Method for representing river channel beach groove pattern

Abstract

The invention relates to the technical field of water conservancy projects, in particular to a method for representing a river channel beach groove pattern, which comprises the following steps of: 1, extracting a geometric figure enclosed by a water cross section of a research river reach and a flat beach water level; 2, solving the centroid position of the geometric figure; 3, determining centroid parameters according to the centroid position, and carrying out nondimensionalization on the centroid parameters; and 4, according to a geometric figure surrounded by the flow cross section of the time sequence of the research river reach and the flat beach water level of the corresponding time, the change of the cross section centroid parameter along with the time can be solved. The concept of the centroid is introduced, and the change of the section centroid parameter along with time is solved through the steps, so that the evolution process of the river section with violent beach and trough pattern adjustment can be well represented through the change of the section centroid parameter along with time.

Description

Technical Field

[0001] The invention relates to the technical field of water conservancy engineering, and in particular to a method for characterizing a river channel pattern. Background Art

[0002] At present, the commonly used parameters to represent the cross-sectional morphology of the river channel are the cross-sectional area, the width of the water surface, the average water depth and the width-to-depth ratio, which are basically reasonable when studying the overall scouring and silting of the river channel. After the construction of large-scale water conservancy hubs, the bends of the downstream river channel generally experience the evolution process of "convex erosion and concave siltation" such as cutting the beach and turning the bend (such as the lower reaches of the Han River and the lower Jingjiang River section), that is, the convex bank of the bend is eroded and cut down, gradually forming a new river channel; siltation occurs in the deep groove of the concave bank, and gradually forms a river beach.

[0003] The traditional cross-sectional morphology of water flow can only represent the average scouring and silting conditions of the entire cross-section, and cannot capture the river channel evolution process in which the shoal pattern changes dramatically. Summary of the invention

[0004] In view of this, the present invention provides a method for characterizing the channel pattern of a river to solve the problem that the traditional water-passing cross-section morphology cannot capture the channel evolution process in which the channel pattern evolves dramatically.

[0005] In a first aspect, the present invention provides a method for characterizing a river channel pattern, comprising the following steps:

[0006] Step 1: Extract the geometric figure enclosed by the water-passing section and the flat water level of the studied river section;

[0007] Step 2: Find the centroid position of the geometric figure;

[0008] Step 3: Determine the centroid parameters from the centroid position, and convert the centroid parameters into dimensionless;

[0009] Step 4: Based on the geometric figure formed by the water-passing section of the study section time series and the flat water level at the corresponding time, the change of the centroid parameter over time can be calculated.

[0010] In an optional implementation, in step 2, the centroid position is obtained by a centroid calculation formula:

[0011]

[0012] Among them, x is the horizontal coordinate, y is the vertical coordinate, A is the cross-sectional area of ​​the water flow, That is, the centroid coordinates.

[0013] In an optional implementation, in step 2, the centroid position is obtained by drawing software.

[0014] In an optional implementation, the specific steps of obtaining the centroid position are:

[0015] Select the geometric figure enclosed by the water-passing section and the flat water level, first use the region command REG, and then use the massprop command to obtain the centroid.

[0016] In an optional implementation, in step three, the centroid parameters are determined from the centroid position, specifically:

[0017] The position of the centroid below the water surface is H c ;

[0018] The intersection of the concave bank and the flat water level is taken as point o, and the lateral distance from the centroid to point o is B c .

[0019] In an optional implementation, in step three, the centroid parameter is dimensionless as follows:

[0020] The average water depth of the water-passing section is H = A / B, where A is the area of ​​the water-passing section, B is the river width, and B c / B and H c / H is the dimensionless centroid parameter.

[0021] In an optional embodiment, the water-passing section of the study river section is extracted by a measurement unit.

[0022] In an optional implementation, in step 4, the time series is annual or monthly or a specific time period.

