A method for analyzing mountain torrent formation disaster-causing mechanism based on pregnant disaster environment

Abstract

This invention discloses a method for analyzing the formation and disaster-causing mechanism of flash floods based on disaster-prone environments, comprising the following steps: Step 1, constructing a set of historical flash flood disaster attributes and environmental factors for the study area; Step 2, determining the zoning of flash flood disaster-prone environments and their characteristics; Step 3, determining the explanatory power and uncertainty range of environmental categories and their environmental factors for changes in flash flood disaster attributes in each zoning; Step 4, determining the dominant environmental factors in each disaster-prone environment zoning; Step 5, analyzing the impact of changes in dominant environmental factors on the flash flood formation and disaster-causing process. The method of this invention fully considers the spatiotemporal heterogeneity of meteorological, geographical, and socioeconomic factors in the affected watershed, and separates and quantifies the contributions and uncertainties of different environmental factors such as meteorology, geography, and socioeconomic factors to flash flood formation and disaster-causing factors. It can improve the comprehensive prevention and control level of flash flood disasters, has strong applicability, and provides a scientific basis for flash flood disaster prevention and management.

Description

Technical Field

[0001] This invention belongs to the field of flash flood disaster management technology, and in particular relates to a method for analyzing the disaster-causing mechanism of flash floods based on disaster-prone environments. Background Technology

[0002] Flash floods are among the most dangerous and devastating natural disasters in mountainous areas worldwide. The formation and destructive process of flash floods are influenced by a combination of meteorological, watershed geographical, and socioeconomic conditions, and are highly uncertain. Therefore, scientifically revealing and comparing the disaster-prone environment and its meteorological, geographical, and socioeconomic components are crucial for objectively understanding the formation mechanism of flash floods and for developing targeted flood management measures.

[0003] Currently, the methods for analyzing the formation and disaster-causing mechanisms of flash floods mainly include two categories: (1) Post-disaster investigation: After a major flash flood disaster occurs, a rapid on-site investigation is conducted to clarify the causes, processes, and weaknesses in the disaster prevention process through visits and surveys. (2) Numerical simulation: By collecting data on topography, land use, hydrology, meteorology, and disaster losses before and after the disaster, a watershed hydrological model or watershed hydrodynamic model is constructed to reproduce the physical scene at the time of the disaster and clarify the causes of the flash flood disaster. However, the above methods mainly analyze a major flash flood disaster at the event or watershed scale. On the one hand, they can only depict the formation and disaster-causing mechanism of flash floods under specific environments, and the analysis results are difficult to apply to watersheds or disaster events with different meteorological, geographical, and socio-economic environments. On the other hand, they mainly analyze major disaster events that cause significant casualties or property losses, ignoring a large number of disaster events with low mortality rates, and the analysis results are not representative. In addition, different combinations of meteorological, geographical, and socio-economic environments have different effects on the formation and disaster-causing process of flash floods, resulting in significantly different disaster losses.

[0004] Therefore, given the complex and varied mechanisms by which different types of disaster-prone environments contribute to flash flood formation, there is an urgent need for a method to analyze the mechanisms of flash flood formation based on disaster-prone environments. This method would explore the quantitative causal relationships between various environmental factors and flash flood losses, providing a basis for flash flood prevention and management. Summary of the Invention

[0005] The purpose of this invention is to provide a method for analyzing the formation and disaster-causing mechanism of flash floods based on disaster-prone environments, so as to solve the above-mentioned technical problems.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] This invention discloses a method for analyzing the formation and disaster-causing mechanism of flash floods based on disaster-prone environments. The method includes the following steps:

[0008] Step 1: Constructing the historical flash flood disaster attribute set and environmental factor set for the study area: Collect and organize environmental factor data for each environmental category within the study area, as well as attribute data for historical flash flood disaster events within the study area. The environmental categories include meteorological, geographical, and socioeconomic categories. The environmental factors include meteorological, geographical, and socioeconomic factors. The attribute data for historical flash flood disaster events include the location of the disaster, the time of occurrence, the number of deaths or missing persons, the number of collapsed houses, and the direct economic losses. Then, using the watershed where the historical flash flood disaster event occurred as the unit and the time of occurrence of the historical flash flood disaster event as the benchmark, construct the historical flash flood disaster attribute set and the corresponding environmental factor set for the study area.

[0009] Step 2: Determine the zoning of flash flood disaster-prone environmental types and their characteristics: Based on the historical flash flood disaster attribute set and corresponding environmental factor set of the study area constructed in Step 1, determine the preliminary zoning of flash flood disaster-prone environmental types. Then, assess the significant differences of all environmental factors and flash flood disaster attributes in the preliminary zoning of flash flood disaster-prone environmental types to determine the final zoning of flash flood disaster-prone environmental types. For the determined final zoning of flash flood disaster-prone environmental types, identify the meteorological category factors, geographical category factors, socio-economic category factors, and flash flood disaster attribute characteristics and their spatial distribution patterns for each environmental type.

[0010] Step 3: Determine the explanatory power and uncertainty range of the environmental categories and environmental factors of each zone on the changes in flash flood disaster attributes: Taking the final flash flood disaster-prone environmental type zones determined in Step 2 as units, the N-fold uncertainty analysis method is used to randomly select the environmental categories and environmental factors of each zone, as well as the flash flood disaster attributes. The explanatory power and uncertainty range of different environmental categories on the changes in flash flood disaster attributes are quantified, as are the explanatory power, uncertainty range, and significance of each environmental factor on the changes in flash flood disaster attributes.

