RNC2 Weather and Wildfire Landslide Project: analysis of recent rainfall-induced landslide datasets for vulnerability functions

Abstract

The Resilience to Nature’s Challenges Weather & Wildfire programme endeavours to increase resilience of Aotearoa New Zealand’s population by investigating high-resolution case studies related to ex-tropical cyclone scenarios. Within a sub-project, we have investigated building damage due to rainfall-induced landslides triggered by significant storm events. In this brief report, we present the rainfall-event-response datasets and methodology used to update vulnerability functions. Our database includes 28 landslides and 46 buildings, each investigated in detail based on storms in the Wellington, Napier and Marlborough areas from 2017 to 2022. This report serves as background to an upcoming publication on applying the updated vulnerability functions to Auckland case studies. We analysed slippage and debris inundation (falling debris) impacts separately. Our dataset contains five slippage cases, where a landslide has undermined buildings, and 23 debris inundation cases, where landslide debris has run out and impacted buildings. The landslides in our dataset are smaller than most internationally analysed landslides but have damaged buildings significantly. Damage states of the buildings that we assessed during field surveys ranged from DS0 (no damage) to DS5 (critical damage), with seven of the 46 cases classified as DS5. We contribute to an improved understanding of small landslides and their impact. We also contribute to vulnerability function research based on detailed empirical datasets. Our work is a starting point for several ongoing and future research projects.