NSW farmers could lose $750m from floods

The agricultural industry is expected to suffer losses of at least $750 million as a result of the devastating NSW floods, with tens of thousands of livestock at risk.

As floodwaters from Queensland and northern NSW slowly flow towards western NSW townships such as Walgett and Bourke, farmers are already counting the cost of flooding around Moree and in the Brewarrina district.

Department of Primary Industries (DPI) Flood Incident Controller, Simon Oliver, said up 10,000 sheep had most likely been lost to the floodwaters, while extensive damage to crops, pastures and infrastructure was also being recorded.

A further 100,000 livestock in areas downstream were also at risk, and the DPI was now working to help farmers relocate animals to higher ground.

"There is a conservative figure being thrown around from a preliminary estimate of $750 million, that includes all impacts on primary industries like damage to infrastructure, the cotton fields and roads, buildings and fodder storages, estimated stock losses, pasture losses and crop losses," Mr Oliver told AAP.

"Obviously those figures are going to change significantly as we can get a better idea as the water clears."

Mr Oliver said struggling farmers had a mixed response to the devastation.

"In a lot of cases the farmers haven't really had that much opportunity to get out and have a good look around," he said.

"It's a mixed response. Some of them are devastated because they've lost stock. The ones that have been through it many times, they take it on the chin as part of farming."

Touring Moree on Wednesday, NSW Emergency Services Minister Mike Gallacher said the damage bill for the town and surrounds could run into the hundreds of millions of dollars, with the extent of the destruction not yet known.

He said it was "probably a bit early" to put a dollar figure on the damage caused by the flooding, the worst the town has seen since 1955.

"But talking to people on the ground up here, we're going to be well into the hundreds and hundreds of millions of dollars," he said.

"We still have no understanding of the outlying areas of councils in this area, just how bad the impact has been on infrastructure."

SES Commissioner Murray Kear praised the clean-up of Moree, saying CBD streets flooded on the weekend had already been cleared of mud from the Mehi River.

"I was here at the height of the flood in Moree only a few days ago, where water was a metre deep up against some homes," said Mr Kear, who visited Moree with Mr Gallacher.

"Today the water has completely moved away, but what it has left is a terrible mud residue, which is being cleared up very quickly.

"But it will be many many days until a figure can be placed on the damage to roads, to infrastructure, and of course people's private property."

Mr Gallacher and Mr Kear also visited Walgett in the state's west on Wednesday, where preparations are being made for the oncoming floodwaters, expected on Monday.

Mr Kear said 5000 people around the state were still isolated, but that figure could rise to 10,000 as floodwaters reached towns like Walgett, Brewarrina and Bourke.

"We are now planning across a large area of the state for this large body of water to very slowly move in a south-westerly direction," Mr Kear said.

"The waters coming down from Queensland ... is already in these western rivers heading west, and (there is) an already major flooded Darling River.

"Those three components are joining together to mean some possible major flooding for towns on the way down the Darling system."

Mr Gallacher on Wednesday extended natural disaster declarations to the Liverpool Plains, Ballina, Upper Hunter and Gloucester local government areas.

The latest declaration brings the number of disaster zones to 21.

President of the NSW Farmers Association Fiona Simson said it was hard to predict flood damage so early into the disaster, but the estimated cost to the agricultural industry of $750 million "could be quite conservative".

"The concern is that some of the crops may well be harvestable, but the infrastructure to actually get those crops out has gone," Ms Simson told AAP.

"Until we know how quickly we can get some of that infrastructure up, until we know we can get some of that infrastructure up, until we know how quickly the water dissipates, those sort of figures could change dramatically."