JP2021042519A - Relieving method of influence by underwater noise to aquatic organism - Google Patents

Abstract

To provide a relieving method of influence to aquatic organisms caused by underwater noise during construction work, capable of effectively suppressing and relieving the influence to aquatic organisms.SOLUTION: In a relieving method of influence to aquatic organisms by underwater noise, when performing the construction work generating underwater noise, the underwater noise caused by the construction work is measured, actions of the objective aquatic organisms are confirmed, and the construction work is performed on the basis of the measuring results and action confirmation results of the aquatic organisms.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for alleviating the influence of aquatic organisms due to underwater noise generated by construction work.

There is concern about the impact on aquatic organisms due to the noise of underwater works such as pile driving and blasting in water. So far, frequencies that affect living organisms and distances that are affected by stakeout sounds (for example, up to 20 km at low frequencies) have been reported (Non-Patent Document 1). In addition, it has been clarified that fish have a level of damage (220 dB or more), a threatening level indicating repellent (avoidance) behavior (140 to 160 dB), and that underwater noise is attenuated with distance (). Non-Patent Document 2).

As a method for mitigating the influence of underwater noise on fish and marine mammals, an underwater noise reduction device and deployment system (Patent Document 1), a bubble curtain (Patent Document 2), a pile sleeve (Non-Patent Document 3), etc. Has been proposed.

Special Table 2017-504844 Jikkenhei 01-19431

Tomonari Akamatsu, Riko Kimura, Kotaro Ichikawa "Underwater Bioacoustics-Voice-Exploring Behavior and Ecology-" Corona Publishing Co., Ltd. (January 2019) Japan Dredging and Reclamation Association "Port Construction Environmental Conservation Technology Manual Doctor of the Sea (Revised 3rd Edition)" (2015) National Research and Development Corporation New Energy and Industrial Technology Development Organization "Implantation type offshore wind power generation introduction guidebook (final version)" (March 2018) https://www.nedo.go.jp/news/press/AA5_101085 .html

It is said that when the underwater noise caused by stakeout reaches a threatening level, underwater creatures such as fish escape from the surrounding sea area and return after the noise has subsided. There is no case of tracking the behavior of an individual, and the effect of underwater noise on the behavior has not been clarified. For this reason, no effective measures have been taken.

Regarding fish, it is known that there are general hearing fish and fish that are insensitive to sound (flatfish, flatfish, etc. without a swim bladder), and the threat level etc. may differ depending on the species, but the target It is difficult to take effective measures unless the sensitivity to the sound of the species is clarified.

In view of the above-mentioned problems of the prior art, the present invention provides a method for mitigating the influence of underwater noise caused by underwater noise, which can be effectively suppressed and mitigated by investigating the influence of underwater noise on underwater organisms in construction work. The purpose.

The method of mitigating the influence of underwater organisms due to underwater noise to achieve the above objectives is to measure the underwater noise caused by the construction work and confirm the behavior of the target aquatic organisms when carrying out the construction work that generates underwater noise. The construction is carried out based on the measurement result and the behavior confirmation result of the aquatic organism.

According to this method of mitigating the effects of underwater organisms due to underwater noise, even if underwater noise is generated due to construction work, underwater noise due to construction work is measured, the behavior of target underwater organisms is confirmed, and the measurement results of underwater noise and underwater noise are measured. Underwater noise can be taken because noise reduction measures can be taken when the sound pressure of the sound source is higher than expected or when abnormalities are confirmed in the behavior of the target aquatic organisms. Can effectively suppress and mitigate the effects of this on aquatic organisms. In addition, since the behavior of the target aquatic organism can be confirmed each time and the effect can be appropriately evaluated according to the aquatic organism, the effect on the aquatic organism can be effectively suppressed.

In the method for mitigating the influence of aquatic organisms due to underwater noise, it is preferable to investigate and predict the influence of the underwater noise on aquatic organisms in advance, and if an adverse effect is predicted, take measures such as noise reduction in advance.

Further, in the above prediction, it is preferable to judge the influence at a position away from the noise generation position based on the distance attenuation of the sound pressure in water.

In addition, it is preferable to use at least one of a fish finder (including fishery sonar) and biologging / biotelemetry in order to confirm the behavior of the target aquatic organism.

In addition, it is preferable to determine whether or not the underwater noise has an effect on the aquatic organism based on the avoidance behavior of the aquatic organism at the time of underwater noise obtained from the behavior confirmation result. For example, when it is confirmed that the target underwater organism has moved to a distant place while avoiding the underwater noise when the underwater noise is generated, it can be judged that there is no influence of the underwater noise.

Further, when any one of the death, damage, or abnormal behavior of the aquatic organism is confirmed from the behavior confirmation result, it is preferable to suspend the construction and take measures such as noise reduction.

According to the present invention, it is possible to provide a method for mitigating the influence of underwater organisms due to underwater noise, which can effectively suppress and mitigate the influence of underwater noise on underwater organisms in construction work.

It is a flowchart for demonstrating each step of the method of mitigating the influence of marine organisms by underwater noise by this embodiment. It is a figure which shows schematicly the measurement system which measures the underwater noise generated by the construction work and confirms the behavior of the target marine organism in this embodiment. It is a graph which shows the frequency of various underwater noise sources and the audible range of aquatic organisms (see FIG. 6.1 of Non-Patent Document 1). It is a figure which shows the sound pressure level (a) of the underwater sound and the reaction (b) of a fish (see Non-Patent Document 2). It is a figure which shows the sound pressure level and reaction level for each type of fish (see Non-Patent Document 2). It is a graph which shows the distance attenuation model of the sound pressure in water.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a flowchart for explaining each step of the method for mitigating the influence of marine organisms due to underwater noise according to the present embodiment. FIG. 2 is a diagram schematically showing a measurement system for measuring underwater noise generated by construction work and confirming the behavior of a target marine organism in the present embodiment. FIG. 3 is a graph showing the frequencies of various underwater noise sources and the audible range of aquatic organisms (see FIG. 6.1 of Non-Patent Document 1). FIG. 4 is a diagram showing the sound pressure level (a) of underwater sound and the reaction (b) of fish (see Non-Patent Document 2). FIG. 5 is a diagram showing a sound pressure level and a reaction level for each type of fish (see Non-Patent Document 2). FIG. 6 is a graph showing a distance attenuation model of sound pressure in water.

First, the measurement system according to the present embodiment will be described with reference to FIG. As shown in FIG. 2, when the pile driving ship SP is used to drive the pile P onto the seabed with the hammer H, underwater noise is generated. At the time of this driving, the underwater sound level meter M1 is used to drive the underwater noise at the driving point. To measure. In addition, the behavior status of the school of fish at the driving position is confirmed by the fish finder S1 or S2 mounted on the pile driving ship SP or the measuring ship MS.

In addition, the measuring vessel MS measures the underwater noise with the underwater sound level meter M2 at a position away from the casting point in the surrounding sea area, and confirms the behavior status of the school of fish with the fish finder S2. Further, after the sensor SE is attached to the fish FI and released, the receivers R1 and R2 placed in the water receive the signal from the sensor SE and analyze the position of the fish FI and the like.

Fishfinders S1 and S2 were used to confirm the behavior of fish before, during, and after noise generation at the casting point and the surrounding sea area, and when underwater noise was generated, the target marine organisms were selected at the casting point and the surrounding sea area. Check the situation where the school of fish moved while avoiding underwater noise. The fish finder S1 and S2 include a fishery sonar capable of exploring 360 ° in the horizontal direction toward the seabed, a multi-beam sonar, and a graph fish finder (body length and individual abundance can be measured). In addition, by biologging and biotelemetry, sensors SE (Pinger, acceleration, water pressure, water temperature, data logger, etc.) can be attached to aquatic organisms such as fish and released into the sea area at the casting point to check the movement status of individuals.

