Rain properties controlling soil splash detachment

Laboratory experiments have been conducted to study the effects of various rain properties on sand detachment resulting from raindrop impact. Splash c ups were exposed to simulated rainfall intensities ranging between 10 and 1 40 mm h(-1). The detached sand was collected and weighed whereas rain inten sity, equivalent drop diameter and fall velocity of raindrops were measured with an optical spectro-pluviometer (OSP). The properties of the simulated rain (i.e, median volume diameter and kinetic energy) were compared with t hose observed in natural conditions. Statistical analyses have been underta ken in order to evaluate which rain variable best predicts the mass of sand detached. Linear and non-linear correlations between the mass of detached sediment and the product of drop size (d) by drop velocity (v), i.e. (DVbet a)-V-alpha, with values of alpha varying between 1 and 6 and beta between 0 and 3, have been computed. The results indicate that the coefficient of de termination (R-2) for alpha ranging between 3 and 5 and beta lower or equal to 2 are satisfying. Although kinetic energy ((DV2)-V-3) described splash detachment relatively well, the product of momentum by drop diameter (D-4 V ) was slightly superior in describing splash detachment. Therefore, the mom entum multiplied by the drop diameter is recommended as the best rain Varia ble to describe splash detachment. Copyright (C) 2000 John Wiley & Sons, Lt d.