Method, system, storage medium and equipment for determining occurrence time and frequency of debris flow in depopulated area based on lichen size

Abstract

The invention discloses a method, a system, a storage medium and equipment for determining the occurrence time and frequency of debris flow in an unmanned area based on the size of lichen, and relates to the technical field of geological disaster monitoring and dating, and the method comprises the steps of S1, condition setting, S2, lichen data acquisition, S3, lichen growth rate fitting, and S4, time and frequency determination. The method is characterized in that the exposure time of lichens is calculated according to the average diameter of ground clothes and the actual growth rate of the lichens in combination with the initial diameter of the lichens, the occurrence time of debris flow is determined according to the exposure time of the ground clothes, and the occurrence frequency of the debris flow is obtained according to the occurrence time of the debris flow. The technical problem that the time and frequency of debris flow events in depopulated areas are difficult to determine is effectively solved.

Description

Technical Field

[0001] This invention relates to the field of geological disaster monitoring and dating technology, specifically to a method, system, storage medium, and equipment for determining the occurrence time and frequency of debris flows in uninhabited areas based on lichen size. Background Technology

[0002] Debris flows, a common natural disaster, mostly occur in mountainous valleys and are characterized by their sudden onset and destructive power, causing numerous casualties and property losses every year. With the development of uninhabited areas such as the western plateaus and mountains in my country, many major projects (such as roads and power transmission lines) need to pass through these areas. A high frequency of debris flows in a region indicates a significant geological hazard risk, requiring targeted prevention and control measures. However, in uninhabited areas, due to the lack of long-term monitoring equipment and historical records, the timing and frequency of debris flows are difficult to determine accurately, making it impossible to assess their frequency and scale, thus posing safety hazards to engineering construction.

[0003] Currently, the main methods for determining the timing of debris flows include historical disaster statistics, remote sensing monitoring, and on-site geological surveys. However, these methods have significant limitations in uninhabited areas: historical statistics have low applicability due to data gaps; remote sensing monitoring is costly, has limited resolution, and struggles to obtain long-term data; and on-site surveys are limited by rugged terrain and poor accessibility. Furthermore, existing technologies rarely use biomarkers to infer debris flow timing, resulting in unsatisfactory application results in data-scarce areas.

[0004] Lichen dating, as a biogeological dating method, has been used to determine the age of geological events such as glacial deposits and earthquakes. Lichens are algal-fungal symbiotic organisms whose growth rate is related to environmental conditions, and their diameter increases with exposure time. However, traditional lichen dating has focused primarily on glacial or earthquake events, with limited application to debris flow events and a lack of systematic methods. Especially in uninhabited areas, the growth record of lichens within debris flow channels is not fully utilized, making it impossible to accurately extrapolate the time of debris flows. Therefore, it is necessary to develop a new technique based on lichen size to determine the time and frequency of debris flows, addressing the challenge of determining debris flow occurrence time in uninhabited areas where data is scarce. Summary of the Invention

[0005] To address the shortcomings and defects of the existing technology, this invention proposes a method, system, storage medium, and equipment for determining the occurrence time and frequency of debris flows in uninhabited areas based on lichen size. This method is applicable to debris flow gullies suitable for lichen growth and unaffected by human activity. It aims to determine the occurrence time and frequency of debris flows by measuring the size of lichens within the debris flow gully and combining this with the lichen growth rate to infer the lichen's exposure time. This solves the technical problem of the difficulty in determining the age and frequency of debris flow events in uninhabited areas.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This invention provides a method for determining the occurrence time and frequency of debris flows in uninhabited areas based on lichen size, comprising the following steps: S1: Condition Setting After a debris flow event occurs in the uninhabited research area, lichens begin to grow on the surface of the boulders in the debris flow channel, and the diameter of the lichens is positively correlated with the exposure time. The lichen growth stage is assumed to be linear, and the influence of the time difference between the start of lichen growth and the exposure of the boulders to the surface is ignored.

