Outburst of a glacial lake and overflow water level early warning method and application thereof

Abstract

The application discloses an ice lake outburst overflow water level early warning method, and belongs to the technical field of water conservancy projects, characterized in that the method comprises the following steps: a. investigating and measuring the overflow channel of the moraine lake, measuring the average medium diameter particle size D of the coarse particle armor layer of the overflow channel, measuring the slope alpha of the gentle slope section and the slope beta of the steep slope section of the overflow channel, and measuring the height difference h0 between the existing water level of the moraine lake and the surface of the coarse particle armor layer at the entrance section of the overflow outlet; b. determining the failure mode of the coarse particle armor layer of the overflow channel being started, and then determining the moraine lake outburst critical water level H C ; c. establishing the moraine lake water level monitoring point around the overflow outlet, measuring the existing water level of the moraine lake as the basic water level, and monitoring and early warning according to the existing water level of the moraine lake; and d. dividing the early warning levels. The application comprehensively considers the influencing factors of the moraine lake outburst critical overflow water depth, the calculated result is more in line with the actual situation, the early warning accuracy is greatly improved, and the applicability is better.

Description

Technical Field

[0001] This invention relates to the field of water conservancy engineering technology, and in particular to a method for early warning of overflow water levels in glacial lake outbursts and its application. Background Technology

[0002] Glacial lake outburst floods are a natural phenomenon occurring in high-altitude glacier regions. The primary cause is an overflow-type flood caused by glacial landslides or avalanches entering the lake. When glacial landslides or avalanches enter the lake, the water level rises, creating overflow channels on the glacial moraine. At high overflow levels, the water flow carries and erodes large boulders within the overflow channel, further eroding the sediment and silt deposited beneath them. This erosion continues, eventually leading to the complete erosion of the overflow channel and a glacial lake outburst. In addition, landslides or collapses causing large amounts of sediment to enter the glacial lake, heavy rainfall or snowmelt, and upstream glacial lake outbursts can all contribute to rising water levels and ultimately cause a glacial lake outburst flood. Therefore, studying the critical water level conditions for glacial lake outburst floods is fundamental to predicting and forecasting such disasters. Domestic and international research on the critical overflow depth calculation for glacial lake outburst floods is mainly based on the assumption that the rising water depth is equal to the outburst depth, i.e., the original glacial lake water level is zero, which is obviously not realistic. Or, when calculating the outburst flood, the glacial lake water depth is used instead of the overflow water depth (these two water depths differ by about one order of magnitude), resulting in a large error in the calculation results. (Jiang Zhongxin, Cui Peng, Jiang Liangwei, Critical Hydrological Conditions for Glacial Lake Overflow Outburst Floods, Journal of Railway Engineering, 2004, 84(4): 21-26.). The inducing factor for glacial lake outburst floods caused by ice avalanches is the rise in temperature, which causes ice avalanches on the glaciers at the back edge of the glacial lake. Large ice masses enter the glacial lake, causing a sharp rise in water level. The overflow water level rises sharply, eroding the sediment at the overflow outlet of the glacial dike and causing the glacial dike to break. A sharp rise in water level is a direct influencing condition, so it is possible to monitor sudden changes in water level to warn of glacial lake outburst floods. Many factors influence the water level of a glacial lake, which can generally be summarized as: the thickness of the glacial dike crest, the slope of the glacial dike's back slope, and the area of ​​the glacial lake (Institute of Mountain Hazards and Environment, Chengdu, Chinese Academy of Sciences; Tibet Autonomous Region Transportation Science Research Institute; Debris Flow and Environment in Tibet; Chengdu University of Science and Technology Press, 1999, 79-89). However, after a sudden rise in water level, the water overflowing from the glacial dike's spillway will cause the rising water level to fall back. If the fall is rapid, and the water level drops to a level that cannot erode sediment before the glacial dike's crest thickness is completely eroded, the glacial lake will not breach its banks. Therefore, the critical water level for glacial lake outburst is related to factors such as the thickness of the glacial dike crest, the width of the glacial dike overflow outlet, the sediment particle size at the dike overflow outlet, the area of ​​the glacial lake, the morphology of the glacial lake surface (average width and aspect ratio), and the average slope of the glacial lake shore. These factors must be considered to obtain reliable conditions for glacial lake outburst.

