Joint Probability Study of Destructive Factors Related to the “Triad” Phenomenon during Typhoon Events in the Coastal Regions: Taking Jiangsu Province as an Example

Abstract

Strong winds (W), storm tides (Z), and heavy rains (R) are the main destructive factors related to typhoons that affect the coastal regions of Jiangsu, where the “triad” phenomenon is obvious. Statistical results from 1960 to 2014 during typhoon events with a “triad” feature indicate that the mean high tide level, mean wind speed, and mean 24 h rainfall in three coastal cities (Lianyungang, Yancheng and Nantong) are approximately 2.96 m, 12.5 m/s, and 74.8 mm, respectively. Copulas and the particle swarm optimization (PSO) method are applied, indicating that the Gumbel copula and Weibull distribution are appropriate theoretical models for joint and marginal distributions of these destructive factors, respectively. However, a reanalysis of the parameters of the Weibull function and Gumbel copula is necessary, given that a strong typhoon may appear in the future. Typhoon-induced rains and tides are the main disaster factors of flooding in the coastal regions of Jiangsu. This paper proposes the cost-oriented method, the safety-oriented method, and a compromise between cost reduction and safety insurance to optimize the combination of rains and tides.