Method for measuring and calculating dynamic reserves of debris flow channel sources based on unmanned aerial vehicle aerial photography and application

Abstract

The application discloses a method for measuring and calculating a dynamic storage of a debris flow channel source based on unmanned aerial vehicle aerial photography and application, and belongs to the technical field of debris flow prevention engineering, and the method comprises the following steps: S1, acquiring channel parameters through unmanned aerial vehicle aerial photography; S2, dividing the channel, and dividing the channel into a U-shaped channel and a V-shaped channel; S3, calculating rainfall parameters R* of different rainfall frequencies; S4, calculating a judgment index of each source section under different rainfall frequencies through formula 1; S5, calculating and determining the dynamic storage V of the source according to the channel bed width W0, the channel width W1 and the judgment index Z i ; and S6, calculating the total dynamic storage of the channel source under different rainfall conditions in the debris flow basin through formula 8. The application acquires channel geometric and source characteristic parameters through unmanned aerial vehicle aerial photography, significantly improves the efficiency and accuracy of field data collection, and establishes a multi-factor comprehensive judgment index, so that the dynamic storage of the debris flow channel source is quickly and accurately measured and calculated.

Description

Technical Field

[0001] This invention relates to the field of debris flow prevention and control engineering technology, and in particular to a method and application for calculating the dynamic storage capacity of debris flow channels based on drone aerial photography. Background Technology

[0002] Towns and villages located in high mountain valleys are mostly built on debris flow or flash flood fans, and mountain roads and railways mostly pass through debris flow fans. Most rainfall in mountainous areas triggers flash floods, with only a small portion resulting in debris flows. The main difference between flash floods and debris flows lies in the amount of solid matter in the fluid: flash floods have a lower proportion of solid matter, generally not exceeding 20%, while debris flows can exceed 20%, sometimes reaching over 80%. If there is little or no solid matter within the watershed that can be transported by flash floods, debris flows are unlikely to form. Therefore, the amount of solid matter in a potential debris flow watershed, i.e., the solid matter source reserve, is an important parameter for assessing the possibility of debris flows. Solid matter source reserves are divided into two categories: static reserves and dynamic reserves. Static reserves refer to the total amount of solid matter that may participate in debris flow activity, including solid matter that may participate many years later; dynamic reserves refer to the amount of solid matter that can directly participate in the next rainfall-induced flash flood. Therefore, dynamic reserves are even more important, as they determine whether a debris flow will occur. Among these, gully sediment sources are the most common and primary debris flow sources. However, determining dynamic reserves is also a challenge: the amount of solid matter involved in debris flows varies under different rainfall conditions. Generally speaking, the greater the rainfall or the lower the rainfall frequency, the greater the flash flood flow, the more gully sediment sources can be activated and transported, and this can even expand gullies, erode the gully bank slopes, cause gully bank instability, and erode the gully banks to form more debris flow sources.

[0003] Currently, the estimation of static storage capacity of debris flows mainly involves roughly estimating the volume of unstable slopes within the watershed and calculating the total static storage capacity by combining the length, width, and depth of the source material in the channel. However, the estimation of dynamic storage capacity is even more coarse: some empirical methods consider all static storage sources in the channel as dynamic storage sources; others calculate dynamic storage capacity based on a certain proportion of the total static storage capacity, according to the static storage capacity of landslide-blocking sources, collapse-covered sources, and debris-colluvial sources (Qiao Jianping et al., 2012, Discussion on Statistical Methods for Dynamic Storage Capacity of Debris Flow Sources in Earthquake-Stricken Areas); or the corresponding dynamic storage capacity is calculated as a function of the static storage capacity of landslide bodies, channel sources, and slope sources, where the static storage capacity of channel sources and dynamic storage capacity have a power function relationship (Fang Qunsheng et al., 2016, Research on Calculation Methods of Flow Storage Capacity and Total Source Material in Debris Flow in Wenchuan Earthquake-Stricken Areas). These methods primarily rely on on-site investigations. However, when it is impossible to reach the debris flow formation area, especially after a strong earthquake that disrupts roads, it is difficult to obtain detailed information on the source material of the gully, making it impossible to estimate the dynamic reserves of the debris flow source. When remote sensing imagery is used to analyze the source material of a debris flow basin, the data accuracy is often insufficient; gully width, gully bank depth, and especially the source particle size cannot be measured, resulting in poor prediction accuracy.

[0004] The sediment source in gullies is the most important source of debris flows in valleys. Other sediment sources cannot enter the gully during flash floods and therefore cannot become debris flow sources. Thus, the calculation of gully sediment sources directly determines whether most debris flows will occur. Existing technical solutions do not consider the different sediment participation rates of gully sources under different flash flood flow conditions. Whether it is the empirical method of treating all static storage as dynamic storage or the calculation of dynamic storage based on static storage using a power function, neither can accurately calculate the dynamic storage of gully sources, resulting in poor prediction accuracy.

