The East Cape slip map created by Dragonfly Data Science shows "before" and "after" satellite images of the damage. This picture is a partial image of "before" while the majority is of "after". The pink indicates landslides – 11,000 in all – while the purple is silt, which covers around 900 hectares.
The East Cape slip map created by Dragonfly Data Science shows "before" and "after" satellite images of the damage. This picture is a partial image of "before" while the majority is of "after". The pink indicates landslides – 11,000 in all – while the purple is silt, which covers around 900 hectares.
New work by scientists is shedding light on the effects of slips on the East Cape after the January storm, with more than 11,000 identified by the team from Dragonfly Data Science.
The scientists, who are Wellington-based, mapped the scale of damage by using satellite technology, said Dr Finlay Thompson,director of data science at Dragonfly.
They worked rapidly to produce the East Cape slip map, he said.
“It took about a week to pull it together.”
Their work identified more than 11,000 landslips and around 900 hectares of silt damage.
Patterns were identified from the work, which used “before-and-after satellite imagery to create a clear, regionwide snapshot of what actually happened on the ground”.
Thompson expanded on the trends they had spotted.
Dragonfly director of data science Dr Finlay Thompson is part of a team who have been mapping the effects of slips on the East Cape.
“One of them is that it’s very localised to the far north end of the East Cape, so Te Araroa and Hicks Bay primarily.
“When Cyclone Gabrielle hit, it was much broader. It affected a much larger area, of course, as everybody knows.”
Of the recent storm he said: “There are a lot of landslides and slips on land that is covered with regenerating forest or regenerating native bush, rather than on land that has pine forests or has recently been cleared. I think that it’s clear that the rainfall was very high.
“We are hoping to make this available more broadly, basically as a monitoring tool for people, rather than as a risk identification tool. It’s more about what has happened, rather than what might happen in the future.”
He said the data was “extremely useful” straight after a storm.
“You want to know ‘should I go up that back road and check out the land or maybe I don’t need to because it’s actually fine?’”
He explained how the satellite imaging worked.
“There’s an algorithm which we developed that looks at the satellite imagery before and after the event, so you can see the impact of a specific event by making the comparison.
“If it’s steep hill country, then it’s likely going to be a slip. If it’s flat land, then it’s likely to be a whole lot of sedimentation, rather than a slip.”
Dragonfly created a similar impact map after Cyclone Gabrielle in 2023 that identified flooding, slips and affected communities at scale to support response and recovery planning.
Thompson said their latest work could be used to help local agencies after weather events.
“We made it available publicly, so we’re not charging for it. We’re showcasing what we can do. We would like to see this be made available publicly in a user-friendly way so that access is not limited to the council organisations and so on. We imagine that everybody in the community can make use of it.”
Thompson said they had received inquiries about making it available across New Zealand continuously rather than in response to a big storm. They were hoping for support from central agencies or sponsorship “to make it happen”.
A slip on State Highway 35 at the top of East Cape.
The work was timely and it could potentially be updated with another storm looming.
“We’ll see what happens, but it might be that we try and update it with the impacts of the upcoming storm. Depends a little bit on the timing.”
Data came from a satellite system that was updated every nine days, he said.
“It’s becoming quite serious, obviously, for Tairāwhiti and I feel there’s a bit of soul-searching that we all need to do.
“It was interesting listening to the community in Te Araroa that they feel a little bit like, well, if these roads are not maintained and supported, then people won’t be able to live there at all.
“Our hearts go out to all the people who are being affected by these storms. The East Cape has really had it bad over the last little while and I think ... we all know somebody who lives up there.”
