The Landslide Blog is written by Dave Petley, who is widely recognized as a world leader in the study and management of landslides.
On 24 August 2023, a large landslide occurred in Anni, located in Kullu district of Himachal Pradesh in northern India. This landslide was captured on two videos, both posted on Twitter. This is the first:-
And this is the same failure from another perspective:-
According to local news reports, eight buildings collapsed, four of which were commercial properties, whilst the other four were residential. I suspect that the residential properties were located higher on the slope. Two further buildings were damaged.
Cracks had been noticed in the buildings in recent weeks, such that they had been vacated prior to the landslide. As I have noted in previous posts, Himachal Pradesh has suffered very high levels of rainfall through the monsoon, so the Anni landslide is probably associated with high pore water pressures.
It might appear, on first inspection, that the buildings were under construction, but this may well not be the case. In South Asia it is common to build the shells of upper floors on buildings, to be occupied when needed.
The location of this event appears to be [31.43558, 77.42079]. This is a Google Earth image of this part of the town and the area behind:-
The area affected by the landslide has the place marker that says “Anni District Kullu Himachal Pradesh”. The large area upslope is interesting – on first inspection, the whole area may be an ancient landslide complex that extends all the way up to the ridgelines. If so, it is likely that the lower slope would have been potentially more unstable.
There are two most likely explanations for the causes of the Anni landslide. The first is that the slope had been cut and oversteepened to create benches for the buildings at the foot of the slope, and indeed those higher up. The second is that water was being poorly managed on the slope – natural pathways blocked and/or water being released from buildings in an uncontrolled manner. Very often, failures such as this are a combination of these factors, with the effects accumulating over several years.
As the 2023 summer monsoon starts to decline in South Asia, we have seen extensive damage to infrastructure caused by landslides, especially in NW India. I cannot remember a monsoon season like this. But attention will now start to switch to the peak of the typhoon season in the West Pacific. Current models suggest that the next two weeks could be interesting in the Philippines, Taiwan, China and Japan.