An integrated simulation method for flood routing

Abstract

The application discloses an integrated simulation method for flood evolution, characterized in that the method comprises the following steps: sketching the plane profile of ground objects in a research area, identifying and classifying the ground objects; performing fine modeling of the ground objects in the research area; performing time-space numerical discretization of two-dimensional control equations describing water flow movement on a calculation grid, and constructing a two-dimensional water dynamic solver; establishing a ground object calculation module of a river channel and towns along the river channel / retaining and detention flood storage areas, and a connection calculation module; establishing a time-space connectivity control module of the river channel and the towns along the river channel / retaining and detention flood storage areas, and performing simulation of flood evolution and regulation of the river channel and the towns along the river channel / retaining and detention flood storage areas at a time step; saving the results of a water flow plane physical field, a cross-section water level and a flow process calculated by a flood pre-forecast cooperative work system in a hard disk, and performing flood regulation analysis and evaluation. The application has the advantages of good stability, high reliability, high calculation efficiency and strong universality.

Description

Technical Field

[0001] This application belongs to the field of water conservancy simulation, specifically an integrated simulation method for flood evolution. Background Technology

[0002] Flood evolution simulation is a fundamental task frequently required in watershed flood management. In the information age, moving flood simulation online, enabling online calculations, and utilizing visualization engines to create digital twins of water conservancy (watersheds) is a growing trend in the industry. Flood evolution in rivers and along riverside towns / flood detention areas is often closely linked; therefore, conducting integrated synchronous simulations of these two systems and carrying out flood risk assessments are common practical needs. Researching integrated simulation methods for flood evolution in rivers and along riverside towns / flood detention areas has significant practical value. However, integrated simulation of flood evolution in rivers and along riverside towns / flood detention areas is a complex and systematic task, involving modeling various types of complex areas, flood evolution calculations, and flood control, making it highly challenging. The following analysis addresses three main difficulties.

[0003] River channels and riverside towns / flood detention areas typically contain various land features that may or may not be submerged, such as submerged dams, groynes, and bridge piers in the river channel, and houses, roads, and infrastructure in riverside towns. Previously, when simulating flood evolution in rivers and riverside towns / flood detention areas, the "additional roughness method" (using a larger-scale two-dimensional grid to partition the land features and their surrounding area, and empirically increasing the roughness of the land feature area to reflect its water-blocking effect) was commonly used to indirectly describe the impact of land features on water flow. Its drawback is that it cannot accurately describe the land features or simulate the real flow scenario in and around them. If a grid of the same scale as the land features is used to cover the land features and their surrounding area, the corresponding fine-grained two-dimensional modeling will generate a large number of small-scale grids and easily cause computational instability in hydrodynamic solvers (such as Mike21). Therefore, two-dimensional modeling of rivers and riverside towns / flood detention areas faces the difficult challenge of simultaneously achieving "precise depiction of land features" and "ensuring the stability of the hydrodynamic solver."

[0004] One-dimensional (1D), two-dimensional (2D), and nested hydrodynamic models are commonly used model types for flood evolution calculations. One-dimensional models can simulate macroscopic flood processes at river and lake cross-sections in real time, while two-dimensional models can finely reproduce flooding and receding scenarios in towns and various floodplains. Therefore, nested 1D and 2D models have traditionally been used to conduct integrated simulations of flood evolution in rivers and their surrounding towns / flood detention areas (using a 1D model to calculate the river channel and a 2D model to calculate the towns / flood detention areas). However, nested 1D and 2D models often require empirical formulas (such as the weir flow formula used in Hec-ras) for flow calculations at the junction of the river channel and the surrounding area, often resulting in large calculation errors and poor simulation effects. Using a 2D model to synchronously simulate the river channel and its surrounding area is an effective solution, but it introduces new problems, such as large water level gradient scenarios that may occur at the junction of the river channel and the surrounding area (e.g., large water level gradient flows caused by dike breaches or sudden opening of flood diversion gates, and intermittent water level flows). The large time-step stable solution techniques for these scenarios still require further research.

