Runoff Generation Processes on Hillslopes and Their Susceptibility to Global Change

Global change will influence hillslope hydrological processes for a variety of reasons. On the one hand, climate change might alter the hydrological input, i.e. precipitation and snow melt, which might cause an increase or decrease in the intensity of specific hillslope processes. For instance, overland flow might be amplified by increased rain intensities (Horton 1933) or by reduced infiltration due to surface crusts (Yair 1990) or increased hydrophobicity (Doerr et al. 2002), triggered by longer and more pronounced drought periods. However, overland flow could also be significantly influenced by antecedent moisture conditions of the substrate that were either altered due to wetter climate and reduced evapotranspiration at a site or due to different snow and snow melt regimes, changing the hydrological input for a specific precipitation event. On the other hand, global change in the form of land use changes will play a key role in defining the dominant runoff generation processes on hillslopes (cf. summary given in DVWK 1999).