A community rainwaterlogging numerical simulation method based on hydrological and hydrodynamic coupling model

Abstract

The application discloses a community rainwater logging numerical simulation method based on a hydrology and hydrodynamic coupling model, and comprises the following steps: collecting basic data in a research area; constructing a pipe network hydrology and hydrodynamic model through the basic data; constructing a surface flow model based on grid operation through the basic data; coupling the pipe network hydrology and hydrodynamic model and the surface flow model; and after verifying the coupled model, simulating and predicting rainwater logging water distribution and water depth. The application combines hydrology, hydrodynamics and a GIS method, establishes a pipe network hydrology and hydrodynamic model and a two-dimensional surface flow model, realizes two-way water exchange of a drainage pipe network and a city surface, and is more accurate and reasonable in simulating and predicting results; the two-dimensional hydrodynamic model based on grid operation is used to solve a simplified two-dimensional shallow water equation, realize dynamic simulation of a waterlogging submerged range and waterlogging depth in a city area, and improve model calculation efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of urban rainstorm waterlogging numerical simulation, and particularly relates to a community rainwaterlogging numerical simulation method based on a hydrology and hydrodynamics coupled model. BACKGROUND

[0002] Urban areas are densely built with buildings and roads crisscrossing, forming special runoff and confluence characteristics different from natural basins. Numerical simulation can better reveal the formation mechanism and evolution process of urban rainstorm waterlogging, and is an important technical means for waterlogging disaster risk warning and assessment. Domestic and foreign scholars have carried out a lot of researches by using hydrology and hydrodynamics methods. Based on the principle of hydrology, the calculation of urban runoff and confluence is simple in structure and high in efficiency, but the hydraulic characteristic factors at specific positions cannot be obtained; based on the hydrodynamics method, one-dimensional Saint-Venant equation and two-dimensional shallow water equation are used to simulate urban drainage pipe network and surface flow, which is high in calculation accuracy but low in efficiency. The combination of hydrology and hydrodynamics methods can effectively utilize the advantages of both, and has good hydrology basis while improving the calculation efficiency.

[0003] The exchange of water between underground drainage pipe network and surface is a key problem in urban waterlogging numerical simulation. In recent years, the bidirectional exchange problem of underground pipe network and surface flow has been further studied, and some commercial model software such as InfoWorks ICM, Mike21, PCSWMM and the like realizes the simulation of rainwaterlogging process through the coupling of one-dimensional and two-dimensional models, but these commercial software is usually high in price, which limits its popularization and application to a certain extent, and the contradiction between the refinement degree and calculation efficiency of the model also needs to be further solved. The two-dimensional hydrodynamic model based on grid operation can more efficiently utilize digital elevation model (DEM) data, and the moderate simplification of two-dimensional shallow water equation can further balance the contradiction between refined simulation and calculation efficiency, and better adapt to the needs of rapid risk assessment and early warning decision of urban waterlogging disasters.

[0004] The refined simulation and analysis of community rainstorm waterlogging scenarios can better understand and master the mechanism of urban rainstorm waterlogging, so that more effective measures can be taken. Although there have been a lot of studies on urban waterlogging simulation, there is still a lack of widely used and recognized model method for rapid and accurate simulation of rainstorm waterlogging process in complex community environment of urban areas. SUMMARY

[0005] This section is intended to summarize some aspects of the embodiments of the present application and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of the specification of the present application to avoid obscuring the purpose of this section, the abstract and the title, and such simplifications or omissions cannot be used to limit the scope of the present application.

[0006] In view of the above existing problems, the present application is proposed.

[0007] Therefore, the present application provides a community rainwater logging numerical simulation method based on a hydrological and hydrodynamic coupling model, which solves the problem that the current rainwater logging calculation method under complex community environment cannot quickly, accurately and simply predict and is not widely applicable.

[0008] To solve the above technical problems, the present application provides the following technical solutions:

[0009] Collecting basic data in the research area;

[0010] Building a pipe network hydrological and hydrodynamic model through the basic data;

[0011] Building a surface flow model based on grid operation through the basic data;

[0012] Coupling the pipe network hydrological and hydrodynamic model and the surface flow model;

[0013] After verifying the coupled model, simulating and predicting the rainwater logging distribution and water depth.

