Geological Experts Explain Temporary Lake Formation in Bhagirathi River Following Dharali Disaster

A geological team has clarified how a temporary lake formed in the Bhagirathi River after flash floods in Uttarkashi's Dharali village. Efforts are ongoing to manage water outflow to prevent downstream flooding.

A geological team has explained the formation of a temporary lake in the Bhagirathi River after flash floods hit Uttarkashi's Dharali village. The floods also caused extensive damage to Harshil town. Efforts are ongoing to manually puncture the lake, allowing water to flow out gradually and prevent downstream flooding. The team inspected the affected areas, assessing potential dangers and rescue measures, according to an official release.

The disaster on August 5 activated a local stream named Telgad near an Army camp in Harshil due to heavy rain. This resulted in one death and 68 missing persons, as reported by the administration. The camp suffered significant damage, with nine personnel missing, including a junior commissioned officer and eight jawans. Debris and water accumulated at the stream's confluence with the Bhagirathi River, forming a large alluvial fan of sediments.

Temporary Lake Formation

This sediment fan obstructed the Bhagirathi River's original channel, creating a temporary lake on its right bank. The newly formed lake measured about 1,500 metres in length and had an estimated depth of 12 to 15 feet. The flooding submerged part of the national highway and a helipad, posing a serious threat to Harshil town.

The event significantly altered the Bhagirathi River's topography. Sand dunes on the right bank eroded while new sediment deposited on the left side exposed Harshil's northern part. Continued erosion in this area partially damaged structures at the camp, including part of the Garhwal Mandal Vikas Nigam Guest House.

Challenges in Debris Clearance

On August 12, geological inspections revealed that a saturated alluvial fan blocked the Bhagirathi River's left bank. Due to its high moisture content, this fan was weak, preventing heavy machinery like JCBs from being used — these were the only available equipment locally. Geologists devised a plan for debris clearance and partial water flow restoration based on field data and resources.

The plan involved creating small diversion channels about 9-12 inches deep to gradually release stagnant water. Discussions with Uttarkashi District Magistrate Prashant Arya and Inspector General SDRF Arun Mohan Joshi highlighted that lake outflow channels should open in stages to avoid sudden downstream flooding.

Controlled Water Drainage Efforts

The State Disaster Response Force (SDRF) and Uttarkashi's Irrigation Department immediately began work. Through careful execution over two days, teams facilitated controlled water drainage from the lake. This phased approach aimed to mitigate further risks while restoring some normalcy to affected areas.

Efforts continue as authorities work towards stabilising conditions in Uttarkashi following this natural disaster. The focus remains on ensuring safety and preventing additional damage through strategic interventions and ongoing monitoring.

With inputs from PTI