Debris flow rapid quantitative identification method and application

Abstract

The invention discloses a debris flow rapid quantitative identification method and application, and belongs to the technical field of hydraulic engineering, and the method comprises the following steps: a, determining a potential gully type debris flow basin, and enclosing a basin range; b, topographic parameters of the potential gully-type debris flow are measured, and the drainage basin area A and the gully bed longitudinal gradient J of the potential gully-type debris flow are obtained; and c, quantitatively judging and identifying gully-type debris flow according to the drainage basin area A and the gully bed longitudinal gradient J. According to the method, rapid quantitative identification of gully-type debris flow can be realized only through two topographic parameters, namely the drainage basin area and the gully bed longitudinal gradient, which are easy to obtain, screening efficiency is greatly improved, a complex debris flow forming mechanism is converted into a topographic judgment criterion capable of being quantitatively calculated, and the method is simple, high in universality and convenient to popularize in a large range.

Description

Technical Field

[0001] This invention relates to the field of water conservancy engineering technology, and in particular to a rapid quantitative identification method for debris flows and its application. Background Technology

[0002] Geomorphological conditions are a common classification indicator used for debris flow classification. Gully-type debris flows are a widely distributed and highly concealed type of debris flow. Based on the location and morphology of the gully, a third type of debris flow is distinguished between slope-type and gully-type debris flows: gully-type debris flows. These develop within juvenile erosion gullies on slopes. The formation mechanism of gully-type debris flows mainly involves rainfall causing landslides to occur within the watershed, enter the gully, and then flow out and deposit along a straight gully. The occurrence of gully-type debris flows is closely related to landslides. Domestic and international studies show that areas prone to landslides are more likely to experience gully-type debris flow events, sometimes even clusters of such events. Watersheds that would not normally experience gully-type debris flows may be identified as such in the field. Conversely, watersheds that might normally experience gully-type debris flows may be identified as gully-type debris flows. The above phenomena are mainly due to differences in the classification of debris flows. Currently, there is no quantitative identification method for the topographic features of gully-type debris flows, both domestically and internationally; only a few qualitative identification methods exist. The greater the longitudinal gradient of a slope, the greater the likelihood of a gully-type debris flow. The solid particles in gully-type debris flows primarily originate from landslides occurring at the top of the gully during rainfall. Without landslides, this type of debris flow is unlikely to form. Slope gradient is a major factor influencing landslides, and water catchment capacity is related to the catchment area. Only by understanding and identifying the location of gully-type debris flows can the damage caused by them be effectively reduced in advance. Currently, there are few quantitative identification studies on gully-type debris flows; most studies use factors such as catchment area, slope gradient, and relative elevation difference of the catchment area as indicators to define slope-type and valley-type debris flows. Gully-type debris flows mostly occur in young erosion gullies on slopes, with no tributaries, weak drainage systems, and small catchment areas—these are all qualitative identification methods. More importantly, there are differences in the classification of debris flows, making it impossible to accurately identify gully-type debris flows.

[0003] Chinese patent application document CN119048972A, published on November 29, 2024, discloses a debris flow image recognition method, characterized by comprising the following steps: Step 1: Use a camera or video camera to continuously photograph the debris flow channel in the observation area to obtain several pictures or videos. Then, transmit the pictures or videos to a computer via the network for processing to obtain several consecutive pictures or video frame screenshots. Step 2: In the debris flow gully detection area in the image, set three or more warning lines perpendicular to the debris flow direction and one sampling line in the center of the gully, and set the color difference warning value for the warning lines. Step 3: Extract the RGB values ​​of all pixels on the warning line. When the difference between the maximum and minimum RGB values ​​on the warning line is less than the warning value, a warning is issued. When the color difference warning values ​​of three or more sampling lines are issued simultaneously, it can be determined that a mudslide has occurred. Step 4: After determining that a debris flow has occurred in Step 3, continuously read the RGB values ​​of all pixels on the sampling line. Divide the number of consecutive adjacent pixels with the same color difference on the warning line by the total number of pixels on the warning line, and multiply by the channel width to calculate the width of the debris flow when it passes through the warning line. Then, determine the scale of the debris flow and its position in the channel by the size of the peak. Continue to extract the RGB value peak position on the sampling line of the next image and compare it with the position in the previous image to calculate the speed of the debris flow.

