JP4375676B2 - Riverbed scour monitoring method - Google Patents

Description

  The present invention installs a riverbed water level meter on the riverbed and measures the relative water level over time, including the riverbed scouring amount, and installs a water level measuring water level meter at a fixed point to measure the absolute water level. It relates to a method of monitoring river scouring conditions by measuring and synchronizing the water level data and obtaining the difference sequentially. This technology is useful, for example, for monitoring riverbed scouring conditions over time caused by torrents during floods.

  The riverbed is scoured by torrents during floods. For river managers, accurately grasping the actual condition of this riverbed scouring action is extremely important for disaster prevention. By measuring the riverbed position by acoustic sounding before and after the flood, the amount of scouring can be obtained, but the progress of riverbed deformation (how the riverbed has been deformed over time) cannot be determined. Also, not only when scouring during flooding, but depending on the flow conditions, it may be buried with sediment sent from upstream, but only depth measurements before and after flooding indicate the maximum depth of scouring. I can't figure it out.

  In order to solve such problems, much research has been conducted on riverbed scour monitoring technology. For example, Patent Document 1 discloses a method of detecting a scouring situation from a temperature distribution along an optical fiber by burying a water flow sensor in which a heating wire is disposed along the optical fiber and integrated with a heat-resistant insulating coating. It is disclosed. However, since a large flow pressure acts on the torrent during a large-scale flood, there is a possibility that the flow sensor may break or be lost, and there is a limit to the measurement target.

  In Patent Document 2, a plurality of sensors with built-in small radio wave transmitters are piled up and buried in the river bed, and the sensors are removed and flowed out from the top as the river bed is scoured. A method for monitoring the scouring situation in real time by sending and receiving it is described. However, this method must be buried deeply in advance in a state where a large number of sensors are stacked, so that it is difficult to install unless the river bed is depleted so that there is almost no water flow in normal times. In other words, it cannot be applied to large rivers with a depth of several meters even under normal conditions. In addition, since a sensor removed by riverbed scouring cannot communicate unless it floats to the surface of the water, it may be caught in a turbulent vortex during a flood and not flow up to the surface of the water, which may make measurement impossible. Even if the detached sensor immediately rises, there is a problem that the resolution of measurement is low because each sensor has a certain height.

In areas such as downstream of weirs installed in large rivers, there are areas where several meters of deep digging occur over a wide area during floods. In such deep digging areas, it is necessary to monitor the riverbed scouring situation in detail, but in any case, it is difficult to install the equipment with the conventional technology, and it is not possible to reliably obtain the required accuracy information. difficult.
Japanese Patent Laid-Open No. 6-74768 JP 2004-271243 A

  The problem to be solved by the present invention is to make it possible to install a measuring device relatively easily even in a large-scale river with a deep water depth, and to monitor the riverbed scouring status over time with the required accuracy. .

  The present invention provides a riverbed water level meter having a structure in which a hydrometer equipped with a data logger function is built in a protective vessel having a weight function, and is installed on the riverbed to determine the relative water level including the riverbed scouring amount over time. Measure and accumulate data, install a water level meter at a fixed point to measure the absolute water level, and read the water level measured by the river bed level meter and the water level measured by the water level meter It is a riverbed scour monitoring method characterized by making it possible to monitor the progress of riverbed deformation by synchronizing them and obtaining the difference between them sequentially. The measurement result by the water level meter located in the water cannot be transmitted to the ground device by radio waves. Transmission of information in the water is not impossible if ultrasonic waves are used, but it is impossible to carry out due to the noise in the torrent during a flood. Therefore, in the present invention, instead of real-time processing, the water level meter located in the water has a data logger function, and during the flood, the water level measurement value is regularly measured and accumulated, and the appropriate time after the flood has subsided. The water level gauge is raised to collect data, collect data for a certain period, and batch process (batch processing).

  For example, a plurality of fixed piles are distributed and arranged in a linear or two-dimensional matrix on the river bed, and a plurality of river bed water level meters are moored to each fixed pile so as to be movable along the fixed piles. Only one water level gauge can be installed. Here, it is preferable to use a water level gauge of the same detection type as the river bed level gauge and the water level measurement level gauge. By using a water level meter of the same detection type, by taking the difference, components due to other than the scouring amount are offset, and only the scouring amount can be easily obtained.

