Evaluating New Zealand’s building risk to fluvial and pluvial flooding

Flooding from fluvial and pluvial sources pose a significant and growing risk to buildings in New Zealand, yet national-scale assessments of direct economic loss are limited. This study addresses that gap by applying an end-to-end workflow that integrates state-of-the-art hydraulic modelling with a modular flood risk analysis framework, enabling consistent expected annual damage (EAD) calculation at the building scale and enumeration at different jurisdictional levels. National EAD of NZD 190 million was estimated, with Canterbury and Waikato regions contributing 35% of this total. Residential and appurtenant buildings account for the majority (71%) of national EAD. These findings provide the first comprehensive baseline for direct building economic flood risk in New Zealand, and advances that availability of flood risk models for location-based risk mitigation strategies.