AI Insight
On June 29, 2026, a large valley-blocking landslide occurred on the Siji River in Lower Siang district, Arunachal Pradesh, India, triggered by heavy early monsoon rainfall. The landslide completely blocked the river valley and was captured on video, including footage of a motorcyclist narrowly escaping while crossing the slide area. Google Earth imagery reveals significant slope disturbance from quarrying operations in the affected area, suggesting human activity may have contributed to slope instability.
Why it matters
This event affected approximately 3,100 people across 14 communities through associated flooding and landslides, highlighting the compound risks of monsoon rainfall, land disturbance from quarrying, and valley-blocking landslides in mountainous regions. The landslide barrier has begun releasing water naturally, reducing the immediate threat of catastrophic dam-break flooding downstream.
Understand the Science
A large landslide in India, triggered by monsoon rainfall, was captured on a remarkable video.
On Monday 29 June 2026, a valley-blocking landsldie occurred on the Siji River in Lower Siang district, Arunachal Pradesh, India. I have yet to track down the precise location of this event, but it is in the region of [27.7146, 94.69135]. The Hindu has a version of this video on its Youtube channel, although this is not the full civerage:-
The full version, which includes the extremely lucky escape of the motorcyclist who was crossing the landslide at the time, is on Facebook. This includes the image below, which shows the blockage of the valley:-
Fortunately, reports indicate that the landslide has already started to release water, so this is unlikely to pose a long term risk. The trigger has been very heavy early monsoon rainfall. But the Google Earth imagery of the area also shows massive disturbance of the slopes in this area from quarrying:-
Whilst this was the highest profile event, there has been widespread flooding and landslides across Lower Siang, reportedly affecting 3,100 people across 14 communities. Fortunately, to date there have been no reported fatalities.
Text © 2026. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.
Source: A valley-blocking landslide in Lower Siang district, Arunachal Pradesh, India