[0005] Chinese patent application document with publication number CN105868442A and publication date of August 17, 2016 discloses a method for calculating the dynamic reserves of debris flow sources under rainfall conditions. Based on extensive field surveys and debris flow source types, a geological model of source destruction and transformation is established. In-situ artificial rainfall experiments are conducted to reveal the correlation between slope destruction in the debris flow source area and the transformation into debris flow source scale under different rainfall conditions, thereby establishing a calculation model for debris flow sources under rainfall-induced conditions.

[0006] The patent application discloses a method for calculating the dynamic storage capacity of debris flow sources under rainfall conditions. This method can calculate the dynamic storage capacity of debris flows based on the cumulative rainfall, thus providing key parameters for debris flow exploration, design, and engineering prevention, and meeting the needs of disaster prevention projects. However, it relies on time-consuming and labor-intensive field investigations and artificial rainfall experiments to establish site-dependent empirical models. This results in low data acquisition efficiency and poor model universality, making it difficult to achieve rapid and accurate calculation of the dynamic storage capacity of debris flow channels. Summary of the Invention

[0007] To overcome the shortcomings of the prior art, this invention provides a method and application for calculating the dynamic reserves of debris flow channels based on UAV aerial photography. This invention obtains the geometric and material source characteristic parameters of the channel through UAV aerial photography, which significantly improves the efficiency and accuracy of field data collection. Based on this, a multi-factor comprehensive judgment index is established, realizing the rapid and accurate calculation of the dynamic reserves of debris flow channels.

[0008] This invention is achieved through the following technical solution: A method for calculating the dynamic reserves of debris flow channels based on drone aerial photography includes the following steps: S1. Obtain gully parameters through drone aerial photography, including gully bed width W0, gully width W1, gully bank height H, average median diameter of surface coarse particles D, gully bed slope α, difference in elevation between bank colluvium and gully bank H1, gully source thickness Ds, segmented gully length L1 and upstream gully length L, and determine the upstream catchment area A of the gully through topographic maps. S2. Divide the trenches into U-shaped trenches and V-shaped trenches; S3. Check the local annual average rainfall R0 and find the local 10-minute rainfall variation coefficient C from the local hydrological manual. v The local 24-hour average rainfall H was obtained from the local hydrological manual. 24 and coefficient of variation Cv 24 Calculate the local 1-hour average rainfall H1 and coefficient of variation Cv1, the modulus ratio K of 24-hour and 1-hour rainfall at different rainfall frequencies, and the rainfall parameter R* at different rainfall frequencies; S4. Calculate the judgment index of each source segment under different rainfall frequencies using Equation 1; Z=R*A 0.24 [tan(α)] 0.2 D0 0.38 / [L 0.4 W0 0.08 R0C v D 0.38 Formula 1; Where Z is the judgment index; R* is the rainfall parameter, mm; and A is the upstream watershed area of ​​the gully, m². 2 ; denoted as: ditch slope (degrees); D0 as coarse particle size (D0=0.002m); L as upstream ditch length (m); W0 as ditch width (m); R0 as local average annual rainfall (mm); Cv as 10-minute rainfall variation coefficient; D as average median diameter of surface coarse particles (m). S5. Calculate and determine the source dynamic reserves V based on the trench width W0, the trench width W1, and the judgment index Z. i ; S6. Calculate the total dynamic storage of sediment source in the gully under different rainfall conditions in the debris flow basin using Equation 8. V T =∑V i Formula 8; Among them, V T The total dynamic reserves of the channel material, m 3 ; ∑ represents the sum; V i For material source dynamic reserves, m 3 .

[0009] In S1, the median diameter refers to the particle size of a single surface coarse particle constituting the material source in the surface layer of the debris flow channel bed, where the median diameter is greater than 5 cm.

[0010] In S2, the ditch division refers to the following: when the ditch width W1 is less than 5m, it is divided into a V-shaped ditch; when the ditch width W1 is greater than 20m, it is divided into a U-shaped ditch; when the ditch width W1 is between 5m and 20m, it is determined by the ratio of the ditch width W1 to the upstream watershed area A, where W1 / A ≤ 10. -6 m / m 2 When W1 / A > 10, it is divided into V-shaped channels; -6 m / m 2 At that time, it was divided into U-shaped channels.

[0011] In S3, different rainfall frequencies refer to preset rainfall frequencies P, where P is 1%, 2%, 5% and 10%.

