Assessing physical vulnerability to wildfire: a Physical Vulnerability Index (PVI) for buildings

Recent wildfire events (e.g. Mediterranean region, USA, and Australia) showed that this hazard poses a serious threat for wildland-urban interface (WUI) areas around the globe. Furthermore, recent events in regions where wildfire does not constitute a frequent hazard (e.g. European Alps, Siberia, Scandinavia) indicated that the spatial pattern of wildfire risk might have significantly changed. To prepare for upcoming extreme events, it is critical for decision-makers not only to have a thorough understanding of fire ignition, propagation, and associated forecasting and modelling, but also of the vulnerability of the built environment to wildfire. Building quality and design standards are important not only because building loss is costly but also because robust buildings may offer shelter when evacuation is not possible. However, studies aiming at the analysis of wildfire vulnerability for the built environment are limited so far.

The present contribution focuses on the development of a Physical Vulnerability Index (PVI) for buildings subject to wildfire, that considers different building characteristics and their surroundings and uses weighting based on statistical methods. Data from a recent and systematically documented wildfire event in Greece are used to select and weigh the relevant indicators using the random-forest-based all-relevant feature selection algorithm Boruta. One of the main advantages of the method is its predictive capacity and the ability, once established, to indicate houses with great damage potential in areas susceptible to wildfires in the future. The PVI for buildings subject to wildfire may be used in other places in Europe and beyond by decision-makers giving an overview of the vulnerability of buildings at the local level, supporting in this way evacuation planning. Furthermore, it can be the basis for local adaptation measures and reinforcement of buildings that can support shelter-in-place.