A quick calculation method of design flood for small watershed in any location of the world

Abstract

The application provides a global arbitrary position small watershed design flood rapid calculation method, relates to the technical field of hydrology and water resources technology, defines a to-be-calculated design flood region as a target point, obtains watershed characteristic parameters, rainstorm statistical parameters and runoff yield statistical parameters of the target point, combines a reasoning formula of a target watershed, and calculates each frequency design flood of the small watershed; the obtaining process of the watershed characteristic parameters comprises the following steps: generating a target region water system and a watershed boundary vector data set based on DEM data, obtaining a watershed boundary above the target point according to the target region water system and the watershed boundary vector data set, and obtaining the watershed characteristic parameters through the watershed boundary above the target point. The application realizes the extraction of the watershed boundary above a global arbitrary section point by establishing spatial indexes on the basis of a global sub-watershed boundary data set and a global water system data set, and greatly improves the flood analysis efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hydrology and water resources, and particularly relates to a quick calculation method of design flood of small watershed at any global position. BACKGROUND

[0002] The analysis and calculation of design flood of small watershed are important basis for engineering construction and disaster prevention and reduction, and are of great significance to ensure the flood control safety standard of water conservancy and hydropower, transportation, municipal engineering and other projects, guide the engineering scale and investment decision, evaluate flood risk through design flood analysis, guide flood control early warning and emergency response, reduce the loss of life and property caused by flood disasters, and have important value for rational utilization of water resources, protection of water ecological environment, promotion of watershed sustainable development, and guarantee of regional economic and social development.

[0003] The calculation methods of design flood of small watershed mainly include reasoning formula method, regional empirical formula method, historical flood analysis method and comprehensive instantaneous unit line method, etc. The reasoning formula method is one of the main methods for calculating design flood peak flow, and is relatively mature in the application of storm flood analysis and calculation in dataless areas. The reasoning formula method directly calculates the flood peak at the outlet of the watershed by summarizing the runoff and confluence conditions of the watershed. The main calculation parameters of the reasoning formula of design flood of small watershed include watershed characteristic parameters such as watershed area (F), river length (L), main river channel gradient (J), and design storm (P), etc. Given the above parameters, the design flood of small watershed can be quickly calculated in combination with regional empirical parameters.

[0004] The invention patent with publication number CN112231907A discloses a method for calculating the temporal and spatial distribution of watershed design flood. When analyzing and calculating the design flood of small watershed in dataless areas, the watershed boundary and river system of the small watershed are first manually outlined based on the topographic map or generated with the help of GIS software, the main watershed characteristic parameters are analyzed and calculated, the storm rain statistical parameters are obtained by consulting the storm rain atlas of the region where the design watershed is located, the design storm is then calculated through the storm rain statistical parameters, and finally the design flood results of the outlet section of the watershed are calculated by using the reasoning formula and the unit line method. This method needs to manually consult the storm rain atlas of the region, generally calculates the storm rain statistical parameters according to the center of gravity of the watershed, has very low work efficiency and certain subjectivity, and different designers have no uniformity in the value selection. In addition, the processes of analyzing and calculating the above-mentioned watershed characteristic parameters and storm rain are relatively independent, and each time only the design flood of a single small watershed can be calculated, which has low flexibility and efficiency, and cannot quickly respond when a large range of small watershed design flood analysis and calculation is needed.

[0005] Under the background of intelligent water conservancy construction and the improvement of mountain flood disaster prevention ability, the traditional small watershed design flood calculation method has problems of low efficiency, strong subjectivity and lack of uniformity. Especially when a large range of small watershed design flood analysis is needed, the existing method needs to manually consult the rainstorm atlas, calculate the watershed characteristic parameters one by one, and each link is relatively independent, which cannot meet the demand of rapid response. Therefore, developing a global small watershed design flood rapid calculation method, realizing automatic extraction of watershed characteristic parameters, intelligent acquisition of rainstorm parameters and rapid calculation of design flood, has important practical significance and application value for improving the mountain flood disaster prediction and early warning ability and supporting the intelligent water conservancy construction. SUMMARY

[0006] The present application provides a global small watershed design flood rapid calculation method, which aims to at least solve the technical problems existing in the prior art mentioned in the background.

