Urban local waterlogging simulation method based on SWMM model

Abstract

The invention relates to the technical field of electric digital data processing, in particular to a city local waterlogging simulation method based on an SWMM model, and the method is executed by a processor and comprises the steps: drawing a waterlogging curve for local waterlogging points of a target area based on a digital elevation model in cooperation with geographic information software; establishing an SWMM model based on the local water accumulation point of the target area; executing calibration on the SWMM model; and executing local waterlogging simulation of the target area based on the calibration model. The method can be independently applied to simulation of urban local waterlogging, and aiming at the limitation that two-dimensional diffusion characteristics of flood in irregular terrains are difficult to fully capture in the prior art, a two-dimensional surface water flow model does not need to be combined; the problem that in the prior art, due to the fact that an urban local waterlogging simulation model is coupled with a two-dimensional model, the requirements for computing resources and time are high is solved.

Description

Technical Field

[0001] The present application relates to the technical field of electrical digital data processing, and in particular to a method for simulating local urban waterlogging based on a SWMM model. Background Art

[0002] The simulation of urban waterlogging can predict and assess the risk of waterlogging in advance, provide a scientific basis for urban management departments, optimize the design and operation of drainage systems, reduce the probability and impact of waterlogging, and help urban managers respond quickly to extreme weather, reduce disaster losses, and enhance the city's risk resistance and resilience. The existing storm flood management model, namely the SWMM model, is mainly based on one-dimensional hydrodynamic principles and cannot fully capture the two-dimensional diffusion characteristics of floods in irregular terrain, especially in areas with insufficient or old basic data. The application scope of the existing model is relatively limited and the simulation situations are limited. In addition, the existing technology has high requirements for computing resources and time during the simulation process. Summary of the invention

[0003] The purpose of this application is to provide a method for simulating local urban waterlogging based on the SWMM model, which solves the problem of high computing resource and time requirements in the existing local urban waterlogging simulation model due to the coupling of two-dimensional models.

[0004] The technical solution of this application:

[0005] The present application provides a method for simulating local urban flooding based on a SWMM model, which is executed by a processor and includes:

[0006] Based on the digital elevation model, the waterlogging curve is drawn for the local waterlogging points in the target area in conjunction with geographic information software;

[0007] Establish a SWMM model based on local waterlogging points in the target area;

[0008] Perform calibration on the SWMM model;

[0009] Perform local waterlogging simulation in the target area based on the calibrated model.

[0010] Furthermore, the digital elevation model is used in conjunction with geographic information software to draw a waterlogging curve for local waterlogging points in the target area, specifically:

[0011] Enter the height interval parameters of the contour lines in the geographic information software;

[0012] Run the software and generate contour lines;

[0013] Generate contour surfaces based on contour lines to obtain at least one set of elevation-area data;

[0014] Get the elevation of the lowest point of the water accumulation point;

[0015] Based on the elevation of the lowest point of the waterlogging point, the elevation-area is converted into water depth-area data;

[0016] Convert water depth-area data to water depth-volume data;

[0017] Based on the water depth-volume data, the water accumulation curve of the local water accumulation point is obtained.

[0018] Furthermore, the calibration of the SWMM model specifically includes:

[0019] Determine the overflow nodes related to the target waterlogging point and adjust the parameters to simulate the overflow scenario of the overflow nodes;

[0020] Get the overflow curve of the overflow node;

[0021] Based on the overflow curve, the water volume at the water accumulation point of the overflow curve is calculated and a process line is formed;

[0022] The ponding volume calculation process is input into the ponding curve, and the ponding depth is obtained using linear interpolation;

[0023] simulate flood scenarios;

[0024] Perform parameter tuning on the SWMM model until a specified accuracy is achieved.

[0025] Furthermore, the overflow curve of the overflow node is obtained by at least including an accumulation phase and a reflux phase.

[0026] Furthermore, the accumulation stage calculates the sum of the overflow volumes of each time period and the previous time period.

[0027] Furthermore, the water volume at the water accumulation point is calculated during the reflux stage.

