Assessment of tangible coastal inundation damage related to critical infrastructure and buildings: The case of Mauritius Island

Storm tides, which combine sea level rise (SLR), astronomical tides, and storm surges generated by tropical cyclones, pose significant threats to coastal zones, leading to flooding and substantial damage to property and infrastructure.There is a clear upward trend in the frequency of storms reaching tropical cyclone strength. A notable example is Cyclone Belal, which struck Mauritius on January 2024, during high tide, causing extensive infrastructure damage. This underscores the importance of conducting risk assessments to identify vulnerable areas and develop risk reduction strategies. However, quantitative risk assessments of storm tides are often challenging due to the lack of long-term projections. To address this, we developed a GIS-based flood model for Mauritius to simulate inundation areas and quantify the assets exposed to flooding. Under current conditions, the estimated damage exposure from extreme coastal flood events with return periods of 50–500 years is significant, with 6.2 % and 27.1 % of the area inundated, respectively. By 2100, damage exposure associated with these events is projected to increase by a factor of 1.1, with minimal variation between sea-level rise scenarios (0.3m). However, by 2200 and 2300, damage exposure is expected to rise by factors of 3.1 and 6.6, respectively. In the worst-case scenario for 2500, Mauritius could experience maximum inundation of 66.3 km², with buildings covering 5.02 km² submerged. Additionally, this study presents a detemporalized inundation scenario to assess impacts from any coastal flood event. This approach enables the identification of critical thresholds (1.5 m and 4.5 m) and, beyond which significant increases in damage exposure are likely, and allows for evaluating adaptation strategies against user-defined levels of change, rather than relying solely on predefined scenarios. These findings highlight the urgent need for strategic sectoral interventions to address the widespread consequences of coastal inundation, especially in light of critical thresholds for remedial action.