Sheet-flow sediment transport refers to transport of sandy sediments as a fluidized thin surface layer (thickness of ten to a few tens of grains).
Sheet flow is a particular form of bedload sediment transport in which the seabed is flattened and the top soil layer is fluidized. Sheet flow transport occurs when the seabed is subjected to high shear stresses, especially shear stresses generated by strong wave action (wave orbital velocity greater than 1 m/s). In the sheet-flow layer, continuous contacts between sand grains create an intergranular stress. This stress decreases the velocity in the sheet-flow layer to about one half the velocity in the top layer. The sediment concentration in the sheet-flow layer is in the order of 100 to 1000 kg/m3.
The formation of a sheet flow layer is promoted by cyclic wave loading of the seabed, see Wave-induced soil liquefaction.
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