[0007] The present application provides the following technical solutions to achieve the above-mentioned purposes:

[0008] A global small watershed design flood rapid calculation method, comprising the following steps:

[0009] S1, based on the global DEM data set, the river system vector data set V_Str and the watershed boundary vector data set V_Bou are established;

[0010] S2, record the outlet coordinates of any small watershed as the target point, and count the watershed boundary above the target point with the target point as the starting point;

[0011] S3, based on the watershed boundary above the target point, the watershed characteristic parameters, the rainstorm statistical parameters and the runoff yield statistical parameters are generated;

[0012] S4, based on the watershed characteristic parameters, the rainstorm statistical parameters and the runoff yield statistical parameters, combined with the target watershed inference formula, the design flood of each frequency of the small watershed is calculated;

[0013] Further, the step S1 comprises the following steps:

[0014] S1.1, prepare the global DEM data set, correct the original DEM data by using the water system data extracted from remote sensing image or other ways, ensure the hydrological logic correctness of the DEM data, and obtain the corrected DEM data set Adj_DEM;

[0015] S1.2, after filling the corrected DEM data set Adj_DEM, the flow direction and cumulative flow tool of the GIS software is used to generate the global flow direction raster data set R_Dir and the cumulative flow raster data set R_Acc;

[0016] S1.3 Based on the global flow direction raster dataset R_Dir and the cumulative flow raster dataset R_Acc, the global river system vector dataset V_Str and the basin boundary vector dataset V_Bou are generated by the GIS software. When generating the basin boundary, a minimum sub-basin area threshold is set to obtain the sub-basin boundary vector dataset V_Bou and the river system vector dataset V_Riv above the area threshold.

[0017] Further, the step S2 comprises the following steps:

[0018] S2.1 A unique ID value Reach_ID is added to each vector river section of the generated river system vector dataset V_Str, and all upstream river section ID values are recorded in the attribute of each vector river section;

[0019] S2.2 In the generated sub-basin boundary V_Bou, the river section ID value belonging to the sub-basin is assigned to the sub-basin;

[0020] S2.3 The outlet coordinates of an arbitrary small basin are obtained, the target point coordinates are used to quickly locate the sub-basin belonging to the target point through spatial query, and the upstream of the river section where the sub-basin is located is queried, all upstream river sections are found according to all upstream river section ID values, all upstream sub-basins are located, and the upstream basin boundary V_Up_Bou1 is generated by merging;

[0021] S2.4 According to the sub-basin boundary V_Target_SubBou where the target point is located, the flow direction raster dataset R_Dir is cut by using the spatial analysis tool to obtain the flow direction raster data R_Target_Dir within the sub-basin boundary V_Target_SubBou where the target point is located;

[0022] S2.5 According to the flow direction raster data R_Target_Dir within the sub-basin boundary V_Target_SubBou and the target point coordinates, all upstream areas flowing to the target point within the sub-basin V_Target_SubBou are tracked, so as to determine the sub-basin raster above the target point within the sub-basin V_Target_SubBou, and the vector boundary V_Target_Bou is generated;

[0023] S2.6 The vector boundary V_Target_Bou in S2.5 is combined with the upstream basin boundary V_Up_Bou1 generated in S2.3 to generate the basin boundary V_Up_Bou above the target point of the arbitrary small basin.

[0024] Further, the step S3 comprises:

[0025] S3.1 The steps of generating the basin characteristic parameters are as follows:

[0026] S3.1.1 Obtain the statistical basin area F based on the basin boundary V_Up_Bou above the target point of any small watershed;

[0027] S3.1.2 Generate the global maximum river length grid dataset R_Len containing the upstream maximum river length value at any grid in the world based on the global flow direction grid dataset R_Dir using the flow length tool of GIS software;

[0028] S3.1.3 Generate the global elevation difference grid dataset R_Diff containing the height difference value between the upstream maximum river length source and the current grid at any grid in the world based on the corrected DEM dataset Adj_DEM, the flow direction grid dataset R_Dir and the cumulative flow grid dataset R_Acc as input data using the distance tool of GIS software;

[0029] S3.1.4 Obtain the gradient grid dataset R_J of the maximum river length above any target point in the world based on the global elevation difference grid dataset R_Diff and the global maximum river length grid dataset R_Len, R_J = R_Diff / R_Len;

[0030] S3.2 The steps for generating the storm statistical parameters are as follows:

[0031] S3.2.1 Prepare the contour map of storm statistical parameters such as mean value and Cv value of rainstorm in different time periods in each region in the world and rasterize to generate the global storm statistical parameter grid dataset R_Storm_P; the dataset R_Storm_P contains the storm statistical parameter value at any grid position in the world;

[0032] S3.2.2 Cut the storm statistical parameter grid dataset R_Storm_P using the spatial analysis tool with the basin boundary V_Up_Bou above the target point of any small watershed as a mask to obtain the storm statistical parameter grid dataset R_Up_Bou_Storm_P in any small watershed, and then average to obtain the average storm statistical parameter value in any small watershed;

[0033] S3.3 The steps for generating the runoff yield statistical parameters are as follows:

[0034] S3.3.1 Prepare the contour map of runoff yield parameters in different regions in the world and rasterize to generate the global runoff yield parameter grid dataset R_P;

[0035] S3.3.2 Cut the runoff yield parameter grid dataset R_P in S3.3.1 using the spatial analysis tool with the basin boundary V_Up_Bou above the target point of any small watershed as a mask to obtain the runoff yield parameter grid dataset R_Up_Bou_P in any small watershed, and then average to obtain the average runoff yield parameter value in any small watershed.

