JP2023003518A - Surface collapse risk assessment device, surface collapse risk assessment method and program - Google Patents

Abstract

To provide a surface collapse risk assessment device suitable for improving the accuracy of risk assessment of surface collapse.SOLUTION: In a surface collapse risk assessment device 1, a terrain evaluation unit 5 evaluates a terrain of a target point, and a water flow evaluation unit 7 evaluates the target point based on the situation in which water gathers from the surroundings. In addition to the terrain evaluation by the terrain evaluation unit 5, a risk assessment unit 9 considers the evaluation by the water flow evaluation unit 7 based on the locations where water gathers, such as valleys and mountain streams, and evaluates the risk of slope failure at the target point in an analysis target area.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a surface landslide risk evaluation device, a surface landslide risk evaluation method, and a program, and more particularly to a surface landslide risk evaluation device and the like for evaluating the risk of surface landslides at a target point.

Conventionally, it has been known to use rainfall to predict disasters near steel towers, but the applicant proposed extracting dangerous slopes using topographical information (see Non-Patent Document 1).

Kyushu Dengi Kaihatsu Co., Ltd., "Dengi Dayori No. 65 Improvement of Steel Tower Site Slope Disaster Prediction System", [online], Internet, <URL: http://www.dengi.co.jp/dengidayori/no65/ index.html>

The technique described in Non-Patent Document 1 focuses on the similarity with the collapsed terrain in the terrain information. However, even if the landform had the same shape as the landform where the collapse occurred, the risk of collapse was not necessarily the same. Therefore, there is a demand for more accurate risk determination.

Therefore, an object of the present invention is to propose a surface collapse risk evaluation device and the like suitable for enhancing the accuracy of evaluating the risk of surface collapse.

A first aspect of the present invention is a surface failure risk evaluation device for evaluating the risk of slope failure at a target point in an analysis target area, comprising a reference water flow rate storage unit that stores a reference water flow rate, and the analysis target area a mainstream point group extraction unit that calculates a mainstream point group whose cumulative water flow rate is equal to or greater than the reference water flow rate, and a water flow evaluation value calculation that calculates a water flow evaluation value using the distance between the target point and the mainstream point group and a risk evaluation unit that evaluates the risk of surface collapse at the target point using the water flow evaluation value.

A second aspect of the present invention is the surface landslide risk evaluation device of the first aspect, wherein the reference water flow rate is set for each collapse point of the collapse point group and the above-mentioned Regarding the distribution of the number of collapse points with respect to the distance from the main stream point group, it belongs to at least the first distance division, the second distance division that is farther than the first distance division, and the third distance division that is farther than the second distance division. Regarding the first number, the second number, and the third number, which are the numbers of collapse points, the first number is the largest, the third number is the smallest, and the second number is less than the first number and greater than the third number. is.

A third aspect of the present invention is the surface collapse risk evaluation device according to the first or second aspect, comprising a terrain evaluation value calculation unit for calculating a terrain evaluation value for evaluating terrain at the target point, The degree evaluation unit calculates a risk evaluation value using the landform evaluation value and the water flow evaluation value, and uses the risk evaluation value to evaluate the risk of surface collapse at the target point.

A fourth aspect of the present invention is the surface collapse risk evaluation device of the third aspect, wherein the terrain evaluation value is a terrain having a convex longitudinal shape and a concave transverse shape at the target point is a value that is evaluated to be more dangerous than other shapes, and is a value that is evaluated to be more dangerous as the slope of the ground surface increases. The water flow evaluation value is, at the target point, It is a value that evaluates the degree of risk to be higher as the cumulative water flow is closer to the main stream point group where it is equal to or higher than the standard water flow.

A fifth aspect of the present invention is a collapse risk evaluation method for evaluating the risk of slope failure at a target point, wherein the collapse risk evaluation device comprises a terrain evaluation value calculation unit, a water flow evaluation value calculation unit, and a degree of risk an evaluation unit, wherein the terrain evaluation value calculation unit and the water flow evaluation value calculation unit calculate a terrain evaluation value and a water flow evaluation value, respectively; A risk calculation unit that evaluates the risk of surface collapse at the target point using the water flow evaluation value, and the terrain evaluation value is such that the longitudinal shape is convex and the cross-sectional shape is concave at the target point. is a value that is evaluated as having a higher degree of danger than other shapes, and is a value that is evaluated as having a higher degree of danger as the slope of the ground surface increases. At points, the closer to the main stream points where the accumulated water flow rate is equal to or higher than the standard water flow rate, the higher the risk is evaluated.

