Method and system for estimating maximum sediment yield of river session rainstorm flood and medium

Abstract

The invention provides a method for estimating the maximum sediment yield of river session rainstorm flood. The method comprises the following steps: step 1, screening river session rainstorm flood sample data; 2, river annual sediment transport jump nodes are identified; step 3, calculating the average sediment content of the flood in the session; and 4, fitting an upper envelope from the flood volume of the session to the average sediment content, and calculating the maximum sediment yield. According to the method, the actual problems that high-intensity sediment production and transportation caused by local rainstorm flood represented by the session flood are difficult to predict, and risks and influences brought to reservoir dispatching operation are increasingly prominent are solved, and the maximum sediment production threshold value of the session flood is quantitatively estimated by establishing an outsourcing relation curve of the flood volume of the session flood and the sediment content; technical support can be provided for risk analysis of extra-large water and sediment possibly existing in rivers, and decision basis is provided for prolonging the service life of cascade reservoirs and giving full play to comprehensive benefits of the reservoirs.

Description

Technical Field

[0001] The invention relates to the technical field of water conservancy river channel sediment transport, in particular to a method, system and medium for estimating the maximum sediment yield of a river rainstorm flood. Background Art

[0002] Heavy rain and floods in mountainous rivers have the basic characteristics of steep rise and fall, short duration and high intensity, strong destructive power and high sand content. The sand production and transportation of rivers are closely related to the intensity, location and range of heavy rain. When heavy rain and floods occur in some rivers, the amount of sand is large and concentrated. In some years, the amount of sand in just a few days during the flood season can reach more than 50% of the annual sand volume. For example, in August 2020, due to the influence of continuous heavy rainfall, the Minjiang River, Tuojiang River and the Fujiang River, a tributary of the Jialing River in the upper reaches of the Yangtze River, experienced large sand peaks. The sand peak content at the Gaochang Station of the Minjiang River was 7.54kg / m 3 The sand content of the sand peak at Fushun Station of Tuojiang River reached 8.51kg / m 3 The sand peak at Xiaoheba Station on the Fujiang River has a sand content of 22.7 kg / m 3 Another example is that in mid-September of the 2022 flood season, heavy rainfall in Zhaotong, Yunnan, caused the Xiaojiang Station in Baihetan to reach 415kg / m 3 On the other hand, in recent years, under the influence of climate change, water and soil conservation projects, and the construction of main and tributary reservoirs, new phenomena such as a sharp decrease in sediment entering reservoirs and high-intensity concentrated sediment transport by rainstorms and floods have gradually emerged. The impact of river rainstorms and floods on sediment deposition in reservoirs is still unclear, which brings certain difficulties to the accurate calculation of reservoir capacity loss and reservoir scheduling and operation. It is one of the hot issues that all sectors of society are very concerned about. Estimating the maximum sediment production that may be caused by a rainstorm and flood is of great significance to the sustainable development of river functions such as flood control, shipping, and ecology, and plays an important role in extending the service life of reservoirs and giving full play to the comprehensive benefits of reservoirs.

[0003] In order to further reveal the extremely serious water and sediment risks that may exist in rivers in the future, reasonably evaluate the impact of extreme water and sediment conditions on reservoir siltation, and provide technical support for predicting reservoir siltation trends, this paper relies on historical samples of river rainstorm and flood sediment production and transport as basic data to quantitatively estimate the maximum amount of sediment that may be caused by a rainstorm and flood, laying the foundation for the prediction of river water and sediment conditions and the optimal scheduling of reservoirs. Summary of the invention

[0004] This method is based on the analysis and calculation of flood volume and sediment yield of multiple rainstorm floods in a long time series of rivers, establishes the relationship between flood volume and average sediment content during floods, and uses a parabolic curve to fit the upper envelope of flood volume and average sediment content, thereby deducing the extreme value of average sediment content and its corresponding flood volume, and calculating the maximum sediment yield of rivers under extreme conditions of rainstorms and floods, so as to better predict the risk of extremely large water and sediment in rivers and ensure the performance of basic river functions.