[0012] In step S5, the dynamic storage capacity V of the material source is calculated and determined. i This refers to: When Z < 0.22, the dynamic reserves are 0. When Z ≥ 0.22, the dynamic reserves V1 of the first stage channel are calculated by Equation 2. V1=L1×W0×D s Formula 2; Where L1 is the segmented channel length, m; W0 is the channel bed width, m; Ds is the channel source thickness, m; for U-shaped valleys, D s =2m; During the V-shaped valley, D s =1m; When Z≥0.28 and W1≥1.25W0, the dynamic storage capacity V2 of the second-stage channel is calculated using Equation 3; when Z≥0.28 and W1<1.25W0, the dynamic storage capacity V2 of the second-stage channel is calculated using Equation 4. V2=0.25W0(H+D s L1 formula 3; V2=(W1-W0)×(H+D s L1 formula 4; Where H is the height of the ditch bank, in meters; and W1 is the width of the ditch, in meters. When Z≥0.35 and W1≥1.68W0, the dynamic channel reserve V3 at the 3rd stage is calculated by Equation 5; when Z≥0.35 and 1.25W0<W1<1.68W0, the dynamic channel reserve V3 at the 3rd stage is calculated by Equation 6; V3=0.43W0(H+D s )L1 Equation 5; V3=(W1-1.25W0)×(H+D s )L1 Equation 6; Dynamic source reserve V i is calculated by Equation 7; V i =V1+V2+V3 Equation 7; wherein V1 is the dynamic channel source reserve at the first-stage initiation, m 3 ; V2 is the dynamic channel source reserve at the second-stage initiation, m 3 ; V3 is the dynamic channel source reserve at the third-stage initiation, m 3 .

[0013] The present invention is applicable to the prediction of dynamic source reserves in debris flow gullies with different rainfall frequencies.

[0014] The dynamic channel source reserve at the first-stage initiation as defined in the present invention refers to the total volume of source materials in the surface and shallow loose deposits of the gully that are first initiated and participate in debris flow activities under the action of rainfall infiltration and slope runoff in the early stage of rainfall or under low-intensity rainfall conditions, with the unit being m 3 .

[0015] The dynamic channel source reserve at the second-stage initiation as defined in the present invention refers to the total volume of source materials in the gully source that are further initiated and participate in debris flow activities under moderate-intensity rainfall conditions, with the unit being m 3 .

[0016] The dynamic channel source reserve at the third-stage initiation as defined in the present invention refers to the total volume of source materials in the gully source that can be fully initiated and fully participate in debris flow activities under high-intensity rainfall or extreme rainfall conditions, with the unit being m 3 .

[0017] The beneficial effects of the present invention are mainly manifested in the following aspects: 1. Compared with the prior art, the present invention obtains the gully geometry and source characteristic parameters through UAV aerial photography, which significantly improves the efficiency and accuracy of field data collection, and accordingly establishes a multi-factor comprehensive judgment index to realize rapid and accurate calculation of the dynamic source reserve of debris flow gullies.

[0018] 2. This invention, by introducing rainfall frequency parameters and gully morphology classification, constructs a dynamic storage calculation model covering different rainfall conditions and different types of gullies, enhancing the adaptability of the calculation method to different watershed conditions and meteorological risks, and providing a reliable basis for the quantitative assessment and early warning of debris flow disasters.

[0019] 3. This invention, by studying the mechanism and characteristics of rainfall and flash flood initiation of debris flow channels in gullies, proposes a quantitative method for calculating dynamic reserves by using half of the 24-hour rainfall as the initial rainfall and 1-hour rainfall as the triggering rainfall, which has higher prediction reliability.

[0020] 4. This invention, by studying the initiation mechanism of debris flow in gullies, comprehensively considers topographic parameters such as the catchment area of ​​the upstream gully, the width of the gully bed, the width of the gully, the length of the gully, the longitudinal slope of the gully, and the slope of the colluvial deposits on the gully bank, thus making the prediction more accurate.

[0021] 5. This invention comprehensively considers the impact of 24-hour rainfall and 1-hour rainfall on the initiation of material sources under different rainfall frequencies, avoiding the exaggeration of material source dynamic reserves prediction under extreme rainfall conditions, making dynamic reserves prediction more accurate under different rainfall conditions, and making debris flow hazard assessment more reliable.

[0022] 6. This invention obtains the dynamic storage conditions of debris flow channels through drone aerial photography and calculates the debris flow storage at different rainfall frequencies. It can quickly assess the scale of debris flows and has an irreplaceable advantage in mountainous areas where roads are impassable, especially when it is impossible to reach the area on foot.

[0023] 7. This invention, by studying the initiation process of sediment sources in gully debris flows, proposes a quantitative method for predicting the dynamic reserves of sediment sources in gully debris flows under different rainfall frequencies, which greatly improves the prediction accuracy.

