Artificial swale system and parameter design method thereof

Abstract

The application discloses an artificial tidal ditch system and a parameter design method thereof, relates to the technical field of coastal wetland ecological restoration, and the artificial tidal ditch system comprises a plurality of tidal ditches which are arranged at intervals and are connected with the sea and the inland, and the tidal ditch comprises a plurality of corners which are sequentially connected in front and back, the corners are oppositely connected with each other, the side of the corner which faces the sea extends to the inland direction, and the side of the corner which faces the sea is communicated with the side of the corner which faces the inland through a circular arc. The tidal ditch system can guarantee the water exchange function of the tidal ditch and increase the blocking capacity of the tidal ditch to storm surges.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of coastal wetland ecological restoration, and in particular to an artificial tidal ditch system and a parameter design method thereof. BACKGROUND

[0002] Coastal wetlands are an important part of the coastal zone ecosystem, with multiple ecological functions such as climate regulation, water purification, and provision of biological habitats. Tidal ditch networks, as an important part of coastal wetlands, play a key role in transporting water, sediment, and nutrients to the wetland and maintaining water exchange. However, the presence of tidal ditch networks also greatly reduces the decay rate of disaster-causing long waves such as storm surges in the wetland. The reason is that the water depth in the tidal ditch is larger and the resistance is smaller, which allows the energy of the storm surge to quickly spread to the interior of the wetland, causing damage to the wetland ecosystem and coastal infrastructure.

[0003] In the restoration of coastal wetlands, artificial excavation of tidal ditches is one of the common ecological restoration methods. Traditional tidal ditch design mainly focuses on water exchange and sediment transport functions, without considering the storm surge attenuation capacity. Therefore, how to ensure the water exchange function of the tidal ditch while enhancing its blocking ability against storm surges has become a key technical challenge in the restoration of coastal wetlands.

[0004] In addition, after the design of the artificial tidal ditch system is completed, the parameters of the system need to be calculated, including the density and depth of the tidal ditch. The existing method for calculating the density of the tidal ditch is disconnected from the quantification of ecological processes. The fractal characteristics (fractal dimension D) of natural tidal ditches are affected by the dynamic interaction between sediments and vegetation, but the existing method does not associate D with ecological variables, making static design unable to adapt to wetland evolution. The existing method for calculating the density of the tidal ditch leads to a conflict between disaster prevention and ecology, as high density is beneficial for water exchange but increases the risk of storm surges, and low density is the opposite. It is necessary to quantify the "safe density threshold". The existing method for calculating the depth of the tidal ditch ignores the risk of soil instability by using static hydrology (based on tidal difference △H+E). The existing method for calculating the tidal ditch also faces the problem of the separation of biological activity and engineering parameters.

[0005] In view of the above, the present application is proposed. SUMMARY

[0006] The present application aims to solve the problems in the prior art and provides an artificial tidal ditch system that can increase its blocking ability against storm surges while ensuring the water exchange function of the tidal ditch. In addition, to guide the implementation of the artificial tidal ditch system, the present application also provides a parameter calculation method for the artificial tidal ditch system, which is used to calculate the density and depth of the tidal ditch in the system.

[0007] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0008] An artificial tidal creek system comprises a plurality of tidal creeks arranged at intervals and connecting the sea and the inland, the tidal creeks comprising a plurality of corners connected in sequence, the corners connected to each other in opposite directions, and the corners facing the sea extending towards the inland, and being communicated with the corners facing the inland by a circular arc.

[0009] Further, when the wetland is a scouring risk area, the bifurcation angle of the corner ranges from 30° to 60°; when the water flow of the wetland approaches a critical Froude number, the bifurcation angle of the corner ranges from 30° to 45°; when the wetland is a sediment deposition area, the bifurcation angle of the corner ranges from 50° to 60°; when the wetland needs to strengthen the storm attenuation capacity, the bifurcation angle of the corner ranges from 60° to 70°; the bifurcation angle is the angle between the corner extending towards the inland and the corner facing the inland.

