A method for estimating downstream flood volume of coupled glacial lake outburst flood and snowmelt flood

Abstract

The present invention provides a method for estimating downstream flood volume of coupled glacial lake outburst flood and snowmelt flood, comprising: step 1: extracting lake surface area change information of the target upstream glacial lake by using multi-source remote sensing image data, and estimating the outburst flood volume of the glacial lake in combination with historical parameter information of the glacial lake; step 2: extracting the target sub-basin upstream of the target according to the distributed water model, and obtaining the watershed information of the extracted target sub-basin, estimating the daily snowmelt volume of the corresponding target sub-basin; step 3: determining the outburst flood characteristics of the glacial lake and the snowmelt flood characteristics of the target sub-basin, and estimating the downstream flood volume according to the determined flood characteristic results and the estimated outburst flood volume and daily snowmelt volume. The estimation method of the glacial lake outburst flood volume and the snowmelt flood volume can be integrated to provide support for the risk assessment of downstream water conservancy projects caused by glacial disasters.

Description

Technical Field

[0001] The invention relates to the technical field of risk assessment, and in particular to a method for estimating downstream flood volume of a coupled curling outburst flood and a snowmelt flood. Background Art

[0002] China is a country with abundant glacier resources, which are mainly distributed in the Qinghai-Tibet Plateau and surrounding areas. According to the Second Glacier Catalog of China (published in 2014), there are more than 0.01 km2 of glaciers in China. 2 There are 48,571 glaciers with a total area of ​​51,766 km2 and a total reserve of 4.5×1012 m3. Compared with the data of the "First Glacier Catalog of China" (published in 1999), the area of ​​glaciers in China has shrunk by about 18% and the reserve has decreased by about 20%. Satellite remote sensing data and field observation studies have shown that under the background of global warming, the glaciers in the Qinghai-Tibet Plateau and surrounding areas are generally in a state of rapid melting.

[0003] The rapid changes in glaciers reduce the stability of the glaciers themselves, which in turn increases the risk of glacial disasters. Types of glacial disasters in the Qinghai-Tibet Plateau and surrounding areas include ice avalanches, glacier surges, glacial lake outburst floods, glacial debris flows, and glacial snow floods. Glacial lakes are natural water bodies that are mainly supplied by modern glacial meltwater or accumulated in moraine depressions, including glacial terminal lakes, glacial surface lakes, and glacial recharge lakes. Glacial lake outburst floods are sudden floods caused by the rapid and large-scale drainage of glacial lakes or the collapse of dams.

[0004] Glacial lake outburst floods are the most influential natural disaster among glacial disasters. Increased precipitation or glacial meltwater caused by climate change can trigger glacial lake outbursts. Ice avalanches and materials formed by glacial surges rushing into downstream glacial lakes can also trigger glacial lake outbursts. Therefore, glacial lake outburst floods are the most influential natural disaster among glacial disasters. Glacial lake outburst floods mainly occur in the source areas of the Yarkand River in the Himalayas and Karakoram Mountains and the Aksu River in the Tianshan Mountains. The glacial lakes that burst are mainly divided into two categories: glacier-blocked lakes (ice dam lakes) and moraine-blocked lakes (moraine lakes). Among them, the process of moraine lake embankment breach mainly has two mechanisms: overflow type and piping type. Glacial lake outburst floods are characterized by strong suddenness, large scale, strong destructive power and wide range of damage, which often cause heavy losses of life and property in downstream areas.

[0005] There are many water conservancy projects around glaciers in my country, and it is necessary to strengthen the risk assessment of glacier disasters on water conservancy projects. According to statistics on hydropower stations and reservoirs around glaciers in my country by relevant departments, there are 11 large and medium-sized hydropower stations and 16 reservoirs within a 10km radius, 97 small hydropower stations and 43 reservoirs; within a 20km radius, there are 44 large and medium-sized hydropower stations and 41 reservoirs, 336 small hydropower stations and 117 reservoirs; within a 50km radius, there are 116 large and medium-sized hydropower stations and 135 reservoirs, 1,069 small hydropower stations and 440 reservoirs (see Table 1).

[0006] Table 1 Impact of glaciers on hydropower stations and reservoirs

[0007]

[0008] The occurrence of glacial lake outburst floods is often accompanied by rising temperatures, which will also cause the melting of ice and snow in the basin to intensify. Therefore, the risk assessment of downstream water conservancy projects must take into account the combined impact of glacial lake outburst and snowmelt.

[0009] Therefore, it is necessary to provide an estimation method that can comprehensively estimate the glacial lake outburst flood and snowmelt flood to provide support for the risk assessment of glacial disasters on downstream water conservancy projects. Summary of the invention

[0010] The present invention provides a method for estimating the downstream flood volume of a coupled glacial lake outburst flood and a snowmelt flood, so as to solve the above-mentioned technical problems.

[0011] The present invention provides a method for estimating downstream flood volume of coupled glacial lake outburst flood and snowmelt flood, comprising:

[0012] Step 1: Using multi-source remote sensing image data, extract the lake area change information of the target upstream glacial lake, and combine the historical parameter information of the glacial lake to estimate the outburst flood volume of the glacial lake;

[0013] Step 2: Extract the target sub-basin upstream of the target according to the distributed water model, obtain the watershed information of the extracted target sub-basin, and estimate the daily snowmelt amount of the corresponding target sub-basin;

[0014] Step 3: Determine the dam-break flood characteristics of the glacial lake and the snowmelt flood characteristics of the target sub-basin, and estimate the downstream flood volume based on the determined flood characteristic results and the estimated outburst flood volume and daily snowmelt volume.

