Already thousands of people have been forced to flee their homes after the swollen river burst its banks and reached 4.2 metres on Wednesday.
Premier Anna Bligh is warning despite a slight revision in the expected flood peak, Brisbane residents are going to wake up to a scene of widespread devastation
We will wake tomorrow to an image of Brisbane ... that will shock many of us and I do say to people that we need to be ready for that," she said.
"People need to brace themselves.
"I think we are going to see some extraordinary solidarity overnight ... and I think that we are going to wake up to a shocking and remarkable challenge.
"But I sense that this is a challenge we are up to and a challenge we will meet."
Infrastructure was destroyed, 35 suburbs were deluged, and Lord Mayor Campbell Newman warned sewage was seeping into the floodwaters after treatment plants were inundated.
Councillor Newman said the city's ferry terminals had been "smashed to pieces" while council engineers were forced to demolish the floating RiverWalk around the New Farm cliffs amid fears that it would break away and career downstream.
The Brisbane River was a swirling torrent, with boats, pontoons and other debris being swept towards the sea and muddy water inundating low-lying areas.
The flooding was caused by water surging downstream from the overloaded Wivenhoe Dam meeting a larger than usual high tide.
Authorities warn of a growing risk of disease, including Ross River Fever, hepatitits and gastroenteritis, as the floods linger into the weekend.
Councillor Newman was pleading with locals to heed flood warnings tonight.
"Please, if the water's coming your way, it's not too late, you need to make a decision about evacuation or trying to sandbag," he said.
"People shouldn't muck around. If they're on the flood map, if their street is on the list, make the decision to get out."
Many were carrying mattresses, bags and pillows and their faces were numb as the shock sunk in.