Urban stormwater process simulation method combining road equivalent drainage and main pipe network

Abstract

The urban rain flood process simulation method combining road equivalent drainage and main pipe network disclosed by the application acquires basic data of a research region, constructs a two-dimensional hydrodynamic model, a one-dimensional pipe network model and a Thiessen polygon partition of the research region based on the acquired data, and establishes a coupling relationship of rainwater nodes, a surface grid and the Thiessen polygon partition; calculates rainfall and infiltration processes of the research region to determine whether rainwater nodes overflow, performs overflow calculation if overflow occurs, or drains road rainwater in the Thiessen polygon partition corresponding to the rainwater nodes into the rainwater nodes if no overflow occurs, and updates data according to the calculation results until a set running time is reached, and outputs simulation rain flood results of the research region. The application realizes calculation of a flood process in an urban fine pipe network data missing area, and improves simulation precision and simulation calculation efficiency of a pipe network drainage process in the urban fine pipe network data missing area.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of urban water conservancy numerical simulation methods, and particularly relates to a city rain flood process simulation method combining road equivalent drainage and main pipe network. BACKGROUND

[0002] Under the influence of global warming and accelerated urbanization, waterlogging disasters are becoming more common and the damage is becoming more serious, which makes the demand for urban waterlogging disaster simulation and risk assessment increasing. In recent decades, with the progress of numerical methods and parallel computing technology, the accuracy and simulation efficiency of urban rain flood model have been significantly improved, and the accuracy requirements of basic information such as terrain and pipe network data for model construction are also higher and higher. However, to achieve accurate rain flood simulation, it still needs to rely on high-precision terrain and pipe network data and other basic information.

[0003] The urban drainage pipe network is the main way for rainwater runoff discharge, but since it is mostly distributed underground, data in some areas is not easy to obtain, which brings great challenges to the accuracy and effectiveness of urban rain flood process simulation. In the absence of detailed pipe network data, how to use main pipe network, surface water and other data to study pipe network drainage generalization simulation method has become a big problem in urban rain flood dynamic process simulation. SUMMARY

[0004] The purpose of the present application is to provide a city rain flood process simulation method combining road equivalent drainage and main pipe network, to realize the calculation of flood process in urban areas where detailed pipe network data is missing, and to improve the simulation accuracy and efficiency of pipe network drainage process in urban areas where detailed pipe network data is missing.

[0005] The technical solution adopted by the present application is a city rain flood process simulation method combining road equivalent drainage and main pipe network, obtaining rainfall, terrain, image, main pipe network data of the study area, and determining rainwater node and pipe segment data in the main pipe network, based on the obtained data, constructing a two-dimensional hydrodynamic model, a one-dimensional pipe network model, and a Thiessen polygon partitioning of the study area, and establishing a coupling relationship between rainwater nodes, surface grids and Thiessen polygon partitions;

[0006] The rainfall and infiltration process of the study area is calculated to determine whether the rainwater node overflows, if overflow occurs, overflow calculation is performed, if no overflow occurs, the road rainwater in the Thiessen polygon partition corresponding to the rainwater node is drained into the rainwater node, and data is updated according to the calculation results until the set running time is reached, and the simulation rain flood results of the study area are output.

[0007] The present application is characterized in that,

[0008] Specifically comprising the following steps:

[0009] Step 1, collect the basic data of rainfall, terrain, image, and trunk pipe network in the study area, determine the location, boundary, and area of the region, determine the position of the rainwater node in the trunk pipe network, the bottom elevation and surface elevation of the rainwater node, and determine the length, pipe diameter, and topological relationship between the pipe section and the rainwater node in the trunk pipe network;

[0010] Step 2, according to the terrain of the study area, construct a GAST two-dimensional water dynamic model based on network structure, and assign corresponding land use attributes to each surface grid;

[0011] Step 3, according to the position of the rainwater node in the trunk pipe network in step 1, divide the study area by Thiessen polygon, so that the Thiessen polygon partition corresponds to the rainwater node and the surface grid in the GAST two-dimensional water dynamic model;

