Estimation method for net exchange capacity of river suspended sand and bed sand

Abstract

The invention discloses a river suspended sediment and bed sediment net exchange capacity estimation method, which comprises the following steps of: determining an estimated value of an isoline of a function psi (x, z) near a bed surface of a river reach to be estimated in a time period to be estimated relative to a slope i of a river channel bottom slope; obtaining measurement data of the longitudinal flow velocity # imgabs0 # of water flow near the bed surface of the river bed of the to-be-estimated river reach in the to-be-estimated time period, or estimating # imgabs1 # data; obtaining the measurement data of the local sand content # imgabs2 # of the water body near the bed surface of the river bed of the to-be-estimated river reach in the to-be-estimated time period, or estimating the data of # imgabs3 #; obtaining measurement data of the length L and the water surface width B of the to-be-estimated river reach; calculating the duration of the to-be-estimated time period; estimating the total net exchange capacity of suspended sand and bed sand of the to-be-estimated river reach in the to-be-estimated time period; according to the method, the net exchange capacity of the suspended sediment and the bed sediment of the river can be relatively accurately estimated.

Description

Technical Field

[0001] The present invention relates to the technical field of water conservancy projects, and particularly to a method for estimating the net exchange amount of suspended sediment and bed sediment in a river. Background Art

[0002] River scouring and silting are important issues in the process of river management, and have an important impact on the sustainable utilization of river water resources. River scouring and silting will cause changes in river depth, affecting the operation of waterways and the normal operation of water conservancy projects. In addition, river scouring and silting may also change the river ecological environment, resulting in adverse consequences such as blocking the river channel, changing the riverbed morphology, and destroying the habitats of aquatic organisms.

[0003] In order to achieve efficient management of rivers, it is often necessary to measure or estimate the scouring and silting levels of river channels in water conservancy work, and one of the keys lies in reasonably and accurately estimating the net exchange amount of suspended sediment and bed sediment in the river.

[0004] At present, the saturation recovery theory is widely used in China to estimate the net exchange amount of suspended sediment and bed sediment in a river. This theory holds that the net exchange amount of suspended sediment and bed sediment is determined by the difference between the sediment concentration in the water body and the sediment-carrying capacity of the water flow, and an artificially defined "saturation recovery coefficient" is introduced to measure the magnitude of the exchange intensity.

[0005] Although the saturation recovery theory is widely applied, its disadvantages cannot be ignored.

[0006] First, the sediment-carrying capacity of the water flow is a completely idealized concept, representing the sediment concentration level when the sediment content in the water body just reaches saturation (neither more nor less). Since it is extremely rare for the sediment content in the actual river to exactly reach saturation, the sediment-carrying capacity of the water flow cannot be determined by on-site measurement in actual work and can only be calculated through completely empirical or semi-theoretical and semi-empirical formulas. Even so, the calculation formulas for the sediment-carrying capacity of the water flow lack unity, and there are more than a dozen common formulas, including the Zhang Ruijin formula, the Sha Yuqing formula, the Fan Jiaye formula, etc. The calculation results of each formula vary greatly.

[0007] Second, the saturation recovery coefficient is an artificially introduced empirical parameter, and its influencing factors are still unclear, and there is no consensus on its understanding among all parties. For example, the research by Dou Guoren and Zhang Qishun shows a contradiction regarding whether the value of the saturation recovery coefficient is less than 1 or greater than 1: Dou Guoren believes from the perspective of probability theory that its value is always less than 1; Zhang Qishun believes from the perspective of kinematics that its value is always greater than 1. There are also researchers, such as Han Qiwei, who compromise and believe that the value of the saturation recovery coefficient can be either greater than 1 or less than 1, with a general range of 0.01 - 10, and it is recommended to take 2 times the empirical value during scouring and 0.5 times during silting, but there is no clear theoretical basis.

[0008] In summary, when using the recovery saturation theory to estimate the net exchange volume between river suspended sediment and bed sediment, there is a wide range and significant subjectivity in the calculation or selection of both the sediment-carrying capacity of the water flow and the recovery saturation coefficient, which requires high experience from the operators. This causes difficulties for those without experience. Summary of the Invention

[0009] The objective of the present invention is to overcome the above deficiencies and provide a method for estimating the net exchange volume between river suspended sediment and bed sediment, so as to obtain a relatively accurate estimation result of the net exchange volume between river suspended sediment and bed sediment, and reasonably reflect the rising and falling trend of the net exchange volume between river suspended sediment and bed sediment over time.

[0010] To solve the above technical problems, the technical solution adopted by the present invention is: a method for estimating the net exchange volume between river suspended sediment and bed sediment, which includes the following steps: a method for estimating the net exchange volume between river suspended sediment and bed sediment, which includes the following steps:

[0011] Step 1: Determine the estimated value of the slope i of the contour line of the function ψ(x, z) near the riverbed surface of the river reach to be estimated with respect to the riverbed slope during the period to be estimated.

[0012] Step 2: Obtain the measured data of the longitudinal water velocity of the water flow near the riverbed surface of the river reach to be estimated during the period to be estimated, or estimate the data of the river reach to be estimated during the period to be estimated. data;

[0013] Step 3: Obtain the measured data of the local sediment concentration of the water body near the riverbed surface of the river reach to be estimated during the period to be estimated, or estimate the data of the river reach to be estimated during the period to be estimated. data;

[0014] Step 4: Obtain the measured data of the length L and water surface width B of the river reach to be estimated.

[0015] Step 5: Calculate the duration Δt = t 末 -t 初 of the period to be estimated, where t 初 and t 末 are the initial and final moments of the period to be estimated respectively.

[0016] Step 6: Estimate the total net exchange volume between the suspended sediment and bed sediment of the river reach to be estimated during the period to be estimated.

[0017] Preferably, in Step 1, the function ψ(x, z) is defined by the following formula:

[0018]

[0019] where x and z are the longitudinal coordinate and vertical coordinate of the river channel respectively; x 0 and z0 are the longitudinal coordinate and the vertical coordinate of the reference point respectively; ω is the settling velocity of sediment; is the longitudinal velocity of the water flow near the riverbed surface; is the local sediment concentration of the water body near the riverbed surface; Γ x and Γ z are the longitudinal and vertical sediment diffusion coefficients respectively.

[0020] Preferably, step 1 specifically includes the following processes:

[0021] Step 1.1: Select the time range of the recent historical data and the duration Δt of the statistical period, and divide the time range into several statistical periods according to Δt;

[0022] Step 1.2: Consult the recent historical measurement data of the flow rate Q of the river reach to be estimated within the selected time range, and determine the values Q 初 and Q 末 of Q at the beginning and end of each statistical period according to the divided statistical periods, and calculate the flow rate variation range r data of the river reach to be estimated within the selected time range accordingly;

[0023] Step 1.3: Consult the recent historical measurement data of the total sediment concentration S of the water body of the river reach to be estimated within the selected time range, and determine the values S 初 and S 末 of S at the beginning and end of each statistical period according to the divided statistical periods, and calculate the slope i of the contour line of the function ψ(x, z) near the riverbed surface of the river reach to be estimated within the selected time range relative to the riverbed slope accordingly;

[0024] Step 1.4: Analyze the correlation between i and r, and determine the functional relationship i = f(r) between i and r;

[0025] Step 1.5: Obtain the measurement data Q 初 and Q 末 of the flow rate Q of the river reach to be estimated corresponding to the initial time t 初 and the end time t 末 of the period to be estimated, and calculate the flow rate variation range r of the river reach to be estimated during the period to be estimated accordingly;

[0026] Step 1.6: Substitute the r obtained in Step 1.5 into the function i = f(r) obtained in Step 1.4 to obtain the estimated value of the slope i of the contour line of the function ψ(x, z) near the riverbed surface of the river reach to be estimated during the period to be estimated.

[0027] More preferably, in step 1.2, according to the values Q 初 and Q 末The formula for calculating the flow rate variation range r data of the river reach to be estimated in each statistical period within the selected time range is as follows:

[0028]

[0029] In the formula, Q 初 and Q 末 are the flow rates of the river reach to be estimated at the beginning and end of each statistical period respectively.

