JP6793924B2 - Multiple reservoir inundation analysis device, multiple reservoir inundation analysis method - Google Patents

Description

The present invention relates to a plurality of reservoir inundation analysis device and a plurality of reservoir inundation analysis methods.

Due to natural disasters such as guerrilla rainstorms, earthquakes, and tsunamis that are thought to be caused by abnormal weather in recent years, flood analysis is required when reservoirs such as reservoirs and dams collapse. For example, a flood flow estimation system has been proposed that numerically simulates the increase and decrease of the flood flow in the downstream area due to the overflow collapse of a natural dam in a geographical and time series (Patent Document 1). However, on the premise that equipment such as dams have been designed so as not to collapse, flood analysis at the time of collapse has not received much attention.

However, the Great East Japan Earthquake that occurred on March 11, 2011 broke the Fujinuma Reservoir in Sukagawa City, Fukushima Prefecture, causing a lot of damage. Reservoirs may continue to be damaged by earthquakes such as the Nankai Trough and heavy rains.

Against this background, from the perspective of disaster prevention and mitigation, attention has also been focused on flood analysis due to the collapse of the pond. In particular, there are many old ponds that existed before the Edo period, so it is necessary to consider the risk of collapse.

As mentioned above, attention has been focused on the flood analysis of reservoirs. The collapse of the reservoir has not been expected in the past. However, in recent years, disasters beyond expectations, such as unprecedented catastrophes, have become more frequent once every 1000 years, and the need to consider disaster prevention assuming such a collapse has been called for.

In addition, in areas where there are multiple reservoirs, it is conceivable that these will break in a chain, and such chain breaks have hardly been examined, and flood analysis has not been undertaken at present. is there.

Japanese Patent No. 5600507

"Analysis and verification of flooding of a pond that collapsed due to heavy rain in 2013" Rural Engineering Research Institute Technical Report No. 215 pp91-101, 2014 Costa, J., Floods from Dam Failure, Flood Geomorphology, 436-439 (1988).

In view of such a background, the present invention has been made, and one of the purposes thereof is to provide a plurality of reservoir inundation analysis device and a plurality of reservoir inundation analysis methods capable of analyzing inundation caused by chain breaking of a plurality of reservoirs. To do.

Means for Solving Problems and Effects of Invention

According to the plurality of reservoir inundation analysis apparatus according to the first aspect of the present invention, inundation analysis in which a plurality of reservoirs including an upper pond located on the upstream side and a lower pond located on the downstream side of the upper pond collapse in a chain reaction. It is a multiple reservoir inundation analysis device for performing the above, and the pond information input unit for acquiring the information of the upper pond and the information of the lower pond, and the topographical information for acquiring the topographical data of the area to be inundated. Based on the input unit and the upper pond information input from the pond information input unit, the upper pond outflow amount calculation unit that calculates the outflow amount of water flowing out from the upper pond and the upper pond outflow amount calculation unit calculate the amount. Of the outflow amount, the lower pond inflow calculation unit for calculating the amount of water flowing into the lower pond and the lower pond inflow calculation unit calculated based on the topographical data acquired by the topographical information input unit. From the lower pond inflow amount, the lower pond water storage amount calculation unit that calculates the water storage amount of the lower pond based on the lower pond information input from the pond information input unit, and the lower pond outflow amount that calculates the lower pond outflow amount that flows downstream from the lower pond. The Shimoike outflow calculation unit is provided with a calculation unit, and has a calculation algorithm before the Shimoike collapse and a calculation algorithm after the Shimoike collapse as an algorithm for calculating the Shimoike outflow amount, and the Shimoike water storage amount calculation unit. When the amount of water stored in the lower pond calculated in step 2 reaches the algorithm switching condition given in advance, the amount of runoff of the lower pond can be calculated by changing to the calculation algorithm after the collapse of the lower pond. With the above configuration, it is possible to analyze the inundation after the chain breakage of the upper pond and the lower pond.

Further, according to the plurality of reservoir inundation analysis apparatus according to the second embodiment, in addition to the above configuration, the lower reservoir water storage amount calculation unit can include a lower pond water level calculation unit for calculating the water level of the lower pond.

Further, according to the plurality of reservoir inundation analysis apparatus according to the third embodiment, in addition to any of the above configurations, the pond information input unit is configured to be able to acquire information on the depth of the discharge portion of the lower pond. The algorithm switching condition can be the timing when the water level of the lower pond reaches the depth of the discharge portion acquired by the pond information input unit. With the above configuration, the Shimoike water level calculation unit determines the amount of Shimoike outflow after the water level of the Shimoike reaches the depth from the initial water level to the total overflow head and the discharge part depth acquired by the pond information input unit. You can switch the calculation algorithm of.

Furthermore, according to the plurality of reservoir inundation analysis apparatus according to the fourth embodiment, in addition to any of the above configurations, in order to further display a hydrograph showing the time change of the outflow amount from the time of the breach of the upper pond. Display unit can be provided.

Furthermore, according to the plurality of reservoir inundation analysis apparatus according to the fifth embodiment, in addition to any of the above configurations, the upper pond outflow calculation unit is based on the upper pond information input from the pond information input unit. Assuming that the upper pond will collapse at the analysis start time when the analysis by the multiple reservoir flood analysis device is started, the algorithm for calculating the upper pond runoff amount is a model in which the water amount specified by the following formula flows out. it can.

In the above equation, q _u (t) is the upper pond runoff at time t [m ³ / s]; V _u is the upper pond reservoir [× 10 ⁶ m ³ ]; _Hu is the upper pond bank height [m]; t is the time [sec] .

で演算し、貯水池の初期貯水量を、放流部の下端まで水位があると仮定して

で演算することができる。
（Ｑは流量［ｍ³／ｓ］、Ｃは流量係数、Ｂは水路幅［ｍ］、ｈ_kは越流総水頭［ｍ］、Ｖ_maxは総貯水量［ｍ³］） Furthermore, according to the plurality of reservoir inundation analysis apparatus according to the sixth embodiment, in addition to any of the above configurations, the overflow total head is discharged as an algorithm in which the lower pond runoff calculation unit calculates the lower pond runoff. If the water depth is smaller than the depth of the part, it is assumed that the water flows downstream from the discharge part of the lower pond, and the flow rate discharged downstream is

Calculate with, and assume that the initial water storage amount of the reservoir is the water level up to the lower end of the discharge part.

Can be calculated with.
(Q is the flow rate [m ³ / s], C is the flow coefficient, B is the channel width [m], h _k is the total overflow head [m], and V _max is the total water storage amount [m ³ ])

として演算し、かつ前記下池流出量演算部が、決壊以降に下池流出量を演算するアルゴリズムとして、下池流出箇所から下流への流出量の時間変化を次式で演算するよう切り替えることができる。

（Ａは満水面積［ｍ ² ］、ｑ_l（ｔ）は時刻ｔにおける下池流出量［ｍ³／ｓ］、Ｖ_lは下池貯水量［×１０⁶ｍ³］、Ｈ_lは下池堤高（ｍ）、ｔは下池決壊した時刻からの時間［ｓｅｃ］、ｔ_lは下池決壊時刻［ｓｅｃ］、ｑ_{l_in}は下池決壊後に下池に流入した水量［ｍ³／ｓ］） Furthermore, according to the plurality of reservoir inundation analysis apparatus according to the seventh embodiment, in addition to any of the above configurations, when the total overflow head exceeds the depth of the discharge section, the reservoir water storage amount calculation unit is a reservoir. Assuming that will collapse, the amount of water stored in the lower pond

As an algorithm for calculating the Shimoike outflow amount after the collapse, the Shimoike outflow calculation unit can be switched to calculate the time change of the outflow amount from the Shimoike outflow point to the downstream by the following equation.

( A is the full area [m ² ], q _l (t) is the outflow amount of the lower pond at time t [m ³ / s], V _l is the amount of water stored in the lower pond [× 10 ⁶ m ³ ], and H _l is the height of the lower pond bank ( m), t is the time from the time when the _lower pond broke [sec], t _l is the time when the _lower pond broke [sec], q _{l_in} is the amount of water flowing into the _lower pond after the broke of the _lower pond [m ³ / s])

Furthermore, according to the plurality of reservoir inundation analysis apparatus according to the eighth embodiment, in addition to any of the above configurations, the ground has information on the height difference of the ground surface and calculates the indefinite flow flowing out from the upper pond. The surface layer can be provided with a rainfall setting unit for adding rainfall.
Furthermore, according to the plurality of reservoir flood analysis apparatus according to the ninth aspect, in addition to any of the above configurations, a tide level calculation unit for calculating a tide level that fluctuates with time can be further provided. With the above configuration, the water level under the downstream end condition can be changed over time according to the tide level.

Furthermore, according to the plurality of reservoir inundation analysis apparatus according to the tenth aspect, in addition to any of the above configurations, the flow rate calculated by the inundation analysis of the upper pond is further converted into the water level of the lower pond. A water level conversion unit can be provided.

Furthermore, according to the plurality of reservoir inundation analysis apparatus according to the eleventh embodiment, in addition to any of the above configurations, the pond information input unit can be configured to input a reservoir database. With the above configuration, it is possible to perform inundation analysis without conducting a field survey of reservoirs in each region.

Furthermore, according to the multiple reservoir inundation analysis method according to the twelfth embodiment, inundation analysis in which a plurality of reservoirs including an upper pond located on the upstream side and a lower pond located on the downstream side of the upper pond collapse in a chain reaction. This is a method for analyzing the inundation of multiple reservoirs, and is based on the process of acquiring information on the upper and lower ponds and the topographical data of the area subject to the inundation analysis, and the acquired upper pond information. A step of calculating the outflow amount of water flowing out from the lower pond, a step of calculating the amount of water flowing into the lower pond based on the acquired topographical data, and the calculated lower pond inflow. Based on the acquired lower pond information, the lower pond outflow amount is calculated in the step of calculating the lower pond runoff amount, including the step of calculating the water level of the lower pond and the lower pond runoff amount flowing downstream from the lower pond. As an algorithm to calculate, it has a calculation algorithm before the Shimoike collapse and a calculation algorithm after the Shimoike collapse, and the calculation algorithm before the Shimoike collapse is used when the water level of the Shimoike is from the initial water level to the overflow total head. After reaching the discharge depth obtained as the information of the lower pond, the calculation algorithm of the lower pond outflow amount can be switched so as to use the calculation algorithm after the Shimoike collapse. This makes it possible to analyze the inundation after the chain break of the upper pond and the lower pond.