[0012] Step 4, based on the length, pipe diameter, and topological relationship between the pipe section and the rainwater node in the trunk pipe network, construct a SWMM one-dimensional pipe network model, and establish a one-two-dimensional coupling relationship according to the rainwater node information obtained in step 1 and the two-dimensional surface water dynamic model constructed in step 2, to construct a GAST-SWMM one-two-dimensional coupling model;

[0013] Step 5, let be the calculation time step of the GAST-SWMM one-two-dimensional coupling model, and use the GAST two-dimensional water dynamic model to calculate the rainfall and infiltration process of the study area;

[0014] Step 6, determine whether the rainwater node overflows, if it does, calculate the overflow; if not, drain the road rainwater in the Thiessen polygon partition corresponding to the rainwater node into the rainwater node, and use the nonlinear reservoir to correct the water quantity flowing into the rainwater node;

[0015] Step 7, calculate the two-dimensional surface water depth according to the overflow water quantity or the road reduction water quantity in step 6, and calculate the surface flow process;

[0016] Step 8, according to the water quantity flowing out of the pipe network or flowing into the pipe network in step 6, use the SWMM one-dimensional pipe network model to calculate the pipe network water dynamic process, and obtain the pipe network node water depth, pipe network water head, and flow velocity information;

[0017] Step 9, update the surface water depth and flow velocity calculated in step 7, and update the pipe network node water depth, pipe network water head, and flow velocity calculated in step 8;

[0018] Step 10, let repeat steps 5-9 until output the simulation rain flood results of the study area.

[0019] In step 2, the GAST two-dimensional hydrodynamic model is calculated by solving the two-dimensional shallow water equations, as shown in the following formulas:

[0020] ;

[0021] ;

[0022] ;

[0023] In the formula, t represents time, and the unit is seconds (s). For variable vectors; Water depth, in meters (m). q x and q y They are respectively x and y The unit width flow rate in both directions, in meters. 2 / s; and They are respectively x and y Flux vector in the direction; g This is the acceleration due to gravity, measured in m / s². 2 ; u and v They are respectively x and y Flow velocity in the direction, in m / s; Source term vector; For rainfall infiltration source items; z b This is the elevation of the riverbed bottom, in meters (m). For the Xie Cai coefficient, ,in n This is the Manning coefficient.

[0024] In step 2, land use attributes include roads, buildings, green spaces, and impermeable areas.

[0025] In step 5, the rainfall and infiltration processes in the study area are calculated using the following formulas:

[0026] ;

[0027] In the formula, R Net rainfall rate, in mm / h; i Rainfall intensity, in mm / h; f Soil infiltration rate, in mm / h; To ensure a stable infiltration rate, the unit is mm / h; f 0 represents the initial infiltration rate, in mm / h; t represents time, in seconds. kd is the attenuation coefficient, with the unit of s -1 .

[0028] The judgment of whether the rainwater node overflows in step 6 is specifically determined by comparing the water depth of the rainwater node and the water depth of the ground. If Z 1D >Z 2D it means that the rainwater overflows from the pipe network to the ground; if Z 1D Z 2D it means that the rainwater flows into the pipe network from the ground; wherein, Z 1D is the water depth of the rainwater node, with the unit of m; Z 2D is the water depth of the ground grid, with the unit of m.

[0029] The calculation formula of the node overflow in step 6 is as follows:

[0030] ;

[0031] In the formula, Q out is the overflow amount of the node, with the unit of m 3 / s; m1 is the orifice flow coefficient, ranging from 0 to 1, which is valued according to the specific situation; A is the area of the node, with the unit of m 2 ; g is the acceleration of gravity, with the unit of m / s 2 ; Z 2D is the water depth of the ground grid, with the unit of m; Z 1D is the water depth of the rainwater node, with the unit of m;

[0032] The calculation formula of the node inflow in step 6 is as follows:

[0033] ;

[0034] ;

[0035] In the formula, h old is the initial water depth of the ground, with the unit of m; h new1 is the water depth of the ground when the water has not entered the pipe after the rainfall occurs, with the unit of m; h new2 is the water depth of the ground after the inflow occurs, with the unit of m; is the equivalent drainage reduction rate of the road, which can be determined by rate setting or empirical value.​V jtotal is the inflow of node j, with unit of m 3 ; m is the number of grids of the equivalent drainage area corresponding to node j; A cell is the area of the surface grid, with unit of m 2 ; Q in is the inflow, with unit of m 3 / s; W is the generalized width of the Thiessen polygon partition, with unit of m; S is the slope of the Thiessen polygon partition; n is the Manning roughness coefficient; d j is the net water depth above the area of the Thiessen polygon partition, with unit of m; A j is the area of the Thiessen polygon partition.

