Debris flow power early warning method

Abstract

The invention belongs to the technical field of geological disaster prevention and reduction, and relates to a debris flow dynamic early warning method, which specifically comprises the following steps of: acquiring the quantity of startable material sources in a debris flow basin and the possible runoff volume under a forecast rainfall condition, and calculating the flow of the debris flow according to the quantity of the startable material sources and the possible runoff volume; respectively calculating the density rho d of the water-stone mixture under the forecast day rainfall condition and the density rho h of the water-stone mixture under the extreme hour rainfall condition of the target channel; obtaining the final critical density rho of the water-stone mixture when the debris flow in the main sliding direction is started, and determining a first early warning grade T1 under the condition of forecasting daily rainfall in combination with a daily scale water-stone mixture density early warning grade judgment rule; determining a second early warning grade T2 under an extreme hourly rainfall condition in combination with an hourly-scale water-stone mixture density early warning grade judgment rule; and when the first early warning level T1 and the second early warning level T2 are inconsistent, selecting a higher early warning level as a release early warning level T of the target debris flow basin, thereby effectively preventing mass-occurring debris flow disasters.

Description

Technical Field

[0001] The invention belongs to the technical field of geological disaster prevention and mitigation, relates to meteorological early warning of geological disasters, and specifically to a debris flow dynamic early warning method. Background Art

[0002] Carrying out meteorological warning of geological disasters based on meteorological data such as rainfall forecast can provide early warning and forecast of the possibility of geological disasters before heavy rainfall arrives, which can buy precious time for the threatened people to evacuate. It is one of the important measures for geological disaster prevention and risk avoidance. Among various geological disasters, debris flow often causes mass casualties due to its sudden occurrence and large basin range, so it has become the focus and difficulty of meteorological warning of geological disasters. In addition, the occurrence of debris flow is closely related to the process of rainfall infiltration and runoff generation and convergence. The different hydrological conditions in different basins make the disaster situation of various valleys in the region different. If the regional meteorological warning of debris flow is carried out based on statistical laws only, it is difficult to avoid false reports. Therefore, it is urgent to carry out research on meteorological warning methods of debris flow based on disaster mechanism. Summary of the invention

[0003] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a debris flow dynamic warning method, which establishes a dynamic warning model for each debris flow ditch based on the debris flow disaster mechanism, and carries out targeted runoff generation and initiation risk analysis, which will be beneficial to improving the meteorological warning capability of debris flow disasters.

[0004] The inventors of this application need to emphasize that the mechanism of debris flow initiation is complex. Based on the debris flow initiation and disaster-causing mechanism, simulating the rainfall infiltration, runoff generation and convergence process of each ditch in the basin and setting targeted early warning indicators are the key to carrying out accurate early warning and forecasting.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] This debris flow dynamic early warning method includes the following steps:

[0007] Step 1: Obtain the amount of activatable material sources in the debris flow basin and the possible runoff under the forecast rainfall conditions. According to the activatable material sources and the possible runoff, calculate the water-rock mixture density ρ under the forecast daily rainfall conditions of the target channel. d and water-rock mixture density ρ under extreme hourly rainfall conditions h ;

[0008] Step 2, obtain the final critical density ρ of the water-rock mixture when the debris flow in the main sliding direction starts, and determine the first warning level T1 under the forecast daily rainfall conditions in combination with the daily scale water-rock mixture density warning level judgment rule, and determine the second warning level T2 under the extreme hourly rainfall conditions in combination with the hourly scale water-rock mixture density warning level judgment rule; when the first warning level T1 and the second warning level T2 are inconsistent, select the higher warning level as the warning level T for the target debris flow basin.

[0009] Specifically, the debris flow dynamic early warning method specifically includes:

[0010] ① Obtain the amount of material resources that can be activated in the debris flow basin:

[0011] According to the development law of debris flow in the study area, the history of debris flow development in the target debris flow channel, and the accumulation of channel material sources in the field investigation, the possible types of debris flow are determined, and the amount of activatable material sources is calculated according to the debris flow types. Specifically, for the basin where geodynamic debris flow may occur, the sliding body of the slope instability induced by heavy rainfall is used as the starting material source; for the basin where hydraulic debris flow may occur, the channel material source accumulated in the channel that can be activated under rainfall conditions is used as the starting material source; for the basin where both hydraulic and geodynamic debris flow may occur, the common of the two (i.e. the sliding body of the slope instability induced by heavy rainfall and the part of the channel material source accumulated in the channel that can be activated under heavy rainfall conditions) is used as the starting material source.

[0012] When evaluating the volume of the landslide of a slope instability, the slope is simplified as an infinite slope. The slope unit stability calculation is carried out and the slope units that may be unstable are judged. The volume of the landslide of the slope instability is estimated by multiplying the slope unit area with the average thickness of the landslide. The calculation formula of the landslide volume of the slope instability is as follows (2):

[0013] v s1 =∑S i h Formula (2)

[0014] In formula (2), v s1 is the volume of unstable soil mass on the basin slope under rainfall conditions, S i is the area of ​​the ith slope unit, and h is the average thickness of the sliding body.

[0015] Among them, the amount of material sources that can be activated in the channel under rainfall conditions is determined according to the current maximum one-time discharge volume, that is, the maximum one-time discharge volume of the deposits in the channel is used to estimate the amount of channel-activating material sources, which is determined based on experience.

[0016] ②Calculate the possible runoff under the forecast rainfall conditions

[0017] Determine the scope of the debris flow basin, evaluate the saturation degree of rock and soil in the target channel before heavy rainfall, vegetation type and land use type, use the hydrological model to calculate the possible runoff of the basin under the forecast rainfall conditions (including the total daily runoff and the maximum hourly runoff), and make corrections based on the impact of human domestic water discharge and agricultural irrigation in the basin. If the channel has runoff monitoring, mud water level monitoring, etc., use the actual monitoring data 3 hours before rainfall to make real-time corrections to the possible runoff of the basin.

[0018] The total daily runoff volume is calculated according to formula (3), and the maximum hourly runoff volume is calculated according to formula (4):

[0019]

[0020]

[0021] In formula (3) and formula (4), Q d is the total daily runoff, Q h is the hourly maximum runoff, P d Forecast rainfall on the warning day, P h is the hourly extreme rainfall for the day of the warning, S is the maximum possible retention volume in the basin, C N is a dimensionless parameter, v dw is the total daily runoff under precipitation conditions, v hw is the total hourly runoff under precipitation conditions, and A is the basin area.

[0022] ③ Inverse analysis of critical starting conditions of debris flow

[0023] According to the topography of the target debris flow channel, a typical section is taken along the main channel direction to determine the range of the catchment area, circulation area and accumulation area. For the catchment area and circulation area, the initial density of the water-rock body mixture ρ0 is preliminarily set according to the field survey, and the range of the overlying accumulation layer is set multiple times (-d1, d1), (-d2, d2)... (-d n , d n ), gradually invert the debris flow initiation conditions until the accuracy of the simulated water-rock mixture density meets the requirements, and finally determine the critical density ρ of the water-rock mixture when the debris flow in the main sliding direction starts, see Table 1.

[0024] Table 1 Inversion simulation design conditions

[0025]

[0026]

[0027] ④ According to the amount of startable material sources and possible runoff, calculate the water-rock mixture density ρ of the target channel under the forecast daily rainfall conditions d and water-rock mixture density ρ under extreme hourly rainfall conditionsh , where the calculation formula for the density of water-rock mixture under the forecast daily rainfall condition is the following formula (5), and the calculation formula for the density of water-rock mixture under the extreme hourly rainfall condition is the following formula (6):

[0028]

[0029]

[0030] In formula (5) and formula (6), ρ d is the density of the water-rock mixture on a daily scale, ρ h is the density of water-rock mixture at hourly scale; ρ W is the water density; ρ s is the particle density of the accumulation body; v dw is the total daily runoff under rainfall conditions; v hw is the total hourly runoff under rainfall conditions; v s1 is the volume of the sliding mass of the basin slope instability under rainfall conditions, calculated by formula (1); v s2 is the volume of channel startable material sources under rainfall conditions. The maximum outflow of sediment in the channel is used to estimate the channel startable material volume, which is determined based on experience. α and β are the actual start-up ratios.

