A method for extracting river flooding range

Abstract

The present invention provides a method for extracting the inundation range of a river, including extracting the river centerline, and further comprising the following steps: using the river centerline to divide the buffer zone into two parts, which are respectively defined as the left side and the right side of the river; converting the left side and the right side of the river into grids respectively; dividing the river centerline into small river segments with a length of n meters on average; using the starting point and the ending point of the cross-section inundation range to respectively query the nearest river segment center point, and calculating the distance from the starting point to the nearest river segment center point; performing interpolation calculations on the left distances and the right distances of all river segment center points; calculating whether the grids are inundated respectively according to the two regions of the left side and the right side; extracting the inundated grids to determine the final inundation range. The method for extracting the inundation range of a river proposed by the present invention is directed at the large curvature of the middle river segment between two cross-sections, and uses the inundation water levels of the cross-sections to interpolate to obtain the inundation range of the middle river segment.

Description

Technical Field

[0001] The present invention relates to the technical field of river flood inundation range extraction, and particularly to a method for extracting the river flood inundation range. Background Art

[0002] Generally, the method of setting cross-sections along the river is adopted for river flood calculation. The water levels of each cross-section are calculated by using a hydraulic model, and then the inundation range at the cross-section is obtained. In practical applications such as flood inundation evaluation or risk warning, not only the inundation range at the cross-section is required, but also the inundation range of the whole river. Currently, the commonly used method is to obtain the inundation range of the whole river by interpolating the water surfaces of two cross-sections. However, the shapes of many rivers are curved, especially the small and medium-sized rivers in mountainous areas, with winding and tortuous flows. It is difficult to ensure that the section between two cross-sections is a straight river section. Therefore, the result obtained by directly interpolating the inundated water surfaces of two cross-sections is significantly unreasonable and cannot reflect the river curvature between the two cross-sections.

[0003] In the fourth issue of the 636th issue in total in April 2018 of "Henan Science & Technology", an article titled "Research on Determination of River Channel Inundation Range Based on GIS Spatial Analysis" by Li Xinnan, Lu Xianhe, and Hu Jie was published. This article used the water level data of some sections of Banqiao River and Hezui River in Chongqing. Based on GIS technology, the inverse distance weighting method (IDW), spline function method (TS), and ordinary kriging method (OK) were respectively used for spatial analysis, and the t-test method was used to evaluate the interpolation accuracy. The results showed that the spatial analysis function of GIS can be effectively applied to the calculation of flood inundation range. The kriging method has the best accuracy, but the efficiency is low; the simulated inundation range of the spline function is slightly larger than the other two methods, and it is more conservative and reliable for delimiting the inundation range. This method interpolates the water surface from the calculated cross-sections and cannot solve the problem of curved river channels. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a method for extracting the river flood inundation range. For the middle river section with a large curvature between two cross-sections, the inundation range of the middle river section is obtained by interpolating the inundation water levels of the cross-sections.

[0005] The purpose of the present invention is to provide a method for extracting the river flood inundation range, including extracting the river centerline, and further including the following steps:

[0006] Step 1: Using the river centerline, divide the buffer zone into two parts, which are respectively defined as the left side of the river and the right side of the river;

[0007] Step 2: Respectively convert the left side of the river and the right side of the river into grids;

[0008] Step 3: Divide the river centerline into small river sections with a length of n meters on average, where n < 5;

[0009] Step 4: Use the starting point and ending point of the cross-section inundation range to query the nearest river reach center points respectively, and calculate the distances from the starting point or ending point to the nearest river reach center points.

[0010] Step 5: Perform interpolation calculations on the left-side distances and right-side distances of all river reach center points.

[0011] Step 6: Calculate whether the grids are inundated in two regions of the left side and the right side respectively.

[0012] Step 7: Extract the inundated grids to determine the final inundation range.

[0013] Preferably, the step of extracting the river centerline includes making a buffer zone using the river centerline, and the range of the buffer zone includes all inundation points of the cross-sections.

