A fast construction method of one-dimensional hydrodynamic model based on dem elevation data

Abstract

The application discloses a kind of one-dimensional hydrodynamic model fast construction method based on dem elevation data, it is related to hydrological simulation technical field;The method comprises: obtaining the data of river channel thalweg and dem elevation data;Calculate the length of river section that dynamic adjustment straight coefficient;Obtain section elevation point;Identify river section bank line, retain the elevation point within left and right bank;Based on measured section information correction extracted river section;According to the relationship of river channel thalweg upstream and downstream, construct river connection, form one-dimensional hydrodynamic model;The present application is based on dem data and river channel thalweg vector data, by straight coefficient dynamic division river section, retain the topological connection between river sections, generate section data in line with the curved morphology of river channel, can quickly and accurately obtain river section information, realize one-dimensional hydrodynamic model fast modeling, can improve the accuracy and applicability of hydrological simulation technology in data deficient area.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hydrological simulation, and discloses a one-dimensional hydrodynamic model rapid construction method based on DEM elevation data. BACKGROUND

[0002] In the field of hydrological simulation and the like, a one-dimensional hydrodynamic model is a key tool for simulating river flow movement and predicting flood evolution, and is widely used in the fields of basin flood control planning and water resource management. The construction of a traditional model highly depends on artificially measured river section data. However, in an un-informed area or a harsh environment area, field measurement faces severe challenges, not only in terms of high cost of manpower, material resources and time, but also in terms of great difficulty in implementation due to complex terrain, inconvenient transportation and the like. Meanwhile, artificial measurement is limited in range and is difficult to support systematic research and analysis of a large-scale basin.

[0003] There is also a scheme for extracting a river section by using a digital elevation model (DEM) in the market. The existing DEM-based scheme divides river sections at a fixed interval, which is difficult to adapt to complex river morphologies, especially complex changes in sharp bending areas, resulting in insufficient representativeness of the section. In addition, the DEM data itself is difficult to accurately reflect underwater topographic information, further weakening the reliability of the extracted section.

[0004] Therefore, it is urgent to develop a new method capable of extracting and correcting a river section based on DEM data, dynamically adapting to river morphologies, and constructing a high-precision one-dimensional hydrodynamic model. SUMMARY

[0005] In view of the above-mentioned shortcomings of the prior art, the present application aims to provide a one-dimensional hydrodynamic model rapid construction method based on DEM elevation data, which uses DEM data and river thalweg vector data to automatically divide river sections, retain upstream and downstream topological relations, obtain section data considering changes in river bending morphologies, determine left and right bank positions of each section based on section morphologies, and extract section morphologies based on measured section elevation correction, so as to quickly and accurately obtain river section information and realize rapid modeling of a one-dimensional hydrodynamic model. The method is used to solve the problems that the existing DEM-based scheme divides river sections at a fixed interval and is difficult to adapt to complex river morphologies, and DEM data itself is difficult to accurately reflect underwater topographic information.

[0006] To achieve the above-mentioned purpose, the one-dimensional hydrodynamic model rapid construction method based on DEM elevation data provided by the present application comprises the following steps:

[0007] S1, obtaining river thalweg vector data layers of a target river and DEM data containing the river;

[0008] S2, dividing initial river sections based on the river thalweg vector data layers of the target river;

[0009] S3, calculate the straightness coefficient of the initial river section K and set the minimum length of the initial river section L min The calculation method of the straightness coefficient is:

[0010] ;

[0011] In the formula, is the straightness coefficient of the river section, is the straight line distance from the starting point to the end point of the river section, is the actual length of the thalweg in the river section;

[0012] S4, according to the straightness coefficient K recursively divide the initial river section to form a plurality of sub-river sections, until the straightness coefficient of the initial river section K ≥ 0.8, or the length of the initial river section L min ， Then number each sub-river section according to the upstream and downstream topological relationship of the initial river section;

[0013] S5, based on the micro-topographic changes of the sub-river section, calculate the cross-section direction of each sub-river section, and generate the river cross-section line by extending the midpoint of the thalweg in the river section of the sub-river section to both sides as the cross-section center;