[0011] Step 4: Determine the dominant environmental factors of each disaster-prone environmental type zone: Based on the environmental categories of each zone and the explanatory power and uncertainty range of their environmental factors on the changes in flash flood disaster attributes determined in Step 3, the dominant environmental factors and their differences in effect are determined by causal analysis and comparative analysis, and the formation and disaster-causing mechanism of flash floods under each disaster-prone environmental type zone are characterized.

[0012] Step 5: Analyze the impact of changes in dominant environmental factors on the formation and disaster-causing processes of flash floods: Construct a coupled meteorological-hydrological-hydraulic numerical model for the study area. Automatically optimize the coupled model parameters using measured rainfall and flood data and historical flood trace data from the watershed. For areas lacking measured data, parameter regionalization techniques are used to determine the coupled model parameters. Then, based on the dominant environmental factors for each disaster-prone environmental type zone determined in Step 4, establish a scenario library of dominant environmental factors and analyze the impact of changes in dominant environmental factors on the formation and disaster-causing processes of flash floods in the study area. Finally, propose corresponding disaster prevention and mitigation measures for each disaster-prone environmental type zone.

[0013] Furthermore, the meteorological category factors mentioned in step 1 include humidity, flood season precipitation, and short-duration extreme rainfall characteristics in the year in which the flash flood disaster occurred, including magnitude, variability, and concentration; the geographical category factors include the basin topographic relief, slope, forest area ratio, grassland area ratio, farmland area ratio, soil saturation moisture content, river length, river gradient, and river meandering in the year in which the flash flood disaster occurred; and the socio-economic category factors include GDP and population density in the year in which the flash flood disaster occurred, and water conservancy investment before the flash flood disaster occurred.

[0014] Furthermore, the specific process for determining the preliminary flash flood disaster-prone environmental type zoning in step 2 is as follows:

[0015] Clustering algorithms were used to classify all historical flash flood disaster-related environmental factors in the study area's environmental factor set, determining the flash flood disaster-prone environmental type zoning CE'. N-fold uncertainty analysis was then used to randomly divide the study area's environmental factor set into N parts, selecting N-1 parts for cluster analysis, repeating this process N times to determine the N-fold flash flood disaster-prone environmental type zoning CE. N Hit rate was used to assess the disaster-prone environmental type zoning CE' and N-fold disaster-prone environmental type zoning CE for flash floods. N The degree of agreement is expressed as the mean and standard deviation of the hit rate; if the hit rate reaches 95% or higher, then the flash flood disaster-prone environment type zoning CE' is taken as the preliminary flash flood disaster-prone environment type zoning; the hit rate calculation formula is:

[0016]

[0017] In the formula, PAC q It is the q-fold hit rate, 1≤q≤N; PC iq It is the disaster-inducing environmental type of the i-th historical flash flood disaster event in the q-compromise, 1≤i≤m q PC iq ∈CE N AC iAC represents the disaster-inducing environmental type of the i-th historical flash flood disaster event among all historical flash flood disaster events. i ∈CE';m q It represents the number of historical flash flood disasters;

[0018] in:

[0019]

[0020] The specific process for determining the final disaster-prone environmental type zoning for flash floods is as follows: The Kruskal-Wallis test is used to assess the significant differences in all environmental factors within each disaster-prone environmental type zoning. If the calculated significance level p < 0.01, it indicates a significant difference in environmental factors between zoning areas. If there are more than two disaster-prone environmental type zoning areas, the Nemenyi test is further used to assess the significant differences between any two groups of disaster-prone environmental type zoning areas. If the calculated significance level p < 0.01, it indicates a significant difference in environmental factors between any two groups of zoning areas. A similarity test is used to assess the significant differences in flash flood disaster attributes within each disaster-prone environmental type zoning area. If the calculated significance level p < 0.01, it indicates a significant difference in flash flood disaster attributes between zoning areas. Zoning areas that pass all the above tests can be used as the final disaster-prone environmental type zoning. If the above tests are not passed, the disaster-prone environmental type zoning for flash floods is re-divided until all tests are passed.

[0021] Furthermore, the specific process for quantifying the explanatory power and uncertainty interval of different environmental categories on the changes in flash flood disaster attributes in step 3 is as follows: For a certain flash flood disaster-prone environmental type partition, the meteorological category factor, geographical category factor, socio-economic category factor and corresponding flash flood disaster attributes within the partition are randomly divided into N parts. N-1 environmental categories are selected as independent variables, and the corresponding N-1 flash flood disaster attributes are selected as response variables. The elimination trend correspondence analysis method is used to determine the length of the first ordination axis. Based on the axis length, an appropriate restricted ordination analysis method or canonical correspondence analysis method is further selected to determine the explanatory power of different environmental categories on the changes in flash flood disaster attributes. This process is repeated N times to determine the uncertainty interval of the explanatory power of each environmental category, which is expressed in the form of the mean and standard deviation of the N results.

[0022] The specific process for quantifying the explanatory power, uncertainty interval, and significance of each environmental factor on the changes in flash flood disaster attributes is as follows: For a specific flash flood disaster-prone environmental type zone, the environmental factors and corresponding flash flood disaster attributes within that zone are randomly divided into N parts. N-1 environmental factors are selected as independent variables, and the corresponding N-1 flash flood disaster attributes are selected as response variables. 999 Monte Carlo permutation tests are performed to determine the explanatory power and significance of each environmental factor on the response variable. If the significance level p < 0.01, it indicates that the environmental factor significantly affects the response variable. This process is repeated N times to determine the uncertainty interval and significance of the explanatory power of all environmental factors in the flash flood disaster-prone environmental type zone, expressed as the mean and standard deviation of the N results.

