Prediction method for flood peak flow

Abstract

The invention relates to the field of flood data prediction, in particular to a flood peak flow prediction method, which comprises the following steps of: acquiring a design flood peak flow and a rainwater collection area of a reference river hydrological station; acquiring the rainwater collecting area of the river to be researched; deducing the design peak discharge of the river to be studied by using an area multiple proportion method; the prediction method is obtained by deducing flood data of a river hydrometric station on a river to be studied through an area multiple proportion method, and verification shows that the method is easy to operate, high in accuracy and convenient to apply and popularize.

Description

Technical Field

[0001] The invention relates to the field of flood data prediction, and in particular to a method for predicting flood peak flow. Background Art

[0002] The catchment area of ​​a river basin is 2230.8km 2 , belongs to the subtropical monsoon climate zone, located in low latitudes, with mild climate, abundant rainfall, sufficient sunshine, and precipitation time mainly from April to September, with annual rainfall up to 1,800 mm. The basin includes 23 tributaries, many of which are in areas with no or lack of flood data, which makes flood calculation and forecasting difficult. The ability to quickly and accurately design flood flows is the basis for determining the scale, design parameters and safety of water conservancy projects in the basin area; at the same time, reasonable design flood flows contribute to the rational use and allocation of water resources, such as the water storage and release strategies of reservoirs, to ensure that while meeting flood control safety, the utilization efficiency of water resources is maximized. In short, deriving flood design flows in areas without data is an important means to ensure the safety of water conservancy projects, reduce flood disasters, protect the environment and promote sustainable development.

[0003] At present, in areas without flood data, some indirect methods and techniques are usually needed to deduce design floods, such as the rainstorm inference method: using rainstorm data to calculate the design flood through inference formulas; this usually involves determining the intensity of rainstorms, rainstorm duration, basin characteristics (such as basin area, basin shape, ground slope, etc.) and runoff and confluence parameters, but this method has high requirements for the natural environment and poor adaptability; there is also the unit line method: the design flood is derived through the unit line (the runoff process line generated by rainfall in a unit period of time). First, the unit line needs to be determined, and then it is multiplied by the design rainstorm process to obtain the design flood process. And statistical methods: including frequency analysis and historical flood surveys. Although there is no data, historical flood information can be collected by visiting local residents and historical records, and then statistical analysis can be performed. However, these methods are complicated to operate and have large errors.

[0004] Therefore, developing a method that can quickly and accurately derive the design flood flow in data-free areas is of great significance for achieving reliable flood forecasting in data-free tributaries. Summary of the invention

[0005] The purpose of the present invention is to provide a method for predicting peak flow in response to the problems existing in the prior art. The prediction method utilizes the designed peak flow and catchment area of ​​the river hydrological station on the river to be studied and is derived through the area ratio method. It has been verified that the method is simple to operate, has high accuracy, and is easy to promote and apply.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A method for predicting flood peak flow comprises the following steps:

[0008] Obtain the design peak flow and catchment area of ​​the reference river hydrological station;

[0009] Obtain the catchment area of ​​the river to be studied;

[0010] The design peak flow of the river to be studied is deduced using the area ratio method.

[0011] The present invention provides a method for predicting flood peak flow, which is derived by utilizing the designed flood peak flow and rainwater collection area of ​​a river hydrological station on a river to be studied through an area ratio method. Verification has shown that the method is simple to operate, has high accuracy, and is easy to promote and apply.

[0012] Furthermore, the design peak flow of the reference river hydrological station is obtained by the following method:

[0013] Obtain historical flood data from river hydrological stations and retrieve flood-related data during the period of extreme floods;

[0014] The unified sample method is used to process the measured flood volumes during flood periods and extreme flood periods at river hydrological stations to obtain empirical frequency data sets;

[0015] The P-III curve method is used to process the empirical frequency data set to obtain the standard frequency curve of the design peak flow of the river hydrological station;

[0016] The design peak flows corresponding to a variety of design frequencies are extracted from the standard frequency curve of the design peak flows of the river hydrological station, which is the design peak flows of the river hydrological station.

[0017] The present invention adopts a method for obtaining the design flood flow of a river hydrological station, including obtaining the flood data of the river hydrological station over the years, calling out the flood-related data of the extremely large flood period; using the unified sample method to process the measured flood volume of the river hydrological station during the flood period and the extremely large flood period, and obtaining the empirical frequency data group; using the P-III type curve method to process the empirical frequency data group, and obtain the standard frequency curve of the design flood peak flow of the river hydrological station; from the standard frequency curve of the design flood peak flow of the river hydrological station, extracting the design flood peak flow corresponding to multiple design frequencies, that is, the design flood peak flow of the river hydrological station. This method makes the design flood results more stable and the accuracy is effectively improved by adding historical extremely large floods to the measured data.