[0030] More preferably, in step 1.3, the specific steps for calculating the slope i of the contour line of the function ψ(x, z) near the riverbed surface of the river reach to be estimated with respect to the riverbed slope in each statistical period within the selected time range according to the values S 初 and S 末 of the total sediment concentration S of the water body in the river reach to be estimated at the beginning and end of each statistical period are as follows:

[0031] Step 1.3.1: Consult the recent historical measurement data of the cross-sectional flow area A and the water surface width B of the river reach to be estimated in each statistical period within the selected time range;

[0032] Step 1.3.2: Consult the recent historical measurement data of the longitudinal flow velocity of the water flow near the riverbed surface of the river reach to be estimated in each statistical period within the selected time range, or estimate the data of the river reach to be estimated in each statistical period within the selected time range;

[0033] Step 1.3.3: Consult the recent historical measurement data of the local sediment concentration of the water body near the riverbed surface of the river reach to be estimated in each statistical period within the selected time range, or estimate the data of the river reach to be estimated in each statistical period within the selected time range;

[0034] Step 1.3.4: Calculate the slope i of the contour line of the function ψ(x, z) near the riverbed surface of the river reach to be estimated with respect to the riverbed slope in each statistical period within the selected time range. The formula is as follows:

[0035]

[0036] In the formula, S 初 and S 末 are the total sediment concentrations of the water body in the river reach to be estimated at the beginning and end of each statistical period respectively; Δt is the duration of each statistical period.

[0037] More preferably, in step 1.3.2, the specific steps for estimating the longitudinal flow velocity data of the water flow near the riverbed surface of the river reach to be estimated in each statistical period within the selected time range are as follows:

[0038] Step 1.3.2.1: Determine the gravitational acceleration g at the location of the river section to be estimated, or use its empirical data;

[0039] Step 1.3.2.2: Consult the recent historical measurement data of the water surface longitudinal slope J and hydraulic radius R of the river section to be estimated for each statistical period within the selected time range;

[0040] Step 1.3.2.3: Calculate the friction velocity u of the river section to be estimated for each statistical period within the selected time range * data, the formula is as follows:

[0041]

[0042] Step 1.3.2.4: Calculate the longitudinal velocity of the water flow near the riverbed surface of the river section to be estimated for each statistical period within the selected time range data, the formula is as follows:

[0043]

[0044] More preferably, in the said Step 1.3.3, estimate the local sediment concentration of the water body near the riverbed surface of the river section to be estimated for each statistical period within the selected time range The specific steps of the data are as follows:

[0045] Step 1.3.3.1: Consult the recent historical measurement data of the density ρ, kinematic viscosity v of the water body near the riverbed surface of the river section to be estimated and the submerged specific weight γ′ of the sediment particles for each statistical period within the selected time range, or use their empirical data; s ;

[0046] Step 1.3.3.2: Consult the recent historical measurement data of the median grain size D of the sediment near the riverbed surface of the river section to be estimated for each statistical period within the selected time range; 50 ;

[0047] Step 1.3.3.3: Calculate the dimensionless number Ξ data characterizing the sediment particle properties of the river section to be estimated for each statistical period within the selected time range, the formula is as follows:

[0048]

[0049] Step 1.3.3.4: Obtain or calculate the critical shear stress τ for the incipient motion of the median grain size sediment particles near the riverbed surface of the river section to be estimated for each statistical period within the selected time range through the Shields critical incipient motion curve cr data, if calculating, the formula is as follows:

[0050] τ cr = γ′ s D 50 {0.13Ξ -0.392exp(-0.015Ξ 2 ) + 0.045[1 - exp(-0.068Ξ)]}

[0051] Step 1.3.3.5: Consult the recent historical measurement data of the flow rate Q, cross-sectional flow area A, hydraulic radius R of the river reach to be estimated, and the particle size D when the cumulative sediment content near the riverbed is 90% for each statistical period within the selected time range; 90 for the recent historical measurement data;

[0052] Step 1.3.3.6: Calculate the pure frictional shear stress τ of the riverbed of the river reach to be estimated on the water flow for each statistical period within the selected time range; f The data, and the formula is as follows:

[0053]

[0054] In the formula, κ is the von Kármán constant; ρ is the density of the water body near the riverbed of the river reach to be estimated for each statistical period within the selected time range obtained by consulting the recent historical measurement data or using empirical data in Step 1.3.3.1;

[0055] Step 1.3.3.7: Calculate the dimensionless number T data characterizing the sediment movement state of the river reach to be estimated for each statistical period within the selected time range, and the formula is as follows:

[0056]

[0057] Step 1.3.3.8: Determine the gravitational acceleration g at the location of the river reach to be estimated, or use its empirical data;

[0058] Step 1.3.3.9: Consult the recent historical measurement data of the longitudinal water surface slope J of the river reach to be estimated for each statistical period within the selected time range;

[0059] Step 1.3.3.10: Calculate the friction velocity u of the river reach to be estimated for each statistical period within the selected time range; * The data, and the formula is as follows:

[0060]

[0061] In the formula, R is the hydraulic radius of the river reach to be estimated for each statistical period within the selected time range obtained by consulting the recent historical measurement data in Step 1.3.3.5;

[0062] Step 1.3.3.11: Calculate the equivalent roughness k of the riverbed of the river reach to be estimated for each statistical period within the selected time range; s The data, and the formula is as follows:

[0063]

[0064] In the formula, Q and A are respectively the flow rate and the cross-sectional flow area of the river reach to be estimated in each statistical period within the selected time range obtained by consulting the recent historical measurement data in Step 1.3.3.5;

[0065] Step 1.3.3.12: Calculate the local sediment concentration of the water body near the riverbed surface of the river reach to be estimated in each statistical period within the selected time range Data, the formula is as follows:

[0066]

[0067] Preferably, in Step 1.5, according to the initial time t 初 and the final time t 末 of the period to be estimated, the measured data Q 初 and Q 末 of the flow rate Q of the river reach to be estimated, the formula for calculating the flow rate variation range r of the river reach to be estimated in the period to be estimated is as follows:

[0068]

[0069] In the formula, Q 初 and Q 末 are respectively the flow rates of the river reach to be estimated corresponding to the initial time t 初 and the final time t 末 of the period to be estimated.

[0070] Preferably, in Step 2, the specific steps for estimating the longitudinal flow velocity of the water flow near the riverbed surface of the river reach to be estimated in the period to be estimated are as follows: Data are as follows:

[0071] Step 2.1: Determine the acceleration due to gravity g at the location of the river reach to be estimated, or use its empirical data;

[0072] Step 2.2: Obtain the measured data of the longitudinal water surface slope J and the hydraulic radius R of the river reach to be estimated in the period to be estimated;

[0073] Step 2.3: Calculate the friction velocity u * of the river reach to be estimated in the period to be estimated, the formula is as follows:

[0074]

[0075] Step 2.4: Calculate the longitudinal flow velocity of the water flow near the riverbed surface of the river reach to be estimated in the period to be estimated, the formula is as follows:

[0076]

[0077] Preferably, in Step 3, the specific steps for estimating the local sediment concentration of the water body near the riverbed surface of the river reach to be estimated in the period to be estimated are as follows: Data are as follows:

[0078] Step 3.1: Obtain the measurement data of the density ρ, kinematic viscosity v of the water body near the riverbed surface of the river reach to be estimated during the period to be estimated, and the submerged unit weight γ′ of the sediment particles, or use their empirical data; s of the measurement data, or use their empirical data;

[0079] Step 3.2: Obtain the measurement data of the median grain size D of the sediment near the riverbed surface of the river reach to be estimated during the period to be estimated; 50 of the measurement data;

[0080] Step 3.3: Calculate the dimensionless number Ξ data characterizing the sediment particle properties of the river reach to be estimated during the period to be estimated. The formula is as follows:

[0081]

[0082] Step 3.4: Obtain or calculate the critical shear stress τ for the incipient motion of the sediment particles with median grain size near the riverbed surface of the river reach to be estimated during the period to be estimated through the Shields critical incipient motion curve. If calculated, the formula is as follows: cr data, if calculated, the formula is as follows:

[0083] τ cr = γ′ s D 50 {0.13Ξ -0.392 exp(-0.015Ξ 2 ) + 0.045[1 - exp(-0.068Ξ)]}

[0084] Step 3.5: Obtain the measurement data of the flow rate Q, cross-sectional flow area A, hydraulic radius R of the river reach to be estimated during the period to be estimated, and the grain size D when the cumulative sediment content near the riverbed surface is 90%; 90 of the measurement data;

[0085] Step 3.6: Calculate the pure frictional shear stress τ of the riverbed surface of the river reach to be estimated during the period to be estimated. The data is calculated by the following formula: f data, the formula is as follows:

[0086]

[0087] In the formula, κ is the von Kármán constant; ρ is the density of the water body near the riverbed surface of the river reach to be estimated during the period to be estimated obtained in Step 3.1;

[0088] Step 3.7: Calculate the dimensionless number T data characterizing the sediment motion state of the river reach to be estimated during the period to be estimated. The formula is as follows:

[0089]

[0090] Step 3.8: Determine the acceleration due to gravity g at the location of the river reach to be estimated, or use its empirical data;

[0091] Step 3.9: Obtain the measurement data of the longitudinal water surface slope J of the river reach to be estimated during the period to be estimated;

[0092] Step 3.10: Calculate the friction velocity u of the river reach to be estimated during the period to be estimated * data, the formula is as follows:

[0093]

[0094] In the formula, R is the hydraulic radius of the river reach to be estimated during the period to be estimated obtained in Step 3.5;

[0095] Step 3.11: Calculate the equivalent roughness k of the river bed surface of the river reach to be estimated during the period to be estimated s data, the formula is as follows:

[0096]

[0097] In the formula, Q and A are respectively the flow rate and the cross-sectional flow area of the river reach to be estimated during the period to be estimated obtained in Step 3.5;

[0098] Step 3.12: Calculate the local sediment concentration of the water body near the river bed surface of the river reach to be estimated during the period to be estimated data, the formula is as follows:

[0099]

[0100] Advantages of the present invention:

[0101] 1. The method of the present invention can be used to estimate the net exchange amount of suspended sediment and bed sediment in rivers. Compared with the previous estimation methods, its main parameters i, have clear physical meanings. Among them, and are easy to obtain through on-site measurement or theoretical formula estimation, and i is easy to obtain through statistical analysis of historical data, avoiding the deviation caused by subjective experience.