The river bed water level meter used in such a river bed scour monitoring method includes a hollow spherical protective container having a weight function and having one or more water flow holes opened, and a diaphragm detection built in the protective container. The water pressure gauge has a data logger function, and is attached so that the diaphragm surface is positioned at the center of the protective container, and a mooring member is connected to the protective container by a fixing bracket. and there structure. The mooring member is preferably made of, for example, a looped wire, and the river bed water level meter is preferably installed so as to pass through the fixed pile.

  The riverbed scour monitoring method according to the present invention can be easily implemented because it is basically only necessary to install a riverbed water level meter on the riverbed to be scoured, and the scouring amount is fixed to the water level measurement value by the riverbed water level meter. Since it can be obtained with high accuracy from the difference from the water level measured by the water level meter at the point, it is possible to accurately grasp the progress of river bed deformation by accumulating measurement data over time.

  If a plurality of riverbed level gauges are distributed and arranged on the riverbed in areas that require monitoring, the riverbed scouring situation in those areas can be ascertained three-dimensionally and over time. In addition, if a water level meter of the same detection type is used for the river bed water level meter and the water surface level water level meter, the atmospheric pressure correction and the like are not required, so that the system configuration and data processing can be simplified.

  FIG. 1 schematically shows an example of a riverbed scour monitoring method according to the present invention. As shown to A of FIG. 1, this invention installs the river-bed water level meter 12 on the river-bed part 10, and installs the water level measurement water level meter 14 in a fixed point, and the water level measurement value by the said river-bed water level meter 12 is shown. This is a method of monitoring the progress of river bed deformation by determining the difference between the water level a (water level a) and the water level measurement value (water level b) by the water level measurement water level gauge 14. A fixed pile (rod or steel pipe or the like) 16 is driven into the riverbed 10 using a spat carrier, and the anchoring member 18 is used to fix the fixed pile 16 so that the riverbed water level meter 12 can move freely along the fixed pile 16. Moored. The anchoring member 18 may be made of any material such as a wire, a rope, or a chain, but preferably has a structure in which the wire is anchored through a fixed pile in a large loop shape. Here, the fixed pile 20 is driven in the vicinity of the riverbank, and the water level measurement water level gauge 14 is fixed to the upper end portion thereof.

  The river bed water level gauge 12 is shown in FIG. The river bed water level gauge 12 has a structure in which a water pressure gauge 22 having a data logger function is built in a protective container 24 having a weight function. Here, the protective container 24 is a hollow iron ball (for example, about 20 cm in diameter) in which one or more water circulation holes 26 are opened. The protective container 24 does not rise even in a torrent during a flood, and always stays on the river bed even if it rolls. As such, the iron ball itself functions as a weight. Since the protective container 24 has a hollow structure, water can freely enter and exit through the water circulation hole 26, and the water pressure can be measured by the water pressure gauge 22.

  The water pressure gauge 22 is a diaphragm detection method and has a data logger function. As shown in FIG. 1C, the water pressure gauge 22 includes a water pressure detection diaphragm, a measurement / recording unit, an input / output interface unit, and a battery in a case. Here, the case body 30 has a cylindrical shape, and a cap 34 having a water pressure detection hole 32 formed in the vicinity of the diaphragm surface near the front end is attached, and the rear end is closed by an end plug 36. The water pressure becomes a deformation of the diaphragm surface, which is periodically measured using a timer function in the measurement / recording unit, and measurement data (water pressure data and time data) is accumulated. By removing the end plug 36, it is possible to collect data stored by electrical cable coupling or non-contact optical coupling, clear a recording unit, and the like. During measurement, the necessary power is supplied from the built-in battery.

  Returning to FIG. 1B, the cylindrical water pressure gauge 22 as described above is attached by the holding tool 46 at the rear end so that the diaphragm surface is located at the center of the spherical protective container 24. Thus, when the diaphragm surface is located at the center of the spherical protective container 24, even if the protective container 24 rolls, the vertical position of the diaphragm surface does not change, so the same water level can be measured regardless of the posture, Measurement accuracy of ± several cm or more can be realized. The mooring member 18 is connected to the protective container 24 by a fixing bracket 48. A through-hole is formed in the protective container 24, a rod-shaped fixing bracket 48 is inserted, a locking portion 50 is attached to both ends, and a wire as the anchoring member 18 is attached to both ends of the fixing bracket 48. As described above, the mooring member anchors the river bed water level meter so that it can freely move along the fixed pile.

