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A comparison of the soil loss evaluation index and the RUSLE Model: a case study in the Loess Plateau of China

Author(s): W. W. Zhao | B. J. Fu | L. D. Chen

Journal: Hydrology and Earth System Sciences Discussions
ISSN 1812-2108

Volume: 9;
Issue: 2;
Start page: 2409;
Date: 2012;
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The development of new methods to examine the influence of land use on soil erosion is currently a popular research topic in contemporary research. The multiscale Soil Loss Evaluation Index is a new, simple soil erosion model that can be used to evaluate the relationship between land use and soil erosion; however, applications of this model have been limited, and a comparison with other soil erosion models is needed. In this study, we used the Yanhe watershed in China's Loess Plateau as a case study to calculate the Soil Loss Evaluation Index at the small watershed scale (SLsw), to identify the similarities and differences between results from the Soil Loss Evaluation Index and the Revised Universal Soil Loss Equation (RUSLE), and to determine the key location where land use patterns need to be optimized in the study area. The procedure for calculating the SLsw, namely, using the delineation of the drainage network and the sub-watersheds as starting points, includes the calculation of soil loss horizontal distance index, the soil loss vertical distance index, slope steepness factor, rainfall-runoff erosivity factor, soil erodibility factor, and cover and management practices factor. During the calculation procedure, several functions within geographic information system (GIS), especially the spatial analyst function, are used to calculate these factors layers, and many of the data are expressed in grid format. Moreover, The AVSWAT2000 hydrological model and upscaling methods were used to calculate some of the factors in this study. When comparing the SLsw with the RUSLE, some similarities and differences were discovered. The similarities of the two models include the following: (1) both use GIS techniques at the watershed scale, (2) the same factors appear in both models, (3) and the resolution of the basic data is closely related to the evaluation results. The differences between the SLsw and the RUSLE are as follows: (1) they have different outcomes, namely, the former analyzes the relationship between land use and soil erosion, and the latter analyzes the amount of soil erosion; (2) different grain scales are used in the two models, namely, the former uses the sub-watershed scale, and the latter uses the grid cell; and (3) the evaluation results are different, namely, the former is dimensionless but can identify the key area for land use pattern adjustment, and the latter provides the coarse soil loss rate but may have difficulty identifying the key area where the land use pattern urgently needs adjustment to control the soil loss because of the different soil erosion factors. On the basis of our results regarding the Soil Loss Evaluation Index in the Yanhe watershed and comparisons with the RUSLE, we conclude that the area with substantial soil erosion is primarily located in the middle and southeastern parts of the Yanhe watershed and is a composite effect from different soil erosion factors. Additionally, the sensitive area where land use patterns need to be optimized is primarily located in the middle part of the Yanhe watershed, covering 53.3% of the watershed. In future studies of land use pattern optimization, the calculation of the Soil Loss Evaluation Index at the slope scale may play a key role in identifying where land use patterns need to be adjusted in the sub-watersheds of sensitive areas.
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