Integrated simulation method for flood routing

Abstract

The invention discloses an integrated simulation method for flood routing, and the method is characterized in that the method comprises the following steps: delineating the plane contour of a ground feature in a research region, and carrying out the recognition and classification of the ground feature; fine modeling of ground objects in the research area is carried out; performing space-time numerical discretization on a two-dimensional control equation describing water flow movement on a computational grid, and constructing a two-dimensional hydrodynamic solver; establishing a ground feature calculation module and a connection calculation module of the river channel and the urban / flood storage and detention area along the river; establishing a space-time connectivity control module of the river channel and the urban / detention and detention area along the river, and carrying out simulation of flood routing and regulation and control of the river channel and the urban / detention and detention area along the river step by step; results such as a water flow plane physical field, a section water level and a flow process calculated by the flood rehearsal cooperative work system are stored in a hard disk, and flood regulation and control analysis and evaluation are carried out. The method has the advantages of being good in stability, high in reliability, high in calculation efficiency, high in universality and the like.

Description

Technical Field

[0001] The present application belongs to the field of water conservancy simulation, and specifically is an integrated simulation method for flood evolution. Background Art

[0002] Flood evolution simulation is a basic work that often needs to be carried out in river basin flood management. In the information age, it is a development trend in the industry to move flood simulation to the Internet, realize its online calculation, and use visualization engines to develop water conservancy (watershed) digital twins. The flood evolution of rivers and riverside towns / flood storage areas is often closely related. It is a common demand in practical work to simulate them as a whole and synchronously, and then carry out flood risk assessment. The integrated simulation method of flood evolution of rivers and riverside towns / flood storage areas has important practical value. At the same time, the integrated simulation of flood evolution of rivers and riverside towns / flood storage areas is a complex and systematic work, involving modeling of various types of complex areas, flood evolution calculation, flood control, etc., which is very challenging. The following is an analysis of three main difficulties.

[0003] Rivers and towns / flood storage areas along the river usually contain a variety of features that may be submerged or never submerged, such as submerged dams, groins, bridge piers, etc. in the river, and houses, roads, infrastructure, etc. in the town along the river. In the past, when simulating the evolution of floods in rivers and towns / flood storage areas along the river, people often used the "additional roughness method" (using a larger scale of two-dimensional grids to divide the features and their surrounding areas, and increasing the roughness of the feature area based on experience to reflect its water blocking effect) to indirectly describe the impact of features on water flow. Its disadvantage is that it cannot accurately describe the features or simulate the real flow scene of the features and their vicinity. If the features and their surrounding areas are covered with grids of the same scale as the features, the corresponding two-dimensional fine modeling will generate a large number of small-scale grids and easily cause the calculation instability of the hydrodynamic solver (such as Mike21, etc.). Therefore, the two-dimensional modeling of rivers and towns / flood storage areas along the river has the problem of "finely depicting the features" and "ensuring the stability of the hydrodynamic solver".

[0004] One-dimensional and two-dimensional hydrodynamic models and their nested models are commonly used models for flood evolution calculation. One-dimensional models can simulate the macroscopic flood process of river and lake sections in real time, and two-dimensional models can accurately reproduce the flooding and water retreat scenes of towns and various floodplains. Therefore, in the past, people often used one-dimensional and two-dimensional nested models to carry out integrated simulation of flood evolution of rivers and towns / flood storage areas along the river (using one-dimensional models to calculate rivers and two-dimensional models to calculate towns / flood storage areas along the river). However, one-dimensional and two-dimensional nested models usually need to use empirical formulas (such as Hec-ras and other weir flow formulas) to carry out flow calculations at the junction of rivers and riverside areas, which often results in large calculation errors and poor simulation effects. Using two-dimensional models to simulate rivers and riverside areas as a whole and synchronously is an effective solution, but it will introduce new problems, such as the large water level gradient scene that may appear at the junction between rivers and riverside areas (such as large water level gradient water flow and water level intermittent characteristic water flow formed by the collapse of embankments or the sudden opening of diversion gates), and its large time step stable solution technology needs to be studied.

[0005] The longitudinal strip-shaped area connecting the river and the riverside towns / flood storage and detention areas is generally composed of a mixture of riverbank heights, levees, control gates, etc. During the evolution of the basin flood, the longitudinal strip area (whose geological and engineering properties are uneven) may experience local levee breaches, emergency rescue and blockage of breaches, and the activation and closure of diversion gates, which will cause the connectivity between the river and the riverside towns / flood storage and detention areas to change over time and space. Specifically, the spatiotemporal connectivity indicators of the river and the riverside towns / flood storage and detention areas include the start and end time of the connection, spatial distribution, and scale. The flood evolution law of the river and the riverside towns / flood storage and detention areas, and the response law to the regulation of various spatiotemporal connectivity indicators are usually very complex. In the integrated simulation of flood evolution in the river and the riverside towns / flood storage and detention areas, it is also a problem to be studied to accurately consider the changes in spatiotemporal connectivity and to carry out flood evolution simulation stably and efficiently. Summary of the invention

[0006] The purpose of the embodiments of the present application is to provide an integrated simulation method for flood evolution in a river channel and towns / flood storage areas along the river, so as to solve the problems existing in the overall synchronous simulation method of flood evolution in different regions in the current field of water conservancy simulation technology, such as difficult regional connection and transition, poor simulation effect, weak adaptability, etc.

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

[0008] The present invention provides an integrated flood simulation method, comprising the following steps:

[0009] Step 1: Draw the plane contours of the objects in the study area, identify and classify the objects, and divide the study area into several zones according to the types, characteristics and plane distribution of the objects;

[0010] Step 2: Carry out detailed modeling of the terrain in the study area, and carry out multi-level and multi-scale two-dimensional unstructured grid modeling of the river and the towns / flood storage areas along the river, including grid production and terrain interpolation;

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

[0012] Step 4: Establish the terrain calculation module and connection calculation module of the river and the riverside towns / flood storage areas, and couple them to the two-dimensional hydrodynamic solver to build a flood evolution simulator, which has the ability to simulate the flood evolution of the river and the riverside towns / flood storage areas as a whole and synchronously;

[0013] Step 5: Establish a spatiotemporal connectivity control module between the river and the towns / flood storage areas along the river, coordinate it with the flood evolution simulator, and then form a flood pre-exercise collaborative work system to achieve the integrated simulation function of flood evolution and its regulation between the river and the towns / flood storage areas along the river;

[0014] Step 6: For the selected study area, calibrate the parameters of the hydrodynamic solver, set the inlet and outlet boundary conditions and flood control information of the study area, start the established flood simulation collaborative work system, and simulate the flood evolution and control of the river channel and the towns / flood storage areas along the river step by step;

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

[0016] The step 1 specifically comprises:

[0017] Step 11: Based on GIS and AutoCAD topographic maps, batch outline the plane contours of the river channels and riverside areas, and identify various landforms;

[0018] Step 12: Classify the features, classify the features that may be submerged as submerged features; classify the features that will never flow as non-submerged features; classify the levees between the river and the towns / flood storage areas along the river as submerged features, and use different signs to mark and distinguish the submerged and non-submerged features;

[0019] Step 13: For areas with complex distribution of land features, divide the river channel and riverside towns / flood storage areas into several sub-areas based on the shape, scale and distribution characteristics of the land features on the plane, so as to help control the density of the calculation grid in each local area.

[0020] The step 2 is specifically as follows:

[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-flooded features, the two-dimensional modeling is performed using the hollowing method: the plane area occupied by the features is excluded from the calculation area. For flooded features, the two-dimensional modeling is performed using the solid method: the grid is arranged according to the feature outline so that the grid overlaps the feature, the corresponding grid node attributes are modified according to the features of the feature to describe the feature, and the grid near the feature is locally encrypted to improve the spatial resolution of the grid;

[0023] Step 23: The strip-shaped area between the river channel and the town / flood storage area along the river is called a dike section. The dike section is modeled in two dimensions using the entity method. The grid cells belonging to the dike section are marked and distinguished. The cells of the ordinary dike section are marked as 1, and the cells of the gate-controlled dike section are marked as 2.

[0024] Step 24: partition the two-dimensional unstructured grid into multiple levels and scales, and use the method of gradually enlarging the grid scale to achieve a smooth connection between the fine grid and the large-scale grid, so as to meet the different requirements of different regions for grid resolution;

[0025] Step 25: Splice the scattered topography of the river channel with the DEM topography of the riverside town / flood storage area, and interpolate the topography of the nodes of the two-dimensional computational grid based on this.

