Modelling the Wildfire Risk Components Using Experts Opinions-Based Multicriteria Evaluation: A Focus on Fire Ignition and Outbreak Hazards ^†

Abstract

We designed and tested an expert opinion-based multi-criteria model for the assessment of several components of the wildfire risk, including ignition and outbreak hazards (the probability of ignition “success”), propagation hazard, as well as stakes exposure and vulnerability. The approach also allows formalizing the interaction between these components, in order to specify an integrated analytical risk model. The formal risk model is specified according to the IPCC 2014 conceptual framework, which structures the risk in hazard, vulnerability and exposure components. Only the structural risk is assessed, related to climate, fuel and land management, and not the daily risk (danger). The multicriteria method used in this demarche is the Analytic Hierarchy Process (AHP). The experts opinion-based approach is justified by the lack of spatially precise data related to past events, particularly ignition points and damages databases, while the fire contours are also sometimes imprecise. The model does not give any absolute value of risk, but only hierarchizes the different zones of a whole region in relation to their relative level of risk. The model has to be recalibrated for each context it is designed for, with new expert enquiries. The method was initially specified to the supra-Mediterranean area of a South Eastern France Natural Regional Parc (Parc Naturel Regional des Baronnies Provençales) and is now being calibrated to the MED-STAR/INTERMED French area. In a second step, each of the “atomic” models (for each component assessment) are being validated using statistical tools.