A dam land siltation slope calculation method based on a watershed terrace spatial pattern

Abstract

This invention discloses a method for calculating the sedimentation gradient of dammed land based on the spatial pattern of terraced fields in a watershed. First, a three-dimensional spatial layout simulation coordinate system for terraced fields within the watershed is constructed. Then, the sedimentation gradient calculation expression for dammed land based on the three-dimensional spatial layout of terraced fields within the watershed is used for calculation. The method can be based on conventional meteorological, hydrological, and watershed characteristic parameters (i.e., average channel width B, water depth h, flow velocity v, and sediment carrying capacity S). * Based on data from various sources, this method simulates, calculates, and predicts the sedimentation gradient changes of dam sites under different rainfall, scale, and operational conditions within a watershed with terraced land distribution. This provides a foundation for other hydraulic sedimentation calculations. The calculation expressions designed using this method have clear physical meanings and are easy to calculate. Verified by measured data, the method demonstrates high accuracy. It can be widely applied to the planning and design of silt-retention dams and the risk analysis and assessment of stormwater and flood safety in the Loess Plateau and other ecological restoration areas worldwide.

Description

Technical Field

[0001] This invention belongs to the technical fields of water conservancy, soil and water conservation, land consolidation, and ecological environment construction engineering. Specifically, it relates to a method for calculating the sediment deposition gradient of dam areas based on the spatial pattern of terraces in a watershed. This method can be used for the analysis, calculation, simulation, prediction, planning, and design of high-level small watershed "slope-gully" composite management projects in the loess hilly and gully areas, which are among the most severely affected by soil erosion in the world, including optimization design and preliminary engineering layout. Background Technology

[0002] Terraces and silt-retention dams, as important water conservation measures for slopes and gullies in watersheds, play a vital role in reducing slope and gully erosion and conserving water and soil. Currently, the Loess Plateau, the region with the most severe soil erosion in the world, has over 60 million mu (approximately 4 million hectares) of terraced fields and over 100,000 silt-retention dams of various types, which have played a significant role in curbing soil erosion and reducing sediment in the Yellow River. However, since the 1990s, the amount of water and sediment entering the Yellow River and its tributaries has decreased significantly. Furthermore, in many watersheds in the southern Loess Plateau, the silt-retention rate is slow due to low upstream water and sediment inflow, necessitating artificial gully filling for land reclamation. With the high-quality development of the Loess Plateau and the Yellow River Basin, the construction of terraces and silt-retention dams has entered a new peak, making the proper layout of terraces and silt-retention dams an urgent issue that needs to be addressed.

[0003] The core of calculating the siltation capacity of silt-retaining dams lies in determining the siltation gradient of the longitudinal cross-section of the channel under different water and sediment inflow conditions, and then performing calculations, simulations, and predictions. Once the relationship between the siltation gradient and the watershed terrace pattern under different water and sediment inflow conditions is determined, other hydraulic characteristic parameters and siltation cross-sectional morphology parameters can be further determined, thereby determining the siltation morphology of the silt-retaining dam and providing important support for land use and the safe regulation of silt-retaining dams. Summary of the Invention

[0004] In order to prevent and reduce regional soil erosion, ensure land safety within the dam control area, and achieve efficient utilization of water and soil resources in the dam control area and the watershed where the silt-retaining dam is located, the purpose of this invention is to provide a method for calculating the siltation gradient of dam land based on the spatial pattern of watershed terraces.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for calculating the siltation gradient of dammed land based on the spatial pattern of terraced fields in a watershed is characterized by the following steps: First, a three-dimensional spatial layout simulation coordinate system of terraced fields in the watershed is constructed, namely: the lowest point of the watershed outlet section is taken as the origin O, the right spiral of 90 degrees in the direction of water flow is taken as the x-axis, the opposite direction of water flow is taken as the y-axis, and the vertical direction of the origin O is taken as the z-axis. The three corresponding spatial distribution parameters of terraced fields are: relative horizontal distance L of terraced fields, layout area ratio A, and layout height. Then, the siltation gradient of dammed land based on the three-dimensional spatial layout of terraced fields in the watershed is calculated using the following formula (1):

