Subway station waterlogging risk rapid assessment method based on system water balance

Abstract

The invention relates to a subway station waterlogging risk rapid assessment method based on system water balance, and the method comprises the following steps: S1, dividing a research region through terrain analysis and pipe network partitioning, and taking a catchment region where a subway station is located as an independent system; s2, calculating system inflow Wr by utilizing the designed rainstorm intensity and the comprehensive runoff coefficient; s3, calculating the system displacement Wp based on the design standard of the research area pipe network; s4, calculating the water accumulation amount Wj of the system through a water balance equation; s5, calculating system capacity W0 by means of terrain elevation data and a GIS tool; and S6, judging whether a waterlogging risk exists in the research area or not by comparing calculation results of the system water accumulation amount Wj and the system capacity W0. According to the method, rapid assessment of the metro station waterlogging risk at the initial stage is realized, the data requirement of metro station waterlogging assessment is reduced, and the required cost and time are reduced.

Description

Technical Field

[0001] The present invention belongs to the field of building flood prevention, and in particular relates to a method for quickly assessing the risk of waterlogging in subway stations based on system water balance. Background Art

[0002] Currently, risk assessment of subway station flooding primarily relies on mathematical statistics of historical disasters, coupled analysis of remote sensing imagery and GIS, indicator system assessment, and numerical simulation. These methods utilize historical flooding records, satellite remote sensing data, topographic and meteorological information, and a variety of evaluation indicators to construct risk assessment models, attempting to quantify and predict the potential flooding risk to subway stations under extreme climatic conditions. For example, historical statistics relies on long-term data accumulation to identify patterns of flooding occurrence, while remote sensing and GIS technologies reveal weaknesses in drainage systems through high-resolution imagery and digital elevation models. The indicator system approach comprehensively considers factors such as building density, terrain slope, and pipe network design, while numerical simulation utilizes computational fluid dynamics to simulate rainfall and drainage processes. These technologies offer the potential for quantitative assessment of subway station flooding risk, aiming to provide a scientific basis for flood control planning and emergency response decision-making.

[0003] However, existing technologies have numerous shortcomings: data acquisition is difficult and requires extremely high timeliness and accuracy, resulting in significant uncertainty in overall assessment results; high spatial resolution is required, making high-precision remote sensing and topographic data essential but expensive resources; assessment models often rely on complex mathematical and physical models, which are highly subjective and technically challenging, requiring professional operators and high-end equipment, making the overall modeling process complex, costly, and time-consuming. Furthermore, because different assessment methods rely on different data sources to varying degrees, their results often vary widely, and professional technical service companies charge high fees, making it difficult to achieve rapid and cost-effective pre-assessment of urban flooding risk in the early stages of subway station planning. Summary of the Invention

[0004] To address the above issues, the present invention proposes a simple urban flooding pre-assessment method based on the principle of system water balance, aiming to achieve rapid risk assessment in the initial design stage of subway stations and reduce data requirements and assessment costs.

[0005] To achieve the above object, the technical solution of the present invention is as follows:

[0006] A rapid assessment method for subway station flooding risk based on system water balance includes the following steps:

[0007] S1, the study area was divided by terrain analysis and pipe network zoning, and the catchment area where the subway station is located was treated as an independent system;

[0008] S2, calculate the system inflow Wr using the design rainstorm intensity and comprehensive runoff coefficient;

[0009] S3, calculate the system discharge Wp based on the design standard of the pipe network in the study area;

[0010] S4, calculate the system water volume Wj through the water balance equation;

[0011] S5, calculate the system capacity W0 with the help of terrain elevation data and GIS tools;

[0012] S6, by comparing the calculated results of the system water accumulation Wj with the system holding capacity W0, it is determined whether there is a risk of waterlogging in the study area.

[0013] Preferably, the step S1 includes:

[0014] S11, starting from the subway station that needs to be risk assessed, determine the basic scope of the system based on the slope of the surrounding municipal roads according to relevant drawings;

[0015] S12, within the basic range of the system, determine the final catchment area boundary according to the pipeline layout and the structures and walls that affect the collection of rainwater, and calculate the area S of the area.

