At least 580 people have died and more than 2000 are missing, including 38 Australians, after a landslide of ice and rock burst the banks of the Trishuli River on Wednesday.
Chinese and Nepalese authorities have warned further flooding may occur, complicating rescue efforts and posing a risk to communities in the area.
Several Australians with family in the affected region have flown to assist the search for survivors, combing towns impacted by debris and torrents of mud.
Among them is the husband of NSW mother-of-two Reshma Patel, who was due to touch down in Kathmandu on Friday evening.
Like the majority of the 38 Australians confirmed missing, down from 39 on Friday after one person made contact with family, Ms Patel was making a pilgrimage with a tour group when the floods began.
Her last known location was an immigration office along the Nepal-Tibet border, which was captured on viral footage being inundated by floodwaters.
"She was inside the big building, which you can see in all the videos that had been hit hard by the floods at the border," family friend Chin Valsan told AAP.
"After that, there is no contact whatsoever."
Ms Patel had been travelling with the Isha Foundation for almost two weeks, and was due to catch a flight home to Sydney from Kathmandu on Thursday.
"That hasn't happened," Mr Valsan said.
While search and rescue operations, aided by Australian officials, are ongoing, charities have banded together to launch a national aid appeal.
The Nepal Flood Disaster Appeal was established by a coalition of 15 Australian charities including Oxfam Australia and Save the Children Australia.
The group, known as the Emergency Action Alliance, has warned survivors may find themselves cut off from reliable shelter, food, drinking water and medical care.
It is a fear shared by Kiran Thapa, 46, who told AAP his family in Nepal had survived the floods, but the real "trauma" would come once the dust had settled.
The paddy fields his family relies on for food had been destroyed while he worried his elderly mother may not have access to medication for weeks.
"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.
Foreign Minister Penny Wong unveiled a $5 million assistance package for communities affected by the floods, including $1 million to the Emergency Action Alliance.
The Australian Red Cross has announced all donations to its global emergency fund from Thursday would go to Nepal, while World Vision Australia has launched its own dedicated appeal.
UNICEF is appealing for US$17.2 million to fund its emergency relief and recovery efforts, including for the 17,000 children it estimates have been affected.
"With the death toll still rising, we know this tragedy is far from over," Alice Akunga, UNICEF's Nepal representative, said.
Impacting recovery efforts are fears of possible further flooding, which temporarily halted a Chinese rescue operation on Friday, according to state media.
Smartraveller updated its travel advice on Friday following reports of a lake barrier bursting, warning of a "high risk" of further severe flooding, landslides and debris flows.
"Conditions can change rapidly with little warning," the advice reads.
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