[0014] As a preferred scheme of the community rainwater logging numerical simulation method based on the hydrological and hydrodynamic coupling model, the basic data includes hydrological data, ground elevation data, land use type, drainage pipe network, building and road distribution data.

[0015] As a preferred scheme of the community rainwater logging numerical simulation method based on the hydrological and hydrodynamic coupling model, the hydrological data includes monitoring station rainfall process, flow process and waterlogging point data.

[0016] As a preferred scheme of the community rainwater logging numerical simulation method based on the hydrological and hydrodynamic coupling model, the drainage pipe network data includes inspection well data and pipe data, the inspection well data contains inspection well number, horizontal and vertical coordinates, well mouth ground elevation, well depth and diameter, and the pipe data contains pipe start and end nodes, pipe bottom elevation, pipe section form and pipe size.

[0017] As a preferred scheme of the community rainwater logging numerical simulation method based on the hydrological and hydrodynamic coupling model, building the pipe network hydrological and hydrodynamic model includes:

[0018] Extracting the drainage pipe network data to establish the pipe network hydrodynamic model;

[0019] According to the terrain and pipe network distribution of the research area, dividing sub-catchment areas, determining the runoff yield and concentration parameters, and establishing the pipe network hydrological model;

[0020] connecting the sub-catchment and the inspection well to obtain a pipe network hydrological and hydrodynamic model.

[0021] As a preferred scheme of the community waterlogging numerical simulation method based on the hydrological and hydrodynamic coupling model, the method comprises the following steps:

[0022] The wellhead ground elevation and the building and road distribution data are used to correct the generated ground elevation model.

[0023] The calculation region is orthogonally meshed and attribute values are assigned.

[0024] The boundary conditions of the calculation region are determined.

[0025] The surface flow is discretized on the orthogonal mesh, and the simplified two-dimensional shallow water equation is solved.

[0026]

[0027]

[0028]

[0029] wherein h i,j is the free water surface height at the i,j mesh intersection, m; t is time, s; Δx and Δy are mesh sizes; Q x and Q y respectively represent the flow in the x and y directions, m 3 / s; h flow is the water flow depth between two adjacent meshes; and n is the Manning coefficient.

[0030] As a preferred scheme of the community waterlogging numerical simulation method based on the hydrological and hydrodynamic coupling model, the coupling comprises:

[0031] Based on the rainfall process data, the runoff of the sub-catchment at the current time step is calculated, and it is assumed that the runoff is all collected into the underground pipe network through the corresponding inspection well.

[0032] The underground pipe network and the surface grid unit are connected through the inspection well to perform bidirectional water exchange, specifically as follows:

[0033] When the pipe network node water head h m is greater than the surface grid water level h 2d corresponding to the node, the water flow in the pipe network flows out of the node to the surface, and the node overflow flow at the time step is calculated by SWMM; otherwise, when h 2d > h m , the surface water flows back into the pipe network.

[0034] After the water exchange, the model calculation of the next time step is carried out, and the process is repeated until the set step number is reached.

[0035] As a preferred scheme of the community rainwaterlogging numerical simulation method based on the hydrological and hydrodynamic coupled model, the surface water flows back into the pipe network by nodes, wherein the backflow amount is represented as:

[0036] When h 2d >h z >h m , the node backflow amount is calculated by the free weir flow formula,

[0037]

[0038] wherein Q is the node backflow amount of the current time step, m 3 / s; c w is a weir flow coefficient, taking a value of [0, 1]; h z is the wellhead ground elevation; B is the wellhead width, m; g is the gravitational acceleration, m / s 2 .

[0039] When h 2d >h m >h z , and (h 2d -h z )≤Am / B, the node backflow amount is calculated by the submerged weir flow formula,

[0040]

[0041] wherein A m is the wellhead area, m 2 .

