Soil Erosion – Water and Wind Erosion
Geography › Rocks, Erosion and Landforms · Topic 5.4
Soil erosion is the removal of the topsoil by water, wind, ice or human activity faster than it forms. Water erosion proceeds from splash, sheet and rill erosion to gullies and ravines, and wind erosion occurs by deflation and abrasion in dry, bare lands. It lowers fertility and crop yields, silts up reservoirs and causes land degradation, and is checked by terracing, contour ploughing and tree cover.
6 min read · UPSC Prelims · Geography · Rocks, Erosion and Landforms
At a Glance
- Water erosion stages Splash, sheet, rill, gully
- Wind erosion Deflation, abrasion, saltation
- Ravines Chambal, Yamuna, Mahi valleys
- Soil loss in India About 5.3 billion tonnes a year
- Conservation Terraces, contour ploughing, shelterbelts, check dams
- Exam link UPSC Prelims, Geography: Rocks, Erosion and Landforms
Where Does It Fit?
This is the fourth topic of the category on rocks, erosion and landforms. The previous topics covered the three families of rocks, and this one begins the study of surface processes with the loss of soil. The next topic covers fluvial landforms and drainage patterns. Previous topic: Metamorphic Rocks and the Rock Cycle. Next topic: Fluvial Landforms and Drainage Patterns.
What Is Soil Erosion?
In short: soil erosion is the loss of fertile topsoil faster than nature can replace it.
Soil forms very slowly, at roughly a centimetre in several hundred years, but it can be removed in a single season. Erosion is the detachment, transport and deposition of soil particles by running water, wind, ice and gravity. A natural slow rate of erosion is normal and is balanced by soil formation. Accelerated erosion, mostly the result of human activity such as the clearing of forests, overgrazing, shifting cultivation, ploughing up and down slopes, mining and construction, removes soil much faster than it forms. It is a form of land degradation, which also includes loss of vegetation, salinity and waterlogging. The soils themselves are described in Soil Types and Soil Profile.
How Does Water Erosion Work?
| Stage | Description |
|---|---|
| Splash erosion | Raindrops hit bare soil, break up clods and splash particles |
| Sheet erosion | A thin, uniform layer of topsoil is washed off by surface runoff; hard to notice, and removes the most fertile layer |
| Rill erosion | Small channels, a few centimetres deep, cut by flowing water |
| Gully erosion | Rills enlarge into deep, steep-sided channels that cannot be crossed by ploughing; cutting into the land |
| Ravines | Badlands formed by extensive gullying; common in the Chambal, Yamuna and Mahi valleys |
| Stream bank erosion | River undercuts and collapses its banks |
The Chambal ravines of Madhya Pradesh, Rajasthan and Uttar Pradesh are the best-known example in India. Gullied land is nearly useless for agriculture, and it expands headward. Water erosion is the largest cause of land degradation in India. Floods and silt also come from the same processes, as in Fluvial Landforms and Drainage Patterns.
How Does Wind Erosion Work?
Wind erosion is important in arid and semi-arid regions with sparse vegetation and dry, loose soil, such as the Thar desert of Rajasthan, and in dry cultivated lands. Wind removes particles by three modes of transport. Fine dust is carried in suspension, sand grains hop along the ground in a series of jumps called saltation, and larger grains roll or slide along the surface, called surface creep. The wind causes two processes: deflation, which is the lifting and removal of loose particles that lowers the surface and may create hollows called blowouts, and abrasion, in which sand-laden wind sandblasts rock surfaces. The landforms are in Aeolian Landforms of Deserts. The Dust Bowl of the 1930s in the Great Plains of the United States, when drought and poor farming practices stripped the topsoil and carried it away in huge storms, is the classic example of wind erosion.
How Serious Is Soil Erosion and Land Degradation in India?
Studies estimate that India loses about 5.3 billion tonnes of soil each year, an average of about 16 tonnes per hectare, of which a large part is carried to the sea, some is deposited in reservoirs and the rest is moved elsewhere. According to the Desertification and Land Degradation Atlas of the Indian Space Research Organisation, about 97.85 million hectares, around 30 per cent of the country’s area, was under land degradation in 2018-19, and water erosion was the biggest cause, followed by loss of vegetation and wind erosion. India has committed to restoring 26 million hectares of degraded land by 2030, a pledge announced at the UN Convention to Combat Desertification conference held in New Delhi in 2019. Erosion causes loss of fertility, lower crop yields, siltation of reservoirs and canals, floods, and the loss of nutrients and organic matter.
