A landslide surge simulation method based on SPH near-field and far-field coupling calculation

Abstract

The invention discloses a landslide surge simulation method based on SPH near-field and far-field coupling calculation, comprising the following steps: (1) establishing an SPH near-field landslide surge calculation model; (2) performing SPH near-field landslide surge calculation; (3) extracting the sliding body movement speed, the first wave height, and the opposite bank wave height in the SPH near-field landslide surge; (4) establishing a far-field landslide surge calculation model; (5) based on the first wave height obtained by the SPH near-field landslide surge calculation model, by calibrating the opposite bank wave height of the far-field model, determining the surge input in the far-field landslide surge calculation model; (6) performing far-field surge calculation to obtain the far-field propagation characteristics of the surge; (7) extracting the maximum wave height of each measuring point in the far-field landslide surge calculation model, drawing a surge maximum wave height distribution cloud map, and determining the disaster impact range. The invention solves the problem that the material parameters of the rock and soil mass are difficult to accurately determine and the surge generation boundary is difficult to accurately input in the landslide surge simulation calculation.

Description

Technical Field

[0001] The invention relates to a simulation calculation method of landslide surge in the field of geotechnical engineering, and in particular to a landslide surge simulation method based on SPH far-field and near-field coupling calculation. Background Art

[0002] Landslide surge, as a secondary disaster caused by landslide entering water, seriously threatens the safety of life and property of people on both sides of the river and the stable operation of the dam. Correctly assessing landslide surge disasters and conducting targeted prevention and control has important scientific significance and engineering value.

[0003] Landslide surge mainly includes the surge caused by the landslide entering the water and the propagation of the surge. The evolution characteristics of the landslide movement are the main influencing factors of the landslide surge, which play a controlling role in the size and characteristics of the landslide surge. The mechanical parameters of the rock and soil determine the movement of the landslide, and the accurate input of the parameters is a difficult problem in the simulation calculation. The material parameters of the method of characterizing rock and soil materials with non-Newtonian fluids are difficult to obtain, and the DEM method requires a lot of calibration work. In the simulation calculation of surge propagation, the surge generation boundary is used as the water-rock interaction boundary to control the accuracy of the calculation results.

[0004] The impact range of landslide surge is wide, ranging from tens of kilometers. The accuracy of the numerical method for solving the NS equation is affected by the grid size, and it is difficult to balance the calculation accuracy and calculation time. The surge characteristics of the surge generating boundary in the hydrodynamic method are calculated using formulas, which cannot accurately reflect the entire process of the landslide entering the water and driving the water body to generate surges. Specifically, the hydrodynamic method can better characterize the propagation of surges. This method shortens the calculation time while ensuring the calculation accuracy, and has outstanding advantages in calculating the propagation of surges over a wide range. However, the surge characteristics of the landslide surge generating boundary input in the hydrodynamic method are mostly determined by empirical formulas. The surge characteristics are obtained after a lot of simplification, and it is difficult to reflect the landslide surge characteristics under the conditions of the actual sliding body and sliding surface, resulting in a large deviation between the initial conditions of the far-field propagation of the surge and the actual conditions, and the accuracy of the subsequent calculation results is reduced. Summary of the invention

[0005] Purpose of the invention: In view of the problems existing in the calculation of landslide surge, the present invention provides a landslide surge simulation method based on SPH far-field and near-field coupling calculation. By comparing the wave heights of the opposite bank in the far and near fields, the accuracy of the surge input at the surge generating boundary in the far-field calculation model is determined, thereby solving the problems of the difficulty in accurately determining the material parameters of the rock and soil mass and the difficulty in accurately inputting the surge generating boundary in the calculation of landslide surge.

