Environment Southland is warning boaties and swimmers to watch out for railway irons sticking out of rivers years after they were first used.

The irons were used to control erosion several decades ago but now are a safety hazard on the Makarewa, Ōreti, Mataura and Waikaia rivers.

The irons hve been found protruding from river waters or submerged just below the surface.

Environment Southland has been removing the railway irons but some remain in rivers and pose a hazard.

It has been putting buoys and flags on them as a warning.

According to Environment Southland railway irons have been discovered:

• In the Makarewa River, in a section of the river near North Makarewa Grove Bush Road and Orion Road west.
• In the Ōreti River, at several locations south of State Highway 99 Riverton-Wallacetown Highway and north of West Plains Road.
• In the Mataura River,between Cattle Flat and Riversdale-Waikaia Road.
• In the Waikaia River, adjacent to Waipuru Road and north of Waipounamu Bridge Road.
• The irons are being marked on Environment Southland's beacon mapping app and the organisation is urging people to check the app over summer.

Deputy Harbourmaster Zak Smith said people should "travel with extreme caution".

"The changing nature of our rivers, in the decades since these railway irons were originally placed there for erosion control, has resulted in the railway irons now being in the main river channel making them a major safety hazard to vessels and river users.

"It is possible that there are more that are yet to be discovered on other parts of Southland's rivers, particularly because some have been found submerged under each river's waterline."

Anyone who finds a railway iron can also call the council to report it.

Reproduced with permission