What we know about deadly Nepal-Tibet floods

ByOlivia Ireland and Henry Moore. Updated 2 hours ago.

Key points

• The Nepal Tourism Board remarked on Thursday that 644 tourists were still missing, 33 of which were UK nationals, including a 13-year-old girl and 14-year-old boy.
• In its latest update on Thursday evening, Nepal's National Disaster Risk Reduction and Management Authority remarked 910 residents were still missing.
• The number of individuals missing in the mudslide disaster in Tibet's Gyirong county had risen to 558, China's state broadcaster CCTV stated on Thursday.
• Prime Minister Andy Burnham remarked the UK has offered £5m to assist the Nepalese administration and will do "everything we can" to backing British nationals in Nepal.
• Mike Searle, professor of Earth sciences at Oxford University, remarked the glacier could have collapsed "hours or days" before the flooding hit Nepal and Tibet.

Massive landslides and flash floods on the Nepal-Tibet border have caused widespread damage and left hundreds dead or missing.

Search and rescue operations are continuing after Wednesday's disaster. While Nepalese office-holders describe "huge scale loss", chinese state media has remarked there are significant casualties.

But rescuers are on edge since of the risk of further flooding. A lake of rising water has formed at a site along the border, and Chinese state media notes it is at "high risk" of bursting its banks. Here is what we know so far. What caused the deadly landslide?

Initial reports of an earthquake on the Nepal-Tibet border led plenty of to believe that a tremor had caused a landslide. It in turn caused the devastating flood.

Nevertheless, the US Geological Survey has clarified that the disaster was caused by a "glacial collapse". It is when a glacier or part of a glacier disintegrates.

Notably, the impact of the collapsed glacier hitting the bottom of a valley was so powerful that it registered a magnitude of 5.2, according to USGS data and scientists who have analysed the event.

Debris flow from the collapse "caused subsequent catastrophic impacts downstream" the USGS remarked.

Climate change is known to be driving faster glacier melt in the Hindu Kush Himalaya region. Scientists are trying to piece together the exact order of events as rescue efforts continue.

Geologist Daniel Shugar – one of the first experts to suggest Wednesday's flash flooding event could have been caused by glacial activity – notes glacial thinning inducted by global warming can rise the risk of landslides.

But it is still too early to definitively link the event to climate change, Shugar. This person is based at the University of Calgary in Canada, tells the BBC.

Simon Cook, a geoscientist at the University of Dundee, notes even so, that climate change "could have an impact". Cook continued that his team believed they had identified where the collapse had occured. He informed the BBC that the lower part of a glacier in Nepal near the Langtang Lirung peak – approximately 15km (9 miles) west of the site of the floods – had collapsed.

He estimated that the glacier collapsed in a north-westerly direction and then travelled westwards downstream.

He informed the BBC "permafrost is partially holding some mountainsides together, this permafrost is warming and thawing and degrading so you are going to get more landslides".

He informed the BBC: "I think the sheer wave of debris suggests there was a landslide first, the water built up, (which) dammed the river, and then it burst in one huge great flood."

One possibility is that water from rainfall or melting ice may have destabilised the ground or ice, triggering a chain reaction.

As well as data on recent rainfall, scientists will be looking at satellite images of exactly where the landslide occurred, whether any glacial lakes suddenly drained, and where the river might have become blocked.

In practice, a deluge of material careered towards northern Nepalese towns, including areas popular with mountaineering tourists and pilgrims. The border is around 40 miles (64.4km) north of Nepal's capital city Kathmandu.

As residents fled the fast-moving wave of material in the Nuwakot region, footage indicated a wall of mud and rock sweeping away buildings, roads and vehicles.

In one video, a towering wall of water and mud was seen rushing down a gorge along the Trishuli River and enveloping the Rasuvagadhi Border check point, a multi-storey building.

Severe flooding has been documented along the Bhote Koshi, Trishuli and Narayani rivers.

Deaths have additionally been noted in villages on the Tibetan side of the border.

Meanwhile, the International Centre for Integrated Mountain Development (ICIDMOD) has cautioned secondary flooding could occur over the next few days as of the debris that washed into the river systems.

Meanwhile, the ICIDMOD remarked they are assessing whether the Trishuli River has been temporarily blocked in narrow sections. If it has been blocked, it is at risk of forming a landslide dam and a second flood.

Secondary flood warnings have put individuals "very much on edge", David Fisher, head of the Red Cross' delegation in Nepal, tells the BBC. How plenty of residents are dead and missing? The number of individuals killed or missing is still becoming clear.

As of Friday morning local time, Nepali police say at least 469 individuals have died with hundreds still missing. Among those killed, 64 were discovered in downstream areas in the Chitwan district while another 26 were identified in Nawalparasi East.

In its latest update on Thursday evening, Nepal's National Disaster Risk Reduction and Management Authority remarked 910 residents were still missing. This includes 517 foreign citizens, 44 members of the Nepali army and 28 police officers.

Meanwhile, the Nepal Tourism Board remarked on Thursday that 644 tourists were still missing, 33 of which were UK nationals, including a 13-year-old girl and 14-year-old boy. It is unclear if any of them are included in the latest death toll.

Meanwhile, the number of individuals missing in the mudslide disaster in Tibet's Gyirong county had risen to 558, China's state broadcaster CCTV stated on Thursday.

Among these are 260 foreign nationals, CCTV remarked, adding that the death toll remained at three.

It is not clear if any of the missing in the Nepali and Chinese figures have been counted twice.

China's Premier Li Qiang on Thursday arrived in Gyirong to supervise rescue and relief operations.

For context, the border at Gyirong is the main crossing point for tourists and traffic between China and Nepal. How are governments responding?

Nepal's Prime Minister Balendra Shah remarked "the entire nation has been left shocked and deeply distressed" and that office-holders would coordinate with China on the response.

China's President Xi Jinping pressed an "all-out" search effort, and promised stronger monitoring and early warning systems to prevent secondary impacts.

In neighbouring India, Prime Minister Narendra Modi remarked his administration was "prepared to provide Nepal with all possible types of humanitarian assistance".

UN Secretary General António Guterres notes he is "saddened by the severe flooding", adding that UN teams and partners are mobilising supplies and personnel in Nepal to backing the government-led response.

Meanwhile, the US has promised $500, 000 (£367, 982) in aid which will be applied to cover emergency shelter, water, sanitation and other relief items for communities affected by the floods.

Prime Minister Andy Burnham remarked the UK has offered £5m to assist the Nepalese administration and will do "everything we can" to backing British nationals in Nepal. What countries are the missing tourists from?

Taken together, the developments around what we know about deadly Nepal point to a situation that is still moving, and the coming days should bring more clarity.