The goal of this study is twofold. The first aspect is to develop a model of erosion production for black marls based on data collected in two experimental watersheds of Draix: Laval and Roubine, the surface areas of which are 86 ha and 0.13 ha, respectively. The second aspect is to analyze the temporal and spatial scale effects of the erosion processes. At first, a statistical relationship of erosion production which ties the measured erosion to the rainfall and/or run-off characteristics will be looked for. These relationships are established for both watersheds, each one being considered as a whole. Then, the production relationship set for the small watershed was applied to small watersheds of the larger one to generate solid fractions to its talweg; the solid fractions are then propagated to its outlet. At this point, the Laval is considered as being formed by levels and sub-watersheds with the same behavior as the elementary unit.