[0014] S6, based on the dem data, obtain the cross-section elevation points of the sub-river section, select the sampling points on the river cross-section line of the sub-river section, and obtain the elevation values of each sampling point;

[0015] S7, extract the cross-section shoreline information of each sub-river section, and retain the elevation points on the left and right banks, floodplain and main river channel;

[0016] S8, based on the existing measured river cross-section data, based on the systematic bias propagation correction strategy, correct the extracted cross-section elevation; the cross-section elevation correction method includes the following steps:

[0017] S801, unify the coordinate system and elevation datum of the measured cross-section and the extracted cross-section, and identify the mileage of each measured cross-section on the thalweg;

[0018] S802, calculate the elevation deviation value of the thalweg at the position of each measured cross-section, take the cross-section starting point distance as the x-axis and the thalweg elevation deviation value as the y-axis, and use linear regression to fit the deep thalweg point elevation deviation function of the measured cross-section and the extracted cross-section ;

[0019] S803, for a certain cross-section with a mileage of , correct the deep thalweg point elevation to , wherein, This is the corrected riverbed elevation value. The riverbed elevation extracted for DEM;

[0020] S804. Determine the elevation of the lower side of the left and right banks of this cross-section. For greater than Elevation points are retained to their original values; for elevation values ​​less than [a certain value], [the remaining values ​​are omitted]. The elevation of a given point is corrected according to the following formula:

[0021] ;

[0022] In the formula, The corrected elevation for this elevation point. The elevation of this elevation point is extracted based on DEM data;

[0023] S9. Based on the upstream and downstream topological relationship of the channel line in each sub-river segment, establish the connection relationship of the cross sections of each sub-river segment and construct a one-dimensional hydrodynamic model.

[0024] In one embodiment of the present invention, in step S1, the coordinate system of the channel line vector data layer of the target river is a projected coordinate system, and the resolution of the DEM data is not less than 30 meters.

[0025] In one embodiment of the present invention, in step S4, the recursive partitioning satisfies:

[0026] ;

[0027] In the formula, The initial river segment length, This represents the length of the sub-river segment after division.

[0028] In one embodiment of the present invention, in step S5, the method for determining the cross-sectional direction includes the following steps:

[0029] S501, taking the midpoint of the middle channel line of the sub-river section as the center, construct... x The terrain analysis buffer uses a 3x3 window DEM slope algorithm to calculate the slope and flow direction of each grid cell within the buffer. It is 1.5 times the average width of the river;

[0030] S502. Collect statistics on terrain slope information within the buffer zone, mark grids with a slope ≥ 25° as steep bank areas, and mark the distribution range of steep bank areas (left bank / right bank).

[0031] S503. Statistical topographic analysis: The local flow direction of all river channels within the buffer zone is obtained by averaging the values ​​of the grids through which the threshing line passes. ;

[0032] S504. Calculate the vertical direction of the average flow direction of the raster grid in the steep bank areas on both the left and right banks within the terrain buffer zone, denoted as... (Left Bank) (Right bank), calculate the corrected river flow direction:

[0033] ;

[0034] in, , These represent half of the total number of grid cells in the steep bank areas of the left and right banks within the terrain buffer zone. That is, satisfying 0.5 , , , ;

[0035] S505. Take the direction perpendicular to the corrected river flow direction N as the cross-sectional direction of the river section, and extend it to both banks respectively. Obtain the cross-sectional line of the river channel.

[0036] In one embodiment of the present invention, in step S6, the horizontal distance between the sampling points is half the resolution of the dem elevation data.

[0037] In one embodiment of the present invention, in step S9, the connection relationship of each sub-river section is determined by the segment numbering order of the threshing line in the river channel, and the river channel sections corresponding to adjacent sub-river sections maintain hydraulic connection.

[0038] In step S9, the connection relationship of each sub-river section is determined by the segment numbering order of the threshing line in the river channel, and the river channel sections corresponding to adjacent sub-river sections maintain hydraulic connection.