[0007] J DB =K TS ·W·S (1)

[0008] In the formula, W is the basic characteristic factor of the watershed, S is the characteristic factor of precipitation and sediment, and K TS A comprehensive coefficient is assigned to the three-dimensional spatial layout of terraces in the watershed; where:

[0009] The comprehensive coefficient K of the three-dimensional spatial layout of terraces in the watershed TS The determination, extraction and calculation of each feature value are performed according to the following formula (2):

[0010]

[0011] In the formula, L is the horizontal distance between the terraces, ranging from 0.1 to 1; A is the area of ​​the terraces, ranging from 0.1 to 1; H r The relative height of the terraces is determined, with a value ranging from 0.1 to 1.

[0012] The measurement, extraction, and calculation of each characteristic value in the basic characteristic factor W of the watershed are calculated using the following formula (3):

[0013] W = ζ 1 / 3 (3)

[0014] In the formula, ζ is the cross-sectional river phase coefficient, and its calculation formula is: Where h is the water depth (m); B is the average width of the channel (m).

[0015] The measurement, extraction, and calculation of each characteristic value in the precipitation-sediment characteristic factor S are calculated using the following formula (4):

[0016]

[0017] In the formula, S * For the force of water flow carrying sand, (kg / m 3 The formula for sediment carrying capacity of water flow, as used by Zhang Ruijin, was adopted. The calculations are performed, where K and m represent the sediment-carrying capacity coefficient and exponent value of the water flow, respectively; g is the acceleration due to gravity, taken as 9.8 m / s².2 ); ω represents the settling velocity of a single sediment particle at the breach point in each section, (m / s); Q is the flow rate, (m³ / s). 3 / s); v is the flow velocity, (m / s), using the uniform flow velocity relationship. The calculation is performed, where n is the Manning coefficient.

[0018] Based on the above-mentioned basic characteristic factors of the watershed W, the characteristic factors of precipitation and sediment S, and the comprehensive coefficient K of the three-dimensional spatial layout of terraces in the watershed. TS After verifying that the relevant data obtained were correct, they were substituted into equation (1), and the comprehensive coefficient K was further adjusted. TS After adjustments and corrections, the sedimentation gradient of the gully sedimentation dam can be calculated based on the spatial distribution of different terraces in the watershed under rainfall conditions.

[0019] According to the present invention, the comprehensive coefficient K for the three-dimensional spatial layout of terraced fields described in equations (1) and (2) is... TS When each terraced field in the watershed is located relative to the watershed outlet (origin), there are corresponding "horizontal distance L (range: 0.1~1), area A (range: 0.1~1), and height H" of the terraced fields. r (Value range: 0.1~1), then the measurement and value are carried out according to their respective value ranges; when there are no terraces in the watershed, then the relative horizontal distance L of the terraces, the relative area A of the terraces, and the relative height H of the terraces in equations (1) and (2) are used. r The values ​​are 0, and the comprehensive coefficient K for the three-dimensional spatial layout of terraces in the watershed is 0. TS Take 2.2 directly, or make further adjustments based on the specific circumstances of different regions.

[0020] The method for calculating the siltation gradient of dammed land based on the spatial pattern of watershed terraces in this invention has the following characteristics:

[0021] ① The physical meaning of the calculation equations is clear, and the theoretical generalization is reasonable.

[0022] ② It has wide applicability, meaning it can be used to estimate, simulate, and predict the sediment deposition gradient of dam sites in engineering projects such as gully cascade land preparation and multi-level slope land preparation in watersheds of different scales.

[0023] ③ The calculation is simple, meaning that all the basic parameters required for the calculation can be measured.

