Investigation of Glacial Lakes in Proximity to Failed South Lhonak Lake: A Glacio-Centric Approach to Disaster Risk Assessment

The melting of glaciers in the Himalayan region is connected to the formation and expansion of proglacial lakes. The proliferation of these lakes heightens the risk of glacial lake outburst floods (GLOFs). This study employs geospatial techniques to investigate the glacial systems (glacial bodies and connected glacial lakes) near the South Lhonak glacial system. Using Corona and Landsat datasets spanning from 1967 to 2023, substantial increases in the size of the South Lhonak Glacial Lakes (SLGL) and North Lhonak Glacial Lake (NLGL) are observed. SLGL and NLGL exhibit glaciological and morphological similarities akin to sister glacial lakes. Notably, SLGL receives input from NLGL through a narrow stream, leading to a more rapid increase in its size. Similar characteristics are found in Longbasaba Glacial Lake (LGL) and Kaer Glacial Lake (KGL) in the Nepal Himalayas, categorizing them as sister lakes. Principal Component Analysis is employed to determine the mean albedo of glacial bodies since 1989, with higher glacial debris and a lower mean albedo identified in the South Lhonak glacier. The study also reveals the internal moraine wall's failure in the KGL embankment, indicating the potential instability of naturally deposited moraine embankments and the risk of future hazards. Lastly, a social vulnerability assessment for the Sikkim GLOF on 4
^th
October 2023 is conducted, and a Vulnerability Scoping Diagram (VSD) is developed to prioritize resources and enhance disaster response efforts.