[0023] Furthermore, the specific process for determining the dominant environmental factors and their differences in effect for each disaster-prone environmental type zone in step 4 is as follows: For a specific flash flood disaster-prone environmental type zone, significant environmental factors are screened and arranged in descending order of their mean explanatory power for changes in flash flood disaster attributes. The environmental factor with the highest explanatory power is the first dominant factor, environmental factors with an explanatory power greater than or equal to 0.1 and less than that of the first dominant factor are the main dominant factors, and the remaining environmental factors are the secondary dominant factors. By comparing the ranking of the dominant environmental factors for each flash flood disaster-prone environmental type zone, the role of each environmental factor in the formation and development process of flash floods is analyzed from the perspective of hydrological genesis, and the differences in the effects of the dominant environmental factors for each disaster-prone environmental type zone are determined.

[0024] Furthermore, the specific process of constructing the meteorological-hydrological-hydrodynamic coupled numerical model of the study area in step 5 is as follows: taking small watersheds as the basic calculation unit and the location of historical flash flood disasters as the watershed outlet, the meteorological numerical model, the watershed hydrological model, and the one-dimensional and two-dimensional hydrodynamic model are coupled to construct the meteorological-hydrological-hydrodynamic coupled numerical model of the study area.

[0025] The specific process for analyzing the impact of changes in dominant environmental factors on the formation and disaster-causing processes of flash floods in the study area is as follows: For the values ​​of each dominant environmental factor in each disaster-prone environmental type zone within the study area, the values ​​of each factor are perturbed within a range of ±100% with a step size of 10%. A scenario library of dominant environmental factors is established, and each scenario is input into a calibrated meteorological-hydrological-hydrodynamic coupled numerical model to obtain the flash flood process line, inundation range, inundation depth, and inundation duration information of the study area under different environmental factor scenarios. By comparing the environmental factors and disaster attributes at the time of historical flash flood disasters, the impact of changes in dominant environmental factors on the formation and disaster-causing processes of flash floods in the study area is quantified.

[0026] The beneficial effects of this invention are as follows: The method described in this invention fully considers the spatiotemporal heterogeneity of meteorological, geographical, and socioeconomic factors in disaster-stricken watersheds, separates and quantifies the contributions and uncertainties of different environmental factors such as meteorology, geography, and socioeconomic factors to the formation and disaster-causing of flash floods, and analyzes the formation mechanism of flash floods under different disaster-prone environmental types. The method described in this invention can achieve differentiated prevention and control of flash floods, improve the comprehensive prevention and control level of flash floods, has strong applicability, and provides a scientific basis for the prevention and management of flash floods.

[0027] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the method flow described in this invention;

[0029] Figure 2 This refers to the explanatory power and uncertainty range of different environmental categories on the changes in flash flood disaster attributes in Example 1;

[0030] Figure 3 This represents the explanatory power and uncertainty range of each environmental factor in Example 1 regarding the changes in the attributes of flash flood disasters. Detailed Implementation

[0031] This invention discloses a method for analyzing the formation and disaster-causing mechanism of flash floods based on disaster-prone environments, such as... Figure 1 As shown, the method includes the following steps:

[0032] Step 1: Construct the set of historical flash flood disaster attributes and environmental factors for the study area:

[0033] First, environmental factor data for each environmental category within the study area, as well as attribute data for historical flash flood disasters, were collected and organized. Environmental categories include meteorological, geographical, and socioeconomic categories, with corresponding environmental factors including meteorological, geographical, and socioeconomic factors. Meteorological factors include humidity, flood season precipitation, and short-duration extreme rainfall characteristics (including magnitude, variability, and concentration) for the year the flash flood disaster occurred. Geographical factors include watershed topographic relief, slope, forest area ratio, grassland area ratio, farmland area ratio, soil saturation moisture content, river length, river gradient, and river meandering for the year the flash flood disaster occurred. Socioeconomic factors include GDP and population density for the year the flash flood disaster occurred, and water conservancy investment prior to the event. Attribute data for historical flash flood disasters include disaster location, time of occurrence, number of deaths or missing persons, number of collapsed houses, and direct economic losses.

[0034] Then, taking the watershed where the historical flash flood disaster occurred as the unit and the time of the historical flash flood disaster as the benchmark, a set of historical flash flood disaster attributes and a corresponding set of environmental factors for the study area are constructed.

[0035] Step 2: Determine the zoning of flash flood-prone environments and their characteristics:

[0036] Based on the historical flash flood disaster attribute set and environmental factor set of the study area constructed in step 1, the flash flood disaster-prone environmental type zoning is preliminarily determined. Specifically: clustering algorithms (dynamic K-means clustering, hierarchical clustering, or SOM clustering, etc.) are used to classify all historical flash flood disaster-related environmental factors in the environmental factor set of the study area to determine the flash flood disaster-prone environmental type zoning CE'; the N-fold uncertainty analysis method is used to randomly divide the environmental factor set of the study area into N parts, and N-1 parts of environmental factor data are selected for cluster analysis. This process is repeated N times to determine the N-fold flash flood disaster-prone environmental type zoning CE'. N Hit rate was used to assess the disaster-prone environmental type zoning CE' and N-fold disaster-prone environmental type zoning CE for flash floods. N The accuracy and hit rate are calculated using the formula (1), and the results are expressed as the mean and standard deviation of the hit rate. If the hit rate reaches 95% or more, then the mountain torrent disaster-prone environment type zoning CE' is taken as the preliminary mountain torrent disaster-prone environment type zoning.

