NEW DELHI: A landslide-induced lake outburst triggered a chain reaction among several small lakes, resulting in a massive flash flood that devastated Dharali village in Uttarakhand’s Uttarkashi district on August 5, reveals an internal preliminary report submitted to the Ministry of Home Affairs (MHA).
“There are many small to medium-sized lakes upstream of Dharali village,” said a scientist involved in preparing the report submitted to the MHA on August 14.
The report was prepared in consultation with the Indian Space Research Organisation (ISRO). According to the findings, numerous lakes have formed due to small and mild landslides, covering areas from half a hectare to 10 hectares, particularly over the past three decades as global warming has accelerated the melting of snow.
“Nevertheless, the report does not rule out other contributing factors, such as local landlside, avalanche, small-level glacial lake outburst floods (GLOF) combined with extremely heavy rainfall, which will be detailed in a future report,” said the scientist.
Devastating flash floods, compounded by heavy rains that caused landslides and lake outbursts, buried half of Dharali village, situated 2700 metres above sea level, which had been built on the dried course of the Kheer Ganga water channel. An Army camp situated on the dried riverbed was also washed away. So far, six people have been declared dead, one body was retrieved from sludge, and 69 people are still missing.
The report recommends further puncturing of the lakes formed after the landslides to safely release water and reduce the risk downstream. Based on the recommendation, the Uttarakhand government, in collaboration with the State Disaster Response Force (SDRF), National Disaster Response Force (NDRF), state irrigation department, and Uttarakhand Jal Vidyut Nigam Ltd, successfully punctured Lake Harshil upstream of Dharali village and released water through a newly created channel.
“Over 30 engineers constructed a parallel water channel alongside the existing one to successfully release water from Lake Harshil,” said a bulletin by the Uttarakhand disaster management department.
After the disaster struck Dharali village, it was reported that a massive cloudburst caused flash floods. The government, however, did not confirm whether the floods were caused by a cloudburst, a glacial lake outburst floods, or a combination of factors, including heavy rainfall and landslides. According to IMD data, there is no evidence of a cloudburst as per its definition, which requires 100 mm or more rainfall within an hour over a 10 sqkm area.
