Mt Maunganui landslide: Should the warnings have been seen?

Saturday, 24 January 2026

It was an unprecedented weather event. But the signs were there of a looming catastrophe.

The worst had passed.

The skies had dumped a record deluge overnight, but by the time Tauranga’s red rainfall warning expired at 9am on Thursday, the sun had taken charge again.

But half an hour later, just before checkout time at the Mount Maunganui Beachside Holiday Park on Adams Ave, those venturing out after the drenching heard the first cracks, the first groans and rumbles, the sounds that combined to seem like a freight train was passing just beside them, according to witnesses.

Part of the hillside behind the campground had given way, collapsing with the weight of the water, pouring down and engulfing an area at the back of the camp - an area with holidaymakers starting their day.

Six people remain missing, presumed dead in the slip.

There was little chance of them escaping.

Or was there?

On Friday night, Tauranga City Council announced an independent review into what happened before the mountainside collapsed.

Were there warnings something catastrophic could happen, hours earlier?

And were there signs from years ago that the flanks of Mauao, Mt Maunganui, were a place to be cautious, and perhaps retreat from.

Warning signs

The storm had been predicted. On Wednesday, a state of emergency was issued for Bay of Plenty with up to 240mm of rain forecast in the 24 hours until 9am Thursday.

In the end, Tauranga received 274mm - with 198mm falling in the 12 hours before 6am.

The amount broke records, becoming the city’s wettest day since records began in 1910.

Driven by an easterly wind, it saturated the Mount’s slopes above the campground.

Shortly after 7.30am on Thursday, Mt Maunganui local Colin McGonagle was out walking when he cut through the campground.

He started chatting to a father and daughter who had been evacuated from their tent during the night, because of the rain.

Around them was what McGonagle describes as a wall of mud.

'You could see it was almost moving because the water was coming through it, and [the father] said, 'Oh, that pile of dirt there, that came over about half an hour ago, and that tree that's there, that came down 10 minutes ago'.

'So I was talking with them and saying 'There's a lot of water coming out here, this isn't good.’

'I'm no engineer and I certainly don't understand the geographical, geology of the mountain, but things were moving.'

In photos taken by McGonagle nearly two hours before the fatal slip, trees uprooted by smaller slips in the camp ground can already be seen, along with spreading mud.

Others have reported people warning campers about the rain’s risks after an earlier slip, as dawn broke.

Just before 9am, Tauranga City Council closed tracks around the Mount.

But despite other nearby slips, nothing appears to have been done to move campers.

And then the sun came out, and everybody thought the worst was over.

A history of landslides

Groundwater seepage, as seen by McGonagle, is one of the 'telltale signs' that a landslide is happening, according to the Australian Geomechanics Society's landslide guide.

Others include open cracks, bulges at the lower part of slopes, trees leaning down or with exposed roots, fallen debris at the foot of a cliff, and hummocky ground.

At least seven major slips occurred on the Mount on Thursday, some taking out tracks and boardwalks.

A July 2025 landslide study warned of danger across Mount Maunganui – but the deadly slip that buried at least six people this week hit just outside the zones officials had mapped.

The report, commissioned by Tauranga City Council, used detailed terrain mapping to define high-risk slopes. But its boundaries stopped at Adams Avenue, east of the holiday park, leaving the area unmapped.

The combination of steep terrain and unstable soils in the region has created ongoing landslide risk for more than a century.

The city has recorded documented landslide damage since 1907, with major events triggered by storms in March 1979, May 1995, May 2005, April 2017, and January 2023.

And a 2014 inventory of past landslides includes a large 1977 slip in the same area, behind the holiday park and hot pools.

That history prompted the council to launch a city-wide landslide mapping project in 2023.

Although the July 2025 report, written by consultants WSP, examined Mauao in detail, the study area stopped short of the mountain’s lower slopes and the holiday park.

Experts spoken to by The Post suggest this was likely because there are no permanent properties there requiring LIM notices, however this left tourists and short-term visitors exposed to risk.

The authors highlighted rainfall as the primary trigger for landslides.

They cited 2011’s Cyclone Wilma, when intense rainfall triggered at least eight large landslides on Mauao. (An April 2017 slip, that took out the popular base track during ex-Cyclone Debbie is not referenced).

During Cyclone Wilma, Mauao experienced “multiple slope failures”. These were not minor slips. The heavy rainfall saw the ground became so saturated that the water pressure pushed the soil particles apart, destroying the friction that holds the slope together.

WSP told The Post the council would not allow the report’s authors to speak with media. The council did not respond to questions on Friday night.

Tom Robinson, senior lecturer at the School of Earth and Environment at the University of Canterbury, and an expert in disaster risk and resilience, explained the challenge for councils in areas like Mount Maunganui.

“It’s probably one of the more difficult tasks we have … to forecast when a landslide is going to occur, exactly where it’s going to occur, and then where it’s going to go. All three of those things are very, very, very difficult.”

