Mountain torrent early warning method and system based on meteorological data

Abstract

The invention discloses a mountain torrent early warning method and system based on meteorological data, and relates to the field of mountain torrent early warning, and the method comprises the steps: calculating the geographic position, spatial range and area of a small watershed through a GIS system, and analyzing the features of the mountain torrent of the small watershed; calculating small-watershed runoff and surface runoff according to the small-watershed mountain torrent characteristics; the ratio of the flow peak value to the area of the drainage basin is obtained by calculating the flow peak value obtained in the process of runoff production and surface runoff of the small drainage basin, and early warning is conducted on mountain torrent disasters through the ratio of the flow peak value to the area of the drainage basin. According to the method, the accuracy of mountain torrent early warning is improved, the randomness and uncertainty in the mountain torrent accident process can be effectively dealt with, and enough response time is reserved for mountain torrent early warning.

Description

Technical Field

[0001] The present invention relates to the field of flash flood warning, and in particular to a flash flood warning method and system based on meteorological data. Background Art

[0002] Flash floods are currently widespread in mountainous areas, often causing significant loss of life and property. A disaster prevention and mitigation system has been established in key flash flood control areas, integrating non-engineering measures such as monitoring, communications, and forecasting facilities with engineering measures. This system aims to protect towns and important economic projects in hilly areas and mitigate flash flood damage. Given the large number of people affected by sudden, torrential flash floods, early warning measures for flash floods are crucial for preemptively evacuating those potentially affected and minimizing loss of life and property.

[0003] Different empirical or mathematical models have been developed and established for different regional conditions to simulate and predict the formation and evolution process of flash floods and determine the scope and scale of their impact. However, most models are constructed based on historical results and are static. They do not meet the randomness and uncertainty of the rainfall process and are prone to significant discrepancies with the actual rainfall process.

[0004] Therefore, there is an urgent need for a flash flood warning method and system based on meteorological data. Summary of the Invention

[0005] The present invention provides a flash flood early warning method and system based on meteorological data, which solve the problems of the prior art.

[0006] In a first aspect, the present invention provides a flash flood warning method based on meteorological data, comprising: Calculate the geographical location, spatial extent and drainage area of ​​small watersheds through GIS system, and analyze the characteristics of mountain torrents in small watersheds; Calculate small watershed runoff and surface runoff based on small watershed flash flood characteristics; By calculating the peak flow rate obtained during the flow generation and surface runoff of a small watershed, the ratio of peak flow rate to watershed area is obtained; Early warning of flash flood disasters is provided through the ratio of peak flow rate to basin area.

[0007] Furthermore, the GIS system is used to calculate the geographical location, spatial range and drainage area of ​​the small watershed, and analyze the characteristics of mountain torrents in the small watershed, including: A1: Set thresholds based on watershed area and flow, divide small watersheds, generate small watershed boundaries and generate raster maps; A2: Obtain elevation data and drainage area of ​​small watersheds; A3: Fill the gaps in the elevation data and calculate the flow direction and drainage area of ​​each grid; A4: Extract the watershed line of the small watershed; A5: Compare the watershed line with the historical hydrological data to verify its accuracy. If correct, proceed to A6; If it is inaccurate, the watershed line that does not conform to the historical hydrological data is removed, the watershed area and flow threshold of the small watershed associated with the original watershed line are adjusted, the small watershed boundary and local grid map associated with the watershed line are generated, and the process returns to step A2; A6. Output the attributes of flash floods in small watersheds, including spatial coordinates, area, catchment area, and slope. Analyze the characteristics of flash floods in small watersheds, including topography, land use rate, and vegetation coverage.

[0008] Furthermore, the calculation of small watershed runoff and surface runoff based on small watershed flash flood characteristics includes: B1. Calculate soil hydrological zoning using soil texture types; B2. Calculate the runoff curve value, i.e. CN value, based on land use type and soil hydrological zoning; B3. Correct the CN value according to rainfall.

[0009] Furthermore, the peak flow rate obtained by calculating the flow generation and surface runoff of the small watershed and obtaining the ratio of the peak flow rate to the watershed area includes: Get the average rainfall value in the small watershed, and then divide the area S corresponding to the small watershed into n small areas, each of which corresponds to K 1 ,K 2 , … ,K n , the rainfall intensity corresponding to each small area is r1, r2, ..., r n ; Calculate the runoff of the small watershed: in, P That is, the average rainfall value in the small watershed.

