Satellite-based real-time monitoring of Himalayan glacial catchments can strengthen early flood warning & minimize disaster risk
Satellite-based real-time monitoring of Himalayan glacial catchments would improve understanding of flood risk in the region and help inform an early flood warning system that could help curb disaster and save human lives, says a recent study.
This should be the future strategy to reduce loss of human lives during glacial lake outburst floods (GLOF), said a study carried out by scientists from IIT Kanpur.
The study carried out by Dr. Tanuj Shukla and Prof. Indra Sekhar Sen, Associate Professor from IIT Kanpur, with support from the Department of Science & Technology, Government of India, has been published in the international journal ‘Science’.
Temperature and the numbers of extreme rainfall events are rising at an increased rate because of climate change. Suitably called Earth’s “Third Pole”, the Himalayan region is home to the largest ice mass outside of the planet’s Polar Regions. The glaciers in the Himalayas are melting at a faster rate creating new lakes and expanding the existing ones. Besides, the rising temperatures and extreme precipitation events make the region increasingly prone to a variety of natural hazards, including devastating glacial lake outburst floods (GLOFs).
GLOFs occur when either a natural dam containing a glacial lake bursts or when the lake’s level suddenly increases and overflows its banks, leading to catastrophic downstream destruction.
For example, in 2013, an avalanche caused the glacial moraine holding back Chorabari Lake in northern India to give way, releasing a sudden torrent of water, boulders, and debris that scoured the river valley below, resulting in the deaths of more than 5,000 people. With climate change, these events are likely to increase in frequency and magnitude throughout the Himalayas. However, the remote, challenging Himalayan terrain and the overall lack of cellular connectivity throughout the region have made the development of early flood warning systems virtually impossible.
In their recent work, the Scientists also point out that the surge of meltwater in mountain streams is most commonly caused by cloud-burst events during the monsoon season (June–July–August) time frame.
However, the recent (7 February 2021) sudden surge of meltwater in the river tributary of the Ganga, Dhauli Ganga, during the dry season suggests that this time frame needs to be expanded. The catastrophe in the upper Dhauli Ganga basin is linked to processes other than precipitation events, such as snow avalanches, rock landslides, or other unidentified drivers, and therefore determining all of the potential major and minor drivers behind sudden surges of meltwater into headwater streams is vital for understanding the hazard profile of the region.
The IIT Kanpur team suggests that efforts to help mitigate GLOF events in the future should include the creation of a network of satellite-based monitoring stations that could provide in situ and real-time data on GLOF risk.
“The integration of monitoring devices with satellite networks will not only provide telemetry support in remote locations that lack complete cellular connectivity but will also provide greater connectivity in coverage in the cellular dead zones in extreme topographies such as valleys, cliffs, and steep slopes,” the authors explained.
It may be noted that many of the largest rivers emanate from the Tibetan Plateau and the Himalayas, and are fed by glacial and snow melting as well as monsoon rainfall. A large cross-section of the region’s population reside in the vast agrarian belts along the Yellow, Yangtze, Mekong, Irrawaddy, Ganges, Brahmaputra, and Indus river basins, each of which is subject to periods of widespread and seasonal flooding.
These river basins are also home to large numbers of the poor and vulnerable populations dependent on subsistence agriculture. The climate variability and change often manifest themselves into monsoon variabilities, El Niño and La Niña, and other extreme weather events – resulting in large scale frequent flooding particularly in the transboundary basins. Among all the disasters in the region, floods have been the most frequent and devastating. Floods in the transboundary river basins have had severe impacts beyond geographical boundaries. The Indus, Ganges, Brahmaputra-Meghna, and Mekong, for example, are resources to over 1 billion people, but are at high risk of transboundary flooding.
The impacts of the historical floods in these river basins reveal that the adverse socioeconomic impacts are huge development concerns. Among the transboundary river-bains, Brahamputra-Meghna, Indus, and Ganges accounted for the maximum loss of lives, damages, and flood occurrences . In the Indus river basin, transboundary floods in 2014 across India and Pakistan caused US$ 18 billion in economic impacts (ESCAP, 2015). In 2015, floods comprised twofifths of all disasters in the region, and caused more than US$ 11 billion in economic damage (ESCAP, 2016b).
Many of the large-scale floods have significant impacts, especially on the poor and vulnerable populations dependent on agriculture. Around 40% of the world’s poor live on or close to the major transboundary river basins in South Asia; two-thirds of this population live in the Indus, Ganges and Brahmaputra basins. Annual flood impacts on national economies are highest in Bangladesh and Cambodia in the region , countries that are downstream of the Ganges-Brahmaputra-Meghna and Mekong river systems respectively.
However, flood forecasting has proven effective in reducing economic impacts in many parts of the world. In that sense, the study by the Kanpur IITians will be of immense help.