Calculation method for inverting slope cropland soil erosion rate based on enclosing wall measure

Abstract

The invention relates to a calculation method for inverting a slope farmland soil erosion rate based on enclosing wall measures, which comprises the following steps of: arranging an enclosing wall body which is formed by a top wall, a bottom wall, a left wall and a right wall at the periphery of a slope farmland plot and is closed at the periphery, and blocking slope farmland erosion silt by the enclosing wall body and depositing the slope farmland erosion silt at the periphery of the bottom wall; a longitudinal section line is drawn in the slope direction of the slope farmland through a digital elevation model DEM and a 3D Analyst tool in ArcGIS software, a slope farmland erosion-deposition conversion curve is obtained through a Pwlf piecewise linear regression method, and the sediment amount of a slope farmland deposition area and the soil erosion rate of an erosion area are calculated through geometric operation; enclosing wall measure construction raw materials are convenient to obtain, the manufacturing process is simple, the application benefit maintaining time is long, and maintenance is convenient; the erosion sediment sample treatment in the traditional runoff plot observation and soil bin simulation test is avoided, and a convenient operation process and method for inverting the plot soil erosion rate are provided.

Description

Technical Field

[0001] The present invention relates to the technical field of soil erosion rate measurement, and in particular to a calculation method for inverting the soil erosion rate of sloping farmland based on fence measures. Background Art

[0002] Existing methods for measuring soil erosion rates include runoff plot observation and soil trough simulation tests. The runoff plot observation method requires real-time collection of eroded sediment during rainfall, followed by subsequent processing such as drying and weighing. This is a cumbersome process and the plot construction costs are high. Soil trough simulation tests are often limited by factors such as soil trough size and simulation equipment, making them difficult to conduct and often differing from actual conditions.

[0003] The prior art also discloses a variety of methods for calculating the soil erosion rate of sloping farmland. For example, CN108332719 A discloses a method for rapidly estimating the soil erosion rate of sloping farmland using drone images and high-precision DEM data. This method has the advantages of high data accuracy, no artificial disturbance of the original terrain, and strong operability.

[0004] For example, the "Rapid Estimation Method for Soil Hydraulic Erosion Rate of Sloping Farmland" disclosed in CN108180897A discloses the use of drones to obtain image data of sloping farmland before and after hydraulic erosion under farming conditions; using RTK-GPS to obtain ground control points of the sloping farmland; aligning the image data before and after hydraulic erosion according to the ground control points, and then extracting high-density point cloud data respectively; generating high-precision digital elevation data and orthophotos before and after hydraulic erosion based on the high-density point cloud data before and after hydraulic erosion, and finally estimating the hydraulic erosion rate of sloping farmland soil after farming; it has the advantages of simple operation, high data accuracy, shorter measurement time, and higher efficiency.

[0005] However, the treatment measures or calculation methods adopted in the above-mentioned existing technologies do not take any protective measures against the loss of soil on sloping farmland, resulting in serious soil erosion during the farming process or under the action of hydraulic scouring. After serious soil and water loss on sloping farmland, even for the same piece of farmland, the calculated erosion rate has a large error and low accuracy. Summary of the Invention