[0005] The longitudinal strip-shaped area connecting the river channel and the riverside towns / flood detention areas is generally composed of a mixture of riverbank elevations, dikes, and control gates. During the evolution of floods in the basin, this longitudinal strip-shaped area (whose geological and engineering properties are heterogeneous) may experience events such as local dike breaches, emergency breach repairs, and the activation and closure of flood diversion gates. This causes the connectivity between the river channel and the riverside towns / flood detention areas to change over time and space. Specifically, the spatiotemporal connectivity indicators of the river channel and the riverside towns / flood detention areas include the start and end times of connectivity, spatial distribution, and scale. The flood evolution patterns of the river channel and the riverside towns / flood detention areas, and their response patterns to the regulation of various spatiotemporal connectivity indicators, are usually very complex. Accurately considering the changes in spatiotemporal connectivity and conducting stable and efficient flood evolution simulations in the integrated simulation of flood evolution of the river channel and the riverside towns / flood detention areas are also issues that need further research. Summary of the Invention

[0006] The purpose of this application is to provide an integrated simulation method for the evolution of floods in rivers and riverside towns / flood storage areas, which solves the problems of difficult regional connection and transition, poor simulation effect and weak adaptability of the current synchronous simulation method for the evolution of floods in different regions in the field of water conservancy simulation technology.

[0007] To achieve the above objectives, this application provides the following technical solution:

[0008] This application provides an integrated simulation method for flood evolution, comprising the following steps:

[0009] Step 1: Draw the planar outline of the land features within the study area, identify and classify the land features, and divide the study area into several zones according to the type, characteristics and planar distribution of the land features;

[0010] Step 2: Conduct detailed modeling of terrain features within the study area, and carry out multi-level, multi-scale two-dimensional unstructured mesh modeling of river channels and riverside towns / flood storage areas, specifically including mesh creation and terrain interpolation;

[0011] Step 3: Discretize the two-dimensional governing equations describing the water flow motion in time and space on the computational grid to construct a two-dimensional hydrodynamic solver;

[0012] Step 4: Establish a feature calculation module and a connection calculation module for the river channel and riverside towns / flood storage areas, and couple them to a two-dimensional hydrodynamic solver to build a flood evolution simulator. This simulator has the ability to simulate the flood evolution of the river channel and riverside towns / flood storage areas in a synchronous manner.

[0013] Step 5: Establish a spatiotemporal connectivity control module between the river channel and riverside towns / flood storage areas, so that it can work in coordination with the flood evolution simulator, and then build a flood pre-simulation collaborative working system to realize the integrated simulation function of flood evolution and regulation of the river channel and riverside towns / flood storage areas;

[0014] Step 6: For the selected study area, calibrate the hydrodynamic solver parameters, set the inlet and outlet open boundary conditions and flood control information for the study area, start the established flood simulation collaborative working system, and conduct hourly simulations of the flood evolution and control of the river and riverside towns / flood storage areas.

[0015] Step 7: Save the results of the water flow plane physical field, cross-sectional water level and flow process calculated by the flood pre-simulation collaborative working system to the hard disk, and carry out flood control analysis and evaluation.

[0016] Specifically, step 1 is as follows:

[0017] Step 11: Based on GIS and AutoCAD topographic maps, batch sketch the planar outlines of river channels and features in the riverside area, and identify various features;

[0018] Step 12: Classify land features, classify potentially submerged land features into the submerged category; classify non-submerged land features into the non-submerged category; classify the dikes between the river and riverside towns / flood storage areas into the submerged category; use different signs to distinguish between submerged and non-submerged land features.

[0019] Step 13: For areas with complex land cover distribution, divide the river and riverside towns / flood storage areas into several zones based on the shape, scale and distribution characteristics of the land cover on the plane, in order to help control the density of the computational grid in each local area.

[0020] Step 2 specifically involves:

[0021] Step 21: Select a two-dimensional unstructured grid as the computational grid type for modeling the river channel and riverside towns / flood storage areas;

[0022] Step 22: For non-submerged features, use the cut-out method for 2D modeling: exclude the planar area occupied by the feature from the calculation area. For submerged features, use the solid method for 2D modeling: arrange the grid according to the feature outline to make the grid overlap with the feature, modify the corresponding grid node attributes according to the feature characteristics to describe the feature, and locally refine the grid near the feature to improve the spatial resolution of the grid.

[0023] Step 23: The strip-shaped area between the river channel and the riverside town / flood storage area is called the embankment segment. The embankment segment is modeled in two dimensions using the solid method. The grid cells belonging to the embankment segment are identified and distinguished. The cells of the ordinary embankment segment are identified as 1, and the cells of the gate-controlled embankment segment are identified as 2.

[0024] Step 24: Partitioning into multi-level, multi-scale two-dimensional unstructured meshes, using a progressively enlarged mesh scale method to achieve a smooth transition between fine and large-scale meshes, meeting the different mesh resolution requirements of different regions;

[0025] Step 25: Scatter the scattered topography of the river channel with the DEM topography of the riverside towns / flood storage areas, and perform topographic interpolation on the nodes of the two-dimensional computational grid based on this.

