Emergency crews in northern NSW are undertaking the painful process of checking thousands of homes for missing people after the regional city of Lismore endured its worst-ever flood crisis.
NSW Fire and Rescue Commissioner Paul Baxter says people need to brace for the prospect of more deaths.
Police are still working out how many people are missing and Mr Baxter said "some people just haven't been heard from".
He said in Lismore on Thursday that communications were difficult and many unaccounted-for people may just have been unable to communicate,.
The next step involves emergency workers going house-to-house and speaking with locals in hard-hit areas, to try and find people who have not made contact since the deluge.
"We are talking literally thousands of homes," he said.
The task ahead was "epic", and now included crews from the SES, the RFS, Resilience NSW and the ADF, he said.
"This is a big disaster and it's over such a widespread area. It's going to be hard work."
Lismore Mayor Steve Krieg said the NSW and federal governments needed to listen to the city's residents, after four people were confimeed to have died in the unprecedented flooding this week.
Countless homes and business were ruined as the city was inundated.
"There are plans that have been in place for many, many years to mitigate the flood levels in Lismore," Mr Krieg said on Thursday.
"Unfortunately, no one's been prepared to take the action required.
"Everything's costed, everything's ready to go."
Mr Krieg is hoping to meet with Premier Dominic Perrottet and whichever federal minister is prepared to sit down with him.
Intense rain travelling down from southeast Queensland sparked Lismore's record-breaking deluge.
Up to 100 people were trapped on the roofs of their houses waiting hours for help.
As the waters began to subside, two women in their 80s and a man in his 70s were found dead in their flooded homes and the body of another man was found floating in a street.
On Thursday, the clean-up of the mud-covered city continued as people assessed the damage and counted the losses of homes and businesses.
"We are seeing the recovery underway," Mr Perrottet said.
The devastated town is also facing food shortages - most supermarkets were underwater - as well as petrol shortages.
Residents, many of whom are eligible for government emergency payments, are reporting ATMs have run out of cash.
Nearby Ballina, which was hit hard by flooding, also has food and petrol shortages and is banking on freight lines reopening on Thursday.
"Many people today in the Northern Rivers and over the last 24 hours have returned home, and they are returning home to heartbreaking scenes," Mr Perrottet said.
He noted that ADF helicopters were now being used to drop critical food supplies to evacuation centres and isolated properties.
"We've got a battle on two fronts. We're dealing with the immediate response of keeping people safe ... through the operation centre and there is a substantial focus on recovery," he said.
The government is directing an additional 400 personnel - including NSW SES, RFS and Australian Defence Force teams - into the Ballina and Lismore areas to get the clean-ups done as quickly as possible.
"The challenge is going to be enormous," Emergency Services Minister Steph Cooke said, pointing to issues around the disposal of piles of household waste.
The road to recovery will be "very, very long", she added.
