Risk of glacial lake outburst flood in Himachal Pradesh: current and future threats

by Rohan Nath

Introduction 

Climate change is adversely affecting the Indian Himalayan Region (IHR). The  disappearance of mountain glaciers and the expansion of large glacial lakes are physical  evidence of the dynamic impacts of climate changes in the environment. In addition to the  decrease instability of the ice walls and the surrounding rock, the threat from glacial lake outburst floods is increasing over the years. This is further worsened with tourism,  residential, and hydropower structure expanding into the mountain regions. Therefore,  strategies to diminish the glacial lake outburst flood risk is an urgent requirement.  

Glacial lake outburst flood is the sudden discharge of a water reservoir situated underneath,  in front, underneath, within, on the surface or at the side of a glacier, and related dam structures can be composed of moraine, ice, or bedrock. The catastrophic failure of moraine dammed lakes often leads to flooding hazard. Large impacts of ice or rock in the Himalayas  contribute to over 50% of moraine dam failures.  

The triggering potential of glacial lake outburst flood have been integrally modelled and  studies are being conducted on quantification of affected land areas, resulting flood paths,  and the investigation of the vulnerability of the society due to climate-related disasters and  also implement an assessment of glacial lake outburst flood risk across Himachal Pradesh  (Fig 1). 

Fig. 1. Intergovernmental Panel on Climate Change concept of climate-related risk. Image Source: Allen, S. K., Linsbauer, A., Randhawa, S. S., Huggel, C., Rana, P., &  Kumari, A. (2016). Glacial lake outburst flood risk in Himachal Pradesh, India: an  integrative and anticipatory approach considering current and future threats. Natural  Hazards, 84(3), 1741-1763.

The area of study 

The study is conducted in the north-western Indian Himalaya in Himachal Pradesh (Table 1). 

Characteristics
State Himachal Pradesh
Population 6 million
Land area 55,000 km2
Elevation range 450 to 7000 m above sea level
Climate variation Lower hills – Tropical Middle Himalayan region – Temperate Upper hills – Cold and dry 

Agriculture, hydropower sectors and tourism primarily contribute to the economic growth  and employment in the state. There are four hydrological basins in the glaciated area, and all  of them flow into the Indus River (Fig. 2). 

Fig. 2. The distribution of glacial lake in Himachal Pradesh which comprises of glaciated  land area and four main hydrological basins. Image Source: Allen, S. K., Linsbauer, A.,  Randhawa, S. S., Huggel, C., Rana, P., & Kumari, A. (2016). Glacial lake outburst flood  risk in Himachal Pradesh, India: an integrative and anticipatory approach considering  current and future threats. Natural Hazards, 84(3), 1741-1763.

Risk Assessment and Factors 

The mass movements of rock or ice are important factors for assessing the changing potential  for glacial lake outburst flood. Parameters such as current glacial lake outburst flood hazard  and dam stability which include dam geometry and freeboard height, growth of the lake and  associated glacier retreat, the steepness of the lakefront area, permafrost conditions and the  vegetation coverage in the dam area are important for assessing the risk associated with  moraine-dammed lakes. Extreme hydrometeorological conditions can cause catastrophic  glacial lake outburst flood has been well exhibited in the 2013 Kedarnath flood disaster. For  ongoing research, the priority should be to constrain the temporal evolution of future lake  development.  

Two levels of information that can form a firm scientific basis for adaptation planning are: 

1. Areas, where communities are most exposed and vulnerable to glacier lake outburst  flood, is identified with the help of a standardized risk index. 

R = H.V.E 

where,  

R = Integrated assessment of glacial lake outburst flood risk 

H = Physical hazard 

V = Vulnerability  

E = Exposed People 

2. The early anticipation of where new threats is likely to occur over the next few  decades is assessed using classified hazard maps which focuses only on the physical  threat.  

The fluvial terraces and floodplain areas can be a prime site for assessment of loss and  damage from glacial lake outburst flood. Vital transportation links and significant agricultural  activities concentrated livelihoods and communities face high risk when the glacial lake  outburst flood paths converge with main river valleys. The potential frequency of glacial lake  outburst flood is likely to increase due to the formation of new lakes because the chances of  rock avalanches or falling ice entering into a lake increases leading to a catastrophic  overtopping wave.  

It is possible to form an improved basis for adaptation planning using the characterization of  glacial lake outburst flood exposure where mapped land cover data is available.  

Three situations are identified for opportunities for implementation of adaptation strategies: 

1. Sites currently threatened by glacial lake outburst floods but no new threats are  expected.  

2. Sites where new threats are expected. 

3. Sites that are currently threatened and new threats are expected to emerge.

Conclusion 

The climate risk perspective may be adopted to highlight the interacting social and physical  determinants that can cause glacial lake outburst flood events. The disaster can travel long  distances, throughout the district, states, as well as national boundaries. Hence, a proper  method to identify the risk and predict future challenges is required for the Himalayan region.  Few steps can be taken such as increased community awareness and preparedness, early  warning systems, and sustainable land use planning to overcome the future challenges  regarding glacial lake outburst floods.  

Reference 

1. Allen, S. K., Linsbauer, A., Randhawa, S. S., Huggel, C., Rana, P., & Kumari, A.  (2016). Glacial lake outburst flood risk in Himachal Pradesh, India: an integrative and  anticipatory approach considering current and future threats. Natural Hazards, 84(3),  1741-1763.

Published by LakesOfIndia

Lakes of India is an E.F.I initiative aimed at sensitizing the larger public on freshwater habitats across the country. A blog platform where one can read about lakes across India. You can become a guest blogger to write about a lake in your hometown and initiate an action to protect that lake.

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