Authorities urged thousands of residents to leave the outskirts of Australia's third-largest city today as others sandbagged homes and stockpiled food in anticipation of rising floodwaters and more heavy rain.
Ten people died overnight, with cars and pedestrians swept away in a "super storm" that sent water raging through the streets of Toowoomba, west of Brisbane. More than 40 people were pulled from rooftops by helicopters but 78 were missing.
The worst flooding in Queensland state in 50 years has killed 14 people in the past two weeks, but police warn the death toll could rise significantly, fearing many people may have drowned trapped in submerged cars and homes.
A flight in a small plane over the area around Brisbane revealed a waterlogged landscape with houses marooned in vast muddy lakes, mine sites and factories engulfed, as well as roads severed by streaming torrents.
The streets of Brisbane were largely deserted by Tuesday evening, with 80 suburbs set to be flooded ahead of the crest of the swollen Brisbane River, expected on Thursday.
Families had moved to evacuation centres in Brisbane and neighbouring Ipswich, where a third of the town was expected to be submerged as water levels reach a peak overnight.
Teleah Morrisson (19) said she had gone to a shelter with a few possessions after water had been lapping at her apartment in the South Bank area of Brisbane.
"It was coming over the board walk, only 30 to 40 metres away," added Morrison, who works at a fast food outlet.
About 1,500 people were sheltering in centres as waters spilled from 16 Queensland dams. A further four dams, including Brisbane's big Wivenhoe Dam, released huge quantities of water, adding to the surge.
Police said 9,000 homes in Brisbane would be flooded by Thursday and 30,000 properties would suffer some inundation.
"The situation has obviously demonstrably deteriorated," Brisbane Mayor Campbell Newman told a news conference. "Today is very significant, tomorrow is bad, and Thursday is going to be devastating for the residents and businesses affected."
The floods have at times covered an area bigger than France and Germany combined and caused an estimated $6 billion in damage, inundating 70 towns, some twice in recent weeks.
The floods have brought the state's $25 billion coking coal export industry to a virtual standstill, hit tourism and devastated agriculture.
The floods will also hit economic growth this year, heighten inflation as food prices rise and dampen retail spending. They are also forecast to prompt Australia's central bank to delay an expected interest rate rise from February to May.
The Australian dollar sank to a three-week low on Tuesday on concern that Queensland's flooded coal mines, supplying Asia's steel mills, may take months to return to normal production.
Prime minister Julia Gillard said the flooding would not derail an expected budget surplus in 2012-13. But the National Australia Bank said the disaster would reduce growth by 0.25 per cent over this quarter and last.
Authorities said the situation could even prove worse than devastating floods in 1974, when the Brisbane River burst its banks, cascading into thousands of homes and killing 14 people.
"We need to make every effort to stay calm and stick together. If you live on high ground, now is the time to reach out and offer help to neighbours ... and offer a bed for the night," Queensland state premier Anna Bligh said.
Floodwaters carried trees, boats and large steel pontoons torn from moorings through the centre of Brisbane.
Workers deserted high-rise office towers in the centre of the city as constant rain pushed river levels higher, lapping boardwalks and riverbank buildings. Water edged its way up to the steps of the Queensland state library.
"It's taking on new proportions and getting worse by the minute," said Gary McGowan, a businessman from a western suburb.
Julia Zhu piled sandbags into a Mercedes to defend her high-end gown business. "We have half-a-million dollars worth of stock and no insurance cover," she said.
Shoppers stocking up in a thronged a supermarket in the city's west, with bread and vegetables already sold out.
Crocodiles at a nearby Sunshine Coast zoo founded by the late television wildlife star Steve Irwin were being tied up in case they escaped in the deluge.
The floods have been blamed on a La Nina weather pattern in the Pacific, with Australia recording its third-wettest year on record in 2010, with two wet-season months to go. Weather officials are also forecasting an above average cyclone season.
"The Queensland floods are caused by what is one of the strongest, if not the strongest, La Nina events since our records began in the late 19th century," said Professor Neville Nicholls, an environmental science expert at Monash University.
Television footage showed brown floodwater gushing through the centre of Toowoomba yesterday laden with debris, as people clung to telephone poles and rooftops.
Panicked motorists climbed onto cars to escape the deluge, which destroyed homes and bridges, and hurled cars into trees and buildings like corks.
"Early reports would indicate that what hit Toowoomba could best be described as an inland, instant tsunami, with a massive wall of water that's gone down through the Lockyer Valley," police commissioner Bob Atkinson said.
The Queensland floods have paralysed operations that produce 35 per cent of Australia's estimated 259 million tonnes of exportable coal.
Australia contributes two-thirds of world exports of steelmaking raw material coking coal.
Coal seam gas drilling in the Surat Basin, a big source of gas for an estimated $200 billion in proposed liquefied natural gas projects, was halted yesterday.
Global miners Anglo American , Rio Tinto , Xstrata and BHP Billiton , have been hit by the floods, and all have made force majeure declarations, which release firms from delivery commitments.
Flooding has begun to recede in the main Bowen Basin coal region, but many mines remain flooded and will take weeks to drain and resume full production. While some rail links between mines and the ports have been opened, others are under water.
Stocks were running low at the key coal port of Dalrymple Bay, but it was receiving enough to keep loading ships, while the port of Gladstone said it could be days to weeks before it starts getting coal supplies back to normal.
Hotel operators said the rain had caused cancellations in popular tourist strips on the Sunshine and Gold coasts, which claim a large slice of the $32 billion tourism industry.
Reuters