Method for identifying and delineating slope debris flow risk prevention area of steep slope

Abstract

The invention discloses a method for identifying and delineating a slope debris flow risk prevention area of a steep slope, and the method comprises the steps: collecting topographic data, geological data, meteorological data and historical disaster data of a needed area, and carrying out the arrangement and field rechecking of the collected data; based on the collected data, slope debris flow dynamic parameters are determined and analyzed, and the parameters comprise the gradient, the flow depth, the density, the flow velocity and the volume; based on data and parameter analysis, a peak impact pressure model is constructed, impact damage resistance thresholds of different types of disaster-bearing bodies are determined, and a disaster-causing range is quantified; based on the impact pressure obtained through calculation and the determined shock resistance threshold value of the disaster-bearing body, a high-risk area, a medium-risk area and a low-risk area are divided in combination with the quantified disaster-causing range, the method constructs a model suitable for the debris flow impact pressure of the steep slope surface, determines the shock resistance threshold value of the disaster-bearing body and quantifies the single disaster-causing range, and the risk prevention area is divided; and a basis is provided for disaster assessment.

Description

Technical Field

[0001] This invention relates to a method for identifying and delineating debris flow risk prevention zones on steep slopes. Background Technology

[0002] Southeast Zhejiang Province, with its undulating terrain, sharply dissected landforms, and complex geological structures, is frequently affected by heavy rainfall during the plum rain and typhoon seasons, making it a typical high-risk area for geological disasters, specifically slope debris flows. Slope debris flows often occur on steep slopes with well-developed shallow, loose deposits, and typically in areas without obvious gullies, making disaster prediction and early warning difficult. Due to the complexity of its causes, scientifically delineating slope debris flow geological disaster risk prevention zones and establishing a reasonable risk identification and assessment system have become key priorities and challenges in geological disaster prevention and control. Summary of the Invention

[0003] In view of the shortcomings of the prior art, this application provides a method for identifying and delineating the risk prevention zone of debris flow on steep slopes. This method constructs a debris flow impact pressure model applicable to steep slopes, determines the impact resistance threshold of the disaster-bearing body, and quantifies the single disaster range, thereby realizing the division of risk prevention zones and providing a basis for disaster assessment.

[0004] To achieve the above objectives, this application provides a method for identifying and delineating slope debris flow risk prevention zones on steep slopes, comprising the following steps: S1: Collect the required regional topographic data, geological data, meteorological data, and historical disaster data. The historical disaster data includes the scale, damage, deposition characteristics, and physical and mechanical parameters of typical slope debris flow cases. Organize and verify the collected data in the field. S2: Based on the collected data, determine and analyze the dynamic mechanical parameters of debris flow on the slope, including slope, flow depth, density, flow velocity and volume; S3: Based on data and parameter analysis, construct a peak impact pressure model suitable for debris flows on steep slopes. Where P is the impact pressure per unit area; K The comprehensive correction factor is ρ; ρ is the debris flow density. C represents the velocity of the debris flow. V This is the volume correction factor; S4: Define the impact damage thresholds for different types of disaster-bearing structures, including wooden structures, brick-concrete structures, reinforced concrete structures, and simple structures, and classify the thresholds into three levels: minor damage, severe damage, and complete destruction. S5: Quantify the scope of the disaster; S6: Based on the calculated impact pressure, the determined impact resistance threshold of the disaster-bearing body, and the quantified disaster-causing range, high-risk areas, medium-risk areas, and low-risk areas are divided.

[0005] Furthermore, step S3, the steps for building the model, include: S31: Based on the classical impact pressure formula P=Kρv 2 The comprehensive correction coefficient K is 0.5-1.0, and the comprehensive coefficient K is regionally corrected based on the debris flow on the steep slope. S32: Based on the amplifying effect of debris flow scale on impact pressure, a volume correction factor is introduced. Optimize the peak stamping pressure model; S33: The calculation formula for determining the key parameters flow velocity and density is applicable to debris flows on steep slopes.

