The southeast Queensland town of St. George is preparing for what could be its biggest flood in 120 years.

A state of emergency has been declared and most of the four thousand residents have moved to higher ground as the water level is expected to peak to a level of 45 feet within the next 24 to 48 hours.

Most of southern Queensland's major river basins are flooded and the Balonne River is expected to break a 120-year-old record, peaking at about 45 feet Friday night and into the weekend. The river has already burst its banks about 2 miles on either side of the town.

State emergency workers are on standby to help with the situation and also to assist surrounding towns that might be affected.

Earlier this week, 500 residents were evacuated after the outback town of Charleville came under floodwaters.

Local weather bureau said the massive rainfall was caused by a monsoon low that is moving towards South Australia.