[0039] As described above, the rapid construction method for one-dimensional hydrodynamic models based on DEM proposed in this invention has the following beneficial effects:

[0040] This invention, based on DEM data and channel midstream vector data, dynamically divides river segments using straightness coefficients, preserves the topological connections between river segments, generates cross-sectional data that conforms to the river's meandering morphology, determines the left and right bank positions of each cross-section based on the cross-sectional morphology, and extracts the cross-sectional morphology based on measured cross-sectional elevations. This allows for the rapid and accurate acquisition of river cross-sectional information, enabling rapid modeling of one-dimensional hydrodynamic models and improving the accuracy and applicability of hydrological simulation technology in data-scarce areas. Attached Figure Description

[0041] Figure 1 This is a flowchart illustrating the process of this application.

[0042] Figure 2 This is a schematic diagram illustrating the calculation of the river straightness coefficient in one embodiment of this application.

[0043] Figure 3 This is a schematic diagram of river segment division in one embodiment of this application.

[0044] Figure 4 This is a schematic diagram of the cross-sectional shoreline division in one embodiment of this application.

[0045] Figure 5 This is a schematic diagram of riverbed elevation correction in one embodiment of this application.

[0046] Figure 6 This is a schematic diagram of the river channel cross-sectional shape modification in one embodiment of this application. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. The specific embodiments described herein are merely illustrative and not intended to limit the scope of the invention.

[0048] Please see Figure 1 This invention provides a method for rapidly constructing a one-dimensional hydrodynamic model based on DEM elevation data, comprising the following steps:

[0049] S1. Obtain the channel midline vector data layer of the target river and the DEM data containing the river; the coordinate system of the channel midline vector data layer of the target river is a projected coordinate system, and the resolution of the DEM data is not less than 30 meters.

[0050] S2. Based on the vector data layer of the channel midline, the initial river segment is divided in the target river.

[0051] S3. Calculate the straightness coefficient of the initial river section. K and setting the minimum length of the initial river segment L min The straightness coefficient is calculated as follows:

[0052] ;

[0053] In the formula, The straightness coefficient of the river section. The straight-line distance from the beginning to the end of the river segment. This represents the actual length of the threshing line in the river section.

[0054] S4. Based on the straightness coefficient K The initial river segment is recursively divided into multiple sub-segments until the straightness coefficient of the initial river segment is reached. K ≥0.8, or the length of the initial river segment ≤ Lmin ， Then, each sub-segment is numbered according to the upstream and downstream topological relationship of the initial river segment; in step S4, the recursive segmentation satisfies:

[0055] ;

[0056] In the formula, The initial river segment length, This represents the length of the sub-river segment after division.

[0057] This step uses a dynamic recursive division of river segments by straightness coefficients to overcome the problem of insufficient cross-sectional representativeness in meandering river segments by the traditional fixed-spacing division method, making the cross-sections more closely resemble the actual river channel morphology, and is especially suitable for mountain rivers and meandering river segments.

[0058] S5. Based on the micro-topographical changes of each sub-river segment, calculate the cross-sectional direction for each sub-river segment, and extend the cross-sectional line to both sides from the midpoint of the channel line of that sub-river segment as the cross-sectional center to generate the channel cross-sectional line; after determining the cross-sectional direction, perform elevation sampling along the cross-sectional line to obtain cross-sectional topographic information; in this step, the method for determining the cross-sectional direction includes the following steps:

[0059] S501, taking the midpoint of the middle channel line of the sub-river section as the center, construct... x The terrain analysis buffer uses a 3x3 window DEM slope algorithm to calculate the slope and flow direction of each grid cell within the buffer, specifically employing the D8 flow direction algorithm. It is 1.5 times the average width of the river;

[0060] S502. Collect statistics on terrain slope information within the buffer zone, mark grids with a slope ≥ 25° as steep bank areas, and mark the distribution range of steep bank areas (left bank / right bank).

[0061] S503. Statistical topographic analysis: The local flow direction of all river channels within the buffer zone is obtained by averaging the values ​​of the grids through which the threshing line passes. ;

[0062] S504. Calculate the vertical direction of the average flow direction of the raster grid in the steep bank areas on both the left and right banks within the terrain buffer zone, denoted as... (Left Bank) (Right bank), calculate the corrected river flow direction:

[0063] ;

[0064] in, , These represent half of the total number of grid cells in the steep bank areas of the left and right banks within the terrain buffer zone. That is, satisfying 0.5 , , , .

