A method, device and storage medium for dividing sub-watershed units in the near-dam area

Abstract

The present invention discloses a method, device and storage medium for dividing sub-watershed units in the near-dam area. The method includes: generating the water system and watershed in the near-dam area based on DEM data; combining the generated water system and watershed in the near-dam area, and extracting the topography and geomorphology of the watershed in the near-dam area based on DEM data; combining DEM data and rainfall data to draw a rainstorm center map, and dividing the watershed in the near-dam area into sub-watershed units according to the topography and geomorphology and the rainstorm center map. The present invention can clearly reflect the runoff generation and concentration methods of different underlying surfaces such as mountains and plains, reflect the influence of the rainstorm center on runoff generation and concentration, make the division of sub-watershed units more reasonable, facilitate considering the physical characteristics of watershed runoff generation and concentration, improve the accuracy of flood forecasting, ensure the stable and reliable data source, the calculation results are accurate and reasonable, solve the problem of how to divide the watershed in the near-dam area in humid regions, and is conducive to the in-depth development of sub-watershed division research.

Description

Technical Field

[0001] The present invention relates to a method, device and storage medium for dividing sub - basin units in the near - dam area, belonging to the field of hydrological technology. Background Art

[0002] Through the generalized description of the hydrological process, the watershed hydrological model simulates a certain flood runoff process generated on the watershed by a certain structure and parameters and calculates the flow data at the outlet section. It is an important tool for current flood forecasting work. With the development of geographic information technology, remote sensing technology and computer science, even in areas without data or with scarce data, the watershed geographical conditions can be obtained through remote sensing images such as digital elevation models (DEM), land use and soil classification maps.

[0003] There are characteristics such as the uneven distribution of rainfall, the unevenness of the underlying surface properties and the unevenness of the river network properties on the watershed surface. In order to consider these unevennesses, the computational watershed is often divided into multiple unit watersheds, and rainfall - runoff calculations are carried out separately within each unit watershed. Different numbers of watershed blocks result in different treatments of unevenness, different average effects of relevant influencing factors on the runoff formation process, and corresponding changes in model parameters.

[0004] How to use DEM data and rainfall data to reasonably divide the watershed, so as to consider the influence of the spatial unevenness of geographical features on watershed flood simulation to a certain extent, is also one of the key points and difficulties in the process of distributed and refined watershed flood simulation and forecasting.

[0005] When studying the method of dividing the near - dam area watershed, the first challenge is the number of sub - watershed divisions and the division basis, and the determination of the confluence threshold. In current practical applications, the empirical method is mainly used for sub - watershed division. Since this method has no strong basic basis, its rationality cannot be guaranteed.

[0006] Aiming at the above deficiencies, how to establish a reasonable method for dividing sub - watershed units to facilitate the use of hydrological models for watershed flood forecasting is exactly the problem that the inventor needs to solve. Summary of the Invention

[0007] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a method, device and storage medium for dividing sub - basin units in the near - dam area, which have the advantages of stable and reliable data sources, high calculation efficiency, objective and reasonable results, etc., and are worthy of promotion.

[0008] To achieve the above - mentioned purpose, the present invention is implemented by the following technical solutions:

[0009] In the first aspect, the present invention provides a method for dividing sub - basin units in the near - dam area, including:

[0010] Generate the water system and watershed in the near-dam area based on DEM data;

[0011] Combined with the generated water system and watershed in the near-dam area, extract the topography and geomorphology of the near-dam area watershed based on DEM data;

[0012] Draw the rainstorm center map by combining DEM data and rainfall information;

[0013] Divide the near-dam area watershed into sub-watershed units according to the topography and geomorphology and the rainstorm center map.

