わが国における治水対策の取り組み - ICHARM The International

Flood Management in Japan
１. Vulnerable land for flood disasters
２．Change of socio-economic conditions
３．Change of natural conditions
４．New concept of flood management
December 2, 2007
Takeshi KADOMATSU
Director General of the River Bureau, MLIT
0
Characteristics of rivers in Japan
1. Vulnerable Land
Altitude
標高
ロアーヌ川
River
Loire
常願寺川River
Joganji
Fuji
富士川
River
Kiso
River
木曽川
吉野川
Yoshino
River
信濃川 River
Shinano
コロラド川 River
Colorado
カ スリーン
River
Seine
セーヌ川
ナイル川
River Nile
River
Rhone
ローヌ川
Mogami
最上川
Mississippi River
ミシシッピ川
Amazon
アマゾン川River
Mekong
River
メコン川
River
Tone
River
利根川
Length
延長
●London and Thames River
Altitude
(m)
Thames
River
●Tokyo and Edo River, Ara River and Sumida River
Altitude
(m)
Joban Line
Shinsaka River
Keihin tohoku Line
Sumida
River Ara Ayase
River River
Kita-ku
Arakawa
-ku
Adachi-ku
Naka
River
Daiba
River
Katsushika-ku
Edo
River
Misato City
MusashinoLine
National Highway 6
Saka
River
Matsudo City
Most rivers in Japan are steep with short distance from the source
to the sea, resulting in rapid flow. Furthermore, most of urban
areas are located in low-lying areas below high water level.
1
Major cities are located in low lying areas
ゼロメートル地帯の面積、人口
Areas
and population of Zero-meter regions
○伊勢湾
○
Ise Bay
National
全国計
total
Three major
三大湾計
面積
Area (km2)
(km2)
1,648
576
116
336
124
人口 (万人)
Population
(million)
539
404
176
90
138
いわゆる
So called
Zeroゼロメートル地帯
meter regions
harbors total
Tokyo
東京湾
Bay
伊勢湾
Ise Bay
1. Vulnerable Land
○
Tokyo Bay
○東京湾
大阪湾
Osaka Bay
:T.P. +0 m or lower
■：T.P.±0m以下
■：朔望平均満潮位以下
:Lower than average syzygetic high tide levels
■：計画高潮位(HHWL)以下
:Lower than anticipated high tide levels
○大阪湾
○ Osaka Bay
ゼロメートル地帯の定義
地盤沈下などにより、海抜0メートル以下に低くなった土地。
Definition of Zero-meter Region
※河川・湖沼等の水面の面積については含まない
※３次メッシュ（1km×1km）の標高情報が潮位を下回るものを図示。
※面積、人口は朔望平均満潮位以下の数値。 ３次メッシュデータにより集計したもの。
出典：国土地理院地図を元に作成
Population and city functions are concentrated in areas
below sea level in coastal areas of three major bays.
Catastrophic disasters would occurr in case of bank failure.
2
Population and assets are concentrated in flood prove areas
Areas lower than water level of rivers
Areas below
・・・洪水時の河川水位より低い地域
during
floodshigh water level
Other areas
・・・その他の区域
Approx.
約７５％ 75%
資産率
資産率
Proportion of assets
日
本
Japan
Proportion
of
人口率
population
人口率
Approx. 50%
約５０％
面積率
Approx.
約１０％ 10%
面 area
積率
Proportion of
0%
United
イギリス
Kingdom
※イングランド＋ウェールズの割合
•Proportion
for England and
（スコットランド・北アイルランドを除く）
Proportion
of
人口率
population
人口率
Proportion
面積率
面積率
of area
Wales (excluding Scotland and
Northern Ireland)
United
アメリカ
States
1. Vulnerable Land
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
40%
50%
60%
70%
80%
90%
100%
40%
50%
60%
70%
80%
90%
100%
Approx. 9%
約９%
Approx. 10%
約１０%
0%
Proportion
of
人口率
population
人口率
Proportion
面積率
面積率
of area
10%
20%
30%
Approx. 10%
約１０％
Approx. 8%
約８%
0%
10%
20%
30%
出典：日本の河川 Learning to Live with River CIA The World Fact book
Approximately half of the population and three-quarters of total
assets are concentrated in low-lying areas.
Huge damage would be caused in case of flooding.
