Drainage Patterns in India

The drainage pattern of an Indian river system is determined by the geological time period, nature and structure of rocks, topography, slope, and the amount of water flowing through the channel. These patterns are broadly classified into two categories based on their relationship with the underlying rock structure and topography: Discordant (Consequent) and Concordant (Subsequent).

Discordant Drainage Patterns

These patterns do not follow the topology of the area and are independent of the underlying rock structures. They are further divided into:

• Antecedent Drainage: Rivers that existed before the upheaval of the landmass and cut through the rising landform to maintain their original course. They form deep gorges.
  • Examples: Indus, Satluj, Brahmaputra, Subansiri, Kosi, and Gandak.
• Superimposed (Epigenetic) Drainage: Rivers that developed on a younger upper rock layer, but as they eroded downward, they encountered an older, structurally different underlying rock layer while maintaining their original course.
  • Examples: Damodar, Subarnarekha, Chambal, Banas, and rivers of the Rewa Plateau.

Concordant Drainage Patterns

These patterns are highly dependent on the slope of the terrain and the structural topography of the underlying rocks.

• Consequent Streams: Rivers that follow the general direction of the initial regional slope. Most Peninsular rivers are consequent streams.
  • Examples: Godavari, Krishna, and Cauvery flowing eastwards due to the tilt of the Peninsular plateau.
• Subsequent Streams: Tributaries that develop after the master consequent stream and follow axes of low resistance or weak rock strata, often joining the main river at right angles.
  • Examples: Asan (tributary of Yamuna), Son (tributary of Ganga).

Major Geomorphic Drainage Patterns in India

Dendritic Drainage Pattern

This is the most common tree-like branching pattern that develops in areas underlain by homogeneous material or uniform rock strata where the rock resistance to erosion is equal in all directions.

• Key Characteristics: The tributaries join the main valley at acute angles resembling the twigs and branches of a tree.
• Geographical Distribution in India: It is predominantly found in the Indo-Gangetic Plains and the glaciated regions of the Himalayas.
• Major River Systems: Ganga, Yamuna, Indus, Mahanadi, Godavari, and Krishna.

Trellis Drainage Pattern

This pattern develops in areas where sedimentary rocks have been folded or tilted, and then eroded to varying degrees depending on their resistance.

• Key Characteristics: Primary tributaries flow parallel to each other along the strike of valleys, and secondary tributaries join them at right angles (90°).
• Geographical Distribution in India: Found in the old folded mountains of the Singhbhum region (Chota Nagpur Plateau) and the Appalachian-type topography of the outer Himalayas.
• Major River Systems: The tributaries of the Ganga in the Himalayan foothills and the upper courses of the Son river.

Radial Drainage Pattern

This pattern develops when rivers originate from a central elevated point or dome-like structure and radiate outward in all directions.

• Key Characteristics: It resembles the spokes of a wheel radiating from the hub.
• Geographical Distribution in India: Centered around prominent plateaus, volcanic domes, and isolated hill complexes.
• Major River Systems: The Amarkantak Plateau acts as a classic radial node giving rise to the Narmada (flowing west), Son (flowing north-east), and Mahanadi/Mahanadi tributaries (flowing south-east). The Girnar Hills in Gujarat and the Mikir Hills in Assam also exhibit this pattern.

Centripetal Drainage Pattern

This is the antithesis of the radial pattern, where rivers feed into a low-lying central basin, depression, or inland lake from all directions.

• Key Characteristics: Converging stream courses terminating in an endorheic basin.
• Geographical Distribution in India: Common in the arid and semi-arid regions of Western India and the inner valleys of the Himalayas.
• Major Examples: The streams feeding into the Sambhar Lake in Rajasthan, the Loktak Lake in Manipur, and the Pangong Tso in Ladakh.

Rectangular Drainage Pattern

This pattern develops on strongly jointed, faulted, or fractured bedrock where the joints provide paths of least resistance for erosion.

• Key Characteristics: Streams follow the path of joints and intersect at sharp, nearly right angles. Unlike trellis patterns, it lacks the prominent parallel ridge-and-valley structure.
• Geographical Distribution in India: Found in the hard-rock terrains of Central India.
• Major River Systems: Rivers of the Vindhyan and Satpura mountain ranges, and specific segments of the Chambal, Betwa, and Ken rivers.

Barbed Drainage Pattern

A rare drainage pattern where the tributaries flow in a direction opposite to that of the master stream to which they eventually connect.

• Key Characteristics: Tributaries join the main stream in backward-pointing retrogressive angles, often indicative of river piracy (river capture).
• Geographical Distribution in India: Found in specific structurally disrupted zones of the Himalayas.
• Major Examples: The Arun River (a tributary of the Kosi system) and certain older tributaries of the Indus and Brahmaputra systems in their upper Himalayan reaches.

Angular and Parallel Drainage Patterns

• Parallel Drainage Pattern: Comprises numerous streams flowing parallel to each other over a uniform, steeply sloping landform. In India, this is prominent along the Western Ghats where short, swift rivers flow westwards into the Arabian Sea (e.g., Sharavati, Netravati, Periyar).
• Angular Drainage Pattern: Formed when tributaries join the main channel at acute or obtuse angles that are highly irregular, typically dictated by intersecting joint patterns that do not form perfect rectangles. This is observed in parts of the foothills of the Himalayas.

Comparative Matrix of Drainage Patterns

Key Factoids for UPSC Prelims

• River Capture (Piracy): The process where a structurally dominant river breaches the drainage divide of another river system and captures its upper course. The Kosi and Teesta rivers have historically exhibited high levels of channel migration and capture.
• The Amarkantak Tri-Junction: It represents one of the most unique hydrological nodes in the world, giving rise to three major rivers flowing into different directions: the Narmada (Arabian Sea drainage), the Son (Bay of Bengal drainage via Ganga), and Johilla (tributary of Son).
• Karewa Formations and Drainage: The Jhelum river in the Kashmir valley displays a highly meandering course despite flowing through a mountainous terrain. This anomaly is due to the presence of the lacustrine deposits of the Karewa formation, which acts as a local base level.
• Asymmetrical Drainage Dividends: The Western Ghats act as a primary water divide for Peninsular India. Despite being close to the western coast, the structural tilt of the Deccan plateau causes the longest rivers (Godavari, Krishna, Cauvery) to flow thousands of kilometers eastward to the Bay of Bengal.