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Typhoon-induced rockslide-debris avalanches are among the most dramatic geohazard in coastal mountainous regions, which commonly result in serious casualties and economic loss. In September 2016, typhoon "Catfish" attacked the Su Village in Southeastern China and triggered a devastating rockslide-debris avalanche. The detached mass traveled 1000 m, generated a powerful air blast, and resulted in 27 deaths. In this study, we performed a thorough survey to investigate the avalanche characteristics and damages caused by air blasts. Meanwhile, numerical modeling and video analysis were conducted to investigate the avalanche dynamics and impacts of the air blast. Results indicated that the avalanche movement lasted for approximately 60 s with a maximum velocity of 42 m/s. The entrainment effect greatly enlarged the avalanche volume and extended the avalanche runout. Moreover, the generated air blast indicated a maximum pressure of 2.5 kPa and caused tree breakage beyond the avalanche runout. [ABSTRACT FROM AUTHOR]

On August 10, 2019, typhoon "Lekima" and the associated heavy rainfall triggered a large landslide in Yongjia County, Zhejiang, China. The sliding mass blocked the river, resulted in an air blast and barrier lake disaster chain, and caused 32 deaths. A thorough survey was performed to investigate the characteristics and possible failure mechanisms of the event. The landslide initiation is caused by the combination of rock mass characteristics, wind load, heavy rainfall, and human activities. The presence of roots and cracks in the strongly weathered tuff provides preferential infiltration channels for the rainwater penetration, causing the rapid destabilization of the slope. Furthermore, we used the dynamic model RAMMS and empirical equations to analyze the disaster-causing process of the landslide. Results indicated that the landslide movement lasted for about 30 s with a maximum velocity of 21 m/s. The generated air blast shows a maximum pressure of 1.7 kPa and caused tree breakage on the opposite side of the river. Subsequently, the sliding mass blocked the river and generated a landslide dam with a maximum thickness of about 14 m. Its combination with heavy rainfall led to the rise of the upstream water level and the submersion of houses in the Shanzao village within 20 min. Our work is expected to improve the understanding of typhoon-induced large landslides and promote the risk assessment of this type of geohazard in coastal regions. [ABSTRACT FROM AUTHOR]