[0036] Further, the step S4 comprises:

[0037] S4.1 calculating the design storm value of different frequencies of the arbitrary small watershed based on the average storm statistical parameter value of the arbitrary small watershed by frequency analysis method;

[0038] S4.2 calculating the runoff concentration parameter value of different frequencies of the arbitrary small watershed based on the average runoff concentration parameter value of the arbitrary small watershed in combination with the design storm value of different frequencies;

[0039] S4.3 calculating the design flood and process of each frequency of the global arbitrary small watershed based on the watershed characteristic parameter value, the design storm value and the runoff concentration parameter value in combination with the inference formula of the target watershed.

[0040] A design flood calculation system is configured with program modules for executing the above method, comprising:

[0041] A watershed parameter generation module is used for establishing the water system vector data set V_Str and the watershed boundary vector data set V_Bou and statistically analyzing the watershed boundary V_Up_Bou above the target point of the arbitrary small watershed and generating the watershed parameter based on the watershed boundary V_Up_Bou above the target point of the arbitrary small watershed;

[0042] A storm statistical parameter generation module is used for generating the global storm statistical parameter raster data set R_Storm_P and generating the storm statistical parameter based on the watershed boundary V_Up_Bou above the target point of the arbitrary small watershed;

[0043] A runoff concentration statistical parameter generation module is used for generating the global runoff concentration parameter raster data set R_P of different regions and generating the runoff concentration statistical parameter based on the watershed boundary V_Up_Bou above the target point of the arbitrary small watershed;

[0044] A design flood calculation module is used for calling the watershed parameter, the storm statistical parameter and the runoff concentration statistical parameter and calculating the design flood of each frequency according to the inference formula of the target watershed.

[0045] 1. The application provides a global watershed boundary extraction method above an arbitrary river section point, which prepares the global sub-watershed boundary data set, the global water system data set and establishes a spatial index, and simultaneously prepares the global flow direction and the cumulative flow raster data, so that the extraction efficiency of the watershed boundary is greatly improved by pre-generating the data set, the watershed boundary above the arbitrary section point is extracted in seconds, the watershed boundary result is output as soon as the point is obtained, and the method is embodied in the following aspects:

[0046] (1) When obtaining the basin boundary above the target river section point, it is not necessary to perform spatial analysis steps such as depression filling, flow direction, cumulative flow, river network generation, river network grading, and basin generation each time, but the related data set prepared in advance is directly applied, so that the analysis efficiency is greatly improved;

[0047] (2) According to the target river section point coordinates, the method can quickly locate the sub-basin and all upstream sub-basins of the target river section point, and the upstream basin boundary of the sub-basin can be quickly obtained by merging;

[0048] (3) For the catchment boundary above the target section point in the local sub-basin, the method only needs to analyze the flow direction grid data set in the local sub-basin range, without analyzing and calculating all flow direction grid data sets above the section point, and after obtaining the catchment boundary above the point in the local sub-basin range, the target point above the basin boundary can be quickly obtained by merging with all upstream sub-basins of the sub-basin.

[0049] 2. The global small watershed design flood rapid calculation method disclosed by the application prepares global maximum river length grid data set and global river channel elevation difference grid data set in advance, and can quickly query and extract maximum river length and main river channel gradient according to target river section point coordinates, without the need for analysis and extraction each time, so that the analysis and calculation efficiency is greatly improved.

[0050] 3. The global small watershed design flood rapid calculation method disclosed by the application prepares global storm and runoff parameter grid data set in advance, and prepares global partition reasoning formula and related experience parameters in advance, so that the design flood of any basin can be quickly calculated through the basin characteristic parameters obtained in the foregoing.

