CAMBIAMENTI DI USO DEL SUOLO E MITIGAZIONE DEL RISCHIO IDRAULICO: MODELLI A SUPPORTO DI UNA PIANIFICAZIONE TERRITORIALE SOSTENIBILE

The scientific literature has widely demonstrated that land take and surface sealing significantly affect hydrological processes, increasing peak discharges and flood risk, particularly in small- to medium-sized catchments. These effects highlight the integration of flood risk management into spatial planning, through effective measures for urban transformations, assessing their impacts in advance. In Italy, regional planning has different approaches and application criteria, while at the European level, there is a common set of guidelines towards sustainability and the reduction of land consumption. Within this context, the doctoral research aims to define a replicable territorial analysis methodology to assess the impacts of land-use changes on surface runoff, hydraulic hazard, and ecosystem services. The proposed approach integrates ecosystem service assessment models (InVEST) with hydrological modelling tools (HEC-HMS), allowing for a joint analysis of territorial transformations and system response to intense rainfall events. The research develops a replicable methodological framework intended to evaluate the effects of land-use change on surface runoff and on the territory’s capacity to respond to extreme events. The Emilia-Romagna region was selected as a pilot area due to the wide availability of historical datasets, testing a methodological approach that can be applied to other contexts. Emilia-Romagna is confirmed as one of the Italian regions most exposed to flood events and significant hydrogeological phenomena, as demonstrated by numerous historical records of widespread damage and inundation. The analysis focuses in particular on the recent flood events of May 2023, which affected especially the provinces of Bologna, Ravenna, and Forlì-Cesena, within the Reno, Lamone, and Fiumi Uniti river basins. Analyses were carried out at two planning scales: the provincial–intermunicipal scale (wide-area scale) and the intermunicipal scale (basin scale). At both scales, two scenarios were analyzed: one based on current land use (2020, PRE scenario) and one assuming the full implementation of planned land-use transformations (POST scenario). Although based on different conceptual structures, the models provide consistent results, highlighting an increase in surface runoff associated with urbanization. The results prove that land-use transformations over time have led to a significant increase in surface runoff, closely linked to urban growth and the progressive reduction of permeable surfaces. This effect is particularly critical in lowland areas, where drainage networks—originally designed to convey runoff generated by natural or agricultural soils—are now often inadequate to cope with higher discharge levels. Basin-scale analysis also reveals that the impacts of urban planning choices extend beyond municipal boundaries, generating significant effects on downstream territories.