A river that runs through Brisbane, Australia, has crested at a lower-than-predicted level, although it is expected to remain at near-historic levels for the remainder of the day.

The swollen Brisbane River peaked at 4.46 metres at about 4 a.m. local time (1 p.m. ET), more than a metre lower than the 5.5 metres that meteorologists had predicted.

Evacuations involving some of Brisbane's two million residents were continuing, police said.

What water there was wreaked havoc on the city, the country's third largest.

More than 20,000 people were left homeless and 25,000 homes were affected, freelance reporter Roger Maynard told CBC News.

Weeks of flooding in other parts of the state of Queensland have killed 13 people; dozens more are missing.

The water shut roads and topped traffic lights throughout Brisbane, where residents moved about in kayaks, rowboats and even on surfboards. On the river, boats were torn from their mooring and could be seen floating quickly down the river and crashing into bridge overpasses.

Onlookers take photographs of Brisbane's central business district as the Brisbane River rushes by on Thursday morning. (Tim Wimborne/Reuters)

Bridges throughout the city were closed because of large amounts of debris pressing up against them, reported Bruce Woolley of the Australian Broadcasting Corp.

The closures have cut off the city's central business district from the rest of city, leaving residents there without fresh supplies of fruits, vegetables, bread or milk, Woolley said.

Public transit, including Brisbane's bus and ferry services, have been halted.

Earlier, state officials had urged residents in low-lying areas to seek shelter on higher ground.

Electric company cuts power

Also on Wednesday, Queensland Premier Anna Bligh predicted the floodwater's peak would "cripple parts of [the] city."

"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.

Bligh warned that the dangerous floods were a "deeply serious natural disaster" and not a "tourist event." She asked people to help neighbours and avoid unnecessary travel through affected areas.

On Wednesday, Brisbane residents who had spent two days preparing took cover on higher ground while others scrambled to move their prized possessions to the top floors of their homes. Some stacked furniture on their roof.

A message of inspiration scrawled along a barricade at a downtown building under construction. (Submitted by Rachael Wallis)

Energex, the city's main power company, said it would switch off electricity to some parts of the city starting Wednesday as a precaution against electrocution. Almost 70,000 homes were without power across Queensland by Wednesday afternoon, Bligh said.

"In the inner Brisbane suburb of Rosalie, they've been working through the night to move furniture, cars, personal mementos — anything that will soon be swallowed up by the water," freelance reporter Peter Hadfield told CBC News.

At least 2,100 streets were affected, Brisbane Mayor Campbell Newman said.

'Unreal' situation, Brisbane resident says

Brisbane's office buildings stood empty Wednesday, with the normally bustling central business district transformed into a watery ghost town. One of the city's sports stadiums, which hosts international rugby games, was flooded with muddy, chest-deep water.

"The streets have been vacated, except the building sirens going off, car sirens going off, and it's unreal," Brisbane resident Blair Burchill told CBC News on Wednesday.

Burchill said the Brisbane River has burst its banks in several places, sending water into many areas, including the city's downtown.

"The Brisbane River snakes through the city and so there is a lot of potential areas for flooding," he said.

Two evacuation centres had been established in the city and Newman said up to 6,500 people were expected to use them in coming days.

The flooding in Brisbane comes after deadly flash floods swept through Queensland's Lockyer Valley, killing 12 people. The death toll was revised to 13 by Thursday morning. Search and rescue crews are still searching for about 50 people.

The flooding has transfixed Australia and is shaping up to become the nation's most expensive disaster, with an estimated price tag of $5 billion.

Burchill, who is married to a Canadian, said his wife is stuck in another Queensland town because roads are washed out.

"The highway north of Brisbane is blocked in several places and probably will be for another week," he said.

The relentless waters have affected about 200,000 people, shut down Queensland crucial coal industry and ruined crops across vast swaths of farmland.

With files from The Australian Broadcasting Corporation and The Associated Press