[0031] ⑤Determine early warning indicators

[0032] The density of water-rock mixture under the forecast daily rainfall condition ρ d The numerical range of is the first main judgment rule, see the following formula (7) to preliminarily determine the daily scale warning level T 0d , and combined with the comparison results of the daily runoff volume and the maximum runoff volume in the basin history, the daily scale warning level T 0d Adjustments are made to determine the first warning level T1 under the rainfall conditions on the forecast day;

[0033] The density of water-rock mixture under extreme hourly rainfall conditions ρ h The numerical range of is the second main judgment rule, see the following formula (8) to preliminarily determine the hourly scale warning level T 0h , and the hourly warning level T is calculated by comparing the hourly maximum runoff with the historical maximum runoff of the basin. 0h Adjustments are made to determine the second warning level T2 under extreme hourly rainfall conditions;

[0034]

[0035]

[0036] In formula (7) and formula (8), T 0d is the daily warning level determined under the first main judgment rule, T 0his the hourly warning level determined under the second main judgment rule; ρ is the final critical density of the water-rock mixture when the debris flow in the main sliding direction starts, ρ d is the density of water-rock mixture under the forecast daily rainfall condition, ρ h It is the density of water-rock mixture under extreme hourly rainfall conditions.

[0037] Among them, the daily scale warning level T 0d Adjustment is made, specifically: the water-rock mixture density ρ on that day d Within a specific range, if the daily total runoff is greater than the historical maximum runoff of the basin, the daily scale warning level T under the forecast day rainfall conditions will be determined. 0d Raise the level by 1 to the first warning level T1;

[0038] Hourly warning level T 0h Adjustment is made, specifically: when the hourly scale water-rock mixture density ρ h Within a specific range, if the hourly runoff is greater than the historical maximum runoff of the basin, the hourly scale warning level T under the determined extreme hourly rainfall conditions will be 0h Raise 1 level to the second warning level T2.

[0039] Specifically,

[0040] When performing daily scale early warning calculations, the water-rock mixture density ρ d More than 1.2t / m 3 The minimum value of 0.8ρ and less than or equal to 1.8t / m 3 When the daily runoff exceeds the maximum runoff in the basin history, the daily warning level T calculated by formula (7) is 0d Raise the level by 1 (i.e., the blue warning is adjusted to yellow warning, and the yellow warning is adjusted to orange warning);

[0041] When performing hourly scale early warning calculations, when the hourly scale water-rock mixture density ρ h More than 1.4t / m 3 The minimum value of 1.2ρ and less than or equal to 2.0t / m 3 When the hourly maximum runoff exceeds the historical maximum runoff of the basin, the hourly warning level T calculated by formula (8) is 0h Raise the level by 1 (i.e., the blue alert is adjusted to the yellow alert, the yellow alert is adjusted to the orange alert, and the orange alert is adjusted to the red alert);

[0042] When the first warning level T1 and the second warning level T2 are inconsistent, a higher warning level is selected as the warning level T issued for the target debris flow basin.

[0043] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0044] The technical solution adopted by the present invention fully considers the effects of production, confluence and flow of the basin under the action of heavy rainfall, and can significantly improve the accuracy of regional scale debris flow warning. The warning model established by adopting this technical solution has the characteristics of few input parameters and easy application. It can carry out refined debris flow meteorological warning and forecast for valleys with incomplete or even no monitoring equipment based on rainfall monitoring and forecast data, especially it can make up for the lack of monitoring capacity of valleys with non-debris flow hidden dangers. By carrying out debris flow warning and forecast at the regional scale basin by basin, it can effectively prevent mass debris flow disasters. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The accompanying drawings are incorporated in and constitute a part of this specification and, together with the description, serve to explain the principles of the present invention.

[0046] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor.

[0047] Figure 1 A flow chart of a debris flow dynamic early warning method provided by the present invention;

[0048] Figure 2 A slope unit early warning result diagram provided by an embodiment of the present invention;

[0049] Figure 3 This is a warning result diagram of the target debris flow basin finally determined by the embodiment of the present invention. DETAILED DESCRIPTION

[0050] Here, exemplary embodiments will be described in detail, and the embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Instead, they are only examples consistent with some aspects of the present invention described in detail in the appended claims.

[0051] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0052] Example

[0053] See also Figure 1 As shown, this embodiment provides a debris flow dynamic early warning method, comprising the following steps:

[0054] Step 1: Obtain the amount of activatable material sources in the debris flow basin and the possible runoff under the forecast rainfall conditions. According to the activatable material sources and the possible runoff, calculate the water-rock mixture density ρ under the forecast daily rainfall conditions of the target channel. d and water-rock mixture density ρ under extreme hourly rainfall conditions h ;

[0055] Step 2, obtain the final critical density ρ of the water-rock mixture when the debris flow in the main sliding direction starts, and determine the first warning level T1 under the forecast daily rainfall conditions in combination with the daily scale water-rock mixture density warning level judgment rule, and determine the second warning level T2 under the extreme hourly rainfall conditions in combination with the hourly scale water-rock mixture density warning level judgment rule; when the first warning level T1 and the second warning level T2 are inconsistent, select the higher warning level as the warning level T for the target debris flow basin.

