Thousands of Australians were forced to abandon their homes Sunday as record flooding that has cut off thousands of people threatened to engulf areas devastated by wild weather last year.
Police ordered the 3,800 residents of the town of St George, in northern Queensland state, to evacuate as rising floodwaters raced towards record heights, threatening to cut the one remaining exit road.
"Residents of St George are required to evacuate by road before the Moonie Highway is cut by floodwaters, which is expected to occur sometime in the early part of Sunday evening," police said in a mandatory evacuation order.
"Air evacuation to Brisbane is being organised to ensure evacuations can proceed after the Moonie Highway closes."
The swollen Balonne River, flooding for the third time in less than two years, was expected to peak at 15 metres (50 feet) on Tuesday night, far exceeding the previous record of 13.4 metres set in March 2010.
"This is a very serious situation and I urge people to cooperate," said Queensland Premier Anna Bligh.
Prime Minister Julia Gillard dispatched a Hercules C130 military transport plane to airlift patients from the town's hospital to major medical facilities on the coast, and the local nursing home was also being emptied.
Eight defence helicopters are already assisting search, rescue and resupply operations in the flood zone, winching people to safety and dropping food, bedding, medical supplies and other essentials such as generators.
St George has seen major flooding twice in the past two years, once in March 2010 and again during last year's Queensland flooding disaster, which claimed 35 lives and swamped vast tracts of farmland and tens of thousands of homes.
Deputy Queensland police commissioner Ian Stewart said the situation in the region had "deteriorated" overnight with "very large spikes" in water levels south of Roma, where 200 homes flooded earlier this week.
"We are working on our contingencies to manage the evacuation of areas south of Roma and in particular St George," Stewart said.
"There are very large volumes of water in those systems getting to record levels."
The Bureau of Meteorology said St George was expected to reach the 2010 flood level by Monday morning and "continue rising, possibly above 14 metres on Tuesday and Wednesday."
Residents scrambled to fortify levees still standing from last year's floods, with some locals saying they were prepared for a peak of 14.5 metres or worse.
"If it does reach the peak that they're talking about, if it goes across into the irrigation area, it's going to knock out thousands of hectares of cotton," local farmer Alex Benn told Sky News.
"We're a bit concerned so we're topping all the levees up."
Flood defences held overnight in nearby Charleville, where some 600 people were holed up in an evacuation centre waiting for the Warrego River to subside.
Waters were slowly easing in Roma, where a woman whose car was swept off a road on Friday remained missing.