Method for measuring debris flow channel unit width outflow amount, and monitoring early warning system

Abstract

To disclose a method for measuring a debris flow channel unit width outflow amount, and monitoring early warning method and system.SOLUTION: An optimization plan for a method for measuring a debris flow channel unit width outflow amount includes a method for measuring a feature parameter of a ground surface outflow condition on the basis of an outflow hydrograph, and constructing the outflow hydrograph of a ground surface of a formation area by using rainfall distribution data. The present invention provides a monitoring early warning method for the occurrence of a valley-shaped debris flow realized by using the plan for a method for measuring a debris flow channel unit width outflow amount, and provides a monitoring early warning system for a debris flow channel formation area for measuring the occurrence risk of a debris flow and a rainfall threshold inducing a debris flow. The method for measuring the unit width outflow amount has solved the technical problem of measuring the unit width outflow amount by using a mathematical model scheme, and has expanded the prospect in effective use of the index. The measurement method completes calculation by using a mathematical model, and is easily docked or applied to a technology plan for preventing each type of debris flow.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention belongs to the technical fields of geological disaster monitoring and measurement and geological disaster prevention, and relates to a technology for monitoring and early warning of debris flow, in particular to a method for measuring the single-width runoff volume in a debris flow channel formation area and a method for measuring the debris flow occurrence rainfall threshold based on the same, a method for monitoring and early warning of debris flow, and the applications of each method. [Background technology]

[0002] A ditch-type debris flow is generally a type of debris flow mainly caused by slope erosion, and is the type of debris flow most commonly seen in mountain basins during the rainy season, and it poses a great deal of damage to the socio-economy and ecological environment of mountainous areas.Ditch-type debris flows are mainly caused by a certain amount of precipitation washing and eroding the ground surface, destroying the stable structure inside the soil body, and causing a large amount of debris to be caught in the surface runoff.

[0003] Debris flow monitoring and early warning technology is one of the main research contents in the field of mountain environmental geological disaster prevention. The prior art, CN2018107475705, discloses a river basin debris flow early warning scheme, which is a debris flow monitoring and early warning technology constructed based on the construction method of debris flow occurrence rainfall ID curve threshold. The core part of the method, that is, the ID curve threshold construction method, first obtains the necessary watershed ground data for Richard model and Van Genuchten equation numerical simulation, launches the hydrological simulation process under given rainfall intensity conditions, judges the stability and flow situation of each grid in the river basin along the time sequence, calculates the volume density of water-soil mixture, records the data that matches the control points to fit the ID curve, and finally obtains a group of ID thresholds under the previous rainfall conditions. This method uses the change in precipitation conditions in the debris flow basin from hydrological model simulation as output, and then generates the dynamic change in the bulk density value ρ of the water-soil mixture as an intermediate quantity through analysis based on the change trend of the water-soil coupling characteristics in the debris flow formation physical process, and generates an ID curve equation for determining the monitoring threshold of debris flow occurrence through fitting, thereby realizing monitoring and early warning of debris flow occurrence. This technology represents the basic concept of the conventional ditch-type debris flow monitoring and early warning technology proposal, that is, precipitation data is input as the hydrological model, and the key hydrological parameters that induce the formation of debris flow are obtained through numerical simulation of the hydrological process, and then different types of water-soil characteristic indexes are measured as monitoring objects for early warning of debris flow occurrence.

[0004] Although the conventional debris flow monitoring and early warning technology can be applied to debris flow monitoring and early warning with precipitation as the decisive trigger, it still has defects when applied to ditch valley type debris flow. The main defect is that the water-soil characteristic index type it selected (selecting the bulk density value ρ of the water-soil mixture in CN2018107475705) is not an ideal index to characterize channel erosion. According to previous studies, it was found that the index characterizing the surface runoff characteristics is an effective index to monitor whether the formation of debris flow caused by flood erosion ditch bed has reached a critical condition, where it includes runoff depth, single width runoff volume, etc. However, the conventional technology did not use the single width runoff volume as the monitoring target index of the debris flow monitoring and early warning scheme. Thus, in the field of geological disaster prevention research, the single width runoff volume index is an incidental descriptive index when it is only used as a total runoff volume index in the long term, and has not been effectively used. The reason for this phenomenon is that the problem of calculating single-width runoff volume has not yet been solved with conventional technology, so it cannot be used as an important indicator in the field of research into various types of debris flows or high sand-containing floods, and the measurement technology of this indicator cannot be integrated with the upstream hydrological condition simulation technology and downstream debris flow monitoring and early warning technology. Summary of the Invention

