'Panicked': Nepali migrants reveal scale of destruction

Catastrophic flash floods have torn through towns in Nepal and China, leaving migrants in Australia scrambling to make contact with family.

Thirty-four Australians are missing and at least 162 people have died along the Himalayan border after a wall of mud and rock collapsed into a river on Wednesday.

Rescue efforts to find hundreds more missing are ongoing to minimise loss of life and find those cut off from friends and family.

Members of the Australian Nepali community are anxiously awaiting news from back home.

Nepali migrant Kiran Thapa, 46, was working from his Sydney office on Wednesday afternoon when his wife called with news of the disaster.

They immediately set to work getting in touch with family in the flood-hit Nuwakot District, along the Trishuli River, badly damaged by flooding.

“I was so panicked,” Mr Thapa told AAP, recalling the phone call.

His family has since been found, having relocated to higher ground, clear of the muddy waters that inundated their homes, including his own.

But his nephew’s two daughters, aged nine and seven, remain trapped in a town across the river, sheltering in their school.

“All the bridges (have) collapsed, so there’s no way of getting there,” he said.

“They’re being taken care of ... but still we cannot come and bring them on this side because the only way to get them back is by helicopter.”

It’s an experience shared by many across Australia, including Melbourne-based Shyam Rana, who spent the night speaking with family in Nepal.

Scenes on the ground are chaotic, making rescue operations and communication difficult if not impossible, he said.

“I’ve heard it’s hard to get any rescue emergency vehicles into the area because of the land,” Mr Rama said.

“It’s hard to land helicopters and it’s hard to get the cars, trucks and army vehicles into there.”

He is yet to hear from extended family near the affected region.

The cost of the disaster, the deadliest to hit Nepal since a 2015 earthquake killed almost 9000 people, is not yet clear.

But Mr Thapa has already begun to worry about what life may look like in the days ahead, fearing his family, including his 83-year-old mother, could be stranded for weeks.

The paddy fields they rely on for food have been ruined while Mr Thapa fears it might be weeks before authorities shift their efforts from rescuing to rebuilding.

“At the moment they are all in a defensive mode, but after a few weeks or so, when they come to the realisation that they’ve lost everything ... that may be very hard for them to digest,” he said.