A floodplain.
That flat plain formed by river deposits during a flood is known as a floodplain. It typically consists of fertile soil and is susceptible to periodic flooding due to its proximity to the river. Floodplains play an important role in natural ecosystems and agriculture.
floodplain
Flood plain
Flood plain
lake
nile
The Mississippi river delta.
an old river
A flood plain is formed when a river overflows its banks and deposits sediment on the adjacent low-lying areas. Over time, repeated flooding events deposit layers of fertile soil, creating a flat and fertile plain that is beneficial for agriculture. Floodplains help absorb excess water and reduce the risk of flooding in other areas.
A delta is a result of deposits that are carried by a river. This is usually formed at the mouth of the river.
a delta
it is called a delta