Rainfall represents the major driver of soil detachment in erosion processes. The potential of rainfall to detach soil has been defined as rainfall erosivity. The relationship between rainfall intensity and rainfall drop size distribution (DSD) controls various rainfall characteristics including the rainfall erosivity (Abd Elbasit et al., 2010). The relationship between rainfall intensity and rainfall erosivity differs due to geographical location under natural rainfall (Hudson 1965; Wischmeier and Smith, 1978; Zanchi and Torri, 1980; Van Dijk et al., 2002) and due to type and configuration of rainfall simulators under simulated rainfall (Hall, 1970; Olayemi and Yadav, 1983; Auerswald et al., 1992; Salles and Poesen, 2000). The role of rainfall microstructure on the determination of rainfall erosivity has attracted several researchers in the past. However, our understanding on this subject is still limited due to the lack of equipments that are able to measure the rainfall drop parameters and ultimately the rainfall kinetic energy. Several indices have been suggested to quantify the rainfall erosivity (Abd Elbasit et al., 2010). Generally, the suitable erosivity index must include the drop mass and velocity as major variables for raindrop power determination. The erosivity index has been described by Epema and Riezebos, 1983 as follows: