Sikkim flash flood: Government closely monitoring South Lhonak Lake

The recent disaster as a result of the overflow of South Lhonak Lake is being closely monitored with the help of different satellite data. 

As per the interpretation of the available images on October 6 2023 at 4.36 p.m., the Department of Science and Technology, Government of Sikkim has preliminarily inferred that there has been a detachment of the side wall (northwest side) of the lateral moraine (rocks and debris) of the South Lhonak Lake, measuring approximately 600m length x 225m height x 150m width from the surface level of the lake. 

As per the data available, the moraine eventually plunged into the lake.

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The detached moraine fell and pushed into the deepest portion of the lake resulting in an overflow of a large volume of water from the outlet, which has led to widening and deepening at the outlet of the lake.

The image also depicts the decrease in the water level of the lake as a large volume of water has spilt over. 

The area of the lake has decreased from 162 ha to 144 ha. However, during this entire sequence of events, it has been observed as per the data available that the main moraine damming the lake, remains in its original position and shape.