A method for determining a regulation line for a tidal bifurcated river

Abstract

The present invention relates to a method for determining the regulation line of a tidal bifurcated river channel, comprising: establishing a two-dimensional tidal sediment numerical model, simulating the tidal sediment movement in the regulated river section under typical hydrological conditions, calculating the average ebb tide flow and average ebb tide sediment content in each typical section; calculating the suspended sediment stop flow velocity and bed sand stop flow velocity in the regulated river section; calculating the river width B corresponding to each typical section. i0 ; The river width B at each section i0 Based on the above, the regulation line of the regulated river section is formulated; the tidal and sediment movement of the regulated river section after the implementation of the regulation line is simulated, and the average ebb flow and average ebb sediment content of each typical section after the implementation of the regulation line are calculated; the river width B corresponding to the new tidal and sediment conditions of each typical section after the implementation of the regulation line is calculated i1 ; Compare the river width B at the same section i1 With B i0 ; The river width B at each section i1 Based on this, the final regulation line of the regulated river section is drawn up. This method takes into account the changes in the tidal dynamics of the distributary channel after the regulation project is implemented, and can more accurately determine the river regulation line.

Description

Technical Field

[0001] The present invention relates to the technical field of river channel regulation, and in particular to a method for determining a regulation line for a tidal bifurcated river channel. Background Art

[0002] The regulation line is the boundary line for the layout of river regulation projects. River regulation generally includes flood regulation, reclaimed water regulation, and low-water regulation. Flood regulation primarily involves controlling the safe discharge of floodwaters, such as building levees; reclaimed water regulation primarily involves controlling and directing the flow of river water and stabilizing the river flow, such as building dikes; and low-water regulation primarily involves improving flow conditions and stabilizing water depths during the dry season, such as building spur dikes. Currently, reclaimed water regulation remains a pressing issue due to factors such as reduced sediment inflow at the river estuary and adjustments to river flow. Currently, the reclaimed water regulation line is generally based on a reasonable river width. The reasonable river width of the regulated river section is calculated through a certain river phase relationship, and the river regulation line is then determined. However, this method calculates the reasonable river width using the existing tidal and sediment parameters within the regulated river section, without considering changes in tidal and sediment parameters within the regulated river section after the regulation line is implemented. This results in the proposed bifurcated river regulation line being incompatible with the tidal and sediment dynamics of the river section. In particular, for tidal estuary channels, implementing a regulation project within a channel will cause significant changes in the tidal flow, tidal dynamics, and diversion pattern within that channel. This can result in regulation lines determined based on existing tidal and sediment parameters being unsuitable for the regulated channel. Therefore, it is necessary to develop a method for determining regulation lines for tidal estuaries that takes into account the changes in tidal dynamics within the channel. Summary of the Invention

[0003] In order to overcome the shortcomings of the above-mentioned background technology, the purpose of the present invention is to provide a method for determining the regulation line of a tidal bifurcated river channel, which takes into account the changes in the tidal dynamics of the bifurcated channel after the implementation of the regulation project and can determine the river channel regulation line more accurately.

[0004] To achieve the above object, the present invention is implemented through the following technical solutions:

[0005] The present invention provides a method for determining a regulation line for a tidal bifurcated river channel, comprising the following steps:

[0006] S1: Collect underwater topography, hydrological and sediment data for the regulated river section, establish a two-dimensional tidal and sediment numerical model, and calibrate and verify the model; select typical hydrological conditions to simulate tidal and sediment movement in the regulated river section, with the hydrological conditions including at least one major, medium, and minor tide; arrange a corresponding number of typical sections along the regulated river section at a certain interval along the downstream direction, extract the tidal flow and sediment concentration of each typical section, and calculate the average ebb tidal flow and average ebb sediment concentration of each typical section within a major, medium, and minor tide cycle;

[0007] S2: Based on the measured suspended sediment and bed sediment data, the representative particle size of suspended sediment and bed sediment in the regulated river section is analyzed, and the stopping flow velocity of suspended sediment and bed sediment is calculated;

[0008] S3: Based on the average ebb current flow, average ebb sediment content, and suspended sediment stopping velocity and bed sediment stopping velocity of each section, the Dou Guoren River correlation equation is used to calculate the river width B corresponding to each typical section. i0 ;

