What Is Soil Erosion - Burning Issues

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Soil erosion is the displacement of the upper layer of soil; it is a form of soil degradation.
This natural process is caused by the dynamic activity of erosive agents, that is, water, ice (glaciers), snow, air (wind), plants, animals, and humans. In accordance with these agents, erosion is sometimes divided into water erosion, glacial erosion, snow erosion, wind (aeolean) erosion, zoogenic erosion and anthropogenic erosion.
Human activities have increased by 10–50 times the rate at which erosion is occurring globally. Excessive (or accelerated) erosion causes both “on-site” and “off-site” problems.
On-site impacts include decreases in agricultural productivity and (on natural landscapes) ecological collapse, both because of loss of the nutrient-rich upper soil layers.
In splash erosion, the impact of a falling raindrop creates a small crater in the soil, ejecting soil particles.
The distance these soil particles travel can be as much as 0.6 m (two feet) vertically and 1.5 m (five feet) horizontally on level ground.

If the soil is saturated, or if the rainfall rate is greater than the rate at which water can infiltrate into the soil, surface runoff occurs. If the runoff has sufficient flow energy, it will transport loosened soil particles (sediment) down the slope.
Sheet erosion is the transport of loosened soil particles by overland flow.

Rill erosion refers to the development of small, ephemeral concentrated flow paths which function as both sediment source and sediment delivery systems for erosion on hillslopes.
Generally, where water erosion rates on disturbed upland areas are greatest, rills are active. Flow depths in rills are typically of the order of a few centimeters (about an inch) or less and along-channel slopes may be quite steep.
Gully erosion occurs when runoff water accumulates and rapidly flows in narrow channels during or immediately after heavy rains or melting snow, removing soil to a considerable depth

Bank erosion is the wearing away of the banks of a stream or river. This is distinguished from changes on the bed of the watercourse, which is referred to as scour.
Erosion and changes in the form of river banks may be measured by inserting metal rods into the bank and marking the position of the bank surface along the rods at different times

Thermal erosion is the result of melting and weakening permafrost due to moving water.
It can occur both along rivers and at the coast. Rapid river channel migration observed in the Lena River of Siberia is due to thermal erosion, as these portions of the banks are composed of permafrost-cemented non-cohesive materials
Wind erosion is a major geomorphological force, especially in arid and semi-arid regions.

It is also a major source of land degradation, evaporation, desertification, harmful airborne dust, and crop damage—especially after being increased far above natural rates by human activities such as deforestation, urbanization, and agriculture
Mass movement is an important part of the erosional process, and is often the first stage in the breakdown and transport of weathered materials in mountainous areas.
It moves material from higher elevations to lower elevations where other eroding agents such as streams and glaciers can then pick up the material and move it to even lower elevations. Mass-movement processes are always occurring continuously on all slopes; some mass-movement processes act very slowly; others occur very suddenly, often with disastrous results.

Factors affecting soil erosion

Climate
Soil structure and composition
Vegetative cover
Topography

Activities that increase soil erosion

Unsustainable agricultural practices increase rates of erosion by one to two orders of magnitude over the natural rate and far exceed replacement by soil production.
The tillage of agricultural lands, which breaks up soil into finer particles, is one of the primary factors. The problem has been exacerbated in modern times, due to mechanized agricultural equipment that allows for deep plowing, which severely increases the amount of soil that is available for transport by water erosion.
In an undisturbed forest, the mineral soil is protected by a layer of leaf litter and an humus that cover the forest floor. These two layers form a protective mat over the soil that absorbs the impact of rain drops.
They are porous and highly permeable to rainfall, and allow rainwater to slow percolate into the soil below, instead of flowing over the surface as runoff.
The roots of the trees and plants hold together soil particles, preventing them from being washed away
Urbanization has major effects on erosion processes—first by denuding the land of vegetative cover, altering drainage patterns, and compacting the soil during construction; and next by covering the land in an impermeable layer of asphalt or concrete that increases the amount of surface runoff and increases surface wind speeds.
Much of the sediment carried in runoff from urban areas (especially roads) is highly contaminated with fuel, oil, and other chemicals.
The warmer atmospheric temperatures observed over the past decades are expected to lead to a more vigorous hydrological cycle, including more extreme rainfall events.
The rise in sea levels that has occurred as a result of climate change has also greatly increased coastal erosion rates.

