Erosion has been divided into interril, rill, and gully components. Interrill erosion consists of soil particle detachment by raindrop impact and particle transport by splash and shallow overland flow. Interril erosion and runoff rates were measured from one square-meter drainable flume filled with disturbed soil under simulated rainfall at different slopes ranging from 1.5 to 20%. Three contrasting soil types were used in the study. Rainfall was applied using a rainfall simulator with a single sweeping nozzle located 4 meters above the soil surface that sprayed drops with mean diameter of 1.5 mm. Results indicated that the effect of slope on interrill erosion depends on the soil type and rainfall rate. In other words, there is an interaction between slope, soil type and rainfall rate. Measured interrill erosion rates were compared to soil loss predicted by the proposed equations in WEPP model. Results revealed that the model tends to over-predict the values on the lower end, while under-predicting the values on the upper end of the scale.
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