Fears for third person in NSW floodwaters

Residents in the devastated NSW town of Forbes are breathing a sigh of relief as the Lachlan River holds steady, just below expectations of record flooding, but amid fears a third person has been swept away.

Police are searching for the body of a young man spotted in floodwaters at nearby Eugowra, which was devastated with catastrophic roof-high inundation on Monday.

A police officer was helping a stranded elderly woman when she sighted the body, before losing sight of it.

There are no further reports of people missing from the area and police are appealing for help identifying the man, who is described as being in his 20s, Caucasian in appearance, slimly built and with fair hair.

The body of 60-year-old Dianne Smith has already been recovered from floodwaters in Eugowra and 85-year-old Ljubisa "Les" Vugec, 85, who was last seen at his Eugowra home, remains missing.

Meanwhile, Forbes Mayor Phyllis Miller said the Lachlan River, although not exceeding 10.68m at the town's Iron Bridge, had not yet started to recede.

"Waiting for the peak is like watching grass grow but for now there's some sense of relief," she told AAP on Thursday.

The river, which divides Forbes, was forecast to peak at 10.8 metres, a similar level to the historic inundation of June 1952.

Around 1000 people have been evacuated and the flooding is tipped to continue for days.

The mayor urged federal authorities to reassess eligibility for disaster funds, namely to boost help for farmers from $25,000 up to $75,000.

"We've got people who have lost absolutely everything here," she said.

Ms Miller said the tight-knit community had pulled together during two months of constant flooding.

"It's all about sharing resources and helping each other in times of crisis."

Federal Emergency Management Minister Murray Watt says the clean-up bill will be staggering, with $3 billion allocated for disaster payments and repairs alone.

Hundreds of homes and businesses in Forbes are under water - some for the second time in as many weeks - and hundreds of emergency volunteers and workers are helping evacuees and conducting rescues.

"The overall cost of the current flood disaster, I can guarantee you, is going to be in the billions," Mr Watt told reporters in Brisbane.

"With each week these the floods go on and with each road damaged, the damage bill is going to go up.

"You've literally got homes that have been washed away ... they've been dislodged and moved in some cases tens and hundreds of metres down the street."

Authorities conducted 284 property assessments at Eugowra on Wednesday and determined the vast majority damaged.

Residents described two sudden and intense surges of water, which washed away homes, knocked over structures and left destruction like a "war zone".

The SES performed 12 flood rescues and handled 265 requests for help in the 24 hours until Thursday morning.

Two hours west, the entire town of Condobolin has been cut off.

"We've got a situation now which is just an absolute natural disaster," Lachlan Shire mayor John Medcalf told AAP.

"At the moment, the flood is at one of its highest peaks it's been for many, many years."

With the airport being the town's last port of contact, the community is relying on emergency airdrop supplies after fuel levels and basic products such as milk ran low.

Farmers have lost entire crops, ahead of harvest season.

Across the state, authorities have issued 113 warnings and 23 evacuation orders, including for Forbes and nearby Gooloogong, Gunnedah in the northeast and the southern border town of Moama.

Meanwhile, 18 flood rescue specialists have arrived from the Singapore Civil Defence Force to relieve exhausted workers who have dealt with 65 consecutive days of flood.

They will be deployed to Parkes and Wagga Wagga.

Along the Lachlan, major flooding is also occurring at Nanami, Cottons Weir, Jemalong and Hillston.