Twenty thousand people were ordered to evacuate in New South Wales, and thousands more in Queensland, as rising river systems also threatened communities.
More than half a metre of rain fell in some areas, as the remnants of Tropical Cyclone Debbie passed out to sea.
Days since ex-tropical cyclone Debbie tore through parts of Queensland, devastating floods continue to take their toll.
In the deluged Gold Coast hinterland evacuations across the swollen Logan river began early, and showed no sign of letting up.
From the air, flooded homes, sheds, cars and buses can be seen through the muddied inundation.
Beaudesert Farmer Susan Shay says all of her livestock has been swept away.
The Albert River has hit its highest ever recorded level and flooded more than 100 houses, including that of a Queensland government minister.
The Logan River is still rising, threatening to swamp hundreds more.
The cleanup in Queensland is expected to take months and could cost many millions of dollars.
Further south, in New South Wales, devastating floodwaters have left a trail of destruction through the city of Lismore.
The Wilson River peaked at 11.5 metres, its highest level in more than 40 years.
The surging water topping the city's levee for the first time since it was built 12 years ago.
New South Wales Emergency Services Minister Troy Grant says the treacherous conditions are hampering rescue efforts.
The rising water has blocked access to a number of highways, leaving the towns of Tumbulgum and Murwillumbah isolated.
New South Wales Premier Gladys Berejiklian is urging those in flood-affected areas to stay clear of the surging waters.
