The river system of an area is called drainage. The area drained by a single river system is called the drainage basin.

The word watershed is sometimes used interchangeably with drainage basin or catchment. Ridges and hills that separate two watersheds are called the drainage divide.

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Terminology for the study of rivers

• Drainage basin – the area of land drained by a river.
• Catchment area – the area within the drainage basin.
• Watershed – the edge of highland surrounding a drainage basin. It marks the boundary between two drainage basins.
• Source – The beginning or start of a river.
• Confluence – the point at which two rivers or streams join.
• Tributary – a stream or smaller river which joins a larger stream or river.
• Mouth – the point where the river comes to the end, usually when entering a sea.

Drainage Patterns:

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Depending on the slope of land, underlying rock structure and climate of an area, the streams in a drainage basin form certain patterns. Different types of drainage pattern are as follows:

#1. Dendritic Drainage Pattern:

When the river channel follows the slope of the terrain, it develops dendritic pattern. The stream and its tributaries resemble the branches of a tree. Hence, it is called dendritic pattern.

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#2. Trellis Drainage Pattern:

When a river is joined by its tributaries at almost right angles, it develops a trellis pattern. Trellis pattern develops where hard and soft rocks exist parallel to each other.

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#3. Rectangular Drainage Pattern:

When rocks are strongly joined, rectangular pattern develops.

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#4. Radial Drainage Pattern:

• When the streams flow in different directions from a central peak or dome like structure, a radial pattern is developed.
• It is important to note that a combination of different patterns may develop in the same drainage basin.

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A Quick Recap

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