[0016] Preferably, step S2 includes:

[0017] S21, designing rainstorm data according to actual needs. The rainstorm data can be calculated according to local rainstorm intensity formulas or standards, or can use measured rainfall data, wherein the rainstorm data is the rainstorm intensity of rainfall lasting 24 hours;

[0018] S22, based on the "Outdoor Drainage Design Standard", determine the regional comprehensive runoff coefficient ψ according to the building conditions in the study area, and increase this coefficient accordingly when the design rainfall return period increases;

[0019] S23, calculating the system inflow Wr for the rainfall condition set in the area.

[0020] Preferably, the system inflow Wr is calculated in step S23 using the following formula: Wr = ψ·i·S·t, where ψ is the regional comprehensive runoff coefficient; i is the design rainstorm intensity, mm / min; S is the catchment area, m 2 ; t is the set rainfall duration, min.

[0021] Preferably, in step S3, the system discharge volume Wp is calculated by executing the formula Wp=ψp·H·S / 1000 according to the discharge volume corresponding to the pipe network design recurrence period, where ψp is the comprehensive runoff coefficient corresponding to the pipe network design; H is the rainfall corresponding to the pipe network recurrence period, mm; S is the catchment area, m 2 .

[0022] Preferably, the step S4 obtains the system water volume Wj by calculating the difference between Wr and Wp based on the system water balance principle.

[0023] Preferably, step S5 includes:

[0024] S51, generate DEM of the study area in the GIS platform based on relevant elevation data;

[0025] S52, using the surface volume tool of GIS, after inputting the reference plane height, select the area below the plane to calculate the system capacity W0.

[0026] Preferably, in step S51, for the original elevation data, if there is data error or missing, it is necessary to correct the original elevation and perform interpolation processing on the data error or missing area. When the elevation data meets the actual situation, it is imported into the GIS tool and DEM raster data is generated.

[0027] Preferably, in step S52, the reference plane is the planned flood control elevation of the subway station.

[0028] Preferably, step S6 determines the waterlogging risk by comparing the calculated results of the system water accumulation Wj and the system holding capacity W0. When Wj≤W0, it is considered that there is no waterlogging risk, and when Wj>W0, it is considered that there is waterlogging risk.

[0029] Compared with the prior art, the advantages of the present invention are:

[0030] This invention employs a rapid pre-assessment method based on system water balance, simplifying the complex problem of waterlogging into a quantitative analysis problem, thereby enabling rapid assessment of waterlogging risk in subway stations. This method simplifies the calculation of system inflow and outflow, using whether regional waterlogging exceeds the capacity defined by the subway entrance and exit level to the ground as a waterlogging risk metric. Under pre-set rainfall conditions, the greater the difference between the system capacity and the system waterlogging, the higher the waterlogging risk. This approach offers the advantages of low data requirements, simple calculations, and ease of operation, avoiding the complex calculations of rainfall runoff and hydrodynamic models. Furthermore, this method can be rapidly applied to site selection and flood control elevation design during the subway station planning and design phase. Through rapid pre-assessment, it effectively eliminates areas with no or low waterlogging risk, significantly reducing the workload and cost required for detailed simulation assessments using stormwater and flood control software. Required only basic data such as rainstorm data, terrain elevation, satellite imagery, and drainage network design standards, and computations performed using a GIS platform, this method not only improves assessment efficiency in practical applications but also provides a scientific basis for subway station design and detailed model assessment, demonstrating its high practical value. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Schematic diagram of the principle of the waterlogging risk pre-assessment method of the present invention.

[0032] Figure 2 4 is a calculation flow chart of the method of the present invention.

[0033] Figure 3 Schematic diagram of the area division method of the present invention.

[0034] Figure 4 This is a schematic diagram of the system flow calculation principle of the method of the present invention.

[0035] Figure 5 This is a schematic diagram of the system capacity calculation principle of the method of the present invention. DETAILED DESCRIPTION

[0036] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the present invention.

