Survivors of flash flooding on the Tibet-Nepal border could only cling to trees as they watched loved ones swept away in the chaos.More than 160 people are known to be dead, and at least 1,500 people including tourists and hikers are missing, according to Nepal and China's Tibet authorities.On Thursday, Prime Minister Anthony Albanese confirmed at least 34 Australians were unaccounted for.The deluge washed away homes, flooded cars in mud and engulfed entire villages in water.One of the survivors, 68-year old Keshav Prasad Baral, described the flooding as a huge gush of mud coming straight toward him."As it got closer, it kept rising higher and higher," he said."When I saw it enter our home, I tried to grab my wife's hand and take her to the terrace. But she was swept away by the mud.""My wife is still somewhere beneath the mud. She's gone."Rescuers use earthmovers to reach submerged houses after flash flooding along the Trishuli River in Nepal's Nuwakot district. (AP: Niranjan Shrestha)Tula Bahadur BK, a healthcare worker, said everywhere she looked there was devastation."The settlements next to the river have been completely swept away," she said."Five of my own relatives are missing."The rescue operationAmong the missing are 800 foreign nationals from more than two dozen countries.So far, these include: 177 people from India, 63 from the United States, 33 from Britain and 25 from Canada.A policeman with a sniffer dog looks at the damage in the aftermath of flash floods in Devighat in the Nuwakot district in Nepal. (AP: Niranjan Shrestha)Nepalese police have said they expect the death toll to rise in the coming days."This will go up, as we have resumed the search and more bodies are expected to be recovered," police spokesperson Abi Narayan Kafle said.There at least 826 people missing in Nepal, according to Nepalese authorities.Survivors rescued from flash flooding depart a Nepalese army helicopter at a safer location in Nepal's Nuwakot district. (AP: Niranjan Shrestha)There were also 558 people missing in Tibet's Gyirong county, including 260 foreign nationals, according to Chinese state TV.To aid the search, emergency services in Nepal have used helicopters to locate missing people, and drop supplies to thousands who have been cut off by the floods.The floods swept through communities along the Bhote Koshi and Trishuli rivers in Nepal and Tibet, destroying homes, roads and bridges. (Getty Images: Skanda Gautam/SOPA Images/LightRocket)Authorities also used bulldozers to rescue people from buildings that were damaged along the Trishuli River.One elderly woman who was rescued by bulldozer was later carried to safety clinging with both hands onto one of the first responders.This was not the first time the region has been hit by flash flooding.Last August nine people were killed when a glacial lake in Tibet overflowed due to high temperatures, and critical infrastructure including a bridge connecting Nepal and China was damaged.People walk past damage in the aftermath of flash floods in Devighat in the Nuwakot district in Nepal. (AP: Niranjan Shrestha)But the death toll was already higher, and some residents such as Shoyam Rajbhandar fear it will grow."When I reached Dhunge bazaar, in half an hour, the flood came and damaged all the market. People were preparing to go to office then," Mr Rajbhandari said."How many people are missing or dead, we don't know."ABC/Wires