An
alluvial plain is a largely flat
landform created by the deposition of
sediment over a long period of time by one or more
rivers coming from highland regions, from which
alluvial soil forms. A
floodplain is part of the process, being the smaller area over which the rivers flood at a particular period of time, whereas the alluvial plain is the larger area representing the region over which the floodplains have shifted over geological time.