Thousands of  residents of Australia's third-largest city evacuated homes on  Wednesday as massive floods began to inundate the financial  district, sparked panic buying of food and left authorities  despairing for nearly 70 people missing.

The biggest floods in a century have so far killed 16  people since starting their march across the northern mining  state of 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.     

With a flood surge expected to peak on Thursday in the  state capital of Brisbane, a city of two million, residents  pushed food-laden shopping carts through drowned streets as  supermarkets were stripped of milk and bread staples.

At one business centre, people waded in shoulder-high  water trying to rescue possessions, while on the nearby  riverside boats and pontoons were ripped from moorings,  crashing into bridges as the muddy brown tide gathered in  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.

In the nearby city of Ipswich, which will be hit by the  flood peak in the next few hours, 3,000 homes were already  flooded and one third of the town is expected to be underwater  at the peak.

"The water is rising and swallowing up the city. It's  really heartbreaking," said Ipswich Mayor Paul Pisasale.

Rescue crews took advantage of some rare sunshine to look  for 67 people still missing from tsunami-like flash floods  that tore through townships west of the city this week.

"We can take no comfort from that blue sky," 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. "The water and the rain have already done their damage. This is a deeply serious natural disaster."         

The worsening floods are forcing economists to raise  estimates of the economic impact, with one central bank board  member on Wednesday saying 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 fiscal 2010-11, 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 crops in Queensland and sever distribution networks.

In Brisbane, thousands of homes and businesses were  deserted as swirling floodwaters rose in and around the  riverside city, forcing residents to flee with few possessions  to higher ground and to evacuation centres that were crowded  with more than 3,500 people.

Some of the scenes in the city were surreal, with  early-morning joggers trying to carry on as normal, 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.

Bligh said she expected about 19,700 homes to be flooded  at the river's peak, affecting up to 45,000 people. The  military is running relief flights with helicopters and C-130  transports.

Dams built to protect communities are at bursting point. The Port of Brisbane is closed, shutting down Australia's  third-busiest container port and a 5-million-tonnes-a-year  coal-loading facility.

Australia is the world's biggest exporter of coking coal,  which is used in steel manufacturing and accounts for more  than half of global exports, and is also the second-biggest  exporter of thermal coal used for power generation. - Reuters