Proceedings of the International Symposium on Engineering Lessons Learned fromthe 2011 Great East Japan Earthquake, March 1-4, 2012, Tokyo, JapanDAMAGE TO WATER SUPPLY SYSTEM INDUCED BYTHE 2011 GREAT EAST JAPAN EARTHQUAKE
Masakatsu MIYAJIMAProfessor, School of Environmental Design, Kanazawa University,Kanazawa, Japan, miyajima@t.kanazawa-u.ac.jp

ABSTRACT: This paper is focusing on damage to water supply facilities during the2011 great east Japan earthquake and tsunami. At first, an outline of damage to watersupply facilities is given and the damage to water supply pipelines of Sendai City isanalyzed. An abrupt increase in flow rate and a decrease in water pressure of water
distribution system in spite of no damage to pipeline were discussed through aquestionnaire survey to waterworks bureaus.
Key Words: great east Japan earthquake, water supply system, sloshing of water inreceiving tank

INTRODUCTION
This paper deals with damage to water supply facilities during the 2011 great east Japan earthquakeand tsunami. An earthquake with a magnitude of 9.0 occurred off the coast of northeast Japan onMarch 11, 2011 at 14:46 on local time. The earthquake generated a tsunami of unprecedented heightand special extent along the Pacific coast of east Japan. The earthquake and tsunami caused about
20,000 deaths and missing and injured about 6,000 people. This earthquake and tsunami also caused
extensive damage to water supply facilities. A suspension of water supply was occurred at about
2,300,000 houses in east Japan just after the earthquake. Since residents in the flooded areas bytsunami have not lived there after the event, most of damaged pipelines in the flooded areas are notrepair yet. So, we cannot collect the entire data of damage to water supply pipelines yet.
At first, an outline of damage to water supply facilities is given and the damage to water supply
pipelines of Sendai City is analyzed. Then an unusual phenomenon of distribution system is focused.
An abrupt increase in flow rate and a decrease in water pressure of water distribution system wereoccurred in spite of no damage to pipeline during the earthquake. A questionnaire survey towaterworks bureaus was conducted and situation of the unusual phenomena is revealed. The relation
to response velocity spectra of the past earthquakes was investigated and the causes of the unusual
phenomena are discussed. Finally, lessons learned from the earthquake and tsunami is considered.

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OUTLINE OF DAMAGE TO WATER SUPPLY FACILITIES
Suspension of water supply
A suspension of water supply was occurred at about 2,300,000 houses in the wide area from Tohoku toKanto regions just after the earthquake. About 90% of water outrage was recovered after one monthfrom the event except flooded areas by the tsunami. Newly damage, however, occurred by the strong
aftershocks happed in the middle of April.
Causes of damage to facilities
The damage caused by the earthquake and tsunami seems to be classified into five categories. Firstly
the causes of damage are divided by earthquake and tsunami. Causes of damage by earthquake areclassified into ground shaking itself and ground failure such as liquefaction, slope failure and etc.
Photo 1 shows damage to expansion joint of steel pipe with 2400mm diameter. This damage seems
to be caused by ground shaking and/or ground deformation. Photo 2 shows an uplift of undergroundwater tank induced by liquefaction.
Causes of damage by tsunami are classified into three categories; inundation, washing away andscouring of surface ground. Some intake facilities were inundated by tsunami and became
malfunction for long time because of high density of calcium chloride in water. Photo 3 shows
damage to a water pipe bridge by tsunami. The water pipe bridge was completely washed away.
Photo 4 shows damage to a buried pipeline. The pipeline appeared above ground after tsunami
because of scouring caused by tsunami. The mechanism of damage to pipeline, that is, how muchforce acts on a pipeline is not sure. The mechanism of this kind of damage must be clarified infuture.

Photo 1 Damage to steel pipe with 2400mm
diameter ( Miyagi Pref.)1).

Photo 2 Uplift of underground water tank
(Chiba Pref.) 2).

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Photo 3 Damage to water pipe bridge(Miyagi Pref.) .

Photo 4 Damage to pipe by scouringof tsunami (Miyagi Pref.) .

DAMAGE IN SENDAI CITY
Outline of water supply system of Sendai City
Since the damage to pipeline of Sendai City is obtained except the flooded area, damage rate ofpipelines in Sendai City is discussed here. The water supply system of Sendai City has
approximately 472,775m of transmission and distribution main pipelines. About 74% of the total
piping length is made up of ductile cast iron pipe (DIP), 24% steel pipe (SP).
Damage to pipeline
The number of damage to transmission and distribution main pipelines was 10 and that of damage to
air valve and hydrant was 43. The damage rate of pipelines, defined as the locations of damage
divided by piping length, was 0.02 (locations/km).
The total number of damage to transmission main, distribution main and branch pipelines was 264
except the flooded areas, and the piping length is 3,761km. The damage rate of transmission main,distribution main and branch pipelines was, therefore, 0.07 (locations/km) The damage rate inrelation to pipe type and pipe diameter is shown in Fig. 1 and 2, respectively. Fig. 1 indicates that thedamage rate of polyvinyl chloride pipe (VP) is high. Fig. 2 reveals that the smaller the pipe diameteris, the higher the damage rate.

