Nepal’s Mysterious, Unexplained Floods Leave Devastation Behind
What happens in the mountains is highly unpredictable, but in recent years an unusual number of major disasters have struck the mountainous regions of Nepal, and the causes are still unknown.
Hills and mountains cover about 85% of Nepal’s territory and the country is highly vulnerable to mountain hazards. Nepal’s northern boundary boasts the world’s tallest mountains, including Mount Everest. The region borders China’s Tibetan Autonomous Region (TAR), where Nepal’s major rivers originate and flow down into the Ganga in India.
But when it comes to disasters like floods, the government’s focus is mostly on the southern plains where population density is far greater and the economic damage is high, compared to the sparsely populated and rugged mountain regions.
Little has been done to monitor or mitigate disasters in these mountain areas, despite the growing number of strange flood events in recent years. The fact the region’s rivers originate in TAR has made it even more difficult for researchers and officials to find out the cause and prevent future disasters.
Case I: Mustang’s Winter Flood
December normally brings snow, not floods to Nepal, but this wasn’t the case last year for people in Nepal’s Mustang district. While people were preparing for a harsh winter, a sudden flood on the Dhakmar river wrecked havoc in Ghami village in Upper Mustang — a district bordering Tibet in western Nepal’s Dhaulagiri mountain range. The region falls in the rain shadow area of Annapurna and Dhaulagiri mountains and is known for very low rainfall.
In the floods of 18 December 2016, eight wooden bridges were washed away, houses were damaged, but there were no human casualties, thanks to the harsh winter that had forced the majority of the population in the village to move to a lower altitude.
When you look at Google Maps there isn’t any glacial lake upstream and there wasn’t any rainfall, so it’s hard to say what had exactly triggered the flood in the river. It may be small landslide dam outburst flood or glacial lake outburst flood.Basanta Raj Adhikari, assistant professor from the Centre for Disaster Studies at the Institute of Engineering, Tribhuvan University.
He travelled along the river up to its source in 2007 for research and there wasn’t any glacial lake there then. “We have been asking for time series satellite images from our international research partners to analyse and find out the reality but we haven’t received them yet,” he added.
Case II: Fearsome Floods on the Bhotekoshi
On 5 July 2016 there was a massive flood in the Bhotekoshi river, which originates in TAR and forms a major tributary of the Koshi river. Floods are normal on the Himalayan rivers but the scale of flood in Bhotekoshi last year was unusual even though it was during the monsoon. Some experts believe that the flood was due to a landslide dam outburst in Tibet, though this has not been officially confirmed.
A few days after the event, scientists from the Kathmandu based International Centre for Integrated Mountain Development (ICIMOD) claimed that the flood was due to the landslide dam burst, citing research from China, but no further information has been made public.
Case III: Floods Without Rain on the Seti
On a sunny day in the first week of May in 2012 people were enjoying themselves on the banks of the Seti river, which originates on the slopes of the Annapurna mountain in western Nepal and flows through the Pokhara, Nepal’s most popular tourist city. All of this was swept into disarray as a massive flash flood hit the river. More than 70 people were killed, several villages were swept away, and bridges and schools were destroyed.
Experts proposed several hypotheses of what could have triggered such floods without rain. Some argued heavy rainfall upstream induced a landslide that formed a temporary dam which burst later. Others said rocks and debris brought by an avalanche formed a temporary dam across the river and then was hit by another avalanche resulting the burst of the dam, causing massive flooding. But nobody has yet confirmed the true cause of the flood.
According to a 2011 report by ICIMOD, there have been 10 glacial lake outburst floods recorded since 1935 that originated in TAR and affected areas in Nepal. The cause of half of these floods is still unknown. “In addition to geographical complexity, monitoring mountainous areas is highly expensive. Though we have started to work on some areas like few glacial lakes that are most dangerous (eg: Imja and Tsho Rolpa) in eastern Nepal, a lot needs to be done to cover the country,” said Binod Parajuli.
Nepal has about 3,808 glaciers and 1,466 glacial lakes, out of which 21 glacial lakes are dangerous, at a high risk of bursting, says the DHM. Recent research has shown the area covered by glaciers in Nepal has shrunk by 21% over the last 30 years and the rate of glacier melt is increasing. As a result, the size of the lakes and the volume of water is growing, putting more pressure on fragile areas and increasing the threat of a lake burst.
According to ICIMOD, the glaciers of the Tibetan plateau are retreating at a faster rate than the glaciers of the rugged central Himalayas. However, there hasn’t been any research specifically linking these puzzling mountain disasters in Nepal to climate change.
(This piece was originally published in TheThirdPole.net.It has been edited for length, read the full piece here. )