Modelling Coastal Flooding Induced by Wave Overtopping Using SCHISM Coupled with EurOtop

Coastal cities protected by artificial structures are vulnerable to wave overtopping during typhoons, where flooding can occur even when the still water level stays below the structure crest. This study develops EurOtop-based wave overtopping modules within the cross-scale SCHISM-WWM modelling framework and applies the coupled model to Marine City, Busan, South Korea. At each time step, the module extracts the local water level and wave conditions at a coastal-structure pair-node, computes the overtopping or overflow discharge from the EurOtop formulae while accounting for wave direction, roughness reduction, and crest-width transfer losses, and injects it as a landward source term for inland flood propagation. The framework is evaluated against two typhoon events. For Typhoon Hinnamnor in 2022, comparison with the CCTV-based overtopping record reproduces the timing and intensity of overtopping. For Typhoon Chaba in 2016, validation against field-surveyed inundation marks shows that the modelled maximum inundation depth matches the observed spatial pattern and the survey-point observations to within a mean absolute difference of about 12 cm. These results demonstrate the framework’s applicability to overtopping-induced compound flooding in urbanised coastal cities and, since it is fully coupled within the SCHISM-WWM codebase, its capacity to incorporate further drivers such as pluvial and fluvial flooding.