| The splash and sheet erosion characteristics for three soils were investigated comparatively, which not only provide important theoretical basis for the establishment of soil erosion prediction model, but also provide important guidance for the prevention of soil erosion. However, the comparative study of splash and sheet erosion characteristics for different main eroded soils is still relatively weak. Therefore, three typical eroded soils(Cambisol, Mollisol, Ultisol) were chosen from the Loess Plateau, the Northeast China and the southern hilly region, respectively. The splash erosion and sheet erosion characteristics were analyzed comparatively by adopting uniform experimental technologies. The contribution of splash erosion to sheet erosion were quantified. The flow hydraulic characteristics and dynamic mechanisms of sheet erosion were explored. Additionally, splash erosion and sheet erosion prediction models in China were established and validated. The main results were as follows:(1) The splash erosion characteristics of three main eroded soils were comparatively analyzed. The directional(upslope, lateral, downslope), net(downslope-upslope) and total(upslope+downslope+left+right) splash erosion significantly increased with an increase in rainfall intensity and raindrop kinetic energy. As rainfall intensity increased from 50 to 100 mm h–1, total splash erosion of Cambisol, Mollisol and Ultisol significantly increased by 0.2~14.2, 1.9~10.9 and 1.1~11.3, respectively. Additionally, upslope, downslope and lateral slope splash erosion occupied 14.1%~14.7%, 32.8%~33.3% and 26.0%~26.3% of total splash erosion for three soils, respectively. Furthermore, the order of the directional, net and total splash erosion at different raindrop kinetic energy at the same rainfall intensity was: Mollisol > Ultisol > Cambisol. Moreover, there were significant differences in directional, net and total splash erosion under different antecedent soil moisture regime before and after runoff occurrence for three soils at the same raindrop kinetic energy. Before runoff occurrence, splash erosion in dry run was significantly greater than that in wet run. After runoff occurred, there were three trends for the effects of antecedent soil moisture regime on splash erosion:(i) Antecedent soil moisture had no significant influence on splash erosion.(ii) Splash erosion in dry run was significantly greater than that in wet run.(iii) Splash erosion in wet run was significantly greater than that for dry run.(2) The sheet erosion characteristics of three main eroded soils were clarified. Sheet erosion significantly increased with the increasing rainfall intensity, raindrop kinetic energy and antecedent soil moisture. As rainfall intensity increased from 50 to 100 mm h–1, sheet erosion of Cambisol, Mollisol and Ultisol significantly increased by 8.3~19.3, 15.0~68.8 and 5.1~36.9, respectively. With antecedent soil moisture increased, sheet erosion of Mollisol and Ultisol significantly increased by 1.4~9.0 and 1.2~15.8, respectively. Furthermore, in dry run, sheet erosion of Ultisol was significantly greater than that of Mollisol. While in wet run, sheet erosion of three soils were mainly affected by both of rainfall intensity and raindrop kinetic energy. At 50 mm h–1 rainfall intensity or at 100 mm h–1 rainfall intensity with raindrop kinetic energy lower than 8.52 J m–2 mm–1, the order of sheet erosion for three soils was: Ultisol > Cambisol > Mollisol; at 100 mm h–1 rainfall intensity, when raindrop kinetic energy was greater than 8.52 J m–2 mm–1, the order of sheet erosion for three soils was: Cambisol > Ultisol > Mollisol.(3) The contribution of splash erosion to sheet erosion was quantified, which were affected by both of rainfall physical properties and antecedent soil moisture. For Cambisol, the ratios of upslope, downslope, lateral slope, net and total splash erosion to sheet erosion were 0.2, 0.4, 0.3, 0.2 and 1.2, respectively. For Mollisol, the ratios of upslope, downslope, lateral slope, net and total splash erosion to sheet erosion were 1.1, 2.4, 1.9, 1.3 and 7.3, respectively. For Ultisol, the ratios of upslope, downslope, lateral slope, net and total splash erosion to sheet erosion were 0.4, 0.9, 0.9, 0.5 å'Œ 3.1, respectively. In addition, in dry run, the ratios of total splash erosion to sheet erosion of Mollisol was significantly greater than those of Ultisol. While in wet run, at rainfall intensity of 50 mm h–1, the ratios of total splash erosion to sheet erosion for three soils were in the order: Mollisol > Ultisol > Cambisol. At 100 mm h–1 rainfall intensity, when raindrop kinetic energy was lower than 12.85 J m–2 mm–1, the ratios of total splash erosion to sheet erosion for three soils were in the order: Mollisol > Ultisol > Cambisol; when the raindrop kinetic energy was greater than 12.85 J m–2 mm–1, there were no significant differences in the ratios of total splash erosion to sheet erosion for three soils.(4) The overland flow hydraulic characteristics and dynamic mechanisms of sheet erosion were explored. For three soils, as rainfall intensity, raindrop kinetic energy and antecedent soil moisture increased, flow velocity and Reynolds number significantly increased; there was no differences in Froude number; while Darcy-Weisbach resistance coefficient significantly decreased. The critical shear stress, critical stream power and critical unit stream power of three soils in the order of Mollisol, Ultisol and Cambisol. Furthermore, sheet erosion of three main eroded soils were sensitive to flow velocity and shear stress.(5) The splash and sheet erosion prediction models were established. The Nash-Sutcliffe simulation efficiency of the splash and sheet erosion prediction model established in this study were 0.82 and 0.85, respectively. This indicated that the models had better prediction accuracy. |
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