A pregnant cow has survived a mammoth swim through floodwater between Lismore and Ballina on the north coast of New South Wales.

The Angus-cross cow, which is six months pregnant and due to calve in a few months, clambered up on land at Pimlico, near Ballina at the mouth of the Richmond River, on Sunday morning, much to the surprise of landholders.

John Stead and his wife were watching the Richmond River in full flood and the debris roaring past.

"Next thing this black hulk emerged from the riverbank and up onto the road, and then we realised it was a cow," Mr Stead said.

"We do have a jetty and angled ramp where she could scramble and get a foothold, so that's how she scrambled up here.

"Most of the way it is all mangroves she wouldn't be able to get out of."

The couple called a neighbour and built a temporary yard for the cow they have called Debbie.

"We called her Debbie because of Debbie the cyclone, and because of all the debris floating down the river," Mr Stead said.

Ear tag helps find owner

The cow's electronic identification tag was not working, but she did have a yellow ear tag that helped start the hunt for her home.

Livestock carrier Wayne Bruggy arrived at the Stead family's place to transport the cow away, and noticed the tag looked like one from a farm near Lismore where he had been recently mustering cattle.

"I thought no, it could not be from there, no way. But turns out it was," Mr Bruggy said.

"I went and had a look at the cow, identified the tag, made a few phone calls, and the person who I thought was missing cattle was."

Cow found in wrong postcode

The cow was one of 30 Brangus cattle valued at almost $50,000 swept away in floodwater from Tony Ivey's Gundurimba property, east of Lismore.

Mr Ivey said the cow had survived three days in floodwater.

"Unbelievable. That is a long time in the water, days and days. It's just unreal," he said.

"I love my cattle and spend a lot of time with them. I said to my wife I feel like I'm in the boxing ring with my hands tied behind my back. It's been pretty traumatic."

Five of Mr Ivey's cows have been found, but none as far downstream as Pimlico.

"The young fella that was trying to catch it, he knew my ear tag and he rang me and said I found one of your cows'," Mr Ivey said.

"And I said 'I've found one too, down at Ruthven', and he said 'I can beat that, down at Pimlico', unbelievable.

"They were all in really good condition, the ones that have swum and got out of the water. They were in good nick and I think that's the reason why they have survived.

Mr Bruggy said he had not heard of a cow travelling that far and surviving.

"She came from Riverbank Road, Gundurimba, and ended up at Riverbank Road, Pimlico," he said.

"Just the wrong postcode really, pretty uncanny."