An evaluation and comparison method for reconstruction scheme of old urban drainage system based on rapid urbanization pre-discharge process

Abstract

The application discloses a kind of old city drainage system reconstruction scheme evaluation and comparison method based on quick urbanization front discharge process, it is related to urban flood control and urban rain flood management technical field, this method is first constructed and verified present rain flood model, then rely on homologous architecture and build quick urbanization front scene model;Same design storm is used to carry out simulation, and the discharge difference brought by urbanization is extracted by a plurality of index quantification.Taking historical discharge process as evaluation benchmark, establish dual evaluation rules of recovery and discharge control, after simulating and calculating the index of each reconstruction scheme, scheme screening is completed in combination with pipe network operation safety constraint.The present application makes up for the deficiency of the prior art, which ignores hydrological recovery and has strong subjectivity in evaluation, realizes multi-dimensional quantitative evaluation, can effectively guarantee drainage safety, promotes rain flood discharge to return to natural state, and the comparison result of scheme is more scientific and reliable.

Description

Technical Field

[0001] This invention relates to the field of urban flood control and drainage and urban stormwater management technology, specifically to a method for optimizing and upgrading the drainage system of old urban areas based on pre-rapid urbanization hydrological benchmarks. Background Technology

[0002] In recent years, the increasing frequency of extreme rainstorms and rapid urbanization have led to increasingly prominent problems in the drainage systems of old urban areas, such as low design standards, aging facilities, and insufficient local drainage capacity. These problems have resulted in frequent occurrences of issues like node overloading, pipe overloading, road flooding, and amplified flood peaks at discharge outlets, which seriously affect urban operational safety and the efficiency of flood control and emergency response.

[0003] Existing methods for upgrading drainage systems in old urban areas primarily aim to improve existing drainage capacity, reduce overflows at key points, or alleviate localized waterlogging. These methods typically focus on expanding bottleneck sections, adding storage facilities, or implementing low-impact development (LID) infrastructure. While these approaches can improve existing flood control capacity to some extent, they often lack a target reference that characterizes the reasonable hydrological response state before rapid urbanization, making it difficult to balance drainage safety with the resilience of the discharge process.

[0004] Meanwhile, although existing studies have technical approaches to analyze the impact of urbanization using historical land use data or historical scenario models, most of them only use the pre-rapid urbanization scenario as a reference system to explain the causes of current problems, and rarely explicitly incorporate the hydrological response of discharge outlets before rapid urbanization into the drainage system transformation objectives. As a result, the proposal of transformation schemes still mainly relies on empirical judgment and lacks a systematic optimization method oriented towards hydrological restoration objectives.

[0005] Therefore, it is necessary to provide a method for optimizing and upgrading the drainage system of old urban areas based on the hydrological benchmark before rapid urbanization. Under a unified model framework, the method can quantitatively identify the difference in discharge response before and after rapid urbanization, and transform this difference into a transformation target. Under the premise of ensuring the safe operation of the drainage system, the flow process of the upgraded discharge outlet should be as close as possible to the reasonable response characteristics before rapid urbanization. Summary of the Invention

[0006] The purpose of this invention is to address the problem that existing evaluation methods for drainage system renovation schemes in old urban areas mainly focus on safety indicators such as node overflow, pipe network overload, and water accumulation risk, while paying insufficient attention to the restorative properties of the overall discharge process at the outlets. This makes it difficult to evaluate and compare renovation schemes from the perspective of restoring the hydrological conditions before rapid urbanization. This invention provides a method for evaluating and comparing drainage system renovation schemes in old urban areas based on the discharge process before rapid urbanization. This method uses the discharge process at the outlets under the pre-rapid urbanization scenario as the restorative evaluation benchmark. Under the premise of meeting the operational safety constraints of the drainage system, it comprehensively evaluates and compares the restorative properties of the outlets and the discharge control effects of different renovation schemes, thereby improving the scientific rigor and relevance of the selection of drainage system renovation schemes in old urban areas.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for evaluating and comparing renovation schemes for drainage systems in old urban areas based on pre-rapid urbanization discharge processes includes the following steps:

[0009] S1. Collect data, construct and validate the current stormwater model: Obtain data on the current drainage network, topographic elevation, current land use, land use before rapid urbanization, rainfall, and discharge outlets in the study area; construct the current stormwater model; and complete the calibration and validation of the model parameters.