[0042] When h 2d >h m >h z , and (h 2d -h z )>Am / B, the node backflow amount is calculated by the orifice flow formula,

[0043]

[0044] wherein c o is an orifice flow coefficient, taking a value of [0, 1].

[0045] As a preferred scheme of the community rainwaterlogging numerical simulation method based on the hydrological and hydrodynamic coupled model, the model verification comprises:

[0046] The outflow process, the surface water depth, the waterlogging duration and the inundation range are simulated by using the measured rainfall process. If the error between the simulation result and the measured data meets the set requirement, it is indicated that the selected production and convergence parameters of the model are reasonable and the model precision is better.

[0047] As a preferred scheme of the community rainwaterlogging numerical simulation method based on the hydrological and hydrodynamic coupling model, the simulation prediction comprises:

[0048] The predicted rainfall or the design rainstorm process is input into the model, and the waterlogging inundation range, the water depth distribution and their dynamic change process in the calculation area are solved to realize the simulation result visualization in the GIS environment.

[0049] Compared with the prior art, the community rainwaterlogging numerical simulation method based on the hydrological and hydrodynamic coupling model has the following beneficial effects:

[0050] (1) The community rainwaterlogging numerical simulation method based on the hydrological and hydrodynamic coupling model combines the respective advantages of hydrology, hydrodynamics and the GIS method, establishes the pipe network hydrological and hydrodynamic model and the two-dimensional surface flow model, realizes the bidirectional water exchange between the drainage pipe network and the urban surface, and the simulation prediction result is more accurate and reasonable.

[0051] (2) The community rainwaterlogging numerical simulation method based on the hydrological and hydrodynamic coupling model adopts the two-dimensional hydrodynamic model based on the grid operation, solves the simplified two-dimensional shallow water equation, realizes the dynamic simulation of the waterlogging inundation range and the water depth in the urban area, can improve the model calculation efficiency, and better meets the needs of the rapid risk evaluation and the early warning decision of the urban community waterlogging disaster. BRIEF DESCRIPTION OF DRAWINGS

[0052] In order to more clearly illustrate the technical scheme of the embodiments of the present application, the following will briefly introduce the drawings required to be used in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without paying creative labor. Among them:

[0053] Figure 1 The flow chart of the community rainwaterlogging numerical simulation method based on the hydrological and hydrodynamic coupling model according to an embodiment of the present application;

[0054] Figure 2 The research area drainage system and the subcatchment division of the community rainwaterlogging numerical simulation method based on the hydrological and hydrodynamic coupling model according to an embodiment of the present application;

[0055] Figure 3 The measured rainfall and the simulated drainage outlet flow process of the community rainwaterlogging numerical simulation method based on the hydrological and hydrodynamic coupling model according to an embodiment of the present application;

[0056] Figure 4The measured rainfall simulation water depth distribution map of the community rainwater logging numerical simulation method based on a hydrological and hydrodynamic coupling model according to an embodiment of the present application;

[0057] Figure 5 The 90-minute schematic diagram of the storm simulation water depth distribution of the community rainwater logging numerical simulation method based on a hydrological and hydrodynamic coupling model according to an embodiment of the present application;

[0058] Figure 6 The 120-minute schematic diagram of the storm simulation water depth distribution of the community rainwater logging numerical simulation method based on a hydrological and hydrodynamic coupling model according to an embodiment of the present application;

[0059] Figure 7 The 150-minute schematic diagram of the storm simulation water depth distribution of the community rainwater logging numerical simulation method based on a hydrological and hydrodynamic coupling model according to an embodiment of the present application;

[0060] Figure 8 The 180-minute schematic diagram of the storm simulation water depth distribution of the community rainwater logging numerical simulation method based on a hydrological and hydrodynamic coupling model according to an embodiment of the present application. DETAILED DESCRIPTION

[0061] In order to make the above objectives, features and advantages of the present application more apparent, specific embodiments of the present application are described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work should fall within the protection scope of the present application.

