A method for assessing the sudden transition from drought to flood

Abstract

The present invention discloses a method for evaluating drought-flood sudden transition, comprising the following steps: S1, collecting meteorological and hydrological series data of a certain period; S2, calculating a drought-flood index based on the meteorological and hydrological series data; S3, calculating a standardized drought-flood sudden transition index using the drought-flood index; S4, classifying the obtained standardized drought-flood sudden transition index according to the drought-flood sudden transition grade classification standard. The present invention can solve the problem of misjudgment and missed judgment of drought-flood sudden transition in the prior art, and make the grade classification of drought-flood sudden transition consistent with the conventional drought-flood grade classification in terms of threshold setting and qualitative analysis, which is conducive to the unification of the drought-flood assessment system.

Description

Technical Field

[0001] The invention relates to risk assessment of natural disasters, and in particular to a method for assessing sudden transition from drought to flood. Background Art

[0002] Under the influence of global warming and human activities, extreme hydrological events such as droughts and floods coexist, and their frequency and intensity are increasing. Abnormal drought and flood phenomena mainly include drought-flood abrupt transition events, as well as the coexistence of drought and flood caused by drought-flood abrupt transitions of different scales. It is generally believed that drought-flood abrupt transition is the coexistence or alternation of drought and flood events in a short period of time, that is, the process of rapid change of the previous state, and there are drought-flood events and flood-drought events. Studies have shown that the occurrence of drought-flood abrupt transitions is more prominent in the Yangtze River Basin, Huaihe River Basin, Southwest and South China. It has gradually become a new feature and trend of drought and flood disasters in my country.

[0003] Previous researchers have used meteorological and hydrological series such as precipitation or runoff to construct drought-flood abruptness indexes of different scales and conduct quantitative assessment research on drought-flood abruptness phenomena. Existing technologies include the long-term drought-flood abruptness index LDFAI, the short-term drought-flood abruptness index SDFAI, the runoff drought-flood abruptness index RDFAI, and the daily drought-flood abruptness index DWAAI.

[0004] The calculation of the existing drought-flood sudden transition index is generally based on a standardized precipitation or runoff series of a certain time scale (such as 1-2 months), and the product formula of the difference and absolute value of two adjacent values ​​is adopted, which can better present the drought-flood sudden transition intensity term and drought-flood intensity term. And by setting the weight term (negative exponential function of the absolute value of the sum value), it is attempted to avoid the changes of two drought or flood events with relatively large differences from being misjudged as drought-flood sudden transition. However, the premise of this calculation method is that the original data series adopts 0-1 standardized transformation, and 0.5 is used as the dividing value of drought and flood events, otherwise it is difficult to avoid the problem of judgment and missed judgment. Moreover, there is currently subjective arbitrariness in the base value of the exponential function in the weight term. In addition, in drought and flood risk management, drought and flood levels are usually divided by setting thresholds based on the drought and flood index, such as the Chinese patent with publication number CN111680912 A and publication date 2020.9.18: A method for assessing the risk of drought and flood sudden transition, which constructs a probability distribution function through a threshold to assess the risk. However, when existing studies used the above method to calculate the drought-flood sudden transition index and further divided it into levels, the threshold setting was related to the standardized transformation method and the base value of the weight term exponential function, resulting in different classification standards for different researchers, which was inconsistent with the common drought-flood level classification, and was not conducive to unified cognition in drought-flood assessment and management. Summary of the invention

[0005] The present invention proposes a method for evaluating the sudden transition from drought to flood, which can solve the problems of misjudgment and missed judgment of the sudden transition from drought to flood in the existing technology, and make the grade classification of the sudden transition from drought to flood consistent with the conventional drought and flood grade classification in threshold setting and qualitative analysis, which is conducive to the unification of the drought and flood assessment system.

[0006] The technical solution of the present invention is as follows:

[0007] A method for evaluating drought-flood rapid transition comprises the following steps:

[0008] S1. Collect meteorological and hydrological series data for a certain period of time;

[0009] S2, drought and flood index calculated based on meteorological and hydrological series data;

[0010] S3. Using the drought and flood index, a standardized drought-flood transition index is calculated;

[0011] S4. Classify the obtained values ​​of the standardized drought-flood sudden transition index according to the drought-flood sudden transition classification standard.

