Drone map of the landslide at Te Kuri o Pāoa/Young Nick’s Head. Photo: Murry Cave / supplied
Drone surveys show two areas of Gisborne hit by landslides are likely to fail again.
Last Sunday, a large slip was discovered at Te Kuri o Pāoa/Young Nick's Head cliff face, prompting a warning for people and boaties to stay away.
Gisborne District Council scientist Murry Cave said there were significant ongoing risks along the cliff, and a detailed assessment would take time.
"It was clear from this that there would be an ongoing risk from the landslide and a more detailed assessment would be required.
"There's also significant ongoing risks, not just at the current landslide site but at a number of sites along the cliff."
The Bushy Knoll landslide in Tiniroto, which brought down 70,000 tonnes of debris in July, was also likely to slip again in heavy rain.
"If the rain is heavy enough to trigger a further collapse of this landslide, it could generate a debris flow that could travel downstream for a considerable distance," Cave said.
"The most immediate risk that has been identified is to the bridge on Elmers Road which has very little freeboard (clearance above highwater level) and was damaged during Cyclone Gabrielle."
Aerial map of Bushy Knoll landslide. Photo: Murry Cave / supplied
He said the land failures started with Cyclone Gabrielle and had gotten worse since.
"The slopes in this area are quite steep and the ground remains very wet like it does elsewhere in the region. This means that the landslide is very likely to fail again."
Anyone who noticed "unusual signs of movement on their land", including cracks or hollows developing, should get in touch with the Gisborne District Council, Cave said.