[0023] The method for characterizing the river channel pattern provided by the present invention has the following advantages:

[0024] 1. A method for characterizing a river channel pattern provided by the present invention comprises the following steps:

[0025] Step 1: Extract the geometric figure enclosed by the water-passing section and the flat water level of the studied river section;

[0026] Step 2: Find the centroid position of the geometric figure;

[0027] Step 3: Determine the centroid parameters from the centroid position, and convert the centroid parameters into dimensionless;

[0028] Step 4: Based on the geometric figure formed by the water-passing section of the time series of the studied river section and the flat water level at the corresponding time, the change of the centroid parameters over time can be calculated.

[0029] This method for characterizing the river channel pattern introduces the concept of centroid, extracts the geometric figure surrounded by the water-passing section of the study section and the flat water level, and then finds the centroid position of the geometric figure based on the extracted geometric figure, and then determines the centroid parameter based on the centroid position, and makes the centroid parameter dimensionless. Then, based on the geometric figure surrounded by the water-passing section of the study section of the time series and the flat water level at the corresponding time, the change of the centroid parameter over time can be found, and then the change of the section centroid parameter over time can better characterize the evolution process of the river section with drastic adjustment of the channel pattern.

[0030] 2. The method provided by the present invention for characterizing the river channel pattern can capture the dramatic evolution of the channel in the downstream river channel bend section after the construction of a large-scale water conservancy hub, while the traditional cross-sectional morphological parameters can only capture the scouring and silting process of the entire cross section, and cannot reflect the channel pattern. In addition, the steps for calculating the cross-sectional centroid in the present invention are simple, and it is not only applicable to the bend section, but also to any river channel section, which has a high reference value and practical significance for waterway, revetment, water intake and other projects. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0032] Figure 1 A schematic diagram of a centroid obtained in a method for characterizing a river channel pattern provided in an embodiment of the present invention;

[0033] Figure 2 This is a schematic diagram of the changes in the cross-section of the bend before and after the construction of the Three Gorges Reservoir;

[0034] Figure 3 It is a schematic diagram comparing the changes in the values ​​of the curved section before and after the construction of the Three Gorges Reservoir using traditional section morphological parameters (cross-sectional area, river width, width-to-depth ratio) and the section centroid parameters of the present invention. DETAILED DESCRIPTION

[0035] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. 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.

[0036] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance. In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0037] Example

[0038] At present, the commonly used parameters to represent the cross-sectional morphology of the river channel are the cross-sectional area, the width of the water surface, the average water depth and the width-to-depth ratio, which are basically reasonable when studying the overall scouring and silting of the river channel. After the construction of large-scale water conservancy hubs, the bends of the downstream river channel generally experience the evolution process of "convex erosion and concave silting" such as cutting the beach and turning the bend (such as the lower reaches of the Han River and the lower Jingjiang River section), that is, the convex bank of the bend is eroded and cut down, gradually forming a new river channel; the deep trough of the concave bank is silted up, and the river beach is gradually formed. The traditional cross-sectional morphology can only represent the average scouring and silting of the entire section, and cannot capture the evolution process of the river channel with drastic changes in the beach and channel pattern.

[0039] To this end, this embodiment provides a method for characterizing the river channel pattern, comprising the following steps:

[0040] Step 1: Extract the geometric figure enclosed by the water-passing section and the flat water level of the studied river section;

[0041] Step 2: Find the centroid position of the geometric figure;

[0042] Step 3: Determine the centroid parameters from the centroid position and make the centroid parameters dimensionless;

[0043] Step 4: Based on the geometric figure formed by the water-passing section of the study river section time series and the flat water level at the corresponding time, the change of the section centroid parameters over time can be calculated.

[0044] In this embodiment, by introducing the concept of centroid, the geometric figure surrounded by the water-passing section of the study section and the flat water level is extracted, and then the centroid position of the geometric figure is obtained according to the extracted geometric figure, and then the centroid parameter is determined by the centroid position, and the centroid parameter is dimensionless. Then, according to the geometric figure surrounded by the water-passing section of the study section of the time series and the flat water level at the corresponding time, the change of the centroid parameter of the section over time can be obtained, and then the change of the centroid parameter of the section over time can be better characterized by the evolution process of the river section with drastic adjustment of the river channel pattern.