[0003] Chinese patent document CN107749144A, published on March 2, 2018, discloses a method for early warning of overflow water levels in glacial lake outbursts, including the following steps: a) investigating and measuring the thickness T of the glacial dam crest, the width of the breach, b) the average width w0 of the glacial lake, the length-to-width ratio of the glacial lake, c) the average slope β of the glacial lake shore before the outburst, and the characteristic particle size d of the initiating sediment; b) calculating the critical overflow water depth H of the glacial lake outburst; c) the glacial lake water level above the overflow outlet suddenly rises, lasting for more than 30 seconds, and when H... Cr <0.6H, the probability of a glacial lake outburst is very small; when 0.6H ≤ H Cr <0.8H, the probability of a glacial lake outburst flood is low; when 0.8H ≤ H Cr <H, the probability of a glacial lake outburst is moderate; when H Cr ≥H indicates a high probability of a glacial lake outburst.

[0004] The patent document discloses a method for early warning of overflow water levels in glacial lake outbursts. By studying the critical water depth conditions for glacial moraine breaches, it establishes an early warning and forecasting model for glacial lake outbursts. It comprehensively considers topographical and characteristic parameters such as the width of the breach, the average width and aspect ratio of the glacial lake, and the particle size of initiating particles on the moraine levee. This allows for quantitative prediction of glacial lake outbursts and demonstrates strong applicability. However, this method primarily considers characteristic parameters of the moraine levee, such as the coarse particles on the levee surface as characteristic particle size for sediment initiation, and parameters such as the average width and aspect ratio of the glacial lake. It also considers parameters such as the width of the overflow outlet, making it a comprehensive early warning method for glacial lake outbursts that takes into account factors such as the duration of erosion after water level rise. However, the key factor causing the glacial lake outburst is not the glacial dike itself, but rather the overflow channel on the dike. The coarse-grained armor layer of the overflow channel—the large, rough rocks on its surface—can be activated and damaged in two ways: First, at the inflection point of the overflow channel's slope, where a gentle slope meets a steep slope, a single coarse-grained rock is activated by the water flow, triggering a chain reaction that gradually activates all surrounding coarse-grained rocks. Second, under steep slope conditions, the armor layer on the steep slope of the overflow channel is activated as a whole, a situation known as slope instability. Both scenarios result in the destruction of the armor layer. Without the protection of the coarse-grained armor layer, the glacial lake overflow outlet will be further eroded by the water flow, downwards and outwards, ultimately leading to the glacial lake outburst. Therefore, the duration of the glacial lake's water level rise is not important; what matters is that the higher water level can activate the coarse-grained armor layer immediately. The erosion of coarse particles in the overflow armor layer is a key factor in causing glacial lake outbursts, and the water level of the glacial lake at the overflow outlet is a key condition for triggering a glacial lake outburst. This patent document does not take into account the actual conditions of glacial lake outbursts, which affects the accuracy of the early warning. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, this invention provides an early warning method for overflow water level of glacial moraine outburst floods and its application. This invention comprehensively considers the influencing factors of the critical overflow water depth of glacial moraine outburst floods, and the calculated results are more in line with the actual situation, greatly improving the accuracy of early warning and having better applicability.

[0006] This invention is achieved through the following technical solution:

[0007] A method for early warning of overflow water levels in glacial lake outburst floods, characterized by comprising the following steps:

[0008] a. Investigate and measure the overflow channel of the glacial moraine lake, measure the average median diameter D of the coarse-grained armor layer of the overflow channel, measure the slope α of the gentle slope section and the slope β of the steep slope section of the overflow channel, and measure the height difference h0 between the current water level of the glacial moraine lake at the overflow inlet section and the surface of the coarse-grained armor layer. If the current water level of the glacial moraine lake is lower than the surface of the coarse-grained armor layer, then h0 is positive; if the current water level of the glacial moraine lake is higher than the surface of the coarse-grained armor layer, then h0 is negative.

[0009] b. Based on the slope β of the steep section of the overflow channel, determine the failure mode of the coarse-grained armor layer of the overflow channel, and then determine the critical water level H of the glacial lake outburst. C ;

[0010] c. Establish glacial lake water level monitoring points around the overflow outlet, measure the current water level of the glacial lake and use it as the basic water level, and conduct monitoring and early warning based on the current water level of the glacial lake;

[0011] d. Classify the early warning level. When the monitored water level of the glacial lake H < 0.75H C The probability of a glacial lake outburst flood is very low, issuing a green safety signal; when the monitored water level of the glacial lake H ≥ H C However, if the duration is less than 30 seconds, the probability of a glacial lake outburst flood is low, and a yellow warning signal is issued; when the monitored water level H of the glacial lake is ≥ 0.75H... C If the duration is greater than 30 seconds, and the probability of a glacial lake outburst flood is low, an orange alert signal will be issued; when the monitored water level of the glacial lake H ≥ H C If the duration is greater than 30 seconds, the probability of a glacial lake outburst is high, and a red alert signal is issued.