[0062] In the following description, many specific details are set forth in order to provide a thorough understanding of the present application. However, the present application can be practiced without the specific details, which are not described in the present application, and the skilled in the art can make similar generalization without departing from the scope of the present application. Therefore, the present application is not limited by the specific embodiments disclosed below.

[0063] Secondly, the "one embodiment" or "embodiment" referred to herein can include specific features, structures or characteristics contained in at least one implementation of the present application. The "in one embodiment" appearing in different places in the specification does not refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments.

[0064] The application is described in detail in combination with the schematic diagram, and in the detailed description of the embodiments of the application, the sectional view of the device structure is partially enlarged without the general proportion for the convenience of illustration, and the schematic diagram is only an example, which should not limit the scope of protection of the application herein. In addition, the three-dimensional spatial dimensions of length, width and depth should be included in actual production.

[0065] Meanwhile, in the description of the application, it should be noted that the terms "upper, lower, inner and outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the application and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the application. In addition, the terms "first, second or third" are only for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0066] In the application, unless otherwise explicitly specified and limited, the terms "mounting, connection, connection" should be understood broadly, for example: it can be fixed connection, detachable connection or integral connection; it can also be mechanical connection, electrical connection or direct connection, it can also be indirectly connected through an intermediate medium, or it can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the application can be understood according to the specific circumstances.

[0067] Embodiment 1

[0068] Reference Figure 1 For an embodiment of the application, a community rainwaterlogging numerical simulation method based on a hydrological and hydrodynamic coupling model is provided, comprising:

[0069] S1: Collecting basic data in the research area;

[0070] Further, the basic data includes hydrological data, ground elevation data, land use type, drainage pipe network, building and road distribution data.

[0071] Further, the hydrological data includes monitoring station rainfall process, flow process and water accumulation point data.

[0072] Further, the drainage pipe network data includes inspection well data and pipe data, the inspection well data includes inspection well number, horizontal and vertical coordinates, well mouth ground elevation, well depth and diameter, and the pipe data includes pipe start and end nodes, pipe bottom elevation, pipe section form and pipe size.

[0073] It should be noted that the basic data of the research area can include "internal" and "boundary" data.

[0074] S2: Constructing a pipe network hydrological and hydrodynamic model through the basic data;

[0075] Further, the construction of the pipe network hydrology and hydrodynamic model comprises:

[0076] extracting the drainage pipe network data, and establishing the pipe network hydrodynamic model;

[0077] dividing sub-catchment areas according to the terrain and pipe network distribution of the research area, determining the runoff yield parameters, and establishing the pipe network hydrology model;

[0078] connecting the sub-catchment areas and inspection wells to obtain the pipe network hydrology and hydrodynamic model.

[0079] It should be noted that the pipe network hydrology and hydrodynamic model realizes the simulation of rainfall runoff yield process and one-dimensional pipe network concentration process. Among them, the rainfall runoff yield process simulation calculates the pipe network external inflow such as runoff and rainfall infiltration of each sub-catchment area based on the hydrology method, and serves as the boundary condition of the one-dimensional pipe network concentration simulation.

[0080] S3: constructing a surface overland flow model based on grid operation through basic data;

[0081] Further, the construction of the surface overland flow model based on grid operation comprises,

[0082] correcting the generated ground elevation model using wellhead ground elevation and building and road distribution data;

[0083] orthogonal grid subdivision and attribute assignment are performed on the calculation area;

[0084] determining the boundary conditions of the calculation area;

[0085] discretizing the surface overland flow to the orthogonal grid, and solving the simplified two-dimensional shallow water equation:

[0086]

[0087]

[0088]

[0089] wherein h i,j is the free water surface height at the intersection of the i,j grid, m; t is time, s; Δx and Δy are grid sizes; Q x and Q y represent the flow in x and y directions, m 3 / s; h flow is the water flow depth between two adjacent grids; and n is the Manning coefficient.

[0090] It should be noted that (the surface runoff model based on grid operation can further balance the contradiction between fine simulation and calculation efficiency, and can quickly construct a two-dimensional water dynamic model using ground elevation model data, and accurately simulate and calculate the water depth and submergence duration of each grid cell.