[0037]

[0038] In the formula, PAC q It is the q-fold hit rate, 1≤q≤N; PC iq It is the disaster-inducing environmental type of the i-th historical flash flood disaster event in the q-compromise, 1≤i≤m q PC iq ∈CE N AC i AC represents the disaster-inducing environmental type of the i-th historical flash flood disaster event among all historical flash flood disaster events. i ∈CE';m q It represents the number of historical flash flood disasters.

[0039] in:

[0040]

[0041] Then, the significant differences in all environmental factors and flash flood attributes within the preliminary flash flood disaster-prone environmental type zoning are assessed to determine the final flash flood disaster-prone environmental type zoning. Specifically: the Kruskal-Wallis test is used to assess the significant differences in all environmental factors within each disaster-prone environmental type zoning. If the calculated significance level p < 0.01, it indicates that there are significant differences in environmental factors between zonings. If there are more than two disaster-prone environmental type zonings, the Nemenyi test is further used to assess the significant differences between any two groups of disaster-prone environmental type zonings. If the calculated significance level p < 0.01, it indicates that there are significant differences in environmental factors between any two groups of zonings. The similarity test (Analysis of Similarities) is used to assess the significant differences in flash flood attributes within each disaster-prone environmental type zoning. If the calculated significance level p < 0.01, it indicates that there are significant differences in flash flood attributes between zonings. Zonings that pass the above tests can be used as the final disaster-prone environmental type zoning. If the above tests are not passed, the flash flood disaster-prone environmental type zoning is re-divided until all tests are passed.

[0042] For the determined final flash flood disaster-prone environmental type zoning, identify the meteorological category factors, geographical category factors, socio-economic category factors, and flash flood disaster attribute characteristics and their spatial distribution patterns for each environmental type zoning.

[0043] Step 3: Determine the explanatory power and uncertainty range of the environmental categories and environmental factors of each zone on the changes in flash flood disaster attributes:

[0044] Using the final flash flood disaster-prone environmental type zoning determined in step 2 as the unit, the N-fold uncertainty analysis method was used to randomly select the environmental category and its environmental factors, flash flood disaster attributes of each zoning. The explanatory power and uncertainty interval of different environmental categories on the changes in flash flood disaster attributes were quantified, as were the explanatory power, uncertainty interval and significance of each environmental factor on the changes in flash flood disaster attributes.

[0045] The specific process for quantifying the explanatory power and uncertainty interval of different environmental categories on the changes in flash flood disaster attributes is as follows: For a specific flash flood disaster-prone environmental type partition, the meteorological category factor, geographical category factor, socio-economic category factor, and corresponding flash flood disaster attributes within the partition are randomly divided into N parts. N-1 environmental categories are selected as independent variables, and the corresponding N-1 flash flood disaster attributes are selected as response variables. Detrended correspondence analysis is used to determine the length of the first ordination axis. Based on the axis length, an appropriate restricted ordination analysis method (redundancy analysis or canonical correspondence analysis) is further selected to determine the explanatory power of different environmental categories on the changes in flash flood disaster attributes. This process is repeated N times to determine the uncertainty interval of the explanatory power of each environmental category, which is expressed as the mean and standard deviation of the N results.

[0046] The specific process for quantifying the explanatory power, uncertainty interval, and significance of various environmental factors on the changes in flash flood disaster attributes is as follows: For a specific flash flood disaster-prone environmental type zone, the environmental factors and corresponding flash flood disaster attributes within that zone are randomly divided into N parts. N-1 environmental factors are selected as independent variables, and the corresponding N-1 flash flood disaster attributes are selected as response variables. A Monte Carlo permutation test is performed 999 times to determine the explanatory power and significance of each environmental factor on the response variable. If the significance level p < 0.01, it indicates that the environmental factor significantly affects the response variable. This process is repeated N times to determine the uncertainty interval and significance of the explanatory power of all environmental factors in the flash flood disaster-prone environmental type zone, expressed as the mean and standard deviation of the N results.

[0047] Step 4: Determine the dominant environmental factors for each disaster-prone environmental type zone:

[0048] Based on the environmental categories and their explanatory power and uncertainty range of flash flood disaster attributes determined in step 3, causal analysis and comparative analysis were used to determine the dominant environmental factors and their differences in effect for each disaster-prone environmental type zone. Specifically, for a given flash flood disaster-prone environmental type zone, significant environmental factors were selected and ranked in descending order of their mean explanatory power for flash flood disaster attribute changes. The environmental factor with the highest explanatory power was identified as the first dominant factor, environmental factors with an explanatory power greater than or equal to 0.1 and less than that of the first dominant factor were identified as major dominant factors, and the remaining environmental factors were identified as minor dominant factors. By comparing the ranking of dominant environmental factors in each flash flood disaster-prone environmental type zone, the role of each environmental factor in the formation and development of flash floods was analyzed from a hydrological perspective, and the differences in the effects of dominant environmental factors in each disaster-prone environmental type zone were determined. Then, the disaster-causing mechanism of flash floods under each disaster-prone environmental type zone was characterized.