[0005] The technical solution of the present invention:

[0006] A method for estimating the maximum sediment yield of a river rainstorm flood comprises the following steps:

[0007] Step 1. Filter river-level rainstorm and flood sample data;

[0008] Step 2. Identify the jump nodes of annual sediment discharge in rivers;

[0009] Step 3. Calculate the average sediment content of each flood event;

[0010] Step 4. Fit the flood volume ~ average sediment content upper envelope and calculate the maximum sediment yield.

[0011] The implementation of step 1 is as follows:

[0012] Step 11. Collect the daily average flow and sediment content observation data of the river's controlling hydrological stations;

[0013] Step 12. Draw the daily average flow process line and count the peak flow, sort the peak flow from large to small and divide it into different intervals, comprehensively consider the frequency of peak flow in each interval, and select the flood process with peak flow greater than a certain flow as the sample data of the rainstorm flood.

[0014] The implementation of step 2 is as follows:

[0015] Step 21. Use the long-term series of daily average flow Q and sediment content S of the hydrological station to calculate the annual sediment transport Q i is the flow rate on the i-th day, in m 3 / s,S i is the sediment content on the i-th day, in kg / m 3 , N is the total number of days in a year, and the annual sediment transport volume is in 10,000 tons;

[0016] Step 22. Based on Fisher's optimal segmentation method, identify the years with sudden changes in sediment transport and divide the long time series into multiple different time periods.

[0017] The implementation of step 3 is as follows:

[0018] Step 31. According to the characteristics of river rainstorms and floods, combined with the duration of multiple floods, determine the statistical period of the rainstorm and flood process. Especially for rainstorms in large and medium-sized basins, the flood peak transport and sand peak transport during the flood season are often out of sync. The statistical period of the rainstorm and flood process should include the peak value of the sediment content corresponding to the flood. Generally, G=1, 3, 5, 7, 15, 30, 60d corresponding to the maximum flow is the main time period for sediment production of a rainstorm and flood. The determination of the G value depends on the characteristics of the river rainstorm and flood and its duration.

[0019] Step 32.1 The flood process is divided by the time of peak flow, taking the first (G-1) / 2 days as the flood period and the last (G-1) / 2 days as the flood period, and calculate the flood volume on G day. G Daily sediment transport Q i is the flow rate on the i-th day, in m 3 / s, G daily flood volume unit is 100 million m 3 , S i is the sediment content on the i-th day, in kg / m 3 , the unit of G daily sediment transport is 10,000 tons, so the average sediment content S of G day can be obtained Gd =W Gd ×10 -1 / E Gd , unit is kg / m 3 .

[0020] The implementation of step 4 is as follows:

[0021] Step 41. With the flood volume on G day of each flood as the horizontal coordinate and the corresponding average sediment content on G day as the vertical coordinate, a scatter plot of the relationship between the flood volume on G day and the average sediment content on G day of each flood in each period is drawn according to the different periods divided in step 22;

[0022] Step 42. Use the parabolic curve to calculate the formula S Gd =aW Gd 2 +bW Gd +c fits the upper envelope of flood volume on day G ~ average sediment content on day G of flood event, and obtains the calculation parameters a, b, c of parabola curve in different periods respectively;

[0023] Step 43. Calculate the maximum average sediment content S of each period G according to the parabola vertex coordinate calculation formula Gd-max =(4ac-b 2 ) / 4a, unit is kg / m 3 , the corresponding daily flood volume E Gd-max =-b / 2a, unit is 100 million m 3 , and thus the maximum daily sediment yield W of flood G is obtained Gd-max =EGd-max ×S Gd-max ×10 -3 , the unit is billion tons.

[0024] A system for estimating the maximum sediment yield of a river flood event, including:

[0025] Data screening module, used to screen river rainstorm flood sample data;

[0026] Identification module, used to identify the jump nodes of annual sediment discharge in rivers;

[0027] Average sediment content calculation module, used to calculate the average sediment content of flood events;

[0028] The maximum sediment yield calculation module is used to fit the flood volume ~ average sediment content upper envelope and calculate the maximum sediment yield.

[0029] A computer-readable storage medium stores program code, and when the program code is executed by a processor, the steps of the method for estimating the maximum sediment yield of a river flood event are implemented as described above.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows: the present method only relies on relatively easy-to-obtain hydrological and sediment observation data from hydrological stations, and on the basis of identifying flood processes, by establishing a flood volume-average sediment content outsourcing curve relationship, the maximum sediment production of river storm floods is deduced, the statistical method is clear, the implementation process is clear, the technical means are feasible, the river rainfall, vegetation coverage, soil erosion investigation, and river sediment production and transport simulation and analysis work are reduced, the work difficulty and workload are greatly reduced, and the method is fully applicable to various scale conditions such as large, medium and small basins. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A calculation flow chart of a method for estimating the maximum sediment yield of a river flood event according to an embodiment of the present invention;

[0032] Figure 2 This is the interannual variation and time period division diagram of sediment discharge at CT hydrological station;

[0033] Figure 3 This is the relationship diagram between the 7-day flood volume and average sediment content of multiple floods at CT hydrological stations in different periods;

[0034] Figure 4 To estimate the 7-day average sediment content and maximum sediment transport of flood events at the CT hydrological station. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] A method for estimating the maximum sediment yield of a river rainstorm flood comprises the following steps:

[0037] Step 1: Filter the river rainstorm flood sample data. The implementation method is as follows:

[0038] Step 11. Collect the daily average flow and sediment content observation data of the river's controlling hydrological stations;

[0039] Step 12. Draw the daily average flow process line and count the peak flow, sort the peak flow from large to small and divide it into different intervals, comprehensively consider the frequency of peak flow in each interval, and select the flood process with peak flow greater than a certain flow as the sample data of the rainstorm flood.

[0040] Step 2: Identify the jump node of annual sediment transport in the river. The implementation method is as follows:

[0041] Step 21. Use the long-term series of daily average flow Q and sediment content S of the hydrological station to calculate the annual sediment transport Q i is the flow rate on the i-th day, in m 3 / s,S i is the sediment content on the i-th day, in kg / m 3 , N is the total number of days in a year, and the annual sediment transport volume is in 10,000 tons;

[0042] Step 22. Based on Fisher's optimal segmentation method, identify the years with sudden changes in sediment transport and divide the long time series into multiple different time periods.

[0043] Step 3: Calculate the average sediment content of each flood. The implementation method is as follows:

[0044] Step 31. According to the characteristics of river rainstorms and floods, combined with the duration of multiple floods, determine the statistical period of the rainstorm and flood process. Especially for rainstorms in large and medium-sized basins, the flood peak transport and sand peak transport during the flood season are often out of sync. The statistical period of the rainstorm and flood process should include the peak value of the sediment content corresponding to the flood. Generally, G=1, 3, 5, 7, 15, 30, 60d corresponding to the maximum flow is the main time period for sediment production of a rainstorm and flood. The determination of the G value depends on the characteristics of the river rainstorm and flood and its duration.

[0045] Step 32.1 The flood process is divided by the time of peak flow, taking the first (G-1) / 2 days as the flood period and the last (G-1) / 2 days as the flood period, and calculate the flood volume on G day. G Daily sediment transport Q i is the flow rate on the i-th day, in m 3 / s, G daily flood volume unit is 100 million m 3 , S i is the sediment content on the i-th day, in kg / m 3 , the unit of G daily sediment transport is 10,000 tons, so the average sediment content S of G day can be obtained Gd =W Gd ×10 -1 / E Gd , unit is kg / m 3 .

[0046] Step 4: Fit the flood volume ~ average sediment content upper envelope and calculate the maximum sediment yield. The implementation method is as follows:

[0047] Step 41. With the flood volume on G day of each flood as the horizontal coordinate and the corresponding average sediment content on G day as the vertical coordinate, a scatter plot of the relationship between the flood volume on G day and the average sediment content on G day of each flood in each period is drawn according to the different periods divided in step 22;

[0048] Step 42. Use the parabolic curve to calculate the formula S Gd =aW Gd 2 +bW Gd +c fits the upper envelope of flood volume on day G ~ average sediment content on day G of flood event, and obtains the calculation parameters a, b, c of parabola curve in different periods respectively;

[0049] Step 43. Calculate the maximum average sediment content S of each period G according to the parabola vertex coordinate calculation formula Gd-max =(4ac-b 2 ) / 4a, unit is kg / m 3 , the corresponding daily flood volume E Gd-max =-b / 2a, unit is 100 million m 3 , and thus the maximum daily sediment yield W of flood G is obtained Gd-max =E Gd-max ×S Gd-max ×10 -3 , the unit is billion tons.