1A to 1G are schematic views showing a flow in which a chain break occurs. It is a functional block diagram which shows the multiple reservoir inundation analysis apparatus which concerns on Embodiment 1 of this invention. It is a schematic plan view which shows the definition point of a staggered structural grid and an unknown variable. It is a schematic cross-sectional view which shows the case where a water flow overflows unevenness such as embankment. It is a schematic cross-sectional view which shows the case where the dominant cross section appears between meshes. It is a schematic plan view which shows the definition point of the traveling direction and the flow rate of a drainage channel. It is a schematic diagram which shows the state of associating the ground surface layer and the Shimoike layer. It is a schematic diagram which modeled a reservoir.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the embodiments shown below are examples for embodying the technical idea of the present invention, and the present invention is not specified as the following. Further, the present specification does not specify the members shown in the claims as the members of the embodiment. In particular, the dimensions, materials, shapes, relative arrangements, etc. of the components described in the embodiments are not intended to limit the scope of the present invention to the specific description unless otherwise specified, and are merely described. It's just an example. The size and positional relationship of the members shown in each drawing may be exaggerated to clarify the explanation. Further, in the following description, members of the same or the same quality are shown with the same name and reference numeral, and detailed description thereof will be omitted as appropriate. Further, each element constituting the present invention may be configured such that a plurality of elements are composed of the same member and the plurality of elements are combined with one member, or conversely, the function of one member is performed by the plurality of members. It can also be shared and realized.

The connection between the plurality of reservoir inundation analyzers used in the embodiments of the present invention and the computers, printers, external storage devices and other peripheral devices connected thereto for operations, controls, displays, other processes, etc. Serial or parallel connections such as IEEE 1394, RS-232x, RS-422, RS-423, RS-485, USB, or electrical or magnetic via networks such as 10BASE-T, 100BASE-TX, 1000BASE-T, etc. Communicate by connecting objectively and optically. The connection is not limited to a physical connection using a cable, and may be a wireless LAN such as IEEE802.1x, a wireless connection using Bluetooth (registered trademark), other radio waves such as NFC, infrared rays, optical communication, or the like. Further, a memory card, a magnetic disk, an optical disk, a magneto-optical disk, a semiconductor memory, or the like can be used as a recording medium for exchanging data, storing settings, and the like. In the present specification, the term "multiple reservoir inundation analysis device" is used to include not only the main body of the multiple reservoir inundation analysis device but also an inundation degree real-time prediction system in which peripheral devices such as a computer and an external storage device are combined.
(Embodiment 1)

The plurality of reservoir inundation analysis apparatus according to the first embodiment of the present invention performs inundation analysis in which a plurality of reservoirs including an upper pond located on the upstream side and a lower pond located on the downstream side of the upper pond are broken in a chain reaction. It is a device for. In this specification, the term "reservoir" is used to include dams, farm ponds and other agricultural reservoirs, regulating reservoirs, rivers, landslide dams, etc. In addition, the collapse of Ueike is used to include the inflow of earth and sand from the collapse of the hillside.

First, the process in which the chain break occurs will be described with reference to FIGS. 1A to 1G. As shown in FIG. 1A, consider the case where the upper pond RS1 exists above the inclined surface and the lower pond RS2 exists below the upper pond RS1. Both the upper pond RS1 and the lower pond RS2 are held so that water does not overflow on the wall surface on the downstream side. Conversely, when the water level on the lake surface exceeds the height of the wall surface, water overflows, resulting in a so-called collapse state. In order for the upper pond RS1 and the lower pond RS2 to break in a chain, it is necessary that the upper pond RS1 first breaks and then the lower pond RS2 breaks. In the following example, the chain breakage of the upper pond RS1 and the lower pond RS2 will be described for explanation, but the present invention is not limited to the reservoir, but the water accumulated on the upper side such as rivers, waterways, landslide dams, and landslides on the hillside. It can also be applied when a liquid substance such as the above flows into a reservoir or the like accumulated on the lower side.

First, considering the collapse of the upper pond RS1, as shown in FIG. 1B, the stored water flows out from the upper pond RS1 and flows out to the downstream side. Here, a model or algorithm is adopted in which the amount of water flows downstream according to the hydrograph calculated using the Costa formula. The Costa formula is a regression formula that calculates the peak flow rate based on the dam height and water storage capacity, which are the dam factors, based on statistical data (see Non-Patent Document 2). However, the present invention does not limit the flow rate calculation method to the Costa method, and other methods such as the Florich method, the cost-effectiveness calculation method for the land improvement project, and the arbitrary hydrograph can also be used.

Next, let us consider the collapse of Shimoike RS2. As shown in FIG. 1C, due to the collapse of the upper pond RS1, the water stored in the upper pond RS1 flows into the lower pond RS2. Here, the case where the lower pond RS2 is not full as shown in FIG. 1D and the case where the lower pond RS2 is full as shown in FIG. 1F are considered separately.

