Gisborne/Tairāwhiti is particularly susceptible to rainfall‐triggered landslides on account of (1) steep slopes, (2) young, soft geology, (3) landuse change effects. The interplay of these factors led to a particularly damaging rainfall‐induced landsliding event during 3–7 November 2021, following >200 mm of rainfall. This caused a Multiple Occurrence Regional Landslide Event, impacting residential properties and infrastructure in the city and rural areas. We report mainly on landslides in Gisborne city and suburbs, based on field reconnaissance and interferometric synthetic aperture radar monitoring of slopes. This highlights prevailing land instability prior to the more recent ex‐Tropical Cyclone Gabrielle (2023).
<p>Landslides are widespread natural hazards that are responsible for substantial economic and societal damage globally each year. In New Zealand, landslides frequently occur on soil and rock, often triggered by high rainfall and/or seismic activity. This study focuses on the Gisborne district on New Zealand&#8217;s North Island. The area is particularly susceptible to landslide hazards due to (1) the region's location on an active plate boundary, (2) steep slopes, (3) relatively young, soft geology, (4) land use change, and (5) extreme rainfall events including landfall of extra-tropical cyclones. The interplay of several of these factors led to a particularly damaging rainfall-induced landsliding event after 4th November 2021, following >200 mm of rain falling in parts of the district over 24 hours. Effects across the region were widespread. Damage to, and evacuation of, residential properties occurred in Gisborne city itself, from shallow rotational slumping and earthflows. The vulnerability of the city&#8217;s water supply (via the Te Arai Pipeline) was highlighted by the reactivation of a large complex landslide, that extended to within a few meters of the pipeline. Destruction of the (mothballed) Gisborne-Wairoa railway line occurred near Beach Loop due to reactivation of the Whareongaonga Landslide. Across the Gisborne district, detecting ground deformation related to landslides is vital for identifying and managing areas at risk. Interferometric synthetic aperture radar (InSAR) revealed that many of the landslides that occurred following the November 2021 rainfall event were on slopes that had been actively deforming for several years. Thus, in future, InSAR should prove useful for detecting, mapping and monitoring landslides in the district, and assisting with planning decision-making.</p>
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.