[0050] The specific steps of the embodiment are as follows:

[0051] Step 1: CT station is an important control station for the inflow of a certain reservoir. The daily flow and sediment content observation data of CT station from 1980 to 2020 are collected; the daily average flow process line is drawn, and a total of 380 flood peak processes of CT station from 1980 to 2020 are counted, among which the peak flow is higher than 30000m 3 There were 161 floods with a frequency of 42% and a flood rate of 30,000 m 3 The proportion of flood sediment transported by floods with a peak flow of more than 30,000 m / s in the annual sediment transport volume is as high as 48%. 3 The flood process with a rate of / s is taken as the sample data of heavy rain and flood for analysis.

[0052] Step 2: Use the daily average flow and sediment content data of the CT station long-term series to calculate the annual sediment discharge. Based on the Fisher optimal segmentation method, identify the years of sudden changes in sediment discharge at the CT station, and identify 1991, 2001, and 2012 as jump nodes. Based on this, divide the CT station long-term series into four periods: 1980-1991, 1992-2001, 2002-2012, and 2013-2020. Figure 2 .

[0053] Step 3: Based on the long-term series of multiple floods at the CT station, the seven days corresponding to the peak flow are selected as the main time period for the flow and sediment production of a rainstorm flood. The peak flow time is used as the boundary for a flood process, with the first three days as the flood period and the last three days as the flood period. The seven-day flood volume and seven-day sediment transport are calculated to obtain the seven-day average sediment content.

[0054] Step 4: With the 7-day flood volume of each flood as the horizontal axis and the corresponding 7-day average sediment content as the vertical axis, draw a scatter plot of the relationship between the 7-day flood volume and the 7-day average sediment content of the four periods of 1980-1991, 1992-2001, 2002-2012, and 2013-2020, see Figure 3 . Using the parabolic curve calculation formula S 7d =aW 7d 2 +bW 7d +c fitted the upper envelope of the 7-day flood volume ~ 7-day average sediment content of the flood event, and obtained the parabola calculation parameters a, b, and c for the four periods of 1980-1991, 1992-2001, 2002-2012, and 2013-2020 respectively; according to the parabola vertex coordinate calculation formula, the 7-day maximum average sediment content was calculated, see Figure 4 The results show that the maximum average sediment content at CT station in 7 days does not exceed 4.8kg / m 3 The 7-day flood volume corresponding to the maximum average sediment content in different periods is between 20 billion and 26 billion m 3During the 7-day period, the sediment transport volume of each flood did not exceed 120 million tons.

[0055] The present application also provides a system for estimating the maximum sediment yield of a river flood event, including:

[0056] Data screening module, used to screen river rainstorm flood sample data;

[0057] Identification module, used to identify the jump nodes of annual sediment discharge in rivers;

[0058] Average sediment content calculation module, used to calculate the average sediment content of flood events;

[0059] The maximum sediment yield calculation module is used to fit the flood volume ~ average sediment content upper envelope and calculate the maximum sediment yield.

[0060] The present application also provides a computer-readable storage medium, which stores program code. When the program code is executed by a processor, the steps of the method for estimating the maximum sediment yield of a river flood caused by a rainstorm are implemented as described above.

[0061] The above embodiments are merely examples of the technical solutions of the present invention. The method for constructing the time-varying form of the parameters of the hydrodynamic mathematical model involved in the present invention is not limited to the contents described in the above embodiments, but is subject to the scope defined in the claims. Any modification, supplement or equivalent replacement made by a person skilled in the art of the present invention on the basis of the embodiment is within the scope of protection claimed by the present invention.

Claims

1. A method for estimating the maximum sediment yield of a river flood event, characterized in that: The following steps are involved: Step 1. Filter river-level rainstorm and flood sample data; Step 2. Identify the jump nodes of annual sediment discharge in rivers; Step 3. Calculate the average sediment content of each flood event; Step 4. Fit the flood volume ~ average sediment content upper envelope and calculate the maximum sediment yield.

