Flood damage to agricultural crops in New South Wales has been estimated at more than $500 million, but authorities say the figure is conservative and they expect it to rise.

More than 200 landholders have filed flood damage reports, as the continuing wet weather creates ongoing flooding across affected catchments.

Department of Primary Industries emergency coordinator Simon Oliver said authorities expected the damage bill would continue to rise as farmers were able to get out and assess their losses.

"Our early estimates are there's probably $500 million worth of damage to crops," he said.

"That's probably being reasonably conservative at this stage. There's a lot of stock that are either missing or unaccounted for, or have deceased.

"And we have probably got about 400 kilometres of fencing that we know has already been lost, 500km of internal roads, and obviously there are other infrastructure issues, so it is starting to get quite severe."

Damage bill expected to rise as farmers assess impact

Mr Oliver expected more flood damage reports to be filed in coming days and weeks, as landholders were able to quantify what damage they had suffered.

"In the Forbes area they are starting to open up the recovery centres, so they are recognising that this has a long and devastating impact on the local communities," he said.

"We are particularly concerned about livestock in the west that are already isolated.

"With the length of this inundation they will eventually run out of feed and that will increase the need for assistance.

"It is important that farmers report the damage, as soon as they are able to get out and assess it, because we need that information to help paint the whole picture."

Landholders can report flood damage, stock losses and other issues related to the flooding by phoning 1300 795 299.

They can also email emergency.centralwest@lls.nsw.gov.au or contact their nearest Local Land Services office.