[0006] Technical solution: The landslide surge simulation method based on SPH far-field and near-field coupling calculation of the present invention comprises the following steps:

[0007] (1) Establishing the SPH near-field landslide surge calculation model; including steps (1.1) to (1.5):

[0008] (1.1) Process the geological profile to preserve the bottom sliding surface, sliding body with lithological boundary, sliding belt and water level line;

[0009] (1.2) Use the lithology boundary line and water level line to cut the sliding body, and use the sliding bodies with different lithology and saturation as the sliding bodies of the SPH near-field landslide surge calculation model;

[0010] (1.3) The bottom sliding surface is shifted downward to a surface with thickness, and the surface with thickness is used as the bottom boundary of the SPH near-field landslide surge calculation model;

[0011] (1.4) Establish water bodies based on the water level and the terrain below the water level;

[0012] (1.5) Fill the sliding body of step (1.2), the sliding belt of step (1.1), the bottom boundary of step (1.3) and the water body (1.4) of step (1.4) with particles of the same interval to determine the distribution of SPH particles;

[0013] (2) Perform SPH near-field landslide surge calculations, including steps (2.1) to (2.3):

[0014] (2.1) Using the Mohr-Coulomb constitutive model, the rock and soil parameters in the SPH near-field landslide surge calculation model are assigned according to the mechanical properties of the sliding body and the sliding belt, and the pressure p of the water body is calculated using the state equation;

[0015] (2.2) The bottom boundary is set as a fixed boundary to restrict the movement of the sliding body and the water body;

[0016] (2.3) Set gravity, calculation time and smoothing length, perform SPH near-field landslide surge calculation, and obtain the evolution process of landslide surge and surge height characteristics;

[0017] (3) Extracting the sliding body movement velocity, the first wave height, and the opposite bank wave height in the SPH near-field landslide surge; including steps (3.1) to (3.3):

[0018] (3.1) Arrange a velocity monitoring point at the center of the sliding body in step (1.2), extract the velocity change curve of the particles at the center of the sliding body, and obtain the velocity change process of the sliding body;

[0019] (3.2) arranging surge height measuring points at the leading edge of the sliding body in step (1.2), extracting the wave height change of the water surface at the leading edge of the sliding body, and obtaining the first wave wave height change curve;

[0020] (3.3) Set up wave height measuring points on the opposite bank, extract the wave height changes on the opposite bank of the landslide, and obtain the maximum wave height on the opposite bank;

[0021] (4) Establishing a remote-field landslide surge calculation model; including steps (4.1) to (4.4):

[0022] (4.1) According to the positional relationship between the key impact area of ​​landslide surge and the distance from the landslide, determine the calculation range of the upstream and downstream of the landslide surge;

[0023] (4.2) According to the position of each control point in the geological plane map and the surface elevation, a far-field landslide surge calculation model that conforms to the terrain characteristics is established;

[0024] (4.3) According to the position, area and volume of the section used in the SPH near-field landslide surge calculation model, determine the length and direction of the surge generation boundary in the far-field landslide surge calculation model;

[0025] (4.4) Set the upstream and downstream boundaries in the far-field landslide surge calculation model as fixed water level boundaries, and set the water level at which the landslide starts to slide as the calculation water level;

[0026] (5) Based on the head wave height obtained by the SPH near-field landslide surge calculation model in step (3.2), calibrate the opposite bank wave height of the far-field model and determine the surge input in the far-field landslide surge calculation model;

[0027] (6) Calculate the far-field landslide surge calculation model to obtain the changes of wave height over time and space during surge propagation;

[0028] (7) Extract the maximum wave height of each measuring point in the far-field landslide surge calculation model, draw a cloud map of the maximum wave height distribution, and determine the impact range of the landslide surge.

[0029] The soil parameters in step (2.1) include cohesion, internal friction angle, elastic modulus, Poisson's ratio and density.

[0030] The pressure p of the water body calculated in step (2.1) is:

[0031]

[0032] Where γ is a constant, which is 7 in water; ρ0 is the initial density of water; ρ is the density of the set water body, and k0 is a function of the speed of sound in water.

[0033] The key impact areas of landslide surge in step (4.1) include dams or residential areas.

[0034] In step (4.3), the calculation method of the surge generation boundary length is: sliding body volume / section area, and the direction of the surge generation boundary is the direction perpendicular to the section line.

[0035] Step (5) includes steps (5.1) to (5.2):

[0036] (5.1) Based on the first wave high water line in the SPH near-field landslide surge calculation model, the surge waveform at the surge generation boundary is calibrated;

[0037] (5.2) The accuracy of the surge wave input of the surge wave generation boundary in the far-field landslide surge wave calculation model is determined based on whether the difference between the opposite-shore wave heights of the far-field landslide surge wave calculation model and the SPH near-field landslide surge wave calculation model and the opposite-shore wave height of the SPH near-field landslide surge wave calculation model are less than the set value.

