Sydney: Power was cut to Brisbane homes for safety reasons and residents ordered to higher ground as Australia's third-biggest city braced for its worst soaking in living memory.
Flood waters barreling toward the Queensland state capital were set to inundate 9,000 properties - 10 per cent of the city's stock - and a further 30,000 were expected to sustain some damage.
Thousands have fled to evacuation centres ahead of Thursday's expected flood crest, and Queensland Premier Anna Bligh urged residents with space on higher ground to offer shelter to those not so lucky.
"Now is not a time to panic; it's a time for us to stick together," she said as supermarkets were stripped of groceries by frantic shoppers, and motorists caused traffic gridlock as they raced to get out of the city.
Queensland's floods have been a month-long moving disaster, with 10 confirmed deaths and more than 90 unaccounted for as town after town has been hit by flood waters racing to the Pacific Ocean.
Two-thirds of the state is flooded, industry at a standstill and agriculture beset by lost harvests.
The repair bill has been put at five billion Australian dollars ($4.9 billion) and lost production at nine billion Australian dollars.
"This is a very grim situation, and Queensland is going to need us to stand shoulder to shoulder with Queenslanders over months and months and months of recovery," Prime Minister Julia Gillard said.
Brisbane Lord Mayor Campbell Newman urged residents to stay at home, as most commercial life had ceased and public transport was crippled on many routes.
"It's about whether your job's going to be vital to keeping the wheels of this city turning," he said. "If you're doing something that means the supermarket shelves are stacked or the petrol stations get supplied with fuel, please, we need you."
In Ipswich, a commuter town 30 km from the centre of Brisbane, the local supermarket is under 2.5 metres of water. Ipswich city councilor said two petrol stations were awash and fuel was mingling with the flood waters.
"It's total chaos," he said, estimating that the water was rising early Wednesday at a rate of one metre an hour.
Brisbane people spoke of their amazement at the debris - trees, pontoons, yachts, motor boats - being sluiced down the swollen Brisbane River.
"I've never seen anything like it," Charlie Gibbs said. "I'm pretty worried someone's going to end up being killed by it all."
Brisbane's first casualty was a 4-year-old boy who fell from a rescue boat into the torrent.
"If we see these sorts of levels in the Brisbane River we would expect to see somewhere above 9,000 properties affected significantly and more than 30,000 other properties having some impact," Bligh said.