[0026] The two-dimensional hydrodynamic solver in step 3 refers to a hydraulic calculation program based on a two-dimensional unstructured grid, open boundary conditions, initial conditions of the calculation area, etc., including functions such as discretization and solution of the two-dimensional control equation of water flow and result output. The two-dimensional control equation of water flow is as follows:

[0027] The two-dimensional water flow control equation is as follows:

[0028] (1)

[0029] (2) (3)

[0030] Where h(x, y, t) is the water depth, u(x, y, t) and v(x, y, t) are the average water velocity in the horizontal x and y directions, t is time, g is the gravitational acceleration, η(x, y, t) is the height of the free water surface, and υ is τ is the horizontal eddy viscosity coefficient, n m For the roughness.

[0031] The step 4 is specifically as follows:

[0032] Step 41: Establish a land feature calculation module for riverside towns / flood storage areas. This module first identifies land features and their types based on the plane area characteristics. For the cavity formed by the hole digging method, when performing its hydrodynamic calculation, the cavity boundary is regarded as a solid wall boundary and solid wall boundary conditions with normal flow velocity of 0 and normal water level gradient of 0 are applied. The expressions of these boundary conditions are:

[0033] u=0,∂η / ∂x=0 (4)

[0034] Step 42: Establish a calculation module for the connection between the river channel and the riverside area. The module first identifies the area type according to the identification of the grid cells in the riverside strip area. On this basis, it processes and calculates the large water level gradient scene that may appear in the riverside strip area, including the following steps:

[0035] Step 421: For the cell edge of the cell in the strip region along the river, define the limit value Δ of the normal water level gradient ∂η / ∂x when it flows. max , as an additional condition for jointly using the θ semi-implicit method and the Euler-Lagrangian method to solve the flow control equations,

[0036] Step 422: For the cell edge of the cell in the strip region along the river, first determine whether its normal water level gradient is positive or negative. When ∂η / ∂x≥0, the water level gradient term in the water flow momentum equation is calculated as follows:

[0037] -g∂η / ∂x = -gMin(∂η / ∂x, Δ max ) (5a)

[0038] When ∂η / ∂x<0, the water level gradient term in the flow momentum equation is calculated as follows:

[0039] -g∂η / ∂x = -gMax(∂η / ∂x, -Δ max ) (5b)

[0040] Step 43: The terrain calculation module and the connection calculation module are coupled to the two-dimensional hydrodynamic solver, and the resulting flood evolution simulator still deduces the evolution process of the flood forward at intervals of Δt:

[0041] Step 431: At the beginning of each time step, the two-dimensional hydrodynamic solver calls the judgment and operation formula of the connection calculation module and the hollowing boundary operation rule of the ground object calculation module, combines the water level gradient term of the momentum equation discretized by the θ semi-implicit method, and then solves the momentum equation and even the entire water flow control equation.

[0042] Step 432: At the end of each time step, the two-dimensional hydrodynamic solver calls the terrain calculation module to set the normal flow velocity at the hollowing boundary by applying the u=0 condition at the hollowing boundary.

[0043] Step 433: The two-dimensional hydrodynamic solver completes other work in the Δt time step.

[0044] The step 5 is specifically as follows:

[0045] Step 51: Establish a spatiotemporal connectivity control module to set or update the connectivity between the river and the towns / flood storage areas along the river by modifying the attributes of the river bank section. The spatiotemporal connectivity control implemented by this module includes the following steps:

[0046] Step 511: Set the spatiotemporal connectivity control index. For ordinary embankment sections, according to the selected flood rehearsal plan and embankment section stability data, set the start and end time of embankment section breach, breach range, and breach topography. The end time of breach flow can be estimated based on the emergency rescue intensity selected in the flood rehearsal plan or previous experience.

[0047] Step 512: Standardize the spatiotemporal connectivity control index. For ordinary dike sections, the data include the start and end time of the terrain rise and fall of the breached dike section, the unit list, and the unit terrain rise and fall value. For the gate-controlled dike section, the data include the gate opening / closing time, the gate hole range unit list, the gate bottom plate elevation, and the gate height.

[0048] Step 513: Based on the provisions and information in steps 511 to 512, the connectivity between the river channel and the towns / flood storage areas along the river is set or updated by modifying the attributes of the grid cells of the river bank range;

[0049] Step 52: The established flood simulation collaborative work system still advances forward time by time step at intervals of Δt, wherein the collaborative work of the flood evolution simulator and the spatiotemporal connectivity control module includes the following steps:

[0050] Step 521: At each initial time Δt, call the spatiotemporal connectivity control module to update the connectivity status of the river channel and the towns / flood storage areas along the river. If no connectivity change event occurs, proceed to step 525; if the connectivity of the dike section changes, proceed to step 522;

[0051] Step 522: If the connectivity of a certain dike section changes from "blocked→connected", step 523 is executed; if the connectivity of a certain dike section changes from "connected→blocked", step 524 is executed, wherein connected means that the dike section is breached or the gate is opened for flow, and blocked means that the gap in the dike section is filled as before or the gate is closed;

[0052] Step 523: lower the unit riverbed elevation within the embankment section to the design value, and initialize the water flow state of these units and their edges;

[0053] Step 524: Raise the unit terrain elevation within the breached embankment section to the design value, treat the unit within the restored water retaining embankment section as a solid boundary, and set the unit water depth, unit center and flow velocity of each edge to 0, so as to create a scenario where the current embankment section is blocked;

[0054] Step 525: After calling the spatiotemporal connectivity control module to complete the connectivity index update of the dike section range unit and the matching water flow state initialization, continue to perform the flood evolution process calculation;

[0055] Step 526: obtaining and storing the plane physical field data of water flow at regular time intervals, constructing flooding and water withdrawal scenarios of towns and flood storage areas along the river based on the plane physical field data of water flow, and obtaining the change process of the average water level and flow of the section over time by averaging or integrating;

[0056] Step 527: Complete the integrated simulation of flood evolution in the river channel and towns / flood storage areas along the river. Based on the physical field data of the water flow plane, obtain the evolution path of the flood between the landforms in the riverside area, formulate evacuation routes, calculate flood indicators and urban flood inundation losses, and then analyze the flood control effect and optimize the control plan.

[0057] Compared with the prior art, the present invention has the following beneficial effects:

[0058] Using two-dimensional fine modeling of land features instead of the previous generalized method can truly depict the water flow patterns of land features and their vicinity in the river channel and riverside areas. The new method combines the θ semi-implicit method and the Euler-Lagrange method to overcome the instability problem of hydrodynamic model calculation caused by two-dimensional fine modeling (generating a large number of small-scale grids) and realizes the calculation of flood evolution with a large time step. Previous similar studies mostly used explicit hydrodynamic solvers, with a very small calculation time step (often less than 1 second) and low efficiency. Second, the land feature calculation module and the connection calculation module of the river channel and the riverside area are coupled into the two-dimensional hydrodynamic solver. The resulting flood evolution simulator has the ability to simulate the flood evolution of the river channel and the riverside town / flood storage area as a whole and synchronously. Third, a spatiotemporal connectivity control module of the river channel and the riverside town / flood storage area is established to coordinate with the flood evolution simulator to realize the simulation of flood evolution and its regulation in the river channel and the riverside town / flood storage area.

[0059] The present invention solves the problems existing in the overall synchronous simulation method of flood evolution in different regions in the field of water conservancy simulation technology, such as difficult regional connection and transition, poor simulation effect, weak adaptability, etc., and at the same time has the advantages of good stability, high reliability, high calculation efficiency, strong versatility, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 It is a schematic diagram of the execution process of the integrated simulation method for flood evolution of the river channel and the riverside towns / flood storage areas of the present invention.

[0061] Figure 2 It is a schematic diagram of the distribution of land features in the river channel and the towns / flood storage areas along the river for implementing the present invention.

[0062] Figure 3 It is a schematic diagram of a multi-level and multi-scale computational grid for partitioning a research area for implementing the present invention.

[0063] Figure 4 It is a schematic diagram of the multi-level and multi-scale modeling effect of the research area partitioning according to the present invention.

[0064] Figure 5 It is the physical field calculation result of the integrated simulation of flood evolution in the river channel and the towns / flood storage areas along the river implemented by the present invention.

[0065] Figure 6 It is the calculation result of the flooding and water retreat process of the riverside town by implementing the integrated simulation of the flood evolution of the river channel and the riverside town / flood storage area of ​​the present invention.

[0066] Figure 7 It is the calculation result of the flood diversion process of the integrated simulation of flood evolution of the river channel and the towns / flood storage areas along the river implemented in the present invention. DETAILED DESCRIPTION

[0067] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0068] As attached Figure 1 As shown, Figure 1 It is a schematic diagram of the execution process of the integrated simulation method for flood evolution of the river channel and the riverside towns / flood storage areas of the present invention. Figure 1 middle,

[0069] Step 1: Outline the plane contours of the features within the study area (including various types of plane areas such as rivers, towns along rivers, flood storage areas, etc.), identify and classify the features, and divide the study area into several sub-areas based on the types, characteristics and plane distribution of the features.