[0037] In addition, described feature, structure or characteristic can be combined in one or more embodiments in any suitable manner.In the following description, many specific details are provided so as to provide a full understanding of the embodiments of the present application. However, it will be appreciated by those skilled in the art that the technical scheme of the present application can be put into practice without one or more of the specific details, or other methods, components, devices, steps etc. can be adopted. In other cases, known methods, devices, implementations or operations are not shown or described in detail to avoid blurring the various aspects of the application.

[0038] See also Figure 1-3 This embodiment discloses a rapid assessment method for the risk of flooding in subway stations based on system water balance. The area where the subway station is located is regarded as an independent system, and the independent system is generalized into a "basin-shaped" water reservoir. It is assumed that the pipe networks between the systems are independent of each other. According to the principle of urban rainstorm water accumulation, the rainfall water accumulation process is generalized into inflow, discharge, and water accumulation based on the water balance principle. Through simplified calculation of inflow and pipe network discharge, it is analyzed whether the amount of retained water exceeds the spatial volume below the subway station entrance and exit, so as to preliminarily determine the level of flooding risk. The following steps are included:

[0039] S1, the study area is divided through terrain analysis and pipe network zoning, and the catchment area where the subway station is located is regarded as an independent system.

[0040] This step clarifies the boundaries of the catchment area by making a detailed division of the terrain and pipe network, and treats the area as an independent water balance unit, laying the foundation for subsequent calculations of rainfall inflow and discharge.

[0041] S2, uses the design rainstorm intensity and comprehensive runoff coefficient to calculate the system inflow Wr; by using the design rainstorm intensity and comprehensive runoff coefficient, the amount of water converted from rainfall in the area into inflow can be quantitatively calculated under specified rainfall conditions, providing key data for urban waterlogging risk assessment.

[0042] S3, calculate the system drainage volume Wp based on the design standards of the study area pipeline network, and calculate the drainage capacity according to the regional pipeline network design standards to ensure that the effectiveness of the actual drainage system is fully considered during the evaluation process.

[0043] S4, calculate the system water volume Wj through the water balance equation. Using the water balance principle, the calculated inflow volume is compared with the discharge volume to obtain the actual water volume under specific rainfall conditions.

[0044] S5, with the help of terrain elevation data and GIS tools, calculate the system capacity W0. Using terrain elevation data and GIS technology to generate a digital elevation model DEM, the capacity space from the entrance and exit of the subway station to the ground can be accurately calculated, providing a capacity indicator for risk assessment.

[0045] S6, by comparing the calculated results of the system water accumulation Wj and the system holding capacity W0, it is determined whether there is a risk of urban flooding in the study area. By comparing the actual water accumulation with the holding capacity, it is possible to intuitively determine whether there is a risk of urban flooding in the area under rainfall conditions, thereby achieving rapid pre-assessment.

[0046] In this example, the system boundary is set as a basin-shaped depression encompassing the subway station, bounded by the surrounding higher terrain. During rainfall, runoff and overflow water converge along the terrain slope to the lowest point within this area, gradually accumulating in the low-lying area. Water only overflows the system after the water level gradually rises above the basin's boundary. This ensures that the system's internal water volume remains contained during initial rainfall events, providing an accurate basis for subsequent water balance calculations.

[0047] In this embodiment, step S1 includes:

[0048] S11, starting from the subway station that needs to be risk assessed, determine the basic scope of the system based on the slope of the surrounding municipal roads according to relevant drawings. By analyzing the terrain elevation data around the subway station, identify the location of the lowest point to determine the main direction of rainwater runoff. Determine the slope change points of the municipal roads based on the slope of the municipal roads around the lowest point. Combined with the slope information of the municipal roads, determine the location where the road elevation changes, that is, the slope change points, as important boundary conditions for delineating the catchment area. Determine the basic scope of the system by connecting the slope change points of the surrounding roads. Using the spatial distribution of the road slope change points, form the preliminary boundary of the system, thereby determining the catchment area including the subway station, providing an accurate regional division basis for subsequent waterlogging risk assessment.

