Mountain torrent forecasting method and system based on mountain pond flood regulation coupling

Abstract

The invention discloses a mountain torrent forecasting method and system based on mountain pond flood regulation coupling, and belongs to the technical field of mountain area small watershed flood forecasting. An existing drainage basin flood forecasting method does not consider the adjusting effect of a hilly pond on runoff, and consequently the error of a mountain flood forecasting result is large. According to the mountain torrent forecasting method based on the mountain pond flood regulation coupling, the initial water level data of the mountain pond is obtained by processing the basic information of the mountain pond; coupling the rainfall data, the evaporation data and the initial water level data to obtain a hilly pond outflow volume; according to the method, the influence of the hilly pond on the mountain torrents can be fully considered, so that the mountain torrent disaster forecasting precision can be effectively improved. Furthermore, accurate mountain torrent forecasting can be realized, so that related departments can issue early warning information in advance, people are reminded to transfer in time, and the emergency response speed and efficiency are improved.

Description

Technical Field

[0001] The present invention relates to a mountain flood forecasting method and system based on the coupling of mountain pond flood regulation, and belongs to the technical field of flood forecasting in mountainous small watersheds. Background Art

[0002] Floods are one of the most frequently occurring natural disasters in the world. Especially in mountainous areas, due to high mountains, steep slopes, and dense rivers, surface runoff with impact force will form within dozens of minutes to several hours after short-term heavy rainfall. And because the flow velocity of the runoff is relatively large, its destructiveness is very strong, and the resulting hazards are often more serious. Therefore, accurate mountain flood forecasting is of crucial importance.

[0003] At the same time, in order to meet the irrigation and drinking water needs of mountain villagers, mountain ponds will be built. These mountain ponds are generally located in the upper reaches of the watershed, with a water storage capacity of 10,000 - 100,000 cubic meters and a water depth of 3 - 8 meters, mainly used for agricultural irrigation and flood control regulation. The catchment area of mountain ponds is generally 0.5 - 5 square kilometers.

[0004] For large watersheds with flat terrain, whose watershed area reaches thousands of square kilometers, the proportion of the catchment area of mountain ponds in the watershed area is very small. Therefore, mountain ponds have little impact on the runoff of large watersheds.

[0005] However, for mountainous small watersheds, whose area is generally 10 - 50 square kilometers, at this time the proportion of the catchment area of mountain ponds in the watershed area is relatively large, thus significantly changing the runoff process within the mountain pond watershed. According to experience, a mountain pond can approximately reduce the peak flood flow by 20% - 40%. If there are multiple mountain ponds, a superposition effect will also occur. Therefore, for mountain flood disaster prediction schemes, if the regulating effect of mountain ponds is not considered, it will lead to a large difference between the mountain flood forecasting results and the actual situation, making it impossible to accurately forecast mountain floods, and further affecting the speed and efficiency of emergency response.

[0006] The information disclosed in this background art is only used to understand the background of the inventive concept of the present invention, and thus it may include information that does not constitute the prior art. Summary of the Invention

[0007] Aiming at the above problems or one of the above problems, the first object of the present invention is to provide a mountain flood forecasting method and system based on the coupling of mountain pond flood regulation, which processes the basic information of mountain ponds to obtain the initial water level data of mountain ponds; and couples rainfall data, evaporation data, and the initial water level data to obtain the outflow discharge of mountain ponds; and then evolves the outflow discharge of mountain ponds to the downstream forecasting section to obtain the forecasting flood process in the downstream area. Therefore, the present invention can fully consider the impact of mountain ponds on mountain floods, thereby effectively improving the accuracy of mountain flood disaster forecasting and the level of flood control decision-making support.

[0008] In view of the above problems or one of the above problems, the second object of the present invention is to provide a mountain flood forecasting method and system based on the coupling of mountain pond flood regulation, which can achieve accurate mountain flood forecasting, enable relevant departments to issue early warning information in advance to remind the public to transfer in time; and can provide data support for the formulation and drill of emergency plans, improving the speed and efficiency of emergency response.

[0009] To achieve one of the above objects, the first technical solution of the present invention is as follows: A mountain flood forecasting method based on the coupling of mountain pond flood regulation, comprising the following steps: Step 1, obtaining the basic information of mountain ponds in the area to be predicted; Step 2, processing the basic information of mountain ponds to obtain the initial water level data of mountain ponds; Step 3, coupling rainfall data, evaporation data and the initial water level data of mountain ponds to obtain the discharge from the mountain ponds; Step 4, evolving the discharge from the mountain ponds to the downstream forecasting section to obtain the forecasting flood process in the downstream area, realizing mountain flood forecasting based on the coupling of mountain pond flood regulation.

[0010] Through continuous exploration and experiments, the present invention processes the basic information of mountain ponds to obtain the initial water level data of mountain ponds; couples rainfall data, evaporation data and the initial water level data to obtain the discharge from the mountain ponds; and then evolves the discharge from the mountain ponds to the downstream forecasting section to obtain the forecasting flood process in the downstream area. Therefore, the present invention can fully consider the influence of mountain ponds on mountain floods, thereby effectively improving the accuracy of mountain flood disaster forecasting and the level of flood control decision-making support.

[0011] Furthermore, applying the present invention can achieve accurate mountain flood forecasting, enabling relevant departments to issue early warning information in advance to remind the public to transfer in time, minimizing casualties to the greatest extent. According to the forecast flood magnitude and arrival time, relevant departments can take reasonable measures according to the circumstances to reduce property losses such as infrastructure, farmland, and houses.