[0005] The objective of the present invention is to address the shortcomings of the prior art by providing a method for measuring single width runoff on the ground surface and a debris flow monitoring and early warning scheme based on the method.

[0006] In order to achieve the above object, the present invention first provides a method for measuring the single width discharge of a debris-flow channel to measure the single width discharge of the ground surface in a debris-flow channel formation area. The technical solution is as follows:

[0007] A method for measuring the single width runoff of a debris flow channel, comprising: measuring the single width runoff of a calculation unit on the ground surface of a debris flow channel formation area; obtaining basic data through a field survey; setting up a calculation unit; performing calculations for each calculation unit based on Equation 1-1 and Equation 1-2; and taking the larger value of the calculation result as the single width runoff q measurement result of the calculation unit; JPEG2024176988000002.jpg56170In Equation 1-1 and Equation 1-2, q-formation area calculation unit surface runoff, m 3 , JPEG2024176988000003.jpg5170h - Surface runoff depth, m, which is collected by in situ monitoring or determined based on baseline data; ρ - water density, constant, t / m 3 , g - gravitational acceleration constant, m / s 2 , n-Roughness coefficient, value 0.035-0.04; u, v - components of the mean outflow velocity V in the x and y directions, m 3 / s, which are collected by on-site monitoring or determined based on baseline data; C-Chezy coefficient, which is determined based on fundamental data, The x direction is the normal groove flow direction, and the y direction is the vertical debris flow channel direction.

[0008] In the above-mentioned method for measuring the single width runoff of a debris flow channel, the parameters h, u, and v characterize the surface runoff condition characteristics and are important data basis for calculating the single width runoff. Generally, the surface runoff depth h and the runoff average flow velocity V can be obtained by field measurement, historical observation records, and conventional techniques for measuring h and V, and there are relatively mature field monitoring technical schemes, especially in the field of debris flow monitoring. However, the h, u, and v values ​​determined by historical records do not have a scientific mathematical expression form and cannot provide a sufficient data scale for building a related model, and the h, u, and v values ​​determined by the conventional calculation method are not completely consistent with the measurement of the single width runoff of the present invention in terms of measurement principle, which is disadvantageous to the construction of a complete and comprehensive calculation model. The present invention further provides an optimization scheme for the above-mentioned method for measuring the single width runoff of a debris flow channel, and establishes a mathematical expression form for the parameters h, u, and v based on the runoff hydrograph. Specifically, Obtain runoff hydrograph data on the ground surface in the debris flow channel formation area, and use the runoff hydrograph data as input to simultaneously calculate Equations 2 to 7 to measure three indices of runoff condition characteristics on the ground surface in the formation area, h, u, and v; JPEG2024176988000004.jpg129170In the above formulas 2 to 7, t-calculation time variable, s, a-flow conserved quantity vector, f, j - components of the flow flux vector in the x and y directions, JPEG2024176988000005.jpg11170β-ditch bed slope, °, which is determined based on foundation data.

[0009] Generally, the surface runoff hydrograph is obtained by local historical observation records, or may be scientifically borrowed data from similar areas of topographical and hydrological conditions. In order to improve the field relevance of the measurement of the single width runoff, the method of obtaining the surface runoff hydrograph is further optimized, specifically, The acquisition of the runoff hydrograph data of the surface of the formation area is based on the steps of acquiring rainfall distribution data, establishing a runoff calculation model (Equation 8, Equation 9) of the surface of the formation area represented by H, and obtaining the runoff hydrograph of the surface of the formation area; JPEG2024176988000006.jpg42170In Equation 8 and Equation 9, the surface flow depth of the H-formation region, mm, JPEG2024176988000007.jpg14170

