Method, system and equipment for calculating morphological change characteristics of wandering river reach main groove and medium

Abstract

The invention discloses a wandering type river reach main groove form change characteristic calculation method, system and device and a medium, and relates to the technical field of water conservancy projects. The method comprises the following steps: acquiring multi-source data of a wandering river reach; the multi-source data comprises meteorological data, hydrological sediment data, river topographic data and remote sensing image data; performing water and sediment situation change influence factor analysis according to the basic data, and determining a water and sediment mutation point; carrying out wandering section river channel evolution analysis on the basis of the water and sediment abrupt change points, determining river channel change data, and determining typical sections and corresponding river reach morphological parameters according to the river channel change data; performing ENVI processing and GIS calculation on the remote sensing image data in sequence to obtain main channel change data, and determining main channel on-way change data according to the main channel change data, the typical section and the corresponding river reach morphological parameters; the main channel on-way change data is used for representing wandering type river reach main channel form change characteristics. The method is beneficial to exploring and analyzing the wandering law of the main river channel in the wandering section.

Description

Technical Field

[0001] The present invention relates to the technical field of water conservancy engineering, and in particular to a method, system, equipment and medium for calculating the morphological change characteristics of a main channel of a wandering river section. Background Art

[0002] In the field of river geomorphology and hydrology, wandering river sections have attracted much attention due to their unstable flow paths and frequent changes in riverbed morphology. The flow characteristics of such river sections are complex, often accompanied by frequent floods, sediment transport, and riverbed erosion and siltation, which have a significant impact on river ecosystems, flood control safety, and waterway navigability. Therefore, accurately understanding and predicting the changing characteristics of the main channel morphology of wandering river sections is crucial for formulating effective river governance and management strategies.

[0003] Traditionally, the study of wandering river sections has relied on field surveys, hydrological observations, and topographic mapping. Although these methods can provide relatively accurate data, they are time-consuming, labor-intensive, costly, and have long data acquisition cycles. With the rapid development of remote sensing technology and geographic information systems (GIS), a new perspective and efficient data processing methods have been provided for the study of wandering river sections. Remote sensing technology can quickly obtain a wide range of surface information, including river water bodies, river banks, river channel morphology, etc., while GIS can perform spatial analysis, visualization, and model simulation on these data, thereby revealing the internal laws and external manifestations of river evolution.

[0004] However, the method of effectively integrating remote sensing image data with basic data such as meteorology, hydrology, sediment, and river topography, and using it to calculate the changing characteristics of the main channel morphology of wandering river sections still needs further exploration and improvement. Summary of the invention

[0005] The purpose of the present invention is to provide a method, system, equipment and medium for calculating the morphological change characteristics of the main channel of a wandering river section, which is helpful to explore the swing law of the main channel of the wandering section.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] A method for calculating the morphological change characteristics of the main channel of a wandering river section, comprising:

[0008] Acquire multi-source data of wandering river sections; the multi-source data include basic data and remote sensing image data; wherein the basic data include meteorological data, hydrological sediment data and river topography data;

[0009] Analyze the factors affecting the change of water and sediment situation based on the basic data and determine the sudden change point of water and sediment;

[0010] Based on the water-sediment mutation point, the wandering section river channel evolution analysis is performed to determine the river channel change data, and the typical section and the corresponding river section morphological parameters are determined according to the river channel change data; the river channel change data includes water and sediment response data, section morphological change data and river section water and sediment scouring and silting data;

[0011] The remote sensing image data are processed by ENVI and calculated by GIS in sequence to obtain the main channel change data, and the main channel along-course change data are determined according to the main channel change data, the typical sections and the corresponding river section morphological parameters; the main channel along-course change data are used to represent the main channel morphological change characteristics of the wandering river section; the main channel change data include swing direction, swing area and migration distance.

[0012] Optionally, the calculation method used for analyzing the factors affecting the change of water and sediment situation includes a water-sediment joint probability distribution model and a cumulative slope change method; the water-sediment joint probability distribution model is constructed based on the marginal distribution function and the Copula function.

[0013] Optionally, the specific process of sequentially performing ENVI processing and GIS calculation on the remote sensing image data is as follows:

[0014] Preprocessing the remote sensing image data using ENVI algorithm to obtain water area extraction data;

[0015] The GIS algorithm is used to calculate the data extracted from the water area to obtain the swing direction, swing area and migration distance.

[0016] Optionally, in the step of "preprocessing the remote sensing image data using the ENVI algorithm", the specific process of the preprocessing includes: image cropping and geometric correction, radiation calibration, atmospheric correction, image stitching and water area extraction.

[0017] Optionally, the swing direction is obtained by calculating the swing area of ​​the main trough of each region toward the left bank and the swing area toward the right bank.

