RAS hydrodynamic model, the framework allows for high-resolution simulation of compound coastal inundation. The approach leverages multi-sensor datasets, including SRTM DEM for topography, GEBCO bathymetry, MODIS/Sentinel land cover, IMDAA rainfall and discharge data, and Sentinel‑1 SAR flood imagery. Results reveal that the coupled modelling captures nonlinear interactions among surge, river discharge, and local rainfall, highlighting pronounced bidirectional flows at the Devi River mouth. Here, ocean currents (0.8–1.2 m/s) intruded upstream against river discharge (0.5–0.7 m/s), producing stagnation zones and elevating water levels by approximately 0.3 m relative to uncoupled simulations. The coupled ADCIRC–HEC-RAS approach generated a 486 km² inundation extent, closely matching the Sentinel‑1 SAR-observed 480 km² and outperforming the HEC-RAS-only result of 452 km².