Criteria for determining sand‐transport by surface‐creep and saltation

One of the most important problems relating to sand‐movement by wind or water is the determination of the conditions for initial movement. Experimenters have recognized what appear to be three distinct methods of sand‐and‐silt movement by fluids: Surface‐creep (called bed‐load movement in hydraulics literature); saltation; and suspension. These three classifications seem to be fundamentally sound since each type of movement is controlled by a different set of forces acting on the sand‐particles.