It is called the flood plain.
Flood plain
Flood plain
Floodplain
farter
Floodplain
Floodplain
Floodplain
farter bank
ping pong on a donkey cage!
A foodplain is a flat or nearly flat land adjacent a stream or river that stretches from the banks of its channel to the base of the enclosing valley walls and experiences flooding during periods of high discharge.
The mature stage of river development is characterized by flat floodplains. During this stage, the river has carved a wide valley and deposited sediment along its banks, creating a broad, flat floodplain that may experience periodic flooding.
A flood plain is a flat or gently sloping area near a river or stream that is prone to flooding. It forms when the river overflows its banks and deposits sediment on the adjacent land. Over time, this repeated flooding creates the flat surface of a flood plain.