A landfill expert says broken dumps like the West Coast's Fox River and Dunedin's Kettle Park are just the tip of the iceberg.

Clean-up of the Old Fox River landfill's due to end today, after rubbish breached out into about 20-kilometres of the Fox River during a storm in March.

However, it comes as large swells have stripped away sand protecting the old landfill under Dunedin's Kettle Park, and forecasts of more big seas to come have the Dunedin City Council on alert.

Council infrastructure services general manager Simon Drew said high seas in recent days had eaten into sand dunes at Ocean Beach, near Kettle Park, along a 200m front.

Between 5m and 10m of dune had been lost, leaving behind a near-vertical scarp and exposing pieces of concrete, brick and other rubble placed there in 2007 to protect the old landfill buried behind the dune.

Drew said the rubble now exposed on the beach was not landfill material, and there was no immediate risk to people or the environment.

However, with more big swells expected next week, the situation was being taken "seriously", he said.

The risk of a repeat of events on the West Coast, where an old landfill breached and deposited rubbish along the coastline, was still "low".

AUT senior lecturer Dr Jeff Seadon says there's more than 200 old landfills around New Zealand that could do the same as these sites. 

He told Andrew Dickens these old landfills were built near water as a convenient way to build new recreation areas.

"You put your waste down there, build it up above the water level, then you can just put a nice small cap over it, put some grass over it, and away you go, you've got yourself a rugby field."