The Landslide Blog is written by Dave Petley, who is widely recognized as a world leader in the study and management of landslides.
The extraordinary impact of landslides in 2024 continues to become apparent. One major event was the passage of Typhoon Yagi across Vietnam and Myanmar in early September. It has been difficult to fully understand the impact of this event. I previously noted that at least one major landslide had occurred, but I had been unable to track it down.
A splendid new paper has been published in the journal Landslides (Tien et al. 2025) that starts to provide insight. The work provides a brief overview of the impact of the typhoon in Vietnam, before describing the most significant landslide, which occurred on 10 September 2024 at Lang Nu hamlet in Lao Cai Province.
So, starting with the national level impact for Vietnam, Typhoon Yagi left 333 people dead or missing, and inflicted losses estimated at US$2.47 billion (0.15% of GDP). Of the fatalities, 264 (79%) were caused by landslides, including 124 deaths in Lao Cai.
Tien et al. (2025) note that the most significant event was the 10 September 2024 Lang Nu landslide, which occurred in Bao Yen District at [22.11888, 104.52616]. The authors describe this as the worst recorded disaster caused by a natural hazard in the history of Vietnam, killing 67 people and destroying 37 houses.
The image below is a satellite image of the site, captured by Planet on 06 September 2024 before the passage of Typhoon Yagi. I have draped the image onto the Google Earth DEM:-
Whilst the image below shows the aftermath of the Lang Nu landslide:-
And below is a slider to allow the images to be compared:-
Tien et al. (2025) describe this landslide as a rockslide that tranistioned into a secondary (channelised) debris flow, with a volume of 1.1 million m3 and a runout distance of 4,220 metres. The landslide, which entrained about 300,000m3 of debris along its track, had high mobility and velocity (estimated to have peaked at c.10 m/sec).
The landslide was triggered by exceptional rainfall – the nearest rain gauge recorded 357 mm over a 55 hour period.
This type of landslide is extremely difficult to anticipate – there are no obvious precursory indicators in the imagery that is available, although there may be landslide scars on the adjacent slopes. Thus, mitigation of the risk must rely on managing the channel down which the flow travelled, and on ensuring that houses are not in the path of potential flows. This is challenging in a mountainous terrain. I will return to this theme in a future post.
Reference and acknowledgement
Planet Team (2025). Planet Application Program Interface: In Space for Life on Earth. San Francisco, CA. https://www.planet.com/
Tien, P.V., Minh, V.C., Duc, D.M. et al. 2025 Rainfall-induced catastrophic rapid and long-traveling landslide in Lang Nu hamlet: the worst natural landslide disaster in Vietnam. Landslides. https://doi.org/10.1007/s10346-025-02490-2