Meander River System
A typical river course can be divided into the upper course, middle course, and lower course. As we all know, the upper course is close to the river’s source, which is mainly in the mountains (for snow-fed rivers). The middle course of a river starts when it enters into the plainland; then, the slope suddenly gets reduced. Here, the river transports the eroded material while continuing with lateral erosion. Some of the typical landforms and features of this part of a river course are meanders, oxbow lakes, flood plains, levees, etc. In this article, we are going to discuss a meander river system and its components.
What Do You Mean by the Meander River System?
Look at the diagram to know how a meandering river system looks like:
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In its middle course, a river generally starts to erode one bank and deposit on the other. Thus, sinuous curves or bends are formed, known as the meanders, and the course itself is known as the meandering course. The term meander has been derived from the Greek word “Maiandros,” the old name of a river in Turkey, Menderes. That river has a winding course. The meandering river system is formed due to the deposition process of the river.
A river generally erodes non-homogenous materials present in the bedrock or the bank's walls unevenly; that is why irregularities are found in the meandering river system. For this reason, the bends or the curves of the meander get deeper day by day, and after a certain point in time, the goose-neck formed in one of the bends gets cut off, leaving behind that bend as a standalone waterbody. The lake thus formed is known as an oxbow lake. The river flows again in a straight path.
How are the Components of a Meander River System Formed?
Stages of a Meander
A meander river system generally forms due to the natural forces acting on a river during its course. In the middle course, the river starts to deposit its load on the basin itself. As a result, the river's flow is obstructed, and it takes a winding course, and the bends get deeper along with the time. The river cuts and erodes its outer bank or concave bank and deposits the material on its inner or convex bank. Therefore, a point bar is formed thereon the inner bank. After the formation of the point bar, the meandering course of the river starts to shift within its valley floor or floodplain. The area within which the meander shifts is known as the meander belt.
Each of the bends of the meandering river system gets deeper, and after a certain point in time, they cut the neck and start to follow in the new path.
In a meander, the secondary flow (the force that exists between centrifugal force, which points outer bend, and the pressure forces pointing to the convex bend) dominates the irrotational flow (where fluid velocity is low in the outer bend and higher in the inner bend).
Components of a Meander
A meander river system has several components like -
1. Meander Wavelength:
The distance between two meanders from one crest to another.
2. Meander Amplitude:
The height of the meander between its own valley and the sinuous axis.
3. Width of Meander:
The area between the two banks.
Components of a Meander
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Whether a river will flow straight or become sinuous or meander is determined by its Sinuosity Index. The sinuosity index is determined by the actual length of the river divided by the shortest path. If the value is less than or equals one, then the river is straight. If the value varies from 1-1.5, the river has a sinuous course. And if the value of the index is more than 1.5, then it is known as the meander river system.
Associated Landforms of a Meandering River System
The associated features or landforms of a meandering river system are as follows:
Associated Features of Meander River System
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1. Meandering Channel:
The first and the most crucial feature of the meander river system is a winding channel having a number of bends and curves.
2. Flood Plain:
A significant landform of river found in the middle and lower course. These are formed by the deposition of alluvium during floods.
3. Pointed Bars:
These bars are formed by the deposition process of the river on the inner bank of the curves or bends.
4. Scroll Bar:
It is formed due to the movement and shifting of meanders.
5. Cut off and Ox-Bow Lake:
When a bend of the meandering course of the river gets deeper, a goose-neck-like structure is formed. After a certain period of time, the river cuts that neck of the horseshoe bend and flows in a straight path leaving behind that bend as a lake. That lake resembles an ox-bow. That’s why this type of lake is known as ox-Bow lakes.
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Did You Know?
The Kanwar Lake of Bihar is the largest freshwater oxbow lake in Asia.
Other features and landforms associated with a meander river system are intervalley depression, sediment, etc.
So, this is all about a meander river system. Meanders are found in almost all rivers of the world, and they look fascinating with their associated features like pointed bars, ox-bow lake, etc.
FAQs on Meander - River System Component
1. What is a river meander in geography?
In geography, a meander is a prominent, winding curve or bend in a river's channel. It develops as the river flows across a relatively flat plain or valley floor. Instead of flowing in a straight line, the water erodes and deposits sediment, creating a snake-like pattern. These landforms are typically associated with the mature stage of a river, where the flow is slower and lateral (sideways) erosion is more dominant than vertical erosion.
2. What are the main features of a river meander?
A river meander has several distinct features formed by the continuous processes of erosion and deposition. The key components are:
Cut Bank: This is the outer bank of the meander bend where the river's flow is fastest and strongest. The high energy causes significant erosion, creating a steep, cliff-like bank.
Point Bar: This is the inner bank of the meander bend where the river's flow is slower. Due to the low energy, the river deposits its load of sediment (like sand and gravel), forming a gently sloping feature known as a point bar.
Meander Neck: This refers to the narrow strip of land that separates two adjacent meander bends. Over time, erosion can cause this neck to become progressively narrower.
3. How is a river meander formed?
A meander is formed through a continuous cycle of erosion and deposition. The process begins with a slight disturbance in the river's path, forcing water to swing to one side. This initiates a centrifugal force that pushes the fastest-flowing water towards the outer bank, causing erosion and forming a cut bank. Simultaneously, the slower-moving water on the inner bank deposits sediment, building a point bar. This dual action exaggerates the curve over time, deepening the bend and creating the characteristic winding shape of a meander.
4. Why do rivers form meanders instead of flowing in a straight line?
Rivers rarely flow in a perfectly straight line due to a combination of factors. The riverbed and banks are made of non-uniform materials with varying resistance to erosion. Even a small obstruction, like a boulder or a patch of resistant rock, can deflect the flow and initiate a slight bend. Once a curve begins, the water develops a corkscrew-like or helical flow. This flow pattern directs the highest energy to the outer bank, enhancing erosion there, and the lowest energy to the inner bank, causing deposition. This feedback loop makes the bend more pronounced, transforming a straight channel into a meandering one.
5. In which stage of a river's life are meanders most common and why?
Meanders are a characteristic feature of the mature stage of a river's life. In this stage, the river flows over gentler slopes compared to its youthful stage. As a result, its energy for vertical (downward) cutting decreases, and it begins to expend more energy on lateral (sideways) erosion. This sideways erosion, combined with the deposition of sediment on the inside of bends, is the primary mechanism for meander formation and is most active when the river crosses wide, flat floodplains.
6. What is the difference between a meander and an oxbow lake?
A meander is an active, flowing bend in a river channel. An oxbow lake, on the other hand, is a landform that is created from a meander. It forms when a meander becomes extremely curved, causing the narrow strip of land between two bends (the meander neck) to be eroded away. The river then takes the shorter, straighter path, abandoning the old meander loop. Sediment deposition eventually seals off the ends of the abandoned loop, leaving behind a crescent-shaped, stationary body of water called an oxbow lake.
7. How does the position of a meander change over time?
The position of a meander is not static; it is a dynamic feature that constantly changes. Through the process of meander migration, the continuous erosion on the cut bank and deposition on the point bar cause the entire meander loop to gradually shift across the floodplain. Over long periods, a meander can migrate downstream, become more exaggerated in shape, or be cut off entirely to form an oxbow lake. This dynamic nature is a key characteristic of rivers in their mature stage and is responsible for shaping wide river valleys and floodplains.
