A full-frequency adaptive correction method and system for staged design flood

Abstract

The present invention discloses a method and system for adaptively correcting the full frequency of staged design floods, which belongs to the technical field of engineering hydrological analysis, including: dividing the flood season and the non-flood season into two major stages according to the annual distribution characteristics of the target section flood, flood control requirements and flood stage targets, and calculating the staged design floods; considering the flood control standard constraints of the flood stages, constructing a two-dimensional combined frequency analysis model, and obtaining the combined frequency of staged floods of the two major stages; comparing the annual flood frequency and the combined frequency of staged floods to obtain the correction threshold, and adaptively correcting the staged design floods; according to the stage targets, adopting the binary hierarchical distribution substitution idea, dividing the flood season or the non-flood season into stages, repeating the above steps to cyclically calculate and correct each staged design flood until the flood control standard constraint requirements are met. The present invention improves the reliability of the results of the staged design floods, and better provides security for the staged scheduling of water conservancy projects and flood control and disaster reduction in the basin.

Description

Technical Field

[0001] The present invention relates to the technical field of engineering hydrological analysis, and in particular to a full-frequency adaptive correction method and system for staged design floods. Background Art

[0002] The staged design flood refers to the design flood calculated with different phase periods as units, which is widely used in water conservancy project phased scheduling, flood control design during the construction period of the project, etc. In the field of engineering hydrological technology, the annual design flood is calculated by sampling the annual maximum value, while the staged design flood is calculated by sampling the maximum value of different phase periods in the year. At present, the calculation of the staged design flood is mainly based on the practice of the relevant specifications for design flood calculation, and each staged design flood is sampled separately, and then calculated using the hydrological frequency analysis method. Although this approach can ensure the relative rationality of the results of each staged design flood, it does not fully reflect the seasonal and random laws of floods. There is a common problem of inconsistency between the annual flood frequency and the combined frequency of staged floods, which reduces the flood control standard of the reservoir staged regulation and is not conducive to the safety of project operation. In response to this defect, the engineering community often adopts the idea of ​​annual design floods instead of main flood season floods to ensure flood control safety during the flood season, but this approach also ignores the possibility of the annual maximum flood occurring during the non-main flood season. In response to this type of problem, the academic community has conducted in-depth research from the perspectives of the recurrence period of staged design floods, the calculation of the combined frequency of staged floods and annual floods, etc., in order to improve the calculation method of staged design floods and increase the combined frequency of staged floods. At present, most of this type of research is discussed from the perspective of probability theory, which needs to be supported by abundant flood samples. Moreover, as the number of flood stages increases, the probability method calculation will involve the bottleneck of solving multi-dimensional combined probability. The calculation process is often complicated, and the reliability of the calculation results has not been effectively verified. At this stage, it is difficult to promote and apply it in engineering practice.

[0003] In view of this, the present invention improves the relevant practices of the existing design flood calculation specifications, and attempts to develop a phased design flood adaptive correction technology from the perspective of rationality correction of design flood results. It is proposed to cyclically adopt a two-dimensional combined frequency calculation method, and gradually replace the calculation of different phased design flood frequencies in layers and steps, and construct different frequency design flood correction thresholds, and adaptively correct the phased design flood results to solve the inconsistency problem between the annual flood frequency and the phased flood combination frequency, thereby improving the reliability of the phased design flood and providing better security support for phased scheduling of water projects and flood control and disaster reduction in river basins. Summary of the invention

[0004] In order to solve the above problems, the purpose of the present invention is to provide a full-frequency adaptive correction technology for staged design floods to solve the problem of mismatch between the staged design flood calculation standard and the annual design flood standard in the prior art, and further improve the reliability of the staged design flood results.

[0005] In order to achieve the above technical objectives, the present application provides a full-frequency adaptive correction method for staged design floods, comprising the following steps:

[0006] According to the annual distribution characteristics of floods in the target section, flood control requirements and flood stage targets, the flood season and non-flood season are divided into two stages, and the frequency analysis method is used to design floods in stages;

[0007] Considering the flood control standard constraints of flood stages, a two-dimensional combined frequency analysis model of flood season and non-flood season is constructed to obtain the combined frequency of flood stages with joint distribution of flood season and non-flood season.

[0008] Compare the annual flood frequency and the combined frequency of staged floods to determine the rationality of staged design floods; calculate the correction threshold based on the rationality determination results and adaptively modify the staged design floods;

[0009] According to the stage targets, the binary stratified distribution substitution approach is adopted to carry out stage division in the flood season or non-flood season, and the above steps are repeated to cyclically calculate and modify the design flood of each stage until the design flood of each target stage meets the constraints of the flood control standards.

[0010] Preferably, in the process of designing floods in stages, the frequency analysis method is used to deduce the initial values ​​of the design floods in different stages for the whole year, flood season, and non-flood season, respectively. The frequency analysis method means: first, the moment method is used to calculate the statistical parameters of the Pearson type III frequency curve, and then the visual estimation method of fitting or the linear moment method is used to adjust and determine.

