Post-event Flood Damage Surveys: A New Zealand Experience and Implications for Flood Risk Analysis

Abstract

Disaster risk managers are shifting from hazard-centric identification of asset exposure, to quantitative risk assessments based on an understanding of asset vulnerability to impacts. For flood hazard management this shift is support by empirical data detailing the damage reponse of asset typologies when exposed to varying flood hazard intensities. This data is rarely available to reserchers therefore, developing this understanding requires its post-event collection following flood events. This study presents a survey methodology applied to five flood events in New Zealand to develop an empirical residential building damage database for post-hoc vulnerability analysis. Damage data collected is described for building and component attribute susceptibility to damage from exposure to flood inundation depths. Quantity survey guidelines were used during post-hoc analysis to convert observed component damage ratios to asset-level damage ratios. We observe for four strucutral and non-structural building components that internal finishes and service components contributed the most to asset-level damage ratios up to 1.5 m above building floor levels. These detailed component observations coupled with damage ratio estimates for residential building typologies can inform future post-hoc empirical or synthetic methods to develop relative damage curves.