Fast Modelling of Wave-Driven Flooding for Sandy and Coral Reef-Lined Coasts

Coastal communities worldwide face flooding threats from tides, surge, rain and rivers, yet wave-driven impacts are often inadequately considered in large-scale assessments due to high computational costs. The SFINCS model enables the efficient computation of wave-driven flooding, but until now it required boundary conditions from expensive models like XBeach. Here we overcome this problem and apply and validate a method to efficiently derive nearshore infragravity wave conditions using the fast wave spectral model SnapWave. These nearshore conditions are then used to drive dynamic infragravity waves in SFINCS. The method is validated using a laboratory case of a sandy beach and a field case from Hernani, Philippines, affected by Typhoon Haiyan (2013). This is a first application on a coral-reef lined coast, which is beyond the application area of the methodology to determine infragravity wave transfer. The results indicate that SFINCS can model overland wave heights and flooding extent with reasonable accuracy compared to XBeach, but with a significantly reduced computation time; from over three hours to just 20 s. Overall, the SFINCS-SnapWaveIG methodology demonstrates promise for large-scale applications in coastal hazard studies.