The 5 April 2021 Tiejiangwan landslide in Sichuan Province, China

The journal Landslides has just published an interesting article (Liu et al. 2021) about the 5 April 2021 Tiejiangwan landslide in Sichuan Province, China.  This failure, triggered by heavy rainfall, destroyed five houses, killing three people.  The article provides a brief commentary on the events.

The image below shows the aftermath of the landslide (unfortunately the image appears to be mistitled as, according to the article, the landslide occurred in 2021 not 2020.  This error occurs throughout the article):-

The aftermath of the 5 April 2021 Tiejiangwan landslide in Sichuan Province, China. Image from Liu et al. (2021).

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As the image shows the landslide, which was triggered by heavy rainfall, initiated as a 30,800 cubic metre near-vertical rock slope collapse in thick-bedded sandstones with thin-bedded silty mudstones.  The source area of the collapse was about 134 m long and 92 m wide.  The debris initiated a debris slide that entrained colluvium on the slope.  The debris ran out for a distance of about 1050 metres.

On 10 April 2021 further heavy rainfall triggered a debris flow in the landslide deposits.  Further rainfall on 14 April 2021 triggered another debris flow.  The debris dammed the main channel downstream, presumably requiring mitigation (although this is not described), to a height of over 3 metres.

This is an interesting example of a complex landslide involving a cascade of hazards starting with a fatal rock slope collapse.  The evolution over time into debris flows that then blocked the main channel, inducing the risk of an outburst flood, illustrates very well the challenges of managing slope hazards in high mountain areas.  Such landslides occur naturally (although changing patterns of rainfall mean that the frequency might be changing, and remobilised debris flows might be more likely.  Such events are disasters because people are living in places that have a high level of vulnerability.

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Reference

Liu, B., Hu, X., He, K. et al. 2021. Preliminary analyses of the Tiejiangwan landslide occurred on April 5, 2021 in Hongya County, Sichuan Province, China. Landslides (2021). https://doi.org/10.1007/s10346-021-01763-w