[0010] In the above optimization plan, the rainfall distribution data can be obtained by using weather forecast data, or by using extreme rainfall event data, or by using real-time monitored rainfall data. The three are future, historical, and current rainfall distribution data, respectively. To construct the rainfall distribution data using extreme rainfall event data, the rainfall recurrence period data can be specifically used. When constructing the rainfall distribution data using extreme rainfall event data, different recurrence periods can be calculated based on Equation 10. JPEG2024176988000008.jpg43170

[0011] Based on the above-mentioned method for measuring the single width discharge of a debris flow channel, the present invention further provides a method for monitoring and early warning the occurrence of a ditch-type debris flow, the technical scheme of which is as follows:

[0012] A method for monitoring and early warning the occurrence of a ditch-valley type debris flow, which is realized by using the above-mentioned method for measuring the single width runoff of a debris flow channel, is to set the debris flow channel formation area as a monitoring and early warning area, and measure the single width runoff q of the ground surface of each calculation unit within the monitoring and early warning area. In this case, the calculation unit is marked as an unstable unit, and conversely, it is marked as a stable unit. If the ratio of the number of unstable units to the number of all calculation units reaches the instability ratio threshold, it is determined that there is a risk of occurrence of a ditch valley type debris flow in the monitoring early warning area. JPEG2024176988000010.jpg5170, JPEG2024176988000011.jpg17170JPEG2024176988000012.jpg5170θ - average slope of the debris flow channel formation area, °, it is determined based on the basic data, JPEG2024176988000013.jpg28170

[0013] The above-mentioned monitoring and early warning method for the occurrence of ditch valley type debris flow is as follows: JPEG2024176988000014.jpg5170, the calculation unit is marked as an unstable unit, and when the proportion of the number of unstable units in the total number of calculation units in the monitoring early warning area reaches the instability proportion threshold, it is determined that there is a risk of occurrence of a ditch valley type debris flow in the monitoring early warning area, and a corresponding warning signal must be issued. Furthermore, by setting different levels of instability proportion threshold, it is possible to initially realize a gradual early warning of the risk of occurrence of a debris flow. The instability proportion threshold may be determined with reference to a conventional method. This monitoring and early warning method for the occurrence of a ditch valley type debris flow may directly take the single width runoff volume q as the monitoring target index. In the optimization plan, when the surface runoff hydrograph data of the debris flow channel formation area is used as input to measure the surface runoff condition characteristics of the formation area, the rainfall events (which may be called risk rainfall events) that cause the proportion of the number of instability calculation units in the entire formation area to reach the instability proportion threshold can be calculated and marked, and the rainfall conditions of the risk rainfall events can be further statistically calculated to establish a rainfall condition threshold for early warning of the occurrence of debris flow in the formation area. In this optimization plan, the rainfall distribution data is used as the starting point, and the rainfall data is directly used as the monitoring target indicator, thereby shortening the technical route of debris flow monitoring and early warning.

[0014] In addition, the above monitoring and early warning method can further measure the rainfall threshold that induces the ditch valley type debris flow in the monitoring and early warning area. Specifically, the rainfall distribution data of the study area is constructed, and the rainfall distribution data is used as input to measure the surface runoff condition characteristics of the formation area under different rainfall conditions and the corresponding surface runoff volume q, and a two-dimensional curve of the rainfall distribution data of the formation area and the surface runoff volume q is constructed, and each calculation unit is calculated based on Equation 11. A change curve of the proportion amount of unstable calculation units of JPEG2024176988000015.jpg5170 along the real-time width runoff volume is constructed, and the rainfall event that causes the proportion amount of unstable calculation units in the study area to reach the unstable proportion threshold is marked as an unstable rainfall event, and the rainfall condition threshold in the unstable rainfall event is statistically calculated.