[0036] The two-dimensional surface water depth in step 7 is calculated as shown in the following formula:

[0037] ;

[0038] In the formula, h new3 is the new grid water level considering the rainwater node overflow or inflow flux at the time step, is the simulated time step, with unit of s; Q in is the node inflow, with unit of m 3 / s; Q out is the node overflow, with unit of m 3 / s; W is the generalized width of the Thiessen polygon partition, with unit of m; A cell is the area of the surface grid, with unit of m 2 ; Z 2D is the grid water level without considering the rainwater node overflow or inflow flux.

[0039] The formula for calculating the pipe network hydrodynamic process in step 8 is shown in the following formula:

[0040] ;

[0041] In the formula, x is the distance, with unit of m; t is the time, with unit of s; A is the flow area, with unit of m 3 ; Q is the flow, with unit of m3 / s; H is the water head in the pipe channel, and the unit is m; Z is the bottom elevation in the pipe channel, and the unit is m; Y is the water depth in the pipe channel, and the unit is m; S f is the friction slope; g is the acceleration of gravity, and the unit is m / s 2 .

[0042] The beneficial effects of the present application are:

[0043] The urban rain flood process simulation method combining road equivalent drainage and main pipe network of the present application makes the numerical simulation of the area where the fine pipe network data is missing closer to the actual rain flood process by using the main pipe network, regional rainfall, terrain, image and determining the main pipe network node and pipe segment information, can realize the calculation of the flood process of the urban area where the fine pipe network data is missing, and adopts GPU parallel to accelerate the calculation, improves the simulation precision and simulation calculation efficiency of the pipe network drainage process simulation of the urban area where the fine pipe network data is missing, and provides strong pipe network model support for urban flood control and drainage decision-making.

[0044] Meanwhile, when calculating the rainwater node inflow process, the rainwater in the corresponding regional road is drained into the node to equivalent fine pipe network drainage capacity, which further improves the simulation accuracy of the area where the fine pipe network data is missing. DETAILED DESCRIPTION

[0045] Figure 1 is the flowchart of the urban rain flood process simulation method combining road equivalent drainage and main pipe network of the present application.

[0046] Figure 2 is the pipe network layout diagram in embodiment 2 of the present application.

[0047] Figure 3 is the comparison diagram of simulation results and fine pipe network simulation results in embodiment 2 of the present application.

[0048] Figure 4 is the terrain map in embodiment 3 of the present application.

[0049] Figure 5 is the pipe network layout diagram in embodiment 3 of the present application.

[0050] Figure 6 is the comparison diagram of simulation results and fine pipe network simulation results in embodiment 3 of the present application. DETAILED DESCRIPTION

[0051] The present application will be described in detail below in combination with the drawings and specific embodiments.

[0052] This invention combines road equivalent drainage with a method for simulating urban stormwater processes using main pipe networks. It acquires rainfall, topography, imagery, and main pipe network data for the study area, determines rainwater nodes and pipe segment data in the main pipe network, constructs a two-dimensional hydrodynamic model and a one-dimensional pipe network model based on the acquired data, divides the study area into Thiessen polygon partitions, and establishes the coupling relationship between rainwater nodes, surface grids, and Thiessen polygon partitions.

[0053] The system calculates rainfall and infiltration processes in the study area to determine whether rainwater nodes overflow. If overflow occurs, overflow calculations are performed. If no overflow occurs, rainwater from roads in the Thiessen polygon partition corresponding to the rainwater node is discharged into that rainwater node. Data is updated based on the calculation results until the set running time is reached, and the simulated stormwater results for the study area are output.