[0010] To achieve the above object, the present application also adopts the following technical scheme:

[0011] A parameter design method of an artificial tidal creek system, applied to any one of the artificial tidal creek systems provided by the present application, comprising the following steps:

[0012] S1: calculating the initial tidal creek density according to the fractal dimension, and optimizing the initial tidal creek density according to the competition intensity coefficient to obtain the final tidal creek density;

[0013] S2: calculating the number of tidal creeks according to the size of the wetland, the length of the tidal creek and the density of the tidal creek;

[0014] S3: calculating the initial tidal creek depth according to the elevation of the intertidal zone platform and the highest tide level, and optimizing the initial tidal creek depth according to the fixed effect coefficient and the biological disturbance coefficient to obtain the final tidal creek depth;

[0015] S4: calculating the initial tidal creek width according to the tidal creek depth, the tidal flow and the flow velocity distribution, and optimizing the initial tidal creek width according to the sediment particle size and the vegetation density to obtain the final tidal creek width;

[0016] S5: calculating the initial tidal creek curvature according to the flow velocity distribution and the transverse slope of the bend, and correcting the initial tidal creek curvature according to the artificial roughness element and the drag coefficient to obtain the final tidal creek curvature;

[0017] S6: calculating the number of bifurcation-reflux units according to the tidal creek curvature and the bifurcation angle of the tidal creek.

[0018] Further, the S1 comprises the following steps:

[0019] S11: determining the initial fractal dimension D0;

[0020] S12: Calculate the fractal dimension D according to the sediment flux change and vegetation coverage change, and the calculation formula is as follows:

[0021] ;

[0022] Wherein, α and β are weight coefficients, △S is the sediment flux change, S0 is the original sediment content, and V is the vegetation coverage change;

[0023] S13: Calculate the initial tidal creek density p0 according to the following formula:

[0024] ;

[0025] Wherein, C is the regional constant;

[0026] S14: Calculate the tidal creek density p according to the competition driving, and the calculation formula is as follows:

[0027] ;

[0028] Wherein, C i is the competition intensity coefficient, Fr is the Froude number, and F r,crit is the critical Froude number.

[0029] Further, the S2 comprises the following steps:

[0030] S21: Calculate the number of tidal creeks M according to the following formula:

[0031] ;

[0032] Wherein, p is the tidal creek density, S is the wetland area, is the length of a single tidal creek.

[0033] Further, the S3 comprises the following steps:

[0034] S31: Calculate the initial tidal creek depth h0 according to the intertidal zone platform elevation and the highest tide level, and the calculation formula is as follows:

[0035] ;

[0036] Wherein, △H is the difference between the highest tide level and the tidal flat elevation, and E is the average tidal range;

[0037] S32: Calculate the tidal creek depth h according to the fixed effect coefficient and the biological disturbance coefficient, and the calculation formula is as follows:

[0038] ;

[0039] Wherein, k1 and k2 are ecological action coefficients, F s is the fixed effect coefficient, and B dThe biological disturbance coefficient.

[0040] Further, the S4 comprises the following steps:

[0041] S41: Calculate the initial tidal ditch width B0 according to the tidal ditch depth, the design tidal flow and the design flow velocity, and the calculation formula is as follows:

[0042] ;

[0043] Wherein, Q is the design tidal flow, v is the design flow velocity, and h is the tidal ditch depth;

[0044] S42: Calculate the tidal ditch width B according to the sediment particle size and the vegetation density, and the calculation formula is as follows:

[0045] ;

[0046] Wherein, γ and λ are fitting coefficients, d is the sediment particle size, d0 is the reference particle size, ρ v is the vegetation density.

[0047] Further, the S5 comprises the following steps:

[0048] S51: Calculate the initial tidal ditch curvature R0 according to the design flow velocity and the lateral slope of the curve, and the calculation formula is as follows:

[0049] ;

[0050] Wherein, v is the design flow velocity, g is the acceleration of gravity, and s is the lateral slope of the curve;

[0051] S52: Calculate the tidal ditch curvature R according to the artificial roughness element and the drag coefficient, and the calculation formula is as follows:

[0052] ;

[0053] Wherein, C d is the drag coefficient, and N r is the roughness element density.

[0054] Further, the S6 comprises the following steps:

[0055] S61: Calculate the number of shunt-reflux units N according to the following formula:

[0056] ;

[0057] ;

[0058] Wherein, is the length of a single tidal ditch, R is the tidal ditch curvature, θ is the tidal ditch shunt junction angle, and △L is 20%-30% of the arc length of the reflux part.

[0059] Compared with the prior art, the present application has the following beneficial effects:

[0060] 1. The artificial tidal ditch system of the present application maintains the water exchange function and sediment transport function: during ebb tide, the geometric shape of the tidal ditch can maintain a small flow resistance, ensuring smooth water backflow and avoiding the formation of retention, thereby maintaining the water exchange function and sediment transport function of the wetland;

[0061] 2. The artificial tidal ditch system of the present application enhances the storm surge attenuation capacity: through the geometric shape and network structure of the new type of tidal ditch, a larger flow resistance can be generated when a storm surge hits, hindering the propagation of water to the interior of the wetland, thereby significantly enhancing the attenuation capacity of the wetland to the storm surge;

[0062] 3. The artificial tidal ditch system of the present application is eco-friendly: suitable wetland vegetation can be planted on both sides of the tidal ditch, which not only enhances the stability of the tidal ditch, but also further attenuates the energy of the storm surge through the flow resistance of the vegetation, having significant ecological benefits;

[0063] 4. In the parameter design method S1 of the artificial tidal ditch system of the present application: in S11-S12, the dynamic fractal dimension calculation takes the sediment flux change (△S) and the vegetation coverage (V) as the dynamic input of the fractal dimension D, so that the density basic parameter has ecological adaptability; in S13, the initial density correlation fractal feature utilizes the fractal dimension D to construct the nonlinear relationship between the tidal ditch density and the wetland area A, reflecting the fractal law of natural tidal ditches; in S14, the competition-driven density optimization introduces the Froude number (Fr) and the critical value (Fr,crit) to quantify the hydrodynamic risk, and the competition intensity coefficient Ci is used to represent the inhibitory effect of resource competition between tidal ditches on density, and the density is actively reduced to inhibit the propagation of storm surge energy when Fr is high (near critical flow state);

[0064] 5. In the parameter design method S3 of the artificial tidal ditch system of the present application: in S31, the calculation of the basic hydrological depth calculation ensures the basic tidal flow capacity through the highest tidal level difference △H and the average tidal range E; in S32, the ecological-mechanical coupling optimization introduces the fixed effect coefficient F s to enhance the shear strength and inhibit the shear failure of the storm surge; the biological disturbance coefficient B d quantifies the negative correction of burrowing activities on depth, achieving ecological disturbance compatibility. BRIEF DESCRIPTION OF DRAWINGS

[0065] Figure 1 is a layout schematic diagram of an embodiment of an artificial tidal ditch system;

[0066] Figure 2 is a flow schematic diagram of water flow in a split-reflow type tidal ditch network structure during flood tide;

[0067] Figure 3 This is a schematic diagram of water flow within a diversion-return tidal channel network structure during low tide.

[0068] Figure 4 A comparison diagram of water level changes along the course of the two tidal channels at the highest tide level;

[0069] Figure 5 A comparative diagram showing the changes in marsh surface water level along the course of two types of tidal creek wetlands at the highest tide level;

[0070] Figure 6 This is a flow field diagram of the tidal channel system in Example 1 at the highest tide level;

[0071] Figure 7 This is a flow field diagram of a traditional tidal channel system at the highest tide level.

[0072] Figure 8 A diagram showing the sediment deposition in the tidal channel system of Example 1 after low tide;

[0073] Figure 9 A diagram showing the amount of sediment deposited in a traditional tidal channel system after low tide.

[0074] Figure 10 This is a flowchart of the parameter design method for the artificial tidal channel system in Example 2. Detailed Implementation

[0075] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0076] Example 1:

[0077] An artificial tidal channel system, such as Figure 1 As shown, the tidal channel includes several spaced-apart channels connecting the ocean and the inland. The tidal channel includes several corners connected in sequence, with the corners facing opposite directions. The side of the corner facing the ocean extends towards the inland and is connected to the side of the corner facing the inland by an arc.