[0015] In a possible implementation method, step 1: using multi-source remote sensing image data to extract the lake area change information of the glacial lake upstream of the target, and combining the historical parameter information of the glacial lake to estimate the outburst flood volume of the glacial lake, including:

[0016] Using multi-source remote sensing image data, the daily changes in the surface area of ​​the glacial lake after the glacial lake is filled with water are extracted;

[0017] Using the topographic map of the glacial lake in the empty state in the corresponding year, a digital elevation model of the glacial lake basin and its surroundings was constructed;

[0018] Based on the digital elevation model and using the spatial analysis method, the lake surface elevation value, the volume of the lake basin, and the lake surface area of ​​the ice lake are calculated, and a lake surface elevation-volume change curve and a lake surface elevation-area change curve are constructed, and then the lake surface area-water storage capacity change curve of the ice lake is calculated;

[0019] Based on the extracted lake area changes and the estimated results, the daily change in the glacial lake water storage corresponding to the glacial lake outburst, i.e., the outburst flood volume, is estimated:

[0020] B t =V(S t )-V(S t-1 )=a×S t b -a×S t-1 b

[0021] Among them: B t is the outburst volume at time t, S t is the lake area monitored at time t, S t-1 is the lake area monitored at time t-1, V(S t ) is the glacial lake storage capacity at time t, V(S t-1 ) is the storage capacity of the glacial lake at time t-1. According to the lake surface area-water storage capacity change curve, the functional relationship between the water storage capacity of the glacial lake and the lake surface area is exponential, and a and b are the two coefficients of the exponential function.

[0022] In a possible implementation, step 2: obtaining the watershed information of the extracted target sub-watershed and estimating the daily snowmelt amount of the corresponding target sub-watershed includes:

[0023] Monitoring the target sub-basin based on the snow cover device, obtaining snow-covered pixels and non-snow-covered pixels corresponding to the target sub-basin, and determining the snow cover percentage of the target sub-basin based on the snow-covered pixels and the non-snow-covered pixels;

[0024]

[0025] Among them, P snow,t is the percentage of snow cover area corresponding to the target sub-basin at time t, Cover snow,t is the number of snow-covered pixels in the target sub-basin at time t. subasin is the total number of pixels in the corresponding watershed, Coverno-snow,t is the number of non-snow pixels in the target sub-basin at time t;

[0026] Based on the snow depth remote sensing inversion dataset, the first snow depth corresponding to the target sub-basin within a specific period is selected;

[0027] Obtaining the current snow depth of the target sub-basin monitored by remote sensing on that day;

[0028] Determine an average snow depth of the corresponding target sub-basin based on the first snow depth and the current snow depth;

[0029]

[0030] Among them, H snow,t is the average snow depth of the target sub-basin at time t, H t is the current snow depth of the target sub-basin at time t, H t-i represents the first snow depth of the corresponding target sub-basin at the time of historical screening, H t+i represents the first snow depth of the corresponding target sub-basin at time t+i of historical screening, and the specific period is 14 days;

[0031] Calculate the daily snowmelt amount of the corresponding target sub-basin according to the snow cover percentage, the average snow depth and the watershed area of ​​the corresponding target sub-basin;

[0032] M t =S subbasin ×P snow,t ×H snow,t

[0033] Among them, M t is the daily snowmelt amount of the corresponding target sub-basin at time t.

[0034] In a possible implementation, step 4, before estimating the downstream flood volume based on the determined flood characteristic results and the estimated flood outburst volume and daily snowmelt volume, further includes:

[0035] Determine the inflow boundary conditions of the corresponding target river section, wherein the inflow boundary conditions are related to the outburst flood volume and the daily snowmelt volume;

[0036] Determine the water system distribution of the corresponding target river section, and at the same time, determine the basic characteristics of the corresponding target river section;

[0037] Based on the inflow boundary conditions, water system distribution and basic characteristics, the outlet flow process of the corresponding target river section is obtained, and the outlet flow process is related to the downstream flood volume.

[0038] In one possible implementation, the inflow boundary conditions corresponding to the target river section are determined, including:

[0039] Determine the first flow process of the estimated daily snowmelt to the corresponding outlet of each target sub-basin;

[0040] Determine the second flow process of the estimated outburst flood volume of each glacial lake to the corresponding outlet;

[0041] The first flow process and the second flow process are superimposed, and the superposition result is used as an inflow boundary condition.

[0042] In a possible implementation, the process of obtaining the outlet flow of the corresponding target river section based on the inflow boundary conditions, water system distribution and basic characteristics also includes:

[0043] According to the following formula (1), the water storage capacity of the corresponding target river section is simulated, and the water storage capacity of the prism and the water storage capacity of the wedge are simulated:

[0044]

[0045] Among them, B t-1 and B t are the glacial lake outburst values ​​at t-1 and at t respectively; M t-1 and M t are the glacier snowmelt values ​​during the inflow process at time t-1 and time t, respectively; Q t-1 and Q t are the outflow process values ​​at t-1 and t respectively; S t-1 and S t are the water storage of the river section at time t-1 and time t respectively; Δt represents the time difference between time t-1 and time t;

[0046] According to formula (2), the water storage capacity S t To define:

[0047] S t =KQ t +KX(B t +M t -Q t )=K(X(B t +M t )+(1-X)Q t ) (2)

[0048] Where K is the movement time of the flood wave through the evolution section of the corresponding target river section; X represents the weight of the glacial lake outburst value and the glacier snowmelt value compared with the outflow, with a value range of 0-0.5; Q t is the outflow rate of the prism storage at time t;

[0049] Substituting formula (2) into formula (1) yields formula (3):

[0050]

[0051] In one possible implementation, the water storage capacity S t The definition process also includes:

[0052] According to the following formulas (4) and (5), the parameters K and X are estimated:

[0053]

[0054]

[0055] Among them, V w is the flood velocity of the corresponding target river section, which is g times the corresponding average flow velocity, and the value range of g is [1.33, 1.67]; B is the width of the top of the corresponding flood water surface; Q0 is the reference flow taken from the inflow process line; S0 is the bottom slope or friction angle of the corresponding target river section; c is the flood wave velocity of the corresponding target river section; Δx is the length of the river section of the corresponding target river section.

