The floods -- which have turned an area twice the size of Texas into a disaster zone -- have killed at least 23 people and left 75 missing. Officials said they have grave fears about the many people reported missing in the Lockyer valley and Toowoomba, The Guardian reported.
There are reports of dead livestock and debris choking receding floodwaters. Vegetables, fruit and sugarcane crops have been ruined, and officials say they expect prices to rise sharply across Australia as a consequence.
Queensland Premier Anna Bligh, calling the flood the worst natural disaster in the Australian state ever, said cleanup and reconstruction costs could reach an estimated $5 billion.
"Queensland is reeling this morning (Thursday) from the worst natural disaster in our history and possibly in the history of our nation," Bligh said during a news conference. "We've seen three-quarters of our state having experienced the devastation of raging floodwaters and we now face a reconstruction task of postwar proportions."
Brisbane Mayor Campbell Newman said 11,900 homes and 2,500 businesses were submerged and another 14,700 houses and 2,500 businesses were partially covered by water. Nearly 115,000 homes were without power and more than 4,000 people were in evacuation centers.
The Brisbane River, which runs through the heart of the Queensland state capital, peaked Thursday, 40 inches below feared catastrophic levels. But waters remained above flood stage, rising again slightly during high tide Thursday afternoon, and could rise significantly again in the coming weeks, with the wet season continuing until March and dams protecting the city of 2 million near the breach point, officials said.
Forecasters said the river would remain dangerously high until early next week.
A return of torrential rains during the wet season could bring new flooding, Bligh said.
New South Wales state was also hit hard by flooding, with thousands evacuated. Australian Prime Minister Julia Gillard said she would send more military support to help search and rescue efforts.
Western, northern and central Victoria was under a severe weather warning Thursday after the state's southeast area was belted with torrential rain, flash flooding and landslides.
Bligh urged Queenslanders to remember their heritage during the crisis, The Guardian reported.
"We're the people that they breed tough north of the (New South Wales) border," she said. "We're the ones that they knock down and we get up again. This weather may break our hearts but it will not break our will."