River channel dike burst simulation method based on one-dimensional and two-dimensional coupling hydrodynamic model

Abstract

The invention discloses a riverway dike burst simulation method based on a one-dimensional and two-dimensional coupling hydrodynamic model, and the method specifically comprises the steps: obtaining basic data of a calculation region, and building a one-dimensional river network model and a two-dimensional surface water dynamic model; coupling the one-dimensional river network model and the two-dimensional surface water power model to obtain a one-dimensional and two-dimensional coupling water power model, solving, and calculating exchange flow; solving the dike burst process of the model, and calculating the flow process of the river channel breach; coupling the breach flow into the model to carry out dam burst flood routing calculation; updating the section water depth, the flow process, the grid water depth and the flow velocity in the model; the information is output; and repeating the steps until the simulation reaches the preset simulation duration, and completing the simulation calculation. The method solves the problems of inaccurate calculation of the embankment bursting process caused by the river flood and complex arrangement of the breach, is an effective method for calculating the embankment bursting process caused by the river flood, and is clear in process and simple and convenient to operate.

Description

Technical Field

[0001] The invention belongs to the technical field of water environment numerical simulation methods, and in particular relates to a river channel embankment breach simulation method based on a one- and two-dimensional coupled hydrodynamic model. Background Art

[0002] Floods are serious natural disasters caused by natural factors such as heavy rainfall, rapid melting of ice and snow, and storm surges. In terms of frequency and impact, floods are one of the most widespread disasters threatening human society. In order to reduce the impact of flood disasters on human production and life, embankments are usually built in areas susceptible to floods to resist floods. However, when encountering super-standard floods, the floods may overflow the top of the embankment, causing embankment breaches and resulting in embankment breach floods, leading to serious consequences such as casualties, property losses, and ecological damage. In addition, with the continuous change of the global climate, the frequency of various extreme weather events, especially heavy rainfall, has continued to increase, further exacerbating the threat of such natural disasters. Therefore, the study of the disaster-causing process of embankment breach floods has always been a research hotspot in the field of water conservancy.

[0003] Although flood disasters are usually difficult to completely eliminate, the losses caused by them can be significantly reduced through a series of effective strategies. For example, floods can be classified based on risk levels, public education on flood disaster escape can be strengthened, evacuation routes can be optimized, and flood disasters can be predicted using numerical simulation. Among them, flood numerical simulation, as a key means of disaster prevention and mitigation, usually requires the collection of hydrological, meteorological and underlying surface data in the study area, and then the development of corresponding numerical models. After parameter calibration and verification, flood disaster events that may occur in the study area can be predicted in advance, thereby achieving the purpose of disaster prevention and mitigation. However, since the dyke breach flood process is affected by multiple factors such as river flood level, dyke elevation, and breach characteristics, the amount of data required for accurate simulation is large, and modeling is difficult. Therefore, there is an urgent need for a method that can quickly and accurately simulate the dyke breach flood process based on one-dimensional river network data, dyke data, and simple two-dimensional surface data to improve flood disaster prediction and defense capabilities. Summary of the invention

[0004] The purpose of the present invention is to provide a river breach simulation method based on a one-two-dimensional coupled hydrodynamic model to solve the problem that the existing simulation technology cannot accurately locate the river breach position.

[0005] The technical solution adopted by the present invention is a river bank breach simulation method based on a one-two-dimensional coupled hydrodynamic model, which is specifically implemented according to the following steps:

[0006] S1. Obtain basic data of the calculation area, including one-dimensional river section data, two-dimensional surface DEM data, and underlying surface data;

[0007] S2. Establish a one-dimensional river network model and a two-dimensional surface water dynamics model based on basic data;

[0008] S3, coupling the one-dimensional river network model and the two-dimensional surface hydrodynamic model to obtain a one-dimensional and two-dimensional coupled hydrodynamic model;

[0009] S4, solving the one- and two-dimensional coupled hydrodynamic model and calculating the exchange flow;

