JP2013167115A - Method for arranging sediment in river - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the flow-down of a first sediment with a first grain diameter by means of a second sediment with a second grain diameter larger than the first grain diameter when the current speed of a river is less than a specific current speed, and allow the second sediment to flow down with the first sediment when the current speed of the river is a specific current speed or more.SOLUTION: In a river in which a water inflow from the upstream side is adjusted, a first sediment with a first grain diameter is arranged to adjoin along the river end while a second sediment with a second grain diameter larger than the first grain diameter is arranged along the river end to adjoin the first sediment. In the river, the second sediment is the sediment with such a grain diameter as the second sediment serves as a bank for preventing the flow-down of the first sediment when the current speed of the river is less than a specific current speed and as the second sediment flows down with the first sediment when the current speed of the river is a specific current speed or more.

Description

  The present invention relates to a method for arranging earth and sand in a river.

  For example, Patent Document 1 discloses a dredge device for dredging sediment deposited on the bottom of a dam lake.

JP 2005-42392 A

  The earth and sand dredged by the dredging device of Patent Document 1 is arranged at an appropriate location in the river in order to prevent, for example, a decrease in the riverbed in the river or a receding coastline downstream of the river. The earth and sand arranged in the river will flow down when the flow velocity of the river exceeds a predetermined flow velocity. However, when sediment having a relatively large particle size is disposed in the river, the sediment disposed in the river may not flow downstream even if the flow velocity of the river exceeds a predetermined flow velocity. In that case, there is a possibility that the sediment cannot be returned to the downstream of the river, so that the river bed in the river is not lowered, the coastline downstream of the river is not retreated, or the like. On the other hand, when sediment with a relatively small particle size is placed in the river, the sediment placed in the river may flow downstream, even though the flow velocity of the river is not higher than the predetermined flow velocity. is there. In that case, there is a possibility that the river water may become cloudy even when the flow velocity of the river is not equal to or higher than the predetermined flow velocity.

  The main present invention that solves the above-mentioned problem is to arrange the first sediment with the first particle size so as to be adjacent to the edge of the river in the river in which the inflow amount of water from the upstream is adjusted, A second soil having a second particle size larger than the first particle size is disposed along the edge of the river so as to be adjacent to the first soil, and the flow rate of the river is less than a predetermined flow rate as the second soil. If there is, it becomes a soil embankment that prevents the first earth and sand from flowing down, and when the flow velocity of the river is equal to or higher than the predetermined flow velocity, the earth and sand having a particle size that flows along with the first earth and sand is used. This is a characteristic method for placing sediment in rivers.

  Other features of the present invention will become apparent from the accompanying drawings and the description of this specification.

  According to the present invention, when the flow velocity of the river is less than the predetermined flow velocity, the flow of the first sediment having the first particle size is prevented by the second sediment having the second particle size larger than the first particle size, and the flow velocity of the river The second earth and sand can flow down together with the first earth and sand when is equal to or higher than a predetermined flow velocity.

It is a figure which shows the hydroelectric power plant to which 1st Embodiment of this invention is applied. It is a figure which shows the river to which 1st Embodiment of this invention is applied. It is sectional drawing of the river to which 1st Embodiment of this invention is applied. It is sectional drawing of the river at the time of the water discharge to which 1st Embodiment of this invention is applied. It is a figure which shows an example of the particle size of the earth and sand in 1st Embodiment of this invention. It is sectional drawing of the river in the state where the earth and sand in 1st Embodiment of this invention are flowing down. It is sectional drawing which shows the river to which 2nd Embodiment of this invention is applied. It is sectional drawing which shows the river with which 3rd Embodiment of this invention is applied.

  At least the following matters will become apparent from the description of this specification and the accompanying drawings.

[First embodiment]
=== Hydroelectric power plant ===
Hereinafter, with reference to FIG. 1, the hydroelectric power station to which this embodiment is applied is demonstrated.
The hydroelectric power plant 100 is provided upstream of the river 200 (FIG. 2). The hydroelectric power plant 100 includes a reservoir 101 and a generator 16.

