Modification And Application Of Soil Erosion Assessment Index Model In Small Watershed Scale

Soil erosion is one of the most serious environmental problems in the world. The soil erosion is particularly serious in China, and the Loess Plateau of Northern Shaanxi is the main source of sediment in the Yellow River. Soil erosion model is an effective tool for the study of soil erosion, which is of great significance for the development of soil erosion assessment and related research. But previous research of some physical models involving many parameters, practical applicability is limited, so fu Bojie proposed soil erosion evaluation index model, but the model to study the effect of soil erosion parameters is too simple, not good to show the degree of soil erosion. Therefore, this study combined with previous research and the local actual situation, to modified the watershed of Ansai soil erosion evaluation index model. It provides a scientific basis for the prevention and control of soil erosion in the Loess Hilly and gully region.This study chose the Loess Hilly Gully Region of Ansai watershed as the research area, and used GIS technology to calculate the SLSW based on the data of Ansai catchment DEM data, daily rainfall data of hydrological observation station, soil sampling data and land use data. Then the topographic factor and rainfall erosion force factor were modified. The measured sediment transport volume in Ansai watershed was used to verify the modified index. And then the soil erosion intensity and its temporal and spatial variation characteristics of Ansai watershed were analyzed. The main conclusions are as follows:1. Soil erosion evaluation index model is a empirical model between empirical model and physical model, it can be use of land evaluation effect on soil erosion, and can avoid the error caused by too much calculation parameters. And the sub basin is the calculation unit of soil erosion evaluation index.In order to study the soil erosion index of each sub watershed in the study area, it is necessary to evaluate the value of the soil erosion index.2. In the analysis of Rainfall Erosivity Factor (R), take division isoline method analyzes the distribution of R value, draw in the northwest, Liandaowan’s rainfall erosion force was the lowest, to the surrounding gradually increased. In the middle part of the central region, the Huziping’s rainfall erosion is the largest, and decreases from the south to the north. In the southeast area, the west of Wangjiayao, rainfall erosion force gradually decreases, while the east gradually increases. In the calculation of crop cover and management factor (C), considering the different types of land use and vegetation coverage in the region, it is concluded that the higher the crop growth, the higher the degree of vegetation coverage. Other factors can be Ansai catchment in upstream area soil erosion evaluation index is higher, mainly because of the higher terrain of the area, vegetation growth is poorer, loose soil structure which leads to the more serious soil erosion.3. Revised and validated the topographic index, rainfall erosion force factor and multiple factor of soil erosion assessment index, we can be drawn the correction of the index before and after all through the T test. Compared with the measured sediment transport volume, the correlation between the modified index and the measured volume was greater than the correlation between the original index and the measured volume. It can be concluded that the modified index can better explain the regional soil erosion of the study area.4. By SL index erosion zoning research shows, watershed of Ansai belongs to moderate erosion, mainly showed a patchy distribution in the basin, and micro degree erosion and mild are mainly distributed in the gentle slope terrain along the river valley strongly above erosion mainly distributed in Ansai catchment in upstream and South East region. And Ansai catchments of different slope soil erosion characteristics analysis shows that, with the increasing of the slope, the proportion of micro degree erosion will be decreased with the increasing of the slope, and moderate, strong and very strong erosion ratio, with the slope increased with increasing, but to a certain slope, slope degree change of soil erosion intensity distribution changes little.5. For the upper reaches of the watershed of Ansai, should give priority to with grass, combination of planting shrubs and trees of the restoration and reduce soil erosion. And some slope fluctuations in the region, should be raised as much as possible erosion of the base surface, reducing the runoff of the slope surface, slow down the runoff rate, improve soil water absorption capacity and slope resistance. The measures of returning farmland to forest and forest (grass) should be applied in the areas of farmland and less vegetation.