[0051] 4. The global small watershed design flood rapid calculation method disclosed by the application can realize click-to-calculate of global small watershed design flood after being developed into an application based on B / S architecture, greatly improves the small watershed flood analysis and calculation efficiency, and meets the practical needs of mountain flood disaster rapid analysis and smart water conservancy platform construction. DETAILED DESCRIPTION

[0052] Figure 1 River section ID value assignment operation schematic diagram of the application Figure 1 ;

[0053] Figure 2 River section ID value assignment operation schematic diagram of the application Figure 2 ;

[0054] Figure 3 Target point positioning schematic diagram of the application

[0055] Figure 4 Target point upstream sub-basin positioning schematic diagram of the application

[0056] Figure 5 Schematic diagram for merging sub-basins upstream of the target point of the present application;

[0057] Figure 6 Schematic diagram for clipping flow direction raster data for the target point of the present application Figure 1 ;

[0058] Figure 7 Schematic diagram for clipping flow direction raster data for the target point of the present application Figure 2 ;

[0059] Figure 8 Schematic diagram for generating vector boundary V_Target_Bou of the present application;

[0060] Figure 9 Schematic diagram for merging basin boundaries of the present application Figure 1 ;

[0061] Figure 10 Schematic diagram for merging basin boundaries of the present application Figure 2 ;

[0062] Figure 11 Schematic diagram for generating maximum river length raster data set of the present application;

[0063] Figure 12 Schematic diagram for generating global elevation difference raster data set of the present application;

[0064] Figure 13 Flow chart of the present application;

[0065] Figure 14 Schematic diagram for quickly extracting basin feature parameters of the present application. DETAILED DESCRIPTION

[0066] In order to facilitate the understanding of the present application, the present application will be described in more detail below with reference to the relevant drawings; the preferred embodiments of the present application are shown in the drawings, however, the present application can be realized in many different forms and is not limited to the embodiments described herein; on the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0067] It should be noted that the terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used herein are only for the purpose of illustration and do not represent the only embodiment.

[0068] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to limit the invention; the term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0069] Example. A method for rapid calculation of design floods in small watersheds at any location globally, such as... Figure 13 , 14 As shown, it includes the following steps:

[0070] S1. Establish a water system vector dataset V_Str and a watershed boundary vector dataset V_Bou based on the global DEM dataset;

[0071] S2. Let the coordinates of the outlet of any small watershed be the target point, and count the watershed boundary above the target point starting from the target point.

[0072] S3. Based on the watershed boundary above the target point, generate watershed characteristic parameters, rainstorm statistical parameters, and runoff generation and runoff statistical parameters;

[0073] S4. Based on the watershed characteristic parameters, rainstorm statistical parameters, and runoff generation and confluence statistical parameters, and combined with the target watershed reasoning formula, calculate the design floods at various frequencies for this small watershed.

[0074] Step S1 includes the following steps:

[0075] S1.1 Prepare the global DEM dataset. Use water system data extracted by remote sensing images or other methods to correct the original DEM data to ensure the correctness of the hydrological logic of the DEM data, and obtain the corrected DEM dataset Adj_DEM.

[0076] S1.2 After performing depression filling calculations on the corrected DEM dataset Adj_DEM, the global flow direction raster dataset R_Dir and the cumulative flow raster dataset R_Acc are generated using the flow direction and cumulative flow tools of GIS software.

[0077] S1.3 Based on the global flow direction raster dataset R_Dir and the cumulative flow raster dataset R_Acc, the global water system vector dataset V_Str and the watershed boundary vector dataset V_Bou are generated using GIS software. When generating the watershed boundary, a minimum sub-watershed area threshold is set to obtain the sub-watershed boundary vector dataset V_Bou and the water system vector dataset V_Riv that are above the area threshold.

[0078] Step S2 includes the following steps:

[0079] S2.1 adding a unique ID value Reach_ID to each vector river segment of the generated water system vector data set V_Str, while recording all upstream river segment ID values in the attribute of each vector river segment;

[0080] S2.2 assigning the river segment ID value to the sub-basin in the generated sub-basin boundary V_Bou;

[0081] S2.3 obtaining the coordinates of the outlet of the arbitrary small sub-basin, quickly locating the sub-basin to which the target point belongs according to the target point coordinates, and querying upstream along the river segment where the sub-basin is located, to find all upstream river segments according to all upstream river segment IDs, locate all upstream sub-basins, and merge to generate an upstream basin boundary V_Up_Bou1;

[0082] S2.4 according to the sub-basin boundary V_Target_SubBou where the target point is located, using spatial analysis tools to clip the global flow direction raster data set R_Dir to obtain the flow direction raster data R_Target_Dir within the sub-basin boundary V_Target_SubBou where the target point is located;

[0083] S2.5 according to the flow direction raster data R_Target_Dir within the sub-basin boundary V_Target_SubBou and the target point coordinates, tracing all upstream areas within the sub-basin V_Target_SubBou that flow to the target point, to determine the sub-basin raster above the target point within the sub-basin V_Target_SubBou, and generating a vector boundary V_Target_Bou;

[0084] S2.6 merging the vector boundary V_Target_Bou in S2.5 and the upstream basin boundary V_Up_Bou1 generated in S2.3 to generate the basin boundary V_Up_Bou above the target point of the arbitrary small sub-basin.