[0056] Specifically, the debris flow dynamic early warning method specifically includes:

[0057] ① Obtain the amount of material resources that can be activated in the debris flow basin:

[0058] According to the development law of debris flow in the study area and the historical debris flow survey in the target basin, it is found that both hydraulic debris flow and soil debris flow occur in the area. The field investigation revealed that the target channel is rich in loose deposits and has a large amount of material sources; some slopes have poor stability and may become unstable under heavy rainfall, providing material sources for debris flow. Based on this, it is judged that hydraulic-soil debris flow may occur in the target channel, and the channel material sources accumulated in the channel can be started under heavy rainfall conditions and the volume of the unstable sliding body of the slope are used as the starting material sources.

[0059] Input daily rainfall to calculate and determine the stability of slope units under rainfall conditions. Use SINMAP to calculate the regional stability coefficient, superimpose the stability coefficient grid layer with the slope unit layer, and count the grid area proportions of each warning level in each slope unit. A, b, c, and d represent the grid area proportions of warning levels 1, 2, 3, and 4, respectively. Determine the warning level T of the i-th slope unit according to the following formula (1): ixp , and output the warning level determination results of each slope unit according to the current standard RGB requirements.

[0060]

[0061] It was determined that three slope units may become unstable under the forecast rainfall conditions (see Figure 2 ), the slope is simplified to an infinite slope, and the calculation formula of the sliding body volume of the slope instability is as follows (2):

[0062] v s1 =∑S i h Formula (2)

[0063] In formula (2), v s1 is the volume of the unstable sliding mass of the basin slope under rainfall conditions, S i is the area of ​​the ith slope unit, and h is the average thickness of the sliding body.

[0064] ②Calculate the possible runoff under the forecast rainfall conditions

[0065] Determine the debris flow basin, assess the medium saturation of the rock and soil in the target channel before heavy rainfall, determine the seepage capacity based on vegetation type and land use type, and use the SCS (Soil Conservation Service) model or other hydrological models to calculate the possible runoff of the basin under the forecast rainfall conditions. The daily forecast rainfall is 100 mm / d, and the hourly extreme rainfall forecast value is 35 mm / h. Calculate the total daily runoff according to formula (3), and calculate the hourly maximum runoff according to formula (4):

[0066]

[0067]

[0068] In formula (3) and formula (4), Q d is the total daily runoff, Q h is the hourly maximum runoff, P d Forecast rainfall on the warning day, P h is the hourly extreme rainfall for the day of the warning, S is the maximum possible retention volume in the basin, C N is a dimensionless parameter, v dw is the total daily runoff under rainfall conditions, v hw is the total hourly runoff under rainfall conditions, and A is the basin area.

[0069] ③ Inverse analysis of critical starting conditions of debris flow

[0070] According to the topography of the target debris flow channel, a typical section was taken along the main channel direction to determine the range of the catchment area, circulation area and accumulation area. For the catchment area and circulation area, the density of the water-rock mixture was preliminarily determined to be 1.7 based on field investigations. Different water content intervals (-0.1, 0.1) and (-0.05, 0.05) of the overlying accumulation layer were set through Table 2, and the debris flow initiation conditions were gradually inverted. Finally, the critical density ρ of the water-rock mixture when the debris flow in the main sliding direction was started was determined to be 1.8 t / m 3 .

[0071] Table 2 Inversion simulation design conditions

[0072]

[0073] ④ According to the amount of startable material sources and possible runoff, calculate the water-rock mixture density ρ of the target channel under the forecast daily rainfall conditions d 1.41t / m 3 , water-rock mixture density ρ under extreme hourly rainfall conditions h 1.81t / m 3 , where the calculation formula for the density of water-rock mixture under the forecast daily rainfall condition is the following formula (5), and the calculation formula for the density of water-rock mixture under the extreme hourly rainfall condition is the following formula (6):

[0074]

[0075]

[0076] In formula (5) and formula (6), ρ d is the density of the water-rock mixture on a daily scale, ρ h is the density of water-rock mixture at hourly scale; ρ w is the water density; ρ s is the particle density of the accumulation body; v dw is the total daily runoff under rainfall conditions; v hw is the total hourly runoff under rainfall conditions; v s1 v is the volume of unstable soil mass on the basin slope under rainfall conditions; s2 is the volume of channel source that can be activated under rainfall conditions; α is 0.3, and β is 0.5.

