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.
|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.
|Types of Drainage Patterns
Types of drainage patterns
Dendritic drainage patterns
Dendritic drainage patterns, which are by far the most common, also known as pinnate drainage, perhaps the most common on Earth, resembles a tree's intricate branching structure. The defining characteristic is the branching pattern of streams. Streams begin as small headwaters in high areas, gradually joining to form larger tributaries, and ultimately draining into a single main river or body of water.
Unlike parallel drainage, dendritic patterns don't exhibit strictly parallel streams. Tributaries typically join the main branch at various angles, creating a more intricate and organic network.
This pattern is most common in areas with relatively uniform geology, where there are no major faults, folds, or variations in rock hardness to dictate the flow direction, 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.
The formation of dendritic drainage patterns is largely controlled by the interplay of:
Gravity: Water flows downhill, seeking the lowest path towards an outlet. This downward pull drives the initial formation of small headwater streams.
Erosion: As water flows, it erodes the land, carving out channels and valleys. This process gradually expands the stream network, with tributaries joining the main channel as they encounter it.
Topography: Slopes and depressions guide the direction of flow, influencing the angles at which tributaries meet the main stream and contributing to the overall branching pattern.
Common Examples: Dendritic patterns are found across the globe, from the Amazon rainforest to the mountainous regions of Nepal. The Nile River in Africa and the Mississippi River in North America are classic examples.
Trellis drainage pattern
A trellis drainage pattern is characterized by nearly parallel main tributaries that are joined by short, perpendicular subsequent streams. These tributaries join the main streams at nearly right angles, creating a distinctive grid-like pattern.
Trellis drainage patterns typically develop in areas where there are alternating bands of resistant and non-resistant rocks. The resistant rocks, such as sandstone or quartzite, form ridges that run parallel to the folds in the rock strata. The non-resistant rocks, such as shale or limestone, erode more easily and form valleys between the ridges. The main tributaries of the trellis drainage pattern flow along the valleys, and the subsequent streams flow down the sides of the ridges.
Key features of trellis drainage patterns:
- Nearly parallel main tributaries: These tributaries flow along the strike of the rock layers, which is the direction in which the layers are oriented.
- Perpendicular subsequent streams: These streams flow down the dip of the rock layers, which is the angle at which the layers are tilted.
- Right-angle junctions: The subsequent streams typically join the main tributaries at right angles.
- Grid-like pattern: The overall pattern of the drainage system resembles a grid.
Trellis drainage patterns can have a number of implications for the environment. For example, they can:
Increase the risk of flooding: The straight, channelized nature of trellis streams can cause them to overflow their banks more easily during heavy rains.
Make it difficult to develop land: The ridges and valleys associated with trellis drainage patterns can create barriers to transportation and development.
Improve water quality: The filtering action of the soil along the sides of the ridges can help to improve the quality of the water in the main tributaries.
Provide habitat for a variety of plants and animals: The varied terrain associated with trellis drainage patterns can provide habitat for a wide range of plant and animal species.
Some examples of rivers with trellis drainage patterns include the Indus River in Pakistan, the Brahmaputra River in India, and the Rhine River in Europe.
Rectangular drainage pattern
The rectangular drainage pattern is characterized by rivers and streams flowing in a series of right-angled bends, creating a network that resembles a grid of rectangles. Unlike the familiar dendritic (tree-like) or trellis (grid-like) patterns, the rectangular pattern stands out for its sharp turns and geometric regularity.
The formation of this pattern is closely linked to the underlying rock structure, specifically areas with:
Joint Systems: When underlying rocks possess sets of well-defined cracks or joints, intersecting at right angles, these joints guide the development of straight stream segments and sharp bends, often at 90° angles.
Fault Lines: In areas with major fault lines, streams may preferentially follow the linear paths of the faults, resulting in straight segments and right-angled intersections at fault junctions.
Example: Great Basin in the United States: Certain areas within the Great Basin exhibit rectangular drainage patterns due to the influence of fault lines and underlying rock formations.
Parallel drainage pattern
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.
The parallel drainage pattern is characterized by rivers and streams flowing in roughly parallel lines over a sloping surface. Imagine a group of friends marching in step; that's a good analogy for how these streams seem to move together. Unlike the dendritic (tree-like) or trellis (grid-like) patterns, parallel drainage stands out for its consistent direction and spacing of streams.
Parallel drainage pattern typically occurs in regions with pronounced slopes, often exceeding 5 degrees. The constant downward gradient drives the parallel flow of water, preventing significant meandering or branching.
Parallel drainage is often found in areas with uniform rock resistance, meaning the rock erodes at a similar rate throughout the landscape. This prevents the formation of distinct channels or valleys that might disrupt the parallel flow.
