What we know about the environmental causes behind the Nepal landslide

Deadly floods along the Nepal-Tibet border on Wednesday highlighted the near-impossible task of predicting sudden landslides and mudflows in the Himalayas. Experts say the terrain can turn a blocked river into a devastating torrent within minutes, while climate change may be increasing the risks of such disasters.

By: FRANCE 24 Lethal surges of mud and water that hit "like liquid concrete" are nearly impossible to predict and cannot be outrun.

The cause of the deadly landslide and flood along the Nepal-Tibet border is not yet certain, but experts say the risk of such events is compounded by the extreme topography of the Himalayas.

At least 160 people were killed and hundreds are missing in the wake of the disaster on Wednesday morning.

Video from the Chinese side shows a raging wall of mud and debris crashing over a building several storeys high, engulfing it and sweeping away buses and cars as if they were toys.

It is too soon to draw any firm links to climate change, but there are well-documented trends in the "Roof of the World" that have increased the likelihood of such hazards.

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Nepal's Foreign Minister Shishir Khanal said an earthquake likely triggered a landslide that in turn blocked a river, sending water gushing downstream after it eventually breached the obstruction.

But in a new note, the US Geological Survey said that while the event was initially reported as a magnitude 4.4 earthquake, "additional analysis of long period seismic waves indicate that the seismic energy was instead generated by a landslide".

A preliminary assessment by the Kathmandu-based International Centre for Integrated Mountain Development (ICIMOD) found "no anomalies" from the Chinese side of the border.

"We believe a rock-ice avalanche occurred in Nepal, blocking the Lhende river and causing the cascading flood event," Sarthak Shrestha, a remote sensing and geo-information analyst with the intergovernmental institute, told AFP.

Hatim Sharif, a hydrologist at the University of Texas San Antonio, told AFP one thing that struck him was the lack of rainfall beforehand.

"That defeats essentially every operational flood warning system in the world," he said.

"Running will not help", nor will trying to flee by vehicle, Sharif added, because the mud and water moving at high speed form a lethal combination "like liquid concrete".

The only solution is to climb up a hill, at least 20 feet (six metres), he estimates.

One possible long-term remedy might be river-level gauges that relay changes to authorities in real time, giving residents 20-30 minutes of warning, he said.