[0018] Furthermore, flood-related data include peak flow data and flood volume data.

[0019] Furthermore, when the flood volume of a particular flood period is not recorded, the peak ratio method is used to deduce it using the known flood volume of another flood period.

[0020] Furthermore, the unified sample method is operated using the following formula:

[0021]

[0022]

[0023] Where: N is the length of the investigation period; n is the number of years in the measured series; a is the number of extremely large values ​​in N years; l is the number of extremely large values ​​from the measured series; M is the ranking of extremely large floods in the investigation period; m is the ranking of measured floods in the measured period; P a is the empirical frequency of the major flood ranked a during the investigation period; P m is the empirical frequency of the major flood ranked M during the investigation period; P m is the empirical frequency of the measured flood with rank m during the measurement period.

[0024] Furthermore, the standard frequency curve of the design peak flow of the river hydrological station is obtained by the following steps:

[0025] The specific operation process of processing the empirical frequency data group using the P-III curve method is as follows: using the P-III curve, the empirical frequency is calculated using the discontinuous series mathematical expectation formula, the moment method is used to preliminarily estimate the mean, coefficient of variation (Cv), and skewness coefficient (Cs), and then the fitting method is used to adjust the parameters to obtain the standard frequency curve of the design peak flow of the river hydrological station.

[0026] Furthermore, the design peak flows corresponding to four design frequencies are extracted from the standard frequency curve of the design peak flows of the river hydrological stations, which are the design peak flows when P is 1%, 2%, 5% and 10%, respectively.

[0027] Furthermore, the area ratio method uses the following formula to deduce the design flood peak of the river to be studied:

[0028]

[0029] Where: Q 参 、F 参 are the design flood peak and catchment area of ​​the reference river hydrological station; Q 研 、F 研 are the design flood peak and catchment area of ​​the study river or hydrological station respectively.

[0030] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements the above-mentioned method for predicting flood peak flow.

[0031] A computer device comprises: a processor and a memory storing a computer program, wherein the processor is configured to execute the above-mentioned method for predicting flood peak flow when running the computer program.

[0032] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0033] 1. The present invention provides a method for predicting flood peak flow, which is derived by using the designed flood peak flow and catchment area of ​​the river hydrological station on the river to be studied through the area ratio method. It has been verified that the method is simple to operate, has high accuracy, and is easy to promote and apply.

[0034] 2. The present invention adopts a method for obtaining the design flood flow of a river hydrological station, including obtaining the flood data of the river hydrological station over the years, calling out the flood-related data of the extremely large flood period; using the unified sample method to process the measured flood volume of the river hydrological station during the flood period and the extremely large flood period, and obtaining the empirical frequency data group; using the P-III type curve method to process the empirical frequency data group to obtain the standard frequency curve of the design flood peak flow of the river hydrological station; from the standard frequency curve of the design flood peak flow of the river hydrological station, extracting the design flood peak flow corresponding to multiple design frequencies, that is, the design flood peak flow of the river hydrological station. This method makes the design flood results more stable and the accuracy is effectively improved by adding historical extremely large floods to the measured data. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The present invention is a flow chart of a method for predicting flood peak flow.

[0036] Figure 2 The present invention provides a flow chart for obtaining the design peak flow of the river hydrological station.

[0037] Figure 3 Design flood volume PⅢ frequency curve for LW station.

[0038] Figure 4 Design the peak standard frequency curve for LW station.

[0039] Figure 5 Design the peak frequency curve for LW station reporting Cv-Cs-Ex according to the Comprehensive Management Plan. DETAILED DESCRIPTION

[0040] The present invention will be described in detail below in conjunction with the accompanying drawings.

[0041] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0042] Example

[0043] The design flood of LW station is taken into account by taking into account historical floods according to the measured series of LW station (1953-2020).

[0044] like Figure 1 and Figure 2 As shown, the present invention provides a method for predicting flood peak flow, and the specific process is as follows:

[0045] A method for predicting flood peak flow comprises the following steps:

[0046] Obtain the design peak flow and catchment area of ​​the reference river hydrological station;

[0047] Obtain the catchment area of ​​the river to be studied;

[0048] The design peak flow of the river to be studied is deduced using the area ratio method.