[0038] In step (5.2), whether the ratio of the difference between the opposite bank wave height of the far-field landslide surge calculation model and the SPH near-field landslide surge calculation model and the opposite bank wave height of the SPH near-field landslide surge calculation model is less than a set value, the set value ranges from 0 to 5%.

[0039] In step (6), the far-field landslide surge calculation model is calculated, the calculation time is increased, and the far-field landslide surge calculation model is recalculated so that the surge completes the propagation in the entire basin and obtains the change of wave height with time and space during the far-field surge propagation process.

[0040] In step (7), wave height measuring points are arranged at equal intervals in the far-field landslide surge calculation model, the maximum wave height of each measuring point in the far-field landslide surge calculation model is extracted, and a maximum wave height distribution cloud map is drawn. The influence range of the landslide surge is determined by the distribution of the maximum wave height of the surge reflected in the cloud map.

[0041] Working principle: The present invention is based on the landslide surge simulation method of SPH near-field coupling calculation. The method uses the Moore-Coulomb constitutive model to characterize the rock and soil materials, combines the landslide surge evolution process obtained by the SPH near-field landslide surge calculation model with the landslide surge far-field calculation model, and obtains the impact range of the landslide surge. This method solves the problem that the parameters of the rock and soil materials in the landslide surge calculation are difficult to accurately determine and the surge generation boundary is difficult to accurately input, and provides an effective way to evaluate the impact of landslide surges.

[0042] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0043] (1) The present invention adopts the Mohr-Coulomb constitutive model to characterize the landslide material. By comparing the wave heights on the opposite bank of the far-field and near-field models, the accuracy of the surge input of the boundary surge generated by the surge in the far-field calculation model is determined. The influence range of the landslide surge is determined in combination with the surge far-field propagation model.

[0044] (2) The present invention solves the problem that it is difficult to accurately determine the material parameters of rock and soil masses and the boundary of surge generation in landslide surge calculations, and provides an effective way to evaluate the impact of landslide surges. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 The flowchart of the landslide surge simulation method based on SPH near-field and far-field coupling calculation of the present invention is as follows;

[0046] Figure 2 This is a diagram of the SPH near-field landslide surge calculation model in an embodiment of the present invention;

[0047] Figure 3 Graph showing the evolution of SPH near-field landslide surge in an embodiment of the present invention;

[0048] Figure 4 The curve diagram of the movement speed of the landslide surge sliding body and the first wave high water level in the embodiment of the present invention;

[0049] Figure 5 This is a diagram of a far-field landslide surge calculation model in an embodiment of the present invention;

[0050] Figure 6 This is a characteristic diagram of far-field propagation of surge waves in an embodiment of the present invention;

[0051] Figure 7 This is a cloud diagram of the maximum wave height and water level distribution in an embodiment of the present invention. DETAILED DESCRIPTION

[0052] like Figure 1 and Figure 2 As shown, the landslide surge simulation method based on SPH far-field and near-field coupling calculation of the present invention includes the following steps:

[0053] (1) Establish the SPH near-field landslide surge calculation model. This step specifically includes steps (1.1) to (1.5):

[0054] (1.1) Process the geological profile to preserve the bottom sliding surface, sliding body (including lithological boundary), sliding belt and water level;

[0055] (1.2) Use the lithology boundary line and water level line to cut the sliding body, and use the sliding bodies with different lithology and saturation as the sliding bodies of the SPH near-field landslide surge calculation model;

[0056] (1.3) The bottom sliding surface is shifted downward to a surface with thickness, and the surface with thickness is used as the bottom boundary of the SPH near-field landslide surge calculation model;

[0057] (1.4) Establish water bodies based on the water level and the terrain below the water level;

[0058] (1.5) Use particles with the same spacing to fill the sliding body of step (1.2), the sliding belt of step (1.1), the bottom boundary of step (1.3) and the water body (1.4) of step (1.4) to determine the distribution of SPH particles.

[0059] (2) Perform SPH near-field landslide surge calculation; this step includes steps (2.1) to (2.3):

[0060] (2.1) Using the Mohr-Coulomb constitutive model, the rock and soil parameters in the SPH near-field landslide surge calculation model are assigned according to the mechanical properties of the sliding body and the sliding belt. The rock and soil parameters include cohesion, internal friction angle, elastic modulus, Poisson's ratio, density, and the pressure of the water body is calculated using the state equation; the state equation is shown as follows:

[0061]

[0062] In the formula, γ is a constant, which is 7 in water; ρ0 is the initial density of water; ρ is the density of the water body, and k0 is a function of the speed of sound in water.

