Tsunami and Storm Surge Hazard Map Manual

March 2004
Cabinet Office (Disaster Management)
Rural Development Bureau of the Ministry of Agriculture, Forestry and Fisheries
Fisheries Agency of the Ministry of Agriculture, Forestry and Fisheries
River Bureau of the Ministry of Land, Infrastructure and Transport
Ports and Harbours Bureau of the Ministry of Land, Infrastructure and TransportForeword
Japan lies on the boundary of tectonic plates, and is prone to tsunamis during earthquakes that occur insubmarine trenches. These have caused serious damage. Tsunamis are predicted to occur during earthquakes
along the Japan Trench and Kuril Trench and during Tokai, Tonankai, and Nankai earthquakes. The country
is also in the path of typhoons, and has frequently suffered storm surge damage. Rises in sea level due toclimatic changes and increases in the scale of typhoons will probably increase storm surges. Thus, measuresagainst tsunamis and storm surges must quickly be taken in Japan.
Advanced case studies have shown that hazard maps are an effective evacuation measure, and various
attempts have been made to prepare hazard maps for tsunamis and storm surges. However, preparation of
hazard maps that cover the entire country is at a standstill. This is probably because:
1) The staff of municipal governments in charge of disaster prevention and preparing hazard maps have noclear concept of tsunami and storm surge hazard maps,
2) The staff has no understanding of for whom tsunami and storm surge hazard maps are to be prepared, nor
how to use such maps, and
3) Preparation of tsunami and storm surge hazard maps is technically difficult and expensive.
This manual aims to promote preparation of tsunami and storm surge hazard maps that cover the whole ofJapan, and to assist the people in charge of preparation by providing information on 1) basic concepts oftsunami and storm surge hazard maps, such as the purposes of preparation, role allotment (support fromnational and prefectural governments), and utilization policies, and 2) standard methods for preparing
tsunami and storm surge hazard maps, such as methods for identifying inundation risk areas, determining
details to be stated on the maps, expressing those details, and utilizing the maps.
The manual assists in preparing and utilizing tsunami and storm surge hazard maps and shows essential
points of technological systems and utilization methods. The methods described in this manual are merely asummary at today’s technical levels, and need to be revised along with technological development. New
technologies, which are being constantly developed, should be actively incorporated according to the
purposes of this manual.
Finally, we would like to thank the chair (Prof. Yoshiaki Kawata of Kyoto University) and members of theStudy Committee on Tsunami and Storm Surge Hazard Maps, which was established in November 2002 andheld 5 meetings in total, together with the committee’s administrative staff, for their active discussion andhard work that led to the formation of this manual.
March 2004
S h u h e i K a z u s a: Counselor of the Cabinet Office (in charge of disaster prevention)
M a s a k i n e T a k e d a: Director of the Disaster Prevention and Restoration Division, Rural
Bureau of the Ministry of Agriculture, Forestry and Fisheries

Development

Tomomasa Kageyama: Director of Fishing Communities Promotion and Disaster Prevention Division,
Fisheries Agency of the Ministry of Agriculture, Forestry and Fisheries
Y u t a k a H o s o m i: Director of the Coast Office, River Bureau of the Ministry of Land, Infrastructure
and Transport
Y u t a k a S u n o h a r a: Director of the Coast Administration and Disaster Prevention Division, Ports andHarbours Bureau of the Ministry of Land, Infrastructure and Transport

Members of the Study Committee on Tsunami and Storm Surge Hazard Maps
C h a i r: Y o s h i a k i K a w a t a, Professor and Director of the Research Center for Disaster Reduction
Systems, Disaster Prevention Research Institute, Kyoto University
Members: M a s a h i k o I s o b e, Professor of Environmental Studies, Graduate School of Frontier Sciences,
The University of Tokyo
Fumihiko Imamura, Professor of the Disaster Control Research Center, Graduate School ofEngineering, Tohoku University
Toshitaka Katada, Associate Professor of the Department of Civil Engineering, Faculty ofEngineering, Gunma University
S u s u m u N a k a n o, Associate Professor of the Department of Environmental Engineering,
Faculty of Engineering, the University of Tokushima
O s a m u H i r o i, Professor of the Institute of Socio-Information and Communication
Studies
Yoichiro Fujiyoshi, Commentator of NHK, Professor of Otsuma Women’s University
T a d a s h i Y a m a d a, Professor of Hydrology Laboratory, Department of Civil Engineering,
Faculty of Science and Engineering, Chuo University
People from administrative organizations (Fire and Disaster Management Agency, Meteorological Agency,
Japan Coast Guard, and municipal governments) also participated.
Meetings held on:
November 22, 2002
February 25, 2003
May 1, 2003
June 17, 2003, andDecember 16, 2003

Table of contents
ManualIntroduction....................................................................................................................................................... 1
Chapter 1 Need for and roles of tsunami and storm surge hazard maps………………………………..….. 4
1.1 Present state of measures for preventing disasters caused by tsunamis and storm surges…………… ..4
1.2 Issues concerning disaster prevention measures against tsunamis and storm surges………………… ..9
1.3 Direction of development of measures to prevent disasters caused by tsunamis and storm surges…...15
1.4 Roles of hazard maps as a measure for preventing disasters by tsunamis and storm surges…………..21
Chapter 2 Overview of tsunami and storm surge hazard maps…………………………………………….24
2.1 Purposes of preparing tsunami and storm surge hazard maps…………………………………………24
2.2 Target disasters and range of tsunami and storm surge hazard maps………………………………….25
2.3 Bodies in charge of preparing tsunami and storm surge hazard maps and their roles…………………26
2.4 Forms and expressions of hazard maps………………………………………………………………...29
2.5 Procedure for preparing tsunami and storm surge hazard maps……………………………………….30
2.6 Utilization of hazard maps during evacuation…………………………………………………………33
Chapter 3 Methods for identifying inundation risk areas…………………………………………………...34
3.1 Characteristics of tsunamis and storm surges…………………………………………...……………..34
3.2 Conditions for identifying inundation risk areas……………………………………………………….37
3.3 Choosing a method for predicting inundation………………………………………………………….41
Chapter 4

Methods for preparing tsunami and storm surge hazard maps from the results of inundation
prediction………………………………………………………………………………...………49
4.1 Considerations for preparing hazard maps for specific purposes……………………………………...49
4.2 Information to be included in hazard maps for residents………………………………………………54
4.3 Information to be included in hazard maps for administrators……………………...…………………58
4.4 Methods for displaying predicted inundation risk areas and evacuation zones………...……………...60

Chapter 5 Use of tsunami and storm surge hazard maps…………………………………..……………….65
5.1 Disseminating tsunami and storm surge hazard maps…………………………………………………65
5.2 Ways to promote the understanding of residents about hazard maps………………………………….67
5.3 Utilization of tsunami and storm surge hazard maps for developing measures against tsunamis andstorm surges……………………………………………………………………………………………72
5.4 Review and revision of tsunami and storm surge hazard maps………………………………………..75
5.5 Measures for encouraging preparation…………………………………………………………………76

References
Reference 1: Predicting inundation by time-series numerical simulation……………………………………78
Chapter 1 Calculations for predicting inundation during tsunamis………………………………………...78
1.1 Flow of calculations for predicting inundation………………………………………………………...78
1.2 Earthquake fault model………………………………………………………………………………...79
1.3 Initial water level simulated by the earthquake fault model…………………………………………...81
1.4 Grid intervals…………………………………………………………………………………………..82
1.5 Elevation……………………………………………………………………………………………….84
1.6 Conditions of river topography………………………………………………………………………...88
1.7 Tide (astronomical tide)………………………………………………………………………………..89
1.8 Conditions of structures………………………………………………………………………………..89
1.9 Damage to structures during earthquakes……………………………………………………………...90
1.10 Method of numerical analysis for tsunami……………………………………………………………90
Chapter 2 Calculations for predicting inundation during storm surges……………………….……………92
2.1 Flow of calculations for predicting inundation………………………………………………………...92
2.2 Scale and route of typhoon……………………………………………………………………………..93
2.3 Tide (astronomical tide)………………………………………………………………………………..94
2.4 Calculated wave height………………………………………………………………………………...95
2.5 Grid intervals…………………………………………………………………………………………...95
2.6 Elevation……………………………………………………………………………………………….95
2.7 Run-up along river……………………………………………………………………………………..96
2.8 Conditions of structure damage………………………………………………………………………..96
2.9 Operational states of facilities………………………………………………………………………….97
2.10 Method of numerical analysis for storm surge………………………………………………………..97
Reference 2: Examples of utilizing tsunami and storm surge hazard maps for developing measures forpreventing disasters……………………………………………….……….……….……...…..99
1. Methods for enhancing residents’ self defense capabilities by utilizing tsunami and storm surge hazard
maps……………………………………………………………………………………………………100
2. Drawing up evacuation plans by using tsunami and storm surge hazard maps (for administrative
bodies)…………………………………………………………………………………………………...102
3. Investigating emergency measures and restoration plans using real-time information………………..109
Reference 3: List of related web sites……………………………………………………………………….111
Rider: Explanation of terms…………………………………………………………………………………112

Introduction
Tsunami and storm surge hazard maps show areas on which inundation is anticipated, the degree ofinundation and, when necessary, disaster prevention information, such as evacuation sites and routes.
Their purpose is to assist administrative bodies in deciding evacuation of residents during tsunamis andstorm surges, and in the construction of disaster prevention facilities.
This manual aims to promote the nation-wide preparation of tsunami and storm surge hazard maps. It
states basic concepts such as the objectives of preparation, bodies in charge of preparation, roles ofnational and prefectural governments, and utilization methods, and summarizes the presently available
standard information concerning tsunami and storm surge hazard maps, such as methods for predicting
inundation, items to be included in hazard maps, expression methods, and methods for utilizing themaps.

(1) Definition of tsunami and storm surge hazard maps
Hazard maps ・In this manual, maps that show predicted inundation risk areas and, when necessary,
information related to disaster prevention are called “hazard maps”.
・ This manual describes “hazard maps for residents”, which should be used byresidents for evacuation, and “hazard maps for administrators”, which should be
used by administrative bodies to investigate disaster prevention measures.
Inundation risk ・In this manual, an area where inundation is predicted when an assumed external forcearea(tsunami and storm surge) occurs is called an “inundation risk area”.
Assumed・In this manual, external forces of the following three levels are considered asexternal force
assumed external forces. Details of the methods for setting the external force
conditions are described in 3.2 (2) Setting external force conditions.
1) External force level 1: External force that occurs at frequencies that can be sensed
2) External force level 2: Designed external force of a facility, consistent with its
protection goal
3) External force level 3: External force that causes the worst degree of inundation(2) Anticipated readership of the manualThis manual is for bodies in charge of preparing tsunami and storm surge hazard maps and those who
support such preparation (See 2.3 Bodies in charge of preparing tsunami and storm surge hazard maps andtheir roles, for information about bodies in charge of preparation and supporting bodies).
(3) ScopeThis manual describes the preparation and utilization of tsunami and storm surge hazard maps. It should
be used in conjunction with existing plans and manuals, such as regional disaster prevention plans and theManual for Developing Measures Against Tsunamis.
This manual summarizes the presently available knowledge and should be appropriately revised inaccordance with future technology development.

1

Disaster

TsunamiReference Existing manuals related to tsunami and storm surge measures
Manual (date of issue)
Body in charge
Manualforenhancing Investigation Committee on Disaster Prevention Plan
measures against tsunamis in Methods against Tsunamis along the Pacific Coast during
regional disaster prevention Earthquakes (National Land Agency, Agricultural Structureplans (March 1998)
Improvement Bureau and Fisheries Agency of the Ministryof Agriculture, Forestry and Fisheries, Ministry ofTransport, Meteorology Agency, Ministry of Construction,
and Fire and Disaster Management Agency)
ManualTsunami1998)

forPredicting Investigation Committee on the Manual for Predicting
Disasters (March Tsunami Disasters (National Land Agency, Fire andDisaster Management Agency, and Meteorological Agency)

ManualforDeveloping Investigation Committee on the Manual for Promoting
Measures against Tsunamis Measures against Tsunamis (Fire and Disaster Management(March 2002)
Agency)

Storm
surge

Manualfor
Enhancing
MeasuresagainstStorm
Surges in Regional Disaster
Prevention
Plans(March
2001)

Study Committee on Storm Surge Disaster Prevention
Information(Cabinet Office (in charge of disaster prevention), Fire andDisaster Management Agency, Rural Development Bureau
and Fisheries Agency of the Ministry of Agriculture,
Forestry and Fisheries, River Bureau and Ports andHarbours Bureau of the Ministry of Land, Infrastructure andTransport, Meteorological Agency)2(4) Organization of the manualThis manual consists of the main chapters (1-5) and references. The main chapters summarize the basic
concepts of significance and methods for preparing and utilizing tsunami and storm surge hazard maps. The
references describe recommended methods for predicting inundation to prepare tsunami and storm surge
hazard maps and examples of using such hazard maps.
Since tsunami hazard maps and storm surge hazard maps have much in common, the common information
is first described and second the phenomenon and operation methods that differ between tsunamis and storm
surges are described separately.
ManualChapter 1 Need for and status of tsunami and storm surge hazard
maps

References

Chapter 2 Overview of tsunami and storm surge hazard maps

Chapter 3 Methods for investigating inundation risk areas

Chapter 4 Methods for preparing tsunami and storm surge
hazard maps from the results of inundation prediction

Chapter 5 Publishing tsunami and storm surge hazard maps,
informing residents, and utilization

Reference1: Predicting inundation by time-series
numerical simulation
1. Calculations for predicting inundation during
tsunamis
2. Calculations for predicting inundation duringstorm surges

Reference 2: Examples of utilizing tsunami andstorm surge hazard maps for developing measuresfor preventing disasters caused by tsunamis andstorm surges

Reference 3: List of related web sites

Constitution of the manual3Chapter 1

Need for and roles of tsunami and storm surge hazard maps

1.1 The present state of measures for preventing disasters caused by tsunamis and storm surges(1) History of measures for preventing disasters caused by tsunamis and storm surges
Conventional disaster prevention measures, which mainly rely on facility construction, have sharply
reduced damage by tsunamis and storm surges. However, the level of coastal safety is still insufficient.

Measures for coastal protection against tsunamis and storm surges have changed as described below.
These measures have sharply reduced damage.
(1) After World War II, Japan suffered serious damage from tsunamis and storm surges. Ways to protect
coasts at that time mainly consisted of restoration activities.
(2) The Coast Law was enacted in 1956, around which time the construction of structures, such as banks,
revetments, groins, and parapets, started to protect coastlines under the concept of “the linear protection
method”.
(3) After 1975, projects based on the concept of “the area protection method” started, including constructing
two or more structures (detached breakwaters, submerged breakwaters, artificial reefs, and sandy beaches) togradually reduce external forces such as waves.
(4) Subsequently, more advanced structural measures were taken by employing earthquake resistant
structures and anti-liquefaction structures. Non-structural measures were also taken by constructing tsunami
and storm surge disaster prevention stations.
【Damage by storm surge in the past】
Persons

Houses300,000

100,000

263,087Houses

250,000

Damage tobuildings

222,931Houses

Injury topeople200,000
154,709Houses

150,000

80,00060,00048,463Persons

40,00038,229Persons

100,000
21,996Persons

20,00050,0004,870Houses
1,095Houses 1,580Persons
1,326Persons

0

0

1912
1935

1936
1955

1956
1975

1976
1995

After 1995-

* Source: Announcement (Dec. 31, 2002) by the Fire and Disaster Management Agency. “Injury to people” denotes the total numberof people killed, injured and missing. “Damage to buildings” denotes the total number of buildings destroyed, semi-destroyed, andwashed away.

Figure 1.1.1 Reduction of storm-surge damage by disaster prevention measures

4However, the present protection levels far from satisfy the indices for protection, information transmission,
erosion and earthquake resistance, which are shown in Table 1.1.1.
Table 1.1.1

Present protection levels of coastal protection
Outcome index
Present level
Class
Population and area of districts where a certain level of safety
3.9 million people
Protection is not ensured against tsunamis and storm surges
150 thousand ha
Population and area of districts where there is risk due to
1.4 million people
50 thousand hainsufficiency of facilitie
Number and percentage of districts where it takes too long to
180 districts 17%
close water gates and prepare against tsunamis, etc.
Tsunami:Number and percentage of districts where necessary tsunami 1,200 districts 62%
Storm surge:
and storm surge hazard maps have not been prepared
Information
1,500 districts 88%
transmission
Number and percentage of districts where necessary
information facilities for coastal risk management are 1,000 districts 43%
insufficient
Length and percentage of eroded/eroding coasts where erosion
750 km 24%
Erosioncontrol facilities have not been completed
Percentage of coasts which need to be restored but have not yet
45%
Population and area of districts protected by insufficient
1 million people
Earthquake facilities
40 thousand haresistance Population and area of zero-elevation districts that are prone to 200 thousand people
12 thousand ha
floods by earthquakes
Cited from “Report on New Coastal Protection Methods based on Intermediate-term Prospects” (February 13, 2003,
Investigatory Committee on New Coastal Protection Methods based on Intermediate-term Prospects)

Length of facilities completed:
about 61%
Length not yet completed:
施設
未整備延
about
39%

Length of facilities needing
improvement: about 13%

Cited from “Reference for Investigating New Coastal Protection
Methods based on Intermediate-term Prospects” (May 2002)

The required safety is not ensured in 150 thousand ha of coastal
area to protect, where about 3.9 million people live.
Figure 1.1.2

Completion state of coastal protection facilities

5Figure 1.1.2 Transition of coastal protection concept(Period)(Laws)

1945-1954(Projects)

Storm surge prevention project (1949)(Concepts of coast protection)(Disasters)

Restoration of damage

Many typhoons struck Japan (1948 to 1951)

Erosion prevention project (1952)
Local improvement project (1952)
Disaster restoration support project (1952)
Disaster related project (1954)
1955-1964

Coast law enacted (1956)
Ise Bay storm surge countermeasures project(1959-1964)
Structure standards prepared(1958)

Rapid progress of coast engineering
Typhoon No. 13 (1953)

Main structural measures: banks,
groins, revetments, and parapets

Chile earthquake tsunami countermeasures project(1960-1966)
Projects under direct control of the national
government started (1960)(Background)

Kanogawa typhoon(1958)

Restoring exhausted country was thefirst priority

Isewan typhoon(1958)
Chile earthquake tsunami(1960)
Dai-2 Muroto typhoon(1961)

Linear protection method

Committee for coast protection administrative central office liaison
established (1963)
1965-1974

Typhoon No. 26 struck Shizuoka (1966)
First detached breakwater

Tokachioki earthquake tsunami (1968)

Increasing
recreation

demandforseasideFive-year project started (1970)
Typhoon No. 10 struck Kochi (1970)
Environment improvement project (1973)
1975-1984

Protecting merely at coast lines isinsufficient.

Typhoon No. 16 struck Kochi (1974)

Coast cleaning project (1975)

Advancing coastal erosion

Seawall construction projects for public land
reclamation (1976)
Repair project (1978)

Ilegal disposal of oil drums at Osaka
Bay (1971)

Typhoon No. 20 struck Kochi and Shizuoka(1979)
Combination of various
countermeasures to protect coastal“areas”

Rapid economic growth
Promoting high-quality infrastructuredevelopment

Gentle-slope revetments constructed.
Coast law agreement (1982)
Nihonkai Chubu earthquake tsunami (1983)
1985-1988

Artificial reef constructed
Okinotorishima protection project (1987-1993)
Headland defense works developed
CCZ project (1987)

Area protection method

Coastal erosion observed in manyareas
Typhoon No. 19 struck Kochi (1987)

Enhanced awareness of the natural

6

environment
1989-1993

Coastal spaces with diverse values

Basicenacted1995

environment

Typhoon No. 11 struck Kagoshima (1989)
Typhoon No. 19 struck many areas of Japan(1990)
Hokkaido Nansei-oki earthquake tsunami(1993)
Hyogo-ken Nanbu earthquakelawLong-term vision for the coast

Measures forenvironments

restoringseaside

and

green

Promotingadministrative/financial
reformPromoting decentralization of power

Harmonizing disaster prevention,
public use and environment
1996

Sixth seven-year project (to 2002)
Eco-coast project
Constructing healthy seaside and green areas

1997

Environment assessment law
enactedComprehensive soil control
subcommittee report1998

Law on prevention of marine
pollution and accidents revised
Proposal from the Coast
management
investigationcommittee
The Coast law revised

1999
2000

2001

2002

Revised coast law enacted
Basic coast protection policies
drawn upPetroleum leak from a ship, Nakhodka

Nagisa project (sand bypass)
Iki-iki umino-ko hama-zukuri project

Direct control of Okinotorishima Island

Comprehensive coastal management

Tyhoon No.18 caused storm surge damage
to western part of Japan

Project for constructing marine and forest
environments rich in natureUrgent projects against large driftwood, etc. during
disasters
Typhoon No. 11 caused storm surge damage

Tsunami and storm surge disaster prevention
stations
Comprehensive grant-aid system for repairingdamageInvestigatory committee on the implementation of a new medium-term coastal
protection
Advanced coastal risk management project
Integration of the grant-aid systems for seawall
construction projects for public land reclamation
Reference: Takeshi Koike, “Past, Present and Future of Coast Disaster Prevention Measures” (September 2002, 2002 Summer Meeting on Water Engineering, Japan Society of Civil
Engineers)

7

Manual2) Present safety against tsunamis and storm surges
Even districts where facilities to counter tsunamis and storm surges are completed may still suffer
damage when the levels of tsunamis and storm surges exceed the assumed levels, and may not be always
safe.
Recent technology has improved prediction accuracy and has revealed that external forces exceeding
the present protection level can possibly occur, and may thus cause tsunami and storm surge damage.

Even districts where protection facilities are completed may still suffer damage by external forces
exceeding the assumed levels. These include such places as Okushiri Island, which suffered tsunami
damage during the Hokkaido Nansei-oki Earthquake in 1993, and Kumamoto Prefecture, which suffered
storm surge damage in 1999.
Recent progress of technology has improved the performance of computers and the precision of
measurements (such as reduced grid sizes for ground elevation measurements) and enabled floods andresultant damage to be predicted accurately. The improvement of accuracy has changed the calculated
scale of external forces of tsunamis and storm surges even when the calculations are made using the same
conditions. The new estimated values exceed the present protection level at some sections of coast,
revealing the true risk of tsunamis and storm surges.
Even areas where structures are completed, as well as those where structures are not completed, are notalways safe against tsunamis and storm surges.

8

1.2 Issues of disaster prevention measures against tsunamis and storm surges(1) Urgency of disaster prevention measures against tsunamis and storm surges
Japan has been frequently struck by earthquakes and has suffered damage caused by tsunamis triggeredby large submarine earthquakes. Tsunamis caused by distant earthquakes, such as the Chile Earthquake,
have also struck Japan, and damage by future tsunamis is a concern. A large earthquake is predicted tooccur at any time soon in the Tokai Area, and Tonankai and Nankai earthquakes are predicted to occur inthe first half of this century. Large earthquakes in the Japan and Kuril Trenches are predicted to cause
large-scale tsunamis.
Comprehensive measures for preventing disasters and mitigating damage during tsunamis must be
urgently and systematically established.
Damage caused by storm surges is recently increasing. Although anti-storm-surge facilities have beensteadily constructed since the Isewan Typhoon, there are still districts affected by storm surges.

1) Time urgency of measures against tsunamis and storm surges
Japan is located on the boundary of tectonic plates that has been frequently struck by earthquakes andtsunamis, the latter arising when large earthquakes occur under the sea. Many large-scale ocean trench type
earthquakes are known to repeatedly occur at certain intervals, and they are predicted to cause tsunamis.
Tokai, Tonankai and Nankai Earthquakes are predicted to occur at intervals of about 100 to 150 years,
and have caused serious damage not only by their strong seismic motions but also by accompanied
tsunamis. Coastal areas suffered serious tsunami damage during the Meiji Sanriku Earthquake, Showa
Sanriku Earthquake, and Tokachioki Earthquake, all of which occurred along the Japan and Kuril Trenches,and during earthquakes that occurred along the eastern edge of the Sea of Japan, such as the Nihonkai
Chubu Earthquake and Hokkaido Nanseioki Earthquake. Moreover, the Chile Earthquake, which occurred
far from Japan, also caused serious tsunami damage.
Especially, a Tokai Earthquake is predicted to occur at any time soon, and Tonankai and Nankai
earthquakes are predicted to occur in the first half of this century. A large-scale earthquake will also occur
off the coast of Miyagi Prefecture in the next 30 years. These earthquakes are imminent.
Conventional technologies cannot accurately predict the time and place of an earthquake, and otherearthquakes may also occur soon.
The imminence of major earthquakes and major earthquake disasters during and after the Showa Period
are shown in Tables 1.2.1 and 1.2.2, respectively.
Recent earthquakes include the Tottori-ken Seibu Earthquake (October 6, 2000, M7.3), the Geiyo
Earthquake (March 24, 2001, M6.7, killed 2), the earthquake off the cost of Miyagi Prefecture (May 26,
2003, M7.0), the earthquakes in the northern part of Miyagi Prefecture (July 26 to 28, 2003, M5.1 to 6.4),
and the Tokachi-oki Earthquake (September 26, 2003, M8.0). Especially, the Tokachi-oki Earthquake
caused tsunami damage.

