Effective flood risk mitigation requires assessing costs and benefits of alternatives of intervention. The European Floods Directive requires to produce risk maps, as a basis of Flood Risk Management Plans. Damage evaluation is a critical step of this process, due to the lack of consolidated practice in the literature and the technical domains. By allowing scientists and practitioners working together, MOVIDA developed a procedure, and supporting IT tools, embracing state of art knowledge on damage modelling, for the appraisal of flood damage in the Po River District. The procedure was applied in areas at significant risk within the district to prioritize mitigation strategies.
Flood damage assessment is a non-consolidated challenging practice for European River District Authorities, which, however, are required to produce flood damage and risk maps to accomplish with the so-called Floods Directive (FD). Such maps are, in fact, the key element for the evaluation of risk mitigation measures to be implemented in Flood Risk Management Plans (FRMPs). Indeed, the effectiveness of a measure is evaluated by comparing its cost to the damage avoided thanks to its implementation, which represents its benefit.
The development of FRMPs ideally requires consistent and comprehensive damage assessment, for all items which are located in potentially flooded areas, and all kinds of expected impacts, being they related to the direct contact with flood water (i.e., direct damage) or being an indirect consequence of it (i.e., indirect damage, like business and services interruption or contamination). Nonetheless, a quantitative/monetary evaluation of damage is crucial when there is a need to prioritize interventions, especially over large geographical areas, and impacts in the present and project states must be compared.
In practice, the goal of exhaustive damage assessment is currently not achievable due to the inhomogeneous levels of development of (and, in some cases the lack of) damage models.
Paucity and low quality of georeferenced data for characterising exposed items further limit the range of damage models that can be implemented for the assessment. In fact, we deal with scarcity of institutional databases (i.e., data are often stored in commercial repositories), legal impediments in the use of data, fragmentation of information among different databases, and their inadequacy in supplying information required as inputs of the damage models; obsolescence of information is sometimes a problem, with data referring up to ten years ago.
At the EU level, lack of models and data is reflected in the tools presently implemented to assess flood damage within the scope of the Floods Directive. Evaluations performed by the European Commision, whose results are summarised in Figure 1, highlight how different levels of analysis can currently be achieved for the various items exposed to floods, where differences strongly depend on the availability of national/local tools and required input data.
Nonetheless, a gap exists between state of art and practice in flood damage modelling; in fact, despite several damage models have been developed, for many regions of the world, flood risk analysis is still mostly focused on the hazard component of risk. The main factor hampering the implementation of available damage models by institutions and technicians is the lack of simple and immediate tools, whose execution does not require specific expertise by end-users. It is often the case that more reliable modelling tools are based on advanced skills and technologies which are usually lacking in the professional world.