[0006] Furthermore, the specific correction method in step S31 includes: S311: Extract N typical slope debris flow cases with a slope range of 25°-45° from historical disaster data, extract the flow depth, slope, density, volume and building damage, calculate V using the flow velocity formula, back-calculate P using the building impact resistance threshold, calculate the K value, and take the average of the N K values ​​as the final value. S312: Based on the regional characteristics of debris flow on steep slopes, non-Newtonian fluids, topographic constraints, and particle impact, a modified formula is constructed: K=αβγ, where the values ​​of α, β, and γ are selected comprehensively based on case data and experimental evidence. Case data includes solid volume fraction, gully width, and proportion of large rocks. S313: Balance the K value derived from the case study with the K value calculated by the correction formula, and adjust the space for extreme scenarios to determine the range of K values.

[0007] Furthermore, based on a slope of 25°-45° and a high solids content of 0.5-0.75%, K is taken as 1.45-1.5.

[0008] Furthermore, the volume correction factor in step S32 The value is determined by the volume: when V < 1000 m³, The value is 1.0; 1000 ≤ V < 10000 m³. The value is 1.2, and V ≥ 10000 m³. The value is 1.5.

[0009] Furthermore, the flow velocity calculation in step S33 adopts the modified Dongchuan formula: In the formula, Here, Hc is the velocity coefficient, Hc is the average mud depth, and Ic is the hydraulic gradient of the debris flow. Density calculation uses a solid-liquid two-phase mixing formula: ,in: It represents the volume fraction of solids. Density of solid particles; This is the density of water.

[0010] Furthermore, the flow velocity coefficient is determined according to the flow depth: 10 when the flow depth is <2.5m, 9 when the flow depth is equal to 3m, 7 when the flow depth is equal to 4m, and 5 when the flow depth is equal to 5m.

[0011] Furthermore, step S5, quantifying the scope of the disaster, specifically includes: S51: Determine that the disaster type is a single disaster, and then collect the core parameters of the disaster area, including the width of the debris flow outlet on the slope, the flow pattern, the downstream terrain type, and the distribution of the disaster-bearing body; S52: The scope of the disaster is determined based on the width and length of the impact. The width of the impact is determined based on the slope flow pattern. When it is in a V-shape or a long strip, it is 1-2 times the width of the debris flow outlet on the slope. When it is in a funnel-shaped convergence, it is 3-5 times or more the width of the debris flow outlet on the slope. The affected length is determined by the downstream terrain; it is 15-30m when the area below is a platform or gentle slope, and covers all buildings below when the area below is the junction of a steep and gentle slope.

[0012] Furthermore, high-risk areas are those where P ≥ the threshold for complete destruction of the disaster-bearing body and are located within the disaster-causing range; medium-risk areas are those where P is between the thresholds for minor and severe damage to the disaster-bearing body and are located at the edge of the disaster-causing range; and low-risk areas are those where P < the threshold for minor damage to the disaster-bearing body or are located outside the disaster-causing range.

[0013] Furthermore, the topographic data includes 0.5m resolution SPOTPAN imagery, 1:10,000 DLG topographic map, and Google Earth remote sensing imagery; the geological data includes regional stratigraphic lithology, residual slope thickness, fault and joint distribution data; and the meteorological data includes typhoon season and plum rain season rainfall data.

[0014] Beneficial effects: 1. This application provides a complete method for identifying and delineating risk prevention zones for debris flows on steep slopes, which solves the problem that existing quantitative research on the destructive effects of debris flows on slopes is of low quality and makes it difficult to accurately assess the potential threat to the disaster-bearing body and delineate the risk zone.

