THE floods in northern NSW could push the state's road repair bill to $500 million, NSW Roads Minister Duncan Gay says.

The floods that turned parts of NSW into an inland sea and cut off towns including Moree and Wee Waa are starting to recede, and councils, farmers and the state government are turning their minds to repairing the damage.

The NSW government has already spent $212 million to repair flood-damaged roads in the 2011-12 financial year, and the most recent disaster could add another $300 million to the bill, Mr Gay said.

"It's pretty horrendous. We're obviously waiting in many areas for the floodwaters to recede, so we can do a full evaluation," Mr Gay told ABC Radio.

"My best guesstimate is that (the disaster repair bill) is going to be somewhere between $300 and $500 million that have been unbudgeted for."

NSW Government natural disaster funding provides councils with 75 per cent of the funds for road repairs up to $116,000, and pays for 100 per cent above that.

"Roads and Maritime Services (RMS) has already contacted local councils affected by recent floods to start the natural disaster road funding processes," a spokesman for Mr Gay said.

"The assessment of damage is continuing and will do so for a while yet, but with the severity of the flooding many areas will be in immediate need."