An urban waterlogging optimization and transformation method and system based on a surface-coupled hydrodynamic model of pipe networks

Abstract

The present invention discloses a method and system for optimizing and transforming urban waterlogging based on a pipe network-surface coupled hydrodynamic model. First, pipes and rainwater wells are generalized and a pipe network confluence model is constructed according to a pipe network hydrodynamic method. Then, sub-catchment areas are divided according to a river network flood evolution method. A comprehensive urban drainage model is established using molecular catchment areas. Subsequently, a surface flood evolution method and a Horton infiltration method are used to establish a surface runoff model. The present invention realizes the function of accurately and efficiently simulating the urban waterlogging process, completely simulates the urban rainwater cycle, and integrates the urban drainage pipe network with the river model. It not only realistically simulates the interaction between the urban drainage system and the surface water body, but also provides necessary support for disaster situation rehearsal and rainwater engineering planning and layout. This enables the urban waterlogging points to be cleared in advance, avoiding the impact on the production and life of the people, and is suitable for being widely promoted and used.

Description

Technical Field

[0001] The present invention relates to the technical field of urban waterlogging optimization and reconstruction, and in particular to an urban waterlogging optimization and reconstruction method and system based on a pipe network-surface coupled hydrodynamic model. Background Art

[0002] Since people first besieged cities and built markets, cities have become a major component of human civilization and have gradually emerged as the center of human social and economic activities in the course of history. However, the agglomeration and construction characteristics of cities also make them a disaster-prone environment for major disasters. When the intensity of an event exceeds the carrying capacity of a city, a chain reaction of disasters is very likely to occur, leading to large-scale losses of life, economy and property.

[0003] At present, due to the impact of climate change, extreme climate events have occurred frequently in recent years. Faced with the new natural situation under the extreme climate change environment, urban flood prevention and disaster reduction is still the top priority of public safety protection; most of the existing urban waterlogging optimization is carried out after the occurrence of urban waterlogging, which will inevitably cause huge direct safety hazards and property losses to the people when waterlogging occurs, and the city will also be brought to a standstill during the occurrence of waterlogging, which has a huge impact on the production and life of the people; therefore, it is necessary to design an urban waterlogging optimization and transformation method and system based on the pipe network surface coupled hydrodynamic model. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and to better and effectively solve the existing urban waterlogging optimization problems. Since most of the optimization and transformation are carried out after the occurrence of urban waterlogging, it will inevitably cause huge direct safety hazards and property losses to the people when waterlogging occurs, and the problem of urban stagnation will also be caused during the occurrence of waterlogging. A method and system for optimizing and transforming urban waterlogging based on a pipe network and surface coupled hydrodynamic model is provided, which realizes the function of accurately and efficiently simulating the urban waterlogging process, and completely simulates the urban rainwater cycle and enables the urban drainage pipe network to be integrated with the river model. It not only simulates the interaction between the urban drainage system and the surface water body more realistically, but also provides necessary support for disaster situation rehearsal and rainwater engineering planning and layout, which makes it possible to clear urban waterlogging points in advance and avoid affecting the production and life of the people.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A method for optimizing and transforming urban waterlogging based on a pipe network-surface coupled hydrodynamic model comprises the following steps:

[0007] Step A, generalize the pipes and rainwater wells and construct the pipe network confluence model according to the pipe network hydrodynamic method;

[0008] Step B: Sub - watersheds are divided according to the river network flood routing method, and then an urban integrated drainage model is established using the sub - watersheds.

[0009] Step C: Based on the urban integrated drainage model, a surface runoff generation and concentration model is established using the surface flood routing method and Horton infiltration method.

[0010] Step D: Based on the surface runoff generation and concentration model, a two - dimensional surface overland flow model is established according to the ground elevation data.

[0011] Step E: The pipe network confluence model and the two - dimensional surface overland flow model are coupled to obtain a one - dimensional pipe network - two - dimensional surface overland flow model, and then the one - dimensional pipe network - two - dimensional surface overland flow model is calibrated and verified to obtain a verified one - dimensional pipe network - two - dimensional surface overland flow model.

[0012] Step F: The rainfall hyetograph is calculated according to the rainfall intensity, and then the drainage capacity of the urban pipe network is judged based on the rainfall hyetograph and the verified one - dimensional pipe network - two - dimensional surface overland flow model to obtain the judgment result of the urban pipe network drainage capacity.

[0013] Step G: The inundation depth map is drawn and the inundation risk levels are divided according to the judgment result of the urban pipe network drainage capacity, and then the factors of urban waterlogging are analyzed using the inundation risk levels to obtain the analysis result of urban waterlogging.

[0014] Step H: According to the analysis result of urban waterlogging, an optimized scheme is selected for the waterlogging points for optimization and transformation.

[0015] For the aforementioned urban waterlogging optimization and transformation method based on the coupled pipe network - surface hydrodynamic model, in step A, the pipes and manholes are generalized and a pipe network confluence model is constructed according to the pipe network hydrodynamic method. The specific steps are as follows.

[0016] Step A1: Generalize the pipes and manholes. Specifically, the unreasonable nodes are removed according to the characteristics of the drainage facilities, and then the pipes with problems such as backflow and adverse slope that do not conform to the actual situation are corrected.

[0017] Step A2: Construct a pipe network confluence model according to the pipe network hydrodynamic method. The continuity equation and momentum equation of the specific pipe network hydrodynamic method are shown in formulas (1) and (2) respectively.

[0018] (1)

[0019] (2)

[0020] Where, is the cross - sectional area of the river channel, is the flow rate, is the time, is the horizontal coordinate along the water flow direction, is the momentum correction coefficient, is the acceleration due to gravity, is the water level, is the horizontal angle, is the bed slope, is the conveying capacity.

