Runoff of the result of complex interactions between atmospheric and soil processes are normally described and synthetized in the rainfall-runoff transformation. Climate change and soil consumption are undoubtedly two of the main factors that influence the hydro-logical response of a basin both in urban and extra-urban contexts. Also, alterations in hydrological extremes are among the evolving processes that most threaten environment and the management policies against natural hazards. At an urban context, the implications of an increase in severity of extreme runoffs may be directly related to the changes in flood frequencies of urban systems, the overflow frequencies of storage facilities, and the design of urban hydraulic infrastructures. Similarly, at a not-urban context, increases on runoff extremes may exacerbate occurrences of flash flood and debris flows. The increase in the degree of urbanization of natural basins, understood as an increase in the impermeable soil fraction deriving from the constant coverage of areas of the basin with artificial impermeable materials such as asphalt and cement, is a phenomenon that is constantly growing around the world. These changes are overlaid by the climatic changes that, among other effects, tend to modify the quantity and the manner in which the rains reach the ground and, at the same time, induce alterations to the thermometric regime, with important repercussions on the evapotranspiration processes characterizing hydrological basins. Natural and anthropic pressures on hydrological systems often coexist and interact mutually, dynamically modifying most of the processes underlying the formation and transfer of runoff.The aim of the present work is to analyze the separate and coupled effect of climate change and urbanization on the hydrological response of a basin. To this end, a numerical experiment has been carried out by considering a real basin and different hypothetical changes scenarios. These last have been generated coupling a weather generator with a land use change model. The hydrological response of the basin has been evaluated through a physically-based and distributed hydrological model, operating at high time-resolution, suitable for the analysis of both extreme discharges and all the key components of the long-term water balance at watershed scale. In particular, the climate scenarios were created by imposing negative and positive trends to the average annual precipitation and, at the same time, an increase in temperature, while the land use scenarios have been created considering variations in the impermeable fraction of a basin. The procedure was also applied to a nested sub-basin, in order to study potential spatial scale effects.The modeling framework resulted particularly suitable in the analysis of some aspects rarely investigated in the past, such as the effects of climate and land-use changes on the different runoff components and their implications on the long-term basin hydrology. For instance, the results showed how urbanization and climate changes have opposite effects on the hydrological response of a basin in the cases with rainfall reduction and concordant effects if a positive trend on rainfall is considered. With the considered changes scenarios, the effects of climate change on the hydrological response of the basin are greater than those due to the urbanization process. The latter, however, can lead to an exacerbation of the fast flow component especially during the occurrence of extreme events.
|Titolo della pubblicazione ospite||Tecniche per la difesa del suolo e dall’inquinamento - Techonologies for Integrated River Basin Management|
|Numero di pagine||14|
|Stato di pubblicazione||Published - 2019|