Director-General Joe Buffone said an earlier national emergency declaration would not have made an impact in sending in additional defence personnel.
Prime Minister Scott Morrison made the emergency declaration on Friday, but Queensland was not included.
"The way this declaration is right at the moment, it actually wouldn't have changed our posture at all," Mr Buffone told reporters in Canberra on Monday.
"The legislation does not change those arrangements ... that we can deploy ADF without the request of the states."
Mr Buffone said it was still up to state governments to request the Australian Defence Force in natural disaster recovery, and not a task for the Commonwealth.
"The Commonwealth does not have the legal authority to take over or respond without authority from the state," he said.
"As the disaster unfolds, the Commonwealth does not become the jurisdiction of responsibility."
The director-general said plans were engaged from February 25, should states request assistance from the ADF.
It comes as the NSW and federal governments continue to be at odds over the timeline of when ADF support was requested in the wake of the floods.
Meanwhile, Mr Morrison said lessons learnt from previous natural disasters had been applied to the recent floods.
As former emergency services chief say they've been ignored by the federal government, Mr Morrison defended the Commonwealth's handling of the disaster.
He said the rollout of ADF troops to the recent floods was quicker than in response to the 2011 Brisbane floods.
"When the floods hit Brisbane a fortnight ago, we saw the ADF turn out in four times the number and about a week earlier," Mr Morrison told reporters on the NSW Central Coast on Monday.
"That says to me that lessons are learnt from one disaster to the next."
It comes as the Emergency Leaders for Climate Action group said the handling of the floods was reminiscent of the lead up to the Black Summer fires.
Former NSW fire commissioner Greg Mullins said the government was warned by its own agencies, such as the Bureau of Meteorology, that flood disasters were forecast.
However, he said the government failed to heed the warnings.
"The Morrison government was missing in action - not listening," he told ABC TV.
"Its their job to prevent this getting worse and into the future, while the emergency services get on with the response."
The prime minister said the group was misinformed about their claims.
"I arranged for our cabinet to be briefed by the Bureau of Meteorology and the director of emergency management on the upcoming weather conditions," Mr Morrison said.
"No one was predicting a one-in-500 year flood - what has occurred there is at a scale that we have never seen before in that part of Australia."
Mr Morrison said national cabinet had also been briefed about the natural disaster forecasts ahead of summer.
NSW and Queensland crews are continuing with a massive clean-up effort following the devastating floods.
As of Monday morning, there were almost 7200 ADF personnel on the ground in Queensland and NSW.
Those numbers are expected to remain the same going into Tuesday.
There have been $713 million in disaster payments made by the federal government to 865,000 flood-affected residents in NSW and Queensland.
Of those, more than $489 million has been paid to NSW residents and more than $224 million has been paid out to affected residents in Queensland.