  The water level gauge 14 can be of any type, but if a water pressure gauge with the same diaphragm as the river bed level gauge 12 is used, the water level fluctuation and atmospheric pressure correction are offset by taking the difference in the water level measurements. This is preferable because it is possible. This water level measurement water level gauge 14 also has a data logger function, and has a structure capable of periodically measuring and storing data (water pressure data and time data).

  The riverbed water level meter 12 installed on the riverbed 10 moves (descends) as the riverbed is scoured and deepened due to floods, etc., and the water surface position also rises and falls, and thus includes both riverbed scouring amount and water surface fluctuation. The relative water level a (the water depth from the river bed to the water surface at that time) is measured periodically (for example, at intervals of several minutes to ten and several minutes), and the data (water level and time data) is accumulated. On the other hand, the water level measuring water level gauge 14 attached so as not to move to the fixed pile 20 is always located at a fixed place (fixed point), and therefore, the absolute water level b (independent of the riverbed scouring amount) The water depth from the fixed point at that time to the water surface) is measured periodically (at a timing synchronized with the measurement of the river bed water level meter), and the data (water level and time data) is accumulated. Such data will continue to be measured and accumulated while the water level gauge is installed, including during floods.

  Then, at an appropriate time after the flood has subsided, as shown in FIG. 2, the riverbed water level gauge 12 and the water surface level gauge 14 are collected and the accumulated data is taken out. In the case of a large river with a depth of several meters, for example, a diver dives and raises the riverbed level gauge 12 and the water level gauge 14 onto the ship 52, removes the water pressure gauge, Data is taken into a computer via an interface unit by optical connection or cable connection. After that, the water pressure gauge is reset, re-installed in the protective container, and the diver dives again to re-install the water level gauge at a predetermined position.

The collected measurement data is processed as follows. By reading out the water level measurement value (water level a) by the river bed water level meter and the water level measurement value (water level b) by the water level measurement water level meter, synchronizing them, and calculating the difference between them, The amount of riverbed scouring can be determined.
(Amount of riverbed scouring) = (water level a)-(water level b)
As described above, the water level a includes the effects of water level fluctuations and atmospheric pressure fluctuations in addition to the scouring amount, and the water level b includes the effects of water level fluctuations and atmospheric pressure fluctuations. This is because the effects of fluctuations in the water surface and atmospheric pressure are offset, so that only the riverbed scouring amount can be obtained. The progress of riverbed deformation can be monitored by obtaining the riverbed scouring amount sequentially over time.

  FIG. 3 is an explanatory diagram showing an example of a method for installing a river bed water level gauge. In large rivers, scouring as deep as several meters may occur depending on the scale and location of the flood. In this embodiment, as shown in FIG. 3A, the mooring member 60 of the river bed level gauge 12 is formed in a large loop shape, and one end thereof is attached to the river bed level gauge 12 and a fixed pile (steel pipe or the like) 62 is passed. The loop is dropped from above and the river bed level gauge 12 is moored. At this time, the locking hole 64a is provided in the upper end part of the fixed pile 62, and the auxiliary wire 66 attached to the loop-shaped part is attached. If the mooring member 60 is looped larger than the fixed pile 16 and passed through the fixed pile 62, the river bed water level meter 12 is smoothly moved along the fixed pile 62 as the river bed 10 is scoured. be able to. Moreover, even if the water is cloudy immediately after a flood, the river bed water level meter 12 can be easily pulled up by dragging the auxiliary wire 66 with the fixed pile 62 as a mark.

