Study On Watershed Geomorphologic Characteristics And Quantitative Based DEM And Sediment Yield Modeling

Basin geomoiphology and sediment yield of rainfall erosion form a complex dynamic system. The scientific quantification of basin geomorphological characteristics is a key scientific problem to define and the expression of the dynamic system prompt mechanism and laws of quantitative. In recent years, with the fractal theory in geography and the application of quantitative geography and fractal geomorphology of the rise and in-depth application of GIS technology, fractal basin geomorphological study has become more in depth. Combination of river basin morphology quantitative geomorphic study of basin-scale erosion and sediment yield effect for basin-scale erosion and sediment yield conversion to provide a good basis for research.In this study, we developed a rapid calculation method of the three-dimensional fractal based on fractal theory, DEM and GIS technology. Using this method, we have calculated three-dimensional fractals of Chabagou and its sub-basins under the different DEM pixel scales. We made regression analysis of relationship between three-dimensional fractals of basin geomorphic and the pixel scales of DEM. And, we made comparative analysis between the calculation results of the three-dimensional fractal and other indicators of basin topography. Finally we built a sediment transport statistical model of rainfall erosion. The experience test shows that the model has good prediction accuracy and reliability. Through the above-mentioned study, the following conclusions can be made:(1)Basin geomorphological three-dimensional fractal dimension as an important indicator of geomorphology, its calculating value is change with the with the DEM pixel scales. In different pixel scale of the DEM, the three-dimensional fractal dimensions have different closeness levels to the true values. For the same basin topography, three-dimensional fractal dimension show a good second-order polynomial with the pixel-scales of DEM. When using DEM to exact three-dimensional fractal dimension of basin geomorphology, consideration of DEM pixel scale should be given. And only under the same pixel scale, the amount of information contained in micro-geomorphology at the same level and three-dimensional information box fractal dimension comparable to the calculated value. (2)For a watershed, the geomorphology factors are not isolated to a certain extent but interrelated and mutually constraining with each other. On quantities, they are also included and overlap each other. Those indicators, some showing a correlation function relationship and some have no significant correlation. Overall, three-dimensional fractal as a characterization factor of basin geomorphology, reflecting the complexity of three-dimensional surface of basin geomorphology. To some extent, the three-dimensional fractal of basin geomorphology contains part information of the total channel length, watershed area, watershed length, watershed average elevation, watershed erosion integral values, and channel density.(3)The comprehensive analysis of factors affecting basin sediment yield in Chabagou show that the major factors impacting watershed sediment yield are rainfall, runoff, and geomorphology. For different rainstorm, sediment transport modulus (Ms) has highly significant correlation with runoff depth (h), flood peak flow modulus (Qs), and significant correlate with the three-dimensional fractal dimension of basin geomorphology (Di). By analyzing the correlation of sub-basin sediment transport modulus, runoff depth, flood peak flow modulus and the three-dimensional fractal dimension of basin geomorphology, we got the rainstorm sediment transport regression equation in Chabagou basin. Validated, the equation can be better simulating sediment transport at rainstorm events.