A method for macroscopic identification of river blocking disasters based on valley width and main river slope change

Abstract

The present invention discloses a method for macroscopically identifying river-blocking disaster events based on the width of the river valley and the slope change of the main river, which relates to the technical field of identifying river-blocking landslides and debris flows, including: S1, obtaining high-precision DEM elevation data; S2, calculating the cross-section fitting average values ​​of the central section, upstream section and downstream section in the direction perpendicular to the main river; S3, calculating the main river gradient of the central section, upstream section and downstream section in the direction parallel to the main river; S4, determining the possibility of the identified slope / channel having a river-blocking disaster event in history, and the possibility of a river-blocking disaster event occurring in the future, based on the results of S2 and S3. This method can not only macroscopically identify whether a river-blocking disaster event has occurred in the area to be identified in history, and whether a river-blocking disaster event will occur in the future, but also provide a verification basis for the results of numerical simulation, and provide a target area for on-site investigation and sampling measurement, thereby improving the accuracy of identifying river-blocking disaster events.

Description

Technical Field

[0001] The present invention relates to the technical field of large-scale river-blocking landslide and debris flow disaster identification, and in particular to a method for macroscopically identifying river-blocking disaster events based on valley width and main river slope variation. Background Art

[0002] Active geological structures, complex topography, frequent earthquakes, and diverse and unusual climate characteristics have led to a strong interweaving of internal and external forces in high mountainous areas such as the Qinghai-Tibet Plateau. River-blocking landslides and mud-rock flows have occurred repeatedly, causing serious casualties and property losses. At the same time, early identification of such disasters has become one of the most urgent issues in disaster prevention and mitigation for important roads or hydropower projects under planning.

[0003] These catastrophic landslides and debris flows often block the main stream, forming a chain of dammed lakes and outburst floods, amplifying the scope of the disaster risk. Although we may think that the number of such geological hazards is relatively small, and in practice we have found that there is relatively little survey or record of such river-blocking landslides and debris flows, this is because these hazards are concentrated in tectonic active high mountainous areas with no human population.

[0004] In order to better prevent river blockage disasters and reduce losses, it is necessary to conduct early identification of river blockage disasters. At this stage, there are mainly two identification methods:

[0005] 1. Identify large landslides through technologies such as InSAR or large-scale debris flows through field surveys, estimate the scale and dynamic parameters based on the identification, and ultimately draw conclusions on whether a river-blocking disaster will occur based on numerical simulations. However, this method has the problem of difficulty in verifying the results.

[0006] 2. The distribution of ancient barrier lakes is studied through on-site investigations and sampling measurements, and the occurrence of historical river blockage events is determined. However, this method has the problems of difficulty in determining the target area, difficulty in macroscopic identification within the region, and relatively high cost.

[0007] Furthermore, data analysis has revealed that river-blocking landslides and debris flows exhibit a recurring pattern in tectonically active high mountainous areas. For example, studies have shown that large-scale landslides and debris flows on the Qinghai-Tibet Plateau have a recurrence period of approximately 3,000-9,000 years. For example, the Yigong landslide occurred twice, in 1900 and 2000. This recurrence of large-scale landslides and debris flows leads to unusual geomorphic features at the intersections of these river-blocking landslides and debris flows with the main river. These features are characterized by valley width and main river slope variation. Therefore, it is necessary to develop new techniques based on these recurring indicators, such as valley width and main river slope variation, to facilitate more accurate, convenient, and efficient macroscopic identification of river-blocking events. Summary of the Invention

[0008] By analyzing the characteristics of repeated occurrence of river-blocking landslides and mud-rock flows, the present invention finds that river-blocking disaster events usually include two indicators of abnormal geomorphological features: river valley width and main river slope change. Therefore, a method for macro-identifying river-blocking disaster events based on river valley width and main river slope change is proposed. This method can not only macroscopically identify whether a river-blocking disaster event has occurred in the history of the area to be identified, and whether a river-blocking disaster event will occur in the future, but also provide a verification basis for the results of numerical simulations, and provide target areas for on-site investigations and sampling measurements, thereby improving the accuracy of river-blocking disaster event identification and solving the technical problems of low accuracy, high difficulty and high cost of existing identification methods.