[0009] S4: The river width B of each section i0 Based on this, formulate the regulation line of the river section;

[0010] S5: Using the tidal and sediment model established in S1 and the selected hydrological conditions, simulate the tidal and sediment movement in the regulated river section after the regulation line is implemented, extract the tidal flow and sediment concentration processes of each typical section arranged in S1, and calculate the average ebb tide flow and average ebb tide sediment concentration of each typical section during a large, medium and small tidal cycle;

[0011] S6: Based on the average ebb flow and average ebb sediment concentration of each typical section calculated in S5, use the Dou Guoren River correlation formula to calculate the corresponding river width B of each typical section i1 ;

[0012] S7: The river width B of the same section i1 With B i0 Compare; if the river width of each section|(B i1 —B i0 ) / B i0 |≤1%, then B i1 The river width is the reasonable river width of section i; if the river width of a section|(B i1 —B i0 ) / B i0 |>1%, repeat S4 (this time with B i1 Based on the proposed regulation line, B i0 =B i1 ), S5 and S6, until all sections |(B i1 —B i0 ) / B i0 |≤1%;

[0013] S8: The river width B of each section i1 Based on this, the final regulation line of the river section is formulated.

[0014] In the above technical solution, in step S1, the underwater topographic data refers to the river system topographic data measured in recent years for the regulated river section, and the hydrological sediment data includes at least two measured tide levels, flow velocities, tidal volumes, sediment concentrations, and other data. The underwater topographic data and the hydrological sediment data should be measured over roughly the same time period. The governing equations of the two-dimensional tidal sediment numerical model consist of the water flow continuity equation, the water flow motion equation, and the sediment transport equation. The relevant equations can be expressed as:

[0015] 1) Continuity equation of water flow

[0016] (1)

[0017] 2) Water flow equation

[0018] (2)

[0019] (3)

[0020] 3) Sediment transport equation

[0021] (4)

[0022] in,

[0023]

[0024] Where: x and y are Cartesian coordinates, u and v are the components of the vertical average velocity in the x and y directions respectively; h = d + η is the total water depth, d is the still water depth, η is the water level; g is the acceleration due to gravity; is the density of water; f is the Coriolis coefficient; 、 is the bottom stress in the x and y directions, 、 is the surface stress in the x and y directions; T xx 、T xy 、T yy is the horizontal viscous stress; c is the vertical average sediment concentration; 、 is the sediment diffusion coefficient; E is the bed scour term; D is the bed deposition term; is the sediment settling velocity, is the suspended sediment concentration near the bottom, is the probability of settlement, is the bed scour coefficient, is the bed shear stress, is the critical scour shear stress of the bed surface, is the washout index, , is the critical settlement shear stress of the bed surface.

[0025] In the above technical solution, in step S1, typical hydrological conditions refer to those consistent with the river regime changes in the regulated river section. These conditions are generally considered to be those of a normal water year or equivalent to the multi-year average ebb tide. The section spacing is determined based on a combination of the width and length of the regulated river section, generally 0.5 to 2 times the river width. The average ebb tide flow and average ebb sediment concentration of the sections in step S1 are calculated using the flow and sediment concentration of the sections during ebb tides, using the following formulas.

[0026] Average ebb flow The calculation formula is

[0027]

[0028] Where: , For adjacent , The ebb flow at the moment. 、 It is the time for rest during rising and falling.

[0029] Average sand content The calculation formula is

[0030]

[0031] Where: , For adjacent , The sand content at low tide at that moment.

[0032] In the above technical solution, in step S2, the representative particle size refers to the particle size of the sediment larger and smaller than a certain particle size that accounts for 50% of the total weight of the sand sample. The suspended sediment stopping velocity is calculated using the representative particle size of suspended sediment. The bottom sand stopping velocity is calculated using the bottom sand representative particle size. .