[0014] In any of the above solutions preferably, step 2 includes that the side length of the grid is preferably between 1 m and 5 m according to the width of general small and medium-sized rivers.

[0015] In any of the above solutions preferably, step 3 includes extracting the center points of each small river reach and sequentially numbering the small river reaches from upstream to downstream.

[0016] In any of the above solutions preferably, step 4 includes taking this distance as the left-side distance or right-side distance of the river reach center point according to the position where the cross-section starting point or ending point is located, and the cross-section starting point or ending point is located in the left buffer zone or the right buffer zone.

[0017] In any of the above solutions preferably, if the cross-section starting point or ending point is within the range of the left buffer zone, it is recorded as the left-side distance; if the starting point or ending point is within the range of the right buffer zone, it is recorded as the right-side distance.

[0018] In any of the above solutions preferably, the interpolation calculation formula for the left-side distance is

[0019]

[0020] where, i is the sequence number of the river reach center point to be interpolated, m is the sequence number of the river reach center point closest to i upstream and with a non-zero left-side distance, n is the sequence number of the river reach center point closest to i downstream and with a non-zero left-side distance, D i-left is the left-side distance of the river reach center point with the sequence number i to be interpolated, D m-left is mThe left-side distance of the point D n-left is n The left-side distance of the point

[0021] Preferably, in any of the above solutions, the interpolation calculation formula for the right-side distance is

[0022]

[0023] wherein D i-right is the right-side distance of the center point of the river reach with the sequence number to be interpolated as i and D m-right is m the right-side distance of the point D n-right is n the right-side distance of the point

[0024] Preferably, in any of the above solutions, the method for determining whether the grids in the left region are flooded is to find the distance from the center point of each grid in the left region to the nearest river reach center point x of d x , and if d x ≤ D x-left , then set this grid as a flooded grid, wherein D x-left is x the left-side distance of the point

[0025] Preferably, in any of the above solutions, the method for determining whether the grids in the right region are flooded is to find the distance y from the center point of each grid in the right region to the nearest river reach center point d y , and if d y ≤ D y-right , then set this grid as a flooded grid, wherein D y-right is y the right-side distance of the point

[0026] The present invention provides a method and system for extracting the flooded range of a river. With the river center as the limit, the possible flooded range is divided into two regions, namely the left and right regions, for interpolation respectively, and finally merged into the flooded range of the whole river BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a flowchart of a preferred embodiment of the method for extracting the flooded range of a river according to the present invention

[0028] Figure 2 It is a flowchart of another preferred embodiment of the method for extracting the river inundation range according to the present invention.

[0029] Figure 3 It is a schematic diagram of an embodiment for making a buffer zone of the river centerline in the method for extracting the river inundation range according to the present invention.

[0030] Figure 4 It is a schematic diagram of an embodiment for zoning the buffer zone in the method for extracting the river inundation range according to the present invention.

[0031] Figure 5 It is a schematic diagram of an embodiment for segmenting the river centerline and dividing the grid in the method for extracting the river inundation range according to the present invention.

[0032] Figure 6 It is a schematic diagram of an embodiment for the final inundation range in the method for extracting the river inundation range according to the present invention. Detailed implementation manners

[0033] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0034] Embodiment 1

[0035] As Figure 1 shown, a method for extracting the river inundation range performs step 100 to extract the river centerline and makes a buffer zone using the river centerline, and the range of the buffer zone covers the inundation points of all cross-sections.

[0036] Perform step 110 to divide the buffer zone into two parts using the river centerline, and define them as the left side of the river and the right side of the river respectively.

[0037] Perform step 120 to convert the left side of the river and the right side of the river into grids respectively, and the grid side length is preferably between 1 m and 5 m.

[0038] Perform step 130 to evenly divide the river centerline into small river segments with a length of n meters, where n < 5; extract the center point of each small river segment and sequentially number the small river segments from upstream to downstream.

