Water-related disaster risk reduction considering climate change
-transition to River Basin Disaster Resilience and Sustainability by All-
Council Report
July 2020
National Land Development Council
Table of Contents
1.Preamble...................................................................................... 2
2.Recent disasters............................................................................ 5
2.1 Frequent and severe disasters.......................................................5
2.2 2018 July Heavy Rain, 2018 Typhoon Jebi...................................... 5
2.3 2019 Typhoon Hagibis................................................................. 6
3 Climate variability........................................................................ 12
3.1 The situation of the climate variability.......................................... 12
3.2 Climate Change prediction.......................................................... 13
4. The trend of the society............................................................... 17
4.1 Change of local communities under decreasing population, declining
birthrate and growing proportion of elderly people...............................17
4.2 Future national planning.............................................................18
4.3 Sustainable Development Goals (SDGs)........................................19
4.4 Technical innovation for Society5.0.............................................. 19
4.5 Conversion to the new lifestyle under new coronavirus infection...... 20
5 Future water-related disaster risk reduction.....................................22
5.1 Policy trend.............................................................................. 22
5.2 Climate change and recent water-related disasters........................ 26
5.3 New water-related disaster risk reduction..................................... 28
6. Water-related disaster risk reduction to be conducted promptly.........33
6.1. Reconsideration of the plans and the standards............................ 33
6.1.1 Application of climate change into flood control planning for target
security in each area....................................................................... 34
6.1.2 No rework measure by reflection to design standards.................. 36
6.1.3 Others...................................................................................37
6.2. Conversion to "River Basin Disaster Resilience and Sustainability by All
"...................................................................................................38
6.2.1. Comprehensive and multi-layered measures reducing hazard,
exposure and vulnerability around a whole basin.................................38
6.2.2. Acceleration of preparation for disasters................................... 57
6.2.3. Social mechanism mainstreaming disaster risk prevention and
reduction - Interdisciplinary approach for "River Basin Disaster Resilience
and Sustainability by All " around a whole basin-.................................59
7. The policy which should be put into effect promptly......................... 68
8. Conclusion..................................................................................72
1.Preamble2The largest mission in Japan had been to utilize a limited country, raise
the productivity and the profitability and achieve material economical
abundance. After serious damages by typhoons and the torrential rainfalls
which occurred frequently in the devastated nation after the WWII, central
government, prefectures and municipal governments improved the nation’
s security significantly through various measures such as dams,
embankment, erosion and sediment control, sewage system as well as
high-level embankment (embankment with widened cross section) and
comprehensive flood controls. There had been few large-scale typhoons
which occurred frequently after the WWII in a high economic growth period.
As such, flooded areas and the number of victims have successfully
decreased. 2019 Typhoon Hagibis showed the improvement of nation ’ s
security through the measures when its damages were small in some areas
compared with those by the similar-scaled typhoons. The improvement of
nation’s security facilitated the land development for additional urbanization
in urban areas, for industry in marginal areas, and for farmland
consolidation for rural areas. This accumulated the land use in the whole
country and increased land productivity with the development of
transportation networks.
However, the threat of water-related disasters remains as imminent all
over the country. IPCC has issued the climate gas emission scenario and
prediction periodically since 1990s, including increased accuracy on climate
variability caused by human activities. The density of the greenhouse gas is
increased steadily every year indeed, and the increased tendency of the
torrential rainfall also becomes clear. 2018 July Heavy Rainfall brought more
than 200 victims, the largest number following the 1982 Nagasaki Flood.
The general amount of rainfall of this torrential rainfall increased about 6.5%
because of climate variability, which showed the influence of climate
variability already became clear. In 2018, climate change adaptive law was
enacted for both mitigation and adaptation.
Paris agreement was concluded for the purpose of suppressing a rise of
the average temperature of the world in 2 degree compared with present
and before the Industrial Revolution, and facilitating restrictive measures of
a greenhouse gas emission worldwide. Even if it's suppressed by 2 degree,
the influence is enormous. The climate variability has already influenced
recent heavy rainfalls, and followed the further increase of torrential rainfalls
in the next 20-30 years.
While a flood control measure of river works and dam construction has3improved the nation’s security and reduced the flood damages, the influence
of climate variability may overcome the improvement. Recent climate
variability has made torrential rainfalls more frequent and severe, which
increased the human loss and financial damage. The increase of the amount
of payment of the insurance delays the economic recovery, so devastates
social fear.
Further, the proportion of elderly people grows and the population
decreases in recent years. The population decrease and the rapid rise of
aging rate except for a large urban area have raised vulnerability of
communities during the disasters. Vacant houses and land uses have
increased both in urban areas and rural areas, which require another land
use planning. Sustainable urban planning under the concept of "compact
plus network" has rebuilt to maintain the regional activities more
sustainable after post-WWII high economic growth followed by a low growth
era upon termination of bubbling economy.
Regarding science and technology, technological innovation is
remarkable especially in information technology. Observation and
information accumulation technology by 5G and other ITs, and IoT,
development of big data and utilization of AI technology by enhanced
computer capacity, these enables the guess and grasp of the phenomenon
difficult so far, which supports evacuation assistance and various disaster
prevention activities.
Under such background, more robustness toward water-related disasters
is necessary through various tools including reorganizing land use and
log-term perspective toward sustainable development. For this, whole
society has to confront this crisis in an inclusive way and out of traditional
thinking, recognizing a threat of water-related disasters under climate
variability.
Traditional disaster countermeasures are based on past experience.
However, as unexpected events occur and society and science and
technology rapidly change, future water-related disaster risk reduction
should be based on the future risk prediction under climate variability.
The River Committee of the National Land Development Council issued its
Report on " water-related disasters conscious society " which made it
conscious that "a facility’s ability is limited, so the facility cannot prevent
severe flooding" after the Torrential Rainfall in 2015 with a lot of isolated
evacuees. cannot be prevented puts it in the Panel on Infrastructure
Development river subcommittee meeting up to now, and receives that a lot4of isolation person; and Report on effective combination of structural and
non-structural measures after complex multi-hazards of riverine flood,
urban flood, landslide and mudflows in 2018 July Heavy Rainfall. Technical
consideration has been also advanced about influence of climate variability
by the Technical Working Group on flood management planning and so on
since April 2018.
This Council Report has recognized the enormous damages by recent
water-related disasters, advanced reconstructive actions based on the
former " water-related DRR conscious society " , and advocated the
water-related DRR with the concept of the "River Basin Disaster Resilience
and Sustainability by All", which calls for all stakeholders to consider DRR as
natural, mainstream DRR, and take collaborative actions in each river basin
including watershed and flood plain area.52.Recent disasters
2.1 Frequent and severe disasters
- Serious floods (riverine, urban, storm surge) and landslides (floods and
landslides are called "water-related disasters" in the following.) recently
occur by the unexperienced torrential rainfall at a various part of Japan
almost every year.
- The 2015 Torrential Rainfall occurred from beyond 600mm in Kanto district
and beyond 500mm in Tohoku district, more than twice of monthly
precipitation in normal September 1)
. The humid air flew into the low air
pressure which changed from 2015 Typhoon Etau and created many linear
precipitation zones. The amount of rainfall renewed 1st place of record for
24 hours at many spots in Miyagi-ken, Ibaraki-ken and Tochigi-ken in
particular 1)
. The floodings from embankment bursts in Kinugawa river etc.
collapsed houses and inundated wide areas for long duration. Delay of
evacuation created a lot of isolation people.
- Hokkaido and Tohoku-districts were seized with typhoons successively in
2016. Three typhoons landed Hokkaido in a year. A typhoon landed from the
Pacific Ocean. These phenomena were first in the meteorological statistics.
The embankment bursts in small and medium sized rivers occurred. The
pitiful damage by which a tenant fails to escape occurred facilities in
mountainous area.
- The 2017 July Torrential Rainfalls occurred when warm and humid air flew
into the seasonal rain front and formed linear precipitation zones with heavy
rain beyond 600 mm per 12 hours in Fukuoka and Oita, especially at a
tributary basin in the right side of the Chikugo river 2). Large amount of
mudflows and driftwoods went down in the tributary and blocked the
channel 3). Large scale landslide also occurred in some channels. Three
embankment bursts 4) damaged 40 people dead, 2 persons missing, 1,476
houses broken and 1,667 houses flooded in Fukuoka and Oita prefectures 5).
2.2 2018 July Heavy Rain, 2018 Typhoon Jebi
- 2018 July Heavy Rain, there was the amount of rainfall in the wide area
around western Japan by a torrential rainfall: over 1800 mm at Shikoku
district, over 1,200mm at Tokai district, around 2-4 times of monthly in
July. It was the record heavy rain at 125 spots for 48 hours, and at 123 spots
for 72 hours out of about 1300 spots of Japan Meteorological Agency (JMA)
observation 6)
. Riverine, urban floods and landslides widely occurred in
simultaneous multiple way with 224 victims, 8 persons missing, 21,4606houses of complete or partial destruction, 30,439 houses of flooding 6)andat most 263,593 houses of no water supply 7).- The general amount of rainfall of the land was calculated by variation in
climate as a test with about 6.5 % more by 2018 July Heavy Rain. The JMA
noted about 2018 July Heavy Rain, "There was contribution of global
warming." first referred to influence by climate variability about an
individual event 8).- 2018 Typhoon Jebi recorded the highest tide level at Osaka Bay, exceeding
1961 Typhoon Nancy, which landed Japan in lowest pressure under uniform
record after 1951 and affected more than 200 people dead or missing. A
runway and a terminal building at Kansai International Airport were flooded.
The connection bridge to the airport was collided by an oil tanker, about
3,000 tourists isolated. Flood damage occurred in houses in Ashiya-shi,
Hyogo.
2.3 2019 Typhoon Hagibis
- 2019 Typhoon Hagibis was born near Minamitorishima Island on 6 October
2019, moved to the Mariana Islands towards west, became larger, changed
its course to the north, landed Izu Peninsula at 19:00 on 12 October with its
strong power, passed Kanto district and changed to an extratropical storm in
the east of Japan at 12:00 on 13 October 9)
. The course and strength were
predicted with smaller error 10).- JMA announced the first alert on 9 October, and then "It will be record
heavy rain equivalanet1958 Super Typhoon Ida" on 11 October 11).- JMA declared the special warning to 13 prefectures (Shizuoka, Kanagawa,
Tokyo, Saitama, Gunma, Yamanashi, Nagano, Ibaraki, Tochigi, Niigata,
Fukushima, Miyagi and Iwate) in sequence from 15:30 on 12 October. All
warning was released by 8:40 on 13 October 12).-Evacuation instructions were announced 7.97 million people at maximum.
- The general amount of rainfall of 4 days reached 1,000mm at Hakone,
Kanagawa, recording the first at 120 spots for 12 hours, and at 103 spots for
24 hours rainfalls. 142 points of embankment were burst with 35,000 ha
area flooded. Damaged people and flooding were not captured enough in the
medium and small rivers where inundation maps were not created.
(The outline of a riverine flood)
- Average rainfall at the upstream watersheds in major rivers exceeded
or nearly exceeded the target rainfall of each river’ s basic management7policy (*). In Abukuma River, peak flow exceeded the target flow of its river
basin plan.
* According to the River Law In Japan, river administrators establish basic
river management policies, then formulate river implementation plans to
provide the target and the measures to be implemented within a few
decades.
- In 40 rivers (managed by central government), the flow levels
exceeded the designated inundation alert levels.
- The embankment burst was observed at 14 spots in 7 rivers under 6
river basins (managed by central government), and at 128 spots in 67 rivers
under 20 river basins (managed by prefectures) 13).- The burst of embankment flooded about 35,000 ha area in total.
- In Chikuma River under Shinano River Basin, the burst of
embankment flooded in train stock yard of Shinkansen with 10 Shinkansen
vehicles (total 120 cars). The train operation was affected for extended
period.
- The operation of 146 dams (managed by MLIT) including Watarase
Retarding Basin, Arakawa Retarding Basin and Yamba Dam, reduced the
flood risks effectively. At 6 dams, the inflow exceeded the dam’s capacity for
flood control, so stopped flood controls when the outflow became equivalent
to the inflow.
(The outline of urban flood)
- The damage by urban floods occurred in 15 prefectures, 135 municipals
around eastern part of Japan.
- By flooding train stations, automatic ticket gates were submerged. Lifeline
(water, electricity) was suspended more than a week in some tower
apartments located in flood areas.
(The outline of storm surge and high wave)
-Storm surges and high waves were observed in Suruga Coast etc., which
damaged shore protection facilities.
(The outline of landslide)
-Landslides occurred at 950 cases in 20 prefectures. More than 40 cases
counted in 8 prefectures.
(The feature of the human damage)8-The number of victims because of floods was higher among 1999-2018
records.
-The ratio of victims more than 60 years old was higher.
-The ratio of victims outside buildings was higher.
- 84 people were dead as of 12 December 12 except for accident related
death: about 65% were those more than 65 years old; about 74% were by
flooding 14).- About 79% of 34 people who died inside houses were those more than 65
years old. More than half people who died outside buildings were dead
during driving.
-Most of the flood victim at indoor occurred in urban areas.
(The feature of economic damage)
-101,673 house damages comprised of 3,308 total damaged, 30,024 half
damaged, 37,320 minor damaged, 8,129 flooded over floor and 22,892
flooded below floor. Medical facilities, senior citizen welfare facilities,
facilities for person with disabilities and child care facilities, etc. were also
damaged.
-Blackout occurred in about 520 thousand houses. Water supply was
stopped in about 170 thousand houses. It took about a month to recover
water supplies because water sources, water intakes and water pipes were
destroyed in some areas in Fukushima, Yamanashi and Nagano. 17 sewage
treatment plants were flooded with function stopped.
(Announcement)
-In Kuji-gawa, the flood occurrence was confirmed and announced after
heavy rain special warning was released at 2:20am on 13 October. Likewise,
flood occurrence was announced after the release of heavy rain special
warning in 7 rivers: Yoshida, Abukuma, Ishida, Sabi, Toki, Oppe and
Chikuma Rivers. In Agano River, heavy rain special warning was released
when preliminary flood alert had been announced. Flood occurrence was
announced after 4 hours.