[0091] S4: coupling the pipe network hydrological and hydrodynamic model and the surface runoff model;

[0092] Further, the coupling includes,

[0093] Based on the rainfall process data, the runoff of the sub-catchment at the current time step is calculated, assuming that the runoff is all collected into the underground pipe network through the corresponding inspection well;

[0094] The underground pipe network and the surface grid cell are connected through the inspection well, and bidirectional water exchange is carried out, specifically:

[0095] When the pipe network node water head h m is greater than the surface grid water level h 2d corresponding to the node, the water flow in the pipe network flows out of the node and flows into the surface, and the node overflow flow at the time step is calculated by SWMM; otherwise, when h 2d > h m , the surface water flows back into the pipe network from the node.

[0096] After water exchange, the model calculation at the next time step is carried out, and the same is repeated until the set number of steps is completed.

[0097] Further, the surface water flows back into the pipe network, wherein the backflow is represented as:

[0098] When h 2d > h z > h m , the node backflow is calculated by the free weir flow formula,

[0099]

[0100] wherein Q is the node backflow at the current time step, m 3 / s; c w is the weir flow coefficient, taking a value of [0, 1]; h z is the well mouth ground elevation; B is the well mouth width, m; g is the acceleration of gravity, m / s 2 .

[0101] When h 2d > h m > h z , and (h 2d -h z )≤Am / B, the node backflow is calculated by the submerged weir flow formula,

[0102]

[0103] wherein A m is the wellhead area, m 2 ;

[0104] When h 2d > h m > h z and (h 2d -h z )>Am / B, the node inflow is calculated by the orifice flow formula,

[0105]

[0106] wherein c o is the orifice flow coefficient, taking a value [0, 1].

[0107] It should be noted that this step realizes the bidirectional flow interaction of the surface and the underground pipe network by coupling the pipe network hydrological and hydrodynamic model and the surface overland flow model. Compared with the conventional method of driving the two-dimensional model of the surface by the overflow of the pipe network node, the bidirectional coupling mode is more in line with the actual situation of urban waterlogging.

[0108] S5: After the verification of the coupled model, the rainwater accumulation distribution and water depth simulation prediction are performed.

[0109] Further, the model verification includes,

[0110] The outflow process, the surface water depth, the waterlogging duration and the inundation range are simulated by using the measured rainfall process. The simulation results and the measured data are compared. If the error of the two meets the set requirement, it is indicated that the selection of the runoff and confluence parameters of the model is reasonable, and the model precision is good.

[0111] It should be noted that as an optional mode, the outflow process, the surface water depth, the waterlogging duration and the inundation range are solved by adjusting the infiltration parameters and the roughness in the established model. The measured data are used for verification, so that the error of the simulation results and the measured results meets certain requirements, and the model parameters are calibrated. Specifically, the outflow error can be controlled within 20%, the water depth and waterlogging duration error can be controlled within 25%, and the inundation area error can be controlled within 30%, that is, the infiltration parameters and the roughness in the model are determined. Otherwise, the parameters are adjusted again, and the calibration is performed again.

[0112] Further, the simulation prediction includes,

[0113] The predicted rainfall or design storm process is input into the model, and the inundation range, water depth distribution and dynamic change process in the calculation area are solved to realize the visualization of the simulation results in the GIS environment. Decision basis is provided for the risk assessment and early warning of urban community rainwaterlogging disasters.

[0114] Embodiment 2

[0115] Reference Figures 2-8 For an embodiment of the present application, a community rainwaterlogging numerical simulation method based on a hydrological and hydrodynamic coupled model is provided, and in order to verify the beneficial effects, the above Shanghai Pudong New Area Yangshan Port Free Trade Zone is taken as a calculation area for example.

[0116] S1: Collecting basic data in the research area;

[0117] The research area is located in the southeast corner of Shanghai, close to the sea, low and flat terrain, small elevation difference, and the total area is about 5km 2 . The buildings in the area are dense, and the ground hardening degree is high, and it is easy to accumulate water when encountering heavy rain.