Biologging / biotelemetry is a research method for investigating behavior and ecology by attaching small transmitters, video cameras, sensors, etc. to living things to acquire behavior data, such as lizards, sea turtles, penguins, and whales. Sensors are often attached to large creatures in Japan, but the miniaturization of the devices is progressing, and research on birds and fish is also underway. By using such technology, it is possible to confirm the influence of noise on fish, etc. during pile driving. In order to confirm the behavior by such biologging and biotelemetry, the behavior is confirmed by attaching a sensor to the target marine organism, releasing it, and using a receiver that displays the signal received from the sensor, or by analysis after the sensor is collected. Do.

Underwater sound pressure is measured at the driving point and at a position away from the driving point by the measurement system shown in FIG. 2, and underwater noise is measured at multiple points in the source of underwater noise and the surrounding sea area before, during, and after noise generation. Can be measured and the behavior of the target marine organism can be confirmed.

A method for mitigating the influence of marine organisms due to underwater noise according to the present embodiment will be described with reference to FIGS. 1 to 6. First, by preliminary examination, the conditions of the target area and the surrounding sea area, the characteristics of the target area (seabed topography, fishing grounds, species to be captured, species to be protected, etc.), construction methods used for construction, existing target marine organisms, etc. are confirmed. (S01).

Next, the effects of underwater noise generated during construction work are predicted based on the materials and data obtained in the preliminary study (S02). For example, as shown in FIG. 3, in the case of pile driving, noise with a frequency in the audible range of the fish is generated, and as shown in FIGS. 4 (a) and 4 (b), the reaction of the fish depending on the sound pressure level of the noise. As shown in Fig. 5, the reaction differs depending on the sound pressure level for each fish, and as shown in Fig. 6, the sound pressure level decreases according to the distance from the sound source in water. Predict the impact.

Next, it is determined whether or not there is an impact on the target marine organism based on the prediction result of the impact prediction step S02 (S03). Here, there are the following contents as a situation where there is no influence on the target marine organisms when underwater noise is generated, including the case where the countermeasure selection in step S05 described later is carried out.

When determining no effect (NO) in step S03
(1) There are no target marine organisms in the sea area around the noise source. In this case, assuming that the target marine organism does not exist (S04), the flow ends (end) without proceeding to the subsequent steps.
(2) Sound source sound pressure is less than the threatening level. Alternatively, the range of habitat of the target marine organism is less than the threatening level.
(3) It is assumed that the target marine organisms that existed in the sea area around the noise source move from the threatening level range to the unaffected sea area.
(4) When there are habitats (rock reefs, etc.) or fishing grounds of the target marine organisms in the surrounding sea area, noise is generated up to the sound pressure that does not affect the target marine organisms due to the attenuation of the noise distance from the noise source to the habitat or fishing grounds. Decreases.

When it is determined in step S03 that there is an effect (YES) and the countermeasure selected in step S05 is implemented.
(5) It is assumed that underwater noise reduction measures for noise sources will be implemented and the noise will be reduced to less than the threatening level that does not affect the target marine organisms.
(6) It is assumed that measures will be taken to reduce underwater noise at the noise source, and the noise will be reduced to below the threatening level (more preferably below the attraction level), and if it is at the threatening level, it will move to an unaffected sea area.
(7) If there are habitats (rock reefs, etc.) or fishing grounds for the target marine organisms in the surrounding sea area, it is assumed that the noise will be reduced to a sound pressure that does not affect the target marine organisms by implementing measures to reduce the underwater noise of the source. To.
However, if the background noise generated in the surrounding sea area other than pile driving is high and marine life is inhabiting at a threatening level or higher, or if there is no sea area at the attraction level in the vicinity, it is preferable to consider separate measures.
The sound pressure / sea area that is not affected here refers to the threat level or less (more preferably, the attraction level or less) of FIG. 4 (b) against marine organisms.

For example, the expected sound pressure level of the target point is predicted by the distance attenuation model of the solid lines A to C in FIG. 6. For example, when the sound source sound pressure is 200 dB, the distance attenuation model A attenuates to 140 dB at the target point 1000 m from the sound source. However, if there is a fish habitat at this 1000m point, which is a target marine organism with a lower limit of 140 dB of threatening level to take evasive action as shown in Fig. 4 (b), this target marine organism moves farther than 1000 m from the sound source. Therefore, it is judged that there is no effect (NO). Although the sound pressure level differs depending on the target marine organism, it is desirable that the sound pressure be below the threatening level (more preferably below the attraction level) in the habitat of the target marine organism.

For example, in the case of a fish that is insensitive to sound and has no swim bladder such as flatfish or flatfish, assuming that the lower limit of the threatening level is 180 dB, the distance attenuation model shown in FIG. 6 when the sound source sound pressure is 200 dB. Since the range of influence is 10 m from A and it is limited to the vicinity of the source in the construction, it is judged that there is no influence (NO). In the above case, the process proceeds to the next step S06.

Further, in the following cases, it is determined that there is an influence (YES). For example, when the sound source sound pressure is 240 dB, the sound pressure becomes 140 dB from the distance attenuation model C in Fig. 6 at a point 100 km from the sound source, and there are some fish that are affected by underwater noise over a wide area and do not have the ability to move to that extent. .. In addition, the range from the sound source to 10 m is the damage level of 220 dB, and if there is a fish in that range, damage will occur, so it is judged to be affected (YES). The distance attenuation model C in FIG. 6 is an estimated value based on a spherical diffusion model having a sound source sound pressure of 240 dB.

Further, for example, when the sound pressure of the sound source is 200 dB, the distance attenuation model A in FIG. 6 shows 146 dB at the target point 500 m from the sound source, but if there is a fish as a target marine organism at the target point 500 m, the mobility of the fish is high. If there is a small concern about the impact, or if there is a fishing ground at the 500m point and countermeasures are required, it is judged as having an impact (YES).

If it is determined in the impact determination step S03 that there is an impact (YES), a measure for mitigating the impact is selected (S05). For example, when the sound source sound pressure is 240 dB, it is necessary to take measures to reduce the sound source sound pressure.

Also, when the sound source sound pressure is 200 dB, if there is a concern about the influence on fish as a target marine organism at the target point 500 m from the sound source, or if there is a fishing spot etc. at the point 500 m from the sound source, if the sound source sound pressure is set to 190 dB Since the sound pressure is less than 140 dB, which is the lower limit of the threatening level for avoiding fish, at the target point 500 m from the sound source from the distance attenuation model B in FIG. 6, take reduction measures such as lowering the sound source sound pressure by at least 10 dB.

Next, preparations for countermeasures and confirmation of the prior situation in the countermeasure selection step S05 are performed (S06). For example, preparations for measures to reduce sound source sound pressure, measurement of underwater noise (before construction work), confirmation of the behavior of target marine organisms, etc. are performed by the measurement system shown in FIG.

In addition, if necessary, soundproofing measures can be taken before construction such as pile driving to reduce the sound pressure level of the noise source, so that the range of influence can be narrowed. In addition, there are measures such as artificially generating a sound in water before casting to avoid the target marine organisms living near the casting site to the surrounding sea area.

Next, when the construction work starts, underwater noise is generated (S07). At the start of construction, underwater noise will be measured and the behavior of target marine organisms will be confirmed (S08). That is, the measurement system of FIG. 2 is used to measure the underwater noise generated by pile driving at a source of underwater noise (placement position) and at a plurality of points in the surrounding sea area.

Further, in step S08, the measurement system of FIG. 2 is used to confirm the behavior such as avoidance of the target marine organism group by the fish finder, and the behavior confirmation such as avoidance by tracking the target marine organism (individual) by biologging or biotelemetry. Do. Such behavioral confirmation includes confirmation of the death / damage status of the target marine organism and the occurrence status of abnormal behavior.

For example, when the sound pressure of the sound source is 200 dB, in the distance attenuation model A of FIG. 6, it becomes 146 dB at the target point 500 m from the sound source. Check the movement status of the fish.

Based on the measurement confirmation result in the measurement / action confirmation step S08, the presence or absence of the influence of underwater noise is determined (S09). For example, if the target marine organism dies, is damaged, or has abnormal behavior, if the sound source sound pressure is higher than expected, or if the effect of the implemented measures is small and the impact on the target marine organism is predicted, there will be an impact. (YES) is determined. In addition, for example, if the target marine organism does not die, be damaged, or have abnormal behavior, or if the target marine organism moves to a distant place while avoiding underwater noise, it is judged as no effect (NO). To do.

If it is determined that there is an influence (YES) in the influence determination step S09 due to the underwater noise, the construction is temporarily interrupted and a countermeasure is selected (S10). As a measure against such noise, in addition to the bubble curtain and pile sleeve mentioned above, a method of controlling the driving so that the sound pressure has less influence, soft start (first driving with a weak force, gradually strengthening I will go) and so on.

After taking the measures selected in step S10, the construction is restarted (S07), and the same steps S08 and S09 are repeated.

If it is determined that there is no effect (NO) in the above-mentioned underwater noise effect determination step S09, it is determined that the preliminary examination, preparation, and countermeasures in steps S01 to S06 before the construction were good, or that there is an effect after the start of the construction. Even in this case, it is probable that the measures taken in step S10 were good. Next, after the construction is completed, if the marine organisms move to a distant place while avoiding underwater noise, post-measurement is performed (S11). Such post-measurement includes measurement of underwater noise similar to step S08, behavior confirmation of the target marine organism group by a fish finder or the like, behavior confirmation by tracking the target marine organism (individual) by biologging or biotelemetry, and the like. .. Here, we will confirm the movement and recovery status of the target marine organisms from the range where there is no influence of the surrounding sea area to the area around the pile driving when the noise such as the threatening level disappears.

As described above, according to the method for mitigating the influence of marine organisms due to underwater noise according to the present embodiment, the characteristics of the target area (seabed topography, fishing grounds, etc.) After considering the species to be captured, the species to be protected, etc.), confirm, examine, prepare, and take measures in advance, measure the underwater noise after the start of construction, confirm the behavior of the target marine organisms, and use the underwater noise. The impact on marine life can be suppressed and mitigated. In addition, since the behavior of the target marine organism can be confirmed each time and the impact can be appropriately evaluated according to the marine organism, the impact on the marine organism can be effectively suppressed. By utilizing a monitoring system for marine organisms, it is possible to implement construction management and noise countermeasures such as pile driving that suppresses the impact on the target marine organisms.

In this embodiment, a fish finder and biologging / biotelemetry are used, but the term is not limited to fish, but marine organisms that can be detected by a detector or sonar, and marine organisms to which a sensor can be attached. The target is general, and may be shellfish, mollusks, dolphins, whales, sea turtles, seals, jugons, penguins, and the like.

Further, in steps S06, S08, and S11 of FIG. 1, an underwater sound level meter, a fish finder, and biologging biotelemetry are used, but an underwater sound level meter and a fish finder or biologging biotelemetry are used. There is also an operation to do.

In addition, a method of using an underwater sound level meter and a fish finder and biologging biotelemetry at the beginning of pile driving, and then using an underwater sound level meter and a fish finder or biologging biotelemetry, or , There is also a method of using an underwater sound level meter or a fish finder alone (when the noise of the sound source is low, when the avoidance pattern of fish has been confirmed, etc.).

Although the embodiments for carrying out the present invention have been described above, the present invention is not limited to these, and various modifications can be made within the scope of the technical idea of the present invention. For example, in Fig. 2 and the like, it is assumed that a large-scale pile driving of offshore wind power generation is performed as the target construction, but the present invention is not limited to this, and of course, it can be applied to all constructions that generate underwater noise. is there.