[0049] S12: Within the basic scope of the system, determine the final catchment area boundaries based on the pipeline layout and structures and walls that affect rainwater collection, and calculate the area S of this area. Based on the determined basic scope, further consider the layout of the drainage network in the area, and comprehensively analyze structures such as buildings and walls that may affect rainwater flow. The final catchment area boundaries are refined and the catchment area S of this area is calculated using GIS tools or engineering measurement methods to provide the necessary parameters for subsequent rainfall inflow calculations.

[0050] See also Figure 4 , step S2 includes:

[0051] S21. Design rainstorm data based on actual needs. This rainstorm data can be calculated using local rainstorm intensity formulas or standards, or measured rainfall data, where the rainstorm data refers to the intensity of rainstorms lasting 24 hours. By referring to regional rainstorm intensity calculation formulas or current standards, combined with historical rainfall monitoring data, determine a rainfall scenario that meets the characteristics of the study area to improve the accuracy of system inflow calculations.

[0052] For S22, based on the "Outdoor Drainage Design Standard," determine the regional comprehensive runoff coefficient ψ based on the building conditions in the study area, and increase this coefficient accordingly as the design rainfall return period increases. Based on the runoff coefficient values corresponding to different surface characteristics in the "Outdoor Drainage Design Standard," combined with factors such as building density and surface material within the study area, select a reasonable initial runoff coefficient and adjust it under high-return-period rainfall conditions to more realistically reflect the surface runoff characteristics under different rainfall intensities. The comprehensive runoff coefficient can be determined according to Table 1.

[0053] Table 1 Initial values of comprehensive runoff coefficient

[0054] Regional situation Comprehensive runoff coefficient Densely built urban areas 0.60-0.70 Densely built urban areas 0.45-0.60 Sparsely built urban areas 0.20-0.45

[0055] For low-return period regional runoff coefficients, refer to the midpoint of the range in Table 4.1.8-2 of the "Outdoor Drainage Design Standard" (GB 50014-2021) for calculation. As the design rainfall return period increases, the regional runoff coefficient should be increased accordingly. For example, for the following return periods, the runoff coefficient should be increased: 10%-15% for 20-30 years, 20%-25% for 30-50 years, and 30%-50% for 50-100 years. If the calculated runoff coefficient is greater than 1, it should be taken as 1. For high-return period inflows, the runoff coefficient corresponding to the inflow is determined according to Section 4.1.8.3 of the "Outdoor Drainage Design Standard" (GB 50014-2021). The final regional runoff coefficients for each rainfall return period are shown in Table 2.

[0056] Table 2 Corrected values of comprehensive runoff coefficient

[0057] Return period (a) 5 10 20 30 50 100 Densely built urban areas 0.65 0.65 0.73 0.73 0.80 0.85 Densely built urban areas 0.53 0.53 0.59 0.59 0.64 0.68 Sparsely built urban areas 0.33 0.53 0.37 0.37 0.40 0.42

[0058] S23, for the rainfall scenario set in the region, calculate the system inflow Wr. By establishing a water balance relationship, calculate the total amount of water entering the study area under specific rainfall conditions. The system inflow Wr is calculated using the following formula:

[0059] Wr=ψ·i·S·t;

[0060] The unit of Wr is m 3 , ψ is the regional comprehensive runoff coefficient; i is the design rainstorm intensity, unit is mm / min; S is the catchment area, unit is m 2 t is the set rainfall duration, in minutes. This formula can be used to quickly calculate system inflow under different rainfall scenarios, providing data support for subsequent waterlogging risk assessments.

[0061] In this embodiment, step S3 executes the formula Wp=ψp·H·S / 1000 to calculate the system drainage volume Wp according to the drainage volume corresponding to the design recurrence period of the pipe network. By setting the design recurrence period of the pipe network, the drainage capacity of the drainage system in the study area is determined, so that the calculation results can truly reflect the operating conditions of the drainage system under specific rainfall conditions. Among them, ψp is the comprehensive runoff coefficient corresponding to the pipe network design, which characterizes the pipe network's ability to collect and discharge surface runoff under different design standards. The coefficient is determined according to the pipe network design specifications and the surface characteristics of the study area; H is the rainfall corresponding to the pipe network recurrence period, in mm, indicating the rainfall intensity that may occur within the set design recurrence period, which can be determined based on historical rainfall data or specifications; S is the area of the catchment basin system, in m 2, representing the total area of the catchment area. This calculation formula can accurately assess the drainage capacity of the pipe network under different rainfall conditions, providing a reliable basis for subsequent system water balance calculations and waterlogging risk assessments.