9

Predicted earthquake
Tokai Earthquake
Tonankai Earthquake
Nankai Earthquake

Table 1.2.1 Imminence of earthquake
Imminence and probability

Magnitude

Note

Soon

M8.0

1)

In the first half of this century
Within 30 years 50%
In the first half of this century
Within 30 years 40%

M8.2
M8.6
-

2)
3)
2)
3)

Inter-plate earthquake along a
trench (Sanriku-oki to Boso-oki) Within 30 years(tsunami-causing earthquake)

20%

M8.2

4)

Miyagi-ken Oki Earthquake

90%

M7.5

4)

Within 30 years

Notes:
1) Central Disaster Prevention Council, “Research Committee on Measures against Tokai Earthquakes” (December 2001)
2) Central Disaster Prevention Council, “Research Committee on Tonankai and Nankai Earthquakes” (December 2003)
3) Center for Earthquake Studies, “Long-term evaluation of Nankai Trough Earthquakes” (September 2001)
4) Earthquake Investigatory Committee of the Center for Earthquake Surveys (September 2002)

Date
March 7, 1927
November 26, 1930
March 3, 1933
September 10, 1943
December 7, 1944
January 13, 1945
December 21, 1946
June 28, 1948
May 23, 1960
May 26, 1983
July 12, 1993
January 17, 1995

Table 1.2.2 Major earthquakes since the Showa Period
M*
Deaths**
Name
7.3
2,925
Kita Tango Earthquake
7.3
272
Kita Izu Earthquake
1,522
8.1
Showa Sanriku Earthquake
1,542
7.2
1,083
Tottori Earthquake
7.9
998
Tonankai Earthquake
6.8
1,961
Mikawa Earthquake
1,330
8.0
Nankai-do Earthquake
113
7.1
3,769
Fukui Earthquake
122
9.5※ Tsunami by Chili Earthquake
20
7.7
104
Nihonkai Chubu Earthquake
201
Hokkaido
Nansei-oki
7.8
Earthquake
29
6,432
7.3
Hyogo-ken Nanbu Earthquake
3

Tsunami
○
○
○
○
○

○
○
○
○

* Scale of the earthquake (magnitude), provided, moment magnitude for the Chile Earthquake** The upper figure denotes the number of people killed. The lower denotes the number of people missing. (Data cited from
Usami, “Nihon Higai Jishin Soran” (Earthquake damage in Japan, in Japanese), reference by the Fire and Disaster Management
Agency)Reference: Website of the Meteorological Agency

On the other hand, coastal improvement works have avoided suffering serious damage from storm
surges since the late 1960s in Japan. However, the country is frequently struck by typhoons and is still
prone to serious storm surge damage. For example, Typhoon No. 18 in 1999 affected Kumamoto and10

Yamaguchi prefectures, and killed or injured many people. The risk of storm surges is possibly
increasing due to rises in sea levels and increases in the size of typhoons due to climatic changes. Major
damages occurred by storm surges are shown in Table 1.2.3.

Date
1934/09/21
1942/08/27
1945/09/17
1950/09/03
1959/09/26
1961/09/16
1985/08/30
1999/09/24

Table 1.2.3 Major storm surge disasters during and after the Showa Period
Injury to people
Principal
Damage to buildings
Typhoonaffected
SemiWashed
Killed Injured Missing Destroyed
area
destroyed away
Osaka Bay
2,702
14,994334
38,771
49,275
4,277 Muroto
Shubonada
891
1,438
267
33,283
66,4862,605Southern
2,076
2,329
1,046
58,43255,0062,546 Makurazaki
KyushuOsaka Bay
393
26,062
141
17,062
101,792
2,069 JaneIse Bay
4,697
38,921
401
38,921
113,052
4,703 Isewan
Osaka Bay
185
3,879
15
13,292
40,954536 Muroto II
Ariake
3
16
0
0
589
－
No. 13Bay
Sea of
12
10
0
52
102
－
No. 18
YashiroReference: Website of the Cabinet Office (in charge of disaster prevention)

2) Urgency of disaster prevention measures against tsunamis and storm surges
Clearly, tsunamis and storm surges can occur at any time. However, the implementation of structuralcountermeasures requires a huge amount of expense and time, and comprehensive countermeasures should
be developed by incorporating non-structural countermeasures, so that damage can be minimized.
The Central Disaster Prevention Council investigated measures against tsunamis that may occur by large
earthquakes, such as Tokai, Tonankai and Nankai Earthquakes, and reported.

Extract from the “Outline of Measures against Tokai Earthquakes”
Urgent execution of measures for assisting evacuation during tsunamis
National and regional public bodies shall urgently prepare tsunami hazard maps of coastal area
based on the predicted damage, etc., ensure that all people have sufficient knowledge of tsunamis,
draw up plans for evacuation of each region during tsunamis, and promote systems for evacuation
during tsunamis.
Evacuation sites and routes shall be quickly constructed in coastal areas by appropriately utilizing
projects of various kinds and giving priority to areas of the greatest need. Also, facilities for quick
evacuation, such as evacuation signs, shall be quickly installed. In areas where evacuation sites are
difficult to construct, evacuation sites shall be quickly ensured by utilizing private buildings and otherstructures that have enough resistance to predicted tsunamis.
Quick transmission of tsunami warnings, etc., is very important to appropriate evacuation fromtsunami regions. Thus, regional public organizations shall urgently install radio transmission systems
and form a network of such systems. For appropriate evacuation of tourists, such as sea bathers,
information transmission systems shall be developed, and signs of various kinds shall be posted toestablish consciousness among them of the need for evacuation from tsunamis.
Reference: “Outline of Measures against Tokai Earthquakes” (May 29, 2003, Central Disaster Prevention Council)

11Extract from the “Outline of Measures against Tonankai and Nankai Earthquakes”
Establishing disaster prevention systems against tsunamis
Tonankai and Nanaki earthquakes may occur in the first half of this century and cause serious
damage over large areas. Comparing this with the damage by the anticipated Tokai earthquake, thedamage could be more serious, especially by tsunamis. Thus, facilities must be systematically andsteadily improved by inspecting anti-tsunami installations, such as coastal and river banks, forearthquake resistance and reinforcing them.
To mitigate damage caused by tsunamis, appropriate evacuation is important. The damage predicted
by investigatory committees also shows that injury to people can be sharply reduced if residents arehighly aware and take quick evacuation action of tsunamis. Intensive education is very important in
districts where there is risk of large tsunamis. Measures against tsunamis, both structural andnon-structural, must be developed; for example, constructing evacuation sites and studying evacuationroutes in advance.
Reference: “Outline of Measures against Tonankai and Nankai Earthquakes” (December 16, 2003, Central Disaster Prevention
Council)(2) Issues concerning tsunami and storm surge disaster prevention in coastal areas
While the urgency and importance of disaster prevention during tsunamis and storm surges arerecognized, there are three issues to be resolved in disaster prevention during tsunamis and storm surges
in coastal areas: 1) reduced self-defensive capability of residents due to lack of awareness, 2) coastal
characteristics prone to disasters, and 3) difficulty of identifying areas that need evacuation.

There are following three issues of disaster prevention during tsunamis and storm surges in coastal
areas:
1) Reduced self-defensive capability of residents due to lack of awarenessA person must always be aware of the danger of disasters in order to defend himself from the danger.
People’s awareness of tsunamis and storm surges rose a great deal after the tsunami during the Hokkaido
Nansei-oki Earthquake, the Hyogo-ken Nanbu Earthquake, and storm surge disasters during Typhoon No.
18 in 1999. However, such awareness level is rapidly decreasing as the years pass by.
【Decreasing awareness level of disaster prevention】

July 1991

40.7

September 1995

59.1

September 1997

57.9

June 1999

50.2

September 2002

46.6
0

10

20

30

40

50

60

70 %

Cited from the 2003 disaster prevention white paper “Public Opinion Poll on Disaster
Prevention” (September 2002, Cabinet Office)Figure 1.2.1 Decreasing awareness level of disaster prevention
To minimize damage to people during tsunamis and storm surges, they themselves need to appropriately

12evacuate dangerous areas based on information from administrative bodies and the mass media. Thus,
residents need to be always aware of the danger of tsunamis and storm surges, be prepared for disasters,
and know the norms of actions to take. However, their awareness of disaster prevention is fading as theyears pass by after the Hokkaido Nansei-oki Earthquake, the Hyogo-ken Nanbu Earthquake and the storm
surge during Typhoon No. 18 in 1999. Various projects which steadily improves protection for coastal
areas also help accelerate such tendancy.
Administrative bodies, which are to support residents in evacuation and undertake regional disasterprevention activities, should bear important roles since local communities lack strong relationship among
their residents, but the number of administrative staff who have actually experienced disasters isdecreasing. Local residents and administrative bodies need to cooperate in flood fighting activities, but agreat concern is declining self-defensive capability, due to the residents’ decreasing awareness of the risk
and the decreasing number of capable staff in local governments.

[Column: Disaster prevention awareness and evacuation behavior]Kesennuma City was struck by tsunamis during the Sanriku and Chile Earthquakes. The area has beenvery conscious of tsunami disaster prevention, and tsunami disaster prevention maps have been
distributed to the residents. During the Sanriku Minami Earthquake on May 26, 2003, approximately 90%of the residents spontaneously thought about the possibility of a tsunami. However, only 10% took
evacuation action and the majority did not evacuate but stayed at home collecting information throughTV, etc. until an announcement declared no tsunami 12 minutes after the earthquake. Even people whoare very conscious of disaster prevention do not always take evacuation action, which clarifies thatmethods for enhancing people’s awareness level and for giving them information regarding evacuation
should be improved to bridge knowledge and action.
Do not remember.
Never heard about
3.7%
it.

Was engaging indisaster prevention
activities

Did not think
about it.

Do not remember.

1.8%

Never seen it. 9.7%

12.8%

5.2%

Evacuated.
8.8%

9.7%

Have
heard about it.
聞いたことがある
94.5%
94.5

Do you know abouttsunamis?

見たことはない25.0%

Thought abouttsunamispontaneously.

Have seen it.
見たことがある
65.3%

87.2%

Have you seen a disasterprevention map?

Did you think about atsunami during theearthquake?

Did not evacuate.
避難しなかった
86.0%

What did you do during
the earthquake?

Reference: May 26, 2003, “Survey report on evacuation of Kesennuma citizens from tsunami during the Sanriku Minami
Earthquake”(September 2003, Katada Laboratory, Department of Civil Engineering, Faculty of Engineering, Gunma University)2) Coastal characteristics prone to disasters

13

Japan is surrounded by sea and has coastal characteristics prone to damage from tsunamis and storm
surges. Compared to European and North American countries, Japan has long coasts in relation to its area.
Thus, it needs a vast amount of time and expense to construct coast protection facilities.
Especially, large cities, in which population and assets of various kinds are concentrated, have recently
expanded toward the sea, including residential areas and districts covering various city functions, andbecomes a concern for great damage by tsunamis and storm surges. On the other hand, in districts where
the mountains are close to the sea, villages are scattered in a narrow strip of lowland. Protection of thesevillages from tsunamis and storm surges is a difficult but important issue. Coastal erosion has been noticed
in various parts of Japan since the late 1950s, and non-experienced areas of tsunamis and storm surges
could be struck by such disasters in future.
In lowlands, where the elevation is almost zero, storm surges and tsunamis are known, from the pastinundation record, to cause large areas to inundate. Thus, even sites far from the coast are not always safe.
When a large earthquake occurs near the coast, the resultant tsunami will reach the coast very fast, andthere will be little time to evacuate. Storm surges, which can be predicted to a certain extent, may cause
serious disasters if a levee breaches and allows water to flash inland.
Thus, especially in lowlands, disaster prevention measures must be developed based on thoroughunderstanding of the flood properties of each area.
3) Difficulty of identifying areas that need evacuation.
When damage by tsunamis or storm surges is predicted, the mayor of a city must issue evacuation orders
to residents in areas to be affected. Although the decision standards are to be stated in regional disasterprevention plans, etc., some plans state no such standards, and others state standards which are not specificenough. When a large earthquake occurs near the coast, the resultant tsunami will reach the coast very fast,
and there will be little time of decision of evacuation order. When a levee breaches during a storm surge,
the resultant flood spreads unexpectedly fast. Thus, it is difficult to identify areas over which evacuation
orders and advice are to be issued.

141.3 Direction of development of measures to prevent disasters by tsunamis and storm surges(1) Considerations for disaster prevention measures against tsunamis and storm surges
Disaster prevention measures against tsunamis and storm surges should include education for residents,
providing and sharing information, and enhancing cooperation and measures for mitigating damage.

Disaster prevention measures against tsunamis and storm surges should consider the followings:
1) Educating residents to increase awareness of disaster prevention
Residents should be educated so that they can collect information by themselves and voluntarily
exercise caution and take evacuation actions. Administrative bodies should provide them with disasterprevention information on a regular basis, explain the limits of disaster prevention facilities, and makeefforts to raise residents’ awareness level toward disaster prevention.
Table 1.3.1 Useful knowledge about tsunamis
1. When strong earthquake motion is felt (seismic intensity of over 4) or when earthquake motion is
weak but long, evacuate from the coast to a safe place at once.
2. Even when no earthquake motion is felt, evacuate from the coast to a safe place at once when atsunami warning is issued.
3. Collect accurate information through radio, TV and municipal information cars.
4. Do not bathe or fish when a tsunami advisory is issued, because there is still some risk of a tsunami
reattack.
5. Tsunami strikes come repeatedly. Stay alert until the tsunami warning or advisory is called off.
Cited from: “Thorough understanding of tsunami warnings in coastal areas” (July 1999, Communication Council of
Tsunami-related Ministries and Agencies)2) Providing and sharing information for disaster prevention
When a large earthquake occurs near the coast, the resultant tsunami reaches the coast very fast andthere will be very little time to evacuate. Thus, evacuation action needs to be taken quickly. The need of
evacuation from a storm surge during a typhoon depends on its route. Thus, disaster prevention
information, such as tsunami warnings and storm surge warnings, must be provided in real time and beshared among administrative bodies and residents. Municipal governments and related organizations must
establish systems for sharing information with residents, and must construct a disaster-resistantinformation network.
3) Enhancing cooperation
Local communities, which have become weak, should be reconstructed, and cooperation among
municipal governments and related organizations should be enhanced to smoothly collect and transmit
information. Especially, disaster-vulnerable people, such as the elderly who live alone, will possibly havedifficulty evacuating by themselves during disasters, and administrative bodies and local residents need tocooperate in evacuation activities.
4) Enhancing measures for mitigating damage
Measures for mitigating damage need to be investigated in advance by assuming inundation, sincetsunamis and storm surges that exceed the assumed scale of the facilities can possibly occur. Measures for
mitigating damage include those that are taken before and during a tsunami (storm surge), and also include
stuctural and non-structural measures. All the measures must be developed by considering thecharacteristics of the coast and possible inundation.

15

(2) Direction of development of countermeasures to prevent disasters by tsunami and stormsurge
Tsunamis and storm surges must be counteracted by taking structural measures up to certain external
force levels (the design protection level). Forces exceeding the level are difficult to deal with only by
structures, since they require a huge amount of expense, and thus non-structural measures should be
developed as well. Non-structural measures are effective even when external force levels are within thedesigned range.
The structural and non-structural measures for preventing disasters need to be coordinated so as tominimize the damage, improve the protection standards by constructing appropriate structures, enhance
the self-defense capability of residents through non-structural measures (for example, sharing disasterprevention information),and, as a result, mitigate damage.
1) Structural and non-structural measures for preventing disasters during tsunamis and storm surges
Structural measures for preventing disasters denote those for improving the protection level using
tsunami and storm surge control structures and damage prevention structures. Non-structural measuresdenote those against tsunami and storm surge disasters that cannot be controlled by structures alone, andinclude provision of disaster information before, immediately before, immediately after, and after thedisasters, construction of evacuation sites, and development of systems and facilities for mitigating
damage. Preparation of hazard maps is one of the non-structural measures.
Typical structural and non-structural measures for preventing tsunami and storm surge disasters areshown in Table 1.3.2. Note that some non-structural measures involve structural factors (such as
construction of evacuation routes).
Table 1.3.2

Examples of structural and non-structural measures for preventing tsunami and storm surge disasters

Class

Structural

Non-structural

Objectives

Controltsunamisand storm
surgesMeasures
Structural
・ Breakwaters against storm
surges and tsunamis
・Tide embankments, banks, andrevetments
・Water gates and land locks
・Seaside forest
・Reinforced concrete, and steel
reinforced concrete, buildings
・ Evacuation routes and sites
・ Information communication
facilities

Mitigate
damageduringtsunamisand storm
surges

Non-structural
・Maintaining and inspecting facilities
・Checking the functions of the facilities
・Effective and efficient operation of the
facilities

・Establishing land use plans
・ Measures to encourage voluntaryevacuation of residents when a typhoon
approaches and after an earthquake
・ Issuing tsunami and storm surge
warnings
・Sharing knowledge on past tsunamis
and storm surges
・ Providing education on disasterprevention
・ Executing evacuation drills
・ Establishing self-defensive
organizations
・Preparing tsunami and storm surge
hazard maps
・Assuming damage and examining local
disaster prevention plans

Reference: Yoshiaki Kawata “Coast Disaster Prevention as Risk Management” (in Japanese)(September 2002, 2002 Summer Study Session on Water Engineering, Japan Society of Civil Engineers)

16

<Preventing
damage>Protection goal by
non-structural measures(external force level 3)

Probability ofoccurrence

Design protection goal(external force level 2)2) Coordination between structural and non-structural measures for preventing tsunami and storm surge
disasters
The relationship between structural and non-structural measures for preventing disasters is shown in
Figure 1.3.1. Up to a certain level (the design protection level), external forces should in principle becontrolled by structures. Forces exceeding the design level are difficult to be controlled by the structures
alone mainly due to high costs, and non-structural measures need to be implemented. non-structural
measures are also effective against external forces below the design level for areas where structures are notyet completed and when the structures fail to function. However, the structures are indispensable for
ensuring safety and must be steadily constructed and improved. Especially in areas where population andassets concentrate and the need of reducing risk is high, the protection level should be raised by improving
protection structures so that the design level approaches the maximum permissible risk.

<Mitigating damage>

Limit of disaster prevention

Risk mounts toward the
maximum permissible risk asassets are concentrated.

Permissible
Disaster prevention
using structures(structural)

Maximum permissible risk

Serious disaster

Disaster prevention
using information(non-structural)

Scale of external forceNodamageFigure 1.3.1

Serious damage

Non-serious damage

Relationship between structural and non-structural measures for preventing disasters
Reference: Yoshiaki Kawata “Coast Disaster Prevention as Risk Management (in Japanese)”(September 2002, 2002 Summer Study Session on Water Engineering, Japan Society of Civil Engineers)

As shown in Figure 1.3.2, the structural and non-structural measures for preventing disasters need to becoordinated so as to minimize the damage, improve the protection standards by constructing appropriate
structures, enhance the self-defense capability of residents through non-structural measures (for example,
sharing disaster prevention information) and, as a result, mitigate damage.

17

Serious disaster
External
force
exceeding thecapacity

Capacity ofstructuresforpreventing
disaster

<Inte
nsity
of
exter
nal
force
>

Intensityofexternal
force

Structures alone<Less likely><Very likely>

Figure 1.3.2

Non-structural measures to cover the difference
non-structural measures+
structures

Schematic diagram of coordination between structural and non-structural measures forpreventing disasters

Actual methods for coordinating structural and non-structural measures for preventing disasters include:a) Understanding the performance of coast protection facilities in the area (crown height, earthquake
resistance, etc.), estimating possible damage in the area, and assessing the present risk.
b) Deciding the permissible damage level and safety level.
c) Deciding priority for construction, improvement or repair of coast protection facilities, including
installation of a remote control system for closing and opening water gates and land locks, based on theperformance of coast protection facilities and risk assessments, and efficiently executing projects that are
immediately effective for mitigating damage. (Structural measures)d) Informing local residents about what external force would cause what degree of inundation at that site inthat district based on the present status of facility construction, since constructing coast protection facilities
requires expense and time.
e) Providing tsunami and storm surge hazard maps to residents so that they know the evacuation routes andevacuation sites during disasters, prepare against disasters and enhance their defensive capability. Roads
and sites for quick evacuation are to be constructed. (Structural measures)f) The priority should be given to constructing evacuation sites and various facilities in areas containing
hospitals and other welfare facilities accommodating many people who cannot evacuate by themselves,densely populated districts, and areas that have wooden buildings prone to collapsing and blocking
evacuation routes since residents in such areas and districts may have difficulty evacuating by themselves.
Land use plans and land use regulations may also need to be revised for areas prone to serious damage.
(Disaster prevention measures for enhancing further safety)

18

a)

Assessing the present risk by evaluating the performance of existing facilities andestimating possible damagee) Non-structural measures for disaster prevention
Enhancing self-defensive capability during disaster by providing tsunami andstorm surge hazard maps to residentsf) Disaster prevention measures for enhancing safety
Giving priority to constructing evacuation sites and related facilities in areas
where people have difficulty evacuating by themselves, and revising land use
regulations

Figure 1.3.3

C)Structures for disaster preventiond) Informing of the risk of disaster

Promoting the construction of immediately effective
structuresb) Deciding permissible damage and safety level

Coordination of flow between structural and non-strucutural measures for disasterprevention

19

As a reference, structural and non-sturucutural measures for preventing tsunami disasters and theposition of hazard maps are shown in Figure 1.3.4.

Overflow from the point
where the crown height islowControlling
overflow

Controlling run up

Construc Construcand ting andConstructi tingreinforci
ng tsunami reinforcing
water
breakwater walls sea nggates

Preventing
destruction

Controlling
overflowConstru
cting
river
banks

Constructing
systems forpreventing
ships andwood fromfloating
away

Failure to close land lockControlling
driftwood andfloating ships

Constructing
system for closing
land locks

Moving Installing
Maintai Checking the sites automatic
Reconstr
ning andthefoructingsystems
controlli performa mooring
operationforng
nce of ships andclosing systems
facilities facilities storing land
locks
wood

Not all can be controlled
Inundation

Delay in deciding
evacuation
Providinginformation to
help decideevacuation,
checking
evacuation

Providingmutualassistanceby residents

Need time to evacuate
Ensuring
nearbyevacuation
sites

PrepariIssuing
ng and Executi Formitsunaming warnings
ng
distrib
self-deuting evacuat fensiveandion
hazard drillsorgani watchingmaps
the seazations surface

Evacuation routes
not clear

Providing
Providing
Ensuring
information information
alongfor early on evacuation safety
evacuation
evacuationroutesroutesConstru
cting Design
tsunami ating
disaster evacua
tion
preventi sitesonsystems

Constru Installingcting
signageevacuattoion sites evacuatio
n sites: Issues in tsunami disaster prevention: Non-structural

Figure 1.3.4

Dangerous spots
on evacuationroutesConcentration offacilities and assets

Providinginformation onProviding
dangerous concentra
tedspots onevacuation protectionroutesMovingassetsandfacilities

Non-structural measures

Investigating facility
Developing
non-sturctural
measures

Hazard map

Controlling tsunami height

Destruction of revetment,
etc., by driftwood, ship, etc.

Overflow from riverbank due to run up

Structural measures

TsunamiReinfor Protecti Movingng
cing
importahouses important
nt
facilitie
facilitiess: Thrust of tsunami disaster prevention: Structural

Position of hazard maps in structural and non-structural measures for preventing tsunami
disasters

20

1.4 Roles of hazard maps as a measure for preventing disasters caused by tsunamis and storm
surges(1) Roles of tsunami and storm surge hazard maps
Tsunami and storm surge hazard maps are tools for mitigating damage during tsunamis and storm
surges, mainly in a self supportive and mutually supportive manner, and to help administrative bodies todraw up evacuation plans, provide education on disaster prevention, increase public awareness of
disaster prevention, construct strong communities against disasters, and enhance communication withresidents regarding risks.

1) Three support classifications of disaster prevention
Disaster prevention can be classified into “self support”, “mutual support”, and “public support”
activities. National and regional public organizations have mainly promoted public support projects, suchas construction of coast protection facilities. However, public support activities alone are insufficient for
preventing disasters. Substantial mutual support systems, which involve cooperation with local residents,
volunteer groups, and private companies, and self support activities to protect oneself are also needed. As
the Hyogo-ken Nanbu Earthquake revealed, the majority of activities during the earthquake were either
self support or mutual support in nature, as residents made their own escape from houses that collapsed
during the earthquake and reconstructed new houses, but people in general still feel that disaster prevention
is a role of governments, which proves a strong dependency of the public toward public support. Self
support and mutual support activities are likely to be increasingly important especially during the period
immediately after a disaster until public support activities start; one should naturally realize their further
importance when considering the disaster-vulnerable population, which will become larger and larger as
the aging society progresses. Of residents in areas prone to damage, some may be elderly and living alone,and some may need help to evacuate. To help these people, residents in high-risk areas need to be
conscious of self support and mutual support activities for disaster prevention.
It is important to make the most of tsunami and storm surge hazard maps as tools to assist self andmutual support activities in coordination with evacuation plans, disaster prevention education, activities toincrease public awareness of disaster prevention, construction of strong communities against disasters, andcommunication enhancement with residents about risks.

Self
supportMutualsupportFigure 1.4.1

PublicsupportThree support classifications of disaster prevention212) Role of hazard maps
The most important non-structural measure of information provision for preventing disasters during
tsunamis and storm surges is tsunami and storm surge hazard maps. The maps will enable residents toquickly evacuate from dangerous areas, obtain knowledge about the predictable risks, and be aware ofdisaster prevention. They will also be effective to promote construction of strong communities against
disasters.
The contents of and investment for projects against unexpected disasters should be decided by not only
governmental advice but also communication with residents about degree of risk, costs involved. Tsunami
and storm surge hazard maps can be used as a tool for risk communication, in which local residents andadministrative bodies share information about disasters and jointly investigate countermeasures.

[Column: Risk communication]
All phenomena in this world, including scientific technologies, can be both useful and dangerous.
Therefore, administrators and companies, which are the owners of certain information, should inform
people of the usefulness and danger of the phenomena and discuss how to deal with it to save people
from the risk. Disclosing not only the positive side of a subject but also all of its negative side, such as
risks, in a fair manner, is called “risk communication”.
Regarding risk management in terms of the way for a group of people to confront risk, exchange of
information, experience, sense and knowledge, and mutual understanding among people, are called “riskcommunication”. When people confront risks, many seek for strategic management to avoid, reduce, andmitigate damage and exercise risk communication by actively providing and exchanging information.
Risk communication also denotes two-way communication among interested parties on risks andcountermeasures by increasing the parties’ involvement. Here, communication is regarded as part of“management” in a broad sense, and both are interpreted together.
Reference: “Encyclopedia of Risk” (in Japanese) (2000, The Society for Risk Analysis, Japan-Section)22

(2) Roles of tsunami and storm surge hazard maps
In disaster prevention during tsunamis and storm surges, tsunami and storm surge hazard map
functions as non-structural measures for enhancing the self defensive capability and evacuation activities
of residents, and also as structural measures for supporting the investigation of what facilities toconstruct to improve protection levels.

Typical structural and non-structural roles of tsunami and storm surge hazard maps include:[Non-structural roles]
1) Providing residents with information about disasters, evacuation, etc.
2) Providing administrators with information about disasters and evacuation,3) Serving as a tool for risk communication between residents and administrators.
[Structural roles]
1) Providing support for investigating about what facilities to construct (improve) to improve protectionlevels2) Providing support for investigating about construction of evacuation sites, systems for monitoring coast
protection facilities, and other counter-disaster systems, and
3) Providing support for investigating about post-disaster restoration measures.

Table 1.4.1 Roles of tsunami and storm surge hazard maps in disaster prevention
Class
TargetExample of measure
Role of hazard map
Providing information about
Non-structural
Residents• Raising awarenessdisasters to residents• Providing evacuation information• Evacuation drill
Providing information about
Administrators • Measures for preventing disasterdisasters to administrators• Disaster prevention activity plans• Preparing for evacuation• Evacuation plan, support plan
• Constructing
counter-tsunami andstorm surge systems• Information about tsunami and storm
surge warnings
communication
between Tool for risk communication
Residents and • Risk
residents and administrators
administrators
Structural
Administrators • Constructing and improving structures Providing information about
for improving protection levels
priority of facilities• Constructing
disasterprevention Providing
supportforstations
investigation of construction of• Providing information about sites that evacuation sites, systems formonitoring coast protection
must be urgently dealt with• Constructing systems for operating facilities, and other systems
and monitoring facilities (water gates, against disasters
land locks, etc.)• Restoration plan by understanding Providing
supports
tostates of damage in real time
investigate
post-disaster
restoration measures

23

Chapter 2

Overview of tsunami and storm surge hazard maps

2.1 Purposes of preparing tsunami and storm surge hazard maps
Hazard maps for residents are prepared to provide residents with the information necessary for taking
appropriate evacuation actions, such as the risks of tsunamis and storm surges, and evacuation sites androutes.
Hazard maps for administrators are prepared to assist administrative bodies in carring out their duties,
such as devising and taking disaster prevention and emergency measures.

Hazard maps for residents are prepared to provide residents with the information necessary for taking
appropriate evacuation actions, such as the risks of tsunamis and storm surges, and evacuation sites androutes, in an easy-to-understand manner.
Hazard maps for administrators are prepared to assist administrative bodies and management bodies incarrying out their duties, such as devising and taking disaster prevention measures and taking emergency
measures. For example, such maps can help those in charge of disaster prevention to draw up evacuationplans and also support those of coast, ports and fishing ports to plan construction of facilities and safetymeasures for users.
Hazard maps for private companies are also effective to select locations appropriate for building offices
and factories, to draw up evacuation plans from offices and factories located in inundation-prone areas,
especially from factories and research facilities handling hazardous materials, and to investigate managementof the hazardous materials.

242.2 Target disasters and range of tsunami and storm surge hazard maps
Tsunami and storm surge hazard maps are to be prepared for each municipality, which is the unit ofadministrative rights and responsibility. Coordination with adjacent municipalities may be consideredwhen it is necessary in terms of topography and evacuation.
Tsunami hazard maps and storm surge hazard maps should in principle be prepared separately.

1) Range
Since the chief of a municipality is responsible for evacuation from the area (Article 60 of the Disaster
Countermeasures Basic Law), tsunami and storm surge hazard maps are to be prepared for eachmunicipality.
However, in areas that belong to different municipalities but which should be regarded as a single area interms of topography (for example, an area surrounded by a large river), an inundation risk area should be
identified regardless of municipal boundaries. It is important to keep consistency in terms of the setting of
external forces among neighboring municipalities. Similarly, it should be noted that evacuation plans are also
to be investigated regardless of municipal boudaries in some cases.
Evacuation sites and routes from the shore side of coast protection facilities must also be shown on hazard
maps when there are possibilities of users and workers being in the zone. Foreshore reclaimed land, wharfs,
marinas, beaches, coastal parks, etc., must be included in the maps, and evacuation sites and routes must be
decided.
2) Target disaster
Both tsunamis and storm surges cause inundation, but are substantially different in cause, inundation
pattern, and evacuation method. Thus, tsunami hazard maps and storm surge hazard maps should in principle
be prepared separately.
For residents to use hazard maps, a comprehensive hazard map which contains information about storm
surges, tsunamis, floods, and sediment-related disasters is desirable. However, the scope of this manual is fortsunami hazard maps and storm surge hazard maps, which are to be given priority over the preparation of acomprehensive map because:a) Hazard maps for tsunamis and storm surges need to be urgently prepared, andb) Individual maps are needed to prepare a comprehensive map.
This manual describes preparation of tsunami hazard maps and storm surge hazard maps as a preliminary
process of preparing a comprehensive hazard map.

25

2.3 Bodies in charge of preparing tsunami and storm surge hazard maps and their roles
Tsunami and storm surge hazard maps for residents should be prepared by municipal governments,
which are responsible for evacuation of residents, and tsunami and storm surge hazard maps foradministrators should be prepared by the appropriate administrative divisions with the support ofprefectural and national governments.
Municipal, prefectural, and national governments should bear appropriate roles in preparing tsunami
and storm surge hazard maps for residents according to the areas covered by the maps. Hazard maps
should be prepared by both administrative bodies and residents working together, not be prepared byadministrative bodies alone and distributed to residents in a completed form. Residents’ participation
should be encouraged in preparation of the maps through workshops, etc., so that more regional
characteristics can be incorporated into the maps, residents can be more aware of hazard maps and be
more encouraged to utilize the maps.
Prefectural and national governments should support municipal governments in preparing tsunami andstorm surge hazard maps by providing data on inundation prediction and constructing a database forcoastal topology.

1) Main body in charge of preparing hazard maps
Since the ultimate objective of hazard maps for residents is to assist them in evacuating quickly during
disasters, the maps should be prepared by municipal governments, which are responsible for evacuation of
local residents and carry detailed information around the target areas.
Hazard maps for administrators should be prepared by individual divisions depending on the purposes ofthe maps.
The basic concepts of role allotment for administrative bodies at each level are described in the following
section, but prefectural and national governments should provide support flexibly based on regional
characteristics and conditions.
2) Role allotment in preparing hazard maps for residents
Joint preparation of a integrated map for inundation-prone areas by neighboring municipalities isdesireable in some cases so that they can avoid redundancy in calculations and ensure consistency in terms ofexternal forces and damage. In such cases, prefectural and national governments assist municipal
governments by providing the necessary data and conditions for prediction, conducting inundation prediction,and coordinating neighboring municipalities for cooperation. Constructing a coast database for the entire
Japan will also a great contribution by prefectural and national governements to efficient preparation oftsunami and storm surge hazard maps.
Participation of residents in the preparation of tsunami and storm surge hazard maps is an effective way toincorporate regional characteristics into the maps, raise residents’ awareness toward the maps, and encouragethem to utilize the maps. Municipal governments should construct a system for enabling residents to actively
participate in preparation of tsunami and storm surge hazard maps through workshops, etc.
Inundation-prone areas may need to be identified by prefectural and national governments depending on
the financial conditions and technological capacities of individual municipal governments.
The concepts of roll allotment among residents, municipalities, and prefectural and national governments
in preparing tsunami and storm surge hazard maps are shown in Table 2.3.1

26

Table 2.3.1
Body
Municipal
government

Prefectural
government

National
government

Residents

Roles of residents, municipalities, and prefectural and national governments in preparing
tsunami and storm surge hazard maps
Roles1) Prepare tsunami and storm surge hazard maps
• Establish preparation conditions appropriate to the region• Prepare maps, and predict inundation and assume damage in individual zones
2) Encourage participation of residents to devise original safety measures, enhance theconsciousness of self-defense, and understand the risks
1) Assist preparation of tsunami and storm surge hazard maps when the maps are to cover
two or more municipalities or when municipal governments have difficulty preparing themaps independently• Identify external forces and inundation areas, and assume damage
1) Provide technical assistance to prefectural and municipal governments when the area forwhich a hazard map is to be prepared extends over two or more prefectures or whenprefectural governments alone have difficulty preparing the maps2) Develop and reinforce administrative methods• Solve issues regarding preparing tsunami and storm surge hazard maps
• Construct systems for supporting preparation of hazard maps
3) Provide and share knowledge and information• Prepare the manual for tsunami and storm surge hazard maps
• Provide information to, and share the knowledge of risks with, municipal governments topromote preparation of hazard maps
• Actively cooperate with bodies in charge of hazard map preparation
4) Construct databases on basic coast information• Improve the efficiency of hazard map preparation by constructing databases5) Support disaster prevention activities of municipal governments by providing real-time
information in connection with and by utilizing hazard maps
1) Participate in preparation of tsunami and storm surge hazard maps
• Participate in hazard map workshops to help incorporate regional characteristics into themaps, enhance understanding of those characteristics, and promote more frequent use of themaps.

3) Roles of disaster prevention organizations and coast administrators
Both organizations related to disaster prevention and coast administrators should actively support bodies
in charge of tsunami and storm surge hazard map preparation. This cooperation is expected to reinforce theconsciousness of disaster prevention organizations and coast administrators about disaster prevention andabout information sharing in the field of disaster prevention.
In practice, coast administrators should provide various kinds of information that are necessary forpredicting inundation during tsunamis and storm surges to bodies in charge of preparing the maps.
Information that should be provided includes the mechanisms of damage to coast protection facilities, water
depth and elevation data used to predict inundation during tsunamis and storm surges, and areas thatinundated during disasters in the past. Port management bodies and administrators of fishing ports should
also provide various kinds of information concerning facilities in ports and fishing ports to bodies in chargeof preparing the maps.

27

Municipal
government

National
government

Residents
Participate

SupportHazard maps for residents

SupportPrefectural
government
SupportDivisions in charge(municipal andprefectural Active support
governments)
Hazard maps for administrators

Disasterprevention
organizations
and coastadministrators

Body in charge of preparing tsunami
and storm surge hazard maps

Figure 2.3.1

Bodies in charge of preparing tsunami and storm surge hazard maps

4) Supporting the preparation of tsunami and storm surge hazard maps by constructing a coast database
In order to minimize damage, an appropreate combination of structural and non-structural measures isnecessary. In particular, to mitigate damage from tsunamis and storm surges, a coast database needs to beconstructed for storing various kinds of information necessary for assessing the risk of indivisual coastal
areas. Construction and utilization of the coast database will reduce the load of collecting and analyzing thedata necessary for preparing tsunami and storm surge hazard maps and enable the maps to be efficiently
prepared.
Table 2.3.2

Examples of data necessary for preparing tsunami and storm surge hazard maps
Class of data
Example of data
Data necessary for predicting inundation• Crown height of facility• Type of facility• Elevation of the ground
Data to be shown on tsunami and storm surge • Inundation prediction data (tsunami, storm surge)• Population
hazard maps
• Land use data
• Disaster records5) Schedule of tsunami and storm surge hazard map preparation
As described in Chapter 1, measures against tsunamis and storm surges must be urgently taken, andtsunami and storm surge hazard maps should be prepared as quickly as possible depending on the urgency ineach district, with the support and cooperation of related organizations.

28

2.4 Forms and expressions of hazard maps
Hazard maps for residents must be easy to understand and use. To use the hazard maps for evacuation
during disasters, use of fluorescent inks and water-proof materials and other methods should beconsidered. Information to be used during evacuation must be expressed in a simple manner and in a way
different from information that is used for education in normal times.
Hazard maps for administrators must also have forms and expressions appropriate for the purpose ofuse.

1) Forms of tsunami and storm surge hazard maps
Tsunami and storm surge hazard maps must have forms (media, materials, size, etc.) that are easy to use
and to understand. Especially, hazard maps for residents are desirably posted at homes and thus should be informs that can be posted on places that are easy to see. For example, the proper size of the maps may be
about A3, considering posting on a refrigerator together with a schedule of garbage collection, list of phone
numbers, and notices from governments. Also considering the carrying of the maps during disasters, theyshould be readable at night and water-proof.
The foregoing is draft ideas of hazard maps to be distributed to homes for residents. Hazard maps foroutdoor display (evacuation signs, sign boards) and for educational display should take different forms andexpressions to serve their specific purposes.
2) Expressions of tsunami and storm surge hazard maps
Expressions used in tsunami and storm surge hazard maps should be carefully chosen so as to be correctly
understood by residents. Especially, hazard maps for residents are to be used for evacuation during disasters,
and residents may face danger and even be killed when they fail to correctly understand information on
hazard maps. Thus, hazard maps for residents must be simple and easy to understand.
However, showing inundation risk areas and evacuation zones in an easy-to-understand manner may give
residents a false idea that only the areas shown in the maps will always inundate during tsunamis and storm
surges. Thus, measures should be devised to avoid giving false ideas. (See 4.4 Methods for displaying
predicted inundation risk areas and evacuation areas for details of displaying inundation-prone areas andareas that need to be evacuated.)29

2.5 Procedure for preparing tsunami and storm surge hazard maps
Tsunami and storm surge hazard maps should be prepared by 1) identifying inundation risk areas, and
2) displaying disaster prevention information about tsunamis and storm surges.
Inundation risk areas should be identified by setting conditions, such as external forces and facilities,
and conducting simulation analyses for predicting inundation, assessing the risks of facilities, etc.
Disaster prevention information about tsunamis and storm surges should be displayed by identifying
items and contents of information to be displayed and deciding display methods, such as symbolization,of the information. Information characteristic to each region, which is identified in workshops, should
also be displayed.

1) Procedure for preparing tsunami and storm surge hazard maps
A flow of preparing and utilizing tsunami and storm surge hazard maps is shown in Figure 2.5.1. A
procedure for preparing tsunami and storm surge hazard maps is shown in Figure 2.5.2.

Preparing tsunami and storm surge hazard map

Deciding the purposes, etc. of map preparation○Purposes○Assumed uses
○Body in charge

Identifying
inundationrisk areas

Setting conditions○External forces ○Facilities
Simulation analysis○Predicting inundation ○ Assessing the risks
of facilities

Inundation risk areas

Displaying disasterprevention
information abouttsunamis andstorm surges

Deciding information to be displayed○Items○Display methods
Preparing information to be displayed○Stating necessary information ○Symbolizing○Adding regional characteristics

Hazard map (information necessary for preventing disasters)

Disseminating, checking, and utilizing hazard maps

○Disseminating maps ○Residents checking○ Smooth evacuation of
to residents
the maps
residents

Comprehensive measures for preventing disasters during tsunamis and storm surges

Figure 2.5.1

Flow of preparing and utilizing tsunami and storm surge hazard maps

30

As shown in Figure 2.5.2, hazard maps for residents are prepared by adding basic information forevacuation (minimum information indispensable for evacuation) and additional information for evacuation(such as maximum water depths predicted and estimated arrival time) to maps showing inundation risk areas.
Hazard maps for administrators are prepared using basic information (information that can be shared, such as
inundation risk areas and coast protection facilities) and information related to purposes specific to eachadministrative group (disaster prevention centers, police stations, fire departments, etc.). (See Chapter 4 forthe information to be displayed in tsunami and storm surge hazard maps.)

Table 2.5.1 Information to be stated in tsunami and storm surge hazard maps
Map
Information
Hazard maps Information for evacuation Basic information for evacuation (See p.
for residents(See p. 55)
57)
Information necessary for Basic information indispensable for
evacuation,such
as evacuation
evacuation sites and routes
Additional information for evacuation(See p. 57)
Minimum additional information neededin the region
Educational information on disasters (See p. 55)
Information for enhancing the knowledge of residents about tsunamis
and storm surges
Hazard maps Informationforpreventive Basic information (See p. 59)
Shared informationformeasures (See p. 59)
administrators Information useful for taking
Information based on different
preventive measures
Informationforemergency purposes (See p. 59)
Information necessary for eachmeasures (See p. 59)
Information useful for taking specific purpose
emergency measures

31

Notes

Added to thehazardmaps
depending on
regionDistributed
separately, etc.

Inundation risk areas

Basic information indispensablefor evacuation

Basic informationfor evacuation

Additional information forevacuation that need to be added
depending on region, such as
maximum water depths

Additional
information forevacuation

Basic information

Information needed by eachadministrative division

Hazard map forresidents

Information related
to the purpose of themaps

Information such as
disaster prevention
centers, police stations,and fire departments

Examining and revising
the hazard map

Learning at workshops, etc.

Locally devised
measures

Examining and revising thehazard map

Hazard map for residents(for each region)

Hazard map for
administrators(for each purpose)

Disseminating,checking, and utilizing

Utilization at eachadministrative body

Figure 2.5.2

Common information suchas the results of inundation
prediction and conditionsof coast protection
facilities

Flow of preparing hazard maps for residents and administrators

2) Identifying inundation risk areas by considering the characteristics of tsunamis and storm surges
Highly precise inundation prediction should be conducted by considering the characteristics of tsunamis
and storm surges, including time sequential information such as inundation depth, velocity, and inundation
initiation time. This information is used to execute non-structural disaster prevention measures, such as
evacuation, and structural measures, such as construction and improvement of coast protection facilities.
Those in charge of preparing tsunami and storm surge hazard maps should conduct thoroughinvestigations to determine the kinds and precision of inundation information that are needed for the maps to
identify inundation risk areas. Prediction of inundation is the core of tsunami and storm surge hazard maps,
and should be improved in accuracy by conducting numerical simulations, which can reflect precise settingsof external forces and facilities and calculate time sequential data, such as inundation depth, velocity andinundation initiation time. (See Chapter 3 for methods for identifying inundation risk areas.)
When numerical simulations are difficult to perform, tsunami and storm surge hazard maps can beprepared just by using available data. For example, past inundation records can be used instead of inundation
prediction calculations, and hazard maps can be prepared using the results of inundation prediction
conducted using simple methods, records of disasters in the past, and records of evacuation sites and routes
that could not be used due to inundation and collapse of buildings. In such a case, the possibility ofinundation damage that exceeds the recorded damage in the past should be stated, and the estimatedinundation risk areas and the information on the maps should be revised afterward in stages.
It should also be noted that prediction of inundation using numerical simulation contains uncertainty. (See
4.4 Methods for displaying predicted inundation risk areas and evacuation areas for methods for dealing
with uncertainty.)

32

2.6 Utilization of hazard maps during evacuation
Residents collect information such as evacuation sites and routes from hazard maps for residents andtake evacuation action. Evacuation sign boards which conform with the hazard maps should be installed,
and real-time information should be provided for people who do not look at the hazard maps and for
preparatio for situations that can not be assumed from the maps.

Hazard maps for residents are used to take appropriate evacuation action during emergencies.
Relationships between tsunami and storm surge hazard maps, evacuation measures, and evacuation action,
are shown in Table 2.6.1. Past records showed that the time of obtaining information affected the evacuation
behavior of residents, and delays in transmitting disaster information will lead to delays in evacuation action.
Thus, information must be quickly transmitted at appropriate timing. Evacuating as soon as an earthquake isfelt is the basic of evacuation from tsunami risk areas.
Table 2.6.1 Relationships between tsunami and storm surge hazard maps, evacuation measures, andevacuation action
Hazard map
Evacuation measures and evacuation action• Hazard
map for residents Local residents collect information that helps them decide evacuation,(printed on paper)
such as the risk of tsunamis and storm surges, evacuation sites, andevacuation routes• Hazard map for administrators
Administrators utilize the map to construct evacuation sites and routes,
select appropriate sites for establishing countermeasures centers,
construct and improve disaster prevention facilities along rivers andcoasts and at ports, educate people on disaster prevention, and draw up
land use and regional development plans
Information shown in hazard maps for residents is preliminary information, and residents are expected toevacuate during an emergency based on the actual situation and the information on the maps. However,residents can collect little information about the situation during an emergency and may fail to make a soundjudgment. Measures are also needed for people who do not look at the maps and for preparation forsituations that can not be assumed from the maps. Thus, appropriate evacuation action should be assisted byinstalling evacuation sign boards which conform with hazard maps and by providing real-time information.
For example, real-time information provision through radio communication systems of municipal
governments should also be in conformity with information shown on hazard maps. IT-based two-way
systems for reading hazard maps are a possible method for providing real-time information during
emergencies.

33

Chapter 3

Methods for identifying inundation risk areas

3.1 Characteristics of tsunamis and storm surges
Tsunamis and storm surges differ from each other in cause and phenomena. Inundation risk areas should
be identified based on the understanding of individual characteristics.
(1) Characteristics of tsunamis
A tsunami is caused by an earthquake, and it strikes and inundates districts near the epicenter very soonafter the earthquake, leaving little time to evacuate, inform residents, and close water gates and land locks.
A tsunami travels fast and damages structures, especially when it recedes. Inundation is also possibly causedby damage to coast protection facilities due to earthquake motion or to collision by ships during a tsunami.
(2) Characteristics of storm surges
Most storm surges occur during large-scale typhoons and can be predicted to a certain extent. However,once a levee breaches during a storm surge, the damage spreads over a large area since water levels are highover all waterside land.

1) Characteristics of tsunamis
The time and scale of earthquakes, landslides, and volcanic eruptions, which are causes of tsunamis, aredifficult to predict. Thus, although tsunami warning systems are set to work right after an earthquake, there
will be very little time left for tsunami warning when the earthquake occurs near the coast, since tsunamis
propagate very fast. Tsunamis can also arrive from unexpected directions when the topography iscomplicated. Essentially, urgent and quick evacuation based on local information is necessary. As areference, arrival times of tsunamis are shown in Figure 3.1.1.
Tsunamis can exceed the heights of ordinary revetments and levees, and can affect even districts wheresuch revetments and levees are completed. Tsunamis can also cause serious damage when they recede.
The area of inundation depends mainly on the height of a tsunami and the elevation of the land. The heightof a tsunami depends on the scale of the causal earthquake, its hypocenter location, and submarine
topography.
A tsunami arrives several times, and in some cases, the second or later wave can be the highest. The
hydrodynamics of tsunamis should be considered as forces affecting facilities. Inundation from rivers should
also be assessed when necessary.

34

Wave height more than 3 m(Structures higher than the tsunami wave are notplotted.)Areas of inundation depth more than 2 m(Structures higher than the tsunami wave are notplotted.)

想定震源域

Assumed epicenter area

Legend□Wave height of at least 3 m□ Inundation depth of at least 2 m

Figure 3.1.1

Arrival times of tsunami waves

Reference: “Reference of the 7th Meeting of the Investigatory Committee on Countermeasures against Tokai Earthquakes”(March 3, 2003, the Central Disaster Prevention Council)

2) Characteristics of storm surges
Most storm surges occur during large-scale typhoons and can be predicted to a certain extent. In mostcases, inundation occurs when the tidal deviation reached the maximum during a high astronomical tide, but
strong typhoons can cause inundation even when not coincident with high tides.
Once a levee breaches during a storm surge, the damage spreads over a large area since the water level ishigh over the entire waterside land and water is supplied from the sea. Thus, damage during storm surges
varies greatly depending on the levee breach. Evacuation is usually difficult, since typhoon winds can blow
away window glass and signboards.
Site of observation: Ohura
Tidal level measured
Astronomical tide

8.0

Tidal level T.P.(cm)

7.0
6.0
5.0
4.0
3.0
2.0
1.0
18
21
0
September 23

3

6

9

35

12
15
September 24

18

21

(h)

1.2

Misumi (9918)
Ohura (9918)
Kuchinotsu (9918)

1.0

Tidal deviation（ｍ）

0.8
0.6
0.4
0.2
0.0

-0.2
-0.4
-40

-20

0
20
Time from the peak of tidal deviation

40

60

Changes in tidal deviation (Typhoon No. 9918)

Figure 3.1.2

Changes in tidal level and tidal deviation during storm surges in the past
(Typhoon no. 9918, along the Ariake Sea)36

3.2 Conditions for identifying inundation risk areas(1) Conditions
To identify inundation risk areas, both the external force conditions and the facility conditions should beappropriately set so that disaster prevention measures are studied properly. The external force condisions
refer to relevant external forces; the facility conditions concern about how a facility typically would bedestroyed and how operational it would be at a disastrous event.
When disasters may affect two or more municipalities, extra attention should be given to be consistent
between those municipalities when they set the conditions.

1) Conditions
Generally, the conditions shown in Table 3.2.1 need to be taken into account to identify inundation risk
areas for tsunami and storm surge hazard maps. Besides those conditions, the traveling speed of a typhoon
may also affect inundation and may need to be considered for storm surge hazard maps, and volcanic
eruptions and large-scale landslides, as well as earthquakes, are possible causes of tsunamis and may need tobe considered for tsunami hazard maps.
Although other conditions besides those are difficult to display on paper-printed hazard maps, possible
risk areas and the risk of disasters exceeding assumptions may need to be stated on the maps to cope with theworst case (See 4.4 Methods for displaying predicted inundation risk areas and evacuation areas formethods for identifying possible risk areas).
Table 3.2.1
Class
External force conditions

Facility conditions

General conditions for identifying inundation risk areas
Tsunami hazard map
Storm surge hazard map
1. Scale of earthquake
1. Scale of typhoon
2. Hypocenter location
2. Course of typhoon
3. Displacement of the ground
3. Astronomical tide
4. Astronomical tide
4. River conditions
5. River conditions
1. Types of destruction
2. Operational state of facility2) Precautions to determine the level of each conditiona) Consistency among adjacent municipalities
When considering disasters that may affect two or more municipalities or in the case of studying preventive
measures for a large area, extra attention should be given to keep consistency among adjacent municipalities
in terms of the level of each condition.
b) Inundation in underground spaces
Inundation in underground spaces such as subways and underground malls should be separately investigated.

37

(2) Setting external force conditions
In identification of inundation risk areas, the level of each external force should be rationally set inconsideration of purposes and regional characteristics with the worst case in mind.

1) External force level
In Tables 3.2.2 and 3.2.3, the external forces related to inundation prediction during tsunamis and storm
surges are divided into three different levels.
Tsunami and storm surge hazard maps should be prepared by rationally setting a external force level withthe worst case in mind – namely, the highest external force level (Level 3 in Tables 3.2.2, 3.2.3 and 3.2.4) –and by considering the purposes of the maps and the characteristics of the region. For example, to simulatesituations under Level 2 (design external force) should be useful for districts where protection facilities are
insufficient.
When considering disasters that may affect two or more municipalities, extra attention should be given to
keep consistency between adjacent municipalities in terms of the level of external forces.
Level ofexternal force

Level 1

Level 2

Level 3

Table 3.2.2

Objectives of analysis and external force levels

Definition

Objective of analysis

External force that is To investigate measures against
realistically assumed to disasters
that
occur
duringoccur
construction
To investigate measures against
disasters that occur on the seaward
side of the protection line, such as
on beaches
Design external force Design construction goal of the Using
non-structuralthat meets the protection facility
measures for those thatgoal
cannot be prevented bystructural measures alone
Changesbytime(towards Level 3)
External
force
that Estimation of the worst possible Cannot be prevented bycausestheworst situation
structural measures
Non-structural measuresinundationneed to be used to the
maximum extent
Table 3.2.3

Level ofexternal force
Level 1
Level 2

Level 3

Notes

Levels of external force and scales of tsunamis and storm surges
TsunamiStorm surge

Possible damage to marine culture Frequently observablefacilities and such, but not to the land
Devastating as design external force (the Devastating as design external force (thelargest tsunami in the past)
maximum force in the past and assumed
maximum force (maximum scale and worst
route of typhoon in the region in the past))
Devastating as assumed maximum Devastating as assumed maximum storm
tsunamis (assumed earthquake scale, surges (maximum scale and worst route ofworst hypocenter location)
typhoon in the past)38

Level 1

Level 2

Level 3

Table 3.2.4 Comparison of external force levels used (example)
Tsunami and Storm Surge Hazard
Map Study Meeting
Conventional standards, etc
External force conditions for
estimating inundation
Design high tide level inEarthquake motion level
Technical Standards and performance-based
Explanations for Port and designing
Storm surge level
Harbour Facilities in Japan (Port and Airport Research Tsunami level(May 1999, The Japan Institute)*
PortandHarbour
Association, p. 258)
Expectedearthquake 30 to 100 years
External force that is realisticallymotion of a return period (Tidal deviation during
assumed to occur
typhoonofrelativelyof 75 years
Frequent storm
frequent scale and mean(all facilities)
None
surge
high tide level)
Expectedearthquake 100 to 1,000 years
Design external force that meets the
motion of a return period (Tidal deviation during
protection goalof several hundreds of typhoon of the largest
Design external
years,
intraplate known scale and ordinary Design external
force
earthquake motion, plate mean high water spring(largest in the pastforce
boundary
earthquake tide)and assumed(largest in the
motion(earthquake
maximum in thepast)resistant facilities)
region)External force that causes the worst
5,000 to 10,000 years
inundation(Tidal deviation during
typhoon of the largest
Assumed maximum
possible scale and mean Assumed(maximum scale, worst
high water spring tide maximum
route)
during typhoon)

Reference: Takahashi, Kawai and Takayama “Future measures against storm surge during Typhoon No. 18 in 2000” (October 2002,
Journal of the Japan Society of Civil Engineers)

2) Considerations for setting external force conditions
External force conditions used to identify inundation risk areas should be set by considering the purposesof preparing the maps, which disasters to analyze, and the characteristics of the region. Conditions thatcannot be analyzed by the present technologies should be considered in the future when the necessary
technologies are developed. It should also be noted that disasters can occur under conditions other than thosepresented in this section.

39

(3) Setting facility conditions
Facility conditions for identifying inundation risk areas should be set by considering the purposes ofpreparing the maps, the characteristics of disasters, and the characteristics of the region.

Facility conditions that are commonly used to prepare tsunami and storm surge hazard maps are types ofdestruction and operational states of facilities.
Tsunami hazard maps should show types of destruction by earthquake motion, such as overturning ofbuildings, sliding, and liquefaction. Thus, the earthquake resistance of facilities must be inspected. Collisionof vessels and ships with facilities may also need to be considered. For storm surge hazard maps, destructionof facilities by overflowing and overtopping during storms must be considered. When there is a risk of levee
breaches and thus causing inundation, the possible breach points must be marked. On the other hand, actual
data should be used as much as possible for the operational states of facilities, including the operational
states of water gates and land locks (closing and opening).
The conditions and the methods for setting facility conditions should be adjusted according to thecharacteristics of disasters, the objectives of map preparation, and the characteristics of the region.
Conditions that cannot be identified by today’s technologies should also be considered in the future whenmore advanced technologies are available. It should also be noted that disasters can possibly occur underconditions other than those presented in this section. In order to choose necessary information for the maps,
such as the types of destruction, an appropriate method should be selected by referring to “2000 Coastal
Facility Design Handbook” (November 2000, Japan Society of Civil Engineers) and“Technical Standards
and Explanations for Port and Harbour Facilities in Japan” (May 1999, Japan Port and Harbour Association).

40

3.3 Choosing a method for predicting inundation
Inundation prediction should be carried out by a method with accuracy suited to the purposes of map
preparation and the characteristics of the region. The method should also be the one that has taken an
appropriate external force and facility condition. Ideally, numerical simulation should be used, in whichtimesequence is considered.
Data used for prediction as well as the results should be processed into the form that is compatible with
the Geographical Information System (GIS), so that they can be easily applicable to hazard maps, readily
available for future reviews, and shared with others. It should be noted that the results of inundation
prediction always carry uncertainty, and that the validity of the results should be appropriately evaluated.

1) Methods for predicting inundation
Inundation prediction should be carried out by a method with accuracy suited to the purposes of map
preparation and the characteristics of the region. The method should also be the one that has taken an
appropriate external force and facility condition. Ideally, numerical simulation should be used, in whichtimesequence is considered. When a simulation is difficult to perform, simpler alternatives are available
for inundation prediction. Principal methods for predicting inundation, including simple ones, are shown in
Table 3.3.1.

41

Table 3.3.1(1) Principal methods for predicting inundation

MethodMethod for simulating
inundation

Advangages (○)
Disadvantages (●)

Prediction image (for tsunami)＜Inundation zones and inundation depths＞

Numerical simulation ・ Prediction by simulating ○ Can precisely estimate the datain time sequence
tsunamis and storm surges necessary for preparing hazard maps
(See 2))(inundation zones in time series andinundation depth at each point)● Requires skills and costs

Estimates waterlevel and inundation
depth at each point

Gives data intime series

0～1m

2～3m
1～2m

35～40 分Reflects the effectsof breakwaters, sea
walls, land locks,
water gates, etc.

Level filling method

・The amount of flood water ○ Requires no special skills

is determined by multiplying
the width of breach, duration,and the amount of flood
water per unit length and unit
time, which are estimatedfrom waves and tides that are
predicted from the assumed
external force level.
・Inundation risk areas andinundation
depthsareestimated by assuming thatinundation starts from low
elevation zones.

○ Has a certain calculation basis fordetermining the amount of flood
water and inundation zones from thelevel of external force● Ignores reduction in force bybuildings (overestimates inundationarea) and the momentum of waterflow (underestimates inundation area)● May result in unrealistic
estimations depending on the area
topography, such as showing an
enclave in the inundation area, since
the flow of water is ignored● Can predict only the final
inundation zones and cannot predict
the speed or a time series ofinundation.

Does not estimate
expansion ofinundation zones by
the momentum ofwater flow

＜Changes over time＞

Does notestimate
reduction inforce bybuildings, etc.

Assumes thatwater level isuniform
throughout theentire area
(leveled
inundation)

30～35 分
25～30 分Assesses the effectsof breakwaters, sea
walls, land locks,
water gates, etc.

Estimates only the ultimate inundation zones (no time
sequential data)
Cannot evaluate the effects of breakwaters, sea walls, land
locks, water gates, etc.

Assumes that land isinundated up to thecontour line where
the amount of
overflow andovertopping is equal
to the amount ofwater filled

Evaluates sea walls, land
locks, water gates, etc., interms of their crown height
Reflects noeffects ofbreakwaters,etc.

Dashed blue line: inundation zone predicted by the numerical simulation analysis

42

Table 3.3.1(2) Principal methods for predicting inundation

MethodMethod for simulating
inundation

Prediction based on ・A time series, zones, andpast inundation
depths of inundation are
predicted based on the pastinundation events.

Estimation based ・Estimates to be inundation risk
on ground elevation areas those zones where theelevation is lower than theheight of tsunamis and storm
surges predicted from theassumed level of external force
・Predicts inundation depths by
subtracting ground elevationfrom the height of the tsunami
and the storm surge level
・The possible tsunami height isavailable from the Central
Disaster Prevention Council,
and the possible tide level canbe predicted by using theprobability tide levels

Advantages (○)
Disadvantages (●)

Prediction image (for tsunami)＜Inundation zones and inundation depths＞○ Is simple and inexpensive● Cannot be used for areas that havenot suffered inundation● May underestimate inundation riskzones, inundation depths andinundation initiation time since theexternal force level of the pastinundation may not the be the worst● Cannot reflect the effects ofprotection facilities constructed after
the past inundation● Cannot provide data that were notmonitored
duringthepastinundation○ Is simple and inexpensive● Ignores reduction in force bybuildings (overestimates inundationarea) and the momentum of waterflow (underestimates inundation area)● Cannot reflect the effects ofprotection facilities since inundation
risk zones are predicted only from thetsunami height, the tidal level, and theground elevation.
● Can predict only the final
inundation zones and cannot predict
the speed or a time series ofinundation.

A tsunami in the past
may not be one thatcaused the worst possible
inundation (Level 3
tsunami)＜Changes over time＞
The tsunami during the pastearthquake may not havecaused the worst inundation
initiation time (Level 3
external force)
The only available
data on inundation
initiation time isthat of past record

Inundation data
only applies tosites for whichpast records areavailable

The present
land form is
not reflected
Estimatedinundation zones of
the tsunami during
the ## Earthquake(####)

Water
reached theceiling of
the first
floor during
a tsunami inthe past

No effects are reflectedof breakwaters, sea walls,
land locks, water gates,
etc., constructed after thetsunami during the ##Earthquake

Dashed blue line: inundation zone predicted by the numerical simulation analysis

Assumes that zones up
to elevation equal tothe predicted tsunami
height will beinundated

Reflects noeffects bybuildings

Assumes thatwater level isuniform
throughout theentire area

Cannot evaluate the effectsof breakwaters, sea walls,
land locks, water gates, etc.

Dashed blue line: inundation zone predicted by the numerical simulation analysis

43

No effects are reflectedof breakwaters, sea
walls, land locks, water
gates, etc., constructed
after the tsunami during
the ## Earthquake

Dashed blue line: inundation zone predicted by the numerical simulation analysis

Estimates only the ultimate inundation zones (no time
sequential data)
Cannot evaluate the effects of breakwaters, sea walls, land
locks, water gates, etc.

Elevation:
4m
Reflects no expansionof inundation zone by
the momentum ofwater flow

Estimatedinundation zonesof the tsunami
during the ##Earthquake(####)

Inundation
started 30
minutes
after theearthquake.

2) Prediction by numerical simulation in time sequence
An overview of numerical simulation in time sequence is shown in Table 3.3.2. Numerical simulation byconsidering time series enables the collection of precise time-sequential data, such as inundation depth, flow
speed, and inundation initiation time. Such data is necessary for devising non-structural measures likeaccurate tsunami and storm surge hazard maps, which helps people to evacuate safely. It is also useful todesign structural measures suited to the characteristics of the inundation in the region.

Class
Tsunami simulation

Storm surge simulation

Table 3.3.2 Numerical simulation in time sequence
Contents• Numerical calculations for tsunamis should be in principle based on the
non-linear long-wave theory. However, tsunami movements in the deep sea canbe approximated to linear long waves.
• Tsunami movements in shallow sea areas, including run-up on the land, should in
principle be simulated using the theoretical equation of non-linear long waves(the shallow water theory), in which friction at the ocean bottom and advection
are considered.
• Cross oceanic propagation of a tsunami should in principle be calculated using
the theory of linear dispersive waves.
• Uncertain factors of calculation, such as the reflection rate, the conditions ofwave tips, the coarseness of the ground, and the precision of calculation, should
be decided based on the purpose of preparation, subjects of assessment, andtechnical levels at the time of preparation.
• Tsunamis may not always exhibit the maximum rise and drop in water level
during the first wave, and thus a sufficiently long period of time should besecured for estimating the maximum values.
• Storm surges should in principle be simulated by using the non-linear long-wave
theory, and storm surge movements in the deep sea can be approximated to linear
long waves.
• Storm surge movements in shallow sea areas and inundation of the land should in
principle be simulated using the theoretical equation of non-linear long waves(shallow water theory), in which friction at the ocean bottom and advection are
considered.
• Uncertain factors of external force, such as the traveling speed of a typhoon, anduncertain factors of calculation, such as wave set-ups by breaking waves, theovertopping rate of irregular waves, the coarseness of the ground, and theprecision of calculation, should be decided based on the purpose of preparation,subjects of assessment, and technical levels at the time of preparation.
• Calculations must be conducted over a period until tidal deviations are notshown.

a) Earthquake fault model and initial water level (tsunami)
The largest possible tsunami that may strike a region must be considered for studying regional disasterprevention measures. An earthquake may cause vertical displacements of the ground (upheaval andsedimentation); an earthquake that causes the largest tsunami height is not necessarily an earthquake thatcauses the maximum inundation depth. Thus, earthquake fault models for tsunami hazard maps should be
evaluated not only in terms of tsunami height but also in terms of inundation depth (difference between
tsunami level and the ground elevation after a displacement). Inundation depth should be calculated by using
the ground elevation described below in order to construct an earthquake fault model that can simulate thedeepest inundation that has ever occurred or may possibly occur:1) the ground elevation after sedimentation when the ground is predicted to subside,2) the ground elevation before upheaval when the ground is predicted to upheaval.
The initial water level to be used in tsunami calculation for preparing tsunami hazard maps should in
principle be determined by an earthquake fault model that is proven valid by tsunami reproducing

44

calculations.
b) Scale and route of a typhoon (storm surge)
External forces to be considered in preparing storm surge hazard maps should be decided by the body incharge of preparing the map, based on the tidal deviation that can occur during a typhoon of the largest
possible scale.
The scale of the largest possible typhoon should be assumed to be equivalent to that of the strongest
typhoon which struck the region in the past or the Isewan Typhoon. As for the route of the typhoon to beconsidered for estimating inundation, the route that could cause the most serious damage in the region should
be chosen by studying the routes of past typhoons.
c) Tidal level (astronomical tide) and wave height (tsunami and storm surge)
Tidal level (astronomical tide) for calculating tsunamis and storm surges should in principle be the syndic
mean high water level (H.W.L.). Also, storm surge calculation should use the tidal deviation and wave heightcalculated based on the largest possible typhoon. When the maximum tidal deviation ever recorded is to be
used for an assumed external force, the wave height should be decided by referring to measurements of the
past.
Sea

Land

Tsunami water level

T.P. level
Run-up height
Inundation depth
Tsunami height
Wave height
Tidal level (astronomical tide): H.W.L., etc.
Tsunami water level: height of the water)from the reference levelsurface (Note: Tsunami height denotes the height of a tsunami.

Figure 3.3.1

Relationships among tidal level, wave height, tsunami height, inundation depth, and run-up
height during a tsunami

45

Sea

Land

Tidal level

T.P. level
Inundation depth
Tidal deviation
Tidal level (astronomical tide): H.W.L., etc.

Figure 3.3.2

Tidal level during storm surge: height of
the water surface () from thereference level

Relationship among tidal level, tidal deviation and inundation depth during storm surged) Grid intervals (tsunami and storm surge)
Grid intervals for calculating tsunamis and storm surges in the sea and land areas to be assessed should beappropriately determined so that:
The accuracy of inundation prediction is ensured, and modeled land forms, such as streams, are appropriatelyreflected in inundation prediction, andBuildings and other structures are appropriately expressed as topographic models.
e) Elevation data (tsunami and storm surge)
Elevation data must have an accuracy of at least 1 m to properly estimate inundation depth. In areas wheresuch precise data are not available, the necessary accuracy should be ensured by correcting topographic maps
by using survey stations, conducting field surveys, having coast specialists check data or using other means.
f) Rivers (tsunami and storm surge)
Run-up of water along rivers should be calculated when necessary. The topographic conditions of rivers(shape and river bed elevation) should be expressed in calculation grids and elevation (water depth), and theconditions of structures, such as the crown height of river banks, should be set as well.
When inundation is predicted to occur from a river during storm surges, the discharge of the rivershould be appropriately determined based on the properties of the river and data from the past.
g) Structures (tsunami and storm surge)
To predict inundation by tsunami, damage to strucures should be first calculated by using the earthquake
motion based on the selected earthquake fault model as an assumed external force. Then, inundation
prediction should be performed, considering the calculated damage to structures.
When predicting inundation by tsunami for preparing hazard maps for residents, attention should be paid
to structures that are higher than the water level during the propagation process of the tsunami (for example,
banks, revetments, breakwaters, walls, and highway banks). Protection facilities, such as water gates andland locks, should be assumed to be open since it will possibly be difficult to close them before the tsunami
arrives, considering that tsunamis travel fast and earthquake motion may possibly cause damage to thefacilities. On the other hand, the following facilities should be assumed to be closed:1) automated earthquake resistant facilities,
2) facilities that are always closed, and3) earthquake resistant facilities that can be closed very quickly before a tsunami arrives.

46

To predict inundation during storm surges for preparing hazard maps for residents, damage to coast
protection facilities by overflowing of storm surges and overtopping by high waves should be estimated,based on the present state of the facilities.
Water gates and land locks should be assumed to be closed except those that are evidently out of order.
When the gates and locks are likely to be difficult to close, calculations should be performed, assumingthat they are open.
For preparing hazard maps for administrators, the condition of coast protection facilities should beappropriately decided based on the purpose of investigation.
Table 3.3.3 Examples of facility conditions used for predicting inundation
Inundation prediction during tsunami Inundation prediction during storm surges
Banks, revetments,
Damage to facilities by earthquake Facilities are assumed to function
breakwaters, etc.
should be considered.
properly.
Water gates and land locks are Water gates and land locks are assumed toassumed to be open (tsunamis arrive be closed.
fast and facilities are possibly Those that are known to not function (duedamaged).
to deterioration, etc.) are assumed to be
They are assumed to be closed when open.
Water gates, land
they are:locks, etc.
1) automated, earthquake resistantfacilities,2) always closed, and3) earthquake resistant facilities thatcan be closed very quickly before atsunami arrives.
Conditions are decided based on the purpose of investigation for hazard maps foradministrators.
Notes
Example: The worst case – gates and locks are all open or there are no gates orlocks. The maximum protection case – gates and locks are all closed.
h) Data used for prediction and output data (tsunami and storm surge)
Care must be taken that the results of inundation prediction contain uncertainties. Tsunami and storm
surge hazard maps are prepared by superimposing necessary information on maps of inundation risk areas
and evacuation zones, which are identified based on the inundation areas identified by inundation prediction.
Thus, the results of prediction should be prepared in forms that can be processed with the geologicalinformation system (GIS). The same is true for data used for prediction, since they will possibly be processed
into hazard maps and revised in the future. The data format should be a general format to facilitate efficientconstruction and revision of hazard maps and sharing of data among related parties and experts.
3) Possibility of disaster beyond prediction
It must also be noted that disasters can possibly occur with external forces that are beyond prediction.
Extra care should be taken to keep consistency among adjacent municipalities in terms of condition settings
when the disaster to investigate is likely to cause damage over two or more municipalities. Conditions thatcannot be analyzed with today’s technologies should be considered in the future. Conditions that are not yet
established today are shown in Table 3.3.4.

47

Table 3.3.4

Class
TsunamiStorm surge

Non-established conditions
Non-established conditions• Standardized method for analyzing ground displacement• Optimum values of fault parameters and coefficient of coast friction• Method for considering buildings, houses, and other structures in grid systems• Simulation of formation of undular bore in rivers• Simulation of soliton fission and undular bore
• Behavior of water when storm surge water runs up a river and floodwater flows down theriver at the same time
• Conditions for levee breaches• Predicting the width of levee breaches• Predicting the time of levee breaches

4) Evaluating prediction
Underestimation is likely to result in predicting the inundation depth in the worst case scenario as being
too low, which may lead to insufficient evacuation measures and loss of human life. On the other hand,overestimation causes disaster prevention facilities to be constructed in excess. To prevent both under- andoverestimation, prediction results should be appropriately validated by regional development bureaus, and/or
the coast division of each prefectural government, before the results are open to residents.

48

Chapter 4 Methods for preparing tsunami and storm surge hazard maps
from the results of inundation prediction
4.1 Considerations for preparing hazard maps for specific purposes
4.1.1 Purposes of hazard maps
Tsunami and storm surge hazard maps should be prepared to serve specific purposes. This manual
describes methods for preparing two types of hazard maps as typical examples: those for residents andthose for administrators. Hazard maps can also be prepared to serve region-specific purposes.

The contents and expressions of tsunami and storm surge hazard maps must correspond to the purpose of
preparation. In Chapter 4, the contents and expressions of two typical types of hazard maps, namely those forresidents and administrators, are described. Main users of the maps, and the utilization methods of such maps
at each stage of a disaster, are shown in Table 4.1.1, and considerations for each hazard maps are shown in
Table 4.1.2.
Hazard maps should also be prepared if necessary for other parties other than residents and administrators,
such as for companies that have factories in inundation risk areas, fishermen, and people working at ports
and harbours, by including information and expressions appropriate to the purposes of the maps.
Hazard maps can be used as a tool for risk communication between residents and governments, and canhelp them share information about risks, costs, and ways disaster prevention measures should be carried out.
Table 4.1.1 Users of tsunami and storm surge maps and utilization methods at each stage of disaster
Stage of disaster
Users
Utilization method
Collect information for evacuation activities, and learn
Residents
about disasters and the region (land use, etc.)
Before disaster
Draw up and execute preventive measures (by constructing
Administrators
evacuation sites and disaster prevention facilities)
Collect information about tsunami or storm surge (such as
Residents
the height of high tides) and evacuation sites
Immediately before
disaster (storm surge)
Draw up and execute emergency measures (evacuation
Administrators
plans, rescue plans, etc.)
Collect information after evacuation (orders from
Residents
municipal governments, etc.)
After disaster
Draw up and execute emergency measures (evacuation and
Administrators
rescue plans)

49

Who
Residents

Residents

Table 4.1.2
When and where
Before disaster, at
home
Immediately
before disaster, ata place to decideevacuation
After disaster, atevacuation site

Considerations for each hazard map
What
Why and how to use
To understand the risks of tsunamis and storm
Hazard maps
surges at residences, and to be aware of evacuation
for residents
sites and routes
To appropriately decide on evacuation based on
Hazard maps meteorologicalinformation
andperipheral
for residents conditions

To collect basic information from municipal
governments after evacuation
To draw up plans for evacuation, construction,
Before,operation, and rescue, according to disaster
Hazard maps
immediately
situations (for example, for coast administrators toAdministrators before, and afterforgain a correct understanding of the performances ofdisasterat administrators
protection facilities against tsunamis and storm
working places
surges)Residents

Hazard maps
for residents

4.1.2 External forces for different purposes
It is important to set external forces appropriate for individual purposes of hazard maps, so thatinundation risk areas for tsunami and storm surge hazard maps can be appropriately identified based on the
purpose of preparation and the characteristics of the region.

It is important to set external forces appropriate for individual purposes of hazard maps, so that inundation
risk areas can be appropriately identified based on the purpose of preparation and the characteristics of theregion. As described in Chapter 3, external forces for predicting inundation should be decided bycomparatively investigating two or more patterns, depending on different conditions. The three external force
levels shown in Tables 3.2.2 and 3.2.3 should be at least taken into consideration.
Hazard maps for residents must show the worst possible inundation in order to ensure evacuation ofresidents. On the other hand, hazard maps for administrators need to be prepared to serve different
possibilities, including situations caused by relatively small-scale disasters that are more likely to occur
before the completion of structural measures than large-scale ones (Table 4.1.3).
In this manual, inundation risk areas are to be identified by individually considering either tsunamis or
storm surges as the external force, and inundation information for cases where they occur simultaneously
should be included by devising appropriate display methods (See 4.4 Methods for displaying predicted
inundation risk areas and evacuation areas for display methods). Maps may be prepared by considering
simultaneous occurrence of tsunamis and storm surges depending on regional characteristics.

50

Table 4.1.3 Inundation information and external force levelfor each hazard map purpose
User

PurposeResidents

Stage of utilization

SmoothBefore disasterevacuation To understand risk
Immediately before
disaster
To know a safe place(evacuation site)
Division
SmoothBefore disasterin charge evacuation To plan evacuationof disasterprevention
Immediately before
and during disastersTo
issue
evacuation-relatedorders
Effective
Beforedisasters
Division(whenconstruction
in charge facilities
plans are drawn up)of disasterTo decide the need ofprevention
constructing
andfacilities
improving facilities

4.1.3

Inundation to be prevented by facilities
Worst inundation case
Inundation to be prevented by facilities
Worst inundation case

Externalforce
Level 2
Level 3
Level 2
Level 3Inundation during facility construction
Inundation to be prevented by facilities
Worst inundation case
Inundation during facility construction
Inundation to be prevented by facilities
Worst inundation case

Level 1
Level 2
Level 3
Level 1
Level 2
Level 3Inundation during facility construction
Inundation to be prevented by facilities
Worst inundation case

Level 1
Level 2
Level 3Inundation information to be included

Other considerations(1) Userfriendliness
Tsunami and storm surge hazard maps for residents must be userfrendly.

Hazard maps for residents will be used for evacuation during disasters. If residents fail to correctly
understand the information on the map and make an incorrect decision, they may lose their lives. Thus,
hazard maps for residents must be easy-to-understand for all of them.

(2) Flexibility of ideas
Tsunami and storm surge hazard maps should be prepared so as to help flexibility of ideas.

Inundation risk areas and evacuation zones shown in a tsunami and storm surge hazard map is merely the
result of prediction under a certain condition. Showing the areas on the maps may cause residents to believethat only the areas shown on the maps will inundate during disasters.
Fixed ideas about disasters may give residents false feelings of safety and inhibit smooth evacuation. Thus,
measures should be taken to prevent residents from having fixed ideas, such as by printing in bold letters“Areas other than those shown may inundate,” and “The actual inundation depth may exceed this value,”51

although few measures are available for displaying information on paper maps. Other measures should also
be taken such as distributing leaflets showing such additional information as inundation predictions under
different conditions, communicating risks to residents using tsunami and storm surge hazard maps, andparticipation of residents in preparing the maps.

(3) Participation of residents in preparing tsunami and storm surge hazard maps for residents
By participating in preparation of tsunami and storm surge hazard maps, residents can help incorporate
regional characteristics into the maps, become aware of them, confirm them as well as find more
opportunities to use the maps.

In preparing hazard maps for residents, their participation is extremely important to incorporate regional
characteristics into the maps as well as for residents to become aware of and confirm those characteristics
and to find more opportunities to use the maps. By adding, for example, evacuation routes to the maps byresidents themselves based on their own judgment regarding the regional characteristics and possible
situations, the maps can serve their purposes more usefully and effectively at evacuation than the ones
completed and distributed by an administrative body.
Participation of residents in preparing tsunami and storm surge maps can promote risk communication
between residents and administrative bodies, and it can also make residents feel that they are voluntarily
preparing the maps, which is an indispensable feeling for promoting frequent and effective use of the maps.
Workshops are one of the effective ways to promote residents’ participation (See 5.2 Measures forpromoting the understanding of residents for workshops).

(4) Characteristics of tsunami and storm surge disasters
Tsunami and storm surge hazard maps must be prepared by considering the characteristics of tsunami
and storm surge disasters, and the risks and related information must be appropriately expressed.

Table 4.1.4 shows characteristics of tsunami and storm surge disasters and the corresponding precautions
to be taken when prepareing tsunami and storm surge hazard maps for residents.
Table 4.1.4Class
TsunamiStorm surge

BothCharacteristics of tsunami and storm surge disasters and the corresponding precautions
when preparing hazard maps for residents
Characteristics to note
● A tsunami may arrive soon after an earthquake.
→ Residents need to evacuate as soon as earthquake motion is felt.
●Buildings may collapse during an earthquake.
→ Collapsed buildings may block evacuation routes.
●Tsunamis cause characteristic damage→ Care must be taken regarding backwash and flow speed.
●A storm surge can be predicted by monitoring an approaching typhoon.
→ Residents have time to decide on evacuation.
●Typhoons bring storms when they approach→ Evacuation is difficult during storms.
●Residents may create fixed impressions of disasters from hazard maps.
→ Effors must be made to avoid creating fixed impressions. (Information such as detailed
simulation results should be included not in a map but in a separate booklet for residents tolearn about disasters since such information may lead them to create fixed impressions.)

52

4.1.4

Naming hazard maps for residents
Easy-to-understand names should be given to hazard maps when they are distributed to residents.

Maps that carries necessary information for disaster prevention in addition to inundation risk areas during
tsunamis and storm surges are called “hazard maps”, but names that are easy to understand should be given
to them when they are distributed to residents, such as “disaster prevention map”, “tsunami evacuation map”,
and “storm surge risk map”.

Results of inundation
prediction

Figure 4.1.1

Information about
inundation

Processing

AddingDisaster prevention
information (evacuation sites,
etc.)

Tsunami and storm surge
hazard map (name of themap when distributed toresidents: disasterprevention map,
evacuation map, etc.)

Concept of giving a name to tsunami and storm surge hazard maps for residents

53

4.2 Information to be included in hazard maps for residents(1) “Information for evacuation” and “information for understanding disasters”
Information needed for smooth evacuation of residents is classified into “information for evacuation”
and “information for understanding disasters”. “Information for evacuation” is necessary information
regarding evacuation, such as evacuation sites and routes. “Information for understanding disasters” isinformation, such as outlines of tsunami and storm surge disasters, for increasing local residents’awareness about disasters. Especially, critical information about the characteristics of disasters, regional
characteristics, and earthquakes related to tsunamis are important as “information for understanding
disasters”.

1) “Information for evacuation” and “information for understanding disasters”
Information needed for smooth evacuation of residents includes an illustrated or written form of“information for evacuation” and “information for understanding disasters”.
Information for evacuation must include inundation risk areas, evacuation sites, evacuation routes, andother indispensable information for evacuation. Notes about external forces that exceed assumptions should
be stated, and to ensure safe evacuation, possible risk areas may be added outside inundation risk areas, bothof which form evacuation zones. (possible risk areas and evacuation zones are described in 4.4 Methods fordisplaying predicted inundation risk areas and evacuation areas). Tsunami hazard maps must include theestimated inundation initiation time, the direction of inundation, inundation depth; buildings that will notinundate, evacuation sites, and evacuation routes must be marked in the way they are easily recognized.
Storm surge hazard maps must include precise inundation depths, inundation risk areas; evacuation sites,
evacuation routes, and individual buildings must be presented in a simple and easy-to-recognize manner.
Information for understanding disasters is information helping residents to understand what tsunami/storm
surge disasters are like. Records of disasters in the past (inundated areas, etc.), the current status of coast
protection facilities and their effects may also be useful information for increasing residents’ awarenessabout disaster prevention and about self-help and mutual assistnace as well as enhancing residents’
understanding of the development of disaster prevention facilities.
2) Other information
Information specific to each region should also be included. For example, statements in languages otherthan Japanese should be included in maps for areas where many residents are non-Japanese speakers.
Information on disaster characteristics should be included, such as the strong backwash and high flow speeds
of tsunamis. For tsunami hazard maps, information related to earthquakes (such as densely-packed areas ofwooden buildings that are prone to collapse and block streets during an earthquake, and steep slopes that areprone to cause landslides) is also important, since such information influence people’s decisions about whereto evacuate and/or which routes to take.
Which site to evacuate should be determined by considering its capacity and the extent of the damage it
has suffered.
Adding photographs of past disasters can be an effective way for people to realize how devastating they
can be.
Displaying all these on a single map may result in a map which is complicated and difficult to understand.
Thus, information to be included must be selected by considering the purpose of the map as shown in Table
4.2.1.

54

To
evacuate

To learnor
educateTable 4.2.1 Information needed for smooth evacuation of residents at each stageClass
Information
Notes
Information
・ Inundation prediction (inundation risk areas, ・Must be displayed inneeded during inundation depth, arrival time, etc.)asimpleand・ Evacuation sites (including public facilities, easy-to-understandevacuation
schools, hospitals, buildings specified for manner.
evacuation, etc.)
・Evacuation routes and dangerous spots (including ・Should be included inspots prone to sediment-related disasters)
principal maps.
・ Information on earthquake-related disasters(including landslide risk areas and the locations ofchemical factories, etc.)
Information for ・Risk information based on the characteristics of ・Should be displayedinvestigating
disasters (including the fast approaching separately
fromevacuation
speed/strong receding force of tsunamis, etc.)
information that isduring normal ・Inundation in the past (largest inundation area, needed
duringmaximum inundation depth)
times
evacuation.
・State of coast protection facilities (crown height ofbanks, revetments, design crown height, ・Should be separately
printed on the other
deterioration, etc.)
・Evacuation zones (risk rank, facilities needing side of the map or inassistance in evacuate, locations of subways and leaflets, etc.
underground malls, etc.)
・ Evacuation standards (standards for issuing ・Should be stated in
evacuation orders, determination of external force an easy-to-understandvalues, importance of voluntary evacuation, etc.)
manner.
・Tips for evacuation, family rules about evacuation,
etc.
・Methods for transmitting information (routes andmeans of transmitting information to residents, andmethods for collecting information)
・Distribution of earthquake motion when strong
tremors are anticipatedInformation to ・Generation mechanisms of tsunamis and storm
educateon surges (meteorological factors, earthquakes, anddisasters
topographic characteristics)
during normal ・ Risk of tsunamis and storm surges (flood
configuration, damage, and flooding and damage bytimes
multiple causes)
・ Basic knowledge about meteorology andearthquakes (terms, rain patterns, earthquake
intensity, etc.)
・Information about tsunamis and storm surges in
the past (meteorological and hydrological data,hypocenters, earthquake intensity, inundation,
damage, and evacuation)
・History of protection facility construction and theeffects of the facilities
・ History of the region (history of landformformation, city formation, disasters)

55

Explanations
・Methods for reading and using hazard mapsofhazard ・ Routes of transmitting disaster prevention
information
maps, etc.
・Tips for normal times, tsunamis, and storm surges
・Contact numbers during emergencies (lifelines,
police, and fire department)
・Ways to deal with the situations after evacuation
・Body in charge of preparing maps, leaflets, etc.
(name and date)(2) Basic information to be included in hazard maps for residents
Hazard maps for residents should include the minimum amount of information that is indispensable for
evacuation. The information should be expressed in a simple and easy-to-understand manner so as to be
helpful for everyone.

Hazard maps for residents should include the minimum amount of information that is indispensable for
evacuation since the map size is limited. Also, the information should be expressed in a simple andeasy-to-understand manner so as to be helpful for everyone.
Information for evacuation is more relevant to hazard maps for residents than information forunderstanding disasters. Information for evacuation includes basic information for evacuation, which isessential and fundamental, and additional information for evacuation, which is specific to the region; bothkinds should be included in hazard maps for residents. Table 4.2.2 shows a list of information to be included
in hazard maps for residents.
When displaying information in a map, precautions should be taken to avoid giving fixed impressions ofdisasters to residents by stating the uncertainty of inundation prediction. Since the predicted arrival time andinundation initiation time are uncertain, the effects of such uncertainty on residents’ decisions about
evacuation should be considered.
Information for understanding disasters and investigating evacuation during normal times should be
distributed in different forms such as leaflets, separately from hazard maps. Measures may also need to betaken such as displaying the inundation risk areas in the entire municipality on the front and displaying
regional evacuation information for each district on the back.
Table 4.2.2

Information to be included in hazard maps for residents (basic design)

Item

Basic design (draft) (B: Basic information, N: points to note)

Concept

Minimum amount of information indispensable for evacuation should be displayed in a
simple and easy-to-understand manner.

Scale

Scale enabling residents to investigate evacuation (each house should be able to be
identified if necessary)

Information
to beincluded inhazard maps
for residents

Basic
informationfor evacuation(theinformationwhichbasically

Externalforce

One of the assumed B: External force that may cause theexternal forces
most serious inundation (Level 3)(Level 2 (design force) may be used)
N: It should be consistent withassumed damage already announced.

Inundation Inundation risk area

56

B: Care must be taken to avoid
giving fixed ideas.

should
included)be

Possible risk area

Disaster Evacuation site
prevention

B:
Designatedevacuationsites/buildings
N: Hills and tall buildings should
also be examined.

Evacuation route

B: Designated evacuation routes andimportant points on the routes (suchas bridges and cliffs)
N: They should be examined atworkshops, etc.

Additional
External External
forcesinformation
force
other than the one
for evacuation
assumed in the(thebasic information
region-specificfor evacuation
information
Inundation Predicted deepest
whichiswater depth, arrival
necessary totime, and dangerous
display for thesites
minimum
amount)Disaster Inundation records,
prevention state of protection
facilities,
groundelevation, facilities
that need assistancetoevacuate,
underground spacestoevacuate,evacuation
standards,
tips,
rules, etc.
Size
shape

B: Possible risk areas should be set
by either elevation, district numbers,
or principal highways, depending on
regional characteristics.

B: Tsunami level predicted by theMeteorological Agency and typhoon
information when residents can judge
the differences in external force.
B: Predicted deepest water depth andarrival time should also be statedwhen they should be published.
N: The information may be stated intext.
N: The minimum amount may be
included depending on regional
needs.

and -Size and shape should be adjusted for home use (about A3, for posting on a refrigerator,
coordination with garbage collection schedules, municipal information booklets, etc.)-Form should be adjusted for portable use upon evacuation (use of fluorescent ink,
water-proof paper, etc.)

Note: The table assumes hazard maps for residents, and the size and shape presented here may not apply to hazard maps forworkshops and educational activities.

57

4.3 Information to be included in hazard maps for administrators
Hazard maps for administrators should include “information for preventive measures” and“information for emergency measures” depending on preparation purposes of each governmental
division. Information for each purpose should be superimposed on a map showing basic information,
which is common information such as precise inundation risk areas.

Hazard maps for administrators should include “information for preventive measures” and “informationfor emergency measures” depending on preparation purposes of each governmental division. Informationneeded for each purpose should be superimposed on a map showing precise inundation risk areas.
Information for preventive measures includes information needed for constructing evacuation sites androutes, selecting appropriate sites for establishing disaster prevention headquarters, educating governmental
personnel in disaster prevention, and drawing up land use and regional development plans (Table 4.3.1). On
the other hand, information for emergency measures includes information that can be used for drawing up
plans for evacuation, rescue and facility operation.
Table 4.3.1

PurposePreventive
measures

Emergency
measures

Example of using hazard maps for administration
Utilization(1) Constructing evacuation sites and routes(2) Selecting appropriate sites for establishing disaster prevention headquarters(3) Educating personnel about disaster prevention(4) Drawing up land use and regional development plans(5) Reviewing facility construction and improvement(1) Drawing up evacuation and rescue plans(2) Drawing up plan for operating facilities

Hazard maps for disaster prevention should include the predicted number of affected people, its
distribution, and the locations/capacities of evacuation sites and routes, which are considered useful for bothpreventive and emergency measures.
Hazard maps for coast management administrators should include facility information, such as thelocations/structures of facilities, facilities that are prone to damage, and the results of stability
calculations/liquefaction reviews, which are considered useful for taking preventive and emergency
measures. Table 4.3.2 shows information that is considered necessary for inclusion, based on the Manual for
Predicting Tsunami Disasters. Information must be selected so as to cope with objectives of each map (Table
4.3.3).
For reference, methods for utilizing information during disasters and when taking disaster prevention
measures are shown in Reference 2.

58

Table 4.3.2 Basic information to be included in hazard maps for administrators
Basic information
Information for each purpose
External force
・One of the assumed external forces
・Other external forces depending on
purposeInundation
・Inundation risk areas
・Disasters in the past・Predicted deepest inundation depth・Predicted inundation initiation time andplace
・Evacuation zones
Disaster・Protection line
・Disaster prevention centers
・Population distribution
・Police, fire department
prevention
・Land use
・Public facilities
・Transportation routes during emergency ・ Facilities needing assistance to・Earthquake-resistant berths
evacuate
・Evacuation facilities
・Power facilities
・Evacuation sites
・Coast protection facilities
・Evacuation routes
Table 4.3.3 Examples of information to be included in hazard maps for administrators
Class
Examples of information to be included (information to be layered)
Notes
Basic
Precise inundation prediction (inundation risk area, predicted deepest Basic
information inundation depth, initiation time, initiation site, and evacuation zone)
information for
all kinds ofTopography
investigation
Protection facility
into tsunami andOverview of the region (population distribution and land use)
surge
Emergency transportation routes, earthquake-proof berths, and storm
disasters
evacuation facilities
Information Tsunami and storm surge disasters in the past (inundation areas and Necessary
depending damaged areas)
information
on purpose Disaster prevention centers (national, prefectural and municipal shouldbelayeredover
thegovernments)[Police stations/boxes, fire headquarters/stations, meteorological basic
observatories/stations, disaster prevention centers, communication information
facilities, governmental radio communication network for disaster considering theprevention, seawalls, water gates, flood prevention warehouse, water following:-Planning stage
supply centers, emergency vehicle bases]
Evacuation facilities (emergency meeting places, evacuation sites (preventive(emergency shelters), evacuation routes, heliports, evacuation ports, measures,
emergencyetc.), capacities and earthquake resistance of evacuation sites
Public facilities (transportation facilities (roads, railways, ports, airports, measures)etc.), specifications of subways and underground malls (locations, -Disaster stage(immediately
elevations of entrances, etc.)[Power facilities (power stations, substations, and transmission lines), before and aftergas supply facilities, water supply facilities, sewerage facilities, disaster,
telephone/telecommunication facilities (stations and principal lines), emergency
schools, community halls, hospitals, health centers, elderly care response, andrestoration)
facilities, kindergartens, nursery schools, welfare facilities]ofControlled areas under the laws concerning disaster prevention (coastal -Kinds
serviceprotection areas, harbour areas, fishery port areas, national parks,
quasi-national parks, control traffic zones, etc.)
Coastal protection facilities (locations and structures, facilities that areprone to damage, results of stability calculation/liquefaction review,
elevation of pumping stations)594.4 Methods for displaying predicted inundation risk areas and evacuation zones(1) Inundation risk areas and evacuation zones
Inundation risk areas and evacuation zones should be displayed on a hazard map so as to serve thepurpose of the map. It should be noted that the prediction of inundation risk areas contains uncertainty.

The results of inundation prediction conducted in Chapter 3 should be processed according to the purposeof the hazard map, and should be displayed as inundation risk areas and evacuation zones. It should be notedthat the prediction is made based on a certain assumption and contains uncertainty. The flow of processing
inundation prediction results into inundation risk areas and evacuation zones is shown in Figure 4.4.1.

External forces
facilities, topography

Setting conditions

Estimating inundation

Inundation prediction
results

Identifying
possible risk areas(See 4.4(3))

Inundation risk areas
evacuation zones

Adding related
information, etc.
Hazard map(Information fordisaster prevention)

Figure 4.4.1

Flow of processing inundation prediction results into inundation risk areas
and evacuation zones

60(2) Accuracy of displaying inundation risk areas
Inundation risk areas should be displayed in as small a grid size as possible and by using as detailed
topography as possible so as to correctly reflect actual landforms.

Inundation risk areas are the basis of all kinds of investigation and must be correctly displayed. Tsunami
and storm surge hazard maps should show topographic data as precisely as possible in the smallest grid size
possible so that users can identify inundation areas, inundation depth, each building, evacuation sites andinundation conditions along evacuation routes in order to make sound judgment for evacuation and to selecta safe evacuation route. The maps should be prepared with representational accuracy that is good enough toallow users to identify side ditches along evacuation routes, houses and bridges that may collapse, thestructural characteristics of water gates and land locks, topographic characteristics, and the characteristics ofrivers. Here, grid size denotes the side of the grid to be displayed on maps, not the grid intervals forpredicting inundation.
Precise inundation depth can be displayed by the method in Figure 4.4.2 using precise topographic data,such as elevation. However, it should be noted that the precision of displayed inundation depth depends on
the precision of the prediction.
Water surface
Output of inundation prediction(water level)

GroundsurfaceWater
surface
Groundsurface

Topographic
Base level

Inundation depth
to be shown on
hazard map
More precise
topographic
information

Base level@2m
Grid size used for hazard map display@50m
Grid interval used for inundation prediction@50m
Grid interval used for inundation prediction

Figure 4.4.2

Method for precise display of inundation depth(3) Methods for displaying inundation risk areas and evacuation zones
Inundation-related information that is used to investigate evacuation includes inundation area,
inundation depth, inundation initiation time, and innundation speed. To ensure evacuation, possible risk
areas, in addition to inundation risk areas, should be included in evacuation zones. Possible risk areas
are areas that are not predicted to be inundated but are possible to be inundated considering theuncertainty of prediction. Such zones should be designated outside inundation risk areas by considering
the characteristics of disasters, topography and occupancy of the areas.

1) Information on inundation for investigating evacuation
Information on inundation for investigating evacuation includes inundation area, inundation depth,
inundation initiation time, and flow speed.
2) Method for displaying inundation areas to investigate evacuation
Inundation depth should be shown on tsunami and storm surge hazard maps on the basis of elevation(T.P.). Maps should also show a statement describing the need to consider external forces larger than thoseassumed, since the prediction of inundation areas contains uncertainty. Measures should also be devised for61drawing users’ attention to the uncertainty of prediction.
One of such measures is to show two or more prediction results by using different external forces. For
example, the prediction results based on the largest storm surge in the area and the largest external force
experienced by the country (for example, Isewan Typhoon for Japan) can be stated on hazard maps. Sinceusing two different external forces may often complicate the prediction procedure, however, a simple method
for estimating inundation risk areas based on one external force is shown in Figure 4.4.3. The figure
illustrates how possible risk areas can be displayed outside inundation risk areas. Here, “possible risk area”
denotes an area that is predicted to escape inundation but which cannot rule out the possibility of innundation
if the uncertainty of prediction is taken into account. In most cases, there being almost no difference in risk
between either side of the boundary, the areas should be shown in color gradation to prevent
misunderstanding, as illustrated in Figure 4.4.3. Prediction may give completely different results depending
on conditions used, and conditions appropriate for each region must be considered.
Possible risk aras can be identified using the method shown in Table 4.4.1. However, other methods
should also be considered so as to use a method which is appropriate for the region and other conditions. For
example, areas below certain elevation can be designated as possible risk areas, but evacuation orders can beissued to residents according to administrative district boundaries. When this method results in anexcessively large possible risk area which is unrealistic, multiple inundation predictions by using different
external forces and facility conditions are a possible way to accommodate the uncertainty of prediction.

Outside inundation risk area
Park

Possible risk area}

Evacuationzone

Inundation risk area

Sea
Figure 4.4.3

Schematic diagram of possible risk area

Table 4.4.1

Based onlandform
Based onadministrative
perspectives

Methods for setting areas to evacuate
Class
MethodElevation
Areas lower than X m in elevation (predictedmaximum inundation depth plus Y percent) are set as
evacuation zones.
Streets and highways
Areas that are outside an inundation risk area andsurrounded by large streets and highways are set as
evacuation zones.
Districts
Districts adjacent to inundation risk areas are set as
evacuation zones.

62

(4) Methods for displaying information about inundation
Hazard maps must transmit appropriate information about inundation. Display methods should be
devised so that residents can easily imagine inundation damage.
Tsunami hazard maps should display information so that users understand the direction to evacuate andlocate buildings and sites that will not inundate.
Storm surge maps should display information so that users understand the time and direction toevacuate, locate buildings and sites that will not be inundated, and avoid inundation risk spots alongevacuation routes.

1) Displaying information about inundation on tsunami hazard maps
Inundation depths should be displayed, such as inundation up to the first floor, to the second floor, etc.
Hazard maps should also be devised to carry information characteristic of tsunamis, such as backwash andfast flow speed, and buildings that will not be inundated and can be used for emergency shelter.
Inundation initiation time should be displayed in units of 5 minutes after an earthquake when it is effective
for deciding the time and direction to evacuate. In some cases, it is better not to show inundation initiation
time. When inundation initiation time is displayed together with inundation depth, use of arrows to show
directions of inundation, use of contours and hatching to show inundation initiation time, and use of othermethods, should be considered to prevent misinterpretation.
2) Displaying information about inundation on storm surge hazard maps
Inundation depths should be shown in relation to human body parts (heel (15 cm), knee (50 cm), waist (80cm), chest (1.2 m), and over).
Inundation initiation time should be displayed in units of 30 minutes after the start of inundation. Wheninundation initiation time is displayed together with inundation depth, use of contours and hatching to show
inundation initiation time, and other methods, should be considered to prevent misinterpretation.
3) Considerations for displaying information about inundation
Information about inundation can be displayed by using the methods described above and by flexibly
meeting the requests of residents which are collected during workshops.
(5) Superimposing necessary information
In preparing tsunami and storm surge hazard maps, inundation information and other relevant information
should be based on data from the geological information system (GIS), so that such information can beprovided upon request for various investigations using those maps.

1) Necessary data for displaying inundation and background information
To display inundation and background information, the following data are needed:
Inundation depth data: used for two-dimensional expression of information related inundation risk areas suchas inundation initiation time and deepest inundation depth;
Ground elevation data: used to express inundation states;
Data on buildings and evacuation sites: used to express individual houses, and facilities/buildings that willserve as evacuation sites, andOther background data: used to express information along evacuation routes.
2) Overview of basic dataa) Inundation depth data
Inundation depth data should be collected from the results of inundation prediction. The data includes
location, inundation initiation time, and deepest inundation depth. The data should be converted into GIS63data to be superimposed with other background data for investigations. To express precise inundation depth
estimated from inundation prediction, the precise ground elevation data in b) should be used.
b) Ground elevation data
Ground elevation data throughout Japan is available from “numerical maps 50m mesh (elevation)” of theGeographical Survey Institute. The maps are inexpensive, but care must be taken since they have relatively
coarse grid intervals and contain errors. City plan maps, etc. can be used to correct elevation.
Recently introduced aerial laser survey technology can provide precise ground elevation data, which can
express inundation areas in 2 m grids, but surveys are quite expensive.
c) Data on buildings and evacuation sites
When a municipal government has electronic city plan maps of 1:2,500, such maps can be used. However,most of the maps show no names of buildings, and names should be added for evacuation sites.
Other available data on buildings is electronic residential map data sold by map makers. Names and floor
numbers of buildings are already included in the data. When hazard maps using this data are to be distributed,
it should be noted that contracts may need to be made with the makers.
d) Other background data
Data on roads is available from electronic 1:2,500 city plan maps prepared by municipal governments andfrom the numerical map 2500 (national land space data infrastructure) of the Geographical Survey Institute.
Electronic residential map data described in c) also contains precise background data.
Precise ground elevation data collected by aerial laser survey and images from satellites can besuperimposed by using GIS.
3) Coordination with various investigations
Data should be prepared by using the geological information system (GIS), so that the data can beprovided on request for various investigations using hazard maps.

64Chapter 5

Use of tsunami and storm surge hazard maps

5.1 Disseminating tsunami and storm surge hazard maps
(1) Importance of disseminating tsunami and storm surge hazard maps
To effectively utilize hazard maps for residents in the prevention of disasters during tsunamis andstorm surges, it is important to thoroughly inform residents of the maps, and measures should be taken to
do so.
Measures should also be employed to prevent users from having fixed ideas on disasters, since theinundation information shown on the maps contains uncertainty.

Mere distribution of tsunami and storm surge hazard maps to residents does not serve their fundamental
purposes. It is important for residents to understand the risks of disasters and ways to seek safety such as
evacuation procedures. Thus, educating residents about hazard maps is essential. Also, users may not takeproper evacuation actions, mistakenly assuming that only the inundation risk areas on the maps will be
dangerous. Thus, measures should be devised to avoid giving users fixed ideas in distributing or postinghazard maps. (See 4.1.3 Basic considerations for preparing tsunami and storm surge hazard maps formethods of avoiding fixed ideas.)(2) Ways to disseminating hazard maps
Tsunami and storm surge hazard maps should be distributed to each household and posted oncommunity bulletin boards to promote residents’ awareness of disasters.
Information related to disaster prevention can be provided to residents by distributing printed materials,
setting up bulletin boards, using the Internet, etc.
Methods should also be devised for disaster-vulnerable people, such as the handicapped, elderly, andchildren as well as for foreigners, tourists, drivers, etc.

