SEDIMENT TRANSPORT FROM INTERRILL AREAS UNDER WIND-DRIVEN RAIN

Abstract

In nature, erosive rainstorms are usually associated with high winds. Therefore, a quantification of wind and rain interactions and the effects of wind on detachment and transport processes provides a great opportunity for a given prediction technology to improve the estimation of erosion. This paper presents experimental data obtained on interrill erosion processes under wind-driven rain. In a wind tunnel facility equipped with a rainfall simulator, windless rains and the rains driven by horizontal wind velocities of 6, 10, and 14ms-1 were applied to three agricultural soils packed into 20 by 55cm soil pan at both windward and leeward slopes of 7, 15, and 20%. Wind-driven rainsplash transport was measured by trapping the splashed particles at distances on a 7-m uniform slope segment in the upslope and downslope directions, respectively, for windward and leeward slopes. The process was adequately described by relating the rainsplash transport rate to the rainfall parameter, fluxes of rain energy or momentum, and wind shear velocity by log-linear regression technique. Sediment transport by rain-impacted thin flow was measured by collecting sediment and runoff samples at 5-min intervals after runoff onset. This process was also adequately described by rainfall and flow parameters. Comparing the process contribution to the total sediment transport, it is concluded that rainsplash transport is a significant process that should not be neglected in accurately predicting interrill water erosion under wind-driven rain. Mean values for the ratio of rainsplash erosion to the corresponding total sediment transport were 14.6+/-6.4, 23.9+/-7.8, and 38.1+/-8.7% for the rains driven by 6, 10, and 14ms-1 wind, respectively.