[0011] Preferably, in the process of obtaining flood control standard constraints for flood stages, the flood control standard constraints include that the combined frequency of stage floods is not lower than the annual design flood frequency, and that the combined frequency of stage floods is not lower than the design flood frequency of each stage.

[0012] Preferably, in the process of constructing the two-dimensional combined frequency analysis model, if the flood season and the non-flood season floods are independent of each other, the two-dimensional combined frequency analysis model is expressed as:

[0013]

[0014] Where: is the combined frequency of staged floods.

[0015] If floods during the flood season and non-flood season are not independent of each other, the two-dimensional combined frequency analysis model can be expressed as:

[0016]

[0017] In the formula, C θ is the copula function, C θ (P 1 (Q), P2 (Q)) indicates P 1 (Q) and P 2 The joint distribution probability of (Q), that is, the probability of flood Q occurring simultaneously in the flood season and the non-flood season, P(Q), P 1 (Q), P 2 (Q) represents the design flood frequency of the whole year, flood season and non-flood season under the flood Q condition, Represents the combined frequency of staged floods.

[0018] Preferably, in the process of obtaining the combined frequency of staged floods, copula functions such as Clayton, Frank and Gumble are selected for joint distribution fitting, and the Kolmogorov-Smimov method, the least squares method and the minimum information criterion are selected to comprehensively determine the fitting accuracy assessment.

[0019] Preferably, in the process of obtaining the combined frequency of staged floods, the mutual independence of floods in the flood season and non-flood season is first determined to construct a two-dimensional combined frequency analysis model. Then, according to the maximum and minimum values ​​of the flood series of different periods over the years, different flood magnitude domains are set, and the combined frequency of staged floods under different flood magnitudes is jointly deduced based on the flood frequency curves prepared in the flood season and non-flood season.

[0020] Preferably, in the process of judging the mutual independence of floods in the flood season and non-flood season, a chi-square test method is used to judge the mutual independence of floods in the flood season and non-flood season.

[0021] Preferably, in the process of adaptively correcting the staged design flood, the annual flood frequency and the combined frequency of the staged flood are compared; if the combined frequency is greater than the annual frequency, further stage division is performed within the flood season or the non-flood season according to the stage target, and the binary stratified distribution substitution idea is adopted to gradually calculate and adaptively correct the staged design flood until the target staged design flood meets the constraints of the flood control standards; if the combined frequency is less than the annual frequency and the calculation of the staged design flood is unreasonable, the correction threshold of the staged design flood is calculated, and the design floods in the flood season and the non-flood season are adaptively corrected until the calculation of the staged design flood is reasonable.

[0022] Preferably, when calculating the staged design flood correction threshold to adaptively correct the staged flood, a flood correction calculation model is constructed, and the calculation formula is expressed as follows:

[0023]

[0024] Where: It represents the revised design flood frequency during the flood season; It represents the corrected design flood frequency in the non-flood season; β is the probability coefficient, which is calculated by the following formula.

[0025]

[0026] Where: n is the total number of years; m represents the number of years when the largest flood occurs during the flood season.

[0027] The present invention also discloses a full-frequency adaptive correction system for staged flood design, comprising:

[0028] The phased design module is used to divide the flood season and non-flood season into two phases according to the annual distribution characteristics of the target section flood, flood control requirements and flood phase targets, and calculate the phased design flood using the frequency analysis method;

[0029] The model building module is used to consider the flood control standard constraints of flood stages, build a two-dimensional combined frequency analysis model of flood season and non-flood season, and obtain the combined frequency of flood stages jointly distributed in flood season and non-flood season;

[0030] The design correction module is used to compare the annual flood frequency and the combined frequency of staged floods to determine the rationality of the staged design floods; calculate the correction threshold based on the rationality judgment result and adaptively correct the staged design floods; based on the staged targets, adopt the binary stratified distribution substitution idea to divide the stages into flood seasons or non-flood seasons, cyclically calculate and adaptively correct each staged design flood until each target staged design flood meets the flood control standard constraint requirements.

[0031] Preferably, the design correction module is also used to compare the annual flood frequency and the combined frequency of staged floods. If the combined frequency is greater than the annual frequency, the staged design floods are further divided into stages within the flood season or the non-flood season according to the staged target, and the binary layered distribution substitution idea is adopted to gradually calculate and adaptively correct the staged design floods until the target staged design floods meet the constraints of the flood control standards; if the combined frequency is less than the annual frequency and the calculation of the staged design floods is unreasonable, the correction threshold of the staged design floods is calculated, and the staged design floods are adaptively corrected until the calculation of the staged design floods is reasonable.

[0032] The present invention discloses the following technical effects:

[0033] The revised staged flood design results of the present invention can meet the requirements of existing design flood calculation specifications, solve the inconsistency between the annual flood frequency and the staged flood combination frequency, improve the reliability of the staged design flood results, and better provide safety guarantees for the staged scheduling of water conservancy projects and flood control and disaster reduction in river basins. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0035] Figure 1 It is a comparison of the distribution curves of flood frequency during the flood season and the combined frequency of floods in different stages as described in the present invention;

[0036] Figure 2 It is a comparison diagram of flood frequency curves before and after correction of the pre-flood period of the present invention;

[0037] Figure 3 It is a comparison diagram of flood frequency curves before and after correction in the post-flood period of the present invention;

[0038] Figure 4 It is a schematic diagram of the method flow of the present invention. DETAILED DESCRIPTION

[0039] To make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. The components of the embodiments of the present application generally described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the application claimed for protection, but merely represents the selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present application.

[0040] like Figure 1-4 As shown, the present invention provides a method for adaptively correcting the calculation of staged design floods at all frequencies. By frequency combination and correction threshold calculation, the rationality of flood control standard constraints is considered, and the binary layered and step-by-step substitution calculation idea is cyclically adopted to adaptively calculate and correct the staged design floods, thereby further improving the reliability of the overall staged flood results. The method specifically includes the following steps:

[0041] Step 1: Divide the target section into two stages: flood season and non-flood season according to the annual distribution characteristics of floods, flood control requirements and flood stage targets. Use the traditional frequency analysis method to derive the design floods for different stages such as year, flood season and non-flood season.

[0042] Step 2: Considering the flood control standard constraints of flood stages, a two-dimensional combined frequency analysis model of flood season and non-flood season is constructed to calculate the combined frequency of flood stages jointly distributed in flood season and non-flood season.

[0043] Step 3: Compare the annual flood frequency and the combined frequency of staged floods. If the combined frequency is greater than the annual frequency, the calculation of the staged design flood is reasonable and no correction is required. Go to step 5.

[0044] Step 4: If the combined frequency is less than the annual frequency, the calculation of the phased design flood is unreasonable, then calculate the phased design flood correction threshold, and adaptively correct the flood season and non-flood season design floods. Repeat step 3 until the phased design flood calculation is reasonable, stop the correction, and go to step 5.

[0045] Step 5: According to the staged target, in the flood season or non-flood season, the binary stratified distribution alternative calculation method is adopted to repeat steps 1 to 4, and the staged design flood is gradually calculated and adaptively corrected until the target staged design flood meets the flood control standard constraint requirements.

[0046] By considering the flood control standard constraints of flood stages, the binary layered distribution alternative calculation idea is cyclically adopted, and a two-dimensional combined frequency analysis model and correction threshold are gradually constructed. The design floods of different target stages can be reasonably judged and adaptively corrected. The calculation procedure is simple and fast, which can meet the requirements of existing design flood calculation specifications, and can also solve the inconsistency between the annual flood frequency and the combined frequency of staged floods, further improving the reliability of the staged design flood results and providing better basic support for the staged scheduling of water conservancy projects and flood control and disaster reduction in river basins.

[0047] Step 1: Divide the flood season and non-flood season according to the annual distribution characteristics of the target section flood, flood control requirements and flood stage targets. Use the frequency analysis method to derive the design flood for different stages such as year, flood season and non-flood season, further including:

[0048] Step 1.1: According to the needs of staged regulation of water conservancy projects, the target number of flood stages for a given target section A is set to m, that is, the year is divided into m stages, and the design flood for each stage needs to be calculated separately. First, collect the data on the maximum flood elements of the target section A in previous years and months and the time when the flood elements occur, among which the flood elements are not limited to the maximum flood peak, the maximum flood volume in a period, etc.; if the flood element is the maximum flood peak, the flood occurrence time is the time when the maximum flood peak occurs; if the flood element is the maximum flood volume in a period, the flood occurrence time is the starting time within the maximum flood volume period.

[0049] Assume that according to the staged regulation of water conservancy projects, the number of flood stage targets for target section A is 3, that is, the year is divided into 3 stages, each stage time is: non-flood season (November to March), pre-flood season (April to July) and post-flood season (August to October), and the design flood for each stage (non-flood season, pre-flood season, post-flood season) needs to be calculated. This example takes the maximum flood peak element as an example, and first collects the maximum flood peak and its occurrence time of each month (January to December) of the target section A in the past years (1961 to 2022).

[0050] Step 1.2: Based on the occurrence time of the maximum flood element in each month of the target section A over the years and the existing flood control requirements of the river section, the one-year period is first divided into two phases: flood season and non-flood season.

[0051] According to the occurrence time of the largest flood in target section A in previous years and months, combined with the existing flood control requirements of the river section, the flood season period from January to December of the year is determined to be April to October, and the non-flood season period is determined to be November to March. The flood season period is further divided into the pre-flood season (April-July) and the post-flood season (August to October).

