Submitted to: Geomorphology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/12/2004
Publication Date: 3/12/2004
Citation: Erpul, G., Norton, L.D., Gabriels, D. 2004. Splash - saltation trajectories of soil particle under wind-driven rain. Geomorphology. Article S0169555X03003118. Available: http://authors.elsevier.com/sd/article/S0169555X03003118
Interpretive Summary: This research examined the combined effects of wind and water at detaching soil particles during a rainstorm. An experiment was conducted in a unique facility consisting of a wind tunnel that was also equipped with a rainfall simulator, to study the effects of wind speed, soil slope, and slope aspect on soil erosion. Three different common agricultural soils were put into small erosion pans, and then the pans were set at different slopes either facing into or away from the wind and wind-driven raindrops. Soil that was detached from the pans could be captured up to 7 meters away to study the sediment movement. We found that wind has a significant effect on the movement of soil particles once they are detached. The addition of wind moved up to three times the amount of particles compared to a no wind comparison. This research impacts scientists, modelers, soil conservationists and others who need to either better understand and model how sediment is detached and transported by wind and water, or need to develop and implement conservation practices to protect soil from these types of combined erosive forces. These findings show that wind should be considered as a variable when designing conservation practices to control erosion by water. This research helps in efforts to conserve soil resources.
Technical Abstract: It is usually recognized that relatively large amounts of soil particles cannot be transported by raindrop splashes under windless rain. However, the splash-saltation process can cause net transportation in the prevailing wind direction since variations in splash-saltation trajectory due to the wind are expected in wind-driven rain. Therefore, determining the combined effect of rain and wind on the process should enable improvement of the estimation of erosion for any given prediction technique. This paper presents experimental data on the effects of slope aspect, slope gradient, and horizontal wind velocity on the splash-saltation trajectories of soil particles under wind-driven rain. In a wind tunnel facility equipped with a rainfall simulator, the rains driven by horizontal wind velocities of 6, 10, and 14 m s-1 were allowed to impact three agricultural soils packed into 20 by 55 cm soil pans placed at both windward and leeward slopes of 7, 15, and 20%. Splash-saltation trajectories were measured by trapping the splashed particles at distances downwind on a 7 m uniform slope segment in the upslope and downslope directions, respectively, for windward and leeward slopes. Exponential decay curves were fitted for the mass distribution of splash-saltation sediment as a function of travel distance, and the average splash-saltation trajectory was derived from the average value of the fitted functions. The results demonstrated that the average trajectory of a raindrop-induced and wind-driven soil particle was substantially affected by the wind shear velocity, and it had the greatest correlation (r = 0.96 for all data) with the shear velocity; however, neither slope aspect nor slope gradient significantly predicted the splash-saltation trajectory. More significantly, a statistical analysis conducted with non-linear regression model of showed that average trajectory of splash-saltation was approximately three times greater than that of typical saltating sand grain.