[0065] S505. Take the direction perpendicular to the corrected river flow direction N as the cross-sectional direction of the river section, and extend it to both banks respectively. Obtain the cross-sectional line of the river channel.

[0066] This step combines information on DEM slope, flow direction, and steep bank areas to intelligently determine the cross-sectional orientation, reducing deviations in cross-sectional orientation caused by complex terrain and improving the realism of cross-sectional morphology and the accuracy of hydrodynamic simulation.

[0067] S6. Based on the DEM data, obtain the cross-sectional elevation points of the sub-river section, select sampling points on the river channel cross-section line of the sub-river section, and obtain the elevation values ​​of each sampling point; the horizontal distance between the sampling points is half the resolution of the DEM elevation data.

[0068] S7. Extract the cross-sectional shoreline information of each sub-river section and retain the elevation points of the left and right banks, floodplains and main channel.

[0069] S8. Based on existing measured cross-sectional data of the river channel, and using a systematic deviation propagation correction strategy, the extracted cross-sectional elevation is corrected. The cross-sectional elevation correction method includes the following steps:

[0070] S801. Unify the coordinate system and elevation benchmark of the measured cross section and the extracted cross section, and identify the mileage of each measured cross section on the middle channel line of the river.

[0071] S802. Calculate the elevation deviation of the thalweg line at the location of each measured cross-section. Using the distance from the cross-section starting point as the x-axis and the elevation deviation of the thalweg line as the y-axis, use linear regression to obtain the elevation deviation function of the deep thalweg point between the measured cross-section and the extracted cross-section. ;

[0072] S803, for mileage At a certain cross section, the elevation of its thalweg point is corrected to ,in, This is the corrected riverbed elevation value. The riverbed elevation extracted for DEM;

[0073] S804. Determine the elevation of the lower side of the left and right banks of this cross-section. For greater than Elevation points are retained to their original values; for elevation values ​​less than [a certain value], [the remaining values ​​are omitted]. The elevation of a given point is corrected according to the following formula:

[0074] ;

[0075] In the formula, The corrected elevation for this elevation point. The elevation of this elevation point is extracted based on DEM data.

[0076] This step establishes a functional relationship between the elevation deviation of the thalweg point and the mileage, and systematically corrects the elevation extracted by DEM, which significantly improves the accuracy of underwater topography simulation in areas without measured data, and enhances the reliability and applicability of the model.

[0077] S9. Based on the upstream and downstream topological relationship of the threshing line in each sub-river segment, establish the connection relationship of the cross sections of each sub-river segment and construct a one-dimensional hydrodynamic model. In this step, the connection relationship of the cross sections of each sub-river segment is determined by the segment numbering order of the threshing line in the river channel, and the corresponding river channel cross sections of adjacent sub-river segments maintain hydraulic connection.

[0078] The entire process of this invention is based on algorithms to automatically complete river segment division, cross-section extraction and correction, and topological relationship construction, significantly reducing the need for manual intervention and field measurement, and is suitable for rapid modeling of large-scale watersheds.

[0079] Example 1, taking a section of a river as an example, specifically provides a method for rapidly constructing a one-dimensional hydrodynamic model based on DEM elevation data. The method includes the following steps:

[0080] S1. Obtain the channel midline vector data layer and high-resolution DEM data containing the river of the target river. The channel midline vector data used for this section of the river is in the CGCS2000 coordinate system, and the DEM data is at a resolution of 30 meters.

[0081] S2. Based on the channel threshing line vector data layer obtained in step S1, divide the river into segments with an initial segment length of 400 meters.

[0082] S3, such as Figure 2 As shown, the straightness coefficient for each initial river segment is calculated using the following formula:

[0083] ;

[0084] In the formula, Here, is the straightness coefficient of the river segment, and is the straight-line distance between the start and end points of the river segment. This represents the actual length of the threshing line in the river section.