[0078] The artificial tidal channel system in this embodiment adds a forward-extending curve at the corner of the tidal channel, forming an internal structure of a diversion-return type tidal channel network. This structure can generate greater flow resistance in one direction while maintaining less flow resistance in the opposite direction. (See reference...) Figure 2 , 3 This design generates significant turbulent energy dissipation and flow resistance during storm surges (i.e., high tide), hindering the propagation of water into the wetland. During low tide, the geometry of the tidal channel maintains low flow resistance, ensuring smooth water return and preventing stagnation.

[0079] The artificial tidal ditch system of the embodiment has the following effects: (1) maintaining water exchange function and sediment transport function: at ebb tide, the geometric shape of the tidal ditch can maintain a small flow resistance to ensure smooth water return and avoid stagnation, thereby maintaining the water exchange function and sediment transport function of the wetland; (2) enhancing the storm surge attenuation capacity: through the geometric shape and network structure of the new type of tidal ditch, a larger flow resistance can be generated when a storm surge hits, thereby hindering the propagation of water to the interior of the wetland, thereby significantly enhancing the attenuation capacity of the wetland to the storm surge; (3) ecological friendly: suitable wetland vegetation can be planted on both sides of the tidal ditch, which not only can enhance the stability of the tidal ditch, but also can further attenuate the energy of the storm surge through the flow resistance of the vegetation, having significant ecological benefits.

[0080] In an optional embodiment, when the wetland is a scouring risk area, the split bifurcation angle of the corner is in the range of 30°≤θ≤60°; when the water flow of the wetland approaches the critical Froude number, the split bifurcation angle of the corner is in the range of 30°≤θ≤45°; when the wetland is a sediment deposition area, the split bifurcation angle of the corner is in the range of 50°≤θ≤60°; when the wetland needs to enhance the storm surge attenuation capacity, the split bifurcation angle of the corner is in the range of 60°≤θ≤70°; the split bifurcation angle is the angle between the edge of the corner extending towards the inland direction and the edge towards the inland direction.

[0081] To verify the effectiveness of the method of embodiment one, the tidal ditch designed in embodiment one is compared with the traditional tidal ditch in simulation verification. The traditional tidal ditch is a tidal ditch that only sets a corner without a curve extending forward.

[0082] Based on the Delft3D hydrodynamic numerical simulation platform, a tidal-storm surge coupled wetland hydrodynamic model is constructed. The equivalent hydrodynamic resistance structure of the intertidal zone and the beach vegetation zone are included to simulate the biogeomorphological coupling effect. The model domain is set as a rectangular wetland area of 1000 m × 1000 m, and three parallel tidal ditches are designed inside. The single tidal ditch width of the cross section is 50 m, and the depth is 3 m; the bifurcation angle of the main tidal ditch and the branch is 45°, and the streamline transition design is adopted. The initial water level is set to-1.0 m (based on the average sea level), and the suspended sediment concentration is 0.1 kg / m 3The intertidal zone on both sides of the tidal ditch is configured with a salt marsh vegetation zone, and the vegetation type is a local dominant halophyte (such as Suaeda salsa, Phragmites australis, etc.). The terrain outside the model domain is connected to the edge of the wetland through a 1:500 gentle slope, ensuring a gentle terrain gradient and avoiding terrain discontinuity problems in numerical simulation. The left open boundary adopts a cosine function to define the storm surge water level process, with a period of 12 hours, a maximum tide level of 1.0 m, and a minimum tide level of -1.0 m. The simulation of the periodic water level fluctuation is performed when the high tide level exceeds the wetland bottom elevation and the low tide level is lower than the wetland bottom elevation. The control group does not change the simulation conditions except for the shape of the tidal ditch.

[0083] Through the above model setting and parameter comparison, the system evaluates the optimization effect of the tidal ditch grid designed by the method of example one in terms of storm surge attenuation, water exchange efficiency, and sediment regulation. Three core hydrodynamic parameters, water level dynamic response, flow velocity field distribution, and sediment deposition amount, are selected for comparison between the two systems.

[0084] Reference Figure 4 and 5 When the storm surge is at the highest tide level, the water level response of the two wetlands. The results show that the water level in the tidal ditch and the water level on the marsh surface in the wetland system with the tidal ditch designed by the method of example one are lower than those in the traditional tidal ditch wetland system. It can be seen that the tidal ditch designed by the method of example one has a more obvious effect on storm surge attenuation.

