What is a Drainage and a drainage pattern? What are drainage basin and drainage divide? What are the different types of drainage patterns? To answer these questions, read further.
Drainage is the term for the movement of water through clearly defined channels. A drainage system is a common term for the network of such channels.
The drainage pattern is the shape that the lakes, rivers, and streams make in a specific drainage basin.
Over time, the pattern left behind by stream erosion provides information about the types of rocks and geologic structures in a section of the landscape subject to streams.
Read: Major River systems in India
Drainage basin
The phrases catchment, catchment area, catchment basin, drainage area, river basin, and water basin are also used to refer to drainage basins.
The land surface and the rivers and streams make up the drainage basin.
The drainage basin serves as a funnel, gathering all the water in the area it drains and directing it to a single location.
Drainage Divide
A drainage divide separates adjacent drainage basins from one another. Typically, a drainage divide is a ridge or a high platform.
Different Drainage Pattern Types
Several drainage patterns depend on the shape and creation of river patterns. It can be broadly divided into two types:
Discordant Drainage Pattern
Concordant Drainage Pattern
Discordant Drainage Pattern
It has no relation to the local topography or geology. Despite topographic changes, the river in the discordant drainage pattern stays on its original course.
The discordant drainage pattern is further divided into Antecedent and the Superimposed drainage pattern.
Antecedent Drainage (Discordant Drainage)
It is also known as inconsequential drainage. When a piece of a river slope and its surroundings are raised, the river maintains its previous slope while cutting through the uplifted area, creating deep gorges known as vertical erosion or vertical downcutting.
Rivers like the Indus, Sutlej, Brahmaputra, and other Himalayan rivers are examples of antecedent rivers or drainage.
Superimposed Drainage Pattern(Discordant Drainage)
The harder basal rocks appear unrelated to the tougher rock bed when a river flowing over a softer rock stratum reaches them while following the initial slope. The term “superimposed drainage” refers to this sort of drainage.
The hardness and softness of the rock and the patterns of faults or fractures frequently have a significant impact on the drainage patterns (dendritic, trellis, etc.).
However, on occasion, the land swiftly rises with the stream’s initial level. Increasing the stream’s gradient increases the erosive force of the stream.
Some excellent examples of superimposed drainage may be seen in the rivers flowing at the Rewa Plateau, including the Damodar, Subarnarekha, Chambal, Banas, and others.
Concordant Drainage Pattern
It is related to the local topology and geology. The slope of the river and the topography have a significant role in determining the course of the river in a concordant drainage pattern.
These drainage systems are the most prevalent and can be divided into two groups: Consequent drainage rivers and Subsequent drainage rivers.
Consequent Drainage Rivers (Concordant Drainage)
When the river flows generally in the direction of the slope, there is a consequent drainage system.
Peninsular Indian rivers including the Godavari, Krishna, and Cauvery pour into the Bay of Bengal after descending from the Western Ghats. They are the examples of the consequent Drainage pattern.
Subsequent River System (Concordant Drainage)
Streams that are formed after the original stream (which is consequent rivers) are considered as the Subsequent River System.
Once the primary drainage pattern has been formed, it is a subsidiary stream that erodes along an underlying band of non-resistant rock.
For instance, the Yamuna and the Ganga are met at right angles by the drainage rivers Chambal, Sind, Ken, Betwa, Tons, and Son.
Different Drainage Pattern Types
Dendritic Drainage Pattern
The most typical type is called a dendritic drainage pattern. It resembles tree roots’ branching pattern.
A dendritic pattern forms where the river channel follows the terrain’s slope.
The pattern appears where there is no distinctive structure in the rock under the stream and where erosion is equally easy in all directions.
E.g. The Indus, Ganga, and Brahmaputra rivers that flow through the northern plains.
Parallel Drainage Pattern
It grows in areas with elongated, parallel landforms and a sharp slope to the surface.
In general, tributary streams follow the slope of the surface by spreading out in a parallel-like pattern.
Like the Godavari, Kaveri, Krishna, and Tungabhadra rivers, which have their source in the Western Ghats.
Radial Drainage Pattern
The radial drainage pattern, which forms around a central high point, is typical of conically shaped objects like volcanoes.
The drainage pattern is referred to as “radial” when the rivers originate on a hill and flow in all directions.
For instance, the Narmada and Son rivers, flow from the Amarkantak range.
The pattern of Centripetal Drainage
It is the exact opposite of the radial as here streams move in the direction of a central depression.
These streams nourish ephemeral lakes throughout the rainier seasons of the year, but they vanish during the drier seasons.
When salt dissolved in lakewater precipitates out of the solution and is left behind when the water evaporates, salt flats can also occasionally be formed in these dry lake beds.
For instance, Manipur’s Loktak Lake.
Trellis Drainage Pattern
Hard and soft rocks are parallel to one another in folded topography, where trellis drainage arises.
Synclines, which are downturned folds, create valleys where the main channel of the stream is located.
When secondary tributaries join principal tributaries of main rivers at right angles, a pattern similar to this is created.
For instance, the Indus, Ganga, and Brahmaputra rivers in the high Himalayan region.
Rectangular Drainage Pattern
In areas that have experienced faulting, the rectangular drainage pattern is present. It grows on rocky ground that is tightly connected.
Streams cluster in areas where exposed rock is weakest because they take the path of least resistance. The tributary streams enter the mainstream at acute angles and create steep bends. E.g. streams in Chambal, ken, and betwa.
Barbed Drainage Pattern
It is a drainage pattern in which the confluence of a tributary with the main river is indicated by a discordant junction, as if the tributary meant to flow upward rather than downstream.
This pattern develops when the main river is captured and changes its flow direction, while the tributaries continue to point in the previous flow direction.
An intriguing example of a barbed drainage system is the Arun River in Nepal, a tributary of the Kosi.
Annular Drainage Pattern
The radial streams develop further tributaries. These tributaries attempt to follow a circular drainage pattern around the top when the upland has an outer soft layer. In India, this drainage pattern is not particularly typical.
For instance, South Dakota’s Black Hill streams
Deranged Drainage Pattern
The rivers and lakes do not follow a logical pattern.
These patterns are developed when the previous drainage system is disturbed.
For instance, the glaciated valleys of the Karakoram.
Angular Drainage Pattern
These patterns are created where the bedrock joints and faults connect at sharper angles.
This pattern is typical in the foothills of the Himalayas.
Article written by Chetna Yadav.
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