[0018] The present invention also provides a system for calculating the morphological change characteristics of the main channel of a wandering river section, comprising:

[0019] A data acquisition unit, used to obtain multi-source data of wandering river sections; the multi-source data includes basic data and remote sensing image data; wherein the basic data includes meteorological data, hydrological sediment data and river topography data;

[0020] A water and sediment situation change influencing factor analysis unit, used to analyze the water and sediment situation change influencing factor analysis based on the basic data and determine the water and sediment mutation point;

[0021] A wandering section river channel evolution analysis unit is used to perform a wandering section river channel evolution analysis based on the water and sediment mutation point, determine the river channel change data, and determine the typical section and the corresponding river section morphological parameters according to the river channel change data; the river channel change data includes water and sediment response data, section morphological change data and river section water and sediment scouring and silting data;

[0022] The wandering river section main channel morphological change characteristic calculation unit is used to perform ENVI processing and GIS calculation on the remote sensing image data in sequence to obtain the main channel change data, and determine the main channel along-the-way change data according to the main channel change data, the typical section and the corresponding river section morphological parameters; the main channel along-the-way change data is used to represent the main channel morphological change characteristics of the wandering river section; the main channel change data includes swing direction, swing area and migration distance.

[0023] The present invention also provides an electronic device, including a memory and a processor, wherein the memory is used to store a computer program, and the processor runs the computer program to enable the electronic device to execute the above-mentioned method for calculating the morphological change characteristics of the main channel of the wandering river section.

[0024] The present invention also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the method for calculating the morphological change characteristics of the main channel of a wandering river section as described above.

[0025] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0026] The present invention discloses a method, system, equipment and medium for calculating the morphological change characteristics of the main channel of a wandering river section. The method comprises obtaining multi-source data of the wandering river section; the multi-source data comprises meteorological data, hydrological sediment data, river channel topography data and remote sensing image data; analyzing the factors affecting the change of water and sediment situation according to the basic data, and determining the water and sediment mutation point; analyzing the evolution of the river channel of the wandering section based on the water and sediment mutation point, determining the river channel change data, and determining the typical section and the corresponding river section morphological parameters according to the river channel change data; performing ENVI processing and GIS calculation on the remote sensing image data in sequence, obtaining the main channel change data, and determining the main channel change data along the way according to the main channel change data, the typical section and the corresponding river section morphological parameters; the main channel change data along the way is used to represent the morphological change characteristics of the main channel of the wandering river section. The present invention is helpful to explore the swing law of the main channel of the wandering section. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0028] Figure 1 It is a schematic flow chart of a method for calculating the morphological change characteristics of the main channel of a wandering river section according to the present invention;

[0029] Figure 2 It is a technical roadmap of the method for calculating the morphological change characteristics of the main channel of the wandering river section in this embodiment;

[0030] Figure 3 This is a schematic diagram of the wandering cross-section change in this embodiment;

[0031] Figure 4 This is the image after the wandering segment is stitched in this embodiment;

[0032] Figure 5 This is a schematic diagram of the wandering waters section after extraction by the MNDWI method in this embodiment;

[0033] Figure 6 The schematic diagram of the result of GIS processing of the water area in this embodiment; wherein, part (a) represents the input image processed by GIS; part (b) represents the result of surface synthesis after completion so that the wandering section becomes a whole surface; part (c) represents the result of converting the main channel of the river section into a line element; part (d) represents the result after the centerline is extracted;

[0034] Figure 7 This is a schematic cross-sectional view of the wandering section of the Yellow River in this embodiment;

[0035] Figure 8 This is a schematic diagram of the division of the GIS surface in this embodiment;

[0036] Fig. 9 This is a remote sensing image of the main channel of the wandering section of the Yellow River from 1986 to 2019 in this embodiment. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] The purpose of the present invention is to provide a method, system, equipment and medium for calculating the morphological change characteristics of the main channel of a wandering river section, which is helpful to explore the swing law of the main channel of the wandering section.

[0039] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0040] like Figure 1-Figure 2 As shown, the present invention provides a method for calculating the morphological change characteristics of the main channel of a wandering river section, comprising:

[0041] Step 1: Analyze the changing characteristics of the water-sediment situation in the wandering section of the Yellow River. Obtain multi-source data of the wandering river section; the multi-source data includes basic data and remote sensing image data; wherein the basic data includes meteorological data, hydrological sediment data and river topography data; and analyze the factors affecting the change of water-sediment situation based on the basic data to determine the water-sediment mutation point. As a further description:

[0042] Through data collection, literature reading and collection of long-series water and sediment data of the wandering section of the Yellow River, the water and sediment variation diagnostic system was used to systematically identify and verify the interannual water and sediment series of runoff and sediment transport at the representative stations of the wandering section of the Yellow River, including Xiaolangdi Hydrological Station, Huayuankou Hydrological Station and Gaocun Hydrological Station from 1960 to 2019, as well as the water and sediment series during the flood and non-flood seasons. The trend, mutation point and periodic characteristics of the water and sediment situation changes in the wandering section of the Yellow River were obtained. According to the time nodes of the water and sediment sequence mutation, a water and sediment joint distribution model of the wandering section of the Yellow River was constructed based on the Copula function, the water and sediment correlation of the wandering section was analyzed, and the water and sediment flood and drought encounters were calculated. At the same time, the cumulative slope change method was used to analyze the influencing factors of water and sediment situation changes, and the construction of large-scale water conservancy projects was comprehensively considered. The results were verified and summarized to lay the foundation for subsequent river channel evolution research.

[0043] Step 2: Study on the evolution of the wandering section river based on the river section data. Based on the water and sediment mutation point, the wandering section river evolution analysis is carried out to determine the river channel change data, and the typical section and the corresponding river section morphological parameters are determined according to the river channel change data; the river channel change data includes water and sediment response data, section morphological change data and river section water and sediment scouring and silting data. As a further description:

[0044] Through data collection, cross-sectional data of the wandering section of the Yellow River were analyzed, and the long series of river section data of typical sections of the wandering section, Huayuankou, Jiahetan and Gaocun from 1960 to 2019 were analyzed. The interannual changes of cross-sectional morphological parameters such as flat beach area and river phase coefficient were calculated, and the response relationship between cross-sectional morphological parameters and incoming water and sand as well as the changes in typical cross-sectional morphology were studied. Then, through a series of cross-sectional data, the wandering section was divided into three river sections, Xiaolangdi-Huayuankou, Huayuankou-Jiahetan, and Jiahetan-Gaocun, to calculate the section morphological parameters of the wandering section of the Yellow River from 1986 to 2019, and the changes in its section morphological parameters and water and sand scouring and siltation were analyzed.

[0045] Step 3: Study on the evolution of the wandering river channel based on remote sensing images. The remote sensing image data is processed by ENVI and calculated by GIS in turn to obtain the main river channel change data, and the main channel change data along the way are determined based on the main river channel change data, the typical cross-section and the corresponding river section morphological parameters; the main channel change data along the way are used to represent the main channel morphological change characteristics of the wandering river section; the main channel change data include swing direction, swing area and migration distance. As a further description:

[0046] Landsat 5 and Landsat 8 image data were downloaded through the geospatial data cloud to obtain long-sequence remote sensing images of the wandering section. The remote sensing image data were preprocessed using ENVI, and the MNDWI method was used to extract the water area data of the remote sensing image of the wandering section of the Yellow River from 1986 to 2019. GIS was used to process and calculate the water area of ​​the wandering section, and the swing law of the main channel of the wandering section of the Yellow River was explored. The swing direction, swing area and migration distance of the main channel were calculated, and the changes along the way were further calculated.

[0047] Based on the above steps, a specific implementation example is provided by taking the following data source as an example.

[0048] The statistical analysis of the wandering section of the Yellow River involved in this embodiment includes data such as meteorology, hydrology, sediment, river section and remote sensing images of the wandering section. The sources of various data are as follows:

[0049] (1) Meteorological data

[0050] The meteorological data in this embodiment is used to analyze the factors affecting runoff and sediment transport in the wandering section due to rainfall. The meteorological data mainly involve the temperature and rainfall data of the wandering section, which comes from the National Meteorological Science Data Center. The mean of the temperature and rainfall at the three representative stations of the wandering section, Xiaolangdi Station, Huayuankou Station and Gaocun Hydrological Station, is used as the temperature and rainfall of the entire wandering section. The time series of the stations is selected from 1960 to 2019.

[0051] (2) Hydrological and sediment data

[0052] A large amount of hydrological and sediment data used in this embodiment include the daily flow, water level and sediment transport of the three representative stations in the wandering section, Xiaolangdi Station, Huayuankou Station and Gaocun Station from 1960 to 2019.

[0053] (3) River terrain data

[0054] This embodiment collects the river channel topography section data from Xiaolangdi Hydrological Station to Gaocun Station in the Wandering Section, providing basic data support for the refinement of the evolution process of the river channel topography in the Wandering Section. The river channel topography section data mainly includes the riverbed elevation and topographic data from the Baihe Town section to the Gaocun Station section, which is the closest to the Xiaolangdi Hydrological Station.