2. The method for estimating the maximum sediment yield of a river flood event according to claim 1 is characterized in that: The implementation of step 1 is as follows: Step 11. Collect the daily average flow and sediment content observation data of the river's controlling hydrological stations; Step 12. Draw the daily average flow process line and count the peak flow, sort the peak flow from large to small and divide it into different intervals, comprehensively consider the frequency of peak flow in each interval, and select the flood process with peak flow greater than a certain flow as the sample data of the rainstorm flood.

3. The method for estimating the maximum sediment yield of a river flood event according to claim 2 is characterized in that: The implementation of step 2 is as follows: Step 21. Use the long-term series of daily average flow Q and sediment content S of the hydrological station to calculate the annual sediment transport Q i is the flow rate on the i-th day, in m 3 / s,S i is the sediment content on the i-th day, in kg / m 3 , N is the total number of days in a year, and the annual sediment transport volume is in 10,000 tons; Step 22. Based on the Fisher optimal segmentation method, identify the years with sudden changes in sediment transport and divide the long time series into multiple different time periods.

4. The method for estimating the maximum sediment yield of a river flood event according to claim 3 is characterized in that: The implementation of step 3 is as follows: Step 31. According to the characteristics of river rainstorms and floods, combined with the duration of multiple floods, determine the statistical period of the rainstorm and flood process. Especially for rainstorms in large and medium-sized basins, the flood peak transport and sand peak transport during the flood season are often out of sync. The statistical period of the rainstorm and flood process should include the peak value of the sediment content corresponding to the flood. Generally, G=1, 3, 5, 7, 15, 30, 60d corresponding to the maximum flow is the main time period for sediment production of a rainstorm and flood. The determination of the G value depends on the characteristics of the river rainstorm and flood and its duration. Step 32.1 The flood process is divided by the time of peak flow, taking the first (G-1) / 2 days as the flood period and the last (G-1) / 2 days as the flood period, and calculate the flood volume on G day. G Daily sediment transport Q i is the flow rate on the i-th day, in m 3 / s, G daily flood volume unit is 100 million m 3 , S i is the sediment content on the i-th day, in kg / m 3 , the unit of G daily sediment transport is 10,000 tons, so the average sediment content S of G day can be obtained Gd =W Gd ×10 -1 / E Gd , unit is kg / m 3 .

5. The method for estimating the maximum sediment yield of a river flood event according to claim 4, characterized in that: The implementation of step 4 is as follows: Step 41. With the flood volume on G day of each flood as the horizontal coordinate and the corresponding average sediment content on G day as the vertical coordinate, a scatter plot of the relationship between the flood volume on G day and the average sediment content on G day of each flood in each period is drawn according to the different periods divided in step 22; Step 42. Use the parabolic curve to calculate the formula S Gd =aW Gd 2 +bW Gd +c fits the upper envelope of flood volume on day G ~ average sediment content on day G of flood event, and obtains the calculation parameters a, b, c of parabola curve in different periods respectively; Step 43. Calculate the maximum average sediment content S of each period G according to the parabola vertex coordinate calculation formula Gd-max =(4ac-b 2 ) / 4a, unit is kg / m 3 , the corresponding daily flood volume E Gd-max =-b / 2a, unit is 100 million m 3 , and thus the maximum daily sediment yield W of flood G is obtained Gd-max =E Gd-max ×S Gd-max ×10 -3 , the unit is billion tons.

6. A system for estimating the maximum sediment yield of a river flood event, characterized in that: include, Data screening module, used to screen river rainstorm flood sample data; Identification module, used to identify the jump nodes of annual sediment discharge in rivers; Average sediment content calculation module, used to calculate the average sediment content of flood events; The maximum sediment yield calculation module is used to fit the flood volume ~ average sediment content upper envelope and calculate the maximum sediment yield.

7. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores program codes, and when the program codes are executed by a processor, the steps of the method for estimating the maximum sediment yield of a river rainstorm flood as described in any one of claims 1 to 5 are implemented.

Images