  In the reservoir 101, water 11 for rotating a water wheel (not shown) of the generator 16 is stored. The reservoir 101 is formed by damming river water flowing from the upstream side with a dam 10 (weir). Sediment 12 flowing down from the upstream of the river where the dam 10 is provided accumulates on the bottom 13 of the reservoir 101. The dam 10 and earth and sand 12 will be described later.

  The generator 16 is a device that generates electricity by rotating the water wheel in the generator 16 by the kinetic energy from which the water 11 in the reservoir 101 falls. The generator 16 is provided at a position where the water 11 in the reservoir 101 falls toward the generator 16. A pipe 15 for supplying the water 11 in the reservoir 101 to the generator 16 is connected between the reservoir 101 and the generator 16. One end of the pipe 15 communicates with the reservoir 101 via the dam 10. The water 11 supplied from the reservoir 101 to the generator 16 is discharged to the river 200 provided at a position relatively lower than the generator 16 through the pipe 17.

=== River ===
Hereinafter, the river in this embodiment is demonstrated with reference to FIG. 2 thru | or FIG. FIG. 2 is a diagram illustrating a river to which the present embodiment is applied. FIG. 3 is a cross-sectional view of a river to which the present embodiment is applied, as viewed from the A1-A2 cross section of FIG. 2 toward the upstream. FIG. 4 is a cross-sectional view of a river at the time of flooding to which the present embodiment is applied, as viewed from the A1-A2 cross section in FIG. 2 toward the upstream.

  The river 200 has a downward slope from upstream to downstream. It is assumed that a plurality of rivers (not shown) including the river where the dam 10 is provided are joined upstream of the river 200. In the river 200, for example, groundwater and rainfall that springs upstream of the river 200 flow. Further, the water 11 in the reservoir 101 described above flows into the river 200. In the river 200, earth and sand 23 (first earth and sand) and earth and sand 24 (second earth and sand) are arranged. The particle size of the earth and sand 23 corresponds to the first particle size. The particle size of the earth and sand 24 corresponds to the second particle size. The earth and sand 23 and 24 will be described later.

  When the amount of water flowing through the river 200 increases for some reason and reaches a certain amount (hereinafter referred to as “during flooding”), the flow velocity of the river 200 becomes the flow velocity v1. When the water 11 in the reservoir 101 is not discharged into the river 200 (hereinafter referred to as “normal time”), the flow velocity of the river 200 is a flow velocity v2 smaller than the flow velocity v1. Note that the amount of water in the river 200 at the time of flooding increases compared to the amount of water in the river 200 at the normal time. Therefore, the water level H4 from the bottom 26 of the river 200 at the time of flooding is higher than the water level H3 from the bottom 26 of the river 200 at the normal time. For some reason, for example, when the water 11 in the reservoir 101 is discharged into the river 200 via the pipes 15 and 17 or when there is a large amount of inflow water into the reservoir 101, it is installed at the top of the dam 10. This is the case when a gate (not shown) is opened and discharged. Further, for example, the amount of water flowing in from the upstream of the river 200 is adjusted by the weather and the discharge of water from the reservoir 101 to the upstream of the river 200.

=== Position ===
Hereinafter, with reference to FIG. 1 thru | or FIG. 3, the placement soil in this embodiment is demonstrated.
The laying soil is, for example, arranging the earth and sand 12 deposited on the bottom 13 of the reservoir 101 upstream of the river 200 in the river 200. Placement is performed to remove the sediment 12 in the reservoir 101 from the reservoir 101 and prevent the reservoir capacity of the reservoir 101 from being reduced by the sediment 12 deposited on the bottom 13. Placement is performed in order to prevent the river bed in the river 200 from being lowered and the coastline downstream from the river 200 from being lowered due to the sediment 12 not flowing from the upstream of the river 200 to the downstream of the river 200. That is, the soil is placed in order to return the sediment 12 accumulated in the reservoir 101 to the downstream of the river 200.

