Gangtok, Dec 2 To safeguard downstream communities from potential Glacial Lake Outburst Floods (GLOFs) in Sikkim, an expedition team reached the Lhonak Valley at a height of more than 17,000 feet to conduct a detailed study, officials said on Monday.
The Lhonak Valley is a Trans-Himalayan grassland in the exposed river valley of Goma Chu in the northwest part of the mountain state
A senior official said, “The ongoing studies are expected to refine glacial flood modelling, provide critical insights into subsurface geology, and inform the design of effective retention structures to safeguard downstream communities from potential Glacial Lake Outburst Floods (GLOFs).”
An official statement mentioned that on the fifth day of the ongoing expedition, the team departed from Thangu Army Camp early morning, crossing the Lugnakla Pass (17,000 ft) to reach the Muguthang Indo-Tibetan Border Police (ITBP) camp. From there, they proceeded to Dolma Sampa in Lhonak Valley to evaluate the feasibility of a proposed retention structure aimed at mitigating future glacial flood risks.
“What brings the expedition to Dolma Sampa is the unique geometry of this valley. The Goma Chu River flows through the Lhonak Valley, which features a distinctive topography. Downstream of South Lhonak Lake, the valley narrows and takes an S-shaped turn at Goma, acting as a natural speed breaker for potential glacial floods,” it added.
Beyond this point, the valley broadens into a gently sloping expanse known as Dolma Sampa -- a one km wide and three km long flat area. The study aims to determine whether Dolma Sampa is a suitable site for a retention structure, as the upper valley serves as a natural buffer for debris and floodwater.
According to officials, initial observations of debris deposition patterns from the glacial flood on October 3, 2023, indicate that larger materials such as boulders are deposited in the upper reaches of Dolma Sampa, supporting its potential as a viable retention site.
With support from the ITBP, the team initiated detailed investigations at Dolma Sampa, including subsurface geophysical studies, debris deposition analysis, and 2023 glacial flood-level measurements. Despite freezing conditions --temperatures plummeted to zero degrees Celsius by afternoon and further dropped to minus 10 degrees Celsius at night -- strong winds and challenging terrain, the team successfully completed their fieldwork for the day, said the officials.
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