[0015] The present invention further provides a system for monitoring the formation area of ​​a debris flow channel, which uses the above-mentioned method for measuring the single width runoff of a debris flow channel and the method for monitoring and early warning the occurrence of a ditch valley type debris flow of the present invention as its technical core, and can monitor the single width runoff of the calculation unit on the ground surface of the formation area, and monitor the occurrence risk of a debris flow in the formation area. The technical solution is as follows:

[0016] A monitoring system for a debris flow channel formation area, comprising: monitoring a single-width runoff volume on the ground surface of the debris flow channel formation area; setting the debris flow channel formation area as a monitoring early warning area; determining a measurement cross section of a calculation unit within the monitoring early warning area; arranging a measuring device at the measurement cross section and connecting it to a host / calculation center signal; inputting basic data of the monitoring early warning area to the host / calculation center; the measuring device collecting runoff characteristic data and inputting it to the host / calculation center; and the host / calculation center measuring the single-width runoff volume of the calculation unit on the ground surface of the debris flow channel formation area based on the above-mentioned method for measuring the single-width runoff volume of a debris flow channel of the present invention.

[0017] If the above monitoring system further places a rain gauge within the monitoring early warning area and inputs rainfall data to a host computer / computing center in real time, the host computer / computing center can monitor the risk of debris flow occurrence within the formation area using the above-mentioned monitoring and early warning method for the occurrence of ditch-type debris flow of the present invention.

[0018] The on-site investigation in this technology includes various geological surveys, reconnaissance, surveying, measurement operation of the mountain flood debris flow channel site where the project is located, as well as conventional simulation experiments, test experiments, observation experiments, analysis experiments, and acquisition of historical disaster records in the field, and acquisition of related technical standards, and reference empirical methods and data, etc. The data acquired in the on-site investigation is collectively referred to as the basic data of this technology proposal.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) In response to the defect of the prior art lacking a method for measuring the single width runoff on the ground surface in the debris flow formation area, the present invention specifically provides a method for measuring the single width runoff on the ground surface in the debris flow formation area, solving the technical problems that the prior art could not solve. This method for measuring the single width runoff uses a mathematical model to complete the calculation based on previous survey data, and is highly scientific and easy to apply to various types of debris flow prevention technical solutions or extend to the relevant debris flow prevention technical solutions. The method for measuring the single width runoff of the present invention solves the technical problem of measuring the single width runoff by using a mathematical model method in the debris flow research field, thereby expanding the effective use prospects of this indicator in research and technological development. (2) A method for monitoring and early warning the occurrence of a ditch-valley debris flow based on the method for measuring the single width runoff is provided, which can measure the occurrence risk of a debris flow in an early warning area and the rainfall threshold that induces a debris flow. (3) A monitoring and early warning system for debris flow channel formation areas is provided, which can monitor the single-width runoff volume and the risk of debris flow occurrence in the early warning formation area. [Brief description of the drawings]

[0020] [Figure 1] This is a schematic diagram of the technical route for monitoring and early warning methods for the occurrence of ditch-type debris flows. [Figure 2a-2b] Runoff hydrographs under different rainfall durations and different rainfall return periods. [Figure 3a-3d] The single-width runoff q monitoring curves of the monitoring early warning area under different rainfall return period conditions are shown. [Figure 4]ID rainfall threshold curve. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] In the following, preferred embodiments of the present invention will be further described in conjunction with the drawings.

[0022] <Example 1> As shown in Figures 1 to 4, the present invention is used to design a monitoring and early warning technology scheme for the occurrence of valley-type debris flow for a certain debris flow channel.

[0023] Figure 1 is a schematic diagram of the technical route for monitoring and early warning methods for the occurrence of ditch valley debris flows.

[0024] 1. On-site investigation of monitoring and early warning areas The small debris flow basin (i.e., debris flow channel) of Provincial Highway 33 in Fenghua City, Zhejiang Province, belongs to the topography prone to occurrence of groove valley type debris flow. This channel formation area is defined as the monitoring early warning area of ​​the monitoring and early warning system of this project, and is called the early warning area.

[0025] Obtaining baseline data through field surveys of monitoring and early warning areas includes:

[0026] (1) Debris flow channel DEM grid data. The DEM grid is set as the calculation unit. The area of ​​each calculation unit is approximately 8*8m 2 The monitoring and early warning area has a total of 720 calculation units.

