Post-fire Damage Assessment of Buildings at the Wildland Urban Interface

Abstract

Wildfires are considered one of the costliest natural hazards in Canada. Significant fire events that occurred had threatened and destroyed buildings at the Wildland Urban Interface (WUI). Standard methods for wildfire risk assessment include hazards’ analysis, inventory of exposed buildings and vulnerability analysis that correlates expected losses to fire intensity measure and distance from forest boundary. On the other hand, there is limited research on buildings’ vulnerability assessment to wildfire impacts and scarcity of models that correlate the likely response and expected loss of different types of buildings to varying levels of fire intensity. This article presents a methodology for geospatial data collection of post-fire buildings damage at Canadian WUI communities with the objective of developing community-scale empirical building fire vulnerability models that can be integrated in community-scale wildfire risk assessment tools. In this study, the empirical fire vulnerability model is developed in terms of the loss rate defined by the proportion of buildings burned as a percentage of the total exposed buildings as a function of the distance from forest edge and the corresponding fire intensity. The methodology consists of consecutive steps including geospatial digitization of burned and survived buildings from post-fire open-source satellite imagery; characterization of building types and occupancy based on open-source municipal databases; estimation of distances to burned forest boundary based on burn scar satellite imagery and the measurement of distance increments to buildings. The buildings data are then combined to develop an empirical fire vulnerability model. The methodology is demonstrated by a case study WUI community in Canada that was exposed to a damaging wildfire event.