[0056] In a possible implementation, step 3, determining the snowmelt flood characteristics of the target sub-basin, includes:

[0057] Determining initial snowmelt characteristics of the target sub-basin based on historical remote sensing monitoring information;

[0058] Monitoring the temperature set of the target sub-basin in the current time period, and also monitoring the current sensing information corresponding to the target sub-basin;

[0059] Establishing a first snowmelt characteristic of the target sub-basin based on the temperature set and the sensing information;

[0060] Monitor the surrounding environment of the target sub-basin, analyze the monitoring results, and construct an impact set and a location set;

[0061] Based on the set of locations, determining a connected inlet associated with the target sub-basin;

[0062] Performing a first pre-analysis on the impact set and a second pre-analysis on the connected inlet to extract the impact factors on the target sub-basin, and inputting the impact factors into the impact constraint model to obtain the impact constraint conditions;

[0063] Based on the detection devices set at several detection points of the target sub-basin, the historical moisture information of the corresponding detection points is obtained to determine the moisture constraint conditions of the target sub-basin, wherein the historical moisture information includes: the influence of vegetation coverage on the moisture infiltration of the corresponding detection point, the moisture infiltration of the corresponding detection point, the moisture consumption of the corresponding detection point at the corresponding temperature, and the influencing factors of the moisture measurement of the corresponding detection point affected by the external environment;

[0064] Based on the impact constraint and the moisture constraint, determine the second snowmelt characteristics for the target sub-basin;

[0065] The initial snowmelt characteristics are adjusted based on the first snowmelt characteristics and the second snowmelt characteristics to obtain the snowmelt flood characteristics.

[0066] The initial snowmelt characteristics are adjusted based on the first snowmelt characteristics and the second snowmelt characteristics to obtain snowmelt flood characteristics.

[0067] In a possible implementation manner, the initial snowmelt characteristic is adjusted based on the first snowmelt characteristic and the second snowmelt characteristic to obtain a snowmelt flood characteristic, including:

[0068] Acquire a first sequence of the first snowmelt characteristics, a second sequence of the second snowmelt characteristics, and an initial sequence of the initial snowmelt characteristics;

[0069] Placing the initial sequence on a base layer of a sequence resetting framework, matching the first snowmelt feature and the second snowmelt feature with layer attributes of remaining layers on the sequence resetting framework, and placing the first sequence and the second sequence on corresponding matching layers;

[0070] Extracting first special description information of the first sequence on the corresponding matching layer, and extracting second special description information of the second sequence on the corresponding matching layer;

[0071] Determine the layer element of the corresponding matching layer, and calibrate the special element in the layer element, determine whether there is a special sequence related to the special element in the sequence existing in the corresponding matching layer, if so, retain the special sequence, and determine the position attribute of the sequence position of the retained special sequence;

[0072] If it does not exist, the sequence corresponding to the matching layer is transmitted to the storage unit for storage;

[0073] Determine whether there is a location area related to the location attribute in the base layer, and if so, determine the area capacity of the location area, and if the area capacity is greater than or equal to the sequence capacity of the corresponding special sequence, place the corresponding special sequence in the location area, and if the area capacity is less than the sequence capacity of the corresponding special sequence, establish a special index corresponding to the special sequence in the location area and retain it;

[0074] If it does not exist, a blank area is expanded in the base layer, and the corresponding special sequence is placed in the blank area;

[0075] All the sequences arranged sequentially in the base layer are input into the snowmelt output model in turn to obtain the snowmelt flood characteristics.

[0076] In one possible implementation, after estimating the downstream flood volume, step 3 further includes:

[0077] Determine the total number of years n1 in the N-year history of the corresponding downstream that belong to the flood history, and determine the number of flood volumes n3 that belong to the maximum historical flood volume planning in the total number of years n1, and determine the continuous flood duration and flood rise time points corresponding to the maximum historical flood volume;

[0078] According to the following formula, calculate the historical flood disaster index Z corresponding to the downstream;

[0079]

[0080] Among them, β1 represents the planning weight for the planning that does not belong to the maximum historical flood volume, β2 represents the planning weight for the planning that belongs to the maximum historical flood volume, and Y i1 represents the current flood volume that does not correspond to the maximum historical flood volume planning; Y i2，j1 represents the flood volume at the i2th flood time point corresponding to the j1th maximum historical flood volume plan; Y j1 represents the current flood volume corresponding to the j1th maximum historical flood volume planning; T j1 It indicates the duration of continuous flood corresponding to the j1th maximum historical flood volume planning;

[0081] According to the flood disaster index Z and the downstream flood volume, corresponding disaster prevention measures are retrieved from the flood disaster database, and preventive reminders are issued.

[0082] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the written description, claims, and drawings.

[0083] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0084] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0085] Figure 1 It is a flow chart of a method for estimating downstream flood volume of a coupled glacial lake outburst flood and snowmelt flood in an embodiment of the present invention;

[0086] Figure 2 A schematic diagram of river confluence in an embodiment of the present invention;

[0087] Figure 3 4 is a sequence reset framework diagram in an embodiment of the present invention. DETAILED DESCRIPTION

[0088] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0089] The present invention provides a method for estimating the downstream flood volume of coupled glacial lake outburst flood and snowmelt flood, such as Figure 1 As shown, including:

[0090] Step 1: Use multi-source remote sensing image data to extract the change information of the glacial lake surface area upstream of the target, and combine the historical parameter information of the glacial lake to estimate the outburst flood volume of the glacial lake;

[0091] Step 2: Extract the target sub-basin upstream of the target according to the distributed water model, obtain the watershed information of the extracted target sub-basin, and estimate the daily snowmelt amount of the corresponding target sub-basin;

[0092] Step 3: Determine the characteristics of dam-break floods in the glacial lake and snowmelt floods in the target sub-basin, and estimate the downstream flood volume based on the determined flood characteristics and the estimated outburst flood volume and daily snowmelt volume.