[0028] Furthermore, the water volume of the overflow curve at the water accumulation point is calculated based on the overflow curve, specifically:

[0029] Based on the orifice flow calculation formula, the backflow flow of the accumulated water is obtained;

[0030] Based on the reflux flow rate, calculate the corresponding water volume at each moment in the reflux stage;

[0031] The calculation stops when the water volume is equal to or less than 0. The orifice flow calculation formula is:

[0032]

[0033] Where: C dis the flow coefficient, A is the opening area, g is the acceleration of gravity, and h is the water level difference between the upstream and downstream of the orifice.

[0034] The technical solution of the present application has at least the following advantages and beneficial effects:

[0035] The present application provides a method for simulating local urban waterlogging based on a SWMM model, which draws a waterlogging curve for a target local waterlogging point in the city, then establishes a SWMM model of the target area based on the waterlogging curve, then selects an overflow node and extracts the overflow process of the overflow node, uses the waterlogging curve of the waterlogging point to calculate the extracted overflow process and the waterlogging process at the waterlogging point, and finally simulates the local waterlogging in the target area based on the waterlogging process at the waterlogging point. Compared with the prior art, the present application can be independently applied to the simulation of local urban waterlogging. In view of the limitation that the original SWMM model is difficult to fully capture the two-dimensional diffusion characteristics of floods in irregular terrain, the method for simulating local urban waterlogging provided by the present application does not need to be combined with a two-dimensional surface water flow model, thereby solving the problem of high computing resource and time requirements of the local urban waterlogging simulation model in the prior art due to the coupling of the two-dimensional model. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 A flow chart of the method for simulating local urban waterlogging provided for this application;

[0037] Figure 2 The water depth-volume curve diagram of the water accumulation point in Example 2;

[0038] Figure 3 A schematic diagram of the visual modeling object and the connection structure of the objects in Example 2;

[0039] Figure 4 This is a simulation effect diagram of Example 2 on April 23, 2022;

[0040] Figure 5 This is a simulation effect diagram of Example 2 on June 7, 2022; DETAILED DESCRIPTION

[0041] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0042] Application Overview:

[0043] The existing SWMM model, namely the Storm Flood Management Model, is a hydrological and hydraulic model used to simulate urban drainage systems. However, since it is based on one-dimensional hydrodynamic principles, it cannot fully capture the two-dimensional diffusion characteristics of floods in irregular terrain, which makes the application scope of the model relatively limited and the simulation situations limited. On the other hand, when simulating flood depth and inundated area, it needs to be combined with a two-dimensional surface water flow model to supplement its deficiencies in spatial dimension, which makes the model inconvenient to use.

[0044] Based on the foregoing, the present application provides a method for simulating local urban waterlogging, which draws a water accumulation curve, i.e., a water depth-volume curve, for a target local waterlogging point in the city, and then establishes a SWMM model of the target area based on the water accumulation curve. Next, an overflow node is selected and the overflow process of the overflow node is extracted. The water accumulation process at the water accumulation point, i.e., a flood process, is calculated using the water accumulation curve of the water accumulation point. Finally, local waterlogging simulation of the target area is achieved based on the flood process.

[0045] Example 1

[0046] Please refer to Figure 1-5 The present application provides a method for simulating local urban waterlogging based on a SWMM model. The method is executed by a processor and includes: drawing a waterlogging curve for local waterlogging points in a target area based on a digital elevation model in conjunction with geographic information software; establishing a SWMM model based on local waterlogging points in the target area; calibrating the SWMM model; and performing local waterlogging simulation in the target area based on the calibrated model.

[0047] The method of the present application can be independently applied to the simulation of local urban waterlogging without the need to be combined with a two-dimensional surface water flow model, thereby making the application scope of local urban waterlogging simulation wider and more adaptable to more scenarios. At the same time, the use process is more convenient, which solves the problem that the existing models used to simulate local urban waterlogging in the prior art have a small application range and fewer simulation situations.

[0048] The following is a detailed description of the application method:

[0049] In some implementations, based on the digital elevation model, geographic information software is used to draw a waterlogging curve for local waterlogging points in the target area, specifically:

[0050] Enter the height interval parameters of the contour lines in the geographic information software;

[0051] Run the software and generate contour lines;

[0052] Generate contour surfaces based on contour lines to obtain at least one set of elevation-area data;

[0053] Get the elevation of the lowest point of the water accumulation point;

[0054] Based on the elevation of the lowest point of the waterlogging point, the elevation-area is converted into water depth-area data;

[0055] Convert water depth-area data to water depth-volume data;

[0056] Based on the water depth-volume data, the water accumulation curve of the local water accumulation point is obtained.

