The Landslide Blog is written by Dave Petley, who is widely recognized as a world leader in the study and management of landslides.
The Gisborne area of New Zealand was severely impacted by Cyclone Gabrielle in February 2023, an event that triggered many thousands of landslides in the area. One effect of such large events is a legacy of potentially unstable slopes that then fail in subsequent rainstorms. In the last few months, Gisborne has seen two such events.
The first, known as the Bushy Knoll landslide, occurred after heavy rainfall on 24 to 26 June 2024 near to Tiniroto. These two images, collected by Dr Murry Cave of Gisborne District Council, show the failure:-
The Bushy Knoll landslide near to Tiniroto in Gisborne, New Zealand. Image by Dr Murry Cave of Gisborne District Council.
The Bushy Knoll landslide near to Tiniroto in Gisborne, New Zealand. Image by Dr Murry Cave of Gisborne District Council.
This landslide is estimated to have a mass of about 70,000 tonnes. Note that the landslide has choked the valley, creating the potential for a dam break debris flow that could pose a hazard downstream. Fortunately, this is a sparsely populated area.
The second occurred on 11 August 2024 at Kuri o Pāoa/Young Nick’s Head. This is a large scale coastal cliff collapse, again pictured by Dr Murry Cave:-
The Te Kurī a Paoa / Young Nick’s Head landslide in Gisborne, New Zealand. Image by Dr Murry Cave of Gisborne District Council.
Gisborne District Council has also collected a rather nice drone image of this landslide:-
Vertical aerial image of the Te Kurī a Paoa / Young Nick’s Head landslide in Gisborne, New Zealand. Image by Dr Murry Cave of Gisborne District Council.
Elevated levels of instability in this area of New Zealand is likely to continue for some years, posing a significant challenge for the local community.
Acknowledgement
Many thanks to Dr Murry Cave for highlighting these landslides and for making the images available publicly.
Text © 2023. The authors. CC BY-NC-ND 3.0Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.
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