Equatorial storm surge risks revealed by the 2001 tropical cyclone Vamei

Abstract. Tropical Cyclone Vamei, which emerged at 1.5° N on December 27, 2001, challenged the prevailing idea that near-equatorial areas are safe from storm surges, as it resulted in localised flooding in Singapore and Malaysia, revealing a rare yet critical regional hazard. Thus, we investigated storm surge risk assessment in Singapore based on numerical simulations using Delft3D in multiple scenarios. We first validated the accuracy of our simulation results by comparing them with nine observation points around Singapore Island. We then conducted the simulations as a suite of alternative scenarios created by moving the known track of Tropical Cyclone Vamei, modelling more intense storms corresponding to a 1-in-1000-year scenario and considering future sea level rise induced by global warming. When a 1000-year probability of occurrence was assumed, the maximum storm surge height around Singapore increased to 0.595 m. For a 1000-year cyclone with its path shifted 0.8° southward, sea level rise scenarios of +0.7 m and +2.0 m resulted in inundation areas of 34.5 km² and 90.7 km², respectively. While the calculated storm surge height remained largely unchanged despite future sea level rise, the inundation area in Singapore expanded significantly. This indicates that sea level rise is a primary contributor to this expansion, highlighting the importance of considering future sea levels in inundation assessments. Further research is necessary to assess potential changes in the frequency and intensity of tropical cyclones impacting Singapore under future climate scenarios.