Delta is the name for such a piece of land.
A river delta.
There are five nouns. They are piece, land, mouth, river, and delta.
Delta
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).
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).
It is called a delta because its triangular shape resembles the Greek letter delta.
The area of fertile soil at the mouth of a river is called river delta.
Land formed by silt deposited by a river is called a delta.
it is caled a delta
A river delta.
An alluvial plain, sometimes also referred to as a fluvial plain.
a delta
This is the river delta.