Australian troops and emergency workers were Monday battling huge flooding in the country's northeast that has left at least two people dead, with the worst devastation yet to come for some areas.

Up to 200,000 people are estimated to have been hit by the fast-flowing waters that have left 22 rural towns under water or substantially inundated by flooding stretching to an area the size of France and Germany combined.

The military was flying food and medical supplies into the coastal city of Rockhampton, population 75,000, on Monday as it braced to be entirely cut off by the waters, which are expected to flood hundreds more homes.

"Looks like Rockhampton's in the middle of an inland sea," Queensland Premier Anna Bligh said after flying over the area. "The amount of water coming down these river systems is nothing short of astonishing."

The airport to the regional hub was closed while roads to the south and west were blocked by floodwaters, prompting concerns among officials that the sizable population centre could run low on food.

"The affected area is greater than the size of New South Wales (state), with the worst still to come in communities like Rockhampton," Bligh said.

"Supplying them with food, ensuring that we keep them safe during this flood is absolutely critical."

The floods prompted Prime Minister Julia Gillard to offer emergency funds to those affected, including farmers more used to battling crippling droughts, as well as small businesses.

"When the floodwaters recede, we are going to see a lot of damage but we will obviously be working with the state government to rebuild that essential community infrastructure," Gillard told reporters in Sydney.

"All in all, we know hundreds of millions of dollars are going to flow into Queensland."

Gillard, who toured some of the devastated areas on Friday, said for some communities these were "the biggest floods they have ever seen" as she warned people to beware of the risks of the fast-flowing waters.

Police confirmed the second death since the floods were declared a disaster, that of a man who abandoned his boat after it took on water.

It follows that of a woman who drowned after she was swept away by surging waters after her car became swamped over the weekend.

It brings to nine the number of people who have died in flood-related accidents since November 30 -- including three people whose vehicles were swept away, two people who attempted to swim in fast-flowing waters, a man who was knocked off a footbridge by waters and a girl who drowned while trying to walk across a river.

Queensland state assistant police commissioner Alistair Dawson has warned the emergency could drag on for another month, saying while parts of the state were in recovery mode, others were bracing for the worst.

"It's hard to make the call that the worst is behind us," he said Sunday.

The floods are wreaking untold billions of dollars in damage to crops and Australia's key mining industry, while farmers, small businesses and tourism are also expected to suffer.

While more people were expected to throng evacuation centres in places such as Rockhampton on Monday, in other parts of the state residents were beginning to return to their homes to begin the massive clean-up.

In Bundaberg, in Queensland's southeast, the clean-up had begun in about 300 homes and 120 businesses as flood waters recede, but other towns such as Theodore and Condamine remained empty of residents.

"It's just devastating," Queenslander Beryl Callaghan told Sky News after returning to her water-damaged home.