[0085] Through the foregoing steps S1 and S2, when the basin boundary above the target river cross-section point is needed, it is not necessary to perform spatial analysis steps such as filling, flow direction, cumulative flow, river network generation, river network grading, and basin generation each time, but to directly apply the related data sets prepared in advance, which greatly improves the analysis efficiency; at the same time, the sub-basin where the target river cross-section point is located and all upstream sub-basins can be quickly located through the target river cross-section point coordinates, and the upstream basin boundary of the sub-basin can be obtained by merging;

[0086] The step S3 includes:

[0087] S3.1 the steps of generating the basin characteristic parameters are as follows:

[0088] S3.1.1 obtaining the statistical basin area F based on the basin boundary V_Up_Bou above the target point of the arbitrary small sub-basin;

[0089] S3.1.2 Based on the global flow direction raster dataset R_Dir, the global maximum river length raster dataset R_Len is generated by using the flow length tool of GIS software, which contains the upstream maximum river length value at any grid in the world;

[0090] S3.1.3 Based on the corrected DEM dataset Adj_DEM, the flow direction raster dataset R_Dir and the cumulative flow raster dataset R_Acc as input data, the global elevation difference raster dataset R_Diff is generated by using the distance tool of GIS software, which contains the height difference value between the upstream maximum river length source and the current grid at any grid in the world;

[0091] S3.1.4 Based on the global elevation difference raster dataset R_Diff and the global maximum river length raster dataset R_Len, the gradient raster dataset R_J of the upstream maximum river length of any target point in the world is obtained, R_J = R_Diff / R_Len;

[0092] S3.2 The steps of generating the storm statistical parameters are as follows:

[0093] S3.2.1 Prepare the contour map of the storm statistical parameters such as mean value, Cv value and the like of the global regions at different time periods and rasterize it to generate the global storm statistical parameter raster dataset R_Storm_P; the dataset R_Storm_P contains the storm statistical parameter value at any grid position in the world;

[0094] S3.2.2 With the upstream basin boundary V_Up_Bou above the target point of any small basin as a mask, the storm statistical parameter raster dataset R_Storm_P is cut by using the spatial analysis tool to obtain the storm statistical parameter raster dataset R_Up_Bou_Storm_P within any small basin, and the average storm statistical parameter value of any small basin is obtained after averaging;

[0095] S3.3 The steps of generating the runoff yield statistical parameters are as follows:

[0096] S3.3.1 Prepare the contour map of the runoff yield parameters of different regions in the world and rasterize it to generate the global runoff yield parameter raster dataset R_P;

[0097] S3.3.2 With the upstream basin boundary V_Up_Bou above the target point of any small basin as a mask, the runoff yield parameter raster dataset R_P in S3.3.1 is cut by using the spatial analysis tool to obtain the runoff yield parameter raster dataset R_Up_Bou_P within any small basin, and the average runoff yield parameter value of any small basin is obtained after averaging.

[0098] The step S4 comprises:

[0099] S4.1 Based on the average statistical parameter value of the rainstorm of the arbitrary small watershed, the frequency analysis method is used to calculate the design rainstorm value of the arbitrary small watershed with different frequencies;

[0100] S4.2 Based on the average runoff concentration parameter value of the arbitrary small watershed, the design rainstorm value with different frequencies is combined to calculate the runoff concentration parameter value of the arbitrary small watershed with different frequencies;

[0101] S4.3 Based on the watershed characteristic parameter value, the design rainstorm value and the runoff concentration parameter value, the global arbitrary small watershed is combined with the target watershed inference formula to calculate the design flood and process with different frequencies; the target watershed inference formula uses the inference formula method commonly used in the prior art, which was proposed by an Irish engineer T.J. Mulvaney in 1851, and then improved by scientists of various countries according to the characteristics of the watershed of their own country. The specific inference formula is disclosed in Engineering Hydrology;

[0102] Through the foregoing steps, compared with the prior art, a method for generating watershed parameters, rainstorm statistical parameters and runoff concentration statistical parameters is provided, which eliminates the subjectivity of manual calculation of the foregoing parameters and ensures the uniformity of the calculation process.