[0052] Step 1.3: In the whole year, flood season and non-flood season, the annual maximum value sampling method is adopted, that is, a maximum flood element value is selected each year in the whole year, flood season and non-flood season to form the annual, flood season and non-flood season maximum flood analysis series, which are recorded as Q m (i) Q x (i) and Q f (i), where i = 1, 2, 3, ..., n, and n is the total number of years.

[0053] Taking the flood peak flow as an example, the annual maximum value sampling method is used for sampling in the whole year, flood season and non-flood season. That is, from the maximum flood peak flow series of each month in the calendar year from 1961 to 2022, one maximum flood peak flow value is selected each year in the whole year (January to December), flood season (April to October) and non-flood season (November to March) to form the maximum flood analysis series of the whole year, flood season and non-flood season from 1961 to 2022, which are recorded as Q m (i) Q x (i) and Q f (i), where i = 1, 2, 3, ..., 62, and 62 is the total number of years from 1961 to 2022.

[0054] Step 1.4: Use frequency analysis method to derive the initial values ​​of design flood for different periods, such as the whole year, flood season, and non-flood season, respectively, denoted as Q Pm , Q Px , Q Pf Frequency analysis method According to the requirements of "Code for Flood Calculation of Water Conservancy and Hydropower Engineering Design" (SL44-2006), the moment method is first used to analyze the statistical parameters (mean, C v and C s ) is calculated, and then the eye estimation method or linear moment method (not limited in the present invention) is used for adjustment and determination. Considering that this method is relatively mature, the present invention will not repeat it in detail.

[0055] The frequency analysis method is used to derive the initial values ​​of the design flood for different periods, including the whole year (January to December), the flood season (April to October) and the non-flood season (November to March), which are denoted as Q Pm , Q Px , Q PfFrequency analysis method According to the requirements of "Code for Flood Calculation of Water Conservancy and Hydropower Engineering Design" (SL44-2006), the moment method is first used to analyze the statistical parameters (mean, C v and C s ) is calculated, and then the eye-estimation fitting method is used to adjust and determine. The calculation results are shown in Table 1, which are the initial values ​​of the design flood for different periods such as year, flood season, and non-flood season.

[0056] Table 1

[0057]

[0058] Step 2, considering the flood control standard constraints of flood stages, constructing a two-dimensional combined frequency analysis model of flood season and non-flood season, and calculating the combined frequency of flood stages jointly distributed in flood season and non-flood season, further includes:

[0059] Step 2.1, considering the flood control standard constraints of flood stages, construct a two-dimensional combined frequency analysis model for flood season and non-flood season. The flood control standard constraints of flood stages are: ① The combined frequency of floods in stages shall not be lower than the annual design flood frequency; ② The combined frequency of floods in stages shall not be lower than the design flood frequency of each stage.

[0060] Assume that P(Q), P 1 (Q), P 2 (Q) represents the design flood frequency of the whole year, flood season and non-flood season under the flood Q condition. If it is judged that the occurrence of flood Q in the flood season and non-flood season is independent of each other, that is, it is impossible for flood Q to occur simultaneously in the flood season and non-flood season or the probability of flood Q occurring simultaneously is small, then from the perspective of probability statistics, a two-dimensional combined model of floods in the flood season and non-flood season can be constructed, which is expressed as:

[0061]

[0062] Where: Represents the combined frequency of staged floods.

[0063] If it is judged that floods in the flood season and non-flood season are not independent, that is, the flood Q can occur simultaneously in the flood season and non-flood season or the probability of flood Q occurring simultaneously is high, then the Copula function is introduced, and the co-occurrence probability is introduced from the perspective of probability statistics to construct a two-dimensional joint distribution model of floods in the flood season and non-flood season, which can be expressed as:

[0064]

[0065] Where: C θ is the copula function, C θ (P 1 (Q), P 2 (Q)) indicates P 1 (Q) and P2 The joint distribution probability of (Q), that is, the probability of flood Q occurring simultaneously in the flood season and the non-flood season.

[0066] Commonly used methods of Copula functions in hydrological research include Clayton, Frank and Gumble functions, which are not limited in the present invention. They are all single-parameter functions that are easy to construct, and the expressions are as follows:

[0067]

[0068] Where θ is the parameter of the copula function.

[0069] The two-dimensional copula function parameter θ is estimated using the Kendal correlation coefficient, and the expression is as follows:

[0070]

[0071] Where θ is the parameter of the copula function; τ is the Kendal correlation coefficient; D 1 () is the first kind of Debye function.

[0072] Usually, Clayton, Frank and Gumble functions are selected for joint distribution fitting (not limited in the present invention), and the fitting accuracy is evaluated by Kolmogorov–Smimov (KS) method, ordinary least squares (OLS) and Akaike information criterion (AIC). Assuming that the cross-sectional flood element series is Q(i) and the fitting series is Q′(i), the accuracy evaluation index is as follows:

[0073]

[0074] Where C represents the comprehensive evaluation target; n is the total number of years in the series; and k is the number of parameters in the marginal distribution.