[0012] In step b, when the slope β ≥ 25° on the steep slope section, the failure mode of the coarse-grained armor layer is overall initiation, and the critical water level H of the glacial lake outburst flood is reached. C Calculated using Equation 1;

[0013] H C =h0+0.75D Equation 1

[0014] When the slope β < 25° on a steep slope, the failure mode of the coarse-grained armor layer is single-initiation, and the critical water level H of the glacial lake outburst is [missing information]. C Calculated using Equation 2;

[0015] H C =h0+(2.45-0.1K)D Equation 2;

[0016] Among them, H C β is the critical water level for the glacial lake to burst; D is the average median diameter of the coarse-grained armor layer in the overflow channel; β is the slope of the steep section; K is the slope difference between the steep and gentle sections of the overflow channel, K≤20, and when K>20, K is taken as 20; h0 is the surface elevation difference between the current water level of the glacial lake at the overflow inlet section and the coarse-grained armor layer.

[0017] In step d, the monitored water level H of the glacial lake refers to the water level after comparing it with the water level measured at that time.

[0018] This invention is applicable to early warning of glacial lake outburst floods caused by rising water levels in glacial lakes.

[0019] This invention is applicable to early warning of glacial outburst floods caused by glacial avalanches, landslides, or collapses into glacial lakes, leading to rising water levels in these lakes.

[0020] Furthermore, this invention is applicable to early warning of glacial lake outbursts caused by rainfall or snowmelt leading to rising water levels in glacial lakes.

[0021] Furthermore, this invention is applicable to early warning of glacial lake outbursts caused by upstream glacial lake outbursts leading to rising water levels in moraine lakes.

[0022] The basic principle of this invention is as follows:

[0023] Glacial moraine lakes have overflow channels. Generally, during the rainy season or summer, meltwater from the snow and ice flows into the lake and then through the overflow outlets into these channels to flow downstream. The overflow channels are covered by coarse boulders, forming a coarse-grained armor layer that protects the mixed particles beneath. When the overflow level is low, the water flow cannot erode the coarse particles transporting the overflow channels, which are protected by this armor layer and the moraine lake remains stable, preventing breaches. However, when the lake level rises, the overflow level at the outlet also rises, as does the water level in the overflow channels. At this point, two scenarios may occur:

[0024] Firstly, the steep slope section of the overflow channel, with a gradient of 25 degrees or more, causes the coarse-grained armor layer to become unstable as a whole under high water levels, and the coarse-grained armor layer moves downstream together.

[0025] Secondly, when the slope of the steep section of the overflow channel is less than 25 degrees, the coarse-grained armor layer will not become unstable as a whole. However, at the turning point between the steep and gentle slope sections, due to the sudden change in slope, the coarse particles are most exposed at the turning point. Under higher water levels, some coarse particles, due to their relatively small particle size or excessive exposure, are stirred by the water flow. At this time, the balance of coarse particles around the particle is broken, and the coarse particles upstream, downstream, and on both sides will also be stirred and moved downstream. The overflow channel, which has lost the protection of the coarse-grained armor layer, is rapidly eroded, cuts down, and erodes to both sides, causing the glacial lake to burst.

[0026] The basic principle of this invention is that when the water level of a glacial lake rises above the critical level of the overflow outlet, a high water level forms in the overflow channel, which can lead to a glacial lake outburst. Based on this mechanism, and through extensive research, accurate derivation, and calculation, this invention proposes an early warning method and judgment criteria.

[0027] The beneficial effects of this invention are mainly reflected in the following aspects:

[0028] 1. This invention comprehensively considers the influencing factors of the critical overflow depth of glacial lake outburst floods, and the calculated results are more consistent with the actual situation, greatly improving the accuracy of early warning and having better applicability.

[0029] 2. The direct cause of glacial lake outbursts is that the water level of the glacial lake exceeds the critical level for initiating erosion overflow channels. Indirect causes include rising temperatures leading to snowmelt or rainfall; large-volume ice avalanches; large ice avalanches entering the glacial lake, causing a significant rise in water level; large-volume landslides or collapses entering the glacial lake, causing a significant rise in water level; and glacial lake outbursts upstream of the glacial lake, causing a large amount of water to enter the glacial lake and rise in water level. This invention more directly considers the rising water level of the glacial lake, which directly leads to glacial lake outbursts, as an early warning indicator. Without the uncertainty of other indirect influencing factors, the early warning accuracy is higher and the adaptability is stronger.