A sixth aspect of the present invention is a program for causing a computer to function as the surface collapse risk evaluation device according to any one of the first to fourth aspects.

The present invention may be regarded as a computer-readable recording medium for recording the program of the sixth aspect of the present invention.

In the technique described in Non-Patent Document 1, for example, each point tends to be analyzed individually, such as the amount of precipitation and topography at each point. The applicant focused on water flow (for example, the flow of water between meshes dividing the target area) and analyzed the surface failure points where surface failures actually occurred. Focusing on the cumulative water discharge, which is the accumulation of the discharge flowing from nearby points to each point, we found a relationship that the closer the surface collapse point is to the main stream point group where the accumulated water discharge is more than a predetermined value, the more it is, and the further it is, the less it is. .

According to each aspect of the present invention, based on the applicant's new knowledge, focusing on water flow, surface collapse is evaluated by using the distance from the main stream point group to the target point to evaluate the risk of collapse It is possible to improve the prediction accuracy of the risk of

Furthermore, as in the third aspect of the present invention, the terrain evaluation value indicating the danger of the terrain at the target point is corrected using the water flow evaluation value, and the water flow evaluation value determines the terrain evaluation value. It is possible to improve the accuracy of prediction by

It is a block diagram (a) showing an example of a structure of the surface collapse risk-evaluation apparatus 1 which concerns on embodiment of this invention, (b), (c), and (d) is a flow chart which shows an example of operation|movement. It is a figure for demonstrating curvature. (a), (b) and (c) are graphs showing distributions of collapse starting points depending on the reference water flow rate when the reference water flow rate is 20, 100 and 50, respectively. A water flow diagram when the reference water flow rate is 20 is shown. Fig. 3(a) is a graph showing the relationship between the distance (m) (horizontal axis) from the collapse starting point to the mainstream cell group and the data number ratio (%). FIG. 10 is a diagram showing an example of a case where the landform evaluation value is corrected by the water flow evaluation value;

Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be noted that the present invention is not limited to this embodiment.

FIG. 1 is a block diagram showing (a) an example of the configuration of a surface collapse risk assessment apparatus 1 according to an embodiment of the present invention, and (b), (c) and (d) a flow chart showing an example of operations. be.

Referring to FIG. 1(a), the surface landslide risk evaluation device 1 includes a terrain information analysis unit 3, a terrain evaluation unit 5, a water flow evaluation unit 7, and a risk evaluation unit 9 ("risk (an example of an evaluation unit) and a parameter storage unit 10 .

The terrain information analysis unit 3 includes a geospatial information storage unit 11 , a division processing unit 12 , a shape analysis unit 13 and a hydrological analysis unit 15 .

The landform evaluation unit 5 includes a slope curvature calculation unit 17 and a landform evaluation value calculation unit 21 (an example of a “landform evaluation value calculation unit” in the claims of the present application).

The water flow evaluation unit 7 includes a reference water flow rate storage unit 23 (an example of a "reference water flow rate storage unit" in the claims of the present application) and a mainstream point group extraction unit 25 (an example of the "mainstream point group extraction unit" in the claims of the present application). and a water flow evaluation value calculation unit 27 (an example of a "water flow evaluation value calculation unit" in the claims of the present application).

The risk evaluation unit 9 includes a risk evaluation value calculation unit 29 and a risk determination unit 31 .

The parameter storage unit 10 stores parameters used when calculating evaluation values and the like.

In the geographic information analysis unit 3, the geospatial information storage unit 11 stores geospatial information. Geospatial information is, for example, information (location information) indicating the position of a specific point or area in space and information related to various events associated therewith. Alternatively, the information may be information consisting only of position information. Geospatial information includes land use maps, geological maps, thematic maps such as hazard maps, city planning maps, topographic maps, place name information, ledger information, statistical information, aerial photographs, satellite images, and the like. Moreover, the information measured on site by the user of the surface collapse risk evaluation device 1 or the like may be used.

From the geospatial information stored in the geospatial information storage unit 11, the division processing unit 12 selects an analysis target area (" An example of "analysis target area") is extracted to generate division information. The division information is, for example, mesh data obtained by dividing the analysis target area into a grid at regular intervals (for example, 5 m intervals). Each rectangular area resulting from the division is hereinafter referred to as a cell.

The shape analysis unit 13 associates each cell of the division information with the elevation value data in the geospatial information to obtain divided elevation data. The altitude value data corresponding to each cell may be, for example, part or all of the altitude value data in the geospatial information, or may be obtained by statistically processing these altitude value data.

