Wind erosion

 It is the detachment and transportation of soil particles by the forces generated by wind. Occurs on all types of soil but fine single grain particles are most susceptible. Wind erosion, in India, is commonly observed in arid and semi-arid areas where the precipitation is inadequate, e.g. Rajasthan and some parts of Gujarat, Punjab, and Haryana. About 13.5 Mha area representing 4.1% of TGA of the country is affected by wind erosion.

Mechanisms of Wind Erosion

Wind erosion means detachment and transportation of soil particles by the forces generated by wind. The intensity of wind erosion varies with surface roughness, slope, and types of cover on the soil surface and wind velocity, duration, and angle of incidence. It can occur on all types of soil but fine single grain particles are most susceptible. The wind erosion process can be divided into three simple but distinct phases,

1. Initiation of Movement/Detachment: The lifting and abrasive action of the wind results in the detachment of tiny soil grains from the aggregates or clods of which these are a part. The initiation of the movement of soil particles is caused by several forces acting separately in combination. Three forces are involved in the detachment of soil particles which are lift, drag, and ballistic impact. In the course of the collision of grains rolling and bumping on the surface, some particles may be bounced up. It occurs when the wind force or the impact of moving particles is strong enough to dislodge stationary soil particles.

2. Transportation/Soil movement: The transportation of the particles once they are dislodged take place in three ways:

i) Saltation – In saltation soil particles of medium size (0.1-0.5 mm diameter) are carried by wind in a series of short bounces. These bounces are caused by the direct pressure of the wind on soil particles. This process may account for 50-75% of the total movement of soil.

ii) Soil Creep – saltation also encourages soil creep (rolling or sliding) along the surface of the particles (0.5-1.0 mm diameter). The bouncing particles carried by saltation strike the large aggregates and speed up their movement along the surface. It accounts for about 5 to 25% of the soil erosion through the wind.

iii) Suspension – When the particles of soil are very small (less than 0.1 mm) they are carried over long distances. It accounts for about 40% of the total soil movement.

3. Deposition: Deposition of the particles occurs when the gravitational force is greater than the forces holding the particles in the air. The deposition could occur when the wind velocity is decreased due to surface obstructions or other natural causes.

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