[0055] (4) Remote sensing image data

[0056] The U.S. Landsat 5TM and Landsat 8OLI satellites were obtained through the "Geospatial Data Cloud" of the Chinese Academy of Sciences. The earliest year for which Landsat 5TM can obtain remote sensing images of the wandering section of the Yellow River is 1986. A total of 12 multispectral remote sensing images of Landsat 5TM (1986, 1989, 1992, 1995, 1998, 2001, 2004, 2006, 2010) and Landsat 8OLI (2013, 2017, 2019) were downloaded as data sources, with a spatial resolution of 30m. The river channel images are from October to December after the end of the flood season of the year. At this time, the river morphology is relatively stable, which is convenient for identifying the main river channel. The cloud cover is required to be less than 10% to avoid cloud interference in the extraction of the wandering section.

[0057] For the step "Study on the evolution of the wandering section river channel based on river channel cross-section data", the specific steps are:

[0058] 2.1、Parameters of the main channel of the typical section of the wandering section:

[0059] Here, the flat beach area and river phase coefficient are used as indicators to measure the morphological parameters. The flat beach area refers to the cross-sectional area when the water level of the cross-section reaches the same level as its floodplain, and the water level refers to the water level that is flush with the lip of the cross-sectional tender beach. The flat beach area is very clear in physical concept, but because the cross-sectional morphology of the wandering channel of the Yellow River varies greatly, and the scouring and silting variation is also large, there is considerable difficulty in determining the flat beach water level and the width of the cross-sectional main channel. Therefore, when determining the flat beach water level of a section, there are the following principles: when the beach lip of the main channel of the section can be clearly judged, the average value of the beach lip elevation on both sides of the section is used as the flat beach water level, and the distance between the beach lips on both sides is used as the width of the main channel; when the beach lip of the main channel of the section cannot be clearly judged or there are beach lips of level 2 or above in the section, the positions of both sides of the beach lip should be considered when determining the position of the beach lip of the main channel of the section, and the beach lip position should be changed as little as possible. The flat beach water level is calculated based on the average elevation of the beach lip position on both sides of the section; if the beach lip position of the main channel of the section is obvious, but the height difference between the two sides of the beach lip is very significant and obviously unreasonable, it is generally determined based on the beach lip elevation of the adjacent section. The river phase coefficient is a comprehensive indicator used to characterize the riverbed morphology, and has a corresponding relationship with the water depth and width of the riverbed. In the calculation of the river phase coefficient of the wandering section, the width-to-depth ratio of the main channel is used for calculation:

[0060]

[0061] Where ε is the river phase coefficient; B is the water surface width at the flat water level (m); H is the average water depth at the flat water level (m).

[0062] The changes of water and sediment scouring and silting in the river section are not only related to the current water and sediment inflow, but also to the changes in the riverbed boundary conditions. In the constant changes of riverbed boundary conditions, the water and sediment conditions in the early stage of the section play an important role, which is generally expressed by the superimposed water volume of several years:

[0063]

[0064] Where n is the number of years of the moving average; W 汛 is the flood season water volume (m 3 );W n汛 is the sliding mean of the flood season water volume in the nth year (m 3 ).

[0065] 2.2. Correlation coefficient and regression equation:

[0066] The correlation coefficient can show the correlation between variables, and its mathematical formula is:

[0067] x t =a+bt t=1,2,…,n

[0068] The estimated values ​​of parameters a and b obtained by the least squares method are:

[0069]

[0070] Sequence x t The correlation coefficient with the time series t is:

[0071]

[0072] In the formula, Using a significance level of 99%, calculate the critical value r of the correlation coefficient α , if r satisfies r|≥r α , then the correlation is considered to meet the requirements.

[0073] The least squares estimate of the regression parameters first performs a linear estimate on the population:

[0074] y i =α+βx i +u i

[0075] Taking the expected value of both sides gives the overall equation:

[0076] E(y i )=α+βx i

[0077] Set the sample variance to:

[0078]

[0079] Using the observed value y i Its fitted value or regression value The difference is recorded as:

[0080]

[0081] ε i is the regression residual, so the sample regression model is:

[0082]

[0083] Ordinary least squares (OLS) method is used to minimize it.

[0084]

[0085] In the formula, x t is the series data value of the variable, t is the time series value, a and b are parameters, are the estimated values ​​of parameters a and b, r is the correlation coefficient, is the mean value of the variable, is the average value of the time series, r α is the critical value of the correlation coefficient, xi is the independent variable series, y i is the dependent variable series, α and β are the regression equation parameters, u i , ε i is the residual of the regression equation, E(y i ) is the expected value of the independent variable series, is the estimated value of the regression equation parameter, is the regression value, and Q is the minimum value of the sum of squares of the series residuals.

