Flash flooding which swept away an entire village in Nepal originated with a minor rockslide, scientists said Tuesday, warning that the disaster could be repeated.
More than 70 people are believed to have died when the Seti River burst its banks on May 5, 2012 and hit Kharapani—a village in the central Annapurna region with a population of just 100.
A team of Nepalese and US scientists investigating the cause of the flood said that a "comparatively small" rockslide had dammed an upstream gorge, forming a reservoir over several weeks.
This reservoir was then hit by a large avalanche from the Annapurna IV peak. The research team found that the impact of the avalanche had overfilled the reservoir and had "caused such stress as to break the rockslide dam. The huge outburst flood resulted."
Satellite images had shown that there had been rockslides between 2003 and 2008 with a 'significant reactivation' weeks before the disaster, they said.
The scientists, from the Nepalese government and the University of Arizona, recommended research into an early-warning system and warned villagers to be vigilant.
They cited the area's "unique" geography as a potential danger as its deep, marble gorges cause rivers to "cut directly downward like a hot knife slicing through a stick of butter".
Their report followed an expedition they had made to the region earlier in the month.
The village of Kharapani stood in the shadow of Mount Annapurna, one of Nepal's most popular tourist destinations.
The fast-flowing floodwaters smashed into two buildings and a number of shacks, as well as swamping families enjoying picnics.
Although there was never any official death toll, 23 bodies were recovered and around 50 people remain missing, including three Ukrainian tourists.
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