Assessment of 2016 Mantam Landslide at Mangan, North Sikkim Himalayas using Geospatial Techniques

Abstract

North Sikkim Road Corridor in Sikkim Himalayas is characterized by fine-grained, less permeable earth material and is thus vulnerable to landslides. Mantam is one of the new and active massive rock-cum-debris slides, initiated during the rainy season of 2016.In the Himalayan foot-hills, rainfall precipitation is a major triggering factor for the incidence of landslides. There is no previous study of the rain-induced landslide in the region with geospatial analysis of landslide data and application of rainfall threshold model. In the present study, the causative factors of the Mantam landslide is derived from the analysis of Very High-Resolution satellite images (Cartosat-2B) and High-Resolution LANDSAT 8 (30m) retrieved from National Remote Sensing Center and USGS. This paper presents geological, and geo-hydrological analysis of the Mantam landslide using High-Resolution satellite images and a rainfall threshold is suggested for the prognosticate sliding. This present study suggests a threshold value of ≥284.1 mm of cumulative rainfall over a 10 days period for the Mantam landslide initiation. After examining all the data, it is observed that groundwater seepages from the uncovered joint planes are common across the area. This is indicative of the role of the aquifer induced pore pressure, antecedent rainfall, and escarpment stress condition as probable causative factors of the Mantam landslide occurrence.