Thousands of people were stranded by floodwaters in eastern Australia on Saturday as the surging deluge poured into hundreds of homes and rescuers searched for a woman swept away by the torrent.

Prime Minister Julia Gillard ordered eight military helicopters to help in search, evacuation and resupply missions in Queensland state, where days of heavy rainfall have prompted hundreds of evacuations and dozens of rescues.

And in neighbouring New South Wales, emergency officials said 16,550 people were stranded, with the worst affected areas around Moree in the state's north where floodwaters are expected to remain at their peak for several days.

In the inland Queensland town of Charleville fears a temporary levee would collapse as the Warrego River swelled, flooding the whole town, appeared to have abated but authorities remain on high alert.

"Right now the levee is holding and on all current forecasts it's likely to keep doing that, but there's not very much room for error," Queensland Premier Anna Bligh told reporters in a visit to the town.

"We have a 24-hour watch on the levee to make sure we are ready if anything happens."

Bligh, who just over a year ago was dealing with epic floods that swamped the state, sweeping away entire hamlets and flooding thousands of homes, said Charleville was suffering its third flood in as many years.

"That's too many, and there's a lot of heartache here today," she said.

"I've spoken to people who are very close to tears."

In the town of Roma to the east, where more than 200 homes had been flooded, police were continuing their search for a woman missing since Friday after her vehicle was swept off the side of a road.

"A boy was rescued from the car and a woman got out of the vehicle but rescuers could not keep hold of her," police said in a statement. "The woman was swept away in fast flowing flood waters."

As the flooding eased in Roma and nearby Mitchell, authorities said their focus would switch south to the town of St George downstream as it prepared for major flooding as the waters moved south.

Maranoa Mayor Robert Loughnan said while it was relief that floodwaters were receding in parts, the damage to towns such as Mitchell and Roma, which have suffered floods three years in a row, would be "gobsmacking".

"It's a massive flood," he told the ABC. "We talk about the 2010 flood being the big one in Roma and of course last year's was just as damaging.

"This third one is just amazing in its scope and I guess the true scale will become clearer as the waters recede in the next few days."

In New South Wales, some residents were returning to their homes in Moree to view the damage caused as the Mehi River steadily fell, but communities remained isolated by the floodwaters.

The extent of the damage is not yet known but the State Emergency Service said some 300 homes and businesses were inundated.

The SES has carried out 18 flood rescues since Friday, including airlifting a group of people trapped on the roof of a building as snakes swam in the water beneath them.

SES assistant commissioner Andrew Edwards said while the rain was easing, the amount of flooding in the region and to the north meant that "we can expect these floods to be going on for months" in some pockets.

Australia suffered epic floods late 2010 and in the January 2011 which swamped a huge area of Queensland, inundating thousands of homes and businesses, sweeping away small villages and leaving more than 30 people dead.