[0010] S5, solving the dam breach process of the one- and two-dimensional coupled hydrodynamic model, and calculating the flow process of the river breach according to the set dam breach form and dam breach location information;

[0011] S6. Couple the breach flow into a one- and two-dimensional coupled hydrodynamic model to calculate the evolution of the breach flood;

[0012] S7, update the cross-section water depth, flow process, grid water depth, and flow velocity in the one- and two-dimensional coupled hydrodynamic model;

[0013] S8, outputting the water depth, flow velocity and breach flow process information calculated by the one-dimensional river network model, and the surface flooding depth and flooding range information obtained by the two-dimensional surface hydrodynamic model;

[0014] S9, repeat S4 to S8 until the simulation reaches the preset simulation time and the simulation calculation is completed.

[0015] The present invention is also characterized in that:

[0016] In step S2, specifically:

[0017] Read one-dimensional river section data, including section number, section spacing, deep point elevation, initial water level, topological relationship, initial flow, slope, and Manning coefficient, and other key information and parameters of the section, and construct a one-dimensional river network model;

[0018] Read basic data such as DEM raster data, land use type data, and infiltration data to build a two-dimensional surface hydrodynamic model.

[0019] In step S3, specifically:

[0020] Firstly, the spatial topological relationship is associated with the one-dimensional river network model, and the area where the river grid is located is calculated using the one-dimensional river network model; secondly, the grids adjacent to the river are determined, hereinafter referred to as coupled grids, and the coupled grids are considered as the exchange boundaries between the two-dimensional surface and the one-dimensional river network, and the water exchange of the one-dimensional and two-dimensional model occurs on the coupled grids; to ensure the conservation of water volume, the edges connecting the coupled grids and the river grids are set as closed boundaries. At the same time, the water level of the one-dimensional river network is interpolated so that the river water level corresponding to each coupled grid on the coupling boundary is more consistent with the change trend of the actual river water level along the way, ensuring the accuracy of the river water level used in the coupling calculation; the coupling relationship between the one-dimensional river network model and the two-dimensional surface hydrodynamic model is established, and finally a one-dimensional and two-dimensional coupled hydrodynamic model is formed.

[0021] In step S4, specifically:

[0022] Firstly, the one-dimensional river network model and the two-dimensional surface hydrodynamic model are solved according to their respective boundary conditions. Then, the one-dimensional and two-dimensional water exchange directions are divided into the following four categories according to the river water level, levee elevation and surface water level: when the river water level is lower than the levee elevation and the surface water level is lower than the levee elevation, there is no water exchange; when the river water level is lower than the levee elevation and the surface water level is higher than the levee elevation, the water flows from the two-dimensional surface into the river; when the river water level is higher than the levee elevation and the surface water level is lower than the levee elevation, the water flows from the river into the two-dimensional surface; when the river water level is equal to the surface water level and both are higher than the levee elevation, there is still water exchange and the water exchange direction needs to be determined according to the flow direction on the coupled grid.

[0023] The exchange volume is expressed by the following formula (1):

[0024]

[0025] Among them, Q S is the exchange volume calculated at the coupling boundary of the one-dimensional coupled hydrodynamic model, in m 3 / s; b is the weir width, in m; g is the gravitational acceleration, in m / s 2 ;h max =max(Z R ,Z G )-Z D ;h min =min(Z R ,Z G )-Z D ; Z R Indicates the river water level, in m; Z G Indicates the surface elevation in meters; Z D Indicates the embankment elevation in meters.

[0026] In step S5, specifically:

[0027] The elevations of the left and right bank embankments of each section along the one-dimensional river network model, the breach form: instantaneous breach or gradual breach, breach direction, breach elevation, and breach bottom elevation are read from the one-dimensional and two-dimensional coupled hydrodynamic model input file. Then, the breach process is calculated to obtain the flow at the breach in the one-dimensional and two-dimensional coupled hydrodynamic model.

