In the 2000s, experts had anticipated glacial origin floods to hit the Hindu Kush Himalaya region once every 5 to 10 years. And, true to it, during May and June earlier this year three glacial origin floods hit Limi in Nepal, Andorab valley in Afghanistan, and Chitral, Hunza in Pakistan, thereby establishing the truth of that anticipated calculation more than 20 years back.
By Salam Rajesh
The conversations on the three planetary crises – global warming, climate change and extreme weather events – are increasingly gaining momentum with equally increasing examples of disasters causing deaths, destruction and sufferings everywhere across the globe, sparing almost none.
On this footnote, Kathmandu-based international organization, the International Centre for Integrated Mountain Development (ICIMOD) has long been monitoring the changes taking shape in the fragile Himalayas, and is now bringing forward results of their studies, which is dampening indeed.
In the 2000s, experts had anticipated glacial origin floods to hit the Hindu Kush Himalaya region once every 5 to 10 years. And, true to it, during May and June earlier this year three glacial origin floods hit Limi in Nepal, Andorab valley in Afghanistan, and Chitral, Hunza in Pakistan, thereby establishing the truth of that anticipated calculation more than 20 years back.
ICIMOD’s scientists has been mapping and monitoring glacial lakes and glacial origin hazards since the year 1985 when the Dig Tsho lake-outburst in Khumbu, Nepal, flatten a micro-hydroelectric dam and caused 3 million USD worth of economic damages.
Qianggong Zhang, head of Climate and Environmental Risks at ICIMOD, places the reality on record, saying “We are talking about a huge expanse of terrain where these sorts of lakes can develop, and the monitoring data and method on the pace of these changes simply does not yet exist”.
Experts at ICIMOD showed concern at the increased frequency of glacial origin hazards in the HKH region. Saswata Sanyal, ICIMOD Disaster Risk Reduction Lead, places this concern as: “The acceleration of these types of events is completely unprecedented in the HKH region. We need to delve deeper into the triggers that are resulting in cascading impacts”.
According to the Centre, future disaster risks are quite pronounced, with Nepal having 21 potentially dangerous lakes, Tibet Autonomous Region of China with 25 lakes, and one high risk glacial lake in India.
ICIMOD researchers are particularly worried on the supraglacial lakes. These small, almost hidden lakes form on the surface of glaciers, particularly in debris-covered areas, and are highly dynamic and ephemeral, often beginning as small meltwater ponds that gradually expand and sometimes merge to form larger supraglacial lakes. The detection of these lakes largely depends on the spatial resolution of satellite imagery, the researchers say.
The recent glacial lake-outburst incident in Himachal, and extreme flash floods in Uttarakhand and Sikkim, resulting in massive deaths and destruction is a lurid example of how glacial melts and the resulting glacial lake formation in the upper reaches of the Hindu Kush Himalayas can be extremely violent and dangerous for the lower riparian communities.
The recent China-Nepal devastating floods were caused by draining supraglacial lakes that started forming as small ponds by the end of December last year, and which grew significantly in June this year.
Two intense floods hitting Nepal within a very short period of 24 hours was completely unprecedented, ICIMOD researchers said. This was evident of the extremity of glacial melts and the resulting impacts.
For achieving mitigation measures, mapping and monitoring of these Potentially Dangerous Glacial Lakes and the compilation of inventories on these high-risk lakes requires to be more frequently updated, the researchers observed.
The smaller, short-lived ice dammed lakes need to be analyzed regularly, and at the same time the dynamics of glacier retreat and lake formation require to be incorporated for more dynamic and accurate hazard assessment, they said.
Several factors would be contributing to this trend, of which one factor could be the thawing of permafrost – previously frozen ground – which destabilizes the surface and makes it more susceptible to erosion by floodwaters, ICIMOD researchers observed.
Another factor would be the shift in precipitation patterns in periglacial areas where more rainfall, instead of snowfall, leads to increased runoff and excessive erosion. These changes are closely linked to climate change, particularly rising temperatures, which are altering both the quantity and the nature of what flows downstream, the researcher said.
Sharad Prashad Joshi, cryosphere monitoring specialist at ICIMOD is skeptical when he says, ‘These events are signals and symptoms of really rising temperatures, and are more destructive than normal flood due to the debris and steep topography’.
The relative size of the lakes had previously been one of the criteria for analysis of potential danger, with those greater than 0.02 square kilometer being considered only, and priority given to potential downstream impacts and moraine-dammed glacial lakes, since these are considered particularly unstable, ICIMOD noted.
Recent events occurring by draining of newly formed supraglacial ice-dammed glacial lakes, like the recent flood in Bhotekoshi Nadi in Rasuwa, and the rock avalanche in the bedrock dammed glacial lake, and sequential breach of moraine dammed glacial lake in Thame, Everest region last year, has hastened mapping of more potentially dangerous lakes regardless of size, it further noted.
Temperature rise is attributed in playing a key role in the increasing frequency of glacial origin floods, outlined in two key ways. Firstly, the formation and gradual expansion of glacial lakes – a longer-term process driven by sustained warming.
Secondly, short-term temperature extremes on individual days can act as triggers for sudden events such as ice avalanches, ice calving, or slope failures related to permafrost thaw, ICIMOD researchers observed.
Floods carrying heavily debris-laden water, known as non-Newtonian flow, have significantly greater impacts than floods involving water alone. In recent events, such flows have become more common, with floods increasingly mixed with large volumes of sediment and debris, causing severe damage downstream, the researchers noted.
Outlining measures initiated to tackle possible future impacts on communities as result of GLOB, ICIMOD confirmed major investments are being made in disaster management in the region with the Asian Development Bank commencing its BAR-HKH initiative in Nepal and Bhutan, which has specific focus on mountain hazards.
The GCF also approved a 36.1 million USD package for the United Nations Development Programme to lower four large glacial lakes in Nepal that ICIMOD had identified as of risk in its Potentially Dangerous Glacial Lake report. These lakes include Thulagi, Lower Barun, Lumding Tsho and Hongu-2.
ICIMOD, established 1983, is based in Kathmandu, Nepal. Its outreach covers the Hindu Kush Himalaya (HKH) region stretching 3500 km across Asia and spanning across eight countries – Afghanistan, Pakistan, Nepal, Bhutan, China, India, Myanmar and Bangladesh. It seeks solutions for the fragile HKH region in the face of impacts of the triple planetary crises.