A slip at Whareongaonga Bay as seen from a helicopter. Photo: GNS Science /Brenda Rosser
The slip has come after recent flooding, and is one of the biggest scientists have seen in recent times.
The slip at Whareongaonga, south of Gisborne is plastered all over the hill and the shoreline.
It has destroyed some wāhi tapu, or sacred land, close to the manawa or heart of Ngāti Rangiwaho, a hapū of the iwi Ngāi Tāmanuhiri.
Jody Toroa, a representative the Rangiwaho hapū whanaū, said the places were important.
Jody Toroa, whānau of Rangiwaho hapū of Ngāi Tāmanuhiri iwi. Photo: Tom Kitchin
"There's the gathering places, traditional, and the wāhi tapu, we've gone to places to wananga, to learn these places ourselves, 'cause we need to, and then our whānau still gathering kai as did our tūpuna in those places."
There was even a pā site, but it had all disappeared.
"The whole ecology and that whole whakapapa, well that's gone, that went with this whole landslide. And you can't see it - it's gone. And the worst thing is, even the whenua's gone into the moana and it's taken out all this taonga ika - traditional fishing grounds."
GNS scientists were surveying the slip. One of them, Brenda Rosser said it was "really big".
GNS scientists Andrea Wolter (left) and Brenda Rosser. Photo: RNZ/Tom Kitchin
"This is the largest rainfall induced landslide that we've seen in a very long time. This landslide is on a similar scale to the landslides we've seen in Kaikoura from the earthquake."
Rosser and her colleague Andrea Wolter were in Tairāwhiti to observe the hundreds of landslides after the flooding three weeks ago, and get data for a national programme.
"We're developing a model where you can predict where the landslides are going to occur, given the amount of rainfall," Rosser said.
Gisborne District Council principal scientist Dr Murry Cave said, although they had stopped rapidly running around after the flooding three weeks ago, the work was far from over.
"So it's getting into a bit more, less frantic phase - it is one of those situations - we have cyclone season arriving now, keep on monitoring them."
Cave said the council would "have a discussion" with the relevant agencies around the Whareongaonga slip, to see "what we can do to ensure that we can keep people safe there".
The railway line was mothballed after a slip in 2012 - now this most recent landslide has left it even more twisted and ripped apart.
Rail advocate Ken Crispin. Photo: Tom Kitchin
Rail advocate Ken Crispin, who divides his time between Napier and Tairāwhiti, said it was a government failure.
"I think it's a system again of the government of the day - it doesn't matter what government we're talking about, the government of the day doesn't pay call to the area where the problems exist."
KiwiRail general manager of operations for the Lower North Island Paul Ashton said the cost of repairing and maintaining the line was way over its commercial value at the time of the 2012 slip.
"KiwiRail has no plans for any further work on the unused parts of the line.
This is despite opening the Napier to Wairoa line for logs last year.
But Ken Crispin said nothing would stop him pushing for rail.
"We can never give up, Gisborne deserves better."
A 2019 report commissioned by a Gisborne based trust said it was worth spending millions on the line to get it up and running again.