Drainage patterns are categorized based on their shape and texture. Their shape or pattern evolves as a result of the local terrain and underlying geology. Drainage channels form where surface runoff is increased and soil materials have the least resistance to erosion. This article will explain about Types of Drainage Patterns that will be helpful in Geography preparation for the UPSC Civil service exam.

Drainage Pattern

• A drainage pattern refers to the system of surface water movement formed over time by stream erosion.
• The pattern formed by stream erosion over time exposes features of the types of rocks and geologic formations found in a stream drained landscape region.
• The drainage pattern is determined by the land's topography, gradient, and whether a specific location is dominated by hard or soft rocks.
• Drainage patterns are categorised based on their shape and texture.
• Their shape or pattern evolves as a result of the local terrain and underlying geology.
• These patterns are discernible when viewed from above or on topographical maps.

Types of Drainage Patterns

• There are various drainage patterns based on the shape and creation of river patterns. It is broadly divided into two types:
  • Discordant Drainage Pattern
  • Concordant Drainage Pattern

Discordant Drainage pattern

• It has nothing to do with the area's topography or geology.
• Regardless of topographic changes, the river in the discordant drainage pattern follows its original channel.
• It is broadly divided into two types:
  • Antecedents
  • Superimposed antecedents

Antecedents

• Inconsequent drainage is another name for it.
• A section of a river's slope and the surrounding region is elevated, and the river remains on its original slope, sawing through the uplifted segment and generating deep gorges.
• Indus, Sutlej, Brahmaputra, and other Himalayan rivers are examples of antecedent rivers or drainage.

Superimposed Antecedents

• Also known as epigenetic drainage or superinduced drainage.
• A river moving through softer rock strata eventually reaches the harder base rocks, yet it stays on the same slope.
• The stream's erosive force allows it to break through any type of bedrock while preserving its previous drainage pattern.
• It is out of sync with the underlying rock structure because it arose from a cover of rocks that has since vanished, and its courses are untouched by the newly exposed formations.
• The Damodar, the Subarnarekha, the Chambal, the Banas, and the rivers flowing through the Rewa Plateau are examples of superimposed drainage or rivers.

Concordant Drainage Pattern

• It is related to the area's topography and geology.
• The river's route is heavily influenced by the geography and slope of the river.
• The following are the most popular drainage systems.
• Consequent drainage rivers and Subsequent drainage rivers are the two types of rivers classified under Concordant Drainage pattern

Consequent Drainage

• When the river follows the slope's general direction, it is referred to as a consequent drainage system.
• Peninsular India's rivers, such as the Godavari, Krishna, and Cauvery, are resultant rivers that run into the Bay of Bengal after descending from the western ghats.

Subsequent Drainage

• The term "subsequent river" refers to streams that have emerged after the initial stream (Consequent River).
• After the primary drainage pattern has been created, a tributary stream is eroded along an underlying band of non-resistant rock.
• Chambal, Sind, Ken, Betwa, Tons, and Son are examples of downstream drainage rivers that meet the Yamuna and Ganga at right angles.
• The following are the types of drainage patterns seen in subsequent and Consequent drainage systems:
  • Dendritic Drainage Pattern
  • Parallel Drainage Pattern
  • Rectangular Drainage Pattern
  • Trellis Drainage Pattern
  • Radial Drainage Pattern
  • Centripetal Drainage Pattern

Dendritic Drainage Pattern

• It is the most common kind and has a branching structure similar to tree roots.
• The dendritic pattern forms as the river channel follows the terrain's slope.
• The pattern appears in regions where the rock underneath the stream has no discernible structure and may be eroded in all directions equally easily.
• At sharp bends, tributaries join bigger streams.
• It is also known as pinnate drainage, because it resembles the branching of a tree. It is prevalent in areas with homogeneous material.
• These form in regions where the rock under the stream, such as granite, gneiss, volcanic rock, and sedimentary rock that has not been folded (or unconsolidated material), has no specific fabric or structure and may be eroded equally quickly in all directions.
• It forms on terrain with homogenous lithology and in which faulting and jointing are minimal.
• These are by far the most prevalent, and examples include the Indus, Godavari, Mahanadi, Cauvery, and Krishna rivers.

Parallel Drainage Pattern

• It develops in areas with parallel, elongated landforms and a steep slope to the surface.
• Following the slope of the surface, tributary streams tend to expand out in a parallel-like pattern.
• A river pattern formed by steep slopes with some relief. It forms where there is an incline.
• In a consistently sloped area, the tributaries run parallel to each other.
• Rivers of the lower Himalayas, for example, and tiny and rapid rivers originating in the Western Ghats and flowing into the Arabian Sea.
• E.g. Godavari, Kaveri, Krishna, and Tungabhadra are rivers that originate in the Western Ghats.

Rectangular Drainage Pattern

• The rectangular drainage pattern is prevalent in faulted areas.
• It grows in a tightly packed rocky ground.
• Streams choose the path of least resistance and hence congregate in areas with the weakest exposed rock.
• The tributary streams curve sharply and enter the main stream at steep angles.
• The main stream bends at right angles, and the tributaries connect at right angles as well, resulting in rectangular patterns.
• These are found in areas where there has been faulting.
• It forms in areas with limited topography and a network of bedding planes, fractures, or faults that create a rectangular network.
• Streams found in the Vindhya mountain range, for example, Chambal, Betwa, and Ken.

Trellis Drainage Pattern

• Trellis drainage forms in folded terrain when hard and soft rocks run parallel to one another.
• The primary course of the stream is located in valleys formed by down-turned folds known as synclines.
• When principal tributaries of major rivers flow parallel to one other and secondary streams join them at right angles, this pattern is generated.
• Patterns resemble the standard garden trellis.
• These form when sedimentary rocks are bent or inclined and subsequently eroded to varied degrees based on their strength.
• The short succeeding streams meet the main stream at right angles in this kind.
• Differential erosion prepares the route for tributaries via soft rocks.
• For example, the rivers of the Himalayan region's upper reaches, such as the Indus, Ganga, and Brahmaputra.

Radial Drainage Pattern

• Radial drainage patterns form around a central high point and are typical in conically shaped objects such as volcanoes.
• The drainage pattern is called 'radial' when rivers begin on a hill and flow in all directions.
• Develops around a central elevated point, with streams radiating away from the centre.
• A summit's tributaries follow the slope downwards and drain in all directions.
• For example, the rivers that flow from the Amarkantak range, such as the Narmada and Son (tributary of Ganga).

Centripetal Drainage Pattern

• As streams travel toward a central depression, it is the polar opposite of the radial.
• During the wetter seasons, these streams nourish ephemeral lakes, which evaporate during the dry seasons.
• Salt flats can form in these dry lake beds when salt dissolved in lake water precipitates out of solution and is left behind after the water evaporates.
• In the low lying basins, streams converge from all sides.
• The stream is flowing toward a central depression.
• It is identical to the radial drainage system, except that radial drainage flows out and centripetal drainage flows in.
• Streams in Ladakh, Tibet, and Nepal, for example, include the Baghmati and its tributaries.

Conclusion

A drainage pattern refers to the spatial configuration and the interconnected network of streams and rivers in a particular drainage basin or watershed. The layout and form of these networks depend on the topography, underlying rock structure, geological history, and sometimes even human activity.