JP7836722B2 - Flood monitoring device, flood monitoring system, and flood monitoring method - Google Patents

Description

This invention relates to a flood monitoring device, a flood monitoring system, and a flood monitoring method.

In recent years, due to the increasing frequency of natural disasters such as heavy rains and earthquakes, flood damage has become more common in areas near the sea or rivers, caused by tsunamis or river flooding.

As a technology for monitoring such floods, a method for measuring river water levels (water depth) by analyzing the difference between monitoring images from river monitoring cameras and monitoring images under normal conditions has been disclosed (for example, Patent Document 1). Furthermore, a method for distributing real-time flood information that changes moment by moment due to factors such as water level and rainfall to encourage evacuation has also been disclosed (for example, Patent Documents 2 and 3).

Japanese Patent Publication No. 2008-057994 Japanese Patent Publication No. 2004-197554 Japanese Patent Publication No. 2003-162785

However, conventional technology, while capable of measuring water depth (water level), cannot measure water flow velocity in rivers. This lack of information is insufficient for predicting flood areas, resulting in inaccurate predictions. Furthermore, deploying a large number of expensive sensors along rivers to measure water levels and other parameters significantly increases costs.

This invention has been made in view of the above, and aims to provide a flood monitoring device, a flood monitoring system, and a flood monitoring method that can accurately calculate river water depth and water flow velocity without using expensive sensors.

To solve the above-mentioned problems and achieve the objective, the present invention provides a buoy-type sensor comprising a buoy floating on a river and a deployment mechanism fixed to the riverbed or near the riverbed, connected to the buoy by a connecting wire and capable of deploying and retracting the connecting wire. The sensor is characterized by comprising: an acquisition unit that acquires an image captured by an imaging device that images the buoy on the water surface; and a first calculation unit that derives the horizontal displacement of the buoy from a position on the water surface perpendicular to the deployment mechanism, and the submersion state of the buoy, from the captured image, and calculates the river's water depth and water flow velocity based on the displacement, the submersion state, and a first relationship of equilibrium between gravity, buoyancy, force due to water flow, and tension acting on the buoy.

According to this invention, the water depth and flow velocity of a river can be calculated accurately without using expensive sensors.

Figure 1 is a diagram illustrating the overall configuration of a flood monitoring system according to an embodiment of this system. Figure 2 illustrates the forces acting on the buoy. Figure 3 shows an example of the hardware configuration of the predictive management server according to the embodiment. Figure 4 shows an example of the hardware configuration of an information terminal according to the present invention. Figure 5 shows an example of the configuration of a functional block in the predictive management server according to the embodiment. Figure 6 is a flowchart showing an example of the calculation process flow for water depth and water flow velocity of the predictive management server according to the embodiment. Figure 7 is a flowchart showing an example of the calculation process flow for another water depth and water flow velocity in the predictive management server according to the embodiment. Figure 8 shows an example of a state in which evacuation routes are displayed on map information in an information terminal according to the embodiment. Figure 9 shows an example of a state in which the predicted flood area and the detour route for evacuation are displayed on the map information of the information terminal according to the embodiment. Figure 10 illustrates the forces and moments acting on the buoy. Figure 11 is a flowchart showing an example of the calculation process flow for water depth and water flow velocity of the predictive management server according to Modification 1. Figure 12 illustrates the forces and moments acting on an asymmetrical buoy. Figure 13 is a flowchart showing an example of the water flow velocity calculation process of the predictive management server according to Modification 2.

The following describes in detail embodiments of the flood monitoring device, flood monitoring system, and flood monitoring method according to the present invention, with reference to the drawings. Furthermore, the present invention is not limited by the following embodiments, and the components in the following embodiments include those easily conceivable by those skilled in the art, those substantially identical, and those within the so-called equivalent range. Moreover, various omissions, substitutions, modifications, and combinations of components can be made without departing from the spirit of the following embodiments.

Computer software refers to programs related to the operation of a computer, and other information used for computer processing that is similar to a program (hereinafter, computer software is referred to as "software"). Application software is a general term for software used to perform specific tasks. On the other hand, an operating system (OS) is software that controls the computer and enables application software to utilize computer resources. The OS performs basic computer management and control, such as input/output control, management of hardware such as memory and hard disks, and process management. Application software operates by utilizing the functions provided by the OS. A program is a set of instructions for a computer, combined to produce a specific result. Furthermore, something similar to a program refers to something that is not a direct instruction to the computer and therefore cannot be called a program, but has similar properties to a program in that it defines computer processing. For example, a data structure (the logical structure of data, represented by the interrelationships between data elements) falls under the category of something similar to a program.

(Overall configuration of the flood monitoring system)
Figure 1 is a diagram illustrating the overall configuration of the flood monitoring system according to this embodiment. The overall configuration of the flood monitoring system 1 according to this embodiment will be described with reference to Figure 1.

The flood monitoring system 1 shown in Figure 1 is a system that calculates the water depth and flow velocity of rivers, etc., and predicts the flooded area in the event of a flood caused by overflowing or other flooding. In this embodiment, the operation of the flood monitoring system 1 in calculating the water depth and flow velocity in a river and predicting the flooded area in the event of a flood will be described. As shown in Figure 1, the flood monitoring system 1 includes a prediction management server 10 (flood monitoring device), multiple buoy-type sensors 20 installed in rivers, etc., and a monitoring camera 30.

The prediction management server 10 is a server device that calculates river water depth and water flow velocity based on images captured by the buoy-type sensor 20 from the surveillance camera 30, and predicts the flooded area in the event of a flood caused by overflowing or other flooding.

The buoy-type sensor 20 is a sensor mechanism that is installed in multiple locations in the river and, when imaged by the surveillance camera 30, contributes to the calculation of river water depth and water flow velocity by the predictive management server 10. As shown in Figure 1, the buoy-type sensor 20 includes a buoy 21, a wire feed mechanism 22, and a wire 23 (connecting wire).