[0039] Execute step 140. Using the starting point and the ending point of the cross-section inundation range, query the nearest river reach center points respectively, and calculate the distances from the starting point or the ending point to the nearest river reach center points. According to the positions where the cross-section starting point or the cross-section ending point is located, take these distances as the left distances or the right distances of the river reach center points. If the cross-section starting point or the cross-section ending point is within the left buffer zone or the right buffer zone, if the cross-section starting point or the cross-section ending point is within the left buffer zone range, record it as the left distance; if the cross-section starting point or the cross-section ending point is within the right buffer zone range, record it as the right distance.

[0040] Execute step 150 to perform interpolation calculations on the left distances and the right distances of all river reach center points. Execute step 151 to calculate the interpolation of the left distances. The formula is

[0041]

[0042] Where, i is the sequence number of the river reach center point to be interpolated, m is the sequence number of the river reach center point that is the nearest upstream to i and whose left distance is not 0, n is the sequence number of the river reach center point that is the nearest downstream to i and whose left distance is not 0, D i-left is the left distance of the river reach center point with the sequence number i to be interpolated, D m-left is m the left distance of the point, D n-left is n the left distance of the point.

[0043] Meanwhile, execute step 152 to calculate the interpolation of the right distances. The formula is

[0044]

[0045] Where, D i-right is the right distance of the river reach center point with the sequence number i to be interpolated, D m-right is m the left distance of the point, D n-right is n the right distance of the point.

[0046] Execute step 160 to calculate whether the grids are inundated respectively according to the two regions of the left side and the right side. The determination method for the grids in the left region being inundated is to find the distance from the center point of each grid in the left region to the nearest river reach center point x tod x , if d x ≤ D x-left , then set this grid as a flooded grid, where D x-left is x the left distance of the point. The determination method for the grids in the right area being flooded is to find the distance from the center point of each grid in the right area to the center point of the nearest river section y distance d y , if d y ≤ D y-right , then set this grid as a flooded grid, where D y-right is y the right distance of the point.

[0047] Execute step 170, extract the flooded grids, and determine the final flooded range.

[0048] Embodiment 2

[0049] The present invention designs an interpolation method for the flooded range of the entire river section of a meandering river. This method mainly solves the problem of obtaining the flooded range of the middle river section with a large bend between two cross-sections by interpolating the flooded water levels of the cross-sections. The main innovation point of this method is to divide the possible flooded range into two areas, the left and right, with the river center as the limit, perform interpolation separately, and finally merge into the flooded range of the entire river.

[0050] The present invention is also applicable to obtaining the flooded range of a river using the flooded water levels of cross-sections in a straight river channel.

[0051] The method flow is as Figure 2 shown.

[0052] The first step, as Figure 3 shown, extract the river centerline, and use the river centerline to create a buffer zone, and the buffer zone range should cover all the flooded points of the cross-sections.

[0053] The second step, as Figure 4 shown, use the river centerline to divide the buffer zone into two parts, defined as the left and right sides of the river.

[0054] The third step, convert the left and right sides of the river into grids respectively, and the grid side length is preferably between 1m and 5m.

[0055] The fourth step, as Figure 5As shown in the figure, the centerline of the river is evenly divided into very short river segments using ArcGIS software. The center points of the river segments are extracted and numbered sequentially from upstream to downstream. Under the condition that the computational workload permits, it should be as short as possible. Generally, less than 5 meters is more appropriate.

[0056] In the fifth step, using the starting point and the ending point of the cross-section inundation range, query the nearest river segment center points respectively, and calculate the distances from the starting point and the ending point to the nearest river segment center points. Record this distance and the area where the starting point or the ending point is located into the river segment center points: denoted as the left distance and the right distance of the river segment center point.

[0057] In the sixth step, interpolate the left distances and right distances of all river segment center points. Taking the left distance as an example, the calculation method is shown in the following formula:

[0058]

[0059] In the formula, D i-right is the left distance with the sequence number i to be interpolated; m is i upstream of the i point, and is the sequence number of the river segment center point that is closest to the D m-right point and has the left distance obtained in the previous step calculated; n is i downstream of the i point, and is the sequence number of the river segment center point that is closest to the D n-right point and has the left distance obtained in the previous step calculated.