[0004] The debris flow image recognition method disclosed in this patent application utilizes the color change characteristics of debris flow channel images during normal times and during debris flows. By processing the images, the flow velocity of the debris flow is calculated, thus achieving the purpose of debris flow early warning and prevention. However, the recognition process is complex, cannot achieve rapid quantitative recognition, and lacks universality. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, this invention provides a rapid quantitative identification method and application for debris flows. This invention can achieve rapid quantitative identification of gully-type debris flows using only two easily obtainable topographic parameters: watershed area and longitudinal slope of the gully bed. This greatly improves screening efficiency and transforms the complex debris flow formation mechanism into a quantifiable topographic discrimination criterion. The method is simple, universal, and easy to promote on a large scale.

[0006] This invention is achieved through the following technical solution: A rapid quantitative identification method for debris flows includes the following steps: a. Identify potential gully-type debris flow basins and delineate the basin boundaries; b. Measure the topographic parameters of potential gully debris flows to obtain the catchment area A and the longitudinal slope J of the gully bed. c. Quantitatively identify gully-type debris flows based on the catchment area A and the longitudinal slope of the gully bed J.

[0007] In step a, identifying a potential gully-type debris flow basin means that if a gully exists without tributaries and the gully is straight, it is identified as a gully-type debris flow basin by observing Google Maps imagery.

[0008] In step a, identifying a potential gully-type debris flow basin means that, through observation of a topographic map, if there is a gully without tributaries and the gully is straight, it is judged to be a gully-type debris flow basin.

[0009] In step c, quantitatively identifying gully-type debris flows means that when the distance is 0.001 km... 2 ≤A≤0.1 km 2 Furthermore, if the longitudinal slope of the gully bed J simultaneously satisfies J≥0.4, it is identified as a gully-type debris flow; otherwise, it is not a gully-type debris flow.

[0010] In step c, when quantitatively identifying gully-type debris flows, it also includes the loose sediment reserve S per unit watershed area, which is 0.001 km². 2 ≤A≤0.1km 2 J≥0.4 and the loose sediment reserves per unit watershed area S≥10×10 4 m 3 / km 2 At that time, it was identified as a gully-type debris flow.

[0011] The loose sediment reserves S per unit watershed area are obtained through field surveys or by weighted averaging of soil layer thickness measurements.

[0012] This invention is applicable to the identification of rainfall-triggered gully debris flows.

[0013] Furthermore, this invention is applicable to the identification of gully debris flows caused by erosion and transport.

[0014] The basic principle of this invention is as follows: The formation of gully debris flows is caused by rainfall causing the slope at the top of the gully to become unstable, forming debris flows within the gully. The debris flows then scrape along the straight gully and rush downstream, finally rushing out of the gully mouth and accumulating in the downstream deposition area.

[0015] The basic principle for quantitatively determining gully debris flows is: 1) If the catchment area is too small, A < 0.001 km 2 If there is too little water, the loose material on the gully bed cannot undergo shallow landslides in the gully, thus forming gully debris flows; or if shallow landslides occur on the slope and enter the gully, they cannot be washed away and form gully debris flows. 2) If the longitudinal gradient of the gully bed is too small, J < 0.4, the loose material on the gully bed is unlikely to become unstable and form a shallow landslide and then a debris flow; or the loose material on the slope may become unstable and form a shallow landslide, but it is difficult to form a debris flow in the gully, and it will only accumulate in the gully and cannot form a gully debris flow.

[0016] 3) If there is too little sediment in the watershed, such as most of the area being bedrock slopes with no soil sediment, even with heavy rainfall, a large watershed area, and a large longitudinal gradient of the gullies, it will only result in flash floods and will not form gully debris flows.