[0010] Furthermore, the calculation of small watershed runoff specifically includes calculating the cumulative rainfall through water holding capacity: right P t is the cumulative rainfall at time t, calculated as: The 0.2 in the formula is a core empirical coefficient, which means: the initial loss before runoff I a Equal to 20% of the soil's maximum water holding capacity S; The water holding capacity is calculated as: , the water holding capacity S is an empirical formula, which is the metric version of the original SCS formula; Original imperial formula: ; The unit is inches; 1 inch is 25.4 mm, therefore, ; in, P t Unit: mm; S Unit: mm; I a is the initial absorption depth of soil, I a =0.2 S , unit: mm; cumulative net rainfall at time t, unit: mm.

[0011] Furthermore, the calculation of small watershed runoff also includes calculating the peak flow rate through the accumulated rainfall and watershed area, specifically: Among them, 25400 / CN Indicates the maximum possible water holding capacity under ideal conditions, 254• CN is a correction term used to reflect the actual CN Values ​​limit water holding capacity; In the formula, 0.208 is the unit line peak coefficient. This is a coefficient that combines theoretical derivation with experience. Its physical meaning is: the theoretical peak flow generated when the basin area is 1 km², the net rainfall is 1 mm, and the peak delay is 1 hour. The theoretical peak flow rate unit is m³ / s, which is used to establish the dimensional relationship between flow, area, and rainfall. 0.208 is an approximate value of 1 / 4.8, where 4.8 is the unit conversion factor, that is, from imperial mu-inch / hour to metric m³ / s; 2 is the time interval weight coefficient, which calculates half of the time interval Δt as the effective impact time, that is, the peak effect of a rainfall occurs at the midpoint of its duration. In the formula, 0.8, 0.7, and 0.5 are nonlinear empirical indices in this invention, which are used to reflect the intensity of the nonlinear influence of various physical factors on the peak delay. Among them, 0.8 indicates that the influence of the confluence path length L is sublinear, 0.7 indicates the influence intensity of the soil water holding capacity S, and 0.5 indicates the influence intensity of the average slope Y. 6233.6 is the empirical calibration coefficient 484 in the original SCS formula. 484 is applicable to the flat areas of the continental United States. 6233.6 is the empirical coefficient adjusted for the characteristics of the target mountainous areas of the present invention. 6.0 is the empirical scaling coefficient used to adjust the overall magnitude of the tlog formula. It is the fitting coefficient obtained after regression analysis, which ensures that the calculation results of the formula can match the observed flood peak delay data. in, The basin area A and the net rainfall are P t The peak flow rate generated when the unit is m 3 / s, Indicates the peak flow rate when the basin area is 1 and the net rainfall is 1, unit: m 3 / s, basin area A, unit km 2 ; Δt is the model calculation interval, unit: h; is the flood peak delay of the small watershed, unit: h; L is the length of the longest confluence path of the small watershed, unit: km; Y is the average slope of the small watershed; Furthermore, the above-mentioned early warning of mountain torrent disasters by using the ratio of peak flow rate to basin area specifically includes: According to the degree of damage caused by flash flood disasters, flash flood warnings are divided into five levels from mild to severe: low risk warning, blue risk warning, yellow risk warning, orange risk warning, and red risk warning; The threshold interval for low-risk warning is set as follows: 0 < ratio of peak flow rate to basin area < 1; The threshold interval for blue risk warning is set as follows: 1≤ratio of peak flow and basin area<1.99; The threshold interval for yellow risk warning is set as follows: 1.99 ≤ the ratio of peak flow to basin area < 2.72; The threshold interval for orange risk warning is set as follows: 2.72 ≤ the ratio of peak flow to basin area < 3.50; The threshold interval for red risk warning is set as: the ratio of peak flow rate to basin area > 3.50.

