Fluvial erosional landforms are those created by the motion and energy of rivers and streams. Both fluvial erosion and fluvial depositional landforms are produces by the fluvial process, which results in two distinct landforms. Among the many types of landforms created by fluvial erosion are gorges, canyons, waterfalls, rapids, and rivers.
- Hydration: the force of running water wearing down rocks.
- Corrosion: chemical action that leads to weathering.
- Attrition: river load particles striking, colliding against each other and breaking down in the process.
- Corrasion or abrasion: solid river load striking against rocks and wearing them down.
- Downcutting (vertical erosion): the erosion of the base of a stream (downcutting leads to valley deepening).
- Lateral erosion: the erosion of the walls of a stream (leads to valley widening).
- Headward erosion: erosion at the origin of a stream channel, which causes the origin to move back away from the direction of the stream flow, and so causes the stream channel to lengthen.
Characteristics of Fluvial Erosional Landforms
- Fluvial erosive action has a variety of effects.
- The chemical action that leads to weathering is called corrosion.
- When a large river load strikes rocks, they corrode or become abraded.
- The erosion of a stream’s bed, known as “vertical erosion” or “downcutting” (which leads to valley deepening), refers to the process.
- Lateral erosion is the term for the deterioration of a stream’s side walls (which leads to valley widening).
The landforms created by a stream can be studied under erosional and depositional categories.
1. River Valleys:
- A river valley is the extended depression on the ground through which a stream flows throughout its course.
- At different stages of the erosional cycle the valley acquires different profiles.
- At a young stage, the valley is deep, narrow with steep wall-like sides and a convex slope.
- The erosional action here is characterises by predominantly vertical downcutting nature.
- The profile of valley here is typically ‘V’ shaped.
- As the cycle attains maturity, the lateral erosion becomes prominent and the valley floor flattens out.
- The valley profile now becomes typically ‘U’ shaped with a broad base and a concave slope.
- A waterfall is simply the fall of an enormous volume of water from a great height, because of a variety of factors such as variation in the relative resistance of rocks, relative difference in topographic reliefs, fall in the sea level and related rejuvenation, earth movements etc.
For example, Jog or Gersoppa falls on Sharavati (a tributary of Cauveri) has a fall of 260 metres.
3. Pot Holes:
- The kettle-like small depressions in the rocky beds of the river valleys are called pot holes which are usually cylindrical in shape.
- Pot holes are generally forms in coarse-grained rocks such as sandstones and granites.
- Potholing is the mechanism where grinding tools caught in water eddies drill and grind rock beds like a machine.
- They thus form small holes which are gradually enlarges by the repetition of the said mechanism.
- The potholes go on increasing in both diameter and depth.
- Terraces are called stepped benches along the river course in a floodplain.
- Terraces represent the level of former valley floors and remnants of former (older) flood plains.
- An incised water-worn channel, which is particularly common in semi-arid areas, is known as a gulley.
- It is forms when water from overland-flows down a slope, especially following heavy rainfall, is concentrates into rills, which merge and enlarge into a gulley.
- The ravines of Chambal Valley in Central India and the Chos of Hoshiarpur in Punjab are examples of gulleys.
- A pronounced curve or loop in the course of a river channel is known as a meander.
- The cliff-slope side of a meander loop characterizes intensive erosion and vertical cliffs.
- This side has a concave slope.
- The slip-off side, which is known for its gentle convex slope, characterizes the deposition on the inner side of the loop.
- Morphologically, the meanders may be wavy, horse-shoe type or ox-bow/ bracelet type.
7. Ox-Bow Lake:
- Sometimes, intensive erosion action accentuates the outer curve of a meander to such an extent that the inner ends of the loop come close enough to disconnect from the main channel and exist as independent water bodies.
- These water bodies are converts into swamps in due course of time.
- In the Indo-Gangetic plains, southwards shifting of Ganga has left many ox-bow lakes to the north of the present course of the Ganga.
8. Peneplane (Or peneplain):
- This refers to an undulating featureless plain punctuated with low- lying residual hills of resistant rocks.
- According to W.M. Davis, it is the end product of an erosional cycle.
Fluvial Erosion and Landforms Thus Formed,Fluvial Erosion and Landforms Thus Formed,Fluvial Erosion and Landforms Thus Formed
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