GIS-based regional risk assessment and its implementation in a decision support systems for studying coastal climate change impacts

Climate change represents a global challenge and is one of the most pressing environmental issues that scientists, economists, policy makers and the whole society is facing today. The main objectives of this thesis are the development of a GIS-based Regional Risk Assessment (RRA) methodology and its implementation within the GIS-based DEcision support SYstem for COastal climate change impact assessment (DESYCO). The methodology aims to evaluate and rank the potential risks of climate change impacts (i.e. storm surge flooding and marine water quality variations) on a variety of terrestrial and marine receptors (e.g. infrastructures, building, agricultural areas, population, marine water ecosystems). The proposed RRA is a cross-sectorial and interdisciplinary methodology considering the complex dynamics and interactions between coastal systems and other systems closely related to them (e.g. surface waters, river basins, estuaries). The implementation of the methodology within the DSS allows to transfer the information about climate-related risks to policy planners and decision makers, in order to guide them in the definition of appropriate adaptation actions. The RRA methodology and the DSS DESYCO were applied to the coastal area of the North Adriatic sea in order to analyse the potential consequences of climate change on storm surge flooding (for extreme events with different return periods, i.e. 20, 50, 100, 200 and 500 years), and on marine water quality variations (for the future scenarios 2070 and 2100). Results of the RRA application concerning the storm surge flooding impact showed that hazard will be quite high all along the coastline of the considered region, where extreme events will be quite intense. Inside the Lagoon of Venice, higher hazard will be in the southern part of the Lagoon due to the dominance of east-winds during extreme events and due to the lower number of islands and to the simpler morphology. The coastal strip exposed to storm surge in usually few km large. The receptor population is characterised by the lower risk, while beaches, wetlands, agricultural and natural areas are characterised by higher relative risk scores. Finally, also risk for buildings will be quite low all over the considered region, with higher risk in places with older urbanization where there is higher concentration of buildings. As far as the analysis of water quality variations on marine coastal water bodies is concerned, results showed that the main drives of hazard and risks are represented by a decrease of salinity and an increment of the temperature. Within the considered region variations of these parameters are mainly due to the presence of river mouths or to the inlets of the Lagoon of Venice. In fact, water bodies close to the Po River delta and up to the Chioggia inlet, and from the Lido’s inlet to Caorle, are characterised by a higher risk. Moreover higher risk will be during the spring season, from April to May. Finally, it was demonstrated that all the area is characterised by medium/low damages scores.