When the lower pond RS2 is not full, the water flowing in from the upper pond RS1 is stored in the lower pond RS2 as shown in FIG. 1D, and the water level of the lower pond RS2 rises with the passage of time. Then, when the water level of the lower pond RS2 exceeds the "discharge portion" formed on the wall surface of the lower pond RS2, the water level flows down from the discharge portion to the downstream side of the lower pond RS2 as shown in FIG. 1E. This outflow amount is smaller than that in the case of collapse, and the calculation is calculated from the HQ formula (details will be described later).

On the other hand, when the lower pond RS2 is full as shown in FIG. 1F, the lower pond RS2 collapses and a large amount of water flows out to the downstream side of the lower pond RS2 as shown in FIG. 1G. As the outflow amount in this case, a Costa type or the like is adopted.
(Multiple Reservoir Flood Analysis Device 100)

FIG. 2 shows a plurality of reservoir flood analysis devices according to the first embodiment of the present invention. The plurality of reservoir inundation analysis device 100 shown in this figure includes an input unit 10, an operation unit 20, a calculation unit 30, a display unit 40, and a data storage unit 50. The plurality of reservoir flood analysis device 100 can be configured by installing a plurality of reservoir flood analysis programs on a general-purpose or dedicated computer in addition to being configured by dedicated hardware.
(Input unit 10)

The input unit 10 is an input interface for receiving data input from the outside, and functions as a data acquisition unit for acquiring necessary information by accessing an external database, for example, by communicating with an external device or the like. .. The data acquisition unit has a communication function for connecting to a specific network via a general-purpose network line such as the Internet or a dedicated line. The input unit 10 includes a pond information input unit 11 and a terrain information input unit 12.

The pond information input unit 11 is a member for acquiring information on the upper pond and information on the lower pond. The pond information input unit 11 preferably inputs a pond database. This makes it possible to perform inundation analysis without conducting a field survey of ponds in various places.

The topographical information input unit 12 is a member for acquiring topographical data of the area to be inundated analysis.
(Operation unit 20)

The operation unit 20 is a member for performing various operations and settings for the plurality of reservoir inundation analysis devices, and input devices such as a mouse, keyboard, and console can be used. The operation unit 20 realizes the functions of the levee position designation unit 21, the Shimoike lake surface setting unit 22, the layer association unit 23, and the rainfall amount setting unit 24.
(Levee breach position designation section 21)

The levee position designation unit 21 is a member for designating the levee position where water flows out when the levee is breached at one or more levee ponds. As a result, the user can manually specify the levee position via the levee position designation unit 21, or the plurality of reservoir flood analysis devices can automatically specify the levee position.

The levee position designation unit 21 can designate the levee position of one or more lower ponds as the position of the discharge portion of the lower pond. This makes it possible to automatically specify the bank breakage position. Alternatively, the levee position may be manually adjusted while the levee position of the lower pond is specified as the initial value at the position of the discharge portion. In this case, after automatically designating the position of the levee breach to the position of the discharge part, it is possible for the user to adjust it as needed, and it is possible to make more flexible settings according to the state of the lower pond. Become.
(Lake Shimoike surface setting section 22)

The Shimoike Lake surface setting unit 22 is a member for designating an area corresponding to the Shimoike lake surface.
(Layer association unit 23)

The layer association unit 23 has information on the height difference of the ground surface including the upper pond, and information on the ground surface layer, which is a two-dimensional indefinite flow layer that calculates the indefinite flow flowing out from the upper pond, and the full area of the lower pond. It is a member for associating with the Shimoike layer, which is a layer of the lake surface having. The layer association unit 23 causes the amount of water flowing into the area corresponding to the Shimoike lake surface defined by the Shimoike lake surface setting unit 22 in the ground surface layer to flow into the area corresponding to the Shimoike lake surface in the Shimoike layer. It is given as the amount of water, and in the lower pond layer, the amount of water flowing out from the lower pond is calculated based on information such as the amount of water stored in the lower pond, and the calculated amount of runoff from the lower pond is calculated in advance by the breach position designation part of the ground surface layer. It can be configured to give as the amount of water flowing out from the breach position of the lower pond specified in 21.
(Rainfall setting unit 24)

The rainfall amount setting unit 24 is a member for adding a rainfall amount to the ground surface layer. The rainfall setting unit 24 makes it possible to calculate the flow caused by rainfall on the ground surface layer of the two-dimensional indefinite flow analysis. In addition, this amount of rainfall can be changed over time. Therefore, not only the amount of water caused by the breach of the upper pond but also the amount of water caused by rainfall flows into the lower pond. By comparing the results of the analysis considering precipitation and the analysis not considering precipitation, it is possible to examine the effect of precipitation on the levee of the reservoir. The rainfall data is acquired by, for example, the input unit 10 via a communication network. This makes it easy to update the latest information one by one.