[0006] In view of the above-mentioned deficiencies in the prior art, the technical problem to be solved by the present invention is: how to provide a calculation method for inverting the soil erosion rate of sloping farmland based on wall measures, so as to avoid the real-time collection and subsequent processing of eroded sediment during rainfall by existing measurement methods, and provide a wall measure that can preserve the eroded sediment information of sloping farmland and prevent soil and water loss in the sloping farmland that is the measurement target; the second purpose is to obtain a quantitative process and method for inverting the long-term soil erosion rate of sloping farmland through the said wall measures.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions: A method for calculating soil erosion rate of sloping farmland based on wall measures, characterized by comprising the following steps: 1) Select the target sloping farmland according to the process requirements; 2) According to the process requirements, a wall is set up around the target sloping farmland; the wall is composed of a top wall, a bottom wall, a left wall, and a right wall. The top wall is located at the top of the target sloping farmland. The left and right ends of the top wall are connected to one end of the left wall and the right wall respectively. The other ends of the left wall and the right wall are connected to the two ends of the bottom wall respectively. The bottom wall is located at the bottom of the target sloping farmland. 3) After each rainfall, a 3D laser scanner is used to obtain a digital elevation model of the sloping farmland within the fence; 4) Using the 3D Analyst tool in ArcGIS software, draw longitudinal profile lines along the slope of the sloping farmland at intervals of 1-2 m from left to right, based on the width of the sloping farmland plots; 5) Export the longitudinal section line data. Select a point on the inner wall surface of the bottom wall as the coordinate origin. The horizontal coordinate of a point in the target sloping farmland is the horizontal distance from the origin, and the vertical coordinate is the height difference relative to the origin. 6) The processed longitudinal profile data were subjected to global optimized least squares linear fitting using the Pwlf library in Python software; 7) By setting the number of fitting segments, iteratively optimizing the slope and intercept of the adjustment segment, and calculating the residual between the fitting curve and the data point, a piecewise linear function that meets the requirements is obtained; 8) By fitting the piecewise linear model, we get the turning point x value, and put it into the fitting function to get the turning point coordinates, which are the erosion-deposition transition points A0, A1, A2, A 3…… A i ; 9) These erosion-deposition conversion points A0, A1, A2, A 3…… Connect them to form the conversion curve A0A i ; 10) The longitudinal section lines A0B, A1B, A 21 B、A3B、 …… A iB, approximating a straight line, uses the following geometric method to calculate the longitudinal section area S of the sedimentation area; When the original slope of the sedimentation area is straight: S=1 / 2d AB ×h BC ×sin(a) When the original slope of the sedimentation area is convex: S=1 / 2d AB ×h BC ×sin(a)- 1 / 2d AC ×h EAC When the original slope of the sedimentation area is concave: S=1 / 2d AB ×h BC ×sin(a)+ 1 / 2d AC ×h DAC Where: d AB 、h BC d AC A i B is long, BC is high, A i C is the length; BC is the height which can be obtained from RTK or tape measurement data. a is A i The sum of the slope of B and 90°; h EAC 、h DAC The distances from the convex slope vertex E and the concave slope vertex D to AC are respectively; the length unit is m and the area unit is hm 2 .

[0008] 11) Convert the conversion curve A0A i The area between the bottom wall of the enclosure wall is divided from the turning point A0 into i sections of approximately triangular bodies along the slope of the erosion area toward the bottom wall A0C; 12) Determine the slope type based on the original topography of the left and right side walls of the sedimentary area. Simplify the straight slope, convex slope, and concave slope into triangles. Calculate the cross-sectional area of the sedimentary area and the amount of sediment in the plot through geometric calculations. Let the distance be d i The areas of the two adjacent sections are S i and S i+1 , then the amount of sedimentation between the two profile lines (V i )for: V i =(S i +S i+1 ) × d i / 2 The sedimentation of the plot (V s )for: V s =∑V i 13) Calculate the plot area Ae , the investigation obtains the wall construction years t, and calculates the multi-year average soil erosion rate R in the erosion area: R= ((V s × p) / A e ) / t Where p is the soil bulk density, t = the length of time the fence is in use (years); A further feature is that the top wall, bottom wall, left wall and right wall are straight lines or arbitrary curves.

[0009] A further feature is that the top wall, bottom wall, left wall and right wall are made of clay, stone, brick, or a mixture of stone and brick.

[0010] A further feature is that the bottom wall is located at the downhill position of the target sloping farmland and is substantially perpendicular to the direction of water flow.

[0011] A further characteristic is that, during actual rainfall, if the erosion-deposition conversion curve A0A is observed i , using real-time dynamic carrier phase differential technology to measure and correct the calculated conversion curve A0A i .

[0012] A further feature is that the parameter t is the length of time the wall has been in use, obtained by subtracting the year the wall was built from the year the wall was surveyed.