[0070] Step 2: Carry out detailed modeling of the terrain in the study area, and carry out multi-level and multi-scale two-dimensional unstructured grid modeling of the river and riverside towns / flood storage areas, including grid production, terrain interpolation, etc.

[0071] Step 3: The two-dimensional control equations describing the water flow are numerically discretized in time and space on the computational grid to construct a two-dimensional hydrodynamic solver.

[0072] Step 4: Establish the terrain calculation module and connection calculation module of the river and the riverside towns / flood storage areas, and couple them to the two-dimensional hydrodynamic solver to construct a flood evolution simulator, which has the ability to simulate the flood evolution of the river and the riverside towns / flood storage areas as a whole and synchronously.

[0073] Step 5: Establish a spatiotemporal connectivity control module between the river and riverside towns / flood storage areas, coordinate it with the flood evolution simulator, and then form a flood rehearsal collaborative work system to achieve integrated simulation functions such as flood evolution and its regulation in the river and riverside towns / flood storage areas.

[0074] Step 6: For the selected study area, set the open boundary conditions such as inlet and outlet flow, water level and flood control information of the study area, start the established flood simulation collaborative work system, and simulate the flood evolution and control of the river channel and riverside towns / flood storage areas step by step.

[0075] Step 7: Save the results of the water flow plane physical field, cross-sectional water level and flow process calculated by the flood simulation collaborative work system to the hard disk, and conduct flood control analysis and evaluation based on them.

[0076] Figure 2 It is a schematic diagram of the distribution of land features in the river channel and riverside towns / flood storage areas for implementing the present invention (a tributary of the Yangtze River and its riverside towns are selected as an example). Figure 2 middle,

[0077] The study area includes the river and towns along the river. The river is 300m~400m wide, and there are highlands, standard embankment sections (elevation greater than the design flood level), and damaged embankment sections (lower terrain and gaps) distributed along the river bank. As can be seen from the figure, the landforms in the urban area mainly include buildings, roads, various infrastructures, etc., which are characterized by large number, different shapes and sizes, and irregular distribution.

[0078] Figure 3 It is a schematic diagram of a multi-level and multi-scale computational grid for partitioning a research area for implementing the present invention. Figure 3 middle,

[0079] The study area includes rivers and towns along the river. The modeling process (the hollowing method is used to carry out fine modeling for urban features) is as follows. ① The town is divided into several sub-areas according to the shape, scale and distribution of the features on the plane to help control the density of the grid in each local area. ② The area representing the building is removed from each sub-area, and a high-resolution grid is generated based on the remaining area. ③ The urban grid and the river grid are connected, and the grid scale is enlarged step by step (for example, the urban area → the river along the city → the upstream and downstream rivers) to achieve a smooth connection between the fine grid and the large-scale grid, so as to meet the different requirements of different regions for grid resolution. Figure 3The scales of the medium quadrilateral unstructured grid are as follows: ① The grid scale of urban features and their vicinity is 2~5m; ② In the transition zone from urban area to river channel through the city, the grid scale increases to 8~10m; ③ In the upstream and downstream river sections, the grid scale is further increased to 20m along the direction of water flow.

[0080] Figure 4 It is a schematic diagram of the multi-level and multi-scale modeling effect of the research area partitioning according to the present invention. Figure 4 middle,

[0081] The river and the towns along the river have been divided into a fine two-dimensional grid. The terrain interpolation based on the computational grid is used to establish a two-dimensional model of the river and the towns along the river, which can truly reflect the river conditions and the complex distribution and landforms of the towns in the study area, and has achieved good modeling results.

[0082] Figure 5 It is the physical field calculation result of the integrated simulation of flood evolution of the river channel and the towns and flood storage areas along the river implemented in the present invention (in terms of Figure 2 study area as an example). Figure 5 middle,

[0083] The scenario of flooding the urban area at the peak flow of the river is given, including the flow field, water depth and plane distribution of the towns along the river. As can be seen from the figure, the method of the present invention accurately simulates the flow field and water flow morphology when the urban area is invaded by floods (such as bypass flow near buildings, local plane return flow, etc.), clearly outlines the evolution path of the flood, and realizes the fine simulation of the evolution of river floods in urban land. Based on the flooding scenario of the urban area, the formulation of risk avoidance and transfer routes can be carried out. The stability test shows that the model can be stably calculated under the condition of a large time step of Δt≥60s, and reasonable calculation results are given (steep rise and fall of river floods, flooding and retreat process of towns, etc.). The maximum flow velocity of the river is 4.3m / s (CFL>25); the maximum flow velocity at the junction of the town and the river is 2.0m / s (CFL>15). The efficiency test shows that the established model (number of units 20,000, Δt=60s) takes only 6 minutes to simulate a 15-day flood on the mainstream workstation, which is very efficient.

