Response of particle detachment and hydrological processes on windward slope in laboratory flume experiments at different wind velocities and rainfall intensities

Abstract

Wind-driven rain (WDR) is a natural phenomenon that causes soil erosion, a decline in land productivity, water pollution, and other environmental problems. Owing to the influence of topography on atmospheric circulation, WDR occurs most frequently on windward slopes. Studying the physical mechanisms of soil erosion on windward slopes is challenging because of the complex co-occurrence of wind and rainfall. This study aimed to investigate the effects of rainfall intensity (30, 60, and 90 mm h−1), wind velocity (0, 2, 3, 5, 7, and 8 m s−1), and induced flow hydraulic characteristics on the processes of runoff occurrence, infiltration, and sediment detachment on windward slopes based on an indoor artificial simulated WDR soil flume experiments with three replicates. The results showed that both rainfall intensity and wind velocity exerted significant effects on runoff and sediment transport on the windward slopes (P < 0.05). The contribution rates of wind velocity on runoff occurrence time, steady infiltration rate, runoff rate, and sediment detachment rate were 20.53 %, 39.44 %, 3.36 %, and 6.24 %, respectively. When the rainfall intensity was constant, the steady infiltration rate on the windward slope increased linearly with the increasing wind velocity, whereas the runoff and sediment detachment rates decreased with increasing wind velocity. The decrease in hydraulic parameters of average flow velocity (v), stream power (Ω), unit stream power (U), and unit energy of cross-section (E) influenced by wind blowing on overland flow is the main reason for the decrease in the sediment detachment rate on the windward slope. Meanwhile, the increase in flow depth (h) and shear stress (τ) caused an increase in the infiltration rate. Because of the inclusion of Ω and E in the total work done and total energy consumption of overland flow, respectively, the relationship between Ω and E of the windward water flow with the sediment detachment rate showed an exponentially increasing curve for all treatments (R2 greater than 0.97). The hydraulic parameters Ω and E of the windward water flow are the optimal factors for constructing an erosion dynamic model under WDR conditions.