[0063] (2.2) The bottom sliding surface is set as a fixed boundary to restrict the movement of the sliding body and the water body;

[0064] (2.3) Set gravity, calculation time and smoothing length, perform SPH near-field landslide surge calculation, and obtain the evolution process of landslide surge and surge height characteristics;

[0065] (3) Extract the sliding body movement velocity, the first wave height, and the opposite bank wave height in the SPH near-field landslide surge.

[0066] This step specifically includes steps (3.1) to (3.3):

[0067] (3.1) Arrange a velocity monitoring point at the center of the sliding body in step (1.2), extract the velocity change curve of the particles at the center of the sliding body, and obtain the velocity change process of the sliding body;

[0068] (3.2) arranging surge height measuring points at the leading edge of the sliding body in step (1.2), extracting the wave height change of the water surface at the leading edge of the sliding body, and obtaining the first wave wave height change curve;

[0069] (3.3) Set up wave height measurement points on the opposite bank, extract the wave height changes on the opposite bank of the landslide, and obtain the maximum wave height on the opposite bank.

[0070] (4) Establishing the SPH landslide surge far-field calculation model, including steps (4.1) to (4.4):

[0071] (4.1) According to the positional relationship between the key impact area of ​​landslide surge of the dam or residential area and the distance of the landslide, determine the upstream and downstream calculation range of the landslide surge so that the boundary conditions will not affect the key impact area of ​​the landslide surge;

[0072] (4.2) According to the position of each control point and the surface elevation in the geological plane map, a far-field landslide surge calculation model that conforms to the actual terrain characteristics is established;

[0073] (4.3) According to the position, area and volume of the section used in the SPH near-field landslide surge calculation model, determine the length and direction of the surge generation boundary in the far-field landslide surge calculation model;

[0074] (4.4) The upstream and downstream boundaries in the far-field landslide surge calculation model are set as fixed water level boundaries, and the water level height at which the landslide begins to slide is set as the calculation water level.

[0075] Among them, in step (4.3), the calculation method of the surge generation boundary length is: sliding body volume / section area; the direction of the surge generation boundary is the direction perpendicular to the section line.

[0076] (5) Based on the head wave height obtained by the SPH near-field landslide surge calculation model in step (3.2), calibrate the opposite bank wave height of the far-field landslide surge calculation model and determine the surge input in the far-field landslide surge calculation model;

[0077] This step includes steps (5.1) to (5.2):

[0078] (5.1) Based on the first wave high water line in the SPH near-field landslide surge calculation model, the surge waveform at the surge generation boundary is calibrated;

[0079] (5.2) The accuracy of the surge wave input of the surge wave generation boundary in the far-field landslide surge wave calculation model is determined by determining whether the difference between the opposite-shore wave heights of the far-field landslide surge wave calculation model and the SPH near-field landslide surge wave calculation model and the opposite-shore wave height of the SPH near-field landslide surge wave calculation model is less than 5%.

[0080] (6) Calculate the far-field landslide surge calculation model to obtain the changes of wave height over time and space during surge propagation;

[0081] The specific method of this step is: increase the calculation time, recalculate the far-field landslide surge calculation model, make the surge complete the propagation in the entire basin, and obtain the far-field propagation characteristics of the surge.

[0082] (7) Extract the maximum wave height of each measuring point in the far-field landslide surge calculation model, draw a cloud map of the maximum wave height distribution, determine the impact range of the landslide surge, and then determine the impact range of the disaster.

[0083] The specific method of this step is: after the calculation is completed, wave height measurement points are arranged at the same distance in the far-field landslide surge calculation model, the maximum wave height of each measurement point in the far-field landslide surge calculation model is extracted, and a maximum wave height distribution cloud map is drawn. The influence range of the landslide surge is determined through the distribution of the maximum wave height of the surge reflected in the cloud map.

[0084] Example

[0085] Taking the landslide surge generated by a certain landslide as an example, the landslide surge simulation method based on SPH far-field and near-field coupling calculation of the present invention is introduced.