[0030] 3. This invention takes into account the different mechanisms by which rising water levels in glacial lakes initiate erosion of the coarse-grained armor layer in overflow channels. By utilizing the mechanism of the overall particle initiation of the coarse-grained armor layer, it provides suitable breach water level conditions under the steep slope conditions of the overflow channel, thus making it highly applicable.

[0031] 4. This invention takes into account the different mechanisms by which rising water levels in glacial lakes initiate erosion of the coarse-grained armor layer in overflow channels. By utilizing the mechanism of individual particles initiating erosion in the coarse-grained armor layer, erosion can occur at the turning point between steep and gentle slope sections of the overflow channel, with steep slopes below 25 degrees, providing suitable breaching water level conditions and enhancing applicability.

[0032] 5. The mechanism of this invention is the rise in water level at the point where the coarse-grained armor layer of the overflow channel is eroded. Specifically, this is the rise in water level at the steep slope section or the turning point between the steep and gentle slope sections. However, it is very difficult to set up water level monitoring at this location. The monitored water level fluctuates greatly due to the influence of boulders, making it difficult to give an accurate monitoring water level. However, by using the inlet water level of the overflow channel at the time of monitoring, combined with the water level of the glacial lake at that time, monitoring and early warning can effectively predict glacial lake outbursts and has strong applicability.

[0033] 6. This invention is applicable to early warning of glacial lake outbursts caused by rising water levels in glacial lakes; applicable to early warning of glacial lake outbursts caused by glacial avalanches, landslides, or collapses entering glacial lakes and causing rising water levels in glacial lakes; applicable to early warning of glacial lake outbursts caused by rainfall or snowmelt; applicable to early warning of glacial lake outbursts caused by upstream glacial lake outbursts, and has broad applicability. Attached Figure Description

[0034] The present invention will now be further described in detail with reference to the accompanying drawings and specific embodiments, wherein:

[0035] Figure 1 This is a graph showing the relationship between the average median diameter D of the coarse-grained armor layer in the overflow channel and the monitoring water level H of the glacial lake. Detailed Implementation

[0036] Example 1

[0037] A method for early warning of overflow water levels in glacial lake outburst floods includes the following steps:

[0038] a. Investigate and measure the overflow channel of the glacial moraine lake, measure the average median diameter D of the coarse-grained armor layer of the overflow channel, measure the slope α of the gentle slope section and the slope β of the steep slope section of the overflow channel, and measure the height difference h0 between the current water level of the glacial moraine lake at the overflow inlet section and the surface of the coarse-grained armor layer. If the current water level of the glacial moraine lake is lower than the surface of the coarse-grained armor layer, then h0 is positive; if the current water level of the glacial moraine lake is higher than the surface of the coarse-grained armor layer, then h0 is negative.

[0039] b. Based on the slope β of the steep section of the overflow channel, determine the failure mode of the coarse-grained armor layer of the overflow channel, and then determine the critical water level H of the glacial lake outburst. C ;

[0040] c. Establish glacial lake water level monitoring points around the overflow outlet, measure the current water level of the glacial lake and use it as the basic water level, and conduct monitoring and early warning based on the current water level of the glacial lake;

[0041] d. Classify the early warning level. When the monitored water level of the glacial lake H < 0.75H C The probability of a glacial lake outburst flood is very low, issuing a green safety signal; when the monitored water level of the glacial lake H ≥ HC However, if the duration is less than 30 seconds, the probability of a glacial lake outburst flood is low, and a yellow warning signal is issued; when the monitored water level H of the glacial lake is ≥ 0.75H... C If the duration is greater than 30 seconds, and the probability of a glacial lake outburst flood is low, an orange alert signal will be issued; when the monitored water level of the glacial lake H ≥ H C If the duration is greater than 30 seconds, the probability of a glacial lake outburst is high, and a red alert signal is issued.

[0042] This embodiment is the most basic implementation method, which fully considers the influencing factors of the critical overflow depth of glacial lake outburst floods. The calculated results are more consistent with the actual situation, greatly improving the accuracy of early warning and having better applicability.

[0043] Example 2

[0044] A method for early warning of overflow water levels in glacial lake outburst floods includes the following steps:

[0045] a. Investigate and measure the overflow channel of the glacial moraine lake, measure the average median diameter D of the coarse-grained armor layer of the overflow channel, measure the slope α of the gentle slope section and the slope β of the steep slope section of the overflow channel, and measure the height difference h0 between the current water level of the glacial moraine lake at the overflow inlet section and the surface of the coarse-grained armor layer. If the current water level of the glacial moraine lake is lower than the surface of the coarse-grained armor layer, then h0 is positive; if the current water level of the glacial moraine lake is higher than the surface of the coarse-grained armor layer, then h0 is negative.

