Question.
Explain the landforms formed by river erosion. (UPPSC 2016)
Answer.
The landforms formed by rivers or running water are called fluvial landforms. The geomorphic agents of running water are active in areas with a humid climate where there is heavy rainfall.
- In India, fluvial landforms are found in all regions except deserts and some highlands in the Himalayas.
- Running water has two major components. First, the water flowing over the normal land surface flows in the form of a sheet. Second, flowing water flows linearly in the form of a stream or river.
The river forms two types of landforms during the entire erosion cycle (young, mature, and old stage)-
- Erosional fluvial topography
- Deposition fluvial topography
Most of the erosive landforms are formed by young river channels on steep slopes.
The following are the landforms formed by river erosion:
- Valleys
- Potholes and Plunge pools
- Meandering river
- Oxbow Lake
- River Terrace
- Waterfall
- Peneplains
Valleys:
The formation of valleys starts with narrow small channels called rills. Over time, the narrow small rills gradually turn into long wide gullies, and later these gullies deepen and widen to form a valley.
There are several types of valleys on the basis of shape and size:
- V-shaped valley
- Gorge
- Canyon
- U shaped valley
The gorge is a deep valley with very steep slopes while the canyon is characterized by steep step-like sides.
Potholes and Plunge Pools:
The river makes circular depressions on the rocky bed called potholes. As a series of potholes joins and deepen, this new form of landform is called a plunge pool. The plunge pool is also formed by the waterfall (at the base of the waterfall).
Meandering River :
Due to the lateral erosion of river channels on gentle sloping landscapes, they develop a sinuous course known as the incised meanders.
Oxbow Lakes:
If a part of the channel of the meandering river has cut off from the main river stream, they formed oxbow lakes.
River Terraces:
River terraces mark the level surface of the floodplain. It is formed by vertical erosion. It refers to the number of levels of the river bed.
Waterfall:
In the young stage of the river, a waterfall is usually formed where there is a presence of soft rock on top of hard rocks.
Peneplain:
Peneplains are featureless plains that form at the end of the river's erosion cycle.
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