[0026] In step 3, the two-dimensional hydrodynamic solver refers to a hydrodynamic calculation program based on a planar two-dimensional unstructured mesh, open boundary conditions, and initial conditions of the computational domain. It includes functions such as discretizing and solving the two-dimensional control equations of the flow, and outputting the results. The two-dimensional control equations of the flow are as follows:

[0027] The two-dimensional governing equations for the water flow are as follows:

[0028] (1)

[0029] (2)

[0030] (3)

[0031] In the formula, h(x, y, t) is the water depth, u(x, y, t) and v(x, y, t) are the average current velocities at the water depth in the horizontal x and y directions, respectively, t is time, g is the acceleration due to gravity, η(x, y, t) is the height of the free water surface, and υ τ n is the horizontal eddy viscosity coefficient. m This is the roughness coefficient.

[0032] Step 4 specifically involves:

[0033] Step 41: Establish a feature calculation module for riverside towns / flood storage areas. This module first identifies features and their types based on planar regional characteristics. For cavities formed by the borehole method, when performing hydrodynamic calculations, the cavity boundary is treated as a solid wall boundary and solid wall boundary conditions of 0 normal flow velocity and 0 normal water level gradient are applied. The expressions for these boundary conditions are:

[0034] u=0, ∂η / ∂x=0 (4)

[0035] Step 42: Establish a connection calculation module between the river channel and the riverside area. This module first identifies the area type based on the identifier of the grid cells in the riverside strip area. On this basis, it processes and calculates the large water level gradient scenarios that may occur in the riverside strip area, including the following steps:

[0036] Step 421: For the element edges of the cells within the riverside strip region, define the constraint value Δ of the normal water level gradient ∂η / ∂x when it is flowing. max As an additional condition for using the θ semi-implicit method and the Euler-Lagrange method together to solve the flow control equations,

[0037] Step 422: For the element edges of the unit within the river strip region, first determine the sign of its normal water level gradient. When ∂η / ∂x≥0, the water level gradient term in the water flow equation is calculated using the following formula.

[0038] -g∂η / ∂x = -gMin(∂η / ∂x, Δ max (5a)

[0039] When ∂η / ∂x < 0, the water level gradient term in the water flow equation is calculated using the following formula.

[0040] -g∂η / ∂x = -gMax(∂η / ∂x, -Δ max (5b)

[0041] Step 43: Couple the ground feature calculation module and the connection calculation module to the two-dimensional hydrodynamic solver. The resulting flood evolution simulator will still extrapolate the flood evolution process at intervals of Δt.

[0042] Step 431: At the beginning of each time step, the two-dimensional hydrodynamic solver calls the judgment and calculation formulas of the connection calculation module and the excavation boundary calculation rules of the ground feature calculation module, and combines the water level gradient term of the discrete momentum equation using the θ semi-implicit method to solve the momentum equation and even the entire flow control equation.

[0043] Step 432: At the end of each time step, the two-dimensional hydrodynamic solver calls the ground feature calculation module to set the normal flow velocity at the cut-out boundary using the u=0 condition.

[0044] Step 433: The two-dimensional hydrodynamic solver completes other tasks in the Δt time step.

[0045] Step 5 specifically involves:

[0046] Step 51: Establish a spatiotemporal connectivity control module. By modifying the attributes of the river embankment section, the connectivity between the river channel and riverside towns / flood detention areas is set or updated. This module implements spatiotemporal connectivity control, including the following steps:

[0047] Step 511: Set spatiotemporal connectivity control indicators. For ordinary dike sections, based on the selected flood simulation plan and dike section stability data, set the start and end times of dike section breach, breach range, and breach topography. The breach overflow termination time can be estimated based on the selected emergency response intensity in the flood simulation plan or past experience.

[0048] Step 512: Standardize spatiotemporal connectivity control indicators. For ordinary dike sections, the data includes the start and end times of terrain rise and fall in the breached dike section, the unit list, and the unit terrain rise and fall values. For gate-controlled dike sections, the data includes the gate opening / closing time, the gate opening range unit list, the gate bottom plate elevation, and the gate height.

[0049] Step 513: Based on the provisions and information in Steps 511-512, set or update the connectivity between the river channel and the riverside towns / flood storage areas by modifying the properties of the grid cells within the river embankment section.

