Impacts of Rainfall Characteristics and Slope on Splash Detachment and Transport of Loess Soil

To identify the key parameters and develop accurate experimental models of detachment and transport, splash detachment and transport of loess soil were investigated in relation to the rainfall characteristics and slope. The experiment was conducted under 25 combinations of five rainfall intensities (60, 84, 108, 132 and 156 mm h(-1)) and five slope gradients (0 degrees, 5 degrees, 10 degrees, 15 degrees and 20 degrees), using a custom splash pan. Raindrop characteristics (diameter, velocity and kinetics) and splash mass were measured in downslope and upslope. The results indicated that rainfall intensity and slope contributed 94.77% and 0.46%, respectively, to the detachment rate, and 24.39% and 67.82%, respectively, to the transport rate. From a holistic viewpoint, the positive effect of slope became more visible on the detachment rate when the rainfall intensity exceeded 108 mm h(-1), and on the transport rate when the slope exceeded 15 degrees. Based on the rainfall simulator in this study, the rainfall kinetic energy (KE, J), raindrop median particle size (D-50, mm) and raindrop terminal velocity (V, m s(-1)) all increased with increasing rainfall intensity (I) within the 60 similar to 108 mm h(-1) range but decreased with increasing rainfall intensity within the 132 similar to 156 mm h(-1) range. The rainfall intensity and raindrop characteristics (D-50/V/KE) are the key parameters of splash detachment (D-r, g center dot m(-2) min(-1)), and three detachment models were developed: (1) D-r = 0.1153 I-1.09 D-50(0.79) (R-2 = 0.99, NSE = 0.98, p < 0.01); (2) D-r = 0.0162 I-1.11 V-1.22 (R-2 = 0.99, NSE = 0.99, p < 0.01); and (3) D-r = 0.0813 I-1.10 KE0.18 (R-2 = 0.99, NSE = 0.99, p < 0.01). The rainfall intensity and slope are the key parameters for splash transport (T-r, gm(-2) min(-1)), and the developed transport models could be expressed as: (1) T-r = 0.00657 (IS0.116)-S-1.343 (R-2 = 0.914, NSE = 0.874, p < 0.01) (slopes of 0 degrees, 5 degrees and 10 degrees) and (2) T-r = 0.00218 (IS1.033)-S-1.165 (R-2 = 0.986, NSE = 0.986, p < 0.01) (slopes of 15 degrees and 20 degrees). The results of this study could enhance the understanding of soil splash detachment and transport on loess slopes.