Soil erosion in the boundary layer flow along a slope: a theoretical study

To better understand the phenomena involved in hydraulic erosion of soils, the influence of the eroded mass flow rate on the velocity field of the water flow is investigated by an original theoretical model. We consider the situation of a turbulent two-phase fluid flow over an erodable solid medium, with both turbulent stresses and turbulent particles diffusion in the flow. In the reference frame linked to the ground surface, the flow can be considered as a quasi-steady state and modelled by the boundary layer equations with addition of mass injection from the ground to account for erosion. To solve completely the problem, the prescription of a local erosion criterion is necessary to evaluate the local eroded mass flow rate. We consider here a purely mechanical process: the eroded flow rate is proportional to the difference between the tangential stress induced by the flow and a critical value characteristic of the soil. In this theoretical frame, we can study the influence of several parameters, as the slope of the ground or the sediments density. One of the main results obtained is the existence for a given set of the parameters of a critical slope angle separating two different erosion regimes. (c) 2007 Elsevier Masson SAS. All rights reserved.