Sikkim expedition team crosses 17,000 ft to assess glacial flood risks in Lhonak

Gangtok, Dec 5: An expedition team in Sikkim on the fifth day of their mission crossed the Lugnakla Pass at 17,000 feet from Thangu Army Camp to reach the Muguthang ITBP Camp on 1 December. From there, the team advanced to Dolma Sampa in Lhonak Valley to assess the feasibility of a proposed retention structure aimed at reducing risks from future glacial floods.

The study is focused on the unique topography of the Lhonak Valley. The Goma Chu River flows through this area, which narrows downstream of South Lhonak Lake, forming an S-shaped curve at Goma. This natural feature acts as a speed breaker for potential glacial floods. Beyond this, the valley widens into a gently sloping expanse called Dolma Sampa, a flat area stretching 1 km in width and 3 km in length. Initial findings from the October 3, 2023, glacial flood suggest that Dolma Sampa's upper reaches serve as a natural buffer for debris and floodwater, making it a promising site for a retention structure.

Supported by the ITBP, the team carried out detailed investigations at Dolma Sampa. These included subsurface geophysical studies, debris deposition analysis, and flood-level measurements from the 2023 disaster. Despite freezing conditions—temperatures dropped from 0°C in the afternoon to -10°C at night—strong winds, and rugged terrain, the team successfully completed the day's fieldwork.

This study aims to enhance glacial flood modelling, provide crucial insights into subsurface geology, and design effective retention structures to safeguard downstream communities from potential Glacial Lake Outburst Floods (GLOFs).