[0012] In a second aspect, the present invention provides a flash flood warning system based on meteorological data, which is used to implement a flash flood warning method based on meteorological data as described in any one of the first aspects, including: Feature extraction module: used to calculate the geographical location, spatial range and drainage area of ​​small watersheds, and analyze the characteristics of mountain torrents in small watersheds; Calculation module: used to calculate small watershed runoff and surface runoff based on small watershed flash flood characteristics; Early warning module: used to calculate the ratio of peak flow rate and basin area in case of flash flood disasters in small watersheds.

[0013] Preferably, the early warning module is also used to receive historical meteorological data, forecast meteorological data, and historical monitoring station monitoring data of the area associated with the early warning information, and to confirm and judge the real-time early warning information, and to set the ratio of peak flow rate to basin area. The ratio of peak flow rate to basin area is the ratio of peak flow rate to basin area, and to divide the flash flood warning into five levels from mild to severe: low risk warning, blue risk warning, yellow risk warning, orange risk warning, and red risk warning. When the peak flow rate / basin area ratio reaches the red risk warning, an external early warning will be issued. The present invention obtains surface runoff, average rainfall value, runoff and surface runoff in the small watershed by analyzing the meteorological characteristics of flash floods in the small watershed, and obtains the important factors of flash flood warning within the range in detail. It also improves the accuracy of flash flood warning by dynamically correcting the CN value. By setting the flash flood warning threshold at multiple levels, it accurately covers flash floods of different degrees, can effectively deal with the randomness and uncertainty in the flash flood incident process, and reserve sufficient reaction time for flash flood warning. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of the present invention, and do not constitute a limitation of the embodiments of the present invention. In the drawings: Figure 1 A flow chart of a flash flood warning method based on meteorological data is provided as an exemplary embodiment of the present invention.

[0015] Figure 2 An architecture diagram of a flash flood warning system based on meteorological data is provided as an exemplary embodiment of the present invention.

[0016] Figure 3 A schematic diagram of dividing a small watershed into small areas in a flash flood warning method based on meteorological data provided by an exemplary embodiment of the present invention.

[0017] Figure 4 Schematic diagram of the SCS unit line model. DETAILED DESCRIPTION

[0018] Exemplary embodiments are described in detail herein, with examples illustrated in the accompanying drawings. When the following description refers to the drawings, identical numerals in different figures represent identical or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments are not intended to represent all embodiments consistent with the present invention.

[0019] Glossary: ​​GIS, Geographic Information System; DEM, Digital Elevation Model; SCS, Soil Conservation Service, Watershed Hydrology; The present invention aims to solve the problems of inaccurate rainfall prediction and low reliability of flash flood prediction in the prior art. It obtains a digital elevation model, fills data holes, calculates water flow direction and drainage area, extracts watershed lines, divides small watersheds according to area / flow thresholds, outputs characteristic data such as spatial coordinates / area / slope, compares the watershed accuracy with field hydrological data, performs feedback correction, calculates surface runoff and dynamically corrects CN values, calculates runoff, divides small watersheds into multiple sub-areas, speeds up the calculation of average rainfall, and then calculates the flow peak. The judgment parameters are set according to the flow peak / watershed area to perform early warning classification.

[0020] The specific application scenario of the present invention is a flash flood early warning system.

[0021] The present invention provides a flash flood warning method and system based on meteorological data, aiming to solve the above technical problems in the prior art.

[0022] The following describes in detail the technical solution of the present invention and how the technical solution of the present invention solves the above-mentioned technical problems using specific embodiments. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. The following embodiments of the present invention are described in conjunction with the accompanying drawings.