[0012] Furthermore, the meteorological and hydrological series data in step S1 include precipitation series data or runoff series data.

[0013] Furthermore, in step S2, when the calculation is based on the precipitation series data, the drought and flood index obtained is the standardized precipitation index SPI; when the calculation is based on the runoff series data, the drought and flood index obtained is the standardized runoff index SSI.

[0014] Further, the process of calculating the drought and flood index in step S2 is as follows:

[0015] If the precipitation or runoff in a certain period is x, x>0, then the probability density function of its Γ distribution is as follows:

[0016]

[0017] Where β and γ are scale and shape parameters, respectively, β>0, γ>0;

[0018] For a period of precipitation or runoff x 0 , the random variable x is less than x 0 The probability of the event is:

[0019]

[0020] The probability of an event when precipitation or runoff is 0 is as follows:

[0021]

[0022] Where: N is the number of samples with precipitation or runoff of 0, and m is the total number of samples;

[0023] Standardize the probability of Γ distribution:

[0024]

[0025] Where: Z is the drought and flood index; c 0 =2.515517, c 1 =0.802853, c 2 =0.010328; d 1 =1.432788, d 2 =0.189269, d 3 =0.001308; F is the event probability, when F≤0.5, S=-1; when F>0.5, S=1.

[0026] Furthermore, β and γ are obtained using the maximum likelihood estimation method:

[0027]

[0028]

[0029]

[0030] Where: x i is a sample of precipitation or runoff data, is the average value of precipitation or runoff, and A is the parameter of the maximum likelihood estimation method (without practical significance).

[0031] Further, the process of calculating the standardized drought-flood sudden transition index using the drought-flood index in step S3 is as follows:

[0032]

[0033] Where: SDWAI is the standardized drought-flood transition index, Z i+1 and Z i Meteorological and hydrological series data

[0034] The drought and flood index after standardized changes at adjacent times i+1 and i, where i=1,2,…,n-1,

[0035] n is the series length, S a is the absolute distance of drought and flood index, that is:

[0036]

[0037] Furthermore, the drought-flood rapid transition classification standard in step S4 includes 9 levels, namely: extreme drought-to-flood, severe drought-to-flood, moderate drought-to-flood, mild drought-to-flood, normal, mild flood-to-drought, moderate flood-to-drought, severe flood-to-drought, and extreme flood-to-drought.

[0038] The present invention also provides a drought-flood rapid transition assessment device, comprising a data acquisition module, a drought-flood index calculation module, a standardized drought-flood rapid transition index module and a division module which are sequentially communicatively connected;

[0039] Among them, the data acquisition module is used to collect meteorological and hydrological series data for a certain period of time;

[0040] Drought and flood index calculation module: used to calculate the drought and flood index according to the meteorological and hydrological series data collected by the data collection module;

[0041] A standardized drought-flood sudden transition index module is used to calculate a standardized drought-flood sudden transition index according to the drought-flood index obtained by the drought-flood index calculation module;

[0042] Classification module: used to classify the values ​​obtained by the standardized drought-flood sudden transition index module according to the drought-flood sudden transition grade classification standard.

[0043] The present invention also provides an electronic device, including a processor, a communication interface, a memory and a communication bus, wherein the processor, the communication interface and the memory communicate with each other through the communication bus; the memory is used to store computer programs; and the processor is used to execute the programs stored in the memory to implement the above-mentioned drought-flood rapid transition assessment method.

[0044] The present invention also provides a computer-readable storage medium, in which a computer program is stored. When the computer program is executed by a processor, the above-mentioned drought-flood rapid transition assessment method is implemented.

