Modeling rain erosivity using disdrometric techniques

The erosive effect produced by direct raindrop impact on the soil surface may be quantified in terms of the raindrop kinetic energy (KE). This variable is usually calculated from the rainfall rate even though a precise description of the raindrop size distribution is required. In this study, raindrop size and fall velocities were measured for 2 yr in Barcelona, Spain, with an optical disdrometer. Fitted drop-size distributions were used to obtain relationships between raindrop ICE and rainfall rate. A comparison between KE calculated from experimental distributions indicated that the lognormal distribution model was most suitable to provide a ICE-rainfall rate relation. Predicted KE values from this relationship had better agreement with observations (differences of 7%) than predicted values from other models based on different rainfall conditions.