The hydrological analysis unit 15 associates the cumulative water flow rate with each cell of the divided elevation data to obtain landform information. For example, the segmented elevation data is used to determine the direction of flow from each cell to the steepest descending neighboring cell. Then, for each cell, the amount of water assumed to flow from neighboring cells to the cell is accumulated to calculate the accumulated water amount, which is used as topographical information.

In this way, the terrain information is, for example, mesh data in which the analysis target area is divided into grids at regular intervals, and each cell is associated with the elevation value data and the cumulative water flow rate in the geospatial information. be.

The division processing unit 12, the shape analysis unit 13, and the hydrological analysis unit 15 can be realized by, for example, ArcGIS (Esri Japan Co., Ltd.). For example, using DEM data at 5 m intervals to create raster data, remove small defects, and generate raster data showing the direction of flow from each cell to its steepest descending neighbor cell, each cell It is sufficient to create raster data of the accumulated flow rate.

FIG. 1(b) is a flowchart showing an example of the operation of the terrain evaluation section 5. As shown in FIG. FIG. 2 is a diagram for explaining curvature. The operation of the terrain evaluation unit 5 will be described with reference to FIGS. 1(b) and 2. FIG.

Referring to FIG. 1(b), the slope curvature calculation unit 17 uses the terrain information to calculate slope and curvature (step STA1). The terrain evaluation value calculator 21 calculates a terrain evaluation value (step STA2).

First, the inclination will be explained. Inclination is a terrain quantity that indicates the inclination of each cell from the horizontal plane. For example, the tilt angle can be obtained by comparing the target cell and its neighboring cells and calculating the maximum rate of change of their values. In this case, in principle, when comparing the altitudes of the target cell and its eight neighbors, their maximum altitude change over distance will be the steepest descent from the target cell.

Next, the curvature calculation will be described with reference to FIG. Curvature is a numerical value that indicates whether a slope is ridge-shaped or valley-shaped. The longitudinal shape and transverse shape are shapes in directions parallel and orthogonal to the direction of maximum inclination, respectively. Cross-sectional curvature and planar curvature are curvatures that indicate irregularities in the longitudinal and transverse directions, respectively.

FIG. 2A is a diagram for explaining cross-sectional curvature. Cross-sectional curvature is parallel to the slope and affects the acceleration and deceleration of water flow. The shape on the left side of FIG. 2(a) (when the cross-sectional curvature is negative) is upwardly convex and slows down the flow. The shape in the center of FIG. 2(a) (when the cross-sectional curvature is positive) is upwardly concave, and the flow is accelerated. The shape on the right side of FIG. 2(c) (where the cross-sectional curvature is zero) has a straight surface.

FIG.2(b) is a figure for demonstrating plane curvature. Cross-sectional curvature is perpendicular to the slope and is related to the convergence and divergence of water flow. The shape on the left side of FIG. 2(b) (when the plane curvature is positive) is convex upward, and the flow tends to branch. The shape at the center of FIG. 2(b) (when the planar curvature is negative) is concave upward, and the flow tends to converge. The shape on the right side of FIG. 2(c) (where the planar curvature is zero) has a straight surface.

The tilt curvature calculator 17 calculates the combined curvature of each cell using the following formula. Here, a is a positive number and is stored in the parameter storage unit 10 .
Reformed composite curvature = planar curvature (concave is negative) + a × cross-sectional curvature (convex is negative)

In general, the composite curvature is calculated by "planar curvature (concave is negative) - cross-sectional curvature (convex is negative)" so that there is a strong tendency to be concave. Therefore, the value calculated by the above formula is called the "modified composite curvature".

For calculation of the curvature of each cell, for example, altitude value data included in the cell to be calculated and neighboring cells may be used.

The location where the collapse actually occurred was investigated. Below, the location where the collapse has occurred is referred to as the “collapsed location”, and the location where the collapse has not occurred, which is used for comparison, is referred to as the “healthy location”.

The plane curvature was generally in the range of -5 to +5 at the sound portion, and from -15 to +5 at the collapsed portion. The cross-sectional curvature was generally in the range of -5 to +5 at healthy sites, and from -5 to +10 at collapsed sites. FIG. 2(c) is a combination of cross-sectional curvature and planar curvature. It was confirmed that the collapsed portion was generally a portion with a convex (negative) cross-sectional curvature and a concave (negative) planar curvature (see the upper right column in FIG. 2(c)). Therefore, the modified compound curvature is adopted as one of the indices for slope evaluation. The larger the negative value of the modified composite curvature, the more likely the slope is to collapse.

