<P> A floodplain or flood plain is an area of land adjacent to a stream or river which stretches from the banks of its channel to the base of the enclosing valley walls, and which experiences flooding during periods of high discharge . The soils usually consist of levees, silts, and sands deposited during floods . Levees are the heaviest materials (usually pebble - size) and they are deposited first; silts and sands are finer materials . </P> <P> Floodplains are made by a meander eroding sideways as it travels downstream . When a river breaks its banks, it leaves behind layers of alluvium (silt). These gradually build up to create the floor of the plain . Floodplains generally contain unconsolidated sediments, often extending below the bed of the stream . These are accumulations of sand, gravel, loam, silt, and / or clay, and are often important aquifers, the water drawn from them being pre-filtered compared to the water in the river . </P>

An area of land near a river that may be covered with water during a flood is called a