[0017] The catchment area A determines the scale of water that can be collected, with a lower limit of A ≥ 0.001 km². 2 Sufficient water flow is ensured to infiltrate, saturate, and initiate the loose material in the channel bed or side slopes, providing the initial liquid phase and transport medium for debris flows. The longitudinal gradient J of the channel bed determines the energy of the water flow and potential fluid moving along the channel. A lower limit J ≥ 0.4 ensures that the water flow has sufficient shear force to continuously scrape and entrain channel material, effectively converting potential energy into kinetic energy, thereby maintaining the long-distance movement of debris flow without stagnation and sedimentation. These two parameters together define a "hydrodynamic-energy" critical window: only when a potential catchment area falls within this window simultaneously, i.e., both the catchment area A and the longitudinal gradient J of the channel bed are higher than the threshold, does the topography possess the basic physical prerequisites for efficiently converting local rainfall into destructive solid runoff. This is the deep scientific basis for the rapid quantitative identification of debris flow in this invention. Furthermore, ensuring a solid material source is crucial to ensuring sufficient sediment, and that the fluid is a debris flow rather than a flood or high-sediment-laden flow.

[0018] The beneficial effects of this invention are mainly reflected in the following aspects: 1. Compared with the prior art, the present invention can achieve rapid quantitative identification of gully debris flows using only two easily obtainable topographic parameters: watershed area and longitudinal slope of the gully bed. This greatly improves the screening efficiency and transforms the complex debris flow formation mechanism into a quantifiable topographic discrimination criterion. The method is simple, universal, and easy to promote on a large scale. 2. This invention utilizes Google Maps imagery to visually determine the morphology of gullies, enabling the rapid identification of potential gully-type debris flow basins and achieving low-cost, rapid preliminary delineation. 3. This invention identifies gully morphology based on topographic maps. The method is stable and reliable, not limited by the timeliness of network and image data, and is applicable to various basic geographic information environments, demonstrating good applicability. 4. This invention extracts precise thresholds for key topographic parameters through extensive empirical research, transforming qualitative descriptions into rigid quantitative standards. It clearly provides quantitative critical values ​​for a watershed area of ​​0.001-0.1 km² and a gully bed longitudinal gradient J ≥ 0.4, ensuring objective and unified judgment standards and eliminating errors caused by subjective experience.

[0019] 5. This invention, based on the dual parameters of watershed area and longitudinal slope of the gully bed, adds the key material condition of loose sediment reserves, creatively coupling the judgment of "geological energy" and "sediment source conditions", which more completely reflects the three basic elements of debris flow formation: topography, water and sediment source, significantly improving the accuracy and reliability of identification and reducing misjudgment.

[0020] 6. In this invention, the loose sediment reserves S per unit watershed area are obtained through field surveys or by weighted averaging of soil layer thickness measurements, ensuring the accuracy and reliability of the core data source and laying a solid foundation for accurate identification. Attached Figure Description The present invention will now be further described in detail with reference to the accompanying drawings and specific embodiments: Figure 1 This is a flowchart of the present invention. Detailed Implementation

[0021] Example 1 See Figure 1 A rapid quantitative identification method for debris flows includes the following steps: a. Identify potential gully-type debris flow basins and delineate the basin boundaries; b. Measure the topographic parameters of potential gully debris flows to obtain the catchment area A and the longitudinal slope J of the gully bed. c. Quantitatively identify gully-type debris flows based on the catchment area A and the longitudinal slope of the gully bed J.

[0022] This embodiment is the most basic implementation method. Compared with the prior art, it can achieve rapid quantitative identification of gully debris flows by using only two easily obtainable topographic parameters: watershed area and longitudinal slope of the gully bed. This greatly improves the screening efficiency and transforms the complex debris flow formation mechanism into a quantifiable topographic discrimination criterion. The method is simple, universal, and easy to promote on a large scale. Example 2 See Figure 1 A rapid quantitative identification method for debris flows includes the following steps: a. Identify potential gully-type debris flow basins and delineate the basin boundaries; b. Measure the topographic parameters of potential gully debris flows to obtain the catchment area A and the longitudinal slope J of the gully bed. c. Quantitatively identify gully-type debris flows based on the catchment area A and the longitudinal slope of the gully bed J.