[0086] 2.3. Combination of geometric mean based on logarithmic transformation and weighted average of section spacing:

[0087] Since the measured section spacing is often not completely equal, let the total length of a study section of the wandering section be L, the number of measured sections in the section be N, and the spacing between two adjacent sections (i, i+1) can be expressed as (z i+1 -z i ), then the morphological parameters of the flat river channel at the river section scale can be calculated by the following formula:

[0088]

[0089] In the formula, It is the average river width, water depth and area of ​​the flat beach in the river section; as well as and are the river width of the flat beach at the i-th and i+1-th sections, the depth of the main channel at the section, and the flat beach area at the section; z i (m) and z i+1 (m) is the distance between two adjacent sections (x i+1 , x i+1 ) spacing; L (m) is the length of the wandering section; N is the number of calculation sections.

[0090] 2.4. Calculation of scouring and sedimentation volume in the wandering section of the Yellow River:

[0091] The position on the cross section of the wandering section is taken as the river boundary, and the area between the river channel and the abscissa is taken as the cross-sectional area. Figure 3 As shown, the change in cross-sectional area is then calculated using the following formula:

[0092] ΔS=S2-S1

[0093] In the formula, ΔS(m 2 ) refers to the change in the area of ​​the same cross section at different times; S1, S2 (m 2 ) refers to the same cross-sectional area in two adjacent time periods. If ΔS is positive, it indicates that sediment deposition occurred during this period; conversely, if ΔS is negative, sediment erosion occurred during this period.

[0094] Schematic diagram of cross-sectional area calculation: S1(m 2 ) is the previous river channel area (within the brown-yellow curve); S2 (m 2 ) is the later river channel area (blue curve range). The change in cross-sectional volume can be measured by ΔS (m 2 ) multiplied by the horizontal distance and then integrated step by step. However, since the horizontal distance between the sections is too large, it is unlikely that the area change values ​​of the two sections are equal. Therefore, in actual calculations, the average value is used to obtain the cross-sectional volume change value.

[0095] ΔV=D×(ΔS U +ΔS D ) / 2

[0096] In the formula, ΔV(m 3 ) is the volume change between two adjacent sections. If ΔV is positive, it means that sediment deposition occurred during this period. On the contrary, if ΔV is negative, sediment erosion occurred during this period. ΔS U (m 2 ) is the area change of the upstream section between two adjacent cross sections; ΔS D is the area change of the downstream section between two adjacent sections; D(m) is the horizontal distance between two adjacent sections.

[0097] This step is based on the data of the river section of the wandering section. By analyzing the changes in the morphological parameters of the typical sections of the wandering section from 1960 to 2019, it was found that the flat beach area of ​​the section first decreased and then increased, and the river phase coefficients of Huayuankou and Gaocun changed from violent fluctuations to a stable state. The cross-section of the river beach continued to fluctuate violently, but compared with the mutation point of runoff sediment transport, its flat beach area did not reflect quickly, and almost reached the bottom in 1999, and the direct correlation with the river phase coefficient was even weaker; the process of water volume shaping the river boundary is a continuous process. From 1986 to 2019, the factors that had the greatest impact on the flat beach area of ​​the three sections were the sediment coefficient, and the factors that had the greatest impact on the river phase coefficient were annual sediment transport, flood season sediment transport, and sediment coefficient.

[0098] Through the measured data of the sections, the cross-sectional morphological changes of the three sections from 1986 to 2019 were analyzed. It was found that from the late 1980s to the late 1990s, the three typical sections developed towards a state of cross-sectional siltation, accompanied by drastic migration and swing of the main channel, and the positions of the floodplain and the beach lip also changed dramatically. In the early 21st century, the floodplains of the three sections began to stabilize, and the position of the beach lip tended to be stable, with mostly only lateral position changes, but the main channel was still undergoing relatively significant changes. After 2010, the main channel changes became weaker and weaker, and the section with the most drastic changes was the river beach section.

[0099] The changes of the river section morphological parameters were calculated based on the cross-sectional data, and the changes of the river section morphological parameters were similar to the cross-sectional morphological parameters. The morphological parameters of the three river sections all changed around 1999. The main channel width first decreased and then increased; the average water depth of the main channel first fluctuated and then increased; the flat beach area first decreased and then increased; the river phase coefficient decreased and then remained relatively stable. The river section morphological parameters were more stable than the cross-sectional morphological parameters. By calculating the changes in scouring and silting of the river section, the scouring and silting of the river channel in the Huayuankou-Jiahetan section changed most dramatically, and the silting amount first increased and then decreased, and reached its peak around 1999. Among them, the Huayuankou-Jiahetan section accounted for 48.22% of the total silting of the wandering section. At the same time, it was continuously silted up in the previous flood season and scoured in the non-flood season. After that, it was scoured in both the flood season and the non-flood season. This shows that the effect of Xiaolangdi water and sand regulation in promoting the slowing of downstream siltation is obvious.

