By Ed Davies
BRISBANE, Australia (Reuters) - - Massive floods shut down the center of Australia's third-largest city, sent thousands fleeing from their homes and sparked panic buying of food on Wednesday as rescuers searched for 51 people missing in floodwaters.
Australia's biggest floods in a century have so far killed 16 people since starting their onslaught across northern mining state Queensland last month, crippling the coking coal industry, destroying infrastructure, putting a brake on the economy and sending the local currency to four-week lows.
The flood surge is expected to peak in Brisbane, a riverside city of two million people, before sunrise on Thursday and last for days. However, the peak hit Ipswich, a satellite town to the west, late on Wednesday.
"The water is rising and swallowing up the city. It's really heartbreaking," said Ipswich Mayor Paul Pisasale.
More than 1,500 Ipswich residents sheltered in evacuation centers, but others fled their homes with little more than what they are wearing, as floodwater rose around the city.
Pisasale said the flood peak on Wednesday at 19.4 meters was about a meter below expectations, saving some 6,000 homes from flooding. Brisbane authorities slightly downgraded their flood peak forecast to 5.2 meters for Thursday.
Brisbane residents on Wednesday pushed food-laden shopping carts through submerged streets, others waded in shoulder-high water to rescue possessions, while boats and pontoons were ripped from moorings in the Brisbane River and smashed into bridges as the muddy brown tide gathered strength.
At flooded intersections people paddled surfboards through floodwaters, balancing their possessions on the deck of the boards, while boats ferried evacuees to dry ground.
"I am feeling a sense of horror and awe at the power of the river. Sadly in coming hours we will see bits of people's homes float down the river," Brisbane Mayor Campbell Newman said, warning the torrent could take three to four days to subside.
Economists have raised their estimates of the economic impact of the flooding, with one central bank board member saying on Wednesday the disaster could cut 1 percent off growth -- equal to almost $13 billion, double the previous highest estimate.
The Australian dollar sank to a fresh four-week low of $0.9803 on the comments from Warwick McKibbin, an academic and a member of the central bank's policymaking board.
Treasurer Wayne Swan in November forecast GDP growth of 3.25 percent in the 2010-11 fiscal year, up from a 3.0 percent projection, but said spending would be cut to ensure a surplus of A$3.1 billion or 0.2 percent of GDP in 2012/13.
Food prices are surging around the country as the floods ruin Queensland crops and distribution networks. Prices for tomatoes have leapt about 200 percent in two weeks, while beef is up 11 percent and wheat has risen 4 percent in four months.
Rescue crews took advantage of some rare sunshine to look for 51 people still missing from tsunami-like flash floods that tore through townships west of the city this week.
BRISBANE A DESERTED CITY
In Brisbane, thousands of homes and businesses were deserted as swirling floodwaters rose in and around the city, forcing residents to flee with a few possessions to higher ground and to evacuation centers crowded with more than 3,500 people.
"If you start to see water in your yard, get out. Take your family and get to safety. This water could rise very, very quickly," Queensland state premier Anna Bligh told reporters, predicting almost 20,000 homes could be flooded at the river's peak in what she called Queensland's worst natural disaster.
Some Brisbane residents tried to carry on as normal, with early-morning joggers running even though parts of their routes were underwater. Others were distraught.
"This is my whole life, everything is gone. I never thought it would get this bad," said Kim Hung, manager of the Salt 'n' Pepper catering business, as two friends floated a coffee machine toward higher ground.
As the waters rose strangers formed human chains, sometimes in chest high water, to pass family possessions from flooded homes to dry land and into cars and trucks and safety.
Raw sewage began spilling into the river and creeks, prompting authorities to warn of heightened disease risk as spillage from damaged water treatment works polluted the floodwaters.
Dams built to protect Brisbane and outlying towns were spilling floodwaters into swollen rivers. The Port of Brisbane was closed, shutting down Australia's third-busiest container port and a 5 million tons per year coal-loading facility.
Australia exports more than half the world's coking coal, which is used in steel manufacturing, and is also the second-biggest exporter of thermal coal used for power generation.
Power company Energex shut power to some low-lying areas of Brisbane, including parts of the financial district, for fear that live power lines could electrify floodwaters. Some 78,000 homes in the southeast of Queensland were without electricity.
"TERRIFYING, CHAOS"
Prime Minister Julia Gillard arrived in Brisbane to inspect the devastation and said she was deeply concerned about the impact on jobs and livelihoods.
"I have been shocked. I think we've all been shocked by the images of that wall of water just wreaking such devastation. The dimensions of it are truly mind-boggling," Gillard said.
The floods have been blamed on a La Nina weather pattern in the Pacific, with Australia recording its third-wettest year on record in 2010, with two wet-season months to go. Weather officials are also forecasting an above-average cyclone season.
As the Queensland floods and rains move south, major rivers in New South Wales state have begun flooding or threatening to break their banks, forcing 3,000 people to leave some rural areas. In Victoria state in the southeast, heavy rain caused flash flooding and landslides, prompting fears a lake near Horsham could break its banks.
(Additional reporting by Rob Taylor in Canberra and Balazs Koranyi, Wayne Cole and Amy Pyett in Sydney)
(Writing by Michael Perry; Editing by Daniel Magnowski)