[0050] Step 52: The established flood simulation collaborative system continues to advance step by step at intervals of Δt. The collaborative operation of the flood evolution simulator and the spatiotemporal connectivity control module includes the following steps:

[0051] Step 521: At each initial time Δt, call the spatiotemporal connectivity control module to update the connectivity status between the river channel and the riverside towns / flood storage areas. If no connectivity change event occurs, proceed to step 525; if the connectivity of a levee section changes, proceed to step 522.

[0052] Step 522: If the connectivity of a certain section of the dike changes from "blocked → connected", then proceed to step 523; if the connectivity of a certain section of the dike changes from "connected → blocked", then proceed to step 524. Here, "connected" means that the dike section breaches or the sluice gate is opened for flow, and "blocked" means that the gap in the dike section is filled back to its original state or the sluice gate is closed.

[0053] Step 523: Lower the elevation of the riverbed within the embankment section to the design value, and initialize the flow state of these units and their edges;

[0054] Step 524: Raise the unit topographic elevation within the breach section to the design value, treat the units within the restored water-retaining section as solid boundaries, and set the unit water depth, unit center and flow velocity on each side to 0 to create a scenario where the current section of the dike is blocked.

[0055] Step 525: After calling the spatiotemporal connectivity control module to complete the update of connectivity indicators of the levee section unit and the corresponding water flow status initialization, continue to execute the flood evolution process calculation;

[0056] Step 526: At regular intervals, obtain and store the planar physical field data of the water flow. Based on the planar physical field data of the water flow, construct the flooding and receding scenario of the riverside town / flood storage area. Obtain the change process of the cross-sectional average water level and flow rate over time by averaging or integration.

[0057] Step 527: Complete the integrated simulation of flood evolution in the river channel and along the river towns / flood storage areas. Based on the water flow plane physical field data, obtain the evolution path of the flood among the land features in the river area, formulate evacuation routes, calculate flood indicators and urban flood inundation losses, and then analyze the flood control effect and optimize the control plan.

[0058] Compared with the prior art, the beneficial effects of the present invention are:

[0059] Replacing previous generalized methods with refined 2D ground feature modeling, this new method realistically depicts ground features and nearby water flow patterns in river channels and along riverbanks. The new method combines the theta semi-implicit and Eulerian-Lagrange methods to overcome the computational instability of hydrodynamic models caused by refined 2D modeling (which generates numerous small-scale grids), enabling large-time-step flood evolution calculations. Previous studies of this type often employed explicit hydrodynamic solvers with very small computation time steps (often less than 1 second), resulting in low efficiency. Secondly, by coupling the ground feature calculation module and the river channel and along-river area connection calculation module into the 2D hydrodynamic solver, the resulting flood evolution simulator possesses the ability to synchronously simulate the flood evolution of the river channel and along-river towns / flood detention areas. Thirdly, a spatiotemporal connectivity control module for the river channel and along-river towns / flood detention areas is established, enabling it to work in coordination with the flood evolution simulator and simulate the flood evolution and regulation of the river channel and along-river towns / flood detention areas.

[0060] This invention solves the problems of difficult regional transition, poor simulation effect, and weak adaptability in the overall synchronous simulation method of flood evolution in different regions in the field of water conservancy simulation technology. At the same time, it has the advantages of good stability, high reliability, high computational efficiency, and strong versatility. Attached Figure Description

[0061] Figure 1 This is a schematic diagram illustrating the execution flow of the integrated simulation method for flood evolution of rivers and riverside towns / flood storage areas according to the present invention.

[0062] Figure 2 This is a schematic diagram showing the distribution of features in the river and riverside towns / flood storage areas where the present invention is implemented.

[0063] Figure 3 This is a schematic diagram of a multi-level, multi-scale computational grid for partitioning the research area in which this invention is implemented.

[0064] Figure 4 This is a schematic diagram illustrating the multi-level, multi-scale modeling effect of the research area partitioning in implementing this invention.

[0065] Figure 5 The results are physical field calculations from the integrated simulation of flood evolution in rivers and riverside towns / flood storage areas, which implements the present invention.

[0066] Figure 6 The results are the calculation results of the flooding and receding process of riverside towns / flood storage areas, which are the result of the integrated simulation of flood evolution of river channels and riverside towns / flood storage areas implemented in this invention.