[0021] For the aforementioned urban waterlogging optimization and renovation method based on the pipe network - surface coupled hydrodynamic model, in step B, divide the sub - catchment area according to the river network flood routing method, and then establish an urban comprehensive drainage model using the sub - catchment area. The specific steps are as follows,

[0022] Step B1, divide the sub - catchment area according to the river network flood routing method. The continuity equation and momentum equation in the basic control equations of the specific river network flood routing method are shown in formulas (3) and (4) respectively,

[0023] (3)

[0024] (4)

[0025] Among them, is the velocity of the lateral inflow in the river channel direction, S f is the friction slope, is the lateral inflow of the river channel;

[0026] Step B2, establish an urban comprehensive drainage model using the sub - catchment area. Specifically, generate Thiessen polygons using the generalized distribution of rainwater wells, and each polygon corresponds to the catchment area of a rainwater well.

[0027] For the aforementioned urban waterlogging optimization and renovation method based on the pipe network - surface coupled hydrodynamic model, in step C, establish a surface runoff - generation and - concentration model based on the urban comprehensive drainage model and using the surface flood routing method and Horton infiltration method. The specific steps are as follows,

[0028] Step C1, construct the basic control equation of the surface flood routing method. The specific steps are as follows,

[0029] Step C11, construct the water flow continuity equation, as shown in formula (5),

[0030] (5)

[0031] Among them, is the water depth, is the effective rainfall intensity, and are respectively and the vertical average unit - width flow in the

[0032] Step C12, construct the water flow momentum equation as shown in formula (6),

[0033] ;

[0034] (6)

[0035] wherein, and are respectively the components of the vertical average flow velocity in the and directions, and is the Manning roughness coefficient;

[0036] Step C2, construct the basic equation for calculating the infiltration process by the Horton infiltration method as shown in formula (7),

[0037] (7)

[0038] wherein, is the steady infiltration rate, is the infiltration rate, is the initial infiltration rate, and k is the decay coefficient related to the soil.

[0039] For the aforementioned urban waterlogging optimization and renovation method based on the pipe network - surface coupled hydrodynamic model, in step D, establish a two - dimensional surface overland flow model based on the surface runoff generation and concentration model and according to the ground elevation data. Specifically, the water depth, flow velocity, and waterlogging time in each triangular grid are used as the basis for judging the waterlogging risk. The two - dimensional surface overland flow model is used to simulate the movement of rainwater on the ground after overflowing from the inspection well and obtain the velocity, flow direction, depth, and time indexes of the ground flood.

[0040] For the aforementioned urban waterlogging optimization and renovation method based on the pipe network - surface coupled hydrodynamic model, in step E, couple the pipe network confluence model and the two - dimensional surface overland flow model to obtain a one - dimensional pipe network - two - dimensional surface overland flow model, and then calibrate and verify the one - dimensional pipe network - two - dimensional surface overland flow model to obtain the verified one - dimensional pipe network - two - dimensional surface overland flow model. Specifically, the coupling of the one - dimensional pipe network - two - dimensional surface overland flow model is carried out in the way of orifice connection. The bottom orifice of the one - dimensional pipe network - two - dimensional surface overland flow model starts from a one - dimensional inspection well and ends at a two - dimensional inspection well, and the inlet offset is the elevation difference between the lower edge elevations of the two - dimensional inspection well and the one - dimensional inspection well. The specific steps are as follows,

[0041] Step E1, couple the pipe network confluence model and the two - dimensional surface overland flow model to obtain a one - dimensional pipe network - two - dimensional surface overland flow model. The specific steps are as follows,

[0042] Step E11, let the surface runoff flow into the drainage pipe network through the stormwater inlets to conduct the water volume interaction between the surface runoff and pipe network models, then set the pointing relationship between the sub-catchments and inspection wells and couple the surface runoff and pipe network runoff models. Each sub-catchment can only be connected to one stormwater inlet, and one stormwater inlet has multiple sub-catchments flowing into it;

[0043] Step E12, when the water volume in the pipe network exceeds the drainage capacity of the pipe network, the rainwater will overflow to the ground through the stormwater inlets of the pipe network, then flow along the ground and form ponding at low-lying areas or be re-drained into the drainage pipe network. As the connection between the drainage pipe network and the ground, the stormwater inlets enable the coupling of pipe network runoff and two-dimensional overland flow on the surface;

[0044] Step E2, use the one-dimensional pipe network - two-dimensional overland flow model for calibration and verification. Specifically, model calibration is to conduct parameter calibration, and the parameters include literature parameters, hydraulic parameters, deterministic parameters, and empirical parameters. Model verification is specifically to verify using the measurement data of flow rate, liquid level, ponding range, and ponding depth.

[0045] For the aforementioned urban waterlogging optimization and transformation method based on the pipe network - surface coupling hydrodynamic model, step F, calculate the rainfall hyetograph according to the storm intensity, and then judge the drainage capacity of the urban pipe network based on the rainfall hyetograph and the verified one-dimensional pipe network - two-dimensional overland flow model to obtain the judgment result of the drainage capacity of the urban pipe network. The specific steps are as follows,

[0046] Step F1, calculate the rainfall hyetograph according to the storm intensity, where the storm intensity formula is as shown in formula (8),

[0047] (8)

[0048] where, is the storm intensity, and P is the recurrence interval;

[0049] Step F2, judge the drainage capacity of the urban pipe network based on the rainfall hyetograph and the verified one-dimensional pipe network - two-dimensional overland flow model to obtain the judgment result of the drainage capacity of the urban pipe network. Specifically, judge whether there is overflow in the inspection well, that is, whether the hydraulic grade line of the pipeline exceeds the ground line, and the pipeline overload judgment process is as shown in formula (9),

[0050] (9)

[0051] where, is the pipeline overload judgment result, is the head of the pipe network node, is the ground elevation; if the pipeline overload judgment result δ ≤ 0, it means that the drainage capacity of the pipeline meets the requirements of the corresponding recurrence interval; if the pipeline overload judgment result δ > 0, it means that the drainage capacity of the pipeline does not meet the requirements of the corresponding recurrence interval.

