Ipswich's entire CBD has been shut down and streets cordoned off while residents and tourists, as well as onlookers caught off-guard, rush to vacate the city.
The speed of the rising flood has dramatically picked up since 5am.
It is expected to increase by another two metres by 11am.
Meanwhile, anger is mounting over reports of looting in the city.
Evacuation centre are overflowing, Mayor Paul Pisasale said.
The mayor was furious after hearing of several reports of looting taking place in flood-affected areas.
“If I find anybody looting in our city they will be used as flood markers,” he said.
The Bremer River had risen to 18.5 metres at 5am this morning.
The expected 11am peak of 21.5 metres is half a metre higher than the devastating 1974 floods.
Queensland Premier Anna Bligh said the situation was escalating rapidly.
“That’s five metres the river is expected to rise in five hours ... that’s how fast this is rising,” she told Channel Nine.
The river rose about one metre every two hours yesterday, a situation which shocked onlookers.
The main street, which was dry yesterday afternoon, has been swamped in just 12 hours.
A riverside boardwalk disappeared under water by lunchtime yesterday, while shopping centres, car parks, ovals, residential streets and homes become inundated as stunned residents could only watch on helplessly.
“Half of our CBD down the bottom end is covered in water, we’re just waiting to see [how much worse it will get],” Cr Pisasale said.
“I’m watching a third of the [wider] city under water.”
Several people caught in the floodwaters had to be rescued from their homes and cars overnight.
However, there were no life threatening injuries or fatalities, police said.
A four-year-old boy died yesterday after he fell from a rescue boat. He was the 10th person confirmed dead in floods across southeast Queensland since Monday, while another 90 are officially missing.
Power was cut in the city about 11pm last night as a safety precaution.
More than 1000 Ipswich residents are staying in official evacuation centres, with an unknown number at unofficial locations.
Department of Communities regional executive director Brooke Winters said “a crush of people” had arrived at the centres yesterday afternoon as residents saw media reports of the unfolding situation.
About 100 elderly people from retirement homes were transferred from Ipswich Showground to Ipswich Girls Grammar School.
Families were also were bunkering down at other school halls in the city.
Lee-ann Anderson spent a sleepless night with her three children on the floor of an indoor cricket stadium.
With only a few plastic bags of their personal items and blankets, the family waited to hear how their Bundamba house had fared in the floods.
“I feel in shock because I’ve never seen anything like this before,” Ms Anderson said. “Fair enough we’ve had flooding before but nothing like what’s happening around us now.”
Meanwhile, Ms Winters said “horrific” scenes had devastated southwest Queensland.
To the west of Ipswich, Dalby, Chinchilla and Condamine were continuing to suffer after almost a month of flooding.
“We’re seeing water completely inundate houses, people have lost everything in terms of personal effects,” Ms Winters said.
“It’s just been absolutely horrific. Some houses have been inundated to their roofs, it’s just been shocking.”
Further showers are forecast for Ipswich today, with fine conditions predicted for tomorrow.
Further resources about the Queensland flooding for our Austrailian folks, as well as online donations.