[0085] Reference Figure 6 and 7 When the storm surge is at the highest tide level, the flow velocity field distribution of the two wetlands. The results show that the water flow velocity in the tidal ditch designed by the method of example one is significantly lower than that in the traditional tidal ditch. It can be seen that the tidal ditch designed by the method of example one has a more obvious effect on slowing down the water flow velocity.

[0086] Reference Figure 8 and 9 After the ebb tide, the sediment deposition amount of the two wetlands. The results show that the sediment deposition amount of the wetland system with the tidal ditch designed by the method of example one is significantly smaller than that of the traditional tidal ditch wetland system. It can be seen that the tidal ditch designed by the method of example one has a more obvious effect on preventing sediment deposition.

[0087] Example Two:

[0088] A parameter design method of an artificial tidal ditch system is applied to any one of the artificial tidal ditch systems provided in example one to guide the implementation of the artificial tidal ditch system.

[0089] The parameter design method of the artificial tidal ditch system in this example, as shown in Figure 10 , includes the following steps:

[0090] S1: Calculate the initial ditch density according to the fractal dimension, and optimize the initial ditch density according to the competition intensity coefficient to obtain the final ditch density;

[0091] S2: Calculate the number of ditches according to the wetland size, ditch length and ditch density;

[0092] S3: Calculate the initial ditch depth according to the intertidal zone platform elevation and the highest tide level, and optimize the initial ditch depth according to the fixed effect coefficient and the biological disturbance coefficient to obtain the final ditch depth;

[0093] S4: Calculate the initial ditch width according to the ditch depth, as well as the tidal flow and flow velocity distribution, and optimize the initial ditch width according to the sediment particle size and vegetation density to obtain the final ditch width;

[0094] S5: Calculate the initial ditch curvature according to the flow velocity distribution and the lateral slope of the bend, and correct the initial ditch curvature according to the artificial roughness element and the drag coefficient to obtain the final ditch curvature;

[0095] S6: Calculate the number of split-backflow units according to the ditch curvature and the ditch split junction angle.

[0096] In an optional embodiment, the S1 comprises the following steps:

[0097] S11: Determine the initial fractal dimension D0;

[0098] S12: Calculate the fractal dimension D according to the sediment flux change and the vegetation coverage change, and the calculation formula is as follows:

[0099] ;

[0100] Wherein, α and β are weight coefficients, △S is the sediment flux change, S0 is the original sediment content, and V is the vegetation coverage change;

[0101] S13: Calculate the initial ditch density ρ0 according to the following formula:

[0102] ;

[0103] Wherein, C is the regional constant;

[0104] S14: Calculate the ditch density ρ according to the competition driving, and the calculation formula is as follows:

[0105] ;

[0106] Wherein, C i is the competition intensity coefficient, Fr is the Froude number, and F r,crit is the critical Froude number.

[0107] In calculating the density of the tidal ditch, the water exchange efficiency needs to be considered. The density of the tidal ditch needs to meet the material transport demand of the water body inside the wetland and the ocean. If the density is too low, it will lead to insufficient tidal penetration range. In addition, it also needs to meet the requirement of inhibiting the energy propagation of storm surge. When the density of the tidal ditch is high, a low-resistance channel will be formed, which will accelerate the invasion of storm surge. Therefore, the density needs to be controlled below the critical value to increase the resistance of water flow. In addition, it also needs to adapt to the dynamic evolution of the wetland.

[0108] The existing calculation method of the density of the tidal ditch is disconnected with the quantification of the ecological process. The fractal characteristics (fractal dimension D) of the natural tidal ditch are affected by the dynamic of the sediment-vegetation. The existing method does not associate D with the ecological variables, which leads to the fact that the static design cannot adapt to the evolution of the wetland. In addition, the existing calculation method of the density of the tidal ditch leads to the conflict between disaster prevention and ecology. High density is beneficial to water exchange but increases the risk of storm surge. Low density is the opposite. The "safe density threshold" needs to be quantified.

