More than half the country's historic landfills could be exposed to the risks of climate change, according to a new report.

The report, commissioned by the Ministry for the Environment in the wake of the Fox River disaster in 2019, is the first time there has been an in-depth level of data on a national scale.

It looked at three factors of climate change: coastal inundation, proximity to the sea, and flooding. It found 1797 of the country's historic landfills could be impacted by at least one of the three factors and 176 are exposed to all three.

"Historically our work in this area has been around contamination from old industry activity but with the increasing energy from storm events, we're seeing that more of these landfills are at risk of being exposed," Ministry for the Environment's Glenn Wigley said.

Wigley said councils will now need to look at those site which are high risk, with the ministry rolling out a tool to give them more information from next year.

"Some sites may need to be removed and some sites may need to be strengthened to enable them to remain safely," he said.

Most of the landfills in the report are between 40 to 100 years old, from a time when climate change wasn't a consideration. While some are dumps from household waste, others may be farmers' burn piles and they can vary in size.

The region with the most high risk landfills – which are potentially exposed to all three climate change factors – is Auckland, followed by Tasman and Canterbury.

Tasman District Council's Rob Smith said they monitor these sites at least every two years and have already done a lot of work to manage risks.

"The most prominent ones of these sites are actually contained. So, they have a clay cap on them to stop material coming through," Smith said.

"You'll see we had some right at coastline, those ones have rock bunds around them so they are protected from erosion so it's not that they are just open and exposed."

One example is the Appleby dump which took household waste from 1971 to 1991. While there's no immediate concerns with the site, it sits right beside the Waimea River.

"That's next year's job," Smith said. "We've actually put some budget aside to actually go and do test pitting around that one to quantify the size and then, also, so we can work out the cost of remediation."

In September, a new government fund was set up with $30 million across the next two years to help councils and private property owners remedy situations like this.

It comes in the wake of the Fox River disaster in 2019 when an old landfill was exposed by a storm and rubbish flooded the local waterways, requiring a huge clean-up effort.

Fox River clean-up organiser Mike Bilodeau said at the time he was shocked something like that could happen.

"I was blown away because you just don't think about landfills in that way. You think, you know, your rubbish is out of sight, out of mind."

Bilodeau said as he learnt more, he was surprised how many of these historic landfill sites were around the country.

He said with the new report, the council should come up with individual plans for each high-risk site so that there isn't a repeat of Fox River.

"I'm surprised it hasn't happened already."