[0067] Figure 7 This is the calculation result of the flood diversion process in the integrated simulation of flood evolution of river channels and riverside towns / flood storage areas implemented in this invention. Detailed Implementation

[0068] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0069] As attached Figure 1 As shown, Figure 1 This is a schematic diagram illustrating the execution flow of the integrated simulation method for flood evolution of rivers and riverside towns / flood storage areas according to the present invention. Figure 1 middle,

[0070] Step 1: Draw the planar outline of land features within the study area (including various types of planar areas such as rivers, riverside towns, and flood storage areas), identify and classify the land features, and divide the study area into several zones according to the types, characteristics, and planar distribution of the land features.

[0071] Step 2: Conduct detailed modeling of terrain features within the study area, and carry out multi-level, multi-scale two-dimensional unstructured mesh modeling of river channels and riverside towns / flood storage areas, including mesh creation and terrain interpolation.

[0072] Step 3: Discretize the two-dimensional governing equations describing water flow motion in space and time on the computational grid to construct a two-dimensional hydrodynamic solver.

[0073] Step 4: Establish a feature calculation module and a connection calculation module for the river channel and riverside towns / flood storage areas, and couple them to a two-dimensional hydrodynamic solver to build a flood evolution simulator. This simulator has the ability to simulate the flood evolution of the river channel and riverside towns / flood storage areas in a synchronous manner.

[0074] Step 5: Establish a spatiotemporal connectivity control module between the river channel and riverside towns / flood storage areas, so that it can work in coordination with the flood evolution simulator, and then build a flood pre-simulation collaborative working system to realize the integrated simulation function of flood evolution and regulation of the river channel and riverside towns / flood storage areas.

[0075] Step 6: For the selected study area, set the open boundary conditions such as inflow and outflow rates and water levels, as well as flood control information. Start the established flood simulation collaborative working system and conduct hourly simulations of the flood evolution and control of the river and riverside towns / flood storage areas.

[0076] Step 7: Save the results of the water flow plane physical field, cross-sectional water level and flow process calculated by the flood pre-simulation collaborative working system to the hard disk, and carry out flood control analysis and assessment based on them.

[0077] Figure 2 This is a schematic diagram of the distribution of land features in the river and riverside towns / flood storage areas where the present invention is implemented (taking a tributary of the Yangtze River and its riverside towns as an example). Figure 2 middle,

[0078] The study area includes the river channel and towns along the river. The river channel is 300m to 400m wide, and along the riverbank are highlands, sections of compliant dikes (elevation greater than the design flood level), and damaged sections of dikes (lower terrain with gaps). As shown in the figure, the features in the urban area mainly include buildings, roads, and various infrastructure, characterized by their large number, varying shapes and sizes, and irregular distribution.

[0079] Figure 3 This is a schematic diagram of a multi-level, multi-scale computational grid for partitioning the research area in which this invention is implemented. Figure 3 middle,

[0080] The study area includes rivers and towns along the rivers. The modeling process (using the cutout method for detailed modeling of urban features) is as follows: ① The town is divided into several zones based on the shape, scale, and distribution of features on the plane to help control the grid density of each local area. ② The areas representing buildings are removed from each zone, and a high-resolution grid is generated based on the remaining area. ③ The urban grid and the river grid are connected by a step-by-step grid scaling method (e.g., multi-level scaling from urban area → riverside → upstream and downstream river channels) to achieve a smooth transition between the detailed and large-scale grids, meeting the different grid resolution requirements of different areas. Figure 3The grid scale for the unstructured quadrilateral is as follows: ① The grid scale for urban features and their vicinity is 2-5m; ② In the transition zone between the urban area and the river channel, the grid scale increases to 8-10m; ③ In the upstream and downstream river sections, the grid scale further increases to 20m in the direction of water flow.

[0081] Figure 4 This is a schematic diagram illustrating the multi-level, multi-scale modeling effect of the research area partitioning in implementing this invention. Figure 4 middle,

[0082] The river channel and the towns along the river were obtained through a finely detailed two-dimensional grid. Based on this computational grid, topographic interpolation was performed, and the resulting two-dimensional model of the river channel and the towns along the river can realistically reflect the river conditions and the complex distribution of urban features and landforms in the study area, achieving excellent modeling results.

