Comment on nhess-2022-296

Abstract

The NW Himalaya has been one of most affected terrains of Himalaya subjected to frequent disastrous landslides owing to active tectonics and multiple precipitation sources. This article aims at two towns (Joshimath and Bhatwari) of the Uttarakhand in the NW Himalaya (India), which have been witnessing subsidence for decades. In the last 1–2 weeks, Joshimath has witnessed widespread cracks in more than 500 houses that has created the social unrest. The hillslopes accommodating both the towns comprise highly jointed gneisses with schistose interlayers rockmass, subsidence in road, broken retaining wall, holes, displacing boulders, and cracks in the houses. Recently, such slope instability phenomena have increased that is leading to social movements in the region seeking government action for possible evacuation and rehabilitation. Present study has involved continuum modeling-based slope stability simulation to determine the response of these hillslopes under various loading conditions; gravity, rainfall, building load, domestic discharge, and seismic load. Results revealed that the displacement in these hillslopes might reach up to 20–25 m that will further aggravate the situation. Occurrence of frequent extreme rainfalls in these towns and three major earthquakes i.e., 1 Sep. 1803 (Mw7.8), 20 Oct. 1991 (Mw 6.8), and 29 Mar. 1999 (Mw 6.6) having hypocentral distance less than 30 km make such study more viable for decision making.