| a level or gently sloping surface formed of sediments laid down by streams, generally during flooding. |
alluvial plain
flat land area adjacent to a stream, composed of unconsolidated sedimentary deposits (alluvium) and subject to periodic inundation by the stream. Floodplains are produced by lateral movement of a stream and by overbank deposition; therefore they are absent where downcutting is dominant. Any erosional widening of one bank is approximately equalled by deposition on the opposite side of the channel in the form of bar development along the inside of meander bends. Thus, the simplest floodplain is made up of a strip of sinuous scrolls immediately adjacent to the stream.
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