Successful application of the Taguchi method to simulated soil erosion experiments at the slope scale under various conditions

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The benefits of the Taguchi method have been demonstrated in diverse fields. However, its applicability to soil erosion experiments at the slope scale under various conditions remains unclear. Using 6 published datasets that included the dependent variables of erosion rate (D), runoff rate (R), sediment concentration (C), flow velocity (V) and transport capacity (Tc), we compared the results from the full-factorial design method with those from the Taguchi and orthogonal design methods to validate the applicability of the Taguchi method to simulated soil erosion experiments at the slope scale under different conditions. The statistical parameters of the dependent variables from the orthogonal design and Taguchi method were very close to those from the full-factorial design for all dependent variables. The trends of the main effects based on different factor levels were consistent for 35 out of 45 sets from the full-factorial design and Taguchi method and for 27 sets from the orthogonal design. The optimum conditions for 10 and 7 dependent variables (out of 14) for the Taguchi and orthogonal design methods were the same as those for the full-factorial design, respectively. In addition, 13 and 8 dependent variables (out of 14) for the Taguchi and orthogonal design methods had the same factor rank order of percentage contributions as the full-factorial design method, respectively. Based on a univariate analysis of variance, the evaluating indicators for predictive power, including the determination coefficient, Nash-Sutcliffe efficiency, relative root mean squared error, mean absolute percentage error and Thiel inequality coefficient, indicated that the Taguchi method predictions were better than the orthogonal design predictions. Overall, the Taguchi method could obtain more reliable conclusions for soil erosion than the orthogonal design method at the slope scale. These findings suggest that the Taguchi method could be successfully applied to soil erosion experiments and could better replace the full-factorial design method at the slope scale compared with the orthogonal design method.