[0024] 8. This invention, by studying the three stages of erosion initiation of debris flow channel sources in gullies, establishes a three-stage model that combines rainfall and three processes of channel sources, as well as a dynamic storage calculation model for channel sources considering slope erosion, which has better applicability for source prediction. Attached Figure Description

[0025] The present invention will now be further described in detail with reference to the accompanying drawings and specific embodiments, wherein: Figure 1 This is a flowchart of the present invention. Detailed Implementation

[0026] Example 1 See Figure 1 A method for calculating the dynamic reserves of debris flow channels based on drone aerial photography includes the following steps: S1. Obtain gully parameters through drone aerial photography, including gully bed width W0, gully width W1, gully bank height H, average median diameter of surface coarse particles D, gully bed slope α, difference in elevation between bank colluvium and gully bank H1, gully source thickness Ds, segmented gully length L1 and upstream gully length L, and determine the upstream catchment area A of the gully through topographic maps. S2. Divide the trenches into U-shaped trenches and V-shaped trenches; S3. Check the local annual average rainfall R0 and find the local 10-minute rainfall variation coefficient C from the local hydrological manual. v The local 24-hour average rainfall H was obtained from the local hydrological manual. 24 and coefficient of variation Cv 24 Calculate the local 1-hour average rainfall H1 and coefficient of variation Cv1, the modulus ratio K of 24-hour and 1-hour rainfall at different rainfall frequencies, and the rainfall parameter R* at different rainfall frequencies; S4. Calculate the judgment index of each source segment under different rainfall frequencies using Equation 1; Z=R*A 0.24 [tan(α)] 0.2 D0 0.38 / [L 0.4 W0 0.08 R0C v D 0.38 Formula 1; Where Z is the judgment index; R* is the rainfall parameter, mm; and A is the upstream watershed area of ​​the gully, m². 2 ; denoted as: ditch slope (degrees); D0 as coarse particle size (D0=0.002m); L as upstream ditch length (m); W0 as ditch width (m); R0 as local average annual rainfall (mm); Cv as 10-minute rainfall variation coefficient; D as average median diameter of surface coarse particles (m). S5. Calculate and determine the source dynamic reserves V based on the trench width W0, the trench width W1, and the judgment index Z. i ; S6. Calculate the total dynamic storage of sediment source in the gully under different rainfall conditions in the debris flow basin using Equation 8. V T =∑V i Formula 8; Among them, V T The total dynamic reserves of the channel material, m 3 ; ∑ represents the sum; V i For material source dynamic reserves, m 3 .

[0027] This embodiment is the most basic implementation method. Compared with the prior art, it significantly improves the efficiency and accuracy of field data collection by acquiring the geometric and material source characteristics parameters of the gully through drone aerial photography. Based on this, a multi-factor comprehensive judgment index is established, realizing the rapid and accurate calculation of the dynamic storage of debris flow gullies.

[0028] Example 2 See Figure 1 A method for calculating the dynamic reserves of debris flow channels based on drone aerial photography includes the following steps: S1. Obtain gully parameters through drone aerial photography, including gully bed width W0, gully width W1, gully bank height H, average median diameter of surface coarse particles D, gully bed slope α, difference in elevation between bank colluvium and gully bank H1, gully source thickness Ds, segmented gully length L1 and upstream gully length L, and determine the upstream catchment area A of the gully through topographic maps. S2. Divide the trenches into U-shaped trenches and V-shaped trenches; S3. Check the local annual average rainfall R0 and find the local 10-minute rainfall variation coefficient C from the local hydrological manual. v The local 24-hour average rainfall H was obtained from the local hydrological manual. 24 and coefficient of variation Cv 24 Calculate the local 1-hour average rainfall H1 and coefficient of variation Cv1, the modulus ratio K of 24-hour and 1-hour rainfall at different rainfall frequencies, and the rainfall parameter R* at different rainfall frequencies; S4. Calculate the judgment index of each source segment under different rainfall frequencies using Equation 1; Z=R*A 0.24 [tan(α)] 0.2 D0 0.38 / [L 0.4 W0 0.08 R0C v D 0.38 Formula 1; Where Z is the judgment index; R* is the rainfall parameter, mm; and A is the upstream watershed area of ​​the gully, m². 2 ; denoted as: ditch slope (degrees); D0 as coarse particle size (D0=0.002m); L as upstream ditch length (m); W0 as ditch width (m); R0 as local average annual rainfall (mm); Cv as 10-minute rainfall variation coefficient; D as average median diameter of surface coarse particles (m). S5. Calculate and determine the source dynamic reserves V based on the trench width W0, the trench width W1, and the judgment index Z. i ; S6. Calculate the total dynamic storage of sediment source in the gully under different rainfall conditions in the debris flow basin using Equation 8. V T =∑Vi Formula 8; Among them, V T The total dynamic reserves of the channel material, m 3 ; ∑ represents the sum; V i For material source dynamic reserves, m 3 .

[0029] In S1, the median diameter refers to the particle size of a single surface coarse particle constituting the material source in the surface layer of the debris flow channel bed, where the median diameter is greater than 5 cm.

[0030] In S2, the ditch division refers to the following: when the ditch width W1 is less than 5m, it is divided into a V-shaped ditch; when the ditch width W1 is greater than 20m, it is divided into a U-shaped ditch; when the ditch width W1 is between 5m and 20m, it is determined by the ratio of the ditch width W1 to the upstream watershed area A, where W1 / A ≤ 10. -6 m / m 2 When W1 / A > 10, it is divided into V-shaped channels; -6 m / m 2 At that time, it was divided into U-shaped channels.

