Study On The Depositing Information Of Check Dam And The Correlation Among Rainfall, Runoff And Sediment In Watershed

On the basis of literatures reviewing on the check dam development from domestic and abroad, sediment deposition process and its relation with rainfall runoff and sediment yield from single rainfall in typical check dam were studied by combining the field survey and soil sampling analysis, and using runoff generation and flood routing theory on watershed scale, as well as mathematical statistics.Related results obtained in this research provided a valuable reference for solving the problem of water-induced damage of check dams, and the optimized collocation of soil and water measures for watershed comprehensive harness in ungauged watershed in Leoss Plateau, and for the environmental impact assessment of small watershed soil and water conservation comprehensive harness, as well as the establishment of small watershed soil erosion prediction model. The following conclusions were obtained:(1) Dry density result of depositing matter from layers of the warped farmland indicated that the dry density of each layer was generally stabilized when depositing thickness less than 10 m; and it increased when depositing thickness was over 10 m. When depositing degree similar, i.e. designed years or the depositing thickness was close, changes of dry density with depth were similar too.(2) Grain composition analysis of depositing matter on layers in the warped farmland indicated that the grain diameter of depositing matter had no clear relation with topography; grain distribution curve on each layer was well-proportioned, the grain diameter was mainly distributed among the range from 0.025 mm to 0.1 mm, and its changing scope of the mass percentage was maximum.(3) To the check dam without flood releasing measures, the relation between sediment deposition and rainfall erosivity was established as power function (y = axh, where a and b were constants; y was sediment yield on each layer; x was wasrainfall erosivity), and result of hypothesis testing verified that the its correlation was good.(4) To the check dam without flood releasing measures, relation between sediment deposition and the maximum rainfall intensity in thirty minutes (I30) was established. Results indicated that exponential function (y = ae^bx, where a and b were constants; y was sediment yield on each layer; x was the maximum rainfall intensity in thirty minutes) was existed between sediment deposition and the maximum rainfall intensity in thirty minutes (I30). Hypothesis testing a indicated that its correlation was good, and was well in accordance with the observed data.