Green infrastructures as a climate change adaptation measure: community awareness and hydrological modeling of green roofs under different emission scenarios

Many recent studies indicate the climate change as a phenomenon that significantly alters the water cycle in different regions of the world, also implying new challenges in water management and drought risk assessment. In addition to this problem, the loss of natural soil and vegetation within the urban environment can significantly affect the hydrological cycle, increasing the risk of urban flooding. To mitigate these changes in urban areas, engineered systems are developed, such as green roofs, to mimic and replace functions (evapotranspiration, infiltration, percolation) that have been altered due to the impact of human development. These adaptation systems are able to reestablish the natural processes of the water cycle and to operate the hydrological control of the runoff of rainwater with consequent attenuation of the peak flow, reduction of the flow volume and increase of the concentration time. In order to investigate the hydrological response of a green roof, the University of Catania (Italy) has recently built a green roof of about 800 m2 to study the benefits that this infrastructure can bring in a Mediterranean climate. The objectives of this thesis are to provide detailed information on the performance of the green roof in the current and future Mediterranean climate and to identify a suitable modeling approach to describe the associated hydrological response. After investigating the research context through a survey for the local population on the perception of climate change and the need for adaptation measures, we proceeded with a modeling approach. First, the data collected during a monitoring campaign of about two years at the experimental site of the green roof of the University of Catania (Italy) are presented together with the results obtained in quantifying the hydrological performance of the green roof. To examine the hydrological response of the green roof, the Hydrus 1D model was implemented, which solves the Richards equation for the flow of water over the soil column. The model adequately reproduces the moisture trend in the soil both during rain events and during dry periods. In order to study the impact that a green roof can have in the future climate, therefore in the different climate change scenarios, it is of fundamental importance to ascertain the quality of the regional climate models (RCM), which are commonly used to evaluate the future impacts of climate change on hydrological events. In this thesis, a statistical methodological framework was proposed to evaluate the quality of the EURO-CORDEX RCMs with regard to their ability to simulate the historical climate (temperature and precipitation, the basic variables that determine meteorological drought) in Mediterranean regions, subsequently a study was conducted in various meteorological stations in Sicily to ascertain the ability of RCMs to reproduce the climate even on a reduced time scale. The final results, with the application of RCMs on the physicallybased model of the green roof, show that green roofs can be a valid infrastructure for the reduction of volumes and rain peaks in the next future. With its capacity to retain volumes and reduce peaks, the green roof effectively manages to bring the outflow to a level similar to that of the historical scenario, removing, partially or completely, the negative effect of climate change.