Storm damage is costing the Department of Conservation millions of dollars with repair bills rising nearly fivefold over the past five financial years.

Engineers have found the 147-metre long flood-damaged Heaphy Bridge on the Heaphy Track cannot be repaired.

The total storm damage spending was $28 million for the five financial years between 2017 and 2022 across its tracks, huts and other visitor infrastructure.

That's compared to $4.8m spent on storm damage in the four financial years between 2013 and 2017.

DOC's heritage and visitors director, Tim Bamford, says it was difficult to determine the impact of climate changes on costs.

"We would be looking at very long-term data to accurately attribute damage to climate change," says Tim..

"However, the data on DOC's spending in response to storm damage and urgent inspection... to address visitor safety over the last five years illustrates the impact of changing weather patterns."

Storm damage to the Great Walks has cost $5.6m in the five financial years between 2017 and 2022.

The five-year average budget for storm damage was $5.6m between 2017 and 2022 compared to the $1.2m average between 2013 and 2017.

The department had allocated an average of $3.2m over each of the past five financial years towards a reactive storm budget. It spent less than that on storm damage in the 2017/2018, 2018/2019 and 2020/2021 financial years.

However, in the 2021/2022 financial year, an extra $5m was earmarked to cover damage caused by Cyclone Dovi.

In 2019/2020, DOC allocated $13.7m for a storm recovery programme, bumping up the budget from the allocated $2.2m to $15m.

The Heaphy Track accounted for more than $1.8m alone while $1.3m was spent on the Routeburn Track and $1.2m was needed for the Milford Track.

Logistics has been a massive challenge for the crews repairing Milford Track after floods caused damage in early 2020.

Repairs underway on an area of the Milford Track damaged by floods in early 2020. Photo: RNZ / Tess Brunton