[0031] This embodiment is a preferred implementation method. By introducing rainfall frequency parameters and gully morphology classification, a dynamic storage calculation model covering different rainfall conditions and different types of gullies is constructed, which enhances the adaptability of the calculation method to different watershed conditions and meteorological risks, and provides a reliable basis for the quantitative assessment and early warning of debris flow disasters.

[0032] By studying the mechanism and characteristics of rainfall and flash flood initiation of debris flow channels in gullies, and using half of the 24-hour rainfall as the initial rainfall and 1-hour rainfall as the triggering rainfall, a quantitative method for calculating dynamic reserves is proposed, which has higher prediction reliability.

[0033] Example 3 See Figure 1 A method for calculating the dynamic reserves of debris flow channels based on drone aerial photography includes the following steps: S1. Obtain gully parameters through drone aerial photography, including gully bed width W0, gully width W1, gully bank height H, average median diameter of surface coarse particles D, gully bed slope α, difference in elevation between bank colluvium and gully bank H1, gully source thickness Ds, segmented gully length L1 and upstream gully length L, and determine the upstream catchment area A of the gully through topographic maps. S2. Divide the trenches into U-shaped trenches and V-shaped trenches; S3. Check the local annual average rainfall R0 and find the local 10-minute rainfall variation coefficient C from the local hydrological manual. v The local 24-hour average rainfall H was obtained from the local hydrological manual. 24 and coefficient of variation Cv24 Calculate the local 1-hour average rainfall H1 and coefficient of variation Cv1, the modulus ratio K of 24-hour and 1-hour rainfall at different rainfall frequencies, and the rainfall parameter R* at different rainfall frequencies; S4. Calculate the judgment index of each source segment under different rainfall frequencies using Equation 1; Z=R*A 0.24 [tan(α)] 0.2 D0 0.38 / [L 0.4 W0 0.08 R0C v D 0.38 Formula 1; Where Z is the judgment index; R* is the rainfall parameter, mm; and A is the upstream watershed area of ​​the gully, m². 2 ; denoted as: ditch slope (degrees); D0 as coarse particle size (D0=0.002m); L as upstream ditch length (m); W0 as ditch width (m); R0 as local average annual rainfall (mm); Cv as 10-minute rainfall variation coefficient; D as average median diameter of surface coarse particles (m). S5. Calculate and determine the source dynamic reserves V based on the trench width W0, the trench width W1, and the judgment index Z. i ; S6. Calculate the total dynamic storage of sediment source in the gully under different rainfall conditions in the debris flow basin using Equation 8. V T =∑V i Formula 8; Among them, V T The total dynamic reserves of the channel material, m 3 ; ∑ represents the sum; V i For material source dynamic reserves, m 3 .

[0034] In S1, the median diameter refers to the particle size of a single surface coarse particle constituting the material source in the surface layer of the debris flow channel bed, where the median diameter is greater than 5 cm.

[0035] In S2, the ditch division refers to the following: when the ditch width W1 is less than 5m, it is divided into a V-shaped ditch; when the ditch width W1 is greater than 20m, it is divided into a U-shaped ditch; when the ditch width W1 is between 5m and 20m, it is determined by the ratio of the ditch width W1 to the upstream watershed area A, where W1 / A ≤ 10. -6 m / m 2 When W1 / A > 10, it is divided into V-shaped channels; -6 m / m 2 At that time, it was divided into U-shaped channels.

[0036] In S3, different rainfall frequencies refer to preset rainfall frequencies P, where P is 1%, 2%, 5% and 10%.

[0037] This embodiment is a preferred implementation method. By studying the initiation mechanism of debris flow in gullies, it comprehensively considers topographic parameters such as the catchment area of ​​the upstream gully, the width of the gully bed, the width of the gully, the length of the gully, the longitudinal slope of the gully, and the slope of the pleural deposits on the gully bank, thus making the prediction more accurate.

[0038] By comprehensively considering the impact of 24-hour and 1-hour rainfall on the initiation of sediment sources under different rainfall frequencies, the prediction of dynamic reserves of sediment sources is avoided under extreme rainfall conditions. This makes the prediction of dynamic reserves under different rainfall conditions more accurate and the assessment of debris flow hazards more reliable.

[0039] Example 4 See Figure 1 A method for calculating the dynamic reserves of debris flow channels based on drone aerial photography includes the following steps: S1. Obtain gully parameters through drone aerial photography, including gully bed width W0, gully width W1, gully bank height H, average median diameter of surface coarse particles D, gully bed slope α, difference in elevation between bank colluvium and gully bank H1, gully source thickness Ds, segmented gully length L1 and upstream gully length L, and determine the upstream catchment area A of the gully through topographic maps. S2. Divide the trenches into U-shaped trenches and V-shaped trenches; S3. Check the local annual average rainfall R0 and find the local 10-minute rainfall variation coefficient C from the local hydrological manual. v The local 24-hour average rainfall H was obtained from the local hydrological manual. 24 and coefficient of variation Cv 24 The local 1-hour average rainfall H1 and coefficient of variation Cv1, the modulus ratio K of 24-hour and 1-hour rainfall at different rainfall frequencies, and the rainfall parameter R* at different rainfall frequencies are calculated; the calculation method of rainfall parameter R* is shown in Table 1. The modulus coefficient K for 24 hours under different rainfall frequencies is: K 1-24 K 2-24 K 5-24 K 10-24 ; The modulus coefficient K for 1 hour under different rainfall frequencies is: K 1-1 K 2-1 K 5-1 K 10-1 .