Radial drainage pattern
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.
Radial drainage exhibits streams originating from a central high point and flowing away in all directions. Imagine water cascading down a cone or a dome, creating diverging streams.
This pattern typically forms in landscapes with a central high point such as:
Volcanoes: Volcanic cones, with their characteristic slopes, often exhibit radial drainage due to rainwater and melted snow flowing down their sides.
Domes: Uplifted geological formations like domes, with their concentric ridges, can also create radial drainage as streams follow the sloping terrain.
Calderas: The sunken depressions within volcanic craters can act as central points for radial drainage, with streams flowing outwards from the crater rim.
Mount Fuji in Japan: A prime example of a volcano showcasing a spectacular radial drainage pattern.
Centripetal drainage pattern
A centripetal drainage pattern, also known as an endorheic drainage system, exhibits a distinct hydrological characteristic: riverine and fluvial networks converge towards a central depression instead of radiating outwards to join larger bodies of water like oceans or lakes. This pattern resembles the spokes of a wheel converging at the hub, representing the inward direction of surface water flow.
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.
Internal Drainage: Unlike exoreic drainage patterns that flow to external water bodies, centripetal systems have closed basins with no outlet to the sea. All water from rivers and streams ends up in the central depression.
Central Depression: This depression can be various forms, such as a sinkhole, a closed valley, or an endorheic lake like the Dead Sea or the Caspian Sea. In some cases, the depression may be dry for most of the year, forming a salt flat due to water evaporation.
Deranged drainage pattern
A deranged drainage pattern, also known as disorganized drainage or chaotic drainage, is a hydrological feature characterized by the absence of a well-defined, organized network of rivers and streams. The configuration of streams in deranged drainage is heavily influenced by local topography. Factors like hills, valleys, and depressions dictate the flow paths, resulting in a patchy and unpredictable network.
It happens in areas where there has been much geological disruption. Develop from the disruption of a pre-existing drainage pattern.
Angular drainage pattern
An angular drainage pattern is a distinctive arrangement of rivers and streams characterized by straight stretches connected by sharp, often right-angled bends. Imagine cracks in a tiled floor forming a network of waterways; that's a simplified visualization of this pattern. Compared to the dendritic (tree-like) or trellis (grid-like) patterns, angular drainage stands out for its angular intersections and rectilinear segments.
The formation of angular drainage is closely linked to the underlying rock structure of the landscape. Specifically, this pattern occurs in areas with:
Joint systems: When underlying rocks possess sets of well-defined cracks or joints, intersecting at sharp angles, these joints guide the development of straight stream segments and sharp bends.
Fault lines: In areas with major fault lines, streams may preferentially follow the linear paths of the faults, resulting in straight segments and angular intersections at fault junctions.
Barbed Drainage Pattern
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.
The formation of a barbed drainage pattern is typically attributed to river capture events. In this process, a smaller, more energetic stream erodes the headwaters of another, less active stream, effectively stealing its headwaters and diverting its flow. This captured segment of the original stream retains its previous flow direction, creating the discordant junction with the capturing river.
The Arun River in Nepal: A tributary of the Kosi River, the Arun exhibits a classic barbed pattern where its valley abruptly turns upstream before joining the Kosi.
Annular Drainage Pattern
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.
The formation of an annular drainage pattern is tightly linked to the underlying rock structure of the landscape. This pattern typically occurs in areas with:
Domes or Basins: When sedimentary strata are exposed in a dome-shaped structure, with layers of varying hardness, erosion preferentially occurs in the weaker layers, creating concentric depressions and ridges. Streams follow these contours, resulting in an annular pattern.
Astroblemes or Mud Diapirs: These geological features, remnants of meteorite impacts or salt intrusions, respectively, can create circular depressions surrounded by upfaulted layers. Streams flowing around these depressions exhibit an annular pattern.
Red Valley, South Dakota: This striking example encircles the Black Hills dome, showcasing the interplay between resistant granite and softer sedimentary rocks.
Herringbone drainage pattern
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.
V-Shaped Tributaries: Streams branching off the main stem do so at similar angles, typically between 30° and 60°, creating a series of sharp, V-shaped junctions. This angularity is a defining characteristic of this pattern.
The formation of herringbone drainage is often linked to the underlying rock structure of the landscape. Specifically, this pattern can occur in areas with:
Alternating layers of hard and soft rock: When harder and softer rock layers are stacked horizontally, erosion preferentially occurs in the softer layers, carving out V-shaped valleys. Streams flowing through these valleys exhibit a herringbone pattern.
Fault lines: In areas with major fault lines, streams may preferentially follow the linear paths of the faults, resulting in parallel alignments and V-shaped junctions at fault intersections.
Flysch Sequence Formation