For example, detailed ground elevation data of 5m mesh (for example, digital elevation model of basic map information by the Geographical Survey Institute of the Ministry of Land, Infrastructure, Transport and Tourism) and 2m mesh (for example, 2m mesh elevation data by the Japan Map Center) have been published and sold. Therefore, such ground elevation data may reflect the drainage channel as undulations on the ground surface.
(Display unit 40)

The display unit 40 is a member for displaying a map showing an upper pond or a lower pond, displaying a hydrograph, or confirming necessary settings and the like. As the display unit 40, for example, an LCD, an organic EL display, a CRT, or the like can be used. Further, by using a touch panel for the display unit, the operation unit and the display unit can be integrally configured.

The display unit 40 is provided with a hydrograph display area for displaying a hydrograph showing a time change of the outflow amount from the time of the breakage of the upper pond. A hydrograph is a diagram showing the relationship between time and flood water level or flood flow rate.
(Calculation unit 30)

When the water storage amount of the lower pond calculated by the lower pond water storage amount calculation unit reaches the condition that the pre-given lower pond collapses, the calculation unit 30 changes the lower pond outflow amount to the flow rate after the lower pond collapses. This makes it possible to analyze the inundation after the collapse of Shimoike.

The calculation unit 30 includes an upper pond outflow amount calculation unit 31, a lower pond inflow amount calculation unit 32, a lower pond calculation unit 33, a tide level calculation unit 37, and a water level conversion unit 38.

The upper pond outflow calculation unit 31 is a member that calculates the outflow amount of water flowing out from the upper pond based on the upper pond information input from the pond information input unit 11.

The lower pond inflow calculation unit 32 calculates the amount of water flowing into the lower pond based on the topographical data acquired by the topographical information input unit 12 among the total outflow amount calculated by the upper pond outflow calculation unit 31. It is a member of.
(Shimoike calculation unit 33)

The lower pond calculation unit 33 is based on the lower pond inflow amount calculated by the lower pond inflow calculation unit 32 and the lower pond information input from the pond information input unit 11, and the water storage amount of this lower pond and the lower pond flowing downstream from this lower pond. It is a member for calculating the outflow amount. The lower pond calculation unit 33 is configured to switch the algorithm for calculating the flow rate between the time when the water depth of the lower pond reaches the depth of the discharge part and the time between the initial flooding and the total head of the overflow.

The lower pond calculation unit 33 realizes the functions of the lower pond water storage amount calculation unit 34 and the lower pond outflow amount calculation unit 36. The lower pond water storage amount calculation unit 34 is a member for calculating the water storage amount of the lower pond based on the lower pond information input from the pond information input unit 11 from the lower pond inflow amount calculated by the lower pond inflow amount calculation unit 32. is there. The lower pond outflow calculation unit 36 is a member for calculating the amount of lower pond runoff that flows downstream from this lower pond.
(Shimoike water level calculation unit 35)

Further, the lower pond water storage amount calculation unit 34 can also realize the function of the lower pond water level calculation unit 35 that calculates the water level of the lower pond. For example, the algorithm switching condition is the timing when the water level of the lower pond reaches the depth of the discharge part. Information on the depth of the discharge portion of the lower pond is acquired in advance by the pond information input unit 11. As a result, the algorithm for calculating the outflow amount of the lower pond can be switched between the time when the water level of the lower pond reaches the initial water level and the total head of the overflow (there is no breach during this period) and the time when the water level reaches the discharge portion depth.
(Tide level calculation unit 37)

The tide level calculation unit 37 is a member for calculating a tide level that fluctuates with time. The tide level calculation unit 37 can change the water level under the condition of the downstream end of the ground surface layer over time according to the tide level. In addition, at the place where the flooded water from the reservoir flows down to the sea surface, the inundation situation by the reservoir at high tide or low tide can be simulated by linking the time change of the downstream end water level with the tide level. Furthermore, by comparing the analysis results at high tide and low tide, it is possible to examine the effect of tide on the inundation situation.
(Water level conversion unit 38)

The water level conversion unit 38 is a member for converting the flow rate (flowing into the lower pond) of the upper pond into the water level of the lower pond.

It is assumed that the upper pond will collapse at the analysis start time when the analysis by the multiple reservoir inundation analyzer is started. The amount of water according to the hydrograph calculated using the Costa formula flows out to the mesh set as the upper pond outflow point.
(Analysis model)

Hereinafter, the analysis model used in this embodiment will be described.
(Flow of flood water on the ground surface)
<Basic formula>

［ｘ方向運動方程式］
［数２］

［ｙ方向運動方程式］
［数３］

As the basic equation of the inundation flow on the ground surface, the following two-dimensional / unsteady shallow water flow continuity equation and equation of motion are used.
[Continuous]
[Number 1]

[X-direction equation of motion]
[Number 2]

[Y-direction equation of motion]
[Number 3]

［数５］

In the above equation, t is time; x, y are horizontal two-dimensional coordinates; h is water depth; u, v is the flow velocity component in the x, y directions; M, N is the flow flux (unit width flow rate) in the x, y directions. , M = uh and N = vh; H is the water level; r (t) is the supply amount by rainfall; q _CHAN is the amount of water that overflows from the drainage channel to the ground surface, flows out, or flows into the drainage channel from above the ground surface. g is the acceleration of gravity; ρ is the density of water; τ _{b, x} , τ _{b, y} are the surface frictional resistance stresses in the x and y directions, respectively. Note that τ _{b, x} , τ _{b, y} are expressed by the following equations.
[Number 4]

[Number 5]

In the above equation, n is a synthetic equivalent roughness coefficient.
<Discretization of basic equations>

In the numerical calculation of the inundation flow, the equations 1, 2 and 3 are spatially differentiated with respect to the staggered / structured grid, and temporally analyzed numerically by the leap-frog method. FIG. 3 shows the staggered / structured grid and the definition points of unknown variables. In this figure, i and j are division numbers in the axial direction, respectively.
<Calculation method for special cases>

Here, the calculation method for special cases will be examined.
(Overflow of embankment, etc.)