[0083] Figure 5 The results of the physical field calculations for the integrated simulation of flood evolution in river channels and riverside towns / flood detention areas, as described in this invention, are as follows: Figure 2 (Taking the study area as an example). Figure 5 middle,

[0084] The invention presents a scenario of urban flooding caused by external flooding at the peak flow of a river, including the flow field, water depth, and planar distribution in riverside towns. As shown in the figure, the method of this invention accurately simulates the flow field and water flow patterns (e.g., flow around buildings, local planar backflow, etc.) of an urban area during flood intrusion, clearly outlining the flood evolution path and achieving a detailed simulation of the evolution of river floods in urban land areas. Based on the urban flooding scenario, work such as the formulation of evacuation routes can be carried out. Stability tests show that the model can be stably calculated under a large time step of Δt ≥ 60s, and provides reasonable calculation results (rapid rise and fall of river floodwaters, urban flooding and receding processes, etc.). The maximum flow velocity in the river is 4.3 m / s (CFL > 25); the maximum flow velocity at the junction of the town and the river is 2.0 m / s (CFL > 15). Efficiency tests show that the established model (20,000 elements, Δt = 60s) simulates a 15-day flood in only 6 minutes on a mainstream workstation, demonstrating high efficiency.

[0085] Figure 6 This is the calculation result of the flooding and receding process of riverside towns / flood storage areas in the integrated simulation of flood evolution of river channels and riverside towns / flood storage areas implemented in this invention (in the form of...). Figure 2 (Taking the study area as an example). Figure 6 middle,

[0086] Using a 1% frequency flood process, and based on this, the open boundary conditions and flood control information of the study area are set, and the established flood pre-simulation collaborative working system is launched to carry out an integrated simulation of the flood evolution of the river and the towns along the river on an hourly basis. Figure 6The simulation results, presented on a WebGIS 3D topographic map, illustrate four key scenarios of flooding and receding water in a riverside town under conditions of river flood intrusion: ① Initially, the river level is low, and the town is dry; ② The river level rises, and the water overflows damaged embankments and flows into the town along the streets; ③ When the river flow reaches its peak, the town is flooded to its maximum extent; ④ After the flood recedes, water remains in low-lying areas of the town. The simulation results demonstrate that the method of this invention can provide a detailed simulation of the non-constant flow process in and out of towns. Based on the calculated flow field, water depth, and planar distribution, flood risk assessments can be conducted.

[0087] Figure 7 This is the calculation result of the flood diversion process in the integrated simulation of flood evolution of river channels and riverside towns / flood storage areas implemented in this invention (based on the adjacent...). Figure 2 (Taking the downstream section of the river as an example). Figure 7 middle,

[0088] The study area includes the river channel and flood detention area, which are separated by a continuous dike. The river is 400m to 600m wide. A flood diversion gate with a total gate width of 108m is located at a certain point along the dike. The total area of ​​the flood detention area on the right bank of the river is 33.88 km². 2 The flood storage and detention area is mostly farmland with relatively simple terrain features. A quadrilateral unstructured mesh was used for modeling, while solid modeling was used for the flood diversion gates and a few dikes within the flood storage and detention area. Based on this, a method of progressively enlarging the mesh scale (flood control dike → river channel outside the flood storage and detention area → upstream and downstream river channels) was adopted to achieve a smooth transition between fine and large-scale meshes. The mesh scales are as follows: ① Flood diversion gates and their vicinity: 10-20m; ② Flood control dikes and their vicinity: 20×40m; ③ River channel mesh scale: 25×40m near flood control dikes and 50×100m in upstream and downstream sections.

[0089] Using a 1% frequency flood process, and based on this, the open boundary conditions and flood control information of the study area are set, and the established flood pre-simulation collaborative working system is launched to carry out an integrated simulation of the flood evolution of the river and the towns along the river on an hourly basis. Figure 7 The invention illustrates four key scenarios of the flood diversion process: ① the large water level gradient at the moment the river channel connects with the flood storage area (the flood diversion gate opens); ② the characteristic flow of the dam break formed in the early stage of flood diversion (with a significant front); ③ the scene of river water flowing into a wide area through the flood diversion gate; and ④ the evolution of the diverted flood flow in the flood storage area. As shown in the figures, the method of this invention can effectively conduct integrated simulation of the flood evolution of the river channel and the flood storage area, accurately reflecting the flood control (flood diversion) scenario.

[0090] The above embodiments are merely illustrative examples of the technical solutions of the present invention. The inversion model construction method involved in the present invention is not limited to the content described in the above embodiments, but is subject to the scope defined by the claims. Any modifications, additions, or equivalent substitutions made by those skilled in the art based on these embodiments are within the scope of protection claimed by the present invention.