Regarding fish, confirmation starts from general information such as "140 to 160 dB threatening level" as shown in Fig. 4 (b), but in addition to the noise effect confirmation experiment of the target marine organisms in the water tank etc. in advance. By measuring with an underwater sound level meter and biologging / biotelemetry, it is possible to determine the sound pressure level that affects the target marine species during the construction process. By using such a numerical value, it is possible to make a more accurate prediction from the middle of the construction in the same construction. If the same type is targeted for different works, it can be used as basic data. That is, even when known data as shown in FIGS. 2 to 6 are used, in place of or together with them, various original data newly acquired by surveys and measurements before and during construction are used. May be good.

Further, in FIG. 2, the underwater noise measurement at a position away from the casting point is performed by the measuring vessel MS, but the present invention is not limited to this, and the underwater sound level meter is installed at one or a plurality of fixed points. It may be. Further, although the receivers R1 and R2 are installed underwater in FIG. 2, they may be attached to the measuring ship MS for use.

In addition, by the monitoring system for marine organisms as in this embodiment, changes can be seen in the movement behavior of the target marine organisms within 24 hours, within several days, every season, weather conditions, etc., even when no noise is generated. If the behavior is such that the vehicle moves away from the construction site, it is possible to take measures such as placing piles at such times.

Further, in the present embodiment, the target marine organisms are organisms that inhabit the sea area where the construction is carried out, such as fish, shellfish, mollusks, dolphins, whales, sea turtles, penguins, jugons, and seals.

The present invention is a method for alleviating the influence of underwater organisms due to underwater noise, but from another point of view, it can be regarded as a construction management method for construction works in which underwater noise is generated. That is, in this construction construction management method, when carrying out construction that generates underwater noise, the underwater noise due to the construction is measured, the behavior of the target aquatic organism is confirmed, and the measurement result and the behavior of the aquatic organism are confirmed. The construction will be managed based on the confirmation result. It is possible to reliably manage construction work such as pile driving so that underwater noise does not adversely affect the target underwater organisms.

Further, although the present embodiment targets the construction in the ocean, the present invention is not limited to this, and can be applied to the construction in lakes and rivers on land. The aquatic organisms targeted in the present invention include marine organisms.

According to the present invention, when constructing a construction that generates underwater noise, it is possible to carry out construction construction management such as pile driving and noise countermeasures so as not to affect the target underwater organisms.

M1, M2 Underwater Sound Level Meter MS Measuring Vessel R1, R2 Receiver S1, S2 Fishfinder FI Fish SE Sensor P Pile H Hammer SP Pile Driving Vessel

Claims (6)

When carrying out construction that generates underwater noise, measure the underwater noise caused by the construction, confirm the behavior of the target aquatic organisms, and check.
A method for mitigating the influence of aquatic organisms due to underwater noise, which is carried out based on the measurement result and the behavior confirmation result of the aquatic organism. The method for mitigating the effects of underwater noise on aquatic organisms according to claim 1, wherein the effect of the underwater noise on aquatic organisms is investigated and predicted in advance, and if an adverse effect is predicted, countermeasures are taken in advance. The method for mitigating the influence of aquatic organisms due to underwater noise according to claim 2, wherein in the prediction, the influence at a position away from the noise generation position is determined based on the distance attenuation of the sound pressure in water. The method for mitigating the effects of underwater organisms due to underwater noise according to any one of claims 1 to 3, wherein at least one of a fish finder and biologging / biotelemetry is used to confirm the behavior of the target aquatic organism. The aquatic organism due to the underwater noise according to any one of claims 1 to 4, which determines whether or not the underwater noise has an effect on the aquatic organism based on the avoidance behavior of the aquatic organism during the underwater noise obtained from the behavior confirmation result. How to mitigate the impact. Mitigation of the influence of underwater organisms due to underwater noise according to any one of claims 1 to 5, wherein when any of the death, damage, or abnormal behavior of the aquatic organism is confirmed from the behavior confirmation result, the construction is interrupted and countermeasures are taken. Method.

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