Vigorous rainfall, lake breach behind tragedy

Heavy monsoon rainfall and a glacial lake outburst flood (GLOF) that caused severe flooding downstream that's the cause of the human-aided natural disaster in Sikkim that washed away part of the Teesta 3 dam - damaged parts of Teesta 5, wrecked bridges and drowned roads.

- Jayashree Nandi

It was not immediately clear as to what may have triggered the GLOF on Lhonak lake in northwest Sikkim, although this is a risk that has loomed large for at least a decade. "As the GLOF occurred at around Iam (on October 4) on Lhonak lake, a lot of boulders, debris and water came downstream, flooding Teesta. There is no rainfall data available for this remote region from the India Meteorological Department (IMD). Som Swiss ient have also suggested that an earthquake yesterday may have triggered the GLOF. We are trying to assess possible triggers," said a senior official of the Central Water Commission (CWC).

A GLOF is caused when the moraine (the debris accumulated over the years by a glacier) that usually functions as a dam, creating a lake, is breached.

"The moraine dam of the lake may have been breached. That's the understanding," the official added. Parts of northeastern India were jolted by an earthquake on Monday, and parts of northern India, by another on Tuesday.