Damage rate(locations/km)

0.200.15
0.100.05
0.00
DIPSPVP

Pipe typeFig. 1

Damage rate related to pipe type.

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0.200.15
0.100.05

than
less

Pipe diameter (mm)Fig. 2

Damage rate related to pipe diameter.

2.0
1.5
1.0
0.5

As
hiyNi
ash
ino
miya
Na
ga
ok
a
M
onze
Kan
shiw
az
aki

Sen

Ko
be

0.0

dai

Damage rate (locations/km)

φ100150
φ200250
φ30045m0orethan
φ5000.00
φ75

Damage rate (locations/km)

0.25

CityFig. 3Comparison of damage rate.

Fig. 3 illustrates a comparison of damage rate of Sendai City with those of other cities suffereddamage to pipeline in the past earthquakes. Kobe, Ashiya and Nishinomiya Cities suffered damage
to water supply pipeline in the 1995 Hyogo-ken Nambu Earthquake, Nagaoka City in the 2004
Niigata-ken Chuetsu Earthquake, Monzen Town in the 2007 Noto-hanto Earthquake and Kashiwazaki
City in the 2007 Niigata-ken Chuetsu-oki Earthquake, respectively. This figure revels that thedamage rate of Sendai City was very low in comparison with another cities. Magnitude ofearthquake and seismic intensity in each city were different. PGA of K-NET Sendai observation
station was, however, not small; 1,808 (cm/s/s). This value is higher than most of cities listed in Fig.
3. One of reasons of low damage rate in Sendai City seems to be high earthquake-proofing rate.
The earthquake-proofing rate is defined as the piping length of ductile cast iron pipe with earthquake
resistant joint and welded steel pipe divided by the total piping length. The earthquake-proofing rateof Sendai City is 51.2%.
Fig. 4 illustrates the relation between the earthquake-proofing rate and damage rate suffereddamage in the 2011 great east Japan earthquake. The damage rate shown in this figure is calculated
by using the damage to transmission and distribution main pipeline, that is, distribution branchpipeline is not included. This figure indicates that the higher the earthquake-proofing rate, the lower
the damage rate is. There was no damage to the ductile cast iron pipe with earthquake resistant joint.
Effect of earthquake-proofing pipe was, therefore, verified by the earthquake.

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0.25Damage rate (locations/km)

Ishinomaki, SI=6+0.20
Iwaki, SI=6-0.15
0.10

Miyagi Pref., SI=6+
Koriyama, SI=6-0.05

Ichinoseki, SI=6Sendai, SI=6+0.00
020

40

60

80

100

Earthquake proofing rate (%)

Fig. 4

Relation between earthquake
proofing rate and damage rate.

UNUSUAL PHENOMENA OF WATER DISTRIBUTION SYSTEM
Unusual phenomena such as an abrupt increase in flow rate and a decrease in water pressure of water
distribution system in spite of no damage to pipeline was occurred in several cities during the greateast Japan earthquake. Fig. 5 shows time histories of the flow rate and water pressure at a water
distribution plant of the Bureau of Waterworks Tokyo Metropolitan Government. The flow rateincreased and water pressure decreased rapidly just after the earthquake. The higher flow rate andlower water pressure were recovered after about 20 minutes. The similar phenomena were occurredagain by the aftershock.
0.3

450
400

0.25
0.2

300
250

0.15
200
0.1

150

Water pressure(MPa)

Flow rate(m3/h)

3501000.05

Flow rate(m3/h)

0Water Pressure(MPa)

50
0
14:40

14:5415:09

15:23

15:38

TimeFig. 5 Time histories of the flow rate and water pressure
at a water distribution plant of Tokyo.

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A questionnaire survey was conducted on the occurrence of the unusual phenomena of water
distribution system after the great east Japan earthquake for twenty large scale waterworks bureaus not
only in east Japan but also in west Japan. Table 1 lists the occurrence of the unusual phenomena ofwater distribution system in each waterworks bureau. The unusual phenomena occurred at even thecities where JMA seismic intensity was less than 5, that is, Yamagata, Nagoya and Osaka Cities.
Fig. 6 shows time histories of the flow rate and water pressure at a water distribution plant of theOsaka City Waterworks Bureau. This figure shows that the similar phenomena of the Bureau ofWaterworks Tokyo Metropolitan Government occurred in Osaka City where JMA seismic intensity
was 3. It suggests that the unusual phenomena depend on not only magnitude of ground shaking but
also other factors such as frequency characteristics of ground shaking.
Table 1 Occurrence of the unusual phenomena ofwater distribution system in each cities.
NameSeismic Intensity Occurrence
Sapporo City
N/A
3Aomori City
N/A
4Morioka City
N/A
5+
Akita City
N/A
5+
Sendai CityYes
6Yamagata City
Yes
4Niigata City
N/A
4Mito City
N/A
6Utsunomiya City
Yes
5+
Chiba Prefecture
Yes
5+Tokyo Metropolitan
Yes
5Saitama City
Yes
5+
Yokohama City
N/A
5+
Kofu City
N/A
5Nagoya City
Yes
4
Kanazawa City
N/A
3Osaka City
Yes
3
Kobe City
N/A
2
Hiroshima City
N/A
1