[0023] Example 1: This example is a flash flood warning method based on meteorological data. Figure 1 As shown, the following steps are included: Step 1: Calculate the geographical location, spatial range and drainage area of ​​the small watershed through the GIS system, and analyze the characteristics of mountain torrents in the small watershed; The specific implementation of step 1 is as follows: according to the watershed area and flow rate, thresholds are set to divide the small watershed, generate the small watershed boundaries and generate raster maps. The raster maps here are for the convenience of storing elevation data. The elevation data exists in the form of raster data. Each raster represents the elevation value of a certain area. DEM is the basic data for small watershed division. Among them, a larger watershed can be divided into multiple small watersheds according to the size of the flow rate or the confluence area. Obtain the elevation data and drainage area of ​​the small watershed, fill the holes in the elevation data, and calculate the flow direction and drainage area of ​​each grid. To fill the holes, since the elevation data may have depressions or holes caused by measurement errors or missing data, you first need to use terrain analysis tools to "fill" these depressions to ensure the accuracy of the flow direction analysis; flow direction analysis is a key step in the division of small watersheds. In the GIS system, elevation data can be used to calculate the flow direction of each grid; commonly used flow direction algorithms include D8, that is, each grid flows to one of the eight adjacent grids, and D∞, that is, it flows in a continuous infinite number of directions; the drainage area represents the amount of water received by a certain point or area, which is usually calculated through flow direction data. A large drainage area means that the water flow in the watershed area is concentrated, which is suitable for division into smaller watersheds; Then the watershed line of the small watershed is extracted. The watershed line is the boundary line between different watersheds or small watersheds, which defines the convergence area of ​​water flow. The accuracy of the watershed line is verified by comparing the watershed line with historical hydrological data, and inaccurate watershed lines are eliminated. The watershed area and flow threshold of the small watershed associated with the original watershed line are adjusted to generate the small watershed boundary and local grid map associated with the watershed line, and the elevation data and watershed area of ​​the small watershed are obtained again. The gaps in the new elevation data are filled again, and then the water flow direction and confluence area of ​​each grid are calculated to extract the new watershed line of the small watershed until all watershed lines meet the accuracy requirements. The calculation operation and calculation method for the accuracy of the watershed line are as follows: Among them, the calculation operation steps are: superimpose the automatically extracted watershed line with the historical or measured / high-precision watershed data; adjust and set a reasonable buffer zone according to the DEM resolution, such as 10-50 meters; calculate the overlapping area ratio of the two lines in the buffer zone. Among them, the calculation method of watershed line coincidence is as follows: coincidence = (1-buffer analysis difference area / total watershed area) × 100%; Step 2: Calculate the runoff and surface runoff of the small watershed based on the flash flood characteristics of the small watershed; The specific implementation of step 2 is as follows: B1. Calculate soil hydrological zoning using soil texture types; B2. Calculate the runoff curve value, i.e. CN value, based on land use type and soil hydrological zoning; Among them, the relationship between soil texture type and hydrological division is shown in Table 1. Table 1: Soil types calculated from China soil map And the CN value can be obtained by comparing Table 2; Table 2: Land use calculation based on satellite remote sensing data B3. Correct the CN value according to the rainfall. The corrected CN value shall not exceed 100.

[0024] For example: If the rainfall in 24 hours is less than 25 mm, the CN value increases by 5; If the rainfall in 24 hours is greater than 25 mm and less than or equal to 50 mm, the CN value increases by 10; If the rainfall in 24 hours is greater than 50 mm, the CN value increases by 15; The calculation is repeated recursively, but the CN value does not exceed 100 after correction.

[0025] Step 3: Calculate the peak flow rate obtained during the flow generation and surface runoff of the small watershed to obtain the ratio of the peak flow rate to the watershed area; The calculation reasoning logic of step 3 is as follows: Step 3.1: Get the average rainfall value in the small watershed, such as Figure 3 As shown, the area S corresponding to the small watershed is divided into n small areas, each of which corresponds to K 1 ,K 2 , … ,K n , the rainfall intensity corresponding to each small area is r1, r2, ..., r n ; Calculate the runoff of the small watershed: in, P That is, the average rainfall value in the small watershed; and there is a threshold for the generation of runoff in the small watershed. When the rainfall is less than the threshold, the watershed does not generate runoff; when the rainfall is greater than the threshold, the runoff generated by the watershed increases nonlinearly with the increase of rainfall, and the rate of increase is related to the CN value and rainfall. Step 3.2: Calculate the cumulative rainfall using water holding capacity: right P t is the cumulative rainfall at time t, calculated as: The water holding capacity is calculated as: in, P t Unit: mm; S Unit: mm; I a is the initial absorption depth of soil, I a =0.2 S , unit: mm; cumulative net rainfall at time t, unit: mm.