[0060] Calculate the right distances of all cross-sections in the same way.

[0061] In the seventh step, calculate whether the grids are inundated for the left and right regions respectively. Taking the left region as an example, find the distance i from the center point of each grid in the left region to the nearest river segment center point D . If D ≤ D i-right ( D i-right is the left distance obtained in the previous step), then set this grid as an inundated grid.

[0062] In the eighth step, as Figure 6 shown in the figure, extract the inundated grids, which are the final inundation range.

[0063] To better understand the present invention, the above has been described in detail in conjunction with specific embodiments of the present invention, but it is not a limitation of the present invention. Any simple modification made to the above embodiments based on the technical essence of the present invention still belongs to the scope of the technical solution of the present invention. Each embodiment in this specification focuses on the differences from other embodiments, and the same or similar parts between the various embodiments can be referred to each other. For the system embodiments, since they basically correspond to the method embodiments, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiments.

Claims

1. A method for extracting the inundation range of a river, including extracting the river centerline, characterized in that, It also includes the following steps: Step 1: Using the center line of the river, divide the buffer zone into two parts, which are respectively defined as the left side of the river and the right side of the river; Step 2: Respectively convert the left side of the river and the right side of the river into grids; Step 3: Divide the center line of the river into river sections with a length of n meters on average, where n < 5; Step 4: Using the starting point and the ending point of the cross-section flooding range, respectively query the nearest river section center point, and calculate the distance from the starting point or the ending point to the nearest river section center point; Step 5: Perform interpolation calculations on the left-side distances and right-side distances of all river section center points; Step 6: Calculate whether the grids are flooded respectively according to the two regions of the left side and the right side; Step 7: Extract the flooded grids to determine the final flooding range.

2. The method for extracting the inundation range of a river according to claim 1, characterized in that, The step of extracting the center line of the river includes making a buffer zone using the center line of the river, and the range of the buffer zone covers the flooding points of all cross-sections.

3. The method for extracting the inundation range of a river according to claim 2, characterized in that, The Step 2 includes that according to the width of general small and medium-sized rivers, the side length of the grid is 1m - 5m.

4. The method for extracting the inundation range of a river according to claim 3, characterized in that, The Step 3 includes extracting the center points of each small river section and sequentially numbering the small river sections from upstream to downstream.

5. The method for extracting the inundation range of a river according to claim 4, characterized in that, The Step 4 includes taking this distance as the left-side distance or the right-side distance of the river section center point according to the position where the cross-section starting point or ending point is located, and the cross-section starting point or ending point is located in the left buffer zone or the right buffer zone.

6. The method for extracting the inundation range of a river according to claim 5, characterized in that, The interpolation calculation formula for the left-side distance is Among them, i is the sequence number of the center point of the river reach to be interpolated, m is the sequence number of the center point of the river reach closest to i upstream and with a non-zero left-side distance, n is the sequence number of the center point of the river reach closest to i downstream and with a non-zero left-side distance, D i-left is the left-side distance of the center point of the river reach with sequence number i to be interpolated, D m-left is the left-side distance of point m, D n-left is the left-side distance of point n.

7. The method for extracting the inundation range of a river according to claim 6, characterized in that, The interpolation calculation formula for the right-side distance is Among them, D i-right is the right-side distance of the center point of the river reach with sequence number i to be interpolated, D m-right is the right-side distance of point m, D n-right is the right-side distance of point n.

8. The method for extracting the inundation range of a river according to claim 7, characterized in that, The method for determining the inundation of the left - hand area grid is to find the distance d from the center point of each grid in the left - hand area to the center point x of the nearest river section x , if d x ≤D x-left , then set this grid as an inundated grid, where D x-left is the left - hand distance of point x.

9. The method for extracting the inundation range of a river according to claim 8, characterized in that, The method for determining the inundation of the grid in the right region is to find the distance d from the center point of each grid in the right region to the center point y of the nearest river reach y , if d y ≤D y-right , then set this grid as an inundated grid, where D y-right is the right distance of point y

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