Soil Erosion: Types and Causes of Soil Erosion!
The loss of nutrient rich top soil or disturbances to the soil structure by some natural processes or anthropogenic activities is known as soil erosion. According to Odum (1966) soil erosion is a part of the soil pollution.
According to Rama Rao (1962), the soil erosion is creeping death of the soil. When the rate of removal of soil exceeds the rate of soil formation, the soil erosion occurs.
The soil erosions are of two types:
(i) Natural or geological or background soil erosion
(ii) Accelerated soil erosion
The nature soil erosion takes place by normal or natural conditions without any interference of man. But the accelerated soil erosion is due to active interference of man and animals in disturbing the equilibrium in between the rate of soil formation and rate of soil loss.
The magnitude of soil erosion is governed by the factors like corrosively of the eroding agent, erodible of the soil, scope, steepness and length, land use practices and conservation strategies employed. These factors are summarised in the universal soil loss equation as follows.
Where E is annual soil loss, R is rainfall corrosively index, K is soil edibility index : L is slope length, S is slope steepness; C is cropping factor and P is conservation practices.
The process of soil erosions caused by the following agents:
(a) Water erosion:
Water is powerful agent causing soil erosion either in the form of rain drops or in the form of surface flow. When the soil is lost like a thin covering from a large surface area, the process is known as sheet erosion. When the sheet erosion takes place with full momentum, leading to cutting of soil surface as thin channels, it is known as rill erosion. Several rills from the steep slope converge forming wider channel known as gully erosion.
(b) Wind erosion:
In dry (arid) regions, the soil is mainly sandy and the vegetation is grossly inadequate. In such places, wind causes loss of soil.
(c) Land slide or slip erosion:
When the rocks at cliffs face heavy rains, their weights undergo sharp rise due to gravitational forces. Such rocks with high weights slip over lower rocks causing land slide and there by slip erosion.
(d) Stream bank erosion:
During flood, the rivers splash their water against banks and cut through them taking away soil from the bank.
(e) Deforestation and overgrazing:
Loss of natural vegetation due to deforestation and overgrazing leads to dry and dust soil which can be taken away easily by wind and water.
(f) Mining erosion:
A lot of soil is also eroded due to mining and industrial activities.
Since soil is very precious for the existence of living organisms, it is the need of the hour to prevent the loss of soil by adopting suitable mechanisms.
The process of soil loss can be checked by the following means:
(i) Protection of soil from the severity of rain drops through afforestation.
(ii) Preventing water from concentrating and passing through the slopes.
(iii) Slowing down the momentum of water flow adopting various scientific techniques.
(vi) Growing vegetation covers to minimise wind velocity.
(v) Growing soil binders like grasses to prevent direct contact in between soil and eroding agents.
The contribution of different global agent towards total global soil degradation (erosion) are as follows:
(1) Overgrazing accounts for 34.5% of the degraded area
(2) Deforestation accounts for 29.5%
(3) Agricultural activities accounts for 28.1 %
(4) Over exploitation of soil accounts for 7.0%
(5) Bio-industrial activities accounts for 1.2%