[0093] In this embodiment, the historical parameter information of the ice lake is related to the high-precision topographic map of the ice lake when it was empty and the digital elevation model of the ice lake basin and its surroundings.

[0094] In this embodiment, due to the different characteristics of the two flood types, dam-break flood and glacier-snowmelt flood, the dam-break flood has the characteristics of fast rise, large rise rate, short flood duration, and a thin single peak in the flood process, with a high flood peak but a small flood volume. The glacier-snowmelt flood process has a long history, a small flow rate but a large total flood volume. Since snowmelt is closely related to temperature, the flood process caused by snowmelt has obvious daily changes. Therefore, in the process of estimating the downstream flood volume, it is necessary to determine the corresponding type of flood characteristics in advance.

[0095] The beneficial effect of the above technical solution is that it provides support for risk assessment of downstream water conservancy projects posed by glacial disasters through a comprehensive estimation method of glacial lake outburst flood volume and snowmelt flood volume.

[0096] The present invention provides a method for estimating the downstream flood volume of coupled glacial lake outburst flood and snowmelt flood, step 1: using multi-source remote sensing image data to extract the lake surface area change information of the target upstream glacial lake, and combining the historical parameter information of the glacial lake to estimate the outburst flood volume of the glacial lake, including:

[0097] Using multi-source remote sensing image data, the daily changes in the surface area of ​​the glacial lake after the glacial lake is filled with water are extracted;

[0098] Using the topographic map of the glacial lake in the empty state in the corresponding year, a digital elevation model of the glacial lake basin and its surroundings was constructed;

[0099] Based on the digital elevation model and using spatial analysis methods, the lake surface elevation, lake basin volume, and lake surface area of ​​the glacial lake are calculated, and the lake surface elevation-volume change curve and lake surface elevation-area change curve are constructed, and then the lake surface area-water storage capacity change curve of the glacial lake is calculated;

[0100] Based on the extracted lake area changes and the estimated results, the daily change in the glacial lake water storage corresponding to the glacial lake outburst, i.e., the outburst flood volume, is estimated:

[0101] B t =V(S t )-V(S t-1 )=a×S t b -a×S t-1 b

[0102] Among them: B t is the outburst volume at time t, S t is the lake area monitored at time t, S t-1 is the lake area monitored at time t-1, V(S t ) is the glacial lake storage capacity at time t, V(S t-1 ) is the storage capacity of the glacial lake at time t-1. According to the lake surface area-water storage capacity change curve, the functional relationship between the water storage capacity of the glacial lake and the lake surface area is exponential, and a and b are the two coefficients of the exponential function.

[0103] The beneficial effects of the above technical solution are: by estimating the outburst flood volume, a basis is provided for estimating the downstream flood volume, and indirectly support is provided for the risk assessment of glacial disasters on downstream water conservancy projects.

[0104] The present invention provides a method for estimating downstream flood volume of coupled glacial lake outburst flood and snowmelt flood, step 2: obtaining the extracted watershed information of the target sub-watershed, estimating the daily snowmelt volume of the corresponding target sub-watershed, including:

[0105] Monitor the target sub-basin based on the snow cover equipment, obtain the snow-covered pixels and non-snow-covered pixels of the corresponding target sub-basin, and determine the snow cover percentage of the target sub-basin based on the snow-covered pixels and non-snow-covered pixels;

[0106]

[0107] Among them, P snow,t is the percentage of snow cover area corresponding to the target sub-basin at time t, Cover snow,t is the number of snow-covered pixels in the target sub-basin at time t. subasin is the total number of pixels in the corresponding watershed, Cover no-snow,t is the number of non-snow pixels in the target sub-basin at time t;

[0108] Based on the snow depth remote sensing inversion dataset, the first snow depth corresponding to the target sub-basin within a specific period is selected;

[0109] Obtain the current snow depth of the target sub-basin monitored by remote sensing on that day;

[0110] Determine an average snow depth of the corresponding target sub-basin based on the first snow depth and the current snow depth;

[0111]

[0112] Among them, H snow,t is the average snow depth of the target sub-basin at time t, H t is the current snow depth of the target sub-basin at time t, H t-i represents the first snow depth of the corresponding target sub-basin at the time of historical screening, H t+i It represents the first snow depth of the corresponding target sub-basin at time t+i of historical screening, and the specific period is 14 days;

[0113] Calculate the daily snowmelt amount of the corresponding target sub-basin based on the snow cover percentage, the average snow depth and the watershed area of ​​the corresponding target sub-basin;

[0114] M t =S subbasin ×P snow,t ×H snow,t

[0115] Among them, M t is the daily snowmelt amount of the corresponding target sub-basin at time t.

[0116] In this embodiment, the specific period is 14 days. This is because the remote sensing inversion method of snow depth is complex and has many influencing factors. It relies on measured data and cannot be obtained in real time during the disaster risk assessment process. Therefore, the daily snow depth remote sensing inversion dataset for the past 50 years is used to take the multi-year average snow depth on the day within 7 days before and after the specific date.

[0117] The beneficial effects of the above technical solution are: by estimating the daily snowmelt amount, a basis is provided for estimating the downstream flood volume, and indirectly support is provided for the risk assessment of glacier disasters to downstream water conservancy projects.

