Research On Erosion And Sediment Yield Of Huangtuwa Watershed Based On Scale Conversion

The serious problems of soil erosion in the Loess Plateau severely restrict the local production and development.The study on the erosion regularity of loess can provide an effective reference for the local production and living planning and the management of soil erosion.The loess small watershed is a small watershed with a history of full-bleeding and full-bleeding in 440 years.Through its research,the results will be eventually extended to larger river basins to achieve the effect of "covering the surface with points" and provide reference for the research of other watersheds.In this paper,the high-precision loess raft collected by the UAV in 2016 and the digital elevation model(dem)of the surrounding area are used to classify the channel network of the loess ravine and the surrounding area to explain the relationship between the channel channels.The channel types of Loess Plateau were determined by the degree of opening,the degree of splitting,and the main branch groove coefficient;the slope of both sides of the channel and the slope of the valley line were extracted by the five-point section line method,and the channel morphology of the Loess Plateau and surrounding areas was summarized.Based on the rule of channel morphology in Loess Plateau,the 440-year-old amount of erosion in Loess Plateau area was calculated by downscaling,and on this basis,the scale was extended to the Huaining River Basin,and the average annual erosion volume of the calculator was calculated.The following main conclusions are drawn:(1)The eigenvalue(threshold)of the channel grading selection 185000 m3 can retain the minimum channel to be measured in the loess.The results of the grading of the channel indicate that the main road connecting the loess plateau is located in the middle and merges into the advanced channel between the northwest and the adjacent watersheds on the west.The channel narrows from the lower level to the higher level and converges in the northwest direction.The lower channel is different.Angles(up to 90 degrees)are fed into high-level or multi-level advanced channels.Channels of the same level(especially first-order channels)are more or less parallel;low-grade channels are generally longer than high-grade channels.Short,but the number of low-grade channels is much larger than high-grade channels.(2)The gully along the Loess Plateau and its surrounding areas is basically located at a position where the change in gradient is relatively obvious.It is generally rapidly changed from a relatively gentle slope(approximately 0-12 degrees)on a raft and a girder to a relatively steep slope(approximately 13).-30 degrees)location.The main channel of the channel conforms to the law of the river and follows the characteristics of"one convex and one concave";the lower channel is connected on both sides of the advanced channel or the head of the channel,and the lower channel located on both sides of the advanced channel is prone to small gaps.,The width of the ditch is small and the head of the ditch is small,while the lower ditch at the head of the senior ditch is prone to the characteristics of the largest ditch,the second ditch,and the smallest ditch.The reasons for the analysis and the advanced ditch and lower ditch are analyzed.The direction and location are related.(3)The channel area,drainage area,main ditch length,and total ditch length of different channels cannot be directly compared and analyzed.The classification results of the surrounding channel of loess can be classified by calculating the degree of opening,the degree of splitting,and the main branch groove coefficient.Shown semi-extracted type,moderately split type and semi-main type ditch type is the main type.(4)The high-grade channel is suitable for development and utilization,supplemented by governance.The type of low-grade channel should be dominated by governance and supplemented by development,such as taking plant measures.In the area around the Loess Plateau,there are many intermediate-level(semi-extracted,moderately fragmented,and semi-dominated)channels.The topography of this channel is between the first two.Development and utilization and governance should take into account the specific environment.Depending on the local conditions and reasonable development,such as the construction of silting dams for water storage,planting shrubs,etc.(5)In the process of fitting the gradient of the slope by means of a function,through the analysis of the valley line with R2 greater than 0.95,it is concluded that the valley line profile of the Loess Plateau is developed in the form of an approximate straight line in the absence of natural deposition.And the slope of these trend lines is basically between 0.3 and 0.4.A very small number of poorly fitted channels are mainly affected by the scale of the erosion reference,sediment,and channel.(6)Observing the hatching at five points,it was found that the majority of R2 was greater than 0.95,indicating that the slopes on both sides of the channel were basically linear.(7)The slope calculated at the five-point section of the Loess Valley watershed basically revolves around the slope range of the Loess Plateau.The slope of the valley near the entrance of the senior channel is smaller,and the slope of the valley near the middle of the senior channel valley is larger.The reason may be analyzed.It is the close relationship between the small-scale channel and the advanced channel,which results in the decrease of the slope of the valley line.The small-scale channel and the high-level channel in the middle of the advanced valley are almost perpendicular,and the slope of the valley line is the largest at this time.(8)It has been calculated that the accumulation volume of polysilicon in the Loess Loess small watershed for 447 years is 1.51×107 m,and the average annual erosion is 3.3×104 m3.There are basically positive correlations between channels of different scales and sedimentation amount.After sorting the erosion amount of different channels,it is found that the results are highly fitted to the exponential function.Comparing with the results calculated by RUSLE,it is found that the calculation result in this paper is 2.14 times that of the model calculation.The reason for the analysis is that the calculation result in this paper is a long-term effect and represents the deposition state in a longer period of time,followed by the adoption of The amount of sedimentation calculated by the method is equal to the amount of erosion plus the amount of erosion of the underground slope.It is the difference between the "beginning" and the current"final" state at the beginning of the deposition,and the result can be a good interpretation of the loess and the The amount of erosion that the surrounding area should be carried away.(9)The analysis shows that in scale-scale conversion of the Loess Plateau catchment to the Huaining River Basin,elevation factors have become a new and important factor in the climate,soil,vegetation and other factors.The western elevation is high,and the channel Undercuts are deeper and there are relatively few sediments,and the east is the opposite.Based on the dynamic balance principle of the multi-year erosion in the middle and lower reaches of the Huaining River,the mean annual erosion of the loess has been calculated for the 440-year-old full-thickness polysilicon,and the annual average amount of erosion in the Huaining River Basin was calculated using the area of erosion as the basic unit.There may be a relationship between it and the true amount of erosion.The final calculation of Huaining River’s annual average soil erosion was 1.33 × 107m3.