[0086] 1. According to the actual terrain characteristics and geological conditions of a landslide, a near-field calculation model of landslide surge is established. The established model is as follows: Figure 2 Velocity monitoring points are arranged on the sliding body of the landslide surge near-field calculation model, and the first wave height and opposite bank wave height measurement points are arranged at the corresponding positions of the river channel.

[0087] 2. Figure 3 The figure shows the calculation results of the evolution process of the landslide surge in the near field of the landslide every 20 seconds. The sliding body slides into the water along the bottom sliding surface and accumulates at the bottom of the riverbed. Due to the low water level, the water resistance of the sliding body is small, and the sliding body stops after a long distance. After the surge is generated, it propagates along the river channel to the opposite bank. During the propagation process, the wave crest is relatively sharp and steep, and gradually slows down when approaching the opposite bank. The surge rises to a certain extent on the opposite bank and finally gradually disappears.

[0088] 3. Sliding body velocity change curve Figure 4 As shown in (a), the sliding speed increases rapidly after the sliding body starts, reaches the maximum sliding speed at 15s, and then the sliding speed decreases continuously. Figure 4 As shown in (b), the measured wave height on the opposite bank is 5.24m.

[0089] 4. Select the 5km upstream and downstream watershed of the landslide as the calculation area, and establish a far-field landslide surge calculation model based on the terrain characteristics, such as Figure 5 As shown in the figure, A-A' is the position of the SPH near-field landslide surge calculation model, 1 is the head wave height measurement point, and 2 is the opposite bank wave height measurement point.

[0090] 5. Based on the first wave high water level in the SPH near-field landslide surge calculation model, the surge waveform of the surge generation boundary is calibrated. The SPH near-field landslide surge calculation model calculates that the wave height on the opposite bank is 5.24m, and the wave height on the opposite bank in the far-field landslide surge calculation model is 5.23m, which proves the accuracy of the surge input.

[0091] 6. The water level changes during the surge propagation process are as follows Figure 6 As shown in the figure, it can be seen that the surge wave surges to the opposite bank and propagates upstream and downstream.

[0092] 7. Extract the maximum wave height at each location in the far-field landslide surge calculation model and draw a cloud map of the maximum surge height distribution, such as Figure 7 At 5.0 km upstream of the landslide, the surge height is 2.37 m; at 5.5 km downstream of the landslide, the surge height is 1.75 m.

Claims

1. A landslide surge simulation method based on SPH near-field and far-field coupling calculation, characterized by: The following steps are involved: (1) Establishing the SPH near-field landslide surge calculation model; including steps (1.1) to (1.5): (1.1) Process the geological profile to preserve the bottom sliding surface, sliding body with lithological boundary, sliding belt and water level line; (1.2) Use the lithology boundary line and water level line to cut the sliding body, and use the sliding bodies with different lithology and saturation as the sliding bodies of the SPH near-field landslide surge calculation model; (1.3) The bottom sliding surface is shifted downward to a surface with thickness, and the surface with thickness is used as the bottom boundary of the SPH near-field landslide surge calculation model; (1.4) Establish water bodies (1.4) based on the water level and the terrain below the water level; (1.5) Fill the sliding body of step (1.2), the sliding belt of step (1.1), the bottom boundary of step (1.3) and the water body (1.4) of step (1.4) with particles of the same interval to determine the distribution of SPH particles; (2) Perform SPH near-field landslide surge calculations, including steps (2.1) to (2.3): (2.1) Using the Mohr-Coulomb constitutive model, the rock and soil parameters in the SPH near-field landslide surge calculation model are assigned according to the mechanical properties of the sliding body and the sliding belt, and the pressure p of the water body (1.4) is calculated using the state equation; the calculated pressure p of the water body (1.4) is: In the formula, γ is a constant, which is 7 in water; ρ0 is the initial density of water; ρ is the density of the set water body, and k0 is the function of the speed of sound in water; (2.2) Set the bottom boundary as a fixed boundary to restrict the movement of the sliding body and the water body (1.4); (2.3) Set gravity, calculation time and smoothing length, perform SPH near-field landslide surge calculation, and obtain the evolution process of landslide surge and surge height characteristics; (3) Extracting the sliding body movement velocity, the first wave height, and the opposite bank wave height in the SPH near-field landslide surge; including steps (3.1) to (3.3): (3.1) Arrange a velocity monitoring point at the center of the sliding body in step (1.2), extract the velocity change curve of the particles at the center of the sliding body, and obtain the velocity change process of the sliding body; (3.2) arranging surge height measuring points at the leading edge of the sliding body in step (1.2), extracting the wave height change of the water surface at the leading edge of the sliding body, and obtaining the first wave wave height change curve; (3.3) Set up wave height measuring points on the opposite bank, extract the wave height changes on the opposite bank of the landslide, and obtain the maximum wave height on the opposite bank; (4) Establishing the SPH landslide surge far-field calculation model; including steps (4.1) to (4.4): (4.1) According to the positional relationship between the key impact area of ​​landslide surge and the distance from the landslide, determine the calculation range of the upstream and downstream of the landslide surge; (4.2) According to the position of each control point in the geological plane map and the surface elevation, a far-field landslide surge calculation model that conforms to the terrain characteristics is established; (4.3) According to the position, area and volume of the section used in the SPH near-field landslide surge calculation model, determine the length and direction of the surge generation boundary in the far-field landslide surge calculation model; (4.4) Set the upstream and downstream boundaries in the far-field landslide surge calculation model as fixed water level boundaries, and set the water level at which the landslide starts to slide as the calculation water level; (5) Based on the first wave height obtained by the SPH near-field landslide surge calculation model in step (3.2), the surge input in the landslide surge far-field calculation model is determined by calibrating the opposite bank wave height of the far-field model; (6) Calculate the far-field landslide surge calculation model to obtain the changes of wave height over time and space during surge propagation; (7) Extract the maximum wave height of each measuring point in the far-field landslide surge calculation model, draw a cloud map of the maximum wave height distribution, and determine the impact range of the landslide surge.