[0023] In step a, identifying a potential gully-type debris flow basin means that if a gully exists without tributaries and the gully is straight, it is identified as a gully-type debris flow basin by observing Google Maps imagery.

[0024] This embodiment is a preferred implementation method. By using Google Maps imagery and intuitively judging the gully morphology, potential gully-type debris flow basins can be quickly located, achieving low-cost and rapid preliminary delineation. Example 3 See Figure 1 A rapid quantitative identification method for debris flows includes the following steps: a. Identify potential gully-type debris flow basins and delineate the basin boundaries; b. Measure the topographic parameters of potential gully debris flows to obtain the catchment area A and the longitudinal slope J of the gully bed. c. Quantitatively identify gully-type debris flows based on the catchment area A and the longitudinal slope of the gully bed J.

[0025] In step a, identifying a potential gully-type debris flow basin means that, through observation of a topographic map, if there is a gully without tributaries and the gully is straight, it is judged to be a gully-type debris flow basin.

[0026] In step c, quantitatively identifying gully-type debris flows means that when the distance is 0.001 km... 2 ≤A≤0.1 km 2 Furthermore, if the longitudinal slope of the gully bed J simultaneously satisfies J≥0.4, it is identified as a gully-type debris flow; otherwise, it is not a gully-type debris flow.

[0027] This embodiment represents another preferred implementation method. It identifies gully morphology based on topographic maps, offering a stable and reliable approach that is not limited by the timeliness of network and image data. It is applicable to various basic geographic information environments and has good applicability. Through extensive empirical research, precise thresholds for key topographic parameters are extracted, transforming qualitative descriptions into rigid quantitative standards. Quantitative critical values ​​are clearly given for a watershed area of ​​0.001-0.1 km² and a gully bed gradient J ≥ 0.4, ensuring objective and unified judgment criteria and eliminating errors caused by subjective experience.

[0028] Example 4 See Figure 1 A rapid quantitative identification method for debris flows and its application, comprising the following steps: a. Identify potential gully-type debris flow basins and delineate the basin boundaries; b. Measure the topographic parameters of potential gully debris flows to obtain the catchment area A and the longitudinal slope J of the gully bed. c. Quantitatively identify gully-type debris flows based on the catchment area A and the longitudinal slope of the gully bed J.

[0029] In step a, identifying a potential gully-type debris flow basin means that, through observation of a topographic map, if there is a gully without tributaries and the gully is straight, it is judged to be a gully-type debris flow basin.

[0030] In step c, quantitatively identifying gully-type debris flows means that when the distance is 0.001 km... 2 ≤A≤0.1 km 2 Furthermore, if the longitudinal slope of the gully bed J simultaneously satisfies J≥0.4, it is identified as a gully-type debris flow; otherwise, it is not a gully-type debris flow.

[0031] Preferably, in step c, when quantitatively identifying gully-type debris flows, the method further includes determining the loose sediment reserve S per unit watershed area, where S is 0.001 km². 2 ≤A≤0.1km 2 J≥0.4 and the loose sediment reserves per unit watershed area S≥10×10 4 m 3 / km 2 At that time, it was identified as a gully-type debris flow.

[0032] The loose sediment reserves S per unit watershed area are obtained through field surveys or by weighted averaging of soil layer thickness measurements.

[0033] This embodiment represents the optimal implementation method. Based on the dual parameters of watershed area and longitudinal slope of the gully bed, it adds the key material condition of loose sediment reserves. It creatively couples the judgment of "geological energy" and "sediment source conditions," which more completely reflects the three basic elements of debris flow formation: topography, water, and sediment source. This significantly improves the accuracy and reliability of identification and reduces misjudgments.