[0100] For the step "Study on the evolution characteristics of the main channel of wandering river sections based on remote sensing images":

[0101] In the previous step, the cross-section data of the wandering section river channel were used to study the morphological parameters of typical sections and river sections. In this step, remote sensing images are used to study the characteristics and laws of river channel swing based on the water area. First, for remote sensing images, a series of pre-processing measures are used to process and extract the water area. GIS software is used to perform a series of operations on the extracted water area to calculate the swing area, direction and migration distance of each section of the wandering section over time. Finally, the law of the swing of the main channel of the wandering river section is studied through the change characteristics of the wandering section along the way in different time periods. Specific methods include:

[0102] 3.1. Remote sensing image data preprocessing:

[0103] When using remote sensing satellite data to study the swing characteristics of the main channel of a river section, it is necessary to preprocess the original remote sensing images to prevent various influences such as atmosphere, water vapor, and radiation. First, the remote sensing images are preprocessed using ENVI5.3. Since the wandering river sections are located in different map sheets, they need to be cropped and spliced ​​during preprocessing to obtain a complete wandering river section. Remote sensing image data preprocessing mainly includes image cropping and geometric correction, radiation calibration, atmospheric correction, image splicing, and water area extraction.

[0104] This embodiment uses ENVI5.3 software to preprocess Landsat remote sensing satellite data images. ENVI software can quickly process remote sensing images and can recognize a variety of satellite data formats and is widely used.

[0105] Among them, the process of image cropping and geometric correction is:

[0106] As the speed, altitude, longitude and latitude of remote sensing satellites change during operation, they are affected by factors including atmospheric conditions and topography, which causes geometric distortion when satellites acquire remote sensing images. Geometric distortion can be divided into two categories: systematic distortion of the remote sensing satellite system sensor itself and random distortion of the earth's topography. Since geometric distortion causes errors when acquiring remote sensing information, geometric correction is used to make the acquired data more accurate.

[0107] Since a single remote sensing image is too large, only a small part of the study area affects the processing efficiency. Therefore, it is necessary to crop multiple images and intercept the study area to reduce the workload. Geometric correction corrects each pixel of the remote sensing image, including pixel coordinate transformation and grayscale resampling. However, since the pixels are unevenly distributed after coordinate transformation, the brightness values ​​of the pixels must be interpolated and then output. The coordinate transformation is:

[0108]

[0109] Wherein, x and y are the coordinates of the distorted pixel points in the original image; u and v are the conjugate points of the pixel coordinates corresponding to x and y after correction. In mathematical statistics, the spatial conversion between different Cartesian coordinates adopts a two-variable n-order polynomial, and the calculation formula is as follows. In this embodiment, the automatic orthorectification tool RPC of ENVI software is used for geometric correction.

[0110]

[0111] The process of radiation calibration is:

[0112] Radiation calibration is to eliminate the errors caused by radiation distortion and convert the DN value obtained by the remote sensing satellite sensor into emissivity.

[0113] The calculation was performed in ENVI software according to the following formula.

[0114] L B =radiance_scales B (SI B -radiance_offsets B )

[0115] R B =reflectance_scales B (SI B -reflectance_offsets B )

[0116] Where scales is the scaling ratio of the band; offsets is the offset of the band.

[0117] The process of atmospheric correction is:

[0118] Atmospheric reflection, scattering and absorption are the main factors affecting the ground spectral information obtained by satellite sensors. Atmospheric correction can be used to calculate and eliminate the influence of the atmosphere on pixels and grayscale values. The FLAASH atmospheric correction model in ENVI is used. After atmospheric correction, the error caused by the spectral information passing through the atmosphere has been eliminated.

[0119] The process of image stitching and water area extraction in the study area is as follows:

[0120] Since the wandering sections are located in different maps, the maps processed in the previous text are spliced ​​to extract the water area, and the map with better effect is mainly used at the intersection, such as Figure 4 shown.

[0121] For water area information extraction, the best extraction method was selected after comparison, and finally MNDWI was selected for extraction. MNDWI uses the mid-infrared band to replace the near-infrared band of NDWI, making the shadow part of the building and the water area information more obvious in the spectral characteristics. The extracted image is as follows Figure 5 The calculation formula of MNDWI is as follows:

[0122]

[0123] In the formula, R Green is the reflectivity of green light band, R MIR is the reflectivity in the mid-infrared band.

