Deposition
Deposition is the process of eroded material being dropped. This happens when a river loses energy. A river can lose its energy when rainfall reduces, evaporation increases, friction close to river banks and shallow areas which leads to the speed of the river reducing and therefore the energy reduces, when a river has to slow down it reduces its speed (and ability to transport material) and when a river meets the sea.
The Hjulström Curve
When discussing transportation you need to know the difference between the competence and capacity of a river. The competence is the maximum size of load a river is able to carry whereas capacity is the total volume of material a river can transport. The competence of a river is the maximum particle size that a river can transport at a particular point. The Hjulström curve shows the relationship between river velocity and and competence. It shows the velocities at which sediment will normally be eroded, transported or deposited. The critical erosion velocity curve shows the minimum velocity needed to for the river to erode (pick up) and transport material of different sizes (e.g. as bedload or in suspension). A greater velocity is required to erode material compared to just transporting it. The mean settling velocity curve shows the velocities at which different sized particles are deposited.