Report confirms Mt Taranaki erosion getting worse

Mt Taranaki. Photo / Mark Mitchell

Erosion on Mt Taranaki is getting worse and could jeopardise local infrastructure, a new report says.

The Landcare Research report, commissioned by the Taranaki Regional Council, confirmed major erosion was taking place all over the mountain, including an area called Pyramid Stream, on the Stony River track, where millions of tonnes of rock and sand collapsed last week.

The collapse created large dust clouds and panic among some people, who thought the volcano was erupting.

The report, released to the Taranaki Daily News, found several other significant catchments, including the sources of domestic water supplies for New Plymouth and Opunake, had sustained damage.

The authors of the report blamed climate change, saying an increase in both the frequency and intensity of major storms high up the mountain was making erosion worse.

Aerial photographs, taken between 1995 and 2007, showed 14.3 million cubic metres of terrain had collapsed.

Since then at least that amount - possibly even more - had eroded.

"It is clear that the trend of increasingly severe erosion, perhaps linked to increasing storm frequency and intensity, has continued beyond 2007 and may do so in the future," the report said.

"The Stony (River catchment) is the most extreme example of a number of catchments that are experiencing severe, and apparently worsening, erosion in their headwaters.

"The prospect of this situation worsening presents problems to infrastructure and farming on the ring plain.

"This is a consequence of increasing amounts of rock and debris being deposited within river channels, reducing their capacity and increasing the risk of flooding and, in extreme events, damage from debris flows."

Council chief executive Basil Chamberlain told the newspaper people should not be alarmed by the report but that they did need to learn to live with it.

Department of Conservation area manager Phil Mohi yesterday told NZPA Pyramid Stream had been eroding for 40 years.

"I think people are jumping the gun a little bit...it's just cutting into the foot of the mountain and it's accelerating the erosion up in the steeper areas, but basically we do get these events happening when we haven't had rain in a long time," he said.

"And we have the strong winds... it picks up the fine dust (and) creates these dust clouds."

Mr Mohi advised trampers to avoid the area as there was a high chance of rockfall.

"When that winds blowing you're just, like, in a sandstorm," he said.

"You're getting rocks and debris (falling). It's not a place to be."

- NZPA