[0062] In this embodiment, step S4, based on the principle of system water balance, calculates the system water volume Wj by calculating the difference between Wr and Wp: Wj = Wr - Wp. This difference, Wj, represents the water volume in the study area under that rainfall scenario, providing baseline data for subsequent waterlogging risk assessment.

[0063] See also Figure 5 , step S5 includes: S51, generating a DEM of the study area in the GIS platform based on relevant elevation data. By collecting and processing the terrain elevation data of the study area, a digital elevation model (DEM) is constructed in the GIS platform to provide accurate terrain information for the subsequent calculation of the system capacity. S52, using the surface volume tool of GIS, after inputting the reference plane height, select the plane below to calculate the system capacity W0. Based on the DEM data, the volume below a specific elevation, that is, the maximum water capacity of the system, is calculated through the GIS tool, thereby determining the maximum carrying capacity of the area under specific rainfall conditions.

[0064] Furthermore, in step S51, for the original elevation data, if there are data errors or missing data, it is necessary to correct the original elevation and interpolate the data error or missing areas. After the elevation data has been corrected and meets the actual situation, it is imported into the GIS tool and generated into DEM raster data to ensure the accuracy of the calculation system capacity W0 and improve the reliability of the assessment. In step S52, the reference plane is set to the flood control elevation of the planned subway station. The flood control elevation is the flood control level set by the subway station during the design phase. It serves as an important benchmark for assessing the risk of waterlogging and is used to calculate the amount of water that can be accommodated in the study area at this elevation.

[0065] In this embodiment, step S6 determines the risk of flooding by comparing the calculated system water volume Wj with the system capacity W0. When Wj ≤ W0, the space at that elevation is sufficient to accommodate surface water accumulation, and there is no risk of flooding. This means that the water accumulation in the area does not exceed the capacity, and the subway station can operate safely. However, when Wj > W0, the space at that elevation is insufficient to accommodate surface water accumulation, and the accumulated water will overflow the subway station entrances and exits and flow back into the underground space, posing a risk of flooding. This indicates that the accumulated water exceeds the capacity, potentially causing rainwater to overflow into the subway station, impacting normal operation. In this case, a detailed assessment or other measures are required.

[0066] In summary, the present invention discloses a rapid assessment method for subway station flooding risk based on system water balance. By treating the subway station area as an independent water balance system, this method utilizes calculation methods for rainfall inflow, drainage, and accumulated water volume, combined with GIS technology and digital elevation models (DEMs), to quantitatively assess flooding risk. By setting the system capacity and comparing it with the accumulated water volume, this method quickly determines whether a subway station is at risk of flooding, forming a simple and efficient risk pre-assessment mechanism. Without involving complex hydrodynamic model calculations, the present method relies solely on design rainstorm data, terrain elevation information, satellite imagery, and drainage network design standards to rapidly predict subway station flooding risk. Compared to traditional assessment methods that rely on numerical simulation or GIS remote sensing coupled analysis, this method significantly reduces data requirements, computational complexity, and professional operational requirements. This allows for efficient screening of stations with no or minimal flooding risk during the planning and design phase of subway stations, avoiding the need for costly and time-consuming rain and flood software simulation assessments later on. The present invention is of great significance for urban rail transit construction, underground space flood control planning, and subway station safety management. Its high efficiency and low cost enable subway construction companies, design teams, and urban planning departments to consider flooding risks early in the decision-making process, optimizing station site selection and drainage design, and improving overall drainage safety. This approach not only enhances the flood resistance of subway stations but also provides a viable technical support for urban flood control systems, demonstrating high engineering value and potential for widespread adoption.