[0033] In the above technical solution, in step S3, the river width calculation formula in the Dou Guoren River correlation is as follows:

[0034]

[0035] Where b is the proportionality coefficient, which is 0.15; β is the tidal coefficient, which is 1.0 for the river section without tidal bore; g is the acceleration of gravity, which is 9.81 m / s 2 ; is the suspended sediment stopping velocity; is the average low tide sediment concentration in a calculation period; is the average ebb current in one calculation period; is the sand-carrying coefficient, which is taken as 4.0; is the relative stability coefficient of the riverbank and riverbed soil, which is taken as 1.0; is the bottom sand stopping flow velocity;

[0036] In the above technical solution, in step S3, the river width B corresponding to each typical section i0 , subscript i is the section number, generally represented as 1, 2, 3..., and subscript 0 represents the initial condition. i0 Generally expressed as B 10 、B 20 、B 30 、B 40 ...B n0 .

[0037] In the above technical solution, in step S4, the regulation line is planned to be the river width B i0 As the basis, it is smooth and appropriate.

[0038] In the above technical solution, in step S6, the river width B corresponding to each typical section i1 , subscript i is the section number, generally represented as 1, 2, 3..., subscript 1 represents the initial regulation line after the implementation of the tidal sediment dynamics change. i0 Generally expressed as B 11 、B 21 、B 31 、B 41 ...B n1 .

[0039] In the above technical solution, in step S7, repeating S4 is to increase the river width B of each section i1 Re-assume the new B i0 Based on this river width, the regulation line of the regulated river section is drawn up, and then S5 and S6 are repeated to obtain the new B i1 .

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] (1) The present invention takes into account that after the regulation of a tidal bifurcated river channel, the tidal dynamics within the channel will change significantly. The regulation line formulated based on full consideration of this change is closer to reality. Traditional methods do not consider the changes in tidal sediment dynamics. The regulation line formulated will not be able to adapt to the tidal sediment dynamic conditions of the channel after regulation, resulting in the inability to form a relatively good channel shape after regulation.

[0042] (2) The technical route of the present invention is clear, the technical method is relatively simple, and there is no complicated processing process. After collecting the basic hydrological and sediment data of the regulated river section, the river regulation line can be quickly determined with high accuracy according to the process of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 The figure is a flow chart of a method for determining a regulation line of a tidal bifurcated river channel according to the present invention.

[0044] Figure 2 This is the grid map of the two-dimensional tidal sediment model of the Yangtze River Estuary.

[0045] Figure 3 This is the current status map of the regulated river section of the northern branch of the Yangtze River Estuary.

[0046] Figure 4 This is a schematic diagram of the research on the regulation line of the northern branch of the Yangtze River Estuary. DETAILED DESCRIPTION

[0047] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0048] like Figure 1 As shown in the figure, this implementation case is mainly used to determine the regulation line of the North Branch of the Yangtze River Estuary, and includes the following steps:

[0049] Step S1: Collect underwater topographic data of the Yangtze River Estuary in 2016 and hydrological and sediment data in 2016 and 2017, and establish a two-dimensional tidal and sediment numerical model of the Yangtze River Estuary (see Figure 2 The 2016 and 2017 hydrological and sediment data were used to calibrate and verify the tidal current, tide level, and sediment content of the two-dimensional tidal sediment numerical model of the Yangtze River Estuary. The period from September 15 to September 30, 2002, was selected as the typical hydrological conditions to carry out the two-dimensional tidal sediment model simulation of the Yangtze River Estuary. Figure 3 ) One section was arranged every 5 km, for a total of 5 typical sections. The tidal flow and sediment concentration processes of the 5 typical sections under the working conditions in September 2002 were extracted, and the average ebb tidal flow and average ebb tidal sediment concentration corresponding to the 5 typical sections during a large, medium and small tidal cycle were calculated.

[0050] Step S2: Based on the measured suspended sediment and bed sediment data in 2016 and 2017, the representative particle size of suspended sediment and the representative particle size of bed sediment in the regulated river section are analyzed, and the suspended sediment stop flow velocity and the bed sediment stop flow velocity are calculated.

[0051] Step S3: Based on the average ebb current flow, average ebb sediment content, suspended sediment stopping velocity, and bed sediment stopping velocity of each section, the Douguoren River correlation equation is used to obtain the river width corresponding to the five typical sections (B from upstream to downstream, respectively). 10 、B 20 、B 30 、B 40 、B 50 ) are 3830m, 4370m, 5040m, 5880m and 6950m respectively.

