Study of qualitative stability analysis and rainfall thresholds for possible landslide occurrence: a case study of Sikkim Himalaya

Abstract

Landslide hazard characterization in the Setijhora landslide, located near Kalijhora village, along National Highway 10, was carried out in a qualitative way using Rock Mass Rating (RMR), Continuous Slope Mass Rating (CSMR) and Geological Strength Index (GSI). CSMR data helped in the understanding of slope failures (wedge, planner, rotational and toppling), while RMR & GSI data provides a better understanding of rock mass quality and its deformation. RMR was observed between 10–49 in the dry season and 1–39 in the monsoon season. Kinematic/stereographic analyses indicate vulnerability to wedge failure, while CSMR ranges from 13.84 to 50.85 (class III to class V). Rainfall threshold data shows cumulative rainfall of more than 111.3 mm over 20 days and 222 mm in a month indicating a high probability of landslides occurrence. Data generated from the study will be very useful for developing landslide early warning in the study area.