[0040] Table 1

[0041] In Table 1: R1 is the 24-hour rainfall frequency parameter under a specific rainfall frequency; R2 is the 1-hour rainfall frequency parameter under a specific rainfall frequency; R1 and R2 are used together to construct the rainfall parameter R*; S4. Calculate the judgment index of each source segment under different rainfall frequencies using Equation 1; Z=R*A 0.24 [tan(α)] 0.2 D0 0.38 / [L 0.4 W0 0.08 R0C v D 0.38 Formula 1; Where Z is the judgment index; R* is the rainfall parameter, mm; and A is the upstream watershed area of ​​the gully, m². 2 ; denoted as: ditch slope (degrees); D0 as coarse particle size (D0=0.002m); L as upstream ditch length (m); W0 as ditch width (m); R0 as local average annual rainfall (mm); Cv as 10-minute rainfall variation coefficient; D as average median diameter of surface coarse particles (m). S5. Calculate and determine the source dynamic reserves V based on the trench width W0, the trench width W1, and the judgment index Z. i ; S6. Calculate the total dynamic storage of sediment source in the gully under different rainfall conditions in the debris flow basin using Equation 8. V T =∑V i Formula 8; Among them, V T The total dynamic reserves of the channel material, m 3 ; ∑ represents the sum; V i For material source dynamic reserves, m 3 .

[0042] In S1, the median diameter refers to the particle size of a single surface coarse particle constituting the material source in the surface layer of the debris flow channel bed, where the median diameter is greater than 5 cm.

[0043] In S2, the ditch division refers to the following: when the ditch width W1 is less than 5m, it is divided into a V-shaped ditch; when the ditch width W1 is greater than 20m, it is divided into a U-shaped ditch; when the ditch width W1 is between 5m and 20m, it is determined by the ratio of the ditch width W1 to the upstream watershed area A, where W1 / A ≤ 10. -6 m / m 2 When W1 / A > 10, it is divided into V-shaped channels; -6 m / m 2 At that time, it was divided into U-shaped channels.

[0044] In S3, different rainfall frequencies refer to the preset rainfall frequency P, where P is 1%, 2%, 5% and 10%.

[0045] In S5, calculating and determining the dynamic reserve V of the material source i refers to: When Z < 0.22, the dynamic reserve is 0; when Z ≥ 0.22, the dynamic reserve V1 of the channel at the first-level stage is calculated by Formula 2; V1=L1×W0×D s Formula 2; where L1 is the length of the segmented channel, m; W0 is the channel bed width, m; Ds is the thickness of the channel material source, m; for U-shaped valleys, D s =2m; for V-shaped valleys, D s =1m; When Z ≥ 0.28 and W1 ≥ 1.25W0, the dynamic reserve V2 of the channel at the second-level stage is calculated by Formula 3; when Z ≥ 0.28 and W1 < 1.25W0, the dynamic reserve V2 of the channel at the second-level stage is calculated by Formula 4; V2=0.25W0(H+D s )L1 Formula 3; V2=(W1-W0)×(H+D s )L1 Formula 4; where H is the channel bank height, m; W1 is the channel width, m; When Z ≥ 0.35 and W1 ≥ 1.68W0, the dynamic reserve V3 of the channel at the third-level stage is calculated by Formula 5; when Z ≥ 0.35 and 1.25W0<W1<1.68W0, the dynamic reserve V3 of the channel at the third-level stage is calculated by Formula 6; V3=0.43W0(H+D s )L1 Formula 5; V3=(W1-1.25W0)×(H+D s )L1 Formula 6; The dynamic reserve V of the material source i is calculated by Formula 7; V i =V1+V2+V3 Formula 7; where V1 is the dynamic reserve of the channel material source in the first-level starting stage, m 3 ; V2 is the dynamic reserve of the channel material source in the second-level starting stage, m 3 ; V3 is the dynamic reserve of the channel material source in the third-level starting stage, m 3 .

[0046] This embodiment is a preferred implementation method. By using drone aerial photography to obtain the dynamic storage conditions of debris flow channels and to calculate the debris flow storage at different rainfall frequencies, the scale of debris flow can be quickly assessed. This method has an irreplaceable advantage in mountainous areas where roads are impassable, especially when it is impossible to reach the area on foot.

[0047] By studying the initiation process of sediment sources in gully debris flows, a quantitative method for predicting the dynamic reserves of sediment sources in gully debris flows under different rainfall frequencies was proposed, which greatly improved the prediction accuracy.