[0118] The present invention provides a method for estimating downstream flood volume of coupled glacial lake outburst flood and snowmelt flood, wherein step 4, before estimating downstream flood volume based on the determined flood characteristic results and the estimated outburst flood volume and daily snowmelt volume, further comprises:

[0119] Determine the inflow boundary conditions of the corresponding target river section, where the inflow boundary conditions are related to the outburst flood volume and daily snowmelt volume;

[0120] Determine the water system distribution of the corresponding target river section, and at the same time, determine the basic characteristics of the corresponding target river section;

[0121] Based on the inflow boundary conditions, water system distribution and basic characteristics, the outlet flow process of the corresponding target river section is obtained, and the outlet flow process is related to the downstream flood volume.

[0122] Among them, the inflow boundary conditions corresponding to the target river section are determined, including:

[0123] Determine the first flow process of the estimated daily snowmelt to the corresponding outlet of each target sub-basin;

[0124] Determine the second flow process of the estimated outburst flood volume of each glacial lake to the corresponding outlet;

[0125] The first flow process and the second flow process are superimposed, and the superposition result is used as the inflow boundary condition.

[0126] For this embodiment, it is assumed that each sub-basin contains two flow processes, one is the glacial lake outburst flow, and the other is the glacier snowmelt flow. The superposition of the two flow processes at the outlet of the sub-basin is used as the inflow boundary condition of the river section. The river section is based on the distribution of the water system, and is divided according to the basic characteristics such as the cross-section type, slope and roughness of the river section. The improved Muskingum method is used to perform flood evolution calculation to finally obtain the basin outlet flow process.

[0127] The improved Muskingum method is used to calculate flood evolution. The inflow process is divided into two parts: glacial lake outburst and glacier snowmelt. The flow process from the estimated snowmelt in each sub-basin to the sub-basin outlet and the flow process from the estimated glacial lake outburst flow in the sub-basin to the sub-basin outlet are superimposed as the inflow boundary conditions of the upstream river section.

[0128] like Figure 2 As shown, it can be used as a schematic diagram of river confluence.

[0129] The beneficial effect of the above technical solution is that through the superposition of two flow processes, it is convenient to provide an effective process basis for estimating the downstream flood volume, and indirectly provide support for the risk assessment of glacial disasters on downstream water conservancy projects.

[0130] The present invention provides a method for estimating downstream flood volume of coupled glacial lake outburst flood and snowmelt flood, and the process of obtaining the outlet flow process of the corresponding target river section based on the inflow boundary conditions, water system distribution and basic characteristics also includes:

[0131] According to the following formula (1), the water storage capacity of the corresponding target river section is simulated, and the water storage capacity of the prism and the water storage capacity of the wedge are simulated:

[0132]

[0133] Among them, B t-1 and B t are the glacial lake outburst values ​​at t-1 and at t respectively; M t-1 and M t are the glacier snowmelt values ​​during the inflow process at time t-1 and time t, respectively; Q t-1 and Q t are the outflow process values ​​at t-1 and t respectively; S t-1 and S t are the water storage of the river section at time t-1 and time t respectively; Δt represents the time difference between time t-1 and time t;

[0134] According to formula (2), the water storage capacity S t To define:

[0135] S t =KQ t +KX(B t +M t -Q t )=K(X(B t +M t )+(1-X)Q t ) (2)

[0136] Where K is the movement time of the flood wave through the evolution section of the corresponding target river section; X represents the weight of the glacial lake outburst value and the glacier snowmelt value compared with the outflow, with a value range of 0-0.5; Q t is the outflow rate of the prism storage at time t;

[0137] Substituting formula (2) into formula (1) yields formula (3):

[0138]

[0139] In one possible implementation, the water storage capacity S t The definition process also includes:

[0140] According to the following formulas (4) and (5), the parameters K and X are estimated:

[0141]

[0142]

[0143] Among them, V w is the flood velocity of the corresponding target river section, which is g times the corresponding average flow velocity, and the value range of g is [1.33, 1.67]; B is the width of the top of the corresponding flood water surface; Q0 is the reference flow taken from the inflow process line; S0 is the bottom slope or friction angle of the corresponding target river section; c is the flood wave velocity of the corresponding target river section; Δx is the length of the river section of the corresponding target river section.

[0144] The beneficial effect of the above technical solution is that the evolution calculation of formulas (1)-(5) can be effectively recursively deduced to finally obtain the flood flow process at the outlet, which indirectly provides support for the risk assessment of glacier disasters on downstream water conservancy projects.

[0145] The present invention provides a method for estimating downstream flood volume of coupled glacial lake outburst flood and snowmelt flood, wherein step 3 determines the snowmelt flood characteristics of the target sub-basin, including:

[0146] Determine the initial snowmelt characteristics of the target sub-basin based on historical remote sensing monitoring information;

[0147] Monitor the temperature set of the target sub-basin in the current time period, and also monitor the current sensing information corresponding to the target sub-basin;

[0148] Based on the temperature set and the sensing information, a first snowmelt characteristic of the target sub-basin is established;

[0149] Monitor the surrounding environment of the target sub-basin, analyze the monitoring results, and construct the impact set and location set;

[0150] Based on the location set, determine the connected inlets associated with the target sub-basin;

[0151] Performing a first pre-analysis on the impact set and a second pre-analysis on the connected inlet to extract the impact factors on the target sub-basin, and inputting the impact factors into the impact constraint model to obtain the impact constraint conditions;

[0152] Based on the detection devices set at several detection points of the target sub-basin, the historical moisture information of the corresponding detection points is obtained to determine the moisture constraint conditions of the target sub-basin, wherein the historical moisture information includes: the influence of vegetation coverage on the moisture infiltration of the corresponding detection point, the moisture infiltration of the corresponding detection point, the moisture consumption of the corresponding detection point at the corresponding temperature, and the influencing factors of the moisture measurement of the corresponding detection point affected by the external environment;

[0153] Based on the impact constraint and the moisture constraint, determine the second snowmelt characteristics for the target sub-basin;

[0154] The initial snowmelt characteristics are adjusted based on the first snowmelt characteristics and the second snowmelt characteristics to obtain the snowmelt flood characteristics.