[0012] Furthermore, the present invention can also provide data support for the formulation and drill of emergency plans, improving the speed and efficiency of emergency response, and thus has important significance.

[0013] As a preferred technical measure: The method for obtaining the basic information of mountain ponds in the area to be predicted in Step 1 is as follows: The flood discharge mode of the mountain pond is the free open discharge mode; Based on the free open discharge mode, obtain the mountain pond scale, water level - mountain pond storage curve and mountain pond flood discharge structures; Based on the location of the mountain pond, determine the basic information of the basin, including basin area, hydrological characteristics and geological conditions; Summarize the mountain pond scale, water level - mountain pond storage capacity curve, mountain pond flood discharge structures, and basin basic information to obtain the mountain pond basic information of the area to be predicted.

[0014] As an optimal technical measure: The method for determining the basin basic information based on the location of the mountain pond is as follows: According to the location of the mountain pond, obtain the digital elevation data of the basin where the mountain pond is located; Carry out depression filling processing on the digital elevation data to obtain basin raster information; Based on the basin raster information, extract the water flow direction and river channel information; According to the water flow direction and river channel information, analyze the topological relationship among the mountain pond, river channel, and village to obtain the mountain pond reservoir area basin and the intermediate basin; Extract the basin area, hydrological characteristics, and geological conditions from the mountain pond reservoir area basin and the intermediate basin to obtain the basin basic information; the hydrological characteristics include river channel length and river channel slope information.

[0015] As an optimal technical measure: Step two, the method for processing the mountain pond basic information to obtain the initial water level data of the mountain pond is as follows: Obtain the mountain pond basic information; Based on the mountain pond basic information, analyze the scale, design parameters, and historical operation data of the mountain pond to determine the initial discharge flow and the initial water level data of the mountain pond under different working conditions; Combine the real - time monitoring data and the mountain pond operation rules to dynamically adjust the estimated value of the initial water level data of the mountain pond.

[0016] As an optimal technical measure: Step three, the method for coupling the rainfall data, evaporation data, and the initial water level data of the mountain pond to obtain the discharge flow of the mountain pond is as follows: According to the measured rainfall information or the forecast rainfall information, obtain the rainfall data; Based on the rainfall data and the evaporation data, calculate the mountain pond inflow flood process; According to the initial water level data of the mountain pond and the size of the mountain pond flood discharge structure, calculate the discharge capacity of the mountain pond to obtain the discharge capacity relationship curve, which is used to characterize the discharge capacity corresponding to different storage capacities of the mountain pond; Conduct flood routing calculation according to the discharge capacity relationship curve and the time step to obtain the flood routing auxiliary line; Use the polynomial interpolation function to fit the flood routing auxiliary line to obtain the mountain pond fitting function; Take the discharge flow of the mountain pond at the beginning of the time period as the initial flow of the time period, and substitute it into the mountain pond fitting function to iteratively calculate the end - of - period flow of each time period, and finally obtain the discharge flow of the mountain pond and the complete discharge flow process of the mountain pond.

[0017] As a preferred technical measure: According to the initial water level data of the mountain pond and the dimensions of the flood discharge structures of the mountain pond, calculate the downstream discharge capacity of the mountain pond, and the method for obtaining the downstream discharge capacity relationship curve is as follows: Based on the initial water level data of the mountain pond and the dimensions of the flood discharge structures of the mountain pond, generate the digital elevation data of the mountain pond, and perform horizontal slicing on the digital elevation data of the mountain pond to obtain a number of water level slices; According to a number of water level slices, calculate the trapezoidal volume between adjacent water levels; Accumulate the trapezoidal volumes to obtain the reservoir capacities corresponding to different water levels, and combine the downstream discharge capacities of the mountain pond corresponding to different water levels to obtain the downstream discharge capacities corresponding to different mountain pond reservoir capacities, so as to obtain the downstream discharge capacity relationship curve.

[0018] As a preferred technical measure: According to the downstream discharge capacity relationship curve and the time step, perform flood routing calculation to obtain the flood routing auxiliary line, and the method is as follows: Determine the time step, and based on the downstream discharge capacity relationship curve, construct independent variables and dependent variables; The independent variable is the downstream discharge capacity, and the dependent variable is the coupled quantity of the mountain pond reservoir capacity, the downstream discharge capacity, and the time step; According to the independent variables and dependent variables, establish a set of discrete data points; Connect the discrete data points to obtain the flood routing auxiliary line; Or / and, use a polynomial interpolation function to fit the flood routing auxiliary line to obtain the fitting function, and the method is as follows: Use a polynomial interpolation function to fit the flood routing auxiliary line to obtain a system of linear equations: Write the system of linear equations in matrix form to obtain the mountain pond fitting matrix, which includes a design matrix, a coefficient vector, and an observation value vector; Use the least squares method to solve the coefficient vector to obtain a coefficient expression; Based on the coefficient expression, gradually increase the polynomial degree starting from the low degree, and use the sum of squared residuals to evaluate the fitting effect of the mountain pond fitting matrix, so as to determine the optimal polynomial degree; According to the optimal polynomial degree, determine the final mountain pond fitting function.

