Surging waters have poured into Brisbane's empty city centre after leaving a deadly trail across the region in what could be its most devastating floods in a century.
The water reached the top of traffic lights in some parts of the city and the mayor said at least 20,000 homes were in danger of being inundated.
At least 22 people have died and more than 40 are missing across Australia's north-eastern state of Queensland since rains which began in November sent swollen rivers spilling over their banks, flooding an area larger than France and Germany combined.
Brisbane, the state capital with a population of two million, is the latest city to face down the waters and officials expect the death toll to rise. Residents who had spent two days preparing took cover on higher ground while others scrambled to move their prized possessions to the top floors of their homes. Some stacked furniture on their roofs.
The Brisbane River is expected to reach its highest point on Wednesday. After days of bad news in which figures were constantly being revised, the Bureau of Meteorology delivered a small and rare positive forecast - the floodwaters would crest about a foot lower than earlier thought.
If correct, the new forecast means that the waters will not reach the depth of 1974 floods that swept the city. Queensland Premier Anna Bligh said the news was welcome but of little comfort.
She added: "This is still a major event, the city is much bigger, much more populated and has many parts under flood that didn't even exist in 1974. We are still looking at an event which will cripple parts of our city."
The dragged-out crisis escalated when a violent storm sent a 26ft, fast-moving torrent - described as an "inland instant tsunami" - crashing through the city of Toowoomba and smaller towns to the west of Brisbane on Monday. Twelve people were killed in the flash flood. Ms Bligh said the number of missing had been revised down to 43. Prime Minister Julia Gillard said: "This is a truly dire set of circumstances."
Meanwhile, The Queen has made a private donation to relief efforts for the floods in Australia. The private donation, the amount of which is not being disclosed, is to the Premier of Queensland's flood relief appeal.
The Queen issued a statement expressing her sympathies for the people of the state on December 31, saying then: "I have been following with great concern over the last few days the news of the devastating floods in Queensland. Please extend my sincere sympathies to all the people whose communities and livelihoods have been so badly damaged in this disaster."