Evaluation on the influence that offshore wind power
generation facilities give to underwater creatures- An Example in Setana Port E.Naruse, Coastal Institute of Technology(CDIT), Sumitomo Hanzomon Bldg. 6F, 3-16,
Hayabusa-cho Chiyoda-ku Tokyo, 102-0092, JAPAN
tel:+81-3-3234-5862, fax:+81-3-3234-5877, E-mail:naruse@cdit.or.jp;
M.Miyoshi, CDIT; K. Shimada, Metocean Environment Inc.; T.Shigaki, Metocean Environment Inc.;
K.Sumida,

Daioh Construction Co., Ltd.; S.Dohata, Setana Town Office;This research attempted to understand the characteristics of offshore wind farm’s soundpressure level and the impact that offshore wind farm’s foundation works on aquaticcommunity. The method was survey on the sound pressure level and frequency analysis,and survey on aquatic community. The results are summarized as below:
i. The wind speed was 0−10 m/s and underwater sound pressure level was 109 〜 140dB.
ii. Underwater sound pressure level’s frequency was 6 − 10Hz, in strong winds. Thisfrequency is a strong resemblance to wave disturbance. So, this is attributed to the fact thatwave disturbance was made by strong wind and breakwater.
iii. The species number of fish community did not show any difference between 2003 and2004,while individual number increased in 2004.

1. Introduction

farm’s sound pressure level and the impact that

In Japan, most of wind energy projects are

offshore wind farm’s foundation on aquatic

few

exceptions

ofcommunity, for the purpose of gaining insights

operations.

Compared

tointo impacts of offshore wind farms, which will

inlands, port/coastal areas enjoy relatively stable

be constructed in increasing numbers, upon

wind conditions in general, with higher wind

port/coastal areas.

land-based,

withnear-shore/offshore

aspeed and less wind fluctuations. As wind-favored76

80

inland sites are less and less available within thebounds

ofthenation,

extensive

development of port/coastal windmills has beencalled for (Fig.1).
Yet, the construction of wind power facilities inport/coastal areas may involve different types of70
Installed Capacity (MW)limited

60
46

50
40
30

23

20
10

impacts on the environment from the case of

2320002001

0onshore installation. It is expected to give rise to19971998

1999

2002

2003

2004

Fiscal year

the need of assessment of impacts on theenvironment unique to port/coastal areas.
In this research, survey was conducted tounderstand the characteristics of offshore wind

Fig.1: Development of Installed Capacity in Portsand Harbors Areas (including onshore installation;
as of March, 2005)

2. Methodology

underwater vs. the sound pressure and theTo understand the characteristics of offshore

dominant frequency in the air around the offshore

wind farm’s sound pressure level and impacts onwindmills.

Fig.

3showspoints,

twoa

totalofsix

aquatic community arising from the operation ofmeasurement

pointsonthewind farm, we studied sound pressure level

foundations of the windmills (St. 1 and St. 4), two(hereinafter referred to as the sound pressure

points at 50 meters away from the windmills (St.

survey) as well as aquatic community (referred to2. and St. 5), and two points at 200 meters away

as the aquatic community survey).

from the windmills (St. 3 and St. 6), respectively.

Both surveys were conducted on an offshore

A 24-hour measurement was taken, with thewindmills (two 600kw units) situated within andata of sound pressure level collected every 10

eastern breakwater in Setana Port, Setana Town,minutes. The data was examined compared to theHokkaido, as shown in Fig. 2 and photo 1.

operation status of the windmills (running orstopped) and the wind speed, coupled withfrequency analysis, to characterize the underwater

Setana town

sound around the windmills.
●Hokkaido

WNSWindmills
風車E

Breakwater

Breakwater
St.4

堤

St.1

防防波堤

Japan

消波ブロック
波

50m

St.2

St.5

St.3

St.6

測線Ａline
A

測線Ｂ

200m

line B

Fig.2: Location of Setana town
砂浜Sandy beach
凡 例
水中音圧調査地点（調査層：中層）

0200400m

注）調査地点は、風車基礎部、５０ｍ、２００ｍの位置に配置。

■Measurement points of underwater sound pressure

Fig.3: Measurement points of underwatersound pressure

For frequency analysis, 1 minute-stepwise data
was used, and the wind speed data was collectedwith the use of existing anemometers on thePhoto.1: Windmills of Setana port

windmills. In analyzing the frequency, analysis
was made for representative periods of time on(1) Outline of the sound pressure survey
The survey was conducted from 12:00, August
16 to 12:00, August 17, 2004, with the focus on
the sound pressure and the dominant frequency

conditions varying in wind speed and winddirection, as shown in Table1.

