Assessment and prioritization of soil erosion triggering factors using analytical hierarchy process and Taguchi method

Abstract

The main aims of this study are assessing some factors which affect the soil erosion process and evaluating the results of an analytical hierarchy process (AHP) method using the Taguchi method. Firstly, the weights for those factors and levels affecting soil erosion were determined by the AHP method. The determination of weights was based on the opinions of academic researchers, experts, middle managers, and members of the Soil and Water Research Centers in Iran. Secondly, an L32 Taguchi orthogonal array was selected based on the number of factors and levels for the current problem. Accordingly, 32 rainfall events were simulated and sediment yield amounts were measured. Analyzing the results of the Taguchi method, the weights of factors and levels were determined. The results showed that the weights obtained from the AHP method were not in accordance with the results of field measurements and the Taguchi analysis. The AHP method indicated that the main factors have the following order of importance: geological formation, rainfall intensity, silt content of soil as an indicator for the soil texture, vegetation cover, slope steepness, and slope aspect in the study area. However, the Taguchi method found the following order for the main factors: rainfall intensity, geological formation, silt content of soil as an indicator for the soil texture, slope steepness, vegetation cover, and slope aspect. As the Taguchi method works based on the quantitative measurements, the Taguchi results are more reliable rather than subjective methods such as AHP. It was also concluded that the AHP method should be used cautiously in assessing natural phenomena. Therefore, in the cases that in situ measurements are possible, it is better to use quantitative mathematical and statistical methods than to rely to qualitative knowledge based approaches.