[0015] 2. Due to the lack of existing quantitative data on the impact force of slope debris flows, and the fact that existing classical impact pressure formulas for slope debris flows, with a comprehensive correction coefficient k ranging from 0.5 to 1.0, are suitable for low solid volume fractions. This study investigated debris flows in wide gullies (>10m) and applied it to mountainous regions of North America and Europe. Later, flow depth and hydraulic gradient were introduced to consider the concentration effect of gully constraints on kinetic energy. K values ​​were set between 0.7 and 1.2, suitable for narrow gully scenarios. The range of K values ​​did not consider the high solids content on steep slopes as described in this application. Therefore, this application provides a dual-path method for determining the K value for steep slopes with high solid content. The K value is obtained by combining case back-reasoning and theoretical correction, which improves the scientificity and regional adaptability of impact pressure estimation and provides a reliable basis for disaster assessment and risk zoning of slope debris flows.

[0016] 3. Based on the idea of ​​energy conversion, this application selects the kinetic energy of debris flow per unit volume as the core control quantity, and combines debris flow density, volume characteristics and flow complexity to establish a peak impact pressure model with empirical correction coefficient K as the core, so as to realize the quantitative expression of the impact intensity of slope debris flow and support risk assessment.

[0017] 4. Based on the impact pressure model and combined with the building impact pressure threshold, this application assesses the damage risk of slope debris flow to different types of buildings. By comparing and calculating the impact pressure with the building impact pressure threshold and quantifying the disaster range, the risk prevention zone is scientifically and comprehensively divided, which helps to provide assistance for subsequent protective structure design and risk avoidance planning. Attached Figure Description

[0018] Figure 1 This is a flowchart illustrating the delineation method. Detailed Implementation

[0019] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0020] For reference Figure 1 As shown, this application addresses slope debris flows on steep slopes with an angle of 25°-45° and a high solids content of 0.5-0.75%, such as in southeastern Zhejiang Province, which is considered a high-risk area for geological hazards. This type of debris flow, characterized by small watersheds, short distances, and high energy release, is spatially scattered, has a low rainfall threshold, and exhibits short travel distances but limited impact effects. Therefore, scientifically delineating slope debris flow risk prevention zones provides scientific support for subsequent prevention and control. This application specifically illustrates the proposed solution using Wenzhou in southeastern Zhejiang Province as an example.

[0021] S1: Collect the required regional topographic data, geological data, meteorological data, and historical disaster data. The historical disaster data includes the scale, damage, deposition characteristics, and physical and mechanical parameters of typical slope debris flow cases. Organize and verify the collected data in the field. Detailed data collection included topographic, geological, meteorological, and historical disaster data for Wenzhou. This involved comprehensively collecting remote sensing images, regional geological data, and steep slope geological hazard survey data from different periods within the work area. Multi-source information was compiled, and for historically typical steep slope geological hazard areas, relevant literature and field survey data were systematically collected. Ground surveys were conducted, focusing on recording the physical and mechanical parameters of the hazards, topographic features, hazard morphology, and hazard severity. Topographic data primarily consisted of Google Earth remote sensing imagery, 0.5m resolution SPOTPAN data, and relevant DLG format 1:10,000 topographic maps. SPOTPAN data, with a resolution of 10m, provides relatively rich topographic details, which is particularly important for analyzing slope debris flows and basically meets the accuracy requirements for quantitative and qualitative analysis in this study. The location information of the debris flow hazard-causing and hazard-bearing bodies was mainly extracted from Google Earth remote sensing imagery and relevant topographic maps. Google Earth remote sensing imagery supports three-dimensional, all-around observation. Topographic data from the SPOT4 satellite, including historical imagery, was then loaded onto the Wenzhou area, providing crucial support for determining the distribution range of slope debris flows, including distance and elevation. Meteorological and geological data were based on previous survey data and then verified through fieldwork.