3. Findings and Consideration

Table 1: Conditions under frequency analysis
Conditions

UnderLine A

Line B(St.1〜(St.4〜St.3)

St.6)

strongCase(a) Correlation between sound pressure level andwind speedTo

comparethestrong

Case

wind
1-1

(1) The sound pressure survey
Purpose1-2(over 7m/s)
DuringFig 5 shows the maximum value of soundwind with thepressure level and the mean wind speed for ten

weak wind

minutes after every hour. The analysis excluded

Case

Case

2-1

2-2

Sea wind

Case

Case

To

(about 4m/s)

3-1

3-2

the difference

Case

Case

4-1

4-2

stoppedthe affected periods of time with higher soundoperationpressure level due to fishing boats and ships

Land wind(about 4m/s)

compareof

thedirectionofpassing nearby.
The wind speed during the survey ranged from0 to 10 m/s. In the beginning of the survey (12:00)
up to around 15:00, a wind stronger than 7m/s

the wind(2) Outline of the aquatic community survey

was recorded. Later on, it became less windy over

The survey was conducted on August 18 and 19,

time, as weak as 2.0 m/s by 21:00. Then, the wind2003 prior to the construction of the windmills as

direction changed, from a sea wind (westerly) to awell as on August 15, 2004 upon completion,

land wind (easterly), at a varying speed of 2.0 tofocusing on the habitat of fish. As shown in Fig.4,4.0 m/s.

there were a total of six measurement points, two

The changing sound pressure level was withinat the foundations (St. 1 and St. 4), two at 200

the range of 109dB to 140dB. A relatively higher

meters away from the windmills (St. 3 and St. 6),

level was recorded on the foundations (St. 1 andone at a natural shore reef near the windmills (St.

St. 4) at a windy period of time (12:00-14:00), but7), and one at the breakwater near the windmills

even for a less windy period of time at 3m/s

(St.8), respectively. Divers observed and made a(6:00-7:00), nearly 134 dB was recorded, which

record of aquatic life within about 10-meter radius

shows no significant correlation between thefrom each measurement point, so that the data forstrength of the wind and the fluctuating soundthe two years were compared.

pressure level.

St.7

St.1

St.8

St.6

130
6120
3110

0

100
11:00
10:00
9:00
8:00
7:00
6:00
5:00
4:00
3:00
2:00
1:00
0:00
23:00
22:00
21:00
20:00
19:00
18:00
17:00
16:00
15:00
14:00
13:00
12:00

St.3

St.4

140

9

△

砂浜

No.11号機風速(m/s)
unit■st.1（風車0m）
st.1 (foundation)st.2 st.2（風車50m）(50m away)

× st.3（風車200m）
st.3 (200m away)

Fig.5(1): Correlation of wind speed vs.

Sandy beachunderwater sound pressure level (measurement
0200400mline A)

注）調査地点は、風車基礎部、５０ｍ、２００ｍの位置に配置。

Fig.4:

Observation
community

pointsofaquaticsound pressure level(dB)

防波堤

150

水中音圧(dB)

防波
堤E

消波ブロック

12

Maximum value of underwaterNS

Breakwater

Breakwater

Mean wind風速(m/s)
speed(m/s)

W

風車Windmills

3110

0100

△

Fig.5(2):No.2 unit
2号機風速(m/s)■

st.4(foundation)st.4（風車0m）

st.5（風車50m）
st.5 (50maway)×st.6（風車200m）
st.6(200m away)