[0014] Further, the generating the water system and watershed in the near-dam area based on DEM data includes:

[0015] Based on the digital elevation DEM data of the studied watershed, fill the depressions in the watershed, and use the depression filling function to perform depression filling calculations;

[0016] Extract the flow direction of the watershed. The flow direction judgment adopts the following principle: starting from n = 0, represented by 2 to the power of n, and represented by the numbers 1, 2, 4, 8, 16, 32, 64, 128 in counterclockwise order to represent the 8 directions of east, southeast, south, southwest, west, northwest, north, and northeast. On a 3×3 window, calculate the distance-weighted elevation difference between the central grid and each adjacent grid, and determine the flow direction of the grid with the steepest slope among the 8 directions as the water flow direction;

[0017] Perform the flow accumulation calculation on the watershed based on the water flow direction data;

[0018] Given a flow accumulation threshold T, extract the river channels in the watershed. If the generated water system is too sparse, use the threshold calculation formula to change the threshold and re-extract the river channels after calculation;

[0019] Extract the watersheds of the sub-watersheds, divide the basic watershed units, and the number of basic watershed units is the same as the number of extracted river channels.

[0020] Further, the combining the generated water system and watershed in the near-dam area and extracting the topography and geomorphology of the near-dam area watershed based on DEM data includes:

[0021] Use DEM to extract the basic topographic feature elements of the watershed. The basic topography includes points, lines, and surfaces that control the distribution characteristics of the topography and geomorphology, and are used for the research of topography and geomorphology division. The feature elements include slope, aspect, and slope rate change direction;

[0022] After generating the boundary of the studied watershed, calculate the slope and aspect. The slope S and aspect A of any point on the ground surface are functions of the elevation change rates in the east-west and north-south directions of the topographic surface;

[0023] Obtain the area between every two contour lines and the length of each contour line based on the DEM of the studied watershed;

[0024] Based on the extraction of the surface slope, the slope aspect change rate value is extracted for the second time to calculate and obtain the slope aspect change rate.

[0025] Furthermore, combining the DEM data and rainfall information to draw the heavy rain center map, including:

[0026] Obtain the coordinates of hydrological stations, rainfall stations and their historical rainfall amounts. The coordinates are used to determine the positions of the stations on the map, and the historical rainfall amounts are used for subsequent interpolation calculations;

[0027] Perform spatial deterministic interpolation, and use the inverse distance weighted method for interpolation;

[0028] The heavy rain center map calculated by interpolation is a square map covering the entire basin. Further, it is cropped into a suitable basin shape, and the amplitude range and color of the rainfall change are adjusted to ensure that the comparison magnitudes of the heavy rain center maps corresponding to different flood events are consistent.

[0029] Furthermore, dividing the sub-basins in the near-dam area according to the topographic features and the heavy rain center map, including:

[0030] Merge the basic basin units and preliminarily divide the sub-basins;

[0031] According to the calculated slope and slope aspect change rate, distinguish the characteristics of different underlying surfaces in the basin, analyze the topographic features and land use type characteristics in the basin, and then calculate the fractal dimension value of the land use. Among them, when the fractal dimension is small, it means that the influence of human activities is small, and vice versa, the larger the dimension, the greater the influence of human activities;

[0032] Comprehensively use the preliminary sub-basin division results and the heavy rain center map to determine the sub-basin units;

[0033] Extract each divided sub-basin separately, and then extract the centroid of each sub-basin to calculate the length of the longest flow path of the sub-basin.

[0034] Furthermore, it also includes dividing the sub-basins at different positions according to the areas with large human activity influence. The areas with large human activity influence include towns, mountains and plains.

[0035] Furthermore, comprehensively use the preliminary sub-basin division results and the heavy rain center map to determine the sub-basin units, including:

[0036] By the inverse distance weighted method, set a threshold according to the rainfall data of each rainfall station, and calculate the rainfall distribution in the basin space; use colors to represent the magnitude of rainfall, the darker the color, the greater the rainfall, and the lighter the color, the smaller the rainfall. The dark circular areas in the heavy rain center map are the positions of the heavy rain centers;

[0037] For the first flood, based on the rainstorm center map, the preliminary division results of sub-basin units are adjusted by visual method to ensure that multiple rainstorm centers of this flood are in different sub-basins;

[0038] Execute the step of adjusting the division results of sub-basin units. The step of adjusting the division results of sub-basin units includes: for the case where there are multiple rainstorm centers in one sub-basin, further adjust the division results of sub-basin units by visual method;

[0039] Analyze the rainstorm center maps of multiple floods in the basin, and repeat the step of adjusting the division results of sub-basin units until there is no more than one rainstorm center in one sub-basin, so as to obtain the division results of sub-basin units.