[0027] (2) Data on the source grain slope and topographical conditions of the formation area in the monitoring early warning area, and the relevant data are placed in each DEM grid (Table 1 is the grain size distribution of loose sediments in the monitoring early warning area, and Table 2 is the sulcus valley cross-sectional characteristics in the monitoring early warning area).

[0028] JPEG2024176988000016.jpg18170

[0029] JPEG2024176988000017.jpg18170

[0030] (3) Obtaining extreme precipitation event data for the monitoring early warning area is an atlas of once in five years, once in ten years, once in 20 years and once in 100 years heavy precipitation events for the monitoring early warning area.

[0031] 2. Important parameter calculation JPEG2024176988000018.jpg27170

[0032] JPEG2024176988000019.jpg13170

[0033] 2.2 Establishment of monitoring and early warning areas and construction of rainfall distribution data Based on the heavy rain atlas of different return periods, the extreme rainfall event data construction rainfall distribution data of the monitoring early warning area is obtained by calculating with Equation 10. Table 3 shows the rainfall distribution data of different return periods.

[0034] JPEG2024176988000020.jpg47170

[0035] 2.3 Constructing surface runoff hydrographs for monitoring and early warning areas Using the rainfall distribution data in Table 3, the surface runoff hydrograph of the monitoring early warning area is calculated based on Equation 8 and Equation 9. The surface runoff hydrograph is a time curve under the condition of different rainfall return periods with surface runoff depth H. Figures 2a and 2b are runoff hydrographs under different rainfall durations and different rainfall return periods. Figure 2a shows the runoff distribution situation under different rainfall return periods with rainfall durations of 1h and 3h, and Figure 2b shows the runoff distribution situation under different rainfall return periods with rainfall durations of 6h and 24h.

[0036] 2.4 Constructing distribution curves of surface runoff condition characteristics in monitoring and early warning areas Using the runoff hydrograph data as input, Equation 2 to Equation 7 are simultaneously set up to measure the distribution curve of the surface runoff condition characteristics of the monitoring early warning area, where h is the surface runoff depth, V is the average runoff velocity, and V is the components u and v in the x and y directions, respectively. For example, the situation of the hydraulic conditions of part of the formation area when the rainfall condition is 100 years and 33600 seconds of the 24-hour return period is shown in Table 4.

[0037] JPEG2024176988000021.jpg51170

[0038] JPEG2024176988000022.jpg152170

[0039] 3. Determine the rainfall combination thresholds for monitoring early warning areas In a specific embodiment of the present invention, based on the prior art, the instability percentage threshold is set to 10%. Based on Fig. 3a to Fig. 3d, the rainfall events that cause instability of 10% or more of the calculation units are selected and marked as risk rainfall events, and the rainfall condition threshold of the risk rainfall event is calculated as the monitoring early warning rainfall condition threshold. In this embodiment, the ID curve is selected as the rainfall condition threshold. Specifically, the rainfall duration (h) and rainfall intensity (mm / h) of the risk rainfall event are calculated, and the risk rainfall event is plotted on a coordinate system with the rainfall duration (h) as the abscissa and the rainfall intensity (mm / h) as the ordinate, to obtain the ID rainfall threshold curve. Fig. 4I-D Rainfall threshold curve (gray dots represent risk rainfall events). By utilizing the ID rainfall threshold curve, the rainfall combination condition threshold that induces debris flow in the monitoring early warning area can be determined.

