Meander - River System Component

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Meander River System

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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. 

FAQ (Frequently Asked Questions)

1. Which Events Characterise the Formation of a Meander?

Ans. The following events lead to the formation of meanders:

  • In a meandering channel, both erosion and deposition take place simultaneously. The erosion occurs in the concave bank, which is also known as the cut bank, and deposition took place in the convex bank where pointed bars are formed. 

  • When the bends of a meander get deeper, it leaves that bend and flows in the straight path. That abounded bend later became known as the ox-bow lake.

  • The secondary flow is more dominant than the irrotational flow. Irrotational flow is almost absent in a meandering course of the river. 

2. Why Doesn’t a River Flow Straight?

Ans. A river cannot flow straight because when it flows, it either erodes something or deposits. When erosion occurs in a river course, it happens in an uneven manner as the bedrocks and the bank wall is composed of non-homogenous materials. On the other hand, when deposition takes place, it doesn’t occur throughout the course. In the areas where deposition took place, that region becomes shallow, and the river's flow gets obstructed due to the presence of sediment. Due to the reasons mentioned above, a river cannot flow in a straight course. Most of the rivers either flow in a sinuous course or meandering course. Whether a river is sinuous or meandering is determined by the sinuosity index, which is calculated by dividing the river's actual length by the shortest path. The value of the sinuosity index is between 1-1.5, known as a sinuous course, and more than 1.5 is known as a meandering course.