- The access concentration occurred in the MLIT website and made it difficult
to get information. (Access beyond 1.6 times of the former biggest number
of accesses)
-The access concentration also occurred in some local governments and
made it difficult to get important information 15).- Flood damages occurred in the medium and small rivers where inundation9maps were not created 15).(Emergency measure)
- Prepared suspension put it in railroad operations around Tokyo and Nagoya
districts from afternoon on 12 October to morning on 13 October 16)
. The
prepared suspension worked for damage and confusion reduction by 83
enterprisers at 254 routes of railroads and at most 15 sections of 13 routes
of highways 17)
. However, Nagano railroad stock yard of Hokuriku
Shinkansen flooded, and some railroad or road bridges dropped severely
damaged railroad and road networks into pieces so it took periods to recover
traffic function.
- The part of local governments closed evacuation places to avoid flooding
the places, and carried refugees to the other evacuation places 18) 19)
. About
3,200 people evacuated, and 2,200 people among them re-evacuated to the
other safer evacuation places where not for usual evacuation.
-There were some cases that overflown people had to evacuate to the places
with flooding risks because of the capacity of evacuation facilities in some
local areas, Tokyo 20).(Support and response)
-MLIT dispatched TEC-FORCE (Technical Emergency Control FORCE: urgent
disaster countermeasures dispatch experts formed by MLIT experts) from
regional development bureaus all over the country and supported affected
areas in 303 municipals, 34 prefectures. The number of dispatched experts
reached maximum 748 per day on 23 October, and total 30,513 by 27
December, the biggest number since TEC-FORCE established.
-TEC-FORCE conducted the damage surveys and emergency restorations
collaborated with local contractors in Tohoku, Kanto and Hokuriku districts.
- For damage surveys, ICT like drones facilitated the prompt surveys on
public facilities for quick decision making on financial support by central
government. (Official endorsement by the Cabinet on 29 October)
-To response to flood damages, about 200 drainage pump cars were
dispatched. The 24-hour drainage operation finished flooding by the end of
October.
-Collaborated with local contractors, road surface sanitation trucks were
dispatched and the removal of sand and gravel accumulated in cities and
roads, etc.
-Watering activity in the no water areas, grasping needs and other living10support in disaster areas were performed.
-Central government conducted emergency response at 41 spots at 14
rivers under 3 river basins on behalf of local governments, where urgent
response requires for the next flooding in minor rivers managed by local
governments.
Reference (in Japanese)
1) http://www.bousai.go.jp/fusuigai/suigaiworking/pdf/dai1kai/siryo1.pdf2)http://www.qsr.mlit.go.jp/site_files/file/bousai_joho/tecforce/H29hokubug
ouu_data/171122houkokusyo11.pdf3)http://www.qsr.mlit.go.jp/site_files/file/bousai_joho/tecforce/H29hokubug
ouu_data/171122houkokusyo2.pdf4)http://www.qsr.mlit.go.jp/site_files/file/bousai_joho/tecforce/H29hokubug
ouu_data/171122gaiyou2.pdf5)https://www.fdma.go.jp/disaster/info/items/b415db68eb0850414c74aca2
f164cf3dbda5c43a.pdf6)https://www.data.jma.go.jp/obd/stats/data/bosai/report/2018/20180713/
20180713.html7)http://www.bousai.go.jp/updates/h30typhoon7/pdf/310109_1700_h30typ
hoon7_01.pdf8)https://www.jma.go.jp/jma/press/1808/10c/h30goukouon20180810.html9)https://www.data.jma.go.jp/obd/stats/data/bosai/report/2019/20191012/
20191012.html
10) https://www.jma.go.jp/jma/kishou/know/jirei/sokuhou/R011012.pdf
11) http://www.jma.go.jp/jma/press/1910/09a/20191009_1400.pdf12)http://www.bousai.go.jp/updates/r1typhoon19/pdf/r1typhoon19_03.pdf
13) http://www.mlit.go.jp/common/001313204.pdf
14) http://www.bousai.go.jp/fusuigai/typhoonworking/index.html1115)
https://www.mlit.go.jp/river/shinngikai_blog/kaizen_kensho/dai01kai/dai1
kai_shiryou2.pdf
16) https://www.mlit.go.jp/report/press/tetsudo08_hh_000097.html17)http://www.bousai.go.jp/updates/r1typhoon19/pdf/r1typhoon19_03.pdf18)http://www.bousai.go.jp/kaigirep/r1typhoon/pdf/dai3kai_torimatome.pdf19)https://www.city.ota.gunma.jp/005gyosei/0050-004shimin-bouisai/files/1
9kenshouhoukoku.pdf20)https://www.bousai.metro.tokyo.lg.jp/_res/projects/default_project/_pag
e_/001/007/173/sitennbetu3.pdf123 Climate variability
3.1 The situation of the climate variability
(The increase of rainfall)
-"There is no doubt in global warming of a climate system" about the climate
variability in the past 100 years according to the IPCC AR5 published in
2013-2014 1).-0.78 degree rose on the world average ground temperature compares
2003-2012 from 1850-1900 2)
. Also in Japan, JMA observed 1.21 degree rise
in 100 year from 1898 to 2018 3).-It is mostly certain that the water temperature rose on marine surface layer
(water depth 0-700m) from 1971 to 2010 2)
. The increase rate, 1.12 degree
per 100 years, of the sea surface temperature around Japan is higher that
one, 0.54 degree per 100 years, of the average sea surface temperature in
the whole world 4).-The world average sea level rose 0.19 meter from 1901 to 2010 1).-JMA observation shows the increase of frequency is about 1.4 times for
hourly precipitation above 50mm, and about 1.7 times for hourly
precipitation above 80mm, compared with about 30 years before 5). About
30 percent of all observation points in Japan showed the first record for
hourly precipitation after 2013.
(Water-related risk)
-Serious water-related disasters including embankment breaks and
landslides, occurred almost every year in Japan recently: Series of typhoons
in 2016, 2017 North Kyushu Flood, 2018 July Heavy Rain, 2019 Kyusyu
Flood in August, 2019 Typhoon Hagibis in October.
-Meteorological Research Institute calculated about 6.5% increase of land
precipitation at 2018 July Heavy Rain by climate variability using the JMA
55-year re-analysis (JRA55) model. JMA first noted global warming on a
specific event " Observed long-term increase trend on temperature and
water vapor in the atmosphere because of global warming, (omit), and
impact of global warming at the torrential rainfall in July 2018." 6)
-The number of rivers which exceeded the flood dangerous water level by
recent torrential rainfalls downpour is in the increase trend. There is a
possibility that the climate change influence, including the increased rainfall,
has exceeded the progress of river works 7).
-The mudflow and landslide disasters have occurred more frequently and
severely recently and provided damages to people’s lives and assets through
water, debris and woods such as 2011 Kii Major Flood, 2013 Izu Disaster,132014 Hiroshima Disaster, 2016 Typhoons, 2017 Kyushu Heavy Rain, 2018
July Heavy Rain and 2019 Typhoon Hagibis.
-Along with the increase of torrential rainfalls, the number of mudflow and
landslide events has increased. 2,581 events, 2.5 times of annual average,
occurred at 2018 July Heavy Rain, 952 events occurred at 2019 Typhoon
Hagibis 8).-When special rainfall alert announces, there has been number of landslide
events occurred even where sediment disaster designation does not cover
nor where geographical information is not clear 8).-The mudflow and landslide disasters have occurred more frequently and
severely recently because of climate change.
- During the 2018 Typhoon Jebi, highest tidal levels occurred and provided
serious damages along Osaka Bay. When the sea level rises, wide seashore
areas have to be exposed by tidal disasters.
3.2 Climate Change prediction
-According to the IPCC, when keeping discharging a greenhouse gas as it is,
the amount of emission is increased at more than about 2 times in the end
of 21st century compared with the Industrial Revolution before in 21 end of
a century, and the average ground temperature of the world is predicted that
2.6-4.8 degree or 0.3-1.7 degree under RCP8.5 (Global warming was
suppressed most.) or RCP2.9 (Global warming was suppressed least.)
scenario 9)
respectively compared with 1986-an average in 2005 1).-The ocean snow ice area special report, approved by the IPCC general
meeting in September 2019, showed that the prediction rise reach
0.61-1.10 meter or 0.29-0.59m in RCP8.5 or RCP2.6 scenario respectively
in 2100 compared to the average sea level in 1986-2005 10).-There is a possibility that about 80 percent loss in RCP8.5, about 60 loss in
for the beach around Japan 11).-The occurrence total number of the tropical storms in world decreases
about 30 percent in 21 end of a century in RCP8.5, but the thing with a high
possibility that the occurring frequency of the furious tropical storms is
increased around the Japanese southern sea, Hawaii and the Mexican
western sea 12)
. Simulated result was reported that strong typhoon would
land more to Japan 13).-MLIT established the Expert Group meeting for flood control plan under
climate change to estimate the rainfall increase in the future, which provides
the assumed information on facility design based on flood control plan 14).14
-The result estimated about 1.3 times increase on the target rainfall, about
1.4 times increase on the flood flow, and about 4 times on the average
frequency of flood, for flood control plan in the major rivers from the end of
20th century to 21st century in the case of 4 degree rise of world average
temperature compare to before the Industrial Revolution. Even in the case
of 2 degree rise (target scenario for the Paris Agreement), the result
estimated about 1.1 times increase on the target rainfall, about 1.2 times
increase on the flood flow, and about 2 times on the average frequency of
flood, for flood control plan in the major rivers from the end of 20th century
to 2040 in the major rivers.
-This study could not identify how climate change has influenced to the
change in the weather factor and space-time distribution of rainfall, which
affects disasters. Therefore consideration is needed continuously about the
method to reflect a change in space-time distribution of such rainfall in flood
control plan in the whole country.
- MLIT established the Expert Group meeting for urban flood control under
climate change to estimate the rainfall and adaptation, which provides the
assumed information on sewage design in case of frequent heavy rain and
increased risk for urban flooding.
-When the average ground temperature of the world rose 4 degree
compared with before Industrial Revolution, about 1.3 increase of rainfall for
sewage planning from the end of 20th century to 21st century. For the
scenario of 2 degree rise showed about 1.1 increase of rainfall from the end
of 20th century to 2040 15).rainfall before about setting of the external force which becomes the
premise of
- MLIT established the Expert Group meeting for erosion and sediment
control under climate change to estimate the change of the rainfall and the
impact on erosion and sediment disaster.
-Sediment disasters, floods and slope failures more frequently and likely
occur because of the rainfall change under climate change, even where there
is no designation or target for sediment disaster hazard area. There is
urgent need that these risked areas should be identified and appropriate
alert, evacuation and facilities should be equipped 16).- In particular, when the rainfall has increased, the simultaneous landslides
and mudflows are likely to occur, and the duration of rainfall becomes longer,
both sediment disasters and increase of river flow happen. These risked
areas should be checked again.15- MLIT and Ministry of Food and Agriculture and Fishery established the
Expert Group meeting for coastal preservation under climate change to
estimate the change of the hazards and the impact of climate change which
raises the average sea level, tidal deviation and mightier waves.
-Based on both observed and predicted influence on coastal area, further
consideration for new measures and controls should be facilitated as well as
quantification of climate change.
Reference (in Japanese except 11)
1) https://www.env.go.jp/earth/ipcc/5th/pdf/ar5_syr_spmj.pdf2)http://www.data.jma.go.jp/cpdinfo/ipcc/ar5/ipcc_ar5_wg1_spm_jpn.pdf
3) https://www.data.jma.go.jp/cpdinfo/temp/an_jpn.html4)https://www.data.jma.go.jp/gmd/kaiyou/data/shindan/a_1/japan_warm/j
apan_warm.html
5) http://www.data.jma.go.jp/cpdinfo/extreme/extreme_p.html
http://www.bousai.go.jp/updates/h30typhoon7/pdf/310109_1700_h30typ
hoon7_01.pdf6)https://www.jma.go.jp/jma/press/1808/10c/h30goukouon20180810.html7)http://www.mlit.go.jp/river/shinngikai_blog/shaseishin/kasenbunkakai/sh
ouiinkai/daikibokouikigouu/pdf/daikibokouikigouu_ss1.pdf8)https://www.mlit.go.jp/river/sabo/committee_kikohendo/200521/02shiryo.pdf9) https://www.jccca.org/ipcc/ar5/rcp.html
10) https://www.env.go.jp/press/107242.html
11) Udo, K. and Y. Takeda (2017). Projections of future beach loss in Japan
due to sea-level rise and uncertainties in projected beach loss, Coastal
Engineering Journal, 59, 174000612)https://www.mri-jma.go.jp/Topics/H29/291026_d4pdf/press_291026_d4p
df.html
13) https://www.mlit.go.jp/river/shinngikai_blog/hozen/index.html14)16
https://www.mlit.go.jp/river/shinngikai_blog/chisui_kentoukai/pdf/04_teig
enhonbun.pdf
15) https://www.mlit.go.jp/mizukokudo/sewerage/content/001350222.pdf16)https://www.mlit.go.jp/river/sabo/committee_kikohendo/200521/chukan_
torimatome.pdf174. The trend of the society
4.1 Change of local communities under decreasing population, declining
birthrate and growing proportion of elderly people
-A starting point of estimation calculation of the "future's Japanese
estimation population" of the National Institute of Population and Social
Security Research (IPSS, It was estimated in 2017.) was 2015, and the
Japanese total population of this year was 127,090,000 according to the
census.
-Medium estimation showed the population decrease process in the long
term, so total population were predicted about 88,080 thousand in 2065.
- The productive population (15-64 years old) reached its peak 87,260
thousand in 1995, and decreased to 75,450 thousand in 2018. This will
decrease to about 45,290 thousand in 2065 according to IPSS future
estimation.
-The aging rate kept rising after 1990s, and reached its peak about 27.7 %
in 2017. While the total population decreases, the aging rate above 65 years
old keeps rising. The estimate showed that one out of about 2.6 people
would become more than 65-year-old person in 2065.
