Steps of assessment

Flood damage assessment, which is carried out separately for each category and sub-category of exposed assets, can be divided into four consecutive phases:

• Identification of input data: available databases for the definition of the hazard and the exposure scenario are identified, as well as those allowing for the identification of the spatial distribution of the vulnerability parameters within the flooded areas. Flood hazard maps included in the last update of the Flood Risk Management Plan (FRMP) of the Po River District are the main reference for hazard data, especially regarding the flood extent and the distribution of the water depth within the flood perimeter. The databases for the evaluation of exposure and vulnerability vary instead with the typology of assets, although sharing the following characteristics, which allow to compare different areas within the whole District: data are available at the national level, or at least at the district one, and are of institutional nature (if possible).

• Definition of the scale for both the analysis and the representation of results: the scale of the analysis depends on the one hand on the level of detail of available input data; on the other hand, on the scale of implementation of models available for the damage evaluation. In particular, depending on the type of asset under consideration, the analysis can be performed at the level of the individual exposed element (i.e., microscale) or at more aggregated scales, such as the census blocks of Italian National Institute of Statistics or cadastral units (i.e., mesoscale). The scale of representation of results is defined on the basis of the objective of the assessment. Within the scope of the MOVIDA procedure and for the purposes of FRMPs development, damage outcomes are returned at the census block level, according to a District perspective.

• Exposure assessment: the exposure scenario, which represents the maximum (potential) damage in case of flood, is defined in physical and, if possible, in monetary terms, by intersecting the hazard scenario and the data concerning the spatial distribution, the amount and the value of exposed elements.

• Damage assessment: flood damage is evaluated by means of models that have been calibrated and validated in the Italian context. As previously mentioned, according to the category of exposed assets, these models provide a quantitative (and monetary, if possible) or qualitative estimate of the expected (or potential) damage in case of flood.