Verification of the SFINCS Model Applying GPS Measured Flood Marks from the Storm Surge, Babet, in Southern Denmark

Abstract Over the past century, individuals in Denmark have continuously settled closer to the sea, increasing the exposure to flooding tremendously. Paradoxically, the proximity to the sea, which over the decades caused property prices to skyrocket, has now transformed into a substantial risk. The Danish Coastal Authority (DCA) is responsible for national assessment of coastal flood risk under the EU Floods Directive. DCA is continuously seeking “fit for purpose” numerical models to ensure ongoing improvements of risk assessment. The last two years, DCA has tested the SFINCS (Super-Fast INundation of CoastS) model [1, 2] against historical events. However, in October 2023, Denmark was hit by the devastating storm surge “Babet”, which led to an indispensable comparison of in situ flood mark measurements and available water level gauges against the performance of SFINCS. On average, throughout the model domain (in total 13 flood marks and five complete gauge hydrographs), SFINCS predictions of maximum water levels lies within 5 cm (RMSE 6 cm) compared to GPS flood marks and gauge water level measurements. This manuscript presents DCA’s model verification results and describes future application of SFINCS in DCA.