[0124] 3.2. GIS processing of water area data:

[0125] The river waters extracted by MNDWI method are imported into ArcGIS10.6. It can be seen that even if the MNDWI method is used, there are still many other water information and building interference. Therefore, the influencing information is manually deleted here, and only the main channel area of ​​the wandering section waters is retained. The water area is calculated and the boundary of the main channel of the river is extracted. The main channel is generalized, and the part affected by the vacancy of the surface elements in the boundary is completed, and the completed area of ​​each part is recorded in time and subtracted in the following text. After completion, the surface synthesis is performed to make the wandering section become a whole surface, such as Figure 6 As shown in (b) in the figure, the processed surface is converted into a line. Since the length of the river section is much longer than the width of the river section, the problem of interlacing and discontinuity of the lines occurs during the processing. After manual processing, the main channel of the river section is converted into a line element, as shown in Figure 6 As shown in (c), the center line is extracted, as shown in Figure 6 As shown in (d).

[0126] 3.3. Treatment of the main channel section of the wandering section:

[0127] According to the topographic characteristics of the river channel and the location of the hydrological station, the main channel of the river channel is divided into four areas: Figure 7 As shown: R1 (Xiaolangdi-Beijing-Guangzhou Railway), R2 (Beijing-Guangzhou Railway-Heigangkou), R3 (Heigangkou-Dongbatou), R4 (Dongbatou-Gaocun). Among them, the R1 area is close to the downstream of Xiaolangdi, and there are many high cliffs on both sides to constrain the water flow. The water flow is relatively turbulent in the first half of the canyon, and the water flow slows down after leaving the canyon in the second half, and the river flow is scattered; the R2 area is constrained by the Yellow River embankment on both sides, the riverbed is wide and shallow, and it is the key river section for downstream flood control; the R3 area has a wide and shallow riverbed, the mainstream swings frequently, and the high trough and low shoal are the key river sections where the bank protection project plays a role; the R4 area has many low shoals, which is the river channel formed by the diversion from west to northeast after the Tongwaxiang breach in 1855, and is the key river section for the development of secondary hanging rivers.

[0128] At the same time, in order to study the changes in each area more carefully and significantly, the center line of the wandering segment is divided into equal distances and the center point of each segment is extracted. The surface elements are divided into 20 river sections from S1 to S20 using the Thiessen polygon method based on the center of the line segment length. The divided sections are perpendicular to the center line of the river, and the section direction is simplified to vertical and vertical, such as Figure 8 shown.

[0129] The wandering section elements are divided through the above steps, and the above operations are repeated to obtain the river sections after the wandering sections in 1986, 1989, 1992, 1995, 1998, 2001, 2003, 2006, 2010, 2013, 2017 and 2019 are divided into 20 parts and pairwise connection analysis is performed. The swing area and the migration distance of the center point are calculated by taking the inverse of the intersection.

[0130] 3.4. Characteristic parameters of the main channel evolution in the wandering section:

[0131] The swing area, swing direction, migration distance and curvature of the main channel are selected as the characteristic parameters of the evolution of the main channel of the river. The swing area is the area of ​​the lateral movement of the main channel. The main channel is divided according to the method mentioned above, and the swing area S of the main channel of each river section from 1986 to 1989, 1989 to 1992, 1992 to 1995, 1995 to 1998, 1998 to 2001, 2001 to 2003, 2003 to 2006, 2006 to 2010, 2010 to 2013, 2013 to 2017, 2017 to 2019, and 1986 to 2019 are obtained. i , as well as the average main trough swing area and the maximum main trough swing area of ​​each region (due to the lack of data for 2009 and 2016, the adjacent years of 2010 and 2017 are used instead, the same below), the specific formula is as follows:

[0132]

[0133] S max =maxS i (i=1,2,3~n)

[0134] In the formula, S i is the swing area of ​​the main channel of each river section (km 2 ); is the average main trough swing area of ​​each region (km 2 );S max is the maximum main trough swing area of ​​each region (km 2 ).

[0135] The swing direction of the main channel of the river is calculated by calculating the swing area S of the main channel of each area to the left bank. L and the swing area S to the right bank R The migration distance of the main channel of the river channel is obtained by using ArcGIS to convert each river section in 1986 and 2019 into mass points. The direction and distance between the mass center points are the direction and distance of the migration of the main channel of the river channel. The migration of the mass center point to the left bank is positive, and the migration to the right bank is negative. The specific formula is as follows:

[0136]

[0137] In the formula, S il is the distance that the centroid of each river section migrates to the left bank (km); S ir is the distance that the centroid of each river section migrates to the right bank (km); is the average distance (km) that the centroid of each area migrates to the left bank; is the average distance (km) that the centroid of each area migrates to the right bank.

[0138] The river channel curvature coefficient refers to the actual distance compared to the straight-line distance. The river channel curvature coefficient can represent the overall curvature of the river. The formula is as follows:

[0139] K a =L / I

[0140] In the formula, K a is the river section curvature coefficient. The larger the coefficient value, the more curvy the river. The river curvature coefficient is generally divided by 1.3. When it is less than 1.3, the river is usually a wandering river. L is the actual length of the river section (km); I is the straight length of the river section (km).