Correlationofwind※APはオールパスレベル（オールオーバーレベル）を示す。
●：St.1,▲：St.2,◆：St.3

130
120
110
100
90
80
70

1.6
2
2.5
3.15
45
6.3
810
12.5
162025
31.5
40
50
63
80
100
125
160
200
250
315
400
500
630
800
1.0K
1.25
AP

120

Underwatersound pressure level(dB)
音圧レベル（dB）

6

sound pressure level(dB)

130

水中音圧(dB)

140

9Maximum value of underwater

150

11:00
10:00
9:00
8:00
7:00
6:00
5:00
4:00
3:00
2:00
1:00
0:00
23:00
22:00
21:00
20:00
19:00
18:00
17:00
16:00
15:00
14:00
13:00
12:00

Mean windspeed(m/s)
風速(m/s)12

Under strong
wind (line A)
強風時（測線Ａ)
140

Frequency(Hz)
周波数（Ｈｚ）※本分析結果は強風時を代表すると考St1(foundation)St1

St2
St3
えられる1分間のデータを用いた。
St2(50maway)
St3(200m away)

Fig.6(1): Frequency analysis: under strong windspeedvs.

(Case 1-1)

underwater sound pressure level (measurementduring stopped operation)
The results of the frequency analysis for Case
1-1 (measurement line A under strong wind)

Under strong wind(line B)
強風時（測線Ｂ)
140※APはオールパスレベル（オールオーバーレベル）を示す。
●：St.1,▲：St.2,◆：St.3

1301201101009080
70

1.62
2.5
3.15
456.3
810
12.5
16202531.5
40506380100125160200250315400500
630
800
1.0K
1.25
AP(b) Frequency analysis (under strong wind vs.

Underwater音圧レベル（ｄB)sound pressure level(dB)line B)

St4(foundation)
St4

and Case 1-2 (measurement line B under strong

Frequency (Hz)
周波数（Hz)※本分析結果は強風時を代表すると考St5(50mSt6(200m away)
St6away)
えられる1分間のデータを用いた。

St5wind) are shown in Fig. 6. For Case 1-1, theFig.6(2): Frequency analysis: under strong windfoundation (St. 1) had a peak at a 6-10Hz(Case 1-2)

bandwidth, while no significant peaks appeared ata peak at a 6-10Hz bandwidth, while both the50-meter point (St. 5) and the 200-meter point (St.
6) tended to be slightly higher at a bandwidth of
6-10Hz.
Fig. 7 shows the results of the frequency
analysis for Case 2-1 (measurement line A during140※APはオールパスレベル（オールオーバーレベル）を示す。
●：St.1,▲：St.2,◆：St.3

130
120
110
100
90
80
70

1.6
2
2.5
3.15
45
6.3
810
12.5
162025
31.5
40
50
6380
100
125
160
200250315400500630
800
1.0K
1.25
AP

(St. 3). In Case 1-2, the foundation (St. 4) showed

During stopped
operation(line A)
風車停止時（測線Ａ)
音圧レベル（ｄＢ）
Underwater soundpressure level(dB)

the 50-meter point (St. 2) nor the 200-meter point

Frequency(Hz)
周波数（Ｈｚ）

St1(foundation)
St1※本分析結果は風車停止時を代表する

St2(50mSt3(200m away)
St3 away)と考えられる1分間のデータを用いた。

St2※周波数分析は分析時間での平均値を用いた。

Fig.7(1): Frequency analysis: during stopped
operation (Case 2-1)

(St. 1 and St. 4) and the 50-meter points (St. 2 andSt. 5) share a similar pattern of frequency,
whereas the 200-meter points (St. 3 and St. 6)
show some difference in frequency pattern.
Comparison between the measurements understrong wind (Case 1-1 and Case 1-2) and the ones

During風車停止時（測線Ｂ)
stopped operation(line B)
140※APはオールパスレベル（オールオーバーレベル）を示す。
●：St.4,▲：St.5,◆：St.6

130
120
110
100
90
80
70

1.6
2
2.5
3.15
4
5
6.3
8
10
12.5
16
2025
31.5
40
50
6380
100
125
160
200
250
315
400
500
630
800
1.0K
1.25
AP

line B during stopped operation). The foundations

Underwater音圧レベル（ｄB)sound pressure level(dB)stopped operation) and Case 2-2 (measurement