=== Sediment particle size ===
Hereinafter, the particle size of earth and sand in the present embodiment will be described with reference to FIGS. 1 and 3. The earth and sand 23 and 24 are, for example, earth and sand 12 accumulated at a predetermined position on the bottom 13 of the reservoir 101. Based on the relationship between the particle size of the earth and sand and the flow velocity of the river from which the earth and sand flow, the earth and sand 12 dredged from the reservoir 101 is referred to as earth and sand 23 and 24. The dredging of the earth and sand 12 will be described later. The relationship between the particle size of the earth and sand and the flow velocity of the river from which the earth and sand flows will be described.

<Manning formula>
In general, the relationship between water flow and flow velocity / flow rate is expressed by Manning's formula (Equation 1). In Manning's formula, the flow velocity v of the river is determined based on the roughness coefficient n, the longitudinal gradient I of the river, and the diameter depth R. The roughness coefficient n is a coefficient indicating the roughness of the bottom or wall of the water channel. The diameter depth R is determined based on the cross-sectional area (flow product) A of the river and the wet side S of the river (Formula 2). Further, it is known that the flow velocity v of the river is proportional to the flow rate Q of the river (Formula 3). It is assumed that the roughness coefficient n, river longitudinal gradient I, river cross-sectional area A, and river wetness S are set in advance for each river.

式１より河川の縦断勾配Ｉを求めて、式４に当該河川の縦断勾配Ｉを代入することによって、式５が導出される。

粗度係数ｎは、予め設定されている値であり、径深Ｒは、予め設定されている河川の断面積Ａ、河川の潤辺Ｓから算出（式２）される値である。よって、摩擦速度ｕ＊は、河川の流速ｖ（流量Ｑ）に応じて定まることとなる。 <Friction speed>
The friction speed u * is obtained from the gravitational acceleration g, the diameter depth R, and the longitudinal gradient I of the river (Formula 4).

By obtaining the longitudinal gradient I of the river from Equation 1 and substituting the longitudinal gradient I of the river into Equation 4, Equation 5 is derived.

The roughness coefficient n is a preset value, and the diameter depth R is a value calculated from the preset river cross-sectional area A and river wetness S (formula 2). Therefore, the friction speed u * is determined according to the flow velocity v (flow rate Q) of the river.

<Limit friction speed>
In general, the critical frictional speed u * cm is based on the particle size dm of the earth and sand according to the following rock constant formula (Formula 6 to Formula 10) p219).

  The limit friction speed u * cm indicates the friction speed at which the sediment in the river begins to flow down by the friction speed u * based on the flow velocity of the river. For example, when the friction speed u * is equal to or higher than the limit friction speed u * cm, the sediment in the river flows down. On the other hand, for example, when the friction speed u * is less than the limit friction speed u * cm, the sediment in the river does not flow down.

  For example, earth and sand having a particle size dth (hereinafter also referred to as “particle size dth flowing down at a predetermined flow velocity vth”) such that the frictional velocity u * based on the predetermined flow velocity vth becomes the limit frictional velocity u * cm is entered into the river 200. The case where it arrange | positions is demonstrated. The particle diameter dth is calculated from Equation 5, Equation 6 to Equation 10. For example, the predetermined flow velocity vth is smaller than the flow velocity v1 at the time of flooding and larger than the flow velocity v2 at the normal time. When the flow velocity of the river 200 is equal to or higher than the predetermined flow velocity vth, the friction speed u * is equal to or higher than the limit friction speed u * cm of the earth and sand having the particle diameter dth. In that case, the earth and sand having a particle diameter dth disposed in the river 200 flows down. When the flow rate of the river 200 is less than the predetermined flow rate vth, the friction speed u * is less than the limit friction speed u * cm of earth and sand having a particle diameter dth. In that case, the earth and sand having the particle diameter dth arranged in the river 200 will not flow down.