[0022] S2: Based on the collected data, determine and analyze the dynamic parameters of debris flow on the slope, including slope, flow depth, density, flow velocity and volume; In detail: Since slope debris flows do not have stable channels and lack typical hydraulic cross-sections, their dynamic parameters exhibit strong heterogeneity and unsteadiness in space. Traditional gully debris flow models are difficult to accurately fit. Therefore, it is necessary to analyze the dynamic parameters and parameter ranges of slope debris flows, such as flow velocity, flow depth, and density, based on the collected data, to provide a foundation for the subsequent establishment of impact models.

[0023] S3: Based on data and parameter analysis, construct a peak impact pressure model suitable for debris flows on steep slopes. Where P is the impact pressure per unit area; K The comprehensive correction factor is ρ; ρ is the debris flow density. C represents the velocity of the debris flow. V This is the volume correction factor; Specifically: S31: Based on the classical impact pressure formula P=Kρv 2 The comprehensive correction coefficient K is 0.5-1.0, and the comprehensive coefficient K is regionally corrected based on the debris flow on the steep slope. S32: Based on the amplifying effect of debris flow scale on impact pressure, a volume correction factor is introduced. Optimize the peak stamping pressure model; S33: The calculation formula for determining the key parameters flow velocity and density is applicable to debris flows on steep slopes.

[0024] In detail: The impact damage of slope debris flows is essentially a transient, high-speed fluid impact process. Its destructive power on buildings and infrastructure stems from the release of kinetic energy and pressure concentration per unit area. Unlike gully debris flows, slope debris flows have high velocities, shallow depths, and dispersed flow paths, often exhibiting a supercritical flow state. Therefore, the concept of kinetic energy density per unit area is suitable for expressing its impact effect, expressed by the classical kinetic energy density formula in fluid mechanics:

[0025] Where: P is the impact pressure (Pa); ρ is the debris flow density (kg / m³). Let be the velocity of the debris flow (m / s); this formula reveals the kinetic energy per unit volume of fluid (and ). (Related) By impacting the surface of an obstacle, it creates impact pressure per unit area.

[0026] Based on the classic model formula for impact pressure from debris flow on slopes: P=Kρv 2 The comprehensive correction factor K ranges from 0.5 to 1.0 and is suitable for low solid volume fractions. This model is widely used in mountainous regions of North America and Europe for debris flows involving wide gullies >10m. Further modifications to the model, incorporating flow depth and hydraulic gradient, lead to the expression P=K·ρ·v. 2 Considering the concentration effect of gully constraints on kinetic energy, K ranges from 0.7 to 1.2, suitable for scenarios with narrow gullies of 5-15m. These models have internationally accepted K values ​​that are too low and do not fully account for the high solids content in southeastern Zhejiang. The influence of debris flow on steep slopes is considered. Therefore, the comprehensive coefficient K is regionally corrected based on the debris flow on steep slopes. Then, considering that the amplifying effect of debris flow scale on impact force is not negligible, larger debris flows are usually accompanied by higher flow depth, faster velocity, longer impact duration (seconds), and wider impact contact area. Therefore, a volume correction factor is introduced. This indirectly reflects the contribution of scale enhancement to impact pressure. Instead, it is corrected through graded calibration (based on volumetric level). The shortcomings of volume are thus reflected in the nonlinear amplification effect caused by volume.

[0027] Finally, the peak impact pressure model was constructed. Where P is the impact pressure per unit area; K The comprehensive correction factor is ρ; ρ is the debris flow density. C represents the velocity of the debris flow. V This is the volume correction factor.

[0028] The specific methods for correcting the K value in the model include: S311: Extract N typical slope debris flow cases with a slope range of 25°-45° from historical disaster data, extract the flow depth, slope, density, volume and building damage, calculate V using the flow velocity formula, back-calculate P using the building impact resistance threshold, calculate the K value, and take the average of the N K values ​​as the final value. S312: Constructing a modified formula based on the regional characteristics of debris flow on steep slopes, non-Newtonian fluids, topographic constraints, and particle impaction: K=αβγ, where the values ​​of α, β and γ are selected based on a combination of case data and experimental data. Case data includes solid volume fraction, gully width and proportion of large rocks. S313: Balance the K value derived from the case study with the K value calculated by the correction formula, and adjust the space for extreme scenarios to determine the range of K values.