[0155] In this embodiment, the initial snowmelt characteristics are simply determined according to the historical remote sensing monitoring information. For example, the snowmelt speed and snowmelt amount in different time periods are preliminarily determined for historical time periods, such as December last year. The first snowmelt characteristics are mainly based on the temperature and sensing information to obtain the current December snowmelt speed and snowmelt amount.

[0156] In this implementation, the surrounding environment is monitored because there may be operations such as changing tillage and filling around the basin, as well as dangers such as fire, and then the corresponding impact set is constructed. The construction of the location set, such as tributaries 1, 2, and 3 connected to the basin, is used to determine the connected entrances for preliminary analysis in order to determine the impact of different tributaries on the flow of the basin. The impact set is pre-analyzed to determine the impact of the above-mentioned impacts on the flow, to ensure the reliability of the impact, and to provide a basis for the subsequent determination of the downstream flood volume.

[0157] In this embodiment, the impact analysis model is pre-found, and the detection devices and the like are pre-set, and the detection points are feasible detection points of the basin planned based on historical conditions.

[0158] In this embodiment, the influencing factors are, for example, external operating factors, tributary factors, etc., and then the constraints of the corresponding factors are obtained, such as the impact of external operating factors on the river basin, the impact of tributary factors on the river basin, and then the impact constraints are obtained through the impact constraint model.

[0159] The second snowmelt characteristic determined in this embodiment is determined based on a combination of the two constraints.

[0160] The beneficial effect of the above technical solution is: determining the snowmelt characteristics through three types of situations, and using them as a basis to determine the characteristics of snowmelt floods, ensuring the reliability of its determination, and indirectly providing support for the risk assessment of glacier disasters on downstream water conservancy projects.

[0161] The present invention provides a method for estimating downstream flood volume of coupled glacial lake outburst flood and snowmelt flood, and adjusts the initial snowmelt characteristics based on the first snowmelt characteristics and the second snowmelt characteristics to obtain snowmelt flood characteristics, including:

[0162] Obtaining a first sequence of first snowmelt characteristics, a second sequence of second snowmelt characteristics, and an initial sequence of initial snowmelt characteristics;

[0163] Placing the initial sequence on a base layer of a sequence reset frame, matching the first snowmelt feature and the second snowmelt feature with layer attributes of the remaining layers on the sequence reset frame, and placing the first sequence and the second sequence on corresponding matching layers;

[0164] Extracting first special description information of the first sequence on the corresponding matching layer, and extracting second special description information of the second sequence on the corresponding matching layer;

[0165] Determine the layer element of the corresponding matching layer, and calibrate the special element in the layer element, determine whether there is a special sequence related to the special element in the sequence existing in the corresponding matching layer, if so, retain the special sequence, and determine the position attribute of the sequence position of the retained special sequence;

[0166] If it does not exist, the sequence corresponding to the matching layer is transmitted to the storage unit for storage;

[0167] Determine whether there is a location area related to the location attribute in the base layer. If so, determine the area capacity of the location area. If the area capacity is greater than or equal to the sequence capacity of the corresponding special sequence, place the corresponding special sequence in the location area. If the area capacity is less than the sequence capacity of the corresponding special sequence, establish a special index corresponding to the special sequence in the location area and retain it.

[0168] If it does not exist, expand the blank area in the base layer and place the corresponding special sequence in the blank area;

[0169] All the sequences arranged sequentially in the base layer are input into the snowmelt output model in turn to obtain the snowmelt type flood characteristics.

[0170] like Figure 3As shown, it is a structural diagram of the sequence reset framework, 1 represents the base layer, 2 and 3 represent the corresponding matching layers, such as the second sequence placed on 2, the first sequence placed on 3, and the initial sequence placed on 1. At this time, the initial sequence is the corresponding initial snowmelt feature, the first sequence is the corresponding first snowmelt feature, and the second sequence corresponds to the second snowmelt feature.

[0171] For example: the initial sequence is 111, 222, 333 at positions a, b, and c as shown in the figure. There is a special element in the matching layer corresponding to the first sequence, and the corresponding special sequence is 44. There is a special element in the matching layer corresponding to the second sequence, and the corresponding special sequence is 55. The position attribute of the position in the matching layer corresponding to the special sequence determines the corresponding position area in the base layer. At this time, the position area can place the special sequences 44 and 55. Therefore, 44 and 55 are placed in the base layer and output to the snowmelt output model in sequence according to the final sequence order of the base layer to obtain the characteristics of snowmelt flood.

[0172] In this embodiment, the location attribute is, for example, an attribute related to water infiltration or the like.

[0173] In this embodiment, the special element is pre-set for the matching layer and is an inherent element of the matching layer, for example, it is also related to parameters such as water infiltration.

[0174] The beneficial effect of the above technical solution is: by placing the first sequence and the second sequence in the corresponding matching layer, it is convenient to effectively screen the first sequence and the second sequence as special sequences, and by determining the location area, the special sequence is effectively placed, and finally based on the output model, the characteristics of snowmelt floods are obtained, which provides an effective basis for determining the flood volume and indirectly provides support for the risk assessment of glacier disasters on downstream water conservancy projects.