[0007] S2: Lichen Data Collection Select suitable lichen species for dating, then select several angular boulders in the debris flow channel, measure the longest axis diameter of the largest lichen species on each boulder, and calculate the average diameter of the lichen. S3: Lichen growth rate fitting Based on debris flow events with known exact times in the vicinity, historical reference sizes of lichens are obtained. The average diameter and growth time of lichens are then fitted based on these historical reference sizes to obtain the actual growth rate of lichens in the uninhabited study area. S4: Determining Time and Frequency Based on the average diameter and actual growth rate of the lichen, the exposure time of the lichen is calculated in combination with its initial diameter. The occurrence time of debris flows is determined based on the exposure time of the lichen, and the occurrence frequency of debris flows is derived based on the occurrence time of debris flows.

[0008] In step S2, selecting suitable lichen species for dating means selecting lichens that are easy to identify and measure, have a moderate growth rate, and are of a single variety. Lichens that are easy to identify specifically include yellow-green map lichen, Lithops yellow lichen, tea-stained lichen, or plum lichen. Lichens that are easy to measure are those with a shape close to a circle. Lichens of a single variety are those that do not grow or attach together with other lichens.

[0009] In step S2, the number of rolling stones is 10-50.

[0010] In step S2, the method for calculating the average diameter of lichens is as follows: first, remove the maximum and minimum values ​​from the measured data, and then calculate the average value based on the remaining values.

[0011] In step S4, the formula for calculating the exposure time of the lichen is: T = (Db) ÷ a In the formula, T is the exposure time of the lichen in years; D is the average diameter of the lichen in mm; b is the initial diameter of the lichen in mm; and a is the actual growth rate of the lichen in mm / year.

[0012] This invention also provides a system for determining the timing and frequency of debris flows in uninhabited areas based on lichen size, comprising: The condition setting module is used to set that after a debris flow event occurs in the unmanned research area, lichens begin to grow on the surface of the boulders in the debris flow channel, and the diameter of the lichens is positively correlated with the exposure time; the lichen growth stage is set to linear growth, and the influence of the delay time before the lichens begin to grow is ignored. The data acquisition module is used to select suitable lichen species for dating, and to select several angular boulders in the debris flow channel, measure the longest axis diameter of the largest lichen among the selected species on each boulder, and calculate the average diameter of the lichen. The fitting module is used to obtain the historical reference size of lichens based on debris flow events with known exact occurrence times in the vicinity, and to fit the average diameter and growth time of lichens based on the historical reference size to obtain the actual growth rate of lichens in the uninhabited study area. The determination module is used to calculate the exposure time of lichens based on their average diameter and actual growth rate, combined with their initial diameter; to determine the occurrence time of debris flows based on the exposure time of lichens; and to derive the frequency of debris flows based on the occurrence time of debris flows.

[0013] The present invention also provides a storage medium on which a program or instructions are stored, which, when executed by a processor, implement the steps in the above method.

[0014] The present invention also provides an electronic device, including a processor and a memory, the memory storing a program or instructions executable on the processor, the program or instructions being executed by the processor to implement the steps in the above method.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention addresses the problem of scarce debris flow data in uninhabited areas by using lichens as biomarkers. By simply measuring the size of the lichens and combining it with their growth rate, the timing and frequency of debris flow events can be accurately deduced without the need for expensive monitoring equipment, thus greatly reducing costs.

[0016] 2. Based on actual measurement data of lichens and their growth rate, this invention enables accurate determination of the occurrence time and frequency of debris flows under conditions of data scarcity, providing a basis for disaster risk assessment.

[0017] 3. This invention is easy to operate and is especially suitable for rapid application in the field, which is beneficial to engineering construction and disaster prevention planning. Attached Figure Description

[0018] Figure 1 This is a flowchart of Example 1; Figure 2 This is a diagram of lichen species suitable for dating in Example 1; Figure 3 This is a system block diagram of Example 2; Figure 4 This is a lichen measurement diagram from Example 3. Detailed Implementation

[0019] Example 1 like Figure 1 As shown, this embodiment provides a method for determining the occurrence time and frequency of debris flows in uninhabited areas based on lichen size. This method fully utilizes the characteristic that lichens grow on the boulders in the debris flow channel after a debris flow. By measuring the size of the lichens in the debris flow channel and combining this with the lichen growth rate, the exposure time of the lichens is deduced, thus determining the occurrence time and frequency of the debris flow. It includes the following steps: S1: Condition Setting After a debris flow event occurs in the uninhabited research area, lichens begin to grow on the surface of the boulders in the debris flow channel, and the diameter of the lichens is positively correlated with the exposure time. The lichen growth stage is assumed to be linear, and the influence of the time difference between the start of lichen growth and the exposure of the boulders to the surface is ignored.

