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Sediment transport is the movement of solid particles , typically due to a combination of gravity acting on the sediment, and the movement of the fluid in which the sediment is entrained.
The movement of water across the stream bed exerts a shear stress directly onto the bed. If the cohesive strength of the substrate is lower than the shear exerted, or the bed is composed of loose sediment which can be mobilized by such stresses, then the bed will be lowered purely by clearwater flow.
Deposition is the geological process in which sediments, soil and rocks are added to a landform or landmass. Wind, ice, water, and gravity transport previously weathered surface material, which, at the loss of enough kinetic energy in the fluid, is deposited, building up layers of sediment.
The down-current slope is the angle of repose, which depends on the shape of the sediment. These commonly form in fluvial and aeolian depositional environments, and are a signifier of the lower part of the Lower Flow Regime. Ripple cross-laminae forms when deposition takes place during migration of current or wave ripples.
Soft sediment deformation (possibly a seismite) in Dead Sea sediments, Israel. Soft-sediment deformation structures or SSD, is a consequence of the loading of wet sediment as burial continues after deposition. The heavier sediment "squeezes" the water out of the underlying sediment due to its own weight. There are three common variants of SSD:
The graph takes sediment particle size and water velocity into account. [2] The upper curve shows the critical erosion velocity in cm/s as a function of particle size in mm, while the lower curve shows the deposition velocity as a function of particle size. Note that the axes are logarithmic.
However, the term is more particularly applied to the deposition of sediments, and in the strictest sense, it applies only to the mechanical deposition of sediment particles from an initial suspension in air or water. Sedimentation results in the formation of depositional landforms and the rocks that constitute the sedimentary record. [6]
Sediment resuspension by waves, tides, or other disturbing forces (e.g. human feet at a beach) allows sediment pore water and other dissolved components to diffuse out of the sediments and mix with the water above. [5] For resuspension to occur the movement of water has to be powerful enough to have a strong critical shear stress that is ...