Claims

1. An integrated simulation method for flood evolution, characterized in that, Includes the following steps: Step 1: Draw the planar outline of the land features within the study area, identify and classify the land features, and divide the study area into several zones according to the type, characteristics and planar distribution of the land features; Step 2: Conduct detailed modeling of terrain features within the study area, and carry out multi-level, multi-scale two-dimensional unstructured mesh modeling of river channels and riverside towns / flood storage areas, specifically including mesh creation and terrain interpolation; Step 3: Discretize the two-dimensional governing equations describing the water flow motion in time and space on the computational grid to construct a two-dimensional hydrodynamic solver; Step 4: Establish a feature calculation module and a connection calculation module for the river channel and riverside towns / flood storage areas, and couple them to a two-dimensional hydrodynamic solver to build a flood evolution simulator. This simulator has the ability to simulate the flood evolution of the river channel and riverside towns / flood storage areas in a synchronous manner. Step 5: Establish a spatiotemporal connectivity control module between the river channel and riverside towns / flood storage areas, so that it can work in coordination with the flood evolution simulator, and then build a flood pre-simulation collaborative working system to realize the integrated simulation function of flood evolution and regulation between the river channel and riverside towns / flood storage areas; Step 6: For the selected study area, calibrate the hydrodynamic solver parameters, set the inlet and outlet open boundary conditions and flood control information for the study area, start the established flood simulation collaborative working system, and conduct hourly simulations of the flood evolution and control of the river and riverside towns / flood storage areas. Step 7: Save the results of the water flow plane physical field, cross-sectional water level and flow process calculated by the flood pre-simulation collaborative working system to the hard disk, and carry out flood control analysis and evaluation; In step 3, the two-dimensional hydrodynamic solver refers to a hydrodynamic calculation program based on a planar two-dimensional unstructured mesh, open boundary conditions, and initial conditions of the computational domain. It includes functions such as discretizing and solving the two-dimensional control equations of the flow, and outputting the results. The two-dimensional control equations of the flow are as follows: The two-dimensional governing equations for the water flow are as follows: (1) (2) (3) In the formula, Because of the water depth, and denoted by x and y, respectively, represent the average current velocities at depth in the horizontal x and y directions, respectively; t represents time; and g represents the acceleration due to gravity. The height of the free water surface. The viscosity coefficient of the horizontal eddy is... For roughness; Step 4 specifically involves: Step 41: Establish a feature calculation module for riverside towns / flood storage areas. This module first identifies features and their types based on planar regional characteristics. For cavities formed by the borehole method, when performing hydrodynamic calculations, the cavity boundary is treated as a solid wall boundary and solid wall boundary conditions of 0 normal flow velocity and 0 normal water level gradient are applied. The expressions for these boundary conditions are: (4) Step 42: Establish a connection calculation module between the river channel and the riverside area. This module first identifies the area type based on the identifier of the grid cells in the riverside strip area. On this basis, it processes and calculates the large water level gradient scenarios that may occur in the riverside strip area, including the following steps: Step 421: For the cell edges of the unit within the river strip region, define the normal water level gradient when it is flowing. Limits As a joint use Additional conditions for solving the flow control equations using semi-implicit and Eulerian-Lagrange methods. Step 422: For the element edges within the riverside strip region, first determine the sign of their normal water level gradient. The water level gradient term in the hourly water flow equation is calculated using the following formula. (5a) when The water level gradient term in the hourly water flow equation is calculated using the following formula. (5b) Step 43: Couple the ground feature calculation module and the connection calculation module to the two-dimensional hydrodynamic solver. The resulting flood evolution simulator still uses... To reconstruct the evolution of the flood at intervals: Step 431: At the beginning of each time step, the two-dimensional hydrodynamic solver calls the judgment and calculation formulas of the connection calculation module and the excavation boundary calculation rules of the ground feature calculation module, and combines the water level gradient term of the discrete momentum equation using the θ semi-implicit method to solve the momentum equation and even the entire flow control equation. Step 432: At the end of each time step, the two-dimensional hydrodynamic solver calls the ground feature calculation module to apply the solution at the cut-out boundary. The normal flow velocity at the cut-out boundary is set as a condition. Step 433: Two-dimensional hydrodynamic solver completed. Other tasks within the time step.

2. The integrated simulation method for flood evolution according to claim 1, characterized in that, Specifically, step 1 is as follows: Step 11: Based on GIS and AutoCAD topographic maps, batch sketch the planar outlines of river channels and features in the riverside area, and identify various features; Step 12: Classify land features, classify potentially submerged land features into the submerged category; classify non-submerged land features into the non-submerged category; classify the dikes between the river and riverside towns / flood storage areas into the submerged category; use different signs to distinguish between submerged and non-submerged land features. Step 13: For areas with complex land cover distribution, divide the river and riverside towns / flood storage areas into several zones based on the shape, scale and distribution characteristics of the land cover on the plane, in order to help control the density of the computational grid in each local area.