[0046] b. Based on the slope β of the steep section of the overflow channel, determine the failure mode of the coarse-grained armor layer of the overflow channel, and then determine the critical water level H of the glacial lake outburst. C ;

[0047] c. Establish glacial lake water level monitoring points around the overflow outlet, measure the current water level of the glacial lake and use it as the basic water level, and conduct monitoring and early warning based on the current water level of the glacial lake;

[0048] d. Classify the early warning level. When the monitored water level of the glacial lake H < 0.75H C The probability of a glacial lake outburst flood is very low, issuing a green safety signal; when the monitored water level of the glacial lake H ≥ H C However, if the duration is less than 30 seconds, the probability of a glacial lake outburst flood is low, and a yellow warning signal is issued; when the monitored water level H of the glacial lake is ≥ 0.75H... C If the duration is greater than 30 seconds, and the probability of a glacial lake outburst flood is low, an orange alert signal will be issued; when the monitored water level of the glacial lake H ≥ H C If the duration is greater than 30 seconds, the probability of a glacial lake outburst is high, and a red alert signal is issued.

[0049] In step b, when the slope β ≥ 25° on the steep slope section, the failure mode of the coarse-grained armor layer is overall initiation, and the critical water level H of the glacial lake outburst flood is reached. C Calculated using Equation 1;

[0050] H C =h0+0.75D Equation 1

[0051] When the slope β < 25° on a steep slope, the failure mode of the coarse-grained armor layer is single-initiation, and the critical water level H of the glacial lake outburst is [missing information]. C Calculated using Equation 2;

[0052] H C =h0+(2.45-0.1K)D Equation 2;

[0053] Among them, H C β is the critical water level for the glacial lake to burst; D is the average median diameter of the coarse-grained armor layer in the overflow channel; β is the slope of the steep section; K is the slope difference between the steep and gentle sections of the overflow channel, K≤20, and when K>20, K is taken as 20; h0 is the surface elevation difference between the current water level of the glacial lake at the overflow inlet section and the coarse-grained armor layer.

[0054] This embodiment is a preferred implementation. The direct cause of a glacial lake outburst is that the water level of the glacial lake exceeds the critical level for initiating the erosion overflow channel. Indirect causes include rising temperatures causing snowmelt or rainfall; large-volume ice avalanches; large ice avalanches entering the glacial lake, causing a significant rise in water level; large-volume landslides or collapses entering the glacial lake, causing a significant rise in water level; and glacial lake outbursts upstream of the glacial lake causing a large amount of water to enter the glacial lake, leading to a rise in water level. This invention more directly considers the rising water level of the glacial lake, which directly leads to glacial lake outbursts, as an early warning indicator, without the uncertainty of other indirect influencing factors, resulting in higher accuracy and stronger adaptability of the early warning.

[0055] Example 3

[0056] A method for early warning of overflow water levels in glacial lake outburst floods includes the following steps:

[0057] a. Investigate and measure the overflow channel of the glacial moraine lake, measure the average median diameter D of the coarse-grained armor layer of the overflow channel, measure the slope α of the gentle slope section and the slope β of the steep slope section of the overflow channel, and measure the height difference h0 between the current water level of the glacial moraine lake at the overflow inlet section and the surface of the coarse-grained armor layer. If the current water level of the glacial moraine lake is lower than the surface of the coarse-grained armor layer, then h0 is positive; if the current water level of the glacial moraine lake is higher than the surface of the coarse-grained armor layer, then h0 is negative.

[0058] b. Based on the slope β of the steep section of the overflow channel, determine the failure mode of the coarse-grained armor layer of the overflow channel, and then determine the critical water level H of the glacial lake outburst. C ;

[0059] c. Establish glacial lake water level monitoring points around the overflow outlet, measure the current water level of the glacial lake and use it as the basic water level, and conduct monitoring and early warning based on the current water level of the glacial lake;

[0060] d. Classify the early warning level. When the monitored water level of the glacial lake H < 0.75H C The probability of a glacial lake outburst flood is very low, issuing a green safety signal; when the monitored water level of the glacial lake H ≥ H C However, if the duration is less than 30 seconds, the probability of a glacial lake outburst flood is low, and a yellow warning signal is issued; when the monitored water level H of the glacial lake is ≥ 0.75H... C If the duration is greater than 30 seconds, and the probability of a glacial lake outburst flood is low, an orange alert signal will be issued; when the monitored water level of the glacial lake H ≥ H C If the duration is greater than 30 seconds, the probability of a glacial lake outburst is high, and a red alert signal is issued.