[0052] The above-mentioned urban waterlogging optimization and transformation method based on the coupled hydrodynamic model of pipe network and surface. Step G: Draw the inundation depth map and divide the inundation risk levels according to the discrimination result of the drainage capacity of the urban pipe network, and then analyze the urban waterlogging factors using the inundation risk levels to obtain the urban waterlogging analysis result. The specific steps are as follows:

[0053] Step G1: Draw the inundation depth map and divide the inundation risk levels according to the discrimination result of the drainage capacity of the urban pipe network. Specifically, draw the inundation depth maps for each working condition according to the regional waterlogging inundation processes under the rainfall scenarios of once-in-1-year, once-in-2-year, once-in-5-year, once-in-10-year, once-in-20-year, and once-in-50-year, and then count, compare, and analyze the changes in the maximum inundation depth to divide the inundation risk levels. The inundation risk levels include no risk, low risk, medium risk, and high risk.

[0054] Step G2: Analyze the urban waterlogging factors using the inundation risk levels to obtain the urban waterlogging analysis result. The specific analysis factors include drainage system factors, terrain factors, underlying surface factors, and rainfall factors. The urban waterlogging analysis result includes the total inundated area, the maximum water depth at the waterlogging points, the distribution of inundation depth, and the distribution of pipe network overload degree. Among them, the pipe network overload degree As shown in formula (10):

[0055] (10)

[0056] Wherein, is the highest water level of the node, z is the bottom elevation of the node, is the maximum height of the pipe section where the node is located.

[0057] The above-mentioned urban waterlogging optimization and transformation method based on the coupled hydrodynamic model of pipe network and surface. Step H: Select an optimization plan for the waterlogging points according to the urban waterlogging analysis result for optimization and transformation. The optimization plan includes a permeable pavement plan, a green roof plan, and a pipe optimization plan. The specific content of the permeable pavement plan is, from top to bottom, a permeable surface, a permeable leveling layer, a permeable base layer, a permeable sub-base layer, and a soil base. The green roof plan is specifically to make a roof using various environmental materials and plant vegetation on the rooftops of various factories, bridges, and urban buildings to form a plant roof. The pipe optimization plan is specifically to carry out pipe reconstruction and abolition on the pipe sections that can fully meet the discharge standards.

[0058] The optimization and transformation process is to use a single plan or a combination of plans.

[0059] An urban waterlogging optimization and transformation system based on a pipe network-surface coupled hydrodynamic model, comprising a pipe network confluence module, an urban comprehensive drainage module, a surface runoff generation and confluence module, a two-dimensional surface overland flow module, a pipe-ground coupling module, a drainage discrimination module, an urban waterlogging analysis module, and an urban waterlogging optimization and transformation module. The pipe network confluence module is used to generalize pipes and rainwater wells and construct a pipe network confluence model according to the pipe network hydrodynamic method; the urban comprehensive drainage module is used to divide sub-catchments according to the river network flood routing method and then establish an urban comprehensive drainage model using the sub-catchments; the surface runoff generation and confluence module is used to establish a surface runoff generation and confluence model based on the urban comprehensive drainage model and using the surface flood routing method and the Horton infiltration method; the two-dimensional surface overland flow module is used to establish a two-dimensional surface overland flow model based on the surface runoff generation and confluence model and according to the ground elevation data; the pipe-ground coupling module is used to couple the pipe network confluence model and the two-dimensional surface overland flow model to obtain a one-dimensional pipe network-two-dimensional surface overland flow model, and then calibrate and verify the one-dimensional pipe network-two-dimensional surface overland flow model to obtain a verified one-dimensional pipe network-two-dimensional surface overland flow model; the drainage discrimination module is used to calculate the rainfall process line according to the rainfall intensity, and then discriminate the drainage capacity of the urban pipe network according to the rainfall process line and the verified one-dimensional pipe network-two-dimensional surface overland flow model to obtain the drainage capacity discrimination result of the urban pipe network; the urban waterlogging analysis module is used to draw the inundation depth map and divide the inundation risk levels according to the drainage capacity discrimination result of the urban pipe network, and then analyze the urban waterlogging factors using the inundation risk levels to obtain the urban waterlogging analysis result; the urban waterlogging optimization and transformation module is used to select an optimization plan for the waterlogging points according to the urban waterlogging analysis result for optimization and transformation.