[0054] Example 1

[0055] This invention combines equivalent road drainage with a method for simulating urban stormwater processes using main pipe networks, such as... Figure 1 As shown, the specific steps include:

[0056] Step 1: Collect basic data on rainfall, topography, imagery, and main pipeline network in the study area; determine the location, boundaries, and area of ​​the region; determine the location, bottom elevation, and surface elevation of rainwater nodes in the main pipeline network; and determine the length, diameter, and topological relationship between the main pipeline segment and the rainwater node.

[0057] Step 2: Based on the topography of the study area, construct a two-dimensional hydrodynamic model of GAST with a network structure. Specifically, the calculation is performed by solving the two-dimensional shallow water equation, as shown in the following formulas (1), (2), and (3):

[0058] (1);

[0059] (2);

[0060] (3);

[0061] In the formula, t represents time, and the unit is seconds (s). For variable vectors; Water depth, in meters (m). q x and q y They are respectively x and y The unit width flow rate in both directions, in meters. 2 / s; and They are respectively x and yflux vector in the direction of the normal to the surface; g g is the gravitational acceleration, with units of m / s 2 ; u and v are the flow velocities in the directions of the normal to the surface, with units of m / s; x and y are the flow velocities in the directions of the normal to the surface, with units of m / s; is the source term vector; is the source term of rainfall infiltration; z b is the riverbed bottom elevation, with units of m; is the Chezy coefficient, wherein n is the Manning coefficient.

[0062] Further, the GAST two-dimensional hydrodynamic model of the application applies a dynamic wave method to simulate the flood routing process, and adopts a finite volume method of Godunov format to discretely solve the two-dimensional shallow water equation in space.

[0063] Then, the land use properties of roads, buildings, green lands and impervious areas are divided according to the images, and the corresponding land use properties are assigned to each grid;

[0064] Step 3: The study area is divided by the Thiessen polygon according to the positions of the rainwater nodes in the main pipe network in step 1, so that the Thiessen polygon division corresponds to the rainwater nodes and the surface grids in the GAST two-dimensional hydrodynamic model respectively;

[0065] Step 4: Based on the length, diameter and topological relationship between the pipe segments and the rainwater nodes of the main pipe segments, a SWMM one-dimensional pipe network model is constructed, and a one-two-dimensional coupling relationship is established according to the rainwater node information obtained in step 1 and the two-dimensional surface hydrodynamic model constructed in step 2, so as to construct a GAST-SWMM one-two-dimensional coupling model;

[0066] Step 5: Let , be the calculation time step of the GAST-SWMM one-two-dimensional coupling model, be the simulation time step of the two-dimensional hydrodynamic model, be the simulation time step of the one-dimensional pipe network model, and the rainfall and infiltration process of the study area is calculated by the GAST two-dimensional hydrodynamic model, as shown in the following formula (4):

[0067] (4);

[0068] In the formula, R is the net rainfall rate, with units of mm / h; i is the rainfall intensity, with units of mm / h; f is the soil infiltration rate, with units of mm / h; is the stable infiltration rate, with the unit of mm / h; f 0 is the initial infiltration rate, with the unit of mm / h; t is the time, with the unit of s; k d is the attenuation coefficient, with the unit of s -1 .

[0069] Step 6, judging whether the rainwater node overflows, comparing the rainwater node water depth and the ground surface water depth, the following Z 1D is the rainwater node water depth, with the unit of m; the following Z 2D is the ground surface grid water depth, with the unit of m. If Z 1 D>Z 2 D is overflow, i.e. rainwater overflows from the pipe network to the ground surface, and the overflow calculation is performed, and the calculation formula is shown in the following formula (5):

[0070] (5);

[0071] In the formula, Qout is the node overflow flow, with the unit of m3 / s; m1 is the orifice flow coefficient, ranging from [0, 1], and is valued according to the specific situation; A is the node area, with the unit of m2; g is the gravitational acceleration, with the unit of m / s2; Z 2 D is the ground surface grid water depth, with the unit of m; Z 1 D is the rainwater node water depth, with the unit of m;