[0028] The calculation method of instantaneous breach is as follows: when the water level of a one-dimensional river network section is higher than the breach elevation of a dike on one side of the section, it is considered that the dike on this side is instantly breached to the set breach bottom elevation, and then the exchange volume is calculated using the following weir flow formula (2):

[0029]

[0030] Among them, Q S is the flow rate of the breach at the instantaneous breach, in m 3 / s; b is the breach width, in m; Z R is the river water level, in m; Z DIE is the breach bottom elevation, in meters; Z DBE is the breach elevation, in meters; g is the gravitational acceleration, in meters per second 2 ;

[0031] The calculation method of gradual breach is as follows: when the water level of a one-dimensional river network section is higher than the breach elevation of a dike on one side of the section, it is considered that the dike on this side will breach in a certain way, and the breach will gradually expand until it stabilizes. Then the flow process is coupled into the model to calculate the breach process, as shown in formula (3):

[0032]

[0033] Among them, Q Timeseries is the breach flow rate during gradual breach, in m 3 / s;

[0034] In step S6, specifically:

[0035] Within the same calculation time step, the breach flow obtained in S5 is subtracted from the one-dimensional river network model and added to the corresponding breach position in the two-dimensional surface hydrodynamic model. The one-dimensional and two-dimensional coupled hydrodynamic model is used to calculate the evolution of the dam breach flood, and then the inundation range, water depth, and duration of the dam breach flood on the surface are obtained.

[0036] The beneficial effects of the present invention are:

[0037] (1) The method of the present invention uses a one-dimensional river network model based on the HLL format to simulate the river flood process, reasonably judges the location where the breach may occur according to the water level of the river section and its corresponding levee elevation, and can select two different breach forms of instantaneous breach or gradual breach according to actual calculation requirements, and then adds the obtained breach flow process to the two-dimensional hydrodynamic model to perform flood evolution and inundation calculation. The method can quickly obtain the flood inundation range in the basin when the one-dimensional section data is accurate;

[0038] (2) The method of the present invention uses a one-dimensional river network model to simulate the river channel, which can accurately and quickly obtain the water depth of any section of the river network, and can preset the location of the levee that may burst in the model to calculate the river channel burst flood. It can also perform conventional flood calculations based on the relative values ​​of the river channel flood and the levee elevation. Compared with the traditional pure one-dimensional calculation method, this method can accurately calculate the river channel flood process while also obtaining the evolution process of the flood on the two-dimensional surface; compared with the pure two-dimensional calculation method, this method has lower requirements for river channel data and does not need to use the detailed and difficult-to-obtain river channel and levee DEM data in the two-dimensional model. Therefore, this method is an effective method for calculating the river channel flood burst process, and the method of the present invention has a clear process and is easy to operate, which is of great significance for assessing the risk of river channel flood inundation and the preparation of flood risk maps. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a flow chart of a river bank breach simulation method based on a one-two-dimensional coupled hydrodynamic model of the present invention;

[0040] Figure 2 is a schematic diagram of a one- and two-dimensional coupled hydrodynamic model of an ideal river section in an embodiment of the present invention;

[0041] Figure 3 Schematic diagram of the coupling principle of a one-dimensional model in an embodiment of the present invention;

[0042] Figure 4 is a schematic diagram of the change process of the water surface line of the river channel obtained by the model calculation in the embodiment of the present invention;

[0043] Figure 5 Schematic diagram of the water volume change process of each part of the model calculation in the embodiment of the present invention;

[0044] Figure 6 It is a schematic diagram of the calculation setting of flood embankment breach in a certain river section and the surface inundation in an embodiment of the present invention. DETAILED DESCRIPTION

[0045] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0046] Example 1

[0047] The present invention is based on a river bank breach simulation method based on a one-two-dimensional coupled hydrodynamic model. Figure 1 As shown, the specific implementation steps are as follows:

[0048] S1. Obtain basic data of the calculation area, including one-dimensional river section data, two-dimensional surface DEM data, and underlying surface data;

[0049] S2. Establish corresponding one-dimensional river network model and two-dimensional surface water dynamic model based on basic data;

[0050] S3, coupling the one-dimensional river network model and the two-dimensional surface hydrodynamic model according to the spatial topological relationship to obtain a one-dimensional and two-dimensional coupled hydrodynamic model; and setting corresponding boundary conditions;

[0051] S4. Solve the one-dimensional and two-dimensional coupled hydrodynamic model according to the boundary conditions of the one-dimensional river network model and the two-dimensional surface hydrodynamic model, and calculate the exchange flow of the one-dimensional and two-dimensional coupled hydrodynamic model according to the river water level, levee elevation, and surface water level;

[0052] S5, solving the dam breach process of the one- and two-dimensional coupled hydrodynamic model, and calculating the flow process of the river breach according to the set dam breach form and dam breach location information;

[0053] S6, coupling the breach flow obtained in S5 into a one- and two-dimensional coupled hydrodynamic model to calculate the evolution of the breach flood;

[0054] S7, update the key information such as cross-section water depth, flow process, grid water depth, and flow velocity in the one- and two-dimensional coupled hydrodynamic model;

[0055] S8, outputting the water depth, flow velocity and breach flow process information calculated by the one-dimensional river network model, and the surface flooding depth and flooding range information obtained by the two-dimensional surface hydrodynamic model;

[0056] S9, repeat S4 to S8 until the simulation reaches the preset simulation time and the simulation calculation is completed.

[0057] Example 2

[0058] The present invention is based on a river bank breach simulation method based on a one-two-dimensional coupled hydrodynamic model. Figure 1 As shown, the specific implementation steps are as follows:

[0059] S1. Obtain basic data of the calculation area, including one-dimensional river section data, two-dimensional surface DEM data, and underlying surface data;

[0060] S2. Establish the corresponding one-dimensional river network model and two-dimensional surface water dynamic model based on the basic data; specifically:

[0061] Read one-dimensional cross-section data, including cross-section number, cross-section spacing, deep-point elevation, initial water level, topological relationship, initial flow, slope, and Manning coefficient, and construct a one-dimensional river network model; the modeling diagram is as follows Figure 2 As shown;

[0062] Read the basic data such as DEM raster data, land use type data, and infiltration data to build a two-dimensional surface hydrodynamic model; the modeling diagram is as follows Figure 2 As shown;

[0063] S3. According to the spatial topological relationship, the one-dimensional river network model and the two-dimensional surface hydrodynamic model are coupled to obtain a one-dimensional and two-dimensional coupled hydrodynamic model; and the corresponding boundary conditions are set; the coupling principle diagram is shown in Figure 3 As shown; specifically:

[0064] Firstly, the spatial topological relationship is associated with the one-dimensional river network model, and the area where the river grid is located is calculated using the one-dimensional river network model; secondly, the grids adjacent to the river (hereinafter referred to as coupling grids) are determined, and the coupling grids are considered as the exchange boundary between the two-dimensional surface and the one-dimensional river network, and the water volume exchange of the one-dimensional and two-dimensional model occurs on the coupling grids; to ensure the conservation of water volume, the edge connecting the coupling grid and the river grid is set as a closed boundary, and at the same time, the water level of the one-dimensional river network is interpolated, so that the river water level corresponding to each coupling grid on the coupling boundary is more consistent with the change trend of the actual river water level along the way, ensuring the accuracy of the river water level used in the coupling calculation; the coupling relationship between the one-dimensional river network model and the two-dimensional surface hydrodynamic model is established, and finally a one-dimensional coupled hydrodynamic model is formed;