［数７］

First, as shown in FIG. 4, a case of overflowing unevenness such as embankment will be examined. When a band-shaped object such as an embankment or a road exists in this way, the equation of motion cannot be applied as it is. If the water levels on both sides of the strip-shaped object are lower than the height of the crown, the flow flux is set to zero. If this is not the case, the overflow flow flux is calculated by the overflow formula between Honma such as Equations 6 and 7.
[Number 6]

[Number 7]

In the above equation, h ₁ and h ₂ are the water levels from the top of the strip-shaped object, respectively, where the higher one is h ₁ and the lower one is h ₂ . Further, μ is a flow coefficient, and μ = 0.35 in Equation 6 and μ = 0.91 in Equation 7.
(When a dominant cross section appears between meshes)

ただし、
［数９］

［数１０］

ただし、
［数１１］

ｈ_cxは、地表面流におけるｘ方向の限界水深、ｈ_cyは、地表面流におけるｙ方向の限界水深、Ｅはエネルギー水頭である。
（２）排水路内の水の流れ Next, the case where the dominant cross section appears between the meshes will be examined. As shown in the cross-sectional view of FIG. 5, when the elevation difference is large between adjacent meshes and the water surface becomes discontinuous, or when the water level rises sharply, a dominant cross section appears. In this case, the equation of motion is not applied to the calculation of the flow flux, but the calculation is performed as a step-down flow. Here, the flow flux is given as in the equations 8 and 9.
[Number 8]

However,
[Number 9]

[Number 10]

However,
[Number 11]

h _cx is the limit water depth in the x direction in the surface flow, h _cy is the limit water depth in the y direction in the surface flow, and E is the energy head.
(2) Water flow in the drainage channel

Next, the flow of water in the drainage channel will be examined. In the present embodiment, as shown in FIG. 6, the definition points of the traveling direction and the flow rate of the drainage channel are defined. In this way, the drainage channel is considered to be located only in the direction of the coordinate axes. In addition, it shall pass through the center of the set mesh (definition point of water depth).

［方向運動方程式］
［数１３］

［方向運動方程式］
［数１４］

The following continuity equation and equation of motion are used as the basic equations for the flow of the drainage channel. The equation of motion is the two-dimensional shallow water flow with the advection term omitted.
[Continuous]
[Number 12]

[Directional equation of motion]
[Number 13]

[Directional equation of motion]
[Number 14]

［数１６］

In the above equation, h is the water depth, q is the unit width flow rate in the drainage channel, and is a positive value when the flow direction matches the direction of the coordinate axes, and a negative value when the flow direction is opposite. q _GROUND is the amount of water that overflows from the drainage channel onto the ground surface, flows out, or flows into the drainage channel from above the ground surface. H indicates the water level, and τ indicates the frictional resistance stress. Note that x and y indicated by subscripts indicate that they are equations for drainage channels running in the x and y directions, respectively. The frictional resistance term is expressed by the following equation.
[Number 15]

[Number 16]

In the above equation, R is the diameter depth and n is the Manning roughness coefficient. Further, the subscripts x and y indicate that the equations are for drainage channels running in the x and y directions, respectively.
(3) Reservoir setting 1) Upper pond

［数１８］

［数１９］

As described above, it is assumed that the upper pond collapses at the analysis start time when the analysis by the multiple reservoir inundation analyzer is started. The amount of water according to the hydrograph calculated using the Costa formula flows out to the mesh set as the upper pond outflow point. Here, the Costa equation is shown in Equation 17, and the time change of the outflow amount is shown in Equation 18. This number 18 is set so that the total outflow amount becomes the water storage amount, that is, the number 19 is satisfied.
[Number 17]

[Number 18]

[Number 19]

In the above equation, q _u (t) is the upper reservoir outflow at time ^{t [m 3 / s];} V u is the upper reservoir storage volume ^{[× 10 6 m 3];} H u is the upper reservoir dam height [m]; t is the time [sec].
(2) Shimoike (inflow to Shimoike)

First, set the surface of Lake Shimoike. The mesh set on the surface of Lake Shimoike is always in a state of no water depth. Therefore, the amount of water flows from the adjacent mesh to the mesh set as the surface of Lake Shimoike. This is the inflow to the lower pond. The amount of water flowing into the lower pond shifts from the ground surface model to the lower pond model (described later) as shown in FIG. Then, the amount of water corresponding to the numbers 20 and 23, which will be described later, shifts from the lower pond model to the ground surface model and flows down the ground surface.
(Outflow from the discharge part of Shimoike)