[0084] Figure 6 The calculation results of the flooding and drainage process of the riverside town / flood storage area by implementing the integrated simulation of the flood evolution of the river channel and the riverside town / flood storage area of ​​the present invention (in terms of Figure 2 study area as an example). Figure 6 middle,

[0085] A 1% frequency flood process was selected, and the open boundary conditions and flood control information of the study area were set based on it. The established flood rehearsal collaborative work system was started to carry out an integrated simulation of the flood evolution of the river channel and towns along the river step by step. Figure 6Four key scenarios of flooding and receding of towns along the river under the condition of river flood intrusion are shown on the WebGIS three-dimensional topographic map: ① The initial river water level is low and there is no water in the urban area; ② The river water level rises, the river water overflows the damaged embankment section and flows into the urban area along the streets; ③ When the river flow reaches the peak value, the urban area is flooded to the maximum; ④ After the flood recedes, the low-lying areas of the town still retain water. The simulation results show that the method of the present invention can provide a fine simulation of the process of non-steady water flow entering and leaving the town, and based on the calculated flow field, water depth and its plane distribution, flood risk assessment and other work can be carried out.

[0086] Figure 7 The calculation result of the flood diversion process of the integrated simulation of flood evolution of the river channel and the riverside town / flood storage area of ​​the present invention (based on the adjacent Figure 2 take the downstream section of the river as an example). Figure 7 middle,

[0087] The study area includes the river channel and the flood storage area, which are separated by a continuous embankment. The river width is 400m~600m. A flood diversion gate is set at a certain position along the river embankment, with a total gate width of 108m. The total area of ​​the flood storage area on the right bank of the river is 33.88km 2 , the flood storage area is mostly farmland, and the landforms are relatively simple. Quadrilateral unstructured grids are used for modeling, and the entity method is used for modeling the flood diversion gates and a small number of dikes in the flood storage area. On this basis, the grid scale is gradually enlarged (flood control dike → river channel outside the flood storage area → upstream and downstream river channel) to achieve smooth connection between fine grids and large-scale grids. The grid scales are: ① The grid scale of the flood diversion gate and its vicinity is 10~20m; ② The grid scale near the flood control dike is 20×40m; ③ The grid scale of the river channel is 25×40m near the flood control dike and 50×100m in the upstream and downstream sections.

[0088] A 1% frequency flood process was selected, and the open boundary conditions and flood control information of the study area were set based on it. The established flood rehearsal collaborative work system was started to carry out an integrated simulation of the flood evolution of the river channel and towns along the river step by step. Figure 7 Four key scenes of the flood diversion process are shown: ① the large water level gradient scene at the moment when the river channel is connected to the flood storage area (the diversion gate is opened); ② the characteristic water flow of the dam break formed in the early stage of the diversion (with a significant front); ③ the scene of the river channel water flowing into a wide area from the diversion gate hole; ④ the scene of the diversion flow evolving in the flood storage area. As can be seen from the figure, the method of the present invention can better carry out the integrated simulation of the evolution of floods in the river channel and the flood storage area, and truthfully reflect the flood control (flood diversion) scene.

[0089] The above embodiments are merely examples of the technical solutions of the present invention. The inversion model construction method involved in the present invention is not limited to the contents described in the above embodiments, but is subject to the scope defined in the claims. Any modification, supplement or equivalent replacement made by a person skilled in the art of the present invention on the basis of the embodiment is within the scope of protection claimed by the present invention.