[0061] In step b, when the slope β ≥ 25° on the steep slope section, the failure mode of the coarse-grained armor layer is overall initiation, and the critical water level H of the glacial lake outburst flood is reached. C Calculated using Equation 1;

[0062] H C =h0+0.75D Equation 1

[0063] When the slope β < 25° on a steep slope, the failure mode of the coarse-grained armor layer is single-initiation, and the critical water level H of the glacial lake outburst is [missing information]. C Calculated using Equation 2;

[0064] H C =h0+(2.45-0.1K)D Equation 2;

[0065] Among them, H C β is the critical water level for the glacial lake to burst; D is the average median diameter of the coarse-grained armor layer in the overflow channel; β is the slope of the steep section; K is the slope difference between the steep and gentle sections of the overflow channel, K≤20, and when K>20, K is taken as 20; h0 is the surface elevation difference between the current water level of the glacial lake at the overflow inlet section and the coarse-grained armor layer.

[0066] In step d, the monitored water level H of the glacial lake refers to the water level after comparing it with the water level measured at that time.

[0067] This embodiment is another preferred implementation. Considering the different mechanisms by which rising water levels in glacial moraine lakes initiate erosion of the coarse-grained armor layer in the overflow channel, it utilizes the mechanism of overall particle initiation of the coarse-grained armor layer to provide suitable breach water level conditions under the steep slope conditions of the overflow channel, thus making it highly applicable.

[0068] Considering the different mechanisms by which rising water levels in glacial moraine lakes initiate erosion of the coarse-grained armor layer in overflow channels, this study utilizes the mechanism of individual particles initiating erosion in the coarse-grained armor layer. At the turning point between steep and gentle slope sections of the overflow channel, erosion can occur at a steep slope of less than 25 degrees, providing suitable conditions for breaching the breach and enhancing its applicability.

[0069] Example 4

[0070] A method for early warning of overflow water levels in glacial lake outburst floods includes the following steps:

[0071] a. Investigate and measure the overflow channel of the glacial moraine lake, measure the average median diameter D of the coarse-grained armor layer of the overflow channel, measure the slope α of the gentle slope section and the slope β of the steep slope section of the overflow channel, and measure the height difference h0 between the current water level of the glacial moraine lake at the overflow inlet section and the surface of the coarse-grained armor layer. If the current water level of the glacial moraine lake is lower than the surface of the coarse-grained armor layer, then h0 is positive; if the current water level of the glacial moraine lake is higher than the surface of the coarse-grained armor layer, then h0 is negative.

[0072] b. Based on the slope β of the steep section of the overflow channel, determine the failure mode of the coarse-grained armor layer of the overflow channel, and then determine the critical water level H of the glacial lake outburst. C ;

[0073] c. Establish glacial lake water level monitoring points around the overflow outlet, measure the current water level of the glacial lake and use it as the basic water level, and conduct monitoring and early warning based on the current water level of the glacial lake;

[0074] d. Classify the early warning level. When the monitored water level of the glacial lake H < 0.75H C The probability of a glacial lake outburst flood is very low, issuing a green safety signal; when the monitored water level of the glacial lake H ≥ H C However, if the duration is less than 30 seconds, the probability of a glacial lake outburst flood is low, and a yellow warning signal is issued; when the monitored water level H of the glacial lake is ≥ 0.75H... C If the duration is greater than 30 seconds, and the probability of a glacial lake outburst flood is low, an orange alert signal will be issued; when the monitored water level of the glacial lake H ≥ H C If the duration is greater than 30 seconds, the probability of a glacial lake outburst is high, and a red alert signal is issued.

[0075] In step b, when the slope β ≥ 25° on the steep slope section, the failure mode of the coarse-grained armor layer is overall initiation, and the critical water level H of the glacial lake outburst flood is reached. C Calculated using Equation 1;

[0076] H C =h0+0.75D Equation 1

[0077] When the slope β < 25° on a steep slope, the failure mode of the coarse-grained armor layer is single-initiation, and the critical water level H of the glacial lake outburst is [missing information]. CCalculated using Equation 2;

[0078] H C =h0+(2.45-0.1K)D Equation 2;

[0079] Among them, H C β is the critical water level for the glacial lake to burst; D is the average median diameter of the coarse-grained armor layer in the overflow channel; β is the slope of the steep section; K is the slope difference between the steep and gentle sections of the overflow channel, K≤20, and when K>20, K is taken as 20; h0 is the surface elevation difference between the current water level of the glacial lake at the overflow inlet section and the coarse-grained armor layer.

