• Erosive potential of rain
• R = ΣEI
  • E is the Energy in the Rainfall
  • I is the maximum half-hour rainfall intensity for the storm.
• EI values represent ‘Rainfall Erosion Index’.
• R varies with the climate at a particular location.

E = 916 + 331 log₁₀ I,

where E is kinetic energy in foot-tons per acre-inch and I is intensity in inches per hour