Thousands of residents have begun evacuating the outskirts of Australia's third-largest city as other people piled sandbags outside their homes and stockpiled food amid rising floodwaters and more heavy rain.
The streets of Brisbane in the state of Queensland were largely deserted, with 80 suburbs expected to be flooded if the Brisbane river bursts its banks as expected on Thursday.
About 20,000 homes were expected to be hit by the flooding in the coming days, Anna Bligh, the premier of Queensland state, said on Wednesday.
"I understand that we could see up to 20,000 properties in Brisbane affected by the water and people do need to take that very seriously," she said.
"That is an extraordinary amount of people and homes."
About 1,500 Brisbane residents were already sheltering in evacuation centres after waters spilled from 16 dams in the state on Tuesday.
Four other dams, including Brisbane's Wivenhoe dam, released huge quantities of water, adding to the surge.
On Wednesday, Campbell Newman, the Brisbane mayor, said that more than 6,500 of the eastern city's residents were expected to move into three evacuation centres, while thousands of others who live in threatened areas were expected to move in with family and friends.
"I don't want to be in a position where we can't look after evacuees who turn up on our doorsteps," he told state broadcaster ABC.
Many businesses in the centre of Brisbane were forced to shut down as energy suppliers prepared to cut power to about 100,000 city customers, as generation facilities were threatened by water.
Officials warned residents of the city and nearby Ipswich not to drive and to conserve drinking water.
Under the latest estimates, a further 3,500 commercial properties were expected to be deluged while 2,100 streets and around 30 suburbs in the city were at risk of inundation.
"There will be considerable impact on large number of homes and businesses, and we need people to be taking action now to respond to that situation," Neil Roberts, the emergency services minister for the state, said.
Authorities said the situation could even prove worse than the devastating floods in 1974, when the Brisbane river burst its banks, cascading into thousands of homes and killing 14 people.
|Tens of thousands of residents in Brisbane are bracing for major flooding in the days to come [EPA]
At least 12 people have died as raging torrents have swept through several towns in the state, washing away cars and houses. Another 67 people were missing and authorities warned that the death toll was likely to rise.
Queensland has battered by heavy rains and floods since November and at least 20 people have been killed in flood-related incidents.
The floodwaters have already carried off trees, torn boats and large steel pontoons from moorings on their way through the centre of Brisbane.
Workers deserted high-rise office towers in the centre of the city as constant rain pushed river levels higher, lapping boardwalks and riverbank buildings. Water edged its way up to the steps of the Queensland state library.
Speaking to Al Jazeera, Liz Bentley, a member of Britain's Royal Metereological Society and the founder of the Weather Club, said one of the key factors leading to Australia's devastating floods is the La Nina weather phenomenon, a cooling phase that occurs in the eastern Pacific Ocean off the coast of Peru.
"There were lots of warning signs of potential flooding following continuous rain over the last few weeks.
"The river levels are rising significantly and can get up to nine metres deep and then it will drop away, followed by months of massive cleanup operations because the floodwaters will also bring mud and sewerage downriver."
Bentley said La Nina occurs much less frequently compared to El Nino, which causes severe drought, happens about every 10 years, adding that Queensland experienced similar flooding during the last major La Nina event in 1974.
Julia Gillard, the Australian prime minister, said 150 regions across three states had been hit by the deluge since November.
More than 8,000 claims for emergency assistance have been made, worth $10m, and many more were expected.
But the damage bill would take some time to process, Gillard warned, with the end of the crisis not yet in sight and many roads, rail and bridge assets still under water.
The floods have at times covered an area bigger than France and Germany combined and caused an estimated $6bn in damage, inundating 70 towns, some twice in recent weeks.
The disaster has brought the state's $25bn coking coal export industry to a virtual standstill, hit tourism and devastated agriculture.
The floods will also hit economic growth this year, heighten inflation as food prices rise and dampen retail spending. They are also forecast to prompt Australia's central bank to delay an expected interest rate rise from February to May.