28 October 2021
The 21 July 2020 Mazhe Village landslide in Enshi, China
Back in July 2020 I wrote about a landslide that had just occurred on the banks of the Qingjiang River in Enshi Tujia and Miao Autonomous Prefecture in Hubei Province, China. This was a really impressive event, triggered by heavy rainfall:-
As the above image shows the failure, now known as the Shaziba landslide, temporarily blocked the river. In a paper recently published in the journal Landslides, Xue et al. (2021) have investigated the precursory movement of this landslide using satellite imagery.
The results are interesting. Their InSAR data demonstrates that the landslide seen above is part of a much larger complex, as shown in the figure from the paper below:-
The July 2020 landslide involved a volume of 250,000 cubic metres, with a length of 1,500 m, a width of up to 580 m and an average depth of 25 m.
The InSAR data shows that the landslide was creeping in the years leading up to the major failure. The creep was seasonal, with the higher rates of movement associated with the rainy season. This is unsurprising – presumably the landslide was responding to elevated pore water pressures. Detailed analysis of the data suggests that over time the landslide was becoming more responsive to rainfall, presumably an indication of the evolution of the landslide towards failure, and a possible indicator for a warning system.
Interestingly, Xue et al. (2021) have used InSAR to look at other slopes on the banks of the Qingjiang River, and have detected three further large landslide complexes that are showing seasonal patterns of displacement. These landslides, and the unfailed portion of the Shaziba landslide, now need monitoring. Fortunately InSAR represents a technique through which this can be achieved if there is sufficient funding for the processing.
Xue, C., Chen, K., Tang, H. et al. 2021. Heavy rainfall drives slow-moving landslide in Mazhe Village, Enshi to a catastrophic collapse on 21 July 2020. Landslides (2021). https://doi.org/10.1007/s10346-021-01782-7