[0118] According to the modeling requirements of rainwaterlogging, the hydrological data, land use type, drainage pipe network, building distribution and ground elevation data of the research area are collected. Among them, the hydrological data includes the rainfall process and historical waterlogging point data of the monitoring station; the drainage pipe network data includes the inspection well data and the pipe data, wherein the inspection well data includes the inspection well number, the horizontal and vertical coordinates, the well mouth ground elevation, the well depth and the diameter, and the pipe data includes the pipe start node, the pipe bottom elevation, the pipe section form and the pipe size.

[0119] S2: Building a pipe network hydrological and hydrodynamic model through the basic data;

[0120] The drainage pipes and inspection wells in the research area are extracted, some overlapping pipes and nodes are excluded, the outer branch pipes with a pipe diameter less than a set value are removed, the topological relationship of the pipe network is checked and reconstructed, a one-dimensional pipe network hydrodynamic model is established, and the continuity equation and momentum equation are solved:

[0121]

[0122]

[0123] In the formula: Q is the flow in the pipe, m 3 / s; A is the area of the flow section, m 2 ; q is the lateral flow, m 3 / s; S0 is the pipe slope, P is the wet perimeter, m; n is the Manning friction coefficient, and h is the water depth, m.

[0124] According to the terrain and pipe network topology of the study area, the sub-catchment is divided by using the Thiessen polygon, ensuring that each sub-catchment corresponds to a manhole. Based on GIS calculation, the important parameters such as characteristic width, slope, and impervious rate of each sub-catchment are extracted. The infiltration parameters of the sub-catchment are calibrated by the measured data, and the pipe network hydrological model is established.

[0125] Taking the sub-catchment as the unit, the runoff is calculated according to the rainfall process data. The sub-catchment and the manhole are connected, that is, it is assumed that the runoff generated by the rainfall of each sub-catchment is all collected into the underground pipe network through the corresponding manhole, and the pipe network hydrological and hydrodynamic model is obtained.

[0126] Figure 2 The drainage system and sub-catchment division results of the study area are given. After generalization, the model has a total of 942 nodes, 976 drainage channels, 5 gravity drainage outlets, and 2 pump station drainage outlets.

[0127] S3: Construct a surface flow model based on grid operation through basic data;

[0128] Using the collected elevation point data, combined with the pipe network wellhead ground elevation information, the inverse distance weighted average interpolation method (IDW) is used to generate the DEM model of the study area. The urban underlying surface is densely covered with buildings, and the roads are crisscrossed. Considering the water resistance of buildings and the flood discharge of roads, the distribution data of buildings and roads are used to further correct the ground elevation, and the corrected DEM is obtained.

[0129] The calculation area is divided by using a 2m×2m orthogonal grid, and each grid cell is assigned a corresponding roughness according to the underlying land use type. The boundary conditions of the calculation area are determined, including the upstream inflow boundary condition, the downstream outflow boundary condition, the pipe network overflow node, and the flow process as a point source time-varying boundary driving two-dimensional model calculation.

[0130] The surface flow is discretized on the orthogonal grid, and the two-dimensional flow on the surface is simulated by solving the simplified shallow water equation, whose corresponding continuity equation and momentum equation are expressed as:

[0131]

[0132]

[0133]

[0134] where h i,j is the free water surface height at the intersection of i,j grid, m; t is time, s; Δx and Δy are grid sizes; Q x and Q y are the flow rates in x and y directions, m 3 / s; h flowis the water depth between two adjacent grids; n is the Manning coefficient.

[0135] S4: coupling the pipe network hydrological and hydrodynamic model and the surface flow model;

[0136] The coupling method and process of the pipe network hydrological and hydrodynamic model and the surface flow model are as follows:

[0137] ①Based on the rainfall process data, the runoff of the current time step in the catchment area is calculated, and it is assumed that the runoff is all collected into the underground pipe network through the corresponding inspection well;

[0138] ②The pipe network and the surface grid unit are connected through the inspection well, and bidirectional water exchange is carried out, specifically: when the pipe network node water head h m is greater than the surface grid water level h 2d corresponding to the node, the water flow in the pipe network flows out of the node and flows into the surface; on the contrary, when h 2d >h m , the surface water flows back into the pipe network.