Buoy 21 is a floating buoy connected via wire 23 to a wire-feeding mechanism 22 installed on the riverbed or elsewhere, and floated on the surface of the river. As shown in Figure 1, the surface of buoy 21 is marked with letters, figures, or symbols (marks 21a) to indicate the buoy's tilt, etc.

The wire payout mechanism 22 comprises a reel containing a spring coil around which the wire 23 is wound. The wire 23 is pulled out from the reel and connected to the buoy 21. The wire 23 is paid out from the reel in response to the force exerted by the buoy 21 as it moves across the water surface. This mechanism utilizes the force generated by the spring coil to pull the wire 23 back, thereby creating tension in the wire 23. The wire payout mechanism 22 is fixedly installed, for example, on the riverbed or on a bridge near the riverbed.

The wire 23 connects the buoy 21 and the wire feeding mechanism 22, and is a connecting wire that transmits the tension generated by the wire feeding mechanism 22 to the buoy 21. For example, an elastic body such as a coil spring is connected to one part of the wire 23, and the elastic body stretches by a predetermined length according to the spring constant of the elastic body and the tension generated by the wire feeding mechanism 22. Therefore, the length of the wire 23 and the tension generated in the wire 23 (the combined force of the tension generated by the wire feeding mechanism 22 and the tension from the elastic body connected to one part of the wire 23) are related by a predetermined equation, and if one is determined, the other can be derived. The relationship between the length of the wire 23 and the tension generated in the wire 23 may be obtained experimentally in advance. In principle, the longer the length of the wire 23, the greater the tension. Note that the wire 23 is not limited to metal; for example, it may be a wire made of resin.

The surveillance camera 30 is an imaging device that captures images of multiple buoys 21 floating on the water surface. The surveillance camera 30 wirelessly transmits the captured images to the information terminal 40. Examples of wireless communication standards include 3G, LTE (Long Term Evolution), 4G, 5G, or Wi-Fi® (Wireless Fidelity).

The information terminal 40 is an information processing device such as a smartphone, tablet, or PC (Personal Computer) on which an application (hereinafter sometimes simply referred to as "the app") is installed that receives information such as predicted flood areas predicted by the prediction management server 10 and displays it on the map information. The app installed on the information terminal 40 may be either a native app or a web app.

(Regarding the forces acting on the buoy, etc.)
Figure 2 illustrates the forces acting on the buoy. The forces acting on buoy 21 will be explained with reference to Figure 2.

First, let's explain the forces acting on buoy 21. Since buoy 21 has a known mass, we can consider that a downward gravitational force G acts on its center of gravity (the hatched "x" mark in Figure 2). As mentioned above, since the mass of buoy 21 is known, the value of the gravitational force G is also a known constant. The reason why the center of gravity of buoy 21 is offset from the center (the filled "x" mark in Figure 2) is that a weight 21b is embedded near the fulcrum 21c (connection point) where buoy 21 connects to wire 23, in order to suppress the swaying of buoy 21.

Furthermore, since buoy 21 is a floating buoy on the water surface, there is a portion of its volume that is submerged below the water surface (submerged volume), and a vertically upward buoyant force U acts on it due to the water pressure difference in this submerged portion. Specifically, the buoyant force U is calculated as the product of the submerged volume, the density of water, and the acceleration due to gravity. In Figure 1, this buoyant force U is illustrated as a force acting on the center of buoy 21. Here, the height from the water surface of the portion of buoy 21 that is visible above the water surface is defined as the apex height Δh (an example of a submerged state).

Furthermore, since buoy 21 is a floating buoy on the river, it is subjected to a force W due to the river's current, i.e., the force W due to the water flow. Also, as described above, since buoy 21 is connected to the wire payout mechanism 22 by a wire 23, it receives a tension T from the wire 23 at the fulcrum 21c in the direction of the wire 23, corresponding to the wire length L.

Furthermore, because the river has a current, the buoy 21 is subjected to a force W from the water flow, causing it to move horizontally by a displacement Δx from the vertical water surface position of the wire payout mechanism 22. As a result of this horizontal displacement Δx, the direction of the wire 23 becomes inclined by an angle θ from the vertical, as shown in Figure 1.

The following explains the relationships between the variables and constants mentioned above. Here, the depth of the river to be calculated by the prediction management server 10 is denoted as water depth d, and the flow velocity as water flow velocity v.

As shown in Figure 2, the relationships Lcosθ = d and Lsinθ = Δx exist between the wire length L, inclination angle θ, displacement Δx, and water depth d. Therefore, tanθ = Δx/d can be derived. That is, since the inclination angle θ is a function of the displacement Δx and water depth d, it should be denoted as θ(d, Δx) when specifically indicated.

Furthermore, the vertex height Δh can be derived from the image captured by the surveillance camera 30. Alternatively, the position of the mark 21a on the surface of the buoy 21 may be used to derive the vertex height Δh from the image. For example, if the buoy 21 is spherical and its volume is known, the submerged volume of the buoy 21 can be calculated by deriving the vertex height Δh. Then, as described above, the buoyancy U can be calculated by the product of the submerged volume, the density of water, and the acceleration due to gravity. That is, since the buoyancy U is a function of the vertex height Δh, it should be denoted as U(Δh) when specifically indicated.

Furthermore, as described above, the wire length L of wire 23 and the tension generated in wire 23 are related by a predetermined equation. Since one can be derived from the other, the tension T is a function of the wire length L, and when specifically indicated, it will be denoted as T(L). Also, due to the inclination angle θ of wire 23, the tension T can be decomposed into a horizontal component Tsinθ and a vertical component Tcosθ, as shown in Figure 2.

Furthermore, the force W acting on buoy 21 due to the water flow in the river is a function of the water flow velocity v, and when specifically indicated, it shall be denoted as W(v).

