Geotechnical and Geospatial Analysis of the Chaten Landslide Near the Chaten Army Camp, Lachen, North Sikkim Himalayas

ABSTRACT

The study of Landslides in the Himalayas is crucial due to considerable threats to human life and infrastructure. A catastrophic landslide struck the Army camp at Chaten, near Lachen in the Mangan district of Sikkim, on June 1, 2025 (Sunday) at around 7 p.m., resulting in the deaths of two Army personnel and a porter, while six personnel remain missing. The principal objective is to examine the preliminary causes of such a devastating landslide. The rainfall dataset of Lachen station was collected from the India‐WRIS website. C‐band SAR images (Synthetic Aperture Radar, Sentinel‐1A) were applied for the InSAR coherence analysis. An assessment of slope stability (using the Limit Equilibrium Method) has been considered here for the determination of the Factor of Safety (FoS). The total quantity of rainfall in May (01‐05‐2025 to 30‐05‐2025) was 240.6 mm, yet the rainfall on 31st May and 1st June was 299 mm, and as a result, a landslide was triggered by the augmentation of pore water pressure due to vertically directed infiltration, through flow, and concentration of short‐duration rainfall with high rainfall intensity. The result of the Limit Equilibrium Method shows that the sliding slope is in a critical stage (FoS = 0.987) and is highly sensitive to landslides. The InSAR coherence analysis shows a significant lowering of coherence value over the landslide slopes, which also signifies the occurrence of slope deformation. This type of landslide case study provides critical insights into several localized factors, and it bridges the theoretical model and the real‐world dataset.