Dozens of towns braced for unprecedented river levels in Victoria state, where 14,000 homes were waterlogged and 3,500 people had fled, days after the flooding emergency peaked in northeastern Queensland.
Homes were swamped to waist height as waters swept through the southeast, levelling fences and trees and tearing up roads.
"It's shocking, devastating, heart wrenching," said Charlton resident Peter Gretgrix. "It's just total devastation, some of the shops in the lowish area are just a mess, windows smashed out, it's terrible."
"I've never seen anything like it, (and) I'm 57," he added.
Devastated by the worst wildfires in Australia's history just two years ago which killed 173 people, parts of Victoria were now facing once-in-a-century flooding, with some towns having never experienced such inundation.
Soldiers were helping people evacuate from their homes while desperate sandbagging was under way in a number of towns, where a season's worth of rain had fallen in just one or two days.
"We are facing an unprecedented flood event on the Campaspe river," said emergency spokesman Lachlan Quick. "Water volumes of this size have never been seen down this river before."
Flooding also swept through the island state of Tasmania, washing away bridges and forcing hundreds of evacuations.
It follows a six-week crisis in Queensland, where floodwaters swallowed an area the size of France and Germany combined, culminating in the swamping last week of Brisbane, Australia's third largest city, and utter devastation of towns to the west.
Experts have linked Australia's downpours to an especially strong La Nina weather pattern bringing cooler water temperatures and exacerbating the traditional tropical cyclone season. Five of the nation's seven states and territories have seen flooding since January 1.
Queensland state Premier Anna Bligh said the death toll had climbed to 17 since January 10, with the discovery of a woman's body in a house in the worst-hit Lockyer Valley, west of Brisbane, where a wall of water virtually razed towns.
The Grantham house was so wrecked Bligh said police found the woman's body on only their third search of the ruins. Debris is piled three metres high, three metres wide and 100 metres long in the shattered town.
Residents gathered at the Murphy's Creek pub, one of few buildings still standing, to mourn the dead and pray for 14 people still missing -- the first chance for many in the tight-knit community to grieve with neighbours and friends.
"There are going to be neighbours that don't return home after this aftermath, families that don't return, there's going to be empty desks at schools," said local MP Scott Buchholz. "Words really cannot express what the people of the Lockyer Valley are feeling at the moment."
Soldiers and police combed through buildings and fields in the search for bodies in the Lockyer Valley, where shipping containers were to provide temporary shelter for those whose homes were swept away.
As waters receded in Queensland, Bligh said the full scale of destruction was emerging, with the number of flooded homes and evacuations doubling in the past week and the number of properties affected by the waters trebling across an area with a population of 2.1 million.
She warned people to stay out of floodwaters where possible, describing them as a "toxic" soup of rotting animal corpses and food, chemicals and debris.
Treasurer Wayne Swan toured the ravaged Brisbane suburb of Rocklea with friends hit by the disaster as the federal and Queensland governments pledged Aus$10 million ($9.86 million) each to the relief fund, which has now raised more than Aus$84 million.
"In terms of cost it's far too early to evaluate," Swan told AFP of the damage bill.
Tennis stars including Roger Federer and Rafael Nadal drew sellout crowds to a "Rally for Relief" fundraiser for flood victims in Melbourne on Sunday, with a cricket charity day and major concerts also planned.