Queensland town facing 'catastrophic' flood

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A catastrophic flood will engulf Charleville in southwest Queensland if its levee banks fail, the weather bureau has warned.

On Saturday morning, the flood-swollen Warrego River was lapping the top of the town's main levee.

Senior Hydrologist Paul Birch says if the banks break under the pressure, there's nothing to stop the backed-up floodwater cascading into the town.

"If it does that you find it tends to erode out part of the levee fairly quickly so then it would just open up the river into town, so yes it's quite catastrophic," he told the ABC.

The river continues to rise slowly and Mr Birch warned it would be touch-and-go for some time.

Overnight, hundreds of Charleville residents were evacuated from their homes to a temporary shelter at the town's racecourse.

Mayor Mark O'Brien said it was a precautionary measure and there was renewed hope that the levee would hold after a second emergency bank was erected overnight.

Premier Anna Bligh was due to visit Charleville to assess the situation on Saturday.

Meanwhile, District Disaster Coordinator, Inspector Roger Whyte, said services at Mitchell, another threatened outback Queensland township, were stretched to the limit.

But the arrival of two Defence Force Blackhawk helicopters had eased the situation and the Maranoa River had fallen to 9.35 metres on Saturday morning.

"It looks like it's dropped about half a metre since 6pm (AEST) last night," he said.

However, the river height upstream has risen slightly and that could push levels at Mitchell up again temporarily later in the day.

Meanwhile, grave fears are held for a woman swept away from a stranded car in Roma during a rescue bid on Friday.

Emergency teams managed to save a child from the vehicle but the woman disappeared.

The search for her was called off on Friday night and resumed at first light on Saturday.

Insp Whyte said flood levels in Roma fell to 7.6m on Saturday after peaking at 8.4m on Friday afternoon.

He appealed to locals not to go sightseeing or drive into floodwater.

"If they do that I'll buy them all a box of chocolates," he said.

Ergon Energy began disconnecting power supply in Charleville on Saturday morning as the flood threat increased, but in Roma power is being restored.

Once roads into Roma reopen, extra crews from the Darling Downs and Wide Bay-Burnett will move in to help check homes that have been flooded, and reconnect them.

In Mitchell more than 270 homes have been disconnected from the grid and others in St George and Augathella have also been cut off as a precaution.

- AAP