Characteristics of Soil Erosion Caused by Rain Water Flow -On the Sheet Flow Velocity Distribution Related to the Cohesive Soil Layer Conditions-

An experimental approach to the soil erosion mechanism caused by the sheet flow is described. The purpose of the experiment is to analyze the relation between the grain size distribution and the flow velocity distribution in the case that the sheet flow is acting on the soil surface. The shear velocity (u_*), Nikuradse's sand-grain roughness (k), and the laminar sublayer (δ_L), in various cases of flow and slope, are calculated to find the relations of u/u_* to u_*h/ν, and q_w/(b/gi)u_*^3 to k/h. The relations are shown to have a pretty correlation excepting a case of the soil layer with a small angle. If the value of k obtained experimentally can be applied to the average grain size d_k, it is possible to explain the fundamental relation between the tractive force of flow and the resistance force of soil.