[0109] In this optional embodiment, the dynamic fractal dimension calculation in S11-S12 takes the sediment flux change (△S) and the vegetation coverage (V) as the dynamic input of the fractal dimension D, so that the density basic parameter has ecological adaptability; the initial density associated fractal characteristics in S13 use the fractal dimension D to construct the nonlinear relationship between the density of the tidal ditch and the area A of the wetland, which reflects the fractal law of the natural tidal ditch; the competition driven density optimization in S14 introduces the Froude number (Fr) and the critical value (Fr,crit) to quantify the hydrodynamic risk. The competition intensity coefficient Ci is used to represent the inhibition of the density by the resource competition between the tidal ditches. When Fr is high (near critical flow state), the density is actively reduced to inhibit the energy propagation of storm surge.

[0110] In one optional embodiment, the S2 comprises the following steps:

[0111] S21: calculate the number of the tidal ditches M according to the following formula:

[0112] ;

[0113] wherein, p is the density of the tidal ditch, S is the area of the wetland, is the length of a single tidal ditch.

[0114] In combination with the previous optional embodiment, S1 and S2 use the fractal dimension D and the competition intensity Ci to generate the dynamic density p and the number M, which solves the fragmentation between ecology and disaster prevention.

[0115] In one optional embodiment, the S3 comprises the following steps:

[0116] S31: calculate the initial depth h0 of the tidal ditch according to the intertidal zone platform elevation and the highest tide level, and the calculation formula is as follows:

[0117] ;

[0118] wherein, △H is the difference between the highest tidal level and the elevation of tidal flat, E is the average tidal range;

[0119] S32: calculating the depth of the tidal creek h according to the fixed effect coefficient and the biological disturbance coefficient, the calculation formula being as follows:

[0120] ;

[0121] wherein, k1, k2 are ecological action coefficients, F s is the fixed effect coefficient, B d is the biological disturbance coefficient.

[0122] In the calculation of the depth of the tidal creek, the tidal flow capacity needs to be ensured, the depth needs to meet the water delivery demand of the design tidal flow Q, and it is ensured that the tide can reach the interior of the wetland; in addition, the storm surge shear failure needs to be considered, the water flow shear force increases dramatically during the storm surge, and the depth design needs to avoid the collapse of the creek wall.

[0123] The existing tidal creek depth calculation method ignores the risk of soil instability by static hydrology (according to the tidal level difference △H+E); in addition, the existing tidal creek calculation method also faces the separation of biological activity and engineering parameters.

[0124] In this optional embodiment, the calculation of the basic hydrological depth in S31 ensures the basic tidal flow capacity through the highest tidal level difference △H and the average tidal range E; in S32, the fixed effect coefficient F s is introduced to enhance the shear strength and inhibit the storm surge shear failure; the biological disturbance coefficient B d quantifies the negative correction of burrowing activity on the depth, and realizes the compatibility of ecological disturbance.

[0125] In one optional embodiment, the S4 comprises the following steps:

[0126] S41: calculating the initial tidal creek width B0 according to the depth of the tidal creek, the design tidal flow and the design flow rate, the calculation formula being as follows:

[0127] ;

[0128] wherein, Q is the design tidal flow, v is the design flow rate, and h is the depth of the tidal creek;

[0129] S42: calculating the tidal creek width B according to the sediment particle size and the vegetation density, the calculation formula being as follows:

[0130] ;

[0131] wherein, γ, λ are fitting coefficients, d is the sediment particle size, d0 is the reference particle size, and ρ v is the vegetation density.

[0132] In calculating the width of the tidal ditch, the designed tidal flow needs to be matched, that is, the width of the tidal ditch needs to meet the cross-section requirements of the designed tidal flow to ensure the water exchange efficiency; in addition, it is also necessary to ensure that the abnormal deposition / scouring of sediment can be inhibited.

[0133] The existing method for calculating the width of the tidal ditch is based on the hydraulic formula, which cannot respond to the sediment sorting, ignores the influence of the particle size of the sediment on the critical non-deposition flow velocity, and leads to the design deviation of the width of the coarse / fine particle zone; in addition, the existing method for calculating the width of the tidal ditch is difficult to quantify the flow resistance effect of vegetation.