[0049] Among them, the design peak flow of the reference river hydrological station is obtained by the following method:

[0050] Obtain historical flood data from river hydrological stations and retrieve flood-related data during the period of extreme floods;

[0051] The unified sample method is used to process the measured flood volumes during flood periods and extreme flood periods at river hydrological stations to obtain empirical frequency data sets;

[0052] The P-III curve method is used to process the empirical frequency data set to obtain the standard frequency curve of the design peak flow of the river hydrological station;

[0053] The design peak flows corresponding to a variety of design frequencies are extracted from the standard frequency curve of the design peak flows of the river hydrological station, which is the design peak flows of the river hydrological station.

[0054] The specific operation process is as follows:

[0055] (1) Historical flood peak flows

[0056] According to the "QZ Chronicles", "Historical Data on Natural Disasters in Guangxi" compiled by the Second Library of Guangxi, and "Climate History Data of Guangxi Zhuang Autonomous Region in the Past Five Hundred Years" compiled by the Information Room of the Guangxi Meteorological Observatory, since the 51st year of Emperor Kangxi (1712), a total of 23 major floods have occurred, of which the largest was in 1893. According to the literature, "heavy rains and surging waters in Lingshan Linwei and Xixiang collapsed countless houses, and the floods in Wuli and Bolao were particularly severe." According to the survey results of the Guangxi Rainfall and Flood Office, the water level at the LW hydrological station was 34.16m and the peak flow was 6910m 3 / s; the second largest flood was in 1780, and other major floods included 1781, 1794, 1864, 1895, 1904, 1971, 1941, and 1942. However, the accuracy of these flood surveys was insufficient, and the magnitude of the floods was difficult to determine; the flood in 1971 was the largest flood after liberation, with a measured flow of 3850m 3 / s (after Jianlingdong), according to the rainfall and disaster situation, the flood in 1971 was the first since 1949.

[0057] (2) Historical flood recurrence period

[0058] According to historical data, the reports such as the Preliminary Design Report of the Yujiang River Water Diversion Project for the Water Supply Source Project of the Coastal Industrial Park in QZ City, Guangxi, the Preliminary Design Report of the Youth Sluice Reinforcement Project in QZ City, Guangxi, and the Feasibility Study Report of the PLYH Project have determined that the Qinjiang River Basin was severely flooded and the peak flow and historical verification period were recorded in 1893 and 1971. According to the Comprehensive Management Plan for the Qinjiang River Basin in QZ City, Guangxi 2018, the flood in 1893 was the largest since 1712, and the flood in 1971 was the first since 1949. Therefore, the recurrence period of the historical flood in 1893 is N1=2020-1712+1=309 years, and the recurrence period of the historical flood in 1971 is N2=2020-1949+1=72 years.

[0059] (III) Design flood calculation

[0060] Adding historical extreme floods to measured data can make the design flood results more stable and improve the accuracy of design flood results. After adding historical extreme floods, the extreme flood data needs to be processed. Regarding the flood experience frequency in the "Specifications for Calculation of Design Floods for Water Conservancy and Hydropower Engineering" SL44-2006, there are two methods for processing discontinuous series: unified sample method and independent sample method.

[0061] (1) Unified sample method for major floods

[0062] The unified sample method believes that the flood series is composed of a historical flood and n measured floods, forming an N (investigation period or verification period) year series. The order of the measured flood of n is uncertain, and the Nan flood value is unknown. Therefore, there is an empirical frequency formula:

[0063]

[0064] Where: N is the length of the investigation period; n is the number of years in the measured series; a is the number of extremely large values ​​in N years; l is the number of extremely large values ​​from the measured series; M is the ranking of extremely large floods in the investigation period; m is the ranking of measured floods in the measured period; P a is the empirical frequency of the major flood ranked a during the investigation period; P m is the empirical frequency of the major flood ranked M during the investigation period; P m is the empirical frequency of the measured flood with rank m during the measurement period.

[0065] (2) Independent sample method for major floods

[0066] The independent sample method treats the measured series and the extreme flood series as independent series in the population and can be sorted separately. The former a item of extreme flood is still calculated using formula (1), and the empirical formula of the nl item in the measured series is calculated according to formula (3):

[0067]

[0068] During the calculation, the rank of the previous extreme flood remains "empty", and the empirical frequencies of other items are calculated starting from m=l+1.

