A drainage pattern can be well briefed concerning the topological features from where a stream gets runoff through its flow and the groundwater flow. These flows can be well divided by the watersheds (topological barriers). A watershed is the combined stream tributaries that flow to someplace along the channel of the stream.
There are various types of drainage patterns across the World, but in this article, we will focus more on the Trellis Drainage pattern and its various details.
Trellis Drainage Pattern
Also known as the Trellis drainage system or the Trellis River pattern is the one that we can mostly find across the Southern regions of a map. Experts define the Trellis Drainage pattern as the indication of structural control by varying types of eroded and folded sedimentary rocks. Across a humid region, resistant rocks like sandstone from the ridges and the non-resistant ones like shale and limestone form the valleys. Sometimes, there is the occurrence of a dip angle, causing the asymmetric ridges.
A Trellis pattern of the river has the same geometry as the standard garden trellis; along a strike valley, smaller tributaries are fed into from the steeper slopes across the mountain's sides. These tributaries then enter into the main river perpendicularly, leading to a trellis-like appearance of the system. Trellis drainage definition states that they form where the hard and soft formations exist on both sides of any river. The formations must also be reflective of height and accentuated by erosion. Trellis drainage pattern is the folded mountains' characteristic, like that of the Appalachian Mountains in Northern America and Northern Trinidad.
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Example of Trellis Drainage Pattern
The streams near the Southeast of Piney Mountain and Little Allegheny Mountain are known to form a trellis stream pattern. Here, the resistant bedrock ridges get drained by the shorter stream, and the non-resistant units form valleys with the SUBSEQUENT streams. As is expected from a general Trellis drainage pattern definition, the stream locations before exposure of this surface imprints upon the current Pattern. This imprint is then evident in how the streams cut through the ridges.
Formation and Flow in a Trellis Drainage Pattern Diagram and Actuality
By the time the erosion wears away the surface and exposes the folded sedimentary rocks below, the streams stay there. They further continue eroding down, and there they encounter the resistant beds; the streams continue eroding them too. This leads to the formation of newer slopes and streams on the slopes, and these then become the tributaries for the mainstream in the area. The principal streams are SUPERIMPOSED on the current landscape. These landforms where the streams cut through ridges are called the WATER GAPS, and they form with the running water and Fluvial Processes.
Streams then continue flowing from higher elevation to lower, down the slope. The stream extends its headwaters and forms tributaries near the source; this process is called Headward Erosion.
Difference Between Trellis and Rectangular Drainage Pattern
Rectangular Drainage Pattern:
It is the drainage pattern where the main streams and their tributaries display numerous right-angle bends and exhibit sections of approximately the same length. It indicates the streams that follow prominent faults or the joint systems that break the rocks into rectangular blocks. Various forms of weathering on the joint systems or faults in any bedrock localize the streamflow, leading to the production of a Rectangular pattern.
These drainage patterns are developed mainly on the firmly joined rocky terrains.
Trellis Drainage System:
This type of drainage system occurs when the sub-parallel streams erode a valley across the less resistant formations and sides. These beds are mainly visualized as steeply dipping and might also be a part of a folding system. These tributaries also intersect at right angles where the water gap cuts through some more complex formations.
A river joined by the tributaries at approximately right angles develops a Trellis drainage pattern. It is mainly found where the hard and soft rocks exist parallel to one another.
Difference Between Dendritic and Trellis Drainage Pattern
The dendritic drainage pattern develops at the regions where the river channels follow the terrain's slope. Here the mainstream and its tributaries resemble the branches of a tree. In contrast, a Trellis river pattern is formed when a river and its tributaries join at approximately 90-degrees and are found where hard and soft rocks exist parallel to each other.