[0026] Step 3.3: Calculate the peak flow rate by accumulating rainfall and drainage area. In this embodiment, Figure 4 As shown in the figure, the SCS unit line is used in surface runoff calculation. The relationship between the final SCS unit line peak value and the unit line peak time satisfies the formula, specifically: in, The basin area A and the net rainfall are P t The peak flow rate generated when the unit is m 3 / s, Indicates the peak flow rate when the basin area is 1 and the net rainfall is 1, unit: m 3 / s, basin area A, unit km 2 ; Δt is the model calculation interval, unit: h; is the flood peak delay of the small watershed, unit: h; L is the length of the longest confluence path of the small watershed, unit: km; Y is the average slope of the small watershed; Here, It is defined as the time difference between the peak time of the unit line and the position of the rainfall center, that is, the time difference from the rainfall peak to the flood peak. The estimation formula is: In summary, it can be seen that The law of multiple proportions is satisfied between them. If it is known that Unit line, then we can get according to the law of multiple proportions If the unit line of The main unit lines are and Δt. Therefore, according to With different combinations of Δt, 18 parameters can be obtained through HEC-HMS software. The corresponding standard unit line. Different curve types are obtained through HEC-HMS software value and compare it with Comparing the values ​​obtained by the calculation formula, we can find that the two are basically consistent, which also verifies that 18 different combinations of Δt and The accuracy of the corresponding standard unit line.

[0027] Step 4: Early warning of flash flood disasters based on the ratio of peak flow rate to basin area; It also includes risk level classification, which divides flash flood warnings into five levels from mild to severe: low risk warning, blue risk warning, yellow risk warning, orange risk warning, and red risk warning; The threshold interval for low-risk warning is set as follows: 0 < ratio of peak flow rate to basin area < 1; The threshold interval for blue risk warning is set as follows: 1≤ratio of peak flow and basin area<1.99; The threshold interval for yellow risk warning is set as follows: 1.99 ≤ the ratio of peak flow to basin area < 2.72; The threshold interval for orange risk warning is set as follows: 2.72 ≤ the ratio of peak flow to basin area < 3.50; The threshold interval for red risk warning is set as: the ratio of peak flow rate to basin area > 3.50.

[0028] Example 2: This example is a flash flood warning system based on meteorological data, such as Figure 2 As shown, on the basis of the modules of this embodiment 2, the calculation in embodiment 1 is completed; step 1 is calculated in the feature extraction module, steps 2 to 3.3 are calculated in the calculation module, and step 4 is calculated in the early warning module; specifically: feature extraction module: used to calculate the geographical location, spatial range and basin area of ​​the small watershed, and analyze the characteristics of mountain torrents in the small watershed; calculation module: used to calculate the runoff and surface runoff of the small watershed based on the characteristics of mountain torrents in the small watershed; early warning module: used to calculate the ratio of the peak flow rate and basin area of ​​mountain torrents in the small watershed.

[0029] Example 3: Based on Example 2, the following process is used for system-level early warning operation and maintenance: a: Add, modify, and delete pipeline monitoring sites, evaluate the access and communication status of various sensors at existing and newly built monitoring sites, and collect, display, and store data in real time; b: Display and query historical meteorological data, real-time meteorological data, and forecast meteorological data; c: Release flash flood warning information in real time and support query and display of historical warning information; d: Confirm and judge the real-time warning information based on the historical meteorological data, forecast meteorological data and historical monitoring station monitoring data of the warning information-related area; e: Provide early warning of flash flood disasters by setting the ratio of peak flow rate to basin area.

[0030] During the actual early warning process, red alerts accounted for about 3%, orange alerts accounted for about 10%, yellow alerts accounted for about 20%, and blue alerts accounted for about 67%.

[0031] In the embodiments provided by the present invention, it should be understood that the disclosed systems and methods can be implemented in other ways. For example, the system embodiments described above are merely illustrative. The modules described as separate components may or may not be physically separate, and the components shown as modules may or may not be physical modules, that is, they may be located in one place or distributed across multiple network modules. Some or all of the modules may be selected to achieve the purpose of the present embodiment according to actual needs.

[0032] In addition, the functional modules in the embodiments of the present invention may be integrated into a single processing module, each module may exist physically separately, or two or more modules may be integrated into a single module. The integrated modules may be implemented in the form of hardware or hardware plus software functional modules.

