Soil Erosion
Soil erosion is the displacement of the upper layer of soil, one form of soil degradation.
This natural process is caused by the dynamic activity of erosive agents, that is, water, ice, snow, air, plants, animals, and humans.
Soil erosion is a natural process where the natural top soil cover gets removed.
It becomes a problem when human activity causes it to occur much faster than under natural conditions.
Soil erosion also results in water loss as water percolation gets reduced, induces frequent flood and drought, and soil nutrient is also lost.
Causes of Soil Erosion
Wind and water are the main physical agents of soil erosion.
The amount of soil they can carry away is influenced by two related factors:
1. Speed – The faster it moves, the more soil it can erode. On farmed slopes, steps like terracing and contour farming are helpful in cutting the speed of water flow down the slope.
2. Plant Cover – Plants protect the soil and in their absence wind and water can do much more damage. Therefore conserving soil is all about maintaining adequate vegetation cover.
Natural Factors causing soil erosion
Heavy rains on weak soil: Rain drops loosen soil particles which gets transported downhill by water.
Steep slopes: Water flows faster; soil creeps, slips or slumps down falls.
Rainfall: Erosion increases with unexpected rapidity with severe rainstorms.
Drought: Water dries up and dry soil is blown off more easily by the winds. A sudden rain causes enormous damage and especially more when vegetation cover is depleted due to drought.
Changing winds: Areas previously sheltered, become exposed.
Human-Induced factors causing Soil Erosion
1. Deforestation
2. Intensive Farming – Excessive fertilizer and irrigation damage the land.
3. Housing Development – Soil is bared; massive earthworks are done to landscape the area and all these leaves soil unprotected.
4. Road Construction – when roads are cut, massive earthworks leave scars behind. Not enough attention is paid to rainwater flow and maintenance of road sides.Types of Soil Erosion
1. Sheet Erosion – When there is uniform removal of a thin layer of soil usually by run off, from a large surface area, it is called sheet erosion.
2. Rill Erosion – When there is rainfall and rapidly running water produces finger - shaped grooves or rills over the area it is called rill erosion.
3. Gully Erosion – When the rainfall is very heavy, deeper cavities or gullies are formed which may be U or V shaped
4. Slip Erosion – The soil layer slips due to heavy rainfall on slopes of hills and mountains.
5. Stream Bank Erosion – During the rainy season, the fast running streams take a turn in some other direction cutting the soil and making caves in the banks.
6. Wind Induced Soil Erosion
Saltation – Due to the stormy wind the soil particles of 1-1.5 mm diameter move up in a vertical direction.
Suspension – The fine Soil Particles less than 1 mm diameter which are suspended in the air carried in that manner to distant places.
Surface creep – Here larger particles (5-10 mm diameter) creep over the soil surface along with wind
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