[0103] A design flood calculation system is configured with program modules for executing the above method, comprising:

[0104] A watershed parameter generation module is used to establish a water system vector data set V_Str and a watershed boundary vector data set V_Bou, and to count the watershed boundary V_Up_Bou above the target point of the arbitrary small watershed, and generate the watershed parameters based on the watershed boundary V_Up_Bou above the target point of the arbitrary small watershed;

[0105] A rainstorm statistical parameter generation module is used to generate a global rainstorm statistical parameter grid data set R_Storm_P, and to generate the rainstorm statistical parameters based on the watershed boundary V_Up_Bou above the target point of the arbitrary small watershed;

[0106] A runoff concentration statistical parameter generation module is used to generate a global runoff concentration parameter grid data set R_P, and to generate the runoff concentration statistical parameters based on the watershed boundary V_Up_Bou above the target point of the arbitrary small watershed;

[0107] A design flood calculation module is used to call the watershed parameters, the rainstorm statistical parameters and the runoff concentration statistical parameters, and to calculate the design flood with different frequencies according to the target watershed inference formula. The present application has been applied in engineering examples, and the steps for rapid analysis and calculation of the design flood of the small watershed at any position in the world are as follows:

[0108] 1. Generation of watershed characteristic parameters

[0109] Step 1: generating global flow direction raster dataset R_Dir, cumulative flow raster dataset R_Acc, river system vector dataset V_Str and basin boundary vector dataset V_Bou:

[0110] Prepare a global DEM dataset, correct the original DEM data with river system data extracted from remote sensing images or other means, ensure the hydrological logic correctness of the DEM data, and obtain the corrected DEM dataset Adj_DEM;

[0111] After filling the depression calculation on the corrected DEM dataset Adj_DEM, the global flow direction raster dataset R_Dir and the cumulative flow raster dataset R_Acc are generated by using the flow direction and cumulative flow tools of GIS software;

[0112] Based on the flow direction raster dataset R_Dir and the cumulative flow raster dataset R_Acc, the global river system V_Str and the basin boundary V_Bou data are generated by GIS software. When generating the basin boundary, set the minimum sub-basin area threshold (such as 0.5 km²), and obtain the sub-basin boundary vector dataset V_Bou and the river system vector dataset V_Riv above the area threshold;

[0113] Step 2: preprocessing river system vector dataset V_Str and basin boundary vector dataset V_Bou:

[0114] Add a unique ID value Reach_ID to each vector river segment of the generated river system vector dataset V_Str, and record all upstream river segment ID values in the attribute of each vector river segment;

[0115] In the generated sub-basin boundary V_Bou, assign the river segment ID value to the sub-basin; as shown in Figure 1 、 2 ;

[0116] Step 3: obtain the coordinates of the outlet of any small watershed, according to the target point coordinates, quickly locate the belonging sub-basin through spatial query, and query upstream along the river segment where the sub-basin is located, find all upstream river segments according to all upstream river segment ID values, locate all upstream sub-basins, and merge to generate upstream watershed boundary V_Up_Bou1; as shown in Figure 3 、 4 and 5;

[0117] Step 4: according to the target point sub-basin boundary V_Target_SubBou, use spatial analysis tool to clip the flow direction raster dataset R_Dir, and obtain the flow direction raster data R_Target_Dir within the target point sub-basin boundary V_Target_SubBou; as shown in Figure 6 、 7 ;

[0118] Step 5: According to the flow direction grid data R_Target_Dir within the sub-basin boundary V_Target_SubBou and the target point coordinates, trace all upstream areas of the target point within the sub-basin V_Target_SubBou, so as to determine the sub-basin grid above the target point within the sub-basin V_Target_SubBou, and generate the vector boundary V_Target_Bou; as shown in Figure 8

[0119] Step 6: Merge the vector boundary V_Target_Bou in step 5 with the upstream basin boundary generated in step 3 to generate the basin boundary V_Up_Bou above the target point of any small basin, and count the basin area F; as shown in Figure 9 10

[0120] Step 7: According to the global flow direction grid data set R_Dir generated in step 1, use the water flow length tool of GIS software to generate the global maximum river length grid data set R_Len, which contains the upstream maximum river length value of any grid in the world; as shown in Figure 11

[0121] Step 8: Take the DEM data set Adj_DEM, the flow direction grid data set R_Dir and the cumulative flow grid data set R_Acc in step 1 as input data, and use the distance tool of GIS software to generate the global height difference grid data set R_Diff, which contains the height difference value between the upstream maximum river length source and the grid at any grid in the world; as shown in Figure 12

[0122] Step 9: Use the grid calculator tool to calculate the gradient grid data set R_J of the global maximum river length above any target point, R_J=R_Diff / R_Len;

[0123] 2. Rainstorm statistical parameter generation

[0124] Step 10: Prepare the rainstorm statistical parameter contour map of each region (such as Guizhou Province) in the world, such as 10min, 30min, 1h, 3h, 6h, 12h, and rasterize to generate the global rainstorm statistical parameter grid data set R_Storm_P. The data set R_Storm_P contains the rainstorm statistical parameter value of any grid position in the world;

