Drainage pattern a pattern created by stream erosion over time that reveals characteristics of the kind of rocks and geologic structures in a landscape region drained by streams.
Drainage pattern is the pattern formed by the streams, rivers, and lakes in a particular drainage basin. They are governed by the topography of the land, whether a particular region is dominated by hard or soft rocks, and the gradient of the land.
Geomorphologists and hydrologists often view streams as being part of drainage basins. A drainage basin is the topographic region from which a stream receives runoff, throughflow, and groundwater flow. Drainage basins are divided from each other by topographic barriers called a watershed.
A watershed represents all of the stream tributaries that flow to some location along the stream channel. The number, size, and shape of the drainage basins found in an area varies and the larger the topographic map, the more information on the drainage basin is available.
❖ Drainage patterns are formed by the process of stream incision. As streams flow over the land, they erode the bedrock and create valleys. The tributaries to the main stream join at the mouths of the valleys, forming the drainage pattern.
❖ Drainage patterns can be used to map the underlying geology of an area. For example, a dendritic drainage pattern suggests that the underlying bedrock is uniform, while a parallel drainage pattern suggests that the underlying bedrock is folded or faulted.
❖ Drainage patterns can also be used to map the topography of an area. For example, a dendritic drainage pattern suggests that the slopes are gentle, while a parallel drainage pattern suggests that the slopes are steep.
❖ Drainage patterns can be affected by a number of factors, including climate, vegetation, and human activity. For example, climate can affect the rate of stream incision, vegetation can affect the amount of erosion, and human activity can change the course of streams.
➤ Trellis drainage patterns typically develop where sedimentary rocks have been folded or tilted and then eroded to varying degrees depending on their strength. In this type, the short subsequent streams meet the main stream at right angles. Through soft rocks differential erosion paves the way for tributaries. Trellis drainage patterns have a number of implications for the environment. They can increase the risk of flooding, as the streams are more likely to overflow their banks during heavy rains. They can also make it difficult to develop land, as the streams can create barriers to transportation and development.However, trellis drainage patterns can also have some benefits. They can help to improve water quality, as the streams are more likely to filter through the soil before reaching the main stream. They can also provide habitat for a variety of plants and animals, as the streams create a variety of habitats, such as wetlands and riparian forests.
➤ Rectangular patterns develop in areas that have very little topography and a system of bedding planes, fractures, or faults that form a rectangular network. These are found in regions that have undergone faulting. It develops in the area that have very little topography and a system of bedding planes, fractures, or faults that form a rectangular network.
➤ Barbed Drainage Pattern – This pattern is developed where the confluence of a tributary with the main river is characterized by a discordant junction, as if the tributary intends to flow upstream and not downstream. It 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.
➤ Annular Drainage Pattern- When the upland has an outer soft stratum, the radial streams develop subsequent tributaries which try to follow a circular drainage around the summit. It is best displayed by streams draining a maturely dissected structural dome or basin where erosion has exposed rimming sedimentary strata of greatly varying degrees of hardness.
➤ Herringbone drainage pattern is characterized by a series of streams that flow in a series of V-shaped patterns. Herringbone drainage patterns are typically found in areas with areas with a regular pattern of faults or joints.
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| Types of Drainage Patterns |
Geomorphologists and hydrologists often view streams as being part of drainage basins. A drainage basin is the topographic region from which a stream receives runoff, throughflow, and groundwater flow. Drainage basins are divided from each other by topographic barriers called a watershed.
A watershed represents all of the stream tributaries that flow to some location along the stream channel. The number, size, and shape of the drainage basins found in an area varies and the larger the topographic map, the more information on the drainage basin is available.
❖ The pattern of tributaries within a drainage basin depends largely on the type of rock beneath, and on structures within that rock (folds, fractures, faults, etc.).
❖ Drainage patterns are formed by the process of stream incision. As streams flow over the land, they erode the bedrock and create valleys. The tributaries to the main stream join at the mouths of the valleys, forming the drainage pattern.
❖ Drainage patterns can be used to map the underlying geology of an area. For example, a dendritic drainage pattern suggests that the underlying bedrock is uniform, while a parallel drainage pattern suggests that the underlying bedrock is folded or faulted.
