Increasing Risk of Silent Disaster in Uttarakhand Himalaya: An Example from Higher Himalaya

Land subsidence is an abrupt and silent disaster worldwide caused by various factors such as tectonics, nature of rocks and climatic variability etc. It is directly triggered by anthropogenic activities. The Uttarakhand Himalayan province in India has witnessed several earthquakes, landslides, avalanches, droughts, and flash floods/floods in the recent past. Among these incidences landslides frequently occurs in the Himalayan region, particularly during the monsoon season. Seismically, this region falls in seismic zones V and IV due to which area witnesses frequent earthquakes. An attempt was made for preparation of an inventory of land subsidence across the state of Uttarakhand to determine the key factors that are responsible for land subsidence. Previous studies and field evidences suggests that land subsidence events mainly occur due to several factors such as carbonate rocks, topography, tectonics, seismicity, climate, flash floods/floods and reservoir drawdown effect in this region. Furthermore, anthropogenic activities such as mining, underground water, unscientifically civil constructions, inadequate drainage, heavy load on ground/slope, and modification of slope for infrastructure developments aggravates the problem. This study also highlights the problem of ongoing chronic land subsidence in Joshimath town which is situated over an old landslide mass as well as its proximity to Vaikrita Thrust.