Landslides triggered by the December 2021 Eastern Bays storm, Banks Peninsula, New Zealand

ABSTRACT On 16 December 2021, the Eastern Bays region of Banks Peninsula, Canterbury, was affected by a high intensity rainfall event which triggered >1300 landslides. Landslides triggered by the event caused widespread damage to agricultural land and infrastructure, which cut off road access to several communities. A landslide inventory has been developed to examine factors that have contributed to the distribution of slope failures in this region. Generally, landslides triggered were shallow earthflows in loess and loess‐derived soils largely confined to slopes 26°–35° within steepened valley systems formed by erosion of the underlying volcanics. Landsliding was also absent at high elevations (> 600 m) southwest of the main ridge line and along the summit edges of the valleys due to sparse distribution of loessial deposits in this area. Three deep‐seated slope failures were observed in highly weathered volcanics and were associated with the day lighting of spring flow. This event highlights the complexity of landslide hazard in Banks Peninsula, and the influence of soil distribution and the underlying complex hydrogeology on landslide occurrence.