［数２１］

The concept of the Shimoike model is shown in FIG. Here, the reservoir is modeled as a rectangular parallelepiped. In addition, a discharge section for discharging a part of the stored water is provided in a part of the downstream side of the reservoir. The discharge part is a flood discharge part such as a reservoir or an overflow part such as a river embankment. For example, a part of a concrete reservoir is formed in a notch shape, and when the water is almost full, the discharge part is passed through. It is configured so that the water in the part can flow down stably. As the shape of the discharge portion, polygonal or rectangular cuts such as a triangular weir or a square weir can be used. In the example of FIG. 8, a rectangular notch is adopted. Further, in the present specification, the cut height of the discharge portion is referred to as the depth of the discharge portion. When the water level of the reservoir exceeds the depth of the discharge part, it can be determined that the reservoir overflows. When the total head of the overflow is smaller than the depth of the discharge part, it is assumed that the head flows downstream from the discharge part, and the head is discharged downstream from the HQ equation of several tens. Further, the initial water storage amount of the reservoir is set to the number 21, and the water level is set to the lower end of the discharge portion.
[Number 20]

[Number 21]

In the above equation, Q is the flow rate [m ³ / s], C is the flow coefficient, B is the channel width [m], H _max is the bank height [m], h _k is the total overflow head [m], and V _max is the total. The amount of water stored [m ³ ] and A indicate the full area [m ² ], respectively.
(Collapse of Shimoike)

［数２３］

［数２４］

［数２５］

If the total head of the overflow exceeds the depth of the discharge part, it is assumed that the reservoir will collapse and it will flow downstream from the Costa type. Here, the Costa equation is shown in Equation 23, and the time change of the outflow amount is shown in Equation 24, respectively. Here, the number 23 is set so that the total outflow of the upper pond becomes the amount of water stored, that is, the following number 24 is satisfied. In addition, since the inflow to the lower pond is expected even after the collapse of the lower pond, the inflow amount to the lower pond is made to flow out from the lower pond outflow point in addition to the Costa type when the outflow amount changes with time (Equation 23).
[Number 22]

[Number 23]

[Number 24]

[Number 25]

In the above equation, q _l (t) is the outflow amount of the lower pond at time t [m ³ / s], V _l is the amount of water stored in the lower pond [× 10 ⁶ m ³ ], H _l is the height of the lower pond bank (m), and t is the lower pond. The time [sec] from the time of the collapse, t _l indicates the time of the collapse of the _lower pond [sec], and q _{l_in} indicates the amount of water [m ³ / s] that flowed into the _lower pond after the collapse of the _lower pond.

Since the multiple reservoir flood analysis device and the multiple reservoir flood analysis method of the present invention can perform flood analysis of a plurality of reservoirs, the flood analysis can be performed in real time during actual rainfall, or the flood pattern can be calculated and estimated in advance. It can also be used for disaster prevention such as analysis of past flooding mechanisms, prediction of future inundation areas, damage prediction and evacuation route formulation.

100 ... Multiple reservoir inundation analyzer 10 ... Input unit 11 ... Pond information input unit 12 ... Topographic information input unit 20 ... Operation unit 21 ... Bank breakage position designation unit 22 ... Shimoike lake surface setting unit 23 ... Layer association unit 24 ... Rainfall setting Unit 30 ... Calculation unit 31 ... Upper pond outflow calculation unit 32 ... Shimoike inflow calculation unit 33 ... Shimoike calculation unit 34 ... Shimoike water storage amount calculation unit 35 ... Shimoike water level calculation unit 36 ... Shimoike outflow calculation unit 37 ... Tide level calculation Unit 38 ... Water level conversion unit 40 ... Display unit 50 ... Data storage unit RS1 ... Upper pond RS2 ... Shimoike

Claims (12)

It is a multiple reservoir inundation analysis device for performing inundation analysis in which a plurality of reservoirs including an upper pond located on the upstream side and a lower reservoir located on the downstream side of the upper pond collapse in a chain reaction.
Pond information input section for acquiring information on the upper pond and information on the lower pond,
A topographical information input unit for acquiring topographical data of the area subject to flood analysis,
Based on the upper pond information input from the pond information input unit, the upper pond outflow amount calculation unit that calculates the outflow amount of water flowing out from the upper pond, and the upper pond outflow amount calculation unit.
Of the outflow amount calculated by the upper pond outflow calculation unit, the lower pond inflow calculation unit for calculating the amount of water flowing into the lower pond based on the topographical data acquired by the topographic information input unit,
A lower pond water storage amount calculation unit that calculates the water storage amount of the lower pond based on the lower pond information input from the pond information input unit from the lower pond inflow amount calculated by the lower pond inflow amount calculation unit.
A lower pond outflow calculation unit that calculates the amount of lower pond outflow from the lower pond,
Is equipped with
The Shimoike runoff calculation unit has a calculation algorithm before the Shimoike collapse and a calculation algorithm after the Shimoike collapse as an algorithm for calculating the Shimoike runoff amount, and the Shimoike water storage amount calculated by the Shimoike water storage amount calculation unit. However, when the algorithm switching condition given in advance is reached, a multiple reservoir inundation analyzer that calculates the amount of runoff of the lower pond by changing to the calculation algorithm after the collapse of the lower pond. The plurality of reservoir inundation analysis apparatus according to claim 1.
A plurality of reservoir inundation analysis devices including a lower pond water level calculation unit in which the lower pond water storage amount calculation unit calculates the water level of the lower pond. The plurality of reservoir inundation analysis apparatus according to claim 2.
The pond information input unit is configured to be able to acquire information on the depth of the discharge part of the lower pond.
A multi-reservoir flood analysis device in which the algorithm switching condition is the timing when the water level of the lower pond reaches the depth of the discharge section acquired by the pond information input section. The plurality of reservoir inundation analysis device according to claim 3, further
A multi-reservoir inundation analysis device equipped with a display unit for displaying a hydrograph showing the time change of the outflow amount from the time of the breach of the upper pond. The plurality of reservoir inundation analysis apparatus according to claim 4.
The Ueike outflow calculation unit
Based on the upper pond information input from the pond information input unit, it is assumed that the upper pond will collapse at the analysis start time when the analysis by the multiple reservoir inundation analyzer starts.
A multi-reservoir inundation analysis device that uses the algorithm for calculating the upper pond runoff as a model for the outflow of water specified by the following formula.