[0057] It can be understood that the specific steps of drawing waterlogging curves for urban waterlogging points based on the digital elevation model, i.e., DEM, using geographic information software are as follows:

[0058] Calculate and generate contour lines based on DEM data in geographic information software; then, use the generated contour lines to draw contour surfaces to obtain at least one set of elevation-area data, and convert the elevation-area into water depth-area data based on the elevation of the lowest point of the waterlogging point; use the platform (usually a truncated pyramid or a truncated cone) volume calculation formula to convert the water depth-area data into water depth-volume data, which is the water depth-volume curve of the local waterlogging point, also known as the waterlogging curve.

[0059] In some embodiments, calibration is performed on the SWMM model, including:

[0060] Determine the overflow nodes related to the target waterlogging point, and adjust the parameters to simulate the overflow of the overflow nodes;

[0061] Get the overflow curve of the overflow node;

[0062] Based on the overflow curve, the water volume at the water accumulation point of the overflow curve is calculated and a process line is formed;

[0063] The ponding volume calculation process is input into the ponding curve, and the ponding depth is obtained using linear interpolation;

[0064] simulate flood scenarios;

[0065] Perform parameter tuning on the SWMM model until a specified accuracy is achieved.

[0066] In detail, the purpose of adjusting the parameters is to make the target overflow node overflow. By continuously adjusting the parameters of the SWMM model, the water accumulation curve obtained through the above steps and the measured water accumulation curve can achieve the greatest possible overlap until a satisfactory accuracy is achieved.

[0067] In some implementations, obtaining an overflow curve of an overflow node includes at least an accumulation phase and a return phase.

[0068] In some embodiments, the accumulation phase calculates the sum of the overflow volumes of each time period and its previous time period. Specifically, the accumulation phase starts from the moment when the selected target node begins to overflow and lasts until the moment when the overflow ends. During the time period of this phase, the volume of overflow water continues to accumulate at the water accumulation point. Therefore, the sum of the overflow volumes of each time period and its previous time period is calculated in the accumulation phase.

[0069] In some embodiments, the water volume of the water accumulation point is calculated in the backflow stage. Specifically, the water volume calculation starts from the end of the time period when the overflow of the selected node ends in the backflow stage. Specifically, the water volume of the water accumulation point is calculated by using the equivalent drainage method.

[0070] In some embodiments, based on the overflow curve, the water volume at the water accumulation point of the overflow curve is calculated, specifically:

[0071] Based on the orifice flow calculation formula, the backflow flow of the accumulated water is obtained;

[0072] Based on the reflux flow rate, calculate the corresponding water volume at each moment in the reflux stage;

[0073] The calculation stops when the water volume is equal to or less than 0. The orifice flow calculation formula is:

[0074]

[0075] Where: C d is the flow coefficient, A is the opening area, g is the acceleration of gravity, and h is the water level difference between the upstream and downstream of the orifice.

[0076] In detail, the unit of orifice flow rate Q is m 3 / s; flow coefficient C d It is dimensionless and its value is related to the shape of the orifice and the fluid characteristics. It is determined based on experience or experiments. The most commonly used value is 0.59-0.67, and 0.65 can be selected. For orifices with uneven edges, 0.4 is preferred, depending on the orifice shape, size and effective head. The unit of the opening area A is m 2 , determined by trial calculation during the calibration process; the unit of gravity acceleration g is m / s 2 , the standard value is 9.81m / s 2 ; The unit of the water level difference h upstream and downstream of the orifice is m, and the water level difference h upstream and downstream of the orifice is also the head difference.

[0077] It can be understood that the orifice in the above formula of this embodiment belongs to submerged outflow, the opening area is equal to the orifice area, the orifice area is determined by trial calculation, and the geometric shape and size of the orifice can be set according to actual conditions. The value of h is the water depth at the beginning of the time period. Through this embodiment, a virtual orifice with equivalent drainage performance can be obtained based on the performance of measured flood data.