[0072] If Z 1 D < Z 2 D is inflow, i.e. rainwater is drained from the ground surface into the pipe network, and the road rainwater in the rainwater node corresponding to the Thiessen polygon partition is drained into the rainwater node, in order to reflect the hysteresis process of regional rainwater converging to the rainwater node, and the water volume converging to the rainwater node is corrected by using a nonlinear reservoir, and the calculation formula is shown in the following formula (6) and formula (7):

[0073] (6);

[0074] (7);

[0075] In the formula, hold is the initial ground surface water depth, with the unit of m; hnew1 is the ground surface water depth when the water has not entered the pipe after the rainfall occurs, with the unit of m; hnew2 is the ground surface water depth after the inflow occurs, with the unit of m; The equivalent drainage reduction rate of the road is determined by calibration or empirical value. Vjtotal The inflow of node j is m3; m is the number of grids of the equivalent drainage area corresponding to node j. Acell The surface grid area is m2. Qin The inflow is m3 / s; W The generalized width of the Thiessen polygon partition is m; S The slope of the Thiessen polygon partition; n The Manning roughness coefficient; dj The net water depth above the Thiessen polygon partition area is m; Aj The area of the Thiessen polygon partition.

[0076] Step 7, according to the overflow water amount or the water amount reduced on the road in step 6, calculate the two-dimensional surface water depth, and calculate the surface flow process, the calculation formula is shown in the following formula (8):

[0077] (8);

[0078] In the formula, h new3 The new grid water level considering the time step of rainwater node overflow or inflow flux calculation, The simulated time step is s; Q in The node inflow is m 3 / s; Q out The node overflow is m 3 / s; W The generalized width of the Thiessen polygon partition is m; A cell The surface grid area is m 2 ; Z 2D The grid water level without considering the rainwater node overflow or inflow flux.

[0079] Step 8, according to the water amount of the outflow pipe network or the inflow pipe network in step 6, adopt the SWMM one-dimensional pipe network model to calculate the pipe network hydrodynamic process, obtain the main pipe network node water depth and pipe network water head and flow velocity information, the calculation formula is shown in the following formula (9):

[0080] (9);

[0081] In the formula, x The distance is m; t The time is s; A The flow area is m 3; Q is the flow rate, unit: m / s 3 / s; H is the water head in the pipe network, unit: m; Z is the bottom elevation in the pipe network, unit: m; Y is the water depth in the pipe network, unit: m; S f is the friction slope; g is the gravity acceleration, unit: m / s 2 .

[0082] Step 9, update the ground water depth and flow rate calculated in step 7, and update the main pipe network node water depth and pipe network water head and flow rate calculated in step 8;

[0083] Step 10, let repeat steps 5-9 until output the simulation rain flood results of the study area. Among them, t is the simulation time, is the simulation time step, is the total simulation time.

[0084] Example 2

[0085] An ideal city example is constructed, and the ideal city study area is 240 m long and 284 m wide, and the cross section is composed of a 24 m wide road in the middle and a 130 m wide catchment area on both sides. The vertical and horizontal slopes of the city area are 0.003 and 0.005 respectively, the road is 0.2 m lower than the catchment area on both sides, and the slope from the road ridge to the road edge on both sides is 0.02.

[0086] The size of the rainwater well is 0.4 m x 0.7 m, the rainwater well interval is 35 m, and the main drainage pipe is laid in the middle of the road. The ideal city area fine pipe network includes 21 rainwater nodes, 1 drainage outlet and 20 pipe sections; the main pipe network includes 7 rainwater nodes, 1 drainage outlet and 7 pipe sections, and the pipe network layout is as shown in Figure 2 According to the rainwater nodes of the main pipe network, 7 Thiessen polygons are constructed. The simulation time is 2 h.

[0087] The calculation results of the outlet flow process of the fine pipe network coupling model in this embodiment are compared as shown in Figure 3 The calculation peak error is 9.38%, which is less than 10%, indicating that the simulation effect of this embodiment is good.

[0088] Example 3

[0089] This embodiment takes the area west of Longwangmiao River in Lubei District of Tangshan City as an example to calculate the rainfall runoff and pipe network drainage process under the fine pipe network of the area, and generalizes a set of main pipe network for calculating the rainfall runoff and pipe network drainage process under this embodiment. The maximum rain intensity of the research area on August 18, 2022 is 91.2 mm / h, and the rainfall duration is 20 h. Taking this rainfall as the rainfall condition of the model, the fine pipe network coupling model and the simulation method of the application are used to simulate the urban rainfall runoff and drainage process.

