Spatial and temporal dynamics of soil erosion across different landscapes

Soil erosion and sediment transport are highly variable in time and space. Spatial variations generally imply a decrease in the runoff coefficient when moving from the local to the hillslope scale, as landscape patchiness and heterogeneity enhance the infiltration of the overland flow. However, runoff coefficient stops decreasing with increasing observation scales because of water exfiltration downslope and its contribution to the river flow. Similar phenomena may be observed for soil erosion with the occurrence of additional processes when changing scales, as, for example when moving from local splash erosion to large gullies in the valleys. Large variations in soil erosion rates may also depend on the time scale of interest, from the influence of the characteristics of the rainfall events to the impact of seasonal climatic patterns. This is illustrated by the ongoing debate on the relative influence of low magnitude/ high frequency events when they are compared to high magnitude/ low frequency storms. Depending on the context, these dynamics of landscape evolution can also vary and take different forms. Based on a synthesis of monitoring data collected at monitored sites located in contrasted environments, the objective of this paper is to quantify and discuss the spatial and temporal dynamics of runoff and erosion. This study will focus on three different landscapes. First, the importance of landscape connectivity will be emphasized in a lowland flat area where the sediment exports is mainly driven by seasonal soil saturation and anthropogenic features that artificially increase sediment connectivity. Then, the importance of soil surface characteristics and rainfall event erosivity will be discussed in an erosive loamy cultivated region. Finally, the impact of extreme events and land use change will be illustrated in tropical environments.