[0139] Further, the pipe network node overflow is calculated by the SWMM model, and the backflow is calculated by the weir flow formula or the orifice flow formula, specifically as follows:

[0140] When h 2d >h z >h m , the node backflow is calculated by the free weir flow formula,

[0141]

[0142] wherein Q is the node backflow at the current time step, m 3 / s; c w is the weir flow coefficient, taking a value of [0, 1]; h z is the well mouth ground elevation; B is the well mouth width, m; g is the gravitational acceleration, m / s 2 .

[0143] When h 2d >h m >h z , and (h 2d -h z )≤Am / B, the node backflow is calculated by the submerged weir flow formula,

[0144]

[0145] wherein A m is the well mouth area, m 2 .

[0146] When h 2d >h m>h z and (h 2d -h z When Am / B, the node backflow is calculated by the orifice flow formula,

[0147]

[0148] where c o is the orifice flow coefficient, taking values in [0, 1].

[0149] ③ After the water exchange, the model calculation of the next time step is carried out, and the same is repeated until the set number of steps is completed.

[0150] S5: After the verification of the coupled model, the rainwater accumulation and water depth simulation and prediction are carried out.

[0151] The rationality of the model is verified by using the rainfall data of the Shanghai heavy rain on September 13, 2013. This rainfall is a short-time heavy rain, and the rainfall is mainly concentrated in 15:30-17:30. By inputting the rainfall process data into the model, the drainage outlet flow process (see Figure 3 ) and the maximum water depth distribution in the calculation area ( Figure 4 ) are obtained. Figure 3 The drainage outlet flow process basically reflects the rainwater and flood characteristics of the small-scale urban watershed, but due to the lack of measured flow data, the model accuracy cannot be directly verified. By comparing the simulated water depth and the measured water accumulation point distribution, the simulation results are generally consistent with the actual situation, indicating that the constructed rainwater logging model has good applicability in the study area.

[0152] By inputting the predicted rainfall or design rainstorm process into the model, the rainwater logging inundation range, water depth distribution and dynamic change process in the calculation area are simulated, and the simulation results are visualized in the GIS environment, providing decision basis for urban community rainwater logging disaster risk assessment and early warning.

[0153] Under different return period short duration design rainstorm scenarios, the Shanghai rainstorm intensity formula is used:

[0154]

[0155] In the formula, i is the design rainfall intensity, L / (s·ha); P is the design rainfall return period, a; t is the rainfall duration, min. The Chicago rain type is used, the rainfall duration is 2 hr, and the simulation duration is 4 hr.

[0156] Figures 5-8 The rainwater logging accumulation and recession processes under the 20-year design rainfall scenario in the study area are given. By coupling one-dimensional pipe network confluence and two-dimensional surface flow, the pipe network node overflow and backflow can be quantitatively calculated, and the dynamic process of urban community rainwater logging inundation can be more accurately described.

[0157] It should be noted that the above examples are only used to illustrate the technical solutions of the present application but not to limit the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or equivalently replaced without departing from the spirit and scope of the present application, and all modifications and equivalents should be included in the scope of the claims of the present application.

