A recent glacial break in the Tapovan-Reni area of Chamoli District in Uttarakhand triggered an enormous flash flood. This natural disaster impacted the Dhauli Ganga and Alaknanda Rivers, leading to significant damage to houses in the vicinity and the proximate Rishiganga power project. The event bears unfortunate resemblance to the June 2013 flash floods in Uttarakhand that led to wide-scale destruction.
The Cause of the Flash Flood
The flood was a result of a section of the Nanda Devi glacier breaking off and falling into the Rishi Ganga river. This led to a massive increase in water volume. With the Rishiganga meeting the Dhauli Ganga near Raini, the latter river flooded as well.
Power Projects Impacted by the Flash Flood
The Rishi Ganga Power Project, a private 130MW undertaking, and the Tapovan Vishnugad Hydropower Project on the Dhauliganga, a 520 MW run-of-river hydroelectric project also suffered significant losses due to the floods. In addition to these, several other projects in the Alaknanda and Bhagirathi river basins saw disruptions.
Understanding Flash Floods
Flash floods are rapid increases in water levels, typically occurring after intense rainfall. These events peak swiftly – usually within six hours from the onset of rainfall. Flash floods can worsen if drainage lines are blocked or natural water flows are obstructed. They can be caused by heavy rain from thunderstorms, hurricanes, tropical storms, or meltwater from ice or snow flowing over ice sheets and snowfields.
Glaciers and Their Connection with Floods
Glaciers are large masses of ice that slowly move due to their own weight. They form in areas where the accumulation of snow surpasses its melting and sublimation over many years. The Continental Glacier and Mountain Glacier are two main types, with the former moving outward in all directions and the latter from a higher to a lower altitude.
Glacial Lakes and Floods
Retreating glaciers often lead to the creation of proglacial lakes. If these lakes overflow or their boundaries are breached, it can result in flooding downstream.
Climate Change Influence
Erratic weather patterns such as increased snowfall and rainfall and warmer winters leading to more snow melting is attributable to climate change. Increased glacier retreat and permafrost thawing can lead to decreased stability of mountain slopes and increased number and area of glacier lakes.
Dhauliganga River: Origin and Impact
Originating from Vasudhara Tal, perhaps the largest glacial lake in Uttarakhand, Dhauliganga is an important tributary of Alaknanda, which also includes the Nandakini, Pindar, Mandakini and Bhagirathi. It merges with the Alaknanda at Vishnuprayag and then continues its journey through various locations until it meets the Ganga at Devprayag.
Nanda Devi National Park: A Glacial Hub
Situated around the peak of Nanda Devi in Uttarakhand, the Nanda Devi National Park encompasses the Nanda Devi Sanctuary, a glacial basin surrounded by a ring of peaks and drained by the Rishi Ganga through the Rishi Ganga Gorge. Established in 1982, the park is a World Heritage Site and houses 312 floral species including 17 rare species and a variety of fauna.
