At least three people have been killed and thousands have been stranded by the severe weather system that was once Tropical Cyclone Oswald, the Australian Broadcasting Corp. reported. The severe weather could extend as far south as Sydney.
Queensland Premier Campbell Newman told ABC rescue personnel would evacuate about 131 patients from a hospital in Bundaberg.
Bruce Grady of Emergency Management Queensland said a huge air rescue operation in Bundaberg saw about 1,000 people airlifted in North Bundaberg to safety.
"What we're concerned about is the rivers continue to rise, essentially houses then being swept away," Newman said. "That happened in Brisbane in the 1893 flood -- literally lifted off their stumps and then swept away in the floodwaters."
Newman said flooding in the Bundaberg area has cut off portions of the city.
"[What] we're seeing is North Bundaberg being sort of split up into at least a couple of islands and people have been cut off by the floodwaters," he said.
Parts of Bundaberg were under mandatory evacuations as were other cities along flood-swollen waterways.
Evacuation orders also were in place in Lockyer Valley. In Grafton, flooding cut off 7,000 people and 1,000 were on standby to evacuate.
Forecasters said as many as 3,600 homes and 1,250 businesses could be affected by flooding in Brisbane, ABC said.
More than 250,000 customers in southeast Queensland were without power.
Emergency Services Minister Jack Dempsey said more than 200 emergency workers were trying to rescue people whose lives could be in danger.
"What we've got to be reminded is there are still people at risk and that they don't distract emergency services from doing their job," Dempsey said.
Ipswich Mayor Paul Pisasale said he was anxious to learn whether the Bremer River has peaked. Forecasters said it was expected to hit 15 meters (about 49 feet), 4 meters (about 13 feet) below the level of a devastating flood in 2011.
"I'm hoping it will stop at 14 [meters]. If it stops at 14 we're going to be a very happy city," Pisasale said. "That means the pressures on our city and some of the houses won't be there."
Federal Treasurer Wayne Swan told ABC he has been monitoring the flooding in Queensland and will determine the cost once everyone is safe.
"We have processes which we'll put in place which will deal with the recovery phase," Swan said. "It is far too early to be talking about putting dollars and numbers down on a piece of paper."