Climatic against land use variability impact on soil erosion in two contrasting environments

At continental and geological time scales, tectonic forces and climate are the first landscape evolution drivers. However, since the Neolithic, human is recognised as being a new geomorphic agent, indirectly or directly moving significant amount of materials across landscapes. In a context of global changes, when both climate and human activities are rapidly evolving, the question of the relative contribution of climate variability and anthropogenic activities to soil erosion remains poorly quantified. Understanding this contribution is however key to the design of appropriate soil erosion management plans. Based on two catchment-scale hydrosedimentary observatories, the objective of this study is to quantify the relative importance of climate variability and land use change on the erosive response of two headwater catchments located in contrasted environments. The first study area is in a volcanic tropical island and the second one is in a lowland, intensively cultivated plain under an oceanic temperate climate. More particularly, we will investigate the importance of rainfall and associated flood events intensity and frequency on the water and sediment fluxes. The influence of these temporal dynamics (i.e. frequency/intensity of events) will be studied according to different land uses, as the two questions (spatial/temporal variabilities) are closely interlinked.