140,000 landslides were triggered in New Zealand by Cyclone Gabrielle.

Dave Petley, an expert in the study and management of landslides, is the author of The Landslide Blog which is highly regarded globally.

In February 2023, I brought attention to the significant occurrence of landslides and their consequences caused by Cyclone Gabrielle in the North Island of New Zealand. One specific landslide at Manukau Heads resulted in the unfortunate death of a firefighter, and there were also multiple close calls and significant damage.

GNS Science is a New Zealand-based organization that aims to comprehend the occurrence of landslides and how they affect society. Following the occurrence of Cyclone Gabrielle, a team led by Chris Massey, a former PhD student of mine, and Kerry Leith has been working on mapping the landslides caused by it. GNS Science has a well-constructed website that provides information on the ongoing research, which involves collaborating with various other organizations. The initial findings are beginning to be revealed. Furthermore, the New Zealand Herald has published a helpful article on the research.

The data is surprising – the team has surveyed an area of 50,000 square kilometers and discovered 140,000 landslides. This task of mapping such a large number of landslides is quite formidable, but the team has utilized a unique approach that identifies the source of the landslide and a line representing the center of the debris trail leading to the base. The included visualization from GNS Science displays this method for a series of landslides caused by Cyclone Gabrielle.

There are a few reasons for undertaking this type of work. Firstly, the processes that lead to large-scale landslides are still not fully understood, making it a valuable area of study. Additionally, it is important to properly understand the causes of catastrophic events like landslides in order to better prepare for future incidents. As the climate continues to warm, there is a need to plan for an increase in these events. Thorough investigations can provide valuable information for predicting and responding to future landslides. Lastly, there is a movement in New Zealand to create a predictive system for landslides, similar to one already in place in Hong Kong but covering a larger area. Understanding the relationship between rainfall and landslides is crucial in this effort.

Following Cyclone Gabrielle, more than 1,500 homes have needed to undergo risk assessment for potential landslides. These occurrences pose a significant danger and financial burden to New Zealand, making it crucial to obtain a thorough scientific comprehension of them. GNS Science, along with its collaborators, has a strong track record of publishing their findings, and I am eager to see the results of this intriguing project.

Text © 2023. The authors. CC BY-NC-ND 3.0

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