[0080] In step d, the monitored water level H of the glacial lake refers to the water level after comparing it with the water level measured at that time.

[0081] This invention is applicable to early warning of glacial lake outburst floods caused by rising water levels in glacial lakes.

[0082] This invention is applicable to early warning of glacial outburst floods caused by glacial avalanches, landslides, or collapses into glacial lakes, leading to rising water levels in these lakes.

[0083] Furthermore, this invention is applicable to early warning of glacial lake outbursts caused by rainfall or snowmelt leading to rising water levels in glacial lakes.

[0084] Furthermore, this invention is applicable to early warning of glacial lake outbursts caused by upstream glacial lake outbursts leading to rising water levels in moraine lakes.

[0085] This embodiment represents the optimal implementation method. The outburst mechanism involves the rise in water level at the location where the coarse-grained armor layer of the overflow channel is eroded. Specifically, this occurs at the steep slope section or the turning point between the steep and gentle slope sections. However, it is very difficult to establish water level monitoring at this location, as the monitored water level fluctuates greatly due to the influence of boulders, making it difficult to provide an accurate monitoring water level. Instead, monitoring the inlet water level of the overflow channel at the time of monitoring, combined with the water level of the moraine lake at that time, can effectively provide early warning of moraine lake outbursts and has strong applicability.

[0086] It is applicable to early warning of glacial lake outbursts caused by rising water levels in glacial lakes; it is applicable to early warning of glacial lake outbursts caused by glacial avalanches, landslides, or collapses entering glacial lakes and causing rising water levels in glacial lakes; it is applicable to early warning of glacial lake outbursts caused by rainfall or snowmelt; and it is applicable to early warning of glacial lake outbursts caused by upstream glacial lake outbursts, and has wide applicability.

[0087] The present invention is used below to determine the breach of water levels in six breached glacial lakes and two non-breached glacial lakes:

[0088] Outburst and non-outburst moraine lakes are mainly distributed in Tibet, with only one located in British Columbia, Canada (Queen Bees). The rising water levels of some moraine lakes are calculated based on the volume of the glacial avalanche and the area of ​​the lake, while others are directly derived from literature. Since detailed information on the slope of the steep and gentle sections upstream and downstream of the overflow channel turning point of these outburst moraine lakes is unavailable, for safety reasons, we use a lower water level for assessment, i.e., selecting the lowest water level. Therefore, K is taken as its maximum value: K = 20. At this point, the individual critical water level for initiation is lower than the overall critical water level for initiation on a large slope; therefore, this critical water level is used as the warning critical water level.

[0089] Furthermore, assuming h0 = 0.5D, which is the water level before the sudden event, typically occurring in summer or the rainy season, such as during ice avalanches, landslides, collapses, sudden heavy rains or high-temperature snowmelt, or the water level before a sudden glacial lake outburst upstream, then Equations 1 and 2 can be combined as follows:

[0090] H C =0.5D + 0.45D = 0.95D (Equation 3)

[0091] From Equation 3 and the warning levels, we know that H = 0.95D is the red warning line; H = 0.75 * 0.95D = 0.71D is the orange warning line. Based on literature data, we assume that the diameter of the armor layer particles is between 0.5 and 2 m. Table 1 gives the names of the moraine lakes involved in these events, the time of breach and non-breach, the cause of breach, and the monitored water level H of the moraine lakes. Figure 1 The relationship between the average median diameter D of the coarse-grained armor layer of the overflow channel and the monitoring water level H of the glacial lake in these events was established. These data verified the accuracy of the prediction of these ice avalanche / landslide events in this invention, except that: 1) when D = 0.5m, the two points that did not experience a breach were within the orange warning range; 2) when D = 2m, the warning for the flash flood was lower than the orange warning.