[0102] 2. The operation steps or calculation process of the method of the present invention are simple, clear, logically rigorous, easy to understand and operate. Even technical personnel without a professional background can quickly master and proficiently apply it.

[0103] 3. The method of the present invention is not limited to specific river types or hydrological conditions and can be applied to different river environments, such as: different flow rates, different river channel morphologies, different sediment characteristics, etc.

[0104] 4. Using the method of the present invention to estimate the net exchange amount of suspended sediment and bed sediment in rivers can not only obtain relatively accurate estimation results, but also reasonably reflect the fluctuation trend of the net exchange amount of suspended sediment and bed sediment in rivers over time, thus providing a more reliable basis for the management and decision-making of water conservancy projects. Description of the Drawings

[0105] Figure 1 It is a flow chart of an estimation method for the net exchange volume of suspended sediment and bed sediment in a river;

[0106] Figure 2 It is a flow chart for estimating the slope i of the contour line of the function ψ(x,z) near the riverbed surface of the reach to be estimated with respect to the riverbed slope during the period to be estimated in step 1;

[0107] Figure 3 In step 1.3, it is for calculating the slope i of the contour line of the function ψ(x,z) near the riverbed surface of the reach to be estimated with respect to the riverbed slope during each statistical period within the selected time range based on the values S 初 、S 末 of the total sediment concentration S of the water body in the reach to be estimated at the beginning and end of each statistical period within the selected time range;

[0108] Figure 4 It is a flow chart for estimating the longitudinal flow velocity data of the water flow near the riverbed surface of the reach to be estimated during each statistical period within the selected time range in step 1.3.2;

[0109] Figure 5 It is a flow chart for estimating the local sediment concentration data of the water body near the riverbed surface of the reach to be estimated during each statistical period within the selected time range in step 1.3.3;

[0110] Figure 6 It is a flow chart for estimating the longitudinal flow velocity data of the water flow near the riverbed surface of the reach to be estimated during the period to be estimated in step 2;

[0111] Figure 7 It is a flow chart for estimating the local sediment concentration data of the water body near the riverbed surface of the reach to be estimated during the period to be estimated in step 3;

[0112] Figure 8 It is the function i = f(r) determined by daily statistical analysis of the measurement data of the Zhutuo section of the Yangtze River from 2003 to 2004;

[0113] Figure 9 It is the comparison situation between the daily net exchange volume process line of suspended sediment and bed sediment in the Zhutuo section of the Yangtze River in 2005 estimated by using the technical solution of the present invention and the measured data process line;

[0114] Figure 10 It is the comparison situation between the daily net exchange volume of suspended sediment and bed sediment in the Zhutuo section of the Yangtze River in 2005 estimated by using the technical solution of the present invention and the measured data. Specific implementation mode

[0115] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0116] Embodiment 1: In this embodiment, starting from the two-dimensional vertical convection-diffusion equation satisfied by the suspended sediment movement near the riverbed surface, formula derivation is carried out through appropriate assumptions and simplifications, and a technical solution is constructed based on the derived formula. The brief derivation process is as follows:

[0117] For simplicity, the vertical flow velocity, which is generally extremely small in actual situations near the riverbed surface, is ignored, and the equation is approximately simplified to a steady motion situation for processing. The form of the two-dimensional vertical convection-diffusion equation satisfied by the suspended sediment movement near the bed surface is

[0118]

[0119] In the formula, x and z are the longitudinal coordinate and the vertical coordinate of the river channel respectively; ω is the settling velocity of the sediment; is the longitudinal flow velocity of the water near the riverbed surface; is the local sediment concentration of the water body near the riverbed surface; Γ x and Γ z are the longitudinal and vertical sediment diffusion coefficients respectively.

[0120] After transposing and arranging Equation (1), we get

[0121]

[0122] Assume that there exists a function ψ(x, z), whose second-order mixed partial derivatives with respect to x and z are continuous, so the derivative operations can be exchanged. Then, we have

[0123]

[0124] Comparing Equation (2) and Equation (3), we can see that

[0125]

[0126] According to Equation (4) and Equation (5), the total differential dψ of the function ψ(x, z) has the following form:

[0127]

[0128] In other words, the defining formula of ψ(x, z) is

[0129]

[0130] In the formula, x 0 and z 0 are the longitudinal coordinate and the vertical coordinate of the reference point respectively, and the reference point can be arbitrarily selected.

[0131] Now, select an isoline of the function ψ(x, z) near the riverbed, which should satisfy

[0132]

[0133] Denote the slope of this isoline relative to the riverbed slope as i. Then, we have

[0134] dz = i dx (9)

[0135] Substitute Equation (9) into Equation (8), we get

[0136]

[0137] This means that the part in the brackets of Equation (10) must be equal to zero. Thus, we further obtain

[0138]

[0139] According to the basic principles of river dynamics, the subsidence amount W per unit area of the riverbed per unit time 沉 should be equal to the product of the sediment settling velocity ω and the sediment concentration near the riverbed surface, that is

[0140]

[0141] On the other hand, the uplift amount W of the bed sediment per unit area of the riverbed per unit time 浮 should consider the vertical diffusion effect of the sediment near the riverbed surface, and we have

[0142]

[0143] Since is theoretically less than zero, a negative sign is introduced in Equation (13).

[0144] For the convenience of later explanation, it is considered that when the uplift amount of the bed sediment is more than the subsidence amount of the suspended sediment, the net exchange amount W of the suspended sediment and the bed sediment per unit area of the riverbed per unit time takes a positive value; otherwise, it takes a negative value. Thus, according to Equations (12) and (13), the net exchange amount W of the suspended sediment and the bed sediment per unit area of the riverbed per unit time should be expressed as

[0145]

[0146] The W expressed by Equation (14) is exactly the expression on the left side of the equal sign in Equation (11). Thus, substitute Equation (14) into Equation (11), we get

[0147]

[0148] The sediment concentration near the riverbed surface usually does not change significantly along the flow direction, so it can be approximately taken as Thus, Equation (15) can be further simplified to

[0149]

[0150] Assuming that the exchange property between suspended sediment and bed sediment on the river bed of the river reach under investigation is invariant in space and time, the total net exchange amount between suspended sediment and bed sediment on the river bed of the river reach under investigation during the period under investigation can be calculated as

[0151]

[0152] where Δt is the duration of the period under investigation; L is the length of the river reach under investigation; and B is the water surface width of the river reach under investigation.

[0153] In actual situations, the exchange property between suspended sediment and bed sediment on the river bed of a river reach always varies with time and space, meaning that the values of i and will also vary with time and space. Therefore, theoretically, i and on the right side of Equation (17) should be their average values over the entire river reach during the entire period. However, the cost of obtaining the average values may be too high. Since the estimations in actual water conservancy work often do not require high precision, i and can also take their values at representative times and representative locations.

[0154] The longitudinal velocity of the water flow near the river bed surface and the local sediment concentration of the water body can be obtained through on-site measurement, and and should theoretically be measured on the contour line of the selected ψ(x, z), consistent with i. However, considering again that the estimations in actual water conservancy work often do not require high precision, and it is reasonable as long as they are measured at a certain position close to the bed surface.

[0155] If there are no conditions to carry out and on-site measurement, they can be estimated respectively according to the following methods.

[0156] (1) Estimation of

[0157] Assume that the water flow in the river reach under investigation is fully rough turbulent flow, and its longitudinal velocity u at any depth conforms to the Prandtl-Kármán logarithmic velocity distribution law along the vertical line, that is, there is

[0158]

[0159] In the formula, κ is the Kármán constant, and its value is approximately 0.4; k s is the equivalent roughness of the riverbed surface of the reach under investigation; u * is the friction velocity of the riverbed of the reach under investigation.

