Drainage pattern

A Drainage pattern can be defined in the shadow of topographical features from which a stream gets runoff, through flow, and groundwater flow which can be divided by topographic barriers called a watershed. A watershed can be defined as all of the stream tributaries that flow to some location along the stream channel.

A geometric arrangement of streams in a region is known as a drainage pattern. The factors controlling the pattern of drainage in a region include the topography, slope, structural control, and nature of rocks, tectonic activities, a supply of water, and above all, the geological history of that region

Types of drainage patterns found in India

1. Antecedent or Inconsequent Drainage

The Rivers that existed before the upheaval of the Himalayas and cut their courses southward by making gorges in the mountains are known as the antecedent rivers. The Indus, Satluj, Ganga, Sarju (Kali), Arun (a tributary of Kosi), Tista and Brahmaputra are some of the important antecedent rivers, originating from beyond the Greater Himalayas.

2. Consequent Rivers

The Rivers which follow the general direction of slope are known as the consequent rivers. Most of the rivers of peninsular India are consequent rivers. For example, rivers like Godavari, Krishna and Kaveri, descending from the Western Ghats and flowing into the Bay of Bengal, are some of the consequent rivers of Peninsular India.

3. Subsequent Rivers

A tributary stream that is eroded along an underlying belt of non-resistant rock after the main drainage pattern (Consequent River) has been established is known as a subsequent river. Due to the northward slope of the Peninsula towards the Great Plains, the rivers originating from the Vindhyan and the Satpura ranges flow northward into the Ganga system. The Chambal, Sind, Ken, Betwa, Tons and Son meet the Yamuna and the Ganga at right angles.

4. Superimposed, Epigenetic (Discordant) or Superinduced Drainage

It is formed when a stream with a course originally established on a cover of rock now removed by erosion, so that the stream or drainage system is independent of the newly exposed rocks and structures. The Damodar, the Subarnarekha, the Chambal, the Banas and the rivers flowing at the Rewa Plateau present some good examples of superimposed drainage.

5. Dendritic Drainage

A pattern of drainage which is branching, ramifying or dichotomising, thereby giving the appearance of a tree. Most of the rivers of the Indo-Gangetic Plains are of dendritic type.

6. Trellis Drainage

It is a rectangular pattern formed where two sets of structural controls occurs at right angles. In a trellis pattern, the river forms a net like system and the tributaries flow roughly parallel to each other. The old folded mountains of the Singhbhum (Chotanagpur Plateau) have drainage of trellis pattern.

7. Barbed Pattern

A pattern of drainage in which the confluence of a tributary with the main river is characterised by a discordant junction—as if the tributary intends to flow upstream and not downstream. This pattern is the result of capture of the main river which completely reverses its direction of flow, while the tributaries continue to point in the direction of former flow. The Arun River (Nepal), a tributary of the Kosi is an interesting example of barbed drainage pattern.

8. Rectangular Drainage

The drainage pattern marked by right-angled bends and right-angled junctions between tributaries and the main stream is known as rectangular drainage. It differs from the trellis pattern in so far as it is more irregular and its tributary streams are neither as long, nor parallel as in trellis drainage. A typical example of this drainage pattern is found is the Vindhyan Mountains of India.

9. Radial Pattern

It is a pattern characterised by out flowing rivers, away from a central point, analogous with the spokes of a wheel. It tends to develop on the flanks of a dome or a volcanic cone. A good example of a radial drainage pattern is provided by the rivers originating from the Amarkantak Mountain. Rivers like Narmada, Son and Mahanadi originating from Amarkantak Hills flow in different directions and are good examples of radial pattern. This pattern is also found in the Girnar Hills (Kathiwar, Gujarat), and Mikir Hills of Assam.

10. Annular Pattern

In this drainage pattern, the subsequent streams follow curving or actuate courses prior to joining the consequent stream. This results from a partial adaptation to an underground circular struc-ture; a dome like igneous intrusion (batholith). The subsequent streams find it easier to erode the concentric, less resistant strata. This is not a very common drainage pattern in India. Some examples of this are however found in Pithoragarh (Uttarakhand), Nilgiri Hills in Tamil Nadu and Kerala.

11. Parallel Drainage

The drainage pattern in which the rivers flow almost parallel to each other is known as parallel drainage. The small and swift rivers originating in the Western Ghats and discharging their water into the Arabian Sea provide a good example of parallel drainage pattern in India.

12. Deranged Pattern

This is an uncoordinated pattern of drainage characteristic of a region recently vacated by an ice-sheet. This is probably due to the irregularities produced by glacially deposited materials, e.g., Kame and Kettle, and by the fact that there has been insufficient time for the drainage to become adjusted to the structures of the solid rock underlying the glacial drift. The picture is one of numerous water courses, lakes and marshes; some inter-connected and some in local drainage basins of their own. This type of drainage is found in the glaciated valleys of Karakoram.