How Can Soil Erosion Be Controlled?
| Method | How it works |
|---|---|
| Contour ploughing and bunding | Ploughing along contours, not up and down slopes, slows runoff |
| Terrace farming | Steps cut in slopes reduce slope length and speed of water |
| Strip cropping and mulching | Alternate strips of crops and cover; residue keeps soil protected |
| Afforestation and cover crops | Roots bind the soil and canopy reduces the impact of raindrops |
| Check dams and gully plugging | Stop gully growth and trap silt |
| Shelterbelts and windbreaks | Rows of trees reduce wind speed in dry areas; used in the Thar |
| Watershed management | Treating the whole catchment with the people; supported by schemes such as the watershed component of the Pradhan Mantri Krishi Sinchayee Yojana |
As an analytical point, conservation works best when it is linked with the livelihoods of farmers, since measures that do not raise incomes are rarely maintained; this is why watershed programmes combine soil work with water, fodder and income activities.
Why Is This Topic Important?
- Land degradation Frequent theme in GS 1 and 3
- Ravines Chambal
- Conservation Methods and schemes
What Came Next?
The next topic describes fluvial landforms and drainage patterns. Next topic: Fluvial Landforms and Drainage Patterns.
Key People and Terms
- Sheet erosion Uniform removal of topsoil
- Gully erosion Deep channel cutting
- Deflation Wind lifting of loose particles
- Saltation Hopping transport of sand
- Ravine Badland of deep gullies
- Shelterbelt Rows of trees to check wind
Exam Corner
Points to Remember
- Sheet erosion is hard to notice but removes fertile soil.
- Chambal is famous for ravines.
- India loses about 5.3 billion tonnes of soil a year.
- Wind erosion works by deflation and abrasion.
- Target of 26 million hectares restoration by 2030.
Do Not Confuse With
- Weathering and erosion In place versus with transport
- Deflation and abrasion Lifting loose particles versus sandblasting
- Rill and gully Small versus large channel
Memory Hook
Splash, sheet, rill, gully, ravine: water cuts deeper each time.
Mains Angle
Questions ask for causes and conservation. These points add depth.
- Causes Deforestation and overgrazing
- Effects Fertility loss and siltation
- Methods Terraces, cover and watershed work
A Question You May Face
An original practice question, not a past paper question.
“Discuss the causes and consequences of soil erosion in India and suggest conservation measures.”
How to Answer
- Types Water and wind erosion.
- Causes Human and natural.
- Effects Fertility and siltation.
- Measures Terraces, cover, watersheds.
GS Relevance
Frequently Asked Questions
What is soil erosion?
Soil erosion is the removal of topsoil by water, wind, ice or human activity at a rate faster than the soil forms. It reduces fertility, lowers crop yields, silts up rivers and reservoirs, and is a major form of land degradation.
What are the stages of water erosion?
Water erosion begins with splash erosion by raindrops, then sheet erosion, which removes a thin layer of topsoil, then rill erosion in small channels, and gully erosion in deep channels. Extensive gullying produces ravines or badlands, as in the Chambal valley.
How does wind erosion occur?
Wind erosion occurs in dry, bare lands where loose soil is lifted and carried. Fine dust moves in suspension, sand hops in saltation and larger grains creep along the surface. Deflation removes material and abrasion sandblasts rocks and soil.
What are ravines?
Ravines are badlands formed by extensive gully erosion, a network of deep, steep-sided channels cut into soft alluvium. They are common in the Chambal, Yamuna and Mahi valleys of India and are mostly unfit for farming, though they can be reclaimed with tree planting.
How can soil erosion be controlled?
Soil erosion can be controlled by contour ploughing, terracing, strip cropping, mulching, afforestation, check dams for gullies, shelterbelts in dry areas and watershed management. These measures slow runoff and wind, hold the soil with roots and cover, and trap eroded material.
PYQ Practice — Statement Analysis
1 Sheet erosion removes a thin uniform layer of topsoil.
It is the first stage of widespread water erosion.
2 Ravines are formed by wind erosion in deserts.
They are formed by gully erosion by water.
3 Deflation is the removal of loose particles by wind.
It lowers the surface.
4 Contour ploughing means ploughing up and down the slope.
It is ploughing across the slope along contours.
Related Topics
Browse the full Geography index