25 October 2021
A rockslide video from Pyuthan in Nepal
The heavy rainfall last week in Nepal and India caused widespread damage including many landslides. Interestingly, as I type an atmospheric river event is affecting the West Coast of the USA, also with reports of of landslides. It will be interesting to see what the effects of that event will be, especially in areas affected by recent wildfires.
Pyuthan is a hill district located to the west of Nepal. A video emerged over the weekend of a very interesting landslide in Pyuthan, apparently triggered in this event (although this remains to be verified). This video was originally posted onto Tiktok by aashishsenchury10, but it has also been posted onto Twitter:-
Unfortunately there is little information that I can find about the location of this dramatic failure. However, there are a few things to note. First it appears to be a wedge failure in bedrock. The post failure images show that the sliding was controlled by two very clear, pre-existing discontinuities in the mass. One of these is very clear in the image below, whilst the other is orientated towards the camera:-
Second, there is landslide debris between the houses and the rockslide, indicating that this was not the first failure in this area. The age of this debris is not clear.
Third, immediately below the slope there is a road. I can only speculate on whether the construction of the road has been a factor in destabilising the slope. That is a factor that is common in many slope failures in rural Nepal.
And finally, perhaps most worryingly, some versions of this video (for example this one on Twitter) end with a view of the setting of the houses in the foreground:
This appears to show that the houses have been built adjacent to a very high, unsupported cut slope in colluvium. That does not appear to be a safe situation.