Glacial lake outburst caused Sikkim flashfloods

Kolkata: Three days after the devastating Sikkim flash flood, the state government, using satellite data, identified that a detachment of one of the side walls of the moraine at Lhonak Lake had caused the overflow of water leading to the disaster. The lake's water level and size decreased later, it was found.

The Sikkim government said in a statement on Saturday, "The recent disaster as a result of overflow of South Lhonak Lake is being closely monitored with the help of different satellite data. As per the interpretation of the available images (Sentinel 2: 6" October 2023, 4.36 pm), the Department of Science and Technology, Government of Sikkim has preliminarily inferred that there has been a detachment of the side wall (north west 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."

It pointed out, "As per the data available, the moraine eventually plunged into the lake. The detached moraine fell and pushed into the deepest portion of the lake resulting in overflow of large volume of water from the outlet, which has led to widening and deepening at the outlet of the lake."

The statement added, "The image also depicts the decrease in water level of the lake as large volume of water has spilled 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."

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