Transport - the movement of material, in this case by river water. There are 2 types of material that we consider in rivers - the bedload and the suspended load. Bed load is the large, heavy stones that are generally found on the river bed. Suspended load is smaller sediments that are carried or suspended in the water itself. Processes include;
Solution - where material is dissolved within the water
Suspension - where small particles are held up or suspended in the water
Saltation - the bouncing motion of larger particles along the river bed
Traction - the rolling motion of sediment along the bed - normally much larger sediment.
Obviously the larger sediments will only be moved during periods of high river flow.