[0060] The beneficial effects of the present invention are as follows: the present invention provides an urban waterlogging optimization and transformation method and system based on a pipe network-surface coupled hydrodynamic model, firstly generalizes pipes and rainwater wells and constructs a pipe network confluence model according to a pipe network hydrodynamic method, then divides sub-catchment areas according to a river network flood evolution method, and then uses molecular catchment areas to establish an urban comprehensive drainage model, and then establishes a surface runoff model based on the urban comprehensive drainage model and using a surface flood evolution method and a Horton infiltration method, and then establishes a two-dimensional overland flow model based on the surface runoff model and according to ground elevation data, and then couples the pipe network confluence model with the two-dimensional overland flow model to obtain a one-dimensional pipe network-two-dimensional overland flow model, and then uses the one-dimensional pipe network-two-dimensional overland flow model to perform calibration and verification and obtain a verified one-dimensional pipe network-two-dimensional overland flow model, and then calculates a rainfall process line according to the intensity of a rainstorm, and then judges the drainage capacity of the urban pipe network according to the rainfall process line and the verified one-dimensional pipe network-two-dimensional overland flow model and obtains a judgment result of the drainage capacity of the urban pipe network. The results are obtained, and then a flood depth map is drawn and the flood risk level is divided according to the judgment result of the drainage capacity of the urban pipe network. The flood risk level is then used to analyze the urban waterlogging factors and obtain the urban waterlogging analysis results. Finally, the optimization plan is selected for the waterlogging points according to the urban waterlogging analysis results for optimization and transformation. The invention effectively realizes the function of simulating the urban waterlogging process accurately and efficiently, and completely simulates the urban rainwater cycle and enables the urban drainage pipe network to be integrated with the river model. It not only simulates the interaction between the urban drainage system and the surface water body more realistically, but also provides necessary support for disaster situation rehearsal and rainwater engineering planning and layout. It also realizes the function of using the urban waterlogging model to optimize the layout of rainwater engineering facilities in the study area and comprehensively considers the design rainfall and measured rainfall conditions to improve the rainwater engineering facilities. This enables the present invention to provide data support for optimizing the transformation of urban pipe networks for waterlogging in the non-rainy season, which can not only clear the urban waterlogging points in advance, but also avoid affecting the production and life of the people. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 It is an overall flow chart of an urban waterlogging optimization and transformation method based on a pipe network-surface coupled hydrodynamic model of the present invention;

[0062] Figure 2 It is a schematic diagram of the pipe network confluence model of the present invention;

[0063] Figure 3 is a schematic diagram of the molecular water catchment area of the present invention;

[0064] Figure 4 It is a schematic diagram of a rainfall process line of the present invention;

[0065] Figure 5 It is a schematic diagram of the result of judging the drainage capacity of the urban pipe network of the present invention;

[0066] Figure 6 It is a schematic diagram of the urban waterlogging analysis results of the present invention;

[0067] Figure 7 It is a schematic diagram of the permeable pavement solution of the present invention;

[0068] Figure 8 It is a schematic diagram of the green roof solution of the present invention. Detailed implementation manners

[0069] The present invention will be further described below in conjunction with the accompanying drawings of the specification.

[0070] As Figure 1 shown, a method for optimizing and transforming urban waterlogging based on a coupled hydrodynamic model of pipe network and surface in the present invention includes the following steps.

[0071] As Figure 2 shown, step A, generalizing pipes and rainwater wells and constructing a pipe network confluence model according to the pipe network hydrodynamic method. The specific steps are as follows.

[0072] Step A1, generalizing pipes and rainwater wells, specifically removing unreasonable nodes according to the characteristics of drainage facilities, and then correcting the pipes that do not conform to the actual situation such as reverse flow and reverse slope.

[0073] Step A2, constructing a pipe network confluence model according to the pipe network hydrodynamic method. The continuity equation and momentum equation of the specific pipe network hydrodynamic method are shown in formulas (1) and (2) respectively.

[0074] (1)

[0075] (2)

[0076] Among them, is the cross-sectional area of the river channel, is the flow rate, is the time, is the horizontal coordinate along the water flow direction, is the momentum correction coefficient, is the acceleration due to gravity, is the water level, is the horizontal angle, is the bed slope, is the transport volume.

[0077] As Figure 3 shown, step B, dividing the sub-catchments according to the river network flood routing method, and then establishing an urban comprehensive drainage model using the sub-catchments. The specific steps are as follows.

[0078] Step B1: Sub - watersheds are delineated according to the river network flood routing method. Specifically, the continuity equation and momentum equation in the basic control equations of the river network flood routing method are shown in Formulas (3) and (4) respectively.

[0079] (3)

[0080] (4)

[0081] Where, is the velocity of the lateral inflow in the river channel direction, and S f is the friction slope, is the lateral inflow of the river channel;

[0082] Step B2: A urban comprehensive drainage model is established using the sub - watersheds. Specifically, Thiessen polygons are generated using the generalized distribution of rainwater wells, and each polygon corresponds to the catchment area of a rainwater well.

[0083] Step C: Based on the urban comprehensive drainage model, a surface runoff generation and concentration model is established using the surface flood routing method and Horton infiltration method. The specific steps are as follows.

[0084] Step C1: The basic control equations of the surface flood routing method are constructed. The specific steps are as follows.

[0085] Step C11: The water continuity equation is constructed, as shown in Formula (5).

[0086] (5)

[0087] Where, is the water depth, is the effective rainfall intensity, and are respectively and the vertical average unit - width flow in the

[0088] Step C12: The water momentum equation is constructed, as shown in Formula (6).

[0089] ;

[0090] (6)

[0091] Where, and are respectively the components of the vertical average velocity in the and directions, is the Manning roughness coefficient;

[0092] Step C2, construct the basic equation for calculating the infiltration process by the Horton infiltration method, as shown in formula (7):

[0093] (7)

[0094] where is the stable infiltration rate, is the infiltration rate, is the initial infiltration rate, and k is the attenuation coefficient related to the soil.

[0095] Step D, based on the surface runoff generation and concentration model and according to the ground elevation data, establish a two-dimensional overland flow model. Specifically, the water depth, flow velocity, and water accumulation time in each triangular grid are used as the basis for judging the waterlogging risk. The two-dimensional overland flow model is used to simulate the movement of rainwater on the ground after overflowing from the inspection well and obtain the velocity, flow direction, depth, and time indexes of the ground flood.