[0067] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. Under the concept of the present invention, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the present invention as described above. For the sake of simplicity, they are not provided in detail. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in this field should understand that it is still possible to modify the technical solutions described in the above embodiments, or to make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A rapid assessment method for subway station flooding risk based on system water balance, characterized by: The following steps are involved: S1, the study area was divided by terrain analysis and pipe network zoning, and the catchment area where the subway station is located was treated as an independent system; S2, calculate the system inflow Wr using the design rainstorm intensity and comprehensive runoff coefficient; S3, calculate the system discharge Wp based on the design standard of the pipe network in the study area; S4, calculate the system water volume Wj through the water balance equation; S5, calculate the system capacity W0 with the help of terrain elevation data and GIS tools; S6, by comparing the calculated results of the system water accumulation Wj with the system holding capacity W0, it is determined whether there is a risk of waterlogging in the study area.

2. The method for rapid assessment of subway station flooding risk based on system water balance according to claim 1 is characterized in that: The step S1 comprises: S11, starting from the subway station that needs to be risk assessed, determine the basic scope of the system based on the slope of the surrounding municipal roads according to relevant drawings; S12, within the basic range of the system, determine the final catchment area boundary according to the pipeline layout and the structures and walls that affect the collection of rainwater, and calculate the area S of the area.

3. The method for rapid assessment of subway station flooding risk based on system water balance according to claim 2 is characterized in that: The step S2 comprises: S21, designing rainstorm data according to actual needs. The rainstorm data can be calculated according to local rainstorm intensity formulas or standards, or can use measured rainfall data, wherein the rainstorm data is the rainstorm intensity of rainfall lasting 24 hours; S22, based on the "Outdoor Drainage Design Standard", determine the regional comprehensive runoff coefficient ψ according to the building conditions in the study area, and increase this coefficient accordingly when the design rainfall return period increases; S23, calculating the system inflow Wr for the rainfall condition set in the area.

4. The method for rapid assessment of subway station flooding risk based on system water balance according to claim 3 is characterized in that: In step S23, the system inflow Wr is calculated using the following formula: Wr = ψ·i·S·t, where ψ is the regional comprehensive runoff coefficient; i is the design rainstorm intensity, mm / min; S is the catchment area, m 2 ; t is the set rainfall duration, min.

5. The method for rapid assessment of subway station flooding risk based on system water balance according to claim 4 is characterized in that: In step S3, the system discharge volume Wp is calculated by executing the formula Wp=ψp·H·S / 1000 according to the discharge volume corresponding to the pipe network design recurrence period, where ψp is the comprehensive runoff coefficient corresponding to the pipe network design; H is the rainfall corresponding to the pipe network recurrence period, mm; S is the catchment area, m 2 .

6. The method for rapid assessment of subway station flooding risk based on system water balance according to claim 5 is characterized in that: In step S4, the system water volume Wj is obtained by calculating the difference between Wr and Wp based on the system water balance principle.

7. The method for rapid assessment of subway station flooding risk based on system water balance according to claim 6 is characterized in that: The step S5 comprises: S51, generate DEM of the study area in the GIS platform based on relevant elevation data; S52, using the surface volume tool of GIS, after inputting the reference plane height, select the area below the plane to calculate the system capacity W0.

8. The method for rapid assessment of subway station flooding risk based on system water balance according to claim 7 is characterized in that: In step S51, if there are data errors or missing in the original elevation data, the original elevation needs to be corrected and the data error or missing areas need to be interpolated. When the elevation data meets the actual situation, it is imported into the GIS tool and DEM raster data is generated.

9. The method for rapid assessment of subway station flooding risk based on system water balance according to claim 7 is characterized in that: In step S52, the reference plane is the planned flood control elevation of the subway station.

10. The method for rapid assessment of subway station flooding risk based on system water balance according to claim 7, characterized in that: The step S6 determines the waterlogging risk by comparing the calculated result of the system water accumulation Wj with the system holding capacity W0. When Wj≤W0, it is considered that there is no waterlogging risk, and when Wj>W0, it is considered that there is waterlogging risk.

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