[0034] The loose sediment reserves S per unit watershed area were obtained through field surveys or by weighted averaging of soil layer thickness measurements, ensuring the accuracy and reliability of the core data source and laying a solid foundation for accurate identification. The implementation method of the present invention will be described in detail below with reference to specific examples.

[0035] According to the investigation, there were 95 gullies where debris flows occurred, including: a gully-type debris flow in Nanping, Fujian on June 18, 2010; a gully-type debris flow in Shunchang County, Fujian on June 18, 2010; a gully-type debris flow in Yangkou Town, Fujian on June 18, 2010; a gully-type debris flow in Jiangle County, Fujian on June 18, 2010; a gully-type debris flow in Yanping, Fujian on June 18, 2010; a gully-type debris flow in Mibei Village, Guangdong in 2019; a gully-type debris flow in Pucheng, Fujian on July 9, 2019; and a gully-type debris flow in Ji'an County, Zhejiang on August 9, 2019.

[0036] First, potential gully debris flows are visually identified using remote sensing images. Small watersheds with gullies that are straight and without tributaries are selected as potential gully debris flows. Then, the watershed area and longitudinal slope of the gully bed are obtained from the topographic map to determine whether it is a gully debris flow.

[0037] The topographic parameters and identification status of the 95 gullies are shown in Table 1.

[0038] Table 1

[0039]

[0040]

[0041]

[0042] According to the identification criteria for gully-type debris flows: a potential gully-type debris flow that meets the following conditions: has a channel without tributaries, and the channel is straight, when the length is 0.001 km... 2 ≤A≤0.1km 2 When J≥0.4, it is identified as a gully-type debris flow. Table 1 shows 95 instances that can be identified as gully-type debris flows, all of which resulted in debris flows.

[0043] In summary, the method described in this invention has a high accuracy in identifying gully-type debris flows.

Claims

1. A rapid quantitative identification method for debris flows, characterized in that, Includes the following steps: a. Identify potential gully-type debris flow basins and delineate the basin boundaries; b. Measure the topographic parameters of potential gully debris flows to obtain the catchment area A and the longitudinal slope J of the gully bed. c. Quantitatively identify gully-type debris flows based on the catchment area A and the longitudinal slope of the gully bed J.

2. The rapid quantitative identification method for debris flows according to claim 1, characterized in that: In step a, identifying a potential gully-type debris flow basin means that if a gully exists without tributaries and the gully is straight, it is identified as a gully-type debris flow basin by observing Google Maps imagery.

3. The rapid quantitative identification method for debris flows according to claim 1, characterized in that: In step a, identifying a potential gully-type debris flow basin means that, through observation of a topographic map, if there is a gully without tributaries and the gully is straight, it is judged to be a gully-type debris flow basin.

4. The rapid quantitative identification method for debris flows according to claim 1, characterized in that: In step c, quantitatively identifying gully-type debris flows means that when the distance is 0.001 km... 2 ≤A≤0.1 km 2 Furthermore, if the longitudinal slope of the gully bed J simultaneously satisfies J≥0.4, it is identified as a gully-type debris flow; otherwise, it is not a gully-type debris flow.

5. The rapid quantitative identification method for debris flows according to claim 1, characterized in that: In step c, when quantitatively identifying gully-type debris flows, it also includes the loose sediment reserve S per unit watershed area, which is 0.001 km². 2 ≤A≤0.1km 2 J≥0.4 and the loose sediment reserves per unit watershed area S≥10×10 4 m 3 / km 2 At that time, it was identified as a gully-type debris flow.

6. The rapid quantitative identification method for debris flows according to claim 5, characterized in that: The loose sediment reserves S per unit watershed area are obtained through field surveys or by weighted averaging of soil layer thickness measurements.

7. An application for rapid quantitative identification of debris flows, characterized in that: The rapid quantitative identification method for debris flows as described in claim 1 is applicable to the identification of rainfall-triggered gully debris flows.

8. An application for rapid quantitative identification of debris flows, characterized in that: The rapid quantitative identification method for debris flows as described in claim 1 is applicable to the identification of gully debris flows caused by erosion and transport.

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