Recurrent Water-related Disasters in Japan

-their Mechanism and Future Trends-

International Symposium on Water and Disasters -Learning from Historical Lessons and Good Practices -

Toshio Koike Director, International Centre for Water Hazard and Risk Management (ICHARM)

Council Member, Science Council of Japan (SCJ), Cabinet Office of Japan Professor Emeritus, the University of Tokyo

Chair, River Council of Japan

気象庁資料

Hiroshima Pref.

Flood Levee Breach

Sediment Disasters

Overflow & Inundation

Okayama Pref.

Western Japan Floods 2018 Maximum 48hrs Rainfall from June 28th to July 8th (JMA)

Ehime Pref.

Sediment Disasters

2

気象庁資料

Western Japan Floods 2018 Maximum 48hrs Rainfall from June 28th to July 8th (JMA)

Mortality: 224 (the worst case after 1982)

Hiroshima

Okayama

Ehime

● > 100yrs Rainfall

● < 100yrs Rainfall Major River of each Prefecture Maximum Flood by Typhoon

Top 5 Floods by Typhoons and Frontal Activities.

Hiroshima Okayama Ehime

by courtesy Dr. M. Ohara, ICHARM

3

June 03 June 04 June 05

June 06 June 07 June 08 Anomalously Long Stay of Active Frontal Line.

500hPa

Anomalous Evaporation and Wind from the Northern and Southern Anti-cyclones .

The Strongest Water Vapor Convergence since 1958.

Convergence

1958 to 2017 2018

by courtesy Prof. H. Nakamura, U-Tokyo.

Anomalous Patterns of the Polar Jet and the Sub-tropical Jet.

4

Aug., 2014 Hiroshima City (Sediment) • 121mm/hr (Typhoon, Frontal Line) • Human Loss: 74 • evacuation warning, land use

Recurrent Water-related Disasters in Japan Events and Countermeasures

Oct., 2013 Izu Oshima Island（Sediment） • 824mm/24hrs (Typhoon) • Human Loss: 39 • evacuation warning

Sep., 2015 Kanto & Tohoku (Bank Breach) • 551mm/24hrs (Typhoons) • Human Loss：8 • evacuated by helicopter: 1339

and by boat: 2919

Aug., 2016 Hokkaido & Tohoku (Bank Breach and Sediment) • 251mm/72hrs (Typhoons) • Human Loss: 27 • evacuation of physical handicaps • local socio-economic impact

June, 2017 Northern Kyushu (Sediment) • 299mm/6hrs (Frontal Line) • Human Loss: 42 • sediment and flood complex

Nov., 2014 Amendment: Sediment Disasters Prevention Act

Jan., 2015： Policy Vision: Disaster Prevention and Mitigation against a New Stage

May, 2015 Amendment: Flood Risk Management Act • Probable Maximum Rainfall for Life-

Saving

Dec., 2015 Policy Vision: Rebuilding Flood-Conscious Societies: Class A Rivers • Raising public awareness • Structural measures for crisis

management

Jan., 2017 Policy Vision: Rebuilding Flood-Conscious Societies: Class B Rivers • Life-saving of physical handicaps • Local socio-economical continuity

May, 2017 Amendment: Flood Risk Management Act • Joint Stakeholder Committee for FRR • Evacuation planning and drilling for

handicap-accessible facilities • Recovery by the national government

5

Recurrent Water-related Disasters in Japan Changing Hazards

0

20

40

60

80

100

120

Number of rain gauge stations where the historical maximum 24hrs rainfall were updated in each year.

1976 1990 2003 2018 21.2/year 18.2/year 51.8/year

Torrential heavy rainfall happens everywhere more frequently. No exceptions. The areas where have not experienced heavy rainfall are likely to be seriously damaged. The June 2018 floods raised two new issues: 1) Simultaneous events in the wider area. 2) Longer duration.

time

River Discharge

Design Flood

River Capacity

Flood Control Capacity by Dam

48hrs Rainfall Record

from June 28 to July 8

Heaviest on record

6

1 01

0

31 0

15

19

11

0

年代

0-9歳 10-19歳 20-29歳30-39歳 40-49歳 50-59歳60-64歳 65-74歳 74-85歳85歳以上 不明unknown >85

Recurrent Water-related Disasters in Japan Changing Society

Flood Levee Breach

Mabi, Okayama Pref. 1 0

1

0

31 0

15

19

11

0

年代

0-9歳 10-19歳 20-29歳30-39歳 40-49歳 50-59歳60-64歳 65-74歳 74-85歳85歳以上 不明

58.9% ≧65 88.2% ≧65

Nation-wide (224)

Cabinet Office

now

by courtesy Dr. M. Ohara, ICHARM

Rapid Aging:

• increase of the number of those

who should be supported.

• decrease of the number of

those who can support.

Mabi (51)

7

Recurrent Water-related Disasters in Japan Changing Society

Flood Hazard Map

Sediment Disaster Prevention Act special alert area: red zone alert area: yellow zone

Flood Levee Breach

Mabi, Okayama Pref.

Debris Flow

Kure, Hiroshima Pref.

Risk has been informed but not recognized.

Fully Collapsed: 17 houses

Death: 1

8

Recurrent Water-related Disasters in Japan Changing Society

0

10

20

30

40

50

60

70

80

1 2 3 4 5 6 7 8 9 1011121314151

00

% まで回復した事業所

の割合

(%)

売上額

職場の環境

Number of months elapsed

Sep. 2016 (one year after)

Stop

Stop + Stagnation

Percentage of the number of business facilities (%)

How long does it take to recover fully?

Number of days for full recovery

Inundation Depth (cm) Number of days for full recovery and inundation depth

manufacturing

service-industry

Sales Amount

Office Condition

A follow-up survey of the Kanto-Tohoku Floods by courtesy Dr. M. Ohara, ICHARM

Can we recover fully from the devastating water-related disasters?

Direct Damage of the Western Japan Floods: ～10 Billion USD (QE) (the largest damage on record since 1961)

9

Recurrent Water-related Disasters in Japan Our Challenges

preparedness

Socie

ty F

unctio

n

evacuation

response

recovery

Observation & Simulation

Monitoring &

Prediction

Climate Change

Community

Mutual Support Self-Help

Virtual Reality

Training/ Exercise

Public Support

Non-structural

Structural

Infrastructure Planning Disaster

Risk

Risk Reduction

10

Build Back Better

Recurrent Water-related Disasters in Japan Our Challenges

3,100ha

No Damage

Sep. 1961 Sep. 2018

130,000

No Damage

Inundated Area Inundated Houses

Sep. 3 Sep. 4 Sep. 5

Sep. 2018: 329cm

Sep. 1961 Sep. 2018

Infrastructure Investment Effect: 170Billion USD

Stopped by the Debris Barrier

Debris Flow

Kumano-cho Hiroshima Pref. Western Japan Floods

in June 2018

5050

00

1000

2000

3000

4000

5000

6000

放水路が無かった場合 放水路整備後

（戸）

No Damage

5050 Diversion

Without the Diversion Actual in June 2018

Estimated Damage without

the Diversion

11

Largest Storm Surge

on Record

Sep. 1961: 293cm

Recurrent Water-related Disasters in Japan Our Challenges

12

by High-Level Panel on Water

on March 14, 2018

HEADLINE RECOMMENDATION

Shift focus of disaster

management from response

to preparedness and resilience.

• Political leadership • Dialogue and community-based practices • Long-term Planning • Financing for and investment in water- related DRR to be doubled within the next five years. • Integration of science and policy including higher education • Biannual Special Thematic Sessions on Water and Disaster