[0069] 2. Area ratio method to calculate design flood for hydrological stations and tributaries

[0070] (I) Calculation of LW design flood volume

[0071] Since the historical flood survey data of LW station in 1893 only have peak flow data, no flood volume record. Analyzing the relationship between flood peak and flood volume from 1953 to 2020, the peak flow in 1971 was the largest, with a peak-volume ratio of 0.1, which was not the largest among all years, but in the other years with a peak-volume ratio greater than 0.1, the flood peak and flood volume were not large. Therefore, the 3-day flood process in 1971 with measured data was selected as the typical flood process. The 3-day flood process of LW station in 1893 was obtained by using the peak multiple ratio of the historical major floods in 1971 and 1893, and then the historical flood volume of LW station in 1893 was obtained to be 659.1817 million m 3 The peak volume ratios are shown in Table 1.

[0072] Table 1 Measured flood peak volume ratio at LW hydrological station

[0073]

[0074]

[0075] The unified sample method and independent sample method were used to process the three-day flood volumes of the measured series of LW station (1953-2020) and the historical extreme floods in 1893 and 1971, and the empirical frequencies are shown in Table 2.

[0076] Table 2 Ranking of historical flood surveys and measured floods and calculation of empirical frequencies

[0077]

[0078]

[0079]

[0080]

[0081]

[0082] The P-III curve is used, the empirical frequency is calculated using the discontinuous series mathematical expectation formula, the mean, Cv, and Cs are preliminarily estimated using the moment method, and the parameters are adjusted using the fitting method to obtain the two LW station design flood standard frequency curves using the unified sample method and the independent sample method, as shown below: Figure 3 shown.

[0083] The design flood volumes corresponding to the four design frequencies are obtained from the standard frequency curve as shown in Table 3. The empirical frequencies in 1971 calculated by the unified sample method and the independent sample method are very close, so the standard frequencies and design flood volumes obtained are basically the same, and the calculation results of the unified sample method are directly used in subsequent calculations.

[0084] Table 3 Results of 3-day design flood volume of LW station

[0085]

[0086] (II) LW design flood peak calculation

[0087] (1) Calculate the peak flow according to the Cv, Cs, and Ex used in this design

[0088] According to the above method, the standard frequency curve is obtained by using the peak discharge of the LW station measured series (1953-2020) and the historical extreme floods in 1893 and 1971, see Figure 4 , and design flood peak flow, see Table 4.

[0089] Table 4 LW station design flood peak results

[0090]

[0091] (2) Restore the Cv, Cs, and Ex reported in the Comprehensive Management Plan to the design flood peak

[0092] Restore Cv, Cs, and Ex in "Comprehensive Management Plan" etc. to the sample sequence of this design calculation. Compare the calculated design flood peak of LW Station with that in "Comprehensive Management Plan" and the design flood peak calculated after restoring Cv, Cs, and Ex in the report to the current sample sequence. See Table 5 and Figure 5 。

[0093] Comparison of Design Flood Peak Results of Relevant Data of LW Station

[0094]

[0095] The design flood peak of LW Station in this design is smaller than the results reported in "Comprehensive Management Plan" etc. However, the frequency curve fitting degree obtained by combining the statistical parameters reported in "Comprehensive Management Plan" with the current sample sequence is low. Considering that the actual measurement series used in this design for LW is from 1953 to 2020, a total of 68 years, compared with the actual measurement series data used in "Comprehensive Management Plan" from 1954 to 2011, a total of 58 years, the sample sequence length is longer and the data is more abundant. Therefore, the design result of this design is more reliable. For safety consideration in the most unfavorable situation, the LW design flood in "Comprehensive Management Plan" can be retained for reference.

[0096] (3) Calculation of Design Flood Volume of Tributaries

[0097] Taking LW Hydrological Station as the reference station and based on its design flood volume, given the catchment areas of LW Hydrological Station and the tributaries, according to the relationship of catchment areas between basins, the design flood volume of LW Hydrological Station is multiplied by a ratio to each tributary, as shown in Equation (4). Thus, the design flood volumes of the tributaries are obtained. See Table 6.

[0098]

[0099] In the formula: Wref and Fref are the design flood volume and catchment area of the reference river hydrological station respectively; Wres and Fres are the design flood volume and catchment area of the river or hydrological station under study respectively;

[0100] Table 6 Results of Calculating Design Flood Volumes of Tributaries Using Area Multiplication Method

[0101]

[0102] (4) Calculation of Design Flood Peak of Tributaries

[0103] Taking LW Hydrological Station as the reference station and based on its design flood peak, given the catchment areas of LW Hydrological Station and the tributaries, according to the relationship of catchment areas between basins, the design flood peak of LW Hydrological Station is multiplied by a ratio to each tributary, as shown in Equation (5). Thus, the design flood volumes of each tributary are obtained. See Table 7.

