Erosion
Erosion is the process by which the surface of the Earth is worn away mainly by the action of wind, water and glacier.
• Soil is most valuable natural resource, we cannot synthesize artificially
• Medium of plants mean it provide support, water or nutrients to plant for survival
• Habitat of many organisms like microbe
• Soil fulfilled vital need of human by producing the food (protein, lipids, carbohydrates), clotting, furniture, medicine etc.
Present status
Soil is worldwide rock 75 billion ton fertile soil loss due to erosion
In Pakistan 20% land is affected by erosion.
Causes of soil Degradation
• Extensive farming
• Deforestation
• Overgrazing
• Excessive use of pesticides and fertilizers
Why we need to conserve soil?
Its valuable and formation of 1 cm of soil takes about 8-10,000 years.
Soil erosion
It is the process of detachment of soil particles from parent body or surface of soil and transportation of detached soil particles by wind and water.
Mechanism
Two mechanism of soil erosion
1) Detachment _ detaching of particle from its span material, detaching agents is raindrop, wind and channel flow.
2) Transportation_ movements of soil particles like (throwing water, wind)
Types of soil erosion
1) Water Erosion
2) Wind Erosion
Types of water Erosion
The movements of water along soil
i. Sheet Erosion
ii. Rill Erosion
iii. Gully Erosion
iv. Ravine Erosion
v. Landslide Erosion
Sheet Erosion
It is uniform deletion of top soil in thin layer from field. In which when rainfall occurs, dropped gender topsoil and long runoff the muddy water moves away from the field.
Rill Erosion
When continuous rainfall there is no longer uniform removal of water and channelization begins.
Gully Erosion
It is most remarkable form of erosion and deep cuts are formed on the ground. Mainly gullies are formed due to high velocity of water for a longer period of time.
Ravine Erosion
It is formed doe to prolonged process of gully erosion; when water flowing continuously for a longer period of time with high velocity then gullies ultimately converted into revine.
Landslide Erosion
Sliding down of large chunk of soil due to step slopes is called landslide.
It is mainly occur in mountain area or hilly areas where the large chunk of soil gets sliding down due to step slopes and because of it leads to the sever soil erosion .
Factor influencing soil erosion
➢ Rainfall
It affects both mechanism of erosion Detachment and transportation. Under rainfall three factors duration, amount and intensity are correlated. If the intensity is low but duration is long then water flows continuously soil become susceptible to erosion secondly the amount of rainfall means types of precipitation (sleet, hail, rain, snow) these are categorized based on drop size or diameter drop. The drop size id directly proportion to soil lose. If intensity of rainfall is very high it will affect detachment mechanism of soil that leads to soil erosion.
➢ Vegetation
In land where there is no vegetation when rainfall occur the rain drop will directly come contact with soil surface because of this there will be more detachment and runoff and in other case land is covered with crop when the rainfall occur the raindrops will not directly come into contact with soil surface then firstly contact with vegetation that help to reduce the impact raindrop because vegetation had root system which are tightly bind with soil particles in this way it control the soil erosion. The density of vegetation or plant height is inversely proportion to erosion.
➢ Soil
In sandy or delight soil particles are not tightly attached with other so detachment is easy but transportation is difficult due to large particles or heavy weight of particles and it has more porosity so there is high infiltration rate and less runoff. In clay or heavy soil the particles are tightly attached with other so detachment is difficult but transportation is easy due to its low weight and clay soil has less porosity so is low infiltration rate and more runoff so silt soil has less erode ability then other two.
➢ Man and Animal
Man is responsible for the soil erosion by extractive forming or construction while animals destroy vegetation by excessive grazing.
Losses due to erosion
▪ Loss of rain water
▪ Loss of fertile soil
▪ Losses of nutrients
▪ Silting of reservoir
Wind erosion
Definition
It is process of detachment or transportation and deposition of soil material by wind. Wind picks up the light particles, lift them from the surface and transport them to long distance.
Types of wind erosion
➢ Saltation
➢ surface creep
➢ suspension
Saltation
Soil particles jump up vertically into air and rise to height of 30- 60 cm and fall through the air soil particles has 0.1- 0.5 mm diameter and the weight 50-70 % of soil is eroded by saltation.
Surface creep
The coarse sand particles which has diameter 0.5- 0.3mm, they get rolled over the surface because of large particles or high weight that rolls over the surface instead of jumping and 5-25% soil gets erosion.
Suspension
In this fine dust particles float in the air due to its low weight or small sized soil particles. The diameter is less than 0.1 mm and only 3-4% soil gets erosion.
Factor affecting wind erosion
➢ Wind velocity
Wind erosion is directly proportional to soil erosion
➢ Soil
If soil structure is well formed or sufficient moisture is present then there will be less erosion
➢ Vegetation
It is inversely proportional to erosion.
Wind erosion measurements
• Vegetative measure
It is used to reduce the velocity of wind and in which heighted plants are planted in field across the direction of wind then these plants reduce the speed of wind and decrease the erosion.
• Tillage
It decease the erodibility of soil because in which soil structure improved and the water holding capacity is increase.
• Mechanical measure
In which use the fences that helps to reduce the wind velocity and control the movement of soil particles.
Written by : sumayya latif
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