[0009] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0010] A method for macroscopically identifying river blocking disasters based on valley width and main river slope changes comprises the following steps:

[0011] Step S1, obtaining high-precision DEM elevation data within the ridge lines on both sides of the river section where the slope / channel is identified;

[0012] Step S2: In the direction perpendicular to the main river, with the identified slope / channel as the center section, based on the high-precision DEM elevation data, use the power function fitting method to calculate multiple cross-sectional values ​​representing the width of the river valley in the center section, multiple cross-sectional values ​​representing the width of the river valley in the upstream section, and multiple cross-sectional values ​​representing the width of the river valley in the downstream section, and then calculate the cross-sectional fitting average value b of the center section. c , the average value of the cross-section fitting of the upstream section and the average value of the cross-section fitting of the downstream section

[0013] Step S3: In the direction parallel to the main river, with the river section where the slope / channel is identified as the central section, multiple elevation points are obtained in the central section, upstream section, and downstream section according to the high-precision DEM elevation data. The main river gradient i of the central section is calculated by performing linear fitting on the multiple elevation points of the central section, the multiple elevation points of the upstream section, and the multiple elevation points of the downstream section. c , the main river gradient in the upstream section i u and the main river gradient i in the downstream section d ;

[0014] Step S4: According to the results of S2 and S3, when and (i c / i u -1)(i c / i d -1)>0, it is judged that the slope / channel has a high possibility of having a river blocking disaster event in history, and the possibility of a river blocking disaster event in the future is high; conversely, it is judged that the slope / channel has a low possibility of having a river blocking disaster event in history, and the possibility of a river blocking disaster event in the future is low.

[0015] In step S1, high-precision DEM elevation data is used to identify the river section where the slope / channel is located and the range of 10 km upstream and downstream.

[0016] In step S1, the resolution of the high-precision DEM elevation data is 30m or 12.5m.

[0017] In step S2, the cross-sectional values ​​of the central segment, the cross-sectional values ​​of the upstream segment, and the cross-sectional values ​​of the downstream segment are all at least three.

[0018] In step S2, the distance between sections corresponding to each section value is no more than 1 km.

[0019] The advantages of adopting the present invention are:

[0020] 1. Based on the characteristics of repeated occurrence of river-blocking landslides and debris flows, the present invention conducts in-depth research starting from two abnormal geomorphological features: the width of the river valley and the slope change of the main river. The method can not only judge from a macro perspective whether a river-blocking disaster event has occurred in the history of the area to be identified, and whether a river-blocking disaster event will occur in the future, but also provide a verification basis for the results of numerical simulations, and provide target areas for on-site investigations and sampling measurements. It not only improves the accuracy of river-blocking disaster event identification, but also solves the technical problems of low accuracy, high difficulty and high cost of existing identification methods.

[0021] 2. The research objects and research scenarios identified by the present invention are relatively special. Since the occurrence of giant or large disasters in space is repetitive, it is particularly important to identify river blocking disaster events in high-altitude and cold mountainous areas at this stage. Then, based on the characteristics of landform changes caused by historical giant and large river blocking disasters or the easy occurrence of large-scale geological disasters in certain special sections under the action of geological structures, the landform characteristics of the slope / channel section in the direction perpendicular to the main river and parallel to the main river are identified through research, and the indicators used to characterize the width of the river channel perpendicular to the main river and the gradient of the main river parallel to the main river are calculated. The macroscopic identification of river blocking disaster events is carried out according to the threshold of the identification index, which is conducive to more accurate and effective identification of giant or large disasters.

[0022] 3. The present invention sets high-precision DEM elevation data to identify the river section where the slope / channel is located and the range of 10 km upstream and downstream. Its advantage is that the data is open source data, and the data acquisition is convenient, fast and low-cost, which can overcome the problem of difficult on-site measurement in high-altitude uninhabited areas.

[0023] 4. The present invention sets the resolution of high-precision DEM elevation data to 30m or 12.5m. The advantage is that DEM data with this resolution is commonly used in the industry with high accuracy and reliable data accuracy, facilitating the accurate acquisition and fitting analysis of cross-section two-dimensional coordinate data.

[0024] 5. The present invention sets the cross-sectional values ​​of the central section, the upstream section and the downstream section to at least 3. The advantage is that it avoids the situation where the local section is significantly different from the overall section, and ensures that the cross-sectional values ​​of the central section, the upstream section and the downstream of the midline section can represent the slope characteristics of the corresponding sections parallel to the main river direction.

[0025] 6. The present invention sets the distance between the sections corresponding to each section value to no more than 2 km. Its advantage is to ensure that the number of sections in each section is sufficient, thereby ensuring that multiple section values ​​can be obtained for the central section, upstream section and downstream section, and finally ensuring that the obtained section fitting average value b c 、 and They can well characterize the geomorphological characteristics of each section. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is the flowchart of the present invention; the diagram needs to be modified accordingly according to the file content. Please provide me with the source file.

