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In a flowingstream, ariffle-pool sequence (also known as a pool-riffle sequence) develops as a stream's hydrological flow structure alternates from areas of relatively shallow to deeper water. This sequence is present only instreams carrying gravel or coarsersediments.Riffles are formed in shallow areas by coarser materials, such asgravel deposits, over which water flows. Pools are deeper, calmer areas whosebed load (in general) is made up of finer material such as silt.[1] Streams with onlysand orsilt laden beds do not develop the feature. The sequence within a stream bed commonly occurs at intervals of from 5 to 7 stream widths.Meandering streams with relatively coarse bed load tend to develop a riffle-pool sequence withpools in the outsides of the bends and riffles in thecrossovers between onemeander to the next on the opposite margin of the stream. The pools are areas of active erosion and the material eroded tends to be deposited in the riffle areas between them.