[0065] S4. Solve the one-dimensional and two-dimensional coupled hydrodynamic model according to the boundary conditions of the one-dimensional river network model and the two-dimensional surface hydrodynamic model, and calculate the exchange flow of the one-dimensional and two-dimensional coupled hydrodynamic model according to the river water level, levee elevation, and surface water level; specifically:

[0066] First, the one-dimensional river network model and the two-dimensional surface hydrodynamic model are solved according to their respective boundary conditions. Then, the one-dimensional and two-dimensional water exchange directions are divided into the following four categories according to the river water level, levee elevation, and surface water level: (a) The river water level is lower than the levee elevation and the surface water level is lower than the levee elevation, and there is no water exchange; (b) The river water level is lower than the levee elevation and the surface water level is higher than the levee elevation, and the water flows from the two-dimensional surface into the river; (c) The river water level is higher than the levee elevation and the surface water level is lower than the levee elevation, and the water flows from the river into the two-dimensional surface; (d) The river water level is equal to the surface water level, and both are higher than the levee elevation. At this time, there is still water exchange, and the water exchange direction needs to be determined according to the water flow direction on the coupled grid. The specific exchange amount is shown in the following formula (1):

[0067]

[0068] Among them, Q S is the exchange volume calculated at the coupling boundary of the one-dimensional coupled hydrodynamic model, in m 3 / s; b is the weir width, in m, which is numerically equal to the grid size in the coupling method of the present invention; g is the gravitational acceleration, in m / s 2 ;h max =max(Z R ,Z G )-Z D ;h min =min(Z R ,Z G )-Z D ; Z R Indicates the river water level, in m; Z G Indicates the surface elevation in meters; Z D Indicates the embankment elevation in meters.

[0069] S5. Solve the dam breach process of the one- and two-dimensional coupled hydrodynamic model, and calculate the flow process of the river breach according to the set dam breach form and dam breach location information; specifically:

[0070] First, the left and right bank levee top elevations, breach form (instantaneous breach or gradual breach), breach direction, breach elevation, breach bottom elevation and other calculation parameters of each section along the one-dimensional river network model are read from the one-dimensional and two-dimensional coupled hydrodynamic model input file, and then the breach process is calculated. The calculation method of instantaneous breach is as follows: when the water level of the one-dimensional river network section is higher than the breach elevation of a certain side of the levee set in the section, it is considered that the levee on this side is instantly breached to the set breach bottom elevation, and then the exchange volume is calculated using the following weir flow formula (2):

[0071]

[0072] Among them, Q S is the flow rate of the breach at the instantaneous breach, in m 3 / s; b is the breach width, in m; Z R is the river water level, in m; Z DIE is the breach bottom elevation, in meters; Z DBE is the breach elevation, in meters; g is the gravitational acceleration, in meters per second 2 .

[0073] The calculation method of gradual breach is as follows: when the water level of a one-dimensional river network section is higher than the breach elevation of a dike on one side of the section, it is considered that the dike on this side is breached in a certain breach mode, and the breach gradually expands until it stabilizes. The flow process can be calculated using a model such as DB-IAHR, and then the flow process is coupled into the model to calculate the dike breach process, as shown in formula (3):

[0074]

[0075] Among them, Q Timeseries is the breach flow rate during gradual breach, in m 3 / s, which can be calculated by a variety of breach models;

[0076] By solving this step, the flow rate at the breach in the one- and two-dimensional coupled hydrodynamic model can be obtained;

[0077] S6. Couple the breach flow obtained in S5 into the one- and two-dimensional coupled hydrodynamic model to calculate the evolution of the breach flood, specifically:

[0078] In the same calculation time step, the breach flow obtained in S5 is subtracted from the one-dimensional river network model (according to the principle of water conservation, the amount of water allowed to be subtracted from the one-dimensional river network model in each calculation time step shall not exceed the total water volume of the river section at the current moment), and added to the corresponding breach position in the two-dimensional surface hydrodynamic model. The one- and two-dimensional coupled hydrodynamic model is used to calculate the evolution of the dam breach flood, and then the inundation range, water depth, and duration of the dam breach flood on the surface are obtained.