[0090] The surface grid accuracy of the research area is 8 m x 8 m, and the number of grids is 253506, as shown in Figure 4 The fine pipe network model has a total of 1378 rainwater nodes and 1388 rainwater pipes; the main pipe network has a total of 166 rainwater nodes and 169 rainwater pipes, as shown in Figure 5 According to the main pipe network, the Thiessen polygon partition is established, and the rainwater nodes and the partition are numbered to make them one-to-one correspondence. There are a total of 166 Thiessen polygon partitions, and 12 drainage outlets are set without considering the urban river. The above-mentioned measured rainfall on August 18, 2022 is input for coupling simulation, and the urban rainstorm process for 24 h is simulated.

[0091] The comparison process of the calculation results of the coupling model of this embodiment and the fine pipe network in the outlet flow process is shown in Figure 6 The Nash efficiency coefficient is 0.85, indicating that the simulation method of the application has high feasibility.

Claims

1. A method for urban stormwater process simulation combining road equivalent drainage and trunk network, characterized in that, Acquire rainfall, terrain, image, and trunk pipe network data of a study area, determine rainwater node and pipe section data in the trunk pipe network, construct a two-dimensional water dynamic model, a one-dimensional pipe network model based on the acquired data, and divide the study area into Thiessen polygons, and establish a coupling relationship among rainwater nodes, surface grids, and Thiessen polygon partitions; Calculate rainfall and infiltration processes of the study area to determine whether rainwater nodes overflow, perform overflow calculation if overflow occurs, or drain road rainwater in the Thiessen polygon partition corresponding to the rainwater node into the rainwater node if no overflow occurs, and update data according to the calculation results until a set running time is reached, and output simulation rain flood results of the study area; Specifically, the method comprises the following steps: Step 1: Collect basic data of rainfall, terrain, image, and trunk pipe network in the study area, determine the area location, boundary, and area, determine the rainwater node position, rainwater node bottom elevation, and surface elevation in the trunk pipe network, and determine the length, pipe diameter, and topological relationship between the pipe section and the rainwater node; Step 2: Construct a GAST two-dimensional water dynamic model based on the network structure according to the terrain of the study area, and assign a corresponding land use attribute to each surface grid; Step 3: Divide the study area into Thiessen polygon partitions according to the rainwater node position in the trunk pipe network in step 1, so that the Thiessen polygon partitions correspond to the rainwater nodes and the surface grids in the GAST two-dimensional water dynamic model respectively; Step 4: Construct a SWMM one-dimensional pipe network model based on the length, pipe diameter, and topological relationship between the pipe section and the rainwater node, establish a one-two-dimensional coupling relationship according to the rainwater node information obtained in step 1 and the two-dimensional surface water dynamic model constructed in step 2, and construct a GAST-SWMM one-two-dimensional coupling model; Step 5, let The time step of the GAST-SWMM two-dimensional coupled model is calculated, and the GAST two-dimensional hydrodynamic model is used to calculate the rainfall and infiltration process of the study area. Step 6: Determine whether rainwater nodes overflow, and perform overflow calculation if overflow occurs; if no overflow occurs, drain road rainwater in the Thiessen polygon partition corresponding to the rainwater node into the rainwater node, and correct the water quantity flowing into the rainwater node by using a nonlinear reservoir; Step 7: Calculate the two-dimensional surface water depth according to the overflow water quantity or the road water reduction quantity in step 6, and calculate the surface flow process; Step 8: Calculate the pipe network water dynamic process by using the SWMM one-dimensional pipe network model according to the water quantity flowing out of or into the pipe network in step 6, and obtain the pipe network node water depth, pipe network water head, and flow velocity information; Step 9: Update the surface water depth and flow velocity calculated in step 7, and update the pipe network node water depth, pipe network water head, and flow velocity calculated in step 8; Step 10, instruct , repeat steps 5-9 until , output the simulated stormwater results for the study area; The rainfall and infiltration process of the study area in step 5 is calculated by using the following formula: ； wherein R is the net rain rate in mm / h; i is the rainfall intensity in mm / h; f is the soil infiltration rate in mm / h; is the steady infiltration rate in mm / h; f 0 is the initial infiltration rate in mm / h; t is the time in s; k d is the decay coefficient in s -1 ; The step 6 of judging whether the rainwater node overflows is specifically judging by comparing the water depth of the rainwater node and the water depth of the ground surface. If Z 1D >Z 2D it is overflow, i.e. rainwater overflows from the pipe network to the ground surface. If Z 1D Z 2D it is inflow, i.e. rainwater flows from the ground surface into the pipe network. Wherein, Z 1D is the water depth of the rainwater node, and the unit is m; Z 2D is the water depth of the ground surface grid, and the unit is m.​ The node overflow calculation formula in step 6 is as follows: ； wherein Q out is the node overflow flow, in m 3 ; m1 is the orifice flow coefficient, ranging [0, 1], which is valued according to the specific case; A is the node area, in m2 2 ; g is the gravitational acceleration, in m / s2 2 ; Z 2D is the surface grid water depth, in m; Z 1D is the rainwater node water depth, in m; The node inflow calculation formula in step 6 is as follows: ； ； wherein, h old is the initial surface water depth, unit: m; h new1 is the surface water depth before the rainfall occurs, unit: m; h new2 is the surface water depth after the inflow occurs, unit: m; is the equivalent drainage reduction rate of the road, which can be determined by rating or empirical value; V jtotal is the inflow of node j, unit: m 3 ; m is the number of grids of the equivalent drainage area corresponding to node j; A cell is the surface grid area, unit: m 2 ; Q in is the inflow, unit: m 3 / s; W is the generalization width of the Thiessen polygon partition, unit: m; S is the slope of the Thiessen polygon partition; n is the Manning roughness coefficient; d j is the net water depth on the Thiessen polygon partition area, unit: m; A j is the area of the Thiessen polygon partition; R is the net rainfall rate.