[0160] The friction velocity u * can be calculated by the following formula:

[0161]

[0162] In the formula, g is the acceleration due to gravity at the location of the reach under investigation (usually taken as g≈9.81m 2 / s); J is the longitudinal water surface slope of the reach under investigation; R is the hydraulic radius of the reach under investigation (the ratio of the cross-sectional flow area to the wetted perimeter).

[0163] It is considered that the height of the contour line of the taken ψ(x,z) near the riverbed surface is consistent with the equivalent roughness k s , substitute z = k s into formula (17), at this time, it can be obtained

[0164]

[0165] (2) Estimation of:

[0166] Consistent with the estimation of , it is also considered that the height of the contour line of the taken ψ(x,z) near the riverbed surface is consistent with the equivalent roughness k s . The local sediment concentration s of the water body near the bed surface at the height z = k can be estimated by the van Rijn formula, and there is

[0167]

[0168] In the formula, ρ is the density of the water body of the reach under investigation; D 50 is the median grain size of the sediment near the riverbed surface of the reach under investigation (i.e., the grain size when the cumulative content is 50%); Ξ and T are dimensionless numbers characterizing the sediment particle characteristics and movement states of the reach under investigation.

[0169] Ξ has the following form:

[0170]

[0171] In the formula, γ′ s is the submerged specific weight of the sediment particles of the reach under investigation (i.e., the difference between the specific weight of the sediment particles and the specific weight of water); v is the kinematic viscosity of the water of the reach under investigation.

[0172] T has the following form:

[0173]

[0174] where τ f is the pure frictional shear stress (grain resistance) of the riverbed surface of the reach under investigation; τ cr is the critical shear stress for the incipient motion of the median-size sediment particles near the riverbed surface of the reach under investigation.

[0175] τ f Under the assumption that the flow in the reach under investigation is fully rough turbulent flow and the longitudinal velocity u at any depth conforms to the Prandtl-Kármán logarithmic velocity distribution law along the vertical line, it can be calculated by the following formula:

[0176]

[0177] where Q is the flow rate of the reach under investigation; A is the cross-sectional flow area of the reach under investigation; D 90 is the particle size when the cumulative sediment content near the riverbed surface of the reach under investigation is 90%, and 3D 90 is the value of the grain roughness recommended by van Rijn. The meanings of the other symbols are as described above.

[0178] τ cr can be obtained from the Shields critical incipient motion curve or calculated using the following Yalin formula:

[0179] τ cr =γ′ s D 50 {0.13Ξ -0.392 exp(-0.015Ξ 2 ) + 0.045[1 - exp(-0.068Ξ)]} (25)

[0180] The meanings of the symbols in the formula are as described above.

[0181] As for k s in formula (21), under the assumption that the flow in the reach under investigation is fully rough turbulent flow and the longitudinal velocity u at any depth conforms to the Prandtl-Kármán logarithmic velocity distribution law along the vertical line, it can be calculated by the following formula:

[0182]

[0183] The meanings of the symbols in the formula are as described above, and u is also calculated according to formula (19).

[0184] Thus, combining equations (22) to (26), the estimation can be made according to equation (21).

[0185] In the above and estimation methods, Q and J are generally obtained through on-site measurement; A and R are generally determined based on the underwater topography of the river reach on the basis of obtaining the water level Z through on-site measurement (if there is no underwater topography data of the river reach, additional underwater topography surveys of the river reach need to be carried out, or appropriate techniques are used to estimate the underwater topography of the river reach); D 50 and D 90 are generally obtained through sediment particle size distribution analysis after sampling sediment on-site; the water body physical parameters ρ, v and the sediment physical parameter γ′ s can obtain relatively accurate data through sampling and measurement of the water body and sediment on-site, or empirical values can also be used (for example, ρ = 1000 kg / m 3 ; v = 1.0×10 -6 m 2 / s; γ′ s = 16.2 kN / m 3 ).

[0186] To estimate the net exchange amount W 总 of suspended sediment and bed sediment on the river bed of the river reach through equation (17), it is also necessary to know the slope i of the contour line of the function ψ(x, z) near the river bed surface taken with respect to the river bed slope. In addition to being related to the morphology of the river reach itself, under uniform flow conditions, i mainly depends on the change of the incoming flow discharge. Specifically, when the incoming flow discharge is greater than the discharge of the river reach itself, the discharge of the river reach will rise and the hydrodynamic force will increase. At this time, i will also become steeper (steeper than the river bed slope), and the upward floating amount of bed sediment is more than the downward sinking amount of suspended sediment, and the river reach shows erosion; when the incoming flow discharge is less than the discharge of the river reach itself, the discharge of the river reach will fall and the hydrodynamic force will weaken. At this time, i will also become gentler (gentler than the river bed slope), and the upward floating amount of bed sediment is less than the downward sinking amount of suspended sediment, and the river reach shows deposition.

[0187] i can obtain the statistical result applicable to the river reach by statistically analyzing the correlation between its recent historical data and the recent historical data of the river reach discharge variation range r. Among them, the river reach discharge variation range r should preferably use a relative value and is calculated according to the following formula:

[0188]

[0189] In the formula, r is the river reach discharge variation range during the investigated period; Q 初 and Q 末 are the river reach discharges at the beginning and end of the investigated period respectively.

[0190] When Equation (27) is used for statistical work, considering the statistical accuracy and the convenience of actual work, the duration of the statistical period Δt can be one day, three days, five days, seven days, etc., and should not be higher; Q 初 and Q 末 Adopt historical data obtained from recent on-site measurements.

[0191] i cannot be directly obtained through on-site measurement at present, so its recent historical data needs to be W 总 Based on the recent historical data of, and obtained by back-calculation using Equation (17). Wherein: and The recent historical data of can either adopt the historical data obtained from recent on-site measurements or, according to the aforementioned estimation method, be estimated based on the recent historical data of parameters such as ρ, v, γ′ s , D 50 , D 90 , Q, J, A, R, etc. In particular, considering that the physical properties of water and sediment in the river reach generally do not change significantly recently, ρ, v, γ′ s , D 50 and D 90 can also use the current on-site measurement data to replace their recent historical data; while ρ, v, γ′ s can also use their empirical values. W 总 If the recent historical data of is difficult to obtain through recent on-site measurement, then, on the basis of ignoring the convective-diffusive transport of sediment in the river reach, it is approximately calculated as follows:

[0192] W 总 =(S 末 -S 初 )AL (28)

[0193] In the formula, S 初 and S 末 are the total sediment concentrations of the river reach water body at the beginning and end of the investigated period respectively, and their recent historical data can be obtained through recent on-site measurement.

[0194] Substitute Equation (29) into Equation (17), solve for i, and obtain

[0195]

[0196] The analysis methods for the correlation relationship between i and r include but are not limited to visual curve fitting, regression analysis, machine learning, etc. The principle is to determine the functional relationship i = f(r) between i and r through the scatter relationship formed by the recent historical data of i and the recent historical data of r.

[0197] After obtaining the functional relationship between i and r, i = f(r), the total net exchange amount W of suspended sediment and bed sediment on the riverbed of the reach to be estimated within the time period to be estimated can be estimated according to Equation (17) by observing the change in the flow rate of the reach and combining relevant on-site measurement data. 总 。

[0198] Embodiment 2:

[0199] Appendix Figure 1 is a flow chart of the technical solution of the present invention. For the reach to be estimated under the time period to be estimated, the typical implementation steps of the present invention are as follows:

[0200] Step 1: Determine the estimated value of the slope i of the contour line of the function ψ(x, z) near the riverbed surface of the reach to be estimated with respect to the river bottom slope during the time period to be estimated;

[0201] Step 2: Obtain the measurement data of the longitudinal flow velocity of the water flow near the riverbed surface of the reach to be estimated during the time period to be estimated, or estimate the data of the reach to be estimated during the time period to be estimated; data;

[0202] Step 3: Obtain the measurement data of the local sediment concentration of the water body near the riverbed surface of the reach to be estimated during the time period to be estimated, or estimate the data of the reach to be estimated during the time period to be estimated; data;

[0203] Step 4: Obtain the measurement data of the length L and the water surface width B of the reach to be estimated;

[0204] Step 5: Calculate the duration Δt of the time period to be estimated = t 末 -t 初 , where t 初 and t 末 are the initial time and the end time of the time period to be estimated, respectively;

[0205] Step 6: Estimate the total net exchange amount of suspended sediment and bed sediment of the reach to be estimated during the time period to be estimated

[0206] Further, Appendix Figure 2 is a flow chart for determining the estimated value of the slope i of the contour line of the function ψ(x, z) near the riverbed surface of the reach to be estimated during the time period to be estimated in Step 1. The specific implementation steps are as follows:

[0207] Step 1.1: Select the time range of the recent historical data and the duration Δt of the statistical time period, and divide the time range into several statistical time periods according to Δt;

[0208] Step 1.2: Consult the recent historical measurement data of the flow rate Q of the reach to be estimated within the selected time range, and determine the values Q 初 、Q末 , and calculate the flow amplitude r data of the river section to be estimated in each statistical period within the selected time range accordingly;

[0209] Step 1.3: Consult the recent historical measurement data of the overall sediment content S of the water body in the river section to be estimated within the selected time range, and determine the values of S at the beginning and end of each statistical period, S 初 、S 末 , and calculate the gradient i of the contour line of the function ψ(x, z) near the riverbed surface of the river section to be estimated relative to the riverbed slope within each statistical period within the selected time range accordingly;

[0210] Step 1.4: Analyze the correlation between i and r, and determine the functional relationship between i and r, i = f(r);

[0211] Step 1.5: Obtain the measurement data Q 初 、Q at the initial time t 末 and the end time t of the period to be estimated 初 、Q 末 , and calculate the flow amplitude r of the river section to be estimated during the period to be estimated accordingly;

[0212] Step 1.6: Substitute the r obtained in Step 1.5 into the function i = f(r) obtained in Step 1.4 to obtain the estimated value of the gradient i of the contour line of the function ψ(x, z) near the riverbed surface of the river section to be estimated relative to the riverbed slope during the period to be estimated.

