Determination and Analysis of Interrill Erosion of a Soil with Coarse Fragments in Taiwan

Abstract

To evaluate the effects of coarse fragments in soil on interrill soil erosion, a programmable rainfall simulator and soil erosion boxes were designed and fabricated. Simulated rainfall erosion tests were conducted on soils with coarse fragment contents of 0%, 7.5%, 15%, 30%, and 45%; at slope steepnesses of 9%, 20%, and 30%; and under simulated rainfall intensities of 40, 60, 80, and 100 mm h-1. A total of 132 data sets were obtained. It was found from the test results that coarse fragments had a mitigating effect on soil erosion at high rainfall intensities, and the steeper the slope, the better the effect. However, there was no apparent positive correlation between such mitigating effect and the percentage of coarse fragments in test samples. When part of the coarse fragments were exposed at the soil surface, both positive and negative effects might result, and a quantitative evaluation thereof requires further study. Furthermore, regression analysis and an artificial neural network were used in this study to establish a general equation and a three-layer back-propagation neural network model for estimating interrill soil erosion. While the regression equation is in harmony with the conceptual mechanisms of soil erosion, with an R2 value of 0.900 and an RMSE of 0.429, the artificial neural network model has a higher R2 value of 0.962 and a lower RMSE of 0.342, indicating that the artificial neural network model may provide better estimation of interrill soil erosion.