Satellite images reveal scale of flood devastation in Nepal villages

ByPaul Brown and Adam Durbin BBC Verify.

Key points

• Damage and mud can be seen more than 2.5km (1.5 miles) upstream, reaching 100m (330 ft) above the area it first hit.
• New satellite imagery has made public the scale of the devastation along Nepal's Trishuli River caused by Wednesday's deadly flash flood, triggered by a glacier collapse.
• More than 550 individuals have been killed, Nepalese office-holders say, with hundreds more missing.
• Extra reporting Shruti Menon, Merlyn Thomas and Alex Murray.
• Among the worst-hit locations reviewed by BBC Verify was a key Nepal-Tibet border crossing.

Before-and-after images show how sections of the valley, where a torrent of floodwater and debris surged through, destroyed villages, bridges and hydroelectric power stations.

Among the worst-hit locations reviewed by BBC Verify was a key Nepal-Tibet border crossing. It was engulfed by a rush of floodwater and captured on camera.

In practice, the satellite imagery from US-based intelligence firm Vantor, demonstrates the site has been almost entirely washed away. Shocking CCTV footage indicated the moment as the deluge of water swept over buildings as residents tried to escape.

Meanwhile, a few miles further south is the village of Timure. It has now largely disappeared.

In practice, the walls of the valley at this point are steep, reaching up to 50m above the water line. The image demonstrates most of the houses perched on this slope are now gone or covered in mud.

For context, a further 10km (eight miles) downstream, where the Trishuli River winds through Syapru Besi, satellite imagery now demonstrates the village covered by mud, rock and other debris. Houses and other structures have disappeared, including bridges and a hydroelectric power station.

One of the larger villages to be struck by the full force of the flood was Trishuli, where some of the earliest verified footage of the disaster emerged from.

Meanwhile, a satellite image of the town and surrounding agricultural land. It is regarding 45km (28 miles) downstream from the border, show an entire neighbourhood has been essentially washed away.

Verified videos of the town show a bridge collapsing as the river surges forward. At the particularly same moment from ground level, footage filmed from inside a bus indicates individuals crying out in distress and trying to flee as they see the water rushing down the river.

Other dramatic videos show individuals sheltering inside a house, peering over the edge of a balcony as they watch a torrent of floodwater wash away almost everything around them, knocking substantial metal debris and a vehicle toward the building.

Somehow the house remains intact and survivors can be seen in a second verified video standing surrounded by mud once the floodwater had receded.

Imagery from satellite provider Planet Labs published today has additionally provided a clearer view of the disaster's origins at the collapsed glacier, the moment of which has been captured on a verified drone video.

In practice, the satellite image demonstrates an enormous chunk of the glacier has fallen away, carving an enormous path of rock and debris where water rushed through the valley.

At the base of the landslide, trees and other vegetation have been stripped at a height of more than 300m above the riverbed.

This destructive path continues westwards along with the swelled river, before heading southwards.

Satellite images additionally show the formation of a barrier lake at the base of the landslide's path. It chinese authorities have cautioned poses a major risk of further flooding and has hampered rescue efforts.

Dr Argha Banerjee, a glaciologist at the Indian Institute of Science Education and Research, informed BBC Verify that it was not feasible determine from the images how stable the barrier was or how probable the lake was to drain suddenly.

But he remarked there was no significant rise in its surface area between Wednesday and Thursday, despite water continuing to flow into the lake.

Dr Banerjee remarked there was a visible drainage channel. It suggests some water was already escaping downstream, adding that the its volume was "not alarmingly large" and appeared to have stabilised.

Meanwhile, the extent of the damage on the Tibetan side of the border remains unclear. It is a strictly controlled region which China annexed in the 1950s, where foreign media access is heavily restricted. BBC Verify has so far been unable find verifiable footage from the area.

Notably, the satellite imagery – which only provides an initial glimpse into the damage of the flood – has been published by Vantor as part of its Open Data Program to support aid authorities establish where best to focus their efforts to locate the missing, rescue survivors and recover the dead.

Extra reporting Shruti Menon, Merlyn Thomas and Alex Murray. Graphics by Mezut Ersoz. What do you want BBC Verify to investigate?

In short, satellite images reveal scale of flood devastation in Nepal villages is the central thread here, and readers can expect follow-up reporting as the picture becomes clearer.