Nearly 415,000 flood victims in NSW have received a total of $340 million in disaster support from the federal government.

The latest crisis has impacted communities from the Blue Mountains to the south coast, with some facing their fourth flood disaster in 18 months.

Residents in 29 local government areas are eligible for the assistance, a one-off $1000 payment for every adult and $400 for every child affected by flooding.

A disaster recovery allowance is also available for employees and sole traders who lose income as a direct result of a major disaster, and lasts for up to 13 weeks.

Prime Minister Anthony Albanese triggered the federal support payments on Wednesday and people could begin claiming them on Thursday afternoon.

Social Services Minister Bill Shorten will visit the Services Australia Smart Centre in Liverpool on Sunday for a briefing on support activities.

Staff have been working around the clock and through the weekend to process the claims, Mr Shorten said.

“The fact these payments have been delivered in under three days is a great credit to Services Australia staff,” he said.

“The commitment to help out their fellow Australians is tangible.”

Flood-affected residents are starting to return to their homes to assess the damage caused by days of unrelenting rain and severe storms.

The government has mobilised some 250 Australian Defence Force troops and three helicopters to assist with the flood response and clean up.

-AAP