[0033] Those skilled in the art will appreciate that the embodiments of the present invention may be provided as methods or systems. Thus, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware.

[0034] It should also be noted that the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, commodity, or apparatus that includes a series of elements includes not only those elements but also other elements not explicitly listed, or includes elements inherent to such process, method, commodity, or apparatus. In the absence of further limitations, an element defined by the phrase "comprises a ..." does not exclude the presence of other identical elements in the process, method, commodity, or apparatus that includes the element.

[0035] The above are merely embodiments of the present invention and are not intended to limit the present invention. It will be apparent to those skilled in the art that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are intended to be included within the scope of the claims of the present invention.

[0036] Those skilled in the art will readily recognize other embodiments of the present invention after considering the invention disclosed herein in the specification and examples. The present invention is intended to cover any variations, uses, or adaptations of the present invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The description and examples are to be considered as exemplary only, with the true scope and spirit of the invention being indicated by the following claims.

[0037] It should be understood that the present invention is not limited to the exact construction described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof, which is limited only by the appended claims.

Claims

1. A flash flood warning method based on meteorological data, characterized in that: include: Calculate the geographical location, spatial extent and drainage area of ​​small watersheds through GIS system, and analyze the characteristics of mountain torrents in small watersheds; Calculate small watershed runoff and surface runoff based on small watershed flash flood characteristics; By calculating the peak flow rate obtained during the flow generation and surface runoff of a small watershed, the ratio of peak flow rate to watershed area is obtained; Early warning of flash flood disasters is provided through the ratio of peak flow rate to basin area.

2. A flash flood early warning method based on meteorological data according to claim 1, characterized in that: The GIS system is used to calculate the geographical location, spatial range and drainage area of ​​small watersheds and analyze the characteristics of flash floods in small watersheds, including: A1: Set thresholds based on watershed area and flow, divide small watersheds, generate small watershed boundaries and generate raster maps; A2: Obtain elevation data and drainage area of ​​small watersheds; A3: Fill the gaps in the elevation data and calculate the flow direction and drainage area of ​​each grid; A4: Extract the watershed line of the small watershed; A5: Compare the watershed line with the historical hydrological data to verify its accuracy. If correct, proceed to A6; If it is inaccurate, the watershed line that does not conform to the historical hydrological data is removed, the watershed area and flow threshold of the small watershed associated with the original watershed line are adjusted, the small watershed boundary and local grid map associated with the watershed line are generated, and the process returns to step A2; A6. Output the attributes of flash floods in small watersheds, including spatial coordinates, area, catchment area, and slope. Analyze the characteristics of flash floods in small watersheds, including topography, land use rate, and vegetation coverage.

3. A flash flood warning method based on meteorological data according to claim 2, characterized in that: The calculation of small watershed runoff and surface runoff based on small watershed flash flood characteristics includes: B1. Calculate soil hydrological zoning using soil texture types; B2. Calculate the runoff curve value, i.e. CN value, based on land use type and soil hydrological zoning; B3. Correct the CN value according to rainfall.

4. A flash flood warning method based on meteorological data according to claim 3, characterized in that: The peak flow rate obtained by calculating the flow generation and surface runoff of the small watershed and obtaining the ratio of the peak flow rate to the watershed area includes: Get the average rainfall value in the small watershed, and then divide the area S corresponding to the small watershed into n small areas, each of which corresponds to K 1 ,K 2 , … ,K n , the rainfall intensity corresponding to each small area is r1, r2, ..., r n ; Calculate the runoff of the small watershed: in, P That is, the average rainfall value in the small watershed.

5. The flash flood warning method based on meteorological data according to claim 4, characterized in that: The calculation of small watershed runoff specifically includes calculating the cumulative rainfall through water holding capacity: right P t is the cumulative rainfall at time t, calculated as: The 0.2 in the formula is a core empirical coefficient, which means: the initial loss before runoff I a Equal to 20% of the soil's maximum water holding capacity S; The water holding capacity is calculated as: , water holding capacity S is an empirical formula; Original imperial formula: ; The unit is inches; One inch is 25.4 mm, so ; in, Indicates the maximum possible water holding capacity under ideal conditions, 254· CN is a correction term used to reflect the limitation of the actual CN value on water holding capacity; in, P t Unit: mm; S Unit: mm; I a is the initial absorption depth of soil, I a =0.2 S , unit: mm; cumulative net rainfall at time t, unit: mm.

