A flood channel return calculation method and simulation system based on overflow process correction

Abstract

The present invention relates to the technical field of flood disaster prevention, and particularly relates to a flood channeling calculation method and simulation system based on overflow process correction. The method includes the following steps: collecting and processing topographic data of the floodplain area to obtain topographic characteristic parameters; collecting historical flood measured data of the floodplain to obtain the measured flood water level and flow process of the river channel; simulating the out-of-channel and in-channel flood processes according to the topographic characteristic parameters and the measured flood water level process of the river channel based on the principle of water balance to obtain the simulated floodplain flow process; correcting the measured flood flow process of the river channel according to the floodplain flow process to obtain the channeled flood flow process of the river channel, and using this process as the basis for the design of channeled flood. The present invention realizes the channeling correction of the river channel flood process by simulating the floodplain process, requires less data, has complete flood elements, and is highly operable.

Description

Technical Field

[0001] The present invention relates to the technical field of flood disaster prevention, and particularly relates to a flood channeling calculation method and simulation system based on overflow process correction. Background Art

[0002] In flood prevention and emergency management, towns and villages along rivers mainly rely on building dikes to cope with floods. Although the dikes effectively control the flood water overflowing the river channel within the river course and ensure the flood control safety of the river banks, new problems are also brought: after the flood water returns to the channel, the flood peak increases and the water level rises, thus generating new flood control risks. Therefore, in flood control planning, engineering design and flood regulation, the impact of flood channeling must be fully considered to ensure overall flood control safety. Before the construction of the dike, when the river channel flood enters the low-lying area of the river bank (natural flood detention area), part of the water volume will be temporarily stored in the flood detention area; after the construction of the dike, the river channel flood returns to the river channel because it cannot overflow the channel, and the flood water returning to the channel will raise the water level of the river channel. Therefore, with the large-scale construction of river dikes, when conducting flood control design, the impact of flood channeling must be considered, and the flood process after channeling should be accurately calculated to provide a scientific basis for flood control planning, dike design and flood risk assessment. However, the traditional flood channeling calculation methods mainly include the flood routing method, the simplified water balance method and the cubic spline interpolation method. The flood routing method has a strong dependence on measured flood data and high data requirements; the simplified water balance method can only calculate the flood peak flow rate and cannot give the flood process; the cubic spline interpolation method has a complex calculation process and a large amount of calculation, and is inconvenient for practical application. These methods are difficult to meet the requirements of current flood control projects for the calculation accuracy and efficiency of flood channeling. Summary of the Invention

[0003] Based on this, the present invention provides a flood channeling calculation method and simulation system based on overflow process correction to solve at least one of the above technical problems.

[0004] To achieve the above object, a flood channeling calculation method based on overflow process correction includes the following steps:

[0005] Step S1: Obtain the historical flood event data of the river channel; identify the floodplain area according to the historical flood event data of the river channel to obtain the floodplain area data of the river channel flood; determine the flood overflow elevation for the floodplain area data of the river channel to generate the flood overflow elevation data; draw the water level - volume curve of the flood detention area according to the flood overflow elevation data to generate the water level - volume curve parameters of the flood detention area;

[0006] Step S2: Obtain the measured historical flood data of the floodplain; perform historical flood time - series processing on the measured historical flood data of the floodplain to obtain the measured flood flow process data of the river channel and the measured flood water level process data of the river channel respectively;

[0007] Step S3: Construct a river channel - flood detention area exchange simulation model based on flood overflow elevation data, flood detention area water level - volume curve parameters, and measured river channel flood water level process data; use the river channel - flood detention area exchange simulation model to conduct water balance simulations of out - of - channel and in - channel flood process water volumes for the measured river channel flood flow process data, and obtain the river channel overflow flow process data;

[0008] Step S4: Conduct flood back - into - channel correction on the measured river channel flood flow process data through the river channel overflow flow process data to obtain the corrected river channel flood flow process data for back - into - channel; use this process as the basis for back - into - channel flood design.

[0009] Through in-depth mining and analysis of historical flood event data of river channels, the present invention realizes accurate identification of floodplain areas, accurately determines the flood overflow elevation, and then scientifically draws the water level - volume curve of the flood detention area. This process fully considers the actual occurrence of historical floods. Compared with traditional methods, the present invention avoids over-reliance on a large amount of measured flood data, reduces the difficulty and cost of data acquisition, and is particularly applicable to areas with relatively scarce historical data. By using historical floodplain measured flood data and through time series processing, the measured flood discharge and water level process data of the river channel are obtained. Combining historical experience with modern simulation techniques ensures that the calculation process can be based on real flood events and can more accurately capture the dynamic exchange law between the river channel and the flood detention area. A unique river channel - flood detention area exchange simulation model is constructed. Based on flood overflow elevation data, water level - volume curve parameters of the flood detention area, and measured flood water level process data of the river channel, the model conducts water balance simulations of the out-of-channel and in-channel flood process water volumes for the measured flood discharge process data of the river channel, and finally accurately calculates the out-of-channel flood discharge process data, breaking through the limitations of traditional methods that can only calculate the peak flood discharge or have a cumbersome calculation process, and realizing the dynamic simulation of the entire process of flood return to the channel. The model can finely depict the water volume exchange process between the flood detention area and the river channel, including the formation of flood peaks, the rise and fall of water levels in the flood detention area, and the speed and flow changes of flood return to the channel, thus greatly improving the accuracy and reliability of flood return to the channel calculations. The accurate simulation of the flood return to the channel process significantly improves the scientificity and safety of flood control project design. Therefore, compared with existing flood return to the channel calculation methods, a flood return to the channel calculation method based on overflow process correction of the present invention has the following beneficial effects: 1) The flood routing method requires measured flood data from multiple sites in multiple flood events under non-out-of-channel and out-of-channel conditions. This technology innovatively proposes to correct the measured flood process with a generalized flood overflow process, only requiring the measured flood process of the flood being studied in this river section and the topography of the flood detention area, with relatively low data requirements; 2) The simplified water balance method calculates the peak flood discharge of flood return based on the total flood volume and the flood detention volume, but cannot give the flood process after flood return. This technology innovatively proposes to correct the measured flood process with a simulated flood overflow process, and the entire flood process after flood return can be obtained, and the derived flood elements are complete; 3) The cubic spline interpolation method derives the flood process after flood return according to the cubic spline interpolation theory, but the construction and solution process of the cubic spline function are complex and the calculation amount is large. This technology innovatively proposes to correct the measured flood process with a simulated flood overflow process, in which the flood overflow process is generalized according to the water volume as a triangle or a straight line, and the process mainly involves chart lookup and four arithmetic operations, with strong operability.

[0010] Preferably, step S1 includes the following steps:

[0011] Step S11: Obtain historical flood event data of the river channel;

[0012] Step S12: Identify the floodplain area based on the historical flood event data of the river channel to obtain the floodplain area data of the river channel;

[0013] Step S13: Conduct topographic survey of the floodplain area based on the floodplain area data of the river channel to obtain the topographic data of the floodplain area;

[0014] Step S14: Use the topographic data of the floodplain area to build a digital elevation model of the terrain, generating a digital elevation model of the river channel floodplain terrain;

[0015] Step S15: Determine the flood overflow elevation for the historical flood event data of the river channel through the digital elevation model of the river channel floodplain terrain, generating flood overflow elevation data;

[0016] Step S16: Use the digital elevation model of the river channel floodplain terrain to analyze the topographic characteristics of the flood detention area for the flood overflow elevation data, and draw the water level - volume curve of the flood detention area, generating the water level - volume curve parameters of the flood detention area.

[0017] Based on the identified floodplain area, the present invention conducts topographic survey to obtain fine topographic data, which reflect the geomorphic characteristics of the actual flood - affected area. Further, using these topographic data to establish a digital elevation model of the river channel floodplain terrain, which can display the complex terrain of the river channel in a high - precision three - dimensional form. Analyzing the historical flood event data can accurately determine the flood overflow elevation, which is a key parameter for constructing the river - flood detention area exchange simulation model and directly relates to the accuracy of the model's simulation of the flood out - of - channel and in - channel processes. Through the digital elevation model, the topographic characteristics of the flood detention area can also be analyzed, and then the water level - volume curve of the flood detention area can be drawn, which reflects the relationship between the water storage capacity and water level of the flood detention area.

[0018] Preferably, step S16 includes the following steps:

[0019] Step S161: Use the digital elevation model of the river channel floodplain terrain to analyze the flood inundation range at different elevations for the flood overflow elevation data, obtaining the flood inundation boundary data at different elevations;

[0020] Step S162: Identify the inundated area of the flood detention area based on the flood inundation boundary data at different elevations, generating the topographic characteristic parameter - inundated area data of the flood detention area at different elevations;

[0021] Step S163: Use the digital elevation model of the river channel floodplain terrain to discretize the topographic characteristic parameter - inundated area data of the flood detention area at different elevations, generating the micro - unit data of the flood detention area;

[0022] Step S164: Calculate the micro-unit inundation depth of the flood detention area micro-unit data through the flood overflow elevation data to obtain the micro-unit inundation depth data;

[0023] Step S165: Divide the water level intervals according to the micro-unit inundation depth data to obtain the flood detention area water level interval data;

[0024] Step S166: Calculate the micro-unit storage capacity of the flood detention area micro-unit data based on the flood detention area water level interval data to obtain the micro-unit storage capacity data;

[0025] Step S167: Accumulate the storage capacity of the flood detention area according to the micro-unit storage capacity data, and draw the water level - volume curve according to the flood detention area water level interval data to obtain the flood detention area water level - volume curve parameters.

