[H-DS05] Landslides and related phenomena

[HDS05-P05] Detection of Early Signatures of Landslides in Western Himalayas, India

*Deepti Kumari Dwivedi¹, Arun Kumar Saraf¹, Josodhir Das¹ (1.Indian Institute of Technology Roorkee)

Keywords:landslide , landslide damming, slope failure, RAMMS

Landslide is a complex naturally occurring phenomenon involving the downslope movement of surface material under gravity which affects 12.6% of India’s total land area excluding snow-covered areas, mainly in the Himalayas, the Western Ghats, the Eastern Ghats, the Northeastern hill ranges, and the Nilgiris. Modern-day satellites with rapid image acquisition cycles allow for near-real-time imaging of hazards-affected areas which helps in studying the spatial extent of the events. Publicly accessible multi-spectral datasets derived from earth observation images can be used in analyzing manual or automated landslide detection. In the present study, high-resolution multi-temporal images were used in landslide detection of different parts of Western Himalayan regions showing the evident signature of slope failures a few years before the actual events. Starting with the study of the Urni landslide, sited on the right bank of the Satluj River, Kinnaur, Himachal Pradesh, is an example of a complex landslide that has evolved in the last two decades (2000-2016) and has also resulted in the partial damming of the Satluj River since the year 2013. The signature of slope failure was observed from the year 2004 whereas the landslide actually happened in the year 2016 and the detachment of mass is still going on. Similarly, the triangular wedge of Raunti saddle which failed on 07^th February 2021 in Chamoli district, Uttarakhand, had distinct cracks visible from the year 2017 and it eventually failed in the year 2021 causing the devastating flash flood in the downstream areas. The third case study is of a huge landslide near Nalda village in the Lahaul-Spiti district of Himachal Pradesh, which blocked the flow of the Chenab River, on the morning of 13^th August 2021. The slope failed due to toe cutting in the year 2021 had clear signatures of failure since the year 2008 i.e., thirteen years before the event. The probable causes of all three landslides were evaluated along with the simulation of the events using the Rapid Mass Movement Simulation (RAMMS) model. The result from the above studies shows that any landslide event shows clear signatures of slope failures before a few days to a few years of the actual occurrence of the event. Therefore, this paper emphasizes monitoring such vulnerable areas based on high-resolution time series satellite images which are available on a regular basis to avoid the loss of human lives in the future.