Climate change impacts on precipitation and future erosion rates in a pre-Alpine region

Climate change is expected to affect precipitation, streamflow, and sediment transport. These changes are particularly relevant in mountainous environments that play a crucial role in water resources and sediment supply for downstream reaches. We investigated the impact of climate change on hydrology and geomorphology in the upper Emme catchment (127 km²) in the Swiss pre-Alps by simulating its hydromorphological response to present climate and three climate scenarios at the end of the century using the distributed CAESAR-Lisflood landscape evolution model. The mean seasonal changes, intensification of short-duration rainfall extremes, and snow processes were explicitly modeled. The results highlight the importance of the intensity of rainfall events to predict sediment transport at the outlet, while changes to snow processes are predominant to understand the seasonal hydrological shift. For the highest emission scenario (RCP8.5), the sediment yield at the outlet increased by 6% despite a reduction in precipitation by 7% compared to the present climate, as a result of heavy precipitation intensification. On a seasonal scale, discharge increased in winter while it decreased in spring in all scenarios due to changes in snow accumulation and melting. Furthermore, we found that erosion and deposition will change spatially by the end of the century, with a shift from erosion- to deposition-dominated valleys.