- The present investigation deals with the effects of shear and gravity on the motion of small particles in turbulent boundary layers near horizontal and vertical surfaces. These effects are important for the prediction of particle motion inside the viscous sublayer, where together with turbulence, they affect particle deposition and resuspension. The equations of particle motion are derived using the existing expressions for the hydrodynamic forces of lift and drag acting on a small particle near a surface. These are combined with the secondary turbulent flow field, which is modeled numerically. Then, particle motion in the obtained flow field is simulated under conditions of combined shear and turbulent effects. It is shown how the initial particle velocity and distance from the wall affects its motion at high shear rates. Special attention is paid to the role of gravity in the vicinity of upward- and downward-facing horizontal surfaces.