-A senior citizen generally more likely to become sacrifice during disasters
because of failing to escape, so serious aging leads to victim's rise.
-245 people was dead or missing persons in 2018 July Heavy Rain, the
largest number since 1990. Half of victims during the sediment disaster in
Hiroshima and about 90 % during the flood in Mabi town, Kurashiki city,
Okayama were more than 65 years old.
- A local community plays a very important role on disaster risk reduction.
For instance, about 80 % people was rescued by community from broken
houses during 1995 Great Hanshin Earthquake. Quick and effective rescues
of elderly people by community were reported during 2007 Noto Peninsula
Earthquake and Niigata Chuetsu Earthquake.
-Thus it's expected that the role mutual assistance in an area will become
bigger while the decline tendency of mutual disaster prevention power has
become serious.
-For example, community firemen, who play as rescuers during disasters
collaborated with fire department, were more than 2 million in 1954, but its
number has decreased to less than a million in 1990 and 890 thousand in
2007. The age composition of the fireman changed: the percentage more
than 50-year-old member was about 7% in 1985, and increased about
14.4 % in 2007. A fire brigade consists of resident's voluntary participation.
Its area close adherence, mobilization power of personnel and quick18response play the important role. The decrease and aging trend shows the
decline of community disaster risk reduction. The similar situation is also
seen about the flood fighter party charged with the role for stopping
expansion of damage on the occasion of floods.
-It's pointed out as the background where such flood fighter party decreased
came from the decrease of younger population, the population decrease in
rural areas, and increase of the employee, who mainly supported the activity
of flood fighter party. While the big role is desired by mutual assistance,
moreover to secure safe relief in an area such as various utilization of a new
technology and cooperation with the person concerned, how to secure the
local safety should be considered comprehensively.
4.2 Future national planning
-After the WWII, the population tended to increase consistently to
128,060,000 in 2010 from 84,110,000 in 1950. River works for the flood
control security in floodplains where the population and the development
pressure of land use increased, had supported Japanese high economic
growth and its productivity improvement. However, such development
pressure becomes weaker under the population decrease. The way of
thinking for flood control measure should be transformed and moved to a
new concept for further momentum and productivity.
-While the population has decreased and the birthrate declined, unused
lands have increased both in urban and rural areas after the change of
industrial structure. National planning based on the "compact plus network"
which maintains community’s momentum, has become important.
-City revival special measures law revised in May 2014 established location
rationalization plan system for compact city planning.
-City revival special measures law revised in April 2018 institutionalized the
low under developed land right setting and location lead promotion
agreement of facilities to promote the use of vacant lots and vacant houses
crowd creation in the urban areas.
-City revival special measures law revised in June 2020 facilitated "restraint
of new location in hazard area", "promotion of move from hazard area" and
"safety ensuring in a resident area" to promote disaster-prone community
and response to the frequent and severe natural disasters.
-A new style of how to work spreads over society telework duties for
prevention of the new coronavirus infection has become more popular.
Various progress of digitalization, change of business activity and lifestyle,19and structure of the city and rural areas by IT have influenced to the land
structure and community development.
4.3 Sustainable Development Goals (SDGs)
- 2030 Agenda for Sustainable Development was adopted at UN General
Assembly in 2015. Sustainable Development Goals (SDGs) require the
action for sustainable, diversified and inclusive society in interdisciplinaryway.-SDGs include robust and adaptive capacity building toward climate-related
natural disasters. Our action for water-related disaster risk reduction can
contribute to the international society.
-The actions for SDGs in Japan showed 8 priorities including:
(Sustainable robust country and quality infrastructure)
Vital society and disaster risk reduction
Compact plus network
Investment for quality infrastructure
(Efficient and renewable energy, climate change, recycling)
Efficient and renewable energy in global stage
Climate change
Recycling
-Climate change variability in whole society needs water-related disaster
risk reduction in a whole basin with all stakeholders.
4.4 Technical innovation for Society5.0
- AI, data-driven society by big data, 5G IT, observation technology and
computer calculation have developed rapidly recently. Our country takes
these high technologies in our society and creates new value from
innovation for human-based Society 5.0 prior to the world.
-Traditional society focused too much on economy and institutional system
and created a gap on goods and services depending on each ability. In
Society 5.0, IoT connects all people and goods and create new value through
various knowledge and information. AI and robots using big data substitute
works and arrangement traditionally done by people, and make all people
from such complex and hard chores, so all people can live with high vigorous
quality and comfortably.
-This can be human-centered society, which contribute not only to our
country but also to all the other countries for SDGs.20-To adapt a non-contact and remote working style under new coronavirus
infection and improve productivity and safety, infrastructure development
needs the conversion to the BIM/CIM utilization for which three-dimensional
data and promote DX (Digital Transformation) which utilized key technology
for 5G.
-More effective river information by numerous points of a water level and
river monitoring camera, drone or satellite monitoring, community
information, SNS, AI utilized information, user-based smart phone
information, and two-way communication will work for disaster risk
reduction and early recovery in water-related disaster risk reduction.
- Disaster risk reduction Society 5.0 should be sought through various new
technology and application in water-related disasters, and further
innovation and interdisciplinary integration of technology under
collaboration with stakeholders.
4.5 Conversion to the new lifestyle under new coronavirus infection
- Emergency declaration based on the special measures law for infectious
diseases was issued on 7 April 2020 to 7 prefectures (Saitama-ken,
Chiba-ken, Tokyo-to, Kanagawa-ken, Osaka-fu, Hyogo-ken and
Fukuoka-ken) for the new coronavirus infection.
- On 16 April, 7 prefectures plus 6 prefectures (Hokkaido, Ibaraki-ken,
Ishikawa-ken, Gifu-ken, Aichi-ken and Kyoto-fu9, total 13 prefectures were
designated as specific cautious urban and rural prefectures. Including these
prefectures, all over the country became under emergency declaration.
- Until the release of emergency declaration on 25 May, the avoidance of
"three dense", the reduction of a contact chance of a person to person to
80%, at least 70% through commutation restraint by promotion of
consecutive holidays and remote-working and staying at home. Even after
the release, the avoidance of "three, dense" was recommended.
- Re-expansion of infection happened after the release of behavior
restriction in some countries. This infection is expected to stay longer.
- Therefore the government experts ’ group showed a new lifestyle to
prevent infection expansion including remote-working, rotation duties, flex
commutation and offices with enough space for each worker.
- Further infection measures in evacuation shelters are necessary when a
disaster happens under the expansion of infection. Therefore the improve of
ventilation in evacuation shelters, more evacuation shelters including
hotels, and the reduction of evacuee concentration through lift-up of21resident area and more evacuation spaces, were sought all over the country.
-This experience and a suggestion of new lifestyle won't stop at
remote-working, and further bring to the change of supply chain, land use
planning and countermeasures for water-related disasters.225 Future water-related disaster risk reduction
5.1 Policy trend
(Change in flood control)
-Old River Law was established in 1896, with systematic legal system about
river management, as the first modern public property management system
in Japan. Multi-purpose Dam Law in 1957 and New River Law in 1964 were
established for comprehensive river basin management and water use. The
River Law introduced the national administration so national government
took responsibility of river works and water use arrangement in major river
basins as a river administrator. The river administrator decides the master
plan of river works for flood management.
-The flow volume was based on the maximum record rainfall, but to be
updated in the 1950s. The maximum rainfall had to be revised frequently
after major rainfalls which occur randomly without normal probability. The
universal unified linear measure was considered. The Yodo River Master Plan
in 1954 first included the annual over probability "1/100" based on the
accumulated hydrological data 1). Ministry of Construction river erosion and
sediment control technical standard in 1958 introduced the concept "Annual
over probability was considered according to the importance in a plan target
area." 2)
- In the same period, basic method of statistical survey for flood damage and
project survey for economical validity was established. The statistical survey
for flood damage comprised of a flood damage actual condition survey and
flood damage resource research, based on the guideline for statistical
survey for flood damage in 1961, the unified guideline for estimation of
assets in flood district in 1962, and some updates in 1970. The method of
project survey for economical validity was based on the economic survey
principle and guideline, which applied in major rivers all over the country.
- These planning methods and economic estimation methods facilitated the
flood management projects efficiently and effectively for pre investment for
disasters all around the country.
- Concentration of the population and fortune and a rise of volume of run-off
to a river at the time of a flood, etc. were brought by development in and
around urban area. A rise of flood damage risk has put the comprehensive
flood control program which cooperates improvement and maintenance of
collection facilities in a basin since 1979.
- Embankment has been upgraded (high standard embankment) with wider
width than before since 1987 to avoid embankment burst and serious
damage to the dense population and fortune along the major river by the23flood in which the scale of the plan is exceeded.
- The River Law revised in 1997 added the maintenance of river environment
into its purpose, and introduced new planning system for river development,
which divided the former construction implementation master plan to the
river development basic management policy and implementation plan. River
development set the target which should be achieved in the future, and was
performed based on this. As the river development takes the great budget
and time, middle-term development target should be set for the
implementation plan while the implementation could be arranged among
river basins all over the country.
-The measure and process to get comments from experts and opinions from
the related resident, and hear from the head of local government, were set
in decision process of the implementation plan for consensus building in the
river basin.
(Change in flood fighting)
- "Flood fighting" has its historical tradition in Japan, based on community
autonomy of villages, for flood control work. The Flood Fighting Law in 1949
designated the flood control work as community autonomy work and "flood
fighting group", flood fighting administration association or flood prevention
association, which takes primary responsibility on flood fighting works such
as team building of flood fighting and flood inspection.
- The Flood Fighting Law revised in 1955 established flood forecast system
(flood forecast river) and the revision in 2005 established notice system of
water level (water level monitoring river), which introduced river
information for evacuation actions. The revision in 2001 established the
announcement of inundation area and depth (point information) to make
resident people understand water-related risks. These river information for
evacuation actions and point information have been maintained for
securement of evacuation.
- More revision for the Flood Fighting Law established further institutional
actions for water-related disaster risk reduction, through preparatory
evacuation for floods well before the hazard, river information update for
resident safe evacuation, various preparatory planning for stakeholders.
These includes broader definition of flood fighting in addition to the
traditional on-site flood fighting (*).
* The precaution activity for embankment monitoring during flooding and
the sandbag accumulation for flood response to protect embankment from24burst as much as possible.
- The 2011 Great East Japan Earthquake, the 2011 Typhoon Talas etc.
showed the frequent water-related disasters exceeding the record. The
2015 revision obliged flood assumption mapping (flood, storm surge, and
rainwater overflow) with record-high external hazards in addition to flood
assumption mapping for river implementation plan to protect human lives
and assets from flooding by non-structural measures.
- The revision in 2017 shifted the mindset on flood fundamentally from
protecting floods by facility to exceeding facilities capacity by flood. It
integrated structural and non-structural measures for flood risk reduction
with wider participation of stakeholders. It also reorganized the "water
protection against disasters conscious society" which prepares for floods by
the whole society, by foundation of large-scale flood risk reduction steering
committee.
- Torrential rainfall flooding occurs frequently all over the country in recent
years, while there is fear of the decline of community power toward flooding.
The 2005 revision reinforced flood control system, established the flood
control cooperation team by public foundations collaborated with firefighting
sectors and flood fighter teams, and established a retirement bonus
provision regulation. The 2017 revision introduced private sectors which
receive a part of authority for flood fighting, and facilitated the private
involvement in flood fighting. Reinforcement of the flood fighting power by
community will be desired more.
(Comprehensive flood control)
- "Comprehensive flood control programme specific river project" started in
1979 and guided land use change from hazard, secured more detention
function, conducted the river works more efficiently, and considered the
change of basin with harmonizing land use. By March 2020, 17 rivers in
Hokkaido, Chubu and Kanto districts, have been designated as the specific
rivers.
- Comprehensive flood control programme specific river project has
contributed to a certain degree, but showed its limitation because of the
weak voluntary consensus in the basins.
- The Specific Urban River Flood Preservation Law started in May 2004 for
new scheme. 8 rivers have been designated for the specific rivers.
- The characteristics of the law provided legal binding such as retarding
ponds and rainwater infiltration obstruction for developers, compared to the25original comprehensive flood control measures.
- The river administrator, sewage administrator, local government and local
residents, etc. cooperate for flood damage measure at the Tsurumi River
basin first designated as a specific municipal river in 2005.
- Local heavy rain occurs frequently in the short duration at small location.
For such floods, municipal government, river administrator and sewage
administrator collaborated for flood risk reduction by registration plan,
called "100mm/h Relieved plan". This plan includes flood management
projects for river basin improvement, such as river works by river
administrator, sewage works by sewage administrator, distributed typed
rainwater storage penetration facilities by local resident groups and private
companies, information network for flood hazard. These projects seek flood
risk reduction at 24 locations by March 2020.
- Hyogo-ken carries out "comprehensive flood control measures regulation"
in 2012 as a precedent measure for comprehensive flood control. Under this
regulation, the prefecture, municipal governments and resident people
collaboratively work for flood control by local comprehensive flood control
plan. The regulation clarifies the responsibility of each stakeholders, asks for
local comprehensive plan, and obligates the developers to set important
retarding pond for the development activity beyond the fixation scale
volume of run-off of rainwater increases.
- Shiga-ken carried out "regulation about promotion of Shiga-ken basin
flood control" in 2014 for land use control and building license system in the
flood areas. The prefecture also announced the flood risk information on
inundation under various scaled rainfalls, called "local security map", which
worked for land use, housing and evacuation behaviors.
- Nara-ken carries out "regulation about promotion of comprehensive flood
control measures in Yamato River basin" in 2018 with three pillars of "the
measure let run", "saved measure" and "the measure cut down". The
regulation included the reinforcement of the target area of the protection
against disasters regulation pond (application of a penalty), the restriction
of urban area to flood hazards, and the promotion of MoU among municipal
governments.
(Reinforcement of local government support)
- Local heavy rain by seasonal rain front as well as landing of 10 typhoons
which become record most provided severe flood damage in 2004. This
showed the delay of evacuation alert by local government. Since 2005, MLIT26local office can directly provide the information and forecast about rivers for
early evacuation alert by local government. This also applied to the sediment
disasters and small rivers administered by prefecture. After the 2015 Kanto
Tohoku September Heavy Rain, workshops for mayors were organized for
appropriate evacuation alert.
- MLIT founded TEC-FORCE in April 2008 in order to support local
governments quickly in the case of large-scale natural disasters, for
prevention of expansion, grasp of disaster damage area, and technical
guidance for early response to the damaged area. Since the foundation of
TEC - FORCE, personnel and equipment have been secured and properly
trained for quick and effective correspondence.
- The number of dispatched staffs were about 115 thousand at 106 disasters
since its foundation. At East Japan Earthquake in 2011, the first dispatched
staffs arrived at the disaster area, and more than 18 thousand staffs were
dispatched for early response through damage observation and pumping. At
the 2018 July Heavy Rain, more than 10 thousand staffs were dispatched at
the 2019 Typhoon Hagibis, about 30 thousand staffs were dispatched, the
largest number.
- The smooth receiver capacity has been built at the local government
through joint training in case of disaster and cooperation for the dispatch of
TEC – FORCE.
- The lack of personnel and technical knowledge in local government may
create the difficulties on dam renovation projects, emergency embankment
recovery. The River Law revision in 2017 establish a right vicarious
execution system by MLIT. The system worked at the 2017 North Kyushu
Torrential Rainfall and 2019 Typhoon Hagibis.
-There were similar system for vicarious execution of disaster recovery
business based on "law about rehabilitation from a large-scale accident", but
this is limited to the extraordinary disasters, such as 2011 Great East Japan
Earthquake and 2016 Kumamoto Earthquake. The law revision made it
possible that national government put construction which requires high
technical power or mechanical effort into effect for disaster rehabilitation
works.
5.2 Climate change and recent water-related disasters
- MLIT installs the flood control measure consideration subcommittee under
climate change in August 2007 and has made the policies to protect the
people’s lives from external forces exceeding the ability of the facilities,27based on the Council Report " Climate change adaptation in the field of
water-related disasters" in August 2015 3)
. The 2015 Flood Fighting Law
revision facilitated the designation of flooding assumption district (flood,
storm surge and rainwater overflow) for record-high external force and
evacuation planning.
- The 2015 September Kanto and Tohoku Torrential Rainfall indicated that
the ability of the facilities was limited, and there would be certain that the
facilities could not finish cataclysm. MLIT decided to promote "water disaster
prevention conscious society" which combined structural and non-structural
measures comprehensively for disaster risk reduction.
- The 2016 August Hokkaido and Tohoku Torrential Rainfall showed the
damages to social welfare facilities, school and a medical facility, etc. in
prefecture management rivers in Tohoku-district by the evacuation delay.
MLIT revised the Flood Fighting Law and River Law to enforce the measures
in the medium and small sized rivers managed by prefecture governments.
- The 2018 July Heavy Rain showed the enormous financial damage as well
as human damage. MLIT put into effect in urgent measures to accelerate the
reorganization of "water protection against disasters conscious society" 4).- The 2018 July Heavy Rain, Typhoon Jebi, and Hokkaido East Iburi
Earthquake and recent disasters showed the serious damages by losing the
function of essential infrastructure necessary to the nation ’ s social and
economic activities. The Cabinet meeting on urgent check of essential
infrastructure issued the 3-year emergency countermeasures for robust
nation with disaster risk reduction especially on urgent structural and
non-structural measures on 14 December 2018, by intense investment in
three years by 2020.
- The 3-year emergency countermeasures facilitated the comprehensive and
intensive measures in three years, both structural measures of embankment
reinforcement in the part where danger to human life is high when bank
break has formed by soil excavation and the back water phenomenon, etc.,
and non-structural measures of risk information announcement including
hazard mapping etc.
- The additional measures included the comprehensive disaster risk
reduction by society as a whole in multiple ways by utilizing large-scale flood
risk reduction committees joined by public entities in designated river
basins, and enforcing preparatory measures and collaboration by many
stakeholders.285.3 New water-related disaster risk reduction
- The future forecast by climate change assumed the intense rain in short
duration, more frequent and intensified rainfall, more total rainfall, rise of
the average sea level, more sea level deviation from normal. There is fear of
occurrence of severe and frequent water-related disasters and another
mega disaster combined landslide, flood, storm surge and inundation.
- The river improvement works and urban works take long duration of time,
so these planning should consider the climate change despite of the
uncertainty on the forecast. Without the consideration, frequent change and
additional works may happen so it should take longer period to complete
necessary works.
- Only structural measures traditionally by river administrator in river area
cannot catch up the increase of external force by severe and frequent
water-related disasters from climate change as it takes more time to deliver
the flood security.
- Therefore it's necessary to accelerate traditional preparatory disaster risk
reduction by administrators, consider the river basin as one comprehensive
system from its catchment to river area including the floodplain, and involve
all stakeholders there even who did not join before for the disaster risk
reduction.
- Population decrease, the declining birthrate and growing proportion of
elderly people, and rise of vacant land use and abandoning cultivation
farmlands appear in river basins. The land use in the basins needs to be
changed dramatically to "compact plus network". Such changes require the
water-related disaster risk sharing in the basins by reconsidering land use
planning and water-related disaster risk reduction by new land use. The risk
sharing needs the knowledge sharing among stakeholders, and combination
of water-related disaster risk reduction and land use/urban planning. It's
also necessary to use effectively the existence stock in the basin such as
retarding securement of new place and utilization of the multilateral function
for overflow.
- Remarkable development has been observed in information: acquisition of
information by new tools such as the IT utilization like 5G, IoT, artificial
satellite and drone, processing of information by AI technology and these big
data. The digitalization in society like contactless and remote-typed
measures has developed under the new coronavirus infection. The platform
where all stakeholders in the basin can work for water-related disaster risk
reduction, should be built to utilize these technology, share information and29knowledge on water-related disasters, accumulate them sustainably and
use the information effectively. Interdisciplinary innovation for
water-related disaster may happen in the fields of the assessment of current
conditions and the forecast of water-related hazard risk, the information
sharing, and risk reduction methods. Such technologies should be
introduced early and advanced for application in fields.
- These change of climate change and society, and the technological
innovation will provide the various impacts in wide fields. The protection of
people’s lives and assets from water-related disasters needs inclusive risk
communication on knowledge and information on water-related disasters,
land use planning, community vitalization and more productivity for
population decrease and ageing society, resilience , and sustainability under
positive participation of all stakeholders.
Resilience: Tough and flexible society with minimizing the loss of human
lives and the economic damages even under the worst situation under
maximum water-related disasters, responding and recovering early and
avoiding falling malfunction on economic activity.
Sustainability: Even if a catastrophe occurs, community can be restored
promptly, moreover improve the international competitiveness and also
contribute to national growth strategy.
Inclusiveness: All stakeholders in the basin interdisciplinary from various
fields always pay attention to water-related disaster risk reduction
collaboratively, and advance countermeasures on water-related disaster risk
reduction on a viewpoint jointly from various technological innovation.
(1) Water-related disaster risk reduction from phenomena in the past to
climate change forecast
- The method to estimate accurately about a phenomenon with various
uncertainty has been developed in the field of flood management. For fair
and effective flood management in the country, the method changed from
the accumulated observation maximum in the past to the extreme
probability value in 1958. However, climate change will make this method
difficult in efficient management as the phenomenon do not follow the
estimation from trend probability data. The correspondent change often
needs reconsideration of the flood management plan and further
reinforcement in facilities. Therefore the flood management should be based
on the forecast simulated by climate change, not based on the phenomenon
occurred in the past.30(2) Conversion to "River Basin Disaster Resilience and Sustainability by All"
- The recent severe water-related hazards have led the assumption that the
floods exceeding the ability of facilities may occur. The assumption needs
the reorganization of "water protection against disasters conscious society"
which prepares for floods by the whole society has been advanced. "River
Basin Disaster Resilience and Sustainability by All" calls for all stakeholders,
including the national government, local municipalities, private sectors and
residents. All the stakeholders are encouraged to work together to take all
possible actions towards water-related disaster risk reduction, in each river
basin from the upstream to downstream areas of the main streams and
tributaries. - "River Basin Disaster Resilience and Sustainability by All" is
defined as follows.
"In addition to the actions that public administrators for rivers, sewages,
erosion and sediment controls and coastal areas etc. have taken mainly, all
the stakeholders are encouraged to work together in each river basin from
the upstream to downstream areas of the main streams and tributaries,
including floodplain, (i) to prevent and reduce the inundation as much as
possible, (ii) to minimize the exposure, and (iii) to take all possible actions
from risk reduction early response and recovery."
An area: The catchment area where rainfall pours, the river area managed
by public administrators, and floodplain where flooding is assumed.
Concept: The comprehensive management for water-related disasters,
controlling the hazards such as rainwater, running flow, inundated flows,
sediment and high tide, land use control, planning and flood proofing,
evacuation during flooding, reduction of economic damages, response and
recovery from floods, enhancement of resilience.
-Further the report in which Japan Society of Civil Engineers was released
after the 2019 East Japan Typhoons, and proposed the "River Basin Disaster
Resilience and Sustainability by All". 5)
(Comprehensive and multilayered concept based on the feature of river
basins)
- All the stakeholders are encouraged to work together for the "River Basin
Disaster Resilience and Sustainability by All" including the following three
measures comprehensively and multi-layeredly around a river basin.
(i) hazard control : to improve flood control facilities and reduce the
inundation as much as possible, (ii) exposure reduction: to improve urban31planning and way of living for damage avoidance by assuming possible
flooding, and (iii) vulnerability decrease: to conduct proper evacuation and
carry out early response and recovery during flooding.
(Acceleration of preliminary disaster risk reduction)
- The preliminary disaster risk reduction should be emphasized to prevent
the loss of people ’ s lives and economic assets, rather than the ex post
measures which restore for response and recovery after suffering.
- Severe water-related disasters occur almost every year, which clearly
noted as the influence of climate change. The improvement of flood control
facilities suffered from such disasters is still on the way, but it can be noted
that the damages by the disasters should be much smaller if these facilities
had been completed when the disasters occurred. There are growing
concern that the effects of climate change will further exacerbate the risk of
water-related disasters through more frequent and severe torrential
rainfalls and higher tides. The improvement of flood control facilities cannot
secure the expected safety if the improvement follows the traditional
estimation.
- Therefore the ongoing improvement should be facilitated. Further effective
preliminary disaster prevention measures are also necessary by sharing
present targets among national government, local governments, private
sectors and local residents, etc., and combining structural and
non-structural measures effectively based on the concept of "River Basin
Disaster Resilience and Sustainability by All".
- The flood management planning should facilitate and accelerate the
improvement works by converting the mindset from the data "based on
results in the past" into those "considering the increase of rainfall and the
rise of tide level under climate change".
Reference (in Japanese)
1) https://www.kkr.mlit.go.jp/river/kasen/yodogawa.html2)https://www.mlit.go.jp/river/shishin_guideline/gijutsu/gijutsukijunn/index
2.html
3) https://www.mlit.go.jp/report/press/mizukokudo03_hh_000892.html4)https://www.mlit.go.jp/river/shinngikai_blog/shaseishin/kasenbunkakai/s32houiinkai/daikibokouikigouu/pdf/daikibokouikigouu_toushin_honbun.pdf
5) http://www.jsce.or.jp/strategy/files/hagibis_20200123.pdf336. Water-related disaster risk reduction to be conducted promptly
6.1. Reconsideration of the plans and the standards
- The flood control facilities for rivers, sewage and coasts have been
planned, designed and arranged based on precipitation and tide level
records in the past or their statistical analysis.
- The river management basic management policy, the long-term goals for
the river improvement, sets a target flood which shows the basis of a flood
protection plan, the annual probability of exceedance 1/100-1/200 in case
of major rivers administrated by national government. The river
improvement plan set the lists of the improvement works in 20-30 years
based on the basic management policy. In most of the major rivers
administrated by national government, the improvement works try to
prevent from the biggest torrential rainfall in the past (after the WWII in
most cases). The coast protection facilities have been targeted to the
highest tide level occurred in the 1959 Typhoon Vera, which affected the
worst flood damage, more than 5,000 people dead or missing after WWII.
However, there is a possibility that the security made these targets can't be
secured any more as the increase of rainfall etc. considering the climate
change.
- River management facilities and coast protection facilities, etc. are
designed so that safety by which the facilities or their parts, etc. are required
in their whole service duration may be secured. If the external force exceeds
the initial condition before the renewal, the safety levels and required
functions cannot be secured.
- Climate change may exacerbate the water-related disaster risks, so the
target of flood control plan, sewage plan, coast protection plan and erosion
and sediment control plan (hereafter, flood control plans) and the design
level of the facilities should apply the external force by which floods, urban
floods, sediment induced disasters, storm surges and high waves forecasted
during their target duration.
(Climate change scenario for water-related disaster risk reduction)
- The climate change scenario for water-related disaster risk reduction
should be based on the ongoing mitigation efforts to reduce greenhouse gas
set by the Paris Agreement on climate change in November 2016, " an
average temperature rise of the world is suppressed in less than 2 degrees
compared with the Industrial Revolution before, 1.5 degrees by the effort".
The current security level is less than the final target in most of the rivers.
It will take a considerable period before reaching the target.34- The scenario, which make the standard of the external force for current
flood control plan, should be based on the average external force calculated
under 2 degrees rise 1)
. There should be the variation and change on this
external force under the 2 degrees scenario, and further more rise on
temperature. As such, the scenario under 4 degrees rise should be also
considered for the reference, as well as the possible further climate change
in temperature and extreme hazard.
-It is suitable to utilize the 4 degrees scenario for the check and reference on
full improvement works and their redundancy, and fail-safe on the facilities.
The 4 degrees scenario can also apply to the long-term and overall aspects
such as national land use and land use controls.
- Only the precipitation change magnification has been estimated
quantitatively are nationwide as the change of external force so far. Various
estimation could be applied for flood control planning and individual
structure designing.
6.1.1 Application of climate change into flood control planning for target
security in each area
-Flood control plan should be reconsidered in order to secure the target
safety in the final year of the flood control plan. It is necessary to reflect the
increase of the external force such as the amount of rainfall directly in the
present plan when considering the target safety.
(Reconsideration of maximum probable flood in river management basic
management policy)
- The peak flow at the reference point in the case of maximum probable flood
should be set appropriately based on the rainfall forecast advancely
calculated for future climate change under global warming.
- The river improvement is still on the way, so the target of the river
implementation plan is much lower than that of the river basic management
policy in the most of major rivers. The priority should be focused on the work
under the present river basic management policy.
- There is uncertainty in climate change forecast, and there is also a
possibility that future forecast will be reconsidered in the future. However,
it's certain to increase in the amount of rainfall, and it takes certain period
for the improvement of flood control facilities. It is desirable to revise river
basic management policy and establish a target based on climate change.
Specifically, maximum probable flood under climate change should be35applied at first, in the rivers where large-scale flood occurred and exceeded
maximum probable, and where the distribution flow rate should be changed
between the channels and dams.
- For "River Basin Disaster Resilience and Sustainability by All", the flow rate
reduction effect in the target flood should be calculated and put in the plan
after stakeholders’ arrangement and necessary implementation such as in
operational regulations are taken place regarding various outflow restraint
measures and preliminary discharges by water supply reservoirs.
(Reconsideration of the target flow in river improvement plan)
- All scenarios for climate change forecast, the temperature will rise two
degrees in 2040-2050 compared with before the Industrial Revolution. This
rise of two degrees likely occurs before the target year of the river
improvement plan for river works in 20-30 year. The target flow based on
the increase of the rainfall under climate change, and the prioritized works
on the facilities for early effects or existing facilities should be applied to
secure the target flood safety.
- It's necessary to aim the immediate achievement of the present river
improvement plan based on the flood record in the past, and further to shift
the target of river improvement plan considering the increase of rainfall
under climate change.
(Reconsideration of the plan rainwater in the sewage plan)
- Considering the increase of rainfall under climate change and recent urban
floods, it is necessary to reconsider increase of the rainwater under climate
change and deliberately advance preliminary disaster prevention.
- To advance the preliminary disaster prevention which contemplated
influence of variation in climate, risk analysis on urban floods based on the
updated plan rainfall should apply to the decision and publication of the
stormwater management comprehensive plan which shows a med- or
long-term urban inundation plan by sewage (improvement level for each
area, step-by-step improvement etc.), reconsider the plan based on the
impact of climate change, accelerate and prioritize the sewage work under
the concept of choice and concentration, optimize the existing facilities, and
facilitate urban flood management under the multiple collaboration.
(Reconsideration of the produced earth and sand volume in erosion and
sediment control planning)36- Reconsideration of structural and non-structural measures for frequent and
extreme sediment disasters should be advanced practically. The change in
produced earth and sand volume should be estimated properly by the
analysis on local presumes and triggers characteristics under the increase of
rainfall. The hazard areas for landslides and sediment floods should be
estimated from the analysis on sediment phenomenon. The external force
for the design in erosion and sediment control related facilities should be
updated.
(The reconsideration of target tide levels for coastal protection)
- Necessary height of coastal dyke is normally set by necessary amount to
the design wave and allowance height to the planned tide level. The external
force are likely to increase under climate change through the rise amount of
average sea level and the increment of tide deviation for design storm surge,
and the mightier waves for design wave. Therefore it is necessary to
reconsider these external force for coastal protection considered by the tide
level based on the prediction in the future rather than by historical tide level
of the past.
- It is now difficult to estimate the change in wave and the section
topography by off-shore sediment movement caused by extreme
phenomenon considering climate change accurately. The monitoring should
be enriched and adaptive measures and management should be applied.
- The adjustment and consideration to secure the protection function
successively at river and coastal area are necessary for setting of the water
level for river planning by which river embankment and coastal dyke are
rubbing around the river mouth.
(Comprehensive sediment management)
The rainfall increase by climate change may create the flood increase, the
change in sediment production and transportation in quantity and quality,
and the change in environment. The change in river channel, coast, and dam
sedimentation should be monitored. The comprehensive sediment
management should be facilitated through current sediment supply from
dams, sediment removal of river channel and improvement of coastal areas.
6.1.2 No rework measure by reflection to design standards
-It is necessary to consider so that needed safety has been secured during
the service life of facilities or parts, etc. when river management facilities37and shore protection facilities and sewage facilities are designed. Therefore
when the climate change influence applies to the design in facilities, it's
necessary to reconsider external force by utilizing the increased amount of
rainfall and tide level etc. as of their service life.
- The forecasted change in future external force includes the uncertainty. To
avoid no rework measure because of the further increase of external force,
such as for the 4 degrees rise scenario, it is better to include the design
policy beforehand, whether easy reconstruction design to be set in case of
the increase of external force, or necessary reconstruction work to be added
after the increase of external force cleared.
(Reconsideration of facility design)
-It is necessary to consider a rise of external force by climate change in case
of establishment in facilities. For long-service facilities like barrages and
large-scaled floodgate, the Additional design measures for further climate
change can be included in advance, so the reconstruction work becomes
easy and cheap even in case of the actual increase of external force. It is
desirable to consider influence of climate change into the design of facilities
like pumps, which expire their duration of the services before the
temperature rises 2 degrees.
6.1.3 Others
(Reconsideration of the methods of the biggest external force assumption
for flood assumption district mapping)
- The biggest rainfall for flood assumption district map is basically estimated
district by district in Japan, based on 15 districts where rainfall
characteristics is observed similarly (the district’s biggest rainfall). However,
when being much lower more than the annual 1/1000 probability rainfall,
the annual 1/1000 probability rainfall applies on behalf of the biggest
rainfall. 2)
- The biggest high tide, as well as rivers, is basically estimated under the
condition where a typhoon with the lowest core atmospheric pressure at the
1934 Muroto Typhoon which landed Japan in lowest pressure before uniform
record in 1951 and affected more than 3,000 people dead or missing and the
largest radius and velocity at the 1959 Typhoon Vera attacks during the high
tide by the worst course. The biggest high tide is estimated by the
atmospheric pressure and tide level based on the observed data.
- On the other hand, the flood assumption district map by the maximum38assumption scale applies to the structural measures, such as the flood
preparation and response activities for public building. 3)
- It is not clear so far how climate change gives an impact to the low frequent
phenomenon. Further research on extreme rainfall and climate change
forecast should be conducted cooperated with research institutes etc. for the
method improvement of setting the assumption biggest external force.
6.2. Conversion to "River Basin Disaster Resilience and Sustainability by All"6.2.1. Comprehensive and multi-layered measures reducing hazard,
exposure and vulnerability around a whole basin
6.2.1.1. Flood Prevention to control hazard
- The improvement of area safety, the measure in which rainwater and
running water, etc. are stored up at the whole basin, the measure which
makes flooding goes down and the measure which controls inundation are
necessary respectively as well as the effective combination of them.
- It is first necessary to further accelerate embankment improvement,
channel dredge, levee displacement, dam and retarding basin construction
by river administrators, the improvement of rainwater line and underground
storage by sewage administrators etc.
- The economic loss is influential if flooding occurs in a large river. Low
security is only secured in small or medium rivers. Such district distribution
of water-related disaster risks should be considered, and the basin safety
should be secured in a whole basin from upper to lower area, either main
river channel or tributary.
- It is important to ask for the cooperation to the stakeholders who have not
consult with. The platform where such stakeholders can cooperate for the
basin should be set depending on the characteristics of the basin, such as for
the implementation of preliminary discharge by water users ’ dams,
rainwater storage penetration facilities around rapid populated rivers by
local governments or private sectors, and land preservation for water
holding and overflow function, to improve flood safety and water-related risk
reduction in the basin.
- Further, the technological research and development about embankment
reinforcement should be advanced for "persevering embankment" difficult
to be burst even if flooding occurs. This can reduce the flood amount during
flooding, at higher risks in particular.39(1) Expansion of the storage function of the flow
(Reinforcement of the flood control function of existing dams including water
users’ reservoirs)
-The "preliminary discharge" for which stored water is discharged
beforehand for flood control at multi-purpose dams and water users ’
reservoirs, should expand radically through facilitating the cooperation by
water users.
- For the cooperation, a flood control agreement including implementation
policies of preliminary discharge every basin system has been signed among
MLIT, all dam administrators, and stakeholders in major rivers, for
preliminary discharge during the rainy season from 2020. This should be
applied to the minor rivers in Japan.
-After placing the operating method of the preliminary discharge in
operational regulations, the effect of the preliminary discharge to the target
of flood control plan should be estimated and reflected to the update of the
flood control plan.
- Flood control functional enhancement of existing dam should be advanced
through the collaboration between river administrator and dam
administrators based on water users where the certain effect is expected.
- For more effective preliminary discharge, the technology and system
should be developed for rainfall forecast, dam inflow forecast, dam operation
forecast, and flow forecast of downstream by long-term forecast
improvement using AI and other new knowledge and methods.
(Improvement of the overflow function united with land use)
- To avoid destroying damage in a basin, the land use in the area with the
overflow functions along the river should be restricted appropriately by the
preservation and maintenance of the kasumitei, discontinued levee (*), as
well as secondary levees.
- While river improvement works and the flood control safety improves, the
kasumitei might be replaced by continuous levee or urbanization might
occur behind existing kasumitei. Since possessing the function which
weakens momentum of flood water by making them flow backward from its
discontinued part as well as the function which returns the flooded water
from the upper reach to the river, the kasumitei can contribute to the
destroying damage reduction in the lower reach depending on the
topography, by overflow and flow reduction in the lower reach.
- More frequent floods may exceed the facility capacity under climate40change. The function of the kasumitei should be evaluated, and the
preservation and maintenance of the kasumitei should be promoted with the
collaboration with local people, while development restriction and relocation
should be promoted within the basin in cooperation with district designation
(hazard danger zones) by related local governments.
- If necessary, secondary levees should be constructed and existing banks
should be preserved for the levees, collaborated with various organizations
for damage control of houses from expanded flooding.
*A kasumitei means discontinued levee mostly located in torrent river.
There are some functions such as returning inundated water to the river
from the burst of the levee in upper reach, and storing the part of the flood
tentatively.
(2) The capture of earth, sand and driftwood etc. flown in quantities during
flooding
(Intensive maintenance of and the erosion and sediment control related
facilities to prevent sediment disasters and floods)
- Frequent torrential rainfall occurs recently all over the country. Slope
failure and landslide might occur more frequently under climate change. The
increase of river flow may raise the risk of sediment disasters and floods.
Hazardous rivers for sediment disasters and floods should be identified by
the risk validation methods. The prepared disaster risk reduction should be
conducted intensified in such rivers by effective measures such as erosion
and sediment control dams and sediment capture facilities.
-Effective maintenance of facilities should also be promoted to the
occurrence of driftwood flows in quantities at the time of sediment disasters
and floods.
(Maintenance of the erosion and sediment control facilities for more
frequent movement of earth and sand)
- The change in rainfall under climate change may make the movement of
earthy and sand more frequent. There is a possibility that consideration and
reconsideration happen to the timing and the implementation frequency of
maintenance of the erosion and sediment control dams, as well as the
steady progress of the preliminary disaster prevention of the erosion and
sediment control dams etc. Careful consideration is necessary.
(3) Improvement of the rainwater storage penetration function of the basin41(Reinforcement of the urban flood control measure)
- The cooperation of river and sewage improvements, and the improvement
of large-scale rainwater storage reservation facilities in the underground
should be advanced for the river-side urban area. The rainwater outflow
restraint including the rainwater storage penetration facilities by local
governments, individual and private partners should also be advanced.
(Substantial outflow restraint measure all around the country)
- Comprehensive flood prevention measures in a basin including the
designation of preservation regulation pond and the permission of the
rainwater infiltration obstruction to developers, etc. along with river and
sewage improvements for the rapid urbanized river basin have been working
for the flood safety toward the increase of river flow, based on the specific
municipal river flood damage control act.
- At 2019 Typhoon Hagibis, the disaster prevention pond etc. developed by
local government and private developers worked very well at Tsurumi River,
one of the designated river basins under the specific municipal river flood
damage control act. It is expected that these outflow restraint measures
show the effective effect especially for flood prevention and damage
reduction at small river basins.
- Local government measures should be facilitated for the measure which
produces outflow inhibiting effect at the existing resident area and the
measure more than outflow increase by development is suppressed, as well
as the outflow restraint measure to make the rainwater storage penetration
function convalescent and prevent the rainwater increase by new housing
development or ground pavement. The measures for private sectors should
be also facilitate for their cooperation.
- As the new development for housing and large-scale agriculture farms may
increase river flow, in addition to the measure to make the rainwater storage
penetration function convalescent, the outflow restraint measure for
water-related disaster risk reduction should be facilitated including the
utilization of existing ponds, rice paddies and the abandoning cultivation
places expected, depending on the characteristics of the basin. The
cooperation by various stakeholders should be facilitated for disaster risk
reduction all over the country.
(4) Sustainable maintenance and increase of flow capacity and strategic
operation and maintenance42(Promotion of strategic operation and maintenance)
-There is the fear of many aging river facilities which constructed after the
high economic growth period in Japan. There are a number of facilities which
require urgent cares with visible damages appeared lack of maintenance.
The future climate change will devastate the disasters more severe and
frequent. Preventing maintenance cycle and well prepared operation and
maintenance will become essential for appropriate functioning facilities
event during the disasters in order to secure people’s lives and their social
and economic activities.
- Strategic operation and maintenance will become more necessary, such as
the application of efficient operation and maintenance structures at their
upgrade timing or new river works.
- Renewable power generation using cultivated trees in river channel by
private sectors, as biomass fuels, should be facilitated for reduction of
operation and maintenance costs and climate change mitigation.
(Status monitoring and advance of operation and maintenance)
-The change in river channel shape caused by changes in disposition
characteristic of the river flow and the change in progress of vegetation may
bring a change to production in earth and sand and the movement
environment in the long run though it is not clear so far.