=== Sediment pit, arrangement of earth and sand ===
Hereinafter, the particle size of earth and sand in the present embodiment will be described with reference to FIGS. 1 to 3 and FIG. 5. FIG. 5 is a diagram showing an example of the particle size of earth and sand in the present embodiment. In addition, “particle size d1 flowing down at the time of water discharge” shown in FIG. 5 indicates a particle size such that the friction speed u * based on the flow velocity v1 at the time of water discharge becomes the limit friction speed u * cm. To do. The “particle size d2 flowing down at normal time” indicates a particle size such that the frictional velocity u * based on the normal flow velocity v2 becomes the limit frictional velocity u * cm. The particle diameters d1 and d2 are calculated based on Expression 5, Expression 6 to Expression 10.

  The earth and sand 12 flows down into the reservoir 101 from the upstream and accumulates in the reservoir 101. Since the sediment 12 accumulates from the upstream side in the reservoir 101, the amount of sediment 12 in the upstream in the reservoir 101 increases, and the sediment 12 decreases as it moves downstream of the reservoir 101. Become. Therefore, the water depth in the reservoir 101 becomes deeper as it moves from upstream to downstream. In addition, the particle size of the earth and sand 12 accumulated in the reservoir 101 tends to decrease from the upstream toward the downstream. This is because, for example, sediment with a large particle size is heavy and deposits upstream in the reservoir 101, whereas sediment 12 with a small particle size is light and moves from the upstream to the downstream of the reservoir 101. Therefore, paying attention to the fact that the water depth in the reservoir 101 becomes deeper as it moves from upstream to downstream, and that the particle size of the sediment 12 that accumulates in the reservoir 101 tends to decrease as it goes from upstream to downstream. Thus, the relationship between the water depth of the reservoir 101 and the particle size of the earth and sand 12 accumulated in the reservoir 101 can be obtained, for example, by simulation.

  For example, of the earth and sand 12, the water depth of the reservoir 101 where the earth and sand having the particle diameter dth1 is accumulated, and the water depth of the reservoir 101 where the earth and sand having the particle diameter dth larger than the particle diameter dth1 are accumulated are the water depth. The case where it is calculated | required, for example by simulation etc. that it is H2 and H1 is demonstrated. The earth and sand 12 accumulated at the positions of the water depths H2 and H1 in the reservoir 101 are dredged as earth and sand 23 and 24, respectively. For example, the earth and sand 12 is dredged by a dredger (not shown) having a grab bucket (not shown) for dripping the earth and sand 12. Note that the bottom of the reservoir 101 at the depth H2 upstream of the dam 10 corresponds to the bottom of the first position. In the reservoir 101, the bottom of the water depth H1 that is upstream of the position of the water depth H2 and shallower than the water depth H2 corresponds to the water bottom of the second position. The particle size of the earth and sand 24 is, for example, within the second range (FIG. 5) between the particle size d1 flowing down at the time of flooding and the particle size d2 flowing down at the normal time centering on the particle size dth flowing down at the predetermined flow velocity vth. Will be distributed. The particle size of the earth and sand 23 is, for example, a first range between a particle size d2 flowing down during normal time and a particle size d3 smaller than the particle size dth1 around the particle size dth1 smaller than the particle size d2 (FIG. 5). ). In addition, the particle size d3 shall be smaller than the particle size of the earth and sand 12 accumulated in the deepest position in the reservoir 101 obtained from the above-mentioned simulation, for example. The earth and sand 23 and 24 are arranged in the river 200. The earth and sand 23 is arranged so as to be adjacent to the shore 21 along the shore 21 (edge of the river). The earth and sand 24 is arranged so as to be adjacent to the earth and sand 23 along the shore 21 after the earth and sand 23 is arranged. For example, the upstream side of the position where the earth and sand 23 and 24 are arranged in the river 200 may be dammed, and the earth and sand 24 may be arranged in the river 200 after the earth and sand 24 is arranged in the river 200. The vertical height of the earth and sand 24 from the bottom 26 is such that the vertical direction of the earth and sand 23 from the bottom 26 is such that the earth and sand 24 becomes an earth wall for preventing the earth and sand 23 from flowing down at a normal flow velocity v2. It arrange | positions in the river 200 so that it may become higher than the height of a direction. At that time, the upper surface of the earth and sand 23 arranged in the river 200 is exposed. The earth and sand 23 is sandwiched between the earth and sand 24 and the shore 21. In addition, the earth and sand 23 and 24 shall be arrange | positioned in the river 200 using a heavy machine etc. after being dredged with a dredger, for example.