[0134] In this optional embodiment, the minimum theoretical width under the designed tidal flow is calculated in S41 based on the basic hydrology; in S42, the width is dynamically adjusted according to the ratio of the particle size d to the reference d0 according to the sediment-vegetation coupling optimization, d / d0>1 (coarse particles), the channel is widened, the shear force is reduced to prevent scouring, and d / d0<1 (fine particles), the channel is narrowed, the flow velocity is improved to prevent deposition; in addition, the width is widened according to the exponential of the vegetation density, ρ v increases, B significantly increases, and the flow loss caused by the vegetation resistance is compensated.

[0135] In combination with the previous optional embodiment, S3 and S4 correct h and B through biological disturbance (B d ) and vegetation (ρ v , F s ), and realize the coordination of cross-scale parameters.

[0136] In one optional embodiment, S5 includes the following steps:

[0137] S51: calculate the initial tidal ditch curvature R0 according to the designed flow velocity and the lateral slope of the bend, and the calculation formula is as follows:

[0138] ;

[0139] wherein v is the designed flow velocity, g is the gravity acceleration, and s is the lateral slope of the bend;

[0140] S52: calculate the tidal ditch curvature R according to the artificial roughness element and the drag coefficient, and the calculation formula is as follows:

[0141] ;

[0142] wherein C d is the drag coefficient, and N r is the roughness element density.

[0143] In the calculation of the tidal ditch curvature, the enhanced storm surge energy dissipation needs to be ensured, that is, the tidal ditch curvature needs to support the structure of the shunt-reflux unit, and the storm surge energy is consumed through the friction of the flow in the bend; in addition, the bend secondary flow scour needs to be inhibited, that is, the centrifugal force of the bend under high flow velocity induces the secondary flow, and the tidal ditch curvature radius needs to be avoided to locally scour the ditch wall; in addition, the artificial energy dissipation structure needs to be compatible.

[0144] In the optional embodiment, the calculation of the basis hydraulics in S51 balances the centrifugal force through the transverse slope s to inhibit the secondary flow scour; S52 combines the artificial structure to cooperatively correct the curvature radius (that is, to increase the bending degree) to actively reduce the curvature radius; the higher roughness element density (Nr) makes R significantly smaller than R0 to increase the number of bends, to prolong the flow path, and to improve the rotational energy consumption; the drag coefficient (C d ) quantifies the shape resistance of the roughness element, and Nr together constitutes the energy dissipation enhancement factor.

[0145] In an optional embodiment, the S6 includes the following steps:

[0146] S61: calculating the number of shunt-reflux units N according to the following formula:

[0147] ;

[0148] ;

[0149] wherein, is the length of a single tidal ditch, R is the tidal ditch curvature, θ is the shunt bifurcation angle of the tidal ditch, and △L is 20% to 30% of the arc length of the reflux part.

[0150] In combination with the previous optional embodiment, S5 and S6 calculate the number of shunt-reflux units N based on the curvature R and the angle θ, convert the parameters into physical energy dissipation structures, and finally unify the ecological function and the disaster prevention target.

[0151] The above is only the preferred specific embodiment of the present application, but the protection scope of the present application is not limited to this, any person skilled in the art can make equivalent replacement or change according to the technical solution and the inventive concept of the present application within the technical range disclosed by the present application, which should be covered in the protection scope of the present application.

Claims

1. A parameter design method for an artificial tidal channel system, characterized in that... Includes the following steps: S1: Calculate the initial tidal channel density based on the fractal dimension, and optimize the initial tidal channel density based on the competition intensity coefficient to obtain the final tidal channel density; where the competition intensity coefficient characterizes the inhibitory effect of resource competition between tidal channels on density; S2: Calculate the number of tidal channels based on wetland size, tidal channel length, and tidal channel density; S3: Calculate the initial tidal channel depth based on the intertidal platform elevation and the highest tide level, and optimize the initial tidal channel depth based on the fixed effect coefficient and the bio-disturbance coefficient to obtain the final tidal channel depth; among which, the fixed effect coefficient enhances shear strength, and the bio-disturbance coefficient quantifies the negative correction of depth by burrowing activity; S4: Calculate the initial tidal channel width based on the tidal channel depth, tidal volume and velocity distribution, and optimize the initial tidal channel width based on sediment grain size and vegetation density to obtain the final tidal channel width; S5: Calculate the initial tidal channel curvature based on the flow velocity distribution and the lateral slope of the bend, and correct the initial tidal channel curvature based on the artificial rough element and the drag coefficient to obtain the final tidal channel curvature; wherein, the drag system quantifies the rough element resistance; S6: Calculate the number of diversion-return units based on the curvature of the tidal channel and the angle of the tidal channel diversion junction; S1 includes the following steps: S11: Determine the initial fractal dimension D0; S12: Calculate the fractal dimension D based on changes in sediment flux and vegetation cover. The calculation formula is as follows: ； Where α and β are weighting coefficients, ΔS is the change in sediment flux, S0 is the original sediment content, and V is the change in vegetation cover; S13: Calculate the initial tidal channel density ρ0 according to the following formula: ； Where C is the region constant; S14: Calculate the tidal channel density ρ based on competition-driven calculations. The calculation formula is as follows: ； Among them, C i Fr is the competition intensity coefficient, F is the Froude number, and F r,crit It is the critical Froude number.

