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

Abstract

AbstractRecent 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 4º and 9º with respect to the prevailing wind direction. The average sand particle trajectories by the RD‐WDT process ($\bar X_{RD-WDT}$) were estimated by a mass‐distribution function, which was integrated over a 7‐m uniform slope segment. The results showed that $\bar X_{RD-WDT}$ depended statistically upon the wind shear velocity (u*), and the effect of the slope gradient (θ) was insignificant on $\bar X_{RD-WDT}$. This was different from that of the windless rain process ($\bar X_{RD-ST}$), ‘Raindrop Detachment and Splash‐driven Transport’ (RD‐ST), the spatial range of which relies strongly on θ. Additionally, $\bar X_{RD-WDT}$ was approximately 2·27 ± 2·2 times greater than the average path of a typical saltating sand particle of the rainless wind ($\bar X_{WZ-ST}$), ‘Wind Erosion Saltation Transport’ (WE‐ST). Copyright © 2009 John Wiley & Sons, Ltd.