[0078] Example 2

[0079] Based on Example 1, a simulation is performed by taking a road in a district of a city on June 7, 2022 as an example, as follows:

[0080] First, obtain the DEM required to calculate the water depth-volume curve of the water accumulation point and various infrastructure data required to establish the SWMM model, including at least the following data:

[0081] (1) Geographic data: define the watershed extent, topography, and runoff parameters, including digital elevation models (DEMs), watershed boundaries, river courses, and land use data;

[0082] (2) Meteorological data: providing boundary conditions such as rainfall and evaporation data;

[0083] (3) Hydrological monitoring data: including urban flood levels, inundation areas, and water levels or flows in pipelines or rivers;

[0084] (4) Drainage infrastructure data: detailed information on the drainage system, such as pipe location, elevation, diameter, material, and slope; manhole location and depth; storage unit water depth-area curves; pump station location and operating water level;

[0085] (5) Historical event data: Records of past floods help set model parameters, especially for extreme events;

[0086] (6) Initial parameter setting data: prior knowledge based on literature or model calibration.

[0087] Furthermore, the water depth-volume curve of the water accumulation point is calculated and obtained based on the above data. For specific results, please refer to the attached Figure 2 , Table 1, Table 2, among which, Table 1 is the water depth-area / volume curve parameter result table, and Table 2 is the flood simulation process result data table.

[0088]

[0089] Table 1

[0090]

[0091]

[0092] Table 2

[0093] Furthermore, based on the local waterlogging points in the target area, a SWMM model is established. Please refer to Figure 3 , a schematic diagram of the visual objects and the connection structure of the objects of the model built in this embodiment.

[0094] Furthermore, the SWMM model is calibrated. In this embodiment, the measured waterlogging data on April 23, 2022 and June 7, 2022 are used to calibrate the model. The accuracy of the model simulation results is evaluated by the Nash Sutcliffe Efficiency (NSE) and the relative error (RE). The specific operations are as follows:

[0095] Step 1: Organize the rainfall time series for model calibration, that is, organize the rainfall on April 23, 2022 and June 7, 2022 in the standard format required by the SWMM model and use it as the input of the model;

[0096] Step 2: Adjust the model parameters to make the selected target node overflow, and put the overflow process into Table 2 to calculate the water level;

[0097] Step 3: Repeatedly adjust the model parameters so that the water level process calculated based on the model output is close to the observed data; in detail, SWMM parameters are divided into directly measurable parameters and non-directly measurable parameters. The directly measurable parameters, such as sub-catchment size, pipe length, slope and cross-sectional shape, can be directly calculated based on the basic data obtained; the non-measurable parameters, such as roughness and permeability coefficient, need to be adjusted according to the empirical value range.

[0098] It should be noted that in Table 1, columns (1) and (2) show the overflow process of the SWMM model; column (3) is the overflow volume, which is calculated as (2) × 60; column (4) is the cumulative volume, which is the sum of the overflow volumes of the current and previous time steps; column (5) provides the water level obtained by linear interpolation of the water depth-volume curve; column (6) gives the backflow flow calculated using the orifice flow calculation formula; column (7) shows the water volume after deducting the backflow, which is the source of the water volume after the water retreat moment in column (4), and the numerical value V (7),t =V (4),t+1 ; The calculation stops after the first negative value appears in the value calculated in column (7), and the accumulated water volume is 0 thereafter until the next overflow process occurs again.

[0099] Please note that, please refer to Figure 4 and Figure 5, are the simulation results of the calibrated model. The simulation results in the figure show that the NSE of the simulated flood processes on April 23 and June 7, 2022 were 0.90 and 0.82 respectively, and the RE of the simulated flood peaks were -7.47% and 6.48% respectively. According to the "Specifications for Hydrological Information Forecasting", the simulation accuracy reaches Class B and above standards.