[0040] In a second aspect, the present invention provides a device for dividing sub-basin units in the near-dam area, including:

[0041] A first extraction unit for generating a water system and a basin in the near-dam area based on DEM data;

[0042] A second extraction unit for extracting the topography and geomorphology of the near-dam area basin based on the generated water system and basin in the near-dam area and DEM data;

[0043] A rainstorm center map drawing unit for drawing a rainstorm center map by combining DEM data and rainfall data;

[0044] A sub-basin unit division unit for dividing the near-dam area basin into sub-basin units according to the topography and geomorphology and the rainstorm center map.

[0045] In a third aspect, the present invention provides a device for dividing sub-basin units in the near-dam area, including a processor and a storage medium;

[0046] The storage medium is used for storing instructions;

[0047] The processor is used to operate according to the instructions to execute the steps of the method according to any one of the above.

[0048] In a fourth aspect, the present invention provides a computer-readable storage medium, on which a computer program is stored, and when the program is executed by a processor, the steps of the method according to any one of the above are implemented.

[0049] Compared with the prior art, the beneficial effects achieved by the present invention:

[0050] The present invention comprehensively considers the influence of topography and the position of the rainstorm center on the division of sub - basin units in the near - dam area. By dividing sub - basin units according to topography and the rainstorm center area, it can clearly reflect the runoff generation and concentration patterns of different underlying surfaces such as mountains and plains, embody the influence of the rainstorm center on runoff generation and concentration, make the division of sub - basin units more reasonable, facilitate considering the physical characteristics of basin runoff generation and concentration, improve the accuracy of flood forecasting, ensure the stability and reliability of data sources, and make the calculation results accurate and reasonable. It solves the problem of how to divide the near - dam area basin in humid regions and is conducive to the in - depth development of sub - basin division research. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 FIG. is a schematic flow chart of a method for dividing sub - basin units in the near - dam area provided by an embodiment of the present invention;

[0052] Figure 2 FIG. is a DEM data map of the basin provided by an embodiment of the present invention;

[0053] Figure 3 FIG. is a schematic diagram of the principle for determining the flow direction provided by an embodiment of the present invention;

[0054] Figure 4 FIG. is a topographic and geomorphic map of the study area provided by an embodiment of the present invention;

[0055] Figure 5 FIG. is a rainstorm center map of the study area provided by an embodiment of the present invention;

[0056] Figure 6 FIG. is a map of the division of sub - basin units in the basin provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0057] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and cannot be used to limit the protection scope of the present invention.

[0058] Embodiment 1

[0059] This embodiment introduces a method for dividing sub - basin units in the near - dam area, including:

[0060] Generating the water system and basin in the near - dam area based on DEM data;

[0061] Combining the generated water system and basin in the near - dam area, extracting the topography and geomorphology of the near - dam area basin based on DEM data;

[0062] Drawing a rainstorm center map by combining DEM data and rainfall data;

[0063] Dividing the near - dam area basin into sub - basin units according to the topography and geomorphology and the rainstorm center map.

[0064] As Figures 1 to 6As shown in the figure, the method for dividing the sub - watershed units in the near - dam area provided by this embodiment specifically involves the following steps in its application process:

[0065] S1. A method for dividing sub - watershed units in the near - dam area that comprehensively considers topography and geomorphology and rainstorm centers. In step 1, the depression - filling data, flow - direction data, flow - accumulation data, river channels, watersheds, etc. of the near - dam area watershed are extracted. Specifically, it includes the following steps:

[0066] 1) Prepare the digital elevation model (DEM) data of the research watershed ( Figure 2 ). Since the DEM is a relatively smooth surface simulation map, but there will be sunken areas in the actual terrain, which makes the calculated flow direction inconsistent with the actual situation. Therefore, it is necessary to fill the depressions in the watershed. Use the depression - filling function to perform depression - filling calculations.

[0067] 2) Extract the flow direction of the watershed. The following principles are used for flow - direction judgment ( Figure 3 ): Starting from n = 0, represented by 2 to the power of n, and in the counter - clockwise direction, the eight directions of east, southeast, south, southwest, west, northwest, north, and northeast are represented by the numbers 1, 2, 4, 8, 16, 32, 64, and 128 respectively. That is, on a 3×3 window, calculate the distance - weighted elevation difference between the central grid and each adjacent grid. The flow direction of the grid with the steepest slope among the eight directions is determined as the water flow direction.