[0104]

[0105] Where: Q_ref and F_ref are the design flood volumes and catchment areas of the reference river hydrological station respectively; Q_study and F_study are the design flood peaks and catchment areas of the river or hydrological station under study respectively.

[0106] To ensure the accuracy of the design results this time, the design flood peaks of the tributaries are also compared with the design flood peaks calculated according to the Cv, Cs, and Ex of this design and the design flood peaks calculated after restoring the Cv, Cs, and Ex in the "Comprehensive Treatment Plan" to the sample sequence of this time.

[0107] (1) Calculate the design flood peak of LW according to the Cv, Cs, and Ex adopted in this design, and use the area ratio method to calculate the design flood peaks of each tributary.

[0108] Table 7 Results of calculating the design flood peaks of tributaries using the area ratio method based on the design flood peak of LW station this time

[0109]

[0110]

[0111] (2) Restore the Cv, Cs, and Ex in reports such as the "Comprehensive Treatment Plan" to the design flood peak of LW this time, and use the area ratio method to calculate the design flood peaks of each tributary in the same way as (1).

[0112] Table 8 Results of calculating the design flood peaks of tributaries using the area ratio method based on the restored design flood peak of LW station

[0113]

[0114] The present invention provides a method for predicting flood peak flow, which is obtained by using the design flood peak flow and catchment area of the river hydrological station on the river to be studied and through the area ratio method. Through verification, this method is simple to operate, has high accuracy, and is convenient for popularization and application.

[0115] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for predicting flood peak flow, characterized in that: The following steps are involved: Obtain the design peak flow and catchment area of ​​the reference river hydrological station; Obtain the catchment area of ​​the river to be studied; The design peak flow of the river to be studied is deduced using the area ratio method.

2. The method for predicting flood peak flow according to claim 1, characterized in that: The design peak flow of the reference river hydrological station is obtained by the following method: Obtain historical flood data from river hydrological stations and retrieve flood-related data during the period of extreme floods; The unified sample method is used to process the measured flood volumes during flood periods and extreme flood periods at river hydrological stations to obtain empirical frequency data sets; The P-III curve method is used to process the empirical frequency data set to obtain the standard frequency curve of the design peak flow of the river hydrological station; The design peak flows corresponding to a variety of design frequencies are extracted from the standard frequency curve of the design peak flows of the river hydrological station, which is the design peak flows of the river hydrological station.

3. The method for predicting flood peak flow according to claim 2, characterized in that: Flood-related data include peak flow data and flood volume data.

4. The method for predicting peak flow according to claim 3, characterized in that: When the flood volume of a certain extreme flood period is not recorded, the peak ratio method is used to infer the known flood volume of another extreme flood period.

5. The method for predicting flood peak flow according to claim 2, characterized in that: The uniform sample method operates using the following formula: Where: N is the length of the investigation period; n is the number of years in the measured series; a is the number of extremely large values ​​in N years; l is the number of extremely large values ​​from the measured series; M is the ranking of extremely large floods in the investigation period; m is the ranking of measured floods in the measured period; P a is the empirical frequency of the major flood ranked a during the investigation period; P m is the empirical frequency of the major flood ranked M during the investigation period; P m is the empirical frequency of the measured flood with rank m during the measurement period.

6. The method for predicting flood peak flow according to claim 2, characterized in that: The standard frequency curve of the design peak flow of the river hydrological station is obtained by the following steps: The specific operation process of processing the empirical frequency data group using the P-III curve method is as follows: using the P-III curve, the empirical frequency is calculated using the discontinuous series mathematical expectation formula, the moment method is used to preliminarily estimate the mean, coefficient of variation, and coefficient of skewness, and then the fitting method is used to adjust the parameters to obtain the standard frequency curve of the design peak flow of the river hydrological station.

7. The method for predicting flood peak flow according to claim 2, characterized in that: From the standard frequency curve of design peak flow of river hydrological station, the design peak flow corresponding to four design frequencies are extracted, which are the design peak flow when P is 1%, 2%, 5% and 10% respectively.

8. The method for predicting flood peak flow according to any one of claims 1 to 7, characterized in that: The area ratio method uses the following formula to deduce the design flood peak of the river to be studied: Where: Q 参 、F 参 are the design flood peak and catchment area of ​​the reference river hydrological station; Q 研 、F 研 are the design flood peak and catchment area of ​​the study river or hydrological station respectively.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the method for predicting peak flow according to any one of claims 1 to 8 is implemented.

10. A computer device comprising: A processor and a memory storing a computer program, wherein the processor is configured to execute the method for predicting peak flow as described in any one of claims 1-8 when running the computer program.

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