Numerical modelling of the 1 July 2022 flooding event, Southwest Huvadhoo Atoll, Maldives: Implications for the future.

Abstract

Low-lying atoll islands are among the world's most vulnerable coastal environments to sea-level rise (SLR). Global application of coastal flooding models suggests that centennial flood events may become annual events by 2050 in tropical regions. This article addresses this claim by modelling an island flooding event that occurred in the Maldives on 1 July 2022 as a result of a distant-swell event coinciding with an extra high spring tide. Hydrodynamic data collected after the event on one of the affected islands were used to calibrate and validate a one-dimensional non-hydrostatic XBeach model. The model overpredicted wave setup and underpredicted the water motion at frequencies <0.05 Hz, but the wave run-up elevation was predicted reasonably well. The 1 July flood event was considered in a decadal context using modelled wave data and measured tide data. It was concluded that the 1 July event represents a c. 1:25-year flooding event, but, due to SLR, such flooding could occur every few years by 2050. This prediction ignores natural or anthropogenic adjustments to the island morphology. The expected increase in frequency of coastal flooding in the Maldives requires atoll and island authorities in the Maldives to act swiftly in adapting to future flood risk.