The absolute quantities and the relative proportions of these types of stream load vary from one stream to another, and within a single stream from one time to another. The following animation shows some of the processes that move solid material within a stream channel. Saltation is a process where particles moves from the stream bed to the medium in quick continuous repeated cycles. The action of returning to the surface usually has enough force to cause the entrainment of new particles. Particles that are transported as suspended load remain entrained in the flowing water for long periods of time.
Human activity adds large amounts of dissolved and solid material to streams.
These added materials include fertilizers, animal waste, and soluble compounds that are the by products of agriculture, forestry, and industry. Agriculture and forestry also add large amounts of solid sediment into streams because of their disturbance of vegetated surfaces.