[0068] 3) Perform flow - accumulation calculation on the watershed. The flow - accumulation amount is calculated based on the water - flow direction data. For each grid, the size of its flow - accumulation amount represents how many grids' water flows through this grid in its upstream. The larger the flow - accumulation value, the more likely surface runoff is to form in this area.

[0069] 4) Given a flow - accumulation threshold T, extract the river channels of the watershed. If the generated water system is too sparse, use the threshold calculation formula to change the threshold and re - extract the river channels after calculation.

[0070] Threshold calculation formula:

[0071]

[0072] In the formula: Acc k is the cumulative value within the grid cell numbered k, T is the river - channel threshold of the watershed, r = 1 indicates that this grid cell is a river - channel grid cell, that is, it is defined as a river channel. r = 0 indicates that this grid cell is a slope grid cell, which means it is not defined as a river channel.

[0073] 5) Extract the watersheds of the sub - watersheds and divide the basic watershed units. The number of basic watershed units is the same as the number of extracted river channels. The denser the water - system extraction, the more detailed the sub - watershed division, which is convenient for subsequent merging processing.

[0074] S2. A method for dividing sub - watershed units in the near - dam area considering topographic features and rainstorm centers comprehensively, characterized in that in step 2, based on the generated water system and watershed in the near - dam area, the topographic features of the near - dam area watershed are extracted from DEM data, specifically including the following steps:

[0075] 1) Use DEM to extract the basic topographic feature elements of the watershed ( Figure 4 ), which mainly refer to the points, lines, and surfaces that control the distribution characteristics of topographic features and can be used for topographic feature division research. The feature elements mainly include slope, aspect, and slope rate change direction.

[0076] 2) After generating the boundary of the research watershed, slope and aspect calculations can be carried out. The slope S and aspect A of any point on the ground surface are functions of the elevation change rates in the east - west (Y - axis) and north - south (X - axis) directions of the topographic surface:

[0077]

[0078]

[0079] In the formula: f x —— The elevation change rate in the north - south direction; f y —— The elevation change rate in the east - west direction.

[0080] 3) According to the DEM of the research watershed, the area between every two contour lines and the length of each contour line can be obtained. First, calculate the slope between two contour lines as:

[0081]

[0082] In the formula: ΔH—— Contour interval; b—— The horizontal distance between two contour lines, that is, b = 2f1 / (L0 + L1)

[0083] On this basis, the slope between any two contour lines can be obtained. Assuming there are n contour lines in total, then:

[0084]

[0085] Then the average slope of the watershed is For:

[0086]

[0087] In the formula: F—— The area of the research watershed.

[0088] 4) The aspect change rate is the secondary extraction of the aspect change rate value on the basis of the extraction of the surface slope, that is, the slope of aspect (SOA), which is the change rate of aspect in the horizontal direction.

[0089] First, calculate SOA1 with errors; secondly, calculate SOA2 based on DEM. The specific calculation formula for slope aspect change rate is as follows:

[0090]

[0091] S3. A method for dividing sub - basin units in the near - dam area considering topographic features and rainstorm centers comprehensively, characterized in that in step 3, a rainstorm center map is drawn by combining DEM data and rainfall data, which specifically includes the following steps:

[0092] 1) Obtain the coordinates of hydrological stations, rainfall stations and their historical rainfall amounts. The coordinates are used to determine the positions of the stations on the map, and the historical rainfall amounts are used for subsequent interpolation calculations.

[0093] 2) Perform spatial deterministic interpolation, and use the inverse distance weighted method for interpolation.

[0094] The inverse distance weighted (IDW) interpolation method is based on the principle of proximity and similarity: that is, the closer two objects are, the more similar their properties are; conversely, the farther apart they are, the less similar they are. It performs weighted averaging with the distance between the interpolation point and the sample points as the weight. The closer the sample point is to the interpolation point, the greater its weight. The formula is as follows:

[0095]

[0096] In the formula, Z(s0) is the predicted value at s0;

[0097] N is the number of sample points around the prediction point to be used in the prediction calculation;

[0098] λ i is the weight of each sample point used in the prediction calculation, and this value decreases as the distance between the sample point and the prediction point increases;

[0099] Z(s i ) is the measured value obtained at S i .