[0013] The calculation method of soil erosion rate of sloping farmland based on wall measures of the present invention has the following beneficial effects: 1. The wall maintenance measure for inverting soil erosion rates provided by the present invention can effectively prevent soil and water loss on sloping farmland. Soil that flows downward during tillage and hydraulic scouring accumulates in the bottom wall area and is blocked by the bottom wall, essentially preventing it from flowing outward. The wall maintenance measure has easy access to construction materials, a relatively simple manufacturing process, a long-lasting application benefit, and is easy to maintain. 2. By proposing wall maintenance measures, the present invention avoids the collection, drying, and weighing of eroded sediment samples required in traditional runoff plot and indoor soil trough experiments in soil erosion research, providing a convenient operational process and method for inverting soil erosion rates on plots. 3. The present invention achieves the purpose of inverting the soil erosion rate of sloping farmland over many years by constructing fence measures. The results can provide parameters for the soil erosion prediction model and provide theoretical support for soil and water loss prevention measures.

[0014] 4. Compared with existing calculation methods, the overall calculation method of the present invention significantly improves data accuracy, resulting in higher data accuracy, shorter measurement time and higher efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to make the purpose, technical solutions and advantages of the invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings, in which: Figure 1 This is a schematic diagram of the sloping farmland fence measures of the present invention; Figure 2 The figure is a flow chart of the method for inverting soil erosion rate based on wall measures of the present invention. DETAILED DESCRIPTION

[0016] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise stated, the singular forms "a," "the," and "the" used in the present disclosure are intended to include the plural forms, unless the context clearly indicates otherwise. In addition, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. The terms used in this specification are only for describing specific embodiments and are not intended to limit the present invention.

[0017] Example: This embodiment discloses a calculation method for inverting the soil erosion rate of sloping farmland based on fence measures.

[0018] like Figure 1 As shown, the present invention's fence maintenance measures include a fence structure around a target sloping farmland. The fence structure consists of a top wall 1, a bottom wall 2, a left wall 3, and a right wall 4. The top wall 1 is located at the upper end (higher ground) of the target sloping farmland. Left and right walls 3 and 4 are located on either side of the top wall 1, respectively. A bottom wall 2 is located between the left and right walls 3 and 4, with the bottom wall 2 located at the lower end of the target sloping farmland. The fence structure, consisting of the top wall 1, bottom wall 2, left wall 3, and right wall 4, surrounds the target sloping farmland, partially or completely isolating it from the ground outside, creating a closed or semi-closed area (e.g., with an entry or exit door, drainage ditch, or outlet), preventing erosion and sediment from flowing out of the plot during farming or rainfall. The top wall 1, bottom wall 2, left wall 3, and right wall 4 can be straight or curved. The bottom wall 2 is located downslope from the target sloping farmland, perpendicular or substantially perpendicular to the direction of water flow, thereby preventing erosion and sediment from flowing out of the plot.

[0019] The top wall 1, bottom wall 2, left wall 3 and right wall 4 can be made of clay, stone, brick or a mixture thereof, and are mostly rectangular or curved in shape. Their width and height are variable and determined according to the geometric length of the sloping farmland, and their thickness is approximately 20 cm. The top wall 1, bottom wall 2, left wall 3 and right wall 4 can prevent poultry and livestock from entering the walled sloping farmland and damaging crops. The top wall 1 can block the runoff from above from flowing into the walled sloping farmland plot, and the bottom wall 2 can block the eroded sediment from flowing out of the walled sloping farmland plot, thereby preventing soil erosion. The top wall 1, bottom wall 2, left wall 3 and right wall 4 keep the eroded sediment from the sloping farmland within the plot. As rainfall erosion occurs over many years, the actual multi-year soil erosion rate of the sloping farmland can be inverted and calculated based on the height of the sediment accumulated by the bottom wall 2.

