Researchers from the Divecha Centre for Climate Change (DCCC) at the Indian Institute of Science (IISc) have developed a model to predict a deadly natural calamity causing massive downhill flooding due to melting glaciers that is expected to be common in the Himalayas due to global warming.
Using this model under the Union government’s Impacting Research Innovation and Technology (IMPRINT) initiative, a major programme has been planned to scrutinise a large number of glaciers across the Himalayas to predict where such flooding can take place and forewarn populations that could get affected by it.
This would not only help downhill Himalayan populations to be safe, but would also help forward Indian army positions posted on or close to northern glaciers remain safe by pre-planning their base locations. One project that successfully validated the team’s model was conducted on a glacier in Kargil district of Jammu & Kashmir, a sensitive defence area.
Remember the June 2013 floods in Uttarakhand – considered the second worst natural disaster after the December 2004 tsunami – in which almost 6,000 people, mostly tourists, died? It was caused by heavy rains and increasing water volumes when the Chorabari glacier, at an altitude of 3,800 metres, melted and its glacial lake’s natural dam breached to unleash massive floods and landslides. This was further compounded by the surging Mandakini River and the heavy rains.
The natural calamity that the DCCC researchers can predict now is the glacial lake outburst floods (GLOFs). Scientists say GLOFs could be more common especially in the months of May to July when the tourist season is at its peak in the lower and southern Himalayan regions.
Glacial lakes are very dangerous because of the manner in which they form. When a glacier melts after eroding the ground beneath it – more like what a plough does in a field — the resulting gash in the land caused by the glacier is filled with huge volumes of water when the massive body of the glacier itself melts to fill them up and form lakes.
The rising sides of the glacier-caused gashes become the glacial lake’s natural dam to keep the once-glacier-now-water from flowing downwards. But there is no certainty about its strength to retain the waters as these are made of loose soil and stones which can easily shift under the weight of the massive volumes of water.
If or when a breach occurs, it causes a glacial lake outburst flood downstream, like in the June 2013 calamity.
However, until now, there was no way to tell where these glacial lakes would form and how populations downstream of the glaciers would be affected, and when.
According to glaciologist Dr Anil V Kulkarni, distinguished visiting professor, DCCC at IISc, his team’s new GLOF-predicting model takes into account 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 is done by using remote sensing data like satellite images from the Indian Space Research Organisation and US’ National Aeronautics & Space Administration (NASA) and digital elevation models.
These are complemented by physically collecting on-site data in challenging expeditions, especially during summertime when the glaciers have melted, to allow the scientists easier ways to assess the depth and expanse of the glacial lakes, which turn into ice in winter.
The DCCC team then validated their model using data of two glaciers – Drang Drung glacier, a mountain glacier near the Pensi La mountain pass at the Kargil-Zanaskar Road in the Kargil district of Jammu and Kashmir; and Samudra Tapu, one of the largest glaciers in Chandra basin of Lahaul-Spiti district of Himachal Pradesh.
They used data from the year 2000 to apply their model, identifying 12 sites where the lakes could form or expand. They then checked the 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 of their model was a key part of the team’s investigation.
“The beauty of this model is that it not only predicts how much a lake can expand, but also where new lakes might form. This becomes extremely important in the context of safe planning,” says Kulkarni.
Credits Bangalore Mirror