[0096] Step E, couple the pipe network runoff model and the two-dimensional overland flow model to obtain a one-dimensional pipe network - two-dimensional overland flow model, and then use the one-dimensional pipe network - two-dimensional overland flow model for calibration and verification to obtain the verified one-dimensional pipe network - two-dimensional overland flow model. Specifically, the orifice connection method is used for the coupling of the one-dimensional pipe network - two-dimensional overland flow model. The bottom orifice of the one-dimensional pipe network - two-dimensional overland flow model starts from a one-dimensional inspection well and ends at a two-dimensional inspection well, and the inlet offset is the elevation difference between the lower edge elevation of the two-dimensional inspection well and the one-dimensional inspection well. The specific steps are as follows:

[0097] Step E1, couple the pipe network runoff model and the two-dimensional overland flow model to obtain a one-dimensional pipe network - two-dimensional overland flow model. The specific steps are as follows:

[0098] Step E11, let the surface-generated runoff enter the drainage pipe network from the rainwater inlet for the water volume interaction between the surface runoff generation and concentration model and the pipe network model, and then set the pointing relationship between the sub-catchment area and the inspection well to couple the surface runoff generation and concentration model with the pipe network runoff model. Each sub-catchment area can only be connected to one rainwater inlet, and one rainwater inlet has multiple sub-catchment areas flowing into it;

[0099] Step E12, when the water volume in the pipe network exceeds the drainage capacity of the pipe network, the rainwater will overflow to the ground through the rainwater inlet of the pipe network, then flow along the ground and form water accumulation in the low-lying areas or be re-drained into the drainage pipe network. The rainwater inlet, as the connection between the drainage pipe network and the ground, enables the coupling of the pipe network runoff and the two-dimensional overland flow;

[0100] Step E2: Calibrate and verify using a one-dimensional pipe network - two-dimensional overland flow model. Specifically, for model calibration, parameter calibration is carried out, and the parameters include hydrological parameters, hydraulic parameters, deterministic parameters, and empirical parameters. For model verification, it is specifically verified using measurement data of flow rate, liquid level, ponding range, and ponding depth.

[0101] As Figure 4 shown, in step F, calculate the rainfall hyetograph based on the rainfall intensity, and then determine the drainage capacity of the urban pipe network and obtain the discrimination result of the urban pipe network drainage capacity according to the rainfall hyetograph and the verified one-dimensional pipe network - two-dimensional overland flow model. The specific steps are as follows.

[0102] Step F1: Calculate the rainfall hyetograph based on the rainfall intensity. The rainfall intensity formula is as shown in formula (8).

[0103] (8)

[0104] where is the rainfall intensity and P is the recurrence interval.

[0105] As Figure 5 shown, in step F2, determine the drainage capacity of the urban pipe network and obtain the discrimination result of the urban pipe network drainage capacity according to the rainfall hyetograph and the verified one-dimensional pipe network - two-dimensional overland flow model. Specifically, it is to determine whether there is overflow in the inspection well, that is, whether the hydraulic grade line of the pipeline exceeds the ground line. The pipeline overload discrimination process is as shown in formula (9).

[0106] (9)

[0107] where is the pipeline overload discrimination result, is the head of the pipe network node, is the ground elevation. If the pipeline overload discrimination result δ ≤ 0, it means that the pipeline drainage capacity meets the requirements of the corresponding recurrence interval; if the pipeline overload discrimination result δ > 0, it means that the pipeline drainage capacity does not meet the requirements of the corresponding recurrence interval.

[0108] As Figure 6 shown, in step G, draw the inundation depth map and divide the inundation risk level according to the discrimination result of the urban pipe network drainage capacity, and then analyze the urban waterlogging factors using the inundation risk level and obtain the urban waterlogging analysis result. The specific steps are as follows.

[0109] Step G1: Draw the inundation depth map and divide the inundation risk levels based on the discrimination results of the drainage capacity of the urban pipe network. Specifically, draw the inundation depth maps for each working condition according to the regional waterlogging inundation processes under the rainfall scenarios with return periods of 1, 2, 5, 10, 20, and 50 years. Then, count, compare, and analyze the changes in the maximum inundation depth and divide the inundation risk levels, where the inundation risk levels include no risk, low risk, medium risk, and high risk.

[0110] Step G2: Analyze the urban waterlogging factors using the inundation risk levels and obtain the urban waterlogging analysis results. The specific analysis factors include drainage system factors, terrain factors, underlying surface factors, and rainfall factors. The urban waterlogging analysis results include the total inundated area, the maximum water depth at the waterlogging points, the distribution of inundation depth, and the distribution of pipe network overload degree. Among them, the pipe network overload degree As shown in formula (10),

[0111] (10)

[0112] where, is the highest water level of the node, z is the bottom elevation of the node, is the maximum height of the pipe section where the node is located.

[0113] As Figures 7 - 8 shown, in step H, select an optimization plan for the waterlogging points according to the urban waterlogging analysis results for optimization and transformation. The optimization plan includes a permeable pavement plan, a green roof plan, and a pipe optimization plan. The specific content of the permeable pavement plan is, from top to bottom, a permeable surface, a permeable leveling layer, a permeable base layer, a permeable sub-base layer, and a soil base. The green roof plan is specifically to make a roof using various environmental materials and plant vegetation on the rooftops of various factories, bridges, and urban buildings to form a plant roof. The pipe optimization plan is specifically to carry out pipe reconstruction and abolition on the pipe sections that can fully utilize the original discharge standards.

[0114] The optimization and transformation process is to use a single plan or a combination of plans.