[0100] The formula for determining the weight is;

[0101]

[0102]

[0103] In the formula: P is the exponential value, is the distance between the prediction point S0 and each known sample point S i .

[0104] The weight of a sample point in the calculation of the predicted point value is related to the exponent p. That is to say, if the distance between the sampling point and the predicted value decreases, the weight of the standard sample point's influence on the predicted point will increase exponentially. During the prediction process, the weights of each sample point value's effect on the predicted point value are proportional, and the sum of these weight values is 1.

[0105] 3) The rainstorm center map calculated by IDW interpolation is a square map covering the entire basin, and it needs to be further cropped into a suitable basin shape, as well as adjusted for the range of rainfall variation and color to ensure that the comparison magnitudes of the rainstorm center maps corresponding to different flood events ( Figure 5 ) are consistent.

[0106] S4. A method for dividing sub-basin units in the near-dam area by comprehensively considering topography and rainstorm centers, characterized in that in step 4, the near-dam area basin is divided into sub-basin units according to topography and the rainstorm center map, specifically including the following steps:

[0107] 1) The fractal dimension method can accurately measure the complexity and fragmentation degree of ground objects. The fractal formula applicable to the n-dimensional Euclidean space relationship:

[0108]

[0109] When n = 2, it is the fractal formula for two-dimensional Euclidean space. Let A(r) and P(r) represent the patch area and perimeter measured with r as the measurement scale, and we get:

[0110] P(r) 1 / D = kr (1-D) / D A(r) 1 / 2

[0111] Take the logarithm of both sides, that is

[0112] lg A(r) = (2 / D)lg P(r) + C

[0113] D represents the fractal dimension value, A(r) is the patch area of the land use type, P(r) is the perimeter of the corresponding land use type patch, and C is a constant to be determined.

[0114] 2) Merge the basic catchment units extracted in step 1 to preliminarily divide sub-catchments: According to the slope and aspect change rate calculated in step 2, distinguish different underlying surface characteristics such as mountains and plains within the catchment. The larger the slope and aspect change rate, the steeper the terrain, which means it represents mountains. Then analyze the topographic and geomorphic features and land use type characteristics within the catchment, and then calculate the fractal dimension value of land use according to the above formula. A smaller fractal dimension represents less influence from human activities, and conversely, a larger dimension represents greater influence from human activities. Human activities also have a significant impact on the topography and geomorphology. Areas with a large impact from human activities can be represented as towns, which are distinguished from different terrains such as mountains and plains. Based on the different positions of towns, mountains, and plains within the catchment, make a general division of the sub-catchments.

[0115] 3) Comprehensively use the preliminary sub-catchment division results based on topography and geomorphology and the rainstorm center map mentioned above to determine the sub-catchment units. The specific steps are as follows:

[0116] (1) By the inverse distance weighted method in step 3, set a threshold according to the rainfall data of each rain gauge station and calculate the rainfall distribution in the catchment space; use colors to represent the magnitude of rainfall. The darker the color, the greater the rainfall, and the lighter the color, the smaller the rainfall. The dark circular areas in the rainstorm center map are the positions of the rainstorm centers.

[0117] (2) A flood may have multiple rainstorm centers. For the first flood, based on the rainstorm center map, use the visual method to adjust the preliminary sub-catchment unit division results to ensure that multiple rainstorm centers of this flood are in different sub-catchments.

[0118] (3) If directly adopting the division results of the rainstorm center map of the first flood in step (2), due to the different positions of the rainstorm centers in different flood events, for the second flood, there may be a situation where a sub-catchment has multiple rainstorm centers.

[0119] (4) For the situation where a sub-catchment has multiple rainstorm centers, further use the visual method to adjust the sub-catchment unit division results.

[0120] (5) Analyze the rainstorm center maps of multiple floods in the catchment and repeat the above step (4) until there is no more than one rainstorm center in a sub-catchment, and obtain the sub-catchment unit division results (Figure 6).