[0048] By studying the three stages of erosion initiation of debris flow channel sources in gullies, a three-stage model combining rainfall and three processes of channel sources was established, along with a dynamic storage calculation model for channel sources considering bank erosion. This model has better applicability for source prediction.

[0049] The principle of calculating the material source dynamic reserves of this invention is as follows: The initial stage of debris flow formation is initiated by flash floods, where high-intensity rainfall creates infiltration excess runoff, resulting in runoff and flash floods. The greater the flash flood flow, the larger the particle size of the source material initiating the flow, and the greater the amount of source material mobilized. The narrower the flow channel, the greater the flash flood flow per unit width, and the easier it is to mobilize the source material. The steeper the flow channel slope, the greater the amount of source material mobilized and the larger the particle size. The larger the catchment area of ​​the watershed, the more runoff, the greater the flash flood flow, and the greater the source material mobilized. The shorter the watershed channels, the more concentrated the runoff process, the greater the flash flood flow, the greater the source material mobilized, and the greater the 24-hour rainfall, the more soil infiltration... The lower the permeability, the greater the excess flow, the larger the flash flood flow, and the easier it is for the sediment source to be activated; the greater the 1-hour rainfall, the greater the excess flow, the larger the flash flood flow, and the greater the dynamic sediment source; the lower the local average annual rainfall, the weaker the soil's adaptability to rainfall, the greater the excess flow, and the greater the activated sediment source; the smaller the local 10-minute rainfall variation coefficient, the more uniform the local short-duration rainfall, the weaker the soil's adaptability to rainfall, the greater the excess flow under heavy rainfall, and the greater the dynamic sediment source; the smaller the particle size of the coarsening layer on the ditch bed surface, the easier it is to be activated, and the greater the activated sediment source. Therefore, taking into account these factors and different frequencies of 24-hour and 1-hour rainfall, the present invention proposes a method for calculating the dynamic sediment source of ditches.

[0050] The principle of superimposing the three-stage channel sediment source and bank slope sediment source in this invention is as follows: Under certain hydrodynamic conditions and high-flow flash floods induced by rainfall, the gully sections most conducive to initiation of debris flow are the sections with favorable conditions such as smaller surface coarsening layer particle size, narrow gully bed, and large longitudinal slope.

[0051] The sediment source in each section of a gully may consist of three parts: first, sediment source within the gully bed; second, sediment source from both sides or one side of the gully banks; and third, colluvial deposits on one side of the bank. The sediment source within the gully bed is activated first. With subsequent rainfall and increased flash flood flow, it gradually erodes to both sides or one side, activating the sediment source from the gully banks. Finally, under conditions of very high rainfall and flash flood flow, it gradually erodes to one side, activating the colluvial deposits on the bank. Therefore, the judgment index Z is used to determine the activation of sediment source at each stage. In the first-stage activation stage, the dynamic storage capacity of the gully sediment source is only the sediment source within the gully bed, with moderate rainfall and flash flood flow. In the second-stage activation stage, the dynamic storage capacity of the gully sediment source is the sum of the sediment source within the gully bed and the sediment source from the gully banks, with relatively high rainfall and flash flood flow. In the third-stage activation stage, the dynamic storage capacity of the gully sediment source is the sum of the sediment source within the gully bed and even more sediment source from the gully banks, with very high rainfall and flash flood flow. The dynamic storage capacity V... i It is the sum of the material source in the gully bed, the material source along the entire gully bank, and the material source on the bank slope. At this time, all the material sources in this section of the gully have been activated, and the rainfall and flash flood flow are at their maximum.

[0052] Application examples of this invention are as follows: In 2024, a debris flow occurred in Tianbeizigou, Hanyuan County, Sichuan Province; in 2025, a debris flow occurred in Baojiagou, Hanyuan County; in 2024, a debris flow occurred in Ridigou, Kangding County; and in 2025, a debris flow occurred in Ziergou, Kangding County. Aerial photography was conducted on the above four gullies using drones, and the results of the dynamic storage capacity calculations of debris flow sources in the gullies for 100-year, 50-year, and 20-year return periods were obtained. The results are shown in Table 2, which is a table of examples of gully source calculations based on drone aerial photography.

[0053] Table 2

[0054] As shown in Table 2, the basic data of the debris flow basin obtained by drone aerial photography, combined with rainfall frequency and hydrological manual, can accurately calculate the material source and dynamic storage of channels at different frequencies in the debris flow basin, thus providing an important basis for assessing the occurrence and hazard level of debris flows.