-Therefore the advance of the monitoring technique in river channel should
be promoted with efficient operation and maintenance continually. For
example, the three-dimensional altitude point group data by the laser
measurement should be utilized for capture of yearly quantitative change in
vegetation, sediment accumulation and loss. The big data like
three-dimensional point group data and image data should be utilized for
check and grasp of channel and embankment by the AI technology-based
automatic distinction. Such works should advance the operation and
maintenance.
(Improvement of the flood prevention function with channel and
embankment)
-Channel excavation and the work which improves the flowability by setting
back of embankment have been put into effect to make the flow running
safely up to now. There are also rivers where the flowability declines by
sediment re-accumulation and re-vegetation, and the channel differentiates
into two heights *.43*The decline of the channel bed and accumulation of sediment ground with
vegetation differentiate into lower channel bed and higher ground. The
ground where vegetation becomes widely lush, sometimes declines
flowability, forms water opposition parts, and scours partly. These
phenomena are not good for flood management and environmental
preservation by declining water ponds.
- Channel improvement for more flow and embankment reinforcement put
into effect deliberately based on each idea respectively, but they give
influence each other. The level of flooding and control of flow by an
embankment have an influence on the topography change in the channel.
The topography changes in the ground part of channel have an influence on
the permeation to the foundation ground in an embankment and the flow
velocity change close to the embankment. The channel and embankment
should function in an integrated manner. During large flooding, these
interaction shows conspicuously, so channel and embankment should be
treated appropriately overall.
-In particular, for the flooding beyond the target of improvement, the
evaluation technique of the reductional effect of flood risk in a basin should
be considered for the integration of channel and embankment, in addition to
land use in the back and inundation control.
-It is investigated about the most suitable channel section to preserve and
create the propagation environment and various landscape which a river
possesses primarily, as well as the difficulty in sediment re-accumulation.
The knowledge should try to reflect in channel planning.
-A great deal of sediment movement and accumulation occur during
large-scale disasters, and the channel topography and the propagation
environment change. Therefore the efforts should be toward monitoring for
the grasp of dynamic river system by the basin scale including the
environment, and it should reflect to the plan as needed.
(5) Restraint of the inundation amount
(Embankment reinforcement aiming at "persevering embankment")
- Out of 142 embankment burst points during the 2019 Typhoon Hagibis,
more than 80 percent happened because of overtopping. The maximum
record storm surge and high wave occurred during the 2018 Typhoon Jebi.
-The measure which lowers the water level is a fundamental principle of
flood control. However even in the case that the external force exceeds and
overtopping occurs beyond the ability of the facilities, the embankment with44"the persevering structure" should be considered as difficult to be burst and
a little lengthily before the burst.
- For urgent short-term embankment reinforcement, the construction
method which keeps performance in existing levees should apply for the
proof to the overtopping water, the workability, the cost, the site, operation
and maintenance, and the durability, etc. in the narrow part, the upper part
of bridges, merging section and a bilge where immediate measures are
difficult and the situation of the embankment back place are captured.
-There is a problem of non-explication by the present technology about the
embankment with "the persevering structure". It is important to understand
well that there is uncertainty in the proof strength to the overtopping before
the application.
-When embankment reinforcement is introduced into a site, the
consideration to a view suitable for the respective rivers and areas and
public use, etc. is indispensable because the view shows the geography,
geometry, climate, vegetation, natural environment and human activities
and their relationships in time and space aspects and retrospective works
comprehensively.
-Technological research and development for further reinforcement in an
embankment with "the persevering structure", should be advanced,
considering the operation and maintenance, landscape, the environment,
the cost and the durability, etc. in mind. The research and technology
development system about the structure of the embankment with
government, academy and industry participation should be built for
embankment structure difficult for burst even when exceeding its capacity,
as well as the anti-permeation measures and earthquake-proof measures,
etc. This requires the various material development and the method of
construction as well as planning, evaluation methods and the influence to
the environment by the change in burst.
-Technological research and development about the embankment which
endure to the certain external force toward overtopping (for example, the
overtopping depth and duration, etc.) should also be advanced.
(Reinforcement of local flood fighting system)
-The 2019 Typhoon Hagibis showed the problem about information sharing
for flood fighting and insufficient capacity for a leak of the embankment and
flood occurrence (bank burst) etc.
- Under aging and decrease of flood fighting capacity, the information45sharing structure should be built through maintaining the flood fighting
function cooperated with private sectors, collaborating between flood
fighting and river administration, and sharing the river observation data and
deformation data.
(Sewage facilities waterproof.)
- During the 2019 Typhoon Hagibis, flood damages occurred at 17 sewage
treatment plants. It took a certain duration for their recovery for a part of
facilities.
- Flood proofing technology standards should be set and implemented
deliberately toward more severe recent disasters, to secure the certain
sewage function event during flooding and to minimize the social impact by
the damage of sewage facilities.
6.2.1.2. The measure to reduce a damage target – exposure reduction
-The principle is to prevent flood hazard as much as possible, but it is also
desirable to take the measure for damage minimization as well in case that
flood may occur. Specifically, "regulation" for land use and way of living in
water-related high risk areas, "leading" resident and urban function to the
lower risk areas, "limiting the flooded area", the augmentation in land for
housing in an area with flooding risk, and the device of building structure,
these measures for flood damage reduction are effective.
-Land use and the building structure have been regulated by designating the
high risk area as a hazard area, but these were performed with river works.
There is still new development even in the area with high water-related
hazard risk, and flood damage occurs there. Therefore it is important to
collaborate with urban planning sectors, connecting water-related disaster
risk reduction with "compact plus network", lead to the low risk zones and
give devices of how to live. For local revitalization, the community should
take the leading measures for urban planning resilient to water-related
disasters according to each characteristic.
-It is necessary that all kinds' information about water-related hazard risk is
being estimated appropriately and is being reflected in actual measures.
Risk information about water-related disasters has been published mainly
for smooth evacuation by residents to protect their lives, but these should be
improved for urban planning. Water-related hazard risk evaluation should
apply to the risk reduction around a whole basin.46- "Limiting flood hazard zones " and controlling inundation, such as
secondary levees and ring levees, have been put into effect in some areas.
Flood control measures toward frequent and severed flood which exceeds
the plan under climate change are important when considering the function
of limiting hazard zones and controlling inundation.
(1) Land use and device of how to live in water-related hazard area
(Land use and device of how to live in water-related hazard area)
- It is important to considers disaster prevention in building community, lead
the residents to the lower water-related hazard risk area, facilitate the
measures for flood risk reduction by the measures of building structure in
the water-related hazard area, and apply various risk information to actual
urban planning, as well as prohibiting and making stricter on housing
permission at flood assumption districts in urbanization control areas,
especially with higher risk areas to people’s lives.
-Therefore, the information of water-related hazard risk should be upgraded
for more cooperation between flood disaster management and urban
planning sectors and urban planning based on community water-related
hazard risk assessment. For higher risk areas, land use control and building
structure control should be considered. The pilot studies and guidelines are
necessary.
- Upon community’s consensus, the system and incentive policy should be
announced for sustainable urban planning through transferring to safer
areas by disaster group moving promotion and augmenting housing zonesetc.-For reduction in financial damage and prompt response, the cooperation
with insurance and financial sectors should be strengthened.
(Hill community building in the low-lying areas below sea level (hill and
building))
- Sustainable urban planning with prosperity, communication and more
attraction, is necessary at low-lying zones below sea level in large cities
formed densely and exposed to huge damages for extreme flooding. It is
necessary to make an effort on structure improvement in the cities, and
secure the evacuation living standards without long interruption of social
and economic activities even in case of major flooding.
- Therefore the related sectors should collaboratively work for good urban
atmosphere and resiliency toward water-related disasters to avoid47destroying damages through:
* Hill construction by land readjustment, park space and high standard
embankments, etc.
* Construction and securement of the building with evacuation space
* Construction of routes between buildings enabling to move from buildings
outside flooding, and from riverside buildings to embankment etc.
* Construction of piloti structured buildings and hills with cooperation of
private sectors
(Construction of flood control facilities cooperated with consolidation of area
base)
- The multiple water-related risk reduction should be cooperated with urban
planning sectors through considering disaster risk reduction at compact city
policy, guiding resident and urban function to lower risk area, and
networking between the resident and urban function and center or pivots of
areas, for flood prevention measures.
- The effective flood damage reduction should be implemented at the dense
sewage building districts in the comprehensive rainwater management plans
through promoting the utilization of individual aid programs, and
accelerating new construction of facilities and appropriate function
securement of old facilities as well as improving the operability of sluice
gates etc.
- More rainwater outflow restraint should be facilitated along riverside urban
areas through cooperating between river and sewage works, constructing
major rainwater storages etc. in the underground spaces, and rainwater
storages by local government, individuals and private sectors.
(2) Substantiality of area’s water-related risk information for utilization to
urban planning
(Substantiality of area’s water-related risk information necessary for urban
planning and improved way of living)
- Water-related risk information is useful not only for people’s evacuation
but also for urban planning and flood proofing of facilities. Multi-step flood
hazard information should be developed and announced, such as inundation
forecasting for medium high frequency external force (for example, 1/10* or
1/30 or 1/50 or 1/100) as well as maximum rainfall or target rainfall for flood
planning, and future change in inundation hazard after the river
improvement work.48* 1/10 means yearly probable exceeding probability. "1/10" shows that the
probability that big rainfall beyond the subject of flooding assumption occurs
is 10% every year.
- Water-related risk information should be devised for urban planning
sectors. Risk communication among stakeholders should be advanced for
their actual measures.
(Reduction of water-related risk information blank area)
-When not publishing the information though there is water-related risk
potentially, this may cause misunderstanding that local resident thinks
themselves safe. The human loss occurred at such information blank areas
during the 2019 Typhoon Hagibis, so the information blank areas should be
reduced.
-Therefore early designation of maximum assumption flood, storm surge
and urban flood zones should be advanced. The hazard information like
assumed areas and depth for predicted maximum scale floods should be
announced in the areas outside designation of maximum assumption flood
along medium and small scale rivers, coasts and sewage.
- Early designation of the landslide disaster hazards should be advanced for
the awareness of the risk on landslide disaster. The hazard areas should be
clearly shown in the site. New topographic data with higher resolution should
be applied in the future basic survey (abstraction of a district) for the
improvement of precise abstraction.
(2) Limitation of flooding area and flood control
(Improvement of secondary levee and natural levees for damage area
downsizing for houses)
- The banking structure with the function of secondary levees by local
government should be promoted under the cooperation with road
construction and urban building with community and resident understanding
to limit flooding area as much as possible even during flooding.
- Existing natural levees etc. achieving its function should be preserved by
utilization of flood damage reduction district system based on flood fighting
law to prevent further expansion of flooding in a flood area.
- The secondary levees may sometimes generate disadvantage in part of
area. It is necessary to consider the mechanism to build community
consensus smoothly.496.2.1.3. Damage reduction, early response and recovery –vulnerability
decrease -
- The damage to people ’ s live and social economic assets should be
minimized even when floods and sediment disasters become inevitable.
Public sectors should provide the information on water-related hazard risks
appropriately. It is important that every stakeholder in the basin have
information and attitude on water-related disasters, prepare beforehand,
and take appropriate actions during the disasters.
- Various measures for more effective evacuation have been taken place,
such as designating flood forecast and flood alert rivers for flood suffered
rivers, mapping flood hazard areas with flow observation, and providing
those information to the resident.
- Flood prevention mapping and evacuation practice in underground with
high flood risk, and evacuation securement planning at welfare facilities for
people who need special assistance should be mandated and facilitated
through assistance to users based on the flood fighting law, cooperated
among national, prefecture and municipal governments.
-The evacuation drill and disaster risk reduction education have been
implemented all over the country for awareness raising and effective raising
of evacuation. My timeline has been developed as an individual action plan
for emergency.
- The 2019 Typhoon Hagibis shows the damage to people ’ s lives in the
water-related risk information blanket areas as well as in the designated
flood assumption areas because of escape delay. Further evacuation system
should be advanced by reinforcing existing activities and widening
evacuation.
- Flood prevention plan, flood prevention drill and self-defense organization
establishment have been advanced for economic damage reduction
according to the Flood Fighting Law in voluntary basis. Companies’ practices
and experiences for flood control and prevention have been accumulated
and announced.
- The 2019 Typhoon Hagibis showed extreme water-related disaster
occurred and huge financial damages by damaged infrastructure including
public transportation and facilities. Because of these damages, it is
necessary to lead urban function to lower water-related disaster risk areas,
to reinforce social infrastructure, and to accelerate the works on economic
damage reduction.50- The flood assumption district maps apply to the community building
(location lead), flood prevention in facilities, notice on land and building
trade, and more usages. "Water-related disaster risk information" should
be further upgraded depending to the purposes.
-National support including TEC-FORCE has worked for assistance to
affected areas as measures of early response and recovery. Such support
mechanism by national government should be reinforced and strengthened
by the cooperation among all stakeholders in a whole river basin.
(1) Substantiality of water-related disaster risk information of land
(Reduction of water-related disaster risk information blank area)
- Flood assumption district for maximum flood, storm surge and urban flood
should be designated early. The hazard information such as expected
maximum flood for small or medium rivers, coast, and sewage, should also
be at present so reduce the risk blank area.
- Early designation of sediment disaster hazard district and clear sign in the
site should be advance for higher awareness of the risk about sediment
disasters. Higher resolution topography date should newly apply for future
basic survey (abstraction of the district) so the abstract precision should be
improved.
(Substantiality of the water-related disaster risk information which leads to
water-related disaster measures by various stakeholders)
- Flooding hazard information should be announced in multiple steps from
maximum expected sized, medium-high frequent external force sized
81/10, 1/30, 1/50, 1/100 for example), after the completion of river
improvement in the future.
- All stakeholders should share risk information for resilience for
water-related disasters and sustainable society foundation. The information
providing methods should be enriched so private sectors can use flood
hazard information for BCP.
- These water-related hazard risk information leads to measures by various
stakeholders. These should be enriched and updated depending on their
needs. The research on evaluation method for the effects of information
should be promoted by clear relationships between the costs and effects.
