Evolution characteristics of the rainstorm disaster chains in the Guangdong-Hong Kong-Macao Greater Bay Area, China

Enhancing the resistance of urban agglomeration against rainstorm-induced disasters has become a more urgent mission for the construction of the Guangdong-Hong Kong-Macao Greater Bay Area (GBA). But, few studies have focused on the rainstorm disaster chains at the scale of urban agglomeration. In view of this, in this study, we investigate the classification, mechanism, probability, variation and risk of rainstorm disaster chains in the GBA by using the meteorological observation, physical geography, land-use, socioeconomic and disaster loss data during 1990-2018. The results show that the rainstorms can lead to many disaster chains in the GBA, such as flash flood, riverine flood, debris flow/landslide, urban waterlogging and agricultural waterlogging. Among them, the urban waterlogging disaster chain has the highest probability to occur. Furthermore, these disaster chains are influenced and exacerbated by each other, leading to cascading effects. Since the twenty-first century, the frequency of urban waterlogging has increased and becomes the most prominent rainstorm-induced disaster, while flash flood, riverine flood and debris flow/landslide decreased. The rainstorm disaster loss index in the GBA shows a significant increasing trend (p < 0.05) during 1990-2018. By jointly considering the rainstorm hazard, the exposure of disaster-bearing bodies and the sensitivity of disaster-pregnant environment, Shenzhen, Zhaoqing and Huizhou rank the top three in the frequency of rainstorm disaster chains, and Zhaoqing ranks the first in disaster loss index. In addition, the areas with high rainstorm disaster risk level increase with the augmentation of return period. Guangzhou, Zhaoqing and Shenzhen are at high-risk level for the rainstorm disasters with 10-year and 20-year return periods. We hope that this study can provide a scientific reference for the rainstorm disaster risk management in the GBA.