[0052] Step S4: Take the river width B i0 Based on this, the regulation line of the regulated river section is drawn up (see Figure 4 ).

[0053] Step S5: Using the two-dimensional tidal sediment model of the Yangtze River Estuary, calculate the tidal sediment movement of the north branch of the Yangtze River Estuary after the implementation of the initial regulation line under the conditions from September 15 to September 30, 2002, extract the tidal flow process and sediment concentration process of five typical sections, and calculate the average ebb tide flow and average ebb tide sediment concentration of each typical section during a large, medium and small tidal cycle.

[0054] Step S6: Based on the average ebb current flow and average ebb sediment concentration of each section calculated in S5, and using the Dou Guoren River correlation formula, calculate the reasonable river width corresponding to each typical section after the regulation line is implemented. The river width corresponding to the five typical sections (B 11 、B 21 、B 31 、B 41 、B 51 ) are 3720m, 4220m, 4790m, 5420m and 6250m respectively.

[0055] Step S7: Compare the river width B at the same section i1 With B i0 , at this time |(B 51 —B 50 ) / B 50 |=8%>1%, repeat steps S4, S5 and S6. Repeat step S4, that is, the river width B of each section i0 Basic, B i0 The regulation lines are 3720m, 4220m, 4790m, 5410m and 6230m respectively; repeat steps S5 and S6 to obtain the new river width B corresponding to the five typical sections. i1 (i.e. B 11 、B 21 、B 31 、B 41 、B 51 ) are 3720m, 4220m, 4790m, 5400m, and 6210m respectively. At this time, |(Bi1 —B i0 ) / B i0 |All less than 1%.

[0056] Step S8: Take the river width B of each section i1 (3720m, 4220m, 4790m, 5400m, 6210m ） Based on the above, the final control line of the river section is formulated ( Figure 4 ).

[0057] This paper considers the changes in tidal sediment dynamics after the implementation of tidal bifurcated river regulation lines and proposes a technical method for calculating river width and arranging regulation lines. This method can accurately determine tidal bifurcated river regulation lines, is relatively simple, and is applicable to determining regulation lines for various tidal bifurcated river channels.

[0058] The above are merely preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be construed as limiting the present invention, and the scope of protection of the present invention should be determined by the scope defined in the claims. Persons skilled in the art will appreciate that improvements and modifications may be made without departing from the spirit and scope of the present invention, and such improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for determining a regulation line for a tidal bifurcated river channel, characterized in that: The steps include: S1: Establish a two-dimensional tidal sediment numerical model and select typical hydrological conditions to simulate tidal sediment movement in the regulated river section. Arrange a corresponding number of typical sections along the regulated river section at a certain interval along the flow direction, and calculate the average ebb tide flow and average ebb tide sediment concentration of each typical section. Typical hydrological conditions refer to hydrological conditions that are consistent with the changes in river flow in the regulated river section, and are based on the average ebb tide flow in a normal water year or over multiple years. Typical hydrological conditions include at least one large, medium, or small tide. S2: Based on the measured suspended sediment and bed sediment data, the representative particle size of suspended sediment and bed sediment in the regulated river section is analyzed, and the suspended sediment stop flow velocity and bed sediment stop flow velocity in the regulated river section are calculated; S3: Based on the average ebb current flow, average ebb sediment content, and suspended sediment stopping velocity and bed sediment stopping velocity parameters of each typical section, the Dou Guoren River correlation equation is used to calculate the river width B corresponding to each typical section. i0 ; S4: The river width B of each typical section i0 Based on this, formulate the regulation line of the river section; S5: Based on the two-dimensional tidal sediment numerical model established in step S1 and the selected typical hydrological conditions, simulate the tidal sediment movement in the regulated river section after the regulation line is implemented, and calculate the average ebb tide flow and average ebb tide sediment concentration of each typical section after the regulation line is implemented; S6: Based on the average ebb current flow and average ebb current sediment concentration calculated in step S5, the corresponding river width B of each typical section is calculated using the Dou Guoren River correlation formula. i1 ; S7: Compare the river width B of the same typical section i1 With B i0 , if the river width of each typical section|(B i1 —B i0 ) / B i0 |≤1%, then B i1 The river width is the reasonable river width of section i; If the river width of a typical section|(B i1 —B i0 ) / B i0 |>1%, repeat steps S4, S5 and S6 until all typical sections|(B i1 —B i0 ) / B i0 |≤1%; Repeating step S4 means that the river width B i1 Re-assume the new B i0 Based on the river width, the regulation line of the regulated river section is drawn up, and then steps S5 and S6 are repeated to obtain the new B i1 ; S8: The river width B of each typical section i1 Based on this, the final regulation line of the river section is formulated.