The inclination was generally 30° or less at healthy locations, but varied from 10 to 50° at collapsed locations. When examining the relationship between inclination and curvature, it was generally found that the inclination angle tended to be larger at collapsed sites. Therefore, the slope is adopted as one of the indices for slope evaluation. The larger the slope value, the more likely the slope is to collapse.

The terrain evaluation value calculator 21 calculates the terrain evaluation value of each cell using the following formula. Here, b is a positive number and is stored in the parameter storage unit 10 .
Terrain evaluation value = modified composite curvature - b x slope

The parameters a and b can be determined using healthy and collapsed points. For example, when a was changed with respect to actual collapse points, the number of collapse points tended to increase as the modified composite curvature increased when a = 1. Therefore, the parameter a=1 can be adopted. Also, for example, when examining the actual collapsed locations and sound locations, at b = 0.3, the number of collapsed location data is more -5 to 0 than -10 to -5, and all healthy locations are -13. That's it. In addition, when b=0.35, there was no positive value at the collapsed portion, and all healthy portions were -15 or higher. At b=0.4, there was no positive value in the collapsed portion, but the sound portion reached a low value of -20 to -15. In this case, b = 0.35 is adopted, for example, a terrain evaluation value of -15 or less should be the most important, a terrain evaluation value greater than -15 and less than -10 should be the next most important, and a terrain evaluation value greater than -10 and less than -10 should be the next most important. The following should be noted below, and values greater than 0 are evaluated as relatively stable.

FIG. 1(c) is a flowchart showing an example of the operation of the water flow evaluation unit 7. As shown in FIG. 3 to 5 are diagrams for explaining the water flow evaluation value. The operation of the water flow evaluation unit 7 will be described with reference to FIG. 1(c) and FIGS. 3 to 5. FIG.

The reference water flow rate storage unit 23 stores the reference water flow rate. Referring to FIG. 1(c), the mainstream point group extraction unit 25 uses topographical information to extract a mainstream cell group (an example of a "mainstream point group" in the claims of the present application) whose cumulative water flow rate is equal to or greater than the reference water flow rate. ) is extracted (step STB1). The water flow evaluation value calculator 27 calculates a water flow evaluation value corresponding to each cell (step STB2). The water flow evaluation value is a value calculated using the distance between each cell and the mainstream cell group.

FIG. 3 shows the distribution of collapse starting points with different reference water flow rates. 3(a), (b) and (c) are for reference water flow rates of 20, 100 and 50, respectively. The horizontal axis is the distance (m) between the collapse starting point and the mainstream cell group. The vertical axis shows the ratio (%) of the number of data (percentage of the total number of landslide initiation points for each distance) (see the square graph) and the average terrain evaluation value of landslide initiation points for each distance ( point) (see triangle graph). The reference water flow rate will be described with reference to FIG.

For example, a location with a low cumulative water flow rate is a location with little water coming from the surroundings. As the cumulative water flow increases, we can extract valleys and mountain streams where water gathers from the surroundings. Furthermore, when the cumulative water flow increases, it is possible to extract the situation where a small river (such as a tributary) is formed. As the cumulative water flow increases further, we can extract situations where more water gathers to form a river (such as a mainstream). For example, if the standard water flow rate is 100, it indicates rivers (such as the main stream), if the standard water flow rate is 50, it includes small rivers (such as tributaries), and if the standard water flow rate is 20, it indicates valleys and valleys. It is thought that it also includes mountain streams.

Referring to FIG. 3(a), when the reference water flow rate is 20, there is a tendency that the closer the collapse starting points are to the main flow cell group, the more they are, and the further away they are, the fewer they are (for example, as shown in Table 1, When the distance from the main stream is 0 m (an example of the "first distance segment" in the claim of the present application), the number is the largest at 49, and the distance from the main stream is greater than 50 m (an example of the "third distance segment" in the claim of the present application). ) is one, which is the smallest, and when the distance from the main stream is more than 10 m and 20 m or less (an example of the "second distance division" in the claim of the present application), the number is 21, which is more than 49 It should be noted that, in the present invention, it is not limited to the collapse starting point, and may be, for example, the number of cells having the largest collapse point.). In addition, regarding the terrain evaluation value, there is a tendency that the closer the cell is to the mainstream cell, the smaller it is, and the farther away it is, the larger it becomes. Therefore, 20 is adopted as the reference water flow rate. FIG. 4 shows a water flow diagram when the reference water flow rate is 20. As shown in FIG.

