This physical difference limits the size of particles wind can move. Erosive force increases exponentially with increases in wind velocity . Consequently, fast winds are capable of causing much more erosion than slow winds. At ground level, the roughness of the surface plays an important role in controlling the nature of wind erosion. Boulders, trees, buildings, shrubs, and even small plants like grass and herbs can increase the frictional roughness of the surface and reduce wind velocity.
Vegetation can also reduce the erosional effects of wind by binding soil particles to roots.
Thus, as a general rule, the areas that show considerable amounts of wind erosion are open locations with little or no plant cover. Velocities Threshold velocity can be defined as velocity required to entrain a particle of a particlular size. In general, the larger the particle, the higher the threshold velocity required to move it. This law can sometimes be broken when clay sized particles are involved in the entraiment process. Clay particles have a general tendency to become cohesively bonded to each other.