Lake outburst and debris flow disaster at Kedarnath, June 2013: hydrometeorological triggering and topographic predisposition

Abstract

Lake outburst and debris flow disaster at Kedarnath, June 2013: hydrometeorological triggering and topographic predisposition Abstract Heavy rainfall in June 2013 triggered flash flooding and landslides throughout the Indian Himalayan state of Uttarakhand, killing more than 6000 people. The vast majority of fatalities and destruction resulted directly from a lake outburst and debris flow disaster originating from above the village of Kedarnath on June 16 and 17. Here, we provide a systematic analysis of the contributing factors leading to the Kedarnath disaster, both in terms of hydrometeorological triggering and topographic predisposition. Topographic characteristics of the lake watershed above Kedarnath are compared with other glacial lakes across the north-western Himalayan states of Uttarakhand and Himachal Pradesh, and implications for glacier lake outburst hazard assessment in a changing climate are discussed. Our analysis suggests that the early onset of heavy monsoon rainfall (390 mm, June 10-17) immediately following a 4-week period of unusually rapid snow cover depletion and elevated streamflow was the crucial hydrometeorological factor, resulting in slope saturation and significant run-off into the small seasonal glacial lake. Between mid-May and mid-June 2013, snowcovered area above Kedarnath decreased by around 50 %. The unusual situation of the lake being dammed in a steep, unstable paraglacial environment but fed entirely from snowmelt and rainfall within a fluvial dominated watershed is important in the context of this disaster. A simple scheme enabling large-scale recognition of such an unfavourable topographic setting is introduced. In view of projected 21st century changes in monsoon timing and heavy precipitation in South Asia, more emphasis should be given to potential hydrometeorological triggering of lake outburst and debris flow disasters in the Himalaya.

Glacial lake outburst flood risk in Himachal Pradesh, India: an integrative and anticipatory approach considering current and future threats

“…The expansion of existing lakes and formation of new lakes will increase the potential for mass movements of ice or rock to trigger GLOF events, and new GLOF paths will increase the downstream potentially affected land area. The Tehsil of Kullu (K), within the central District of Kullu is identified thousands of people has highlighted that extreme hydrometeorological conditions can trigger catastrophic GLOFs (Singh et al 2014;Allen et al 2015), yet knowledge on how such conditions may change in the future is limited by uncertainty in regional climate projections. Baseline information on permafrost distribution in the Kullu District has recently been established ), but ground temperature measurements and further field validation is required before the implications of thawing permafrost on GLOF stability can be reasonably quantified and integrated into a hazard assessment.…”

Evaluation of Satellite-Derived Rainfall Estimates for an Extreme Rainfall Event over Uttarakhand, Western Himalayas

“…Prior to 9 June, there was no significant rainfall, but a discharge rate varied from 54 to 65 m 3 /s, suggestive of runoff from glacier and snowmelt. The satellite-based imageries indicated that, in winter 2013, there was increase in snowfall of 30% in the Alaknanda and Mandakini catchment area [59,60]. Previous studies reported that the extreme rainfall in June has caused an acceleration of snowmelt-runoff and accumulation of large volume of water in the Lake [52,61].…”

Uncertainty in the Himalayan energy–water nexus: estimating regional exposure to glacial lake outburst floods

“…Torrential rains rapidly raised the water level of the moraine-dammed Chorabari Lake, Uttarakhand, India, in June 2013. The dam breached and released 400 000 m 3 of water into the already flooded Mandakini River, inundating the pilgrimage city of Kedarnath (Allen et al 2015), and severely damaging at least two HPP sites downstream (Sandrp 2013). The recognition that GLOFs can substantially exceed design floods of HPP at the risk of damage or complete inoperability (Richardson and Reynolds 2000) hinges on a handful of case studies, but the regional picture of GLOF exposure remains illdefined.…”