Rainfall-induced rapid and long-runout catastrophic landslide on July 23, 2019 in Shuicheng, Guizhou, China
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Xiaoyi Fan I Junjie Tang I Shujun Tian I Yuanjun Jiang
Rainfall-induced rapid and long-runout catastrophic landslide on July 23, 2019 in Shuicheng, Guizhou, China
Abstract A large catastrophic landslide occurred on July 23, 2019, after a continuous heavy rainfall at Jichang (N 26°15′22.99″, E 104°40′6.33″), Shuicheng county, Guizhou province, China. This landslide had a maximum runout distance of 1295 m, a maximum falling height of 477 m between the highest point of the source area and the leading edge, and a maximum speed of 45.5 m/s. The 1.4 million cubic meters of debris instantly buried twenty-one buildings, destroyed six buildings, and resulted in 42 fatalities and 9 people missing. This paper analyzes the extent and mechanisms of initiation and runout distance of the landslide. The landslide occurred in the eluvial and deluvial accumulation of basalt, and its initiation mechanisms were different from the bedrock landslides that are typical of the interbedded soft and hard rocks in Guizhou and basalt landslides in Southwest China. The prolonged heavy rainfall, lush vegetation, and road construction played the roles in landslide initiation. Subsequently, the landslide can be divided into three sliding regions caused by the valley on both sides and the stepped terrain in the middle, and the valley topography enhanced the disaster intensity and reach. Keywords Landslide . Rapid and long runout . Topography . Occurrence mechanism Introduction Rapid and long-runout landslides can be exceptionally hazardous because of the large amount of kinetic energy and unexpected long runout. Over the last several decades, numerous rapid and longrunout landslides have occurred throughout China, such as the Guanling landslide (Yin et al. 2011), Ermanshan landslide (Xu et al. 2012), Sanxicun landslide (Gao et al. 2017), Xiaoba landslide (Lin et al. 2018), Xinmo landslide (Scaringi et al. 2018), and Pusa rock avalanche (Fan et al. 2019). The disaster mechanism of the landslides typically consists of two aspects: (1) the steep terrain of a highaltitude landslide is situated on the upper section, which allows for large amounts of kinetic energy to be released during the landslide event. (2) The relatively gentle slopes or valleys are located in the middle and lower sections of the landslide area, where movement and accumulation of the landslide occur, often with buildings, resulting in catastrophic casualties and property losses. The velocity and runout distance are the most critical factors of catastrophic landslides and where the majority of loss and costs occur. Landslide velocity can be classified using the International Union of Geological Sciences Working Group on Landslides (1995). The classifications include extremely slow, very slow, slow, medium rapid, rapid, very rapid, and extremely rapid. The minimum and maximum velocity of extremely rapid landslides range from 5 to 70 m/s. Currently, many researchers accept that the average velocity of a high-speed landslide is higher than 20 m/s. In China, most researchers regard a la
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