[0027] Figure 2 Schematic diagram of calculating the cross-sectional fitting average values ​​of the central section, upstream section, and downstream section respectively according to the present invention;

[0028] Figure 3Schematic diagram of the main river gradient calculated for the central section, upstream section and downstream section respectively according to the present invention. DETAILED DESCRIPTION

[0029] like Figure 1 As shown, the present invention provides a method for macroscopically identifying river blocking disaster events based on the width of the river valley and the slope change of the main river, which includes the following steps:

[0030] Step S1: Obtain high-precision DEM elevation data within the ridge lines on both sides of the river section where the identified slope / channel is located. The resolution of the high-precision DEM elevation data is 30m or 12.5m. The obtained high-precision DEM elevation data is for the river section where the identified slope / channel is located and within 10km upstream and downstream.

[0031] Step S2: perpendicular to the main river direction, with the river section where the slope / channel is identified as the central section, multiple sections representing the width of the river valley are made in the upstream section, the central section, and the downstream section respectively. Based on the high-precision DEM elevation data, the power function fitting method (y = ax b ) Calculate multiple cross-sectional values ​​representing the width of the central section, multiple cross-sectional values ​​representing the width of the upstream section, and multiple cross-sectional values ​​representing the width of the downstream section, and then calculate the cross-sectional fitting average value b of the central section based on the obtained cross-sectional values. c , the average value of the cross-section fitting of the upstream section and the cross-sectional fitting average value of the downstream section

[0032] It should be noted that the upstream section and downstream section in this step are respectively 10 km upstream and downstream in step S1. Usually, the upstream section is 10 km upstream of the center section, and the downstream section is 10 km downstream of the center section.

[0033] Step S3: In the direction parallel to the main river, with the river section where the slope / channel is identified as the central section, multiple elevation points are obtained in the central section, upstream section, and downstream section according to the high-precision DEM elevation data. The main river gradient i of the central section is calculated by performing linear fitting on the multiple elevation points of the central section, the multiple elevation points of the upstream section, and the multiple elevation points of the downstream section. c , the main river gradient in the upstream section i u and the main river gradient i in the downstream section d .

[0034] Step S4: Based on the characteristics of historical large-scale geological disasters blocking rivers, according to the results of S2 and S3, when and (i c / i u -1)(i c / i d-1)>0, it is judged that the slope / channel has a high possibility of having a river blocking disaster event in history, and the possibility of a river blocking disaster event in the future is high; conversely, it is judged that the slope / channel has a low possibility of having a river blocking disaster event in history, and the possibility of a river blocking disaster event in the future is low.

[0035] According to a preferred embodiment of the present invention, to improve the accuracy of macroscopic identification, in step S2, the number of cross-sectional values ​​for the central segment, the upstream segment, and the downstream segment is at least three, for example, five or ten. Furthermore, the distance between the cross-sectional values ​​corresponding to each cross-sectional value is no greater than 1 km.

[0036] It should be noted that the macro-identification method in the present invention refers to: judging the possibility of major river-blocking disasters occurring in history and the possibility of major river-blocking disasters occurring in the future based on the geomorphological characteristics of river-blocking disasters in the directions perpendicular to and parallel to the main river.

[0037] To verify the technical effects of the present invention, the applicant has made a detailed description based on the actual disaster event of the Yigong landslide and debris flow that occurred on the Qinghai-Tibet Plateau on April 9, 2000, and incorporated it into the present invention, as follows:

[0038] A method for macroscopically identifying river blocking disasters based on valley width and main river slope changes comprises the following steps:

[0039] S1. Take the area from the Yigong landslide point to 10 km downstream as the central section, the area above the central section as the upstream section, and the area below the central section as the downstream section. Obtain DEM elevation data with a resolution of 12.5 m for the upstream, central, and downstream sections of the Yigong Zangbo River Valley (from the ridges on both sides to the river).

[0040] S2, such as Figure 2 As shown in the figure, 5 sections were made in the upstream, central and downstream sections perpendicular to the main river direction. The x and y values ​​required for the power function fitting method were extracted based on the high-precision DEM elevation data. The power function fitting method was then used to calculate multiple section values ​​representing the width of the valley in the central section, the width of the valley in the upstream section, and the width of the valley in the downstream section. The calculation results showed that the five section values ​​of the upstream section were 1.98, 2.05, 1.80, 1.60 and 1.27, respectively; the five section values ​​of the central section were 1.15, 1.27, 1.31, 1.22 and 1.30, respectively; and the five section values ​​of the downstream section were 1.40, 1.33, 1.32, 1.53 and 1.53, respectively. Then, based on the obtained section values, the section fitting average value b of the central section was calculated. c , the average value of the cross-section fitting of the upstream section and the average value of the cross-section fitting of the downstream section They are 1.25, 1.74 and 1.42 respectively.