[0019] As a preferred technical measure: Take the mountain pond outflow at the beginning of the time period as the initial flow of the time period, and substitute it into the mountain pond fitting function to iteratively calculate the end-of-period flow of each time period, and finally obtain the mountain pond outflow and the complete mountain pond outflow process, and the method is as follows: Step 1, obtain the mountain pond inflow at the beginning of the time period and the mountain pond inflow at the end of the time period from the mountain pond inflow flood process; Step 2: Obtain the initial pond discharge at the beginning of the time period as the initial flow rate of the time period, and substitute the initial flow rate of the time period into the pond fitting function to obtain an intermediate variable; Step 3: Substitute the intermediate variable, the initial pond inflow at the beginning of the time period, and the final pond inflow at the end of the time period into the water balance equation to obtain a new intermediate variable; Step 4: Substitute the new intermediate variable into the pond fitting function to obtain the final pond discharge at the end of the time period; Step 5: Use the final pond discharge at the end of the time period calculated in the above steps as the initial pond discharge at the beginning of the next time period, and repeat Steps 2 to 4 for iterative calculation to complete the flood routing calculation of the pond for the entire calculation period, and obtain the pond discharge and the entire pond discharge process;

[0020] As a preferred technical measure: Step 4: The method for evolving the pond discharge to the downstream forecast section to obtain the forecast flood process in the downstream area is as follows: Obtain rainfall data based on measured rainfall information or forecast rainfall information; Calculate the flood process in the intermediate basin based on the rainfall data, the pond discharge, and the evaporation data; Determine the flood flow in the intermediate basin at the downstream forecast section based on the flood process in the intermediate basin; Calculate the average channel velocity using the hydrodynamic parameter calculation method; Divide the channel length by the average channel velocity to obtain the evolution time of the pond discharge; Superimpose the evolution time of the pond discharge and the flood flow in the intermediate basin to obtain the forecast flood process in the downstream area;

[0021] To achieve one of the above purposes, the second technical solution of the present invention is: A flash flood forecasting system based on pond flood routing coupling, comprising: One or more processors; A storage device for storing one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors implement the above-mentioned flash flood forecasting method based on pond flood routing coupling;

[0022] Compared with the prior art solutions, the present invention has the following beneficial effects: Through continuous exploration and experiments, the present invention processes the basic information of the mountain pond to obtain the initial water level data of the mountain pond; and couples the rainfall data, evaporation data and initial water level data to obtain the out - flow of the mountain pond; furthermore, the out - flow of the mountain pond is evolved to the downstream forecast section to obtain the forecast flood process in the downstream area. Therefore, the present invention can fully consider the influence of the mountain pond on the mountain flood, thereby effectively improving the accuracy of the mountain flood disaster forecast and the level of flood control decision - making support.

[0023] Furthermore, applying the present invention can achieve accurate mountain flood forecasting, enabling relevant departments to issue early warning information in advance, reminding the public to transfer in time, and minimizing casualties to the greatest extent. According to the forecast flood magnitude and arrival time, relevant departments can take reasonable measures according to the circumstances to reduce property losses such as infrastructure, farmland, and houses.

[0024] Furthermore, the present invention can also provide data support for the formulation and rehearsal of emergency plans, improve the speed and efficiency of emergency response, and thus has important significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a schematic flow chart of a mountain flood forecasting method based on the flood regulation coupling of a mountain pond according to the present invention; Figure 2 is another schematic flow chart of a mountain flood forecasting method based on the flood regulation coupling of a mountain pond according to the present invention; Figure 3 is a schematic diagram of the geographical locations of the mountain pond and the village in an embodiment of the present invention; Figure 4 is a corresponding curve graph of the water level and storage capacity of the mountain pond according to the present invention; Figure 5 is a schematic diagram of the variation relationship between the rainfall process, the inflow flood of the mountain pond and the flood in the intermediate catchment area according to the present invention; Figure 6 is a curve graph of the relationship between the water level of the mountain pond and the discharge capacity according to the present invention; Figure 7 is a curve graph of the relationship between the storage capacity and the discharge capacity of the mountain pond according to the present invention; Figure 8 is a schematic diagram of the variation relationship between the inflow flood process, the outflow flood and the evolved flood of the mountain pond according to the present invention; Figure 9 is a schematic diagram of the forecast flood process according to the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0027] Rather, the present invention covers any alternatives, modifications, equivalent methods and solutions made to the essence and scope of the present invention as defined by the claims. Further, in order to enable the public to better understand the present invention, in the following detailed description of the present invention, some specific details are described in detail. Those skilled in the art can fully understand the present invention without the description of these details.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0029] As Figure 1 shown, the first specific embodiment of the flash flood forecasting method based on the coupling of mountain pond flood regulation of the present invention is as follows: A flash flood forecasting method based on the coupling of mountain pond flood regulation, comprising the following steps: Step 1, obtaining the basic information of mountain ponds in the area to be predicted; Step 2, processing the basic information of mountain ponds to obtain the initial water level data of mountain ponds; Step 3, coupling rainfall data, evaporation data and the initial water level data of mountain ponds to obtain the discharge of mountain ponds; Step 4, evolving the discharge of mountain ponds to the downstream forecasting section to obtain the forecasting flood process in the downstream area, and realizing the flash flood forecasting based on the coupling of mountain pond flood regulation.

[0030] The second specific embodiment of the flash flood forecasting method based on the coupling of mountain pond flood regulation of the present invention is as follows: A flash flood forecasting method based on the coupling of mountain pond flood regulation, comprising the following steps: Step 1, obtaining the geographical basic information of the area to be predicted, which includes basin basic information, mountain pond basic information and mountain pond basic information; the method for obtaining the geographical basic information of the area to be predicted is as follows: First, import the digital elevation data of the small watershed involving mountain ponds; then perform pit filling processing on the digital elevation data of the small watershed, and extract the flow direction and river channels based on the raster after pit filling. Based on the topological relationship among mountain ponds, river channels and villages, divide the mountain pond reservoir area watershed and the interval watershed; and then use the hydrological analysis module to extract geographical characteristic values such as watershed area, river channel length, and river channel slope.