6. A flash flood early warning method based on meteorological data according to claim 5, characterized in that: The calculation of small watershed runoff also includes calculating the peak flow rate through the accumulated rainfall and watershed area, specifically: Where 0.208 is the unit line peak coefficient, which is a coefficient derived from a combination of theoretical derivation and experience. Its physical meaning is: the theoretical peak flow rate generated when the basin area is 1 km², the net rainfall is 1 mm, and the peak delay is 1 hour. The theoretical peak flow rate unit is m³ / s. It is used to establish the dimensional relationship between flow, area, and rainfall. 0.208 is an approximate value of 1 / 4.8, where 4.8 is the unit conversion factor. 6.0 is used to adjust t log The empirical scaling coefficient of the overall magnitude of the formula is the fitting coefficient obtained after regression analysis, which makes the calculation results of the formula match the observed flood peak delay data; 6233.6 is the empirical calibration coefficient 484 in the original SCS formula after adjustment for the target mountainous area characteristics of the present invention. Wherein, 0.8, 0.7, and 0.5 are nonlinear empirical indices in the present invention, which are used to reflect the intensity of the nonlinear influence of various physical factors on the flood peak delay. Among them, 0.8 indicates that the influence of the confluence path length L is sublinear, 0.7 indicates the influence intensity of the soil water holding capacity S, and 0.5 indicates the influence intensity of the average slope Y. 2 is the time interval weight coefficient, and half of the calculation time interval Δt is taken as the effective impact time, that is, the peak effect of a rainfall occurs at the midpoint of its duration. in, The basin area A and the net rainfall are P t The peak flow rate generated when the unit is m 3 / s, Indicates the peak flow rate when the basin area is 1 and the net rainfall is 1, unit: m 3 / s, basin area A, unit km 2 ; Δt is the model calculation interval, unit: h; is the flood peak delay of the small watershed, unit: h; L is the length of the longest confluence path in the small watershed, unit: km; Y is the average slope of the small watershed.

7. A flash flood warning method based on meteorological data according to claim 6, characterized in that: The above-mentioned early warning of flash flood disasters based on the ratio of peak flow and basin area specifically includes: According to the degree of damage caused by flash flood disasters, flash flood warnings are divided into five levels from mild to severe: low risk warning, blue risk warning, yellow risk warning, orange risk warning, and red risk warning; The threshold interval for low-risk warning is set as follows: 0 < ratio of peak flow rate to basin area < 1; The threshold interval for blue risk warning is set as follows: 1≤ratio of peak flow and basin area<1.99; The threshold interval for yellow risk warning is set as follows: 1.99 ≤ the ratio of peak flow to basin area < 2.72; The threshold interval for orange risk warning is set as follows: 2.72 ≤ the ratio of peak flow to basin area < 3.50; The threshold interval for red risk warning is set as: the ratio of peak flow rate to basin area > 3.

50.

8. A flash flood warning system based on meteorological data, characterized in that: A method for implementing a flash flood warning method based on meteorological data as described in any one of claims 1 to 7, comprising: Feature extraction module: used to calculate the geographical location, spatial range and drainage area of ​​small watersheds, and analyze the characteristics of mountain torrents in small watersheds; Calculation module: used to calculate small watershed runoff and surface runoff based on small watershed flash flood characteristics; Early warning module: used to calculate the ratio of peak flow rate and basin area in case of flash flood disasters in small watersheds.

9. A flash flood warning system based on meteorological data according to claim 8, characterized in that: The early warning module is also used to receive historical meteorological data, predicted meteorological data, and historical monitoring site monitoring data of the area associated with the early warning information, and to confirm and judge the real-time early warning information, and to set the ratio of peak flow rate to basin area. The ratio of peak flow rate to basin area is the ratio of peak flow rate to basin area, and to divide flash flood warnings into five levels from mild to severe: low risk warning, blue risk warning, yellow risk warning, orange risk warning, and red risk warning. When the peak flow rate / basin area ratio reaches the red risk warning, an external early warning is issued.

Images