Claims

1. An integrated simulation method for flood evolution, characterized in that: The steps include: Step 1: Draw the plane contours of the objects in the study area, identify and classify the objects, and divide the study area into several zones according to the types, characteristics and plane distribution of the objects; Step 2: Carry out detailed modeling of the terrain in the study area, and carry out multi-level and multi-scale two-dimensional unstructured grid modeling of the river and the towns / flood storage areas along the river, including grid production and terrain interpolation; Step 3: Discretize the two-dimensional control equations describing the water flow in time and space on the computational grid and construct a two-dimensional hydrodynamic solver; Step 4: Establish the terrain calculation module and connection calculation module of the river and the riverside towns / flood storage areas, and couple them to the two-dimensional hydrodynamic solver to build a flood evolution simulator, which has the ability to simulate the flood evolution of the river and the riverside towns / flood storage areas as a whole and synchronously; Step 5: Establish a spatiotemporal connectivity control module between the river and the towns / flood storage areas along the river, coordinate it with the flood evolution simulator, and then form a flood pre-exercise collaborative work system to achieve the integrated simulation function of flood evolution and its regulation between the river and the towns / flood storage areas along the river; Step 6: For the selected study area, calibrate the parameters of the hydrodynamic solver, set the inlet and outlet boundary conditions and flood control information of the study area, start the established flood simulation collaborative work system, and simulate the flood evolution and control of the river channel and the towns / flood storage areas along the river step by step; Step 7: Save the results of the water flow plane physical field, cross-sectional water level and flow process calculated by the flood simulation collaborative work system to the hard disk, and carry out flood control analysis and evaluation.

2. The integrated simulation method for flood evolution according to claim 1, characterized in that: The step 1 specifically comprises: Step 11: Based on GIS and AutoCAD topographic maps, batch outline the plane contours of the river channels and riverside areas, and identify various landforms; Step 12: Classify the features, classify the features that may be submerged as submerged features; classify the features that will never flow as non-submerged features; classify the levees between the river and the towns / flood storage areas along the river as submerged features, and use different signs to mark and distinguish the submerged and non-submerged features; Step 13: For areas with complex distribution of land features, divide the river channel and riverside towns / flood storage areas into several sub-areas based on the shape, scale and distribution characteristics of the land features on the plane, so as to help control the density of the calculation grid in each local area.

3. The integrated simulation method for flood evolution according to claim 2, characterized in that: The step 2 is specifically as follows: 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-flooded features, the two-dimensional modeling is performed using the hollowing method: the plane area occupied by the features is excluded from the calculation area. For flooded features, the two-dimensional modeling is performed using the solid method: the grid is arranged according to the feature outline so that the grid overlaps the feature, the corresponding grid node attributes are modified according to the features of the feature to describe the feature, and the grid near the feature is locally encrypted to improve the spatial resolution of the grid; Step 23: The strip-shaped area between the river channel and the town / flood storage area along the river is called a dike section. The dike section is modeled in two dimensions using the entity method. The grid cells belonging to the dike section are marked and distinguished. The cells of the ordinary dike section are marked as 1, and the cells of the gate-controlled dike section are marked as 2. Step 24: partition the two-dimensional unstructured grid into multiple levels and scales, and use the method of gradually enlarging the grid scale to achieve a smooth connection between the fine grid and the large-scale grid, so as to meet the different requirements of different regions for grid resolution; Step 25: Splice the scattered topography of the river channel with the DEM topography of the riverside town / flood storage area, and interpolate the topography of 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: The two-dimensional hydrodynamic solver in step 3 refers to a hydraulic calculation program based on a two-dimensional unstructured grid, open boundary conditions, initial conditions of the calculation area, etc., including functions such as discretization and solution of the two-dimensional control equation of water flow and result output. The two-dimensional control equation of water flow is as follows: The two-dimensional water flow control equation is as follows: (1) (2) (3) Where h(x, y, t) is the water depth, u(x, y, t) and v(x, y, t) are the average water velocity in the horizontal x and y directions, t is time, g is the gravitational acceleration, η(x, y, t) is the height of the free water surface, and υ is τ is the horizontal eddy viscosity coefficient, n m For the roughness.