2. The parameter design method for an artificial tidal channel system according to claim 1, characterized in that, S2 includes the following steps: S21: Calculate the number of tidal channels M according to the following formula: ； Where ρ is the tidal channel density and S is the wetland area. This refers to the length of a single tidal channel.

3. The parameter design method for an artificial tidal channel system according to claim 1, characterized in that, S3 includes the following steps: S31: Calculate the initial tidal channel depth h0 based on the intertidal platform elevation and the highest tide level. The calculation formula is as follows: ； Where △H is the difference between the highest tide level and the tidal flat elevation, and E is the mean tidal range; S32: Calculate the tidal channel depth h based on the fixed effect coefficient and the biological disturbance coefficient. The calculation formula is as follows: ； Where k1 and k2 are ecological action coefficients, F s B is the fixed effects coefficient. d This represents the biological disturbance coefficient.

4. The parameter design method for an artificial tidal channel system according to claim 1, characterized in that, S4 includes the following steps: S41: Calculate the initial tidal channel width B0 based on the tidal channel depth, design tidal volume, and design velocity. The calculation formula is as follows: ； Where Q is the design tidal current, v is the design velocity, and h is the tidal channel depth; S42: Calculate the tidal channel width B based on sediment grain size and vegetation density. The calculation formula is as follows: ； Where γ and λ are fitting coefficients, d is the sediment grain size, d0 is the reference grain size, and ρ v This refers to vegetation density.

5. The parameter design method for an artificial tidal channel system according to claim 1, characterized in that, S5 includes the following steps: S51: Calculate the initial tidal channel curvature R0 based on the design flow velocity and the transverse slope of the bend. The calculation formula is as follows: ； Where v is the design flow velocity, g is the gravitational acceleration, and s is the lateral slope of the curve; S52: Calculate the tidal channel curvature R based on the artificial roughness element and the drag coefficient. The calculation formula is as follows: ； Among them, C d N is the drag coefficient. r is the rough element density.

6. The parameter design method for an artificial tidal channel system according to claim 1, characterized in that, S6 includes the following steps: S61: Calculate the number of shunt-return units N according to the following formula: ； ； in R is the length of a single tidal channel, θ is the curvature of the tidal channel, θ is the angle of the tidal channel branching point, and ΔL is 20%~30% of the arc length of the backflow section.

7. An artificial tidal channel system designed using the parameter design method according to any one of claims 1 to 6, comprising a plurality of tidal channels spaced apart and connecting the ocean and inland areas, characterized in that, The tidal channel includes several bends connected in a sequential manner. The bends that are connected to each other have opposite orientations. The side of the bend facing the ocean extends inward and is connected to the side of the bend facing inward by an arc.

8. The artificial tidal channel system according to claim 7, characterized in that, When the wetland is a scour risk area, the angle of the diversion junction at the bend is in the range of 30°≤θ≤60°; when the water flow in the wetland is close to the critical Froude number, the angle of the diversion junction at the bend is in the range of 30°≤θ≤45°; when the wetland is a siltation area, the angle of the diversion junction at the bend is in the range of 50°≤θ≤60°; when the wetland needs to enhance its storm attenuation capacity, the angle of the diversion junction at the bend is in the range of 60°≤θ≤70°; the diversion junction angle is the angle between the side of the bend extending inland and the side extending inland.

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