2. The method for determining a regulation line for a tidal bifurcation river according to claim 1, characterized in that: In step S1, a two-dimensional tidal sediment numerical model is established by collecting underwater topography and hydrological sediment data of the regulated river section, and the model is calibrated and verified. The underwater topography data refers to the river system topography data of the regulated river section measured in recent years, and the hydrological sediment data includes at least two measured tide levels, flow velocities, tidal volumes, and sediment content data. The test periods of the underwater topography data and the hydrological sediment data should be basically consistent.

3. The method for determining a regulation line for a tidal bifurcated river according to claim 1 or 2, characterized in that: In step S1, the governing equations of the two-dimensional tidal sediment numerical model include the water flow continuity equation (1), the water flow motion equations (2) and (3), and the sediment transport equation (4), which can be expressed as: （1）； （2）； （3）； （4）； in: ； In the above formula: x and y are Cartesian coordinates, u and v are the components of the vertical average velocity in the x and y directions respectively; h = d + η is the total water depth, d is the still water depth, η is the water level; g is the acceleration due to gravity; is the density of water; f is the Coriolis coefficient; 、 is the bottom stress in the x and y directions, 、 is the surface stress in the x and y directions; T xx 、T xy 、T yy is the horizontal viscous stress; c is the vertical average sediment concentration; 、 is the sediment diffusion coefficient; E is the bed scour term; D is the bed deposition term; is the sediment settling velocity, is the concentration of suspended sediment near the bottom, is the probability of settlement, is the bed scour coefficient, is the bed shear stress, is the critical scour shear stress of the bed surface, is the washout index, , is the critical settlement shear stress of the bed surface.

4. The method for determining a regulation line for a tidal bifurcation river according to claim 1, wherein: In step S1, the section spacing is determined comprehensively based on the width and length of the regulated river section, and is set to 0.5 to 2 times the river width.

5. The method for determining a regulation line for a tidal bifurcated river channel according to claim 1 or 4, characterized in that: In step S1, the average ebb flow and average ebb sediment concentration of each typical section are calculated according to the flow and sediment concentration of the section during the ebb tide period using the following formula: Average ebb flow The calculation formula is: ； Where: , For adjacent , The ebb flow at the moment; 、 It is the time for rising and falling; Average sand content The calculation formula is: ； Where: , For adjacent , The sand content at low tide at that moment.

6. The method for determining a regulation line for a tidal bifurcated river channel according to claim 1, characterized in that: In step S2, the representative particle size refers to the particle size at which the weight of the sediment larger than and smaller than a certain particle size accounts for 50% of the total weight of the sand sample. The suspended sediment stopping velocity is calculated using the representative particle size of the suspended sediment. The bottom sand stopping velocity is calculated using the bottom sand representative particle size. .

7. The method for determining a regulation line for a tidal bifurcated river according to claim 1, characterized in that: In step S3, the river width B in the Douguoren River correlation equation is calculated as follows: ； Where: b is the proportionality coefficient, which is 0.15; β is the tidal coefficient, which is 1.0 for the river section without tidal bore; g is the acceleration of gravity, which is 9.81 m / s 2 ; is the suspended sediment stopping velocity; is the average low tide sediment concentration in a calculation period; is the average ebb current in one calculation period; is the sand-carrying coefficient, which is taken as 4.0; is the relative stability coefficient of the riverbank and riverbed soil, which is taken as 1.0; The bottom sand stopping flow velocity.

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