[0115] An urban waterlogging optimization and transformation system based on a pipe network - surface coupled hydrodynamic model, comprising a pipe network confluence module, an urban comprehensive drainage module, a surface runoff generation and confluence module, a two - dimensional surface overland flow module, a pipe - ground coupling module, a drainage discrimination module, an urban waterlogging analysis module, and an urban waterlogging optimization and transformation module. The pipe network confluence module is used to generalize pipes and rainwater wells and construct a pipe network confluence model according to the pipe network hydrodynamic method; the urban comprehensive drainage module is used to divide sub - catchments according to the river network flood routing method and then establish an urban comprehensive drainage model using the sub - catchments; the surface runoff generation and confluence module is used to establish a surface runoff generation and confluence model based on the urban comprehensive drainage model and using the surface flood routing method and the Horton infiltration method; the two - dimensional surface overland flow module is used to establish a two - dimensional surface overland flow model based on the surface runoff generation and confluence model and according to the ground elevation data; the pipe - ground coupling module is used to couple the pipe network confluence model and the two - dimensional surface overland flow model to obtain a one - dimensional pipe network - two - dimensional surface overland flow model, and then calibrate and verify the one - dimensional pipe network - two - dimensional surface overland flow model to obtain a verified one - dimensional pipe network - two - dimensional surface overland flow model; the drainage discrimination module is used to calculate the rainfall hyetograph according to the rainfall intensity, and then discriminate the drainage capacity of the urban pipe network according to the rainfall hyetograph and the verified one - dimensional pipe network - two - dimensional surface overland flow model to obtain the discrimination result of the urban pipe network drainage capacity; the urban waterlogging analysis module is used to draw the inundation depth map and divide the inundation risk levels according to the discrimination result of the urban pipe network drainage capacity, and then analyze the urban waterlogging factors using the inundation risk levels to obtain the urban waterlogging analysis result; the urban waterlogging optimization and transformation module is used to select an optimization plan for the waterlogging points and carry out optimization and transformation according to the urban waterlogging analysis result.

[0116] In summary, for the urban waterlogging optimization and transformation method and system based on the coupled hydrodynamic model of pipe network and surface, the method and system first generalize pipes and rainwater wells and construct a pipe network confluence model according to the pipe network hydrodynamic method. Then, sub-catchments are divided according to the river network flood routing method. Next, an urban comprehensive drainage model is established using the sub-catchments. Subsequently, a surface runoff generation and confluence model is established based on the urban comprehensive drainage model and using the surface flood routing method and Horton infiltration method. Then, a two-dimensional surface overland flow model is established based on the surface runoff generation and confluence model and according to the ground elevation data. Then, the pipe network confluence model and the two-dimensional surface overland flow model are coupled to obtain a one-dimensional pipe network - two-dimensional surface overland flow model. Then, the one-dimensional pipe network - two-dimensional surface overland flow model is calibrated and verified to obtain a verified one-dimensional pipe network - two-dimensional surface overland flow model. Immediately afterwards, the rainfall hyetograph is calculated according to the rainfall intensity. Then, the drainage capacity of the urban pipe network is judged based on the rainfall hyetograph and the verified one-dimensional pipe network - two-dimensional surface overland flow model to obtain the judgment result of the urban pipe network drainage capacity. Subsequently, the inundation depth map is drawn and the inundation risk levels are divided according to the judgment result of the urban pipe network drainage capacity. Then, the urban waterlogging factors are analyzed using the inundation risk levels to obtain the urban waterlogging analysis result. Finally, an optimization scheme is selected for the waterlogging points according to the urban waterlogging analysis result for optimization and transformation; effectively realizing the function of the invention to accurately and efficiently simulate the urban waterlogging process, and completely simulating the urban rainwater cycle and enabling the urban drainage pipe network to be integrated with the river model, not only more realistically simulating the interaction between the urban drainage system and the surface receiving water body, but also providing necessary support for disaster situation rehearsal and rainwater project planning and layout, and also realizing the function of using the urban waterlogging model to optimize the layout scheme of rainwater engineering facilities in the research area and comprehensively considering the design rainfall and measured rainfall conditions to improve the rainwater engineering facilities, which enables the invention to provide data support for the urban pipe network waterlogging optimization and transformation during the non-rainy season, not only being able to remove urban waterlogging points in advance, but also avoiding affecting the production and life of the people.

[0117] The foregoing has shown and described the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and the descriptions in the specification are only used to illustrate the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. An urban waterlogging optimization and transformation method based on a surface-coupled hydrodynamic model of pipe networks, characterized in that: Including the following steps: Step A: Generalize pipelines and stormwater wells and construct a pipe network confluence model according to the pipe network hydrodynamic method; Step B: Divide sub-catchments according to the river network flood routing method, and then establish an urban comprehensive drainage model using the sub-catchments; Step C: Based on the urban comprehensive drainage model, establish a surface runoff generation and confluence model using the surface flood routing method and Horton infiltration method; Step D: Based on the surface runoff generation and confluence model, establish a two-dimensional surface overland flow model according to the ground elevation data; Step E: Couple the pipe network confluence model and the two-dimensional surface overland flow model to obtain a one-dimensional pipe network - two-dimensional surface overland flow model, and then calibrate and verify the one-dimensional pipe network - two-dimensional surface overland flow model to obtain a verified one-dimensional pipe network - two-dimensional surface overland flow model; Step F: Calculate the rainfall hyetograph according to the rainfall intensity, and then judge the drainage capacity of the urban pipe network based on the rainfall hyetograph and the verified one-dimensional pipe network - two-dimensional surface overland flow model to obtain the judgment result of the urban pipe network drainage capacity; Step G: Draw the inundation depth map and divide the inundation risk levels according to the judgment result of the urban pipe network drainage capacity, and then analyze the urban waterlogging factors using the inundation risk levels to obtain the urban waterlogging analysis result; Step H: Optimize and transform the waterlogging points according to the urban waterlogging analysis result using the optimized scheme.

