Sediment.
A floodplain is the land that is covered by water when a river overflows it's banks. When this happens, silt and clay are deposited over time and the land on either side of the river flattens out. Any depressions in the land will hold water when the river level returns to normal after flooding and therefore more clay and silt will be deposited there filling it up.
The area of fertile soil at the mouth of a river is called river delta.
A flood plain is a flat land bordering a river made up of alluvium (clay, sand and silt) deposited during floods. When a river overflows, the floodplain is covered with water. Hope this helps :)
A "Delta", so-called because of the tendency of the 'channels' created by hydrologic soil deposition to frequently vary their courses due to creation of impedences to linear flow caused by precipitation of the colloidally-suspended particles of soil which fall out of suspension as the velocity of the water is reduced, raising the floor of the channels, thus forcing the flow to seek an easier [more lateral] route. "Delta" is used in a mathematical sense, meaning "variation".
islets
sediment
Fine particles of fertile land that is deposited on the banks of a river after a flood
lake
The landform that is created at the mouth of a river by deposited silt (not salt) is called a river delta.
This land deposit you speak of is called a delta.
The Delta
delta
A delta
the bank of a river
The land formed by deposited soil at the mouth of a river is called a delta (named for the Greek letter, which is similarly triangular in shape).
A delta.
The land area that includes soil carried downstream by a river and deposited at the rivers mouth is called a delta. The delta is also where the river enters the ocean or lake.