(In the above equation, q _u (t) is the upper pond runoff at time t [m ³ / s]; V _u is the upper pond reservoir [× 10 ⁶ m ³ ]; _Hu is the upper pond bank height [m]. ; T is the time [sec].) The plurality of reservoir inundation analysis apparatus according to claim 4 or 5.
As an algorithm for calculating the outflow amount of the lower pond, the lower pond runoff amount calculation unit assumes that when the total overflow head is lower than the depth of the discharge part, it flows downstream from the discharge part of the lower pond and is discharged downstream. Flow rate

Calculate with
The initial reservoir capacity of the reservoir is assumed to be at the bottom of the discharge section.

Multiple reservoir inundation analysis device calculated by.
(Q is the flow rate [m ³ / s], C is the flow coefficient, B is the channel width [m], h _k is the total overflow head [m], and V _max is the total water storage amount [m ³ ]) The plurality of reservoir inundation analysis apparatus according to claim 6.
The Shimoike Reservoir Calculation Unit assumes that the reservoir will collapse when the total overflow head exceeds the depth of the discharge section, and determines the amount of water stored in the Shimoike.

Calculate as
In addition, the multiple reservoir inundation analysis device is switched so that the lower pond runoff calculation unit calculates the time change of the runoff from the lower pond runoff point to the downstream by the following equation as an algorithm for calculating the lower pond runoff after the collapse.

( A is the full area [m ² ], q _l (t) is the outflow amount of the lower pond at time t [m ³ / s], V _l is the amount of water stored in the lower pond [× 10 ⁶ m ³ ], and H _l is the height of the lower pond bank ( m), t is the time from the time when the _lower pond broke [sec], t _l is the time when the _lower pond broke [sec], q _{l_in} is the amount of water flowing into the _lower pond after the broke of the _lower pond [m ³ / s]) The plurality of reservoir inundation analysis apparatus according to any one of claims 1 to 7, further comprising.
A multi-reservoir inundation analysis device equipped with a rainfall setting unit for adding rainfall to the ground surface layer that has information on the height difference of the ground surface and calculates the indefinite flow flowing out from the upper pond . The plurality of reservoir inundation analysis apparatus according to any one of claims 1 to 8, further comprising.
A multi-reservoir flood analysis device equipped with a tide level calculation unit for calculating tide levels that fluctuate with time. The plurality of reservoir inundation analysis apparatus according to any one of claims 1 to 9, further comprising.
A multi-reservoir inundation analysis device equipped with a water level conversion unit that converts the flow rate that flows into the lower pond calculated by the inundation analysis of the upper pond into the water level of the lower pond. The plurality of reservoir inundation analysis apparatus according to any one of claims 1 to 10.
A plurality of reservoir inundation analysis devices configured such that the pond information input unit inputs a reservoir database. This is a multiple reservoir flood analysis method for performing a flood analysis in which multiple reservoirs including the upper pond located on the upstream side and the lower reservoir located on the downstream side of the upper pond collapse in a chain reaction.
The process of acquiring information on the upper and lower ponds and topographical data of the area subject to flood analysis,
Based on the acquired upper pond information, the process of calculating the outflow amount of water flowing out from the upper pond, and
Of the calculated outflow amount, the process of calculating the amount of water flowing into the lower pond based on the acquired topographical data, and
A step of calculating the water level of the lower pond and the amount of the lower pond flowing out downstream from the lower pond based on the acquired lower pond information from the calculated lower pond inflow.
In the process of calculating the Shimoike outflow amount, as an algorithm for calculating the Shimoike outflow amount, there is a calculation algorithm before the Shimoike collapse and a calculation algorithm after the Shimoike collapse.
The water level of the lower pond is
From the initial water level to the total head of overflow, the calculation algorithm before the collapse of Shimoike is used.
After reaching the discharge depth obtained as information on the lower pond, a multiple reservoir inundation analysis method that switches the calculation algorithm for the amount of runoff of the lower pond so as to use the calculation algorithm after the collapse of the lower pond.

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