Emergency crews spent Monday afternoon on rescue missions for people isolated by floodwaters that have reached record heights in parts of Queensland.
The widespread disaster, triggered by heavy rainfall and wind from ex-tropical cyclone Oswald, comes two years after floods devastated much of the same areas of the state, resulting in 35 deaths.
Queensland Premier Campbell Newman has attempted to reassure residents of the affected areas that the overall flooding won't be as severe as in 2011, but concedes locally flooding is worse in some parts of the state.
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In the worst affected city of Bundaberg in central Queensland, 14 aircraft were called upon to rescue 1500 stranded residents as authorities issued mandatory evacuation orders.
Mr Newman said floodwaters moving at more than 70km/h in Bundaberg had the potential to wash away houses.
But with the disaster affecting most of central and southeast Queensland, he said the government had to be careful where it
placed emergency resources.
"Once again, sadly Queensland is facing a major disaster crisis," the premier told reporters in Brisbane.
"(But) this state and its people will rise to the challenge. Together we will get through this."
The disaster has already claimed three lives in Queensland: a motorcyclist whose body was pulled from a creek south of Brisbane, an 81-year-old man whose body was found near Bundaberg, and a 27-year-old man who tried to cross a flooded creek near Gympie.
Both Queensland Treasurer Tim Nicholls and his federal counterpart Wayne Swan have said the disaster will impact budget bottom lines.
"(The damage is) obviously going to be in the tens, and more likely the hundreds of millions of dollars," Mr Nicholls told AAP.
"The damage is going to be as diverse as local schools and local community halls to major infrastructure."
The Insurance Council of Australia says $43 million worth of claims had already been lodged in Queensland since Saturday.
The extent of ex-tropical cyclone Oswald's wrath will not be known for some time, with rivers like the Fitzroy in Rockhampton not expected to peak for days, as water continues to flow from catchment areas upstream.
In Brisbane, a disaster declaration was made late Monday ahead of the flood's expected peak at noon on Tuesday.
NSW has also been preparing for the flood threat and cities, including Sydney, have been issued with weather warnings.
About 2000 people have been cut off in the state's north and flood warnings are in place for seven NSW river systems.
In north Queensland, the storm still made its presence known, causing telecommunications to be knocked out for most of the day, leaving residents without mobile reception and working ATMs.
Prime Minister Julia Gillard said the disaster was heartbreaking so soon after the deadly 2011 floods.
"Across Queensland the wild weather has broken a lot of hearts.
It's a very tough period," she said, and repeated promises of federal help as the state recovers.
Mr Newman also set up the Queensland Flood Appeal on Monday, kicking it off with a $1 million state government donation.
