The Queensland Premier says everything possible is being done to help the victims of Cyclone Marcia, with top priority going to the 100 families whose homes have been destroyed.
Disaster relief funding has been activated for the Rockhampton, Livingstone and Banana Shire council areas.
"We've had assessments of over 1500 houses that have had some kind of structural damage," Premier Annastacia Palaszczuk said.
"In Yeppoon and Rockhampton around 100 are severely impacted. By severe [I mean] that people can't go back into their homes. Our fundamental priority now is on those families who have been the most severely impacted."
Seven Australian Defence Force technicians are beings sent to the region to restore power.
Almost 100 per cent of Yeppoon properties do not have power and 92 per cent are out in Rockhampton.
Further south, the Mary River in Gympie is starting to fall after peaking at 17m, leaving 19 low-lying businesses inundated. But the Premier could not confirm reports up to 200 homes might have gone under in Biloela.
She said assessments were still underway, but it was clear that a bridge linking Biloela to Gladstone has suffered structural damage and would be out of action for some time.
Adding to the disaster, telephone and internet services have been cut in many areas, including in the Banana Shire council area, which takes in Biloela. The cuts have affected the local Disaster Co-ordination Centre's ability to assess the situation and respond.
Clean-up efforts in the Northern Territory have begun as ex-tropical Cyclone Lam brings heavy rainfall to Western Australia.
A severe weather warning is in place for Daly, Gregory and Tanami.
NT Chief Minister Adam Giles inspected the hardest-hit island communities with Acting Police Commissioner Reece Kershaw.
About 5000 residents in Galiwinku on Elcho Island, Gapuwiyak in Arnhem Land, Milingimbi and Ramingining bore the brunt of the category four storm as it carved a path of wreckage through Arnhem Land early on Friday.
The NT Government declared a state of emergency in those areas on Saturday, which it said would help with the recovery effort.
Military mobilises
• Hundreds of defence force personnel to join clean up in Yeppoon and Rockhampton
• Damaged properties 434, with 165 uninhabitable.
• 50,000 customers without power in Yeppoon and Rockhampton
• Gympie cut off; Mary River hit flood peak of 17m
• Biloela also isolated amid reports 200 homes have been swamped
• SES has had more than 6100 calls for help statewide
— AAP