Submitted to: Earth Surface Processes and Landforms
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/15/2004
Publication Date: 1/30/2005
Citation: Erpul, G., Gabriels, D., Norton, L.D. 2005. Sand detachment by wind-driven raindrops. Earth Surface Processes and Landforms. 30:241-250.
Technical Abstract: Wind movement and velocities can have profound effect on some aspects of the soil erosion process. In the case of wind-driven rain, differences in raindrop trajectory are expected: wind-driven raindrops achieve some degree of horizontal velocity, which increases their resultant impact velocity and strike the soil surface with an angle deviated from the vertical under the effects of both gravitational and drag forces. However, not much is known about the physical impact of raindrops on a soil in situations where this impact is at an angle, and it is also not exactly known if oblique raindrops have stronger erosive effects than vertical ones. A series of tests to assess the effect of wind velocities on sand detachment from splash cups were conducted in a wind tunnel facility equipped with a rainfall simulator. Splash cups packed with standard sand were exposed to windless rains and the rains driven by horizontal wind velocities of 6, 10, and 14 m s-1 to evaluate the sand detachment by wind-driven raindrops. The average angle of rain inclination from vertical was calculated from the direct intensity measurements implemented with windward and leeward facing raingauges placed at different slopes. A kinetic energy sensor measured energy of windless and wind-driven rains. Results showed that the kinetic energy flux calculated by the resultant impact velocity of drops adequately described the sand detachment from the splash cups by wind-driven raindrops. However, an additional analysis of Pearson correlation coefficients using the velocity components rather than the resultant velocity of wind-driven raindrops indicated that the energy flux related to the horizontal component of wind-driven raindrops had a greater correlation with the sand detachment than that related to the normal component. This finding contradicted the general assumption that the component of velocity normal to the surface is related to the detachment.