Expedition Team explores glacial flood mitigation plans in Sikkim's Lhonak Valley

The team investigated whether Lhonak lake's behaviour was aligned with typical patterns of glacial floods which carry debris, sediment and boulders with massive destructive potential

Views of South Lhonak Lake before (top) and after it burst its banks on October 3, 2023. | Photo Credit: Maxar/Reuters

PTI, Gangtok, 04.12.24 :  An expedition team from the Sikkim government's Science & Technology Department on Wednesday reached Muguthang in North Sikkim's Lhonak valley to assess the impact of glacial floods and its mitigation through various measures, officials said.

The team investigated whether Lhonak lake's behaviour was aligned with typical patterns of glacial floods which carry debris, sediment and boulders with massive destructive potential, officials said.

The study team observed that flood water from Lhonak lake slowed down as it passed through the wide areas of the valley between Goma and Dolma Sampa sections.

This natural dissipation of force caused debris deposition, reducing the flood's destructive impact downstream, the officials said.

It was only below Dolma Sampa that the flood picked up momentum and debris causing widespread devastation downstream.

The team also analyzed the sub-surface geology at Dolma Sampa and measured discharge of the Lhonak River.

These insights will be crucial in evaluating feasibility of a retention structure at Dolma Sampa, which could regulate floodwaters and protect downstream infrastructure.

The expedition team comprised experts in geology, ecology, engineering, hydrology, and remote sensing from the Departments of Science & Technology, of Mines & Geology and the National Disaster Management Authority.

The team endured freezing temperatures of minus 10 degrees Celsius and high winds while camping in Muguthang at 14,000 feet to conduct their studies.

The expedition team will return to Gangtok on Thursday carrying critical data and insights that will inform future strategies for managing glacial flood risks.

Their findings will form the basis of a concept note, which will undergo wider consultation and feasibility assessments, officials added.

This initiative marks the fourth glacial lake expedition by the Government of Sikkim, aimed at building resilience to safeguard lives, livelihoods, critical infrastructure, and the environment.

The Lhonak lake had burst in October last year triggering a flash flood in Teesta river that claimed more than 40 lives and caused large-scale destruction of road and communication infrastructure in North Sikkim.

Forty glacial lakes in the state have been identified as high-risk by the central government.