A week after a high-altitude collapse of rock and glacial ice sent water and debris surging across the Nepal-Tibet border region, scientists are closely watching the affected Himalayan valley for signs of further danger.

Experts warn that while the initial torrent has passed, it has left behind weakened terrain and huge amounts of mud and rock that could be set in motion again by monsoon rains.

Maximillian Van Wyk de Vries, assistant professor in natural hazards at the University of Cambridge, described the disaster as a “multi-hazard cascade” – where one hazard triggers another in a chain of events.

“This was a landslide of rock and ice that then cascaded and triggered this massive flood that caused so much damage. And we know there have been secondary landslides that have been triggered by it,” he said.

Van Wyk de Vries told CNA’s Asia First on Wednesday (Sep 2) that scientists are closely monitoring both the source of the original collapse and the valley downstream for potential hazards.

“There's the possibility of future collapses around the source area that's been weakened. But also all the way down this valley, it's coated in several meters of mud and rock, all of which, if there's heavy rain, can be picked up again and become a new flood.”

Satellite imagery is helping scientists track changes across the difficult terrain, but there are limits to what can be detected.

Van Wyk de Vries said ground-based data is being incorporated into satellite data sets, with satellite monitoring able to detect some landslides that show warning signs such as cracks on a hillslope or early movement.

He said that researchers were seeing some early indications that the area involved in the glacial collapse may have displayed such signals.

But other landslides can occur without warning signs visible from satellites, with scientists instead havin...