[0121] 4) The sub-catchment unit division results obtained from the above steps can not only better consider the spatial distribution of runoff generation in the catchment, but also facilitate quantitatively considering the physical characteristics of confluence: Extract each divided sub-catchment separately, and then extract the centroid of each sub-catchment to calculate the longest flow path length of the sub-catchment. The peak delay time t p refers to the time difference between the peak time of the unit hydrograph and the centroid time corresponding to the net rainfall distribution map. The calculation formula is:

[0122]

[0123] Wherein, L w is the length of the longest river channel in the sub - watershed, CN is the average curve number in the sub - watershed, S is the slope of the longest river channel in the sub - watershed, and Δt is the analysis time step.

[0124] Example 2

[0125] This example provides a device for dividing sub - watershed units in the near - dam area, including:

[0126] A first extraction unit for generating the water system and watershed in the near - dam area based on DEM data;

[0127] A second extraction unit for extracting the topography and geomorphology of the near - dam area watershed based on the generated water system and watershed in the near - dam area and DEM data;

[0128] A rainstorm center map drawing unit for drawing a rainstorm center map by combining DEM data and rainfall data;

[0129] A sub - watershed unit division unit for dividing the near - dam area watershed into sub - watershed units according to the topography and geomorphology and the rainstorm center map.

[0130] Example 3

[0131] This example provides a device for dividing sub - watershed units in the near - dam area, including a processor and a storage medium;

[0132] The storage medium is used to store instructions;

[0133] The processor is used to operate according to the instructions to execute the steps of the method according to any one of the following:

[0134] Generate the water system and watershed in the near - dam area based on DEM data;

[0135] Combine the generated water system and watershed in the near - dam area, and extract the topography and geomorphology of the near - dam area watershed based on DEM data;

[0136] Combine DEM data and rainfall data to draw a rainstorm center map;

[0137] Divide the near - dam area watershed into sub - watershed units according to the topography and geomorphology and the rainstorm center map.

[0138] Example 4

[0139] This example provides a computer - readable storage medium, on which a computer program is stored, and when the program is executed by a processor, it implements the steps of the method according to any one of the following:

[0140] Generate the water system and watershed in the near - dam area based on DEM data;

[0141] Combined with the generated near-dam area water system and watershed, the topography and geomorphology of the near-dam area watershed are extracted based on the DEM data;

[0142] Combined with the DEM data and rainfall information, a heavy rain center map is drawn;

[0143] The near-dam area watershed is divided into sub-watershed units according to the topography and geomorphology and the heavy rain center map.

[0144] The above are only the preferred embodiments of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A method for dividing sub - watershed units in the near - dam area, characterized in that, Including: Generating the water system and basin in the near-dam area based on DEM data; Combining the generated water system and basin in the near-dam area, and extracting the topography and geomorphology of the basin in the near-dam area based on DEM data; Drawing the rainstorm center map by combining DEM data and rainfall data; Dividing the basin in the near-dam area into sub-basin units according to the topography and geomorphology and the rainstorm center map; The dividing the basin in the near-dam area into sub-basin units according to the topography and geomorphology and the rainstorm center map includes: Merging the basic basin units and preliminarily dividing the sub-basins; Distinguishing the characteristics of different underlying surfaces within the basin according to the calculated slope and slope aspect variability, analyzing the topography and geomorphology and land use type characteristics within the basin, and then calculating and obtaining the fractal dimension value of land use. Among them, when the fractal dimension is small, it represents little influence of human activities, and conversely, the larger the dimension, the greater the influence of human activities; Comprehensively applying the preliminary division result of the sub-basins and the rainstorm center map to determine the sub-basin units; Separately extracting each divided sub-basin, then extracting the centroid of each sub-basin, and calculating the longest flow path length of the sub-basin; Comprehensively applying the preliminary division result of the sub-basins and the rainstorm center map to determine the sub-basin units, including: Based on the inverse distance weighted method, setting a threshold according to the rainfall data of each rain gauge station, and calculating the rainfall distribution in the basin space; using colors to represent the magnitude of rainfall, the darker the color, the greater the rainfall, and the lighter the color, the smaller the rainfall. The dark circular area in the rainstorm center map is the location of the rainstorm center; For the first flood, adjusting the preliminary division result of the sub-basin units by visual method based on the rainstorm center map to ensure that multiple rainstorm centers of this flood are in different sub-basins; Performing the step of adjusting the sub-basin unit division result. The step of adjusting the sub-basin unit division result includes: for the case where there are multiple rainstorm centers in a sub-basin, further adjusting the sub-basin unit division result by visual method; Analyzing the rainstorm center maps of multiple floods in the basin, and repeating the step of adjusting the sub-basin unit division result until there is no more than one rainstorm center in a sub-basin, and obtaining the sub-basin unit division result.

