A floodplain is primarily a result of deposition rather than erosion. Floodplains are the flat or nearly flat areas of land adjacent to a river or stream that are subject to flooding. When a river overflows its banks, it loses energy and its ability to carry sediment. As a result, sediment is deposited on the floodplain, creating a fertile area that is capable of supporting a variety of plant and animal life.
The process of deposition occurs as the water slows down and spreads out over the floodplain, dropping the heavier particles first. This sediment contributes to the formation and renewal of the floodplain over time. While erosion can take place in certain areas of the floodplain, particularly along the riverbanks, the overall formation of floodplains is driven largely by the deposition of sediments during flood events.