He highlighted how nearly identical slopes can behave differently: “From [Cyclone] Gabrielle slopes that look absolutely identical, experiencing exactly the same amount of rainfall, one fails and one doesn’t. The runout is a few tens of metres on one, and hundreds on another.”

And Robinson emphasised the challenge of relying on historical hazard mapping in a changing climate. “Even areas that have never failed before could become vulnerable because a small amount of rain can push a slope over the edge.

“What was considered a safe zone a few years ago might no longer be safe under current or future climate conditions,” Robinson said.

Robinson also put the human cost in perspective.

“Since European settlement, landslides have killed around 1800 people in New Zealand – more than all earthquakes combined. We tend to focus on big events, but it’s these smaller, deadly slips that take lives one or two at a time, often in places people think are safe.”

The science of slips

Everyone knew Mauao acted like a sponge.

After the 2011 storms, locals remember old streams re-emerging and flowing to the sea for months as the mountain’s slopes continued to weep.

Put simply, “it’s a big rock with a whole lot of soil on it,” says one long-time resident.

Jan Kupec, principal geotech engineer with Aurecon, and an urban search and rescue specialist, says slips happen when intense rainfall gets into soil, makes it heavier, and drags it down.

While a slope’s steepness can be a factor, there’s no minimum gradient for slips, Kupec says.

“Even shallow slopes can actually fail. And conversely, we have also slopes in Christchurch, standing vertically for the last 100 years. So it’s a function of the soil type, but also a function of the rain event that’s occurred. So how much water is able to get into the soil itself, and how much is actually running off?”

What’s on top of the land also matters, Kupec says.

“If you have well-established forest, first of all, the canopy will be shedding some of the water away. Second, the roots themselves bind the ground together, and vegetation takes up some moisture as well. Whereas grass, or uncovered slopes, has a problem.”

The best way to predict future landslides, is to mine the past, Kupec says. Slopes that have slipped previously are more likely to go again.

“Even more so with climate change, we'll see more extreme rain events. So a slope that was unstable over the last 50 years will be equally unstable, if not more so, now and in the future.”

Some concerns have been raised about delays in searching by emergency services. While members of the public immediately raced to the scene and began trying to find victims by dismantling rubble, they were then told to stand back by the authorities concerned about the slip being unstable.

Kupec understands better than most the extraordinary challenge of searching for life in mountains of debris. He spent three weeks in the collapsed PGC building and on the Port Hills after the 2011 Christchurch earthquake, and in 2024, was part of a team sent to Papua New Guinea to assess the stability of 14 hectares of slumped hillside that buried hundreds.

When asked how you go about clearing an active landslide, Kupec says “very carefully”.

“To be honest, it's really challenging, and you have to be actually on the ground to make a judgment call. It depends on the topography, on the weather, on the soil, the mass that came down.

“That slope that has failed has a high propensity to fail again, especially when you can see seepage coming out of the face - it's a good indication that the slopes are saturated.

“The consistency is like wet sand or wet concrete when it comes down. So the challenge for rescuers is finding voids that are large enough for individuals to survive within them. Secondly, if people are fully entombed, soil is relatively cold - between 12 to 15 degrees - so there is the consideration of thermal shock as well.”

While the chance of surviving is low in a pure landslide, structures caught inside a slip can create cavities where someone could survive, Kupec says.

Who was responsible?

Ownership of Mt Maunganui, the camp ground and the adjacent hot pools is complex.

So is who was responsible for potentially foreseeing what occurred at the camp ground and issuing warnings.

The Mauao historic reserve that encompasses the mountain is owned by a trust representing three Tauranga iwi, and co-managed by iwi and Tauranga City Council.

However, the holiday park and hot pools lie outside the reserve, and are owned and run by the council and its offshoots.

On Friday, Tauranga Mayor Mahé Drysdale said he had heard there was possibly a small slip earlier on that forced some people to move away from the site.

But he said the focus right now had to be on the search and rescue operation, though it was clear there were big questions to be answered.

'I can just assure you that we will answer those questions.

“We'll go through a proper process. It will be public. We will answer all those questions and understand how we got to the situation we've got to now.”

In announcing an independent review into the response, Drysdale acknowledged the “scale and seriousness” of the disaster, which he said was of “local, national and international importance”.

“It is important that we have a clear and accurate understanding of the facts and events leading up to the landslide, so that we can ensure that the future safety of the community is appropriately safeguarded.”

For now, the mountain is closed.

Iwi kaumatua have suggested the closure could be for many months, or even permanent.

Ngāti Pukenga and Ngāti Ranginui historian and cultural consultant Buddy Mikaere expected an urgent meeting would be called to discuss Mauao’s future protection.

'The arrangement has been, while we have ownership, we've treated it as a public reserve.'

But with close to a million people visiting Mauao every year, Mikaere said consideration had to be given to safety, and possibly closing it.