2. The urban waterlogging optimization and transformation method based on the surface-coupled hydrodynamic model of pipe networks according to claim 1, wherein: Step A: Generalize pipelines and stormwater wells and construct a pipe network confluence model according to the pipe network hydrodynamic method. The specific steps are as follows: Step A1: Generalize pipelines and stormwater wells. Specifically, eliminate unreasonable nodes according to the characteristics of drainage facilities, and then correct the pipelines that do not conform to the actual situation such as reverse flow and reverse slope; Step A2: Construct a pipe network confluence model according to the pipe network hydrodynamic method. The continuous equation and momentum equation of the specific pipe network hydrodynamic method are shown in formulas (1) and (2) respectively; （1） （2） Among them, is the cross-sectional area of the river channel, is the flow rate, is the time, is the horizontal coordinate along the water flow direction, is the momentum correction coefficient, is the acceleration due to gravity, is the water level, is the horizontal angle, is the bed slope, is the conveying capacity.

3. The urban waterlogging optimization and transformation method based on the surface-coupled hydrodynamic model of pipe networks according to claim 2, characterized in that: Step B: Divide sub-catchments according to the river network flood routing method, and then establish an urban comprehensive drainage model using the sub-catchments. The specific steps are as follows: Step B1: Divide sub-catchments according to the river network flood routing method. The continuous equation and momentum equation in the basic control equation of the specific river network flood routing method are shown in formulas (3) and (4) respectively; （3） （4） Among them, is the velocity of the lateral incoming flow in the river channel direction, and S f is the friction slope drop, is the lateral incoming flow rate of the river channel; Step B2: Establish an urban comprehensive drainage model using the sub-catchments. Specifically, generate Thiessen polygons using the generalized distribution of stormwater wells, and each polygon corresponds to the catchment area of a stormwater well.

4. The urban waterlogging optimization and transformation method based on the surface-coupled hydrodynamic model of pipe networks according to claim 3, wherein: Step C: Based on the urban comprehensive drainage model, establish a surface runoff generation and confluence model using the surface flood routing method and Horton infiltration method. The specific steps are as follows: Step C1: Construct the basic control equation of the surface flood routing method. The specific steps are as follows: Step C11: Construct the water flow continuity equation, as shown in formula (5); （5） Among them, is the water depth, is the effective rainfall intensity, and are respectively and the vertically-averaged unit-width discharges in the Step C12: Construct the water flow momentum equation, as shown in formula (6); ； （6） wherein, and are respectively the components of the vertically-averaged flow velocity in the and directions, and is the Manning roughness coefficient; Step C2: Construct the basic equation for calculating the infiltration process using the Horton infiltration method, as shown in formula (7); （7） wherein, is the stable infiltration rate, is the infiltration rate, is the initial infiltration rate, and k is the attenuation coefficient related to the soil.

5. A method for optimizing the transformation of urban waterlogging based on a surface-coupled hydrodynamic model of pipe networks, characterized in that: Step D: Based on the surface runoff and confluence model and according to the ground elevation data, establish a two-dimensional surface overland flow model. Specifically, use the water depth, flow velocity, and water accumulation time in each triangular grid as the basis for judging the waterlogging risk. The two-dimensional surface overland flow model is used to simulate the movement of rainwater on the ground after overflowing from the inspection well and obtain the flow velocity, flow direction, depth, and time indicators of the ground flood.

6. The urban waterlogging optimization and transformation method based on the surface-coupled hydrodynamic model of pipe networks according to claim 5, characterized in that: Step E: Couple the pipe network confluence model and the two-dimensional surface overland flow model to obtain a one-dimensional pipe network - two-dimensional surface overland flow model, and then calibrate and verify the one-dimensional pipe network - two-dimensional surface overland flow model to obtain a verified one-dimensional pipe network - two-dimensional surface overland flow model. Specifically, the coupling of the one-dimensional pipe network - two-dimensional surface overland flow model is carried out by means of orifice connection. The bottom orifice of the one-dimensional pipe network - two-dimensional surface overland flow model starts from a one-dimensional inspection well and ends at a two-dimensional inspection well, and the inlet offset is the elevation difference between the lower edge elevations of the two-dimensional inspection well and the one-dimensional inspection well. The specific steps are as follows. Step E1: Couple the pipe network confluence model and the two-dimensional surface overland flow model to obtain a one-dimensional pipe network - two-dimensional surface overland flow model. The specific steps are as follows. Step E11: Let the surface runoff enter the drainage pipe network from the rainwater inlet for the water volume interaction between the surface runoff and confluence model and the pipe network model, and then set the pointing relationship between the sub-catchment area and the inspection well to couple the surface runoff and confluence model with the pipe network confluence model. Each sub-catchment area can only be connected to one rainwater inlet, and one rainwater inlet has multiple sub-catchment areas flowing into it. Step E12: When the water volume in the pipe network exceeds the drainage capacity of the pipe network, the rainwater will overflow to the ground through the rainwater inlet of the pipe network, then flow on the ground and form water accumulation in low-lying areas or be re-discharged into the drainage pipe network. The rainwater inlet, as the connection between the drainage pipe network and the ground, enables the coupling of the pipe network confluence and the two-dimensional surface overland flow. Step E2: Calibrate and verify the one-dimensional pipe network - two-dimensional surface overland flow model. Among them, model calibration is specifically to carry out parameter calibration. The parameters include literary parameters, hydraulic parameters, deterministic parameters, and empirical parameters. Model verification is specifically to verify using the measured data of flow rate, liquid level, water accumulation range, and water accumulation depth.