[0085] S4. Based on the straightness coefficient Recursively adjust the river segment length, if the straightness coefficient If the straightness coefficient is ≥0.8, retain the river segment; if the straightness coefficient is <0.8, divide the river segment into two sub-segments of half the length of the original river segment, and recursively calculate until the straightness coefficient is reached. ≥0.8 or river length L min The minimum length is 50 meters, and the final sub-segment length is 50 meters, 100 meters, 200 meters, or 400 meters. In this embodiment, in the upstream meandering section, the initial segment straightness coefficient... The initial straightness coefficient is smaller, resulting in a shorter final river segment length; in the straight downstream river segment, the initial straightness coefficient is larger, resulting in a longer final river segment length.

[0086] S5. Based on the micro-topographical changes of each sub-river segment, the cross-sectional direction is calculated for each sub-river segment. The cross-sectional line is generated by extending outwards from the midpoint of the channel's central line in that sub-river segment. After determining the cross-sectional direction, elevation sampling is performed along the cross-sectional line to obtain cross-sectional topographic information. In this embodiment, combined with remote sensing imagery, the estimated width of the river channel is approximately 200 meters. The width is 1.5 times the width, or 300 meters, and the resulting cross-sectional line is shown in the attached figure. Figure 4 As shown, attached Figure 4 The X-axis represents the distance from the starting point, in meters; the Y-axis represents the riverbed elevation, in meters. The method for determining the cross-sectional direction includes the following steps:

[0087] S501, taking the midpoint of the middle channel line of the sub-river section as the center, construct... x The terrain analysis buffer uses a 3x3 window DEM slope algorithm to calculate the slope and flow direction of each grid cell within the buffer (using the D8 flow direction algorithm). It is 1.5 times the average width of the river;

[0088] S502. Collect statistics on terrain slope information within the buffer zone, mark grids with a slope ≥ 25° as steep bank areas, and mark the distribution range of steep bank areas (left bank / right bank).

[0089] S503. Statistical topographic analysis: The local flow direction of all river channels within the buffer zone is obtained by averaging the values ​​of the grids through which the threshing line passes. ;

[0090] S504. Calculate the vertical direction of the average flow direction of the raster grid in the steep bank areas on both the left and right banks within the terrain buffer zone, denoted as... (Left Bank) (Right bank), calculate the corrected river flow direction:

[0091] ;

[0092] in, , These represent half of the total number of grid cells in the steep bank areas of the left and right banks within the terrain buffer zone. That is, satisfying 0.5 , , , .

[0093] S505. Take the direction perpendicular to the corrected river flow direction N as the cross-sectional direction of the river section, and extend it to both banks respectively. Obtain the cross-sectional line of the river channel.

[0094] S6. Based on the DEM elevation data, sampling points are selected along the river cross-section line. In this embodiment, the DEM elevation data used has a resolution of 30 meters. A sampling point is taken every 15 meters along the river cross-section line, and the elevation value of the sampling point is obtained to extract the river cross-section.

[0095] S7. For each extracted section, obtain its lowest point. (Riverbed), in Identify the highest point within the search range on both the left and right sides Left Bank On the right bank, elevation points within the scope of both banks, the floodplain, and the main channel are preserved.

[0096] S8. Based on existing measured cross-sectional data of the river channel, and using a systematic deviation propagation correction strategy, the extracted cross-sectional elevation is corrected. The cross-sectional elevation correction method includes the following steps:

[0097] S801. Unify the coordinate system and elevation benchmark of the measured cross section and the extracted cross section, and identify the mileage of each measured cross section on the middle channel line of the river.

[0098] S802. Calculate the elevation deviation of the thalweg line at the location of each measured cross-section. Using the distance from the cross-section starting point as the x-axis and the elevation deviation of the thalweg line as the y-axis, use linear regression to obtain the elevation deviation function of the deep thalweg point between the measured cross-section and the extracted cross-section. ;

[0099] S803, for mileage At a certain cross section, the elevation of its thalweg point is corrected to ,in, This is the corrected riverbed elevation value. The riverbed elevation extracted for DEM;

[0100] S804. Determine the elevation of the lower side of the left and right banks of this cross-section. For greater than Elevation points are retained to their original values; for elevation values ​​less than [a certain value], [the remaining values ​​are omitted]. The elevation of a given point is corrected according to the following formula:

[0101] ;

[0102] In the formula, The corrected elevation for this elevation point. The elevation of this elevation point is extracted based on DEM data.

