The impact of the aggregation formula on indicator-based method for the assessment of building susceptibility to hydro-meteorological hazards

A crucial variable in risk and vulnerability assessment procedures is the ability of the built environment to resist in case of hazard impact. This component, referred to as “susceptibility”, can be assessed in different ways, among which indicator-based methods are preferable when no data about past hazardous events are available. This type of methodology, considering the building susceptibility independent from the hazard magnitude, relies on the selection of indicators meaningful for the investigated area and their combination via an aggregation formula, leading to a susceptibility index for each building. The current study aims at reviewing and comparing different approaches used in literature to combine the indicators for calculating the susceptibility index. To this end, five indicators, previously selected for a mountainous case study area, are applied and implemented in a GIS platform, generating just as many specific susceptibility maps. Further, the indicators are weighed and combined in different scenarios with two aggregation formulae, which are integrated into the GIS environment so as to spatially display and compare the results. Last, but not least, the HBIM model and a GIS/BIM database of the studied area are created. Results suggest that the aggregation formula and the assigned weights are crucial ingredients, and therefore they should be chosen carefully according to the aim of the study and the needs of the stakeholders.