[0077] ⑤Determine early warning indicators

[0078] The daily scale warning level T under the daily rainfall condition is determined by formula (7): 0d It is a blue warning. As the total daily runoff exceeds the historical maximum runoff of the basin, the daily scale warning level T 0d Adjust to yellow warning (i.e., the first warning level T1); determine the warning level T under hourly extreme rainfall conditions through formula (8): 0h Orange warning. Since the hourly runoff is less than the historical maximum runoff of the basin, there is no need to adjust the hourly warning level T. 0h Adjustment is made, that is, the second warning level T2 is orange warning.

[0079]

[0080]

[0081] In formula (7) and formula (8), T 0d is the daily warning level determined under the first main judgment rule, T 0h is the hourly warning level determined under the second main judgment rule; ρ dThe density of water-rock mixture under daily rainfall conditions is predicted, and the value is 1.41t / m 3 , ρ h The density of water-rock mixture under extreme hourly rainfall conditions is 1.81t / m 3 .

[0082] Since the first warning level T1 and the second warning level T2 are inconsistent, the higher warning level is taken, and the warning level for the target debris flow basin is finally determined to be orange warning. Figure 3 It can be seen that the technical solution adopted in this embodiment fully considers the effects of generation, sink and flow of the basin under the action of heavy rainfall, and can significantly improve the accuracy of regional scale debris flow warning.

[0083] The above description is only a specific embodiment of the present invention, so that those skilled in the art can understand or implement the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention.

[0084] It should be understood that the present invention is not limited to what has been described above and that various modifications and changes may be made without departing from its scope. The scope of the present invention is limited only by the appended claims.

Claims

1. A debris flow dynamic early warning method, characterized in that: The following steps are involved: Step 1: Obtain the amount of activatable material sources in the debris flow basin and the possible runoff under the forecast rainfall conditions. According to the activatable material sources and the possible runoff, calculate the water-rock mixture density ρ under the forecast daily rainfall conditions of the target channel. d and water-rock mixture density ρ under extreme hourly rainfall conditions h ; Step 2, obtain the final critical density ρ of the water-rock mixture when the debris flow in the main sliding direction starts, and determine the first warning level T1 under the forecast daily rainfall conditions in combination with the daily scale water-rock mixture density warning level judgment rule, and determine the second warning level T2 under the extreme hourly rainfall conditions in combination with the hourly scale water-rock mixture density warning level judgment rule; when the first warning level T1 and the second warning level T2 are inconsistent, select the higher warning level as the warning level T for the target debris flow basin.

2. The debris flow dynamic early warning method according to claim 1, characterized in that: The step 1 specifically includes: According to the development law of debris flow in the study area and the history of debris flow in the target debris flow channel, combined with the on-site investigation of the channel material accumulation, determine the possible type of debris flow, and calculate the amount of material that can be activated according to the debris flow type; Determine the scope of the debris flow basin, evaluate the degree of rock and soil saturation, vegetation type and land use type of the target channel before heavy rainfall, and calculate the possible runoff of the basin under the forecast rainfall conditions.

3. The debris flow dynamic early warning method according to claim 2, characterized in that: Calculating the amount of startable material sources according to the debris flow type specifically includes: For watersheds where geodynamic debris flows may occur, the sliding mass caused by slope instability induced by heavy rainfall is used as the activatable source; For watersheds where hydraulic debris flows may occur, the channel material sources accumulated in the channel that can be activated under heavy rainfall conditions are the activatable material sources; For watersheds where both hydraulic and geodynamic debris flows may occur, the sliding body caused by slope instability induced by heavy rainfall and the channel material sources accumulated in the channel that can be started under heavy rainfall conditions are jointly used as the starting material sources.

4. The debris flow dynamic early warning method according to claim 3 is characterized in that: The calculation formula of the sliding mass volume of the slope instability is as follows (2): v s1 =∑S i h Formula (2) In formula (2), v s1 is the volume of unstable soil mass on the basin slope under rainfall conditions, S i is the area of ​​the ith slope unit, and h is the average thickness of the sliding body.

5. The debris flow dynamic early warning method according to claim 1, characterized in that: The possible runoff under the forecast rainfall conditions includes the total daily runoff and the hourly maximum runoff.

