Successful disaster management of the July 2020 Shaziba landslide triggered by heavy rainfall in Mazhe Village, Enshi Ci
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Kun Song I Fawu Wang I Qingjun Zuo I Bolin Huang I Wuwei Mao I Hu Zheng
Successful disaster management of the July 2020 Shaziba landslide triggered by heavy rainfall in Mazhe Village, Enshi City, Hubei Province, China Introduction From June to July 2020, southern China suffered from continuous rainfalls far heavier than those of previous years (Wei et al. 2020). The heavy rains resulted in natural disasters such as floods and landslides in many places. According to the monitoring data supplied by the Hubei Provincial Bureau of Hydrology and Water Resources, between 8 June and 19 July 2020 (the so-called Plum Rain Season), the average rainfall in this period reached 692 mm in Hubei Province, which is 2.45 times that of the same period in the last 10 years (282 mm)—the heaviest rainfall recorded in this region since 1961. Enshi City, located in the southwest region of Hubei Province, also experienced extremely heavy rainfall (Fig. 1a). The accumulated rainfall from 8 June to 19 July 2020 was 823.8 mm, and the maximum daily rainfall was 81.9 mm (17 July 2020). The accumulated rainfall from 16 July to 18 July was 165.5 mm overall (Fig. 1b). These heavy rainfalls have increased the risk of landslides in Hubei Province. The largest to occur as a result was the Shaziba landslide in Mazhe Village, Enshi City. The landslide is located at the upper reaches of the Qingjiang River, a tributary of the Yangtze River, with coordinates of 30.36° N and 109.30° E (Fig. 2). Landslide characteristics and failure process The Shaziba landslide is located on the left bank slope of the Qingjiang River, with the Yunlonghe and Dalongtan dams located upstream and downstream, respectively. The average slope angle of the landslide area is 10 to 15°, with nearly vertical cliffs at the front toe of the landslide, and the main slide direction is 195°. The length of the landslide is about 1500 m, the maximum transverse width is 320 m, and the volume is estimated to be 1.0 × 107 m3 (Fig. 3). The bedrock surrounding the landslide area is composed of medium-thick limestone and a medium-thin layer of Middle and Upper Permian (P2–P3) marl, with a small amount of locally distributed thin coal seam (Hubei Geological Bureau 1984). The bedrock dip azimuth in this vicinity was measured between 197° and 220° with a dip angle of 10° to 15°. The landslide area is mainly composed of Quaternary silty clay with a small number of boulders, which are the weathered colluvium of limestone. This site was recognized previously as an old landslide and has been patrolled daily by residents due to the increased reactivation risk. The patrol was organized according to the Chinese policy of Mass Observation and Mass Preparedness for geo-disaster prevention, which directs all locals to participate in the observation of and preparation for geohazards. On 17 July 2020, the first fresh crack in the Shaziba landslide was found and reported to the local government through WeChat, a smartphone social media application. After the occurrence and
development of the initial landslide
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