Recognizing drainage patterns on topographic maps

A drainage pattern, also known as a river system, is a pattern achieved by a network of river channels and tributaries in a particular drainage basin. The topography of the land and the underlying geology have a great impact on the drainage patterns of rivers. On topographic maps, drainage patterns can be identified by the shape/pattern made by the main river and its tributaries.
Some of the common drainage patterns include:

1. The dendritic drainage pattern
This is a drainage pattern in which the tributaries join the main river at acute angles, resembling the shape of a tree with its branches. (See the figure below).

A dendritic drainage pattern

2. The trellis drainage pattern
This is a drainage pattern in which the short subsequent tributaries join the main stream at right almost angles.(See the figure below).

A trellis drainage pattern

3. The radial drainage pattern, also known as the centrifugal pattern
This is a drainage pattern in which streams diverge from a central high point towards different directions. (See the figure below).

A radial or centrifugal drainage pattern

4. The rectangular drainage pattern 
This is a drainage pattern characterized by many right-angle bends in both the main streams and their tributaries. (See the figure below).

A rectangular drainage pattern

5. The centripetal drainage pattern
This is a drainage pattern in which streams flow from different directions and converge at the same end-point, which is generally a depression or a basin. (See the figure below).

A centripetal drainage pattern

6. The parallel drainage pattern 
This is a drainage pattern in which several rivers flow in the same direction, usually with few tributaries. (See the figure below).

A parallel drainage pattern

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