[0031] Step 2, processing the basin basic information, mountain pond basic information and mountain pond basic information to obtain the initial water flow data of the basin, mountain ponds and mountain ponds.

[0032] Step 3, coupling rainfall data, evaporation data and the initial water flow data to obtain the discharge of mountain ponds.

[0033] Step 4: Route the outflow from the mountain pond to the downstream forecast section to obtain the forecast flood process in the downstream area, thereby realizing mountain flood forecasting based on the coupling of mountain pond flood regulation.

[0034] The third specific embodiment of the mountain flood forecasting method based on the coupling of mountain pond flood regulation according to the present invention: A mountain flood forecasting method based on the coupling of mountain pond flood regulation includes forecasting the inflow of the mountain pond and the inflow from the intermediate area, calculating the discharge capacity of the mountain pond, determining the mountain pond operation rule, conducting mountain pond flood routing calculation, and routing the flood out of the mountain pond.

[0035] Forecasting the inflow of the mountain pond and the inflow from the intermediate area is used for calculating the flood inflow into the mountain pond and the flood from the intermediate area. It describes hydrological phenomena through four levels of calculations, namely: the first-level evapotranspiration calculation, the second-level runoff generation calculation, the third-level water source division, and the fourth-level confluence calculation.

[0036] The present invention uses a hydrological model and a mountain pond flood routing calculation method to conduct flood forecasting for small mountainous basins, and divides the basin above the forecast section into a mountain pond reservoir basin and an intermediate basin, respectively considering the runoff generation and concentration processes in the two areas.

[0037] Mountain ponds are generally located in the upper reaches of the basin, with a water storage capacity of 10,000 to 100,000 cubic meters. The catchment area of mountain ponds is generally 0.5 to 5 square kilometers. Due to the large terrain slope in this basin, rainwater is easily quickly concentrated into floods.

[0038] For the mountain pond reservoir basin, coupling the mountain pond flood routing calculation to calculate the outflow from the mountain pond improves the shortcoming in the original method that does not consider the influence of the mountain pond on the mountain flood process. The present invention comprehensively considers the initial water level of the mountain pond, the initial mountain pond storage capacity, and the influence of the operation rule on the mountain pond flood routing calculation, making the result of the mountain pond flood routing calculation more in line with the actual situation.

[0039] Therefore, the present invention can accurately forecast the flood process in small mountainous basins, improve the flood forecasting accuracy, shorten the flood forecasting operation time, and improve the level of flood control decision-making support.

[0040] In this example, in the evapotranspiration calculation layer, according to the water storage characteristics and soil moisture of the soil, the evapotranspiration amount is considered and calculated in three layers, including the upper-layer evapotranspiration amount , the lower-layer evapotranspiration amount and the deep-layer evapotranspiration amount .

[0041] In the runoff generation calculation layer, the input is the net rainfall after deducting evapotranspiration , and the output is the runoff generation of the basin Due to the spatial distribution differences in the topography and geomorphology of small watersheds, the soil tension water storage capacity within the watershed also varies. The model approximates the distribution of the watershed soil storage capacity as a parabola. The storage capacity distribution curve describes the water storage capacity and runoff generation characteristics of the soil at different water content levels. The mathematical equation of the soil storage capacity distribution curve is:

[0042] In the formula: is the maximum value of the tension water storage capacity within the watershed, is the tension water storage capacity at any point in the watershed, represents the proportion of the watershed area where the tension water storage capacity is less than or equal to value, is the distribution coefficient of the watershed tension water storage capacity curve.

[0043] Runoff The calculation formula is:

[0044] In the formula: is the net rainfall obtained by deducting the rainfall evapotranspiration, is the average storage capacity of the watershed, is the soil water content at the initial moment.

[0045] In the water source division calculation layer, the runoff calculated by the runoff calculation layer enters the mountain pond. When the mountain pond is full, the overflowing water forms surface runoff , and the water flowing out from the side outlet is subsurface flow , and the water flowing out from the bottom outlet is groundwater runoff , and the surface runoff is calculated by the following formula:

[0046] In the formula: is the average free water storage of the watershed, is the free water storage, is the ordinate corresponding to the initial free water storage, is the maximum free water storage of the watershed, is the free water storage distribution curve index, is the proportion of the runoff generation area.

[0047] Subsurface flow runoff , groundwater runoff The calculation formulas are:

[0048] In the formula: , They are the outflow coefficients of interflow and groundwater runoff respectively.

[0049] In the final confluence calculation layer, considering the different characteristics of water flow movement in the slope area and the river channel area, the confluence calculation is divided into two stages: the slope confluence stage and the river network confluence stage. In the slope confluence stage, surface runoff directly flows into the river network. The interflow runoff forms interflow after being regulated by a linear pond , and the groundwater runoff forms groundwater runoff after being regulated by a linear pond . The calculation formula is:

[0050]

[0051] In the formula: is the interflow at the t-th moment, is the groundwater runoff at the t-th moment, is the interflow runoff at the t-th moment, is the groundwater runoff at the t-th moment, is the interflow recession coefficient, is the groundwater recession coefficient, is the unit conversion coefficient for converting rainfall into flow.

[0052] The three kinds of runoff jointly flow into the river network to form the final flow process , and the calculation formula is:

[0053] The discharge capacity of the pond is the sum of the discharge capacity of the spillway and the discharge capacity of the sluice pipe.

[0054] The discharge capacity of the spillway is calculated using the weir flow formula, and its calculation formula is as follows:

[0055] In the formula, is the discharge of the spillway, is the side contraction coefficient of the pier, is the drowning coefficient, is the total net width of the overflow weir, is the head at the weir crest considering the approach velocity, is the head on the weir, is the acceleration due to gravity, is the discharge coefficient, is the upstream slope correction coefficient.

[0056] The discharge capacity of the water release culvert is calculated using the orifice flow formula, and its calculation formula is as follows:

[0057] In the formula, is the discharge flow of the water release culvert, is the discharge coefficient, is the area of the water release culvert, is the orifice head considering the approach velocity.

[0058] For mountain ponds, the general discharge method is free and unconstrained. For the free and unconstrained discharge method, it is necessary to select the initial water level and the initial discharge of the mountain pond, and then perform the flood routing calculation of the mountain pond.

[0059] In this embodiment, the method for performing the flood routing calculation of the mountain pond is as follows, including the following steps: Step 1: Generate high-resolution digital elevation data DEM through the mountain pond surveying and mapping data, horizontally slice the digital elevation data DEM at an interval of 1.0 m, calculate the trapezoidal volume between adjacent water levels layer by layer, accumulate to obtain the reservoir capacity corresponding to different water levels, and combine the discharge capacity of the mountain pond corresponding to different water levels to obtain the discharge capacity corresponding to different reservoir capacities .

[0060] Step 2: Determine the time step , for subsequent calculations.

[0061] Step 3: Take as the independent variable, as the dependent variable, establish a set of discrete data points . Construct a -degree mountain pond fitting function, substitute each data point into the polynomial equation to obtain a system of linear equations, and its expression is as follows:

[0062]

[0063]

[0064] In the formula, , ,...... are the coefficients of the system of equations, , ...... are the variables of the system of equations, , ...... are the constants of the system of equations.

[0065] Write the system of linear equations in matrix form, and its expression is as follows:

[0066] Where: The design matrix is matrix, and its expression is as follows:

[0067] The expression of the coefficient vector is as follows:

[0068] The expression of the observation value vector is as follows:

[0069] Solve using the least squares method to obtain the coefficients, and its expression is as follows:

[0070] The polynomial degree increases gradually from the lower degree and use the residual sum of squares (RSS) to evaluate the fitting effect, select the most appropriate polynomial degree to make the polynomial approximate the given discrete data points as much as possible .

[0071] The residual sum of squares is used to measure the fitting error of the model, and the calculation formula is:

[0072] Where: is the actual value of the th observation point, is the predicted value of the model for the th observation point, is the total number of data points.

[0073] The present invention uses a polynomial interpolation function to fit the flood regulation auxiliary line, and replaces the original method of looking up the chart by calling the fitting function, which can greatly improve the chart lookup efficiency and is easy to implement programmatically.

[0074] Step 4: Obtain the initial and end-of-period reservoir inflow from the flood process of the mountain pond 、 ; Step 5: Obtain the initial reservoir outflow , substitute it into the polynomial interpolation function, and calculate the intermediate variable ; Step 6: Substitute the above items into the rewritten water balance equation, and its expression is as follows:

[0075] Among them, is the initial storage capacity of the mountain pond at the beginning of the time period, is the storage capacity of the mountain pond at the end of the time period, is the outflow discharge at the end of the time period.

[0076] Furthermore, the intermediate variable is obtained; Step 7: Substitute the value of the intermediate variable into the fitting function of the mountain pond to obtain the outflow discharge at the end of the time period; Step 8: Take the outflow discharge calculated in the above steps at the end of the time period as the initial outflow discharge at the beginning of the next time period, and repeat Steps 4 to 7 for iterative calculation to complete the flood routing calculation of the mountain pond and obtain the outflow discharge process of the mountain pond.

[0077] In this embodiment, the method for evolving the outflow discharge of the mountain pond to the downstream forecast section to obtain the forecast flood process in the downstream area is as follows: There is a certain distance between the mountain pond and the downstream village or forecast section, and the outflow discharge of the mountain pond needs to evolve for a period of time before it can reach the downstream village or forecast section. For mountainous rivers, the hydrograph basically does not deform, but only translates with time. Therefore, the key issue is to calculate the evolution time. The evolution time can be obtained by dividing the river length by the average river velocity. The Eagleson Bras method for calculating hydrodynamic parameters is used to calculate the average river velocity , which takes into account natural geographical factors such as river width and river slope that affect the flow velocity, and can reflect the non-linear influence of the flow velocity through the change of net rainfall intensity. The calculation formula is:

[0078]

[0079] In the formula is the net rainfall intensity; is the basin area; is the river width; is the river slope; is the Manning roughness coefficient, generally taken as 0.025.

[0080] The evolution time of the outflow discharge hydrograph is calculated as:

[0081] In the formula is the river length.

[0082] Translate the outflow discharge of the mountain pond by Obtain the time, and superimpose it with the interval flood to obtain the predicted flood process of the downstream village or the predicted section.

[0083] As Figure 2 shown, the fourth specific embodiment of the flash flood forecasting method based on the coupled flood regulation of mountain ponds according to the present invention: A flash flood forecasting method based on the coupled flood regulation of mountain ponds, comprising the following steps: Step 1: Obtain the basic information of the basin to obtain information such as the basin area, hydrological characteristics, and geological conditions; obtain the basic information of the mountain pond to obtain information such as the scale of the mountain pond, the water level - mountain pond storage curve, and the flood discharge structure of the mountain pond.

[0084] Step 2: Forecast the flood process of the mountain pond inflow and the flood process of the interval basin according to the measured or predicted rainfall and evaporation data.

[0085] Step 3: According to the size of the flood discharge structure of the mountain pond, use the weir flow formula and the orifice flow formula to calculate the flood discharge capacity of the mountain pond, and obtain the relationship curve between the mountain pond water level and the flood discharge capacity.

[0086] Step 4: Determine the mountain pond operation rules, and obtain the initial water level and the initial mountain pond outflow discharge of the mountain pond, that is, the initial flood discharge.

[0087] Step 5: Conduct the flood regulation calculation of the mountain pond by the graphical method, construct a mountain pond fitting function that approximates the given discrete data points as much as possible, and the coordinates of the discrete data points are .

[0088] Then, use the initial mountain pond outflow discharge as the mountain pond outflow discharge at the beginning of the time period, and iteratively calculate the mountain pond outflow discharge at the end of each time period, and finally obtain the entire mountain pond outflow discharge process.

[0089] Step 6: Use the Eagleson Bras method of the hydrodynamic parameter calculation method to calculate the average river velocity. Divide the river length by the average river velocity to obtain the propagation time of the mountain pond outflow discharge . Translate the mountain pond outflow discharge time, and superimpose it with the interval flood to obtain the predicted flood process of the downstream village or the predicted section.

[0090] A flash flood forecasting method based on the coupling of a hydrological model and the flood regulation of mountain ponds provided by the embodiment of the present invention uses a hydrological model and a flood regulation calculation method of mountain ponds to conduct flood forecasting for small mountain basins. The present invention improves the defect that the influence of mountain ponds on flash floods is not considered in the original method, can improve the accuracy of flood forecasting, and improve the level of flood control decision - making support.

[0091] Through accurate flash flood forecasting, relevant departments can issue early warning information in advance, reminding the public to evacuate in time and minimizing casualties to the greatest extent. According to the forecast flood volume level and arrival time, relevant departments can take reasonable measures according to the circumstances to reduce property losses such as infrastructure, farmland, and houses. Precise forecasting schemes can also provide data support for the formulation and drill of emergency plans, improving the speed and efficiency of emergency response, so it has important significance.

[0092] In this embodiment, the flood regulation calculation of the mountain pond adopts the static storage capacity flood regulation algorithm. The volume of the mountain pond and the mountain pond water level change linearly within a time period. The discharge of the mountain pond is a function of the water storage volume of the mountain pond. Therefore, the continuity equation can be converted into a water balance equation in finite difference form. The entire flood inflow and outflow process is divided into several time periods. Within each time period, the difference between the average inflow and outflow in the time period is equal to the change in the mountain pond storage capacity.

[0093] Since the discharge and storage capacity of the mountain pond at the end of each time period are unknown, it is also necessary to rely on the relationship between the discharge of the mountain pond and the water storage volume of the mountain pond for solution. Therefore, the flood regulation calculation method of the mountain pond is to jointly solve the water balance equation and the relationship equation between the discharge and the water storage volume. The present invention uses a polynomial interpolation function to fit the flood regulation auxiliary line, and replaces the original way of looking up the chart by calling the fitting function, which can greatly improve the chart lookup efficiency and is easy to be implemented by programming.

[0094] A specific embodiment of applying the present invention to flash flood forecasting for a certain village: There is a mountain pond built upstream of a certain village, and flash flood forecasting is carried out with the village as the forecasting section. Furthermore, the basic information of the mountain pond is obtained, which includes the following content: The length of a certain river from the mountain pond to the village is 3.7 km, the river width is 10 m, and the relative position is as Figure 3 shown. The basin area of the mountain pond reservoir area is 7.4 , and the area of the interval basin between the mountain pond and the village is 6.2 .

[0095] This mountain pond mainly consists of a mountain pond main body, a spillway, and a water conveyance tunnel. The spillway is located on the right side of the mountain pond main body, and the elevation of the inlet weir crest is 281.10 m. It is a practical overflow weir with a weir width of 11 m. The water conveyance tunnel is located in the mountain body on the right side of the mountain pond main body. The cross-section form is circular, the hole diameter is 0.6 m, the total length is 168.30 m, the elevation of the inlet bottom is 257.26 m, and the elevation of the outlet bottom is 240.76 m. The mountain pond water level - storage capacity curve is as Figure 4 shown.

[0096] For the rainfall process, an actual rainfall in July 2022 is selected, with both the rainfall duration and the forecast duration being 24 hours. The evaporation is taken as the monthly average evaporation. The rainfall process, the flood process entering the mountain pond, and the flood process in the intermediate catchment area are as Figure 5 shown.

[0097] According to the dimensions of the spillway and the water conveyance tunnel of the mountain pond, the discharge capacity of the mountain pond at different water levels is calculated using the weir flow formula and the orifice flow formula respectively, and then the discharge capacities of the spillway and the water conveyance tunnel are added together to obtain the relationship curve between the water level of the mountain pond and the discharge capacity, as Figure 6 shown.

[0098] According to the operation regulation of the mountain pond, the flood regulation method of the mountain pond is determined to be the free overflow method, with the initial water level of the mountain pond being 281.10 m and the initial discharge flow being 0.

[0099] In this embodiment, the graphical method is used for the flood regulation calculation of the mountain pond, which includes the following steps; Step 1: According to the water level - mountain pond storage capacity curve and the water level - discharge capacity relationship curve, obtain the discharge capacity corresponding to different mountain pond storage capacities , and the relationship curve is as Figure 7 shown.

[0100] Step 2: Determine the time step to be 1 hour.

[0101] Step 3: Use the polynomial interpolation function for fitting to establish the relationship curve, and its expression is as follows:

[0102] Let , take the polynomial degree as 3, and the fitted polynomial interpolation function is:

[0103] The sum of squared residuals RSS is 0.0005, indicating a high degree of fitting.

[0104] Step 4: Obtain the mountain pond inflow at the beginning and end of the time period from the mountain pond inflow flood process , .

[0105] Step 5: Obtain the mountain pond outflow at the beginning of the time period , substitute it into the relationship curve, and query to obtain .

[0106] Step 6: Substitute the above items into the rewritten water balance equation:

[0107] Obtain .

[0108] Step 7: Query the relationship curve based on the value of to obtain the outflow discharge at the end of the time period . .

[0109] Step 8: Use the outflow discharge at the end of the time period calculated in the above steps as the initial outflow discharge of the next time period , and repeat Steps 4 - 7 for iterative calculation to complete the flood routing calculation of the mountain pond and obtain the outflow discharge process of the mountain pond.

[0110] The inflow flood process and the outflow flood process of the mountain pond are as Figure 8 shown. From the data in Figure 8 , it can be seen that compared with the inflow flood of the mountain pond, the peak discharge of the outflow flood of the mountain pond is reduced by 11%, and the overall flood process is shifted backward by 1 hour.

[0111] Furthermore, import the digital elevation data (DEM) of the basin into the geographic information system software, and perform depression filling on the digital elevation data. Based on the raster after depression filling, extract the flow direction and the river channel, thereby obtaining a channel slope S of 0.01 and a Manning roughness coefficient n of 0.025. The average net rainfall intensity of this rainfall is 40 . Use the Eagleson Bras method for calculating hydrodynamic parameters to calculate the average flow velocity of the river channel as 2.2 , and the evolution time is 1680 seconds, approximately 30 minutes.

[0112] Therefore, shift the outflow flood hydrograph of the mountain pond backward by 30 minutes and add it to the flood process of the interval to finally obtain the predicted flood process of the downstream forecast section, as can be seen in Figure 9 .

[0113] An equipment embodiment applying the method of the present invention: An electronic device, comprising: One or more processors; A storage device for storing one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors implement the above-mentioned mountain flood forecasting method based on mountain pond flood routing coupling.

[0114] A computer medium embodiment applying the method of the present invention: A computer-readable storage medium, on which a computer program is stored, and when the program is executed by a processor, it implements the above-mentioned mountain flood forecasting method based on mountain pond flood routing coupling.

[0115] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art can still modify or equivalently replace the specific implementation manners of the present invention. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention shall be covered by the protection scope of the claims of the present invention.

Claims

1. A flash flood forecasting method based on the coupling of mountain pond flood regulation, characterized in that: It includes the following steps: Step 1, obtain the basic information of the mountain ponds in the area to be predicted; Step 2, process the basic information of the mountain ponds to obtain the initial water level data of the mountain ponds; Step 3, couple the rainfall data, evaporation data and the initial water level data of the mountain ponds to obtain the outflow discharge of the mountain ponds; Step 4, evolve the outflow discharge of the mountain ponds to the downstream forecasting section to obtain the forecasting flood process in the downstream area, and realize the flash flood forecasting based on the coupling of mountain pond flood regulation.

2. A flash flood forecasting method based on the coupling of mountain pond flood regulation according to claim 1, characterized in that: The method for obtaining the basic information of the mountain ponds in the area to be predicted in Step 1 is as follows: The flood discharge mode of the mountain pond is the free open flood discharge mode; Based on the free open flood discharge mode, obtain the scale of the mountain pond, the water level - mountain pond storage capacity curve and the flood discharge structures of the mountain pond; Based on the location of the mountain pond, determine the basic information of the basin, which includes the basin area, hydrological characteristics and geological conditions; Summarize the scale of the mountain pond, the water level - mountain pond storage capacity curve, the flood discharge structures of the mountain pond and the basic information of the basin to obtain the basic information of the mountain ponds in the area to be predicted.

3. A flash flood forecasting method based on the coupling of mountain pond flood regulation according to claim 2, characterized in that: The method for determining the basic information of the basin based on the location of the mountain pond is as follows: According to the location of the mountain pond, obtain the digital elevation data of the basin where the mountain pond is located; Perform depression filling on the digital elevation data to obtain the basin grid information; Based on the basin grid information, extract the water flow direction and river channel information; According to the water flow direction and river channel information, analyze the topological relationship between the mountain pond, the river channel and the village to obtain the mountain pond reservoir area basin and the intermediate basin; Extract the basin area, hydrological characteristics and geological conditions from the mountain pond reservoir area basin and the intermediate basin to obtain the basic information of the basin; the hydrological characteristics include the river channel length and the river channel slope information.

4. A flash flood forecasting method based on the coupling of mountain pond flood regulation according to claim 1, characterized in that: The method for processing the basic information of the mountain ponds in Step 2 to obtain the initial water level data of the mountain ponds is as follows: Obtain the basic information of the mountain ponds; Based on the basic information of the mountain ponds, analyze the scale, design parameters and historical operation data of the mountain ponds to determine the initial outflow discharge and the initial water level data of the mountain ponds under different working conditions; Combine the real - time monitoring data and the mountain pond operation rules to dynamically adjust the estimated value of the initial water level data of the mountain ponds.

5. A flash flood forecasting method based on the coupling of mountain pond flood regulation according to claim 1, characterized in that: The method for coupling the rainfall data, evaporation data and the initial water level data of the mountain ponds in Step 3 to obtain the outflow discharge of the mountain ponds is as follows: Obtain the rainfall data according to the measured rainfall information or the forecast rainfall information; Based on the rainfall data and the evaporation data, calculate the inflow flood process of the mountain pond; According to the initial water level data of the mountain pond and the size of the flood discharge structures of the mountain pond, calculate the discharge capacity of the mountain pond to obtain the discharge capacity relationship curve, which is used to characterize the discharge capacity corresponding to different reservoir capacities of the mountain pond; Conduct flood regulation calculation according to the discharge capacity relationship curve and the time step to obtain the flood regulation auxiliary line; Use a polynomial interpolation function to fit the flood regulation auxiliary line to obtain the reservoir fitting function of the mountain pond; Take the outflow discharge of the mountain pond at the beginning of the time period as the initial flow of the time period, substitute it into the reservoir fitting function of the mountain pond, and iteratively calculate the end-of-period flow of each time period to finally obtain the outflow discharge of the mountain pond and the complete outflow discharge process of the mountain pond.

6. A mountain flood forecasting method based on the coupling of mountain pond flood regulation as claimed in claim 5, wherein: According to the initial water level data of the mountain pond and the dimensions of the flood discharge structures of the mountain pond, calculate the discharge capacity of the mountain pond. The method for obtaining the discharge capacity relationship curve is as follows: Based on the initial water level data of the mountain pond and the dimensions of the flood discharge structures of the mountain pond, generate the digital elevation data of the mountain pond, and perform horizontal slicing on the digital elevation data of the mountain pond to obtain several water level slices; According to several water level slices, calculate the trapezoidal volume between adjacent water levels; Accumulate the trapezoidal volumes to obtain the reservoir capacities corresponding to different water levels, combine the discharge capacities of the mountain pond corresponding to different water levels, obtain the discharge capacities corresponding to different mountain pond reservoir capacities, and thus obtain the discharge capacity relationship curve.

7. A mountain flood forecasting method based on the coupling of mountain pond flood regulation as claimed in claim 6, wherein: According to the discharge capacity relationship curve and the time step, perform flood regulation calculation to obtain the flood regulation auxiliary line. The method is as follows: Determine the time step, and based on the discharge capacity relationship curve, construct the independent variable and the dependent variable; The independent variable is the discharge capacity, and the dependent variable is the coupled quantity of the mountain pond reservoir capacity, the discharge capacity, and the time step; According to the independent variable and the dependent variable, establish a set of discrete data points; Connect the discrete data points to obtain the flood regulation auxiliary line; Or / and, use a polynomial interpolation function to fit the flood regulation auxiliary line. The method for obtaining the fitting function is as follows: Use a polynomial interpolation function to fit the flood regulation auxiliary line to obtain a system of linear equations: Write the system of linear equations in matrix form to obtain the reservoir fitting matrix of the mountain pond, which includes the design matrix, the coefficient vector, and the observation value vector; Use the least squares method to solve the coefficient vector to obtain the coefficient expression; Based on the coefficient expression, gradually increase the polynomial degree starting from the low degree, and use the sum of squared residuals to evaluate the fitting effect of the reservoir fitting matrix of the mountain pond, so as to determine the optimal polynomial degree; According to the optimal polynomial degree, determine the final reservoir fitting function of the mountain pond.

8. A mountain flood forecasting method based on the coupling of mountain pond flood regulation as claimed in claim 7, wherein: Take the outflow discharge of the mountain pond at the beginning of the time period as the initial flow of the time period, substitute it into the reservoir fitting function of the mountain pond, and iteratively calculate the end-of-period flow of each time period. The method for finally obtaining the outflow discharge of the mountain pond and the complete outflow discharge process of the mountain pond is as follows: Step 1, obtain the inflow discharge of the mountain pond at the beginning of the time period and the inflow discharge of the mountain pond at the end of the time period from the mountain pond inflow flood process; Step 2, obtain the outflow discharge of the mountain pond at the beginning of the time period as the initial flow of the time period, and substitute the initial flow of the time period into the reservoir fitting function of the mountain pond to obtain an intermediate variable; Step 3, substitute the intermediate variable, the inflow discharge of the mountain pond at the beginning of the time period, and the inflow discharge of the mountain pond at the end of the time period into the water balance equation to obtain a new intermediate variable; Step 4: Substitute the new intermediate variable into the mountain pond fitting function to obtain the mountain pond outflow at the end of the time period. Step 5: Take the mountain pond outflow at the end of the time period calculated in the above steps as the mountain pond outflow at the beginning of the next time period, and repeat Steps 2 to 4 for iterative calculation to complete the flood routing calculation of the mountain pond for the entire calculation period, and obtain the mountain pond outflow and the entire mountain pond outflow process.

9. A flash flood forecasting method based on mountain pond flood routing coupling according to claim 1, characterized in that: Step Four: The method for evolving the mountain pond outflow to the downstream forecasting section to obtain the forecast flood process in the downstream area is as follows: Obtain rainfall data based on measured rainfall information or forecast rainfall information; Calculate the flood process in the intermediate basin based on the rainfall data, mountain pond outflow, and evaporation data; Determine the intermediate basin flood flow at the downstream forecasting section according to the flood process in the intermediate basin; Calculate the average channel velocity using a hydrodynamic parameter calculation method; Divide the channel length by the average channel velocity to obtain the evolution time of the mountain pond outflow; Superimpose the evolution time of the mountain pond outflow and the intermediate basin flood flow to obtain the forecast flood process in the downstream area.

10. A flash flood forecasting system based on mountain pond flood routing coupling, characterized in that: It includes: One or more processors; A storage device for storing one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors are caused to implement a flash flood forecasting method based on mountain pond flood routing coupling according to any one of claims 1-9.

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