A Time-Evolving Multi-Hazard Risk Assessment of Tropical Cyclones Incorporating Wind, Rainfall, and Social Vulnerability

Tropical cyclones (TCs) pose significant threats to coastal communities, primarily through hazardous wind speeds and intense rainfall that drive storm surge and coastal flooding. These wind and water related hazards often occur simultaneously, amplifying impacts on both the built environment and socially vulnerable populations. Despite extensive prior research on individual TC hazards, limited attention has been given to their joint occurrence and evolving risk characteristics over time in relation to changes in social vulnerability.

This study proposes a comprehensive, time-evolving TC risk assessment framework that explicitly accounts for the likelihood of coinciding wind and rainfall hazards. The analysis covers the period from 1979 to 2022, incorporating long-term hydroclimatic records to characterize TC-related multi-hazard exposure. In parallel, social vulnerability was evaluated using multiple combinations of vulnerability indicators for the period 2000–2022, allowing temporal changes in population sensitivity and adaptive capacity to be captured. By progressively incorporating newly available data and historical records as time advances, this study reflects how TC risk assessments would have evolved under real-world knowledge constraints in past decades.

A total of 29 major TC events impacting the southeastern U.S. coast were examined, and statistical correlations were evaluated between estimated TC risks and observed economic damages. The results indicate that, prior to 2017, fewer than 6% of the cases exhibited stronger correlations when TC risk was quantified using a multi-hazard hurricane index that jointly considers wind and rainfall. In contrast, more recent events demonstrate a growing dominance of wind-based risk metrics in explaining observed damages.

These findings suggest a shifting risk regime in which coastal communities are becoming increasingly vulnerable to wind-related TC impacts, including extreme winds, storm surge, and coastal flooding, rather than rainfall-driven hazards alone. The proposed framework highlights the importance of dynamic, multi-hazard risk assessments that integrate evolving social vulnerability, providing critical insights for future coastal resilience planning and disaster risk reduction strategies.

Acknowledgments: This work was supported by National Research Foundation of Korea funded by the Ministry of Education (RS-2023-00249547).