Comprehensive hazard assessment of tropical cyclone-induced wind, rainfall, and storm surge: A case study of Zhejiang Province, China

In this study, the coastal counties of Zhejiang Province were selected as a case study to assess the hazard of tropical cyclones by comprehensively considering the wind, rainfall, and storm surge. Tropical cyclones pose a significant threat to coastal regions through hazard-inducing factors such as wind, rainfall, and storm surge, whose interactions often lead to amplified impacts. Existing studies often fail to capture the complex dependence among these factors.

The main conclusions from the study are as follows:

1. The numerical model employed in this study successfully reconstructed winds and storm surges for 222 tropical cyclones affecting the Zhejiang coast from 1979 to 2022. Validation results demonstrated that the simulations achieved RMSE below 4 m/s for wind and 0.2 m for storm surge, with CC exceeding 0.75 for both.
2. When the exceedance probability for each single factor was 0.05: For the same number of hazard-inducing factors, return periods under the independence assumption were shorter than those accounting for dependence. 
3. The case study of Wenling City showed that under the same design return period and design lifetime, the failure probability of engineering structures increased with the number of hazard-inducing factors considered, and failure probabilities under the independence assumption exceeded those accounting for dependence. 
4. The CHI revealed a spatial pattern of higher hazard in the south and lower in the north among Zhejiang’s coastal counties. High-hazard counties such as Wenling City were characterized not only by strong winds but also by pronounced compound effects, where synergy among wind, rainfall, and storm surge amplified the overall hazard.