2. The landslide surge simulation method based on SPH near- and far-field coupling calculation according to claim 1 is characterized in that: The soil parameters in step (2.1) include cohesion, internal friction angle, elastic modulus, Poisson's ratio and density.

3. The landslide surge simulation method based on SPH far-field and near-field coupling calculation according to claim 1 is characterized in that: The key impact areas of landslide surge in step (4.1) include dams or residential areas.

4. The landslide surge simulation method based on SPH far-field and near-field coupling calculation according to claim 1 is characterized in that: In step (4.3), the calculation method of the surge generating boundary length is: sliding body volume / section area, and the direction of the surge generating boundary is the direction perpendicular to the section line.

5. The landslide surge simulation method based on SPH far-field and near-field coupling calculation according to claim 1 is characterized in that: Step (5) includes steps (5.1) to (5.2): (5.1) Based on the first wave high water line in the SPH near-field landslide surge calculation model, the surge waveform at the surge generation boundary is calibrated; (5.2) The accuracy of the surge wave input of the surge wave generation boundary in the far-field landslide surge wave calculation model is determined based on whether the difference between the opposite-shore wave heights of the far-field landslide surge wave calculation model and the SPH near-field landslide surge wave calculation model and the opposite-shore wave height of the SPH near-field landslide surge wave calculation model are less than the set value.

6. The landslide surge simulation method based on SPH far-field and near-field coupling calculation according to claim 5 is characterized by: In step (5.2), whether the ratio of the difference between the opposite bank wave height of the far-field landslide surge calculation model and the SPH near-field landslide surge calculation model and the opposite bank wave height of the SPH near-field landslide surge calculation model is less than a set value, the set value ranges from 0 to 5%.

7. The landslide surge simulation method based on SPH far-field and near-field coupling calculation according to claim 1 is characterized by: In step (6), the calculation time is increased and the far-field landslide surge calculation model is recalculated so that the surge completes its propagation in the entire basin and the variation of the wave height with time and space during the far-field surge propagation process is obtained.

8. The landslide surge simulation method based on SPH far-field and near-field coupling calculation according to claim 1 is characterized by: In step (7), wave height measuring points are arranged at equal intervals in the far-field landslide surge calculation model, the maximum wave height of each measuring point in the far-field landslide surge calculation model is extracted, and a maximum wave height distribution cloud map is drawn. The influence range of the landslide surge is determined by the distribution of the maximum wave height of the surge reflected in the cloud map.

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