Temperature effects on heavy rainfall modify catchment hydro-morphological response

Abstract

Abstract. Heavy rainfall is expected to intensify with increasing temperatures, which will likely affect the rainfall spatial characteristics. The spatial variability of rainfall can affect streamflow and sediment transport volumes and peaks. Yet, the effect of climate change on the small-scale spatial structure of heavy rainfall and how those impacts hydrology and geomorphology remains largely unexplored. In this study, the sensitivity of the hydro-morphological response to heavy rainfall at the small-scale of minutes and hundreds of meters was investigated. A numerical experiment was conducted, in which synthetic rainfall fields representing heavy rainfall events of two types, stratiform and convective, were simulated using a space-time rainfall generator model. The rainfall fields were modified to follow different spatial rainfall scenarios, associated with increasing temperatures, and used as inputs into a landscape evolution model. The experiment was conducted over a complex topography medium-size (477 km2) Alpine catchment in central Switzerland. The results highlight that the response of the streamflow and sediment yields are highly sensitive to changes in the rainfall structure at the small-scale, in particular to changes in the areal rainfall intensity and in the area of heavy rainfall, which alters the total rainfall volume, and to a lesser extent to changes in the peak rainfall intensity. The hydro-morphological response is enhanced (reduced) when the local peak rainfall intensified and the area of heavy rainfall increased (decreased). The hydro-morphological response was found to be more sensitive to convective rainfall than stratiform rainfall because of localized runoff and erosion production. It is further shown that assuming heavy rainfall to intensify with increasing temperatures without introducing changes in the rainfall spatial structure might lead to over-estimation of future climate impacts on basin hydro-morphology.

Seasonality, Intensity, and Duration of Rainfall Extremes Change in a Warmer Climate

“…Decreases in storm duration suggest a more limited capacity of vegetation and soil to intercept and absorb water, suggesting increased flood volumes. Changes in the spatial structure of storms could be expected as well and could further alter catchment flood responses (Chen et al., 2020; Peleg et al., 2019; Prein, Liu, Ikeda, Trier, et al., 2017).…”