2. The urban stormwater process simulation method of jointing road equivalent drainage and main pipe network according to claim 1, characterized in that, The GAST two-dimensional water dynamic model in step 2 is calculated by solving a two-dimensional shallow water equation, as shown in the following formula: ； ； ； In the formula, t represents time, and the unit is seconds (s). For variable vectors; Water depth, in meters (m). q x and q y They are respectively x and y The unit width flow rate in both directions, in meters. 2 / s; and They are respectively x and y Flux vector in the direction; g This is the acceleration due to gravity, measured in m / s². 2 ; u and v They are respectively x and y Flow velocity in the direction, in m / s; R is the source term vector; R is the net rainfall rate. z b This is the elevation of the riverbed bottom, in meters (m). For the Xie Cai coefficient, ,in n This is the Manning coefficient.

3. The urban stormwater process simulation method of jointing road equivalent drainage and main pipe network according to claim 1, characterized in that, The land use attribute in step 2 includes roads, buildings, green land, and impervious areas.

4. The urban stormwater process simulation method of jointing road equivalent drainage and main pipe network according to claim 1, characterized in that, The two-dimensional surface water depth in step 7 is calculated as shown in the following formula: ； wherein h new3 new grid water level for considering the calculation of the inflow or outflow flux of the rainwater node at the time step, is the time step of the simulation, in s; Q in is the node inflow, in m 3 / s; Q out is the node outflow, in m 3 / s; W is the generalized width of the Thiessen polygon, in m; A cell is the surface grid area, in m 2 ; Z 2D is the grid water level without considering the rainwater node outflow or inflow flux.

5. The urban stormwater process simulation method of jointing road equivalent drainage and main pipe network according to claim 1, characterized in that, The formula for calculating the water power process of the pipe network in step 8 is as follows: ； In the formula, x is the distance, in meters; t t is time, in s; A A is the cross-sectional flow area, in m2 3 ; Q is the flow rate, in m 3 / s; H is the water head in the pipe, in m; Z is the bottom elevation in the pipe, in m; Y is the water depth in the pipe, in m; S f is the friction slope; g is the gravitational acceleration, in m / s 2 .

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