[0010] S2, Adjust hydrological parameters and build a scenario model before rapid urbanization: While keeping the sub-catchment division, node layout, pipeline structure, outlet location and boundary conditions of the current stormwater model unchanged, adjust the key hydrological parameters of each sub-catchment according to the land use conditions before rapid urbanization to build a scenario model before rapid urbanization.

[0011] S3, Simulation of the same rainstorm condition, extracting indicators and analyzing the differences in hydrological response: Under the same design rainstorm conditions, run the current rainstorm model and the scenario model before rapid urbanization respectively, extract the emission process lines of each discharge outlet and key response indicators, and establish the differences in emission response before and after rapid urbanization.

[0012] S4. Establish comprehensive evaluation rules based on historical emission processes: Establish hydrological restoration evaluation rules for emission outlets, in which the emission process lines of each emission outlet under the pre-rapid urbanization scenario are used as the restoration evaluation benchmark, the degree of fit between the emission outlet flow process line under the evaluation scheme and the emission outlet flow process line under the pre-rapid urbanization scenario is used to characterize the restoration evaluation results, and the emission control evaluation results are characterized by the peak flow reduction rate, outflow reduction rate, peak delay time and comprehensive runoff coefficient reduction rate of the evaluation scheme relative to the current scenario.

[0013] S5, Simulate each renovation scheme and calculate the evaluation indicators one by one: Simulate each renovation scheme to be evaluated, obtain the discharge outlet flow process line and key response indicators under each renovation scheme to be evaluated, calculate the degree of fit between the discharge outlet flow process line under each renovation scheme to be evaluated and the discharge outlet flow process line under the scenario before rapid urbanization, and the peak flow reduction rate, outflow reduction rate, peak delay time and comprehensive runoff coefficient reduction rate of each renovation scheme to be evaluated relative to the current scenario.

[0014] S6. Combining safety constraints with comprehensive comparison, determine the final renovation plan: Under the premise of meeting the safety constraints of the drainage system operation, based on the restorative evaluation results and emission control evaluation results of each renovation plan to be evaluated, conduct a comprehensive evaluation and comparison of each renovation plan to be evaluated, and determine the target drainage system renovation plan.

[0015] Furthermore, the construction of the current stormwater model described in S1 includes: generalizing nodes, pipe segments, and discharge outlets based on drainage network data of the study area; dividing sub-catchments based on topographic elevation and land use data; and calibrating and validating the model parameters based on measured rainstorm processes and corresponding water levels or water accumulation data.

[0016] Furthermore, the construction method of the pre-rapid urbanization scenario model described in S2 is as follows: under the conditions of unified model structure, unified boundary conditions and unified rainfall input, only the key hydrological parameters used to characterize the differences in underlying surface are adjusted to characterize the runoff generation and confluence characteristics during the period when the impact of rapid urbanization has not yet fully manifested.

[0017] Furthermore, the key hydrological parameters mentioned in S2 include the impermeability of the sub-catchment area, the maximum infiltration rate of the permeable surface, the minimum infiltration rate of the permeable surface, the storage capacity of the permeable surface depression, the proportion of zero runoff on the impermeable surface, and the Manning roughness of the permeable surface.

[0018] Furthermore, the impermeability of the sub-catchment area is calculated using the following formula:

[0019]

[0020] in, The total impermeability of the catchment area; The impermeability rate corresponding to the kth land use type; The area of ​​the kth land use type; This represents the total area of ​​each sub-catchment area.

[0021] Furthermore, the same design rainstorm conditions described in S3 include the same return period, the same rainfall duration, and the same rain pattern distribution conditions.

[0022] Furthermore, the design rainstorm adopts the Chicago rain pattern, with a rainfall duration of 120 minutes, a rainfall peak coefficient of 0.4, and a design rainstorm recurrence period including one or more of the following: once a year, once a two-year, once a five-year, once a ten-year, and once a twenty-year.

[0023] Furthermore, the key response indicators mentioned in S3 are the peak flow, peak time, total outflow, and comprehensive runoff coefficient of each emission outlet under the current scenario and the pre-rapid urbanization scenario.

[0024] Furthermore, the peak flow rate, peak occurrence time, total outflow, and comprehensive runoff coefficient are determined as follows:

[0025] (1) Peak flow rate is the maximum instantaneous flow rate at the discharge outlet during the entire rainfall process;

[0026] (2) Peak time is the time interval from the start of rainfall to the moment when the peak flow occurs;

[0027] (3) The total outflow is the integral value of the flow rate passing through the discharge outlet section within a set duration;

[0028] (4) The comprehensive runoff coefficient is calculated according to the following formula:

[0029]

[0030] in, The total impermeability of the catchment area; Let be the runoff coefficient of the i-th sub-catchment area; Let i be the area of ​​the i-th sub-catchment; This represents the catchment area corresponding to the discharge outlet.

[0031] Furthermore, the difference in emission response before and after rapid urbanization described in S4 is characterized by the difference in peak flow, peak time, total outflow, and comprehensive runoff coefficient between the current scenario and the scenario before rapid urbanization.

[0032] Furthermore, the restorative evaluation benchmark described in S4 is the emission process line of each emission outlet under the pre-rapid urbanization scenario.

[0033] Furthermore, the degree of fit between the emission outlet flow process line under the proposed modification scheme described in step five and the emission outlet flow process line under the pre-rapid urbanization scenario is represented by the Nash efficiency coefficient (NSE), which is calculated using the following formula:

[0034]

[0035] in, Let be the emission outlet flow rate under the scenario of rapid urbanization at time t. Let t be the discharge flow rate at the emission outlet under the modification scheme to be evaluated; is the average discharge outlet flow rate under the scenario before rapid urbanization; T is the number of time periods in the flow process.

[0036] Furthermore, in S5, the Nash efficiency coefficient (NSE) of the flow process line of each emission outlet is first calculated, and then the average NSE corresponding to each modification scheme to be evaluated is calculated as the result of the restoration evaluation.

[0037] Furthermore, the peak flow reduction rate, outflow reduction rate, peak delay time, and comprehensive runoff coefficient reduction rate mentioned in step five are calculated according to the following formulas:

[0038]

[0039]

[0040]

[0041]

[0042] In the formula, Peak flow reduction rate; This represents the peak flow rate at the emission outlet under the current scenario. The peak flow rate of the emission outlet under the modification scheme to be evaluated; The outflow reduction rate; This represents the total outflow from the emission outlet under the current scenario. Total outflow from emission outlets under the proposed renovation scheme to be evaluated; This is the peak delay time; This refers to the peak emission time under the current scenario. The peak emission time at the outlet under the proposed modification scheme to be evaluated; The comprehensive runoff coefficient reduction rate; This represents the comprehensive runoff coefficient at the emission outlet under the current scenario. The comprehensive runoff coefficient of the emission outlet under the renovation scheme to be evaluated.

[0043] Furthermore, the drainage system operation safety constraints described in S6 include one or more of the following: regional average runoff coefficient reduction rate, overflow node reduction rate, total overflow reduction rate, overload ratio reduction rate, and maximum overload time reduction rate, all of which must meet preset requirements.

[0044] Furthermore, the indicators used in step six to characterize the operational safety of the drainage system are calculated according to the following formula:

[0045]

[0046]

[0047]

[0048]

[0049]

[0050] In the formula, Let i be the average runoff coefficient reduction rate of scheme i; Let i be the overflow node reduction rate. Let i be the total overflow reduction rate of scheme i; Let be the pipeline overload reduction rate for scheme i; Let be the maximum overload time reduction rate of scheme i; P is the number of rainfall return period conditions; subscript 0,j indicates the index value corresponding to the j-th return period under the current scenario; subscript i,j indicates the index value corresponding to the j-th return period under scheme i.

[0051] Furthermore, the selection criteria for comprehensive evaluation and comparison in step six are as follows: under the premise of meeting the operational safety constraints of the drainage system, priority should be given to the renovation scheme to be evaluated that has a higher average NSE and better overall performance in terms of average peak flow reduction rate, average outflow reduction rate, average peak delay time and average comprehensive runoff coefficient reduction rate.

