In addition to its carbon sequestration potential, biochar has recently been promoted as a soil amendment. However, its impact on soil erosion remains debated in the short-term and unknown in the long-term. Therefore, this thesis aimed to determine both the short- and long-term impact of biochar on erosion by water of cropped soils in Wallonia. To fulfill this purpose, we investigated the short-term (young biochar application) and long-term (kiln sites) impact of biochar on soil mechanical and hydrodynamic properties. Mechanical properties related to interrill and rill erosion processes were determined using rainfall-runoff and flow flume experiments, respectively. Whereas the application of biochar did not affect rill erosion parameters, it had a texture-dependent impact on interrill erosion parameters. Its presence in soil tended to improve interrill erosion parameters on the sandy loam soil, but not on the silt loam soil. Hydrodynamic properties tended to be improved in biochar-enriched plots irrespective of soil texture. We demonstrated that this improvement was attributed to the improvement of soil structure rather than to the porosity of biochar. The effect of biochar aging was more visible on its impact on mechanical properties, compared to on hydrodynamic properties. Overall, the study of the effects of biochar on soil erosion by water revealed contrasting conclusions in both the short- and long-term.