Wind Erosion

Wind Erosion

Wind erosion is a serious problem of dry land regions.

It is mainly encountered in areas where

(a) Soils are loose and dry;

(b) The soil surface is smooth and bare;

(c) High-velocity winds are frequent.

About 40% of the total area of Pakistan is affected by wind erosion.

Types of soil movement

п‚Ñž There are three distinct types of soil movement,

п‚Ñž Which depend upon the size of the soil particles.

Soil can move in any of these ways.

Suspension

Is the movement of very fine particles which are less than 0.1 mm in diameter.

п‚Ñž The soil particles are so small that once they are lifted into the air stream, they remain suspended in the air for a long time by the turbulence and eddy currents of the air arid are carried for a long way.

Creep

Is the movement of soil particles at the other extreme of the size range, greater than 0.5 mm.

п‚Ñž These particles are not lifted in the wind stream but are rolled along the surface of the ground, pushed by the force of the wind and other particles carried by the wind.

Saltation

Is the most important of all the three types of movement. Particles of 0.05вЂ"0.5 mm diameter move mainly by saltation.

п‚Ñž The particles are lifted the wind stream and again fall down, moving by short leaps and bounces.

The Mechanism of Wind Erosion

The Mechanism of Wind Erosion Involves Three Processes:

1. Detachment, of the soil particles

2. Transportation, of the soil particles

3. Deposition of the soil particles.

1. Detachment.

The capacity of the wind to detach sediments depends on the wind velocity, the amount and nature of the sediments, physiographic conditions, and the physical properties of the soil.

п‚Ñž High-velocity winds with abrasive materials have more ability to detach soil particles.

п‚Ñž Particles protruding upward into wind currents and having less cohesive/adhesive sediments can be detached easily.

п‚Ñž Soils having high quantities of organic matter and cementing agents are less prone to detachment.

2. Transportation.

The ability of wind to transport sediment is mainly related to wind velocity.

п‚Ñž Wind blowing at a greater speed for a longer period of time can transport soil mass over a greater distance; fine sediments are transported farther than coarse materials.

3. Deposition.

The distance windborne soil particles travel depends on the velocity of the wind and the size and weight of the sediments.

п‚Ñž Particles moving by creep and saltation are deposited at a short distance whereas those suspended in the airstreams are deposited at a greater distance.

п‚Ñž Coarse particles are deposited on the windward side and fine particles on the leeward side of a barrier

Control of Wind Erosion:

Soil erosion by wind mainly depends upon wind velocity and surface conditions.

The following principles have been suggested as the basis for wind erosion control

i. Improvement in the physical conditions of the soil, making it more resistant to erosion.

ii. Reduction