EXPOSED ASSETS

Roads and railroads

The functional damage linked to the practicability of a road or railway section is in many cases of greater importance than the physical damages suffered by the infrastructure, thus, a specific methodology is proposed for the estimation of the functional damage (i.e., null, low, medium, high impact) expected to the network in case of flooding. Despite the singularities of the two transport systems, the approach developed for road and railway infrastructures is similar and involves the definition of a damage matrix resulting from the combination of two factors: (i) the impact of the flood event in terms of slowdown or interruption of vehicular transit (depending on the hazardous variables; i.e. hydraulic load or water depth) and (ii) the uniqueness of the performance services offered by the infrastructure, depending on the type of flooded section. The overall damage matrix is obtained by carrying out a weighted average of the aforementioned aspects and consulting the existing literature. Detailed database containing the physical and functional characteristics of the infrastructures were built. Spatial identification of the transport networks has been done referring to Open Street Map (OSM), integrated with information coming from the Regional Geoportal and regarding more technical and mechanical characteristics of the networks. As a result, transport sections have been classified in terms of importance (e.g., Highway, Main, Secondary, etc. for roads), as well as topographic characteristics (e.g., sections in elevation, bridges, viaducts overpasses, tunnels, etc.).

Cultural heritage

Damage to cultural heritage is expressed in qualitative terms by using four classes (low, moderate, high, very high) depending on the number and significance of the heritage in each flooded portion of the census polygon. A monetary assessment is in nowadays still object of scientific research especially due to the value that cultural heritage has in social, historical, spiritual, and aesthetic terms. Thus, reconstruction costs estimation is not an appropriate damage metric.

A new GIS database for cultural heritage has been created by merging several existing databases from international, national and regional open cartographic data repositories and by re-classifying with the same taxonomy all the assets based on existing attributes (ca. 250,000 items). Cultural heritage classification is based on (i) asset typology, e.g., religious building, museum, monument, industrial building, that allows for a generalization of susceptibility to floods, and (ii) level of recognition and protection (from international listing, i.e., UNESCO heritage sites, to national and local significance). The impact matrix combines vulnerability (asset typology) and exposure (level of protection) based on expert judgement and stakeholder engagement. Each matrix element corresponds to a weighting coefficient that increases with potential loss. The potential damage index for cultural heritage is obtained by a weighted sum of the assets in the flooded portion of the census polygon divided by the inundated area.

Residential buildings

The expected financial damage is evaluated for the building structure only (thus, excluding contents). Three damage models were selected, calibrated and validated on the Italian territory. These allow to assess damage considering the flood water depth, the economic value, and some vulnerability characteristics of the buildings. The final damage indicators is given by the average of the outcomes of the models, normalized with the flooded building area, thus representing a unitary damage (i.e., €/km2). The characterization of the buildings is based on the regional topographic databases (e.g., footprint area, number of floors, building use, etc.), 2011 census data provided by ISTAT (e.g., construction material, maintenance level, etc.) and reconstruction costs provided by CRESME.

Crops

The expected monetary damage is estimated by the AGRIDE-c model in terms of reduction in the turnover of the farmers due to the flood, for the most common crops in the investigated area: maize, wheat, barley, grassland and rice. According to our knowledge, the model represents the only tool for the assessment of flood damage to crops in the Italian context. For all the other crop types, the only potential damage (i.e. maximum exposed value) is evaluated as the gross output, that is the product between the average yield and price for crop. The AGRIDE-c model needed to be adapted for application at the river district scale. Firstly, the agricultural uses were reclassified in common categories for the whole district to overcome the high heterogeneity of crop species and varieties among the different regional databases. Then, the input data required by the model for the economic evaluation were defined at the regional level, by considering the average values over the period 2015-2020 of yields, prices and production costs. Since damage to crops depends on their vegetative stage at the time of occurrence of the flood, several inundation scenarios were analysed to estimate the expected damage for the months when past flood events typically occurred. The final damage index is expressed as the maximum expected damage divided by the inundated area for the five crops implemented in AGRIDE-c, otherwise as the gross product (i.e. potential damage) per unit of inundated area for all other crops.

Na-tech sites

The potential damage is estimated in terms of the number of hazardous installations within the flooded areas. A unique geographic database for pollution sources was created by merging data from international, national and regional open data repositories and by re-classifying with the same taxonomy. Damage due to the flood of hazardous installations is mainly related to the dynamics of potential contamination of the surrounding areas, that cannot be evaluable on a large scale yet, but only locally at the individual plant scale. Hence, it has not been possible to define a robust damage index for Na-tech sites.