(Abstraction of high probability sites of visible sediment movement
phenomena)51- Sediment moving phenomenon and loss of people’s live occurred in the
sites where sediment disaster hazard zones are not designated or
designation standards do not apply based on sediment disaster prevention
law when heavy rain special warning was issued.
-Thus sediment disaster occurred frequently where topography does not
show the clear risk of sediment disasters, flooding, and visible landslides, or
valley topography is not clear. Such high probability site with disaster risks
should be specified though the hazards are not clear. The method on
specifying such hazard should be promoted.
(Evaluation of frequent and visible sediment disasters clarifies every area)
- Surface failure induced by heavy rain in the west-south Japan inner
geographic zones with widely distributed granite rocks, or simultaneous
multiple landslides occurs with severe damages. Such major sediment
disasters are different because of the feature of sediment moving
phenomenon depending on the basic factors and triggers in each area.
- The rainfall characteristics change under climate change. It should be
appropriately evaluated where and how sediment moving phenomena
become more frequent. The evaluation method should be newly developed.
The result of the evaluation should be shared by the whole society.
(2) Offer of water-related hazard risks using every opportunity
(Offer of water-related hazard risks in case of purchasing land)
- It becomes important to recognize water-related hazard risks in the site
when purchasing land and building, and starting newly living there.
- Therefore the consideration which mandatory requires land and house
dealers to explain flood damage risk on each property by placing one of the
important issues to be explained according to the land and building
transaction business law is advanced, so further cooperation should be
taken place among related agencies.
- The explanation of flood risk information should be continued at the
training opportunities for flood management sectors, disaster management
sectors and real estate groups so land and house dealers can explain flood
damage risk more precisely.
- The information providing tools for information users should be advanced
through identifying water-related disaster risk at each house and identifying
flood depth in the detailed map.52(3) Reinforcement of the evacuation system
(The information for evacuation and damage reducing actions by each
stakeholder)
-The information on water-related disaster risk for each hazard area under
disasters, and the information of river water and inundation levels for
appropriate actions should be upgraded and arranged.
- Evacuation in large area with cooperation by many stakeholders may be
necessary in case of large-scale and huge water-related disasters occurs.
The longer lead-time forecast, comprehensive basin-wide forecast of
flooding in main river channel, tributary, and urban area for torrential
complex rainfall, storm surge forecast in coastal areas, should be upgraded
with more accuracy by technology and science development.
-It is necessary to promote simplification and simplification of the disaster
prevention information by automation of system for certain and prompt
flood forecast and announcement as well as by use of arranged disaster
information and cautious levels.
-Landslide disaster cautious information should work for municipality
evacuation alert. The accuracy of the information should be promoted.
- Monitoring system should be enhanced through river monitoring camera
installment and river gauge. Technical development with private sectors for
gauge, AI camera and SNS information applying to levee overtopping and
burst, real-time inundation mapping by satellite should be promoted.
(The information sharing and providing for evacuation and damage
reduction actions)
-Mechanism to share real-time information on hazard by river
administrators, flood fighting administrators and private sectors quickly
among stakeholders in a basin should be built in order to put appropriate
flood control activity and evacuation support into effect in the area.
-The administrative agencies which send information and the private
enterprises such as the mass media and net media which distribute the
information, etc. should cooperate and make the mechanism to deliver the
imminent information to the resident for their actions timely as well as to
improve terminology and how to tell for each evacuation actions and
damage reduction actions.
- The delivery method on supplemented cautious information for sediment
disaster should be devised as well as understandable way of announcement
on hazard degree and change to the resident.53- The relationships between the information sent from the public and actual
situation, and between the situation and people’s appropriate actions should
be announced to the public in normal time.
(Securement of evacuation place)
- Based on the clear the allocation of responsibility with administrators in
private facilities, utilization for the evacuation space should be promoted
when it is sometimes difficult to reserve enough evacuation space only by
designation in public facilities. The securement of hills or pedestrian deck are
considered for emergency evacuation space to be reserved under the
community voluntary idea just in case that the resident fails to escape.
-Though polity cooperates with people, it'll be an important point of view to
advance securement of evacuation by cooperation between private and
public sectors, including building evacuation facilities by the private and
constructing hills by the public.
- Various stakeholders should collaborate for "three dense measures" at
evacuation places and "dispersion evacuation" under COVID-19 pandemic.
The three dense measures include "improvement of the preservation of
health sanitary society of the shelter" such as other infection, food poisoning
and heat exhaustion measure. The dispersion evacuation includes
evacuation at home, acquaintance home evacuation, vehicle evacuation and
other "various means of evacuation (place)". These evacuation should be
generalized as future standard evacuation.
- Even after the COVID-19 Pandemic is over, it is important for various
stakeholders to cooperate, share the experience of this pandemic and make
an effort toward the improvement of evacuation place.
(Evacuation in large area)
- It is necessary to consider the implementation of evacuation in large area
in case that flooding occurs at large river in large area, sometimes a whole
municipal area. Evacuation in large area takes longer time and more
arrangement among many stakeholders. It is necessary to arrange the
timeline in advance which disaster response actions and each responsibility
are decided in case of disaster, to coordinate it by the large-scale flood
prevention conference, and share the information among stakeholders.
-Concretely, it is necessary to consider the analysis on the target of
evacuation in large area, secure the evacuation place, and plan the means
and route of evacuation etc. in advance. For larger disaster response54operation, long-term forecast of river flow under development should be
utilized. The cooperation mechanism among national government, local
governments and private sectors, as well as smooth coordination scheme
should be considered.
- The planned suspension of the public transport has widely applied recently.
This gives an impact on community activity and evacuation system. The
information should be shared among stakeholders by using the large-scale
flood prevention conference in order to keep smooth evacuation alert
system under the planned suspension of the public transport.
(Preparatory efforts to facilitate the resident's independent evacuation
behavior)
- Preparatory efforts for understanding water-related hazard risks have
been put into effect up to now, such as evacuation drills and workshops with
using a hazard map, education for disaster risk reduction, and inundation
mapping in field.
- For each resident’s individual appropriate action during the disasters not
only by public assistance by the government, but also by mutual assistance
and self-help, the education for disaster risk reduction should be promoted
to provide disaster risk reduction knowledge to children, households and
community. Such efforts should be expanded to all over the country through
good practices at large flood disaster prevention conferences and website.
(Evacuation planning by individuals and community for the residents
individual independent actions)
- It is important for each resident to choose timely evacuation action among
the evacuation place, vertical evacuation within the house, and evacuation
to the relatives or acquaintance house, as well as district disaster prevention
plan, for practical preparatory evacuation reinforcement. Therefore,
preparing my timeline which describes each evacuation action in advance for
the appropriate evacuation depending on each situation and water-related
disaster risk information, my disaster risk reduction map which describes
the route to evacuation place and hazard areas in the map, and disaster risk
reduction applications should be very effective. The support to the actions
by municipals should be promoted for district communication for these
activities.
(4) Reduction of economic damage55(Promotion of community flood prevention and BCP development)
- It is necessary for private sectors to understand the water-related hazard
risk and prepare for it based on the facilities’ priority, for economic damage
minimization. It is also important to consider the damage by an operation
stop as well as material loss by flooding, etc. and prepare for them
appropriately in particular.
-Related public institutes should support owners of factories and private
buildings for their effective and efficient flood prevention measures such as
establishing water sealing plates, constructing flood prevention walls,
augmenting lands, equipping flood-proof electricity facilities and preventing
floods by flood control goods and materials.
-The disfunction of public facilities like city halls, hospitals requiring
electricity for life-keeping patients and social infrastructure like water supply
and sewage created severe impacts because of water-related hazards.
Preparatory actions and response actions such as flood proof wall equipment
and temporally relocation to upstairs should be arranged and implemented
step by step, by scoping the maximum scale flooding and continuing
operation and responding early under flooding.
-Thus all stakeholders should simulate the flooding and prepare, and
conduct drills depending on their activities. Flood BCP should be promoted
for smooth actions under the disasters and early response and recovery.
-Therefore, effective flood prevention measures using water-related hazard
information should be accelerated by sharing information in community and
using the framework of large flood prevention conference.
(Securement of transportation network by cooperation among railroad,
river and road administrators)
-Washing away in railroad bridges and in roads by frequent and severe
torrential rainfalls, and cutting into pieces of railroad and road network by
sediment disasters occur frequently.
-Therefore railroad bridge prevention by railroad enterprises, road
protection by road administrators should be implemented effectively by
providing information by river administrator, cooperating among
stakeholders, and collaborating measures among railroad companies, road
administrators, river administrators and erosion and sediment control
sectors etc.
(Dissemination of information on flood damage risk to finance and insurance56industry, various measures for flood avoidance and for damage reduction)
-There are financial and insurance tools by which the housing loan interest
rates and the insurance fees are discounted when individuals and
enterprises take preventive measures appropriately for water-related
hazard risk reduction. It is expected that affected people can achieve early
response and recovery by using such tools.
-These tools can show the effect on facilitating individuals and companies for
their flood prevention measures, which brings the merit to users as well as
financial and insurance institutes. Water-related hazard risk information and
preventive activities should be informed properly for financial tools
development all over the country.
(5) Reinforcement for early response and recovery cooperated with
stakeholders
(Wide area damage information capture)
-The technical development for prompt wide area damage capture should be
promoted for effective drainage activities for early response by using
artificial satellite, sensor and AI, etc.
(The measure for early drainage of flood water)
- Well advanced drainage planning for damage reduction and early response
and recovery in case of flooding, drainage facility equipment for early
drainage of flooding water, and flood proofing on important drainage
facilities for their continued operation should be promoted. Securement in
an access way and securement of alternative power supply and storage fuel,
etc. for fuel filling should be also promoted.
- As well as drainage by drainage pump car, flood fighting, river and sewage
administrators should collaborate for flooding drainage by using existing
drainage facilities and facilitate early flood drainage in a whole basin.
(Further reinforcement of TEC - FORCE activity)
- Under large scale disaster, personnel and materials have been dispatched
from MLIT reginal development bureau etc. to affected local government as
the TEC-FORCE activity. The further reinforcement of TEC-FORCE activity is
indispensable. The reinforcement of MLIT reginal development bureau,
capacity building and training, equipment of ICT and the others and storage
and installment of materials and goods should be promoted.
- New mechanism for TEC-FORCE activity on behalf of affected local57government should be established.
- Further support and preparation for local government should be prepared
in advance for large and severe water-related disasters.
(TEC-FORCE promotion cooperation between the public and the private)
-Immediate response for securement of necessary personnel and materials
in each area is also indispensable for the support to affected local
government in case of severe water-related disaster occurs in wide area.
The partnerships with local construction companies and local partners, as a
"partner" of TEC-FORCE should be arranged through the MoU for disaster
response.
(Expansion of support to affected local government by national government
for disaster response)
-It is important to utilize the country ’ s high technology and mechanical
effort, grasp the damage promptly and support response in case of large and
simultaneous water-related disaster, considering the decline of capacity and
technology of local government. The country’s institutional substantiality is
only limited to country administrative rivers and prefecture administrative
rivers. The collaborative disaster response cannot apply with the
neighboring municipal administrative rivers, so early response might
become difficult.
- The country’s institutional substantiality should be applied widely for local
rivers so the support for river damage survey and river dredging should be
further promoted.
6.2.2. Acceleration of preparation for disasters
- The disasters take people’s lives, the assets individuals, enterprises and
local community have built up, fortune and the outcome of development
right away, as well as the opportunity of local sustainable development if it
takes a lot of time for response and recovery, which becomes impoverishedbig.- It is the recent situation that large water-related disaster occurs almost
every year. The disaster prevention measures to avoid another disaster
should take place in the affected area. Preparing for disasters in advance
( " preparation for disasters` hereafter), not responding to disasters
tentatively, is indispensable to protect people’s lives and assets under more
severe meteorological situation by climate change and more difficult58disaster administrative situation by aging society in the local area.
- For example, the improvement work is still on the way even in the major
rivers, such as Tone and Ara rivers in Tokyo metropolitan area. Fundamental
disaster prevention facilities, such as Arakawa regulation pond and Yamba
dam, showed the big effects at the 2019 Typhoon Hagibis, but it was a
critical situation. Almost all rivers in the country cannot correspond to
record-high flood after the WWII, and it takes more time for the measures.
- Hypothetically if the ongoing measures (the measures in river
improvement plans) all completed in the rivers damaged by the 2019
Typhoon Hagibis, the social and economic damages should have reduced
significantly in the most part of rivers.
- Based on this experience, it is necessary that the preparation for disasters
should be further accelerated with enough budgets in the country.
- The comprehensive measures combining structural and nonstructural
should be promoted by building back better beyond simple recovery,
building resilient society and updating the land use at affected areas even if
the preparation for disasters has not taken place and a disaster occurs.
- There is fear of increasing water-related disaster risks through more
severe and frequent torrential rainfall and higher tide by future climate
change. The planned safety level cannot be secured only by constructing the
flood prevention facilities based on the current plan. The improvement
should be updated by planning and considering climate change impacts, and
further accelerated.
(1) Acceleration of the preparation for disasters by the "River Basin Disaster
Resilience and Sustainability by All" projects
- The improvement measures for flood safety have been put into effects,
such as embankment, river channel excavation, dam, spillway, and
retarding basin. The 2019 Typhoon Hagibis, which exceeded the record
rainfall in some areas, showed the effect of such improvement measures for
preparation of disasters through reducing and preventing the flood damage.
- For the acceleration of the preparation of disasters combining such
effective structural and non-structural measures, it is effective share the
immediate targets among national government, local governments, private
sectors and the resident and cooperate for the implementation.
- For example, the "River Basin Disaster Resilience and Sustainability by All"
measures have been intensively put under the " urgent flood control
measure project " in seven major river basin systems (Abukuma River,59Yoshida River in Naruse River basin system, Kuji, Naka, Iruma Rivers in Ara
River basin system, Tama River and Shinano River including Chikuma River)
affected in the 2019 Typhoon Hagibis, collaborating by various stakeholders
as well as national government, prefectures and municipal governments in
the basin.