[0020] like Figure 1 、 2 As shown, the calculation method of soil erosion rate of sloping farmland based on wall measures includes the following steps: 1) Select target sloping farmland according to process requirements. The target sloping farmland usually has a certain slope, forming a slope to facilitate observation of soil erosion, etc. 2) In accordance with the process requirements, a wall body consisting of a top wall 1, a bottom wall 2, a left wall 3, and a right wall 4 is set up around the target sloping farmland. The aforementioned wall body is set up around the target sloping farmland; the wall body consists of the top wall 1, the bottom wall 2, the left wall 3, and the right wall 4. The top wall 1 is located at the upper end of the target sloping farmland (at a high point in the terrain). The left and right side ends of the top wall 1 are respectively connected to one end of the left wall 3 and the right wall 4. The other ends of the left wall 3 and the right wall 4 are respectively connected to the two ends of the bottom wall 2. The bottom wall 2 is located at the lower end of the target sloping farmland. The wall body consisting of the top wall 1, the bottom wall 2, the left wall 3, and the right wall 4 surrounds the target sloping farmland. The fence partially or completely isolates the target sloping farmland from the ground outside; check whether the fence is closed all around and does not disturb the interior of the sloping farmland; 3) After each rainfall event, a 3D laser scanner was used to obtain a digital elevation model (DEM) of the sloping farmland within the fence. 4) Use the 3D Analyst tool in ArcGIS to draw longitudinal profile lines along the slope of the sloping farmland at intervals of 1-2 meters from left to right, based on the width of the sloping farmland. The specific intervals are determined by the actual conditions of the slope or process requirements, such as 1.1 meters, 1.2 meters, 1.3 meters, 1.4 meters, 1.5 meters, 1.6 meters, 1.7 meters, 1.8 meters, 1.9 meters, 2.0 meters, etc. ArcGIS is a geographic information processing platform developed by Esri. Its 3D Analyst extension module provides three-dimensional surface modeling, spatial analysis, and visualization capabilities, and is currently available.

[0021] 5) Export the longitudinal profile data. Select a point on the inner wall surface of bottom wall 2 as the coordinate origin. Preferably, it should be a point on the inner wall of bottom wall 2 close to the cultivated land surface, or a point where the inner wall of bottom wall 2 intersects the cultivated land surface. The horizontal coordinate of a point in the target sloping cultivated land is the horizontal distance from the origin, and the vertical coordinate is the height difference relative to the origin. 6) The processed longitudinal profile data were subjected to a globally optimized least squares linear fit using the Pwlf library in Python software. The Pwlf library in Python software can perform one-dimensional continuous piecewise linear fitting. By setting an appropriate number of specified line segments and the termination positions of the continuous segmented lines, it can be used to clearly identify the erosion-deposition transition points within sloping farmland plots, which is an existing technology.

[0022] 7) By setting the number of fitting segments, iteratively optimizing the slope and intercept on the adjustment segment, and calculating the residual between the fitting curve and the data points, a piecewise linear function that meets the requirements (optimal) fitting is obtained; 8) By fitting the piecewise linear model, we get the turning point x value, and put it into the fitting function to get the turning point coordinates, which are the erosion-deposition transition points A0, A1, A2, A 3…… A i ; 9) Erosion-deposition transition points A0, A1, A2, A 3…… Connect them to form the conversion curve A0A i ; Conversion curve A0A i The area between the top wall 1 and the slope farmland erosion area is the conversion curve A0A i The area between the bottom wall 2 is the sloping farmland deposition area.