[0141] In this step, the map of the specific location of the wandering section is downloaded, and a series of preprocessing work is performed using ENVI to extract the water area and GIS is used to process and calculate the changes in the river channel of the wandering section from 1986 to 2019, such as Fig. 9 As shown in the figure, the water area first increased, then decreased, and then gradually remained stable. The curved section of the river gradually increased, increasing by 11.03% over the entire period, evolving towards a curved river. The swing area of ​​each section of the main channel gradually decreased, and the total area of ​​the wandering river section swinging to the left bank was 59.9km 2 The total area of ​​the right bank is 53.3 km 2 ; R1, R3 and R4 areas migrated southward as a whole, and R2 area migrated northward; R2 and R3 areas are the river sections where the river channel is prone to swing and the probability of migration is the highest. As various measures are taken, the swing amplitude of other river sections is weak and they are developing towards a stable state.

[0142] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0143] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for calculating the morphological change characteristics of the main channel of a wandering river section, characterized in that: include: Acquire multi-source data of wandering river sections; the multi-source data include basic data and remote sensing image data; wherein the basic data include meteorological data, hydrological sediment data and river topography data; Analyze the factors affecting the change of water and sediment situation based on the basic data and determine the sudden change point of water and sediment; Based on the water-sediment mutation point, the wandering section river channel evolution analysis is performed to determine the river channel change data, and the typical section and the corresponding river section morphological parameters are determined according to the river channel change data; the river channel change data includes water and sediment response data, section morphological change data and river section water and sediment scouring and silting data; The remote sensing image data is processed by ENVI and calculated by GIS in sequence to obtain the main channel change data, and the main channel along-course change data is determined according to the main channel change data, the typical section and the corresponding river section morphological parameters; the main channel along-course change data is used to represent the main channel morphological change characteristics of the wandering river section; The main river channel change data include swing direction, swing area and migration distance.

2. The method for calculating the morphological change characteristics of the main channel of a wandering river section according to claim 1 is characterized in that: The calculation methods used in the analysis of the factors affecting the change of water and sediment situation include a water-sediment joint probability distribution model and a cumulative slope change method; the water-sediment joint probability distribution model is constructed based on the marginal distribution function and the Copula function.

3. The method for calculating the morphological change characteristics of the main channel of a wandering river section according to claim 1 is characterized in that: The specific process of performing ENVI processing and GIS calculation on the remote sensing image data in turn is as follows: Preprocessing the remote sensing image data using ENVI algorithm to obtain water area extraction data; The GIS algorithm is used to calculate the data extracted from the water area to obtain the swing direction, swing area and migration distance.

4. The method for calculating the morphological change characteristics of the main channel of a wandering river section according to claim 3 is characterized in that: In the step of "preprocessing the remote sensing image data using the ENVI algorithm", the specific process of the preprocessing includes: image cropping and geometric correction, radiation calibration, atmospheric correction, image stitching and water area extraction.

5. The method for calculating the morphological change characteristics of the main channel of a wandering river section according to claim 1 is characterized in that: The swing direction is obtained by calculating the swing area of ​​the main trough of each region toward the left bank and the swing area toward the right bank.

6. A system for calculating the morphological changes of the main channel of a wandering river section, characterized in that: include: A data acquisition unit, used to obtain multi-source data of wandering river sections; the multi-source data includes basic data and remote sensing image data; wherein the basic data includes meteorological data, hydrological sediment data and river topography data; A water and sediment situation change influencing factor analysis unit, used to analyze the water and sediment situation change influencing factor analysis based on the basic data and determine the water and sediment mutation point; A wandering section river channel evolution analysis unit is used to perform a wandering section river channel evolution analysis based on the water and sediment mutation point, determine the river channel change data, and determine the typical section and the corresponding river section morphological parameters according to the river channel change data; the river channel change data includes water and sediment response data, section morphological change data and river section water and sediment scouring and silting data; The wandering river section main channel morphological change characteristic calculation unit is used to sequentially perform ENVI processing and GIS calculation on the remote sensing image data to obtain main channel change data, and determine the main channel along-course change data according to the main channel change data, the typical section and the corresponding river section morphological parameters; the main channel along-course change data is used to represent the main channel morphological change characteristics of the wandering river section; The main river channel change data include swing direction, swing area and migration distance.

7. An electronic device, characterized in that: It includes a memory and a processor, the memory is used to store a computer program, and the processor runs the computer program to enable the electronic device to execute the method for calculating the morphological change characteristics of the main channel of a wandering river section according to any one of claims 1-5.

8. A computer-readable storage medium, characterized in that: It stores a computer program, which, when executed by a processor, implements the method for calculating the morphological change characteristics of the main channel of a wandering river section as described in any one of claims 1-5.

Images