  In FIG. 3A, the riverbed scouring at the time of flooding changes from the current riverbed indicated by the solid line to the scouring riverbed indicated by the dotted line. In the current river bed shown by a solid line before flooding, the driving depth of the fixed pile 62 is required to be at least 3 to 4 m or more. Further, the protruding length of the fixed pile 62 on the river bed is about 1 m so that the mooring member 60 does not come off even if it receives a torrent, and it may be buried instead of scouring. However, during deep floods, deep digging can occur, and riverbed scouring can amount to several meters. Due to several floods, in the long term it may be dug as deep as more than a dozen meters. Assuming such a case, it is necessary to drive the fixed pile 62 deeper. In such a case, when the fixed pile 62 is driven deeply, the fixed pile is added and driven, and a locking hole is provided in the vicinity of the added portion. After re-installing the riverbed water level meter 12 after receiving a large scour, as shown in FIG. 3B, the upper portion 62a of the fixed pile is cut off, leaving only the lower portion 62b of the fixed pile, and remains. The auxiliary wire 66 is attached to the locking hole 64b of the fixed pile portion. Thus, by cutting off the unnecessary upper portion 62a of the fixed pile, the resistance of the water flow can be reduced, and the fixed pile 62 can be prevented from falling down due to a rapid flow during a flood. In the above example, the fixed pile is configured by adding the upper portion and the lower portion. However, the fixed pile may be configured by adding a number of portions as necessary. In that case, it is preferable to provide a locking hole at the upper end of each part so that each part can be removed sequentially.

  FIG. 4 is a plan view showing an example of the installation status of the river bed water level gauge. This is an example in which six river bed level gauges 12 are installed in a river. Six fixed piles are driven into a two-dimensional matrix at the place where scouring occurs in the river, and the riverbed water level gauge 12 is moored in each. The water level gauge 14 may be installed only at one location near the riverbank. In this example, six fixed piles are driven into a two-dimensional matrix, and each riverbed water level gauge is moored. However, the number of fixed piles is arbitrary and installed in a line. Or may be installed in a matrix or randomly, and the installation location may be appropriately set according to the scouring situation. Moreover, it is not always necessary to moor a river bed water level meter for each of the installed fixed piles, and the river bed water level meter may be moored only to a fixed pile appropriately selected according to the location.

  In this way, the water level measurement values by the six river bed level gauges 12 and the water level measurement value by one water level measurement level gauge 14 are sequentially read out, and the difference is calculated by synchronizing them with each river bed level gauge 12. By doing so, the riverbed scouring amount at that position is obtained. By obtaining this riverbed scouring amount sequentially over time, a contour map can be drawn over time, and the progress of three-dimensional riverbed deformation can be monitored.

  FIG. 5 shows another example of the installation status of the river bed water level gauge. A river bed water level meter 12 is moored to each of a plurality of fixed piles 16 driven into the river bed portion 10, and the river bed water level meter 12 is also fixed to a seawall member 72 such as a Tetrapot (trade name) installed on the river bank. Keep it. Although not shown, a water level measuring water level gauge is fixed at a fixed point as in the above embodiment. The movement of the revetment member 72 submerged under the surface of the water cannot be seen by visual observation from above the surface of the water. By fixing the river bed water level meter 12 to the revetment member 72, the movement of the revetment member 72 submerged under the water surface can also be monitored.

Explanatory drawing which shows an example of the riverbed scour monitoring method which concerns on this invention. Explanatory drawing which shows the collection | recovery condition of a water level meter. Explanatory drawing which shows an example of the installation method of a river-bed water level meter. Explanatory drawing which shows an example of the installation condition of a river bed water level meter. Explanatory drawing which shows the other example of the installation condition of a river bed part water level meter.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 River bed part 12 River bed part water level meter 14 Water surface measurement water level meter 16, 20 Fixed pile 18 Mooring member 22 Water pressure gauge 24 Protection container

Claims (3)

It consists of a spherical protective container having a weight function and an open water flow hole, and a diaphragm detection type water pressure gauge built in the protective container, and the water pressure gauge has a data logger function. A river bed water level meter, which is attached by a holding member so that the surface is positioned at the center of the protective container, and a mooring member is connected to the protective container by a fixing bracket , is installed on the river bed, and the river bed is scoured Relative water level including quantity is measured over time and accumulated, and a water level gauge is installed at a fixed point to measure absolute water level. A riverbed scour monitoring method characterized in that the progress of riverbed deformation can be monitored by reading out the water level measurements from the water level gauge and synchronizing them in order to obtain the difference between them.   The river bed according to claim 1, wherein a plurality of fixed piles are distributed in a linear or two-dimensional matrix on the river bed, and a plurality of river bed level gauges are moored to each fixed pile so as to be movable along the fixed piles. Scour monitoring method.   The river bed scour monitoring method according to claim 1 or 2, wherein a water level gauge of the same detection type is used for the river bed level gauge and the water level measurement level gauge.

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