Global Compound Floods from Precipitation and Storm Surge: Hazards and the Roles of Cyclones

• Published in: Journal of climate 2021-10, Vol.34 (20), p.8319-8339
• Main Authors: Lai, Yangchen, Li, Jianfeng, Gu, Xihui, Liu, Cancan, Chen, Yongqin David
• Format: Article
• Language: English
• Subjects: Coastal flooding; Coastal management; Coastal zone; Cyclones; Cyclonic winds; Environmental risk; Extratropical cyclones; Extreme weather; Flood hazards; Flood management; Flood risk; Floods; Hazard assessment; Hazards; Hurricanes; Independent variables; Low pressure; Moisture content; Precipitable water; Precipitation; Probability theory; Risk management; Storm surges; Storms; Tidal waves; Tropical climate; Tropical cyclones; Water content; Weather; Weather conditions; Weather patterns
• ISSN: 0894-8755; 1520-0442
• DOI: 10.1175/JCLI-D-21-0050.1

During simultaneous or successive occurrences of precipitation and storm surges, the interplay of the two types of extremes can exacerbate the impact to a greater extent than either of them in isolation. The compound flood hazards from precipitation and storm surges vary across regions of the world because of the various weather conditions. By analyzing in situ observations of precipitation and storm surges across the globe, we found that the return periods of compound floods with marginal values exceeding the 98.5th percentile (i.e., equivalent to a joint return period of 12 years if the marginal variables are independent) are 8 years due to weaker dependence. Our quantitative assessment shows that cyclones [i.e., tropical cyclones (TCs) and extratropical cyclones (ETCs)] are the major triggers of compound floods. More than 80% of compound floods in East Asia and >50% of those in the Gulf of Mexico and northernAustralia are associated with TCs, while in northern Europe and the higher-latitude coast of North America, ETCs contribute to the majority of compound floods (i.e., 80%). Weather patterns characterized by deep low pressure, cyclonic wind, and abundant precipitable water content are conducive to the occurrence of compound floods. Extreme precipitation and extreme storm surges over Europe tend to occur in different months, which explains the relatively lower probability of compound floods in Europe. The comprehensive hazard assessment of global compound floods in this study serves as an important reference for flood risk management in coastal regions across the globe.