Introduction
A large natural body of running water, more or less confined within banks, is called a river. Rain water and snowmelt water are the principal source of a river.
Generally, a river has its origin in hills or mountains and is formed by the joining of many smaller rivers, called tributaries of the main river in concern.
The great rivers of the earth flow through mountain in its upper course, through plain in its middle course and through the delta of its own creation in its lower course. Such a river (as the Ganges) is called an ideal river. The Ganges, the Godavari, the Krishna, the Cauvery of India are some examples of ideal rivers.
Work of a river:
As a river begins to flow along the slope of the land, it carries out erosion and deposition on its way before reaching the sea. As a result it modifies landscape of the region through which it passes. The work of a river is performed by three processes:
- Erosion,
- Transportation and
- Deposition.
1. Erosion:
In physical geography erosion means the wearing away of the land surface by agents that involve the transportation of materials. The chief agents of erosion are river, glacier and wind.
2. Transportation:
In physical geography transportation means the movement of weathered and eroded earth material I, natural agents such as river, glacier, wind etc.
3. Deposition:
In physical geography deposition means the laying down of material that has been weathered, eroded and transported by natural agents such as river, glacier, winds etc.