Claims

1. A method for measuring the single width outflow of a debris flow channel, comprising: measuring the single width outflow of a calculation unit on the ground surface of a debris flow channel formation area; obtaining basic data by field survey; setting up calculation units; performing calculations for each calculation unit based on Equation 1-1 and Equation 1-2; and taking the larger value of the calculation result as the single width outflow q measurement result of the calculation unit; In Equation 1-1 and Equation 1-2, q-formation area calculation unit surface runoff, m ３ , h - surface runoff depth, m, which is collected by field monitoring or determined based on baseline data; ρ - water density, constant, t / m ３ , g - gravitational acceleration constant, m / s ２ , n-Roughness coefficient, value 0.035-0.04; u, v - components of the mean outflow velocity V in the x and y directions, m ３ / s, which is collected by on-site monitoring or determined based on fundamental data; C-Chézy coefficient, which is determined based on fundamental data; The x-direction is the debris flow channel direction and the y-direction is the vertical debris flow channel direction; A measuring method comprising:

2. Obtain runoff hydrograph data of the ground surface in the debris flow channel formation area, and use the runoff hydrograph data as input to measure runoff condition characteristics of the ground surface in the formation area, the runoff condition characteristics of the ground surface including h, u, and v; In Equation 2 to Equation 7, t is a calculation time variable, s, a - flow conserved quantity vector, f, j - components of the flow flux vector in the x and y directions, β - groove bed slope, °, which is determined based on fundamental data; 2. The measuring method according to claim 1 .

3. The acquisition of the runoff hydrograph data of the ground surface of the formation area is carried out based on the steps of acquiring rainfall distribution data, establishing a runoff calculation model of the ground surface of the formation area represented by H, and obtaining the runoff hydrograph of the ground surface of the formation area; In Equation 8 and Equation 9, H-formation area surface flow depth, mm; - the number of effluent curves, a value between 35 and 80; 3. The measuring method according to claim 2.

4. The rainfall distribution data is constructed using weather forecast data, or constructed using extreme rainfall event data, or constructed by real-time monitored rainfall data; 4. The measuring method according to claim 3.

5. The constructing of the rainfall distribution data using the extreme rainfall event data is carried out by: It was decided, Determined by the Rain Atlas, 5. The measuring method according to claim 4.

6. A method for monitoring and early warning the occurrence of a groove-type debris flow, which is realized by using the method for measuring the single width outflow of a debris flow channel according to any one of claims 1 to 5, The debris flow channel formation area is set as a monitoring early warning area, and the surface runoff volume q of each calculation unit in the monitoring early warning area is measured; If so, mark the computation unit as an unstable unit, and conversely, mark it as a stable unit. If the ratio of the number of unstable units to the number of all calculation units reaches the instability ratio threshold, it is determined that there is a risk of occurrence of a ditch valley type debris flow in the monitoring early warning area; 1. A monitoring and early warning method comprising:

7. measuring a rainfall threshold that triggers a ditch valley type debris flow in the monitoring early warning area; The implementation method is as follows: Construct rainfall distribution data of the research area, and use the rainfall distribution data as input to measure the runoff condition characteristics of the formation area's surface under different rainfall conditions and the corresponding surface runoff volume q, and construct a two-dimensional curve of the rainfall distribution data of the formation area and the surface runoff volume q; Summarizing the entire data, constructing a change curve along the real-time width runoff of the proportion amount of unstable calculation units in the study area, and marking the rainfall event that leads to the proportion amount of unstable calculation units in the study area reaching the unstable proportion threshold as an unstable rainfall event; Statistically determining rainfall condition thresholds for unstable rainfall events; The monitoring and early warning method according to claim 6.

8. A monitoring and early warning system for a debris flow channel formation area, comprising: Monitoring the surface runoff volume in the debris flow channel formation area. The debris flow channel formation area is set as a monitoring and early warning area, a calculation unit measurement cross section within the monitoring and early warning area is determined, measuring equipment is arranged at the measurement cross section, and connected to a host machine / calculation center signal; Input the basic data of the monitoring and early warning area to the host / computing center, and the measuring instruments collect the spill characteristic data and input it to the host / computing center; The host computer / calculation center measures the single width discharge of the calculation unit on the ground surface in the debris flow channel formation area according to the method for measuring the single width discharge of the debris flow channel according to claim 1; A monitoring and early warning system.

9. A rain gauge is further arranged in the monitoring and early warning area to input rainfall data to the host computer / computer center in real time, and the host computer / computer center monitors the risk of debris flow occurrence in the formation area by using the monitoring and early warning method for the occurrence of a ditch-valley-type debris flow as described in claim 6. The monitoring and early warning system according to claim 8.

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