[0024] ④ The calculation accuracy is high. Based on different literature, the measured data of different scale watersheds and corresponding working conditions in the watershed under rainstorm conditions are compared with the estimated data using the present invention, and the verification accuracy is high.

[0025] The resulting technological innovations are:

[0026] ① Solid theoretical foundation

[0027] Based on the principles of water and sediment dynamics and gully-ditch relationships, this study proposes a "method for calculating the sedimentation gradient of dammed areas based on the spatial pattern of terraced fields in a watershed." The theoretical calculation formula is based on water and sediment dynamics, gully-ditch relationships, and the energy consumption principle of sediment transport by water flow. It innovatively links two important water conservation measures in the watershed—slope and gully—into a dynamic relationship. The method boasts a solid theoretical foundation, clear physical meaning of the model, simple calculation methods, and high calculation accuracy.

[0028] ②Easy to obtain parameters

[0029] The basic parameters involved can be calculated by making full use of the hydrological and meteorological parameters of the research area and the characteristics of the watershed itself. The parameters are easy to obtain and can be easily calculated and applied at any time.

[0030] ③ Wide range of applications

[0031] It can be widely used in the planning, design, and risk assessment of slope and gully land reclamation dikes or silt-filled dams and terraces in watersheds of different scales.

[0032] ④ Significant future application benefits

[0033] It can be used to survey, calculate, simulate, and predict relevant parameters for existing terraced and gully land consolidation projects (including silt-retaining dams, watersheds, and tiered land consolidation projects) in different regions and watersheds of varying scales. It can also be used to simulate and predict future sediment deposition changes in downstream dam areas under different working conditions. This optimizes maintenance measures for related projects, saving manpower and material resources. It also optimizes, improves, and promotes the planning, design, construction, and operation management of water conservancy and soil conservation projects. Attached Figure Description

[0034] Figure 1 The three-dimensional spatial coordinate system for simulating terraces in the watershed is constructed. In Figure a, the origin O is the lowest point of the watershed outlet section, the X-axis is the 90-degree rightward spiral of the water flow direction, and the Y-axis is the opposite direction of the water flow. Figures b and c establish a three-dimensional spatial coordinate system with the Z-axis being the direction perpendicular to the origin O.

[0035] Figure 2 This is a verification diagram based on measured data from different scale watersheds and corresponding operating conditions under rainfall conditions, using the dam siltation gradient calculation method of the present invention based on the spatial pattern of watershed terraces.

[0036] Figure 3 This is a technical roadmap for implementing the dam siltation gradient calculation method based on the spatial pattern of watershed terraces, under rainfall conditions, using a real-world engineering case study of the present invention.

[0037] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Detailed Implementation

[0038] The design concept of this invention is based on the principles of hydrodynamics, gully-sediment relationship, and energy consumption in sediment transport. It constructs a comprehensive coefficient K that includes the basic watershed characteristic factor W, the rainfall-sediment characteristic factor S, and the three-dimensional spatial layout coefficient of terraces within the watershed. TS The calculation formula for watershed siltation dams is included. This method is based on meteorological, hydrological, and watershed characteristic parameters (such as average channel width B, water depth h, flow velocity v, and sediment carrying capacity S) measured during the preliminary rainfall period. * Based on the existing methods, this method can calculate, simulate, and predict the sediment deposition ratio reduction of dammed areas in watersheds at different scales and levels of management, and provide a quantitative assessment of corresponding sediment deposition changes in gullies. Its expressions have clear physical meanings, are easy to calculate, have high accuracy, and are widely applicable. This method can be widely applied to the planning, design, and risk assessment of slope and gully land management dikes or silt-filled dams and terraces in watersheds of different scales.

[0039] This embodiment presents a method for calculating the siltation gradient of dammed land based on the spatial pattern of terraced fields in a watershed. First, a three-dimensional spatial layout simulation coordinate system for terraced fields in the watershed is constructed. Figure 1 That is, a three-dimensional spatial coordinate system is established with the lowest point of the outlet section of the watershed as the origin O, the right spiral of 90 degrees in the direction of water flow as the x-axis, the opposite direction of water flow as the y-axis, and the vertical direction of the origin O as the z-axis. The three corresponding spatial distribution parameters of the terraces are: the relative horizontal distance L of the terraces, the proportion of the layout area A, and the layout height. Then, the following formula (1) is used to calculate the siltation gradient of the dam based on the three-dimensional spatial layout of the terraces in the watershed:

[0040] J DB =K TS ·W·S (1)

[0041] In the formula, W is the basic characteristic factor of the watershed, S is the characteristic factor of precipitation and sediment, and K TS A comprehensive coefficient is assigned to the three-dimensional spatial layout of terraces in the watershed; where:

[0042] The comprehensive coefficient K of the three-dimensional spatial layout of terraces in the watershed TS The determination, extraction and calculation of each feature value are performed according to the following formula (2):

[0043]

[0044] In the formula, L is the horizontal distance between the terraces (range: 0.1~1); A is the area of ​​the terraces (range: 0.1~1); H r Set the relative height for the terraces (range: 0.1 to 1).

[0045] The measurement, extraction, and calculation of each characteristic value in the basic characteristic factor W of the watershed are calculated using the following formula (3):

[0046] W = ζ 1 / 3 (3)

[0047] In the formula, ζ is the cross-sectional river phase coefficient, and its calculation formula is: Where h is the water depth (m); B is the average width of the channel (m).

[0048] The measurement, extraction, and calculation of each characteristic value in the precipitation-sediment characteristic factor S are calculated using the following formula (4):

[0049]

[0050] In the formula, S * For the force of water flow carrying sand, (kg / m 3 The formula for sediment carrying capacity of water flow, as used by Zhang Ruijin, was adopted. The calculations are performed, where K and m represent the sediment-carrying capacity coefficient and exponent value of the water flow, respectively; g is the acceleration due to gravity, taken as 9.8 m / s². 2 ); ω represents the settling velocity of a single sediment particle at the breach point in each section, (m / s); Q is the flow rate, (m³ / s). 3 / s); v is the flow velocity, (m / s), using the uniform flow velocity relationship. The calculation is performed, where n is the Manning coefficient.

[0051] Based on the above-mentioned basic characteristic factors of the watershed W, the characteristic factors of precipitation and sediment S, and the comprehensive coefficient K of the three-dimensional spatial layout of terraces in the watershed. TS After verifying that the relevant data obtained were correct, they were substituted into equation (1), and the comprehensive coefficient K was further adjusted. TS After adjustments and corrections, the sedimentation gradient of the gully sedimentation dam can be calculated based on the spatial distribution of different terraces in the watershed under rainfall conditions.

[0052] According to the present invention, the comprehensive coefficient K for the three-dimensional spatial layout of terraced fields proposed in equations (1) and (2) is... TS When each terraced field in the watershed is located relative to the watershed outlet (origin), there are corresponding "horizontal distance L (range: 0.1~1), area A (range: 0.1~1), and height H" of the terraced fields. r (Value range: 0.1~1)”, then the measurement and value shall be determined according to their respective value ranges; when there are no terraces in the watershed, then the relative horizontal distance L of the terraces, the relative area A of the terraces and the relative height H of the terraces in formulas (1) and (2) shall be used. r The values ​​are 0, and the comprehensive coefficient K for the three-dimensional spatial layout of terraces in the watershed is 0. TSTake 2.2 directly, or make further adjustments based on the specific circumstances of different regions.

[0053] The following are specific application examples provided by the inventor.

[0054] Application examples:

[0055] See Figure 2 The Kangjiagelao small watershed (109°20'~109°35'E, 36°21'~36°32'N) in the Yanhe River Basin of the middle reaches of the Yellow River was selected as the research object. The watershed area is 0.35 km². 2 Gully density 3-4 km / km 2 The basin is 0.903 km long, with a maximum width of 0.723 km, an average width of 0.52 km, a shape coefficient of 0.52, and an elevation difference of 189.7 m. A silt-retention dam has been built at the basin outlet. The basin is covered by trees, shrubs, and herbaceous vegetation, with a vegetation coverage exceeding 80%.

[0056] Based on the topographic features of the Kangjiagelao small watershed prototype in 2003 and 2018, a total of 8 terraced fields were constructed, covering a total area of ​​0.163 m². 2 This area accounts for approximately 47.8% of its total area. A silt-retaining dam is constructed at the outlet, serving as the backbone dam at the prototype watershed outlet. Relevant engineering layout parameters are shown in Tables 1 and 2 below.

[0057] Table 1: Basic Parameters for Silt-Retaining Dam Design

[0058]

[0059] Table 2: Basic Parameters for Multi-Level Terraced Field Design

[0060]

[0061] Based on the above research on the watershed overview and basic parameters such as terraces and silt-retention dams, the following steps were taken for surveying and calculation:

[0062] Step 1: The calculation expression for the sedimentation gradient of the dam area based on the three-dimensional spatial layout of terraces in the watershed is shown in the following formula (1).

[0063] J DB =K TS ·W·S (1)

[0064] In the formula, W is the basic characteristic factor of the watershed, S is the characteristic factor of precipitation and sediment, and K TS A comprehensive coefficient is assigned to the three-dimensional spatial layout of terraces in the watershed.

[0065] Step 2: Comprehensive coefficient K for the three-dimensional spatial layout of terraces in the watershed. TSThe measurement, extraction and calculation of each feature value are performed using the following formula (2):

[0066]

[0067] In the formula, L is the horizontal distance between the terraces (range: 0.1~1); A is the area of ​​the terraces (range: 0.1~1); H r Set the relative height for the terraces (range: 0.1 to 1).

[0068] Regarding the values ​​of the corresponding parameters, this embodiment presents a three-dimensional spatial simulation coordinate system for terraces in a watershed. The system is established with the lowest point of the watershed outlet section as the origin O, a 90-degree rightward spiral along the direction of water flow as the X-axis, the opposite direction of water flow as the Y-axis, and the direction perpendicular to the origin O as the Z-axis. The three corresponding spatial distribution parameters for the terraces are: relative horizontal distance between terraces (L), area ratio (A), and height (H). r ).

[0069] Step 3: Measurement, extraction and calculation of each characteristic value in the basic characteristic factor W of the watershed. The calculation formula is as follows (3):

[0070] W = ζ 1 / 3 (3)

[0071] In the formula, ζ is the cross-sectional river phase coefficient, and its calculation formula is: Where h is the water depth (m); B is the average width of the channel (m). Both values ​​were obtained after on-site measurement.

[0072] Step 4: Measurement, extraction, and calculation of each characteristic value in the precipitation-sediment characteristic factor S. The calculation formula is as follows (4):

[0073]

[0074] In the formula, S * For the force of water flow carrying sand, (kg / m 3 The formula for sediment carrying capacity of water flow, as used by Zhang Ruijin, was adopted. The calculations are performed, where K and m represent the sediment-carrying capacity coefficient and exponent value of the water flow, respectively; g is the acceleration due to gravity, taken as 9.8 m / s². 2 ); ω represents the settling velocity of a single sediment particle at the breach point in each section, (m / s); Q is the flow rate, (m³ / s). 3 / s); v is the flow velocity, (m / s), using the uniform flow velocity relationship. The calculation is performed, where n is the Manning coefficient.

[0075] Step 5: After completing steps 1 to 4, adjust and correct the parameters according to the current status of sediment deposition in the watershed channels to obtain the settlement result.

[0076] To further verify the accuracy and applicability of the dam sediment deposition gradient calculated using the dam sediment deposition gradient calculation method based on the spatial pattern of watershed terraces, equation (1) was verified using various data, and the correlation coefficient (R) was used. 2 The formula's conformity, rationality, and feasibility are verified using the Nash coefficient (NSE), root mean square error (RMS), the ratio of the standard deviation of the mean error to the standard deviation of the measured value (RSR), and the percentage deviation (PBIAS). The relevant expressions are shown below, and the verification results are as follows. Figure 3 As shown in Table 3.

[0077]

[0078]

[0079]

[0080]

[0081]

[0082] In the formula, For the i-th observation data, For the i-th simulation data, Y mean The value is the observed average, and n is the number of damage samples; u Ci For calculated value; u Mi These are measured values. NSE ranges from negative infinity to 1. An NSE close to 1 indicates good model simulation results and high model reliability; an NSE close to 0 indicates that the simulation results are close to the average level of the observed values, meaning the overall results are reliable, but the process simulation error is large; an NSE much less than 0 indicates that the model simulation results are unreliable. R 2 The closer the value is to 1, the more accurate the regression model. The minimum value of RMS is 0; the smaller the value, the higher the calculation accuracy. The minimum value of RSR is 0; the lower the value, the better the model simulation results. A negative PBIAS value indicates that the model overestimates the observations; conversely, a positive PBIAS value indicates that the model underestimates the observations.

[0083] Table 3: Accuracy Analysis of Sedimentation Balance Descent of Dam Area under Spatial Distribution Conditions of Terraces

[0084]

[0085]

[0086] Equation (1) was verified using data from the aforementioned sources, including watershed measurements and laboratory physical model simulations, such as... Figure 3 As shown. By Figure 3It can be seen that the overall validation results of the various data are good, and they all fit near the 1:1 regression line. However, there are still large deviations at some points, mainly because of the consideration of different watersheds. When calibrating the spatial parameters of each terrace, a certain degree of data deviation exists. Especially when the terrace construction density is high in the watershed, the spatial parameters are calibrated using the mean values. Overall, this calculation method demonstrates high accuracy across watersheds of varying regions, scales, and levels of management in the Loess Plateau.

[0087] Table 3 summarizes the accuracy evaluation results of Equation (1) of this method under the spatial distribution conditions of different terraces in various watersheds, evaluating the sediment deposition balance gradient of the dam area. Two sets of validation data could not be validated due to insufficient data points. Previous studies have shown that when the simulation results have NSE > 0.50, RSR < 0.70, and |PBIAS| < 25%, the simulation results based on Equation (1) of this method can meet the simulation accuracy requirements. As can be seen from Table 3, the mean values ​​of each accuracy are as follows: R 2 The values ​​are 0.79, NSE is 0.71, RMS is 0.28, RSR is 0.53, and |PBIAS| is 10.07%. This indicates that the method can meet the simulation accuracy requirements for simulating the equilibrium gradient of sediment deposition in dam areas and can realistically reflect the sediment deposition process in dam areas under heavy rainfall conditions in well-managed small watersheds.

[0088] In summary, the dam-land sedimentation gradient calculation method presented in this embodiment, based on the spatial pattern of watershed terraces, is grounded in water and sediment dynamics, gully relationships, and the energy consumption principle of sediment transport. Through a three-dimensional spatial coordinate system derived from the watershed itself, it organically and dynamically links two major engineering projects: slope terraces and gully land management (including silt-retaining dams, watershed systems, and gully tiered land improvement). The proposed formula for calculating dam-land sedimentation gradient can calculate, simulate, and predict gully-dam-land sedimentation gradients under different watershed scales and different engineering layout conditions. This method offers a broad macroscopic description of the watershed, with clear physical meaning in the calculation expressions, simple calculation methods, and high accuracy verified by measured data. It has significant practical value for further optimizing, improving, and promoting the development of related planning, design, construction, and operation management in water conservancy and soil conservation projects.

