Parameterize a territorial risk evaluation scale using multiple experts knowledge through risk assessment examples

Evaluating and comparing the threats and vulnerabilities associated with territorial zones according to multiple criteria (industrial activity, population, etc.) can be a time-consuming task and often requires the participation of several experts and decision makers. Rather than a direct evaluation of these zones, building a risk evaluation scale and using it in a formal procedure permits to automate the assessment and therefore to apply it in a repeated way and in large-scale contexts and, provided the chosen procedure and scale are accepted, to make it objective. One of the main difficulty of building such a formal evaluation procedure is to account for the multiple experts knowledge and decision makers preferences. The procedure used in this article, ELECTRE TRI, uses the performances of each territorial zone on multiple criteria, together with preferential parameters, to qualitatively assess their associated risk level. The preferential parameters to be determined are the category limits, i.e. the limits on each criterion of the performance range associated with a given risk level, and the weights associated with the different criteria. To obtain these parameters with no direct questioning of the stakeholders, tools based on mathematical programming have been developed to deduce these preferential parameters from assessment examples. In this article, several such tools are applied together in order to build a complete example leading to the definition of a territorial risk evaluation scale taking into account the preferences of multiple stakeholders