[0049] Step 5: Analyze the impact of changes in dominant environmental factors on the formation and disaster-causing processes of flash floods:

[0050] A coupled meteorological-hydrological-hydrodynamic numerical model for the study area was constructed. Specifically, the model uses small watersheds as the basic calculation unit and the locations of historical flash flood events as watershed outlets. It couples meteorological numerical models, watershed hydrological models, and one-dimensional and two-dimensional hydrodynamic models to construct a coupled meteorological-hydrological-hydrodynamic numerical model for the study area. The coupled model parameters are automatically optimized using measured rainfall and flood data from the watershed and historical flood trace data. For areas lacking measured data, parameter regionalization techniques are used to determine the coupled model parameters.

[0051] Then, based on the dominant environmental factors of each disaster-prone environmental type zone determined in step 4, a dominant environmental factor scenario library is set up to analyze the impact of changes in dominant environmental factors on the formation and disaster-causing processes of flash floods in the study area. Specifically, for each dominant environmental factor value in each disaster-prone environmental type zone within the study area, a perturbation is performed within ±100% of each factor value at a step size of 10%. A dominant environmental factor scenario library is set up, and each scenario is input into a calibrated meteorological-hydrological-hydrodynamic coupled numerical model to obtain information such as flash flood process lines, inundation range, inundation depth, and inundation duration in the study area under different environmental factor scenarios. By comparing the environmental factors and disaster attributes at the time of historical flash flood disasters, the impact of changes in dominant environmental factors on the formation and disaster-causing processes of flash floods in the study area is quantified.

[0052] Furthermore, corresponding disaster prevention and mitigation measures are proposed for each disaster-prone environmental type zone.

[0053] Example 1

[0054] This embodiment is an application example of the above method.

[0055] This embodiment takes the middle and upper reaches of the Liaohe River as the study area and discloses a method for analyzing the disaster-causing mechanism of flash floods based on the disaster-prone environment, including the following steps:

[0056] Step 1: Construct the set of historical flash flood disaster attributes and environmental factors for the study area:

[0057] Data on 17 environmental factors, including meteorological, geographical, and socioeconomic factors, were collected and organized within the study area, as shown in Table 1. Attribute data on 45 historical flash flood disasters in the study area from 1949 to the present were also collected, including disaster location, time of occurrence, number of deaths or missing persons, number of collapsed houses, and direct economic losses. Using the watersheds where the historical flash flood disasters occurred as units and the time of occurrence as a benchmark, a set of historical flash flood disaster attributes and corresponding environmental factor sets for the study area were constructed.

[0058] Table 1 List of collected environmental factor data

[0059]

[0060]

[0061] Step 2: Determine the zoning of flash flood-prone environments and their characteristics:

[0062] Based on the historical flash flood disaster attribute set and environmental factor set of the study area constructed in step 1, three flash flood disaster-prone environmental type zones were initially determined using the dynamic K-means clustering method. The ten-fold uncertainty analysis method was used for random sampling and cluster analysis. The hit rate statistics are shown in Table 2, all of which are greater than 95%. Therefore, the three flash flood disaster-prone environmental type zones can be used as preliminary flash flood disaster-prone environmental type zones.

[0063] Table 2 Hit Rate Statistics

[0064]

[0065]

[0066] Based on the preliminary flash flood disaster-prone environmental type zoning, the Kruskal-Wallis test and Nemenyi test were used to assess that 17 environmental factors were significantly different between the three preliminary zoning and between any two zoning groups (p<0.01). The similarity test was used to assess that flash flood disaster attributes were significantly different between the preliminary zoning (p<0.01). Therefore, the three flash flood disaster-prone environmental type zoning were determined as the final flash flood disaster-prone environmental type zoning.

[0067] For the final zoning of the disaster-prone environment for flash floods, meteorological category factors, geographical category factors, socio-economic category factors, and flash flood disaster attributes and their spatial distribution patterns were identified for each environmental type. Type 1 was mainly distributed in the northwestern part of the study area, Type 2 was mainly distributed in the central part of the study area, and Type 3 was mainly distributed in the southeastern part of the study area. Type 2 had the highest disaster intensity, followed by Type 3 and Type 1. Humidity, forest area ratio, and water conservancy investment showed an increasing trend from Type 1 to Type 3. 1-hour rainfall variability, river length, and farmland area ratio showed a decreasing trend from Type 1 to Type 3. Type 1 had the highest 1-hour rainfall concentration and grassland area ratio, while Type 2 had the lowest. Type 2 had the highest flood season precipitation, 1-hour rare rainstorm, river meandering rate, GDP, and population density, while Type 1 had the lowest. Type 3 had the highest topographic relief, slope, soil saturated moisture content, and river gradient, while Type 2 had the lowest.

[0068] Step 3: Determine the explanatory power and uncertainty range of the environmental categories and environmental factors of each zone on the changes in flash flood disaster attributes:

[0069] Using the final flash flood disaster-prone environmental type zoning determined in step 2 as the unit, the environmental category and its environmental factors, as well as flash flood disaster attributes, of each zoning were randomly selected using the ten-fold uncertainty analysis method. The results of the eliminated trend correspondence analysis showed that the length of the first ordination axis was less than 1.65 times the standard deviation. Therefore, redundancy analysis was chosen to quantify the explanatory power and uncertainty range of different environmental categories on the changes in flash flood disaster attributes. Figure 2 As shown. The explanatory power, uncertainty range, and significance of each environmental factor for the changes in flash flood disaster attributes are as follows. Figure 3 As shown.

