Understanding Wind Erosion Soil Movement
The rate of soil movement by wind is a complex process influenced by several factors. Empirical models are often used to describe these relationships.
Governing Relationship for Soil Movement
The rate of soil movement (S) is primarily determined by the excess wind energy available to dislodge and transport particles. This energy is related to the difference between the actual wind speed (v) and the minimum wind speed required to initiate movement, known as the threshold wind speed (vm).
- The excess wind speed is represented as (v – vm).
- The transport rate is generally found to be proportional to the cube of this excess wind speed, i.e., S ∝ (v – vm)3.
- The average soil particle size (d) also affects the ease of transport. Smaller particles require less energy to move, but larger particles might be moved by saltation initiated by finer particles. Simplified models often include a term related to particle size. A common inclusion is d1/2, reflecting factors like the energy needed for saltation initiation or impact dynamics.
Combining these dependencies, the interrelationship is expressed as:
$S \propto (v – v_m)^3 d^{1/2}$
Important Questions from Wind Erosion
- A $16 \text{ m}$ high wind break is constructed to protect soil from wind erosion due to wind velocity of $18$ $\text{m s}^{-1}$ at $15 \text{ m}$ height. The minimum wind velocity at $15 \text{ m}$ height capable of moving the soil fraction is $8 \text{ m s}^{-1}$. The angle of deviation of prevailing wind direction from the perpendicular to the wind break is $30^\circ$. The distance of full protection from the wind break in $\text{m}$ is
In wind erosion, the maximum portion of soil is transported by the process of ____________.
A windbreak, 15 m in height and 200 m in length, is established to protect the land from wind erosion in an arid area. The minimum wind velocity at the height of 15 m above the ground required to move the most erodible soil fraction is $9.6\ m\cdot s^{-1}$. If 5-year return period wind velocity at 15 m height is $16\ m\cdot s^{-1}$ and the wind direction deviates $20^\circ$ from the line perpendicular to the windbreak, the area protected by the windbreak in ha is ________________.
[round off to 2 decimal places]- To protect a wheat field from wind erosion, windbreaks of $2.7$ m height are provided. The actual wind velocity at $15$ m height perpendicular to the wind barrier is $9$ m.s$^{-1}$ and the minimum wind velocity at $15$ m height required to move the most erodible soil fraction is $9.6$ m.s$^{-1}$. The distance of full protection from this windbreak is __________ m. (Rounded off to 2 decimal places)
- In wind erosion, the amount of soil transported varies