[0175] The present invention provides a method for estimating downstream flood volume of coupled glacial lake outburst flood and snowmelt flood, wherein step 3, after estimating the downstream flood volume, further comprises:

[0176] Determine the total number of years n1 in the N-year history of the corresponding downstream that belong to the flood history, and determine the number of flood volumes n3 that belong to the maximum historical flood volume planning in the total number of years n1, and determine the continuous flood duration and flood rise time points corresponding to the maximum historical flood volume;

[0177] According to the following formula, calculate the historical flood disaster index Z corresponding to the downstream;

[0178]

[0179] Among them, β1 represents the planning weight for the planning that does not belong to the maximum historical flood volume, β2 represents the planning weight for the planning that belongs to the maximum historical flood volume, and Yi1 represents the current flood volume that does not correspond to the maximum historical flood volume planning; Y i2，j1 represents the flood volume at the i2th flood time point corresponding to the j1th maximum historical flood volume plan; Y j1 represents the current flood volume corresponding to the j1th maximum historical flood volume planning; T j1 It indicates the duration of continuous flood corresponding to the j1th maximum historical flood volume planning;

[0180] According to the flood disaster index Z and the downstream flood volume, the corresponding disaster prevention measures are retrieved from the flood disaster database and preventive reminders are issued.

[0181] In this embodiment, the flood disaster database includes: a flood disaster index range, a downstream flood volume range, and a one-to-one correspondence between measures.

[0182] The beneficial effect of the above technical solution is: by calculating the flood disaster index of the downstream under historical conditions according to the formula, and combining it with the current downstream flood volume, disaster prevention measures are adopted to conduct risk assessment and protection for the downstream.

[0183] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for estimating downstream flood volume of coupled glacial lake outburst flood and snowmelt flood, characterized in that: include: Step 1: Using multi-source remote sensing image data, extract the lake area change information of the target upstream glacial lake, and combine the historical parameter information of the glacial lake to estimate the outburst flood volume of the glacial lake; Step 2: Extract the target sub-basin upstream of the target according to the distributed water model, obtain the watershed information of the extracted target sub-basin, and estimate the daily snowmelt amount of the corresponding target sub-basin; Step 3: Determine the dam-burst flood characteristics of the glacial lake and the snowmelt flood characteristics of the target sub-basin, and estimate the downstream flood volume based on the determined flood characteristic results and the estimated outburst flood volume and daily snowmelt volume; Among them, step 3, based on the determined flood characteristics and the estimated flood outburst volume and daily snowmelt volume, before estimating the downstream flood volume, also includes: Determine the inflow boundary conditions of the corresponding target river section, wherein the inflow boundary conditions are related to the outburst flood volume and the daily snowmelt volume; Determine the water system distribution of the corresponding target river section, and at the same time, determine the basic characteristics of the corresponding target river section; Based on the inflow boundary conditions, water system distribution and basic characteristics, the outlet flow process of the corresponding target river section is obtained, and the outlet flow process is related to the downstream flood volume; The process of obtaining the outlet flow of the corresponding target river section based on the inflow boundary conditions, water system distribution and basic characteristics also includes: According to the following formula (1), the water storage capacity of the corresponding target river section is simulated, and the water storage capacity of the prism and the water storage capacity of the wedge are simulated: (1) in, and are the glacial lake outburst values ​​during the inflow process at t-1 and t, respectively; and are the glacier snowmelt values ​​during the inflow process at time t-1 and time t, respectively; are the outflow process values ​​at t-1 and t respectively; The river sections are t-1 and t The amount of water stored at a given time; It represents the time difference between time t-1 and time t; According to formula (2), the water storage capacity To define: (2) in, K is the movement time of the flood wave through the evolution section of the corresponding target river section; X represents the weight of the GLB and glacier melt values ​​compared to the outflow, ranging from 0 to 0.5; is the outflow rate of the prism storage at time t; Substituting formula (2) into formula (1) yields formula (3): (3)； Step 1: using multi-source remote sensing image data to extract the lake area change information of the target upstream glacial lake, and combining the historical parameter information of the glacial lake to estimate the outburst flood volume of the glacial lake, including: Using multi-source remote sensing image data, the daily changes in the surface area of ​​the glacial lake after the glacial lake is filled with water are extracted; Using the topographic map of the glacial lake in the empty state in the corresponding year, a digital elevation model of the glacial lake basin and its surroundings was constructed; Based on the digital elevation model and using the spatial analysis method, the lake surface elevation value, the volume of the lake basin, and the lake surface area of ​​the ice lake are calculated, and a lake surface elevation-volume change curve and a lake surface elevation-area change curve are constructed, and then the lake surface area-water storage capacity change curve of the ice lake is calculated; Based on the extracted lake area changes and the estimated results, the daily change in the glacial lake water storage corresponding to the glacial lake outburst, i.e., the outburst flood volume, is estimated: ； in: is the outburst flood volume at time t, is the lake area monitored at time t, is the lake area monitored at t-1, is the glacial lake capacity at time t, is the storage capacity of the glacial lake at time t-1. According to the lake surface area-water storage capacity change curve, the functional relationship between the water storage capacity of the glacial lake and the lake surface area is exponential, and a and b are the two coefficients of the exponential function; Among them, step 2: obtaining the watershed information of the extracted target sub-watershed and estimating the daily snowmelt amount of the corresponding target sub-watershed, including: Monitoring the target sub-basin based on the snow cover device, obtaining snow-covered pixels and non-snow-covered pixels corresponding to the target sub-basin, and determining the snow cover percentage of the target sub-basin based on the snow-covered pixels and the non-snow-covered pixels; ； in, is the percentage of snow cover area corresponding to the target sub-basin at time t, is the number of snow-covered pixels in the target sub-basin at time t, is the total number of pixels in the corresponding watershed, is the number of non-snow pixels in the target sub-basin at time t; Based on the snow depth remote sensing inversion dataset, the first snow depth corresponding to the target sub-basin within a specific period is selected; Obtaining the current snow depth of the target sub-basin monitored by remote sensing on that day; Determine an average snow depth of the corresponding target sub-basin based on the first snow depth and the current snow depth; ； in, is the average snow depth of the target sub-basin at time t, is the current snow depth of the target sub-basin at time t, represents the first snow depth of the corresponding target sub-basin at the time of historical screening, It represents the first snow depth of the corresponding target sub-basin at t+i of the historical screening, and the specific period is 14 days; Calculate the daily snowmelt amount of the corresponding target sub-basin according to the snow cover percentage, the average snow depth and the watershed area of ​​the corresponding target sub-basin; ； in, is the daily snowmelt amount corresponding to the target sub-basin at time t, is the watershed area corresponding to the target sub-basin.