7. An urban waterlogging optimization and transformation method based on a surface-coupled hydrodynamic model of pipe networks according to claim 6, characterized in that: Step F: Calculate the rainfall hyetograph according to the rainfall intensity, and then judge the drainage capacity of the urban pipe network based on the rainfall hyetograph and the verified one-dimensional pipe network - two-dimensional surface overland flow model to obtain the judgment result of the urban pipe network drainage capacity. The specific steps are as follows. Step F1: Calculate the rainfall hyetograph according to the rainfall intensity. The rainfall intensity formula is shown in Formula (8). （8） Among them, is the rainstorm intensity and P is the recurrence period; Step F2: Judge the drainage capacity of the urban pipe network based on the rainfall hyetograph and the verified one-dimensional pipe network - two-dimensional surface overland flow model to obtain the judgment result of the urban pipe network drainage capacity. Specifically, judge whether there is overflow in the inspection well, that is, whether the hydraulic grade line of the pipeline exceeds the ground line. The pipeline overload judgment process is shown in Formula (9). （9） Among them, is the discriminant result of pipeline overload, is the water head of the pipe network node, is the ground elevation; if the discriminant result of pipeline overload δ ≤ 0, it means that the drainage capacity of the pipeline meets the requirements of the corresponding return period; if the discriminant result of pipeline overload δ > 0, it means that the drainage capacity of the pipeline does not meet the requirements of the corresponding return period.

8. An urban waterlogging optimization and transformation method based on a surface-coupled hydrodynamic model of pipe networks, as claimed in claim 7, wherein: Step G: Draw the inundation depth map according to the judgment result of the urban pipe network drainage capacity and divide the inundation risk level, and then analyze the urban waterlogging factors using the inundation risk level to obtain the urban waterlogging analysis result. The specific steps are as follows. Step G1: Draw the inundation depth map and divide the inundation risk levels according to the discrimination results of the urban pipe network drainage capacity. Specifically, draw the inundation depth maps for each working condition based on the regional waterlogging inundation processes under rainfall scenarios with return periods of 1, 2, 5, 10, 20, and 50 years. Then, statistically analyze, compare, and analyze the changes in the maximum inundation depth and divide the inundation risk levels, where the inundation risk levels include no risk, low risk, medium risk, and high risk. Step G2, analyze the urban waterlogging factors using the flood risk level and obtain the urban waterlogging analysis results. The specific analysis factors include drainage system factors, terrain factors, underlying surface factors, and rainfall factors. The urban waterlogging analysis results include the total inundated area, the maximum water depth at the waterlogging point, the distribution of inundation water depth, and the distribution of pipe network overload degree, where the pipe network overload degree As shown in formula (10), （10） Among them, is the highest water level of the node, z is the elevation of the bottom of the node, is the maximum height of the pipe section where the node is located.

9. The urban waterlogging optimization and transformation method based on the surface-coupled hydrodynamic model of pipe networks according to claim 8, wherein: Step H: Select an optimization plan for the waterlogging points according to the urban waterlogging analysis results for optimization and transformation. The optimization plan includes a permeable pavement plan, a green roof plan, and a pipeline optimization plan. The specific content of the permeable pavement plan is, from top to bottom, a permeable surface, a permeable leveling layer, a permeable base layer, a permeable sub-base layer, and a soil base. The green roof plan is specifically to use various environmental materials to make a roof and plant vegetation on the rooftops of various factories, bridges, and urban buildings to form a plant roof. The pipeline optimization plan is specifically to reconstruct and abolish pipelines on the pipe sections that can fully utilize the original discharge standards. The optimization and transformation process is the use of a single plan or a combination of plans.

10. An urban waterlogging optimization and renovation system based on a surface-coupled hydrodynamic model of pipe networks. The specific optimization and renovation process of the urban waterlogging optimization and renovation system is based on the urban waterlogging optimization and renovation method described in any one of claims 1-9, and is characterized in that: It includes a pipe network confluence module, an urban comprehensive drainage module, a surface runoff generation and confluence module, a two-dimensional surface overland flow module, a pipe-ground coupling module, a drainage discrimination module, an inner waterlogging analysis module, and an inner waterlogging optimization and transformation module. The pipe network confluence module is used to generalize pipes and rainwater wells and construct a pipe network confluence model according to the pipe network hydrodynamic method. The urban comprehensive drainage module is used to divide sub-catchments according to the river network flood routing method and then establish an urban comprehensive drainage model using the sub-catchments. The surface runoff generation and confluence module is used to establish a surface runoff generation and confluence model based on the urban comprehensive drainage model and using the surface flood routing method and the Horton infiltration method. The two-dimensional surface overland flow module is used to establish a two-dimensional surface overland flow model based on the surface runoff generation and confluence model and according to the ground elevation data. The pipe-ground coupling module is used to couple the pipe network confluence model and the two-dimensional surface overland flow model to obtain a one-dimensional pipe network - two-dimensional surface overland flow model, and then calibrate and verify the one-dimensional pipe network - two-dimensional surface overland flow model to obtain a verified one-dimensional pipe network - two-dimensional surface overland flow model. The drainage discrimination module is used to calculate the rainfall hyetograph according to the rainfall intensity, and then discriminate the urban pipe network drainage capacity according to the rainfall hyetograph and the verified one-dimensional pipe network - two-dimensional surface overland flow model to obtain the urban pipe network drainage capacity discrimination result. The inner waterlogging analysis module is used to draw the inundation depth map and divide the inundation risk levels according to the urban pipe network drainage capacity discrimination result, and then analyze the urban waterlogging factors using the inundation risk levels to obtain the urban waterlogging analysis result. The inner waterlogging optimization and transformation module is used to select an optimization plan for the waterlogging points according to the urban waterlogging analysis result for optimization and transformation.

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