[0020] S2: Lichen Data Collection like Figure 2 As shown, suitable lichen species for dating are selected. Then, several angular boulders are chosen within the debris flow channel, avoiding nearly round stones, to ensure that lichen growth began after the debris flow event and to guarantee the accuracy of subsequent measurements. The number of boulders is 10-50; for example, 30 boulders can be selected. Each boulder should have lichen of a selected species growing on it. The longest axis diameter of the largest lichen of the selected species on each boulder is then measured, and the average diameter of the lichen is calculated.

[0021] The step of selecting suitable lichen species for dating refers to choosing lichens that are easy to identify and measure, have a moderate growth rate, and are of a single variety, such as... Figure 2 As shown, easily identifiable lichens include Rhizocarpon, Xanthoria, Lecanora, or Parmelia; easily measurable lichens are those with a nearly circular shape, facilitating diameter measurement; and lichens of a single species are those that do not grow or attach together with other lichens.

[0022] The method for calculating the average diameter of lichens in this step is as follows: first, remove the maximum and minimum values ​​from the measured data, and then calculate the average value based on the remaining values ​​to ensure that the obtained data is accurate and reliable.

[0023] S3: Lichen growth rate fitting Based on debris flow events with known exact occurrence times in the vicinity, historical reference sizes of lichens were obtained. These historical reference sizes were then used to fit the average diameter and growth time of the lichens to obtain the actual growth rate of lichens in the uninhabited study area. The vicinity area refers to regions with similar climatic conditions to the study area, an elevation difference of no more than 500m, and a straight-line distance of no more than 50km, to ensure the consistency of the lichen growth environment.

[0024] S4: Determining Time and Frequency Based on the average diameter of the lichen obtained in S2 and the actual growth rate of the lichen obtained in S3, the exposure time of the lichen is calculated in combination with the initial diameter of the lichen. The occurrence time of the debris flow is determined based on the exposure time of the lichen, and the occurrence frequency of the debris flow is obtained based on the occurrence time of the debris flow.

[0025] The formula for calculating the exposure time of lichens in this step is: T = (Db) ÷ a In the formula, T is the exposure time of the lichen in years; D is the average diameter of the lichen in mm; b is the initial diameter of the lichen in mm; and a is the actual growth rate of the lichen in mm / year.

[0026] It should be noted that in warm and humid climates, the time difference between the time before lichen begins to grow and the time before the rubble is exposed to the ground (the delay before lichen begins to grow) is usually short and can be ignored. Under the aforementioned conditions, the initial diameter of the lichen can be approximated as b=0mm.

[0027] The method provided by this invention is specifically used for determining debris flows in uninhabited areas. To address the problem of scarce debris flow data in uninhabited areas, lichens are used as biomarkers. By simply measuring the size of the lichens and combining it with their growth rate, the time and frequency of debris flow events can be deduced relatively accurately.

[0028] Example 2 like Figure 3 As shown, this embodiment provides a system for determining the timing and frequency of debris flows in uninhabited areas based on lichen size, including: The condition setting module is used to set that after a debris flow event occurs in the unmanned research area, lichens begin to grow on the surface of the boulders in the debris flow channel, and the diameter of the lichens is positively correlated with the exposure time; the lichen growth stage is set to linear growth, and the influence of the delay time before the lichens begin to grow is ignored. The data acquisition module is used to select suitable lichen species for dating, and to select several angular boulders in the debris flow channel, measure the longest axis diameter of the largest lichen among the selected species on each boulder, and calculate the average diameter of the lichen. The fitting module is used to obtain the historical reference size of lichens based on debris flow events with known exact occurrence times in the vicinity, and to fit the average diameter and growth time of lichens based on the historical reference size to obtain the actual growth rate of lichens in the uninhabited study area. The determination module is used to calculate the exposure time of lichens based on their average diameter and actual growth rate, combined with their initial diameter; to determine the occurrence time of debris flows based on the exposure time of lichens; and to derive the frequency of debris flows based on the occurrence time of debris flows.