3
Lower safety level for flood disasters
Netherland
オランダ
(high
tide
（高潮計画）
planning)
The United
イギリス
Kingdom
（テムズ川）
(Thames
River)
The United
アメリカ
States
(Mississippi
（ミシシッ
River)
ピー川）
France
フランス
(River Seine)
（セーヌ川）
Japan
日本
1. Vulnerable Land
Completion
(1985)
完成（1985年）
Completion
(1983)
完成（1983年）
Achievement rate of
達成率89%（2002年）
89% (2002)
Completion
完成（1988年）
(1988)
Achievement rate of
達成率60%
approx. 60% (2006)
（2006年）
1/100
1回／
years
100年
1/50
1回／ 1/1,000
1回／
years
years
500年
1000年
1/10,000
1回／
years
10000年
1/301回／30～40年（大河川）
to 1/40 years (major rivers)
1/5 to
1/10 years
(medium to minor rivers)
1回／
5～10年（中小河川）（当面の目標）
Compared with other industrialized nations, safety level of national
land protected by flood control facilities is lower in Japan.
4
Increasing flood risk due to changes of social conditions 1
Urbanization in Tsurumi River basin
2. Socio-economic conditions
Occurrence of widespread submergence at the
underground facilities in urban areas
１９５８
京浜急行線
横浜線
東急東横線
南武線
東海道線
小田急小田原線
Urbanization rate：
About10％
Population：
About 450,000
第二京浜
第一京浜
平成１５年７月 福岡市営地下鉄
２００４
市営地下鉄
Urbanization rate：
About 85％
Population：
About 1.88million
各年代間に整備された交通網
平成１６年１０月 東京地下鉄麻布十番駅
Progress of urbanization in flood prone area causes increase of flood risk and
also causes new type of disasters, such as inundation of underground facilities.
5
Increasing flood risk due to changes of social conditions 2
Flood damage for general
assets (JY100 billion)
一般資産被害額(千億円)
水害区域面積(万ha)
Flood disaster areas
(10k hectare)
Flood density for general assets
一般資産水害密度（万円／ha）
(JY10k per hectare)
6,000
2. Socio-economic conditions
Electronic equipments, once submerged in
water, are no longer usable.
6 .0
５，４３３
5,000
5 .0
Waterlogged areas for
宅地等の浸水面積
residential housing
Flood concentration for
一般資産水害密度
general assets
4,000
3,000
4 .0
３．８
Amount of damage
一般資産被害額
for general assets
3 .0
2,000
2 .0
1,000
1 .0
０．７
0
0 .0
’78
’82 58
’83 ’84
’98 11
’99 12
’00 ’01
’03 16
’04 17
’05
53 ’79
54 ’80
55 ’81
56 57
59 ’85
60 ’86
61 ’87
62 ’88
63 ’89
1 ’90
2 ’91
3 ’92
4 ’93
5 ’94
6 ’95
7 ’96
8 9’97 10
13 ’02
14 15
％
(1) Amount of damage (JY10k)/waterlogged areas (hectare) (costs as of 2000)
(2) Figures represent average for past five years.
(3) Non-operation losses for businesses are included in the amount of damage for general assets, as well
as the concentration of waterlogged areas.
(4) Figures were derived from “Flood Statistics” issued by the River Bureau of the Ministry of Land, Infrastructure and Transport.
September, 2000
Heavy rain in Tokai region
Although the flooded areas are definitely decreasing due to flood control
projects having been carried out over many years, the amount of
economic losses in flooded areas has sharply increased due to
increasing number of assets vulnerable to flooding.
6
Increasing flood risk due to changes of social conditions 3
2. Socio-economic conditions
Proportion
of elderly among disaster victims
被災者に占める高齢者の割合
Under
65
６５歳未満
years208人
208
persons
(37%)
37%
６５歳以上
65 years and
359人
over
359
persons
(63%)
63%
Sashiki
Town in
Okinawa Prefecture, 2005
H17年
沖縄県佐敷町
The
slope behind a
平成１７年６月沖
nursing facility
縄県佐敷町におい
collapsed in Sashiki
て、豪雨により老
Town,
Okinawa
人福祉施設の背
Prefecture,
in June
2005
due to the heavy
後斜面が崩壊し、
rainfall,
resulting in the
入所者約７０人全
evacuation of all 70
員が避難。
people
in the facility.
77 kindergarteners were
trapped in school facilities by
flooded water in Niigata.
Asahi Shimbun on July 14, 2004
Due to the aging population, a significant number of victims
were among those who required assistance in case of
disasters, such as the elderly or children in day care facilities.
7
Increasing budget for post disaster responses
2. Socio-economic conditions
More than half of the budget for river
projects is for post-disaster responses
Increasing budget for post
disaster responses
30.0%
12,000
11,093 10,977
10,725
727
10,399
9,988
10,000
9,572
9,091
408
9,206
489
867
462
49%
10,176 10,169
9,785
9,743
25.0%
362
402
810
1,627
326
1,712
51%
1,437
8,453
8,014
8,000
20.0%
1,383
1,168
7,329
17.7%
16.4%
14.7%
1,030
14.6%
6,000
780
6,386
15.8% 6,091
14.1%
15.0%
1,011
8,684
8,881
9,170
9,626
33%
8,933
7.9%
8.3%
8,550
8,458
11.5%
8,348
7,070
6,299
4.2%
3.5%
4.6%
4.4%
3.6%
„
„
67%
6,025
5,374
■ Proportion of costs relating to
◆予算全体に占める大規模
large-scale
disaster response
被災箇所対応費の割合
activities in overall budget
74%
5,012
5.0%
Responsive action for large-scale disaster locations (disaster response strategies,
大規模被災箇所への対応（激特・床上・復緊）
waterlogged above floor level, as well as recovery and emergency response)
その他河川事業
Other river projects
0.0%
0
’90
H2
‘07
’91
H3
’92
H4
’93
H5
’94
H6
H7’95
H8 ’96 H9 ’97 H10 ’98 H11 ’99H12 ’00H13 ’01H14 ’02H15
’03
H16
26%
10.0%
6,846
6.6%
2,000
1,079
10,235 10,366 10,109
9,937
4,000
4.5%
■ River projects budget
(FY2006)
6,804
16.8%
16.0%
’04
H17
’05
H18
’06
H19
■ Directly managed
river projects
(FY2006)
■
Auxiliary river
◆補助河川事業
projects
（平成１８年度）
(FY2006)
Proportion in total budget increased for post disaster measures such
as recovery works for locations afflicted by large-scale disasters, due
to increased occurrence of floods in recent years. It is not possible to
invest necessary amount to preventative measures, which is also due
to reduction in total amount of budget for flood management.
8
Increasing flood risk due to climate change 1
Changes in temperature in the northern hemisphere
during the past one thousand years.
Increasing trend accelerating
近年増加傾向が加速
in recent years
3. Natural conditions
Inter-governmental Panel on Climate
Change (IPCC)
• Global warming is considered to be almost
certain due to increasing greenhouse gases
originating from human activities.
• The last 12 years have been the warmest 12
years since 1850.
Rise in the average temperature and level of
the sea water at the end of 21st century
２１世紀末の平均気温上昇と平均海面水位上昇
Data from thermometer readings
：温度計からのデータ
：年輪、珊瑚、氷床コアからのデータ（推計）
Data from tree rings, corals and ice sheet cores
：５０年平均値
Average value for 50 years
A society wherein a balance
環境の保全と経済
of both the environmental
conservation
and economic
の発展が地球規模
development is on a global
で両立する社会
scale
Rising
気温上昇
temperatures
Excerpts from “Climactic
Change 2001”, a Report of the First Working Group
in the Third
IPCC第三次評価報告書～第一作業部会報告書
気候変化2001より
Evaluation Report of the IPCC
Melties of iceberg in the arctic
Rising
sea levels
海面上昇
Approx.
1.8 degrees
約１．８℃
Celsius (1.1 to 2.9
degrees
Celsius)
(1.1℃～2.9℃)
18
to 38 cm
１８～３８ｃｍ
A化石エネルギー源を
society focused on fossil
fuel, undergoing high
重視しつつ高い経済
economic growth
成長を実現する社会
Approx.
4.0 degrees
約４．０℃
Celsius
(2.4 to 6.4 degrees
Celsius)
(2.4℃～6.4℃)
26 to 59 cm
２６～５９ｃｍ
・Increased
strength of tropical low pressure
systems forecasted.
・Some experts forecast the elimination of
almost all sea ice in the Arctic Sea, during
late summer seasons, by the latter half of the
21st Century.
Global warming is actually in progress. Scientists predicted that global climate change
due to global warming causes increased frequency of heavy rainfall and sea level rise.
9
Increasing flood risk due to climate change 2
Increasing number of inundation
due to storm surge
約100回
年
2000
1970
1960
1980
約40回
1950
（Ashiya City～Osaka City）
1940
（Kawagoe Town～Tokai City）
1930
（Yokohama City～Chiba City）
回
120
100
80
60
40
20 10回以下
0
1920
Osaka Bay
1910
Ise Bay
1900
Tokyo Bay
1990
Expansion of areas below sea level when
sea level rises 60cm
3. Natural conditions
ベニス(イタリア) St Mark’s Squareの年間冠水回数
(STERN REVIEW: The Economics of Climate Changeの記述を図化)
Population
（million）
22
20
17
15
12
10
2006
0
2005
1
2004
2
2003
0
2002
0
2001
0
2000
1
3
1999
1
1998
0
1997
１．５
1
0
1996
879
10 11
7
4
1995
rate
5
1994
After sea level
rise
1993
577
25
1992
Area（k㎡）
260mil.
（After sea
level rise）
1991
Today
138mil.
126mil.
（After sea （Today）
level rise）
1990
333mil.
90mil.
（After sea （Today）
level rise）
1989
176mil.
