In 2013, melting of the Chorabari glacier led to heavy floods in Uttarakhand and Himachal Pradesh, causing massive loss of life and property. Glacier lake outburst floods (GLOF) like this, have become a major safety concern in the Himalayas and other mountainous regions across the world. A group of researchers from the Indian Institute of Science, Bengaluru has now developed a unique model that can help prevent massive damages. Led by Prof. Anil Kulkarni at the Divecha Centre for Climate Change, the model serves as a tool for safe planning and timely monitoring of glaciers.
A glacial lake has its origins in a melted glacier, and is formed when a glacier erodes the land, then melts, filling the space it has created. Over the past few years, glaciers have been retreating at an increasing rate leading to formation or expansion of glacial lakes. They are bound by a ‘natural dam’ made of loose soil and stones and pose a flooding threat to the neighbouring regions if the dam breaches. Hence, there is a need to predict and monitor the lake’s expansion. “It is difficult to predict the volume of a lake using remote sensing since it can give us only aerial data”, explains Prof. Kulkarni. “What we needed to know was the landscape of the bedrock under the glacier, which can be estimated if the depth of the ice before the formation of the lake is known”, he adds.
The researchers of the study propose a new model to predict the lake’s expansion by learning about the lake bed topography, obtained by subtracting the ice thickness from the surface elevation at different points. This was done by using remote sensing data like satellite images and digital elevation models, and by physically collecting on-site data in a challenging expedition.
Over-deepenings – sites where lakes could form or expand into – were identified with this data. “The beauty of this model is that it not only predicts how much a lake can expand, but also where new lakes might be formed. This becomes extremely important in the context of safe planning”, says Prof. Kulkarni.
To validate their model, the team used the data of two glaciers, Drang Drung and Samudra Tapu. They applied the model on the data collected from the year 2000 and identified twelve sites where lakes could potentially form or expand. They then checked data from the year 2015 to check how these sites had evolved. They found that a lake had indeed formed near a predicted site on Drang Drung, whereas a pre-existing lake near Samudra Tapu had expanded into a predicted site. This validation was a key part of the team’s investigation.
The model, with all its merits, however, is only a step forward to a larger goal. As Prof. Kulkarni elaborates, “Ideally, we’d like to know the volume of water entering the flood. For this, we need to know other aspects like strength of the dam, or when the dam would break.”
Nevertheless, with this working model in hand, a major programme is set to be launched. Under the Indian government’s IMPRINT initiative, this model is set to be applied to a large number of glaciers across the Himalayas to predict where lakes might be formed.
This model is also of special importance in the face of changing climate. The rate of retreat of glaciers may increase in the coming years, and hence, this model, if strategically applied, can potentially prevent huge damage to life and property.