Bed load

Ground freight ( engl. bed load) referred to in geomorphology transporting sand to gravel sized grains on the ground, within a medium such as air or water. The three different types of motion, the grains may be moved: by rolling, sliding or saltation ( jumping).

In the case of saltation that can stimulate impinging grain again other grains for saltation again. These granules can be six times larger than the particle excitation. The process can continue a chain reaction, even if the transport of energy is reduced. At the same time, the incident particle finest particles still solves (clay, silt ) from the floor, then go into suspension.

The movement for each particle is determined by the particle shape, the particle size and the available energy ( the larger the grains, the more energy required the medium to put them in motion).