Claims

1. A community waterlogging numerical simulation method based on a hydrological and hydrodynamic coupling model, characterized in that, The application relates to a method for simulating and predicting urban rainwater flooding, and belongs to the technical field of urban rainwater flooding simulation. The method comprises the following steps: Collecting basic data of a research area; Building a pipe network hydrology and hydrodynamic model based on the basic data; Building a surface flow model based on grid operation based on the basic data; Coupling the pipe network hydrology and hydrodynamic model and the surface flow model; The coupling comprises: Based on rainfall process data, calculating the runoff of a sub-catchment at a current time step, assuming that the runoff is all collected into the underground pipe network through corresponding inspection wells; When pipe network node water head h m is greater than the node corresponding ground grid water level h 2d , the water flow in the pipe network flows out of the node to the ground, and the node overflow flow of this time step is calculated by SWMM; on the contrary, when h 2d > h m , the ground water flows back into the pipe network; Connecting the underground pipe network and the surface grid unit through the inspection wells to realize bidirectional water exchange, specifically: After water exchange, model calculation is carried out at a next time step, and the process is repeated until a set number of steps is completed; When h 2d >h z >h m The node backflow is calculated by the free weir flow formula: where Q is the node backflow at the current time step, m 3 / s; c w is the weir flow coefficient, taking values in [0, 1]; h z is the wellhead ground elevation; B is the wellhead width, m; g is the gravitational acceleration, m / s 2 ; When h 2d >h m >h z and (h 2d -h z )≤A m / B, the node backflow is calculated by the submergence weir formula: wherein A m is the wellhead area, m 2 ; When h 2d >h m >h z and (h 2d -h z )>A m / B, the node backflow volume is calculated by the orifice flow equation: where c o is the orifice flow coefficient, taking values [0, 1]; The surface water flows back into the pipe network, and the backflow amount is expressed as: 2.The community rainwater logging numerical simulation method based on a hydrological and hydrodynamic coupling model according to claim 1, wherein, After the coupled model is verified, rainwater flooding distribution and water depth simulation and prediction are carried out. 3.The community rainwater logging numerical simulation method based on a hydrological and hydrodynamic coupling model according to claim 2, wherein, The basic data comprises hydrology data, ground elevation data, land use type, drainage pipe network, building and road distribution data.

4. The community rainwaterlogging numerical simulation method based on a hydrological and hydrodynamic coupling model according to claim 3, characterized in that, The hydrology data comprises monitoring station rainfall process, flow process and waterlogging point data.

5. The community rainwaterlogging numerical simulation method based on a hydrological and hydrodynamic coupling model according to claim 4, characterized in that, The drainage pipe network data comprises inspection well data and pipe data, the inspection well data comprises inspection well number, horizontal and vertical coordinates, well mouth ground elevation, well depth and diameter, and the pipe data comprises pipe start and end nodes, pipe bottom elevation, pipe section form and pipe size. Building the pipe network hydrology and hydrodynamic model comprises: Extracting the drainage pipe network data to establish a pipe network hydrodynamic model; According to the terrain and pipe network distribution of the research area, sub-catchments are divided, and the confluence parameters are determined to establish a pipe network hydrology model; 6. The community rainwaterlogging numerical simulation method based on a hydrological and hydrodynamic coupling model according to claim 5, characterized in that, Connecting the sub-catchments and the inspection wells to obtain the pipe network hydrology and hydrodynamic model. The method for building the surface flow model based on grid operation comprises: Using the well mouth ground elevation and the building and road distribution data to correct the generated ground elevation model; Orthogonal grid subdivision and attribute assignment are carried out on the calculation area; The boundary conditions of the calculation area are determined; where h i,j is the free water surface elevation at the i, j grid intersection, m; t is time, s; Δx and Δy are grid dimensions; Q x and Q y are the flow rates in the x and y directions, m 3 / s; h flow is the depth of flow between two adjacent grids; and n is the Manning coefficient.

7. The community rainwaterlogging numerical simulation method based on a hydrological and hydrodynamic coupling model according to claim 6, characterized in that, The surface flow is discretized on the orthogonal grid to solve the simplified two-dimensional shallow water equation: The model verification comprises:

8. The community rainwaterlogging numerical simulation method based on a hydrological and hydrodynamic coupling model according to claim 7, characterized in that, Using the measured rainfall process to simulate the outlet flow process and the surface water depth, waterlogging duration and inundation range, comparing the simulation results and the measured data, and if the error of the two meets the set requirement, it is indicated that the confluence parameters are selected reasonably, and the model precision is good. The simulation and prediction comprises: Inputting the predicted rainfall or design storm process into the model to solve the waterlogging inundation range, water depth distribution and dynamic change process in the calculation area, and realizing the visualization of the simulation results in the GIS environment.

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