Cute Young Dark Blonde Girl Reveals In White Shorts On The Shore With Saltating Sands During Low Tide

At low fluid velocities, loose material rolls downstream, staying in contact with the surface. This is called creep or reptation. Here the forces exerted by the fluid on the particle are only enough to roll the particle around the point of contact with the surface.
At higher speeds, the lift and moment exerted by the fluid on the particle is enough to pull it away from the surface and into the flow. Initially the particle moves quite rapidly compared to the flow and so has high lift, moving it away from the surface. As the particle moves into the faster flow away from the bed, the velocity difference between particle and flow decreases, and so lift decreases. When the particle weight is greater than the lift force, the particle sinks back towards the surface. During its descent, the particle keeps some of the speed it picked up in the faster moving flow, and so returns to the surface at higher speed than the fluid near the surface.
Depending on the surface, more loose material could be dislodged by the impacting particle, the particle might disintegrate on impact, or the particle could continue bouncing downstream. In rivers, this process repeats continually, gradually eroding away the river bed, but also transporting-in fresh material from upstream.
Suspension generally affects small particles ('small' means 100 micrometres or less for particles in air). These particles experience lift forces which are similar in magnitude to the weight of the particle. These smaller particles are carried by the fluid in suspension, and convected downstream. Particles are carried until the fluid decelerates. When the weight is greater than the lift, the particles settle out.