[0029] In detail, this application takes a steep slope in Wenzhou as an example, with a slope of 25°-45° and a high solids content of 0.5-0.75%. The calculated K value is 1.45-1.5 based on the above steps. First, six typical debris flow cases within the 25°-45° range are extracted from historical disaster data. The flow depth, slope, density, volume, and building damage are extracted for each case, as shown in Table 1 below. Table 1

[0030] The impact pressure P is estimated based on the damage situation, the impact of large rocks, and the degree of burial. Then, the impact pressure model is used to inversely deduce the K value, as shown in Table 2. Table 2

[0031] The average value of K above is 1.39, with a standard deviation of 0.12. The inverse calculation results reflect the high solids content (50%-75%) of slope debris flows, narrow flow zones, and impacts from large rocks (0.2-1m). K=1.39 is higher than the internationally accepted value and is consistent with the regional characteristics.

[0032] Then, based on the distinguishing characteristics of non-Newtonian fluids, terrain constraints, and particle impact, a modified formula is constructed: K=αβγ Here, α, β, and γ quantify the contributions of non-Newtonian fluid properties, topographic constraints, and particle impact to impact pressure, respectively. The following derivation uses correction factors selected based on case data (solid volume fraction, gully width, and proportion of large rocks) and experimental evidence (Coussot, 1996; Takahashi, 2007).

[0033] Non-Newtonian fluid properties: Solid volume fraction in slope debris flow It ranges from 50% to 75%, with an average of This is 30%-50% higher than the international typical value. High solids content leads to shear thinning, enhancing instantaneous impact force. Historical experiments have shown that shear-thinned fluids... This will result in an increase in impact force of 1.2-1.3 times, on average. The corresponding increase is approximately 1.22, calculated using linear interpolation. Therefore, the correction factor is α = 1.22.

[0034] Topographical constraints: Slope debris flows have gully widths of 2-10m, averaging 5m, and depths of 0.3-3m. Narrow gullies concentrate kinetic energy. At a debris flow depth of 3.0m and a gully length >100m, the impact force is 90kPa, and the flow velocity increases. At a debris flow depth of 0.8m and a gully length <50m, the impact force is 20kPa, and the short gully weakens the kinetic energy. Historical experiments show that when the gully width is <10m, the kinetic energy increase is 1.05-1.10. An average width of 5m corresponds to an increase of approximately 1.06, a linear interpolation. Therefore, the correction factor is β=1.06.

[0035] Particle impaction: Large rocks with a diameter of 0.2-1m account for 20%-40% of debris flows, with an average of 30%. With 40% crushed stone, the impact force is 80 kPa; with 20% gravel, the impact force is 20 kPa. When large particles account for 20%-40%, the pressure increase is 1.1-1.2, and with an average proportion of 30%, the increase is 1.15. Therefore, the correction factor is γ = 1.15.

[0036] Calculate the value of K: K = α·β·γ = 1.22 × 1.06 × 1.15 = 1.48747 ≈ 1.49 The inverse calculation of K=1.39 is based on damage data from six typical cases; the theoretical correction K≈1.49 is based on physical evidence provided by non-Newtonian fluid (shear thinning, α=1.22), topographic constraints (narrow gullies, β=1.06), and particle impact (large rocks, γ=1.15), and K=1.45 is determined comprehensively. Applicable conditions: slope: 25°-45°; flow depth: 0.3-3m; solid volume fraction: 0.5-0.75, 0.5-0.6 for small-scale cases, 0.7-0.75 for large-scale cases; hourly rainfall intensity: 50-150mm, high incidence during typhoon season; disaster range: width 1-5 times the outlet, length 15-30m.