[0079] S7, update the key information such as cross-section water depth, flow process, grid water depth, and flow velocity in the one- and two-dimensional coupled hydrodynamic model;

[0080] S8, outputting the water depth, flow velocity and breach flow process information calculated by the one-dimensional river network model, and the surface flooding depth and flooding range information obtained by the two-dimensional surface hydrodynamic model;

[0081] S9, repeat S4 to S8 until the simulation reaches the preset simulation time and the simulation calculation is completed.

[0082] Example 3

[0083] A small watershed was selected with an area of ​​about 50 square kilometers. The main river channel is about 20 kilometers long. The surrounding terrain is a mixture of hills and plains, and there have been several records of small dam breaches.

[0084] One-dimensional river section: 30 section data were measured, with a section spacing of about 500 meters, a deep point elevation of 20-50 meters, an initial water level of 22 meters, an initial flow of 5 cubic meters per second during the dry season, a slope of 0.002, and a Manning coefficient of 0.03.

[0085] Two-dimensional surface DEM: generated from satellite images, with a resolution of 10 meters and an altitude of 15-60 meters.

[0086] Underlying surface: cultivated land accounts for 40%, with an infiltration rate of 5 mm / hour; forest land accounts for 30%, with an infiltration rate of 8 mm / hour; construction land accounts for 20%, with an infiltration rate of 2 mm / hour; water area accounts for 10%.

[0087] Construct a one-dimensional river network model and a two-dimensional surface hydrodynamic model; use the software coupling function to associate topology, mark the 20-meter-wide coupling grid around the main river channel, set closed boundaries, interpolate water levels, and complete the one- and two-dimensional coupling model construction;

[0088] Boundary setting: One-dimensional upstream flow boundary is based on hydrological station data, with a peak value of 50 cubic meters per second during flood season; downstream water level boundary refers to the estuary tide level. Two-dimensional closed boundary or flow boundary is set according to terrain.

[0089] Solution: Start the solver. At a certain moment, the river water level is 23 meters, the surface water level is 24 meters, and the levee top elevation is 25 meters, which belongs to type (b). According to formula (1), the weir width is 10 meters. Calculate the exchange volume.

[0090] Solution of the embankment breach process: Assuming that section 15 of the main river channel gradually breaches, the breach elevation is 24 meters and the bottom elevation is 22 meters, the DB-IAHR model is used to calculate the breach flow and couple it into the model.

[0091] Evolution of dam breach flood: According to the law of water conservation, the breach flow is transferred at the corresponding time step to simulate the flood inundation range and water depth changes.

[0092] At the end of each step, update the key information of the one- and two-dimensional model to prepare for the next calculation. Output data to a file every 2 hours for GIS drawing analysis. The preset time is 24 hours, cycle, monitor the simulation, and obtain the final result to provide a basis for flood control.

[0093] Example 4

[0094] Figure 4 It is a schematic diagram of the change process of the water surface line of the river channel obtained by the model calculation in the embodiment of the present invention, which shows the water surface line of the river channel at the initial moment of calculation and after the calculation reaches a stable state (60 minutes). It can be seen from the figure that the slope of the water surface line of the river channel before the breach after stabilization is consistent with the water surface line slope at the initial moment, while the slope of the water surface line of the river channel after the breach becomes gentler. This indicates that the one-dimensional river network model has experienced water loss at the breach location, resulting in a reduction in the amount of water flowing downstream, which is in line with the principle of water conservation and the water balance equation. At the same time, the model simulation results also compare well with the analytical solution, indicating that the model can simulate the breach process well.

[0095] Figure 5This is a schematic diagram of the water volume change process of each part of the model calculation in the embodiment of the present invention. From the perspective of water conservation, the sum of the water volume flowing into the plain area through the breach and the water volume flowing out of the river outlet should be equal to the total water volume flowing into the river. Figure 5 It can be seen that the sum of the outflowing water is equal to the total water inflowing into the river, which shows that the coupling model constructed in this paper can well maintain the conservation of water volume.

