Ten sections of the iconic Abel Tasman walk are "highly susceptible" to landslides, with some areas expected to get four landslides a year in 20 years' time.
The Abel Tasman Coast Track is one of the country's Great Walks and is the most popular with 190,000 visitors last year.
A new report commissioned by the Department of Conservation detailing the risk of landslides to the track was sparked by an increase of severe weather events in recent years.
"These incidents have led to temporary track closures, increased maintenance costs and in some cases an elevated level of safety risk for visitors and staff," the report read.
Report author and geologist Kevin England said if nothing is done it will be "increasingly difficult to keep the track open".
His report found some sections of the track would get up to four landslides a year by 2043 and in some areas "there is no feasible way to reduce the likelihood of future landslides".
"Yes, there are some sections of the track – particularly the coastal cliff sections – where it's a natural process that you can't stop," England said.
"The track crossing some of those cliffs – when a landslide occurs, it's pretty much impossible to put it back in the same location."
The track was closed for months after a storm last August devastated the top of the south. The area also suffered damage in 2012 and 2018.
The track is largely made up of a rock called separation point granite, sometimes known as sugar granite. It crumbles easily and is what makes the golden sand the area is known for.
The report also found there were 14 bridges at risk of debris flow and potential risks to two of the track's main huts. There is a risk of rockfall at Anchorage Hut and a risk of a future landslide at Bark Bay Hut.
A series of recommendations were made, including DOC starting a landslide catalogue; improving drainage; reinforcing the track; and to raise some bridges by one metre.
But where nothing can be done, it was recommended DOC look to re-route sections of the iconic track.
DOC's operations director for northern South Island, Roy Grose, says the department will look to implement as many recommendations as it can.
"It's not just a case of ripping in there with a digger and opening up a new route that might be required," Grose said. "You've got to put some thinking into if you're gonna invest that sort of money to repair something or to re-route it, then it's worth doing it properly".
As well as landslides, the track is also highly susceptible to coastal inundation with some areas washed away in 2018.
Grose said DOC was committed to preserving the track as it was huge for the local economy and important to future generations.
"There's different ways that we can try and work to reduce some of the impacts. But when it's all said and done, nature has the last say."
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