Effects of climate and land use changes on runoff extremes

Abstract

The analysis of the hydrological changes and their interacting triggering factors are objectives defined within the Panta Rhei decade 2013-2022. Climate change and urbanization are among the most recurrent causes for hydrological changes at the global level. This work proposes a modeling framework for the analysis of the alterations in the watershed hydrological response and, more specifically, in runoff extremes, induced by such perturbations. A weather generator and a cellular automata land-use change model are used to generate hypothetical scenarios accounting for relevant trends at the global level. Such scenarios are successively considered to force a physically-based and spatial-distributed hydrological model, which simulates, at high time-resolution, most of the key hydrological variables at the basin scale. The framework is applied to the Peatcheater Creek at Christie basin (OK, USA), considering a reference scenario derived by the current land-use/cover spatial pattern and climatic observations at the site. The considered climate alterations are negative and positive variations in mean annual precipitation, obtained by different configurations of rainfall intensity and frequency, and simultaneous increase in temperature. Urbanization is conceptualized by an increase in the fraction of impervious areas within the basin. The analysis of the hydrological response simulated under the different scenarios, shows how the considered perturbations, acting separately or combined, may significantly alter the runoff generation mechanisms, resulting in relevant alterations of the extreme runoff events intensity and their associated return period. The results also emphasize the role of rainfall characterization, as well as the consideration of appropriate criteria for urban expansion.