Nepal flood disaster: Himalayan wall of water leaves 160 dead and hundreds missing

A disaster with almost no warning

A wall of water, mud and rock tore through communities along the Nepal-China border, killing at least 160 people and leaving hundreds more missing in one of the Himalayan region's most devastating disasters in years.

The torrents swept through villages, roads and border communities on Wednesday, carrying away buildings, vehicles, bridges and anything else in their path.

Survivors described having almost no time to escape.

In some places, the water rose with terrifying speed, turning normally busy communities into scenes of mud, wreckage and shattered infrastructure within minutes.

Tourists and pilgrims caught in the catastrophe

The disaster has also become an international tragedy.

Nepal's Tourism Board reported hundreds of people missing, including 341 foreign nationals in its preliminary figures. Among those unaccounted for were 133 Indians travelling towards the sacred Mount Kailash pilgrimage route, 47 Americans, 34 Australians, 33 Britons and 24 Canadians.

Many had been travelling through the region on trekking or pilgrimage journeys when the disaster struck.

Mount Kailash, across the border in Tibet, is one of the world's most important Hindu pilgrimage destinations, and the Nepalese valleys provide a major route for travellers heading towards it.

The numbers remain fluid, however, with officials warning that communications remain badly disrupted and that many people in isolated mountain areas have yet to be accounted for.

The terrifying moment the flood arrived

Video from the border area shows the extraordinary force of the disaster.

A seemingly ordinary scene suddenly becomes a torrent as an enormous surge of water and debris crashes through the area, forcing people to run for their lives.

Other images show vehicles buried beneath mud, buildings damaged or partially submerged and roads transformed into rivers of sludge.

In Nepal's Nuwakot district, rescuers were forced to work through thick debris while trying to reach survivors.

The scale of destruction is such that authorities are still struggling to establish how many people have been swept away.

It was not simply a monsoon flood

Perhaps the most extraordinary part of the disaster is what appears to have caused it.

Initial reports suggested that an earthquake had triggered a landslide which blocked a river and sent a huge wave downstream.

But the US Geological Survey later revised its assessment.

The seismic signal originally interpreted as a magnitude 4.4 earthquake was instead identified as the signature of a massive glacial collapse.

Experts say the collapse sent enormous quantities of ice, rock, mud and water cascading into the river system, producing the extraordinary speed and volume of the flood.

The International Centre for Integrated Mountain Development also said an avalanche from a glacier was likely responsible, noting that the Trishuli River rose by as much as nine metres in just half an hour.

Entire communities cut off

The destruction has crippled transport through the mountain valleys.

At least 19 bridges and almost 40 kilometres of roads were swept away, while hydropower projects and villages were also badly damaged.

That presents rescuers with a huge problem.

The same terrain that makes the Himalayas spectacular also makes emergency operations extraordinarily difficult. Roads can disappear overnight, communications fail and helicopters are often the only way to reach isolated communities.

Three army helicopters attempting to reach the disaster zone were forced to turn back because of bad weather, according to Nepal's Tourism Board.

Foreign governments search for their citizens

Governments around the world are now trying to establish whether their citizens are among those missing.

The United States said it was closely monitoring the situation after Americans were reported missing. ABC News reported that at least three missing Americans had been travelling with a Nepalese tour company.

South Korea, Malaysia and other countries have also reported citizens or travellers unaccounted for in the affected region.

India has offered assistance, while international organisations are preparing to help with what the United Nations described as a potentially massive humanitarian need.

A warning from a warming Himalayas

The disaster is also raising uncomfortable questions about the growing instability of the Himalayan environment.

Glaciers across the region are retreating as temperatures rise, while unstable ice and glacial lakes can create enormous hazards for communities living downstream.

The latest catastrophe shows how quickly conditions can change.

A mountain landscape that appears completely stable can suddenly release a wall of ice, rock and water powerful enough to destroy roads, bridges and entire communities within minutes.

And with hundreds still missing, Nepal's disaster may be far from fully counted.

The search for survivors is continuing — but rescuers are now racing against time, weather and the possibility that the final death toll could be considerably higher.

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