Soil Erodibility Assessment for Applications at Watershed Scale.

The term "soil erodibility" indicates the aptitude of a soil, based on its properties, to be eroded by the following processes and exogenous agents: rainfall, runoff, mass movements and wind. The concept of erodibility gained in importance during the last 50 years in the field of soil erosion modelling and applications of soil conservation. However, erodibility is a concept borrowed from geomorphological literature that was developed and adopted up to the beginning of the 20th century. In this context, the concept of erodibility was often used to give a qualitative assessment of the effectiveness of various forms of erosion caused by exogenous agents such as water, ice and wind (Davis, 1909). It was used mainly by geologists and geographers for a long time and related to the processes most effective in the characterization of landform dynamics (Taylor and Eggleton, 2001; Turkington et al., 2005). It is easy to associate varying rates of erodibility to compactness of igneous and metamorphic rock masses compared to marls and clay shale, deeply eroded by gullies. Indeed, the effectiveness of different processes and geomorphic agents is directly linked to the characteristics of the bedrock in its state of weathering.