[0037] For small-scale debris flows <1000m³, the impact pressure can be adjusted by using a lower flow depth of 0.6-1.0m, a density of 1950-2000kg / m³, and CV=1.0~1.2; for extreme rainfall >150mm / h or a high proportion of large rocks, K can be increased to 1.5.

[0038] Regarding the volume correction factor in step S32 The value is determined by the volume, specifically including: when V < 1000 m³, The value is 1.0; 1000 ≤ V < 10000 m³. The value is 1.2, and V ≥ 10000 m³. The value is 1.5.

[0039] Then, regarding the velocity calculation in step S33, the modified Higashikawa formula is used: In the formula, Here, Hc is the velocity coefficient, Hc is the average mud depth, and Ic is the hydraulic gradient of the debris flow. Density calculation uses a solid-liquid two-phase mixing formula: ,in: It represents the volume fraction of solids. Density of solid particles; This is the density of water.

[0040] Regarding the flow velocity formula and the calculation of impact pressure on steep slopes, this application treats slope debris flows as medium-resistance viscous debris flows, adopts the Dongchuan debris flow improved formula, and further modifies it according to regional characteristics. Dongchuan Improved Formula Originally applicable to low-resistivity viscous debris flows, with a flow depth index of The slope index is Flow depth contributes significantly to flow velocity, while slope has a relatively small impact. Considering the medium-resistivity viscosity of surface debris flows and the significant contribution of slope to flow velocity under steep slope conditions, this application modifies the Dongchuan formula as follows:

[0041] After index adjustment, the effect of slope changes from relatively weak to comparable to that of flow depth, which better reflects the significant effect of slope on flow velocity in steep slope environments. Where, k v ---The velocity coefficient, obtained by interpolation from Table 3 below; H c ---Average mud depth, in meters (m); I C ---The hydraulic gradient of debris flow (expressed as a decimal) can generally be replaced by the longitudinal slope of the gully bed or the slope of the main flow surface.

[0042] Table 3 <![CDATA[H c / m]]> ＜2.5 3 4 5 <![CDATA[k v ]]> 10 9 7 5 Formula verification: With a flow depth H = 2m and a slope of 35°, the longitudinal gradient I is... C =tan35°≈0.7, If we take 10, then

[0043] The results are consistent with the characteristics of slope debris flows, therefore they are adopted.

[0044] S4: Define the impact damage thresholds for different types of disaster-bearing structures, including wooden structures, brick-concrete structures, reinforced concrete structures, and simple structures, and classify the thresholds into three levels: minor damage, severe damage, and complete destruction. In detail: Slope debris flows are characterized by high flow velocity, shallow depth, steep slopes, and strong heterogeneity (particle mixing, dispersed flow path), and their impact pressure P poses a significant threat to buildings. To support protective design and risk zoning, this application assesses the damage risk of slope debris flows to different types of buildings based on an impact pressure model and combined with building impact pressure thresholds.

[0045] The impact pressure failure thresholds for different building types, based on domestic and international research, are summarized below and categorized into minor damage (surface cracks, slight deformation), severe damage (structural cracks, localized failure), and complete failure (collapse or loss of function), as shown in Table 4. Table 4

[0046] The thresholds in the table apply to dynamic impact pressure and reflect common rural structures such as timber, brick-concrete, reinforced concrete, and simple structures. Timber and simple structures have low impact resistance, brick-concrete structures have medium impact resistance, and reinforced concrete structures have relatively high impact resistance.

[0047] S5: Quantifying the scope of the disaster, specifically including: S51: Determine that the disaster type is a single disaster, and then collect the core parameters of the disaster area, including the width of the debris flow outlet on the slope, the flow pattern, the downstream terrain type, and the distribution of the disaster-bearing body; S52: The scope of the disaster is determined based on the width and length of the impact. The width of the impact is determined based on the slope flow pattern. When it is in a V-shape or a long strip, it is 1-2 times the width of the debris flow outlet on the slope. When it is in a funnel-shaped convergence, it is 3-5 times or more the width of the debris flow outlet on the slope. The affected length is determined by the downstream terrain; it is 15-30m when the area below is a platform or gentle slope, and covers all buildings below when the area below is the junction of a steep and gentle slope.