[0045] In this embodiment, the geometric figure enclosed by the water-passing section and the flat water level of the river section under study in step 1 is extracted based on the water-passing section results proposed by the hydrological bureau and other surveying units, and then the water-passing section and the flat water level are enclosed to form a geometric figure.

[0046] Generally speaking, the water-passing sections of large rivers, especially those in bends, are mostly composite, that is, they have a main channel and a beach, and the water level on the beach is just enough to submerge the beach.

[0047] In this embodiment, in step 2, the centroid position is obtained by the following centroid calculation formula:

[0048]

[0049] Among them, x is the horizontal coordinate, y is the vertical coordinate, A is the cross-sectional area of ​​the water flow, That is, the centroid coordinates.

[0050] Alternatively, the centroid position can also be obtained through drawing software. For example, the centroid position can be obtained using the centroid command of software such as AutoCAD. For example, the specific steps of obtaining the centroid position using AUTOCAD are: select a geometric figure surrounded by the water-passing section and the flat water level, first use the region command REG, and then use the massprop command to obtain the centroid.

[0051] In this embodiment, in step 3, the centroid parameters are determined by the centroid position, specifically: the position of the centroid below the water surface is H c ; Take the intersection of the concave bank and the flat water level as point o, and the lateral distance from the centroid to point o is B c .

[0052] In this embodiment, in step three, the centroid parameter is dimensionless as follows:

[0053] The average water depth of the water section is H = A / B, where A is the water section area, B is the river width, and B c / B and H c / H is the dimensionless centroid parameter.

[0054] Specific as Figure 1 As shown, Figure 1 The center Q is where the centroid is located.

[0055] In this embodiment, the concave bank is used as point o because the concave bank of the bend is prone to serious bank collapse and generally has revetments, dikes and other projects, so the bank boundary is relatively fixed. On the other hand, the convex bank of the bend has a relatively developed beach, the beach scouring and silting adjustment is relatively drastic, and the bank boundary is unstable.

[0056] In this embodiment, in step 4, the time series is annual or monthly or a specific time period. Specifically, the specific time period is: according to the evolution process of the river channel cross section with drastic adjustment of the river channel beach pattern in a certain time period to be obtained, several time points are selected in this time period and the geometric figures formed by the water-passing cross section of the study river section at these time points and the flat beach water level at the corresponding time are obtained, and the change of the centroid parameter over time is calculated accordingly.

[0057] For further explanation, this embodiment takes the cross section of the diversion bend in the lower Jingjiang River section downstream of the Three Gorges Reservoir as an example to compare the two cross-sectional morphological parameters. Figure 2 The figure shows the changes in the cross-section of the bend before and after the construction of the Three Gorges Reservoir.

[0058] The Three Gorges Project began to store water in 2003. Figure 2 As shown in the figure, from 1998 to 2003, the main characteristics of the evolution of the bend were the erosion and incision of the deep trough of the concave bank, and the siltation and elevation of the convex bank, which was a typical "concave erosion and convex siltation" process of the bend. From 2003 to 2008, the deep trough of the concave bank was silted up, gradually forming the core beach; the convex bank shoal was eroded and incision, forming a new river channel, which was a typical "convex erosion and concave siltation" evolution process. From 2008 to 2012, the concave bank continued to silt up, the core beach continued to silt up, and the convex bank shoal was slightly eroded. From 2012 to 2016, the erosion and siltation of the concave bank did not change much, and the main adjustment process occurred in the new river channel of the convex bank, with the part close to the concave bank eroded and incision, and the part close to the convex bank silted up. In the absence of a large flood that has a strong adjustment on the entire section, the beach-channel pattern did not change much, and most of the adjustments occurred in the new river channel.

[0059] Figure 3 It is a schematic diagram comparing the changes in the values ​​of the curved section before and after the construction of the Three Gorges Reservoir using traditional section morphological parameters (cross-sectional area, river width, width-to-depth ratio) and the section centroid parameters of this embodiment.