[0103] S801. Determine the coordinates and elevation of the lowest point of the measured cross-section, find the cross-section closest to the lowest point of the measured cross-section, and correct the riverbed elevation of that cross-section to the measured riverbed elevation. In this embodiment, the upstream and downstream cross-sections each have a corresponding measured cross-section, and their riverbed elevations are corrected to the measured riverbed elevations of the cross-sections respectively.

[0104] S802. Calculate the elevation deviation of the thalweg line at the location of each measured cross-section. Using the distance from the cross-section starting point as the x-axis and the elevation deviation of the thalweg line as the y-axis, use linear regression to obtain the elevation deviation function of the deep thalweg point between the measured cross-section and the extracted cross-section. For the remaining extracted sections, calculate the arithmetic mean of the riverbed elevation extracted from the DEM data and the measured section elevation using distance-weighted interpolation, and correct it to the riverbed elevation of that section, i.e.:

[0105] ;

[0106] ;

[0107] In the formula, This is the corrected riverbed elevation value. The riverbed elevation extracted for DEM. The riverbed elevation is calculated by distance-weighted interpolation of the measured cross-section. To measure the riverbed elevation at section 1, To measure the riverbed elevation at section 2, The distance between measured section 1 and measured section 2. This represents the distance between this cross-section and the measured cross-section 1. A comparison of the riverbed elevation before and after correction is attached. Figure 5 As shown, attached Figure 5 The X-axis represents the distance from the starting point, in meters; the Y-axis represents the riverbed elevation, in meters. The riverbed elevation was corrected according to the measured cross-section information, while retaining the information on the undulations of the river channel in the DEM elevation data.

[0108] S803, for mileage At a certain cross section, the elevation of its thalweg point is corrected to ,in, This is the corrected riverbed elevation value. The riverbed elevation extracted for DEM;

[0109] S804. Determine the elevation of the lower side of the left and right banks of this cross-section. For greater than Elevation points are retained to their original values; for elevation values ​​less than [a certain value], [the remaining values ​​are omitted]. The elevation of a given point is corrected according to the following formula:

[0110] ;

[0111] In the formula, The corrected elevation for this elevation point. The elevation of this point is extracted based on DEM data. The corrected cross-sectional shape comparison is shown in the attached figure. Figure 6 As shown, attached Figure 6 The X-axis represents the distance from the starting point, in meters; the Y-axis represents the riverbed elevation, in meters.

[0112] S9. Based on the upstream and downstream topological relationship of the thalweg in the river channel, establish the connection relationship of each river section cross section and construct a one-dimensional hydrodynamic model.

[0113] This invention, based on DEM data and channel midstream vector data, dynamically divides river segments using straightness coefficients, preserves the topological connections between river segments, generates cross-sectional data that conforms to the river's meandering morphology, determines the left and right bank positions of each cross-section based on the cross-sectional morphology, and extracts the cross-sectional morphology based on measured cross-sectional elevations. This allows for the rapid and accurate acquisition of river cross-sectional information, enabling rapid modeling of one-dimensional hydrodynamic models and improving the accuracy and applicability of hydrological simulation technology in data-scarce areas.