[0048] In detail: A single debris flow refers to a situation where a debris flow on a single slope directly destroys or deposits debris on buildings or structures below. The width of the impact of a single debris flow is mainly affected by the width of the debris flow path. When a debris flow flows downhill in a V-shape or elongated pattern, its impact width is approximately 1 to 2 times the width of the debris flow outlet. When a debris flow converges in a funnel shape before flowing downhill, its impact width is approximately 3 to 5 times or more the width of the debris flow outlet. The length of the impact of a single debris flow is mainly affected by the terrain below. When the terrain below is a platform or gentle slope, it is generally the length of 1 to 2 rows of houses below, i.e., 15 to 30 meters. When the terrain below is steep or gentle, it affects all houses below.

[0049] S6: Based on the calculated impact pressure, the determined impact resistance threshold of the disaster-bearing body, and the quantified disaster-causing range, high-risk areas, medium-risk areas, and low-risk areas are divided.

[0050] Specifically: high-risk areas are those where P ≥ the threshold for complete destruction of the disaster-bearing body and are located within the disaster-causing area; medium-risk areas are those where P is between the thresholds for minor and severe damage to the disaster-bearing body and are located at the edge of the disaster-causing area; and low-risk areas are those where P < the threshold for minor damage to the disaster-bearing body or are outside the disaster-causing area. For example, if a debris flow on a slope has P = 50 kPa, and the wooden structure at the toe of the slope will be completely destroyed under a compressive strength of 5~10 kPa, and the wooden structure at the toe of the slope is located within the disaster-causing area, it is classified as a high-risk area. Risk zoning, combined with GIS spatial analysis, integrates flow depth, flow velocity, volume, and topographic data to identify high-risk areas in southeastern Zhejiang, providing a foundation for subsequent guidance on protective structure design and hazard mitigation planning.

Claims

1. A method for identifying and delineating debris flow risk prevention zones on steep slopes, characterized in that: Includes the following steps: S1: Collect the required regional topographic data, geological data, meteorological data, and historical disaster data. The historical disaster data includes the scale, damage, deposition characteristics, and physical and mechanical parameters of typical slope debris flow cases. Organize and verify the collected data in the field. S2: Based on the collected data, determine and analyze the dynamic parameters of debris flow on the slope, including slope, flow depth, density, flow velocity and volume; S3: Based on data and parameter analysis, construct a peak impact pressure model suitable for debris flows on steep slopes. Where P is the impact pressure per unit area; K The comprehensive correction factor is ρ; ρ is the debris flow density. C represents the velocity of the debris flow. V This is a volume correction factor; S4: Define the impact damage thresholds for different types of disaster-bearing structures, including wooden structures, brick-concrete structures, reinforced concrete structures, and simple structures, and classify the thresholds into three levels: minor damage, severe damage, and complete destruction. S5: Quantify the scope of the disaster; S6: Based on the calculated impact pressure, the determined impact resistance threshold of the disaster-bearing body, and the quantified disaster-causing range, high-risk areas, medium-risk areas, and low-risk areas are divided.

2. The method for identifying and delineating debris flow risk prevention zones on steep slopes according to claim 1, characterized in that: Step S3 involves the following steps in building the model: S31: Based on the classical impact pressure formula P=Kρv 2 The comprehensive correction coefficient K is 0.5-1.0, and the comprehensive coefficient K is regionally corrected based on the debris flow on the steep slope. S32: Based on the amplifying effect of debris flow scale on impact pressure, a volume correction factor is introduced. Optimize the peak stamping pressure model; S33: The calculation formula for determining the key parameters flow velocity and density is applicable to debris flows on steep slopes.

