A Review on Rainfall Erosivity (R factor) in Universal Soil Loss Equation

Land degradation caused by soil erosion by water can endanger the environment around the world. The estimation of soil erosion rates is mainly dependent on modeling rainfall erosivity, land use changes and influences of management on soil erosion rates. The model of soil erosion prediction often used by researchers around the world is Universal Soil Loss Equation (USLE). Rainfall amount and intensity are the most important variable for rainfall erosivity and written as the R factor in the USLE model. Among the factors in the USLE, rainfall erosivity is of high importance as precipitation is the main driver for soil erosion by water and has a direct impact on the detachment of soil particles, the breakdown of aggregates and the transport of eroded particles via runoff. USLE erosivity combines the energy of the rainfall and the maximum continuous 30-min intensity in the rainfall event. Energy of rainfall is estimated as a function of the storm intensity through the rainfall event.