[0075] Step 2.2: Use the chi-square test method to determine the mutual independence of floods during the flood season and non-flood season. The main calculation steps are as follows:

[0076] Step 2.2.1: Assume that the flood series in the flood season and non-flood season are Q x (i) and Q f (i) There are a and b categories respectively. First, a contingency table matrix A = a × b is constructed, and each cell in the contingency table matrix A contains the frequency of the corresponding combination, where the frequency refers to the number of times each category combination appears.

[0077] Step 2.2.2, calculate the expected frequency. For each cell (i, j) in the contingency table matrix A, the expected frequency E ij The calculation formula is as follows:

[0078]

[0079] In the formula, m 1 is the total frequency of the row where the cell is located; m 2 is the total frequency of the column where the cell is located; m all is the sum of all frequencies in the contingency table matrix A.

[0080] Step 2.2.3, calculate the chi-square statistic, the calculation formula is:

[0081]

[0082] In the formula, O ij is the actual observed frequency, E ij is the expected frequency. The chi-square statistic measures the difference between the actual frequency and the expected frequency.

[0083] Step 2.2.4, calculate the degrees of freedom, the calculation formula is:

[0084] df=(a-1)×(b-1)

[0085] Where a is the flood season Q x (i) is the category number; b is the non-flood season flood Q f (i) The number of categories.

[0086] Step 2.2.5: Based on the calculated chi-square statistic and degrees of freedom, the corresponding p-value can be found from the chi-square distribution table (this table has been published). Select the significance level (usually 0.05) as the judgment threshold. If the calculated p-value is less than the significance level, reject the independence hypothesis and assume that there is a significant association between the two variables. Otherwise, accept the independence hypothesis and assume that there is no significant association between the two variables.

[0087] For example, considering the flood control standard constraints of flood stages, a two-dimensional combined frequency analysis model of flood season and non-flood season is constructed. The flood control standard constraints of flood stages are: ① the combined frequency of floods in stages shall not be lower than the annual design flood frequency; ② the combined frequency of floods in stages shall not be lower than the design flood frequency in stages.

[0088] Step 2.1: First, use the chi-square test method to determine the mutual independence of floods during the flood season and non-flood season. Suppose the flood series during the flood season and non-flood season are Q x and Q f , the length of the series year is 62. According to Q x and Q fThe flood peak data of previous years are removed. The different data amounts are the number of categories, which are recorded as a and b respectively. Q x The number of categories is 59, Q f The number of categories is 60. Then, a contingency table matrix A = 59 × 60 is constructed, and each cell in the contingency table matrix A contains the frequency of the corresponding combination. The frequency refers to Q x and Q f The same number of occurrences in each category combination.

[0089] Next, calculate the expected frequency, chi-square statistic, and degrees of freedom. For each cell (i, j) in the contingency table matrix A, the expected frequency E ij , chi-square statistic x 2 The calculation formula for the degree of freedom df is as follows:

[0090]

[0091] In the formula, m 1 is the total frequency of the row where the cell is located; m 2 is the total frequency of the column where the cell is located; ma ll is the sum of all frequencies in the contingency table matrix A; ij is the actual observed frequency; E ij is the expected frequency; a is the flood season Q x (i) is the category number; b is the non-flood season flood Q f (i) The number of categories.

[0092] Through calculation, the chi-square statistic and degrees of freedom are 3487.5 and 3422 respectively. According to the calculated chi-square statistic and degrees of freedom, the corresponding p=0.2134 is found in the chi-square distribution table. The significance level is selected as P=0.05 as the judgment threshold. Because the calculated p value is greater than the significance level of 0.05, the independence hypothesis is accepted, and it is considered that there is no significant association between the two variables.

[0093] If P(Q), P 1 (Q), P 2 (Q) represents the design flood frequency under the flood Q condition in the whole year (January to December), flood season (April to October) and non-flood season (November to March), and the floods in the flood season and non-flood season are independent of each other. From the perspective of probability statistics, a two-dimensional combined model of floods in the flood season and non-flood season can be constructed, which is expressed as:

[0094]

[0095] Where: Represents the combined frequency of staged floods.

[0096] Step 2.3: According to the maximum and minimum values ​​of the flood series of different periods over the years, different flood magnitude domains are set. Based on the two-dimensional combination model of flood season and non-flood season, the flood frequency curves proposed in flood season and non-flood season can be used to jointly deduce the combined frequency of floods under different flood magnitudes.

[0097] According to the maximum and minimum values ​​of the flood series of different periods, the flood magnitude domain Q∈[130,960] is set, and the corresponding annual design flood frequency is P(Q)∈[0.01,0.99]. Then, according to the two-dimensional combination model of flood season and non-flood season, the combined frequency of floods in different flood magnitudes can be jointly deduced through the Pearson III type (P-III) frequency curves designed for flood season and non-flood season. The calculation results of the example are shown in Table 2, which are the combined frequency values ​​of floods in different flood magnitudes in flood season and non-flood season.

