PSEM_2D: A physically based model of erosion processes at the plot scale

International audienceThis paper presents the development and first applications of the Plot Soil Erosion Model 2D (PSEM_2D). Infiltration is computed using a Green and Ampt model, overland flow is computed using the depth-averaged two-dimensional unsteady flow equations (Saint Venant equations), and soil erosion is computed by combining the equation of mass conservation of sediment and a detachment-transport coupling model for erosion by runoff. A shear stress approach is used to determine the transport capacity. The formation of a covering cohesionless layer as a result of depositing sediment and action of rainfall impact before runoff is considered. The erosion processes involved are rainfall and runoff detachment of original soil, rainfall redetachment, and overland flow entrainment of sediment from the deposited layer, and deposition. The model uses a single representative particle size. Complex rainfall events on natural slopes can be simulated. The accuracy of the predictions for erosion of planar surfaces is tested by comparison with observed data obtained from experiments and with an analytical solution. Good agreement between the calculated results and measured data was found. A sensitivity analysis was also performed. Limitations related to the description of overland flow on plane soil surface are pointed out. Finally, an application to a nonplanar natural surface of 75 m2 illustrated the distribution of erosion and sedimentation over the plot