Claims

1. A method for calculating the dynamic reserves of debris flow channels based on UAV aerial photography, characterized in that, comprising the following steps: S1. Acquire gully parameters through UAV aerial photography, including gully bed width W0, gully width W1, gully bank height H, average median diameter D of surface coarse particles, gully bed gradient α, height difference H1 between bank slope deposits and gully bank, gully material source thickness Ds, segmented gully length L1 and upstream gully length L, and determine the upstream watershed area A of the gully through topographic maps; S2. Divide the gullies, and classify the gullies into U-shaped gullies and V-shaped gullies; S3. Check the local annual average rainfall R0 and find the local 10-minute rainfall variation coefficient C from the local hydrological manual. v The local 24-hour average rainfall H was obtained from the local hydrological manual. 24 and coefficient of variation Cv 24 Calculate the local 1-hour average rainfall H1 and coefficient of variation Cv1, the modulus ratio K of 24-hour and 1-hour rainfall at different rainfall frequencies, and the rainfall parameter R* at different rainfall frequencies; S4. Calculate the judgment index of each material source segment under different rainfall frequencies by Equation 1; Z=R*A 0.24 [tan(α)] 0.2 D0 0.38 / [L 0.4 W0 0.08 R0C v D 0.38 Equation 1; Where Z is the judgment index; R* is the rainfall parameter, mm; and A is the upstream watershed area of ​​the gully, m². 2 ; denoted as: ditch slope (degrees); D0 as coarse particle size (D0=0.002m); L as upstream ditch length (m); W0 as ditch width (m); R0 as local average annual rainfall (mm); Cv as 10-minute rainfall variation coefficient; D as average median diameter of surface coarse particles (m). S5. Calculate and determine the source dynamic reserves V based on the trench width W0, the trench width W1, and the judgment index Z. i ; S6. Calculate the total dynamic reserve of gully material sources in the debris flow watershed under different rainfall conditions by Equation 8; V T =∑V i Formula 8; Among them, V T The total dynamic reserves of the channel material, m 3 ; ∑ represents the sum; V i For material source dynamic reserves, m 3 .

2. The method for calculating the dynamic reserves of debris flow channels based on UAV aerial photography according to claim 1, characterized in that: In S1, the median particle diameter refers to the particle diameter of particles with the major axis diameter of a single surface coarse particle constituting the material source being greater than 5 cm on the surface layer of the debris flow gully bed surface.

3. The method for calculating the dynamic reserves of debris flow channels based on UAV aerial photography according to claim 1, characterized in that: In S2, the ditch division refers to the following: when the ditch width W1 is less than 5m, it is divided into a V-shaped ditch; when the ditch width W1 is greater than 20m, it is divided into a U-shaped ditch; when the ditch width W1 is between 5m and 20m, it is determined by the ratio of the ditch width W1 to the upstream watershed area A, where W1 / A ≤ 10. -6 m / m 2 When W1 / A > 10, it is divided into V-shaped channels; -6 m / m 2 At that time, it was divided into U-shaped channels.

4. The method for calculating the dynamic storage capacity of debris flow channels based on UAV aerial photography according to claim 1, characterized in that: In S3, the different rainfall frequencies refer to preset rainfall frequencies P, where P is 1%, 2%, 5% and 10%.

5. The method for calculating the dynamic reserves of debris flow channels based on UAV aerial photography according to claim 1, characterized in that: In step S5, the dynamic storage capacity V of the material source is calculated and determined. i This refers to: When Z < 0.22, the dynamic reserve is 0; when Z ≥ 0.22, the dynamic reserve V1 of the gully in the first stage is calculated by Equation 2; V1=L1×W0×D s Formula 2; Where L1 is the segmented channel length, m; W0 is the channel bed width, m; Ds is the channel source thickness, m; for U-shaped valleys, D s =2m; During the V-shaped valley, D s =1m; When Z ≥ 0.28 and W1 ≥ 1.25W0, the dynamic reserve V2 of the gully in the second stage is calculated by Equation 3; when Z ≥ 0.28 and W1 < 1.25W0, the dynamic reserve V2 of the gully in the second stage is calculated by Equation 4; V2=0.25W0(H+D s L1 formula 3; V2=(W1-W0)×(H+D s L1 formula 4; wherein, H is the gully bank height, in m; W1 is the gully width, in m; When Z ≥ 0.35 and W1 ≥ 1.68W0, the dynamic reserve V3 of the gully in the third stage is calculated by Equation 5; when Z ≥ 0.35 and 1.25W0 < W1 < 1.68W0, the dynamic reserve V3 of the gully in the third stage is calculated by Equation 6; V3 = 0.43W0(H + D) s L1 formula 5; V3 = (W1 - 1.25W0) × (H + D) s L1 formula 6; Material source dynamic reserves V i Calculated using Equation 7; V i =V1+V2+V3 Equation 7; Wherein, V1 represents the channel material source dynamic reserves during the first-stage start-up phase, m 3 V2 Second-stage start-up phase channel material source dynamic storage, m 3 V3 Level 3 Start-up Stage Channel Material Source Dynamic Reserves, m 3 .

6. The application of drone aerial photography for calculating the dynamic reserves of debris flow channels, characterized by: The method for measuring and calculating the dynamic reserve of debris flow gully material sources based on UAV aerial photography as described in claim 5 is suitable for predicting the dynamic reserve of debris flow gully material sources under different rainfall frequencies.

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