Furthermore, the vertical force acting on buoy 21, as described above, is related by the equilibrium equation shown in equation (1) below.

U(Δh)=G+T(L)・cosθ(d,Δx)...(1)

In other words, the buoyant force U is equal to the resultant force of gravity G and the vertical component Tcosθ of the tension T.

Furthermore, the horizontal forces acting on buoy 21 are related by the equilibrium equation shown in equation (2) below.

W(v)=T(L)・sinθ(d,Δx)...(2)

In other words, the force W due to the water flow is equal to the horizontal component Tsinθ of the tension T.

Based on the above, the prediction management server 10 can calculate the water depth d and water flow velocity v by numerical calculation using the functional relationship between the variables and the above equations (1) and (2). Note that the above equations (1) and (2) correspond to the first relationship.

(Hardware configuration of the predictive management server)
Figure 3 shows an example of the hardware configuration of the predictive management server according to this embodiment. The hardware configuration of the predictive management server 10 according to this embodiment will be described with reference to Figure 3.

As shown in Figure 3, the predictive management server 10 comprises a CPU (Central Processing Unit) 501, a ROM (Read Only Memory) 502, a RAM (Random Access Memory) 503, an auxiliary storage device 505, a network interface 508, a display 509, a keyboard 511, and a mouse 512.

The CPU 501 is a computing unit that controls the overall operation of the predictive management server 10. The ROM 502 is a non-volatile memory device that stores programs for the predictive management server 10. The RAM 503 is a volatile memory device used as the work area for the CPU 501.

The auxiliary storage device 505 is a storage device such as an HDD (Hard Disk Drive) or SSD (Solid State Drive) that stores various data and programs.

The network interface 508 is an interface for wirelessly transmitting data between the surveillance camera 30 and the information terminal 40. Examples of wireless communication standards include 3G, LTE, 4G, 5G, or Wi-Fi®.

The display 509 is a display device composed of liquid crystal or organic EL (electroluminescent) material that displays various information such as cursors, menus, windows, characters, or images.

The keyboard 511 is an input device for selecting characters, numbers, various instructions, and moving the cursor. The mouse 512 is an input device for selecting and executing various instructions, selecting the object to be processed, and moving the cursor.

The CPU 501, ROM 502, RAM 503, auxiliary storage device 505, network interface 508, display 509, keyboard 511, and mouse 512 described above are connected to each other via bus lines 510, such as an address bus and a data bus, enabling communication between them.

Note that the hardware configuration of the predictive management server 10 shown in Figure 3 is an example; it is not necessary to include all the components shown in Figure 3, or other components may be included.

(Hardware configuration of information terminals)
Figure 4 shows an example of the hardware configuration of an information terminal according to this embodiment. The hardware configuration of the information terminal 40 according to this embodiment will be described with reference to Figure 4.

As shown in Figure 4, the information terminal 40 comprises a CPU 401, a ROM 402, a RAM 403, an EEPROM (Electrically Erasable Programmable Read Only Memory) 404, an imaging unit 405, an imaging interface 406, an acceleration/direction sensor 407, and a GPS (Global Positioning System) receiver 408.

The CPU 401 is a processing unit that controls the overall operation of the information terminal 40. The ROM 402 is a non-volatile memory device that stores programs used to drive the CPU 401, such as the IPL (Initial Program Loader). The RAM 403 is a volatile memory device used as the work area for the CPU 401. The EEPROM 404 is a non-volatile memory device that stores programs and various other data.

The imaging unit 405 is a built-in imaging device that, under the control of the CPU 401, captures images of a subject using an image sensor such as a CCD (Charge-Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor) to obtain image data. The imaging I/F 406 is an interface for controlling the operation of the imaging unit 405.

The acceleration/direction sensor 407 is a variety of sensors, including an electronic magnetic compass for detecting the Earth's magnetic field, a gyrocompass, and an acceleration sensor.

The GPS receiver 408 is a receiving device that receives GPS signals from GPS satellites. Note that it is not limited to GPS; other GNSS (Global Navigation Satellite System) systems may also be employed.

Furthermore, as shown in Figure 4, the information terminal 40 also includes a long-range communication circuit 410, an antenna 410a, a short-range communication circuit 411, an antenna 411a, a microphone 412, a speaker 413, an audio input/output interface 414, a display 415, an external device connection interface 416, a vibrator 417, and a touch panel 418.

The long-distance communication circuit 410 is a communication circuit that communicates wirelessly with other devices via antenna 410a using standards such as Wi-Fi (registered trademark).

The short-range communication circuit 411 is a communication circuit that performs short-range wireless communication with other devices via antenna 411a, using standards such as NFC (Near Field Communication) or Bluetooth®.

The microphone 412 is a built-in sound collection device that converts sound into electrical signals. The speaker 413 is a built-in acoustic device that converts electrical signals into physical vibrations to output sound such as music or speech. The sound input/output interface 414 is an interface that processes the input and output of sound signals between the microphone 412 and the speaker 413, according to the control of the CPU 401.

The display 415 is a display device such as a liquid crystal display or an organic EL (Electro-Luminescence) display that displays images of the subject, various icons, etc. The external device connection I/F 416 is an interface conforming to standards such as USB (Universal Serial Bus) for connecting various external devices.

The vibrator 417 is a device that generates physical vibrations according to the control of the CPU 401.

The touch panel 418 is an input device that allows the user to activate various functions of the information terminal 40 by touching the display 415.

The CPU 401, ROM 402, RAM 403, EEPROM 404, imaging interface 406, acceleration/direction sensor 407, GPS receiver 408, long-range communication circuit 410, short-range communication circuit 411, sound input/output interface 414, display 415, external device connection interface 416, vibrator 417, and touch panel 418 are all connected to each other via bus lines 409, such as an address bus and a data bus, enabling communication between them.

Note that the hardware configuration of the information terminal 40 shown in Figure 4 is just one example; it is not necessary to have all the components, and other components may also be included.

(Configuration and operation of the functional blocks of the predictive management server)
Figure 5 shows an example of the configuration of the functional blocks of the predictive management server according to this embodiment. The configuration and operation of the functional blocks of the predictive management server 10 according to this embodiment will be described with reference to Figure 5.

As shown in Figure 5, the prediction management server 10 includes an acquisition unit 101, a first calculation unit 102, a prediction unit 103, a second calculation unit 104, and a display control unit 105.

The acquisition unit 101 is a functional unit that acquires images of the buoys 21 captured by the surveillance camera 30 from multiple buoy-type sensors 20 via the network interface 508.

The first calculation unit 102 is a functional unit that calculates the river's water depth d and water flow velocity v based on the image captured by the acquisition unit 101. Details of the calculation method for water depth d and water flow velocity v by the first calculation unit 102 will be described later in Figures 6 and 7.

The prediction unit 103 is a functional unit that predicts, in the event of a river flood, the area of inundation that will spread from the point of flooding, based on pre-prepared map information and the water depth d and water flow velocity v calculated by the first calculation unit 102, in a time-series manner. In this case, the map information includes, for example, topographic information such as land elevation, road information, and information on the size and location of buildings.

The second calculation unit 104 is a functional unit that calculates evacuation routes that bypass the predicted flood area (predicted flood area) and the evacuation time when using those routes, based on the predicted flood area (predicted flood area) predicted by the prediction unit 103. For example, the second calculation unit 104 calculates the shortest route that bypasses the predicted flood area as the evacuation route from the user's home to a designated evacuation shelter.

The display control unit 105 is a functional unit that controls the display operation of the information terminal 40, for example, a web application, via the network interface 508. For example, the display control unit 105 overlays the predicted flood area predicted by the prediction unit 103 onto the map information displayed on the display 415 of the information terminal 40, and also overlays the evacuation route and evacuation time calculated by the second calculation unit 104.

The acquisition unit 101, the first calculation unit 102, the prediction unit 103, the second calculation unit 104, and the display control unit 105 described above are implemented by the execution of a program by the CPU 501 shown in Figure 3. At least a portion of these functional units may be implemented by hardware circuits such as FPGA (Field-Programmable Gate Array) or ASIC (Application Specific Integrated Circuit).

The functional units of the predictive management server 10 shown in Figure 5 are conceptual representations of their functions and are not limited to this configuration. For example, the multiple functional units shown as independent functional units in the predictive management server 10 in Figure 5 may be configured as a single functional unit. Alternatively, the functions of a single functional unit in the predictive management server 10 shown in Figure 5 may be divided into multiple functions and configured as multiple functional units.

(Process flow for calculating water depth and water flow velocity on the prediction management server)
Figure 6 is a flowchart showing an example of the calculation process for water depth and water flow velocity by the predictive management server according to this embodiment. The calculation process for water depth and water flow velocity by the predictive management server 10 according to this embodiment will be explained with reference to Figure 6.

<Step S11>
The acquisition unit 101 of the predictive management server 10 acquires images of the buoys 21 from multiple buoy-type sensors 20 captured by the surveillance camera 30 via the network interface 508. The first calculation unit 102 of the predictive management server 10 derives the vertex height Δh of the buoys 21 of the buoy-type sensors 20 from the images acquired by the acquisition unit 101. The first calculation unit 102 may use the position of the mark 21a on the surface of the buoy 21 to derive the vertex height Δh from the images. Then, the process proceeds to step S12.

<Step S12>
The first calculation unit 102 derives the horizontal displacement Δx of the buoy 21 floating on the river surface from the image captured by the acquisition unit 101. Then, the process proceeds to step S13.

<Step S13>
The first calculation unit 102 then calculates the water depth d and water flow velocity v based on the buoyancy U determined from gravity G and the apex height Δh, as well as the above-mentioned equations (1) and (2). For example, the inclination angle θ, tension T, wire length L, and force W due to the water flow can be said to be dependent values of the water depth d and water flow velocity v, so the water depth d and water flow velocity v can be calculated by numerical calculation.

Following the steps S11 to S13 described above, the prediction management server 10 performs the calculation process for water depth and water flow velocity.

Here, an example of a specific method for calculating the water depth d and water flow velocity v in step S13 is described below.

The first calculation unit 102 calculates the submerged volume of the buoy 21 from the derived vertex height Δh. Then, the first calculation unit 102 calculates the buoyancy U by multiplying the submerged volume, the density of water, and the acceleration due to gravity.

Next, the first calculation unit 102 calculates the vertical component Tcosθ of the tension T from the known gravity G, the calculated buoyancy U, and the above-mentioned equation (1). Furthermore, the displacement Δx calculated in step S12 is expressed as Δx = Lsinθ, using the wire length L and the inclination angle θ.

Next, the first calculation unit 102 calculates the wire length L and the inclination angle θ from the vertical component Tcosθ of the calculated tension T and the derived displacement Δx (= Lsinθ). Since the tension T is a function of the wire length L, as described above, and can be expressed using the wire length L, it can be solved as a system of simultaneous equations between the wire length L and the inclination angle θ.

Next, the first calculation unit 102 calculates the water depth d (= Lcosθ) from the wire length L and the inclination angle θ.

Next, the first calculation unit 102 calculates the tension T from the calculated wire length L. Then, the first calculation unit 102 calculates the force W due to the water flow using the above-mentioned equation (2) from the calculated tension T and the inclination angle θ. Finally, the first calculation unit 102 calculates the water flow velocity v, which is the inverse function of the force W due to the water flow.

As described above, the first calculation unit 102 calculates the water depth d and the water flow velocity v.