[0052] Compared with the prior art, the technical solution disclosed in this invention has the following beneficial effects:

[0053] This invention first collects basic data on drainage networks, topography, land use, rainfall, and outfalls in the study area to build, calibrate, and validate the current stormwater model. Then, while maintaining complete consistency in sub-catchment division, network structure, node and outfall layout, and boundary conditions, it adjusts key hydrological parameters based on pre-rapid urbanization land use data to construct a historical scenario model with the same source. The two models are then used to accurately isolate the runoff generation and runoff effects caused by underlying surface changes. Subsequently, the two models are run simultaneously under design storm conditions with the same return period, rainfall pattern, and duration to extract outfall flow process lines, peak flow, peak time, total outflow, and integrated runoff system. The study uses key indicators such as data to quantitatively analyze the differences in the discharge response of drainage systems before and after rapid urbanization. Then, using the pre-urbanization discharge process line as a baseline for restorative evaluation, a complete evaluation rule is established. This rule assesses the hydrological restoration effect by evaluating the fit of the flow process line, and measures the discharge control capability based on peak flow reduction rate, total outflow reduction rate, peak delay time, and comprehensive runoff coefficient reduction rate. Simulations are then conducted for each proposed modification scheme, and the values ​​of each evaluation indicator are calculated. Finally, using drainage system operational safety indicators as a hard constraint, the hydrological restoration level and discharge control performance of each scheme are comprehensively compared, and the optimal scheme is selected for final modification. This invention fully utilizes the technical features of the entire process, effectively solving the problems of existing technologies that only focus on improving drainage capacity, lack pre-urbanization hydrological references, and neglect the restoration of the discharge process. At the same time, it changes the shortcomings of the past, which only used historical scenarios for problem cause analysis and relied too much on subjective experience for the evaluation and selection of renovation schemes. Through a unified model architecture, unified rainstorm conditions, and unified evaluation standards, it realizes full-process quantitative analysis and builds a three-dimensional evaluation system that integrates hydrological restoration, discharge control, and pipeline safety. This can not only fully guarantee the safe operation of the drainage system in old urban areas for flood control and drainage, and promote the return of rainwater discharge processes to their natural state before urbanization, but also significantly enhance the standardization, scientificity, and fairness of the evaluation and selection of renovation schemes, and greatly improve the actual effect and engineering adaptability of the scheme implementation. Attached Figure Description

[0054] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0055] Figure 1 This is a flowchart illustrating the evaluation and comparison method for the renovation scheme of old urban drainage systems based on the pre-rapid urbanization discharge process, as provided in an embodiment of the present invention.

[0056] Figure 2This is a simplified schematic diagram of the existing drainage system pipes and rainwater inlets in an embodiment of the present invention.

[0057] Figure 3 This is a simplified schematic diagram of the sub-catchment division in an embodiment of the present invention.

[0058] Figure 4 This is a schematic diagram of the designed rainfall process lines with different return periods in an embodiment of the present invention.

[0059] Figure 5 This is a comparison map of the current status of the study area and the land use types before rapid urbanization in this embodiment of the invention.

[0060] Figure 6 This is a comparison diagram of the impermeability of the catchment areas of each discharge outlet before and after rapid urbanization in an embodiment of the present invention.

[0061] Figure 7 This is a comparison diagram of the flow process of the HD1 to HD6 emission outlets under different modification schemes in the embodiments of the present invention.

[0062] Figure 8 This is a comparison chart of the Nash efficiency coefficients (NSE) of each emission outlet for the three modification schemes in this invention, relative to the flow process before rapid urbanization. Detailed Implementation

[0063] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0064] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0065] Example 1:

[0066] A method for evaluating and comparing renovation schemes for drainage systems in old urban areas based on pre-rapid urbanization discharge processes, such as... Figure 1 As shown, it includes the following steps:

[0067] S1. Collect data, construct and validate the current stormwater model: Obtain data on the current drainage network, topographic elevation, current land use, land use before rapid urbanization, rainfall, and discharge outlets in the study area; construct the current stormwater model; and complete the calibration and validation of the model parameters.

[0068] In one embodiment of the present invention, the study area is selected as the old town area of ​​Tonglu County, Zhejiang Province, which is located at the confluence of the Fuchun River and the Fenshui River, and can reflect the typical layout and discharge characteristics of drainage facilities in an old town area; such as Figure 2 and Figure 3 As shown, based on the drainage network data of the study area, nodes, pipe sections, and discharge outlets were generalized, and sub-catchments were divided according to topographic elevation and land use data, thereby establishing a current stormwater model for the study area. The study area has been generalized into 77 sub-catchments, and the pipes and stormwater outlets have been systematically generalized.

[0069] This step forms the data and model foundation for the entire method. A qualified current stormwater model can accurately reproduce the entire process of current rainfall, runoff generation, confluence, and discharge in the old city, ensuring the authenticity of all subsequent simulation, calculation, and evaluation results and avoiding model distortion that could lead to incorrect evaluation conclusions.

[0070] S2. Adjust hydrological parameters and build a scenario model before rapid urbanization: While keeping the sub-catchment division, node layout, pipeline structure, outlet location and boundary conditions of the current stormwater model unchanged, adjust the key hydrological parameters of each sub-catchment according to the land use conditions before rapid urbanization to build a scenario model before rapid urbanization.

[0071] In one embodiment of the present invention, such as Figure 5 As shown, by comparing the current land use types in the study area with those before rapid urbanization, the land use conditions in 1980 were selected as the basis for constructing the pre-rapid urbanization scenario. Only the key hydrological parameters used to characterize the underlying surface differences were adjusted, without changing the current model structure, to ensure comparability between the historical and current scenarios. The paper clearly points out that the construction of the pre-rapid urbanization scenario does not completely restore the drainage engineering system of the historical period, but rather highlights the impact of underlying surface changes on stormwater processes within a unified model framework.

[0072] Furthermore, the key hydrological parameters include the impermeability of the sub-catchment area, the maximum infiltration rate of permeable surfaces, the minimum infiltration rate of permeable surfaces, the storage capacity of permeable surface depressions, the proportion of zero runoff on impermeable surfaces, and the Manning roughness of permeable surfaces. The impermeability of the sub-catchment area is calculated according to the following formula:

[0073]

[0074] in, The total impermeability of the catchment area; The impermeability rate corresponding to the kth land use type; The area of ​​the kth land use type; This represents the total area of ​​each sub-catchment area.

[0075] The unified model framework eliminates interference caused by differences in model structure and accurately distinguishes the impact of changes in the underlying surface of urbanization on stormwater discharge processes; the constructed historical scenario model can restore the natural runoff state before regional development, providing a unique and standard benchmark for subsequent hydrological restoration assessment.

[0076] S3, Simulating the same heavy rainfall scenario, extracting indicators and analyzing differences in hydrological response: Under the same design heavy rainfall conditions, running the current stormwater model and the pre-rapid urbanization scenario model respectively, extracting the emission process lines and key response indicators of each discharge outlet, and establishing the differences in emission response before and after rapid urbanization. In one embodiment of the present invention, such as Figure 4 As shown, the design rainfall event adopts the Chicago rainfall pattern, with a rainfall duration of 120 minutes and a peak rainfall coefficient of 0.4. The design rainfall event return periods include one or more of the following: 1-year, 2-year, 5-year, 10-year, and 20-year return periods. The paper presents the corresponding 2-hour design rainfall process curves for different return periods.

[0077] Furthermore, the key response indicators are the peak flow, peak occurrence time, total outflow, and comprehensive runoff coefficient of each discharge outlet under the current scenario and the pre-rapid urbanization scenario. Specifically, the peak flow is the maximum instantaneous flow at the discharge outlet during the entire rainfall process; the peak occurrence time is the time interval from the start of rainfall to the moment the peak flow occurs; the total outflow is the integral value of the flow process passing through the discharge outlet cross-section within a set duration; and the comprehensive runoff coefficient is calculated according to the following formula:

[0078]

[0079] in, The total impermeability of the catchment area; Let be the runoff coefficient of the i-th sub-catchment area; Let i be the area of ​​the i-th sub-catchment; This represents the catchment area corresponding to the discharge outlet.

[0080] By comparing the effects of the same external forces (rainfall) under the same conditions, we can accurately quantify the negative impact of rapid urbanization on the drainage and discharge process in old urban areas, intuitively locate the degree of hydrological deterioration at the discharge outlets, and provide data basis for the control targets of subsequent renovation plans.

[0081] S4. Establish comprehensive evaluation rules based on historical emission processes: Establish hydrological restoration evaluation rules for emission outlets. Among them, the emission process lines of each emission outlet under the pre-rapid urbanization scenario are used as the restoration evaluation benchmark. The degree of fit between the emission outlet flow process line under the evaluation scheme and the emission outlet flow process line under the pre-rapid urbanization scenario is used to characterize the restoration evaluation results. The emission control evaluation results are characterized by the peak flow reduction rate, outflow reduction rate, peak delay time, and comprehensive runoff coefficient reduction rate of the evaluation scheme relative to the current scenario.

[0082] In one embodiment of the present invention, such as Figure 6 As shown, by comparing the impermeability of the upstream sub-catchment areas of each discharge outlet before and after rapid urbanization, it can be seen that the impermeability within the control range of each discharge outlet has increased significantly, indicating that rapid urbanization has significantly enhanced the runoff conditions in the study area. Therefore, using the discharge process of the discharge outlet under the scenario before rapid urbanization as the benchmark for restorative evaluation can better characterize whether the flow process of the discharge outlet after the transformation has recovered to a more natural and gentle historical hydrological state.

[0083] Establish standardized and quantitative evaluation rules, unify the evaluation criteria for all proposed solutions, and achieve the decomposition and quantification of the two transformation goals of "hydrological restoration" and "current status optimization" to make the evaluation dimensions more comprehensive.

[0084] S5, Simulate each renovation scheme and calculate the evaluation indicators one by one: Simulate each renovation scheme to be evaluated, obtain the discharge outlet flow process line and key response indicators under each renovation scheme to be evaluated, calculate the degree of fit between the discharge outlet flow process line under each renovation scheme to be evaluated and the discharge outlet flow process line under the scenario before rapid urbanization, and the peak flow reduction rate, outflow reduction rate, peak delay time and comprehensive runoff coefficient reduction rate of each renovation scheme to be evaluated relative to the current scenario.

[0085] In one embodiment of this invention, based on the identified flood-prone nodes and overloaded pipe sections in the current situation, and the characteristics of discharge outlet flow processes under the pre-rapid urbanization scenario, three categories of evaluation schemes are set up: low-impact development source reduction schemes, pipeline capacity improvement and renovation schemes, and comprehensive collaborative renovation schemes. The paper explicitly points out that these three schemes correspond to three different renovation approaches: source reduction, transmission and discharge capacity improvement, and gray-green synergy.

[0086] Furthermore, such as Figure 7 As shown, the flow processes of emission outlets HD1 to HD6 under different retrofit schemes can be compared. The results of this paper indicate that the emission process lines of the integrated and coordinated retrofit scheme and the low-impact development source reduction scheme are generally between the pre-rapid urbanization and current conditions, with a relatively gentle rise and a significantly lower peak flow than the current situation, which is closer to the pre-rapid urbanization scenario. While the simple pipeline capacity improvement scheme can improve local transmission and emission conditions, it still has the problem of high peak flow at some emission outlets.

[0087] Furthermore, the degree of fit between the emission outlet flow process line under the evaluated modification scheme and the emission outlet flow process line under the pre-rapid urbanization scenario is represented by the Nash efficiency coefficient (NSE), which is calculated as follows:

[0088]

[0089] in, Let be the emission outlet flow rate under the scenario of rapid urbanization at time t. Let t be the discharge flow rate at the emission outlet under the modification scheme to be evaluated; is the average discharge outlet flow rate under the scenario before rapid urbanization; T is the number of time periods in the flow process.

[0090] Furthermore, the peak flow reduction rate, outflow reduction rate, peak delay time, and comprehensive runoff coefficient reduction rate are calculated according to the following formulas:

[0091]

[0092]

[0093]

[0094]

[0095] In the formula, , , , These are the peak discharge rate, total outflow, peak time, and comprehensive runoff coefficient at the discharge outlet under the current scenario. , , , These are the corresponding indicators for the renovation schemes to be evaluated.

[0096] Complete the quantitative scoring of all candidate schemes, and transform schemes with different transformation ideas and different transformation efforts into numerical indicators that can be compared horizontally, eliminating the comparison barriers caused by differences in scheme form.

[0097] S6. Combining safety constraints with comprehensive comparison, determine the final renovation plan: Under the premise of meeting the safety constraints of the drainage system operation, based on the restorative evaluation results and emission control evaluation results of each renovation plan to be evaluated, conduct a comprehensive evaluation and comparison of each renovation plan to be evaluated, and determine the target drainage system renovation plan.

[0098] Furthermore, such as Figure 8 As shown, the NSE comparison results of each discharge outlet under the three renovation schemes relative to the pre-rapid urbanization flow process reflect the differences in restoration evaluation. The results of this paper indicate that the comprehensive and coordinated renovation scheme has a higher and more balanced overall NSE across different return periods and discharge outlets, indicating a better degree of restoration of the pre-rapid urbanization discharge process. Furthermore, the paper also points out that the comprehensive and coordinated renovation scheme is more balanced in terms of drainage system operational safety, and therefore can be considered the preferred scheme.

[0099] Adopting the selection logic of "safety first, ecological restoration in mind" and strictly adhering to the construction principle of "safety as the bottom line and restoration as the improvement" for drainage projects in old urban areas, the final selected scheme not only meets the safety requirements of the project, but also restores the original hydrological discharge characteristics of the area to the greatest extent, and the scheme has the highest implementation value.

[0100] The basic principles of the present invention have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in the present invention are merely examples and not limitations, and should not be considered as essential features of each embodiment of the present invention. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the present invention to the necessity of employing the aforementioned specific details.

[0101] The block diagrams of devices, apparatuses, devices, and systems involved in this invention are merely illustrative examples and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the block diagrams. As those skilled in the art will recognize, these devices, apparatuses, devices, and systems can be connected, arranged, and configured in any manner. Words such as “comprising,” “including,” “having,” etc., are open-ended terms meaning “including but not limited to,” and are used interchangeably with them. The terms “or” and “and” as used herein refer to the terms “and / or,” and are used interchangeably with them unless the context clearly indicates otherwise. The term “such as” as used herein refers to the phrase “such as but not limited to,” and is used interchangeably with it.

[0102] It should also be noted that in the apparatus, device, and method of the present invention, the components or steps can be disassembled and / or recombined. These disassemblies and / or recombinations should be considered as equivalent solutions of the present invention.

[0103] The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use the invention. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein can be applied to other aspects without departing from the scope of the invention. Therefore, the invention is not intended to be limited to the aspects shown herein, but rather to be carried out within the widest scope consistent with the principles and novel features disclosed herein.

[0104] It should be understood that the qualifying terms "first", "second", "third", "fourth", "fifth" and "sixth" used in the description of the embodiments of the present invention are only used to more clearly illustrate the technical solutions and are not intended to limit the scope of protection of the present invention.

[0105] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of the invention to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations therein.

Claims

1. A method for evaluating and comparing renovation schemes for drainage systems in old urban areas based on pre-rapid urbanization discharge processes, characterized in that, It includes the following steps: S1. Collect data, construct and validate the current stormwater model: Obtain data on the current drainage network, topographic elevation, current land use, land use before rapid urbanization, rainfall, and discharge outlets in the study area; construct the current stormwater model; and complete the calibration and validation of the model parameters. S2, Adjust hydrological parameters and build a scenario model before rapid urbanization: While keeping the sub-catchment division, node layout, pipeline structure, outlet location and boundary conditions of the current stormwater model unchanged, adjust the key hydrological parameters of each sub-catchment according to the land use conditions before rapid urbanization to build a scenario model before rapid urbanization. S3, Simulation of the same rainstorm condition, extracting indicators and analyzing the differences in hydrological response: Under the same design rainstorm conditions, run the current rainstorm model and the scenario model before rapid urbanization respectively, extract the emission process lines of each discharge outlet and key response indicators, and establish the differences in emission response before and after rapid urbanization. S4. Establish comprehensive evaluation rules based on historical emission processes: Establish hydrological restoration evaluation rules for emission outlets, in which the emission process lines of each emission outlet under the pre-rapid urbanization scenario are used as the restoration evaluation benchmark, the degree of fit between the emission outlet flow process line under the evaluation scheme and the emission outlet flow process line under the pre-rapid urbanization scenario is used to characterize the restoration evaluation results, and the emission control evaluation results are characterized by the peak flow reduction rate, outflow reduction rate, peak delay time and comprehensive runoff coefficient reduction rate of the evaluation scheme relative to the current scenario. S5, Simulate each renovation scheme and calculate the evaluation indicators one by one: Simulate each renovation scheme to be evaluated, obtain the discharge outlet flow process line and key response indicators under each renovation scheme to be evaluated, calculate the degree of fit between the discharge outlet flow process line under each renovation scheme to be evaluated and the discharge outlet flow process line under the scenario before rapid urbanization, and the peak flow reduction rate, outflow reduction rate, peak delay time and comprehensive runoff coefficient reduction rate of each renovation scheme to be evaluated relative to the current scenario. S6. Combining safety constraints with comprehensive comparison, determine the final renovation plan: Under the premise of meeting the safety constraints of the drainage system operation, based on the restorative evaluation results and emission control evaluation results of each renovation plan to be evaluated, conduct a comprehensive evaluation and comparison of each renovation plan to be evaluated, and determine the target drainage system renovation plan.

2. The method for evaluating and comparing renovation schemes of old urban drainage systems based on pre-rapid urbanization discharge processes, as described in claim 1, is characterized in that... The construction of the current stormwater model described in S1 includes: generalizing nodes, pipe sections and discharge outlets based on drainage network data of the study area; dividing sub-catchment areas based on topographic elevation and land use data; and calibrating and validating the model parameters based on measured rainstorm processes and corresponding water levels or water accumulation data. The key hydrological parameters mentioned in S2 include the impermeability of the sub-catchment area, the maximum infiltration rate of the permeable surface, the minimum infiltration rate of the permeable surface, the storage capacity of the permeable surface depression, the proportion of zero runoff on the impermeable surface, and the Manning roughness of the permeable surface. The impermeability of the sub-catchment area is calculated according to the following formula:

3. The method for evaluating and comparing renovation schemes of old urban drainage systems based on pre-rapid urbanization discharge processes, as described in claim 1, is characterized in that... The design storm for S3 adopts the Chicago rainfall pattern, with a rainfall duration of 120 minutes and a peak rainfall coefficient of 0.

4. The design storm return period includes one or more of the following: 1-year, 2-year, 5-year, 10-year, and 20-year return periods. Key response indicators include peak flow, peak time, total outflow, and composite runoff coefficient. Each indicator is determined as follows: (1) Peak flow rate is the maximum instantaneous flow rate at the discharge outlet during the entire rainfall process; (2) Peak time is the time interval from the start of rainfall to the moment when the peak flow occurs; (3) The total outflow is the integral value of the flow rate passing through the discharge outlet section within a set duration; (4) The comprehensive runoff coefficient is calculated according to the following formula: in, The total impermeability of the catchment area; Let be the runoff coefficient of the i-th sub-catchment area; Let i be the area of ​​the i-th sub-catchment; This represents the catchment area corresponding to the discharge outlet.

4. The method for evaluating and comparing renovation schemes of old urban drainage systems based on pre-rapid urbanization discharge processes, as described in claim 1, is characterized in that... The degree of fit between the emission outlet flow process curve under the proposed modification scheme described in S5 and the emission outlet flow process curve under the pre-rapid urbanization scenario is represented by the Nash efficiency coefficient (NSE), which is calculated as follows: in, Let be the emission outlet flow rate under the scenario of rapid urbanization at time t. Let t be the discharge flow rate at the emission outlet under the modification scheme to be evaluated; is the average discharge outlet flow rate under the scenario before rapid urbanization; T is the number of time periods in the flow process. The peak flow reduction rate, total outflow reduction rate, peak delay time, and comprehensive runoff coefficient reduction rate are calculated using the following formulas: In the formula, Peak flow reduction rate; This represents the peak flow rate at the emission outlet under the current scenario. The peak flow rate of the emission outlet under the modification scheme to be evaluated; The outflow reduction rate; This represents the total outflow from the emission outlet under the current scenario. Total outflow from emission outlets under the proposed renovation scheme to be evaluated; This is the peak delay time; This refers to the peak emission time under the current scenario. The peak emission time at the outlet under the proposed modification scheme to be evaluated; The comprehensive runoff coefficient reduction rate; This represents the comprehensive runoff coefficient at the emission outlet under the current scenario. The comprehensive runoff coefficient of the emission outlet under the renovation scheme to be evaluated.

5. The method for evaluating and comparing renovation schemes of old urban drainage systems based on pre-rapid urbanization discharge processes, as described in claim 1, is characterized in that... S6 drainage system operation safety constraints include one or more of the following: regional average runoff coefficient reduction rate, overflow node reduction rate, total overflow reduction rate, pipe overload ratio reduction rate, and maximum overload time reduction rate; all safety indicators are calculated using multiple current-period averages, and the general calculation formula is: In the formula, This refers to the average runoff coefficient reduction rate corresponding to the safety index; Let be the corresponding index value for the j-th return period under the current scenario; Let be the corresponding index value for the j-th return period under the renovation scheme to be evaluated; P is the total number of rainfall return period conditions.

6. The method for evaluating and comparing renovation schemes of old urban drainage systems based on pre-rapid urbanization discharge processes, as described in claim 1, is characterized in that... The selection rule for comprehensive comparison in S6 is as follows: Under the premise of meeting the operational safety constraints of the drainage system, priority is given to the evaluation and renovation scheme with higher average Nash efficiency coefficient and better comprehensive performance in peak flow reduction rate, outflow reduction rate, peak delay time, and comprehensive runoff coefficient reduction rate.

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