Drones helped find people after Nepal floods but the search inside hydropower tunnels is a challenge

KATHMANDU, Nepal (AP) — Drone pilot Manish Maharjan has helped rescue teams in Nepal find people missing after last week’s catastrophic floods, sometimes using speakers mounted on the devices to call out to or play music for those stranded on hillsides.

But the search for hundreds of workers believed to be trapped in power plant tunnels — now a major focus of rescue operations — presents an entirely different challenge, he said.

“We found tunnels were filled with mud like toothpaste in a tube,” Maharjan said. “There was no hollow or empty space inside.”

Maharjan, who is also a filmmaker, joined the Nepal Army’s rescue efforts a day after the Aug. 26 flash floods, which have killed more than 1,000 people and left thousands missing in Nepal and Tibet.

“We used microphone speakers to call out to them. In some places, we even played songs and then waited for a response,” Maharjan said. “That worked in a few cases and helped us locate people.”

The torrent of water unleashed after a glacial collapse caused widespread damage to critical infrastructure, including roads, buildings, bridges and hydropower plants — in the latest sign of the growing risks across the rapidly warming Himalayas. At least 900 workers are still missing from 12 hydropower projects buried under mud and debris. About 500 of them are believed to be trapped inside power plant tunnels.

Some workers in the tunnels managed to call for help when the disaster struck, according to Mohan Kumar Dangi, president of the Independent Power Producers’ Association. But it was unclear whether rescuers have had any contact with the trapped workers since the initial calls for help.

As time slips away, rescuers are finding it increasingly difficult to locate these missing people.

Maharjan, who has been operating thermal drones in the tunnels, said the searches were challenging because of their difficult access and the absence of any empty space.

“I can only fly drones in tunnels that are long and straight,” he said. “Once there are bends, turns or zigzags, it becomes much harder to operate and search effectively.”

At the Rasuwagadhi hydropower project on Monday, Maharjan managed to send a drone to search deep inside and all the way to the end of the tunnel but found no sign of any life.

“We checked repeatedly but it was filled with mud and debris,” he said. “Looking at it, I could only imagine the force of the flood.”

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Hussain reported from New Delhi.