As shown in Figure 2 above, in cases where, for example, the water flow velocity v is above a predetermined value, the inclination of the buoy 21 relative to the vertical (an example of a submerged state) can sometimes be considered as the inclination angle θ in the direction of the wire 23. That is, in this case, the apex of the buoy 21 (the position where mark 21a exists) lies on the extension of the wire 23. The calculation process for the water depth d and water flow velocity v in this case will be explained below with reference to Figure 7.

Figure 7 is a flowchart showing another example of the calculation process for water depth and water flow velocity in the prediction management server according to the embodiment. Referring to Figure 7, the calculation process for water depth and water flow velocity when the apex of buoy 21 (the position where mark 21a exists) is located on the extension of wire 23 will be explained.

<Step S21>
The acquisition unit 101 of the predictive management server 10 acquires images of the buoy 21 from multiple buoy-type sensors 20 captured by the surveillance camera 30 via the network interface 508. The first calculation unit 102 of the predictive management server 10 derives the tilt angle θ of the buoy 21 from the images acquired by the acquisition unit 101, based on the position of the mark 21a on the buoy 21 of the buoy-type sensor 20. Then, the process proceeds to step S22.

<Step S22>
The first calculation unit 102 derives the horizontal displacement Δx of the buoy 21 floating on the river surface from the image captured by the acquisition unit 101. Then, the process proceeds to step S23.

<Step S23>
The first calculation unit 102 calculates the wire length L from the displacement Δx and the inclination angle θ, since the displacement Δx is expressed as Δx = Lsinθ using the wire length L and the inclination angle θ. Next, the first calculation unit 102 calculates the water depth d (= Lcosθ) from the wire length L and the inclination angle θ. Then, it proceeds to step S24.

<Step S24>
The first calculation unit 102 calculates the tension T from the calculated wire length L. Next, the first calculation unit 102 calculates the force W due to the water flow from the calculated tension T and inclination angle θ using the above-mentioned equation (2). Then, the process proceeds to step S25.

<Step S25>
The first calculation unit 102 then calculates the water flow velocity v, which is the inverse function of the force W due to the water flow.

Based on the above, when the apex of buoy 21 (the position where mark 21a is located) lies on the extension of wire 23, the first calculation unit 102 calculates the water depth d and the water flow velocity v.

(Display operation of predicted flood area, evacuation route, and evacuation time on information terminals)
Figure 8 shows an example of a state in which evacuation routes are displayed on the map information in an information terminal according to the embodiment. Figure 9 shows an example of a state in which predicted flood areas and detour routes for evacuation are displayed on the map information in an information terminal according to the embodiment. Referring to Figures 8 and 9, the display operation of predicted flood areas, evacuation routes, and evacuation times on the map information of the information terminal 40 will be explained.

In the example shown in Figure 8, when the river is not flooded, the display control unit 105 displays the evacuation route and evacuation time calculated by the second calculation unit 104 on the display 415 of the information terminal 40, superimposed on the map information. Specifically, in Figure 8, the evacuation route LT1 from the user's home to the evacuation shelter and the evacuation time are displayed on the display 415 of the information terminal 40, superimposed on the map information.

Next, in the example shown in Figure 9, when a river overflows, the display control unit 105 overlays the predicted flood area FA for a specific time, as predicted by the prediction unit 103, and the evacuation route LT2 and evacuation time, calculated by the second calculation unit 104, onto the map information on the display 415 of the information terminal 40.

Furthermore, the information terminal 40 may allow the user to select the predicted flood area FA for a given time interval from the current time. In this case, the predicted flood area after the selected time interval is re-predicted by the prediction unit 103, and the second calculation unit 104 calculates an evacuation route and evacuation time that bypasses the predicted flood area.

As described above, in the prediction management server 10 according to this embodiment, the acquisition unit 101 acquires images captured by a surveillance camera 30 that images the buoy 21 on the water surface, which is part of a buoy-type sensor 20 having a buoy 21 floating on the river and a wire feed mechanism 22 fixed to the riverbed or near the riverbed, connected to the buoy 21 by a wire 23, and capable of extending and retracting the wire 23. The first calculation unit 102 derives from the captured images the horizontal displacement Δx of the buoy 21 from a position on the water surface perpendicular to the wire feed mechanism 22, and the submersion state of the buoy 21 (vertex height Δh, inclination of the buoy 21). Based on the displacement Δx, the submersion state, and the equilibrium equations (1) and (2) of gravity G, buoyancy U, and force W due to water flow acting on the buoy 21, the river water depth d and water flow velocity v are calculated. This eliminates the need for power to transmit or receive signals or information from buoy 21, allowing for accurate calculation of river depth d and water flow velocity v without the use of expensive sensors.

Furthermore, in the prediction management server 10 according to this embodiment, the prediction unit 103 predicts the flooded area from the river in a time series based on predetermined map information and the water depth d and water flow velocity v calculated by the first calculation unit 102. The second calculation unit 104 calculates evacuation routes and evacuation times that bypass the flooded area predicted by the prediction unit 103. The display control unit 105 overlays the flooded area predicted by the prediction unit 103, as well as the evacuation routes and evacuation times calculated by the second calculation unit 104, onto the map information and displays them on the information terminal 40. This allows the user of the information terminal 40 to confirm the flooded area with high prediction accuracy and to confirm evacuation routes and evacuation times that bypass the flooded area, enabling safe evacuation to shelters even in the event of flooding.

(Variation 1)
Next, we will explain the differences between the prediction management server 10 according to Modification 1 and the prediction management server 10 according to the above embodiment. In this modification, we will explain the calculation process for water depth d and water flow velocity v, taking into account the deviation in the tilt of the buoy 21 caused by the force moment around the fulcrum 21c of the buoy 21 in the vertical plane.

Figure 10 illustrates the forces and moments acting on the buoy. Referring to Figure 10, the forces and moments acting on buoy 21 will be explained.

As shown in Figure 10, the forces acting on buoy 21 are the same as those described in Figure 2 above. However, regarding the moment of force around the support point 21c in the vertical plane, as described below, the tension T where the support point 21c lies on the line of the force vector does not contribute to the moment of force around the support point 21c and is therefore not shown in Figure 10.

As shown in Figure 10, the moment of force around the fulcrum 21c in the vertical plane includes the moment of buoyancy U, the moment of gravity G, and the moment of force W due to the water flow. When these moment of force are balanced, the rotational motion of the buoy 21 around the fulcrum 21c ceases.

The moment of buoyancy U is expressed as the product of the component of the buoyancy U vector perpendicular to the line connecting the starting point (the center of buoy 21 in the example of Figure 10) and the pivot point 21c, and the distance between the starting point and the pivot point 21c (hereinafter referred to as distance r1), as shown in Figure 10. More precisely, the moment of buoyancy U is obtained by integrating the product of the component of the buoyancy force vector acting on each point of the submerged volume of buoy 21 perpendicular to the line connecting the starting point and the pivot point 21c, and the distance between the starting point and the pivot point 21c, over the entire submerged volume. In the example shown in Figure 10, the moment of buoyancy U contributes to a clockwise rotation around the pivot point 21c.

The moment of gravity G is expressed as the product of the component of the gravity vector perpendicular to the line connecting the starting point (the center of gravity of buoy 21 in the example of Figure 10) and the pivot point 21c, and the distance between the starting point and the pivot point 21c (hereinafter referred to as distance r²), as shown in Figure 10. More precisely, the moment of gravity G is obtained by integrating the product of the component of the gravity vector acting on each point mass within buoy 21 perpendicular to the line connecting the starting point and the pivot point 21c, and the distance between the starting point and the pivot point 21c, over the entire volume of buoy 21. In the example shown in Figure 10, the moment of gravity G contributes to counterclockwise rotation around the pivot point 21c.

The moment of the force W due to the water flow is obtained by integrating the product of the force vector (directed to the left) acting on each point on the surface of the submerged portion of the buoy 21, the component perpendicular to the line connecting the starting point and the fulcrum 21c, and the distance between the starting point and the fulcrum 21c, over the entire surface of the submerged portion. However, of the moment of the force W due to the water flow, the moment contributing to counterclockwise rotation around the fulcrum 21c is denoted as W1, and the moment contributing to clockwise rotation is denoted as W2.

Assuming that the moment of buoyancy U, the moment of gravity G, and the moment of force W due to the water flow are in equilibrium, they can be related by the equilibrium equation shown in equation (3) below.

r1・U(Δh)・sin(θ−φ)+W2=r2・G・sin(θ−φ)+W1
... (3)

The displacement angle φ shown in equation (3) is the displacement angle of the line connecting the vertex of the buoy 21 (the point where the line connecting the fulcrum 21c and the center of gravity intersects the surface) with respect to the direction of the wire 23, as shown in Figure 10, resulting from the moment of each force acting on the buoy 21 around the fulcrum 21c. Therefore, the inclination of the buoy 21 (an example of a submerged state) is expressed as θ - φ. Note that equation (3) above corresponds to the second relationship.

Figure 11 is a flowchart showing an example of the calculation process flow for water depth and water flow velocity in the prediction management server according to Modification 1. Referring to Figure 11, the calculation process flow for water depth and water flow velocity by the prediction management server 10 according to this modification will be explained.

<Step S31>
The acquisition unit 101 of the predictive management server 10 acquires images of the buoy 21 from multiple buoy-type sensors 20 captured by the surveillance camera 30 via the network interface 508. The first calculation unit 102 of the predictive management server 10 derives the vertex height Δh of the buoy 21 of the buoy-type sensor 20 from the images acquired by the acquisition unit 101. The first calculation unit 102 may use the position of the mark 21a on the surface of the buoy 21 to derive the vertex height Δh from the images. The first calculation unit 102 also derives the inclination of the buoy 21, θ-φ, from the position of the mark 21a on the buoy 21 in the images. Then, the process proceeds to step S32.

<Step S32>
The first calculation unit 102 derives the horizontal displacement Δx of the buoy 21 floating on the river surface from the image captured by the acquisition unit 101. Then, the process proceeds to step S33.

<Step S33>
The first calculation unit 102 then calculates the water depth d, water flow velocity v, and slip angle φ based on the buoyancy U determined from gravity G and vertex height Δh, as well as the above-mentioned equations (1) to (3). For example, since the other values can be said to be dependent on the water depth d, water flow velocity v, and slip angle φ, the water depth d, water flow velocity v, and slip angle φ can be calculated by numerical calculation.

Following the steps S31 to S33 described above, the prediction management server 10 performs the calculation process for water depth and water flow velocity.

As described above, in the prediction management server 10 according to this modified example, the first calculation unit 102 derives the height Δh of the buoy 21 above the water surface as the submerged state from the captured image, and derives the inclination of the buoy with a displacement angle φ with respect to the direction of the wire 23 as the submerged state from the captured image. Based on the displacement Δx, the submerged state, equations (1) and (2), and equation (3) representing the balance of the moments of gravity G, buoyancy U, and force W due to the water flow around the fulcrum 21c, which is the connection point between the buoy 21 and the wire 23 in the vertical plane, the water depth d and water flow velocity v are calculated. This eliminates the need for power to transmit or receive any signals or information regarding the buoy 21, allowing for accurate calculation of the river's water depth d and water flow velocity v without using expensive sensors. Furthermore, it allows for accurate calculation of the water depth d and water flow velocity v even when the inclination of the buoy 21 has a displacement angle φ.

(Variation 2)
Next, we will explain the differences between the predictive management server 10 according to the modified example 2 and the predictive management server 10 according to the embodiment described above. In this modified example, we will explain the process of calculating the water flow velocity v, taking into account the displacement angle of the buoy 21 with respect to the water flow direction, which is caused by the moment of force W due to the water flow around the pivot point 21c of the asymmetrical buoy 21 in the horizontal plane.

