Erodivity of rainfall and runoff

• Rainfall erosivity is the kinetic energy of raindrop’s impact and the rate of associated runoff (Wischmeier and Smith,1978).
• The R-factor is a multi-annual average index that
• The detaching force for a given rainfall is the product of kinetic energy and duration.
• measures rainfall’s kinetic energy and intensity to describe the effect of rainfall on sheet and rill erosion.

Factor affecting erodivity of rainfall

a) Intensity

b) Duration: infiltration decreases

c) Velocity: soil particle detached due to impact of K.E., determined by gravity, air resistance and wind.

d) Drop size

Mechanism for the detachment of soil particle by run off water

a) Rolling or dragging action- horizontal force of flowing water detaches soil particle from the soil mass by rolling or dragging them out of the position.

b) Lifting- turbulence flow on depressions causes vertical currents which detaches soil particle by lifting action.

c) Abrasion- abrasion occurs when particle in transit strike or drag over particle on surface