[0096] Example 5

[0097] Figure 6 This is a simulation example of flood dyke breach and surface inundation process in a river section. The left bank of the river section breaches at section S3 and the right bank breaches at section S8. The breach flow processes are different and the flooding ranges caused are also different. This shows that the method of the present invention can well simulate the flood evolution and inundation process of different breach modes and dyke breach flows.

[0098] Example 6

[0099] The present invention is based on a river embankment breach simulation method of a one-dimensional coupled hydrodynamic model. According to specific steps, basic data is first obtained, a one-dimensional river network model and a two-dimensional surface hydrodynamic model are constructed, and a one-dimensional coupled hydrodynamic model is obtained by coupling. Then, operations such as solution calculation, embankment breach process solution, and embankment breach flood evolution calculation are performed in sequence, and relevant information is continuously updated and output, and the corresponding steps are repeated until the preset simulation time is reached to complete the simulation. This method solves the problems of inaccurate calculation of embankment breach process caused by river floods and complex breach settings. It is an effective method for calculating the embankment breach process of river floods. In addition, the simulation method has a clear process and is easy to operate. It is of great significance for assessing the risk of river flood inundation and the production of flood risk maps.

Claims

1. A river bank breach simulation method based on a one- and two-dimensional coupled hydrodynamic model, characterized in that: Follow the steps below to implement it: S1. Obtain basic data of the calculation area, including one-dimensional river section data, two-dimensional surface DEM data, and underlying surface data; S2. Establish a one-dimensional river network model and a two-dimensional surface water dynamics model based on basic data; S3, coupling the one-dimensional river network model and the two-dimensional surface hydrodynamic model to obtain a one-dimensional and two-dimensional coupled hydrodynamic model; S4, solving the one- and two-dimensional coupled hydrodynamic model and calculating the exchange flow; S5, solving the dam breach process of the one- and two-dimensional coupled hydrodynamic model, and calculating the flow process of the river breach according to the set dam breach form and dam breach location information; S6. Couple the breach flow into a one- and two-dimensional coupled hydrodynamic model to calculate the evolution of the breach flood; S7, update the cross-section water depth, flow process, grid water depth, and flow velocity in the one- and two-dimensional coupled hydrodynamic model; S8, outputting the water depth, flow velocity and breach flow process information calculated by the one-dimensional river network model, and the surface flooding depth and flooding range information obtained by the two-dimensional surface hydrodynamic model; S9, repeat S4 to S8 until the simulation reaches the preset simulation time and the simulation calculation is completed.

2. The river bank breach simulation method based on a one-two-dimensional coupled hydrodynamic model according to claim 1, characterized in that: In the step S2, specifically: Read one-dimensional river section data, including section number, section spacing, deep point elevation, initial water level, topological relationship, initial flow, slope, and Manning coefficient, and other key information and parameters of the section, and construct a one-dimensional river network model; Read basic data such as DEM raster data, land use type data, and infiltration data to build a two-dimensional surface hydrodynamic model.

3. The river bank breach simulation method based on a one-two-dimensional coupled hydrodynamic model according to claim 1, characterized in that: In the step S3, specifically: Firstly, the spatial topological relationship is associated with the one-dimensional river network model, and the area where the river grid is located is calculated using the one-dimensional river network model; secondly, the grids adjacent to the river are determined, hereinafter referred to as coupled grids, and the coupled grids are considered as the exchange boundaries between the two-dimensional surface and the one-dimensional river network, and the water exchange of the one-dimensional and two-dimensional model occurs on the coupled grids; to ensure the conservation of water volume, the edges connecting the coupled grids and the river grids are set as closed boundaries. At the same time, the water level of the one-dimensional river network is interpolated so that the river water level corresponding to each coupled grid on the coupling boundary is more consistent with the change trend of the actual river water level along the way, ensuring the accuracy of the river water level used in the coupling calculation; the coupling relationship between the one-dimensional river network model and the two-dimensional surface hydrodynamic model is established, and finally a one-dimensional and two-dimensional coupled hydrodynamic model is formed.