1) Tools for disseminating hazard mapsa) Printed hazard maps
Distributing a hazard map to each household is the most basic way to inform residents. However, carefulattention should be paid t to the size and a distribution method of the map.
Hazard maps are often seen placed between pages of community information bulletins. In this way, maps
may have little chance to be noticed because people often thrown away those bulletins without reading.
Hazard maps are better delivered alone, or handed out at fire/flood drills. Also, asking residents to bring theirhazard maps to fire/flood drills will be effective in raising their awareness of the maps.
The best size may be just large enough to post on a refrigerator.
b) Bulletin boards and signs
Bulletin boards are useful in posting hazard maps. It is possible to set up such boards specifically fordisaster prevention, or it is also possible to use already existing community bulletin boards. Posting hazard
maps at bus stops, railway stations, and other public spaces, is also effective in informing tourists andvisitors.
Universal design, such as pictograms, should be used for signs on hazard maps, because it ensures easy
understanding for all sorts of people.
c) The Internet
Due to the recent rapid spread of personal computers for home use, a large number of people are now able
to acquire various information through the Internet and CATV on a daily basis. Many municipal
governments are opening and operating websites. Thus, distributing hazard maps to residents though those65

media should be effective.
Unlike information printed on paper, which requires time and cost for revision and redistribution,
information through the Internet and CATV can be updated frequently and delivered immediately. Hazard
maps and related video contents that meet individual needs can be provided through the interactive
communication of the Internet and CATV, which is almost impossible with maps printed on paper. Throughthe Internet, more detailed information on inundation, such as GIS data, can also be provided. When theselatest communication technologies are used, measures should be devised to assist the elderly, who may not
be accustomed to such technologies.
2) Considerations for disseminating hazard maps
Hazard maps must be prepared so as to be easy for the handicapped, elderly, and children to understandand use. Use of the maps by people who are not fluent in Japanese should also be considered.
Since tsunamis may affect not only the land but also ships, etc., at sea, methods should be investigated to
inform people engaged in ship operation (cargo vessels, working ships, fishing boats, pleasure boats, etc.)
and fish farming about the possible disasters and measures to deal with them. Measures should also be
investigated for people working at ports, since their work sites are prone to damage during tsunamis andstorm surges.

66

5.2 Ways to promote the understanding of residents about hazard maps
(1) Need of residents’ participation
Tsunami and storm surge hazard maps should not be unilaterally prepared by governments anddistributed to residents, but should be prepared together with residents to promote their understanding ofinundation risk areas, evacuation zones, and use of the maps.
Residents’ participation should be encouraged in order to reflect local information in tsunami and storm
surge hazard maps and to promote their understanding of the maps.

Local evacuation plans during tsunamis and storm surges must be appropriate to the actual conditions of
the region, and should be drawn up by collecting opinions of residents who know a great deal about theregion. Residents’ participation in preparing the maps is also effective in promoting their understanding anduse of the maps.
Therefore, encouraging residents to voluntarily participate in hazard map preparation through workshops
and through risk communication between residents and administrative bodies is essential for promoting theuse of tsunami and storm surge hazard maps.
Participants should represent various groups, such as communities, chambers of commerce and industry,
and youth associations.
Other ways to promote the understanding of residents include:•
Holding local study meetings,•
Preparing interactive electronic hazard maps and making them available through the Internet, and•Preparing disaster prevention education tools (videos, etc.).

(2) Workshops
Workshops are effective for encouraging residents to participate in preparing tsunami and storm surge
hazard maps, so that local information can be incorporated into the maps. Workshops can also help
residents understand the significance of the maps, the information included in the maps, and evacuation
methods.

1) Holding workshops
Some local information is known only to residents, and hazard maps prepared only based on manual
instructions may miss such important information. To prepare truly effective hazard maps requires residents’voluntary participation in local disaster prevention activities. Workshops can be such useful opportunities.
Core members for workshops can be those shown in Table 5.2.1. Experts and public representatives
express their opinions regarding what should be included and how they should be displayed on hazard maps
form different points of view.
Experts on tsunamis and storm surges must be present at workshops. Also officials of the national andprefectural governments in charge of disaster prevention and coastal areas, should be requested whennecessary.
In a workshop, the administrative side should explain the purpose of the workshop, details about hazard
maps and ways to distribute and use them. Then, participants express their opinions on the information
presented to them. Workshops should be held several times in order to correctly reflect the opinions ofresidents in hazard maps.
Tours can be made to visit possible inundation risk areas and check the necessary time for their evacuation.
To prevent participants from gaining fixed ideas, it should be explained that hazard maps merely show modelcases.

67

ClassChair
Coremembers

OfficeTable 5.2.1 Examples of core members of workshop
Member
Veiwpint /Roles
Learned person, member of Expediting the proceedings, collecting and summarizing
municipal
government,
or opinions
consultant
Expert on tsunami, storm surge, Technological advice
coast engineering
Town
planning
committee Town planning
memberSchool teacher
Evacuating from schools and ensuring the safety of students
Elderly
Presenting an elderly point of view
Resident
Daily living, assisting the elderly, etc.
Employee working for a local Commuting, workplace activities, cooperation with local
factory/corporation
communities, etc.
Fire fighter
Local disaster prevention
Flood fighting volunteer
Local disaster prevention
Welfare facility member
Assisting the handicapped and elderly
Municipal government officials Arranging venues and preparing and explaining references(in charge of disaster prevention)2) Example of workshop
For a workshop, participation of residents is requested directly or through existing community and disasterprevention groups, aiming to gather about 30 persons from the region. At the workshop, evacuation plans forduring tsunamis are usually drawn up for each district in a region, the region should be divided into 4 to 5
districts in advance, and at least several participants should be present from each district. The time andfrequency of holding workshops should be decided so as to conform to regional conditions.
The venue should be large enough to accommodate all participants, and an overhead or liquid-crystal
projector, white board, large-size paper, and other necessary items should be prepared. Tables that are large
enough for spreading maps should be set for each group. Examples of necessary references and tools areshown in Table 5.2.2.
Table 5.2.2

References and tools to prepare for workshop
References and tools to prepare (examples)
Hazard map(Hazard maps) showing inundation risk areas (results of simulation analyses andareas inundated in the past)
References for disaster References of evacuation areas, evacuation sites, and evacuation routes designatedprevention
by the municipal government
Other tools
Pencils, pens, oil-based markers, transparent plastic sheets, solvent, packing tapes
During the workshop, the chair should speak clearly and explain in an easy-to-understand manner for theparticipants. The chair should invite as many residents as possible to ask questions, so as to make them feelthat it is their own issue. Since residents tend to be inexperienced and to view serious disasters as unrealistic,
information to be shown on maps and the expression methods used should be carefully selected to correctly
inform the participants of inundation risk areas and evacuation zones.
Displaying the results of inundation prediction using the Web GIS during a workshop is also effective inmaking matters clear to residents.

68(3) Educational opportunities for residents to promote understanding of tsunami and storm surge hazard
maps
Providing learning opportunities about disasters to residents is one of the effective ways to promote theirunderstanding of tsunami and storm surge hazard maps.
Such opportunities can be provided in volunteer flood fighting groups and at schools. Information
technology should be utilized to enhance residents’ understanding. Training residents to become tsunami
and storm surge advisors is also effective.

1) Volunteer flood fighting groups
One of the effective ways to promote understanding of the maps is to encourage volunteer flood fighting
groups to use tsunami and storm surge hazard maps as tools for studying disaster prevention.
Especially, it will be very effective when the risk in each district and on each evacuation route is reviewed
at meetings of local flood fighting groups, which know the districts very well. The members can prepare
more precise hazard maps for the district by investigating fine details that could not be discussed atworkshops. Flood fighting groups that may cooperate against a common disaster should exchange
information, communicate with each other, and coordinate their disaster fighting measures.
2) Schools
Tsunami and storm surge hazard maps can be used in learning disaster-related issues at schools. Byteaching about tsunami and storm surge disasters from elementary schools, a system can be developed tocontinuously educate people about hazard maps and related issues from childhood to adulthood. Educational
opportunities at schools like this may provide a chance for family members to talk about disaster prevention
and further promote understanding of disaster prevention in the districts.
Considering teaching materials for elementary schools, the content should be described and displayed in away for children to easily understand.
3) Educational resources
Internet web pages that show related information are listed in Reference 3, and can be used as sources forstudying disaster prevention. The pages also have links, which provide a wide variety of related informationand more educational resources.
4) Use of information technology
To encourage residents to study and use hazard maps, measures should be taken to make people feel thattsunamis and storm surges are their personal concern. However, hazard maps showing an entire city on one
or several sheets of paper may not look realistic.
Information technology can be helpful in accommodating information to personal needs. For example, aninteractive hazard map system can be constructed in which a user can see his or her risk, appropriate
evacuation sites and routes, and video clips, just by clicking on his or her house.

69How do you evacuate when a tsunami approaches?
SelectPark B●Evacuation site,●Your home,●Evacuation route.
Park AThe inundation risks of your home, evacuation
site, and evacuation route are:
Park B

Appropriate evacuation site and route from yourhome are:
Park BkPark A

Park A

Figure 5.2.1

Example of an interactive hazard map system

An IT-based comprehensive scenario simulation system for a tsunami disaster is shown in Figure 5.2.2. A
simulation model for each factor (disaster information transmission, evacuation decision, evacuation action,and tsunami (external force)) is individually developed for this system, which calculates and visually outputs
the possibility of safe evacuation when a user inputs a scenario (time of starting evacuation, for example).
IT-based systems for simulating tsunami strikes and evacuation should be effective in assisting public
understanding.

70Blue dots(・)denotehouseholds

Before earthquake
Inundation bytsunami starts (■)

Red dots(・) denote
peopleen-route toevacuationsites

6 minutes after
the earthquake

Municipal
information
cars (yellow
dots(●))
start

20 minutes after
the earthquake

LegendEvacuation site

HouseholdOutdoor speaker(en-route toevacuation sites)

Information car

Elevation from the mean water level

Figure 5.2.2

Comprehensive scenario simulation system for tsunami disasters

Reference: Laboratory of Prof. Katada, Department of Civil Engineering, School of Engineering, Gunma University

5) Training programs
There are people called “river counselors” who have comprehensive knowledge about rivers in their local
areas. Since damage by tsunamis and storm surges varies depending on region, experts called “tsunamis andstorm surge advisors for the region” can be trained as long-term advisors on disaster prevention. Tsunami
and storm surge hazard maps will be useful tools for the advisors to teach children about tsunamis and storm
surges, to supervise school teachers in giving disaster prevention classes, and to give advice on disasterprevention during tsunamis and storm surges. Such activities will be effective in increasing public
understanding of hazard maps.

715.3 Utilization of tsunami and storm surge hazard maps for developing measures against tsunamis
and storm surges
Tsunami and storm surge hazard maps for residents can enhance the self defensive ability of residents
and their smooth evacuation. Hazard maps for administrators can be used to prepare evacuation plans forresidents and investigate facility construction, depending on the purpose of preparation.
The hazard maps can also be used for risk communication between governments and residents on futuredisaster prevention measures.

Tsunami and storm surge hazard maps can be used for comprehensive disaster prevention measures,
including both structural and non-structural measures. Utilization examples during normal times and during
disasters (immediately before and after disasters) are shown in Figure 5.3.1 and Table 5.3.1 for each process.

Hazard map
For residents

For administrators

Before disaster
Immediately
beforedisaster(storm surge)i
Immediately after
disasterDuring disaster

Normal time

Information forstudying disasters

Informing people, and risk communication
between governments and residents
Information fordisaster prevention
Constructing disasterprevention centers (evacuationsites, etc.)）
Constructing and improving coast
protection facilities and otherstructures
Information for
emergency
measures・Preparing to operatefacilities (water gates,
land locks, etc.)
Real-time
Evacuation
・Taking emergency
hazardand rescue
measures (for not
information
completed sections, etc.)
plans

Drawing up
disasterprevention plans
Information forevacuation(storm surge)

Preparing forevacuation(checkingevacuation routes,
etc.)

Rescuing

Evacuation･

Guidingevacuation

Non-structural
measures

・Operating
facilities, etc.

・Necessary
restoration

Structural measures

Figure 5.3.1

Utilization of tsunami and storm surge hazard maps at each stage of a disaster72

Table 5.3.1 Utilization of tsunami and storm surge hazard maps by residents and administrators
User
Residents
Administrators
Utilization Non-structural Enhance their Assisting residents in helping themselves
Drawing up evacuation plans by establishing evacuation
methods
self-defensive
ability(by sites and routes to mitigate damage by tsunamis and storm
surges (supporting residents to help themselves)
helpingthemselves andeach other)
Structural<Normal time>
Maintaining and repairing old facilities (public support)<During disaster>
Urgently repairing and restoring damaged facilities (public
support)Reinforcing and repairing sections prone to secondary
damage (public support)

1) Utilization of hazard maps for residents
Hazard maps for residents can be used during tsunami and storm surges for the purposes shown in Table
5.3.2.
Table 5.3.2

Smooth evacuation
Risk communication

Methods of use by administrators of hazard maps for residents
PurposeTo inform residents about the risk of tsunami and storm surge
For residents to check the risk of tsunami and storm surge
Information provision after evacuation
To communicate with residents on future disaster prevention

2) Utilization of hazard maps for administrators
Utilization of hazard maps for administrators depends on the purpose of preparation. Examples are shownin Table 5.3.3.
Table 5.3.3 Utilization and effects of hazard maps for administrators
Purpose of preparation and measures
Effects of hazard map
PurposeMeasurePreventive Constructing evacuation site Locations of inundation risk areas, candidates for evacuation
measuressites, roads, etc., are easy to understand, enabling evacuation
Constructing disastersites and sign boards to be appropriately located.
prevention facilities(installing sign boards, etc.)
Emergency
Evacuation plan
The number of people that can be accommodated inmeasuresevacuation facilities and the estimated number of people are
Rescue planeasy to understand, enabling an appropriate evacuation planand efficient plan for delivery of emergency supplies to be
drawn up.
3) Utilization at each stage of disaster
Tsunami and storm surge hazard maps are used at each stage of a disaster: before, immediately before, andafter the disaster. Users and utilization methods are shown in Table 5.3.4.

73

Table 5.3.4 Users and utilization methods of tsunami and storm surge hazard maps at each stage of disaster
Stage of disaster
User
Utilization method
Collecting information for evacuation, learning about disasters and the
Residents
region (population distribution and land use), and making risk
communication
Before disaster
Planning and executing disaster prevention measures (constructing
Administrators evacuation sites and disaster prevention facilities) and making risk
communication
Collecting information to decide on evacuation (for storm surge,
Residents
Immediately
inundation depth and evacuation sites)
before disaster
Planning and executing emergency measures (evacuation and rescue
Administrators
plans)
Collecting information after evacuation (instruction by governments,
Residents
etc.)
After disaster
Planning and executing emergency measures (evacuation and rescue
Administrators
plans)
4) Coordination with sign boards
Evacuation must be made very quickly, especially during a tsunami. People’s lives may be at risk if they
don’t know exactly where to go. Thus, sign boards for evacuation that are coordinated with hazard maps
must be installed (See Reference 2 for details).

745.4 Review and revision of tsunami and storm surge hazard maps
Hazard maps should be reviewed and revised along with the progress of coast protection facility
construction, changes in socioeconomic conditions, and development of prediction technologies.

1) Reviewing tsunami and storm surge hazard maps
Hazard maps should be reviewed for evacuation sites, time needed for evacuation and evacuation routes
by executing evacuation drills on a regular basis.
Governments should not only provide information unilaterally but should also lead and support local
disaster prevention organizations to voluntarily review the maps.
2) Revising tsunami and storm surge hazard maps
Residents should always be provided updated information; thus hazard maps must be revised so as toreflect the progress of coast protection facility construction, changes in socioeconomic conditions, anddevelopment of prediction technologies.
The maps should be revised by considering changes in land use, the state of coastal construction, records
of tsunamis and storm surges, the progress of calculation technologies, and also by obtaining the advice ofcoast engineers when necessary.
It is also important to keep track of the revision record. Whenever a revision is made, what is revised whenand how must be clearly documented. Different version numbers may be assigned depending on the content
of revision, as shown in Table 5.4.1.

Table 5.4.1 Example of version control of tsunami and storm surge maps
Original version: ver 1.0

First revision: ver 1.1 (when misspelled words and other minor errors were corrected)
Second version: ver 2.0 (when inundation prediction was revised)75

5.5 Measures for encouraging preparation
Since the utilization of hazard maps enables comprehensive disaster prevention measures against
tsunamis and storm surges to be effectively deployed, including both structural and non-structural
measures, the importance and methods of preparing, publicizing and utilizing hazard maps should bestated in the various disaster prevention plans of municipal governments.

[Including statements about hazard map preparation in the plans of municipal governments]
Few municipal governments have statements about hazard maps in their plans for disaster prevention.
Since utilization of hazard maps will enable comprehensive disaster prevention measures against tsunamis
and storm surges to be effectively deployed, including both structural and non-structural measures,statements about the importance and methods for preparing, publicizing and utilizing hazard maps should be
included in the disaster prevention plans of municipal governments.
The present relationship between hazard maps and disaster prevention plans concerning tsunamis andstorm surges is shown in Table 5.5.1.
Statements about the preparation of hazard maps should be included in, for example, regional disasterprevention plans, basic plans for coast protection, and flood defense plans. Table 5.5.2 shows how hazard
maps are incorporated into those plans.
The Outline of Measures against the Tokai Earthquake (May 29, 2003, the Central Disaster Prevention
Council) mentions preparation of hazard maps as a preventive measure.

Table 5.5.1 Positions of hazard maps in plans for disaster prevention during tsunamis and storm surges
Plan
Present position of hazard maps
Regional disaster ・The plans are the very basis of disaster prevention measures.
prevention plans ・ The Disaster Countermeasures Basic Law states that the heads of municipal(The Disastergovernments are responsible for the evacuation of residents.
Countermeasures ・Some municipal governments mention preparation of hazard maps as a non-structural
measure in their regional disaster prevention plans. For example, the Kochi City
Basic Law)
regional disaster prevention plan (fiscal year 2002) states, in the section headed“Disaster prevention information” of the chapter on “Education and training in disasterprevention,” that “leaflets on disaster prevention and disaster prevention maps should
be distributed to residents, including those involved in disaster prevention activities.”
Basic plans for
・The plans are set by local municipalities and state the basics for protection, utilization,
coast protectionand environment of coastal areas.
(The Coast Law) ・Matters to be included in the plans are to be decided by the bodies in charge ofpreparing the plans.
・Some municipal governments, such as the prefectural governments of Shizuoka andWakayama, include the preparation of hazard maps as a non-structural measure against
disaster in their basic plans for coast protection. In Shizuoka Prefecture, 16 municipal
governments have prepared hazard maps.
Flood fighting
・The plans are the basis of measures against water-related disasters during tsunamisplans
and storm surges.
(The Flood・ The Flood Fighting Act, revised in 2001, states that the Minister of Land,
Fighting Act)Infrastructure and Transport or the prefectural governors are responsible for publicly
announcing inundation risk areas around the rivers subject to flood forecast.
・Based on those inundation risk areas, municipal governments prepare flood hazard
maps.

76

Plan
Regional disasterprevention plans(The Disaster
Countermeasures
Basic Law)

Table 5.5.2 Sample statements for plans of municipal governments
Examples of statements[Disaster prevention]
・Need of preparing hazard maps in conjunction with facility construction
・Examples of utilizing hazard maps (preventive plans by utilizing hazard maps)[Emergency measures]・Examples of utilizing hazard maps (evacuation guidance plan, emergency measures atfacilities)[Restoration]
・Examples of utilizing hazard maps (restoration plans using real-time hazard maps)

Basic plans forcoast protection(The Coast Law)

Basic items concerning coast protection[Items concerning protection of coast]○ Objectives of protection
・Areas to be protected (to be shown on hazard maps)○ Measures for attaining the goals of protection
・The importance is to be stated of comprehensive disaster prevention measures using
hazard maps.
(Examples of statements)
・In areas where population and assets are concentrated, tsunamis and storm surges,
when they occur, are highly likely to cause serious damage over a large area.
・Thus, in addition to the construction of protection facilities, non-structural
measures must be taken such as preparing and using hazard maps for ensuring
evacuation routes and sites during emergency, making people aware of what action
to take during an emergency, and coordinating evacuation routes, and for collecting
and disseminating information quickly and adequately.
・Hazard maps should also be used to create systems for disaster prevention
activities among residents, to educate people about disaster prevention, disseminate
knowledge, and improve safety.
・Hazard maps are also effective for regular inspection and maintenance of coast
protection facilities. They can serve such purposes by helping study monitoring
systems for old facilities while inspecting facilities’ capability to properly functionand ensure safety. They can also help study reporting systems capable to detectdamage or malfunction at an early stage and request repair or improvement. By
studying such systems through use of hazard maps, responsible bodies shouldmake efforts to be equipped with measures that enable them to respond to disasters
quickly and properly.

Flood fighting
plans(The FloodFighting Act)

Flood fighting plans are decided by governors of prefectures by consulting with theDisaster Prevention Council, and should be coordinated with regional disasterprevention plans. Thus, statements on hazard map preparation can be included in theplans as a method for coordinating structural and non-structural measures.
The Flood Fighting Act makes statements regarding floods, including designation ofinundation risk areas and measures for ensuring smooth and quick evacuation. Since
storm surges are included as one of the disasters in this law, statements on hazard map
preparation can be included in the law in line with the policies for floods.

77Tsunami and Storm Surge Hazard Map Manual

ReferencesReference 1: Predicting inundation by time-series numerical simulation
Chapter 1 Calculations for predicting inundation during tsunamis
1.1 Flow of calculations for predicting inundation
A general flow of calculations for predicting inundation is 1) assuming the external force of a tsunami(target earthquake), 2) preparing topographical data, 3) setting and inputting initial conditions, 4)
reproductive simulation, 5) predictive simulation, and 6) outputting results.
1) Flow of calculations for predicting inundation
A general flow of calculations for predicting inundation is shown in
Figure .1.1.
Collecting data, etc.

1)Assuming the external
force of a tsunami(target earthquake)3)Setting and inputting
initial conditions2)Preparing
topographical data

4)Reproductive
simulation

Checking
reproducibilityＮoYes5)Predictive simulation

6)Outputting results

Results of inundation
prediction(inundation risk areas, etc.)

Figure 1.1.1

Flow of calculations for predicting inundation782) Conditions used for preparing tsunami hazard maps
This manual presents an overview of how to deal with uncertain factors, or conditions used for preparing
tsunami hazard maps, while considering how such factors should be set to minimize damage to residents.
Conditions used for preparing tsunami hazard maps are shown in Table 1.1.1.
Table 1.1.1

Conditions used for preparing tsunami hazard maps
Item

External force of tsunami

Conditions used for preparing tsunami hazard maps
1. Earthquake fault model
2. Initial water level expressed in the earthquake fault model
3. Grid intervals

Topographical conditions

4. Elevation
5. Conditions of river topography

Tidal level
Structures
Analytical method

6. Tidal level (astronomical tide)
7. Condition of structures
8. Damage to structures during the earthquake
9. Tsunami numerical analysis

1.2 Earthquake fault model
Disaster prevention for a district should be studied, assuming that the largest possible tsunami*1 would
hit the district. Since the ground may heave up or subside during earthquakes, an earthquake that causes
the highest tsunami may differ from an earthquake that causes the deepest inundation. Thus, theearthquake fault model that is to be used for preparing tsunami hazard maps should be assessed not only
by tsunami height but also by inundation depth (tsunami height minus ground elevation after
displacement).
An earthquake fault model that causes the deepest inundation ever recorded or possible should bechosen by calculating the inundation depth based on the estimated ground elevation after subsidence
when the ground is predicted to subside, and also based on the initial elevation when the ground ispredicted to heave up.

1) Effects on results of inundation prediction
Earthquake fault models (locations, depths, lengths, widths, slippage, strike angles, inclination angles, andsliding angles of faults) determine the initial condition (initial water level) and ground displacement fortsunami simulations. These specifications directly affect the scale of tsunami and inundation effects.
When the ground heaves up or subsides during earthquakes, an earthquake that causes the highest
tsunami*1 may differ from one that causes the deepest inundation. In other words, tsunami damage may not
be positively correlated with earthquake damage. Thus, the earthquake fault model that is to be used for
estimating the most serious inundation damage must be determined after estimating tsunami height andground displacement.
Although the ground displacement may exceed 1 m, existing manuals describe no uniform standards about
displacement, but over years decisions have been made case by case regarding how to consider grounddisplacement:a) disregard ground displacement when it is negligible,b) consider both upheaval and subsidence, orc) consider only subsidence
To estimate the worst inundation case, Case c) should be considered.

79

*1 The highest tsunami should be the tsunami that causes the most serious damage in the region, and should
be determined by the body charged with preparing hazard maps.
When two earthquakes of the same scale but different hypocenters are investigated (Earthquakes A and B)
for a region shown in Figure 1.2.1, their effects at a site (shown with a double open circle in the figure) could
be as shown in Table 1.2.1. In this case, Earthquake A causes more earthquake damage and less tsunami
damage than Earthquake B.

Case

Earthquake

Case 1

A

Table 1.2.1 Effects at a site by two earthquakes
TsunamiEarthquake
Earthquake
Groundwater
damagemotiondisplacement
level
Stronger
Higher More serious thanUpheavalthan B
than BB (proportional to(+ 2 m)(10 m)
earthquake
motion)Case 2
Case 3

B

StrongFigure 1.2.1

No upheaval(+ 0 m)Subsidence(- 1 m)

High
(8 m)

Inundation damage
Small(inundation depth =tsunami water level ground elevation)(10 - 2 = 8 m)

Serious(10 - 0 = 10 m)
Large(8 - (-1) = 9 m)

Conceptual diagram of fault position and site investigated

In Figure 1.2.1, Earthquake B (9 m) causes deeper inundation than Earthquake A (8 m) when inundation
depth is simulated as the difference between tsunami water level and ground elevation after displacement.
When the upheaval during Earthquake A is disregarded, Case 2 (10 m) causes the deepest inundation, andsimulations should be conducted using Earthquake A.
2) Sellection of past earthquakes and assumed earthquakes
Only when reliable data on tsunami and inundation effects are available, past earthquakes should be used
to determine the initial conditions and ground displacement. Assumed earthquakes should be ones based on
already-developed earthquake fault models. Such models include the assumed Tokai Earthquake, the80

assumed Tonankai Earthquake, the assumed Nankai Earthquake (those three are developed by the Central
Disaster Prevention Council), and the models developed by the four ministries related to the coast.
(Reference: Survey on methods for earthquake and tsunami disaster prevention plans along the Pacific coast,
1996, the four ministries related to the coast)

Figure 1.2.2 Example of earthquake fault model (left: earthquake in the past, right: assumed earthquake)3) Causes of tsunamis
Causes of tsunamis include earthquakes, volcanic eruptions, landslides into the sea, submarine landslides,
and meteoritic bombardments. Of these causes, this manual describes tsunamis triggered by earthquakes
caused by fault movement, which are the most frequent and affect the largest area.

1.3 Initial water level simulated by the earthquake fault model
Initial water level used for tsunami simulation in hazard map preparation should in principle bedetermined by conducting a reproductive simulation and using a fault model that has been proved
valid.

1) Effects on the results of inundation prediction
Numerical tsunami simulation uses the equations of motion and continuity over time that use thedisplacement distribution of the sea surface (initial water level) as the initial condition. Thus, the water levelof a tsunami, which is an output of the simulation, largely varies depending on the initial water level.
Initial water level is generally determined using the following fault models. Errors decrease and accuracyof simulation increase in the alphabetical order.
a) Fault model based on seismological and geodetic data,b) Fault model optimized by simulated tsunamis (developed by conducting reproductive simulation oftsunamis and proved valid), and81c) Fault model based on ones that optimized by simulated tsunamis but further modified by using tracevalues, etc. so as to match with the tsunami simulation for a certain investigation.
2) Concepts of determining an initial water level
Two or more fault models may have been proposed for an earthquake in the past, such as a model basedon seismological data and a model developed by conducting reproductive simulation and proved to be valid.
An initial water level for tsunami simulation in hazard map preparation should be determined by using a
fault model optimized by simulated tsunamis. Then, the initial water level is used to conduct a reproductive
simulation by using a tsunami simulation model in order to check the reproducibility. If there are any
systematic errors attributable to the tsunami simulation model, they should also be corrected.
When an initial water level is determined by using an assumed earthquake, the reproducibility should bechecked and any systematic errors attributable to the tsunami simulation model should be corrected.

1.4 Grid intervals
Grid intervals for tsunami simulation in target sea and river areas should be appropriately
determined by ensuring the precision of the target inundation prediction area and taking account ofminute topography, such as structures.

1) Grid interval and results of inundation prediction
An example of the effects of grid intervals on inundation simulation is shown in Figure 1.4.1. When the
topography of the inundation area in District A is approximated by using grids of 50 m x 50 m, water isestimated to reach up to Line B. However, the actual inundation area is up to Line C. Thus, the use of 50 m
grids results in underestimation of the inundation area. Topographic approximation using 12.5 m grids canachieve a more precise estimation. When 50 m grids are used, the building in District A is estimated toescape inundation, whereas the use of 12.5 m grids correctly estimates the inundation of the building.

82

Actual topography
Topography approximated using 50 m grids
Topography approximated using 12.5 m grids
Tsunami level
50m
12.5m

Building

District A

Line C
Actual inundation area

Line B

Inundation area predicted using 50 m grids
Inundation area predicted using 12.5 m grids

Inundation depth
Emphasized by doubling
Actual inundation depth
Inundation depth predicted using 50 m grids
Inundation depth predicted using 12.5 m grids

2m
1m

Figure 1.4.1

Example of the effects of grid dimensions on inundation simulation

2) Determining grid intervals and micro topography
In tsunami simulation, landforms are usually expressed in rectangular grids, and elevation is the meanelevation in each grid. Thus, structures (buildings and houses) in the grids cannot be directly considered. In
tsunami simulation for predicting the behavior of a tsunami on land, use of smaller grids improves theprecision of topographic approximation, the effects of structures and micro topography are reflected, andthus the calculation results are more precise.
To investigate the effects of structures, etc., the following methods may be employed:
1) Use of reliable data and 12.5 m grids
Reliable data, such as 1:2,500 topographical maps and aerial photogrammetry data, as well as grid intervalsof about 12.5 m can be used. When the resolution of the data is larger than 12.5 m, the data itself is notreliable since it should be calculated by interpolating data of larger grid intervals, and the inundation
prediction will not be precise.
2) Use of mean coarseness that shows the land use in the grid (see Table 1.4.1).

83

Table 1.4.1

Coefficient of coarsenessLand use

Coefficient of coarseness
0.04～0.08

Residential district

0.04

Industrial district

0.02

Farmland

0.03

Forest

0.025

Water

0.025

Others (vacant land, green space, etc.)

Reference: Kotani, Misa, Imamura, Fumihiko, and Shudo, Nobuo: Tsunami run-up calculations and damage estimation method using
GIS, (Coastal Engineering Journal, Vol. 45, November 1998)

When simulation is conducted to understand the behavior of and inundation by tsunamis over large areas,such as throughout Japan or a prefecture, inundation areas may be calculated by using large grid intervals of
50-100 m depending on the objective and the size of the target area.
Note: Representation accuracy (dimensions) and grid intervals
The representation accuracy in drawing maps depends on grid intervals, but inundation depth data thatappears to be precise can be prepared from calculation data obtained using large grid intervals. Strictly
speaking, as shown in Figure 4.4.2 of the Manual, maps so prepared do not have the precision expressedsince the grid dimensions used for calculation are large, but they should be accurate to some extent since thewater surface is continuous.
Use of reduced grid dimensions improves calculation precision but requires larger calculation loads andcosts for preparing data. Precision of elevation data has a greater effect on the precision of calculation thandoes that of grid intervals.
1.5 Elevation
Elevation data for tsunami simulation directly affects the resultant estimated inundation depth and thus
should be precise. Especially, the elevation data for areas where inundation is predicted during tsunamis
need a precision smaller than 1 m to estimate inundation depth. When such precise data is not available,
the necessary precision should be ensured by correcting data using the survey points of topographic maps,
reconnaissance surveys, and surveys by coast experts.

1) Effects on inundation prediction
An example of the effects of elevation data on inundation simulation is shown in Figure 1.5.1. When theelevation of District A is expressed in grids of 50 m, Line B is the inundation line and the inundation depth is
1 m. However, the inundation depth in the past was at least 2 m, and the use of 50 m grids leads tounderestimation of the inundation depth in this case. When 12.5 m grids are used to express elevation data,
the estimated inundation line will be Line C, which shows depths of 1.8 and 2.0 m and is similar to the actual
inundation depth.

84

Actual topography
Topography approximated using 50 m grids
Topography approximated using 12.5 m grids
Tsunami level
50m
12.5m

Actual topography
Topography approximated using 50 m grids
Topography approximated using 12.5 m grids
Inundation depth
Emphasized by doubling
District A

Actual inundation area
Inundation area predicted using 50 m grids
Inundation area predicted using 12.5 m grids

Line C2m
1m

Line B

Figure 1.5.1 Example of the effects of elevation data on inundation simulation
2) Determining elevation data
Elevation data is used for simulating tsunamis and estimating inundation. In tsunami simulation, thepropagation of a tsunami is calculated based on the elevation of each grid point to determine the water levelsof the grid points in time sequence. On the other hand, inundation is expressed as the difference between thecalculated tsunami water level and ground elevation.
Usually, one of the following elevation data is used:・Contour lines of 1:50,000 and 1:25,000 topographical maps issued by the Geographical Survey Institute・Elevation data of 50 m grids of numerical maps issued by the Geographical Survey Institute・Contour lines and elevation data of 1:2,500 maps (basic national land maps) prepared by municipal
governments
1:25,000 topographical maps show elevation with contour lines of 10 m intervals. Thus, the elevation ofwaterfront lowlands may be difficult to reproduce accurately. Elevation data of 50 m grids of numericalmaps has been prepared from the contour lines of 1:25,000 maps and has the same precision. On the other
hand, 1:2,500 maps show contour lines at 1 m intervals and enable highly precise elevation data to beprepared.

85

Figure 1.5.2

Example of elevation expression by topographical maps of different scales

For example, Figure 1.5.2 shows topographical maps of Masaki District, Shimizu City. The left is a
topographical map of 1:25,000, and the right is a map of 1:2,500. They are shown at the same scale tocompare the information contained.
No contour lines are shown in the 1:25,000 map since there are no ground sections higher than 10 m inelevation in this district, but elevation at three points is stated. On the other hand, the 1:2,500 map shows
contour lines at 1 m intervals and elevation at many points.
The waterfront in this district is sand beach, the elevation of which cannot be determined from the
1:25,000 map but can be seen on the 1:2,500 map, which shows the 2-m contour line on the beach. Similarly,
the elevation of sites where buildings are located cannot be judged from the 1:25,000 map but can be seen on
the 1:2,500 map.
Elevation of lowlands is not available through 1:25,000 maps, which have been simplified, but needs to becollected from 1:2,500 maps.
A survey on tsunami heights and degrees of damage (Table 1.5.1) showed differences in damage between
tsunami heights of 1 m and 2 m, suggesting that errors of inundation prediction (predicted tsunami waterlevel - ground elevation) should not exceed 1 m. Thus, the latest elevation data needs to be collected from
1:2,500 maps or by aerial photogrammetry data.

86

Table 1.5.1 Tsunami heights and degrees of damage
0

1

2

3

4

5

Tsunamiheight (m)

1

2

4

8

16

32

Tsunami type

Tsunamiintensity

Gentleslope

Water wall off
shore
Secondcrushing wave

Rises at coast

Steep
slope

Fast flow
velocity

Even the first wave produces
plunging breakers

Fast flow
velocity
Continuous sound by front breakers(sea rumbling, storm sound)
Huge sound by entraining breakers at beaches(thunder, not heard at distances)
Huge sound of waves colliding against
cliffs(thunder, blasting, can be heard at
distances)

Sound

WoodenhousesStone-built
housesReinforced
concretebuildings

Partially
destroyed

Totally destroyed
Resists

DamageoccursDamage to
Slight damage
tsunami control
forestEffects of
Mitigatetsunami control damage
forestTotally destroyed(No data)

Resists

Fishing boats

Mariculture
rafts
Coastalvillages
Runupheight(m)Breakers atwave tips

Stopdriftwood

Totally
destroyed(No data)
50% affected

100% affected

Partiallyaffected

Entirely affectedStopdriftwoodNo effect

Affected
Damageoccurs1

2

50% affected
4100% affected
8

16

32

Note: The tsunami height was calculated as the height of the tsunami from the tidal line for ships and mariculture rafts at sea, and as
the inundation depth from the ground surface for houses, tsunami control forests and other structures on land. Damage to coastal
villages, at the bottom of the table, shows the percentage of houses affected in a village by the maximum runup height (m) recordedin the village.
Reference: Shudo, Nomuo: Tsunami intensity and damage, Tsunami Engineering Laboratory Bulletin, No. 9, pp. 101-136, 1992.

87

Note: Precision of elevation data
Elevation data for tsunami simulation are determined by modeling the landform of the district to beinvestigated and by interpolating elevation points. Errors in this process will seriously affect calculation
precision.
For example, the 50 m grid data of the Geographical Survey Institute is prepared by linearly interpolating
the 10-m interval contour lines of 1:25,000 topographic maps. The data is inexpensive and available for all
regions in Japan, and thus is easy to use for simulation. However, the following points should be noted inusing the data:• The inundation depth along the coast is overestimated since elevation is linearly interpolated from thecoastline (0 m elevation).
• Elevation differences smaller than 1 m are not shown.
• There are errors in elevation attributable to linear interpolation.

1.6 Conditions of river topography
In tsunami simulation, river topography (river alignment and riverbed elevation) should be expressed in
calculation grids and elevation (water depth) data, and structural conditions, such as the crown height of ariver bank, should be determined.

1) Effects on inundation prediction
Part of a tsunami that reaches the coast may run up a river, causing the river water to flood. In tsunami
simulation, river topography (river alignment and riverbed elevation) and the crown heights of the river bankshould be considered to appropriately evaluate the flooding of rivers.
When the river topography is not considered, the elevations of the land areas along the river are usuallyused for grids that actually correspond to the river, and tsunamis that overflow the river cannot be calculated.
On the other hand, when the river topography is considered, the elevation of the riverbed, which isdetermined from river profiles, etc., is used, and tsunamis that run up the river can be estimated.
When there are bridges in sections where tsunamis may possibly run up, the heights of the girders and theeffects of the bridges on the run-up of the tsunami and overflowing of river water must be taken into account.
2) Determining the river topography
In tsunami simulation, river topography (river alignment and riverbed elevation) should be expressed in
calculation grids and elevation (water depth) data, and the crown height of river banks should be determined.
Undular bores are sometimes observed in shallow rivers, which cannot be expressed using the shallow water
theory.
A conceptual diagram of tsunami simulation in a river is shown in Figure 1.6.1. The elevation of theriverbed (solid black line) is used as the elevation of the ground (water depth). When there are banks on bothsides of the river, their positions and crown heights (dotted red line) are drawn as a boundary line of thestructure. The water level at the river mouth is assumed, for convenience, to be equal with that of the sea(H.W.L.: mean monthly highest water level).

88

10m

0m

Bank height
Elevation of the landRiver water level
H.W.L

H.W.L

Riverbed
Seabed-10m

River section

Figure 1.6.1

Schematic profile of a river

1.7 Tide (astronomical tide)
In tsunami simulation, tide (astronomical tide) should be the H.W.L. (mean monthly highest waterlevel).

1) Effects on inundation prediction
Generally, the higher the tide, the easier a tsunami will inundate larger areas.
2) Determining tideIn prediction of inundation during tsunamis, the most hazardous inundation damage should be assumed,
and tide (astronomical tide) at the H.W.L. (mean monthly highest water level) should in principle be used.
For tsunami simulation to examine reproducibility, tidal data of a past tsunami should be used if reliable data
is available.

1.8 Conditions of structures
In inundation prediction, the effects of structures higher than the ground (breakwaters, sea walls,
walls, and embanked roads) on the propagation of tsunamis should be considered. Water gates, land
locks, and other tsunami control facilities, should in principle be assumed to be open (not operating)since they may be difficult to close due to the traveling speed of tsunamis, or may not be functional due
to damage during the earthquake. Earthquake-resistant automatic facilities, facilities that are always
closed, and earthquake-resistant facilities that can be closed before tsunamis arrive, are assumed to beclosed.

1) Effects on inundation prediction
Structures higher than the ground (breakwaters, sea walls, walls, and embanked roads) may affect the
propagation of tsunamis and block the run-up of tsunamis. However, tsunami control structures that need to
be closed, such as water gates and land locks, may possibly be left open since tsunamis arrive rapidly, andinundation may expand from this point.
2) Determining the conditions regarding structures
Conditions regarding structures should be appropriately determined to improve the precision of simulation.
Tsunami control structures, such as water gates and land locks, should in principle be assumed to be in thestate that can cause the worst inundation (closed or open), but also should be determined according to the89objective of simulation and the characteristics of the target tsunamis and region.
Tsunami control structures, such as water gates and land locks, should be assumed to be open, since there
may be no time to close them because tsunamis arrive immediately, and they may be deformed by theearthquake motion and not be closeable. However, 1) earthquake-resistant automatic facilities, 2) facilities
that are always closed, and 3) earthquake-resistant facilities that can be closed before tsunamis arrive, should
be assumed to be closed.
When the tsunami control structure to be assessed is smaller than the grid dimension, the size of thestructure should be reflected using the following methods to ensure calculation precision.
1) When there are two or more structures, the structures (water gates and land locks) should be assumed to
be a single structure by considering their planar arrangements.
2) When there is one structure, its effect should be reflected in one grid by considering the estimated heightof the tsunami and the crown height of the structure.

1.9 Damage to structures during earthquakes
Inundation during tsunamis should be predicted by considering the damage to structures by tsunamis.
Such damage should be estimated by using the earthquake motion as the external force, which should be
calculated based on the selected earthquake fault model.

1) Effects on inundation prediction
Structures, such as breakwaters, sea walls, and walls, mitigate inland inundation damage while they
maintain their functionality. When these structures are damaged during earthquake and cannot function, theinland inundation damage expands.
2) Determining damage to structures during earthquakes
Types of damage to structures should be determined, according to the purpose of map preparation, by the
body in charge of preparing hazard maps. When structures are damaged by earthquake motion, they may lose
their function of controlling tsunamis. According to records of earthquake damage to harbour facilities, notmany structures were affected too severely to lose their capacity to control the run-up of tsunamis. However,damage to structures should be estimated by using the earthquake motion as the external force, which should
be calculated based on the selected earthquake fault model.
Earthquake resistance of structures is to be assessed using available technologies, and new technologies
should be used when they are developed. (See “Handbook for Designing Coastal Facilities 2000” (November
2000, Japan Society of Civil Engineers) and “Technical Standards of Harbour Facilities and Explanations”(May 1999, The Japan Port and Harbour Association).)1.10 Method of numerical analysis for tsunamis
In tsunami simulation, the linear long-wave theory may be used for deep sea areas. For shallow sea
areas, including land sections where tsunamis may run up, the non-linear long-wave theory (shallow water
theory), in which sea bottom friction and advection are considered, should be used. Propagation oftsunamis from a distant site over the ocean should in principle be calculated using the theory of linear
dispersive waves.

1) Basic equations for tsunami calculations
The movements of long waves, such as those of tsunamis, are expressed by the non-linear long-wave

90theory (shallow water theory), which can reproduce the basic behavior of tsunami propagation from thesource to the land. For deep sea areas, the linear long wave theory that disregards friction and advection at
the ocean bottom may be used. Tsunamis that reach shoaling coasts may show soliton fission (long waves
dividing into waves of shorter wavelengths) due to the dispersion effect, and the resultant waves become
higher than the waves before division.
2) Concepts of soliton fission
Tsunamis that were observed during the Nihonkai Chubu Earthquake showed soliton fission and undular
bores and are difficult to reproduce unless the Boussinesq equation is used. Waves that underwent soliton
fission during the earthquake showed amplification of wave height due to the waveform curvature effect.
Since amplified waves will break, considering wave breaking models.
3) Coarseness of the land
The effects of structures on the land can be investigated by using the mean coarseness in calculation grids,
which depends on the land use situation (See Table 1.4.1).
4) Tsunamis from distant sites
Propagation of tsunamis from afar may be calculated by using the linearity theory, since the wave heightof such tsunamis is smaller compared to the water depth. When waves of different wavelengths are containedin the initial waveforms, the propagation speed in deep water differs depending on wavelengths, and shortwaves delay in the course of propagating a long distance.
To reproduce this effect, equations of motion that include dispersion terms should be used. Besides
considering the Coriolis force, spherical coordinates should be used to consider the effects of the globe beinga sphere.

91

Chapter 2

Calculations for predicting inundation during storm surges

2.1 Flow of calculations for predicting inundation
A general flow of calculations for predicting inundation during storm surges is 1) assuming theexternal force of a storm surge (target typhoon), 2) preparing topographical data, 3) setting and inputting
initial conditions, 4) reproductive simulation, 5) predictive simulation, and 6) outputting results.

1) Flow of calculations for predicting inundation during storm surges
A general flow of calculations for predicting inundation is shown in Figure 2.1.1.
Collecting data

1)Assuming the external
force of a storm surge(target typhoon)3)Setting and inputting
initial conditions2)Preparing
topographical data

Reproductive simulation

Checking
reproducibilityＮoYes5)Predictive simulation

6)Outputting results

Results of inundation
prediction (inundation risk
areas, etc.)

Figure 2.1.1

Flow of calculations for predicting inundation

922) Conditions used for preparing storm surge hazard maps
This manual presents an overview of how to deal with uncertain factors, or conditions used for preparingstorm surge hazard maps, while keeping in mind how such factors should be set to minimize damage toresidents. Conditions used for preparing tsunami hazard maps are shown in Table 2.1.1.
Table 2.1.1

Conditions used for preparing storm surge hazard maps

Item
TyphoonTidal levels and waves
Topographical conditions andrun-up along river

Conditions used for preparing storm surge hazard maps
1. Scale of typhoon
2. Route of typhoon
3. Tidal level (astronomical tide)
4. Calculated waves
5. Grid intervals
6. Elevation
7. Run-up along river
8. Conditions of structural damage

Structures

9. Operational state of facilities
10. Method of numerical analysis for storm surge

2.2 Scale and route of typhoon
The external force to assume when preparing storm surge hazard maps should be investigated anddetermined by the body in charge of preparing the maps, according to the storm tide that may be causedby the largest possible typhoon and other conditions.
The assumed typhoon for simulations should be the largest typhoon recorded or a typhoon of the scaleof the Ise-wan Typhoon. The route of the typhoon for calculating inundation should be the route thatcauses the most serious damage to the area by referring to the routes of typhoons in the past.

1) Assumed external force
The assumed external force should be determined in reference to the storm tide that would be caused by
the largest possible typhoon*1 assumed based on available knowledge.
2) Assumed typhoon
Unlike river discharge, typhoons are difficult to express in probability distribution because there is little
observation data available regarding typhoons. Therefore, simulations should be performed based on the datafrom both the largest recorded typhoon in the area and/or the Ise-wan Typhoon, which is the largest typhoon
ever recorded in Japan (in terms of atmospheric pressure after landfall). The traveling speed of the typhoon
should also be appropriately determined. Concerning a typhoon of the scale of the Ise-wan Typhoon, data forsimulations do not have to be that of the Ise-wan Typhoon; data that are most suited to the area should be
employed in reference to typhoons in the past. The conditions of bank damage should be determinedaccording to the scale of the typhoon.
*1 The largest typhoon denotes a typhoon that would cause the most serious damage to the target area, and should be
investigated and determined by the body in charge of preparing the hazard map.

93

Reference: Scales and routes of typhoons for Tokyo Bay
For the Tokyo Bay, model scales (Ise-wan and Kitty Typhoons) and routes are assumed to calculate thelargest storm tide using two-dimensional models. The routes used for simulation calculations, and the results,
are shown in Figure 2.2.1.
The largest deviation at the depths of the bay is shown when a typhoon of the scale of the Ise-wan
Typhoon takes almost the route of the Kitty Typhoon.

Fukushim

NiigataTyphoonin 1917

Actual route
Utsunomiya
Kitty
ThphoonModel course

Maebashi
Mito

Tokyo
Kofu
Mt. Fuji

Choshi
Yokohama

Shizuoka

Figure 2.2.1

Model
TyphoonRoute
1
Kitty Thphoon
Ⅰ
2
〃
Ⅱ
3Kitt
〃
Ⅲ
4y Typhoon in 1917
Ⅳ
5
〃
Ⅴ
6
〃
Ⅵ
7
Ise-wan Typhoon
Ⅶ
8
〃
Ⅷ
9
〃
Ⅸ
10
〃
Ⅹ

Routes of typhoons used for storm surge simulation and results

2.3 Tide (astronomical tide)
Tidal levels for storm surge simulation should in principle be the mean monthly highest water level(H.W.L.). A storm tide calculated by using the assumed typhoon or the largest recorded storm tide should
be used.
<Method for determining tidal level>
Tidal levels for storm surge simulation should in principle be the mean monthly highest water level(H.W.L.). The mean monthly highest water level during the typhoon season should be investigated whennecessary. The typhoon season is generally July to October, although this may depend on area.

942.4 Calculated wave height
Wave height for storm surge simulation should in principle be the wave height calculated by thesimulation conducted by using the assumed typhoon. When the largest recorded storm tide is used as theassumed external force, appropriately calculated wave height should be determined by referring torecords.
<Method for determining wave height>
Wave height for storm surge simulation should in principle be the wave height calculated by thesimulation conducted by using the assumed typhoon.
The relationship between storm tide and waves as well as tidal level (astronomical tide) for simulation
should be investigated and determined by the bodies in charge of preparing the maps.
When the largest recorded storm tide is used as the assumed external force, appropriately calculated wave
height should be determined by using the design wave height for facilities and 50 year probability wave
height.

2.5 Grid intervals
Grid intervals for storm surge simulation in the target sea and river areas should be appropriately
determined by ensuring the precision of the target inundation risk area and by taking account of minutetopography, such as structures.

Grid intervals for storm surge simulation should be determined in the same way as those for tsunami
simulation are. (See 1.4 Grid intervals for methods for determining grid intervals for tsunami simulation.)

2.6 Elevation
Elevation data for storm surge simulation directly affects the resultant estimated inundation depth andthus should be precise. Especially, the elevation data for areas where inundation is predicted during
tsunamis need precision smaller than 1 m to estimate inundation depth. When such precise data is notavailable, the necessary precision should be ensured by correcting data by using the survey points of
topographical maps, reconnaissance surveys, and surveys by coast experts.

Elevation for storm surge simulation should be determined as that for tsunami simulation is determined. (See
1.5 Elevation for methods for determining elevation for tsunami simulation.)95

2.7 Run-up along rivers
In areas where inundation from river water during storm surges may occur, the run-up of the high waves
along rivers should be calculated by appropriately determining river discharge based on river characteristics
and records in the past.

1) Rivers for which run-up should be considered
Bays are prone to storm surges when they face the open sea, are shallow in depth, and extend far inward.
Rivers that flow into such bays are prone to run-up of sea water during storm surges. When there are bridges
in river sections where sea water may run up, the heights of the girders must be examined, and the effects ofthe bridges on run-up and swell-head must be considered.
2) River discharge
The effects of river discharge on the run-up of sea water along the river have not been clarified.
Simulations have shown a general tendency that the run-up of sea water causes smaller rises in river water as
river discharge becomes larger. In other words, when the discharge of a river is large, rises in tidal level at
the river mouth are not transmitted along the river, and the water level of the river is determined by the flood
discharge. On the other hand, when the river discharge is small, the rises in tidal level are transmitted along
the river and cause rises in the water level of the river. Thus, rises in water level of a river would be largest
when the discharge of the river were to be zero. Note that the focus here is placed on “rises in water levelcaused by storm surges”, and such rises does not mean rises in river water level itself.
Since the behavior of water when run-up of sea water and downflow of flood water are combined is little
understood, river discharge should be tentatively determined in the following manner:
1) For rivers running in areas where important assets are located, river discharges should be calculated on theassumption that such areas are in a critical situation. Calculations should be conducted by drawing a floodhydrograph in which the design high water peak discharge occurs simultaneously with the highest tidal levelat the river mouth, or by determining a certain design high water peak discharge at the river mouth.
2) For rivers running in areas where no important assets are located or for which no design flood hydrographexists, the run-up along a river during storm surges should be calculated by using the normal discharge of theriver as the river discharge.

2.8 Conditions of structure damage
Damage to coast protection facilities and other structures by overflows and overtopping should beconsidered on the basis of their present conditions.

1) Determining facility conditions
Facility conditions should be determined by surveying the actual states of facilities, investigating thepossibility of overflows and overtopping for each facility, and conducting simulations by using different
conditions.
Facilities may possibly be damaged by collision with containers and driftwood, depending on region.
2) Mechanisms of levee breachs
Levee breachs during storm surges are asummed to be caused by overtopping of sea water, which is
triggered by abnormal rises in sea level, but the detailed mechanisms are not yet understood as in breaches
during non-storm surge periods.

963) Levee breach width
During storm surges, breach widths vary, and the widths are difficult to estimate. The breach width ofriver levees is estimated based on river width, but this method cannot be used for coastal levees, since thebreach widths will vary even along the same coast depending on the landform at each point, the conditions of
the levees, and the actual external force received.
4) Levee breach height
When a coastal levee breaches, its concrete foundation may remain. However, sea water inundates theland. Thus, levees should be assumed to be destroyed down to the foundation, the height of the levees after
destruction should be considered to be as high as the elevation to the inland.
5) Progress of levee breaches
Levee breaches are determined by a combination of tidal level and wave height, which changes over time,
and the start of levee breaches is difficult to estimate. Thus, calculations should be conducted by assumingthat a levee starts breaching at the peak tidal level, when it is most dangerous, or immediately before thepeak (for example when the amount of overtopping exceeds the allowable level). The progress of levee
breaches (expansion of levee breach width) should be ignored in calculations, since coastal levees are likely
to be destroyed in units of certain lengths at once due to their concrete, three surfaces armoring structure.

2.9 Operational states of facilities
For inundation prediction during storm surges, water gates and land locks should be assumed to beclosed except for those that will apparently not function. Simulations should also be conducted byassuming, when necessary, that some are open.
<Determining facility conditions>
Water gates and land locks should be able to be closed before storm surges strike. For large cities, where
the population is large and the damage will be serious, such as ordinance-designated cities, simulations
should be conducted by assuming the water gates and land locks are both open and closed.
The effects of pumping stations should also be investigated when necessary.

2.10 Method of numerical analysis for storm surge
In storm surge simulation, the linear long-wave theory may be used for deep sea areas. For shallow
sea areas, including land sections where tsunamis are likely to run up, the non-linear long-wave theory(shallow water theory), in which ocean bottom friction and advection are considered, should be used.
Calculations should be continued until the highest storm tide appears, including the resurgence period.
1) Characteristics of storm surge calculation
The scale of a storm surge is similar to the causal meteorological disturbance and is much larger thanwater depth. Thus, storm surges are expressed by the equations of the linear long-wave theory. Storm surges
are characterized by rises and drops in water level caused by changes in atmospheric pressure and forced
fluctuations in water surface caused by the continuously acting external forces of winds. Thus, calculations
should be conducted by considering the rotation of the earth, drops in atmospheric pressure, friction of winds
acting on the water surface, and ocean bottom friction. The precision of calculation can be improved when
the deflection of winds by mountains and other landforms is appropriately considered.
Calculations should be continued until the highest storm tide appears, including the resurgence period.

97

Storm tideTime

Figure 2.10.1

Time-series change in storm tide during storm surges

Reference: Iwagaki, Yuichi and Sawaragi, Toru, Coast Engineering (in Japanese), 1979, Kyoritsu Shuppan

2) Other uncertainty factors
The traveling speed of a typhoon, which is an uncertainty factor of external force, and the uncertainty
factors of calculations, such as wave set-ups by wave breaking, the coefficient of friction of the sea surface,
and irregularity of the amount of overtopping, should be considered based on the latest technologies.
3) Coarseness of the land
The effects of structures on the land sections can be investigated using the mean coarseness in calculation
grids, which depends on the land use (see Table 1.4.1).

98Reference 2: Examples of utilizing tsunami and storm surge hazard maps fordeveloping measures for preventing disasters
Utilization of tsunami and storm surge hazard maps enables non-structural measures for avoiding
disasters (such as enhancing residents’ self defense capabilities and drawing up evacuation plans) andstructural measures (such as the investigation of emergency and restoration plans using real-time
information) to be effectively taken.

1) Utilization of hazard maps for taking non-structural measures
Tsunami and storm surge hazard maps, which show information about tsunami and storm surge disasters
and inundation risk areas, are effective for taking non-structural measures for avoiding disasters during
tsunamis and storm surges, such as enhancing residents’ self defense capabilities and drawing up evacuationplans (evacuation sites and routes) (Figure 1). This reference describes examples* of utilizing tsunami andstorm surge hazard maps to help administrators draw up non-structural measures.

Tsunami and storm surge
hazard maps

Information about tsunami and storm surge disasters
Hazard information about risk areas, etc.

••

Self education
Learning
bycommunication•
risk

・ Enhancing residents’ self defense
capabilities (self support and mutual
support)・ Assisting residents’ mutual support

Determining
appropriate evacuationroute based on risk
assessment

Drawing up evacuation plans(evacuation facilities, routes, etc.) tomitigate damage from tsunamis andstorm surges

Figure 1. Flow of investigating non-structural measures against tsunamis and storm surges by utilizing
tsunami and storm surge hazard maps
*Examples described in this reference are mere examples and do not limit the activities to be undertaken.

9912) Utilization of hazard maps for taking structural measures
Tsunami and storm surge hazard maps for administrators, which show information on tsunami and storm
surge disasters and inundation risk areas, and information for each purpose, are effective for taking structural
measures for preventing disasters caused by tsunamis and storm surges by facilitating investigation of
emergency and restoration measures by using real-time information. This reference describes examples ofutilizing tsunami and storm surge hazard maps to help administrators draw up structural measures.

1. Methods for enhancing residents’ self defense capabilities by utilizing tsunami and storm surge
hazard maps
(1) Learning about tsunami and storm surge disasters (residents)
Residents can effectively learn about tsunami and storm surge disasters and enhance their self defense
capabilities by utilizing hazard maps for residents provided by administrative bodies. Residents may
study printed hazard maps and sign boards, visit websites, participate in local meetings of disasterprevention groups, and exchange risk information with administrative bodies.

Tsunami and storm surge hazard maps become effective only when residents themselves use those maps
and learn about tsunami and storm surge disasters and enhance their self defense capabilities. Learning
activities include studying printed hazard maps and sign boards, visiting websites, and sharing awareness of
disaster prevention with other residents through local meetings of disaster prevention groups and throughrisk communication with administrative bodies that prepared the hazard maps.
○Learning at meetings of local disaster prevention groups
Local disaster prevention groups should hold meetings to learn about disasters by utilizing hazard maps to
educate residents and share information. Investigating the risks and evacuation routes for each small district
will be especially effective. It is also helpful to prepare more detailed local hazard maps by investigating
very local and minute details that cannot be discussed at workshops. Local disaster prevention groups that
may confront the same disaster should mutually exchange information and coordinate emergency measures.

(2) Providing residents with information to help them decide evacuation (for administrative bodies)
Information for enabling residents to appropriately evacuate can be supplied by providing accurate
information on tsunamis and storm surges in conjunction with tsunami and storm surge hazard maps,
and by installing signs that are coordinated with the hazard maps for guiding evacuation.

Tsunami and storm surge hazard maps can be used to take appropriate evacuation action during disasters.
The relationships between hazard maps and evacuation actions are summarized in Table 1.1.1. Researches
have revealed that the timing of information acquisition affects the evacuation behavior of residents, anddelays in information provision lead to delays in evacuation. Thus, extra care should be taken regarding thetiming of information provision.

100

2

Table 1.1.1

Relationship between tsunami/storm surge hazard maps and evacuation action/measures before
disasters
Hazard map
Evacuation actions/measures
For residents (paper) Understanding the risk of tsunamis and storm surges, evacuation sites and routes,
other information for deciding evacuation (local residents)
For administrators
Constructing evacuation sites and routes, selecting appropriate sites for establishingdisaster prevention headquarters, constructing river, coastal, and harbour facilities,
providing education on disaster prevention, and utilizing the information for drawing
up land-use and regional plans (administrators)

It should be noted that information shown on tsunami and storm surge hazard maps is based on certain
assumptions and contains uncertainty. Thus, unexpected disasters may occur during actual tsunamis andstorm surges.
1) Providing residents with accurate information on tsunamis and storm surges in conjunction with tsunami
and storm surge hazard maps
Information shown on tsunami and storm surge hazard maps is preliminarily information, and residents
must decide on evacuation, and evacuate during an emergency, on the basis of the information on the maps.
However, during emergencies, residents may not be able to collect sufficient information to correctly decideon evacuation. Disasters beyond the assumptions of the hazard maps may also possibly occur. Thus, forappropriate evacuation, correct information on tsunamis and storm surges must be provided to residents in amanner coordinated with the hazard maps.
For example, information on tsunamis and storm surges broadcast by municipal governments through theirdisaster prevention radio systems should be provided in ways that are coordinated with their hazard maps. A
real-time two-way hazard map provision system using IT is also an effective method for transmitting correct
information on tsunamis and storm surges in emergencies.
2) Installing signs for guiding evacuation in coordination with the hazard maps
Especially during a tsunami, people need to evacuate in a hurry. They may lose their lives if they get lost.
To avoid such situations, signboards showing evacuation routes must be installed in coordination withtsunami and storm surge hazard maps. For example, the signboards shown in Table 1.1.2 should be installed.
When evacuation sites differ from those to be used during fires, different signs should be used to show theevacuation sites, but uniform signs should be used for each kind of disaster.

101

3

Table 1.1.2 Signs for guiding evacuation
Functions
ExamplesEducateabout
theSignboard dimension: 600
Signboard dimension: 450
characteristics and risksof tsunamis
Not exceeding 2,500

Kind of sign
Signs to show risk

Signs to show Transmit information
evacuation sites
about evacuation routes
and sites

Signboarddimension:800x300

Not exceeding
2,400

Signboarddimension:1100x400

Self-standing

Signs to warn of Warn residents abouttsunami approach
approaching tsunami as
quickly as possible

Wall-hanging

Signboard dimension: 4500x2500
Tsunamiapproaching!
Evacuate!

Reference: Kochi Prefectural Government

Diverse evacuation guiding systems, such as those that use sounds and lasers, are needed for nighttime
evacuation and should be used on a trial basis.

2. Drawing up evacuation plans by using tsunami and storm surge hazard maps (for administrative
bodies)(1) Investigating plans for disaster prevention measures and constructing disaster prevention centers (normal
time)
Information shown on tsunami and storm surge hazard maps, such as inundation areas and inundation
depths, can be used to investigate evacuation routes and sites that can minimize damage.
Information on dangerous sites and evacuation routes can be used to investigate the scales of
evacuation sites, routes of emergency vehicles, and the amount of emergency goods to transport and its
transportation routes.

102

4

Information shown on tsunami and storm surge hazard maps, such as inundation areas, inundation depths,
dangerous sites, and evacuation routes, can be used to investigate evacuation routes and sites, routes for
emergency vehicles, and the amount of emergency goods to transport and its transportation routes. Examples
are described in the rest of this section.
<Example 1-1>
Theme
Investigating
evacuation sites duringstorm surges

Information shown
Inundation initiation time
Inundation initiation site
Population distribution inland
Evacuation site

Use the information to understandAffected areas and expansion
Inundation risk areas
Number of people who need to evacuate
Evacuation site

High School B

Junior High School C
Community A
Elementary School A

Inundation
initiation time○：○○

Candidate for evacuation site
Elementary School A
High School B
Junior High School C

Inundation risk area

Inundation risk area
Outside the area
Outside the area
Inside the area

Distance
Far
Near
Near

Judgment

High School B was chosen to be the evacuation site.
Figure 1.2.1

Using tsunami and storm surge hazard maps for determining evacuation sites
during storm surges

103

5

<Example 1-2>
Figure 1.2.2 Using tsunami and storm surge hazard maps for determining evacuation sites during tsunamis
Theme
Information shownUse the information to understand
Investigating
Inundation initiation time
Affected areas and expansion
evacuation sites during Inundation initiation site
Inundation risk areas
tsunamis
Population distribution inland
Number of people who need to evacuate
Evacuation site
Evacuation site

Elementary School A

Community B

Junior High School D

Building X

Inundation
initiation time○：○○

Time allowance
Almost no time
Not much time
Sufficient time
Sufficient time

10 minutes## Hill
30 minutes
20 minutes 40 minutes
Inundation risk area

Candidate for evacuation site
Building X## HillElementary School A
Junior High School C

Inundation risk area
Inside the area
Inside the area
Outside the area
Outside the area

Distance
Very near
Near
Rather far
Far

When there is little time to evacuate, Building X and ## Hill should be set as the evacuation sites.
Evacuation sites during tsunamis must be nearby (which is an important condition for the elderly), since
there will be little time after an earthquake before the resultant tsunamis reach the coast.

104

6

<Example 2>
Figure 1.2.3 Using tsunami and storm surge hazard maps to understand the demand for evacuation sites
Theme
Information shownUse the information to understand
Understanding theInundation initiation time
Affected areas and expansion
demand for evacuation Inundation initiation site
Inundation risk areas
sites
Population distribution inland
Number of people who need to evacuate
Evacuation site
Evacuation site
Capacity of evacuation site
Capacities of evacuation sites

Evacuation site
Capacity: XX people

Evacuation

High School B
Community B
Population: 100
Community A
Population: 60
Community E
Population: 90
Community C
Population: 30

Candidate for
evacuation site
Elementary
School A

Capacity: ZZ people
Community D
Population: 60

Inundation
initiation time○：○○

People who cannot be accommodated
in High School B find shelter in
Elementary School A

Community F
Population: 80

Community
A
B
C
D
E
F

Population

Area

60
100
30
60
90
80
Total

150m2
200m2
100m2
150m2
150m2
100m2

Size ofinundation
risk area
50m2
100m2
100m2
50m2
50m2
0m2
350m2

Number of people evacuating
Within parenthesis, the number of people
evacuating over a long period of time60(20)
100(50)30(30)
60(20)
90(30)0(0)340(150)

Note: The number of people evacuating over a long period of time is calculated from the population of the community and thepercentage of inundated area in the total area of the community.

340 persons are estimated to evacuate to High School B (150 persons will stay there over a long
period of time)
When the number of people finding shelter in High School B exceeds its capacity, some must move toanother evacuation site. The optimum allotment should be decided by combining the results of Examples 1-1
and 2, such as XX persons to High School B and ZZ persons to Elementary School A, to support theevacuation of residents.

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7

<Example 3>
Figure 1.2.4
Theme

Using tsunami and storm surge hazard maps for investigating evacuation routes
Information shownUse the information to understand
Inundation initiation time
Affected areas and expansion
Inundation initiation site
Inundation risk areas
Investigating
evacuation routes
Density of wooden houses
Safety of the district during earthquake
during tsunamis
Evacuation route candidates
Safety of evacuation routes
Evacuation site
Evacuation site

Evacuation site
National Highway No. X
High School A
Community B
Community A

Density ofwooden houses: Community E
Density of
Low
National Highway No. Z
wooden houses:
Density ofIntermediate
woodenCommunity C
houses: HighDensity ofwooden houses:
High Community D
Density ofwooden houses:
InundationHigh
initiation time
Community F○：○○
Density of wooden
houses: Intermediate

Highway

Communities to pass to reach theevacuation site

Density of wooden houses

Judgment

X

Community B

Low○

Community D

HighCommunity E

High

Z

X

National Highway X was decided to be the evacuation route from Community C.

During a tsunami, the earthquake preceding the wave may destroy buildings and bridges, blocking
evacuation routes. Hazard maps can be used to investigate such possibilities.
New evacuation routes may need to be constructed in districts where wooden houses are densely built.

1068

(2) Checking the operation and conditions of systems (during disasters)
Coast protection facilities (water gates and land locks) can be appropriately operated by utilizing
tsunami and storm surge hazard maps.

When a tsunami or storm surge is anticipated, coast protection facilities (water gates and land locks) canbe appropriately operated by utilizing tsunami and storm surge hazard maps together with information on thescale of the tsunami or storm surge. Especially during typhoons, appropriate measures against storm surge
can be taken by utilizing the prediction results for the corresponding typhoon route.
(3) Investigating evacuation and rescue plans (during disasters)
During disasters, evacuation and rescue plans can be investigated, such as methods for evacuating
residents (determination of evacuation routes and sites) and delivering emergency vehicles and goods toevacuation sites, by comparing the scale of the actual disaster with those shown in tsunami and storm surge
hazard maps.

During disasters, appropriate evacuation of residents (by specifying evacuation routes and sites) can besupported by judging the scale of the disaster, comparing the scale with those shown in tsunami and storm
surge hazard maps, and revising the preliminary disaster prevention plans. Special care must be taken when
the actual external force is different from those used to prepare the maps.
After the disaster, tsunami and storm surge hazard maps can be used to figure out the numbers of people
injured and evacuated and to undertake appropriate rescue measures.

107

9

<Example 1>
Evacuation site
CapacityHigh School B

Other information

Community B

Capacities of
evacuation sites

Evacuation site

・Number of available emergency

vehiclesCommunity E
Elementary School A
Community C

Community A

・Places from which goods are to betransported

Capacity
Community
D
Community F・Capacities of
evacuation sites

Hazard map

Reflecting in plans for delivering emergency vehicles and goods

Figure 1.2.5

Necessary number of Necessary amountof goods
emergency vehicles

Evacuation site

Number of people
sheltering

Elementary School A
High School B

○○人

○○台

○○トン

△△人

△△台

△△トン

・・・

・・・

・・・

・・・

Total

・・・

・・・

・・・

Utilization of tsunami and storm surge hazard maps for drawing up evacuation plans(methods of delivering emergency vehicles and goods)<Example 2>

Evacuation routes
High School A

Live images from camera
TsunamiNational Highway No. X

Evacuation site
High School A

Community A
Density ofHazard map
・Understanding
evacuation routes

・Monitoring the actuallyinundated areas
・Monitoring the conditionof facilities

Community B
Density ofwooden houses: Community E
Density ofwooden houses:
woodenC
it C
Density ofhouses: Highwooden houses:C
it D
Density ofwooden houses:
High

Other
information

National Highway No. Z

Real-time info. + Hazard map

Road blocked by collapsedbuildings

Community F
Density of wooden

houses: Intermediate

・Conditions of roads

Informing residents to use National Highway X for evacuation

Figure 1.2.6

Utilization of tsunami and storm surge hazard maps for drawing up evacuation plans(issuing evacuation orders)1083. Investigating emergency measures and restoration plans using real-time information
Coast protection facilities to be operated during disasters (water gates, land locks, etc.) should be shownon tsunami and storm surge hazard maps to ensure their operation. When real-time information fromcameras, etc., is available, the operational conditions should be monitored and the information should be
used for emergency and restoration measures.
After a disaster, the actual damage should be compared with the assumed and predicted damage shownon tsunami and storm surge hazard maps to investigate practical emergency and restoration measures.
Facilities that are little prone to damage should also be monitored in real time and be reinforced andrepaired when necessary.
Facilities may be monitored using cameras for transmitting live images, by inspecting facilities
according to tsunami and storm surge hazard maps, and by preparing real-time hazard maps.

Coast protection facilities that are to be operated during disasters (water gates, land locks, etc.) and which
are shown on tsunami and storm surge hazard maps can be monitored in their operation by utilizing theresults of inundation prediction and real-time information. The information can also be used to investigate
emergency and restoration measures.

Monitoring damage
○
○
○

⋅
⋅

Live cameras
Field inspection (of facilities shown on
hazard maps to be prone to damage)
Real-time hazard map

Identifying points that need emergency andrestoration measures
Identifying points that need to be
reinforced and repaired

Emergency andrestoration measures fordamaged facilities

Figure 1.3.1

Reinforcement and repairof points prone tosecondary damage

Tsunami and storm
surge hazard map•
Understanding
inundation risk areas
and facilities prone todamage (sites whereliquefaction may occur
during an earthquake)•
Monitoring
thepresent conditions offacilities by using areal-time hazard map

Flow of investigating emergency and restoration measures using real-time information

The following is a mere example and does not designate bodies in charge.

109

11

<Example>
Theme

Information shown

Investigating
Inundation initiation time
emergency measures Protection facilities andfor damaged facilities
structures
Population distribution inland

Use the information to understandAffected sitetheir Affected facilities
Priority of restoration

Live camera
Inundation initiation site

TsunamiHazard map

Detecting the inundation
initiation site

• Checking
theactual inundation
area• Monitoringtheactual condition offacilities

Investigating emergency measures

Executingemergency measures

Figure 1.3.2 Utilization of tsunami and storm surge hazard maps for deciding emergency measuresfor damaged facilities

110

12

Reference 3: List of related web sites
Class
Administrative
organization

Research
institute

Other

Site
Pages of the Cabinet Officeinchargeofdisasterprevention
Pages of the Central Disaster
Prevention Council
Headquarters for Earthquake
Research Promotion
Fire
andDisasterManagement Agency
Japan Meteorological Agency
DisasterPrevention
Information Provision Center
Study Committee on Tsunami
and Storm Surge Hazard
Maps
National Research Institutefor Earth Science andDisaster Prevention
Earthquake
Research
Institute, the University ofTokyo
Disaster Prevention ResearchInstitute, Kyoto University
Japan Weather Association
Disaster
Reductionand
HumanRenovation
Institution
NHK Disaster Prevention
Notes

URL
http://www.bousai.go.jp/
http://www.bousai.go.jp/jishin/chubou/index.html
http://www.jishin.go.jp/main/index.html
http://www.fdma.go.jp/
http://www.jma.go.jp/JMA_HP/jma/index.html
http://www.bosaijoho.go.jp/link.html
http://www.mlit.go.jp/kowan/hazard_map/hazard_ma
p.htmlhttp://www.bosai.go.jp/jindex.html
http://www.eri.u-tokyo.ac.jp/Jhome.html
http://www.dpri.kyoto-u.ac.jp/default.j.html
http://www.jwa.or.jp/
http://www.dri.ne.jp/
http://www.nhk.or.jp/nhkvnet/bousai/
As of February 2004

111

13

Explanation of terms
Terms
Outcome index

Explanation
an index for indicating effects and outcomes of measures and projects.

Advection
Overtoppingstate in which fluid or substances in fluid move and change by a flow field.
phenomenon in which sea water passes over the upper surface (crown) of coast
protection facilities, such as breakwaters, sea walls, and walls, by the force ofwaves.
Coriolis force
recurvature force. Apparent force acting on a substance moving on a rotating
coordinate axis, such as the earth.
Wave breaking
phenomenon in which waves lose their stability, cannot maintain the waveform,and break. Waves from offshore cannot maintain their waveform and break
forward when they reach shallow water.
Mean monthly highest water mean of the high water levels of each month, which appear between 2 days
level (H.W.L.)
before and 4 days after the synoidal days.
Geological Information System comprehensive technology for controlling, processing, and visualizing data on(GIS)
position (spatial data), based on geological locations, to enable advanced analyses
and rapid judgment.
WebGIS
GIS provided through the Internet.
Water gate
gates and other structures that open and close at rivers and water channels toregulate the flow of water.
Land lockgates installed at banks, etc., that open and close for the passage of people andvehicles.
Spectrum method
a method for estimating waves. A general term for methods that trace andcalculate the development and attenuation of the spectrum based on the equationof energy equilibrium.
Solinton fission
phenomenon in which waves of certain wavelength divide into waves ofshorter wavelengths.
Borewaves generated by discontinuous changes of water surface when water gates andother structures on a standing open channel flow are suddenly closed or opened.
Crown
the tops of banks and other protection facilities. Crown height is the heightfrom the basic reference level.
Mean sea level of Tokyo Bay
reference level for land elevation in Japan.
(T.P.)
Inlandland protected from floods by river and coast protection facilities.
Hydrograph

Diagram showing time-series changes of river discharge
Explanation
one of the equations for analyzing tsunamis and storm surges. The relative water
depth (the ratio between wave length and water depth) is assumed to be
infinitively small, the vertical acceleration is ignored, and the finite amplitude isincorporated.
term denoting that future results can be judged in advance only in terms ofprobability.
one of the models for analyzing waves. A long-wave equation is used thatconsiders both the non-linearity and dissipation of waves.
waves that have turned into waves of a shorter period by solinton fission.
grid aggregate of data recorded by dividing a two- or three-dimensional coordinate
into grids. Grid intervals are the dimensions of the grids (fineness of data).
one of the methods for estimating waves. A general term for the SMB method,which describes a method for estimating significant waves (1/3 maximum wave),and Wilson’s method, which expands the SMB method for general water areas.

Items
Non-linear long-wave theory

Uncertainty
Boussinesq’s equation
Undular bore
Calculation grid andintervals
Significant wave method

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This manual is translated by following institutes.
For inquiries about this manual, please contact:

Hajime TANJI
National Agriculture and Food Research Organization
National Institute for Rural Engineering
Department of Rural Technologies
Research Team for Ariake Sea and Coastal Areas
2-1-6 Kan-nondai,Tsukuba,Ibaraki 305-8609,JAPAN
Phone: +81-29-838-7568
E-mail: tanji@affrc.go.jp
Akiyoshi NAKAYAMA
Hydraulics Section, Aquaculture and Fishing Port Engineering Division,
National Research Institute of Fisheries Engineering
Hasaki7620-7, kamisu, Ibaraki, 314-0408, Japan
Phone: 81-479-44-5929
E-mail: tetugen@affrc.go.jp
Shigenobu TANAKAInternational Technical Exchange Team,International Centre for Water Hazard and Risk Management, Public Works ResearchInstitute
1-6, Minamihara, Tsukuba, Ibaraki 305-8516, Japan
Phone: +81-29-879-6809
E-mail: s_tanaka@pwri.go.jp
Takashi TOMITA
Tsunami Research Center, Port and Airport Research Institute3-1-1, Nagase, Yokosuka, Kanagawa 239-0826, Japan
Phone:+81-46-844-5052
E-mail: tomita@pari.go.jp