6. The debris flow dynamics early warning method according to claim 5, characterized in that: The calculation formula of the daily runoff volume is as follows: (3), and the calculation formula of the hourly maximum runoff volume is as follows: In formula (3) and formula (4), Q d is the total daily runoff, Q h is the hourly maximum runoff, P d Forecast rainfall on the warning day, P h is the hourly extreme rainfall for the day of the warning, S is the maximum possible retention volume in the basin, C N is a dimensionless parameter, v dw is the total daily runoff under rainfall conditions, v hw is the total hourly runoff under rainfall conditions, and A is the basin area.

7. The debris flow dynamics early warning method according to claim 6, characterized in that: The calculation formula of the water-rock mixture density of the target channel under the forecast daily rainfall condition in step 1 is the following formula (5), and the calculation formula of the water-rock mixture density under the extreme hourly rainfall condition is the following formula (6): In formula (5) and formula (6), ρ d is the density of the water-rock mixture on a daily scale, ρ h is the density of water-rock mixture at hourly scale; ρ w is the water density; ρ s is the particle density of the accumulation body; v dw is the total daily runoff under rainfall conditions; v hw is the total hourly runoff under rainfall conditions; v s1 v is the volume of unstable soil mass on the basin slope under rainfall conditions; s2 is the volume of the channel source that can be activated under rainfall conditions; α and β are the actual activation ratios.

8. The debris flow dynamic early warning method according to claim 1, characterized in that: The specific process of obtaining the final critical density ρ of the water-rock mixture when the debris flow in the main sliding direction starts in step 2 includes: First, according to the topography of the target debris flow channel, a typical section is taken along the main channel direction to determine the scope of the catchment area, flow area and accumulation area; Then, for the catchment area and circulation area, the initial density of the water-rock mixture is defined as ρ0 according to the field survey, and the range of the overlying accumulation layer is set multiple times (-d1, d1), (-d2, d2)... (-d n , d n ), gradually invert the debris flow initiation conditions until the accuracy of the simulated water-rock mixture density meets the requirements; Finally, the final critical density ρ of the water-rock mixture when the debris flow in the main sliding direction starts is determined.

9. The debris flow dynamics early warning method according to claim 1, characterized in that: In step 2, the daily scale water-rock mixture density warning level determination rule is: The numerical range of water-rock mixture density under the forecast day rainfall conditions is used as the first main judgment rule, as shown in the following formula (7), and the daily scale warning level T is determined by combining the comparison results of the daily runoff volume and the maximum runoff volume in the history of the basin. 0d Adjustments are made to determine the first warning level T1 under the rainfall conditions on the forecast day; The hourly scale water-rock mixture density warning level determination rule is: The numerical range of water-rock mixture density under extreme hourly rainfall conditions is used as the second main judgment rule, as shown in formula (8), and the hourly scale warning level T is determined by combining the comparison results of hourly runoff and the maximum runoff in the history of the basin. 0h Adjustments are made to determine the second warning level T2 under hourly extreme rainfall conditions; In formula (7) and formula (8), T 0d is the daily warning level determined under the first main judgment rule, T 0h It is the hourly warning level determined under the second main decision rule; ρ is the final critical density of the water-rock mixture when the debris flow in the main sliding direction starts, ρ d is the density of water-rock mixture under the forecast daily rainfall condition, ρ h It is the density of water-rock mixture under extreme hourly rainfall conditions.

10. The debris flow dynamics early warning method according to claim 9, characterized in that: The warning level is adjusted based on the comparison between the total daily runoff and the maximum historical runoff of the basin, as follows: Density of water-rock mixture at the daily scale ρ d More than 1.2t / m 3 The minimum value of 0.8ρ and less than or equal to 1.8t / m 3 When the minimum value of the two is 1.2ρ, the daily scale warning level T under the forecast day rainfall conditions is determined. 0d Raise the level by 1 to the first warning level T1; The warning level is adjusted based on the comparison results of hourly runoff and the maximum runoff in the basin history, as follows: When the density of water-rock mixture at hourly scale is ρ h More than 1.4t / m 3 The minimum value of 1.2ρ and less than or equal to 2.0t / m 3 When the hourly maximum runoff exceeds the historical maximum runoff of the basin, the hourly scale warning level T under the extreme hourly rainfall conditions will be determined. 0h Raise by 1 level to the second warning level T2.

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