With reference to FIGS. 3(b) and 3(c), when the reference water flow rate is 100 and 50, the terrain evaluation value tends to be smaller the closer to the mainstream cell and larger the farther away, but the data No clear relationship was observed in the distribution of numbers. That is, in general, attention tends to be focused on the main part of the river where the water volume is large, but in the present invention, by adopting the reference water flow rate for the prediction of the collapse starting point, it is possible to focus on the tributary part, which is difficult to focus on in general analysis. can also be focused on, which clarifies the relationship with the collapse starting point, and can improve the prediction accuracy.

FIG. 5 is a graph showing the relationship between the distance (m) (horizontal axis) from the collapse starting point to the mainstream cell group and the data number ratio (%) in FIG. 3(a). When this is approximated by an exponential function, the approximation formula is y=48.138e ^-0.062x . Here, x is the distance from the mainstream cell group, and y is the number of cells (ratio %).

Table 1 shows the water flow ratings determined using a fitted curve. The water flow evaluation value calculator 27 obtains a water flow evaluation value according to the distance of each cell from the mainstream cell group according to Table 1 for each cell.

Next, the operation of the risk assessment unit 9 will be described with reference to FIGS. 1(d) and 6. FIG. FIG. 6 is a diagram showing an example in which the terrain evaluation value is corrected by the water flow evaluation value.

Referring to FIG. 1(d), the risk evaluation value calculator 29 corrects the landform evaluation value by the water flow evaluation value and calculates the risk evaluation value for each cell (step STC1). The risk determination unit 31 uses the risk evaluation value of each cell to determine the risk of surface collapse occurring in each cell (step STC2).

The risk evaluation value will be described with reference to FIG. FIG. 6(a) shows the terrain evaluation value of each cell. FIG. 6(a) shows the state without correction. FIG. 6B shows an example of correction by multiplying and dividing the terrain evaluation value of each cell by the water flow evaluation value. FIG. 6(c) shows an example of correction by adjusting the water flow evaluation value with respect to the landform evaluation value of each cell. Hereinafter, the case where the terrain evaluation value is not corrected is referred to as "no correction". Correction of the landform evaluation value by multiplication and division of the water flow evaluation value is called “x correction”. A case of correcting the terrain evaluation value by adding or subtracting the water flow evaluation value is also referred to as “+correction”.

When determining whether or not the minimum risk value was detected inside the collapsed land in FIG. 6, it was detected with no correction and + correction in FIGS. Not detected by × correction. When a total of 25 points were similarly judged, the correct answer rate without correction was 65% and the correct answer rate with × correction was 65%, while the correct answer rate with +correction was 70%. Therefore, the + correction could be detected with the highest accuracy.

Similarly, the entire score distribution area for no correction, × correction, and + correction was divided into 10 equal parts and classified into 1 to 10 ranks (1 being the most dangerous), and the average rank of the collapse starting point was obtained. The rate of correctness for no correction was 2.21 and for × correction was 3.07, while the rate of correctness for + correction was 2.16. In this case, it can be determined that the closer to 1, the higher the danger. Therefore, + correction can be detected with the highest accuracy.

Therefore, the risk evaluation value calculator 29 calculates the risk evaluation value by, for example, the following formula. Here, water flow evaluation value = water flow value / 10, water flow value = value obtained from the approximate formula for the number of collapses by distance from the main stream cell group (cumulative water flow rate ≥ 20), terrain evaluation value = modified synthetic curvature - 0.35 x tilt, combined curvature=planar curvature (concave is negative) + cross-sectional curvature (convex is negative). In this example, the more negative the risk evaluation value, the more dangerous it is determined, so the water flow evaluation value is corrected to be reduced.
Risk evaluation value = Terrain evaluation value - Water flow evaluation value

In general, the risk evaluation value calculator 29 can calculate the risk evaluation value by the following equation using the positive parameters a, b, and c stored in the parameter storage unit 10 . Here, water flow evaluation value = value obtained from the approximation formula for the number of collapses by distance from the mainstream cell group (cumulative water flow rate ≥ 20), terrain evaluation value = modified composite curvature - b x slope, modified composite curvature = plane curvature ( concave is negative) + a x sectional curvature (convex is negative). In this example, the more negative the danger evaluation value, the more dangerous it is determined, so the water flow evaluation value is corrected to be reduced.
Risk evaluation value = Terrain evaluation value - c x Water flow evaluation value

Note that, for example, the risk evaluation value calculation unit 29 may determine the reference water flow rate and the parameters a, b, and c using the location where the collapse actually occurred. The reference water flow rate is determined, for example, so that the collapse starting point tends to decrease monotonically according to the distance from the mainstream cell group. At this time, a predetermined approximation formula such as an exponential function may be considered to minimize the error from the approximation formula. The parameter a is, for example, a value at which the number of collapsed portions tends to increase as the modified synthetic curvature increases. The parameter b can be determined based on the distribution of the collapsed and healthy areas so that the collapsed areas become smaller and are judged to be dangerous, and the healthy areas become larger and judged to be safe. The parameter c can be determined, for example, by maximizing the correct answer rate when the minimum risk value is detected inside the collapsed area, or by minimizing the average rank of the collapse starting point.

When the risk evaluation value of each cell is small, the risk determination unit 31 determines that the risk of surface collapse is high, and determines that the risk of surface collapse is low if the value is large.

1 surface landslide risk evaluation device, 3 terrain information analysis unit, 5 terrain evaluation unit, 7 water flow evaluation unit, 9 risk evaluation unit, 10 parameter storage unit, 11 geospatial information storage unit, 12 division processing unit, 13 shape analysis unit , 15 hydrological analysis unit, 17 slope curvature calculation unit, 21 terrain evaluation value calculation unit, 23 reference water flow rate storage unit, 25 main stream point group extraction unit, 27 water flow evaluation value calculation unit, 29 danger evaluation value calculation unit, 31 degree of risk Judging part

Claims (6)

A surface failure risk evaluation device for evaluating the risk of slope failure at a target point in an analysis target area,
a reference water flow rate storage unit that stores a reference water flow rate;
a main stream point group extraction unit that extracts a main stream point group having a cumulative water flow rate equal to or greater than a reference water flow rate in the analysis target area;
a water flow evaluation value calculation unit that calculates a water flow evaluation value using the distance between the target point and the main stream point group;
A surface landslide risk evaluation device, comprising a risk assessment unit that evaluates the risk of surface landslide at the target point using the water flow evaluation value. The reference water flow rate is determined in terms of the distribution of the number of collapse points with respect to the distance between each collapse point in the collapse point group and the main flow point group, at least in the first distance division, and Regarding the first number, the second number, and the third number, which are the numbers of collapse points belonging to a second distance division that is farther than the first distance division and a third distance division that is farther than the second distance division, the first number is 2. The surface collapse risk evaluation device according to claim 1, wherein the number is the largest, the third number is the smallest, and the second number is less than the first number and greater than the third number. A terrain evaluation value calculation unit that calculates a terrain evaluation value for evaluating terrain at the target point,
The risk evaluation unit calculates a risk evaluation value using the terrain evaluation value and the water flow evaluation value, and uses the risk evaluation value to evaluate the risk of surface collapse at the target point. 3. The surface collapse risk evaluation device according to 1 or 2. The terrain evaluation value is, at the target point,
A terrain with a convex longitudinal shape and a concave transverse shape is a value that is evaluated as having a higher degree of risk than other shapes,
It is a value that is evaluated to be more dangerous as the slope of the ground surface increases,
4. The surface landslide risk evaluation device according to claim 3, wherein the water flow evaluation value is a value such that the closer the target point is to a group of main flow points having a cumulative water flow rate equal to or greater than a reference water flow rate, the higher the risk is. A collapse risk evaluation method for evaluating the risk of slope failure at a target point,
The collapse risk evaluation device includes a terrain evaluation value calculation unit, a water flow evaluation value calculation unit, and a risk evaluation unit,
an evaluation value calculation step in which the terrain evaluation value calculation unit and the water flow evaluation value calculation unit respectively calculate the terrain evaluation value and the water flow evaluation value;
The risk evaluation unit includes a risk calculation unit that evaluates the risk of surface collapse at the target point using the terrain evaluation value and the water flow evaluation value,
The terrain evaluation value is, at the target point,
A terrain with a convex longitudinal shape and a concave transverse shape is a value that is evaluated as having a higher degree of risk than other shapes,
It is a value that is evaluated to be more dangerous as the slope of the ground surface increases,
The water flow evaluation value is a value that is evaluated such that the closer the target point is to a group of main stream points having a cumulative water flow rate equal to or greater than a reference water flow rate, the higher the risk is. A program for causing a computer to function as the surface collapse risk evaluation device according to any one of claims 1 to 4.

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