Cars jammed the streets in Brisbane’s low-lying central business district, with residents scrambling to secure their possessions and move to safe areas as the swollen Brisbane River began bursting its banks.
The city’s mayor, Campbell Newman, warned that at least 6,500 homes could be flooded by Thursday, when the river is expected to peak at about 20 feet above its usual level, the biggest flood in 35 years.
“We are facing one of our toughest ever tests,” Anna Bligh, the Queensland premier, told reporters in Brisbane. “We do have a very serious natural disaster on our doorstep and we will all have to work together.”
Five children were among the 10 killed late Monday as the deluge tore through Toowoomba and other parts of the Lockyer Valley, west of Brisbane, upending cars and ripping buildings from their foundations.
Some 78 people were still missing late Tuesday, and police warned that they had “very grave fears” for 18 of those missing. At least 20 people have been killed in the floodwaters that have swept vast areas of Australia’s northeastern Queensland state.
Emergency crews worked frantically to rescue hundreds of people left stranded by the raging floodwaters — described by some locals as an “inland tsunami” — that Toowoomba and several smaller towns.
Around 300 people were plucked from the disaster zone by helicopter on Tuesday after the tiny hamlet of Forest Hill was cut off by the torrent, Ms. Bligh said. Some 78 people were still missing late Tuesday, and Queensland police warned that the death toll was likely to rise as emergency crews continued to sift through the wreckage.
“The circumstances in Queensland continue to be very dire indeed,” Prime Minister Julia Gillard told reporters in Canberra. “The nation does need to brace itself for the fact that the death toll as a result of yesterday’s flash flooding is likely to rise.”
Torrential rains and flooding has affected parts of waterlogged Queensland since late December. Officials at Australia’s Bureau of Meteorology have warned that the region’s soil has lost its capacity to absorb more water after more than two weeks of severely wet weather that has flooded an area roughly equal to France and Germany.
After enduring a decade of one of the worst droughts in Australian history, Queensland residents are now facing billions of dollars in costs from the floods, which began in late November and have since razed hundreds of homes and businesses, and brought the region’s lucrative coal and farming industries to a virtual standstill.
Brisbane’s main reservoir, which was created to protect the city from flooding after the last devastating flood in 1974, was overflowing, adding thousands of gallons to the region’s swollen river systems, according to Mr. Newman.
“The situation has obviously demonstrably deteriorated,” Mr. Newman told a meeting of disaster management officials in Brisbane, according to local news reports. “Today is very significant, tomorrow is bad, and Thursday is going to be devastating for the residents and businesses affected.”