=== Sediment flow ===
Hereinafter, the flow of earth and sand in the present embodiment will be described with reference to FIGS. FIG. 6 is a cross-sectional view of the river in a state where the earth and sand according to the present embodiment flows down from the A1-A2 cross section of FIG. 2 toward the upstream.

  For example, when the amount of water flowing through the river 200 is small, the flow velocity of the river 200 is a flow velocity v2 less than a predetermined flow velocity vth. Since the particle size of the earth and sand 24 is larger than the particle size d2 flowing down during normal times, the friction speed u * based on the flow velocity v2 is less than the limit friction speed u * cm of the earth and sand 24. The earth and sand 24 arranged in the river 200 will not flow down (FIG. 3). In that case, the earth and sand 24 becomes an earth wall that prevents the earth and sand 23 from flowing down. On the other hand, when the amount of water flowing through the river 200 increases for some reason, the flow velocity of the river 200 becomes a flow velocity v1 equal to or higher than the predetermined flow velocity vth. Since the particle size of the earth and sand 24 is smaller than the particle size d2 flowing down at the time of flooding, the friction speed u * based on the flow velocity v1 is equal to or higher than the limit friction speed u * cm of the earth and sand 24. The earth and sand 24 arranged in the river 200 will flow down (FIG. 4). In that case, the earth and sand 23 having a particle diameter smaller than that of the earth and sand 24 flows down together with the earth and sand 24 (FIG. 6).

  In addition, by adjusting the predetermined flow velocity vth between the flow velocity v1 and the flow velocity v2, the frequency at which the earth and sand 23 and 24 arranged in the river 200 flow down can be adjusted. For example, when the predetermined flow velocity vth is increased close to the flow velocity v1 at the time of flooding (hereinafter referred to as “when the predetermined flow velocity vth is increased”), the frequency at which the sediments 23 and 24 arranged in the river 200 flow down is reduced. be able to. On the other hand, for example, when the predetermined flow velocity vth is reduced to be closer to the normal flow velocity v2 than when the predetermined flow velocity vth is increased, the frequency with which the sediments 23 and 24 disposed in the river 200 flow down is increased. be able to.

  As described above, the earth and sand 23 and 24 are arranged in the river 200. The earth and sand 24 is earth and sand having a larger particle diameter than the earth and sand 23. The earth and sand 23 is arranged along the shore 21 so as to be adjacent to the shore 21, and the earth and sand 24 is arranged along the shore 21 so as to be adjacent to the earth and sand 23. When the flow velocity of the river 200 is the flow velocity v2 less than the predetermined flow velocity vth, the earth and sand 24 does not flow down. In that case, the earth and sand 24 becomes an earth wall that prevents the earth and sand 23 from flowing down. Therefore, for example, it is possible to prevent the earth and sand 23 and 24 from flowing into the river 200 and flowing down at a normal time when the water 11 in the reservoir 101 is not discharged into the river 200. That is, the earth and sand 23 and 24 arranged in the river 200 can prevent the water in the river 200 from becoming cloudy at normal times. Moreover, since the sediment 23 having a particle size that flows out at the normal flow velocity v2 of the river 200 can be disposed in the river 200 together with the sediment 24, there is no need to newly provide a soil disposal site or the like for discarding the sediment 23. Therefore, it is possible to reduce the cost for placing the soil. When the flow velocity of the river 200 is a flow velocity v1 equal to or higher than the predetermined flow velocity vth, the earth and sand 24 flows down. In that case, the earth and sand 24 flows down together with the earth and sand 23. Therefore, for example, when the water 11 in the reservoir 101 is discharged into the river 200, the earth and sand 23, 24 is caused to flow downstream of the river 200, and the river bed in the river 200 is lowered, or the coastline downstream of the river 200. Can be prevented.

  In the river 200, the earth and sand 24 is arranged after the earth and sand 23 is arranged. Therefore, since the earth and sand 23 and 24 can be sequentially arranged in the river 200 from the side close to the shore 21, the earth and sand 23 and 24 can be easily arranged in the river 200.

  Further, the water 11 in the reservoir 101 dammed up by the dam 10 flows into the river 200. The earth and sand 23 and 24 are earth and sand 12 deposited on the bottom 13 in the reservoir 101. The earth and sand 23 is the earth and sand 12 accumulated at the position of the water depth H2. The earth and sand 24 is the earth and sand 12 accumulated at the position of the water depth H1 shallower than the water depth H2. The earth and sand 12 accumulated in the reservoir 101 upstream of the river 200 is arranged in the river 200. Therefore, the earth and sand 12 accumulated in the reservoir 101 that should flow down from the upstream of the river 200 can be returned to the downstream of the river 200. Therefore, for example, a reservoir 101 is provided on the upstream side of the river 200, and sediment is not allowed to flow down from the upstream to the downstream of the river 200. Can be reliably prevented. Further, for example, the earth and sand 23 and 24 can be arranged in the river 200 without using an apparatus for sieving the earth and sand according to the particle size of the earth and sand. Therefore, the earth and sand 23 and 24 can be arrange | positioned in the river 200 quickly and at low cost.

[Second Embodiment]
In 1st Embodiment, although the case where the earth and sand 23 and 24 are arrange | positioned in the river 200 so that the upper surface of the earth and sand 23 was exposed was demonstrated, it is not limited to this. For example, the earth and sand 23 and 24 may be arranged so that the earth and sand 23 is covered with the earth and sand 24. Hereinafter, the arrangement of the earth and sand 23 and 24 in the present embodiment will be described with reference to FIG. FIG. 7 is a cross-sectional view showing a river to which the present embodiment is applied.

  The earth and sand 23 is disposed along the shore 21 so as to be adjacent to the shore 21. The earth and sand 24 is piled up in the river 200 so as to cover the earth and sand 23. Here, when the earth and sand 23 and 24 are arranged in the river 200, the river width of the river 200 becomes narrow. In this case, for example, although the water 11 in the reservoir 101 is not discharged into the river 200, the height of the water surface 25 from the bottom 26 of the river 200 is the vertical height of the top surface of the earth and sand 24 from the bottom 26. May be exceeded. In this case, since the earth and sand 23 is covered with the earth and sand 24, the earth and sand 23 is prevented from flowing into the river 200. For example, it is possible to reliably prevent the earth and sand 23 from flowing into the river 200 and flowing down during normal times when the water 11 in the reservoir 101 is not discharged into the river 200.

[Third embodiment]
Although 1st Embodiment demonstrated the case where the earth and sand 23 and 24 are arrange | positioned along the one bank 21 of the river 200, it is not limited to this. Hereinafter, the arrangement of the earth and sand 23A, 23B, 24A, and 24B in the present embodiment will be described with reference to FIG. FIG. 8 is a cross-sectional view showing a river to which the present embodiment is applied. The earth and sand 23A and 23B are earth and sand having the same particle diameter as the earth and sand 23, and the earth and sand 24A and 24B are earth and sand having the same particle diameter as the earth and sand 24.