2. The downstream flood volume estimation method according to claim 1, characterized in that: Determine the inflow boundary conditions corresponding to the target river section, including: Determine the first flow process of the estimated daily snowmelt to the corresponding outlet of each target sub-basin; Determine the second flow process of the estimated outburst flood volume of each glacial lake to the corresponding outlet; The first flow process and the second flow process are superimposed, and the superposition result is used as an inflow boundary condition.

3. The downstream flood volume estimation method according to claim 1, characterized in that: Water storage capacity S t The definition process also includes: According to the following formulas (4) and (5), the estimated parameters K and X： (4) (5) in, is the flood velocity of the target river section, which is g times the corresponding average flow velocity, and the value range of g is [1.33, 1.67]; B is the width corresponding to the top of the flood water surface; is the reference flow rate taken from the inflow process line; S 0 is the bottom slope or friction angle corresponding to the target river section; c is the flood wave velocity corresponding to the target river section; is the length of the river section corresponding to the target river section.

4. The downstream flood volume estimation method according to claim 1, characterized in that: Step 3, determining the snowmelt flood characteristics of the target sub-basin, including: Determining initial snowmelt characteristics of the target sub-basin based on historical remote sensing monitoring information; Monitoring the temperature set of the target sub-basin in the current time period, and also monitoring the current sensing information corresponding to the target sub-basin; Establishing a first snowmelt characteristic of the target sub-basin based on the temperature set and the sensing information; Monitor the surrounding environment of the target sub-basin, analyze the monitoring results, and construct an impact set and a location set; Based on the set of locations, determining a connected inlet associated with the target sub-basin; Performing a first pre-analysis on the impact set and a second pre-analysis on the connected inlet to extract the impact factors on the target sub-basin, and inputting the impact factors into the impact constraint model to obtain the impact constraint conditions; Based on the detection devices set at several detection points of the target sub-basin, the historical moisture information of the corresponding detection points is obtained to determine the moisture constraint conditions of the target sub-basin, wherein the historical moisture information includes: the influence of vegetation coverage on the moisture infiltration of the corresponding detection point, the moisture infiltration of the corresponding detection point, the moisture consumption of the corresponding detection point at the corresponding temperature, and the influencing factors of the moisture measurement of the corresponding detection point affected by the external environment; Based on the impact constraint and the moisture constraint, determine the second snowmelt characteristics for the target sub-basin; The initial snowmelt characteristics are adjusted based on the first snowmelt characteristics and the second snowmelt characteristics to obtain the snowmelt flood characteristics.

5. The method for estimating downstream flood volume according to claim 4, characterized in that: The initial snowmelt characteristic is adjusted based on the first snowmelt characteristic and the second snowmelt characteristic to obtain snowmelt flood characteristics, including: Acquire a first sequence of the first snowmelt characteristics, a second sequence of the second snowmelt characteristics, and an initial sequence of the initial snowmelt characteristics; Placing the initial sequence on a base layer of a sequence resetting framework, matching the first snowmelt feature and the second snowmelt feature with layer attributes of remaining layers on the sequence resetting framework, and placing the first sequence and the second sequence on corresponding matching layers; Extracting first special description information of the first sequence on the corresponding matching layer, and extracting second special description information of the second sequence on the corresponding matching layer; Determine the layer element of the corresponding matching layer, and calibrate the special element in the layer element, determine whether there is a special sequence related to the special element in the sequence existing in the corresponding matching layer, if so, retain the special sequence, and determine the position attribute of the sequence position of the retained special sequence; If it does not exist, the sequence corresponding to the matching layer is transmitted to the storage unit for storage; Determine whether there is a location area related to the location attribute in the base layer, and if so, determine the area capacity of the location area, and if the area capacity is greater than or equal to the sequence capacity of the corresponding special sequence, place the corresponding special sequence in the location area, and if the area capacity is less than the sequence capacity of the corresponding special sequence, establish a special index corresponding to the special sequence in the location area and retain it; If it does not exist, a blank area is expanded in the base layer, and the corresponding special sequence is placed in the blank area; All the sequences arranged sequentially in the base layer are input into the snowmelt output model in turn to obtain the snowmelt flood characteristics.

6. The method for estimating downstream flood volume according to claim 1, characterized in that: Step 3, after estimating the downstream flood volume, also includes: Determine the total number of years n1 in the N-year history of the corresponding downstream that belong to the flood history, and determine the number of flood volumes n3 that belong to the maximum historical flood volume planning in the total number of years n1, and determine the continuous flood duration and flood rise time points corresponding to the maximum historical flood volume; According to the following formula, calculate the historical flood disaster index Z corresponding to the downstream; ； in, It represents the planning weight for the plan that does not belong to the maximum historical flood volume plan. Represents the planning weight for the maximum historical flood planning. Indicates the current flood volume that does not correspond to the maximum historical flood volume planning; It represents the flood volume at the i2th flood time point corresponding to the j1th maximum historical flood volume plan; represents the current flood volume corresponding to the j1th maximum historical flood volume planning; It indicates the duration of continuous flood corresponding to the j1th maximum historical flood volume planning; According to the flood disaster index Z and the downstream flood volume, corresponding disaster prevention measures are retrieved from the flood disaster database, and preventive reminders are issued.

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