Nepal tunnel traps hinder flood rescue: How many are dead or missing?

Rescue teams in Nepal continue to search for thousands of missing people, five days after devastating flash floods that have left the Himalayan nation grappling with a major humanitarian crisis.Several hundred of those missing are believed to be trapped in tunnels swamped by debris from the floods, which started in Tibet and were triggered by a glacial collapse last week. More than 900 people have died, and nearly 5,000 people are missing across Nepal and Tibet.Here’s what we know about the latest rescue efforts to recover the people missing due to the floods.What caused the Nepal-Tibet flash flood?A glacier collapse sent a catastrophic flood roaring through Tibet and parts of Nepal on August 26.A glacial collapse refers to when a large mass of glacier ice detaches from its bed. This sometimes involves millions of cubic metres of ice, rock and water, which can transform into a highly mobile ice-rich avalanche or debris flow.Scientists believe part of a glacier near the Langtang Lirung peak had collapsed. The glacier, roughly 5,200 metres high in the Himalayas, plunged about 1,200 metres and collected rock and debris before slamming into the Lende River. The resulting surge swept so...