Riffle-pool sequence

This sequence is present only in streams carrying gravel or coarser sediments.

Riffles are formed in shallow areas by coarser materials, such as gravel deposits, over which water flows.

Pools are deeper, calmer areas whose bed load (in general) is made up of finer material such as silt.

[1] Streams with only sand or silt laden beds do not develop the feature.

Meandering streams with relatively coarse bed load tend to develop a riffle-pool sequence with pools in the outsides of the bends and riffles in the crossovers between one meander to the next on the opposite margin of the stream.