Floodplains are generally flat or low-lying areas that are adjacent and run parallel to river channels and are covered by water during flood stages of the river. The floodplain of a river is built by alluvium carried by the river and deposited in overbank environments, forming layers of silt, clay, and sand. Many narrow elongate channels filled by sands and gravels typically cut overbank deposits, marking places where the river formerly flowed and meandered away from during the course of river evolution. sandy or gravelly levee deposits formed during flood stages of the river typically separate active and buried channels from floodplain deposits. These form because the velocity of floodwater decreases rapidly as it moves out of the channel, causing the current to drop heavy coarse-grained material near the river, forming a levee. Floodplains are also found around some lake basins that experience flood stages.
The increasing development and construction over floodplains creates potential and real hazards during floods. Floodplains are characterized by fertile soils and make excellent farmlands, which are nourished by yearly, decadal, and centurial floods, whereas buildings, towns, and cities have a much more difficult time dealing with periodic flooding.
Was this article helpful?