Frequency
周波数（Hz)(Hz)

St4(foundation)
St4※本分析結果は風車停止時を代表すると考えられる1分間のデータを用いた。
St5(50mSt6(200m away)
St6 away)

St5※周波数分析は分析時間での平均値を用いた。

during stopped operation (Case 2-1 and Case 2-2)

Fig.7(2): Frequency analysis: during stopped

suggests that, with peaks observed at a 6-10Hz

operation (Case 2-2)

bandwidth under strong wind, factors related to
the wind strength might cause changing sound(c) Results of frequency analysis (sea wind vs.

pressure in this bandwidth.

land wind)and Case 4 (land wind) are given in Fig. 8 and Fig.
9.
In both wind directions, the foundations (St. 1and St. 4) showed peaks at a 6-10Hz bandwidth,

Land wind(measurement line B)
陸風（測線Ｂ)
140※APはオールパスレベル（オールオーバーレベル）を示す。
●：St.4,▲：St.5,◆：St.6

130
120
110
100
90
80
70

1.6
2
2.5
3.15
4
5
6.3
8
10
12.5
16
20
25
31.5
40
50
63
80
100
125
160
200
250
315
400
500
630
800
1.0K
1.25
AP

Underwater音圧レベル（ｄＢ）
sound pressure level(dB)

The results of analysis for Case 3 (sea wind)respectively. For the 50-meter points (St. 2 and St.

Frequency(Hz)
周波数（Ｈｚ）※本分析結果は風車停止時を代表する

St4
St4(foundation)※周波数分析は分析時間での平均値を用いた。

5), peaks appeared at the same bandwidth many

Fig.9(2):either of the 200-meter points (St. 3 and St. 6).

(measurement line B)

Frequency

analysis:landwind

Sea wind(measurement line A)
海風（測線Ａ)
140※APはオールパスレベル（オールオーバーレベル）を示す。
●：St.1,▲：St.2,◆：St.3130120(d) Summary of the sound pressure survey
The following outcomes are derived from the110
100survey:

9080-At a wind speed of 0-10 m/s, the sound pressure

70
1.6
2
2.5
3.15
45
6.3
8
10
12.5
16202531.5
40506380100125160200250
315
400
500
630
800
1.0K
1.25K
AP

Underwatersound pressure level(dB)
音圧レベル（ｄB)times. There was no apparent peak observed forFrequency(Hz)
周波数（Hz)St1(foundation) St1※本分析結果は風車停止時を代表する

St2
St3 と考えられる1分間のデータを用いた。
St2(50maway)
St3(200m away)

Fig.8(1):Frequency

level was within a range of 109-140 dB, and there
was no marked fluctuation in underwater sound※周波数分析は分析時間での平均値を用いた。

analysis:

seawindpressure depending on different wind speeds.
-The frequency analysis of underwater sound(measurement line A)

pressure showed frequency characteristics with a

Sea wind(measurement
海風（測線Ｂ) line B)
140※APはオールパスレベル（オールオーバーレベル）を示す。
●：St.4,▲：St.5,◆：St.6

130
120

peak at 6-10Hz under strong wind.
As to the frequency characteristics of the110
10090source of underwater sound, reference data are

80
70
1.6
2
2.5
3.15
4
5
6.3
8
10
12.5
16
20
25
31.5
40
50
6380
100
125
160
200
250
315
400
500
6308001.0K
1.25K
AP

Underwater soundpressure level(dB)
音圧レベル（ｄB)と考えられる1分間のデータを用いた。
St6 away)St5(50mSt6(200m away)

St5

Frequency(Hz)
周波数（Hz)St4(foundation)St4※本分析結果は風車停止時を代表すると考えられる1分間のデータを用いた。

St5
St6
St5(50maway)

St6(200m away)

available as shown in Fig. 10. In this research, thesound pressure level tended to get higher at※周波数分析は分析時間での平均値を用いた。

6-10Hz, which has a strong resemblance to theFig.8(2):Frequency

analysis:

seawinddisturbance as shown in Fig. 10. It is assumed that(measurement line B)

the strong wind disturbed waves in the waters

Land wind(m easurement line A)
陸風（測線Ａ)
140※APはオールパスレベル（オールオーバーレベル）を示す。
●：St.1,▲：St.2,◆：St.3

130
120

under study, which in turn affected the soundpressure level.

110
100
9080
70

Frequency(Hz)
周波数（Ｈｚ）

St1(foundation)St1※本分析結果は風車停止時を代表する

St2(50mSt3(200m away)
St2St3away)と考えられる1分間のデータを用いた。

※周波数分析は分析時間での平均値を用いた。

Fig.9(1):Frequency(measurement line A)

analysis:landwind

Eddy pressure spectrum

1.6
2
2.5
3.15
45
6.3
8
10
12.5
16
20
25
31.540506380100125
160200250315
400500630
800
1.0K
1.25AP

音圧レベル（ｄＢ）
Underwatersound pressure level(dB)frequency pattern of noise caused by wave

Effective eddy flow
speed(30cm/sec)

Meandering ocean
current(10cm/sec)

Frequency (Hz)Fig.10: Eddy pressure spectrum

(2) The aquatic community survey

Table 3: Aquatic community survey: 2003

The findings from a survey conducted in 2004
are shown in Table 2, compared to the previous
year in Table 3.
For the south foundation, Hexagrammos otakii,Cottidae, and Pleuronectidae were observed inScientific name
Hexagrammidae
Hexagrammos otakii
Pleuronectidae
Pleuronectes schrenki (Schmidt)
Ditrema temmincki
Cottidae
Stichaeidae
Pterogobius zacalles
unknown

Southern Northern
Reef
foundation foundation
(0m)
(0m)
5(1)
1

Breakwater
1
1
12
2
1
12(1)

122
1

1
many

both 2003 and 2004. The count in 2004 exceeded
the previous year in individual number as well as
species number.

4. Conclusion
From this research, it is found that the offshore

For the north foundation, Hexagrammos otakii

wind farm power operation has not caused

and Ditreme temmincki were observed in bothfluctuations in sound pressure level or impacts onyears. It was higher in individual number in 2004

the aquatic community. The main findings are asthan 2003.

follows:

In the neighboring survey points (natural reef,(1) The wind speed was within a range of 0-10breakwater), almost the same species werem/s during the survey, and the underwaterobserved for both years, while the year of 2004

sound pressure level fell within 109-140dB.

had more individual number than 2003.

(2) The underwater pressure showed frequency

As shown above, there is no marked difference

characteristics peaking at 6-10Hz under

between 2004 and 2003 in species observed at thestrong wind, which is similar to thefoundations, with higher individual number

bandwidth specific to noise arising fromidentified in 2004 than 2003. However, it is still

wave disturbance. This similarity suggests

too early to derive a conclusion from thesethat the waters under survey significantly

research findings only, because aquatic habitats

disturbed by the adjacent breakwater under

undergo a natural process of change dynamically.

strong wind in turn affected the underwater

Follow-up survey and monitoring of aquaticsound pressure to a large extent.

community is required on a continued basis.

(3) The number of fish species observed in thewater around the off-shore windmill showed

Table 2: Aquatic community survey: 2004
st.1
st.4
st.7
Southern Northern
Reef
foundation foundation
(0m)
(0m)
Hexagrammos otakii
84Oplegnathus fasciatus
8
Sebastes thompsoni
40
Ditrema temmincki
30
1050
Cottidae3
Pleuronectidae
1
Stephanolepis cirrhifer
11
Takifug niphobles
Sparidae
Stichaeidae
Callionymidae
Pterogobius zacalles
20
Scientific namest.8
Breakwater

no significant change from 2003 to 2004,

st.3
Southernpoint(200m)

st.6
Northernpoint(200m)

4while the individual number increased in
2004 from the previous year.

References:

50
413

32541

[1] Ports and Harbors Bureau, Ministry of Land,
Infrastructure and Transport, Japan: The Status

1of Wind Power Farms in Ports and Harbors(http://www.mlit.go.jp/kowan/index.html)[2]Basic and Applied Marine Acoustics, compiledby the Marine Acoustics Society of Japan,
Seizando-shoten, 2004)