The river 200 </ b> A is a river similar to the river 200, and earth and sand are arranged along both the shores 21 and 22.

  The earth and sand 23A is arranged along the shore 21 so as to be adjacent to the shore 21. The earth and sand 24A is disposed along the shore 21 so as to be adjacent to the earth and sand 23A. The earth and sand 23 </ b> B is disposed along the shore 22 so as to be adjacent to the shore 22. The earth and sand 24B is disposed along the shore 22 so as to be adjacent to the earth and sand 23B. Therefore, the water 26 </ b> A in the river 200 </ b> A flows from the upstream to the downstream between the earth and sand 24 </ b> A and 24 </ b> B disposed along the both shores 21 and 22 of the river 200.

  The first and third embodiments are intended to facilitate understanding of the present invention, and are not intended to limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and the present invention includes equivalents thereof.

  In 1st Embodiment, although the earth and sand 12 accumulated in the position of the water depth H2 and H1 in the reservoir 101 was demonstrated in the river 200 as the earth and sand 23 and 24, respectively, it is not limited to this. Absent. For example, the earth and sand 12 accumulated in the reservoir 101 may be sieved and the earth and sand having a particle diameter in the first range may be used as the earth and sand 23, and the earth and sand having a particle diameter in the second range may be used as the earth and sand 24. In that case, as the earth and sand 24, the earth and sand having a particle diameter larger than the particle diameter d2 flowing down at the normal time and smaller than the particle diameter d1 flowing down at the time of water discharge can be reliably arranged in the river 200. As the earth and sand 23, earth and sand smaller than the particle diameter of the earth and sand 24 can be reliably arranged in the river 200. Therefore, when the flow velocity of the river 200 is a flow velocity v2 less than the predetermined flow velocity vth, the sediment 24 can reliably prevent the sediment 23 from flowing down. Accordingly, it is possible to reliably prevent the water in the river 200 from becoming cloudy due to the earth and sand 23 and 24 at normal times. When the flow velocity of the river 200 is the flow velocity v1 that is equal to or higher than the predetermined flow velocity vth, the earth and sand 23 and the earth and sand 24 can be surely flowed down. Therefore, the earth and sand 23 and 24 can be reliably reduced downstream of the river 200.

  In the first embodiment, the particle sizes of the earth and sand 23 and 24 are set based on the flow velocity of the river 200, but are not limited thereto. For example, as shown in Equation 3, the particle velocity of the earth and sand 23 and 24 may be set based on the flow rate of the river 200 such that the river flow velocity v and the river flow rate Q are proportional to each other. .

10 Dam 11, 26A Water 12, 23, 23A, 23B, 24, 24A, 24B Earth and sand 13, 26 Bottom 15, 17 Pipe 16 Generator 21, 22 Shore 25 Water surface 100 Hydroelectric power plant 101 Reservoir 200, 200A River

Claims (4)

In the river where the amount of inflow of water from the upstream is adjusted, the first earth and sand having the first particle diameter are arranged so as to be adjacent along the edge of the river, and the second particle diameter larger than the first particle diameter. The second earth and sand are arranged adjacent to the first earth and sand along the edge of the river,
When the flow velocity of the river is less than a predetermined flow velocity as the second sediment, the first sediment is prevented from flowing down, and when the flow velocity of the river is equal to or higher than the predetermined flow velocity, (1) A method for placing sediment in a river, characterized by using sediment with a particle size that flows down together with sediment. The method according to claim 1, wherein the inflow of water into the river is adjusted by a weir on the upstream side of the river. The first earth and sand is earth and sand dredged from the bottom of the first position upstream of the weir,
The method according to claim 2, wherein the second sediment is dredged from the bottom of the second position upstream of the first position. The second earth and sand is
The method according to any one of claims 1 to 3, wherein the sediment is piled up in the river so as to cover the first sediment.

Images