2. The method for dividing the sub-watershed units in the near-dam area according to claim 1, wherein: The generating the water system and basin in the near-dam area based on DEM data includes: Based on the digital elevation DEM data of the studied basin, filling the depressions in the basin, and using the depression filling function to perform depression filling calculation; Extracting the flow direction of the basin. The flow direction judgment adopts the following principle: starting from n = 0, representing with 2 to the power of n, and using the numbers 1, 2, 4, 8, 16, 32, 64, 128 to represent the 8 directions of east, southeast, south, southwest, west, northwest, north, and northeast in counterclockwise order. On a 3×3 window, calculate the distance weight drop between the central grid and each adjacent grid, and determine the flow direction of the grid with the steepest slope among the 8 directions as the water flow direction; Performing the confluence accumulation calculation on the basin based on the water flow direction data; Given a confluence threshold T, extracting the river channels of the basin. If the generated water system is too sparse, use the threshold calculation formula to change the threshold and re-extract the river channels; Extracting the watershed of the sub-basins and dividing the basic basin units. The number of basic basin units is the same as the number of extracted river channels.

3. The method for dividing the near-dam sub-watershed unit according to claim 1, characterized in that: The generated near-dam area water system and basin, based on the DEM data, extract the topography and geomorphology of the near-dam area basin, including: Using the DEM to extract the basic topographic feature elements of the basin. The basic topography includes points, lines, and planes that control the distribution characteristics of the topography and geomorphology, and are used for the research of topography and geomorphology division. The feature elements include slope and aspect, and slope rate variation; After generating the research basin boundary, calculate the slope and aspect. The slope S and aspect A of any point on the ground surface are functions of the elevation change rates in the east-west and north-south directions of the topographic surface; Obtain the area between every two contour lines and the lengths of each contour line based on the DEM of the research basin; Based on the extraction of the ground surface slope, perform a secondary extraction of the aspect change rate value to calculate and obtain the aspect change rate.

4. The method for dividing the sub - watershed units in the near - dam area according to claim 1, characterized in that: The combination of DEM data and rainfall data is used to draw the storm center map, including: Obtain the coordinates of hydrological stations, rain gauge stations and their historical rainfall amounts. The coordinates are used to determine the station positions on the map, and the historical rainfall amounts are used for subsequent interpolation calculations; Perform spatial deterministic interpolation, and use the inverse distance weighted method for interpolation; The storm center map calculated by interpolation is a square map covering the entire basin. Further, it is cropped into a suitable basin shape, and the amplitude range and color of its rainfall variation are adjusted to ensure that the comparison magnitudes of the storm center maps corresponding to different flood events are consistent.

5. The method for dividing the sub-watershed units in the near-dam area according to claim 1, wherein: It also includes dividing sub-basins at different positions according to the areas greatly affected by human activities. The areas greatly affected by human activities include towns, mountains and plains.

6. A device for dividing sub - watershed units in the near - dam area, which adopts the method for dividing sub - watershed units in the near - dam area described in claim 1, is characterized in that, Including: A first extraction unit for generating a near-dam area water system and basin based on DEM data; A second extraction unit for, in combination with the generated near-dam area water system and basin, extracting the topography and geomorphology of the near-dam area basin based on DEM data; A storm center map drawing unit for drawing a storm center map by combining DEM data and rainfall data; A sub-basin unit division unit for dividing the near-dam area basin into sub-basin units according to the topography and geomorphology and the storm center map.

7. A device for dividing sub - watershed units in the near - dam area, characterized in that: Including a processor and a storage medium; The storage medium is used to store instructions; The processor is used to operate according to the instructions to execute the steps of the method according to any one of claims 1 to 5.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by the processor, it realizes the steps of the method according to any one of claims 1 to 5.

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