The challenges of the valley blocking landslide in the Matia’an Valley in Wanrong township, Taiwan
The 21 July 2025 rock avalanche is generating a lake that could have a volume of 86 million cubic metres at the point of overtopping. This poses a threat to at least seven downstream communities in east Taiwan. Yesterday, I posted about the enormous 21 July 2025 rock avalanche in the Matia’an valley, in Wanrong township in eastern Taiwan. Coincidentally, etaiwan.news has posted an article about the landslide that includes some images of it, and that highlights the growing concerns about the potential hazard from the landslide dammed lake. So, let’s start with the images. This is the headscarp area:…
The 21 July 2025 giant rock avalanche in Wanrong township, Taiwan
On 21 July 2025, a very large rock avalanche occurred in the mountains of Hualien County, Taiwan. Initial measurements suggest that this ran out over about 6 km. On 21 July 2025, an extremely large rock avalanche occurred in the administrative area of Wanrong Township in Hualien Count in Taiwan. This event was detected on seismic data and it has been described on Facebook by Chen-Yu Chen. In the days before the landslide, southern Taiwan had been affected by heavy rainfall associated with the passage of Tropical Storm Wipha. The crown of the landslide is at [23.72645, 121.29021]. A rough…
The possible causes of the Dharali (Tharali) debris flow in Uttarakhand, India
A possible cause of the 5 August 2025 landslide is the failure of a large body of glacial material high in the valley above the village. The imagery that is emerging after the 5 August 2025 debris flow in Dharali (Tharali), in Uttarakhand, northern India make very somber viewing. Melaine Le Roy posted this comparison to BlueSky, which illustrates the scale of the flow that has struck the village:- Meanwhile, India Today has a good article that describes the current situation, highlighting the challenges that the responders are facing due to ongoing heavy monsoon rainfall and the damage to the…
A very initial perspective on the 5 August 2025 debris flow at Tharali / Dharali in northern India
A massive landslide has destroyed a remote Himalayan village. Fifty or more people may have died. Astonishing and terrifying footage has appeared today of a dreadful debris flow that struck the village of Tharali (also called Dharali in some places) in Uttarakhand today. The video has been widely shared on social media. This is a…
The 15 July 2025 quick clay landslide at Portneuf in Canada
A quick clay landslide in the Quebec region has destroyed most of a farm and a local road. Over the next few days I will try to bring the blog up to date with some of the major landslides that have occurred whilst I have been on leave. To start, on 15 July 2025 an…
The inflow angle and channel gradient for large landslides
A new paper (Kharismalatri, Gomi & Sidle 2025) in the journal Natural Hazards uses the concepts of the inflow angle and the channel gradient to examine the behaviour of large landslides after failure. Large landslides in areas with steep terrain that either block the valley or turn into a long runout debris flows are an…
Movement of the Joshimath landslide in India
A new paper (Dalal et al. 2025) in the journal Engineering Geology examines movement of a major landslide complex in India. It shows that the slope reactivated in 2018, probably as a result of the loss of vegetation and poor management of water. Loyal readers will remember a series of posts that I made back…
The official report of the 24 June 2024 landslide at the Eagle Gold Mine heap leach facility
The Independent Review Board has released its report into a 6 million cubic metre landslide in Canada. It indicates that an initial rotational failure triggered a flow slide that travelled 1,400 metres. On 24 June 2024, a very large landslide affected a heap leach facility (HLF) at the Eagle Gold Mine in Yukon, Canada. I…
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About Dave
Dave Petley is the Vice-Chancellor of the University of Hull in the United Kingdom. His blog provides commentary and analysis of landslide events occurring worldwide, including the landslides themselves, latest research, and conferences and meetings.