3. The method for identifying and delineating debris flow risk prevention zones on steep slopes according to claim 2, characterized in that: The specific correction method in step S31 includes: S311: Extract N typical slope debris flow cases with a slope range of 25°-45° from historical disaster data, extract the flow depth, slope, density, volume and building damage, calculate V using the flow velocity formula, back-calculate P using the building impact resistance threshold, calculate the K value, and take the average of the N K values ​​as the final value. S312: Constructing a modified formula based on the regional characteristics of debris flow on steep slopes, non-Newtonian fluids, topographic constraints, and particle impaction: K=αβγ, where the values ​​of α, β and γ are selected based on a combination of case data and experimental data. Case data includes solid volume fraction, gully width and proportion of large rocks. S313: Balance the K value derived from the case study with the K value calculated by the correction formula, and adjust the space for extreme scenarios to determine the range of K values.

4. The method for identifying and delineating debris flow risk prevention zones on steep slopes according to claim 3, characterized in that: Given a slope of 25°-45° and a high solids content of 0.5-0.75%, K is set to 1.45-1.

5.

5. The method for identifying and delineating the slope debris flow risk prevention zone on a steep slope according to claim 3 or 4, characterized in that: Volume correction factor in step S32 The value is determined by the volume: When V < 1000 m³, The value is 1.0; 1000 ≤ V < 10000 m³. The value is 1.2, V≥10000m³, The value is 1.

5.

6. The method for identifying and delineating debris flow risk prevention zones on steep slopes according to claim 5, characterized in that: The flow velocity calculation in step S33 uses the modified Dongchuan formula: In the formula, K v The velocity coefficient is... Hc is the average mud depth, and Ic is the hydraulic gradient of the debris flow. Density calculation uses a solid-liquid two-phase mixing formula: ,in: It represents the volume fraction of solids. Density of solid particles; This is the density of water.

7. The method for identifying and delineating debris flow risk prevention zones on steep slopes according to claim 6, characterized in that: The velocity coefficient is determined according to the flow depth: 10 for flow depth < 2.5m, 9 for flow depth 3m, 7 for flow depth 4m, and 5 for flow depth 5m.

8. The method for identifying and delineating debris flow risk prevention zones on steep slopes according to claim 7, characterized in that: Step S5, quantifying the scope of the disaster, specifically includes: S51: Determine that the disaster type is a single disaster, and then collect the core parameters of the disaster area, including the width of the debris flow outlet on the slope, the flow pattern, the downstream terrain type, and the distribution of the disaster-bearing body; S52: The scope of the disaster is determined based on the width and length of the impact. The width of the impact is determined based on the slope flow pattern. When it is in a V-shape or a long strip, it is 1-2 times the width of the debris flow outlet on the slope. When it is in a funnel-shaped convergence, it is 3-5 times or more the width of the debris flow outlet on the slope. The affected length is determined by the downstream terrain; it is 15-30m when the area below is a platform or gentle slope, and covers all buildings below when the area below is the junction of a steep and gentle slope.

9. The method for identifying and delineating debris flow risk prevention zones on steep slopes according to claim 8, characterized in that: High-risk areas are those where P is greater than or equal to the threshold for complete destruction of the disaster-bearing body and is located within the disaster-causing range; medium-risk areas are those where P is between the thresholds for minor and severe damage to the disaster-bearing body and is located at the edge of the disaster-causing range; and low-risk areas are those where P is less than the threshold for minor damage to the disaster-bearing body or is located outside the disaster-causing range.

10. The method for identifying and delineating debris flow risk prevention zones on steep slopes according to claim 9, characterized in that: The topographic data includes 0.5m resolution SPOTPAN imagery, 1:10,000 DLG topographic maps, and Google Earth remote sensing imagery. The geological data includes regional stratigraphic lithology, residual slope thickness, fault and joint distribution data. The meteorological data includes rainfall data during the typhoon season and plum rain season.

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