[0114] The above description of the disclosed embodiments enables those skilled in the art to implement or use this application. The description of the embodiments above is merely to aid in understanding the methods and core ideas of this application; furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A method for rapidly constructing a one-dimensional hydrodynamic model based on DEM elevation data, characterized in that, Includes the following steps: S1. Obtain the channel threshing vector data layer and the DEM data containing the river of the target river; S2. Initial river segments are delineated in the target river based on the channel midline vector data layer; S3. Calculate the straightness coefficient of the initial river section. K and setting the minimum length of the initial river segment L min The straightness coefficient is calculated as follows: ； In the formula, The straightness coefficient of the river section. The straight-line distance from the beginning to the end of the river segment. This refers to the actual length of the threshing line in the river section. S4. Based on the straightness coefficient K The initial river segment is recursively divided into multiple sub-segments until the straightness coefficient of the initial river segment is reached. K ≥0.8, or the length of the initial river segment ≤ L min ， Then, each sub-segment is numbered according to the upstream and downstream topological relationship of the initial river segment; S5. Based on the micro-topographical changes of each sub-river segment, calculate the cross-sectional direction for each sub-river segment, and extend the cross-sectional line to both sides from the midpoint of the channel line of that sub-river segment as the cross-sectional center to generate the channel cross-sectional line; S6. Based on the DEM data, obtain the cross-sectional elevation points of the sub-river section, select sampling points on the river channel cross-section line of the sub-river section, and obtain the elevation values ​​of each sampling point. S7. Extract the cross-sectional shoreline information of each sub-river section and retain the elevation points of the left and right banks, floodplains and main channel. S8. Based on existing measured cross-sectional data of the river channel, and using a systematic deviation propagation correction strategy, the extracted cross-sectional elevation is corrected; the cross-sectional elevation correction method includes the following steps: S801. Unify the coordinate system and elevation benchmark of the measured cross section and the extracted cross section, and identify the mileage of each measured cross section on the middle channel line of the river. S802. Calculate the elevation deviation of the thalweg line at the location of each measured cross-section. Using the distance from the cross-section starting point as the x-axis and the elevation deviation of the thalweg line as the y-axis, use linear regression to obtain the elevation deviation function of the deep thalweg point between the measured cross-section and the extracted cross-section. ; S803, for mileage At a certain cross section, the elevation of its thalweg point is corrected to ,in, This is the corrected riverbed elevation value. The riverbed elevation extracted for DEM; S804. Determine the elevation of the lower side of the left and right banks of this cross-section. For greater than Elevation points are retained to their original values; for elevation values ​​less than [a certain value], [the remaining values ​​are omitted]. The elevation of a given point is corrected according to the following formula: ； In the formula, The corrected elevation for this elevation point. The elevation of this elevation point is extracted based on DEM data; S9. Based on the upstream and downstream topological relationship of the channel line in each sub-river segment, establish the connection relationship of the cross sections of each sub-river segment and construct a one-dimensional hydrodynamic model.

2. The method for rapid construction of a one-dimensional hydrodynamic model based on DEM elevation data according to claim 1, characterized in that: In step S1, the coordinate system of the channel line vector data layer of the target river is a projected coordinate system, and the resolution of the DEM data is not less than 30 meters.

3. The method for rapid construction of a one-dimensional hydrodynamic model based on DEM elevation data according to claim 1, characterized in that: In step S4, the recursive partitioning satisfies: ； In the formula, The initial river segment length, This represents the length of the sub-river segment after division.

4. The method for rapid construction of a one-dimensional hydrodynamic model based on DEM elevation data according to claim 1, characterized in that: In step S5, the method for determining the cross-sectional direction includes the following steps: S501, taking the midpoint of the middle channel line of the sub-river section as the center, construct... x The terrain analysis buffer uses a 3x3 window DEM slope algorithm to calculate the slope and flow direction of each grid cell within the buffer. It is 1.5 times the average width of the river; S502. Collect terrain slope information within the buffer zone, mark grids with a slope ≥25° as steep bank areas, and mark the distribution range of steep bank areas as left bank / right bank; S503. Statistical topographic analysis: The local flow direction of all river channels within the buffer zone is obtained by averaging the values ​​of the grids through which the threshing line passes. ; S504. Calculate the vertical direction of the average flow direction of the raster grid in the steep bank areas on both the left and right banks within the terrain buffer zone, denoted as... Left Bank On the right bank, calculate the corrected river flow direction: ； in, , These represent half of the total number of grid cells in the steep bank areas of the left and right banks within the terrain buffer zone. That is, satisfying 0.5 , , , ; S505. Take the direction perpendicular to the corrected river flow direction N as the cross-sectional direction of the river section, and extend it to both banks respectively. Obtain the cross-sectional line of the river channel.

5. The method for rapid construction of a one-dimensional hydrodynamic model based on DEM elevation data according to claim 2, characterized in that: In step S6, the horizontal distance between the sampling points is half the resolution of the DEM elevation data.

6. The method for rapid construction of a one-dimensional hydrodynamic model based on DEM elevation data according to claim 1, characterized in that: In step S9, the connection relationship of each sub-river section is determined by the segment numbering order of the threshing line in the river channel, and the river channel sections corresponding to adjacent sub-river sections maintain hydraulic connection.

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