Prime Minister Julia Gillard insisted the cost of the floods would not delay a return to budget surplus in 2012-13, but J P Morgan predicted the disaster would crimp growth this year and could delay another increase in interest rates.
The worst floods in 50 years, affecting an area the size of France and Germany combined, struck last month and have severely hurt Queensland state's US$20 billion (RM61.4 billion) coking coal export industry. They now threaten Australia's most popular tourism destination.
"There's a great inland sea at present," Graeme Lehman, mayor of a flood-stricken town outside Brisbane, told state radio.
The towns of Kilcoy and Toogoolawah were cut off by floodwaters and there were also fears for other communities.
Police urged motorists to stay off the roads as flash floods swept away two people in Queensland state's heavily populated southeast, home to the Sunshine and Gold Coast tourist strips.
"People need to think about how to get out and if you don't need to travel, stay off the roads," said Police Chief Superintendent Alistair Dawson, referring to some of the smaller towns. Brisbane is home to two million people.
Marine park officials and wildlife experts said floodwaters containing toxic farm pesticides were flowing into the Pacific Ocean, threatening Australia's Great Barrier Reef.
"Toxic pollution from flooded farms and towns along the Queensland coast will have a disastrous impact on the Great Barrier Reef's corals and will likely have a significant impact on dugongs, turtles and other marine life," said World Wildlife Fund spokesman Nick Heath.
The Great Barrier Reef Marine Park Authority said floodwaters emptying into the sea had drifted 40km (24 miles) offshore to the Keppel Island group, at the southern end of the World Heritage-listed reef.
The floods have caused an estimated A$6 billion (RM18.32 billion)in damage and economists say they will cut economic growth in 2011 and heighten inflation as food prices rise and reconstruction begins in the nation's second largest state.
Meteorologists said monsoon rains were expected to continue all week, placing further pressure on flooded towns.
"With more rain falling it could be months before the floodwaters clear and the extent of the damage to essential infrastructure is known," said J P Morgan chief economist Stephen Walters.
J P Morgan on Monday cut its GDP growth forecast for 2011 to 3.3% from 3.7% and raised its inflation forecast to 3.8% from 3.2%. That pushed out to May from February the likely timing for the central bank's next interest rate hike.
"Even inflation-conscious RBA (Reserve Bank of Australia) officials won't hike with Queensland under water," said Walters.
Gillard announced more aid on Monday, but added the floods would not derail an expected 2012-13 return to a budget surplus, with economic expansion now well into the 20th year and annual growth at 2.7% in December.
"I can't at this stage tell people what the total cost of recovering from these floods is going to be, because I can't predict the draw-down on infrastructure money until we see what's under the floodwaters," she said.
More than 200,000 people and more than 10,700 properties have been affected in the Christmas-New Year floods.
Five people have been confirmed killed.
The flood threat was expected to be extended to towns in neighbouring New South Wales state, with authorities on standby around Lissome in the Clarence River Valley, and further south.
A major concern now was the ground, so waterlogged that heavy rains were unable to be absorbed. Full rivers, creeks and man-made watercourses were bursting their banks.
About 116,000 mega litres of water — equivalent to more than 100,000 Olympic swimming pools — were being released daily from Queensland's Wive Dam, which may cause road closures, officials said.
Queensland Tourism said rains and flooding would hurt tourism in the country's main holiday playground, but it was too early to quantify the impact. Areas around the Great Barrier Reef in the far north, it said, were untouched by floods.
Australia's A$32 billion tourism sector was already in trouble due to the strength of the local dollar driving off overseas visitors and enticing Australians to go abroad.
Tourist numbers in Queensland were already down 4.5% from two years ago, and inbound air routes to the Sunshine and Gold Coasts down by around 15% last year.
Floods have also paralysed operations that produce 35% of Australia's estimated 259 million tonnes of exportable coal. Australia contributes two-thirds of global coking-coal exports, needed to make steel.
Global miners Anglo American, Rio Tinto, Strata and BHP Billiton have been hit by the floods, and all have made force measure declarations, which release firms from delivery commitments.
Flooding has begun to recede in the main Bowen Basin coal region, but many mines remain flooded and will take weeks to drain and resume full production. While some rail links between mines and the ports have resumed, others remain under water.
Coal stocks were running low at the key coal port of Dalrymple Bay, but it was receiving enough to keep loading ships, while the port of Gladstone said it could be days to weeks before it starts getting coal supplies back to normal. — Reuters
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