[0045] The beneficial effects of the present invention are as follows:

[0046] The present invention calculates the drought-flood index based on the original meteorological and hydrological series data, and obtains the drought-flood sudden transition index through standardization, and classifies the drought-flood sudden transition according to the value of the drought-flood sudden transition index. The present invention avoids the problems of misjudgment and omission of drought-flood sudden transition, and makes the classification of drought-flood sudden transition consistent with the conventional drought-flood classification in terms of threshold setting and qualitative analysis, which is conducive to the unification of the drought-flood assessment system. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is a schematic flow chart of the drought-flood rapid transition assessment method of the present invention;

[0048] Figure 2 This is a schematic diagram of the classification standards for drought-flood rapid transition levels;

[0049] Figure 3 It is a schematic diagram of the monthly series data of runoff in Example 2;

[0050] Figure 4 It is a schematic diagram of the drought and flood index value in Example 2;

[0051] Figure 5 This is a schematic diagram of the standardized drought-flood transition index value in Example 2;

[0052] Figure 6 This is a schematic diagram of the drought-flood rapid transition grade assessment results in Example 2. DETAILED DESCRIPTION

[0053] The drawings are only for illustrative purposes and cannot be construed as limiting the present invention. To better illustrate the present embodiment, some parts of the drawings may be omitted, enlarged, or reduced, and do not represent the size of the actual product. For those skilled in the art, it is understandable that some well-known structures and their descriptions may be omitted in the drawings. The positional relationships described in the drawings are only for illustrative purposes and cannot be construed as limiting the present invention.

[0054] Embodiment 1:

[0055] like Figure 1 and Figure 2 As shown, a drought-flood rapid transition assessment method comprises the following steps:

[0056] S1. Collect meteorological and hydrological series data for a certain period of time;

[0057] S2, drought and flood index calculated based on meteorological and hydrological series data;

[0058] S3. Using the drought and flood index, a standardized drought-flood transition index is calculated;

[0059] S4. Classify the obtained values ​​of the standardized drought-flood sudden transition index according to the drought-flood sudden transition classification standard.

[0060] Among them, the meteorological and hydrological series data in step S1 include precipitation series data or runoff series data. When calculated based on precipitation series data, the drought and flood index obtained is the standardized precipitation index SPI; when calculated based on runoff series data, the drought and flood index obtained is the standardized runoff index SSI.

[0061] In this embodiment, the process of calculating the drought and flood index in step S2 is as follows:

[0062] If the precipitation or runoff in a certain period is x, x>0, then the probability density function of its Γ distribution is as follows:

[0063]

[0064] Where β and γ are scale and shape parameters, respectively, β>0, γ>0;

[0065] β and γ are obtained using the maximum likelihood estimation method:

[0066]

[0067]

[0068]

[0069] Where: x i is a sample of precipitation or runoff data, is the average value of precipitation or runoff, and A is the parameter of the maximum likelihood estimation method.

[0070] After determining the parameters of the probability density function, for a certain period of time, the precipitation or runoff x 0 , we can find that the random variable x is less than x 0 The probability of the event is:

[0071]

[0072] By using numerical integration, we can calculate the approximate estimated value of the event probability after substituting equation (1) into equation (5).

[0073] The probability of an event when precipitation or runoff is 0 is as follows:

[0074]

[0075] Where: N is the number of samples with precipitation or runoff of 0, and m is the total number of samples;

[0076] Standardize the probability of Γ distribution:

[0077]

[0078] Where: Z is the drought and flood index; c 0 =2.515517, c 1 =0.802853, c 2 =0.010328; d 1 =1.432788, d 2 =0.189269, d 3 =0.001308; F is the event probability obtained by formula (5) or formula (6). When F≤0.5, S=-1; when F>0.5, S=1.

[0079] In this embodiment, the process of calculating the standardized drought-flood transition index using the drought-flood index in step S3 is as follows (8):

[0080]

[0081] Where: SDWAI is the standardized drought-flood transition index, Z i+1 and Z i Meteorological and hydrological series data

[0082] The drought and flood index after standardized changes at adjacent times i+1 and i, where i=1,2,…,n-1,

[0083] n is the series length, S a is the absolute distance of drought and flood index, that is:

[0084]

[0085] Formula (8) uses conditional judgment to assign a value of 0 when the adjacent values ​​of the drought and flood index series are the same drought, the same flood, or there is neither drought nor flood. Further calculation is given when the adjacent values ​​are drought and flood respectively. is the drought-flood transition intensity item. In this way, when setting the threshold for drought-flood transition classification, it can be consistent with the drought-flood classification standard. For example, when the adjacent drought-flood indexes are -1.5 and 1.5, which are the thresholds for severe drought and severe flood, respectively, When the adjacent drought-flood index is 1.5 and -1.5, which are the thresholds of severe flood and severe drought respectively, It is -1.5, which can be considered the threshold for severe flooding to drought.

[0086] It is a weight item, and its purpose is to appropriately increase the weight of asymmetric drought-flood transition situations.

[0087] See also Figure 2 In this embodiment, the drought-flood rapid transition classification standard in step S4 includes 9 levels, namely: extreme drought-to-flood, severe drought-to-flood, moderate drought-to-flood, mild drought-to-flood, normal, mild flood-to-drought, moderate flood-to-drought, severe flood-to-drought, and extreme flood-to-drought.

[0088] The present invention also provides a drought-flood rapid transition assessment device, comprising a data acquisition module, a drought-flood index calculation module, a standardized drought-flood rapid transition index module and a division module which are sequentially communicatively connected;

[0089] Among them, the data acquisition module is used to collect meteorological and hydrological series data for a certain period of time;

[0090] Drought and flood index calculation module: used to calculate the drought and flood index according to the meteorological and hydrological series data collected by the data collection module;

[0091] A standardized drought-flood sudden transition index module is used to calculate a standardized drought-flood sudden transition index according to the drought-flood index obtained by the drought-flood index calculation module;

[0092] Classification module: used to classify the values ​​obtained by the standardized drought-flood sudden transition index module according to the drought-flood sudden transition grade classification standard.

[0093] The present invention also provides an electronic device, including a processor, a communication interface, a memory and a communication bus, wherein the processor, the communication interface and the memory communicate with each other through the communication bus; the memory is used to store computer programs; and the processor is used to execute the programs stored in the memory to implement the above-mentioned drought-flood rapid transition assessment method.

[0094] The present invention also provides a computer-readable storage medium, in which a computer program is stored. When the computer program is executed by a processor, the above-mentioned drought-flood rapid transition assessment method is implemented.

[0095] Embodiment 2:

[0096] Taking the sudden change from drought to flood in a certain river basin for many years as the analysis object of the present invention, the specific calculation and analysis steps are as follows:

[0097] 1. Collect the monthly series data of natural runoff from the basin control hydrological stations for many years, such as Figure 3 As shown;

[0098] 2. Substitute the monthly series data into formula (7) to calculate the drought and flood index. The data used in this case is runoff data, that is, the standardized runoff index SSI is calculated, and the drought and flood index value is obtained as follows: Figure 4 As shown;

[0099] 3. Substitute the standardized runoff index SSI value into formula (8) to calculate the standardized drought-flood transition index (SDWAI) value, as follows: Figure 5 As shown;

[0100] 4. According to the classification standards of drought-flood sudden transition in Table 1, determine the level of drought-flood sudden transition, such as Figure 6 shown.

[0101] The present invention calculates the drought-flood index based on the original meteorological and hydrological series data, and obtains the drought-flood sudden transition index through standardization, and classifies the drought-flood sudden transition according to the value of the drought-flood sudden transition index. The present invention avoids the problems of misjudgment and omission of drought-flood sudden transition, and makes the classification of drought-flood sudden transition consistent with the conventional drought-flood classification in terms of threshold setting and qualitative analysis, which is conducive to the unification of the drought-flood assessment system.

[0102] Obviously, the above embodiments of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A method for assessing drought-flood transition, characterized in that: The following steps are involved: S1, collecting meteorological and hydrological series data for a certain period of time; the meteorological and hydrological series data in step S1 is precipitation series data or runoff series data; S2, calculating the drought and flood index based on the meteorological and hydrological series data; the process of calculating the drought and flood index in step S2 is as follows: If the precipitation or runoff in a certain period is x, x>0, then the probability density function of its Γ distribution is as follows: Where β and γ are scale and shape parameters, respectively, β>0, γ>0; For a period of precipitation or runoff x0, the probability of the event when the random variable x is less than x0 is: The probability of an event when precipitation or runoff is 0 is as follows: Where: N is the number of samples with precipitation or runoff of 0, and m is the total number of samples; Standardize the probability of Γ distribution: Where: Z is the drought and flood index; c0 = 2.515517, c1 = 0.802853, c2 = 0.010328; d1 = 1.432788, d2 = 0.189269, d3 = 0.001308; F is the event probability, when F ≤ 0.5, S=-1; when F>0.5, S = 1; β and γ are obtained using the maximum likelihood estimation method: Where: x i is a sample of precipitation or runoff data, is the average value of precipitation or runoff, and A is the parameter of the maximum likelihood estimation method; S3, using the drought and flood index, calculate the standardized drought and flood sudden transition index; the process of calculating the standardized drought and flood sudden transition index using the drought and flood index in step S3 is as follows: Where: SDWAI is the standardized drought-flood transition index, Z i+1 and Z i are the drought and flood indices of the meteorological and hydrological series data at adjacent times i+1 and i after standardized changes, where i=1,2,…,n-1, n is the series length, S a is the absolute distance of drought and flood index, that is: S4. According to the drought-flood transition grade classification standard, the obtained standardized drought-flood transition index value is graded; the drought-flood transition grade classification standard in step S4 is 9 levels, namely: extreme drought-to-flood, severe drought-to-flood, moderate drought-to-flood, mild drought-to-flood, normal, mild flood-to-drought, moderate flood-to-drought, severe flood-to-drought, and extreme flood-to-drought.

2. A drought-flood rapid transition assessment method according to claim 1, characterized in that: In step S2, when the calculation is based on precipitation series data, the drought and flood index obtained is the standardized precipitation index SPI; when the calculation is based on runoff series data, the drought and flood index obtained is the standardized runoff index SSI.

3. A drought-flood rapid transition assessment device, characterized in that: It includes a data acquisition module, a drought and flood index calculation module, a standardized drought and flood sudden change index module and a division module which are sequentially connected in communication; Among them, the data acquisition module is used to collect meteorological and hydrological series data for a certain period of time; the meteorological and hydrological series data include precipitation series data or runoff series data; Drought and flood index calculation module: used to calculate the drought and flood index according to the meteorological and hydrological series data collected by the data collection module; the process of calculating the drought and flood index is as follows: If the precipitation or runoff in a certain period is x, x>0, then the probability density function of its Γ distribution is as follows: Where β and γ are scale and shape parameters, respectively, β>0, γ>0; For a period of precipitation or runoff x0, the probability of the event when the random variable x is less than x0 is: The probability of an event when precipitation or runoff is 0 is as follows: Where: N is the number of samples with precipitation or runoff of 0, and m is the total number of samples; Standardize the probability of Γ distribution: Where: Z is the drought and flood index; c0 = 2.515517, c1 = 0.802853, c2 = 0.010328; d1 = 1.432788, d2 = 0.189269, d3 = 0.001308; F is the event probability, when F ≤ 0.5, S=-1; when F>0.5, S = 1; β and γ are obtained using the maximum likelihood estimation method: Where: x i is a sample of precipitation or runoff data, is the average value of precipitation or runoff, and A is the parameter of the maximum likelihood estimation method; The standardized drought-flood sudden transition index module is used to calculate the standardized drought-flood sudden transition index according to the drought-flood index obtained by the drought-flood index calculation module. The process of calculating the standardized drought-flood sudden transition index using the drought-flood index is as follows: Where: SDWAI is the standardized drought-flood transition index, Z i+1 and Z i are the drought and flood indices of the meteorological and hydrological series data at adjacent times i+1 and i after standardized changes, where i=1,2,…,n-1, n is the series length, S a is the absolute distance of drought and flood index, that is: Classification module: used to classify the values ​​obtained by the standardized drought-flood sudden transition index module according to the drought-flood sudden transition classification standard; the drought-flood sudden transition classification standard has 9 levels, namely: extreme drought to flood, severe drought to flood, moderate drought to flood, mild drought to flood, normal, mild flood to drought, moderate flood to drought, severe flood to drought, and extreme flood to drought.

4. An electronic device, characterized in that: It includes a processor, a communication interface, a memory and a communication bus, wherein the processor, the communication interface and the memory communicate with each other through the communication bus; the memory is used to store computer programs; the processor is used to execute the programs stored in the memory to implement the drought-flood rapid transition assessment method described in any one of claims 1-2.

5. A computer-readable storage medium, characterized in that: A computer program is stored in the computer-readable storage medium, and when the computer program is executed by the processor, the drought-flood rapid transition assessment method described in any one of claims 1-2 is implemented.

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