The Landslide Blog is written by Dave Petley, who is widely recognized as a world leader in the study and management of landslides.
My regular scans of reports of landslides around the world has highlighted interesting updates on three events of the last year or so.
The 14 December 2024 Lions Bay Landslide
The Vancouver Sun has a very impressive article that examines the possible causes of this landslide, which killed two people in British Columbia, Canada. The case is subject to a potential criminal investigation, and so the article is heavily caveated. The landslide was a channelised debris flow – the journalist highlights the presence of a small reservoir and associated access roads, constructed through blast and fill, close to the source of the landslide. The article does not draw any definite conclusions – that is for the formal investigation -but it is clear that there have been previous concerns about the stability of this area.
The 20 November 2023 Wrangell Island landslide in Alaska
Six people were killed in this devastating rainfall triggered landslide in the United States. The Wrangell Sentinel has a report of a public meeting held by a group of academics who have been undertaking detailed research, including Josh Roering of the University of Oregon, Margaret Darrow of the University of Alaska Fairbanks and Annette Patton of Oregon State University. The report describes three key factors:-
a. “Unique bedrock formations”;
b. “A thick layer of loose sediment” – the description appears to imply that this had low or no cohesion;
c. A “concentrated water drainage system flowing down from the ridgetop” – which presumably indicates that water flow was focused into the area that failed.
The team has eliminated the potential role of logging or other forestry activities in the landslide.
The 21 May 2024 landslide on the Meida Highway in Guangdong Province, China
This failure, which was one of the most surprising landslides last year, killed 48 people, most of whom drove into the landslide scar after the failure created a huge crater in the road late at night. An article in the journal Landslides (Xue et al. 2025) provides a detailed description of the failure, whilst the Chinese media is also providing a commentary about the landslide, based upon a report from the Emergency Management Department (EMD) of Guangdong Province, which was released yesterday.
Both reports indicate that, as I speculated at the time, the landslide was a failure of a fill slope triggered by heavy rainfall. The topography and the presence of bedrock faults concentrated the water in the area of the fill slope. The fill itself, which comprised weathered granite (Google Earth imagery suggests that this was a cut and fill project) “exhibits poor hydro-mechanical properties, making the slope particularly susceptible to failure”.
Interestingly, the two sources appear to differ in terms of the dynamics of the failure. Xue et al. (2025) show a describe a circular failure with much of the basal surface close to the interface between the bedrock and the fill. On the other hand, the journalists interpretation of the EMD report describes the failure as follows:
“The embankment’s lower and middle sections, along with a retaining wall, suddenly deformed and slid, triggering the collapse of soil on the upper section.”
Clearly, further work is needed on the mechanisms. Neither report appears to imply that static liquefaction was a factor.
The ECNS report indicates that 32 officials have been punished for “dereliction of duty”.
Reference
Xue, Y., Chen, N., Tang, R. et al. 2025. Slope failure mechanism of the “5·1” Meida Highway collapse in Guangdong, China: Interaction between multi-source water and weathered granite soil. Landslides. https://doi.org/10.1007/s10346-025-02455-5.