[0125] ​​​​​Step 11: using the spatial analysis tool to cut the storm statistical parameter raster data set R_Storm_P obtained in step 10 with the watershed boundary V_Up_Bou above the target point of the arbitrary small watershed as a mask, so as to obtain the storm statistical parameter raster data set R_Up_Bou_Storm_P in the arbitrary small watershed, and then average to obtain the average storm statistical parameter value of the arbitrary small watershed;

[0126] 3. Generation of runoff yield statistical parameters

[0127] Step 12: prepare the runoff yield parameter contour map of each region (such as Guizhou Province) in the world and rasterize it, so as to generate the runoff yield parameter raster data set R_P of different regions in the world;

[0128] Step 13: using the spatial analysis tool to cut the runoff yield parameter raster data set R_P in step 12 with the watershed boundary V_Up_Bou above the target point of the arbitrary small watershed as a mask, so as to obtain the runoff yield parameter raster data set R_Up_Bou_P in the arbitrary small watershed, and then average to obtain the average runoff yield parameter value of the arbitrary small watershed;

[0129] 4. Design of flood analysis and calculation

[0130] Step 14: according to the average storm statistical parameter value of the arbitrary small watershed obtained in step 11, the frequency analysis method is used to calculate the design storm value of different frequencies of the arbitrary small watershed;

[0131] Step 15: according to the average runoff yield parameter value of the arbitrary small watershed obtained in step 13, the design storm value of different frequencies is combined to calculate the runoff yield parameter value of different frequencies of the arbitrary small watershed;

[0132] Step 16: according to the watershed characteristic parameter value, the design storm value and the runoff yield parameter value obtained in steps 1, 2 and 3, the design flood and process of each frequency of the arbitrary small watershed in the world are calculated in combination with the reasoning formula of the target watershed.

[0133] Obviously, the above only describes some embodiments of the present application, but not all the embodiments. The above embodiments are not used to limit the present application, and the present application can have various changes and variations for those skilled in the art. Any combination, modification, equivalent replacement, improvement and other embodiments made by those skilled in the art within the spirit and principle of the present application should be within the protection scope of the present application.

Claims

1. A rapid calculation method for design floods in small watersheds at any location globally, characterized by: Includes the following steps: S1. Establish a river system vector dataset V_Str and a watershed boundary vector dataset V_Bou based on the global DEM dataset; specifically including the following steps: S1.1 Prepare a global DEM dataset. Use water system data extracted from remote sensing images or other methods to correct the original DEM data to ensure the correctness of the hydrological logic of the DEM data, and obtain the corrected DEM dataset Adj_DEM. S1.2 After performing annotation calculations on the corrected DEM dataset Adj_DEM, the global flow direction raster dataset R_Dir and the cumulative flow raster dataset R_Acc are generated using the flow direction and cumulative flow tools in GIS software. S1.3 Based on the global flow direction raster dataset R_Dir and the cumulative flow raster dataset R_Acc, the global water system vector dataset V_Str and the watershed boundary vector dataset V_Bou are generated using GIS software. When generating the watershed boundary, a minimum sub-watershed area threshold is set to obtain the sub-watershed boundary vector dataset V_Bou and the water system vector dataset V_Riv that are above the area threshold. S2. Let the coordinates of the outlet of any small watershed be the target point. Starting from the target point, use the river system vector dataset V_Str and the watershed boundary vector dataset V_Bou to statistically analyze the watershed boundary above the target point. This includes the following steps: S2.1 Add a unique ID value Reach_ID to each vector river segment of the generated river system vector dataset V_Str, and record the ID values ​​of all upstream river segments in the attributes of each vector river segment; S2.2 In the generated sub-basin boundary V_Bou, assign the ID value of the river segment to the sub-basin; S2.3 Obtain the coordinates of the outlet of any small watershed. Based on the coordinates of the target point, quickly locate the sub-watershed through spatial query, and query upstream along the river segment where the sub-watershed is located. Find all upstream river segments based on the IDs of all upstream river segments, locate all upstream sub-watersheds, and merge them to generate the upstream watershed boundary V_Up_Boul. S3. Based on the watershed boundary above the target point, generate watershed characteristic parameters, rainstorm statistical parameters, and runoff generation and runoff statistical parameters; S4. Based on the watershed characteristic parameters, rainstorm statistical parameters, and runoff generation and runoff statistical parameters, and combined with the target watershed reasoning formula, calculate the design floods at various frequencies for this small watershed.

