Analysis on the ‘Jul.20’ extreme rainstorm and flood control countermeasures in Zhengzhou, China

Abstract

ABSTRACT The Jul.20 extreme rainstorm (July 20, 2021) and flood disaster were the most serious urban flood disaster in Zhengzhou, the capital city of Henan Province, China. The Jul. 20 extreme rainstorm had both extreme and unpredictable features, during which both single-day and 3-day cumulative rainfall exceeded the historical records. First, the theoretical analysis methods are proposed, which include rainstorm anomaly analysis and the construction of a rainstorm frequency calculation model. Second, the characteristics of rainstorm frequency and recurrence, spatial and temporal distribution, and formation mechanism are analyzed. Third, urban flood disasters and waterlogging distribution are studied. The studied results show that the coupling actions of typhoons, topography, and urban rain island effect are the natural causes that result in extreme rainstorm weather processes. The results also show from the investigations that poor urban drainage infrastructure, low flood control criteria, shortage of flood emergency plans, and management are human factors. Finally, the paper puts forward flood control countermeasures.