Rainfall erosivity is the driving force of erosion, and it has a direct relationship with soil erosion (Angulo-Martinez and Begueria, 2009).
Rainfall erosivity is usually calculated by summing all of a year's erosive events, quantified by an EI30 index. In this study, the annual rainfall erosivity was calculated using the method of Zhang et al. (2002), a method that has been widely used in China (Cheng et al., 2009; Men et al., 2008).
The annual rainfall erosivity, based on aggradations of half-month rainfall erosivity, was estimated using daily rainfall data as follows: