Tokyo Gate Bridge 2 Solar Heat-blocking Pavement 5 Seismic Retrofit Technique of Asphalt Concrete Pavements 8 Implementation of tsunami disaster management 11 CONTENTS Infrastructure Development Institute – Japan (IDI) New Kojimachi Bldg, 5-3-23, Kojimachi, Chiyoda-ku, Tokyo, 102-0083, JAPAN Tel: +81-3-3263-7813 Fax: +81-3-3230-4030 E-Mail: [email protected] Homepage: http://www.idi.or.jp/english/00index.htm Tokyo Gate Bridge IDI IDI QUARTERLY QUARTERLY Japanese Infrastructure Newsletter Infrastructure Development Institute—JAPAN July 2012 No.60
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Tokyo Gate Bridge 2
Solar Heat-blocking Pavement 5
Seismic Retrofit Technique of Asphalt Concrete Pavements 8
Implementation of tsunami disaster management 11
C O N T E N T S
Infrastructure Development Institute – Japan (IDI) New Kojimachi Bldg, 5-3-23, Kojimachi, Chiyoda-ku, Tokyo, 102-0083, JAPAN
We will make financial assistance for the development
of hazard map and photo images. Since tsunami
spreads wide areas on earth, we have to continue
observation and research activities in collaboration
with other countries.
2.Basic concept for the restoration of damaged
coastal levee
On July, 2011, “Assumed tsunami height for design”
was issued for the coastal levee. On November, 2011,
“Basic concept for the restoration of damaged coastal
levee” was proposed. The following 3 points are basic
concept for the restoration of damaged coastal levee.
(1) We will determine the size of tsunami and its
height for levee design purpose
(2) We will adopt such design, that in case actual
tsunami exceeds the design height, the levee still
stands for alleviating tsunami damages.
(3) Quake-resistance countermeasures are necessary
for levees against such earthquake that causes
tsunami.
(1)How to determine tsunami height: Standard for the
decision of the coastal levee height:
By taking up some portions of consecutive coast line
having similar natural characteristics, we will fix basic
parameters.
(Tsunami height design procedure)
① By checking the historical record in the past, and
studying the evidence of the past tsunami height,
we will list up tsunami height in the past.
② With using computer simulation, we will calculate
the future tsunami height.
③ Making tsunami height graphs for each coastal
areas, we will categorize tsunami according to its
frequency (once in decades, once in hundred year,
and so on)
④ Based on the result obtained in the above ③,
neighboring coastline administrator will make
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July 2012 No.60
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exchange of opinions and determine the
anticipated tsunami height.
Top height of the levee will duly be decided by the
coastline administrator, based on the design tsunami
height, taking all the factors into consideration such as
environmental preservation, natural scenery,
economics, maintenance easiness, construction
easiness and public utilizations.
(2)Adoption of levee strcuture that can withstand
unexpectedly high tsunami height
We have analyzed coastal levee damages and its
mechanism caused by the actual tsunami hit on March,
2011. As a result of this study, we have chosen some
specific levee design structure that demonstrates an
unprecedented ability to withstand such tsunami that
has over design height.
①Scouring prevention at the bottom of back slope
After tsunami overflows the coastal levee, it flows
down on the back slope with accelerating flow velocity.
Then the water stream scours the bottom ground of the
back slope and causes damage (cf. Fig.1). In order to
prevent this, we will place a protective structure at the
bottom and cover the structure. In order to slow the
flowing speed, the back slope angle is turned to be mild
.
②Flow-away prevention of levee crown protective structure,
back slope covering structure, front slope covering
structure. Wash-away prevention of the levee body soil.
When tsunami overflows the levee, crown protective
structure, back slope covering structure, front slope
covering structure will flow away. And the levee body
soil will be washed away from the clearance of the
structure. In order to prevent this, the thickness is
increased for the protective and covering structures.
Also the connections of these individual structures
should be tightened.
③Prevention of parapet collapse
Parapet blocks tidal wave or splash flowing into coast
lines. In case of tsunami attack, the structure
sometimes collapses to the land side, sometimes
collapses to the sea side by backwash. In the design
stage, if we select outer force is tsunami instead of
storm surge, earth fill should be made to the top of the
levee structure in order to prevent crumble, or
sometimes strengthen parapet with reinforced bar. (cf.
Fig.2).
Fig. 1 Scouring prevention at the bottom of back slope (Source: Summary of the report; ”Basic concept for the restoration of coastal levee damaged by the 2011 off the Pacific
coast of Tohoku Earthquake and Tsunami” Coastal Tsunami Countermeasure Investigation Committee, MLIT)
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July 2012 No.60
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(3)A key consideration for the quake-resistance
countermeasures
The coastal levee should withstand the first
earthquake that causes tsunami. Tsunami may come
after twenty, thirty, or forty minutes after quake. If
the coastal levee were all destroyed by the first quake
vibration, it will be useless for the tsunami coming
thirty minutes later. So the quake resistance
capability should be considered.
Traditionally, we are only concerned about the
damages caused by quake vibrations. But in the case
of last year’s giant quake, coastal levee had suffered
the effect of the ground sinkage and ground
liquidations. Hence the effect of sinkage and
liquidation should also be considered and required top
height should be secured.
In case when ground sinkage is estimated as a
result of fault movement following the outbreak of
huge quake: Using computer fault model, the
degree of ground sinkage should be calculated
beforehand, and the height of levee should be
adjusted by adding sinking depth.
In case when ground liquidation is estimated:
Appropriate countermeasure should be taken.
And the height of levee should be adjusted by
adding sinkage of levee.
3.Proposal for the criteria for issuing tsunami
warning and content of information
In April, 2012, the Meteorological Agency has made
a proposal titled “Criteria for issuing tsunami warning
and content of information”. The proposal points out
that there still remain several problems in the content
of conventional tsunami warning and information
given to the general public, and clarified problematic
point and direction for improvement.
(1)Problematic point in tsunami warning and information for
the general public
Followings are the controversial point in tsunami
warning and information disclosure in the Great East
Japan Earthquake of last year.
The first tsunami warning was issued 3 minutes
after the outbreak of earthquake. However, the
magnitude of the quake and height of the tsunami
may be underestimated in the first warning, and
this misleading information led to the delay of
evacuation.
Most of all seismograph indicators went off the
Fig.2 Prevention of parapet collapse (Source: Summary of the report; ”Basic concept for the restoration of coastal levee damaged by the 2011 off the
Pacific coast of Tohoku Earthquake and Tsunami” Coastal Tsunami Countermeasure Investigation Committee, MLIT)
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July 2012 No.60
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scale due to inexperienced vibration of magnitude
9. Therefore, magnitude of the quake could not
be calculated within 10 minutes after quake
because the lack of data, Calculation was finished
and magnitude was determined using other
country’s seismographic data after 55 minutes
from the quake vibration.
The first tsunami warning contains the
information of the first wave of tsunami which is
not necessarily higher than waves afterwards, and
some local residents might have judged to stop
evacuation.
(2)Direction for tsunami warning improvement from technical
viewpoint
It is important not to issue underestimated tsunami
warning especially at the first stage of tsunami
warning. From technological point of view,
We need to introduce seismograph that will not
easily go off the scale even in severe environment.
Using the data obtained from cable-type offshore
water pressure gauges, we should quickly update
tsunami warning. And we should modify
tsunami warning based on the observation data of
actual tsunami.
(3) Criteria for issuing tsunami warning and content of
information
The conventional expression and the style of tsunami
warning and the information transmission should be
revised based on the concept; “Receiver can easily
understand tsunami information and warning.”
“Receiver can easily imagine the tsunami height and
can draw a picture of forthcoming damage in mind.”
“Receiver can immediately take action for disaster
prevention.”
Specifically, in order to transmit important
information in easy-to-understand form, we will
improve the methodology of tsunami warning and
information transmission as mentioned below, in
consideration with the accuracy of information and
releasing timing.
① Expression of mentioning tsunami height, in tsunami alert
or warning.
Simple and understandable expression should be
used (1m, 3m, 5m, 10m, over 10m, ). In case of 1
~3m, the higher side figure 3m should be used.
While the size of the quake is not well determined
yet, the expression “high tsunami” or “huge
tsunami” should be used.
Taking example of the past quake or tsunami,
such as “The magnitude with East Japan Quake
class”, we have to transmit estimated images of
abnormal situation.
② Expression to appeal immediate evacuation
In case that the tsunami is generated off the coast
of Japan, we will use the expression of “immediate
evacuation” regardless the length until estimated
time of arrival.
For the tsunami generated off the coast of Japan, its
arrival time varies from several minutes to 1 or 2 hours
from the quake vibration. If the residents judge that
there is a plenty of time to do something and let their
guard down, this might bring serious situations.
③ Expression of geographical warning/evacuation areas and
residents’ action to be taken subjected to disaster
Rough geographical area should be determined in
the early stage, and clear order must be issued on
“Who should evacuate to where”.
The necessary/sufficient and simple wording should be
used, and should clearly indicate who take what action.
For example, “Huge tsunami is coming and serious
damage will occur. People in coastal areas, or in river
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July 2012 No.60
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side, should immediately evacuate to high ground,
evacuation building, or safe locations. Tsunami comes
many times from now on. Stay in the safe place until
tsunami warning is cleared.”
On the other hand, the disaster afflicted area should
not specifically be mentioned at this stage, because
ambiguity still remains depending on the local
geography or land utilization.
Table: Tsunami height and the risk, and actions to be taken
Warning
classifications
Tsunami
height
Tsunami risk Actions to be taken
Huge tsunami warning 10m< Wooden house will collapse and flow
away. People will be swallowed by
tsunami.
People in coastal areas, river side
should immediately evacuate to the
safe areas
5-10m
3-5m
Tsunami warning 1-3m Wooden house will be inundated.
People will be swallowed by tsunami.
People in coastal areas, river side
should immediately evacuate to the
safe areas
Tsunami alert 0.2-1m Swimmers may be washed away.
Farming raft may be washed away.
Small vessel may turn over.
People staying in or close to the sea
should leave the beach.
The above table is made based on the relationships among tsunami height, flood depth, and actual damages, based on the actual tsunami data, caused by the Great East Japan Earthquake in 2011.
④Expression for the estimated arrival time of tsunami
Delay of the tsunami arrival time is a common practice Even in the adjacent forecasting areas, the arrival time
of tsunami may differ more than 1 hour. So this
information should also be transmitted. For example,
“The estimated time of tsunami arrival is the time
when the tsunami reaches to the beach in the earliest
opportunity. So there can be time difference
depending upon local conditions”.
⑤Expression for the priority when we transmit warning to the
wide area
When we issue a warning across the whole country, we
have to emphasize locations exposed to immediate
hazard. In principle, all warnings and alerts should be issued to
every district and information concerning tsunami
height and estimated time of arrival should be
conveyed. However, for such district that may be hit
by tsunami very soon, special emphasis should be
placed with flags and remarks.
⑥Content and expression for the tsunami observation data
Regarding the first wave of tsunami, actually arrived time
will only be announced and no information of tsunami
height should be released.
Observed maximum tsunami height will gradually be
announced If observed low height of first wave information is
released, and then people feel to take it easy, but much
higher second and third wave may coming soon. So
only information of arrived time and type of wave is
announced and no information of tsunami height is
released for the first wave of tsunami observation.
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4.The law regarding “Construction of
tsunami-resistant society”
When we implement the disaster restoration projects
for quake and tsunami hit areas, a far sighted strategy
is required and promotion of “Construction of
tsunami-resistant society” is required. In order to
prevent or alleviate future tsunami disasters, it is
necessary to build a general and practical system that
can be applicable nationwide, not only disaster hit
areas. To this end, the law regarding “Construction of
tsunami-resistant society” was enacted on December
14th 2011, and that is the multiple defense system
combination of hardware policy and software policy.
According to this law,
(1) Minister of MLIT will lay down basic principles,
(2) Prefectural governor will set up tsunami
inundation assumptions, and make it open to the
public,
(3) Based on the above (1) and (2), local government
will establish promotion plan,
(4) Prefectural governor can nominate “Tsunami
disaster warning district”, and within this warning
district “Special warning zone” is nominated and
land utilization may be restricted.
(5) Prefectural governor and head of local government
will construct, make improvement, and operation
and maintenance of tsunami protection facilities.
(1)Basic principles
Basic principle laid down by the Minister stipulates
the multiple defense system combining hardware policy
and software policy, based on the philosophy, “Even
though the largest class tsunami comes, we will protect
lives of citizens”, based on the experience of the Great
East Japan Earthquake.
(2)Tsunami inundation assumptions
Prefectural governor will set up worst tsunami
inundation assumptions, and implement computer
simulations and specify housing inundation areas and
water depth, and make it open to the public.
(3)Establishment of promotion plan
Local government will establish promotion plan for
“Construction of tsunami-resistant society” based on
the local demand, keeping in mind the above (1) and (2).
And in this promotion plan, the followings are
guidelines.
Local government will effectively combine hardware
facilities) and software policy (nomination of tsunami
warning district).
Also with using private facilities, local government will
secure evacuation facilities effectively.
Local government will make tsunami hazard maps and
notify to the residents, and will also implement practical
evacuation drill.
(4)Nomination of “Tsunami disaster warning district”
Prefectural governor can nominate “Tsunami disaster
warning district” for such areas that need to establish
emergency warning and evacuation systems.
Within the above “Tsunami disaster warning districts”,
prefectural governor can nominate “Tsunami disaster
special warning zone”. In this special zone, land use,
development activity and building construction shall be
limited in order to save lives and properties of the people. One of the examples of such restriction in this special
zone is that “The floor of a hospital room or elder care
facility should have a height much greater than the
estimated tsunami height, in order to save lives of
patient”.
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