Splash detachment and transport of loess aggregate fragments by raindrop action

Splash erosion, which results from the bombardment of raindrops on soil, is the initial stage of soil erosion by water and is mainly responsible for the detachment and transport of soil aggregates. The objective of this study was to estimate the difference between the breakdown and dispersion of soil aggregates for two typical soils (Lou soil and Drab soil) of the Loess Plateau by raindrop action and to determine the relation between raindrop size and splash distance as well as soil aggregate detachment and transport in the loess area. Simulated tests were performed using a custom-made device to generate raindrops of six different sizes (2.67 mm, 3.05 mm, 3.39 mm, 3.79 mm, 4.05 mm and 5.45 mm) and to measure splash erosion at five distance intervals (0-10 cm, 10-20 cm, 20-30 cm, 30-40 cm and 40-50 cm). The results indicated that the splash erosion was distributed at a splash distance of 0-20 cm for the Lou soil and the Drab soil. Under the same type of raindrop, the splash volume of the Drab soil was higher than that of the Lou soil. For the Lou and Drab soils, the relation between the amount of splash and raindrop size increased linearly (r(2) = 0.985 and 0.860, respectively, p < 0.01), and a highly significant exponential relationship was found between splash distance and raindrop size (r(2) >= 0.967, p < 0.01). The amount of splash detachment increased with increasing raindrop size for the two soil types. The maximum splash erosion occurred when the raindrop diameter was 5.45 mm. Macro-aggregates > 0.25 mm broke apart to form micro-aggregates of < 0.25 mm. Models were developed to predict the amount of splash erosion (M) for a given raindrop size (D) and splash distance (S) as follows: M = 0.741D(4.846)S- 1.820, r(2) = 0.916, p < 0.01 and M = 2.104D4.450S- 2.135, r(2) = 0.904, p < 0.01. Thus, large amounts of micro-aggregate dispersion and breakdown result in soil surface sealing and soil pore clogging.