Methods of controlling Soil Erosion

Biological methods: It includes the use of plant of vegetation cover.
(i) Agronomic practices: It includes natural protection by growing vegetation in a manner that reduces soil loss. These are:
(a) Contour farming: In which preparation of fields with alternate furrows and ridges to reduce water flow. Ridges at the same level are known as contour. On slopes, however, this type of farming is coupled with terracing.
(b) Mulching: It is effective against wind as well as waster erosion. Some such plants as maize stalks, cotton stalks etc.., are used as a ‘mulch’ (a protective layer formed by the stubble). Mulches reduce soil moisture evaporation and increase amount of soil moisture by addition of organic matter to soil.
(c) Crop rotation: It decreases soil loss and preserves the productivity of land.
(d) Strip cropping: It involves the planting of crop in rows or strips to check flow of water
(ii) Agrostological methods: Grasses such as Cynodon dactylon are utilized as erosion-resisting stabilizer plants. They are grown in strips between the crops. Such methods include:
(a) Hay farming: This aims to grow grasses in rotation with the fields crops, which helps in building up the structure of soil, preventing soil erosion and improving its fertility
(b) Retiring lands to grass: It involves to grow grasses on such lands where major proportion of the top soil has been eroded. Generally grasses are allowed to grazing under suitable climate conditions.
2. Mechanical methods: These methods are used as supplements to biological methods. These are:
(i) Basin listing: i.e. to construct small basin along the slope to intercept and divert the runoff water.
(ii) Contour terracing: To construct a channel along the slope to intercept and divert the runoff water. This may be:
(a) Channel terrace: To dig channels at suitable intervals and the excavated soil deposited as a wide, low, ridge along, the lower edge of the channel.
(b) Broad based ridge terrace: i.e. to construct ridge along both the sides of the channel:
(c) Bench terrace: To construct a number of platforms along contours or suitable graded lines across the slope.
(i) Stream bank protection: To grow vegetation alongside the river bank, to construct drains, concrete or stone Pitching etc. for checking & cutting and carving ‘of riverbanks.
(ii) Afforestation: Trees as windbreaks are planted at 90° to the prevailing wind in deserts which check the velocity of wind. They check the spread of sand dunes or desert conditions or blowing away of the fertile top soil. Windbreaks may be planted in several rows.

Soil conservation methods

Afforestation.
Contour ploughing (cultivation against the direction of the wind).
Strip cultivation (cultivation in strips).
Flood control by government initiatives.
Reclamation of bad lands.
Wind breaks in land; like trees at borders.
Organic farming.
Control/restrict shifting cultivation.
Construction of proper drainage.
Leveling of gullies, ravines etc.
Control of chemical fertilizers and pesticides in the market.
Proper awareness about the need of conservation.

Qn 1: Among the statements given below, identify the correct statement(s):

Organic farming has a role to play in soil conservation.
Sheet erosion results in the formation of gullies resulting in loss of underground soil.
The largest area affected by soil erosion in India is the State of Rajasthan followed Madhya Pradesh.

Choices:

1 only
2 only
1 and 3 only
1, 2 and 3

Q.)Soil conservation is the process where

soil is aerated
soil is protected against loss
sterile soil is converted to fertile soil
soil erosion is allowed

Q.)Making of Steps on the slopes is known as ?

Strip cropping
Terrace
Shelter Belts
None of these

Q.)Consider the following statements regarding the types of soil erosion:
I . Soil erosion by water occurs by means of raindrops, waves or ice.
II.   Soil erosion by water is termed differently according to the intensity and nature of erosion.
III.   Soil erosion by wind is more common in areas where the natural vegetation has been destroyed.
Which of the following statement(s) is/are correct?
a.   Only I
b.   I and II
c.   II and III
d.   All of the above