[0023] In actual rainfall, if the erosion-deposition conversion curve A0A can be observed i In case of heavy rain, rainstorm or extremely heavy rain, the conversion curve A0A is corrected by using the Real Time Kinematic (RTK) measurement technology. i ; 10) Draw vertical lines perpendicular to the bottom wall 2 from the longitudinal section lines A0B, A1B, A21B, A3B, ... AiB of the sedimentation area, i.e., through points A0, A1, A2, A3, ... Ai, respectively. All of them are approximately (considered) straight lines. Calculate the longitudinal section area S of the sedimentation area using the following geometric method; When the original slope of the sedimentation area is straight: S=1 / 2d AB ×h BC ×sin(a) When the original slope of the sedimentation area is convex: S=1 / 2d AB ×h BC×sin(a)- 1 / 2d AC ×h EAC When the original slope of the sedimentation area is concave: S=1 / 2d AB ×h BC ×sin(a)+ 1 / 2d AC ×h DAC Where: d AB 、h BC d AC A i B is long, BC is high, A i C is the length; BC is the height which can be obtained from RTK or tape measurement data. a is A i The sum of the slope of B and 90°; h EAC 、h DAC The distances from the convex slope vertex E and the concave slope vertex D to AC respectively; the length unit is m and the area unit is hm 2 .

[0024] In the figure, point A0 is the turning point of erosion-deposition in the longitudinal section line, and is also the turning point on the leftmost side of the erosion-deposition conversion curve in the sloping farmland plot; i Point A is the i-th turning point of the erosion-deposition conversion curve from left to right within the sloping farmland plot; Point B is the intersection of the sloping farmland surface and bottom wall 2 in the longitudinal section line; Point C is the intersection of the bottom wall and the bottom wall 2 after extending to the bottom wall according to the slope of the sloping farmland erosion area; Point D is the vertex of the concave slope of the deposition area; Point E is the vertex of the convex slope of the deposition area.

[0025] 11) Convert the conversion curve A0A i The area between the bottom wall 2 of the enclosure wall, i.e. the sedimentation area, starts from the turning point A0 and follows the slope of the erosion area toward the bottom wall 2 in the direction A0C, dividing the sedimentation area into i sections that are approximately triangular.

[0026] 12) Determine the slope type based on the original topography of the left and right side walls of the sedimentary area. Simplify the straight slope, convex slope, and concave slope into triangles. Calculate the cross-sectional area of the sedimentary area and the amount of sediment in the plot through geometric calculations. Let the distance be d i The areas of the two adjacent sections are S i and S i+1 , then the amount of sedimentation between the two profile lines (V i )for: V i =(S i +S i+1 ) × d i / 2 The sedimentation of the plot (V s )for: Vs =∑V i 13) Calculate the plot area A e , investigate and obtain the years of wall construction t, and calculate the multi-year average soil erosion rate R in the erosion area: R= ((V s × p) / A e ) / t Where p is the soil bulk density, t = the length of time the fence is in use (years), which is the length of time the fence is in use (years) minus the year the fence was built (years) after the fence was surveyed. The obtained parameter R is the multi-year average soil erosion rate in the soil erosion area.

