The mechanics of the process by which a sediment particle is removed from a stream bed was investigated. An idealized model, consisting of a one-inch diameter sphere protruding through a flat plate, a sphere-supporting base, and two equal height sphere-restraining pins aligned perpendicular to the flow direction, was used to simulate the condition of a cohesionless particle lying on a stream bed. By means of this model, the statistical variables of the angle of repose, the protrusion condition, and the approach velocity distribution became controllable at deterministic values.