Claims

1. A method for calculating the siltation gradient of dammed land based on the spatial pattern of watershed terraces, characterized in that, This method first constructs a three-dimensional spatial layout simulation coordinate system for terraces in the watershed, namely: taking the lowest point of the watershed outlet section as the origin. O A 90-degree right-hand spiral in the direction of water flow is x The axial direction is opposite to the direction of water flow. y Axial direction, origin O Vertical direction is z A three-dimensional spatial coordinate system is established along the axis, and the corresponding three spatial distribution parameters of the terraces are: relative horizontal distance between terraces. L The relative layout area of ​​terraced fields A And the layout height, and then use the following formula (1) to calculate the siltation gradient of the dam area based on the three-dimensional spatial layout of terraces in the watershed: （1） In the formula, W As the basic characteristic factors of the watershed, S As characteristic factors of precipitation and sediment, K TS A comprehensive coefficient is assigned to the three-dimensional spatial layout of terraces in the watershed; where: Comprehensive coefficient of three-dimensional spatial layout of terraces in the watershed K TS The determination, extraction and calculation of each feature value are performed according to the following formula (2): （2） In the formula, L The horizontal distance between the terraces is set relative to each other, with a value range of 0.1 to 1. A The relative area of ​​the terraced fields, with a value ranging from 0.1 to 1; H r The relative height of the terraces is set, with a value ranging from 0.1 to 1. Basic characteristic factors of watershed W The determination, extraction and calculation of each feature value in the equation are performed using the following formula (3): （3） In the formula, The facies coefficient of the river section is calculated using the following formula: ,in, h Water depth, unit: m; B The average width of the channel is in meters (m). Rainfall and sediment characteristic factors S The determination, extraction and calculation of each feature value in the equation are performed using the following formula (4): （4） In the formula, The sediment-carrying capacity of water flow is expressed in kg / m³, and is calculated using Zhang Ruijin's formula for sediment-carrying capacity. Perform calculations; K and m These represent the sediment-carrying capacity coefficient and the index value, respectively. g The acceleration due to gravity is taken as 9.8 m / s². 2 ; This indicates the settling velocity of a single particle of sediment at the breach point in each section, in m / s. Q Flow rate, unit: m³ / s; The velocity is expressed in m / s, and the velocity relationship under uniform flow is as follows: Perform calculations. n This is the Manning coefficient; Based on the above-mentioned basic characteristic factors of the watershed W Rainfall and sediment characteristic factors S Comprehensive coefficient of three-dimensional spatial layout of terraces in the watershed K TS After verifying that the relevant data obtained were correct, they were substituted into equation (1), and the comprehensive coefficients were further adjusted. K TS After adjustments and corrections, the sedimentation gradient of the gully sedimentation dam can be calculated based on the spatial distribution of different terraces in the watershed under rainfall conditions.

2. The method as described in claim 1, characterized in that, The comprehensive coefficients for the three-dimensional spatial layout of terraced fields mentioned in equations (1) and (2) K TS This refers to the basic correspondence between the terraces laid out in the watershed and the coordinate system of the watershed outlet: the horizontal distance between the terraces and their respective locations. L Value range: 0.1~1, relative layout area of ​​terraced fields. A Value range: 0.1~1, relative height of terrace layout H r ， The value range is 0.1~1, so the measurement and value are determined according to their respective ranges; when there are no terraces in the watershed, the horizontal distance between the terraces and the terraces in equations (1) and (2) is the same. L The relative layout area of ​​terraced fields A The relative height of the terraced fields H r The values ​​are 0, and the comprehensive coefficient of the three-dimensional spatial layout of terraces in the watershed is... K TS Take 2.2 directly, or make further adjustments based on the specific circumstances of different regions.

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