Figure 12 illustrates the forces and moments acting on an asymmetrical buoy. Referring to Figure 12, the moment of the force W due to the water flow acting on buoy 21 in the horizontal plane will be explained.

Figure 12 shows the state of buoy 21 as viewed from above, and assumes that buoy 21 is asymmetrical. The portion 21d above the water surface is the volume of buoy 21 that is exposed above the water surface. As shown in Figure 12, the moment of force around the fulcrum 21c in the horizontal plane is the moment of force W due to the water flow. Buoyancy U and gravity G are forces acting perpendicular to the horizontal plane and therefore do not contribute to the moment of force around the fulcrum 21c in the horizontal plane.

The moment of the force W due to the water flow is obtained by integrating the product of the force vector (directed to the left) acting on each point on the surface of the submerged portion of the buoy 21, which is perpendicular to the line connecting the starting point and the fulcrum 21c, and the distance between the starting point and the fulcrum 21c (hereinafter referred to as distance r), over the entire surface of the submerged portion. Here, with respect to the moment of the force W due to the water flow that contributes to counterclockwise rotation around the fulcrum 21c, the component of the force vector acting on each point on the surface of the submerged portion of the buoy 21 that is perpendicular to the line connecting the starting point and the fulcrum 21c is denoted as W3. On the other hand, with respect to the moment of the force W due to the water flow that contributes to clockwise rotation around the fulcrum 21c, the component of the force vector acting on each point on the surface of the submerged portion of the buoy 21 that is perpendicular to the line connecting the starting point and the fulcrum 21c is denoted as W4.

Assuming that the moment forces due to the water flow acting on each point on the surface of the submerged portion of buoy 21 are in equilibrium, they can be related by the equilibrium equation shown in equation (4) below.

∫r×W3(v,λ,r)dr=∫r×W4(v,λ,r)dr...(4)

The horizontal displacement angle λ shown in equation (4) is the horizontal displacement angle of the line connecting the vertex of the buoy 21 (the point where the line connecting the fulcrum 21c and the center of gravity intersects the surface) with respect to the direction of the wire 23, as shown in Figure 12, resulting from the force moment acting on the buoy 21 due to the water flow centered at the fulcrum 21c. In this case, W3 and W4 are functions of the water flow velocity v, the horizontal displacement angle λ, and the distance r. Note that equation (4) above corresponds to the third relationship.

In a state of equilibrium due to the force moment caused by the water flow, in order to ensure that the buoy 21 does not tip over and maintains asymmetry, more than half of the asymmetrical volume must be submerged. By positioning the weight 21b in the submerged portion of the buoy 21, tipping can be suppressed.

Figure 13 is a flowchart showing an example of the water flow velocity calculation process of the predictive management server according to Modification 2. Referring to Figure 13, the water flow velocity calculation process by the predictive management server 10 according to this modification will be explained.

<Step S41>
The acquisition unit 101 of the prediction management server 10 acquires images of the buoy 21 captured by the surveillance camera 30 from multiple buoy-type sensors 20 via the network interface 508. The first calculation unit 102 derives the horizontal displacement angle λ of the buoy 21 in the horizontal plane from the position of the mark 21a on the buoy 21 in the captured image. Then, the process proceeds to step S42.

<Step S42>
The first calculation unit 102 numerically calculates the water flow velocity v from the horizontal displacement angle λ and the equation (4) for the equilibrium of force moments due to the water flow acting on each point on the surface of the submerged portion of the buoy 21.

Following the steps S41 to S42 described above, the water flow velocity calculation process is performed by the prediction management server 10.

As described above, in the prediction management server 10 according to this modified example, the first calculation unit 102 derives the horizontal displacement angle λ of the buoy 21 in the horizontal plane from the captured image, and calculates the water flow velocity v based on the horizontal displacement angle λ and the equation (4) for the equilibrium of the forces due to the water flow around the fulcrum 21c, which is the connection point between the buoy 21 and the wire 23 in the horizontal plane. This eliminates the need for power to transmit or receive any signals or information regarding the buoy 21, thus enabling accurate calculation of the river water flow velocity v without using expensive sensors.

Furthermore, each function of the embodiments and variations described above can be realized by one or more processing circuits. Here, "processing circuit" includes processors programmed to execute each function by software, such as processors implemented by electronic circuits, as well as devices such as ASICs (Application Specific Integrated Circuits), DSPs (Digital Signal Processors), FPGAs (Field Programmable Gate Arrays), and conventional circuit modules designed to execute the functions described above.

Furthermore, the programs executed by the prediction management server 10 in the above-described embodiments and each of the modified examples may be configured to be pre-loaded and provided in ROM or the like.

Furthermore, the programs executed by the predictive management server 10 in the above-described embodiments and each of its modifications may be configured to be provided as computer program products by recording them as installable or executable files on a computer-readable recording medium such as a CD-ROM (Compact Disc Read Only Memory), flexible disk (FD), CD-R (Compact Disc-Recoverable), or DVD (Digital Versatile Disc).

Furthermore, the programs executed by the predictive management server 10 in the above-described embodiments and their respective modifications may be stored on a computer connected to a network such as the Internet and provided by downloading them via the network. Alternatively, the programs executed by the predictive management server 10 in the above-described embodiments and their respective modifications may be provided or distributed via a network such as the Internet.

Furthermore, the programs executed by the predictive management server 10 in the above-described embodiments and their respective modifications are configured as modules including the aforementioned functional units. In actual hardware, the CPU 501 (processor) reads the program from the ROM 502 or auxiliary storage device 505 and executes it, thereby loading the aforementioned functional units onto the RAM 503 (main memory), and creating each functional unit on the RAM 503.