[0098] Table 2

[0099]

[0100]

[0101]

[0102] Step 3: When comparing the annual flood frequency with the combined frequency of staged floods, if the combined frequency is greater than the annual frequency, the calculation of the staged design flood is reasonable and no correction is required, and then the process proceeds to step 5, further including:

[0103] Step 3.1: Under all given flood magnitude conditions, compare the annual flood frequency and the combined frequency of staged floods. If Δ≥0, the staged design flood calculation is reasonable, go to step 5.

[0104] Given the flood magnitude domain Q∈[130,960], compare the annual flood frequency and the combined frequency of staged floods. Δ 1 The calculation results are shown in Table 3, which shows the calculation results of Δ under different flood magnitudes and the judgment of rationality constraints. It can be seen from the table that the Δ values ​​under all flood magnitudes are greater than 0, indicating that the calculation of the staged design flood is reasonable, and go to step 5.

[0105] Table 3

[0106]

[0107]

[0108] Step 4: If the combined frequency is less than the annual frequency, the calculation of the phased design flood is unreasonable, then the phased design flood correction threshold is calculated, and the design floods in the flood season and non-flood season are adaptively corrected. Repeat step 3 until the phased design flood calculation is reasonable, stop the correction, and go to step 5, which further includes:

[0109] Step 4.1: If the combined frequency of staged floods is less than the annual flood frequency, it is necessary to calculate the staged design flood correction threshold and adaptively correct the design floods in the flood season and non-flood season respectively. Let λ be the initial correction coefficient, and the correction calculation model can be defined according to the probability of the annual maximum flood occurring in the flood season or non-flood season, as follows:

[0110]

[0111] Where: It represents the revised design flood frequency during the flood season; It represents the corrected design flood frequency in the non-flood season; β is the probability coefficient, which is calculated by the following formula.

[0112]

[0113] Where: n is the total number of years; m represents the number of years when the largest flood occurs during the flood season.

[0114] Step 4.2, calculate the correction threshold of the staged design flood, and adaptively correct the design floods in the flood season and non-flood season. Repeat step 3 until the staged design flood calculation is reasonable and stop the correction.

[0115] Step 4.3: According to the corrected flood frequencies of different magnitudes in the flood season and non-flood season, the statistical parameters (mean, C v and C s ) is recalculated and then adjusted using the eye-estimation method.

[0116] It can be seen from Table 3 that the Δ values ​​under all flood magnitudes are greater than 0, and the calculation of the staged design flood is reasonable. There is no need for correction in step 4, and we can directly go to step 5.

[0117] Step 5: According to the staged target, in the flood season or non-flood season, the binary stratified distribution alternative calculation method is adopted to repeat steps 1 to 4, and the staged design flood is gradually calculated and adaptively corrected until the target staged design flood meets the flood control standard constraint requirements, further including:

[0118] Step 5.1: Based on the staged target, the flood season is further divided into the pre-flood season and the post-flood season. The binary stratified distribution alternative calculation method is adopted, that is, the flood season, pre-flood season and post-flood season periods are equivalent to the annual, flood season and non-flood season periods mentioned above. Then repeat step 1 and use the frequency analysis method to deduce the design floods for different stages such as the flood season, pre-flood season and post-flood season. The design flood for the flood season adopts the design flood results for the flood season that have been corrected or judged to be reasonable in the previous text, and is used express.

[0119] According to the phased targets (non-flood season, pre-flood season, post-flood season), the flood season (April to October) is further divided into the pre-flood season (April to July) and the post-flood season (August to October). Then repeat step 1 and use the frequency analysis method to deduce the design floods for different phases such as the pre-flood season and the post-flood season. The design flood for the flood season adopts the reasonable design flood results for the flood season judged in the previous article. The calculation results are shown in Table 4, which shows the initial values ​​of the design floods for different phases such as the pre-flood season and the post-flood season.

[0120] Table 4

[0121]

[0122] Step 5.2: Based on step 2, the chi-square test is used to determine the mutual independence of floods in the pre-flood season and post-flood season.

[0123] Through calculation, the chi-square statistic and degrees of freedom of floods in the pre-flood season and post-flood season are 3177.5 and 3136 respectively. According to the calculated chi-square statistic and degrees of freedom, the corresponding p=0.3 is found from the chi-square distribution table. The significance level is selected as P=0.05 as the judgment threshold. Because the calculated p value is greater than the significance level of 0.05, the independence hypothesis is accepted, and it is considered that there is no significant association between the two variables.

[0124] Step 5.3: According to step 2, considering the flood control standard constraints of flood stages, and the independence of flood variables in the pre-flood season and the post-flood season, a two-dimensional combined frequency analysis model of the pre-flood season and the post-flood season is constructed to calculate the combined frequency of the staged floods in the pre-flood season and the post-flood season. Compare the flood frequency of the flood season with the combined frequency of the staged floods. If the combined frequency is greater than the flood frequency of the flood season, the calculation of the staged design flood is reasonable and no correction is required. If the combined frequency is less than the flood frequency, the calculation of the staged design flood is unreasonable, then calculate the correction threshold of the staged design flood, and adaptively correct the design floods in the pre-flood season and the post-flood season respectively. Repeat step 3 until the correction is stopped when the calculation of the staged design flood is reasonable.

[0125] Given a flood magnitude domain Q∈[101,930], the corresponding flood design frequency during the flood season is P(Q)∈[0.01,0.99]. Based on the two-dimensional combination model of the pre-flood season and the post-flood season, the combined frequency of staged floods under different flood magnitudes can be jointly derived through the Pearson III type (P-III) frequency curves designed for the pre-flood season and the post-flood season. The calculation results of the example are shown in Table 5, which show the combined frequency values ​​of the pre-flood season and the post-flood season floods under different flood magnitudes.

[0126] Table 5

[0127]

[0128]

[0129]

[0130] Compare the magnitude of flood frequency during the flood season and the frequency of combined floods in different stages (e.g. Figure 1 ).set up Δ 2 The calculation results are shown in Table 6, which show the Δ 2 Calculation results and rationality constraint judgment. It can be seen from the table that Δ 2 If the value is less than 0, it means that the calculation of the staged design flood is unreasonable and needs to be corrected. Go to step 4.

[0131] Table 6

[0132]

[0133]

[0134] According to step 4.1 and Table 6, the combined frequency of staged floods of some magnitudes is less than the flood frequency of the flood season. It is necessary to calculate the staged design flood correction threshold under the corresponding magnitude flood to correct the design floods of the pre-flood season and post-flood season respectively. Let λ be the initial correction coefficient. According to the probability of the maximum flood of the flood season occurring in the pre-flood season or post-flood season, the correction calculation model can be defined as follows:

[0135]

[0136] Where: It represents the corrected design flood frequency in the previous flood season; It represents the corrected design flood frequency in the post-flood season; β is the probability coefficient, which is calculated by the following formula.

[0137]

[0138] In the formula: n is 62, which is the total number of years from 1961 to 2022; m is 40, which means that the maximum flood in the flood season occurred in the previous flood season for 40 years. Then β = 40 / 62 = 0.6452.

[0139] According to step 4.2, calculate the correction threshold of the staged design flood, and adaptively correct the design flood of the first and second flood seasons respectively. Repeat step 3, and the calculation results are shown in Table 7, which shows the rationality judgment of the second and fifth adaptive corrections under different flood magnitudes. This automatic calculation is repeated 3 times, and the Δ 2 They are all greater than 0, indicating that the calculation of staged design flood is reasonable.

[0140] Table 7

[0141]

[0142]

[0143] According to step 4.3, based on the corrected flood frequencies of different magnitudes in the pre-flood season and post-flood season, the moment method is used to calculate the statistical parameters (mean, C v and C s ) is recalculated and then adjusted using the eye-estimation method.

[0144] Comparison of flood frequency curves before and after correction in the pre-flood season and post-flood season Figure 2 The design value comparison is shown in Table 8, which shows the comparison table of the design floods before and after the correction of the pre-flood season and post-flood season. Compared with before the correction, the design flood of the pre-flood season has not changed much, but the flood of the post-flood season has changed to a certain extent.

[0145]

[0146] Table 8

[0147] The number of staged flood targets mentioned in the present invention is 3, that is, the year is divided into 3 stages, and the time of each stage is: non-flood season (November to March), pre-flood season (April to July), and post-flood season (August to October). Through the above steps, the rationality judgment and adaptive correction calculation of all target staged floods can be completed. The staged flood design results after correction calculation can meet the requirements of existing design flood calculation specifications, and can also solve the problem of inconsistency between annual flood frequency and staged flood combination frequency, thereby improving the reliability of staged design flood results and better providing safety guarantees for staged scheduling of water conservancy projects and flood control and disaster reduction in river basins.

[0148] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0149] In the description of the present invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0150] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A full-frequency adaptive correction method for staged design flood, characterized in that: The following steps are involved: According to the annual distribution characteristics of floods in the target section, flood control requirements and flood stage targets, the flood stage is divided into two categories: flood season and non-flood season, and the frequency analysis method is used to calculate the stage design flood; Considering the flood control standard constraints of flood stages, a two-dimensional combined frequency analysis model of flood season and non-flood season is constructed to obtain the combined frequency of flood stages with joint distribution of flood season and non-flood season. Compare the annual flood frequency and the combined frequency of staged floods to determine the rationality of staged design floods; calculate the correction threshold based on the rationality determination results and adaptively modify the staged design floods; According to the stage target, adopt the binary method and stratified distribution substitution idea, divide the stage into stages in the flood season or non-flood season, repeat the above steps to calculate and modify the design flood of each stage until the design flood of each target stage meets the flood control standard constraint requirements; In the process of adaptively correcting the staged design flood, the annual flood frequency and the combined frequency of staged floods are compared. If the combined frequency is greater than the annual frequency, further stage division is carried out in the flood season or non-flood season according to the stage target, and the binary stratified distribution substitution idea is adopted to gradually calculate and adaptively correct each staged design flood until the target staged design flood meets the flood control standard constraint requirements; If the combined frequency is less than the annual frequency and the calculation of the staged design flood is unreasonable, the staged design flood correction threshold is calculated and each staged design flood is adaptively corrected until the calculation of the staged design flood is reasonable.

2. According to claim 1, a full-frequency adaptive correction method for staged design flood is characterized by: In the process of designing floods in stages, the frequency analysis method is used to deduce the initial values ​​of the design floods in different stages for the whole year, flood season, and non-flood season. The frequency analysis method means that the statistical parameters of the Pearson type III frequency curve are first calculated using the moment method, and then adjusted and determined using the visual estimation method or the linear moment method.

3. According to claim 2, a full-frequency adaptive correction method for staged design flood is characterized by: In the process of obtaining flood control standard constraints for flood stages, the flood control standard constraints include that the combined frequency of stage floods is not lower than the annual design flood frequency, and that the combined frequency of stage floods is not lower than the design flood frequency of each stage.

4. According to claim 3, a full-frequency adaptive correction method for staged design flood is characterized by: In the process of constructing a two-dimensional combined frequency analysis model, the two-dimensional combined frequency analysis model is expressed as: ， ， Where P(Q), P1(Q), and P2(Q) represent the design flood frequencies of the whole year, flood season, and non-flood season under flood Q conditions, respectively. Represents the combined frequency of staged floods.

5. A full-frequency adaptive correction method for staged design flood according to claim 4, characterized in that: In the process of obtaining the combined frequency of staged floods, the copula functions of Clayton, Frank and Gumble were selected for joint distribution fitting, and the Kolmogorov-Smimov method, least squares method and minimum information criterion were selected to comprehensively determine the fitting accuracy assessment.

6. A full-frequency adaptive correction method for staged design flood according to claim 5, characterized in that: In the process of obtaining the combined frequency of staged floods, based on the two-dimensional combined frequency analysis model, by judging the mutual independence of floods in flood season and non-flood season, different flood magnitude domains are set according to the maximum and minimum values ​​of flood series in different periods, and based on the flood frequency curves formulated in flood season and non-flood season, the combined frequency of staged floods under different flood magnitudes is jointly deduced.

7. A full-frequency adaptive correction method for staged design flood according to claim 6, characterized in that: In the process of judging the mutual independence of floods in the flood season and non-flood season, the chi-square test method is used to judge the mutual independence of floods in the flood season and non-flood season.

8. A full-frequency adaptive correction system for staged flood design, characterized in that: include: The phased design module is used to divide the flood season and non-flood season into two phases according to the annual distribution characteristics of the target section flood, flood control requirements and flood phase targets, and calculate the phased design flood using the frequency analysis method; The model building module is used to consider the flood control standard constraints of flood stages, build a two-dimensional combined frequency analysis model of flood season and non-flood season, and obtain the combined frequency of flood stages jointly distributed in flood season and non-flood season; The design correction module is used to compare the annual flood frequency and the combined frequency of staged floods to determine the rationality of staged design floods; calculate the correction threshold based on the rationality determination result and adaptively correct the staged design floods; According to the phased target, the binary stratified distribution substitution idea is adopted to divide the phases into stages during the flood season or non-flood season, and the design flood of each stage is cyclically calculated and adaptively corrected until the design flood of each target phase meets the flood control standard constraint requirements; In the process of adaptively correcting the staged design flood, the annual flood frequency and the combined frequency of staged floods are compared. If the combined frequency is greater than the annual frequency, further stage division is carried out in the flood season or non-flood season according to the stage target, and the binary stratified distribution substitution idea is adopted to gradually calculate and adaptively correct each staged design flood until the target staged design flood meets the flood control standard constraint requirements; If the combined frequency is less than the annual frequency and the calculation of the staged design flood is unreasonable, the staged design flood correction threshold is calculated and each staged design flood is adaptively corrected until the calculation of the staged design flood is reasonable.

9. A full-frequency adaptive correction system for staged design flood according to claim 8, characterized in that: The design correction module is also used to compare the annual flood frequency and the combined frequency of staged floods. If the combined frequency is greater than the annual frequency, the dichotomy layered distribution substitution idea is further adopted in the flood season or non-flood season according to the staged target to gradually calculate and adaptively correct the staged design flood until the target staged design flood meets the flood control standard constraint requirements; If the combined frequency is less than the annual frequency and the calculation of the staged design flood is unreasonable, the staged design flood correction threshold is calculated and each staged design flood is adaptively corrected until the calculation of the staged design flood is reasonable.

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