[0070] Step 4: Determine the dominant environmental factors for each disaster-prone environmental type zone:

[0071] Based on the explanatory power and uncertainty range of each disaster-prone environmental type zone determined in Step 3 for the environmental categories and their environmental factors, causal analysis and comparative analysis were used to determine the dominant environmental factors and their differences in effect for each disaster-prone environmental type zone. Type 1 has 15 dominant environmental factors, with the primary dominant factor being flood season precipitation. The main dominant environmental factors are 1-hour rainfall variability, soil saturated moisture content, forest area percentage, grassland area percentage, humidity, slope length, farmland area percentage, water conservancy investment, river length, GDP, population density, and 1-hour rare rainstorm. The secondary dominant environmental factors are river gradient and topographic relief. Type 2 has 16 dominant environmental factors, with the primary dominant factor being flood season precipitation. The main dominant environmental factors are 1-hour rainfall variability, 1-hour rare rainstorm, 1-hour rainfall concentration, humidity, and grassland area percentage. The primary environmental factors include forest area ratio, farmland area ratio, river gradient, and population density. Secondary dominant environmental factors include GDP, water conservancy investment, slope length, river length, soil saturation moisture content, and river meandering. Type 3 has 16 dominant environmental factors. The primary dominant environmental factor is 1-hour rare rainstorm. The main dominant environmental factors are flood season precipitation, 1-hour rainfall variability, 1-hour rainfall concentration, humidity, grassland area ratio, soil saturation moisture content, population density, GDP, river meandering, and forest area ratio. Secondary dominant environmental factors include river gradient, slope length, water conservancy investment, topographic relief, and farmland area ratio.

[0072] From the perspective of hydrological genesis, considering the roles and differences of various dominant environmental factors, the formation and disaster-causing mechanisms of flash floods under different disaster-prone environmental types are characterized. The formation and disaster-causing mechanism of flash floods in Type 1 is as follows: In arid climates, the watershed, dominated by farmland, has poor water storage capacity. High altitude variations and concentrated short-duration rainfall lead to rapid rises in flash flood gullies with small flood volumes. Due to low economic development and poor disaster mitigation capabilities, the disaster intensity caused by flooding of riverside villages is low. The formation and disaster-causing mechanism of flash floods in Type 2 is as follows: In humid climates, the watershed, dominated by grassland... Type 3 flash floods have a low water storage capacity. Frequent high-intensity rainfall leads to rapid rise of flash floods in mountain gullies, inundating riverside villages and villages on higher ground due to poor drainage. The disaster intensity is high due to the high level of economic development and moderate disaster reduction capacity. The formation and disaster-causing mechanism of Type 3 flash floods is as follows: Under humid climates, steep watersheds dominated by forests have a strong water storage capacity. Frequent high-intensity concentrated rainfall leads to rapid rise of flash floods in mountain gullies, inundating riverside villages and causing compound flash flood disasters due to the coupling effect of water and sediment. The disaster intensity is moderate due to the moderate level of economic development and strong disaster reduction capacity.

[0073] Step 5: Analyze the impact of changes in dominant environmental factors on the formation and disaster-causing processes of flash floods:

[0074] at 0.5km 2To extract small watersheds based on the catchment area threshold, and using these small watersheds as the basic calculation unit, with the locations of historical flash flood events as the watershed outlets, a coupled meteorological-hydrological-hydraulic numerical model for the study area was constructed. The coupled model parameters were automatically optimized using 20 rainfall and flood events and 10 historical flood trace events in the study area. The relative errors of the average peak flow, the average peak time, and the average inundation depth for all events were 10%, 1 hour, and 8 cm, respectively.

[0075] For the dominant environmental factors of each disaster-prone environmental type zone determined in step 4, the factors are perturbed within a range of ±100% with a step size of 10%. A dominant environmental factor scenario library is set up, and each scenario is input into the calibrated meteorological-hydrological-hydrodynamic coupled numerical model to obtain information such as flash flood process lines, inundation range, inundation depth, and inundation duration in the study area under different environmental factor scenarios. By comparing the environmental factors and disaster attributes when historical flash floods occurred, the impact of changes in dominant environmental factors on the formation and disaster-causing processes of flash floods in the study area is quantified. Among them, the peak flow and inundation range of flash floods of type 1 are significantly affected by factors such as watershed flood season precipitation, 1-hour rainfall variability, soil saturation moisture content, and forest area ratio. The peak flow and inundation range of flash floods of type 2 are significantly affected by factors such as watershed flood season precipitation, 1-hour rainfall variability, 1-hour rare rainstorm, 1-hour rainfall concentration, forest area ratio, farmland area ratio, river gradient, population density, and GDP. The peak flow and inundation range of flash floods of type 3 are significantly affected by factors such as watershed 1-hour rare rainstorm, flood season precipitation, 1-hour rainfall variability, and 1-hour rainfall concentration.

