Some homes in low-lying parts of Rockhampton are already being surrounded by water but residents have been warned the eventual flood peak could linger for days.
The Bureau of Meteorology predicts the Fitzroy River will peak at nine metres in the central Queensland city on Thursday morning, down on the initial forecast of a 9.4m peak on Wednesday.
On Tuesday morning the river was at 7.6m and climbing slowly, with the city likely to see the major flood level of 8.5m later in the day.
Queensland Premier Annastacia Palaszczuk said the latest advice suggested the 9m peak would linger in the region for about 48 hours "if not a bit longer".
Authorities are expecting water to enter more than 1000 homes, with just over 200 having water over their floorboards.
"We're already seeing the waters come through the Fitzroy, they're starting to encroach," Ms Palaszczuk said on Tuesday.
Some low-lying parts of the city, especially around the suburb of Berserker, have had temporary flood levees built to protect homes from the water.
But other suburbs, in particular Depot Hill on the other side of the river, will have to face the full brunt of the Fitzroy at its height.
District disaster co-ordinator Superintendent Ron Van Saane said they were happy the peak had been revised but weren't taking anything for granted.
"By no means are we out of the scrub with this," he said.
"It's still going to be a major flood and we still have a lot to do."
The airport closed just after midday on Monday and will remain closed until at least the weekend.
Rockhampton won't be completely cut off like in previous floods though, with the southern Yeppen crossing remaining open and travellers being diverted to Gladstone airport for flights.
Locals spent Monday filling sandbags as the Fitzoy River's flow began to strengthen following Cyclone Debbie, with some taking a break for a beer at a hotel sharing the river's name.
It also appeared the flood conditions claimed wildlife deaths in the central Queensland city after a kangaroo carrying a joey was struck in the CBD on Tuesday morning.
Prime Minister Malcolm Turnbull said "considerable resources" had been diverted to the city, which was undoubtedly on the cusp of a "tough time".
Meanwhile, a "mud army" of volunteers has gathered in southeast Queensland to help with the clean-up in the Logan and Beenleigh areas, which were hit by flooding late last week.
Last week's flooding claimed at least one life, 77-year-old Nelson Raebel from Eagleby, but three others remain missing: a 65-year-old man who was walking in Lamington National Park, a 50-year-old David Heidemann from Mondure man and 58-year-old John Frost from Mount Pleasant in Mackay.
ROCKHAMPTON FLOOD FORECAST IN NUMBERS:
- Water expected to enter 1809 residences
- Of those, 217 will have water over floorboards
- Water expected to enter 547 commercial properties
- Of those, 120 water above floorboards