[0060] Depend on Figure 3It can be seen that due to the implementation of the bank protection project in the bend section of the lower Jingjiang River, the river width has not changed much, and it was about 1300m in 1998 before the reservoir was built. After the construction of the Three Gorges Reservoir, the river width has increased, but it is basically within the range of 1500-1600m, with little change. The cross-sectional area of ​​the water flow represents the overall scouring and silting volume of the section. From 1998 to 2008, the cross-sectional area did not change much, indicating that the overall scouring and silting volume of the section was small. After 2008, the cross-sectional area increased, indicating that the section was generally scouring. The width-to-depth ratio was slightly less than 4.0 before the reservoir was built, and it increased after the reservoir was built, but it was basically within 4.0-5.0. Traditional cross-sectional morphological parameters can only reflect the overall scouring and silting volume of the section and the widening or narrowing degree of the water surface river width, and cannot characterize the curved section where the beach and slot pattern is drastically adjusted. The total cross-sectional centroid parameter of this embodiment can better capture the beach and slot pattern. For example, before the construction of the Three Gorges Reservoir, the evolution was typical of "concave erosion and convex siltation". The deep troughs on the concave banks were eroded and cut down, and the convex banks were correspondingly silted up. c / B decreases, H c After the construction of the Three Gorges Reservoir, especially in the first five years of the Three Gorges impoundment (2003-2008), the beach-channel pattern was drastically adjusted, the convex bank shoal was greatly eroded and cut, the concave bank was silted up to form a central beach, and the cross section tended to develop in a "W" symmetrical shape, so B c / B increases, H c / H decreased. After 2008, the beach-channel pattern did not change much, so B c / B and H c / H values ​​did not change much.

[0061] Therefore, by introducing the concept of centroid in this embodiment, the evolution process of the river section with drastic adjustment of the beach channel pattern can be better characterized, and the drastic evolution process of the beach channel in the downstream river bend section after the construction of a large-scale water conservancy hub can be captured. The traditional cross-sectional morphological parameters can only capture the scouring and silting process of the entire section, and cannot reflect the beach channel pattern. In addition, the steps for finding the cross-sectional centroid in this embodiment are simple, and it is not only applicable to the bend section, but also to any river section, which has a high reference value and practical significance for waterway, bank protection, water intake and other projects.

[0062] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A method for characterizing the channel pattern of a river, characterized in that: The steps include: Step 1: Extract the geometric figure enclosed by the water-passing section and the flat water level of the studied river section; Step 2: Find the centroid position of the geometric figure; Step 3: Determine the centroid parameters from the centroid position, and convert the centroid parameters into dimensionless; Step 4: Based on the geometric figure formed by the water-passing section of the study section time series and the flat water level at the corresponding time, the change of the centroid parameter over time can be calculated.

2. The method for characterizing the river channel pattern according to claim 1, characterized in that: In step 2, the centroid position is obtained by the centroid calculation formula: Among them, x is the horizontal coordinate, y is the vertical coordinate, A is the cross-sectional area of ​​the water flow, That is, the centroid coordinates.

3. The method for characterizing the river channel pattern according to claim 1, characterized in that: In step 2, the centroid position is obtained by drawing software.

4. The method for characterizing the river channel pattern according to claim 3, characterized in that: The specific steps to obtain the centroid position are: Select the geometric figure enclosed by the water-passing section and the flat water level, first use the region command REG, and then use the massprop command to obtain the centroid.

5. The method for characterizing the river channel pattern according to claim 1, characterized in that: In step three, the centroid parameters are determined from the centroid position, specifically: The position of the centroid below the water surface is H c ; The intersection of the concave bank and the flat water level is taken as point o, and the lateral distance from the centroid to point o is B c .

6. The method for characterizing the river channel pattern according to claim 5, characterized in that: In step three, the centroid parameter is dimensionless as follows: The average water depth of the water-passing section is H=A / B, wherein A is the water-passing section area, B is the river width, and Bc / B and Hc / H are dimensionless centroid parameters.

7. The method for characterizing the river channel pattern according to any one of claims 1 to 6, characterized in that: In step 1, the water-passing cross-section of the study river section is extracted by the measurement unit.

8. The method for characterizing the river channel pattern according to any one of claims 1 to 7, characterized in that: In step 4, the time series is annual or monthly or a specific time period.

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