[0076] Furthermore, disaster prevention and mitigation measures are proposed for different disaster-prone environmental types. For Type 1, the focus should be on afforestation to increase the soil saturation moisture content of the watershed and on improving the monitoring capacity of the watershed by constructing a network of rainfall and flash flood monitoring stations in the upstream watershed of villages. For Type 2, the focus should be on returning farmland to forest to improve the watershed's soil water storage capacity and reduce runoff capacity. Flash flood disaster forecasting and early warning models should be developed for flash flood disaster forecasting and early warning. These models should be applicable to frequent heavy rainfall events, extending the early warning period for flash floods, improving emergency preparedness, and reducing the mortality rate due to disasters. River straightening should be implemented to improve river discharge capacity. For Type 3, the focus should be on remote sensing and radar rainfall measurement in high-altitude areas where conventional rainfall monitoring is difficult to carry out to eliminate monitoring blind spots. The development of comprehensive prevention and control technologies for multi-hazard and complex flash flood disasters should be carried out, as well as the construction of sluice gates to impound floodwaters.

[0077] Finally, it should be noted that the above description is only used to illustrate the technical solution of the present invention and not to limit it. Although the present invention has been described in detail with reference to the preferred arrangement, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for analyzing the formation and disaster-causing mechanism of flash floods based on disaster-prone environments, characterized in that, The method includes the following steps: Step 1: Constructing the historical flash flood disaster attribute set and environmental factor set for the study area: Collect and organize environmental factor data for each environmental category within the study area, as well as attribute data for historical flash flood disaster events within the study area. The environmental categories include meteorological, geographical, and socioeconomic categories. The environmental factors include meteorological, geographical, and socioeconomic factors. The attribute data for historical flash flood disaster events include the location of the disaster, the time of occurrence, the number of deaths or missing persons, the number of collapsed houses, and the direct economic losses. Then, using the watershed where the historical flash flood disaster event occurred as the unit and the time of occurrence of the historical flash flood disaster event as the benchmark, construct the historical flash flood disaster attribute set and the corresponding environmental factor set for the study area. Step 2: Determine the zoning of flash flood disaster-prone environmental types and their characteristics: Based on the historical flash flood disaster attribute set and corresponding environmental factor set of the study area constructed in Step 1, determine the preliminary zoning of flash flood disaster-prone environmental types. Then, assess the significant differences of all environmental factors and flash flood disaster attributes in the preliminary zoning of flash flood disaster-prone environmental types to determine the final zoning of flash flood disaster-prone environmental types. For the determined final zoning of flash flood disaster-prone environmental types, identify the meteorological category factors, geographical category factors, socio-economic category factors, and flash flood disaster attribute characteristics and their spatial distribution patterns for each environmental type. Step 3: Determine the explanatory power and uncertainty range of the environmental categories and environmental factors of each zone on the changes in flash flood disaster attributes: Taking the final flash flood disaster-prone environmental type zones determined in Step 2 as units, the N-fold uncertainty analysis method is used to randomly select the environmental categories and environmental factors of each zone, as well as the flash flood disaster attributes. The explanatory power and uncertainty range of different environmental categories on the changes in flash flood disaster attributes are quantified, as are the explanatory power, uncertainty range, and significance of each environmental factor on the changes in flash flood disaster attributes. Step 4: Determine the dominant environmental factors of each disaster-prone environmental type zone: Based on the environmental categories of each zone and the explanatory power and uncertainty range of their environmental factors on the changes in flash flood disaster attributes determined in Step 3, the dominant environmental factors and their differences in effect are determined by causal analysis and comparative analysis, and the formation and disaster-causing mechanism of flash floods under each disaster-prone environmental type zone are characterized. Step 5: Analyze the impact of changes in dominant environmental factors on the formation and disaster-causing processes of flash floods: Construct a coupled meteorological-hydrological-hydraulic numerical model for the study area. Automatically optimize the coupled model parameters using measured rainfall and flood data and historical flood trace data from the watershed. For areas lacking measured data, parameter regionalization techniques are used to determine the coupled model parameters. Then, based on the dominant environmental factors for each disaster-prone environmental type zone determined in Step 4, establish a scenario library of dominant environmental factors and analyze the impact of changes in dominant environmental factors on the formation and disaster-causing processes of flash floods in the study area. Finally, propose corresponding disaster prevention and mitigation measures for each disaster-prone environmental type zone.

2. The method for analyzing the disaster-causing mechanism of flash floods based on disaster-prone environments according to claim 1, characterized in that, The meteorological category factors mentioned in step 1 include humidity, flood season precipitation, and short-duration extreme rainfall characteristics in the year in which the flash flood disaster occurred. The short-duration extreme rainfall characteristics include magnitude, variability, and concentration. The geographical category factors include the basin topographic relief, slope, forest area ratio, grassland area ratio, farmland area ratio, soil saturation moisture content, river length, river gradient, and river meandering in the year in which the flash flood disaster occurred. The socio-economic category factors include GDP and population density in the year in which the flash flood disaster occurred, and water conservancy investment before the flash flood disaster occurred.

