Adaptation measures for extreme floods
using huge ensemble of high-resolution
climate model simulation in Japan

Tomohito Yamada
Faculty of Engineering
Hokkaido University
This study (dynamical downscaling) is supported by MEXT/SI-CAT.

Background Of The Study ～Extreme Disasters Caused By Heavy Rain In August, 2016
n Three typhoons landed in Hokkaido for the first time in recorded history in a week of August 17th to 23th, 2016. After
that, typhoon No. 10 approached to Hokkaido, and it brought recordable heavy rain in various places. Floods of rivers
and sediment disastersアoccurred
mainly in eastern of Hokkaido.
メダス降水量分布
アメダス降水量分布（ 平成28年8月15日1時～24日24時）

Typhoon（ 日本気象協会
routes in August,2016
配布資料から転載）

Typhoon No.11
landed on
August 21th

Precipitation
distribution（AMEDAS）（ 平成28年8月29日1時～31日9時）

at 1:00 on August
29th, 2016 ～配布資料から転載）
at 9:00 on August 31th, 2016
（ 日本気象協会
串内観測所
Kushinai
Observatory(開発局データ)(Hokkaido Development
Bureau’s data)on August29th～on August 31th
8 月29日～8月31日
cumulative
rainfall:515mm
515mm
累加雨量

Typhoon No.9
landed on
August 23th

Typhoon No.7
landed onAugust 17th

Tottabetsu
River Upper Reaches
戸蔦別川上流観測所
Observatory(開発局データ)(Hokkaido Development Bureau’s data)
8 月29日～8月31日
on August29th～on August 31th
累加雨量505mm
cumulative
rainfall:505mm

Typhoon No. 10
approachedon August 30th

Typhoon No.10（Lionrock）

2

Typhoon Characteristics Approaching Hokkaido
n The typhoon approach route to Hokkaido has changed in recent years, and in the past 60% was the route pass the Sea
of Japan before, but the route pass through the Pacific Oceans is increasing more than 50%.
n Typhoons approaching Hokkaido from the Pacific Ocean tend to head northward keeping central atmospheric pressure
lower than other routes.
The route pass throughthe Pacific Ocean
The route pass throughthe Japanese archipelago
The route pass throughthe Sea of JapanThe route of typhoons approaching
and landing in Hokkaido over the past 56 years

The route pass throughthe Pacific Ocean
The route pass throughThe value in the figure isnumber of typhoons
the Japanese archipelago
The route pass throughthe Sea of Japan
Changes in the number of typhoons approaching and landing in Hokkaido（Definition of approach: The route entered within 300 km from Hokkaido）

N (Number oftyphoons)

The route pass throughthe Pacific Ocean
The route pass throughthe Japanese archipelago
The route pass throughthe Sea of Japan

Apr May Jun JulAug

Sep Oct

Traditionally,
there were manytyphoons of theSea of Japan inAugust.

Nov Dec

Month typhoons occurred

The number of typhoons every month and its approach route

Degree of atmospheric pressure change of central pressure from the north latitude 30 degrees tothe north latitude 40 degrees（hPa/°N）, and number of typhoons (N)（For typhoons that passed through 30 degrees north latitude at a center pressure 980 hPa or less.）
2. The route of
the Japanese archipelago
Degree of atmosphericpressure change

1.
route of the Sea of Japanroute of the Pacific Ocean
全ルート
1 The日本海ルート
2 本州縦断ルート 3.3 The太平洋ルート
Degree of atmosphericDegree of atmosphericDegree of atmosphericpressurechangeYears 気圧変化度
pressure change
年数N
気圧変化度
N
気圧変化度 N
気圧変化度
N
pressurechange
1961-2016
56
2.62 116
2.90
67
2.68
24
1.82
25
Degree of atmosphericpressure change :気圧変化度：中心気圧の変化量［hPa］／緯度変化量［°］，N：対象台風数

Averageperiod
平均期間All routes

Amount of change in central atmospheric pressure [hPa] / Latitude change [°]Typhoons approaching
Hokkaido through the Pacific
Oceans are harder to weaken
than other routes, N : Number of target typhoons [hPa]