[0213] Furthermore, the method for selecting the time range of the recent historical data and the duration Δt of the statistical period in Step 1.1 is to be artificially selected according to the time length and density of the obtained recent historical data in combination with the accuracy required by the estimation work. Among them, considering the statistical accuracy and the convenience of actual work, the duration Δt of the statistical period is preferably selected as one day, three days, five days, seven days, etc., and should not be higher.

[0214] Furthermore, the specific method for determining the values Q 初 、Q at the beginning and end of each statistical period of Q in Step 1.2 末 is as follows: If the measurement data of the flow Q of the river section to be estimated within the selected time range includes Q 初 、Q 末 values, then directly read them; if the measurement data of the flow Q of the river section to be estimated within the selected time range does not include Q 初 、Q 末 values, then interpolate and obtain them according to the measurement data of the flow Q of the river section to be estimated within the selected time range.

[0215] Furthermore, in Step 1.2, according to the values Q 初 、Q at the beginning and end of each statistical period of the flow Q of the river section to be estimated within the selected time range末 The formula for calculating the flow amplitude r data of the river reach to be estimated in each statistical period within the selected time range is as follows:

[0216]

[0217] In the formula, r is the flow amplitude of the river reach to be estimated in each statistical period; Q 初 and Q 末 are the flows of the river reach to be estimated at the beginning and end of each statistical period, respectively.

[0218] Furthermore, the specific method for determining the values of S at the beginning and end of each statistical period, S 初 , S 末 in step 1.3 according to the divided statistical periods is as follows: If the measurement data of the total sediment concentration S of the water body in the river reach to be estimated within the selected time range includes the values of S 初 , S 末 , then directly read them; if the measurement data of the total sediment concentration S of the water body in the river reach to be estimated within the selected time range does not include the values of S 初 , S 末 , then obtain them by interpolation according to the measurement data of the total sediment concentration S of the water body in the river reach to be estimated within the selected time range.

[0219] Furthermore, appendix Figure 3 is the flow chart for calculating the slope i of the contour line of the function ψ(x, z) near the river bed surface of the river reach to be estimated in each statistical period within the selected time range with respect to the river bed slope according to the values of S at the beginning and end of each statistical period, S 初 , S 末 in step 1.3. The specific implementation steps are as follows:

[0220] Step 1.3.1: Consult the recent historical measurement data of the cross-sectional flow area A and the water surface width B of the river reach to be estimated in each statistical period within the selected time range;

[0221] Step 1.3.2: Consult the recent historical measurement data of the longitudinal flow velocity of the water flow near the river bed surface of the river reach to be estimated in each statistical period within the selected time range, or estimate the data of the river reach to be estimated in each statistical period within the selected time range;

[0222] Step 1.3.3: Consult the recent historical measurement data of the local sediment concentration of the water body near the river bed surface of the river reach to be estimated in each statistical period within the selected time range, or estimate the data of the river reach to be estimated in each statistical period within the selected time range;

[0223] Step 1.3.4: Calculate the slope \(i\) of the contour line of the function \(\psi(x,z)\) near the riverbed of the to-be-estimated river reach in each statistical period within the selected time range with respect to the riverbed slope. The formula is as follows:

[0224]

[0225] In the formula, \(i\) is the slope of the contour line of the function \(\psi(x,z)\) near the riverbed of the to-be-estimated river reach in each statistical period with respect to the riverbed slope; \(S\) 初 and \(S\) 末 are the total sediment concentrations of the water body in the to-be-estimated river reach at the beginning and end of each statistical period respectively; \(\Delta t\) is the duration of each statistical period.

[0226] Furthermore, the recent historical measurement data of the cross-sectional flow area \(A\) retrieved in Step 1.3.1 are generally determined based on the recent historical measurement data of the water level \(Z\) obtained through on-site measurement in combination with the underwater topography of the river reach; the recent historical measurement data of the water surface width \(B\) retrieved are generally obtained through on-site measurement.

[0227] Furthermore, the recent historical measurement data of the longitudinal flow velocity of the water flow near the riverbed retrieved in Step 1.3.2 are generally obtained through on-site measurement.

[0228] Furthermore, the recent historical measurement data of the local sediment concentration of the water body near the riverbed retrieved in Step 1.3.3 are generally obtained through on-site measurement.

[0229] Furthermore, Attachment Figure 4 is a flow chart for estimating the longitudinal flow velocity data of the water flow near the riverbed of the to-be-estimated river reach in each statistical period within the selected time range. The specific implementation steps are as follows:

[0230] Step 1.3.2.1: Determine the gravitational acceleration \(g\) at the location of the to-be-estimated river reach, or use its empirical data;

[0231] Step 1.3.2.2: Retrieve the recent historical measurement data of the longitudinal water surface slope \(J\) and hydraulic radius \(R\) of the to-be-estimated river reach in each statistical period within the selected time range;

[0232] Step 1.3.2.3: Calculate the friction velocity \(u\) * data of the to-be-estimated river reach in each statistical period within the selected time range. The formula is as follows:

[0233]

[0234] Step 1.3.2.4: Calculate the longitudinal flow velocity Data, the formula is as follows:

[0235]

[0236] Further, the method for determining the gravitational acceleration g at the location of the river reach to be estimated in Step 1.3.2.1 is to look up the table according to the latitude of the location of the river reach to be estimated or calculate it according to the relevant formula.

[0237] Further, the recent historical measurement data of the water surface longitudinal slope J consulted in Step 1.3.2.2 is generally obtained through on-site measurement; the recent historical measurement data of the hydraulic radius R consulted is generally determined based on the recent historical measurement data of the water level Z obtained through on-site measurement in combination with the underwater topography of the river reach.

[0238] Further, Appendix Figure 5 is the flowchart for estimating the local sediment concentration of the water body near the riverbed of the river reach to be estimated in each statistical period within the selected time range in Step 1.3.3, and the specific implementation steps are as follows: Data

[0239] Step 1.3.3.1: Consult the recent historical measurement data of the density ρ, kinematic viscosity v of the water body near the riverbed of the river reach to be estimated in each statistical period within the selected time range, and the submerged specific weight γ′ of the sediment particles, or use their empirical data; s of the recent historical measurement data, or use their empirical data;

[0240] Step 1.3.3.2: Consult the recent historical measurement data of the median particle size D 50 of the sediment near the riverbed of the river reach to be estimated in each statistical period within the selected time range;

[0241] Step 1.3.3.3: Calculate the dimensionless number Ξ data characterizing the sediment particle properties of the river reach to be estimated in each statistical period within the selected time range, and the formula is as follows:

[0242]

[0243] Step 1.3.3.4: Obtain or calculate the critical shear stress τ cr data for the incipient motion of the median particle size sediment particles near the riverbed of the river reach to be estimated in each statistical period within the selected time range through the Shields critical incipient motion curve. If calculated, the formula is as follows:

[0244] τ cr = γ′ s D 50 {0.13Ξ -0.392 exp(-0.015Ξ 2 ) + 0.045[1 - exp(-0.068Ξ)]}

[0245] Step 1.3.3.5: Consult the recent historical measurement data of the flow rate Q, cross-sectional flow area A, hydraulic radius R of the river reach to be estimated, and the particle size D when the cumulative sediment content near the riverbed surface is 90% for each statistical period within the selected time range; 90 for the recent historical measurement data;

[0246] Step 1.3.3.6: Calculate the pure frictional shear stress τ of the riverbed surface of the river reach to be estimated for each statistical period within the selected time range; f The data, and the formula is as follows:

[0247]

