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.
