Geological experts explained the formation of a temporary lake in the Bhagirathi River following the recent flash floods in Uttarkashi's Dharali village, which subsequently caused large-scale damage to the neighboring Harshil town. At present, manual efforts are being made to puncture the lake, facilitating the controlled and phased outflow of water to prevent flooding downstream.
Prior to this, the team conducted a geological inspection of the disaster-affected areas, during which they saw a local stream named Telgad in Harshil near the Indian Army camp become active due to heavy rainfall during the August 5 disaster. The camp bore the brunt of the disaster, which demolished structures besides leaving nine of its personnel missing, including a junior commissioned officer (JCO) and eight jawans.
A large amount of debris and water came and accumulated in the stream at its point of confluence with the Bhagirathi River and formed a large fan-shaped deposit (alluvial fan) of sediments, the team of experts said. This fan obstructed the original channel of the Bhagirathi River and formed a temporary lake on the right bank of the river.
The length of the newly formed lake was about 1,500 metres, and its estimated depth was 12 to 15 feet. The flooding not only submerged a portion of the national highway and a helipad, but also posed a serious threat to Harshil town.
This event also significantly altered the topography of the Bhagirathi River, as the sand dune located on the right bank was eroded, while fresh sediment was deposited on the left side, exposing the northern part of the town. The continued bedrock erosion in this area had already caused partial structural damage to the camp, including the loss of a portion of the Garhwal Mandal Vikas Nigam Guest House.
Inspection by the geological team on August 12 revealed that the left bank of the Bhagirathi River was blocked by a saturated alluvial fan. Due to its high moisture content, the fan was weak, which prevented heavy machinery such as JCBs from being deployed — the only equipment available locally.
Based on the field data and available resources, the geologists prepared a plan for debris clearance and partial restoration of water flow. The plan involved creating small diversion channels of about 9-12 inches deep to gradually release the stagnant water.
During discussions with Uttarkashi District Magistrate Prashant Arya and Inspector General (SDRF) Arun Mohan Joshi, it was emphasised that the lake outflow channels should be opened in three or four stages to avoid sudden flooding downstream.
Work was immediately started by the State Disaster Response Force (SDRF) and the Irrigation Department, Uttarkashi. Through careful execution of the plan on two successive days, the teams engaged in the exercise were able to facilitate controlled water drainage from the lake.
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