Variability of particle size distributions of upward/downward splashed materials in different rainfall intensities and slopes

- Raindrop Impact Induced Erosion was studied on upward and downward splash cup at plot scale.
- The particle size distribution of splash load was investigated on upward and downward directions.
- The particle size distributions of splash erosion were significantly different from those of the origin soil.
- The splashed particles were larger and well sorted comprehended to origin soil.

The particle size distribution (PSD) of the splashed sediment is expected to vary depending on rainfall intensity, slope steepness and slope position. This study therefore discusses the results of analysis of laboratorial experiments to compare PSDs of splashed materials in upward and downward directions of splash cup with original soil PSDs before runoff initiation from different parts of an erosion plot under different rainfall intensities at various slope gradients. To achieve the objectives, a set of laboratorial experiments were conducted using rainfall simulator at erosion plots scale. The rainfall intensities of 30, 60, and 90 mm h− 1 were applied at 5, 15 and 25% plot slopes for a soil collected from Kojour rangeland watershed in the Alborz Mountains, northern Iran. Besides very oft-reported results of more splashed material in downward direction and positive effects of rainfall intensities (P > 0.05) on rate of splashed materials, it was found that there were significant differences between clay, silt and sand contents of original soil and upward and downward splashed materials on slopes of 5 and 15% in all study rainfall intensities. In general, comparison of D10, D50 and D90 of splashed materials in upward and downward splash cups were larger than those of original soil. Furthermore, the sorting of splashed materials in upward and downward of splash cups with respective amounts of 4.84-6.62 μm and 5.13-6.54 μm under different rainfall intensities and slopes were less than that of the original soil (8.12 μm).