Coupling Relationship Between Rainfall And Deposition Bedding

In recent years, the problem of soil erosion has become the world’s environmental problems of common concern, which is one of the major environmental disasters that limit human survival and development, and constitutes a serious threat to human survival and development. Eolian loess deposits by erosion or siltation in the channel and the plains, or into the ocean by a river, if people can find a better information source of aqueous sediment (siltation), it will help people speculate the erosion process of loess.In this paper, we made the Huangtuwa natural silted which wa the siltation longest in China as the research object, use the1960-2010years of rainfall data, analyze the characteristics of the rainfall of the study area; rainfall erosivity calculated according to the daily rainfall model, analyze the variation characteristics; finishing the the granularity test data, with rainfall data were fitted to match the rainfall events and sediments; using gray relational analysis to explore the coupling between rainfall and sedimentary bedding. The following conclusions:(1) Analysised of the basic features of the regional precipitation. In recent50years, the average annual rainfall of438.8mm in the area of Huangtuwa from1960to2010, the minimum value is254.4mm in the year of1965; the maximum value is745.2mm in the year of1964. Rainfall climate trend coefficient is-0.37, the coefficientawas2.93, the coefficient Cv was0.05, and the coefficient η was0.59, indicating that the trend of rainfall is reduced and the ariation changed significantly that rainfall inter-annual variation; Erosive rainfall climate trend coefficient is-0.007, the coefficient a was10.03, the coefficient Cv was0.34, and the coefficient η was0.52, indicating that the trend of erosive rainfall is little reduced, and the ariation changed by a big margin. The average proportion is56.2%of erosive annual rainfall. During the year, the uneven distribution of erosive rainfall occurs mainly in July, August and September, three months accounted for75.72%of the annual erosion rainfall; they are not consistent which the yaer appeared aggressive maximum annual rainfall total and the year appeared maximum annual rainfall totals. (2) Calculated the rainfall erosivity according to the model that corrected by Zhangwenbo. The coefficient a was18.26, the coefficient Cv was0.51, and the coefficient η was0.34, the trend coefficient r was-0.153, indicating that the interannual variability changed obviously of annual rainfall erosivity, and the annual rainfall erosivity decreases linearly; Like the ariation of erosive rainfall change, uneven distribution during the year, the accounting of frainfall erosivity was80.45%from July to September, but not exactly the same, in July and August, the cumulative the percentage of rainfall erosivity is greater than erosive rainfall’s, in this two months, the cumulative percentage of erosive rainfall was55.59%, the cumulative percentage of rainfall erosivity was61.75%. From July to August, rainfall intensity relatively larger, resulting in raindrop kinetic energy was also larger, the proportion of rainfall erosivity higher than the proportion of Erosive rainfall; other monthly rainfall intensity is relatively smaller, the same description of rainfall erosion force is smaller in the study area, so the the rainfall erosivity proportion is less than the proportion of erosive rainfall.(3) Analysised of the characteristics of grain-size parameters of sediment profile, grain-size composition and grain-size distribution of frequency characteristics, and according to the characteristics of particle size, the section was divided into16layers. From grain-size parameters can be seen, in the lower part of the profile, the particle diameter size is larger, belongs to the whole bad sorting, nearly symmetric partial normal, moderately sharp particle size distribution. Median particle size ranges from6.76～45.76μm, average particle size range between8.39～47.39μm; the soil composition of profile dominated by coarse silt, the average content of50.58%, the entire profile coarse silt particle content on a declining trend from top to bottom, in the layers of the profile, the average contont showed a fluctuant decreaseing trend of colloidal particle, clay, fine silt, the average contont showed a fluctuant decreaseing trend of very fine sand, stand grain, the contant was smaller of olloidal particle, stand grain. The distribution frequency curves of the grain-size in the soil profile was unimodal curve, the soil particle size distribution between0～710μm, peak particle size range between12.62～44.78μm, between content between3.53%～5.37%, the distribution frequency curves of L1,L13,L15were very partial, peak size, indicating that the three cyclothems particle concentration distribution in the thick end part, the L4layer, L9layer, L12layer, peak particle size smaller, the grain-size composition of these layers was fine, the accumulative frequency curves of the grain-size in the profile of the L12layer, L4layer, L9layer, were gentle, particle size difference, poorly sorted, the accumulative frequency curves of the grain-size in the profile of L1layer, L13layer, L15layer, were close, vertical size concentration.(4) Analysised of the coupling relationship between rainfall and sediment layers. In the process of rainfall erosion, heavy rain deposition and sediment thickness, left characteristics, and the cyclic deposition more complete, thick, heavy rain deposition cyclic relatively easy to determine. Heavy rain occurred at a time and deposition of sediments to find its match, and then determine the sediments under heavy rain storm corresponding to the sedimentary cycle layer. To select deposition indicators and rainfall indicators, calculated the correlation matrix between them by using of gray relational analysis. Can be seen through the associated matrix deposition indicators, particle size parameters and the correlation of rainfall, strong coupling effects, clay content and rainfall associated with the smallest coupling effect was weak; deposition of particle size parameters and grit level content and rainfall peak indicators related degree, strong coupling effects, the correlation with total rainfall indicators, the coupling effect was weak; Deposition thickness, the content of clay, the content of coarse silt and total rainfall indicators related degree, strong coupling effects, with peak rainfall index was relatively small, the coupling effect is weak. Rainfall indicators deposition rainfall associated with the largest half months, the strongest coupling effect; of sedimentary indicators with rainfall indicators related degree means are associated with the role of a strong range.