5. The integrated simulation method for flood evolution according to claim 1, characterized in that: The step 4 is specifically as follows: Step 41: Establish a land feature calculation module for riverside towns / flood storage areas. This module first identifies land features and their types based on the plane area characteristics. For the cavity formed by the hole digging method, when performing its hydrodynamic calculation, the cavity boundary is regarded as a solid wall boundary and solid wall boundary conditions with normal flow velocity of 0 and normal water level gradient of 0 are applied. The expressions of these boundary conditions are: u=0,∂η / ∂x=0 (4) Step 42: Establish a calculation module for the connection between the river channel and the riverside area. The module first identifies the area type according to the identification of the grid cells in the riverside strip area. On this basis, it processes and calculates the large water level gradient scene that may appear in the riverside strip area, including the following steps: Step 421: For the cell edge of the cell in the strip region along the river, define the limit value Δ of the normal water level gradient ∂η / ∂x when it flows. max , as an additional condition for solving the flow control equations using the θ semi-implicit method and the Euler-Lagrangian method, Step 422: For the cell edge of the cell in the strip region along the river, first determine whether its normal water level gradient is positive or negative. When ∂η / ∂x≥0, the water level gradient term in the water flow momentum equation is calculated as follows: -g∂η / ∂x = -gMin(∂η / ∂x, Δ max ) (5a) When ∂η / ∂x<0, the water level gradient term in the flow momentum equation is calculated as follows: -g∂η / ∂x = -gMax(∂η / ∂x, -Δ max ) (5b) Step 43: The terrain calculation module and the connection calculation module are coupled to the two-dimensional hydrodynamic solver, and the resulting flood evolution simulator still deduces the evolution process of the flood forward at intervals of Δt: Step 431: At the beginning of each time step, the two-dimensional hydrodynamic solver calls the judgment and operation formula of the connection calculation module and the hollowing boundary operation rule of the ground object calculation module, combines the water level gradient term of the momentum equation discretized by the θ semi-implicit method, and then solves the momentum equation and even the entire water flow control equation. Step 432: At the end of each time step, the two-dimensional hydrodynamic solver calls the terrain calculation module to set the normal flow velocity at the hollowing boundary by applying the u=0 condition at the hollowing boundary. Step 433: The two-dimensional hydrodynamic solver completes other work in the Δt time step.

6. The integrated simulation method for flood evolution according to claim 1, characterized in that: The step 5 is specifically as follows: Step 51: Establish a spatiotemporal connectivity control module to set or update the connectivity between the river and the towns / flood storage areas along the river by modifying the attributes of the river bank section. The spatiotemporal connectivity control implemented by this module includes the following steps: Step 511: Set the spatiotemporal connectivity control index. For ordinary embankment sections, according to the selected flood rehearsal plan and embankment section stability data, set the start and end time of embankment section breach, breach range, and breach topography. The end time of breach flow can be estimated based on the emergency rescue intensity selected in the flood rehearsal plan or previous experience. Step 512: Standardize the spatiotemporal connectivity control index. For ordinary dike sections, the data include the start and end time of the terrain rise and fall of the breached dike section, the unit list, and the unit terrain rise and fall value. For the gate-controlled dike section, the data include the gate opening / closing time, the gate hole range unit list, the gate bottom plate elevation, and the gate height. Step 513: Based on the provisions and information in steps 511 to 512, the connectivity between the river channel and the towns / flood storage areas along the river is set or updated by modifying the attributes of the grid cells of the river bank range; Step 52: The established flood simulation collaborative work system still advances forward time by time step at intervals of Δt, wherein the collaborative work 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 of the river channel and the towns / flood storage areas along the river. If no connectivity change event occurs, proceed to step 525; if the connectivity of the dike section changes, proceed to step 522; Step 522: If the connectivity of a certain dike section changes from "blocked→connected", step 523 is executed; if the connectivity of a certain dike section changes from "connected→blocked", step 524 is executed, wherein connected means that the dike section is breached or the gate is opened for flow, and blocked means that the gap in the dike section is filled as before or the gate is closed; Step 523: lower the unit riverbed elevation within the embankment section to the design value, and initialize the water flow state of these units and their edges; Step 524: Raise the unit terrain elevation within the breached embankment section to the design value, treat the unit within the restored water retaining embankment section as a solid boundary, and set the unit water depth, unit center and flow velocity of each edge to 0, so as to create a scenario where the current embankment section is blocked; Step 525: After calling the spatiotemporal connectivity control module to complete the connectivity index update of the dike section range unit and the matching water flow state initialization, continue to perform the flood evolution process calculation; Step 526: obtaining and storing the plane physical field data of water flow at regular time intervals, constructing flooding and water withdrawal scenarios of towns and flood storage areas along the river based on the plane physical field data of water flow, and obtaining the change process of the average water level and flow of the section over time by averaging or integrating; Step 527: Complete the integrated simulation of flood evolution in the river channel and towns / flood storage areas along the river. Based on the physical field data of the water flow plane, obtain the evolution path of the flood between the landforms in the riverside area, formulate evacuation routes, calculate flood indicators and urban flood inundation losses, and then analyze the flood control effect and optimize the control plan.

Images