Average sand particle trajectory examined by the Raindrop Detachment and Wind-driven Transport (RD-WDT) process

摘要

Recent studies of soil loss by the integrated action of raindrop impact and wind transport have demonstrated the significance of this mechanism. This paper presents data obtained during wind-tunnel experiments examining the 'Raindrop Detachment and Wind-driven Transport' (RD-WDT) process to investigate average sand particle trajectory and the spatial extent at which the process operates. In the experimental design, at the same time as the horizontal wind velocities of 6.4, 10, and 12 m s(-1) passed through the tunnel, rainfall was simulated falling on very well sorted dune sand. The aspect and slope of the sand bed was varied to reproduce both windward (Ww) and leeward (Lw) slopes of 4 degrees and 9 degrees with respect to the prevailing wind direction. The average sand particle trajectories by the RD-WDT process ((X) over bar (RD-WDT)) were estimated by a mass-distribution function, which was integrated over a 7-m uniform slope segment. The results showed that (X) over bar (RD-WDT) depended statistically upon the wind shear velocity (u*), and the effect of the slope gradient (theta) was insignificant on (X) over bar (RD-WDT) This was different from that of the windless rain process ((X) over bar (RD-ST)), 'Raindrop Detachment and Splash-driven Transport' (RD-ST), the spatial range of which relies strongly on theta. Additionally, (X) over bar (RD-WDT) was approximately 2.27 +/- 2.2 times greater than the average path of a typical saltating sand particle of the rainless wind ((X) over bar (RD-ST)) 'Wind Erosion Saltation Transport' (WE-ST).