JP2012021353A - Method for dam recovering nature and flood control of river - Google Patents

Abstract

PROBLEM TO BE SOLVED: To recover a natural bank by accumulating sediment with many stones and rocks on a bank that becomes hardly different in level from the flow of water due to a weir type dam, a concrete revetment, a dike and the like.SOLUTION: A dam is constructed from concrete and the like. Structurally, its height becomes lower at a point closer to the center of a river in the oblique upstream direction of the river from the bank on one side, and sediment with many stones and rocks is accumulated on the bank. Thus, a cross-section of a bottom of the river is returned to a U-shaped structure, and a river condition proper not only for a natural environment but also for flood control measures is recovered.

Description

  This invention relates to a dam that restores nature and flood control in the upstream and middle rivers.

The river collects rainwater and flows it downstream. At the same time, large and small earth and sand produced in the mountains are also flowing down at the same time. The amount of rain falls from time to time and the river water fluctuates irregularly. Because the sediment flowing out of the mountains has different sizes and weights, the speed at which it flows down will also vary.
As a result, relatively large sediments often gather on the banks of the river upstream, and the water flow tends to collect in the middle of the river, which is lower than the banks. Therefore, it is normal for the cross section of the riverbed in the middle and upper part of the river to be U-shaped.

  Many dam-type dams, concrete revetments, and concrete-covered embankments have been installed in the upstream and middle rivers. These play important roles such as preventing sediment flow, protecting the shore, and preventing overflowing water. However, these dam-type dams, revetments and dikes prevent the formation of river U-shaped structures.

When a dam-type dam is constructed, a flat riverbed with little difference in height between the shore and the flow appears upstream. In concrete revetments and concrete-covered embankments, sediments such as relatively large stones and rocks are diffused without being collected on the shore and swept downstream. Eventually, the center of the river is low and the shore is high, the natural aspect of the river changes and the riverbed flattens.
Therefore, these dam-type dams, concrete revetments and concrete embankments change the cross section of the riverbed in the middle and upstream rivers into a concave shape.

The change in the cross section of the river bottom to a concave shape not only worsens the natural environment of the river but also makes it difficult to control the river.
Upstream, the flow of water changed by the presence of stones and rocks on the shore becomes linear. Sediment flow that was blocked by the presence of large stones and rocks will also accelerate. Therefore, there will be more sudden water increases than before.
In the middle stream, the flow of sediment from the upstream increases, the flow of the river becomes shallower, the flow of small sediment such as sand and gravel promoted by the presence of stones and rocks on the shore is stagnant, and the amount of sediment deposited further Will increase. In either case, flood control will change into a difficult situation.

  If large sediments such as stones and rocks can be deposited on the shore, the flow of water and sediment can be restored to its natural state and the river can be restored to its original form. It is to restore the natural environment of the river and at the same time to facilitate the flood control of the river. It is necessary to make it easier for large sediment to accumulate on the shore and to collect the water flow in the center.

The dam-type dams that have been constructed in the past were only interested in damming up sediment, and were not focused on the natural flow of water and sediment.
Therefore, little consideration is given to the problem of the U-shaped shape of the bottom of the river and the importance of large earth and sand such as stones and rocks. The same applies to the construction of dams found in the patent literature. (For example, see Patent Documents 1 and 2.)

Patent No. 4047030 Japanese Patent No. 4275595

  In order to prevent the destruction of the natural environment and to improve the flood control of the river, a U-shaped riverbed cross-sectional structure with a high shore and low water flow is used without unnecessarily flowing stones and rocks downstream. It is necessary to develop a method to create it.

  If you observe natural rivers with stones and rocks that are not artificial revetments, you can see many stones and rocks on those banks. Depending on the location, you can also see where many stones and rocks overlap vertically and horizontally. This is not limited to upstream, and many stones can be seen on the shore as well in the middle stream.

  Many stones and rocks found on the shores of nature are also natural revetments created by combining stones and rocks naturally. These stones and rocks flow from the upstream, and are naturally combined by the power of the water that increases or decreases with increasing or decreasing water.

  By blocking the stones and rocks flowing from the upstream when the water increases, it is possible to reproduce the natural sedimentation of nature where the center of the water is low and the shore is high.

Weirs are made of concrete, steel, wood, etc. The weir is from the shore of one side to the upstream of the river, and the length of the dam is near or in the middle of the river. In addition, the height of the dam will be lowered as it approaches the center of the river.
The length and height are determined by the quality and quantity of sediment to be deposited, and will vary depending on the construction site. If the stones and rocks are small or if you want to reduce the amount of sediment, make the length short and the overall height low. Conversely, if the stones and rocks are large or if you want to increase the amount of sediment, the length is long and the overall height is high.
In addition, if holes and slits are installed in the dam as outlets through which small sediment and water can flow, more large stones and rocks found near the construction site can be deposited on the shore.

  As a result, stones and rocks that flow every time the water increases can be deposited on the shore, and the water flow naturally flows near the center of the river.

