Senior economic ministers will meet to finalise further financial support to flood-ravaged communities, as thousands more defence troops prepare to arrive to assist clean-up efforts.
Federal cabinet's expenditure review committee will convene later on Tuesday, where flood assistance will be discussed.
Prime Minister Scott Morrison said the government was finalising the first wave of what he described as "over and above measures" — disaster funding that is outside of the existing categories of support.
Mr Morrison said the plans would be integrated alongside similar support from the NSW government.
"The Australian government will stand with those communities in the Northern Rivers to support them as they clean up now and in the months and years ahead," he said.
"This is not just a flood event ... this is a catastrophe on a national scale."
The prime minister described the flooding event as mind-boggling, with more than $200 million in disaster recovery payments already made since the crisis began.
As criticism from residents in flood-affected communities intensifies about a lack of federal support from ADF personnel, it's expected the number of troops on the ground will reach 5,000 by the end of the week.
Defence Minister Peter Dutton defended the timing of the ADF's arrival, arguing many areas were inaccessible.
"It's not just a couple of streets or a couple of towns or anything like that, it is a broad area of cultural communities," Mr Dutton told ABC Radio on Tuesday.
"Despite the magnificent work (ADF troops) have done, I think they just became overwhelmed with the scale of it."
Mr Dutton said ADF assistance would increase as flood waters subside.
"We need to be realistic about the situation in northern NSW. It's actually not just a flood, as others have pointed out - this is more of a cyclone," he said.
"There were roads that are no longer there, houses have been condemned, these are circumstances in which they're dealing and it will take time to respond and rebuild."
ADF troops coming into flood areas will spend the coming days helping to clear roads and fix telecommunication networks and will use helicopters to drop critical supplies to cut-off communities.
SES volunteers launch an inflatable rescue boat in Camden, South Western Sydney, on Tuesday, 8 March, 2022. Source: AAP / Dean Lewis
Mr Watt said more ADF personnel and government assistance was needed.
"Locals are really grateful for the small number of ADF personnel who are here, but we need a massive injection of personnel and support more generally," he told ABC TV.
"Right now is when we need to see khaki on the ground, this is a national-scale emergency."
'It's very dangerous out there'
Up to 80,000 people across NSW are subject to evacuation orders as the flood crisis continues to wreak havoc across the state's east coast.
A low pressure system off the mid-north coast has brought torrential rain to the Hunter and Greater Sydney regions and is moving towards the South Coast.
The intense rain is causing minor to major flooding from the Queensland border down to the Victorian border.
The NSW State Emergency Service issued evacuation orders to 60,000 people in 13 suburbs across Sydney's southwest and west along the Georges River overnight.
There are now 54 evacuation orders across the state, as well as 16 evacuation warnings and multiple flood warnings, current for vast swathes of NSW.
SES Commissioner Carlene York said the primary areas of concern are Kempsey, Georges River, the Hawkesbury Nepean River, Wollongong, Shoalhaven, St Georges Basin and Sussex Inlet.
A 67-year-old woman and her 34-year-old son are missing after their car was found in a stormwater canal at Wentworthville in Sydney's west.
NSW Police were alerted when the Mazda 3 was found in the Cooper Creek stormwater canal on Monday afternoon.
"We are quite concerned for their safety," Ms York said.
"It's very dangerous out there. There's a lot of water on the roads and it's prone to flash flooding as the heavy rains come."
The SES received more than 2,500 calls for help in the past 24 hours and undertook around 200 flood rescues, mostly in Sydney.
Residents remove damaged items from a flood-affected house on March 7, 2022 in Woodburn, NSW. Source: Getty / Dan Peled
The Bureau of Meteorology is warning saturated soil and swollen rivers could lead to landslides and flooding with rainfall of up to 200mm possible in Sydney's west and southwest.
Wind gusts of up to 90km/h are forecast, stretching south to the Illawarra region into Wednesday.
The BOM's Dean Narramore said widespread heavy rain overnight brought "devastating flash-flooding to some suburbs".
"It was a dangerous night through parts of southern and south-western Sydney," he said.
"Travel is definitely dangerous today not only because of rainfall ... Tonight we'll see possible trees and power lines down and landslips and flooding of roads.
"It's still dangerous times out there."
There has been 100mm to 200mm of rain in the past 24 hours.
Queensland's flood death toll rises
Southeast Queensland's flood death toll has risen to 13 after man's body was found in the state's south, with another man still missing, amid debate about mitigating future disasters.
Police found the body, believed to be a 31-year-old man who's been missing from Warwick for nine days, in a car in floodwaters in the Condamine River on Monday afternoon.
Another man is still missing and feared dead after falling from a boat on the Brisbane River near Breakfast Creek on February 26.
The weather has largely cleared up across much of the southeast on Tuesday after major floods, which have damaged more than 20,000 homes and businesses.
The state government estimates private insurance claims on homes and businesses will top $936 million and the bill for fixing public infrastructure like roads, bridges, power lines and railways will top $500 million.
The floods are also expected to wipe 0.25 per cent, or $1 billion, off state's economic growth in the current quarter.
Flood waste weighing more than 24 Airbus A380s has already been collected in Brisbane, where properties have been damaged in 190 suburbs.
Brisbane Lord Mayor Adrian Schrinner says more than 20,000 homes have been affected, not to mention businesses.
Members of the ADF help clean up flooded streets in Milton, Brisbane, Monday, on 7 March, 2022. Source: AAP / Jono Searle
"There were 20,000 properties, residential properties that were flooded, if you actually start to calculate the value of those properties we're talking about billions of dollars worth of property," Mr Schrinner told ABC radio on Tuesday.
"So if I came to you and said: 'Look sorry, you live in a flood area, out you go, we're gonna bulldoze your home,' I'm not sure how you'd feel about that."
He said under the council's previous flood buyback scheme the $58 million allocated was enough to buy only 112 homes, and many residents didn't want to sell anyway.
The mayor said options for mitigation was building homes on higher foundations and using more flood-resistant building materials.
He said it was also difficult to change planning laws to make a difference when there were already thousands of homes and businesses built in flood zones.
"These were often settled at the beginning of Brisbane's sort of modern history, so potentially more than 100 years ago, and so in those areas, there's some entire suburbs virtually that do experience some flooding," the mayor said.
"So you can't you couldn't just go in and clear an entire summer and just say: 'Sorry, no one can live here any more'.
"These are people's private properties, and so like I said, there's going to be a combination of responses."