[0100] Based on the above, it can be understood that the method for simulating local urban waterlogging based on the SWMM model provided in this embodiment can simulate surface waterlogging without coupling with a two-dimensional surface model, compared with the prior art, and effectively reduces the complexity of the model. In particular, the method provided in this embodiment can be used in areas with insufficient or outdated basic data. This method not only simplifies the calculation process, but also can respond quickly and flexibly adapt to different regional characteristics and needs. On the other hand, the method provided in this embodiment also greatly reduces the demand for computing resources and computing time.

[0101] In detail, the two-dimensional model simulates the dynamic process of water flow on the surface of the entire area. Usually, the simulation area is divided into many small grid units. Since the higher the spatial resolution, the more grid units there are, the water flow characteristics (such as water depth, flow velocity) of each unit need to be calculated. The more details it depicts, the more iterative calculations are required, which leads to a significant increase in the amount of calculation. As the simulation area increases, a large amount of memory and hard disk space are required to store and process a large amount of input and output data (such as water depth, flow velocity, etc.). In addition, the two-dimensional model usually requires parallel computing to speed up the processing speed, which is very demanding on hardware. The method provided in this embodiment avoids the generation of the above problems, and the model provided in this embodiment simulates a flood event caused by a 24-hour rainfall in an ordinary computer, and the time required is seconds, which can effectively reduce the workload of model calculation and improve the calculation speed of the model.

[0102] The above shows and describes the basic principles and main features of the present application and the advantages of the present application. For those skilled in the art, it is obvious that the present application is not limited to the details of the above exemplary embodiments, and the present application can be implemented in other specific forms without departing from the spirit or basic features of the present application. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present application is defined by the attached claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present application. Any figure mark in the claims should not be regarded as limiting the claims involved.

[0103] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for simulating local urban flooding based on a SWMM model, the method being executed by a processor and characterized in that: include: Based on the digital elevation model, the waterlogging curve is drawn for the local waterlogging points in the target area in conjunction with geographic information software; Establish a SWMM model based on local waterlogging points in the target area; Perform calibration on the SWMM model; Perform local waterlogging simulation in the target area based on the calibrated model.

2. The method for simulating local urban waterlogging according to claim 1, characterized in that: The digital elevation model is used in conjunction with geographic information software to draw a waterlogging curve for local waterlogging points in the target area, specifically: Enter the height interval parameters of the contour lines in the geographic information software; Run the software and generate contour lines; Generate contour surfaces based on contour lines to obtain at least one set of elevation-area data; Get the elevation of the lowest point of the water accumulation point; Based on the elevation of the lowest point of the waterlogging point, the elevation-area is converted into water depth-area data; Convert water depth-area data to water depth-volume data; Based on the water depth-volume data, the water accumulation curve of the local water accumulation point is obtained.

3. The method for simulating local urban waterlogging according to claim 1, characterized in that: The calibration of the SWMM model specifically includes: Determine the overflow nodes related to the target waterlogging point and adjust the parameters to simulate the overflow scenario of the overflow nodes; Get the overflow curve of the overflow node; Based on the overflow curve, the water volume at the water accumulation point of the overflow curve is calculated and a process line is formed; The ponding volume calculation process is input into the ponding curve, and the ponding depth is obtained using linear interpolation; simulate flood scenarios; Perform parameter tuning on the SWMM model until a specified accuracy is achieved.

4. The method for simulating local urban waterlogging according to claim 3, characterized in that: The method of obtaining the overflow curve of the overflow node at least includes an accumulation phase and a reflux phase.

5. The method for simulating local urban waterlogging according to claim 4, characterized in that: The accumulation phase calculates the sum of the overflow volumes of each time period and its preceding time period.

6. The method for simulating local urban waterlogging according to claim 4, characterized in that: The water volume at the water accumulation point is calculated during the reflow stage.

7. The method for simulating local urban waterlogging according to claim 6, characterized in that: The calculation of the water volume at the water accumulation point based on the overflow curve is specifically as follows: Based on the orifice flow calculation formula, the backflow flow of the accumulated water is obtained; Based on the reflux flow rate, calculate the corresponding water volume at each moment in the reflux stage; The calculation stops when the water volume is equal to or less than 0. The orifice flow calculation formula is: Where: C d is the flow coefficient, A is the opening area, g is the acceleration of gravity, and h is the water level difference between the upstream and downstream of the orifice.

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