| Meltwater erosion has become one of the serious environment problems in Qinghai-tibet plateau, it destroys the plateau ecological environment, and it also threatens the environment protecting and developing of humankind. Understanding the meltwater erosion of Qinghai-Tibet plateau, and learning the mechanism and influence factors of meltwater erosion can provide theoretical basis and decision-making reference for comprehensive management of meltwater erosion and ecological restoration. According to the model of alluvial fan index, this paper calculates the alluvial fan index of Naqu district, and then this paper extracts the meltwater erosion deposition of Qinghai-Tibet plateau on basis of GIS and remote sensing technology. This paper analysis the sedimentary characteristics and the main influence factors of meltwater erosion in Naqit district. According to the principle component analysis method, this paper analysis the influence factors of meltwater erosion, to evaluate the Naqu meltwater erosion and drawing in Naqu meltwater erosion intensity classification map. This paper provides a new way for the regional meltwater erosion research. The main content of this dissertation are as following:1. There are large amounts of deposition fan in the study area, the statistic deposition fan area accounts for about1/8of the total area. It is different in regional sedimentary fan distribution, sedimentary fan is mainly distributed in the middle parts of the study area, including the Amdo, Bangor, Xainza and Shuanghu, Nima County south area, which belongs to the plateau lake basin area, Nam Co,Selincuo, many rivers and lakes distribute in the area, the meltwater erosion and rivers scour a large number of alluvial fan. Sedimentary fan distributes in the valley and lakesides, due to the age, the majority are large and significant difference, area of dozens of square kilometers to hundreds of square kilometers, the thickness range from meters to several thousands of meters.2.The main factors of the meltwater erosion deposition is the wind, NDVI, soil erodibility, K value, temperature variety and the slope.Wind speed and NDVI were positively correlated with the meltwater erosion deposition, K value, temperature range and steep slope percentage is negatively correlated with the meltwater erosion deposition. The wind can blow to the snowonthe slope accumulation in the depression, the snow is greater, there is more depression, erosion deposition is morestrength, otherwise the less; NDVI is better, soil erosion resistance is stronger, and the vegetation root interception of runoff and sediment capacity is higher, it is more easy to form the erosion deposition. Soil erodibility value is higher, the soil erosion is more easily, it is also easy to form the erosion deposition; annual temperature range higher, the area rain less, meltwater erosion intensity is low, more hard to form the erosion deposition; it isharder to form the erosion depositionwith more steep slope.3. The four principal component of meltwater erosion are terrain factor, climatic factor, soil factor and snow change factor. The first principal component of terrain factors including elevation, slope and NDVI factors, effectingthe radiation on snow and ice melt.Slope and vegetation directly affect the meltwater runoff, it is important impact on meltwater erosion. Wind speed, lower temperature and sunshine factorform the second principal component, the important influence factors on snow and ice melt. The third principal components including relative humidity and soil erodibility value factors, mainly reflect that the soil influence the erodibility of meltwatererosion. The fourth principal component mainly reflect changes of glaciers and snow meltwater erosion, water erosion power come from the glaciers and snow melt water runoff, the glacier variation is important influence factor of meltwater erosion.4.Meltwater erosion in the study area is divided intosix grades, including mild, moderate, micro, strong, very strong and vigorousgrades, micro, mild and severe grades occupy small proportion, moderate, strong and very strong intensity in study area are more serious. The difference erosion intensity distribute in significantly different area, the spatial distribution is relatively concentrated, and from the east to the west area, meltwater erosion gradually weakened, meltwater erosion is strongin rugged topography east area, west area is located in the plateau lake, meltwater erosion intensity is mild. Meltwater erosion intensity distribution isclosely related with regional topography and climatic factors. |
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