[0026] Based on the flood inundation boundary data at different elevations, the present invention can accurately identify the inundated area of the flood detention area at different flood water levels, and generate the topographic feature parameters, that is, the inundated area data of the flood detention area at different elevations. The digital elevation model is used to discretize the flood detention area, and the continuous flood detention area is divided into multiple micro-units. This refined processing method provides smaller calculation units for subsequent inundation depth and storage capacity calculations, improving the calculation accuracy. Combining the flood overflow elevation data to calculate the inundation depth of these micro-units can accurately obtain the inundation depth of each micro-unit at a specific flood water level. By dividing the micro-unit inundation depth data into water level intervals, the inundation situation under different water level intervals can be obtained, which provides the necessary grading information for constructing the water level - volume curve. Based on the water level interval data, further calculate the storage capacity of each micro-unit, and accumulate these micro-unit storage capacity data, and finally draw the water level - volume curve of the flood detention area. This curve intuitively shows the relationship between the water level and the water storage capacity of the flood detention area.

[0027] Preferably, step S2 includes the following steps:

[0028] Step S21: Obtain the historical flood data of overbank flow measured;

[0029] Step S22: Perform data preprocessing on the historical flood data of overbank flow measured to generate the standard flood data of overbank flow measured;

[0030] Step S23: Perform historical flood time series processing on the standard flood data of overbank flow measured to generate the time series flood data of overbank flow measured;

[0031] Step S24: Perform river channel flood process clustering according to the time series flood data of overbank flow measured to obtain the river channel measured flood discharge process data and the river channel measured flood water level process data respectively.

[0032] The present invention clusters the flood processes in the river channel based on the measured data of overbank floods in time series, which can effectively decompose the complex flood processes to obtain the measured flood discharge process data and the measured flood water level process data in the river channel respectively. This decomposition method enables in-depth analysis of the flow rate and water level respectively, and more clearly reveals the evolution characteristics of floods in the river channel. The flow process data reflects the changes in the flow velocity and water volume of floods in the river channel, while the water level process data reflects the rise and fall of the flood water level. The combination of the two can comprehensively describe the dynamic process of floods. It realizes the effective utilization of historical overbank flood data, extracts key flood process data, can make more full use of historical flood information, avoids over-reliance on a single flood event, and thus more comprehensively reflects the flood characteristics of the river channel.

[0033] Preferably, step S3 includes the following steps:

[0034] Step S31: Use the flood overflow elevation data as the overflow water level threshold of the overflow section, and identify the overflow time points by using the measured flood water level process data in the river channel to obtain the river channel flood overflow time point data;

[0035] Step S32: Construct a water balance finite volume mathematical model according to the river channel flood overflow time point data, the measured flood water level process data in the river channel, and the water level - volume curve parameters of the flood detention area to obtain a river channel - flood detention area exchange simulation model;

[0036] Step S33: Use the river channel - flood detention area exchange simulation model to simulate the water balance of the out - of - channel and in - channel flood overflow processes for the measured flood discharge process data in the river channel to obtain the river channel overflow discharge process data.

[0037] The present invention combines the river channel flood overflow time point data, the measured flood water level process data in the river channel, and the water level - volume curve parameters of the flood detention area to construct a water balance finite volume mathematical model and form a river channel - flood detention area exchange simulation model. This model comprehensively considers the dynamic relationship among the river channel water level, the water storage capacity of the flood detention area, and the flood overflow water volume, and realizes the accurate simulation of the exchange process of floods between the river channel and the flood detention area. This not only improves the accuracy and reliability of the flood return - to - channel calculation, but also provides a more scientific basis for flood control project design and flood warning, thus better protecting the safety of people's lives and property.

[0038] Preferably, step S33 includes the following steps:

[0039] Step S331: Calculate the out - of - channel flood peak according to the measured flood discharge process data in the river channel to obtain the out - of - channel flood peak discharge data; among them, the out - of - channel flood peak calculation formula is as follows:

[0040] ;

[0041] Among them, is the peak discharge out of the channel, is the water volume out of the channel, is the occurrence time of the measured peak flood, is the time when the measured flood level rises to the overflow elevation;

[0042] Step S332: Calculate the inflow discharge according to the measured flood discharge process data of the river channel to obtain the inflow discharge data corresponding to the flood overflow elevation; among them, the calculation formula for the inflow discharge corresponding to the flood overflow elevation is as follows:

[0043] ;

[0044] Among them, is the inflow discharge corresponding to the overflow elevation, is the volume corresponding to the overflow elevation, is the end time of this round of flood, is the time when the measured flood level recedes to the overflow elevation;

[0045] Step S333: Calculate the peak inflow discharge through the peak discharge out of the channel data and the inflow discharge data corresponding to the flood overflow elevation to obtain the peak inflow discharge data corresponding to the flood overflow elevation; among them, the calculation formula for the inflow discharge corresponding to the overflow elevation is as follows:

[0046] ;

[0047] Among them, is the peak inflow discharge, is the water volume out of the channel, is the volume corresponding to the overflow elevation, is the inflow discharge corresponding to the overflow elevation;

[0048] Step S334: Generalize the flood overflow discharge process according to the river channel flood overflow time point data, peak discharge out of the channel data, inflow discharge data corresponding to the flood overflow elevation, and peak inflow discharge data to obtain the river channel overflow discharge process data.

[0049] By analyzing the measured flood flow process data of the river channel, the present invention can calculate key flood characteristic parameters, such as the out-of-channel peak flood flow, the in-channel flow, and the in-channel peak flood flow. The out-of-channel peak flood flow reflects the maximum flow during the out-of-channel process of the flood and is an important indicator for evaluating the impact of the flood on the downstream. The in-channel flow represents the flow of the flood returning from the flood detention area to the river channel and is crucial for understanding the flood routing process. The in-channel peak flood flow is the maximum flow during the in-channel process of the flood, which reflects the release rate of the flood regulation capacity of the flood detention area. Using the provided calculation formulas, these flood characteristic parameters can be accurately calculated, providing a reliable data basis for the subsequent generalization of the flood overflow flow process. These formulas fully consider the water balance relationship and time factors during the out-of-channel and in-channel processes of the flood and can more accurately reflect the dynamic change process of the flood. By comprehensively analyzing the data of the out-of-channel peak flood flow, the in-channel flow, and the in-channel peak flood flow, the flood overflow flow process can be generalized, and a simplified mathematical model can be established to describe the exchange process of the flood between the river channel and the flood detention area. This generalization method can effectively simplify the calculation process while retaining key flood characteristic information.

[0050] Preferably, step S4 is specifically as follows:

[0051] Perform flow process superposition correction based on the river channel overflow flow process data and the measured flood flow process data of the river channel to obtain the river channel flood flow process data after routing.

[0052] The present invention superimposes and corrects the river channel overflow flow process data and the measured flood flow process data of the river channel. Substantially, it adds the flow of the flood overbank overflow part to the measured flood flow process to obtain the river channel flood flow process data after routing, distinguishing the true flow change situation of the flood in the river channel from the influence of the overbank overflow flow, so as to more accurately reflect the evolution process of the flood in the river channel. Through fine flow process superposition correction, the simulation of the river channel flood flow process after routing is realized, improving the reliability and scientificity of the flood routing calculation. The finally obtained river channel flood flow process data after routing provides a more accurate basis for flood control project design and flood risk assessment, and its results have important practical significance for enhancing flood control and disaster reduction capabilities.

[0053] Preferably, the present invention also provides a flood routing simulation system based on overflow process correction, which executes the flood routing calculation method based on overflow process correction as described above. The flood routing simulation system based on overflow process correction includes:

[0054] The flood detention area terrain analysis module is used to obtain historical flood event data of the river channel; identify the floodplain area based on the historical flood event data of the river channel to obtain the floodplain area data of the river channel flood; determine the flood overflow elevation for the floodplain area data of the river channel flood to generate flood overflow elevation data; draw the water level - volume curve of the flood detention area based on the flood overflow elevation data to generate the water level - volume curve parameters of the flood detention area;

[0055] The real - time flood data processing module is used to obtain the historical measured flood data of the floodplain; perform historical flood time - series processing on the historical measured flood data of the floodplain to obtain the river channel measured flood discharge process data and the river channel measured flood water level process data respectively;

[0056] The flood discharge process simulation module is used to construct a river channel - flood detention area exchange simulation model based on the flood overflow elevation data, the water level - volume curve parameters of the flood detention area, and the river channel measured flood water level process data; use the river channel - flood detention area exchange simulation model to perform the water balance simulation of the out - of - channel and in - channel flood processes on the river channel measured flood discharge process data to obtain the river channel overflow discharge process data;

[0057] The flood return - to - channel correction module is used to correct the river channel measured flood discharge process data through the river channel overflow discharge process data to obtain the corrected river channel flood discharge process data for the return - to - channel flood; use this process as the basis for the design of the return - to - channel flood. Description of the Drawings

[0058] Figure 1 It is a schematic diagram of the step - by - step process of a flood return - to - channel calculation method based on overflow process correction according to the present invention;

[0059] Figure 2 is Figure 1 a detailed implementation step - by - step schematic diagram of step S2 in;

[0060] Figure 3 is Figure 1 a detailed implementation step - by - step schematic diagram of step S3 in;

[0061] Figure 4 is a water level - volume curve graph of the flood detention basin;

[0062] Figure 5 is a generalized graph of the flood overflow process;

[0063] Figure 6 is a flood process graph after return - to - channel;

[0064] The realization, functional features, and advantages of the object of the present invention will be further described in conjunction with the embodiments and with reference to the drawings. Detailed Embodiments

[0065] The technical method of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0066] In addition, the accompanying drawings are only schematic illustrations of the present invention and are not necessarily drawn to scale. The same reference numerals in the drawings represent the same or similar parts, and thus repeated descriptions thereof will be omitted. Some of the block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities. The functional entities can be implemented in software form, or in one or more hardware modules or integrated circuits, or in different networks and / or processor methods and / or microcontroller methods.

[0067] It should be understood that although terms such as "first" and "second" may be used here to describe various units, these units should not be limited by these terms. These terms are only used to distinguish one unit from another. For example, without departing from the scope of the exemplary embodiments, the first unit can be called the second unit, and similarly the second unit can be called the first unit. The term "and / or" used here includes any and all combinations of one or more of the listed related items.

[0068] To achieve the above object, please refer to Figures 1 to 3 , the present invention provides a flood channeling calculation method based on overflow process correction, including the following steps:

[0069] Step S1: Obtain historical flood event data of the river channel; identify the floodplain area according to the historical flood event data of the river channel to obtain the floodplain area data of the river channel flood; determine the flood overflow elevation for the floodplain area data of the river channel to generate flood overflow elevation data; draw the water level - volume curve of the flood detention area according to the flood overflow elevation data to generate the water level - volume curve parameters of the flood detention area;

[0070] Step S2: Obtain the measured historical flood data of the floodplain; perform historical flood time - series processing on the measured historical flood data of the floodplain to obtain the measured flood discharge process data of the river channel and the measured flood water level process data of the river channel respectively;

[0071] Step S3: Construct a river channel - flood detention area exchange simulation model according to the flood overflow elevation data, the water level - volume curve parameters of the flood detention area, and the measured flood water level process data of the river channel; use the river channel - flood detention area exchange simulation model to perform water - volume balance simulation on the out - of - channel and in - channel flood process for the measured flood discharge process data of the river channel to obtain the river channel overflow discharge process data;

[0072] Step S4: Use the river channel overflow flow process data to correct the measured flood flow process data of the river channel to obtain the corrected flood flow process data of the river channel after flood return to the channel; use this process as the basis for the design of flood return to the channel.

[0073] In the embodiment of the present invention, the flood return to the channel calculation method based on the overflow process correction includes the following steps:

[0074] Step S1: Obtain the historical flood event data of the river channel; identify the floodplain area based on the historical flood event data of the river channel to obtain the floodplain area data of the river channel; determine the flood overflow elevation for the floodplain area data of the river channel to generate the flood overflow elevation data; draw the water level - volume curve of the flood detention area based on the flood overflow elevation data to generate the water level - volume curve parameters of the flood detention area.

[0075] In the embodiment of the present invention, collect the records of flood events that have occurred in the target river section, including information such as the time of flood occurrence, peak flow, water level, and inundation range. Based on these historical data, use a method combining remote sensing images and digital elevation models (DEMs) to identify the floodplain area. Specifically, select high - resolution remote sensing images before and after multiple flood events, such as satellite images with a resolution better than 1 meter. By comparing and analyzing the changes in the water body range in the images before and after the flood, combined with DEM data, the inundation range of each flood event can be extracted. For each grid cell in the floodplain area, such as a 1 - meter - by - 1 - meter cell, combine the DEM data to extract its elevation value. Compare the water level records when the grid cell is inundated in multiple flood events with the elevation value of the grid cell, and take the minimum value of all the water level records when inundated as the flood overflow elevation of the grid cell. Calculate the flood overflow elevation of all grid cells in turn to obtain the flood overflow elevation data of the floodplain area of the river section. For example, if the elevation of a grid cell is 150 meters and it is inundated at water levels of 151 meters, 152 meters, and 151.5 meters in three flood events, then the flood overflow elevation of this grid cell is 151 meters. Set a series of water level values, for example, from the lowest elevation to the highest elevation, and set a water level value every 0.5 meters. For each set water level value, find all grid cells in the DEM data that are lower than this water level value, and count the total area of these grid cells as the inundation area at this water level. Then, use the elevation values of these grid cells and the set water level value to calculate the water storage capacity of each grid cell. Accumulate the water storage capacities of all grid cells to obtain the total water storage capacity at this water level. Finally, plot a curve of a series of water level values and their corresponding water storage capacities to obtain the water level - volume curve parameters of the flood detention area.

[0076] Step S2: Obtain the historical measured flood data of the floodplain; perform historical flood time series processing on the historical measured flood data of the floodplain to obtain the measured flood discharge process data of the river channel and the measured flood water level process data of the river channel respectively;

[0077] In the embodiments of the present invention, the flood data actually observed during historical floodplain flood events in the target river section are collected, including flow rate and water level data. These data are usually observed by hydrological stations, and it is necessary to ensure the accuracy and reliability of the data and perform necessary quality control. Arrange the flow rate data in chronological order to form a flow rate hydrograph. For example, during a certain flood event, the hydrological station observes the flow rate at 8 am every day, and the series of flow rate data obtained are: 200 cubic meters per second on the first day, 500 cubic meters per second on the second day, 1000 cubic meters per second on the third day, 800 cubic meters per second on the fourth day, and 400 cubic meters per second on the fifth day. Arrange these data in chronological order to obtain the flow rate hydrograph of this flood event. During the above flood event, the hydrological station observes the water level at 8 am every day, and the series of water level data obtained are: 149 meters on the first day, 150.5 meters on the second day, 152 meters on the third day, 151 meters on the fourth day, and 150 meters on the fifth day. Arrange these data in chronological order to obtain the water level hydrograph of this flood event. Through time series processing, the original measured data are converted into time series data reflecting the flood evolution process, providing a basis for subsequent simulation analysis. The interval time of time series processing depends on the data sampling frequency, such as every hour, every 6 hours, daily, etc. If the original data sampling intervals are inconsistent, interpolation processing is required to unify them to a fixed time interval.

[0078] Step S3: Construct a river channel - flood detention area exchange simulation model based on the flood overflow elevation data, flood detention area water level - volume curve parameters, and the measured flood water level process data of the river channel; use the river channel - flood detention area exchange simulation model to perform an out - of - channel and in - channel flood process water balance simulation on the measured flood discharge process data of the river channel to obtain the river channel overflow discharge process data;

[0079] In the embodiment of the present invention, when the river water level is higher than the flood overflow elevation at the corresponding position of the flood detention area, the flood starts to overflow out of the river channel and enter the flood detention area; when the river water level is lower than the water level of the flood detention area, the flood water in the detention area flows back into the river channel (i.e., into the channel). Taking a fixed time step (e.g., 1 hour) as a unit, the measured flood water level process data of the river channel is traversed. According to the measured flood water level process data of the river channel, during the rising period of the measured flood water level of the river channel, when the river water level rises to the flood overflow elevation, the flood starts to overflow out of the river channel and enter the flood detention area. By the time of the measured flood peak water level, the river flood water level reaches the maximum, and the flood stops overflowing out of the river channel. During this period, the out-of-channel flow first increases from 0 and then decreases to 0; the out-of-channel water volume of this flood can be obtained by looking up the water level - volume curve of the flood detention area from the measured flood peak water level; according to the time point when the flood starts to overflow out of the channel, the time point when the flood peak appears, and the out-of-channel water volume, the out-of-channel flood flow process during the simulation generalization period is simulated as an isosceles triangle that first increases and then decreases to obtain the out-of-channel flood peak flow. According to the measured flood water level process data of the river channel, during the falling period of the measured flood water level of the river channel, starting from the measured flood peak water level, when the river water level is lower than the water level of the flood detention area, the flood water in the detention area starts to flow into the river channel until the flood ends. During this period, the in-channel flow first increases from 0 and then decreases to 0; according to the principle of water volume balance, water volume exchange occurs between the river channel and the flood detention area, and the in-channel flood volume is equal to the out-of-channel flood volume; according to the time point when the flood peak appears, the time when the measured flood water level recedes to the overflow elevation, the end time of this round of flood, and the in-channel water volume, the in-channel flood flow process during the simulation generalization period is simulated as first increasing and then decreasing to obtain the in-channel flow corresponding to the overflow elevation and the in-channel flood peak flow. Thus, the out-of-channel flood flow process and the in-channel flood flow process constitute the river channel overflow flow process data in the entire flood process.

[0080] Step S4: The measured flood flow process data of the river channel is corrected for flood backflow through the river channel overflow flow process data to obtain the corrected river channel flood flow process data for backflow; this process is used as the basis for the design of backflow flood.

[0081] After the construction of the dike, the flood that originally overflowed the river channel returns to the river channel because it cannot flow out of the channel. In the embodiment of the present invention, the measured flood flow process data of the river channel and the overflow flow process data of the river channel are aligned in time. For each time step, during the period when the measured flood water level of the river channel rises, the measured flood flow at that moment is added to the overflow flow at that moment to obtain the flood flow after slot return correction at that moment; during the period when the measured flood water level of the river channel drops, the measured flood flow at that moment is subtracted from the overflow flow at that moment to obtain the flood flow after slot return correction at that moment. At each time step, the measured river channel flow is added to or subtracted from the flow that overflows into the flood detention area at that time step, that is, the river channel flow after slot return at that time step is obtained. For example, during the period when the measured flood water level rises, at a certain time step, the measured river channel flow is 200 cubic meters per second and the overflow flow is 50 cubic meters per second, then the river channel flow after slot return is 250 cubic meters per second; during the period when the measured flood water level drops, at a certain time step, the measured river channel flow is 180 cubic meters per second and the overflow flow is 30 cubic meters per second, then the river channel flow after slot return is 150 cubic meters per second. By calculating the entire flood process, the complete flood flow process data of the river channel after slot return correction is obtained. This data reflects the change process of the river channel flood flow after increasing the overbank flood volume, and can more accurately reflect the flood discharge capacity of the river channel after the construction of the dike, providing a more reliable basis for the design of the slot return flood. For example, according to the flood flow process data after slot return correction, the flood control water level of the river channel flood control project can be re-evaluated, or the reservoir operation plan can be optimized.

[0082] Preferably, step S1 includes the following steps:

[0083] Step S11: Obtain the historical flood event data of the river channel;

[0084] Step S12: Identify the flood overbank area according to the historical flood event data of the river channel to obtain the river channel flood overbank area data;

[0085] Step S13: Conduct topographic survey of the overbank area based on the river channel flood overbank area data to obtain the overbank area topographic data;

[0086] Step S14: Use the overbank area topographic data to build a topographic digital elevation model to generate a river channel overbank topographic digital elevation model;

[0087] Step S15: Determine the flood overflow elevation for the historical flood event data of the river channel through the river channel overbank topographic digital elevation model to generate flood overflow elevation data;

[0088] Step S16: Use the river channel overbank topographic digital elevation model to analyze the topographic characteristics of the flood detention area for the flood overflow elevation data, and draw the water level - volume curve of the flood detention area to generate the water level - volume curve parameters of the flood detention area.

[0089] In the embodiments of the present invention, for a certain river, flood event data are collected. These data include the occurrence time, peak flow, peak water level, flood hydrograph of each flood, as well as the measured data of relevant hydrological stations, etc. For example, the hourly flow data of the key upstream hydrological stations and the hourly water level data of multiple hydrological stations along the river can be collected during each flood. Remote sensing images covering the study area before and after the occurrence of flood events are collected, and high-resolution satellite images are preferably selected, such as satellite image data with a resolution better than 1 meter. For each flood event, at least one image before the flood and one image during or after the flood are required. The obtained remote sensing images are preprocessed, including geometric correction, radiometric correction, etc., to ensure the quality and comparability of the image data. Then, using supervised classification or unsupervised classification methods, combined with visual interpretation, water body information is extracted from the images before and after the flood. By comparing the changes in the water body range in the images before and after the flood, the inundation range of each flood event can be determined. The superimposed analysis of all the identified flood inundation ranges is carried out to obtain the maximum inundation range affected by historical flood events, which is the floodplain area of this river section. For example, three flood events respectively inundated three areas A, B, and C, where the area of area A is 30 square kilometers, the area of area B is 40 square kilometers, the area of area C is 25 square kilometers, and there are partial overlaps among the three areas. Through the superimposed analysis, the total coverage range of the three areas is obtained, assumed to be 60 square kilometers, and this 60-square-kilometer area is the floodplain area of this river section. The output result is in the vector data format. High-precision measuring instruments are used. For example, a real-time kinematic differential positioning system (RTK) with a measurement accuracy reaching the centimeter level is used for on-site measurement. According to the area of the floodplain area and the terrain complexity, measurement control points and elevation points are reasonably arranged. For example, within the floodplain area, no less than 25 control points are arranged per square kilometer, and the point position accuracy of the control points needs to be better than 5 centimeters, and the elevation accuracy needs to be better than 10 centimeters. Based on the control points, elevation points are arranged at a certain density. For example, an elevation point is arranged every 50 meters to obtain the undulation changes of the terrain in detail. During the measurement process, the plane coordinates and elevation information of each measurement point need to be recorded in detail, and the quality of the measurement data needs to be ensured. For example, for each elevation point, its X coordinate, Y coordinate, and Z coordinate (elevation value) are recorded, and multiple measurements are carried out, and the average value is taken as the final elevation value. Through on-site measurement, high-precision terrain data covering the entire floodplain area can be obtained. The elevation point data measured are imported into the geographic information system software and spatially located according to their plane coordinates. Then, a suitable spatial interpolation method, such as the inverse distance weighting method or the Kriging interpolation method, is selected to generate a continuous surface elevation model. For example, the Kriging interpolation method is selected, and a suitable variogram model and parameters are set according to the spatial distribution characteristics of the measured elevation data. Assume that the number of measured elevation points is 1000 and the coverage area is 50 square kilometers.Based on the spatial distribution of these elevation points, a spherical model is selected as the variogram model, and parameters such as nugget value, sill value, and range are obtained through data fitting. Using these parameters, spatial interpolation is performed on the entire floodplain area to generate a digital elevation model in raster format. For example, a DEM with a resolution of 1 meter by 1 meter can be generated, that is, each raster cell represents an area of 1 meter by 1 meter on the actual ground, and the value of the raster cell represents the average elevation of this area. The generated DEM needs to be subjected to quality assessment. For example, the accuracy of the DEM can be verified using some measured elevation points that did not participate in the modeling to ensure that the accuracy of the DEM meets the requirements of subsequent analysis. For each DEM raster cell in the floodplain area, such as a 1-meter by 1-meter cell, according to its spatial position, it is associated with the historical flood event data. For each raster cell, find all the flood event records that submerged this cell in history. For example, a certain raster cell was submerged in three historical flood events, and the corresponding flood water levels were 165.2 meters, 166.5 meters, and 165.8 meters respectively. Compare these flood water level records with the elevation value of this raster cell, and take the minimum value among all the flood water level records that submerged this cell as the flood overflow elevation of this raster cell. Calculate the flood overflow elevations of all raster cells in turn to obtain the flood overflow elevation data covering the entire floodplain area. Store the flood overflow elevation data in the form of raster data, and the value of each raster cell represents the flood overflow elevation at this location. For example, a raster data with the same resolution and range as the DEM data can be generated, where the value of each raster cell is the flood overflow elevation at that place. Consider the floodplain area as a whole flood detention area, and calculate the inundated area and the corresponding water storage volume at different water levels according to the DEM data. Set a series of water level values, for example, starting from the lowest elevation value of the DEM, increasing the water level gradually at an interval of 0.1 meter until the highest elevation value of the DEM. For each set water level value, find all the raster cells in the DEM data whose elevation values are lower than this water level value. Statistically calculate the total area of these raster cells as the inundated area at this water level. Then, calculate the water storage volume of each inundated raster cell, and the calculation method is: the area of the raster cell (such as 1 square meter) multiplied by the difference between the elevation value of this raster cell and the set water level value. Accumulate the water storage volumes of all inundated raster cells to obtain the total water storage volume at this water level. Plot all the set water level values and their corresponding inundated areas and water storage volumes respectively into charts, that is, obtain the water level-inundated area curve and water level-volume curve of the flood detention area. For example, a curve with the water level on the abscissa and the water storage volume on the ordinate can be plotted, and this curve clearly shows the water storage capacity of the flood detention area at different water levels.

[0090] Preferably, step S16 includes the following steps:

[0091] Step S161: Analyze the flood inundation range data of different elevations using the digital elevation model of the floodplain terrain to obtain the flood inundation boundary data of different elevations;

[0092] Step S162: Identify the inundated area of the flood detention area based on the flood inundation boundary data of different elevations, and generate the terrain characteristic parameter - the inundated area data of the flood detention area at different elevations;

[0093] Step S163: Discretize the flood detention area using the digital elevation model of the floodplain terrain for the terrain characteristic parameter - the inundated area data of the flood detention area at different elevations to generate the micro-unit data of the flood detention area;

[0094] Step S164: Calculate the submergence depth of the micro-units of the flood detention area through the flood overflow elevation data to obtain the submergence depth data of the micro-units;

[0095] Step S165: Divide the water level intervals according to the submergence depth data of the micro-units to obtain the water level interval data of the flood detention area;

[0096] Step S166: Calculate the storage capacity of the micro-units of the flood detention area based on the water level interval data of the flood detention area to obtain the storage capacity data of the micro-units;

[0097] Step S167: Accumulate the storage capacity of the flood detention area according to the storage capacity data of the micro-units, and draw the water level - volume curve based on the water level interval data of the flood detention area to obtain the water level - volume curve parameters of the flood detention area.

[0098] In the embodiments of the present invention, a series of different elevation values are selected as the benchmarks for inundation analysis. These elevation values should cover the flood water level range occurring within the study area. For example, starting from the lowest flood overflow elevation, an elevation value is selected every 0.5 meters until it covers above the historical highest flood level. For each selected elevation value, in the DEM data, all raster cells below this elevation value are marked as inundated areas, and all raster cells above this elevation value are marked as non-inundated areas. Then, the boundary line between the inundated area and the non-inundated area is extracted, which is the flood inundation boundary corresponding to this elevation value. For example, when the selected elevation value is 165 meters, in the DEM, all raster cells with elevation values lower than 165 meters are identified as inundated areas, and the remaining raster cells are non-inundated areas. The boundary line between the inundated area and the non-inundated area is the flood inundation boundary corresponding to the 165-meter elevation. The flood inundation boundaries corresponding to all elevation values are output in the form of vector data. For example, it is output in the Shapefile format, recording the spatial location information of each boundary line and the corresponding elevation value attribute. For the flood inundation boundary corresponding to each elevation value, calculate the area of the polygon enclosed by it. This area is the inundation area of the flood detention area corresponding to this elevation value. For example, for the flood inundation boundary corresponding to the 165-meter elevation, use the area calculation tool in the geographic information system software to calculate the area of the polygon enclosed by this boundary. Assuming it is 5 square kilometers, then the inundation area of the flood detention area corresponding to the 165-meter elevation is 5 square kilometers. Similarly, for the flood inundation boundary corresponding to the 165.5-meter elevation, the calculated inundation area is 6.2 square kilometers; for the 166-meter elevation, the calculated inundation area is 7.5 square kilometers. Record all elevation values and their corresponding inundation area data of the flood detention area in the form of a table. For example, a table with two columns of data can be generated. The first column is the elevation value, and the second column is the inundation area of the flood detention area corresponding to this elevation value. The flood detention area is divided into multiple small and regular grid cells, i.e., micro-units. The size of the micro-units can be determined according to the resolution of the DEM and the requirements of calculation accuracy. For example, grid cells of 10 meters by 10 meters can be adopted. For each micro-unit, according to its spatial location, determine whether it is located within the flood detention area. The specific determination method is: perform a spatial overlay analysis on the center point coordinates of the micro-unit and the flood detention area inundation boundaries at different elevations. If the center point of the micro-unit is located inside the inundation boundary at a certain elevation, then this micro-unit belongs to the flood detention area corresponding to this elevation. For example, if the center point of a certain micro-unit is located inside the inundation boundary at the 165-meter elevation, then this micro-unit belongs to the flood detention area corresponding to the 165-meter elevation. Record the information of all micro-units belonging to the flood detention area, including the micro-unit number, center point coordinates, and the elevation to which it belongs, etc. For example, a unique ID number can be assigned to each micro-unit, and the X and Y coordinates of its center point, as well as the minimum inundation elevation to which this micro-unit belongs, are recorded.For each micro-unit of the flood detention area, according to the minimum inundation elevation it belongs to, find the corresponding flood overflow elevation value of this micro-unit in the flood overflow elevation data. Then, subtract the flood overflow elevation from the minimum inundation elevation to obtain the inundation depth of this micro-unit. For example, a certain micro-unit belongs to the flood detention area corresponding to the elevation of 166 meters, and its corresponding flood overflow elevation is 165.2 meters. Then the inundation depth of this micro-unit is 166 meters minus 165.2 meters, that is, 0.8 meters. Another micro-unit belongs to the flood detention area corresponding to the elevation of 165.5 meters, and its corresponding flood overflow elevation is 164.8 meters. Then the inundation depth of this micro-unit is 165.5 meters minus 164.8 meters, that is, 0.7 meters. According to the inundation depth values of all micro-units, determine the division range and interval of the water level intervals. For example, between the minimum inundation depth value and the maximum inundation depth value, the water level intervals can be divided at an interval of 0.1 meters. Record the information of all water level intervals, including the upper and lower limit values of the intervals. For example, a water level interval table can be generated, which contains three columns of data: interval number, interval lower limit, and interval upper limit. This table clearly defines the range of each water level interval. For each micro-unit, according to the water level interval it belongs to, calculate the water storage volume of this micro-unit within this water level interval, that is, the micro-unit reservoir capacity. For example, the area of a certain micro-unit is 100 square meters (10 meters by 10 meters), and the water level interval it belongs to is 0.5 - 0.6 meters. Then the reservoir capacity of this micro-unit within this water level interval is calculated as: the micro-unit area (100 square meters) multiplied by the height of the water level interval (0.1 meters), and the result is 10 cubic meters. The area of another micro-unit is also 100 square meters, and the water level interval it belongs to is 1.0 - 1.1 meters, then its reservoir capacity is also 10 cubic meters. For each water level interval, accumulate the reservoir capacities of all flood detention area micro-units within this water level interval to obtain the total reservoir capacity of the flood detention area corresponding to this water level interval. Associate and store the upper limit value of each water level interval as the water level value with its corresponding total reservoir capacity of the flood detention area to form water level - volume data. Using the water level value as the abscissa and the total reservoir capacity of the flood detention area as the ordinate, draw the water level - volume curve of the flood detention area. Then, adopt a suitable mathematical method, such as polynomial fitting, to fit the water level - volume curve to obtain the water level - volume curve parameters of the flood detention area, such as polynomial coefficients.

[0099] Preferably, step S2 includes the following steps:

[0100] Step S21: Obtain historical measured flood data of floodplain inundation;

[0101] Step S22: Perform data preprocessing on the historical measured flood data of floodplain inundation to generate standard measured flood data of floodplain inundation;

[0102] Step S23: Perform historical flood time series processing on the standard measured flood data of floodplain inundation to generate time series measured flood data of floodplain inundation;

[0103] Step S24: Cluster the measured flood data of the floodplain according to the time series to obtain the measured flood flow process data and the measured flood water level process data of the river channel respectively.

[0104] As an example of the present invention, refer to Figure 2 shown, which is Figure 1 a schematic diagram of the detailed implementation steps of step S2 in

[0105] Step S21: Obtain the historical measured flood data of the floodplain;

[0106] In the embodiment of the present invention, data is obtained by contacting the hydrological management department and consulting hydrological yearbooks, databases or relevant archival materials. For example, if there have been three floodplain flood events in a certain river section in history, the measured data of these three flood events can be applied for from the hydrological management department responsible for this river section. Usually, the hydrological station will record the hourly or daily flow and water level data during the flood. For example, in the first flood event, the hydrological station recorded the hourly flow and water level data from the start to the end of the flood, including: start time, end time, hourly flow value and water level value; in the second flood event, the daily flow and water level data were recorded; in the third flood event, the flow and water level data every 3 hours were recorded. During the data collection process, it is necessary to ensure the integrity and accuracy of the data. For missing data, reasonable estimation or interpolation can be carried out according to the existing data and relevant hydrological materials. For example, if part of the hourly flow data is missing in a certain flood event, interpolation can be carried out using a hydrological model based on the flow data of the previous and subsequent periods and the water level data of this period. At the same time, it is also necessary to verify the data source and observation method to ensure the reliability of the data.

[0107] Step S22: Perform data preprocessing on the historical measured flood data of the floodplain to generate standard measured flood data of the floodplain;

[0108] In the embodiments of the present invention, integrity checks are performed on the data to identify and handle missing values. For example, if data for some time periods is missing during a flood event, interpolation can be performed based on the data of the time periods before and after that time period using methods such as linear interpolation and nearest neighbor interpolation. For missing data that cannot be reasonably interpolated, it is marked as an invalid value. Secondly, outlier detection is performed on the data and processed. For example, methods such as box plots and the 3σ principle are used to identify outliers, and the identified outliers are corrected or removed. For example, if the flow data at a certain moment significantly deviates from the flow data of the time periods before and after, and does not match the water level data at that time, it is an outlier and needs to be corrected or removed according to the actual situation. Then, format conversion is performed on the data to unify the data into the same format. For example, data from different sources is unified into the same unit, time format, and data structure. For example, the flow unit is unified to cubic meters per second, the water level unit is unified to meters, the time format is unified to year-month-day hour:minute:second, and the data structure is unified to a time series data table, where each row in the table represents a time step and each column represents a variable (flow or water level).

[0109] Step S23: Perform historical flood time series processing on the standard floodplain flood measured data to generate time series floodplain flood measured data;

[0110] In the embodiments of the present invention, the target time step for time series processing is determined. For example, 1 hour can be selected as the target time step, or other time steps can be selected according to actual needs, such as 30 minutes or 3 hours. Then, the start time of time series processing is determined. For example, the earliest start time among all flood events can be selected as the unified start time. According to the target time step and the start time, interpolation or downsampling is performed on the data. For example, if the original data is recorded hourly and the target time step is 3 hours, then downsampling is required, and a data point is selected every 3 hours. If the original data is recorded daily and the target time step is 1 hour, then interpolation is required. For example, using the linear interpolation method, the flow and water level values per hour are estimated based on the daily flow and water level data. If the recording time points of the original data are not exactly the same, then according to the unified start time and time step, the data needs to be resampled and interpolated. For example, if a certain time point is recorded in some flood events and not recorded in other flood events, then interpolation needs to be performed based on the existing data to estimate the flow and water level values at that time point. After time series processing, time series floodplain flood measured data is generated, which is arranged according to the unified time step and start time, and there is corresponding flow and water level data for each time step.

[0111] Step S24: Perform river channel flood process clustering based on the time series floodplain flood measured data to obtain river channel measured flood flow process data and river channel measured flood water level process data respectively.

[0112] In the embodiments of the present invention, a flow data column and a water level data column are extracted from the measured data of the time-series floodplain flood. For example, the data columns representing the flow and the water level are respectively extracted from the time-series data table. Then, clustering analysis is respectively performed on the flow data column and the water level data column to identify different flood processes. The K-means clustering algorithm can be used to divide the flow data into different categories according to the magnitude and change trend of the flow data, and each category represents a flood process. For example, the flow data can be divided into three categories, representing three different flood processes respectively. The first category has a small flow and a short duration; the second category has a large flow and a long duration; the third category has a flow between the two. Similarly, clustering analysis can be performed on the water level data, and the water level data can be divided into different categories according to the magnitude and change trend of the water level data. According to the clustering results, the flow data and the water level data are respectively organized into independent data sets, namely the measured river channel flood flow process data and the measured river channel flood water level process data. For example, two data tables can be generated. One data table contains the flow data of all flood processes, each row represents a time step, and each column represents the flow data of a flood process; the other data table contains the water level data of all flood processes, each row represents a time step, and each column represents the water level data of a flood process.

[0113] Preferably, step S3 includes the following steps:

[0114] Step S31: Using the flood overflow elevation data as the overflow water level threshold of the overflow section, and identifying the flood overflow time points by using the measured river channel flood water level process data to obtain the river channel flood overflow time point data;

[0115] Step S32: Constructing a water balance finite volume mathematical model according to the river channel flood overflow time point data, the measured river channel flood water level process data and the water level-volume curve parameters of the flood detention area to obtain a river channel-flood detention area exchange simulation model;

[0116] Step S33: Using the river channel-flood detention area exchange simulation model to simulate the water balance of the out-of-channel and in-channel flood overflow processes of the measured river channel flood flow process data to obtain the river channel overflow flow process data.

[0117] As an example of the present invention, referring to Figure 2 shown, it is Figure 1 a schematic diagram of the detailed implementation steps of step S3 in

[0118] Step S31: Using the flood overflow elevation data as the overflow water level threshold of the overflow section, and identifying the flood overflow time points by using the measured river channel flood water level process data to obtain the river channel flood overflow time point data;

[0119] In the embodiment of the present invention, for each river cross-section, the flood overflow elevation data obtained in step S1 is used as the overflow water level threshold for this cross-section. Using the measured river flood water level process data obtained in step S2, the starting time of floodplain inundation is identified. Specifically, the water level process data is compared with the overflow water level threshold. When the water level exceeds the threshold, this time point is recorded as the starting time of floodplain inundation.

[0120] Step S32: Construct a finite volume mathematical model of water balance based on the river flood overflow time point data, the measured river flood water level process data, and the flood detention area water level - volume curve parameters to obtain a river - flood detention area exchange simulation model;

[0121] In the embodiment of the present invention, when the river water level is higher than the flood overflow elevation at the corresponding position in the flood detention area, the flood starts to flow out of the river channel and into the flood detention area; when the river water level is lower than the water level in the flood detention area, the flood detention water body flows back into the river channel (i.e., into the channel). Among them, when the river water level rises to the measured flood peak water level, the water levels of the river channel and the flood detention area are flush, and the outflow water volume reaches the maximum, and the flood will change from outflow to inflow. The outflow water volume of this flood can be obtained by looking up the flood detention area water level - volume curve from the measured flood peak water level. There is an exchange of water volume between the river channel and the flood detention area for inflow and outflow. According to the principle of water balance, the inflow flood volume is equal to the outflow flood volume, and thus a river - flood detention area exchange simulation model is obtained.

[0122] Step S33: Use the river - flood detention area exchange simulation model to conduct a water balance simulation of the outflow and inflow flood overflow process for the measured river flood flow process data to obtain the river channel overflow flow process data.

[0123] Taking a fixed time step (e.g., 1 hour) as the unit, traverse the measured flood water level process data of the river channel. According to the measured flood water level process data of the river channel, during the rising period of the measured flood water level of the river channel, when the river channel water level rises to the flood overflow elevation, the flood begins to overflow the river channel and enter the flood detention area. By the time of the measured flood peak water level, the flood stops overflowing the river channel. During this period, the discharge out of the channel first increases from 0 and then decreases to 0; according to the time point when the flood starts to flow out of the channel, the time point when the flood peak appears, and the water volume flowing out of the channel, simulate and generalize the discharge process of the flood flowing out of the channel during this period according to an isosceles triangle that first increases and then decreases to obtain the peak discharge out of the channel. According to the measured flood water level process data of the river channel, during the falling period of the measured flood water level of the river channel, starting from the measured flood peak water level, the river channel water level is lower than the water level of the flood detention area, and the flood detention water body begins to flow into the river channel until the flood ends. During this period, the inflow into the channel first increases from 0 and then decreases to 0; according to the time point when the flood peak appears, the time when the measured flood water level recedes to the overflow elevation, the end time of this round of flood, and the water volume flowing into the channel, simulate and generalize the inflow process of the flood into the channel during this period according to a process that first increases and then decreases to obtain the inflow corresponding to the overflow elevation and the peak inflow into the channel. Thus, the discharge process of the flood flowing out of the channel and the inflow process of the flood into the channel constitute the data of the river channel overflow discharge process in the entire flood process.

[0124] Preferably, step S33 includes the following steps:

[0125] Step S331: Calculate the peak discharge out of the channel according to the measured flood discharge process data of the river channel to obtain the peak discharge out of the channel data; among them, the formula for calculating the peak discharge out of the channel is as follows:

[0126] ;

[0127] Among them, is the peak discharge out of the channel, is the water volume flowing out of the channel, is the time when the measured flood peak appears, is the time when the measured flood water level rises to the overflow elevation;

[0128] Step S332: Calculate the inflow into the channel according to the measured flood discharge process data of the river channel to obtain the inflow data corresponding to the flood overflow elevation; among them, the formula for calculating the inflow corresponding to the flood overflow elevation is as follows:

[0129] ;

[0130] Among them, is the inflow corresponding to the overflow elevation, is the volume corresponding to the overflow elevation, is the end time of this round of flood, is the time when the measured flood water level recedes to the overflow elevation;

[0131] Step S333: Calculate the incoming peak flood flow by using the outgoing peak flood flow data and the incoming flow data corresponding to the flood overflow elevation, and obtain the incoming peak flood flow data corresponding to the flood overflow elevation. The calculation formula for the incoming flow corresponding to the overflow elevation is as follows:

[0132] ;

[0133] Where, is the incoming peak flood flow, is the outgoing water volume, is the volume corresponding to the overflow elevation, is the incoming flow corresponding to the overflow elevation;

[0134] Step S334: Generalize the flood overflow flow process based on the river channel flood overflow time point data, the outgoing peak flood flow data, the incoming flow data corresponding to the flood overflow elevation, and the incoming peak flood flow data, and obtain the river channel overflow flow process data.

[0135] In the embodiment of the present invention, the required parameters are extracted from the measured river channel flood flow process data and water level process data obtained in step S2. represents the time when the measured peak flood flow appears, which can be determined by finding the time corresponding to the maximum value in the flow process data. represents the time when the measured flood water level rises to the overflow elevation, which can be determined by finding the time when the water level first reaches or exceeds the overflow elevation in the water level process data. represents the outgoing water volume, that is, the total water volume flowing from the river channel into the flood detention area during the floodplain period, which can be estimated by the method in step S32. Substitute these parameters into the outgoing peak flood calculation formula: ; Based on the selected typical floodplain flood event, extract the required parameters from the measured river channel flood flow process data and water level process data obtained in step S2. represents the end time of this round of flood, that is, the time point when the water level process drops back to the base flow level. represents the time when the measured flood water level recedes to the overflow elevation, which can be determined by finding the time when the water level drops from higher than the overflow elevation to equal to or lower than the overflow elevation in the water level process data. represents the flood detention area volume corresponding to the overflow elevation, which can be calculated by substituting the overflow elevation into the curve equation by using the water level - volume curve of the flood detention area obtained in step S1. Substitute these parameters into the incoming flow calculation formula corresponding to the overflow elevation: ; Use the results calculated in the previous steps to calculate the incoming peak flood flow. is the outgoing water volume calculated in step S331, is the volume corresponding to the overflow elevation, that is, the volume below the overflow elevation, which can be calculated by substituting the overflow elevation into the water level - volume curve of the flood detention area. and are respectively the time when the water level recedes to the overflow elevation in step S332 and the time when the measured flood peak appears in step S331. is the inflow rate into the channel corresponding to the overflow elevation calculated in step S332. Substitute these parameters into the formula for calculating the peak inflow rate into the channel: . Based on the peak outflow rate from the channel, the inflow rate into the channel corresponding to the flood overflow elevation, and the peak inflow rate into the channel, as well as the outflow time, flood peak time, and inflow time, the actual flood overflow rate process is generalized into a triangle or trapezoid. For example, for cross-section A, the peak outflow rate from the channel is 617.28 cubic meters per second, occurring at the 3rd hour; the peak inflow rate into the channel is 461.56 cubic meters per second, occurring at the 5th hour; the inflow rate into the channel corresponding to the flood overflow elevation is 257.20 cubic meters per second, occurring at the 7th hour. The overflow rate process can be generalized into a trapezoid, where the upper base of the trapezoid is the peak inflow rate into the channel, the lower base is the inflow rate into the channel corresponding to the flood overflow elevation, the rising section on the left is the outflow stage, and the descending section on the right is the inflow stage. Take the generalized overflow rate process as the input condition and input it into the river channel - flood detention area exchange simulation model constructed in step S33. At each time step, the model calculates the water volume exchange between the river channel and the flood detention area based on the current river channel water level, flood detention area water level, and the generalized overflow rate process. By simulating the entire flood process, the actual overflow rate for each cross-section at each time step can be obtained. Arrange these flow rate data in chronological order to obtain the river channel overflow rate process data.

[0136] Preferably, step S4 is specifically:

[0137] Perform flow rate process superposition correction based on the river channel overflow rate process data and the measured river channel flood flow rate process data to obtain the river channel flood flow rate process data after the flow returns to the channel.

[0138] In the embodiments of the present invention, it is ensured that the time steps of the process data of the river channel overflow discharge and the measured flood discharge process data of the river channel are consistent. For example, both are in steps of 1 hour. If the time steps are inconsistent, interpolation processing is required to unify the time steps. A new time series is created with the same time step as the input data to store the flood discharge process data of the river channel after the water returns to the channel. The following operations are performed for each time step: 1. Determine the overflow discharge direction: Judge the relative magnitudes of the river channel water level and the flood detention area water level at this time step. If the river channel water level is higher than the flood detention area water level, the overflow discharge direction is from the river channel to the flood detention area (positive value); if the river channel water level is lower than the flood detention area water level, the overflow discharge direction is from the flood detention area back to the river channel (negative value). The overflow discharge calculated in S3 is based on the river channel. A positive value indicates water flowing out of the river channel, and a negative value indicates water flowing back into the river channel. 2. Calculate the water return flow: Superimpose the measured flood discharge of the river channel and the overflow discharge at this time step. A positive overflow discharge indicates water flowing out of the river channel, reducing the river channel discharge. Therefore, it needs to be added when calculating the river channel discharge after the water returns to the channel; a negative overflow discharge indicates water flowing back into the river channel, increasing the river channel discharge. Therefore, it needs to be subtracted when calculating the discharge after the water returns to the channel. The calculation formula is as follows: Water return flow = measured discharge + overflow discharge. Arrange the water return flow calculated for each time step in chronological order to form the complete flood discharge process data of the river channel after the water returns to the channel. This data can more accurately reflect the change process of the river channel flood discharge after increasing the flood volume on the floodplain or adding the return flow, and can more accurately reflect the actual flood discharge capacity of the river channel, providing a more reliable basis for the design of the water return flood. For example, according to the flood discharge process data corrected after the water returns to the channel, the flood control water level of the river channel flood control project can be re-evaluated, or the reservoir operation plan can be optimized.

[0139] Preferably, the present invention also provides a flood water return simulation system based on overflow process correction, which executes the flood water return calculation method based on overflow process correction as described above. The flood water return simulation system based on overflow process correction includes:

[0140] A flood detention area terrain analysis module, which is used to obtain the historical flood event data of the river channel; identify the floodplain area according to the historical flood event data of the river channel to obtain the floodplain area data of the river channel flood; determine the flood overflow elevation for the floodplain area data of the river channel flood to generate flood overflow elevation data; draw the water level - volume curve of the flood detention area according to the flood overflow elevation data to generate the water level - volume curve parameters of the flood detention area;

[0141] A real - time flood data processing module, which is used to obtain the historical measured flood data on the floodplain; perform historical flood time - series processing on the historical measured flood data on the floodplain to respectively obtain the measured flood discharge process data and the measured flood water level process data of the river channel;

[0142] The flood discharge process simulation module is used to construct a river channel - flood detention area exchange simulation model based on flood overflow elevation data, flood detention area water level - volume curve parameters, and measured river channel flood water level process data; use the river channel - flood detention area exchange simulation model to conduct water balance simulations of the out - of - channel and in - channel flood process water volumes for the measured river channel flood discharge process data to obtain river channel overflow discharge process data;

[0143] The flood back - into - channel correction module is used to correct the measured river channel flood discharge process data through the river channel overflow discharge process data to obtain the flood back - into - channel corrected river channel flood discharge process data; this process is used as the basis for flood back - into - channel design.

[0144] Preferably, referring to Figure 4 , it is the water level - volume curve graph of the flood detention reservoir basin. The flood detention area is regarded as the flood detention reservoir basin. From topographic data, the basin mouth elevation H_basin_mouth when the flood starts to overflow the floodplain can be obtained, the relationship curve H~V of the reservoir basin flood detention water level - volume is measured, and the volume V_basin_mouth corresponding to H_basin_mouth is obtained by looking up from the H~V curve.

[0145] Preferably, referring to Figure 5 , it is the generalization diagram of the flood overflow process. During the rising stage of the measured river channel flood, when the flood water level rises to H_basin_mouth, the flood starts to flow out of the river channel. By the flood peak water level , the out - of - channel stops during measurement. During this period, the flow rate first increases and then decreases. From the time when the water level rises to H_basin_mouth, the time when the flood peak appears, and the out - of - channel water volume V_out_channel, generalizing the out - of - channel flood process during ~ as an isosceles triangle that first increases and then decreases, the out - of - channel flood peak flow rate can be obtained. During the falling stage of the measured river channel flood, at the flood peak water level , after measurement, the flood water on the floodplain starts to flow into the river channel, the flow rate first increases and then decreases. When the flood water level drops to H_basin_mouth, the flow rate gradually decreases; from the time when the water level drops to H_basin_mouth, the time when this round of flood ends, the volume V_basin_mouth corresponding to H_basin_mouth, generalizing the in - channel flood process during ~ as gradually decreasing and linear, the in - channel flow rate corresponding to the basin mouth elevation is . Then, from , , the remaining water volume in - channel V_out_channel - V_basin_mouth, and , generalizing the out - of - channel flood process from the basin mouth, first increasing and then decreasing to , the basin mouth, linearly and at equal time intervals during ~ The maximum flow rate during this period is , in - channel.

[0146] Preferably, refer to Figure 6 , which is the flood process graph after the floodwater returns to the channel. For the measured river channel flood process, ~ During the rising stage of the flood, the measured flow plus the flood flow out of the channel during the same period, ~ 、 ~ During the falling stage of the flood, the measured flow is respectively subtracted by the flood flow into the channel during the same period, then the flood process after the floodwater returns to the channel and the peak flow of the floodwater returning to the channel can be obtained , and the floodwater returns to the channel.

[0147] This application lies in that by deeply analyzing the data of historical flood events in the river channel, combining the floodplain area identification and topographic survey techniques, the flood overflow elevation is accurately determined, and the water level - volume curve of the flood detention area is scientifically drawn. It makes full use of the existing topographic data and historical flood information, avoids excessive dependence on a large amount of measured flood data, reduces the difficulty and cost of data acquisition, and is especially applicable to areas with relatively scarce historical data. Compared with the traditional flood routing method, the present invention does not require measured flood data for multiple events and multiple stations. Only the measured flood process of the research reach and the topography of the flood detention area are needed to accurately simulate the process of the floodwater returning to the channel, significantly improving the applicability and operability of the floodwater return calculation. The river channel - flood detention area exchange simulation model based on the principle of water balance can finely simulate the dynamic exchange process of floodwater between the river channel and the flood detention area. This model comprehensively considers the flood overflow elevation, the water level - volume relationship of the flood detention area, and the measured flood water level process data of the river channel, and accurately calculates the data of the river channel overflow flow process through the water balance simulation of the flood process of flowing out of and flowing into the channel. Compared with the simplified water balance method, the present invention can not only calculate the peak flow of the floodwater returning to the channel, but also obtain the complete flood process after the floodwater returns to the channel, and all the flood elements obtained are complete, providing more comprehensive flood characteristic information for flood control project design. In the calculation process, a simplified generalization method of the flood overflow flow process is adopted, mainly including looking up charts and four arithmetic operations, avoiding complex mathematical modeling and cumbersome calculation processes. Compared with the cubic spline interpolation method, the calculation process of the present invention is more efficient, concise, with a significant reduction in the amount of calculation, strong operability, and can quickly generate the flood flow process data after the floodwater returns to the channel, providing timely technical support for flood control decision-making and emergency response.

[0148] Therefore, from any perspective, the embodiments should be regarded as exemplary and non - restrictive. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the application documents are intended to be included in the present invention.

[0149] The above are only specific embodiments of the present invention, enabling those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A flood channel calculation method based on overflow process correction, characterized in that: The following steps are involved: Step S1: Obtain historical flood event data of the river; Flood floodplain areas are identified based on historical flood event data of the river channel to obtain flood floodplain area data of the river channel; flood overflow elevations are determined for the flood floodplain area data of the river channel to generate flood overflow elevation data; water level-volume curves of the detention area are drawn based on the flood overflow elevation data to generate water level-volume curve parameters of the detention area; Step S2: Acquire historical floodplain measured flood data; perform historical flood time series processing on the historical floodplain measured flood data to obtain river channel measured flood flow process data and river channel measured flood level process data; Step S3: construct a river channel-detention area exchange simulation model based on flood overflow elevation data, detention area water level-volume curve parameters and river channel measured flood level process data; use the river channel-detention area exchange simulation model to simulate the water balance of the flood process of the river channel measured flood flow process data, and obtain the river channel overflow flow process data; wherein, step S3 is specifically as follows: Step S31: using the flood overflow elevation data as the overflow water level threshold of the overflow section, using the river channel measured flood water level process data to identify the flood overflow time point, and obtaining the river channel flood overflow time point data; Step S32: constructing a water balance finite volume mathematical model based on the river flood overflow time point data, the river measured flood water level process data and the detention area water level-volume curve parameters to obtain a river-detention area exchange simulation model; Step S33: using the river channel-flood detention area exchange simulation model to perform water balance simulation of flood overflow process of the river channel measured flood flow process data, and obtain the river channel overflow flow process data; Step S4: Perform flood channel correction on the measured flood flow process data of the river channel through the river overflow flow process data to obtain channel correction river flood flow process data; this process is used as the basis for channel correction flood design.

2. The flood channel calculation method based on overflow process correction according to claim 1 is characterized in that: Step S1 includes the following steps: Step S11: Acquire historical flood event data of the river; Step S12: identifying flood plain areas according to historical flood event data of the river channel, and obtaining flood plain area data of the river channel; Step S13: performing floodplain area topography measurement based on the river flood floodplain area data to obtain floodplain area topography data; Step S14: using the floodplain area terrain data to perform terrain digital elevation model modeling to generate a river floodplain terrain digital elevation model; Step S15: determining the flood overflow elevation of the historical flood event data of the river channel through the river floodplain terrain digital elevation model to generate flood overflow elevation data; Step S16: Analyze the topographic characteristics of the detention area using the river floodplain terrain digital elevation model based on the flood overflow elevation data, draw the water level-volume curve of the detention area, and generate the water level-volume curve parameters of the detention area.

3. The flood channel calculation method based on overflow process correction according to claim 2 is characterized in that: Step S16 includes the following steps: Step S161: using the river floodplain terrain digital elevation model to analyze the flood inundation range at different elevations on the flood overflow elevation data, and obtain flood inundation boundary data at different elevations; Step S162: Identify the flooded area of ​​the detention area according to the flood boundary data at different elevations, and generate terrain characteristic parameters—the flooded area data of the detention area at different elevations; Step S163: using the river floodplain terrain digital elevation model to discretize the terrain characteristic parameter - the flooded area data of the flood detention areas at different elevations, and generate the flood detention area micro-unit data; Step S164: Calculate the micro-unit flooding depth of the micro-unit data of the flood detention area by using the flood overflow elevation data to obtain the micro-unit flooding depth data; Step S165: Divide the water level interval according to the micro-unit flooding depth data to obtain the water level interval data of the flood detention area; Step S166: Calculating the micro-unit storage capacity of the micro-unit data of the flood detention area based on the water level interval data of the flood detention area to obtain the micro-unit storage capacity data; Step S167: Accumulate the volume of the detention area according to the micro-unit storage capacity data, and draw a water level-volume curve according to the water level interval data of the detention area to obtain the water level-volume curve parameters of the detention area.

4. The flood channel calculation method based on overflow process correction according to claim 1 is characterized in that: Step S2 includes the following steps: Step S21: Obtaining historical floodplain measured flood data; Step S22: preprocessing the historical floodplain measured flood data to generate standard floodplain measured flood data; Step S23: performing historical flood time series processing on the standard floodplain measured data to generate time series floodplain measured data; Step S24: clustering the river flood process according to the measured time series floodplain flood data, and obtaining the measured river flood flow process data and the measured river flood level process data.

5. The flood channel calculation method based on overflow process correction according to claim 1 is characterized in that: Step S33 includes the following steps: Step S331: Calculate the flood peak out of the channel according to the measured flood flow process data of the river channel to obtain the flood peak flow data out of the channel; wherein the flood peak flow calculation formula out of the channel is as follows: ； in, is the peak flow rate out of the channel, is the amount of water out of the tank, To measure the peak flood time, It is the time from the measured flood level rising to the overflow elevation; Step S332: Calculate the inflow flow according to the measured flood flow process data of the river channel to obtain the inflow flow data corresponding to the flood overflow elevation; wherein the calculation formula for the inflow flow corresponding to the flood overflow elevation is as follows: ； in, is the inflow flow corresponding to the flood overflow elevation, is the volume corresponding to the flood overflow elevation, This is the end time of this round of flooding. It is the time from the measured flood level receding to the overflow elevation; Step S333: Calculate the in-channel flood peak flow rate by using the out-channel flood peak flow rate data and the in-channel flow rate data corresponding to the flood overflow elevation, and obtain the in-channel flood peak flow rate data corresponding to the flood overflow elevation; wherein the in-channel flood peak flow rate calculation formula corresponding to the flood overflow elevation is as follows: ； in, is the flood peak flow into the channel corresponding to the flood overflow elevation, is the amount of water out of the tank, is the volume corresponding to the flood overflow elevation, is the inflow flow corresponding to the flood overflow elevation; Step S334: generalize the flood overflow flow process according to the river flood overflow time point data, the outflow peak flow data, the inflow flow data corresponding to the flood overflow elevation, and the inflow peak flow data corresponding to the flood overflow elevation to obtain the river overflow flow process data.

6. The flood channel calculation method based on overflow process correction according to claim 1 is characterized in that: Step S4 is specifically as follows: The flow process is superimposed and corrected based on the river overflow flow process data and the measured flood flow process data of the river to obtain the river flood flow process data after returning to the channel.

7. A flood channel simulation system based on overflow process correction, characterized in that: Used to execute the flood channeling calculation method based on overflow process correction as claimed in claim 1, the flood channeling simulation system based on overflow process correction comprises: The detention area terrain analysis module is used to obtain the historical flood event data of the river channel; identify the flood plain area according to the historical flood event data of the river channel, and obtain the flood plain area data of the river channel; determine the flood overflow elevation of the river channel flood plain area data, and generate the flood overflow elevation data; draw the water level-volume curve of the detention area according to the flood overflow elevation data, and generate the water level-volume curve parameters of the detention area; The real-time flood data processing module is used to obtain the historical flood data measured on the flood plain; the historical flood data measured on the flood plain are processed into historical flood time series to obtain the river channel measured flood flow process data and the river channel measured flood level process data; The flood flow process simulation module is used to construct a river channel-detention area exchange simulation model based on flood overflow elevation data, detention area water level-volume curve parameters and river channel measured flood level process data; the river channel-detention area exchange simulation model is used to simulate the water balance of the flood process of the outflow and inflow of the river channel measured flood flow process data to obtain the river channel overflow flow process data; The flood channel correction module is used to perform flood channel correction on the measured flood flow process data of the river channel through the river overflow flow process data, and obtain the channel correction river flood flow process data; this process is used as the basis for channel flood design.

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