THE devastation caused by the cyclonic weather will continue for days, with thousands of homes inundated, entire communities isolated and the possibility that Brisbane could run out of drinking water.
Four people have died in the disaster, all in Queensland. A three-year-old boy hit by a falling gum tree while watching floodwaters in Brisbane is the latest victim.
His 34-year-old pregnant mother remained in a critical condition in hospital on Tuesday night with several broken bones and severe head injuries.
Sydney's wild weather
Sydney is experiencing its heaviest rainfall in a decade as wild weather from ex-cyclone Oswald passes through the region.Follow us at http://twitter.com/photosSMH Photo: Anthony Johnson
Meanwhile, 130 patients at Bundaberg Hospital had to be flown to Brisbane by the Australian Defence Force, as the city suffered its worst flood.
Four military helicopters and several civilian ones also performed more than 1000 air rescues, lifting stranded residents off roofs in North Bundaberg.
While the rain eased, the immediate danger did not subside.
Residents of Maclean were ordered to evacuate before waters of the Clarence River peaked in the northern NSW town. ''Remaining in flooded areas is dangerous and may place your life at risk,'' the State Emergency Service warning said.
The latest threat came only hours after the neighbouring town of Grafton narrowly escaped disaster when waters peaked just two centimetres below the town's levee wall.
More than 2000 residents had already been evacuated and another 7000 were put on notice before the raging Clarence River peaked at a record 8.08 metres.
''This is a sight that has never been seen by white man,'' said the mayor of Clarence Valley, Richie Williamson.''The Clarence has never been recorded above 7.9 metres. It's an awesome spectacle.
''On Thursday and Friday we were nearly in drought conditions. Here we are on Tuesday morning talking about the biggest flood on the history books.''
Grafton locals said they were ''pretty used'' to the flood threat but conceded this time the sheer volume of water had residents on alert.
It was a combination of ''good planning'' and a ''fair bit of luck'' that ensured most of Grafton was spared, Mr Fletcher said. ''Now the rain will start to evaporate and we will get stuck with all the lovely-smelling flood mud that Grafton gets,'' he said. ''It will smell like a sewer for the next couple of days.''
Ten local government areas hit by flooding in northern NSW have been declared natural disaster areas, allowing relief funds to flow to assist in recovery.
The joint funding from the state and federal governments will be available in Ballina, Bellingen, Byron, Tweed and Nambucca shires, the Clarence Valley, Coffs Harbour City, Kyogle, Lismore City and Richmond Valley.
An SES spokesman, Phil Campbell, said floodwaters had isolated more than 41,000 people across the state, including 18,000 in the Tweed Valley.
In Queensland, Ipswich and Brisbane escaped widespread destruction when waters peaked at lower than forecast levels. It saved Brisbane up to $100 million on its cleaning bill but the city was at risk of running out of drinking water.
Residents were being urged to adopt water-saving measures after a treatment plant was forced to close because of turbidity caused by the flood.
with The Brisbane Times and AAP