This dam can produce a single effect, but depending on the conditions of the construction site, it can be more effective by combining several.
If this dam is constructed alternately from both banks, the flow of water will meander around the center, making it closer to a natural state.
If this dam is constructed from both banks and connected near the center, the structure of a natural river with a low water flow and a high shore can be reproduced while accumulating a large amount of sediment. You can also set up a method that does not connect with the tip close. All of them will correspond according to the situation of the construction site.
If you install multiple dams at short intervals on one side, you can keep the shore high for a long distance and strengthen the revetment.

  Since the method of the present invention can change the setting depending on the installation location, the amount of water and the size and amount of earth and sand are different, and upstream, middle stream, large river, small river, etc. The best effect can be achieved even in places.

  Forming a U-shaped cross section at the bottom of a river by the method of the present invention restores the natural state of the river. By creating a state where stones and rocky sediments are deposited on the shore, the function of stones and rocks can be restored and the water and sediments can flow naturally. Therefore, it also has a beneficial effect on flood control downstream. In addition, the natural environment of the river can be improved and the habitat of organisms can be restored.

  Since the method of the present invention uses the action of stones, rocks, and water in the natural state, it can reproduce the riverbed in the natural state with a little unnatural appearance.

It is a schematic perspective view of the Example at the time of constructing the dam by the method of this invention independently. The example which applied the dam of FIG. 1 is shown, It is a top view of the example when several dams are constructed alternately from both banks. Fig. 2 shows an embodiment in which the dam of Fig. 1 is applied, and is a plan view of the embodiment when the dam is constructed from both banks and connected near the center. Fig. 2 shows an embodiment in which the dam shown in Fig. 1 is applied, and is a plan view of the embodiment when a dam is constructed from both banks and is not connected by approaching the center. The example which applied the dam of FIG. 1 is shown, and is a top view of the example when a plurality of dams are constructed on the shore of one side.

FIG. 1 will be described as an example of the present invention.
A concrete dam (1) will be constructed near the shore. The dam is structured so that it goes diagonally upstream from the shore, is high on the shore, and becomes lower as it goes to the center.
The height of the dam is the height at which the relatively large stones and rocks around it are blocked near the shore. The tip is naturally lowered in anticipation of a drop in the riverbed near the center.
In addition, some slits or holes are installed in the dam so that water and small earth and sand can flow down.
As a result, sediment increases in the upstream of the dam due to increased water. If the water increases and decreases repeatedly, the closer to the shore, the greater the amount of sediment that accumulates, forming a natural river with a high shore and a low center.

FIG. 2 will be described as an example of the present invention.
The dam shown in Fig. 1 is constructed alternately from both banks of the river. As a result, the water stream meanders in the middle of the river, and relatively large stones and rocks accumulate on both sides of the river.

As an embodiment of the present invention, FIG. 3 will be described.
This is a plan view of the embodiment when weirs are constructed from both banks and connected near the center. The dam shown in Fig. 1 is constructed from both banks and connected near the center. As a result, a large amount of sediment can be deposited upstream of the dam. In addition, the water flow gathers near the center, making it a natural river with a high shore and low near the center.

FIG. 4 will be described as an example of the present invention.
This is a plan view of the embodiment when weirs are constructed from both banks and are not connected by approaching near the center. The dam shown in Fig. 1 is constructed from both banks and approached near the center. This allows sediment from the upstream to flow down the dam and deposit on the dam upstream. Therefore, the distribution of earth and sand is evenly close to the upstream and downstream of the dam. Both upstream and downstream, it is possible to make the river in a natural state with a high shore and low near the center.

FIG. 5 will be described as an example of the present invention.
Build several dams shown in Fig. 1 at short intervals on one shore. This allows sediment to accumulate on the shore over a long distance.

1 dam by the method of the present invention 2 discharge port (hole installed in the dam)
3 Discharge port (slit installed in the dam)
4 Direction of water flow 5 Shore or revetment 6 Earth and sand accumulated by the effect of the weir 7 Water surface 8 River bottom

Claims (5)

  In the upstream or middle stream of a river, a river dam is constructed by constructing a dam with a tip extending obliquely upstream from the shore on one side, and the tip having a length near or in the middle of the river. And dam way to restore flood control.   Construct a dam with a tip that extends diagonally upstream from the shore on the side opposite to the shore and the length of the tip is near or midway of the river. Build a dam with the tip end obliquely upstream and the length near the middle of the river or halfway to the middle of the river, on the tip of the dam provided on the shore opposite to the one shore, and on the one shore The method of the dam which restores the natural and flood control of a river according to claim 1, wherein the tip of the provided dam is connected or separated.   The dam method for restoring river nature and flood control according to claim 1, wherein a plurality of dams are continuously installed along one side of the bank.   The method of the dam which restores the natural and flood control of the river in any one of Claims 1-3 characterized by reducing the height of a dam as it advances to a front-end | tip part. The dam is provided with a discharge port for discharging water, soil, sand, gravel and pebbles, and the method of the dam for restoring the natural and flood control of the river according to any one of claims 1 to 4

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