（Today）
厳島神社回廊の年間冠水回数
404
593
１．５
(厳島神社社務日誌より中国地方整備局作成)
If mean sea level rises 60cm due to global warming, area and population
in the area below sea level increases 50% in 3 major bay areas.
10
Increasing flood risk due to climate change 3
3. Natural conditions
The annual occurrences of heavy rain fall per hour
(AMeDAS in approximately 1,300 points in Japan)
Number of occurrences for downpours with
mm
or 以上の降水の発生回数
more per hour
precipitation
of 50５
０㎜
1. １時間降水量
500
（回/年）
Fluctuation of precipitation
for last 100 years
１時間降水量の年間延べ件数
The annual number of rain fall per hour
（全国のアメダス地点
約1,300箇所より）
(AMeDAS in approximately
1,300 points in Japan)
Ｔｉｍｅｓ
／Ｙｅａｒ
400
Annual
precipitation
(mm)
2 ,1 0 0
300
2 ,0 0 0
200
1 ,9 0 0
100
0
Average for
S52～61
1976
to 1985:
平均 209 times 回
Average for
S62～H8
1986 to 1995:
200
234
平均 234 times回
H9～18
Average for
1996 to 2005:
平均 288 times 回
313
52 53 54 55 56 57 58 59 60 61 62 63 H1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
52 53 54 55 56 57 58 59 60 61 62 63 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
Number
of occurrences
with precipitation of 100 mm or more per hour
2. １時間降水量
以上の降水の発生回数
１００for㎜downpours
10
（回/年）
Ｔｉｍｅｓ
／Ｙｅａｒ
5
S52～61for
Average
1976 to 1985:
平均 2.2 times 回
2.2
S62～H8for
Average
1986 to 1995:
平均 2.2 times 回
2.4
トレンド precipitation
Average
５年移動平均
Five-year
moving annual average trend
1 ,8 0 0
1 ,7 0 0
1 ,6 0 0
1 ,5 0 0
1 ,4 0 0
1 ,3 0 0
H9～18
Average for 1996
5.1
to平均
2005: 2.2 times回
1 ,2 0 0
1 ,1 0 0
年降水量precipitation
Annual
1900
明治33
1900
1920
大正9
1920
1940
昭和15
1940
1960
昭和35
1960
1980
昭和55
1980
2000
平成12
2000
0
Source: The graph is made based on the resource from Japan Meteorological Agency
The annual occurrences of heavy rainfall is in increasing trend,
while annual total rainfall is decreasing. Expanding fluctuation
of annual rainfall causes higher risk of flood and drought.
11
Unconventional flood management measures
Conventional flood protection
by continuous levee
Conventional
measures
4. New concept
New concept of flood management
measures
Ring dike
Unconventional
measures for
various land use
Example for Hiji-River
in Ohzu city, Ehime Pref.
矢落川
暫定堤防
古川樋門
湛水区域
Banking of
residential area
Conventional flood
protection to construct
continuous levee from
downstream takes a long
time for completion
Combination of various
measures to minimize
damage of floods
二線堤（市道）
肱川
To prevent spreading of
flooded water by second
line levee
Introduction of disaster mitigation measures to minimize
damage in addition to disaster prevention measures
12
Flood management combining structural and non structural measures 4. New concept
Publication of nationwide
flood hazard maps
Case example of
久留米市の事例
Designation of hazardous areas
for sediment-related disasters
Dangerous locations clarified through zone designations
Kurume City
・Restrictions to land use
・Restrictions to structure of buildings
・Recommendations for the relocation of existing houses
Evacuation assembly
points available during
waterlog disasters are
obvious at a glance.
Time it takes from breaching of levee to
破堤後に浸水するまでの時間
being
waterlogged
Waterlogged above floor level
３０分以内で床上浸水
within
30 minutes
Within two hours (50 m for all locations
exceeding 50 m)
re
es
de
g
tw
o
of
Peak section
nt
ry
na
tio
u
a
ne
ec
zo
P r ne
ry
zo ial ona
ec uti
Sp eca
pr
gr
ad
ie
eep slope
Mountain streams presenting threat
of mud and boulder slides
wi
th
slope
nd
Bottom of land
on steep slope
Land on st
on steep
Mud and
boulder slides
土石流
La
Top of la
nd
Height h of land on steep slope
Chikugo
River
Sp
ec
ial
Pr pre
ec c a
au uti
Inc
tio on
na ary deg lina
ry
zo ree tion
zo
n
n e e s or of 3
mo 0
re
Height h of land on steep slope
がけ崩れ
Land
slides
s
Waterlogged above floor level
６０分以内で床上浸水
within 60 minutes
Waterlogged above floor level
in６０分以上で床上浸水
60 minutes or more
Waterlogged
eventually
最終的に浸水
“Disaster Reduction” strategies by soft measures
for minimizing the total damage
13