4. The river bank breach simulation method based on a one-two-dimensional coupled hydrodynamic model according to claim 3, characterized in that: In the step S4, specifically: Firstly, the one-dimensional river network model and the two-dimensional surface hydrodynamic model are solved according to their respective boundary conditions. Then, the one-dimensional and two-dimensional water exchange directions are divided into the following four categories according to the river water level, levee elevation and surface water level: when the river water level is lower than the levee elevation and the surface water level is lower than the levee elevation, there is no water exchange; when the river water level is lower than the levee elevation and the surface water level is higher than the levee elevation, the water flows from the two-dimensional surface into the river; when the river water level is higher than the levee elevation and the surface water level is lower than the levee elevation, the water flows from the river into the two-dimensional surface; when the river water level is equal to the surface water level and both are higher than the levee elevation, there is still water exchange and the water exchange direction needs to be determined according to the flow direction on the coupled grid.

5. The river bank breach simulation method based on a one-two-dimensional coupled hydrodynamic model according to claim 4, characterized in that: The exchange volume is expressed by the following formula (1): Among them, Q S is the exchange volume calculated at the coupling boundary of the one-dimensional coupled hydrodynamic model, in m 3 / s; b is the weir width, in m; g is the gravitational acceleration, in m / s 2 ;h max =max(Z R ,Z G )-Z D ;h min =min(Z R ,Z G )-Z D ; Z R Indicates the river water level, in m; Z G Indicates the surface elevation in meters; Z D Indicates the embankment elevation in meters.

6. The river bank breach simulation method based on a one-two-dimensional coupled hydrodynamic model according to claim 5, characterized in that: In the step S5, specifically: The elevations of the left and right bank embankments of each section along the one-dimensional river network model, the breach form: instantaneous breach or gradual breach, breach direction, breach elevation, and breach bottom elevation are read from the one-dimensional and two-dimensional coupled hydrodynamic model input file. Then, the breach process is calculated to obtain the flow at the breach in the one-dimensional and two-dimensional coupled hydrodynamic model.

7. The river bank breach simulation method based on a one-two-dimensional coupled hydrodynamic model according to claim 6, characterized in that: The calculation method of instantaneous breach is as follows: when the water level of a one-dimensional river network section is higher than the breach elevation of a dike on one side of the section, it is considered that the dike on this side is instantly breached to the set breach bottom elevation, and then the exchange volume is calculated using the following weir flow formula (2): Among them, Q S is the flow rate of the breach at the instantaneous breach, in m 3 / s; b is the breach width, in m; Z R is the river water level, in m; Z DIE is the breach bottom elevation, in meters; Z DBE is the breach elevation, in meters; g is the acceleration of gravity, in meters per second 2 ; The calculation method of gradual breach is as follows: when the water level of a one-dimensional river network section is higher than the breach elevation of a dike on one side of the section, it is considered that the dike on this side will breach in a certain way, and the breach will gradually expand until it stabilizes. Then the flow process is coupled into the model to calculate the breach process, as shown in formula (3): Among them, Q Timeseries is the breach flow rate during gradual breach, in m 3 / s.

8. The river bank breach simulation method based on a one-two-dimensional coupled hydrodynamic model according to claim 7, characterized in that: In the step S6, specifically: Within the same calculation time step, the breach flow obtained in S5 is subtracted from the one-dimensional river network model and added to the corresponding breach position in the two-dimensional surface hydrodynamic model. The one-dimensional and two-dimensional coupled hydrodynamic model is used to calculate the evolution of the dam breach flood, and then the inundation range, water depth, and duration of the dam breach flood on the surface are obtained.

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