[0029] In detail, based on the same innovative concept, each module in the system described in this embodiment adopts the same technical means as in Embodiment 1 when used, and can produce the same technical effect, which will not be repeated here.

[0030] Example 3 The present invention also provides a storage medium on which a program or instruction is stored, which, when executed by a processor, implements the steps in the above-described method for determining the occurrence time and frequency of debris flows in uninhabited areas based on lichen size.

[0031] The present invention also provides an electronic device, including a processor and a memory, wherein the memory stores a program or instructions that can run on the processor, and the program or instructions, when executed by the processor, implement the steps in the above-described method for determining the occurrence time and frequency of debris flows in uninhabited areas based on lichen size.

[0032] Example 4 This embodiment uses the mud from Baimaxi Rigou in an uninhabited area of ​​Tibet as an example, and further describes the present invention in detail with reference to the method provided in Embodiment 1, as follows: 1. A large-scale debris flow disaster has occurred in the Baima Xiri Gully, an uninhabited area in Tibet. Numerous debris flow depositional fans can be seen at the mouth of the gully, with abundant lichen growing on them. Assume that after the Baima Xiri Gully debris flow event, lichen immediately began to grow on the surface of the boulders on the depositional fans, and that the lichen growth stage was linear.

[0033] 2. Several species of Rhizocarpon, Xanthoria, Lecanora, and Parmelia were selected for dating on the Baimaxi Rigou alluvial fan because they are easy to identify and measure and have moderate growth rates.

[0034] 3. Select angular boulders from the alluvial fan, avoiding nearly circular stones, to ensure lichen growth begins after the debris flow event. Lichens with a nearly circular shape, facilitating diameter measurement, and of a single species are preferred. For example... Figure 4 As shown, the longest axis diameter of the largest lichen on each rolling stone was measured, and the lichen size was recorded. See Table 1 for details.

[0035] Table 1. Dimensions of lichens from the alluvial fan in Baimaxi Rigou. (Survey date: July 2023)

[0036] The above data was first removed, with one maximum and one minimum value (maximum 128mm and minimum 10mm) removed, resulting in 23 valid data points. The average value of the data was then calculated, yielding an average diameter of 31.72mm for the lichen.

[0037] 4. A debris flow is known to have occurred in 2000 in an unnamed gully near Baima Xiri Gully (approximately 5 km from the gully's mouth). Therefore, the lichen size on the debris flow deposit in the unnamed gully can be used as a benchmark. According to field measurements, the longest axis of the lichen on the unnamed gully deposit is approximately 10 mm. The interval between the debris flow in the unnamed gully and the field investigation is 23 years (Note: the investigation was conducted in July 2023). Therefore, through fitting, the actual lichen growth rate *a* during the debris flow event in Baima Xiri Gully can be estimated to be approximately 10 ÷ 23 = 0.435 mm / year. Since the assessment area is located in a warm and humid climate, the time difference between the start of lichen growth and the exposure of the rocks to the surface is usually short and can be ignored. Under these circumstances, the initial diameter *b* can be approximated as 0 mm.

[0038] 5. Based on the above data, the exposure time of the lichen, T = (Db) ÷ a = 31.72 ÷ 0.435 = 72.9 years, can be calculated. Therefore, the last large-scale debris flow in Baima Xiri Gully can be estimated to have occurred approximately 72.9 years before the investigation period, i.e., in 1950 (Note: Investigation time: July 2023). Using the aforementioned lichen dating data, it can be concluded that the frequency of debris flows in Baima Xiri Gully should be once every 50 to 100 years. By consulting local earthquake data, an 8.6 magnitude earthquake occurred in Motuo County, Tibet on August 15, 1950. Debris flows are typically most frequent in the years following such earthquakes. The uninhabited study area is relatively close to the epicenter of this earthquake, and the calculated debris flow time highly matches the earthquake time; as verification, this invention demonstrates high accuracy.

[0039] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar features unless otherwise specified. All features or steps in the disclosed methods or processes may be combined in any way, except for mutually exclusive features and / or steps.

Claims

1. A method for determining the timing and frequency of debris flows in uninhabited areas based on lichen size, characterized in that... Includes the following steps: S1: Condition Setting After a debris flow event occurs in the uninhabited research area, lichens begin to grow on the surface of the boulders in the debris flow channel, and the diameter of the lichens is positively correlated with the exposure time. The lichen growth stage is assumed to be linear, and the influence of the time difference between the start of lichen growth and the exposure of the boulders to the surface is ignored. S2: Lichen Data Collection Select suitable lichen species for dating, then select several angular boulders in the debris flow channel, measure the longest axis diameter of the largest lichen species on each boulder, and calculate the average diameter of the lichen. S3: Lichen growth rate fitting Based on debris flow events with known exact times in the vicinity, historical reference sizes of lichens are obtained. The average diameter and growth time of lichens are then fitted based on these historical reference sizes to obtain the actual growth rate of lichens in the uninhabited study area. S4: Determining Time and Frequency Based on the average diameter and actual growth rate of the lichen, the exposure time of the lichen is calculated in combination with its initial diameter. The occurrence time of debris flows is determined based on the exposure time of the lichen, and the occurrence frequency of debris flows is derived based on the occurrence time of debris flows.

2. The method for determining the occurrence time and frequency of debris flows in uninhabited areas based on lichen size according to claim 1, characterized in that: In step S2, selecting suitable lichen species for dating means selecting lichens that are easy to identify and measure, have a moderate growth rate, and are of a single variety. Lichens that are easy to identify specifically include yellow-green map lichen, Lithops yellow lichen, tea-stained lichen, or plum lichen. Lichens that are easy to measure are those with a shape close to a circle. Lichens of a single variety are those that do not grow or attach together with other lichens.

3. The method for determining the occurrence time and frequency of debris flows in uninhabited areas based on lichen size according to claim 1, characterized in that: In step S2, the number of rolling stones is 10-50.

4. The method for determining the occurrence time and frequency of debris flows in uninhabited areas based on lichen size according to claim 1, characterized in that: In step S2, the method for calculating the average diameter of lichens is as follows: first, remove the maximum and minimum values ​​from the measured data, and then calculate the average value based on the remaining values.

5. The method for determining the occurrence time and frequency of debris flows in uninhabited areas based on lichen size according to claim 1, characterized in that: In step S4, the formula for calculating the exposure time of the lichen is: T = (Db) ÷ a In the formula, T is the exposure time of the lichen in years; D is the average diameter of the lichen in mm; b is the initial diameter of the lichen in mm; and a is the actual growth rate of the lichen in mm / year.

6. A system for determining the timing and frequency of debris flows in uninhabited areas based on lichen size, characterized in that... include: The condition setting module is used to set that after a debris flow event occurs in the unmanned research area, lichens begin to grow on the surface of the boulders in the debris flow channel, and the diameter of the lichens is positively correlated with the exposure time; the lichen growth stage is set to linear growth, and the influence of the delay time before the lichens begin to grow is ignored. The data acquisition module is used to select suitable lichen species for dating, and to select several angular boulders in the debris flow channel, measure the longest axis diameter of the largest lichen among the selected species on each boulder, and calculate the average diameter of the lichen. The fitting module is used to obtain the historical reference size of lichens based on debris flow events with known exact occurrence times in the vicinity, and to fit the average diameter and growth time of lichens based on the historical reference size to obtain the actual growth rate of lichens in the uninhabited study area. The determination module is used to calculate the exposure time of lichens based on their average diameter and actual growth rate, combined with their initial diameter; to determine the occurrence time of debris flows based on the exposure time of the lichens; and to derive the occurrence frequency of debris flows based on the occurrence time of the debris flows.

7. A storage medium on which a program or instructions are stored, characterized in that: When the program or instructions are executed by the processor, they implement the steps in the above method.

8. An electronic device comprising a processor and a memory, characterized in that: The memory stores programs or instructions that can run on the processor, which, when executed by the processor, implement the steps in the above method.

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