New South Wales Premier Dominic Perrottet has promised a new $25 million mental health support package for flood-affected regions while warning the current crisis is "not over".

Eight recovery centres have been established in the state's north to assist flood victims so far.

"Our top three priorities are cleanups, getting people into homes and getting financial assistance out the door," he said.

"We are working tirelessly to achieve that."

He added 1500 people were currently in emergency housing, with the state government working to ensure people had access to safe and secure homes.

"We want to do whatever we can to get as many people in housing as quickly as possible. It's a massive challenge," Mr Perrottet said.

"Whilst the task is significant, we are up to it."

Mass cleanups remain underway, assisted by thousands of Australian Defence Force personnel and local volunteers.

Over 4000 tonnes of debris are being collected every day in areas like the Northern Rivers.

Twenty-three evacuation orders affecting 3470 people remain in place and 1415 people are preparing to evacuate.

The premier warned residents not to be complacent, urging those in flood-impacted regions to heed warnings.

"My key message today is please follow these instructions," Mr Perrottet said.

"This event is not over."

Premier commits $25 million to ongoing mental health support

A $25 million package has been announced to provide mental health support for flood-affected regions.

Mr Perrottet said healing from the current crisis would take months and years.

"It's very clear to me from spending time in emergency evacuation centres that more needs to be done not just right now, but for months and years to come," Mr Perrottet said.

"This has been, for many people, a very distressing and traumatic time ... my message is we will get through it."

Funding will initially be delegated to communities deemed most in need.

Thousands of students wait to return to school

Teachers at Richmond River High School in Lismore said every room had been inundated by floodwaters, leaving a mass of destruction in their wake.

"The damage to Richmond River High is significant - there's not a classroom that hasn't been inundated," the school's principal, Luke Woodward said.

"The smell is next level through the school because of all the floodwater that's been through.

"We've lost literally all our teaching resources, we've lost things like our grand piano for our music students."

"There's so many memories that have been lost by staff and students - it's about the kids - not about the building."

Mr Woodward said the Australian Defence Force had been working to clear debris and rubbish from the facility in efforts to salvage the school.

"They are doing an incredible job," he said.

Works are now underway to accommodate the 500 to 1200 displaced students and teachers from Richmond River High School at Lismore High School, a sister campus of Rivers Secondary College.

Rivers Secondary College Principal Chris Williams said students were still dealing with the destruction of their homes.

"It's just epic, unless you drive down the streets it's indescribable," Mr Williams said.

"Kids have not been doing any learning, half of our kids have been impacted and are out there ripping out the contents of their homes, combing through the mud and helping theidespite the difficultyr families to try and get things back to a sense of normality."

The Richmond River High School will be temporarily reestablished at a new, safe site.

Flood recovery ramped up in Hawkesbury region

Power remains out in the Hawkesbury regions of Lower Mangrove, Green Grove and Mangrove Creek.

Electricity is predicted to return to the Wiseman's Ferry community tomorrow, while the suburbs of Spencer and Marlow will remain without power for the next two days.

Yesterday, Prime Minister Scott Morrison announced a $1 billion package to aid flood recovery, which included additional disaster payments and boosting military personnel on the ground.

The Australian Defence Force has stationed 4300 troops across the state to help with clean up efforts, half of which are stationed in the devastated Northern Rivers region.

In total, military support has increased to 7000 personnel across flood-affected Queensland and New South Wales.

Three Singaporean and ADF chinooks have landed to provide critical aid, like tents, blankets, meals and bottled water to residents.

Australian troops are currently distributing 33 pallets of disaster relief provided by the Singaporean Government.

The Federal Government has also announced a new payment for veterans left homeless by the floods, with a $3000 emergency payment boost and a $100 Coles voucher available for those affected.

Veteran's affairs minister David Elliott will visit Lismore on Thursday this week.

'Raging, unstoppable torrent of water'

Works are underway to clear Queensland's Brisbane River of dangerous debris following the state's historic flood event, as the river's port returns to 24/7 operation.

Queensland Treasurer and Investment Minister Cameron Dick said activity on the Brisbane River was a key contributor to the state's economy, with the recent flooding bringing activity to a stand-still.

"The wettest February we've seen in our state in 130 years," Mr Dick said.

"The Brisbane River itself turned into a raging, unstoppable torrent of water."

This week, two navy vessels and military divers worked to clear dangerous debris from the river, with clean-up efforts continuing.

"The Brisbane River itself remains a place of danger. We know there is danger lurking underneath the water of the Brisbane River," Mr Dick said.

He added activity on the river contributed $50 billion each year to the state's economy.

"The impact on our river and our local economy is significant. We need our ports to operate," Mr Dick said.