2. The method for rapid calculation of design floods in small watersheds at any location globally, as described in claim 1, is characterized in that: Step S2 further includes the following steps: S2.4 Based on the sub-basin boundary V_Target_SubBou where the target point is located, use spatial analysis tools to trim the global flow direction raster dataset R_Dir to obtain the flow direction raster data R_Target_Dir within the sub-basin boundary V_Target_SubBou where the target point is located; S2.5 Based on the flow direction raster data R_Target_Dir and the target point coordinates within the sub-basin boundary V_Target_SubBou, trace all upstream regions within the sub-basin V_Target_SubBou that flow towards the target point, thereby determining the sub-basin raster above the target point within the sub-basin V_Target_SubBou range, and generating the vector boundary V_Target_Bou; S2.6 Merge the vector boundary V_Target_Bou from S2.5 with the upstream basin boundary V_Up_Boul generated in S2.3 to generate the basin boundary V_Up_Bou above the target point of any small basin.

3. The method for rapid calculation of design floods in small watersheds at any location globally, as described in claim 1, is characterized in that: Step S3 includes: The steps for generating watershed characteristic parameters (S3.1) are as follows: S3.1.1 Obtain the statistical watershed area F based on the watershed boundary V_Up_Bou above any small watershed target point; S3.1.2 Based on the global flow direction raster dataset R_Dir, the global maximum river length raster dataset R_Len is generated using the water flow length tool of GIS software. This dataset R_Len contains the maximum upstream river length value at any raster point globally. S3.1.3 Based on the corrected DEM dataset Adj_DEM, the flow direction raster dataset R_Dir, and the cumulative flow raster dataset R_Acc as input data, the global elevation difference raster dataset R_Diff is generated using the distance tool of GIS software. This dataset R_Diff contains the elevation difference between the upstream maximum river length and the source of the river at any raster location globally and the height of the raster itself. S3.1.4 Based on the global elevation difference raster dataset R_Diff and the global maximum river length raster dataset R_Len, obtain the gradient raster dataset R_J of the maximum river length above any target point in the world, R_J=R_Diff / R_Len; The steps for generating heavy rainfall statistical parameters in S3.2 are as follows: S3.2.1 Prepare contour maps of rainfall statistical parameters such as mean rainfall and Cv value for different time periods in various regions of the world and rasterize them to generate a global rainfall statistical parameter raster dataset R_Storm_P; this dataset R_Storm_P contains rainfall statistical parameter values ​​for any raster location in the world; S3.2.2 Using the watershed boundary V_Up_Bou above any small watershed target point as a mask, the storm statistical parameter raster dataset R_Storm_P is cut using spatial analysis tools to obtain the storm statistical parameter raster dataset R_Up_Bou_Storm_P within any small watershed. The average storm statistical parameter value of any small watershed is then obtained by averaging. The steps for generating the flow statistics parameters in S3.3 are as follows: S3.3.1 Prepare contour maps of runoff generation parameters for various regions globally and rasterize them to generate a raster dataset R_P of runoff generation parameters for different regions globally; S3.3.2 Using the watershed boundary V_Up_Bou above the target point in any small watershed as a mask, use spatial analysis tools to cut the raster dataset R_P of runoff generation parameters in S3.3.1 to obtain the raster dataset R_Up_Bou_P of runoff generation parameters within any small watershed, and then average it to obtain the average runoff generation parameter value for any small watershed.

4. The method for rapid calculation of design floods in small watersheds at any location globally, as described in claim 3, is characterized in that: Step S4 includes: S4.1 Based on the average rainfall statistical parameter values ​​of any small watershed, the design rainfall values ​​at different frequencies for any small watershed are calculated using the frequency analysis method. S4.2 Based on the average runoff generation and runoff parameters of the arbitrary small watershed, and combined with the design rainstorm values ​​at different frequencies, the runoff generation and runoff parameters of the arbitrary small watershed at different frequencies are calculated. S4.3 Based on the watershed characteristic parameter values, design rainfall values, and runoff generation and confluence parameter values, and combined with the target watershed reasoning formula, calculate the design floods and processes at various frequencies for any small watershed globally.

5. A design flood calculation system, characterized in that: A program module configured to perform the method according to any one of claims 1-4, comprising: The watershed parameter generation module is used to establish the water system vector dataset V_Str and the watershed boundary vector dataset V_Bou, and to count the watershed boundary V_Up_Bou above any target point in any small watershed. Based on the watershed boundary V_Up_Bou above any target point in any small watershed, watershed parameters are generated. The rainstorm statistical parameter generation module is used to generate a global rainstorm statistical parameter raster dataset R_Storm_P, and to generate rainstorm statistical parameters based on the watershed boundary V_Up_Bou above any small watershed target point; The runoff generation and runoff statistics parameter generation module is used to generate a raster dataset R_P of runoff and runoff parameters for different regions around the world, and to generate runoff and runoff statistics parameters based on the watershed boundary V_Up_Bou above any small watershed target point; The flood calculation module calls upon watershed parameters, rainstorm statistics parameters, and runoff generation and confluence statistics parameters, and calculates design floods at various frequencies based on the target watershed inference formula.

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