1 Flood monitoring system 10 Prediction management server 20 Buoy-type sensor 21 Buoy 21a Mark 21b Weight 21c Pivot point 21d Surface-exposed part 22 Wire payout mechanism 23 Wire 30 Surveillance camera 40 Information terminal 101 Acquisition unit 102 First calculation unit 103 Prediction unit 104 Second calculation unit 105 Display control unit 401 CPU
402 ROM
403 RAM
404 EEPROM
405 Imaging unit 406 Imaging interface
407 Acceleration/direction sensor 408 GPS receiver 409 Bus line 410 Long-range communication circuit 410a Antenna 411 Short-range communication circuit 411a Antenna 412 Microphone 413 Speaker 414 Audio input/output interface
415 Display 416 External device connection interface
417 Vibrator 418 Touch Panel 501 CPU
502 ROM
503 RAM
505 Auxiliary storage device 508 Network interface
509 Display 510 Bus line 511 Keyboard 512 Mouse d Water depth FA Predicted flooded area G Gravity L Wire length LT1, LT2 Evacuation route T Tension U Buoyancy v Water velocity W Force due to water flow θ Inclination angle λ Horizontal displacement angle φ Displacement angle Δh Vertex height Δx Displacement

Claims (11)

A buoy-type sensor having a buoy floating on a river and a deployment mechanism fixed to the riverbed or near the riverbed, which is connected to the buoy by a connecting wire and is capable of deploying and retracting the connecting wire, wherein the sensor includes an acquisition unit that acquires an image captured by an imaging device that images the buoy on the water surface,
A first calculation unit derives from the captured image the horizontal displacement of the buoy from the water surface position vertical to the deployment mechanism, and the submersion state of the buoy, and calculates the water depth and water flow velocity of the river based on the displacement, the submersion state, and a first relationship of equilibrium between gravity, buoyancy, force and tension due to water flow acting on the buoy.
A flood monitoring device equipped with a flood monitoring system. The first calculation unit is,
From the aforementioned captured image, the height of the portion of the buoy that is visible above the water surface is derived as the submerged state.
A flood monitoring device according to claim 1, which calculates the submerged volume of the buoy from the height, calculates the buoyancy of the buoy based on the submerged volume, and calculates the water depth and the water flow velocity based on the displacement, the buoyancy, and the first relationship. The first calculation unit derives the inclination of the buoy with respect to the vertical direction as the submerged state from the captured image, as the angle of inclination of the connecting line with respect to the vertical direction.
From the displacement and the angle of inclination, the length of the connecting wire is calculated, and from the length and the angle of inclination, the water depth is calculated.
The flood monitoring device according to claim 1, which calculates the tension acting on the buoy at the connection point between the buoy and the connecting line from the aforementioned length, calculates the force due to the water flow acting on the buoy based on the aforementioned tension and the aforementioned inclination angle, and calculates the water flow velocity from the force due to the water flow. The buoy has a mark on its surface,
The flood monitoring device according to claim 3, wherein the first calculation unit derives the inclination from the captured image based on the position of the mark on the buoy. The first calculation unit is,
From the aforementioned captured image, the height from the water surface of the portion of the buoy that is visible above the water surface is derived as the submerged state.
From the captured image, the tilt of the buoy having a deviation angle with respect to the direction of the connecting line is derived as the submerged state.
A flood monitoring device according to claim 1, which calculates the water depth and the water flow velocity based on the displacement, the submersion state, the first relationship, and the second relationship of the equilibrium of the moments of gravity, buoyancy, and force due to the water flow around the connection point between the buoy and the connecting line in a vertical plane. The first calculation unit is,
From the aforementioned captured image, the horizontal displacement angle of the buoy in the horizontal plane is derived.
The flood monitoring device according to claim 1, which calculates the water flow velocity based on the horizontal displacement angle and a third relationship of equilibrium of each moment of force due to the water flow around the connection point between the buoy and the connecting line in the horizontal plane. A flood monitoring device according to any one of claims 1 to 6, further comprising a prediction unit that predicts the area of inundation from the river based on predetermined map information and the water depth and water flow velocity calculated by the first calculation unit. The flood monitoring device according to claim 7, further comprising a second calculation unit for calculating evacuation routes and evacuation times that bypass the flooded area predicted by the prediction unit. The flood monitoring device according to claim 8, further comprising a display control unit that superimposes the predicted flood area, calculated by the prediction unit, and the evacuation route and evacuation time, calculated by the second calculation unit, onto the map information and displays them on an information terminal. A buoy-type sensor having a buoy floating in a river, and a deployment mechanism fixed to the riverbed or near the riverbed, which is connected to the buoy by a connecting wire and allows the connecting wire to be extended and retracted.
An imaging device for imaging the buoy on the water surface,
A flood monitoring device that calculates the water depth and water flow velocity of the river based on the images captured by the aforementioned imaging device,
Includes,
The aforementioned flood monitoring device,
An acquisition unit that acquires the captured image from the aforementioned imaging device,
A first calculation unit derives from the captured image the horizontal displacement of the buoy from the water surface position vertical to the deployment mechanism, and the submersion state of the buoy, and calculates the water depth and water flow velocity based on the displacement, the submersion state, and a first relationship of equilibrium between gravity, buoyancy, force and tension due to water flow acting on the buoy,
A flood monitoring system equipped with a flood monitoring system. A flood monitoring method performed by a flood monitoring device,
A buoy-type sensor having a buoy floating on a river and a deployment mechanism fixed to the riverbed or near the riverbed, which is connected to the buoy by a connecting wire and is capable of deploying and retracting the connecting wire, wherein the sensor acquires an image captured by an imaging device that images the buoy on the water surface.
From the captured image, the horizontal displacement of the buoy from the water surface position perpendicular to the deployment mechanism, and the submersion state of the buoy are derived, and based on the displacement, the submersion state, and a first relationship of equilibrium between gravity, buoyancy, force due to water flow, and tension acting on the buoy, the water depth and water flow velocity of the river are calculated.
A flood monitoring method characterized by including the following: