Brief communication: The northwest Himalaya towns slipping towards potential disaster

Abstract

Abstract. The NW Himalaya (India) has been one of the most affected terrains of the Himalaya, subject to frequent disastrous landslides owing to active tectonics and multiple precipitation sources. This article focuses on two towns (Joshimath and Bhatwari) of Uttarakhand in the NW Himalaya, which have been witnessing subsidence for decades. Up until 9 January 2023, Joshimath had witnessed widespread cracks in more than 500 houses, which has prompted social unrest in the region. The hillslopes surrounding both towns comprise highly jointed gneisses with schistose interlayer rock mass. Both towns have subsidences and holes in the road, broken retaining walls, and displaced boulders, and the houses have cracks in the walls and holes. Recently, such slope instability phenomena have increased, which is leading to social movements in the region seeking government action such as possible evacuation and rehabilitation. The present study used a continuum-modelling-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, which will further aggravate the situation. The occurrence of frequent extreme rainfall in these towns and three major earthquakes, which occurred on 1 September 1803 (Mw 7.8), 20 October 1991 (Mw 6.8), and 29 March 1999 (Mw 6.6), having a hypocentral distance less than 30 km makes such a study more viable for decision making.