[0027] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the technical solutions. Those skilled in the art should understand that modifications or equivalent replacements of the technical solutions of the present invention that do not depart from the purpose and scope of the technical solutions of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A method for calculating soil erosion rate of sloping farmland based on wall measures, characterized in that: The following steps are involved: 1) Select the target sloping farmland according to the process requirements; 2) According to the process requirements, a wall is set up around the target sloping farmland; the wall is composed of a top wall 1, a bottom wall 2, a left wall 3, and a right wall 4. The top wall 1 is located at the upper end of the target sloping farmland. The left and right ends of the top wall 1 are connected to one end of the left wall 3 and the right wall 4, respectively. The other ends of the left wall 3 and the right wall 4 are connected to the two ends of the bottom wall 2, respectively. The bottom wall 2 is located at the lower end of the target sloping farmland. 3) After each rainfall, a 3D laser scanner is used to obtain a digital elevation model of the sloping farmland within the fence; 4) Using the 3D Analyst tool in ArcGIS software, draw longitudinal profile lines along the slope of the sloping farmland at intervals of 1-2 m from left to right, based on the width of the sloping farmland plot; 5) Export the longitudinal section line data. Select a point on the inner wall surface of bottom wall 2 as the coordinate origin. The horizontal coordinate of a point in the target sloping farmland is the horizontal distance from the origin, and the vertical coordinate is the height difference relative to the origin. 6) The processed longitudinal profile data were subjected to global optimized least squares linear fitting using the Pwlf library in Python software; 7) By setting the number of fitting segments, iteratively optimizing the slope and intercept of the adjustment segment, and calculating the residual between the fitting curve and the data point, a piecewise linear function that meets the requirements is obtained; 8) The turning point x value is obtained by fitting the piecewise linear model, and the turning point coordinates are obtained by inserting it into the fitting function, which are the erosion-deposition transition points A0, A1, A2, A 3…… A i ; 9) These erosion-deposition conversion points A0, A1, A2, A 3…… Connect them to form the conversion curve A0A i ; Conversion curve A0A i The area between the top wall 1 and the slope farmland erosion area is the conversion curve A0A i The area between the bottom wall 2 is the sloping farmland deposition area; 10) The longitudinal section lines A0B, A1B, A 21 B、A3B、 …… A i B, approximating a straight line, uses the following geometric method to calculate the longitudinal section area S of the sedimentation area; When the original slope of the sedimentation area is straight: S=1 / 2d AB ×h BC ×sin(a) When the original slope of the sedimentation area is convex: S=1 / 2d AB ×h BC ×sin(a)- 1 / 2d AC ×h EAC When the original slope of the sedimentation area is concave: S=1 / 2d AB ×h BC ×sin(a)+ 1 / 2d AC ×h DAC Where: d AB 、h BC d AC A i B is long, BC is high, A i C is the length; BC is the height which can be obtained from RTK or tape measurement data. a is A i The sum of the slope of B and 90°; h EAC 、h DAC The distances from the convex slope vertex E and the concave slope vertex D to AC are respectively; the length unit is m and the area unit is hm 2 ; 11) Convert the conversion curve A0A i The area between the bottom wall 2 of the enclosure wall, starting from the turning point A0, follows the slope of the erosion area toward the bottom wall 2 in the direction A0C to divide the deposition area into i sections that are approximately triangular; 12) Determine the slope type based on the original topography of the left and right side walls of the sedimentary area. Simplify the straight slope, convex slope, and concave slope into triangles. Calculate the cross-sectional area of the sedimentary area and the amount of sediment in the plot through geometric calculations. Let the distance be d i The areas of the two adjacent sections are S i and S i+1 , then the amount of sedimentation between the two profile lines (V i )for: V i =(S i +S i+1 )×d i / 2 The sedimentation of the plot (V s )for: In s =∑V i 13) Calculate the plot area A e , the investigation obtains the wall construction years t, and calculates the multi-year average soil erosion rate R in the erosion area: R= ((V s ×p) / A e ) / t Where p is the soil bulk density and t is the length of time the fence will be used (years).

2. The calculation method for calculating the soil erosion rate of sloping farmland based on wall measures according to claim 1, characterized in that: The top wall 1, bottom wall 2, left wall 3 and right wall 4 are straight lines or arbitrary curves.

3. The method for calculating soil erosion rate of sloping farmland based on wall measures according to claim 1, characterized in that: The top wall 1 , bottom wall 2 , left wall 3 and right wall 4 are made of clay, stone, brick, or a mixture of stone and brick.

4. The method for calculating soil erosion rate of sloping farmland based on wall measures according to any one of claims 1 to 3, characterized in that: The bottom wall 2 is located at the downhill position of the target sloping farmland and is substantially perpendicular to the direction of water flow.

5. The method for calculating soil erosion rate of sloping farmland based on wall measures according to any one of claims 1 to 3, characterized in that: During the actual rainfall process, if the erosion-deposition conversion curve A0Ai is observed, the real-time dynamic carrier phase difference technology is used to measure and correct the calculated conversion curve A0Ai.

6. The method for calculating soil erosion rate of sloping farmland based on wall measures according to any one of claims 1 to 3, characterized in that: The parameter t is the length of time the wall has been in use, obtained by subtracting the year the wall was built from the year the wall was surveyed.

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