3. The method for analyzing the disaster-causing mechanism of flash floods based on disaster-prone environments according to claim 1, characterized in that, The specific process for determining the preliminary flash flood disaster-prone environmental type zoning in step 2 is as follows: Clustering algorithms were used to classify all historical flash flood disaster-related environmental factors in the study area's environmental factor set, determining the flash flood disaster-prone environmental type zoning CE'. N-fold uncertainty analysis was then used to randomly divide the study area's environmental factor set into N parts, selecting N-1 parts for cluster analysis, repeating this process N times to determine the N-fold flash flood disaster-prone environmental type zoning CE. N Hit rate was used to assess the disaster-prone environmental type zoning CE' and N-fold disaster-prone environmental type zoning CE for flash floods. N The degree of agreement is expressed as the mean and standard deviation of the hit rate; if the hit rate reaches 95% or higher, then the flash flood disaster-prone environment type zoning CE' is taken as the preliminary flash flood disaster-prone environment type zoning; the hit rate calculation formula is: In the formula, PAC q It is the q-fold hit rate, 1≤q≤N; PC iq It is the disaster-inducing environmental type of the i-th historical flash flood disaster event in the q-compromise, 1≤i≤m q PC iq ∈CE N AC i AC represents the disaster-inducing environmental type of the i-th historical flash flood disaster event among all historical flash flood disaster events. i ∈CE';m q It represents the number of historical flash flood disasters; in: The specific process for determining the final disaster-prone environmental type zoning for flash floods is as follows: The Kruskal-Wallis test is used to assess the significant differences of all environmental factors in each disaster-prone environmental type zoning. If the calculated significance level p < 0.01, it indicates that there are significant differences in environmental factors between the zoning. If there are more than two disaster-prone environmental type zoning, the Nemenyi test is further used to assess the significant differences between any two groups of disaster-prone environmental type zoning. If the calculated significance level p < 0.01, it indicates that there are significant differences in environmental factors between any two groups of zoning. Similarity tests were used to assess the significant differences in flash flood disaster attributes among different disaster-prone environmental type zones. If the calculated significance level p < 0.01, it indicates that there are significant differences in flash flood disaster attributes among different zones. Zones that pass the above tests can be used as the final disaster-prone environmental type zones. If the above tests are not passed, the flash flood disaster-prone environmental type zones are re-divided until all tests are passed.

4. The method for analyzing the disaster-causing mechanism of flash floods based on disaster-prone environments according to claim 1, characterized in that, The specific process for quantifying the explanatory power and uncertainty interval of different environmental categories on the changes in flash flood disaster attributes in step 3 is as follows: For a certain flash flood disaster-prone environmental type partition, the meteorological category factor, geographical category factor, socio-economic category factor and corresponding flash flood disaster attributes within the partition are randomly divided into N parts. N-1 environmental categories are selected as independent variables, and the corresponding N-1 flash flood disaster attributes are selected as response variables. The elimination trend correspondence analysis method is used to determine the length of the first ordination axis. Based on the axis length, an appropriate restricted ordination analysis method or canonical correspondence analysis method is further selected to determine the explanatory power of different environmental categories on the changes in flash flood disaster attributes. This process is repeated N times to determine the uncertainty interval of the explanatory power of each environmental category, which is expressed in the form of the mean and standard deviation of the N results. The specific process for quantifying the explanatory power, uncertainty interval, and significance of each environmental factor on the changes in flash flood disaster attributes is as follows: For a specific flash flood disaster-prone environmental type zone, the environmental factors and corresponding flash flood disaster attributes within that zone are randomly divided into N parts. N-1 environmental factors are selected as independent variables, and the corresponding N-1 flash flood disaster attributes are selected as response variables. 999 Monte Carlo permutation tests are performed to determine the explanatory power and significance of each environmental factor on the response variable. If the significance level p < 0.01, it indicates that the environmental factor significantly affects the response variable. This process is repeated N times to determine the uncertainty interval and significance of the explanatory power of all environmental factors in the flash flood disaster-prone environmental type zone, expressed as the mean and standard deviation of the N results.

5. The method for analyzing the disaster-causing mechanism of flash floods based on disaster-prone environments according to claim 1, characterized in that, The specific process for determining the dominant environmental factors and their differences in effect for each disaster-prone environmental type zone in step 4 is as follows: For a specific flash flood disaster-prone environmental type zone, significant environmental factors are screened and arranged in descending order of their mean explanatory power for changes in flash flood disaster attributes. The environmental factor with the highest explanatory power is the first dominant factor, environmental factors with an explanatory power greater than or equal to 0.1 and less than that of the first dominant factor are the main dominant factors, and the remaining environmental factors are the secondary dominant factors. By comparing the ranking of the dominant environmental factors for each flash flood disaster-prone environmental type zone, the role of each environmental factor in the formation and development process of flash floods is analyzed from the perspective of hydrological genesis, and the differences in the effects of the dominant environmental factors for each disaster-prone environmental type zone are determined.

6. The method for analyzing the disaster-causing mechanism of flash floods based on disaster-prone environments according to claim 1, characterized in that, The specific process of constructing the meteorological-hydrological-hydrodynamic coupled numerical model of the study area in step 5 is as follows: taking small watersheds as the basic calculation unit and the location of historical flash flood disasters as the watershed outlet, the meteorological numerical model, the watershed hydrological model, and the one-dimensional and two-dimensional hydrodynamic model are coupled to construct the meteorological-hydrological-hydrodynamic coupled numerical model of the study area. The specific process for analyzing the impact of changes in dominant environmental factors on the formation and disaster-causing processes of flash floods in the study area is as follows: For the values ​​of each dominant environmental factor in each disaster-prone environmental type zone within the study area, the values ​​of each factor are perturbed within a range of ±100% with a step size of 10%. A scenario library of dominant environmental factors is established, and each scenario is input into a calibrated meteorological-hydrological-hydrodynamic coupled numerical model to obtain the flash flood process line, inundation range, inundation depth, and inundation duration information of the study area under different environmental factor scenarios. By comparing the environmental factors and disaster attributes at the time of historical flash flood disasters, the impact of changes in dominant environmental factors on the formation and disaster-causing processes of flash floods in the study area is quantified.

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