The threat hanging over Nepal: What happens next after the deadly floods?

At least 1,400 people remain missing after a catastrophic flash flood swept through communities along the Nepal-Tibet border, killing at least 472 people across Nepal and Tibet.

Thirty-nine Australians are among those reported missing as rescue efforts continue.

And the danger is not over, experts warn, with another disaster still possible in Nepal despite the difficulty of predicting when, where or how severe it could be.

"This can be the next day, after a couple of days or can be months later, but it is less likely that we will have this scale of flood again," Monash University glacier researcher Levan Tielidze said.

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Scientists have warned the first collapse may also have left the surrounding mountain slopes unstable, with concerns that further sections of ice or rock could break away, while cracks or fractures could develop in already weakened slopes, potentially triggering another landslide or flood.

"The slope seems like it was unstable and it is even unstable today because of this event," Tielidze said.

That uncertainty means authorities will be required to keep a close watch on the landscape, using helicopters, drones and satellite imagery alongside measurements of temperature, precipitation and river levels.

Tielidze said that while another flood on the same scale as the first is less likely, it cannot be ruled out.

The possibility of another flood is adding another layer of danger to an already difficult rescue operation.

The affected region is remote; roads and bridges have been destroyed, and communications have been disrupted.

"Helicopters are the main way to currently access some of those more difficult-to-reach areas," Australian Red Cross executive director of international programs Alex Mathieson said.

But Mathieson said limited helicopter capacity poses a "major challenge" which could force rescuers to prioritise where those resources are sent while accounting for the risk of further flooding.

He said the priority is to mobilise as many people and resources as possible, but local communities are also critical to the response.