Fig. 6 Time histories of the flow rate and waterpressure at a water distribution plant of Osaka.

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Fig. 7

Response velocity spectra of recorded
waveform at Nagoya City (K-NETAIC004) and Osaka City (K-NETOSK005).

Sloshing of water
Water level before EQ

Displacement dmax

EQ Occurs
Sensor of water level

Sloshing of water inreceiving water tankSensor detects waterlevel becomes low
Draw of water

Fig. 8Mechanism of draw of water from
distribution pipe to receiving tank bysloshing during earthquake.

Fig. 7 illustrates response velocity spectra of recorded waveforms of the great east Japan
earthquake at Nagoya City (K-NET AIC004) and Osaka City (K-NET OSK005). This figure indicatesthat the predominant periods are more than one second.
Murata and Miyajima3) have considered that one of causes of the unusual phenomena seems to besloshing of water in receiving water tank. If sloshing of water in receiving water tank is occurred byan earthquake, draw of water to receiving water tank starts by error of a sensor of water level in thereceiving water tank as shown in Fig. 8. If sloshing of water in many receiving water tanks occurred
simultaneously, an abrupt increase in flow rate and a decrease in water pressure may be occurred.
Occurrence of sloshing of water in receiving water tank depends on the dimensions of receiving watertank and the height of water in the tank. Murata and Miyajima3) have investigated dimensions ofreceiving water tank in a water distribution block of Osaka City and estimated the natural period ofsloshing of the water. Fig. 9 shows cumulative percentage of natural period of water in receiving
water tank in case that the height of water is 3/4 and 1/2 of the height of water tank. The height ofwater is variable and depends on use of water. The natural period of sloshing is more than 1.0 second1473

累積度数(%)

Cumulative percentage (%)

120
1008060Long side,
Water level : 3/4
長辺幅
有効水深3/4の時

40

Short side,
Water level: 3/4
短辺側
有効水深3/4の時
Long side,
Water level : 1/2
長辺側有効水深1/2の時

20

Short side,
Water level: 1/2
短辺側
有効水深1/2の時

002

4

68

10

Naturalperiods of sloshing
固有周期(sec)of water in receiving tank (s)Fig. 9 Cumulative percentage of natural periodof water in receiving water tankof more than 80% of the water tank in the direction of long side in the water distribution block in
Osaka City. This is one example, but long period ground motion more than one second can becaused sloshing of water in receiving water tank. However, the further study is needed to clarify thecause of an abrupt increase in flow rate and a decrease in water pressure of water distribution systemin spite of no damage to pipeline and its effects to emergence response just after large scale disaster.

CONCLUDING REMARKSAn outline of the damage to water supply facilities from the 2011 great eat Japan earthquake andtsunami was presented and the unusual phenomena of water distribution system just after the event
was discussed. The following conclusions may be drawn based on the present study.
(1) The entire damage to water supply pipelines is not revealed, especially flooded areas by tsunami.
We must collect all damage data and analyze it to learn the lessons from this disaster.
(2) Effect of earthquake-proofing for pipeline was verified. We must accelerate the earthquake
proofing, especially for aged facilities.
(3) Force of tsunami acted on a buried pipe is not clear. The effect of tsunami must be studiedsoon.
(4) If sloshing of water in receiving water tank is occurred by an earthquake, draw of water toreceiving water tank from pipeline starts by error of sensor of water level in the receiving watertank. Sloshing of water in receiving water tank, therefore, may be one of the causes of unusual
phenomena.

ACKNOWLEDGEMENTS
The present paper is based on the collected from an investigation by reconnaissance team of theMinistry of Health, Labor and Welfare, Japan. Many individual and organizations generously helpedwith this investigation. This study was supported in part by the Grant-in-Aid for Scientific Researchfrom the Ministry of Education, Culture, Sports, Science and Technology, Japan (No. 20310108).

REFERENCES
1) http://www.pref.miyagi.jp/kigyo/2) http://www.minami-nagareyama.org/20110311/report03a.htm
3) Murata, K. and Miyajima, M.: Influence of Receiving Water Tank Sloshing on Water Distribution
System, Journal of Japan Earthquake Engineering, Vol. 7, No. 1, pp. 27-42, 2007 (in Japanese).

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