[0041] S3, in the direction parallel to the main river, according to the high-precision DEM elevation data, calculate the main river gradient i of the upstream section 10km u , the main river gradient of the downstream section 10km d and the main river gradient i in the central section c .

[0042] Specifically, such as Figure 3 As shown in the figure, 5 elevation points in the upstream, central and downstream sections were selected for linear fitting. The fitting results showed that the linear regression equation of the upstream section was y = -0.5813x + 2175.9 (R 2 =0.62); the linear regression equation of the central segment is y = -11.371x + 2165.3 (R 2 =0.99); the linear regression equation of the downstream section is y = -7.7897x + 2057.6 (R 2 =0.94). After calculation, the main river gradient i of the upstream section 10 km is obtained. u , the main river gradient of the downstream section 10km d and the main river gradient i in the central section c They are 0.5813, 11.371 and 7.7897 respectively.

[0043] S4. According to the results of S2 and S3, when the cross-section of the central segment is fitted with the average value b c is 1.25, the average value of the cross-section fitting in the upstream section and the average value of the cross-section fitting of the downstream section When the values ​​are 1.74 and 1.42 respectively, is 1.33, which satisfies The main river gradient i in the central section c The main river gradient in the upstream section is 0.01376. u The value is 0.0006, and the main river gradient i in the downstream section d The value is 0.0081, which satisfies (i c / i u -1)(i c / i d -1)>0. Therefore, it can be seen that the Yigong landslide also meets the and (i c / i u -1)(i c / i d -1)>0, so it is judged that there has been a disaster blocking the river in this area in history.

[0044] The above description is only a specific embodiment of the present invention. Any feature disclosed in this specification, unless otherwise stated, can be replaced by other equivalent or alternative features with similar purposes; all disclosed features, or all steps in the methods or processes, except for mutually exclusive features and / or steps, can be combined in any way.

Claims

1. A method for macroscopically identifying river-blocking disasters based on valley width and main river slope variation. This method uses geomorphic features of river-blocking disasters in directions perpendicular and parallel to the main river to identify the likelihood of major river-blocking disasters occurring in history and the likelihood of major river-blocking disasters occurring in the future. The method is characterized by: The following steps are involved: Step S1, obtaining high-precision DEM elevation data within the ridge lines on both sides of the river section where the slope / channel is identified; Step S2: In the direction perpendicular to the main river, with the identified slope / channel as the center section, based on the high-precision DEM elevation data, use the power function fitting method to calculate multiple cross-sectional values ​​representing the width of the river valley in the center section, multiple cross-sectional values ​​representing the width of the river valley in the upstream section, and multiple cross-sectional values ​​representing the width of the river valley in the downstream section, and then calculate the cross-sectional fitting average value of the center section. , the average value of the cross-section fitting of the upstream section and the average value of the cross-section fitting of the downstream section ; Step S3: In the direction parallel to the main river, with the river section where the slope / channel is identified as the central section, multiple elevation points are obtained in the central section, upstream section, and downstream section according to the high-precision DEM elevation data. The main river gradient of the central section is calculated by linear fitting the multiple elevation points of the central section, the multiple elevation points of the upstream section, and the multiple elevation points of the downstream section. , the main river gradient in the upstream section and the main river gradient in the downstream section ; Step S4: According to the results of S2 and S3, when ,and When the slope / channel is judged to have a high probability of a river blocking disaster in history, and a high probability of a river blocking disaster in the future; conversely, the slope / channel is judged to have a low probability of a river blocking disaster in history, and a low probability of a river blocking disaster in the future.

2. The method for macroscopically identifying river blocking disasters based on valley width and main river slope changes according to claim 1 is characterized by: In step S1, high-precision DEM elevation data is used to identify the river section where the slope / channel is located and the range of 10 km upstream and downstream.

3. The method for macroscopically identifying river blocking disasters based on valley width and main river slope changes according to claim 1 is characterized by: In step S1, the resolution of the high-precision DEM elevation data is 30m or 12.5m.

4. The method for macroscopically identifying river blocking disasters based on valley width and main river slope changes according to claim 1 is characterized by: In step S2, the cross-sectional values ​​of the central segment, the cross-sectional values ​​of the upstream segment, and the cross-sectional values ​​of the downstream segment are all at least three.

5. The method for macroscopically identifying river blocking disasters based on valley width and main river slope changes according to any one of claims 1 to 4, characterized in that: In step S2, the distance between sections corresponding to each section value is no more than 1 km.

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