McColl, S.T.; Townsend, D.B.; Barrell, D.J.A.; Boyes, A.F.; Leith, K.J.; Rosser, B.J.; Massey, C.I. 2025 GeoNet landslide response: Auckland Anniversary Storm, 26–30 January 2023, northern New Zealand. Lower Hutt, NZ: Earth Sciences New Zealand. GNS Science report 2025/32. 53 p.; doi: 10.21420/FZ4C-D728
Abstract
In late January 2023, a prolonged heavy rainfall event, dubbed the Auckland Anniversary Storm, affected much of the upper North Island of New Zealand, causing widespread damage. States of emergency were declared for the Auckland and Waikato regions. During the storm, news reports and social media highlighted that, as well as severe flooding, there was widespread slope instability, which resulted in three landslide-related deaths and much damage to houses, roads, rail and other infrastructure. The on-call GNS Science Landslide Response Coordinator, in discussion with other GNS Science landslide experts, concluded that criteria justifying a science response had been met. A GeoNet landslide rapid response was activated on 30 January 2023.A GNS Science Incident Management Team was set up and a Controller designated. The response comprised two steps: (1) From 26 January to 2 February 2023, desktop collation of landslide information reported in the media and on social media; and (2) on 3–4 February 2023, helicopter reconnaissance surveys of the main areas affected to collect observations and photographs of landslides. Reconnaissance information was provided to emergency-response agencies andlocal government agencies at the end of each day to alert them to any immediate hazards and assist prioritising of response/recovery efforts. The data also provide an observational record of landslides resulting from this storm, which assisted in subsequent precise mapping of the landslides and helps to support future work, such as training rainfall-induced landslide models being developed to forecast likely locations and severity of landsliding in future rain events. This report documents activities of and summarises observations from the GeoNet landslide rapid response for the Auckland Anniversary Storm. That storm was followed a few days later by Cyclone Gabrielle, which caused further severe flooding and triggering of landslides in the same regions and several other regions of the North Island. That event resulted in another GeoNet landslide rapid response, which is reported separately. (auths)