[0248] In the formula, κ is the von Karman constant, and its value is approximately 0.4; ρ is the density of the water body near the riverbed surface of the river reach to be estimated for each statistical period within the selected time range obtained by consulting the recent historical measurement data or using empirical data in Step 1.3.3.1;

[0249] Step 1.3.3.7: Calculate the dimensionless number T data characterizing the sediment movement state of the river reach to be estimated for each statistical period within the selected time range, and the formula is as follows:

[0250]

[0251] Step 1.3.3.8: Determine the acceleration due to gravity g at the location of the river reach to be estimated, or use its empirical data;

[0252] Step 1.3.3.9: Consult the recent historical measurement data of the longitudinal water surface slope J of the river reach to be estimated for each statistical period within the selected time range;

[0253] Step 1.3.3.10: Calculate the friction velocity u of the river reach to be estimated for each statistical period within the selected time range; * The data, and the formula is as follows:

[0254]

[0255] In the formula, R is the hydraulic radius of the river reach to be estimated for each statistical period within the selected time range obtained by consulting the recent historical measurement data in Step 1.3.3.5;

[0256] Step 1.3.3.11: Calculate the equivalent roughness k of the riverbed surface of the river reach to be estimated for each statistical period within the selected time range; s The data, and the formula is as follows:

[0257]

[0258] In the formula, Q and A are respectively the flow rate and cross-sectional flow area of the river reach to be estimated for each statistical period within the selected time range obtained by consulting the recent historical measurement data in Step 1.3.3.5;

[0259] Step 1.3.3.12: Calculate the local sediment concentration of the water body near the riverbed of the river reach to be estimated for each statistical period within the selected time range. The data, and the formula is as follows:

[0260]

[0261] Furthermore, the density ρ, kinematic viscosity v of the water body near the riverbed and the submerged unit weight γ′ of the sediment particles retrieved in Step 1.3.3.1 s of the recent historical measurement data are generally obtained through on-site measurement.

[0262] Furthermore, the recent historical measurement data of the median particle size D of the sediment near the riverbed retrieved in Step 1.3.3.2 50 and the recent historical measurement data of the particle size D when the cumulative sediment content near the riverbed is 90% retrieved in Step 1.3.3.5 90 are generally obtained by conducting sediment particle size distribution analysis after sampling sediment on-site.

[0263] Furthermore, the recent historical measurement data of the flow rate Q retrieved in Step 1.3.3.5 are generally obtained through on-site measurement; the cross-sectional flow area A and hydraulic radius R retrieved are generally determined based on the recent historical measurement data of the water level Z obtained on-site in combination with the underwater topography of the river reach.

[0264] Furthermore, the method for determining the acceleration due to gravity g at the location of the river reach to be estimated in Step 1.3.3.8 is to look up the table according to the latitude of the location of the river reach to be estimated or calculate according to relevant formulas.

[0265] Furthermore, the recent historical measurement data of the longitudinal water surface slope J retrieved in Step 1.3.3.9 are generally obtained through on-site measurement.

[0266] Furthermore, the methods for analyzing the correlation between i and r in Step 1.4 include, but are not limited to, visual curve fitting, regression analysis, and machine learning, etc.

[0267] Furthermore, the method for obtaining the measurement data Q of the flow rate Q of the river reach to be estimated at the beginning and end of the time period to be estimated in Step 1.5 初 、Q 末 is generally on-site measurement.

[0268] Furthermore, in Step 1.5, according to the measurement data Q of the flow rate Q of the river reach to be estimated corresponding to the initial time t 初 、the end time t 末 of the time period to be estimated, the formula for calculating the flow rate variation amplitude r of the river reach to be estimated during the time period to be estimated is as follows: 初 、Q 末 The formula for calculating the flow rate variation amplitude r of the river reach to be estimated during the time period to be estimated is as follows:

[0269]

[0270] Wherein, Q 初 and Q 末 are respectively the flow rates of the river reach to be estimated corresponding to the initial time t 初 , the end time t 末 of the period to be estimated.

[0271] Furthermore, the method for obtaining the measurement data of the longitudinal flow velocity of the water near the riverbed surface in step 2 is generally on-site measurement.

[0272] Furthermore, Figure 6 is the flow chart for estimating the longitudinal flow velocity data of the water near the riverbed surface of the river reach to be estimated in step 2. The specific implementation steps are as follows:

[0273] Step 2.1: Determine the gravitational acceleration g at the location of the river reach to be estimated, or use its empirical data;

[0274] Step 2.2: Obtain the measurement data of the longitudinal slope J and hydraulic radius R of the water surface of the river reach to be estimated during the period to be estimated;

[0275] Step 2.3: Calculate the friction velocity u * data of the river reach to be estimated during the period to be estimated. The formula is as follows:

[0276]

[0277] Step 2.4: Calculate the longitudinal flow velocity data of the water near the riverbed surface of the river reach to be estimated during the period to be estimated. The formula is as follows:

[0278]

[0279] Furthermore, the method for determining the gravitational acceleration g at the location of the river reach to be estimated in step 2.1 is to look up the table according to the latitude of the location of the river reach to be estimated or calculate according to the relevant formula.

[0280] Furthermore, the method for obtaining the measurement data of the longitudinal slope J of the water surface in step 2.2 is generally on-site measurement; the method for obtaining the measurement data of the hydraulic radius R is generally to first obtain the measurement data of the water level Z through on-site measurement, and then determine R in combination with the underwater topography of the river reach.

[0281] Furthermore, the method for obtaining the measurement data of the local sediment concentration of the water near the riverbed surface in step 3 is generally on-site measurement.

[0282] Furthermore, Figure 7To estimate the local sediment concentration of the water body near the riverbed of the reach to be estimated during the period to be estimated in Step 3 The flowchart of the data, and the specific implementation steps are as follows:

[0283] Step 3.1: Obtain the density ρ, kinematic viscosity v of the water body near the riverbed of the reach to be estimated during the period to be estimated, and the submerged unit weight γ′ of the sediment particles, s measurement data thereof, or use their empirical data;

[0284] Step 3.2: Obtain the measured data of the median grain size D of the sediment near the riverbed of the reach to be estimated during the period to be estimated 50 ;

[0285] Step 3.3: Calculate the dimensionless number Ξ data characterizing the sediment particle properties of the reach to be estimated during the period to be estimated. The formula is as follows:

[0286]

[0287] Step 3.4: Obtain or calculate the critical shear stress τ for the incipient motion of the sediment particles with the median grain size near the riverbed of the reach to be estimated during the period to be estimated through the Shields critical incipient motion curve cr data. If calculated, the formula is as follows:

[0288] τ cr = γ′ s D 50 {0.13Ξ -0.392 exp(-0.015Ξ 2 ) + 0.045[1 - exp(-0.068Ξ)]}

[0289] Step 3.5: Obtain the measured data of the flow rate Q, cross-sectional flow area A, hydraulic radius R of the reach to be estimated during the period to be estimated, and the grain size D when the cumulative sediment content near the riverbed is 90% 90 ;

[0290] Step 3.6: Calculate the pure frictional shear stress τ of the riverbed of the reach to be estimated on the water flow during the period to be estimated f data. The formula is as follows:

[0291]

[0292] In the formula, κ is the von Kármán constant, and its value is about 0.4; ρ is the density of the water body near the riverbed of the reach to be estimated obtained in Step 3.1;

[0293] Step 3.7: Calculate the dimensionless number T data characterizing the sediment movement state of the reach to be estimated during the period to be estimated. The formula is as follows:

[0294]

[0295] Step 3.8: Determine the gravitational acceleration g at the location of the river reach to be estimated, or use its empirical data;

[0296] Step 3.9: Obtain the measurement data of the longitudinal water surface slope J of the river reach to be estimated during the period to be estimated;

[0297] Step 3.10: Calculate the friction velocity u of the river reach to be estimated during the period to be estimated * data, and the formula is as follows:

[0298]

[0299] In the formula, R is the hydraulic radius of the river reach to be estimated during the period to be estimated obtained in Step 3.5;

[0300] Step 3.11: Calculate the equivalent roughness k of the river bed surface of the river reach to be estimated during the period to be estimated s data, and the formula is as follows:

[0301]

[0302] In the formula, Q and A are respectively the flow rate and the cross-sectional flow area of the river reach to be estimated during the period to be estimated obtained in Step 3.5;

[0303] Step 3.12: Calculate the local sediment concentration of the water body near the river bed surface of the river reach to be estimated during the period to be estimated data, and the formula is as follows:

[0304]

[0305] Furthermore, the method for obtaining the measurement data of the density ρ, kinematic viscosity v of the water body near the river bed surface and the submerged specific weight γ′ of the sediment particles in Step 3.1 is generally on-site measurement. s The method for obtaining the measurement data of the median grain size D of the sediment near the river bed surface in Step 3.2 and the measurement data of the grain size D when the cumulative sediment content near the river bed surface reaches 90% obtained in Step 3.5

[0306] is generally to conduct sediment particle size distribution analysis after sampling the sediment on-site. 50 The method for obtaining the measurement data of the median grain size D of the sediment near the river bed surface in Step 3.2 and the measurement data of the grain size D when the cumulative sediment content near the river bed surface reaches 90% obtained in Step 3.5 90 is generally to conduct sediment particle size distribution analysis after sampling the sediment on-site.

[0307] Furthermore, the method for obtaining the measurement data of the flow rate Q in Step 3.5 is generally on-site measurement; the method for obtaining the measurement data of the cross-sectional flow area A and the hydraulic radius R is generally to first obtain the measurement data of the water level Z through on-site measurement, and then determine A and R in combination with the underwater topography of the river reach.

[0308] Furthermore, the method for determining the gravitational acceleration g at the location of the river reach to be estimated in Step 3.8 is to look up the table according to the latitude of the location of the river reach to be estimated or calculate according to the relevant formula.

[0309] Furthermore, the method for obtaining the measured data of the longitudinal water surface slope J in step 3.9 is generally on-site measurement.

[0310] Furthermore, the method for obtaining the measured data of the length L and the water surface width B of the reach to be estimated in step 4 is generally on-site measurement.

[0311] Embodiment 3:

[0312] Apply the technical solution of the present invention to the estimation of the daily net exchange amount of suspended sediment and bed sediment in a 2-kilometer reach near Zhutuo of the Yangtze River in 2005 according to the above implementation steps. Among them, the time range of the recent historical data for determining the functional relationship i = f(r) between the slope i of the contour line of the function ψ(x, z) near the riverbed surface and the range of river flow variation r is selected as 2003 - 2004, and it is statistically counted day by day, that is, the statistical period duration is selected as "one day". The longitudinal velocity of the water flow near the riverbed surface and the local sediment concentration of the water body are both estimated. All the data used for the estimation are daily measured data from 2003 - 2004 (recent historical time range) or 2005 (time range to be estimated) except for the following: gravitational acceleration g, density ρ of the water body near the riverbed surface, kinematic viscosity v, and buoyant unit weight γ' of the sediment particles s Adopt empirical values (g = 9.81 m / s 2 ; ρ = 1000 kg / m 3 ; v = 1.0×10 -6 m 2 / s; γ' s = 16.2 kN / m 3 ); The measured data of the sediment particle size distribution near the riverbed surface are only obtained once a year in 2003, 2004, and 2005, and they are not daily. Since the measurement results show that the particle size distributions of the sediment near the riverbed surface in these three years are very similar, the corresponding median particle size D 50 and the particle size D 90 when the cumulative content is 90% are averaged values of the particle size distribution data of these three years during the estimation process.

[0313] Appendix Figure 8It shows the results of the function i = f(r) determined by the daily statistical analysis of the measurement data of the Zhutuo section of the Yangtze River from 2003 to 2004 in Step 1. Due to the strong influence of random factors on hydrological phenomena and the large random errors in on-site measurements, the distribution of data points in the figure is relatively scattered. Even so, it can still be clearly seen that there is a strong positive correlation between the gradient i of the contour line of the function ψ(x, z) near the riverbed surface and the range of river section flow r, and most of the data points formed by the two fall in the first and third quadrants. Therefore, a linear function passing through the origin is used to fit the data points in the figure, and the result of the function i = f(r) for the Zhutuo section of the Yangtze River is

[0314]

[0315] Using this function, Steps 2 to 8 are continued with each day in 2005 as the period to be estimated, and the estimated data of the daily net exchange amount of suspended sediment and bed sediment in the Zhutuo section of the Yangtze River in 2005 are obtained. Attached Figure 9 It shows the comparison between the hydrograph formed by connecting these estimated data in chronological order and the hydrograph of the measured data. Among them, the measured data are approximately calculated according to Equation (29) on the basis of obtaining the overall sediment content S data of the water body in the Zhutuo section of the Yangtze River in 2005. It can be seen that except for the large differences between the estimated data and the measured data on individual dates, the overall trends of the estimated data hydrograph and the measured data hydrograph match well.

[0316] Attached Figure 10 It further shows the comparison between the estimated data and the measured data of the daily net exchange amount of suspended sediment and bed sediment in the Zhutuo section of the Yangtze River in 2005. It can be seen that although the data points formed by the estimated data and the measured data are somewhat scattered, they are still generally concentrated near the "estimated = measured" diagonal line in the figure. This further indicates that the technical solution of the present invention has considerable rationality and accuracy in estimating the daily net exchange amount of suspended sediment and bed sediment in the Zhutuo section of the Yangtze River in 2005.

[0317] Attached Figure 9 and attached Figure 10 The main reasons for the deviation between the estimated data and the measured data in Figure 7 include two aspects: on the one hand, as an estimation method, there are differences between some assumptions and simplifications made in the process of constructing the technical solution of the present invention and the actual situation, which will inevitably lead to deviations between the estimated data and the measured data; on the other hand,

[0318] The above embodiments are only the preferred technical solutions of the present invention and should not be regarded as limitations on the present invention. The protection scope of the present invention shall be the technical solutions recorded in the claims, including the equivalent replacement solutions of the technical features in the technical solutions recorded in the claims. That is, the equivalent replacement improvements within this scope are also within the protection scope of the present invention.

Claims

1. A method for estimating the net exchange of suspended sediment and bed sediment in a river, characterized by: It includes the following steps: Step 1: Determine the estimated slope i of the contour line of the function ψ(x,z) near the riverbed surface of the river section to be estimated during the estimated period relative to the riverbed slope; Step 2: Obtain the longitudinal flow velocity of the water flow near the riverbed surface of the river section to be estimated during the estimated period The measurement data of the river section to be estimated during the estimated period data; Step 3: Obtain the local sediment content of the water body near the riverbed surface of the river section to be estimated during the estimated period The measurement data of the river section to be estimated during the estimated period data; Step 4: Obtain the measurement data of the length L and water surface width B of the river section to be estimated; Step 5: Calculate the duration of the estimated period Δt = t 末 -t 初 , where t 初 and t 末 are the initial and final moments of the period to be estimated respectively; Step 6: Estimate the total net exchange of suspended sediment and bed sediment in the river section to be estimated during the estimated period 2. The method for estimating the net exchange amount of suspended sediment and bed sediment in a river according to claim 1, characterized in that: In step 1, the function ψ(x,z) is defined as follows: In the formula, x and z are the longitudinal and vertical coordinates of the river channel respectively; x0 and z0 are the longitudinal and vertical coordinates of the reference point respectively; ω is the sedimentation velocity; is the longitudinal velocity of water near the riverbed; is the local sediment content of the water body near the riverbed; Γ x and Γ z are the longitudinal and vertical sediment diffusion coefficients, respectively.

3. A method for estimating the net exchange amount of suspended sediment and bed sediment in a river according to claim 1 or 2, characterized in that: The step 1 specifically includes the following process: Step 1.1: Select the time range of recent historical data and the duration of the statistical period Δt, and divide the time range into several statistical periods according to Δt; Step 1.2: Check the recent historical measurement data of the flow Q of the river section to be estimated within the selected time range, and determine the value Q at the beginning and end of each statistical period according to the statistical period divided. 初 , Q 末 , and calculate the flow variation r data of the river section to be estimated in each statistical period within the selected time range accordingly; Step 1.3: Check the recent historical measurement data of the total sediment content S of the river section to be estimated within the selected time range, and determine the value S of S at the beginning and end of each statistical period according to the statistical period divided. 初 , S 末 , and based on this, calculate the slope i of the contour line of the function ψ(x,z) near the riverbed surface of the river section to be estimated in each statistical period within the selected time range relative to the riverbed slope; Step 1.4: Analyze the correlation between i and r and determine the functional relationship between i and r i = f(r); Step 1.5: Get the initial time t of the period to be estimated 初 , final time t 末 The corresponding measured data Q of the river flow Q to be estimated 初 , Q 末 , and calculate the flow variation r of the river section to be estimated during the estimated period based on this; Step 1.6: Substitute the r obtained in step 1.5 into the function i=f(r) obtained in step 1.4 to obtain an estimate of the slope i of the contour lines of the function ψ(x,z) near the riverbed surface of the river section to be estimated during the estimated period relative to the bottom slope of the river channel.

4. A method for estimating the net exchange of suspended sediment and bed sediment in a river according to claim 3, characterized in that: In step 1.2, the flow rate Q of the river section to be estimated within the selected time range at the beginning and end of each statistical period is calculated. 初 , Q 末 The formula for calculating the flow variation r of the river section to be estimated in each statistical period within the selected time range is: In the formula, Q 初 and Q 末 They are the flow of the river section to be estimated at the beginning and end of each statistical period respectively.

5. The method for estimating the net exchange amount of suspended sediment and bed sediment in a river according to claim 3, characterized in that: In step 1.3, the total sediment content S of the water body of the river section to be estimated within the selected time range at the beginning and end of each statistical period is calculated. 初 , S 末 The specific steps for calculating the slope i of the contour lines of the function ψ(x,z) near the riverbed surface of the river section to be estimated in each statistical period within the selected time range relative to the riverbed slope are as follows: Step 1.3.1: Check the recent historical measurement data of the cross-sectional flow area A and water surface width B of the river section to be estimated in each statistical period within the selected time range; Step 1.3.2: Check the longitudinal flow velocity of the water flow near the riverbed surface of the river section to be estimated in each statistical period within the selected time range Recent historical measurement data, or estimate the river section to be estimated in each statistical period within the selected time range data; Step 1.3.3: Check the local sediment content of the water body near the riverbed of the river section to be estimated in each statistical period within the selected time range Recent historical measurement data, or estimate the river section to be estimated in each statistical period within the selected time range data; Step 1.3.4: Calculate the slope i of the contour line of the function ψ(x,z) near the riverbed surface of the river section to be estimated in each statistical period within the selected time range relative to the riverbed slope. The formula is as follows: In the formula, S 初 and S 末 are the total sediment content of the river section to be estimated at the beginning and end of each statistical period; Δt is the duration of each statistical period.

6. A method for estimating the net exchange of suspended sediment and bed sediment in a river according to claim 5, characterized in that: In step 1.3.2, the longitudinal velocity of the water flow near the riverbed surface of the river section to be estimated in each statistical period within the selected time range is estimated. The specific steps of the data are as follows: Step 1.3.2.1: Determine the gravity acceleration g at the river section to be estimated, or use its empirical data; Step 1.3.2.2: Check the recent historical measurement data of the water surface slope J and hydraulic radius R along the river section to be estimated in each statistical period within the selected time range; Step 1.3.2.3: Calculate the friction flow velocity u of the river section to be estimated in each statistical period within the selected time range * Data, the formula is as follows: Step 1.3.2.4: Calculate the longitudinal velocity of the water flow near the riverbed surface of the river section to be estimated in each statistical period within the selected time range Data, the formula is as follows:

7. A method for estimating the net exchange of suspended sediment and bed sediment in a river according to claim 5, characterized in that: In step 1.3.3, the local sediment content of the water body near the riverbed of the river section to be estimated in each statistical period within the selected time range is estimated. The specific steps of the data are as follows: Step 1.3.3.1: Check the density ρ, kinematic viscosity v and buoyancy density γ of the water body near the riverbed of the river section to be estimated in each statistical period within the selected time range s ′ recent historical measurements of, or empirical data using them; Step 1.3.3.2: Check the median particle size D of the sediment near the riverbed of the river section to be estimated in each statistical period within the selected time range 50 Recent historical measurement data; Step 1.3.3.3: Calculate the dimensionless number Ξ data that characterizes the properties of sediment particles in the river section to be estimated for each statistical period within the selected time range. The formula is as follows: Step 1.3.3.4: Obtain or calculate the critical shear stress τ of the median size of sediment particles near the riverbed surface of the river section to be estimated in each statistical period within the selected time range through the Shields critical start-up curve cr Data, if calculated, the formula is as follows: t cr =c s ′ D 50 {0.13X -0.392 exp(-0.015Ξ 2 )+0.045[1-exp(-0.068Ξ)]} Step 1.3.3.5: Check the flow rate Q, cross-sectional flow area A, hydraulic radius R and particle size D when the cumulative sediment content near the riverbed is 90% for each statistical period within the selected time range. 90 Recent historical measurement data; Step 1.3.3.6: Calculate the pure friction shear stress τ of the riverbed of the river section to be estimated for each statistical period within the selected time range f Data, the formula is as follows: Where κ is the Karman constant; ρ is the density of the water body near the riverbed of the river section to be estimated in each statistical period within the selected time range obtained by consulting recent historical measurement data or using empirical data in step 1.3.3.1; Step 1.3.3.7: Calculate the dimensionless number T data that characterizes the sediment movement state of the river section to be estimated for each statistical period within the selected time range. The formula is as follows: Step 1.3.3.8: Determine the gravity acceleration g at the river section to be estimated, or use its empirical data; Step 1.3.3.9: Check the recent historical measurement data of the water surface slope J along the river section to be estimated in each statistical period within the selected time range; Step 1.3.3.10: Calculate the friction flow velocity u of the river section to be estimated in each statistical period within the selected time range * Data, the formula is as follows: Where R is the hydraulic radius of the river section to be estimated in each statistical period within the selected time range obtained by consulting the recent historical measurement data in step 1.3.3.5; Step 1.3.3.11: Calculate the equivalent roughness k of the riverbed surface of the river section to be estimated in each statistical period within the selected time range s Data, the formula is as follows: Where Q and A are the flow and cross-sectional flow area of ​​the river section to be estimated in each statistical period within the selected time range obtained by consulting the recent historical measurement data in step 1.3.3.5; Step 1.3.3.12: Calculate the local sediment content of the water body near the riverbed surface of the river section to be estimated in each statistical period within the selected time range Data, the formula is as follows:

8. The method for estimating the net exchange of suspended sediment and bed sediment in a river according to claim 3, characterized in that: In step 1.5, according to the initial time t of the estimated period 初 , final time t 末 The corresponding measured data Q of the river flow Q to be estimated 初 , Q 末 The formula for calculating the flow variation r of the river section to be estimated during the estimated period is as follows: In the formula, Q 初 and Q 末 They are the initial time t of the estimated period. 初 , final time t 末 The corresponding flow of the river section to be estimated.

9. The method for estimating the net exchange of suspended sediment and bed sediment in a river according to claim 1, characterized in that: In step 2, the longitudinal velocity of the water flow near the riverbed surface of the river section to be estimated during the estimated period is estimated. The specific steps of the data are as follows: Step 2.1: Determine the gravitational acceleration g at the river section to be estimated, or use its empirical data; Step 2.2: Obtain the measurement data of the water surface slope J and hydraulic radius R along the river section to be estimated during the estimated period; Step 2.3: Calculate the friction flow velocity u of the river section to be estimated during the estimated period * Data, the formula is as follows: Step 2.4: Calculate the longitudinal velocity of the water flow near the riverbed surface of the river section to be estimated during the estimated period Data, the formula is as follows:

10. A method for estimating the net exchange of suspended sediment and bed sediment in a river according to claim 1, characterized in that: In step 3, the local sediment content of the water body near the riverbed of the river section to be estimated during the estimated period is estimated. The specific steps of the data are as follows: Step 3.1: Obtain the density ρ, kinematic viscosity v and buoyancy density γ of the water body near the riverbed of the river section to be estimated during the estimated period s ′ measurement data, or adopt their empirical data; Step 3.2: Obtain the median particle size D of the sediment near the riverbed surface of the river section to be estimated during the estimated period 50 Measurement data; Step 3.3: Calculate the dimensionless number Ξ data that characterizes the properties of sediment particles in the river section to be estimated during the estimated period. The formula is as follows: Step 3.4: Obtain or calculate the critical shear stress τ of the median-size sediment particle near the riverbed surface of the estimated river section during the estimated period through the Shields critical starting curve cr Data, if calculated, the formula is as follows: t cr =c s ′ D 50 {0.13X -0.392 exp(-0.015Ξ 2 )+0.045[1-exp(-0.068Ξ)]} Step 3.5: Obtain the flow rate Q, cross-sectional flow area A, hydraulic radius R, and particle size D when the cumulative sediment content near the riverbed is 90% during the estimated period 90 Measurement data; Step 3.6: Calculate the pure friction shear stress τ of the riverbed on the river section to be estimated during the estimated period f Data, the formula is as follows: Where κ is the Karman constant; ρ is the density of the water body near the riverbed of the river section to be estimated during the estimated period obtained in step 3.1; Step 3.7: Calculate the dimensionless number T data that characterizes the sediment movement state of the river section to be estimated during the estimated period. The formula is as follows: Step 3.8: Determine the gravity acceleration g at the river section to be estimated, or use its empirical data; Step 3.9: Obtain the measurement data of the water surface slope J along the river section to be estimated during the estimated period; Step 3.10: Calculate the friction flow velocity u of the river section to be estimated during the estimated period * Data, the formula is as follows: Where R is the hydraulic radius of the river section to be estimated during the estimated period obtained in step 3.5; Step 3.11: Calculate the equivalent roughness k of the riverbed surface of the river section to be estimated during the estimated period s Data, the formula is as follows: Where Q and A are the flow rate and cross-sectional flow area of ​​the river section to be estimated during the estimated period obtained in step 3.5 respectively; Step 3.12: Calculate the local sediment content of the water body near the riverbed surface of the river section to be estimated during the estimated period Data, the formula is as follows:

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