Raindrop Size Distribution and Soil Erosion

Soil erosion is caused, at least in part, by the effect of kinetic energy on the soil during rainfall. Therefore, a better knowledge of rain parameters is useful. To assess the influence of rain on the amount of soil loss, an experimental site was set up in the Chianti hills (central Italy). Tipping-bucket rain gauges and the Joss-Waldvogel disdrometers were used. A colocated system of gauges provided soil loss and runoff measurements for rainfall events that occurred between September 2006 and June 2007. The reliability of a widely used rainfall erosion index was also assessed and the effect of kinetic energy, computed by the measured drop size distribution, evaluated. The results highlighted the potential of the physical approach in computing the kinetic energy developed by the rain drops to the soil, especially for higher rainrates and when the hydrological balance is positive or slightly negative. The kinetic energy estimate from the rain rate well reproduces the measured values only below 10 J center dot m(-2), whereas an underestimation is present for higher rainrates, because of the contribution of large drops.