3. The integrated simulation method for flood evolution according to claim 2, characterized in that, Step 2 specifically involves: Step 21: Select a two-dimensional unstructured grid as the computational grid type for modeling the river channel and riverside towns / flood storage areas; Step 22: For non-submerged features, use the cut-out method for 2D modeling: exclude the planar area occupied by the feature from the calculation area. For submerged features, use the solid method for 2D modeling: arrange the grid according to the feature outline to make the grid overlap with the feature, modify the corresponding grid node attributes according to the feature characteristics to describe the feature, and locally refine the grid near the feature to improve the spatial resolution of the grid. Step 23: The strip-shaped area between the river channel and the riverside town / flood storage area is called the embankment segment. The embankment segment is modeled in two dimensions using the solid method. The grid cells belonging to the embankment segment are identified and distinguished. The cells of the ordinary embankment segment are identified as 1, and the cells of the gate-controlled embankment segment are identified as 2. Step 24: Partitioning into multi-level, multi-scale two-dimensional unstructured meshes, using a progressively enlarged mesh scale method to achieve a smooth transition between fine and large-scale meshes, meeting the different mesh resolution requirements of different regions; Step 25: Scatter the scattered topography of the river channel with the DEM topography of the riverside towns / flood storage areas, and perform topographic interpolation on the nodes of the two-dimensional computational grid based on this.

4. The integrated simulation method for flood evolution according to claim 1, characterized in that, Step 5 specifically involves: Step 51: Establish a spatiotemporal connectivity control module. By modifying the attributes of the river embankment section, the connectivity between the river channel and riverside towns / flood detention areas is set or updated. This module implements spatiotemporal connectivity control, including the following steps: Step 511: Set spatiotemporal connectivity control indicators. For ordinary dike sections, based on the selected flood simulation plan and dike section stability data, set the start and end times of dike section breach, breach range, and breach topography. The breach overflow termination time can be estimated based on the selected emergency response intensity in the flood simulation plan or past experience. Step 512: Standardize spatiotemporal connectivity control indicators. For ordinary dike sections, the data includes the start and end times of terrain rise and fall in the breached dike section, the unit list, and the unit terrain rise and fall values. For gate-controlled dike sections, the data includes the gate opening / closing time, the gate opening range unit list, the gate bottom plate elevation, and the gate height. Step 513: Based on the provisions and information in Steps 511-512, set or update the connectivity between the river channel and the riverside towns / flood storage areas by modifying the properties of the grid cells within the river embankment section. Step 52: The established flood simulation collaborative system continues to advance step by step at intervals of Δt. The collaborative operation of the flood evolution simulator and the spatiotemporal connectivity control module includes the following steps: Step 521: At each initial time Δt, call the spatiotemporal connectivity control module to update the connectivity status between the river channel and the riverside towns / flood storage areas. If no connectivity change event occurs, proceed to step 525; if the connectivity of a levee section changes, proceed to step 522. Step 522: If the connectivity of a certain section of the dike changes from "blocked → connected", then proceed to step 523; if the connectivity of a certain section of the dike changes from "connected → blocked", then proceed to step 524. Here, "connected" means that the dike section breaches or the sluice gate is opened for flow, and "blocked" means that the gap in the dike section is filled back to its original state or the sluice gate is closed. Step 523: Lower the elevation of the riverbed within the embankment section to the design value, and initialize the flow state of these units and their edges; Step 524: Raise the unit topographic elevation within the breach section to the design value, treat the units within the restored water-retaining section as solid boundaries, and set the unit water depth, unit center and flow velocity on each side to 0 to create a scenario where the current section of the dike is blocked. Step 525: After calling the spatiotemporal connectivity control module to complete the update of connectivity indicators of the levee section unit and the corresponding water flow status initialization, continue to execute the flood evolution process calculation; Step 526: At regular intervals, obtain and store the planar physical field data of the water flow. Based on the planar physical field data of the water flow, construct the flooding and receding scenario of the riverside town / flood storage area. Obtain the change process of the cross-sectional average water level and flow rate over time by averaging or integration. Step 527: Complete the integrated simulation of flood evolution in the river channel and along the river towns / flood storage areas. Based on the water flow plane physical field data, obtain the evolution path of the flood among the land features in the river area, formulate evacuation routes, calculate flood indicators and urban flood inundation losses, and then analyze the flood control effect and optimize the control plan.

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