❖ Drainage patterns can also be used to map the topography of an area. For example, a dendritic drainage pattern suggests that the slopes are gentle, while a parallel drainage pattern suggests that the slopes are steep.
❖ Drainage patterns can be affected by a number of factors, including climate, vegetation, and human activity. For example, climate can affect the rate of stream incision, vegetation can affect the amount of erosion, and human activity can change the course of streams.
The main types of drainage patterns:
➤ Dendritic patterns, which are by far the most common, also known as pinnate drainage, looks like the branching of a tree, found in regions with homogenous material. develop in areas where the rock (or unconsolidated material) beneath the stream has no particular fabric or structure and can be eroded equally easily in all directions. These develop in areas where the rock such as granite, gneiss, volcanic rock, and sedimentary rock which has not been folded (or unconsolidated material) beneath the stream has no particular fabric or structure and can be eroded equally easily in all directions. Truly dendritic systems form in V-shaped valleys; as a result, the rock types must be impervious and non-porous.
➤ Trellis drainage patterns typically develop where sedimentary rocks have been folded or tilted and then eroded to varying degrees depending on their strength. In this type, the short subsequent streams meet the main stream at right angles. Through soft rocks differential erosion paves the way for tributaries. Trellis drainage patterns have a number of implications for the environment. They can increase the risk of flooding, as the streams are more likely to overflow their banks during heavy rains. They can also make it difficult to develop land, as the streams can create barriers to transportation and development.However, trellis drainage patterns can also have some benefits. They can help to improve water quality, as the streams are more likely to filter through the soil before reaching the main stream. They can also provide habitat for a variety of plants and animals, as the streams create a variety of habitats, such as wetlands and riparian forests.
➤ Rectangular patterns develop in areas that have very little topography and a system of bedding planes, fractures, or faults that form a rectangular network. These are found in regions that have undergone faulting. It develops in the area that have very little topography and a system of bedding planes, fractures, or faults that form a rectangular network.
➤ Parallel drainage system is a pattern of rivers caused by steep slopes with some relief. Because of the steep slopes, the streams are swift and straight, with very few tributaries, and all flow in the same direction. Parallel drainage patterns form where there is a pronounced slope to the surface. A parallel pattern also develops in regions of parallel, elongate landforms like outcropping resistant rock bands.
➤ Radial drainage system, the streams radiate outwards from a central high point. Develops around a central elevated point where the streams radiate outwards from a central high point. Volcanoes usually display excellent radial drainage. Other geological features on which radial drainage commonly develops are domes and laccoliths. On these features the drainage may exhibit a combination of radial patterns. The tributaries from a summit follow the slope downwards and drain down in all directions.
➤ The centripetal drainage system is similar to the radial drainage system, with the only exception that radial drainage flows out versus centripetal drainage flows in.
➤ A deranged drainage system is a drainage system in drainage basins where there is no coherent pattern to the rivers and lakes. It happens in areas where there has been much geological disruption. Develop from the disruption of a pre-existing drainage pattern.
➤ Angular drainage patterns form where bedrock joints and faults intersect at more acute angles than rectangular drainage patterns. Angles are both more and less than 90 degrees.
➤ A deranged drainage system is a drainage system in drainage basins where there is no coherent pattern to the rivers and lakes. It happens in areas where there has been much geological disruption. Develop from the disruption of a pre-existing drainage pattern.
➤ Angular drainage patterns form where bedrock joints and faults intersect at more acute angles than rectangular drainage patterns. Angles are both more and less than 90 degrees.
➤ Barbed Drainage Pattern – This pattern is developed where the confluence of a tributary with the main river is characterized by a discordant junction, as if the tributary intends to flow upstream and not downstream. It 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.
➤ Annular Drainage Pattern- When the upland has an outer soft stratum, the radial streams develop subsequent tributaries which try to follow a circular drainage around the summit. It is best displayed by streams draining a maturely dissected structural dome or basin where erosion has exposed rimming sedimentary strata of greatly varying degrees of hardness.
➤ Herringbone drainage pattern is characterized by a series of streams that flow in a series of V-shaped patterns. Herringbone drainage patterns are typically found in areas with areas with a regular pattern of faults or joints.