From document by Associate Professor Tomohito Yamada (Hokkaido University) and Mr. Taro Yamamoto (Hokkaido River Center)2

Freedom of Climate System (an example: dice)

Relative Error against Truth (1/6)!/# − 1/6
×100 [%]
Relative error[%]＝
1/6

M：O（N回サイコロを振り，ある目が出た総数）
N：試行回数（サイコロを振った総数）

N: Number of cases (total number of observation)

Our Mission○We scientifically predict the influence of climate change(rainfall and discharge change) in Hokkaido based on the latest
knowledge.
○We calculate the change of risks (scale, form and frequency, etc) due to the influence of climate change and share themwith society.
Analysis Of Rainfall In The Future Climate

We calculate dynamical downscaling Hokkaido region toseveral km by using “database for Policy Decision making forFuture climate change(d4PDF)“.(Start from 4 degrees risemodel)

JMA/ NHRCM

AGCM（Horizontal resolution 20km）（Horizontal resolution 60km）

Change of
We analyze the occurrence intensity
daily maximum rainfall
and frequency of heavy rain based onhigh resolution and large scale+4K Future
Historicalensemble simulation.
members
・Explanation of Extreme Phenomena・Statistical Analysis

Supported by SOUSEI and SI-CAT (MEXT)
Estimation Of Change Of Discharge On target Basin
常呂川流域

Tokoro Riverbasin

Tokachi River basin

Share the flood risk with society
Change of flooded area

Estimation ofpersonal suffering

Using Tokachi River and Tokoro
River where extensive damageoccurred, we predict changes offlood runoff in future climate.
・Change of the peak discharge
・Reduction of safety level of flood
control

Estimation of damaged
area of agricultural land

Perform risk assessment due to the influenceof climate change, and share with society.
・Increase of flooded area
・Increase of personal suffering
・Increase of social risk
・Comparison with other risks such as traffic
accidents

Discuss adaptation policy for future flood control in nationwide committees (MLIT)

4database for Policy Decision making forFuture climate change (d4PDF)

nIn this study, we downscaled from results of regional climate model experiments(horizontal resolution 20×20km) of d4PDF to 5×5km using the regional climate
model (NHRCM) of Japan Meteorological Agency.
Average ground temperature of global

Temperature in 1850

Resolution and calculation area of AGCM and NHRCM

4

Probability Evaluation Of Historical Climate Simulation Rainfall
And +4K Future Climate Simulation Rainfall【Tokachi River Obihiro Reference Point】
n 95% confidence interval of historical climate simulation based on 1/150 probability rainfall is between 188mm 360mm in Highly compatible GEV distribution. 95% confidence interval of +4K future climate simulation isbetween 252mm - 517mm, which shows the trend of increasing rainfall.
n Multiple samples using weather simulation enable us to respond with maximum value of confidence interval by risk
management.
Tokachi River Obihiro reference point

Samples

GEV distribution
Frequency distribution of 1/150 probability rainfall Tokachi River Obihiro
reference point

SLSC Average of
1.0×105 Sample

The observed actual 1/150
rainfall :266mm/72hr

The observed maximum 284mm/72hr (1981)
Number of Samples

Historical climate
simulation ： 0.014Cumulative frequency

1/150 probability rainfall
Actual256mm
Historical climate simulation
188mm-360mm+4K Future climate simulation
252mm-517mm

frequency

Non-exceedance probability (%)+4K Future climatesimulation ： 0.015

rainfall
Quantile value

6External Force Utilized For Risk Assessment 【 Future Experimant Of Tokachi River 】
n Selected 3 external forces for the risk assessment, within the range of 1/150 probability rainfall of+4K future climate simulation GEV distribution at Tokachi river Obihiro reference point: ①maximum
peak discharge around median ②maximum peak discharge within 95% of confidence interval ③
maximum basin average 72-hour-rainfall within 95% of confidence interval.
n Sampled maximum basin average 72-hour-rainfall out of 5400 cases of +4K future climate
simulations to assume the worst possible scenario in the future Tokachi River basin.
Risk Assessment based on probability rainfall scale7

Maximum Inundation Area【Obihiro Urban Area】
n ①Inundation area increases by 1.58 times in +4K future climate simulation at Obihiro, where the peak discharge
increases 2,300m3/s.
n ②Inundation area increases by 1.32 times in +4K future climate simulation at Obihiro, where the peak discharge
increases 2,900m3/s.
①Maximum peak discharge around medianHistorical climate
simulation

Inundation area 600ha+4K Future climate simulation

Inundation area 950ha
Increase rate
1.58times

Overflow flooding
from the left bank ofSatsunai River②Maximum peak discharge within confidence intervalHistorical climate simulation Inundation area 600ha+4K Future climate
simulation

Inundation area 790ha
Increase rate
1.32times

82018.1 Climate Change Adaptation Delegation to the Netherlands
n There are leading examples of climate change examination in the field of water management in other countries,
while there is little example in Japan. Our attention was drawn to the Netherlands where systematic approach
was done from future rainfall/run-of projection to risk assessment and detailed adaptation measures.
n January 2018, Hokkaido Regional Development Bureau, Ministry of Land, Infrastructure, Transport and Tourism
sent a delegation led by Professor Nakatsugawa from Muroran Institute of Technology, to the Netherlands toexchange with Dutch experts on water management.
Exchanged Organizations and Contents
Organization

Main Contents of Exchange

The executive body“Rijkswaterstaat” of the Ministryof Infrastructure and Water
Management (AdministrativeAgency for Water Management)

Dutch Climate Change Adaptation Measures
・History of Dutch Water Management
・Overview of Relevant Organizations andTasks
・Concept of Safety Standard
・Flood Projection Scheme and Cooperation
with Neighbor Countries
・Climate Change Adaptation Measures inDelta Program
Climate Change Approach in Hokkaido

TU Delft, HKV consultant(Reserchers and Expers on Risk
Assessment)

Details of Dutch Risk Assessment
・Calculation Method of Estimated Loss of Life
・Flood Simulation Method
Climate Change Approach in Hokkaido

Delta Commission(Independent Organization for
Delta Program)

Background of Delta Program Development
・Task and Authority of Delta Commission
・How to deal with Climate Change Scenario
・Determination of Tolerable Risk
Climate Change Approach in Hokkaido

Royal Netherlands Meteorological
Institute “KNMI”(Institute for Weather Forecast)

Details of Climate Change Projection in theNetherlands
・Rainfall Projection Method (Bias Correctionand Resampling)
・Run-off Calculation Method
Climate Change Approach in Hokkaido

Discussion(Delta Commission)

Discussion(KNMI)

9

2018.11 Dutch Water Management Experts’Visit to Japann November 2018, Dutch Water Management Experts (Rijkswaterstaat, Deltares, HKV consultant) visited Japan for anotherexchange. Discussions were focused on themes such as “How to switch water management planning in accordancewith climate change” and “How to explain risk to society.”n During the visit by Dutch water management experts to Japan, River Center of Hokkaido organized “Seminar for Water
Management in Japan and the Netherlands: How to respond to increasing flood risk by climate change,” where moredetails were discussed on response to future climate change.
Exchange

Presentation on Climate Change
Projection in Hokkaido (Japanese side)

Questions to Climate Change Projection Discussion on Water Management inin Hokkaido (Dutch side)
Both Countries (Dutch Side)

Seminar for Water management in Japan and the Netherlands

Lecture (Dutch side)

Lecture (Japanese side)

Discussion on Risk Assessment in Both Countries

102019.6

Climate Change Adaptation Delegation to the Netherlands

n June 2019, Hokkaido Regional Development Bureau sent another delegation led by Prof. Nakatsugawa
to the Netherlands to exchange with Dutch water management experts.
Exchanged Organizations and Contents
Organization

Main Contents

Rijkswaterstaat
Rivierenland Water
Board

Future River Management・Background and Overview of Project, Room for theRiver
・New program for river management
Organization relevant to Water Management in theNetherlands
・Tasks and responsibilities

City of Dordrecht

Risk management in Dordrecht
・Impact analysis method and analysis results
・Overview of Flexible evacuation strategy
・ How to apply Multi-layer safety

Rijkswaterstaat

Depoldering of the Noordwaard
・Development of Evacuation route・Efforts for Ecological Reservation

Rijkswaterstaat/Deltares/TU Delft/HKV
consultant

Discussion(HKV)KICK OFF meeting for Joint Research between Japan andthe Netherlands

Deltares

Details of Climate Change Projection in the Netherlands
・How to determine Delta scenarios
・How to use RCP Scenarios
Cost Benefit Analysis in the Netherlands
・Overview of dynamic/static cost benefit analysis
・Monetizing human life

Rijkswaterstaat

Flood Protection Standard in the Netherlands
・How to determine flood protection standard
・Concept of evacuation rate
Flood Control Scheme in Japan

Discussion(Rijkswaterstaat)

11

Joint Research between the Japan and the Netherlands
nDutch Enterprise Agency(Rijksdienst voor Ondernemend Nederland) has supported innovative
projects by subsidizing scheme “Partners for Water” for internationally oriented Dutch business.
nBy subsidy system of Partners for Water, HKV consultant , Deltares, TU Delft, River Center ofHokkaido, Docon, and Hokkaido University decided to start a joint research between Japan andthe Netherlands on “Flood Risk and Climate Change Hokkaido” (Selected in May 2019 andstarted in August 2019.)
Five work packages in the projectAugust2019
Workweek1

WP1
ClimateChange(LeadDeltares)

December 2019

WP2
Failuremechanis
ms andprobability(LeadDocon)

WP3
Risk
assessment(LeadHKV)

WP5
ProjectManagement
sharing &dissemination(Lead HKV)

Workweek2
May2020

September2020December2020

WP4Roadmaps(LeadRiverCenter ofHokkaido)

WorkPackages

Contents of 5 work packages

WP1

Determine the effect of climate changeon the frequency and scale of flood riskhazards.

WP2

Determine relations between climatechange and meandering rivers related todike failure.

WP3

Combining the results from the first twowork packages, a flood risk assessment
is carried out for Hokkaido taking
typhoons, rainfall (and high riverdischarge) and storm surges intoaccount.

WP4

Determine research roadmaps andbusiness roadmaps.

WP5

Knowledge sharing & dissemination &project management.

Workweek3
出典： ※ Rijksdienst voor Ondernemend Nederland, PARTNERS VOOR WATER, https://www.partnersvoorwater.nl/

12

“Flood Risk and Climate Change Hokkaido” Work week1
nOctober 2019, Dutch team (HKV and Deltares) visited Japan, where Work Week 1 wasorganized.
nTarget area of flood risk assessment in this joint research, Obihiro city, Hokkaido, in themidstream of Tokachi river was mainly visited for field survey, as well as Satsunaigawa Dam,
Satsunai River, Tokachi River main stream and Pekerebetsu River.

Explanation of Dutch Expertise(Dutch side)

Explanation of Tokachi River basin(Japanese side)

Explanation of Satsunaigawa Dam in themanagement office

Explanation at Satsunai River

Explanation on bank of TokachiRiverExplanation at Pekerebetsu River13

“Flood Risk and Climate Change Hokkaido” Work week1
n Work week was concluded by presentations on achievements and future efforts per WP and Q&A on the last day.
n Future approach: Each WP will construct a model and improve accuracy, which will be integrated into risk
assessment in accordance with climate change.
Presentation on Achievement WP1（Deltares and Hokkaido University）

Presentation on Achievement WP2（Docon and HKV）

Presentation on Achievement WP3（HKV and Docon）

14

UNFCCC SB50 (Climate Change Conference, Bonn, Germany)

Transformative adaptation andclimate resilient development

Mr. Abdalah Mokssit (Secretary of IPCC)

Nation Level Committees for Future Flood Policy
2016: MLIT/Hokkaido Prefecture- Agriculture- Climate Change- Risk Based Approach2017: MLIT/Hokkaido Prefecture- Applied thousands ofSimulation for past and future- Risk Assessment

2018: MLIT (headquarter)- Nation wide discussion- Temporal and spatial
characteristics of rainfall2019/6/13

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Showa・Heisei

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Before Meiji

Ensemble(physically-based)
Probability-based Record breaking-based(only observation)

Projected rainfall (past and future)
Hazard-based
Risk-based

Observed rainfall)