[0092] Table 1

[0093] Tsering Ma Tso 1981-07-11 Ice avalanche / piping 12.8 Jilai Lake 1964-09-21 Ice avalanche 7 Damenla cough 1964-09-26 Ice avalanche 23.8 Pogo Lake 1972-07-23 Ice avalanche 10.3 Guang Xie Cuo 1988-07-15 Ice avalanche / piping 1.19 Queen Bees 1997-08-12 Ice avalanche 2.96 Guang Xie Cuo 1990-July-August Ice avalanche / unresolved 0.45 Jiwengcuo 2020-06-21 Landslide / Unbroken Breach 0.39

[0094] In the non-outflow cases of Guangxie Co and Jiweng Co, exceptions only occurred when the diameter of the coarse grains in the glacial layer was around 0.5m. This was clearly due to the assumption that the grain size of the glacial layer in these two glacial lakes was too small, since the coarse grains in the glacial layer of most wild glacial lakes are over 1m. In the case of the outflow of Guangxie Co, the outflow was caused by an ice avalanche. Another factor contributing to the outflow was the occurrence of piping, which made the outflow more likely. Therefore, the early warning for Guangxie Co can be considered successful.

[0095] In summary, the glacial moraine outburst flood warning system of this invention has a high success rate and can effectively provide early warning for glacial moraine outburst floods caused by glacial moraine overflows.

Claims

1. A method for early warning of overflow water levels in glacial lake outburst floods, characterized in that, Includes the following steps: a. Investigate and measure the overflow channel of the glacial lake, measure the average median diameter D of the coarse-grained armor layer of the overflow channel, and measure the slope of the gentle slope section of the overflow channel. and steep slope The difference h0 between the current water level of the glacial moraine lake and the surface of the coarse-grained armor layer at the overflow inlet section is measured. If the current water level of the glacial moraine lake is lower than the surface of the coarse-grained armor layer, then h0 is positive; if the current water level of the glacial moraine lake is higher than the surface of the coarse-grained armor layer, then h0 is negative. b. Based on the slope of the steep section of the overflow channel The failure mode of the coarse-grained armor layer in the overflow channel was determined, and then the critical water level H of the glacial lake outburst was determined. C ; c. Establish glacial lake water level monitoring points around the overflow outlet, measure the current water level of the glacial lake and use it as the basic water level, and conduct monitoring and early warning based on the current water level of the glacial lake; d. Classify the early warning level. When the monitored water level of the glacial lake H < 0.75H C The probability of a glacial lake outburst flood is very low, issuing a green safety signal; when the monitored water level of the glacial lake H ≥ H C However, if the duration is less than 30 seconds, the probability of a glacial lake outburst flood is low, and a yellow warning signal is issued; when the monitored water level H of the glacial lake is ≥ 0.75H... C If the duration is greater than 30 seconds, and the probability of a glacial lake outburst flood is low, an orange alert signal will be issued; when the monitored water level of the glacial lake H ≥ H C If the duration is greater than 30 seconds, the probability of a glacial lake outburst is high, and a red alert signal is issued. In step b, when the slope of the steep section is... At that time, the failure mode of the coarse-grained armor layer was global initiation, and the critical water level H of the glacial lake outburst flood was reached. C Calculated using Equation 1; H C =h0+0.75D Equation 1 When the slope of the steep section At that time, the failure mode of the coarse-grained armor layer was a single initiation, and the critical water level H of the glacial lake outburst was... C Calculated using Equation 2; H C =h0+(2.45-0.1K)D Equation 2; Among them, H C D represents the critical water level for a glacial lake outburst; D represents the average median diameter of the coarse-grained armor layer in the overflow channel. K represents the slope of the steep section, and K is the slope difference between the steep and gentle sections of the overflow channel. K ≤ 20. When K > 20, K is taken as 20. h0 is the surface elevation difference between the existing water level of the glacial lake at the overflow inlet section and the coarse-grained armor layer.

2. The method for early warning of overflow water levels in a glacial lake outburst flood as described in claim 1, characterized in that: In step d, the monitored water level H of the glacial lake refers to the water level after comparing it with the water level measured at that time.

3. The application of the method for early warning of overflow water levels in glacial lake outburst floods according to claim 1, characterized in that: It is applicable to early warning of glacial lake outbursts caused by rising glacial lake water levels.

4. The application of the method for early warning of overflow water levels in glacial lake outburst floods according to claim 1, characterized in that: It is applicable to early warning of glacial outburst floods caused by glacial avalanches, landslides, or collapses into glacial lakes, leading to a rise in the lake's water level.

5. The application of the method for early warning of overflow water levels in glacial lake outburst floods according to claim 1, characterized in that: This is applicable to early warning systems for glacial lake outbursts caused by rising water levels in glacial lakes due to rainfall or snowmelt.

6. The application of the method for early warning of overflow water levels in glacial lake outburst floods according to claim 1, characterized in that: This early warning system is applicable to glacial lake outburst warnings for glacial lakes where upstream glacial lake outbursts cause a rise in glacial lake water levels.

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