- Specifically, the river improvement includes river channel excavation,
retarding basin works, embankment works and reinforcement and other
intensive response as well as responding affected embankment in the next
5-10 years. The measures in the basin includes the outflow restraint of
rainwater through rainwater storage facilities and flood control utilization in
reservoirs, and the land use and way of housing revision through house and
housing land augmentation and land use restriction in the flooding zones.
- Similar measures should be advanced in the other basins outside the 7
major river basin system, considering the expected floods, sediment
disasters and tsunami and storm surge hazards. Specifically, the clear
explanation of the contents and effects of structural and non-structural
measures with the appropriate targets, as well as mid- and long-term whole
pictures of measures, should be shared among local resident and private
sectors for their understanding and conscious improvement, and should be
implemented and accelerated deliberately.
- Early stage manifestation of the effect by the drastic utilization in existence
facilities and the device of improvement procedure, digitalization and
smartization of disaster prevention technology such as ICT technology, the
land use and building regulation in the hazard areas by water-related
disaster risks, should be considered collaboratively.
(2) Start of the "River Basin Disaster Resilience and Sustainability by All"
measures considering the future climate change
- The above measures are not enough when considering the impact of future
climate change. The river improvement plan for current measures should be
reconsidered on its river improvement targets, considering the rainfall
increase, sea level rise and increase of tide departure under climate change.
The flood prevention and reduction measures should be implemented
deliberately with the cooperation among various stakeholders in the basin
under the concept of the "River Basin Disaster Resilience and Sustainability
by All".
6.2.3. Social mechanism mainstreaming disaster risk prevention and60reduction - Interdisciplinary approach for "River Basin Disaster Resilience
and Sustainability by All " around a whole basin-
(1) Daily life considering disaster prevention and reduction
- National government, local governments, private sectors and individual
resident should consider disaster prevention and reduction in their daily lives
for the implementation of the " River Basin Disaster Resilience and
Sustainability by All" with cooperation by all stakeholders. It is important to
include the aspect of disaster prevention and reduction into their daily
knowledge and actions.
- Therefore, the whole society ’ s preparation for disasters (disaster
prevention and reduction capacity) should be advanced through their daily
life considering disaster prevention and reduction, and through
reorganization of administrative processes, economic activities and various
works considering the aspects of disaster prevention and reduction.
- It is important to make the individual more prepared by more disaster
prevention education at schools and more participation in disaster
prevention activities, so the resident can collect necessary information
advancely and take appropriate preventive actions by themselves.
- A river sometimes causes a large-scale flood and is the existence which
threatens human survival and economic activity, but it normally gives rich
natural environment, good atmosphere and community relaxation. The
community ’ s culture and atmosphere deeply connect with rivers, which
mostly form its geography through their flooding. Therefore, it is necessary
to effectively cooperate the education between disaster risk reduction and
the environment, make more resident understand deeply on diversified
aspects of the river, and enhance the people’s consciousness on "River Basin
Disaster Resilience and Sustainability by All".
- It is also important that all stakeholders in the basin should be informed
clearly on the meaning and concept of "River Basin Disaster Resilience and
Sustainability by All" for their collaboration works. Specifically, this might
include the efforts on clarification of each action at each place, target of
climate change action and new growth, and the change of people’s mindset.
(2) Visualization of the effect of the various stakeholders’ cooperation in the
basin
- For the measures by various stakeholders in the basin, it is desirable that
each stakeholder has common understanding on the water-related hazard
risks and their reduction target as well as each action and its effect.61- In most of the cases, the effect of each measures varies and spreads widely
in a multiple way, but its degree is not always elucidated. For example, the
effect of water-related disaster prevention and reduction is not only in the
reduction on the loss of people’s lives and assets, but also in the support of
community’s function and economy. However, such indirect effects have not
been elucidated enough. It is also difficult to estimate the effect of various
outflow restraint measures in the basin uniformly as the size and location of
such measures vary and their effects change depending on the actual rainfall
and basin characteristics. The effect of various non-structural measures has
not be estimated numerically one by one.
- It is necessary to advance quantitative qualitative evaluation about the
effect of the measure by each stakeholder, so various stakeholders can
consider the effective operation and additional measures with enhanced
each motivation toward water-related hazards around the whole basin.
(3) Risk management in the basin considering the flood occurrence
exceeding the capacity of facilities
- The target of river improvement has been emphasized on how to discharge
the certain flooded water safely and secure the local safety. Once the flood
occurs exceeding this scale, the damage should occur all over the basin.
Even in such a case, it is necessary to consider how the cooperation among
stakeholders around the basin can avoid the loss of people’s lives, minimize
the damages at the center of economic and social activities, and avoid
severe water-related disaster damages which require long period for
response.
- To consider an effective measure, it is necessary that the rainfall may occur
in the pattern different from the plan, the design safety of facilities might not
mean their disfunction of such conditions, the smooth evacuation by the
resident cannot always be expected, all measures have actual uncertainty
on their effects, and the multiplied effects may be expected. Therefore, it is
necessary to consider the risk estimation methods which cover the range of
effects with enough actual conditions.
- In the near future, the estimation of local risk considering various flooding
scales should be promoted for comprehensive management methods and
water-related hazard risk sharing in the basin comprehensively by operation
of various facilities under exceeding floods, enhanced retarding capacity
cooperated with land use, minimization of inundation, zoning of lower
water-related hazard risks, limited inundation area by secondary levee62improvement and natural levee preservation, and the reduction of hazard
exposure by inundation control.
(4) The promotion of the "River Basin Disaster Resilience and Sustainability
by All" by interdisciplinary cooperation among different fields and different
sectors
- It is necessary that current situation and risk estimation should be
advanced and shared with society for efficient and effective implementation
of the "River Basin Disaster Resilience and Sustainability by All" measures.
Therefore, it is necessary to build the scheme for interdisciplinary
cooperation among different academic societies, business, fields and sectors
for new technological development and application.
- It is necessary to support evacuation and flood proofing measures by
accumulating water-related disaster data, integrating and consolidating
water-related disaster data with social economic activity data, and sharing
them among all stakeholders in the basin. It is important that technology
and data on water-related disasters should be shared and accumulated in
the basin at all disaster management process from preparedness, disaster
occurrence, response and recovery, and the scheme for their technological
and sustainable development should be constructed.
- Risk evaluation each stakeholder requires is necessary for many
stakeholders ’ participation to "River Basin Disaster Resilience and
Sustainability by All" and appropriate measures for disaster risk reduction
and prevention. For these various needs, the scheme for risk communication
is necessary upon technological development and various application of
technology. It is necessary that public administration should share their data
with required accuracy and reliability, and systems for private sector
utilization and their capacity building should be promoted.
(Promotion of new technical development)
- There is still un-explicating on the impact of climate change. It is necessary
that the monitoring and the research for the estimation on the future
forecast of climate change and the risk change of society should be
promoted for community’s clear understanding.
(New technology application)
-The research and development in the open innovation type (the different
field cooperation type) should be implemented for the development and63prompt application in field by using private sectors’ innovative and existing
technology.
(Urban water-related disaster damage minimization by the smart city
promotion)
- The individual field activity at traffic, sightseeing, disaster prevention,
health & medical, energy etc. has been accelerated to the smart city activity
in trans-disciplinary and optimization of whole city and district, using new
technology and public & private data.
- Prompt damage survey and sharing, and efficient operation and
maintenance of facilities should be promoted in the field of disaster
prevention, using the community information.
(The implementation method on risk communication and public awareness
which contemplated a new lifestyle under the post COVID-19)
- The measures for the COVID-19 pandemic have facilitated the on-line
business rapidly and the society movement toward the new lifestyle. Under
this circumstance, the information sharing among stakeholders by on-line
conference, the conventional promotion by community gathering like
workshops, and new promotion using VR and AR etc. should be promoted
aggressively.
(5) Promotion of "River Basin Disaster Resilience and Sustainability by All"
using the regulating methods and the inductive techniques, etc.
- The water-related disaster risk is maldistributed spatially. The land with
high risk is evaluated low price in the market, so it can be easily transacted
for housing and other development demand. The understanding on the risk
information is important at decision on development, housing purchase and
residence, but the developer, buyer and resident may accept the risk without
enough understanding, and consequently suffer.
- Therefore, it shows the social structural vulnerability that the land with
spatially high risk needs higher resident’s risk burden. The political methods
like land use regulation or leading are necessary considering the spatial
characteristics on water-related disasters, the recognized characteristics on
disaster risk and the market characteristics on land.
- These political methods include the regulation for preventive measures for
people’s live protection and control measures for specific stakeholders, and
leading for actions reducing economic damages and measures difficult to64control specific stakeholders in wide areas. It is important to combine them
according to the situation in the area.
- For the regulation measures to control the increase of outflow to the river
by development, it is natural that an actor bears the cost to prevent the risk
when the actor can be specified as its action increases the risk. On the other
hand, when community safety in wide area improves by an actor ’ s
cooperation, such as more flood control effect by water utility dams and
storage facility construction reducing outflow to the river more than the
development action of reconstructed buildings, the public sectors should
bear the cost for such development depending on the effect.
- Thus, for water-related disaster risk reduction with the cooperation among
all stakeholders in the whole basin, it is necessary to consider how the
necessary cost should be allocated in the basin.
- It is indicated below as examples about the considered regulation and
leading methods for all stakeholders in a basin to cooperate and promote
"River Basin Disaster Resilience and Sustainability by All ".
(Regulation)
-Prohibition of the act which makes the present state be aggravated, and
leads to trouble to others
Example: Obligation of establishing the storage penetration facilities to
prevent increase of outflow to a river, by new housing land development and
pavement in the ground, etc.
-Prohibition of the act with high risk
Example: Restriction of land use and construction in the area where
water-related disaster risk is high in particular
(Leading)
-Land-use lead to the area where water-related disaster risk is lower
Example: Urban function and resident lead to the area where water-related
disaster risk is lower by the compact city policy
(Economic incentive)
-Support of the cost necessary to cooperation to the preventive measure for
flooding
Example: Flood control functional enhancement of water utilization reservoir
and support to flood control capacity securement in a pond, etc.
-Support to the device cost of how to live to avoid and reduce water-related65disaster risk
Example: Move, augmentation in the ground for housing and support to the
additional cost of the piloti structure etc.
-The tax measure to preserve the function of the existing facilities
Example: The reduction and exemption of the fixed asset tax for flood
damage reduction areas, or for the case when putting flood prevention
measure into effect
-Flood damage insurance and financial product according to ups and downs
of the water-related disaster risk
Example: Setting of the flood damage insurance rate according to ups and
downs of the water-related disaster risk in land, the insurance rate and
finance charge privilege when putting flood prevention measure into effect,etc.(Incentive of information)
The visualization of implementation situation and effect for measures in theareaExample: Visualization maps of the measure for the implementation rates of
storage facilities
-Commendation system and introduction for the measures with high
contribution and innovative contribution
Example: Commendation system for contributors on flood fighting, best
example books (introduction of private sectors contributing to disaster
prevention and reduction, etc.)
(6) Establishment of the platform where the "River Basin Disaster Resilience
and Sustainability by All" measures are arranged among stakeholders in a
basin
- For the deliberate implementation on the River Basin Disaster Resilience
and Sustainability by All, it is necessary to share the information on the
evacuation and flood fighting activities coordinated by stakeholders in the
large-scale flood prevention conference etc. as well as river works and dam
construction in the river improvement plan, and coordinate the
stakeholders ’ basin activities for water-related disaster reduction and
prevention such as land use and rainwater storage penetration facilities.
- Therefore, the platform where sharing water-related disaster risk
information among stakeholders in the basin and coordinating the "River
Basin Disaster Resilience and Sustainability by All " measures should be66established.
-It is necessary to study appropriate evaluation methods on the applied area
and effect for each stakeholder’s measures, in order to coordinate various
measures for risk reduction in the whole basin. Each stakeholder has to pile
up the improvement based on monitoring as well as evaluating the effort, as
well as share the information at the platform for the coordination.
(7) Utilization of green infrastructure using the various functions of natural
environment
- The "River Basin Disaster Resilience and Sustainability by All" should be
promoted through utilizing various functions with natural environment, and
introducing the concept of green infrastructure which advance the
sustainable and attractive land, urban and community planning.
- The-basin water holding, the preservation of the overflow function, the
revival and the utilization of the rice paddy and farmland including the
abandoned cultivation place are sometimes effective as flood control
measures we well as the preservation and creation of natural habitat with
the environment.
- The " River Basin Disaster Resilience and Sustainability by All " should
contribute to the sustainable community building cooperated with flood
prevention appropriately, considering multiple factors of the environment,
through preserving and creating natural environment considering ecological
network, revitalizing local economy collaborated with river town planning,
and creating various activities.
- In the phase of disaster response and recovery, it is desirable to consider
the climate change impact, ecological network, and the multiple function of
the place for an ecosystem network, be also conscious of a show of the
multilateral function a place during the water-related disaster prevention
works.
Reference (in Japanese)1)https://www.mlit.go.jp/river/shinngikai_blog/chisui_kentoukai/pdf/04_teig
enhonbun.pdf2)https://www.mlit.go.jp/river/shishin_guideline/pdf/shinsuisoutei_honnbun
_1507.pdf673) https://www.mlit.go.jp/common/001157882.pdf687. The policy which should be put into effect promptly
Among the concrete water-related disaster countermeasures shown in
Chapter 6, those which should be put into effect promptly are indicated
below.
(Change on plans and design standards considering future climate change)
-Reconsideration of river basic management policy and the target of river
improvement plan
- Target flow setting for unregulated hydrograph by using forecast
calculation of rainfall considering the impact of climate change
* The calculation water level of the mouth of a river for river channel
planning considering future sea level and the rise of tide
-Promotion of med- and long-term planning of urban flood prevention by
sewage considering climate change
* Sewage plan rainfall setting by using rainfall forecast considering climate
change
-Reconsideration of a coastal protection basic policy and a coastal protection
master plan
* The tide level setting for coastal protection by using forecasted tide level
considering climate change
- Design standard change for securement of the function of the facilities and
safety
* The designing by reconsidering river erosion and sediment control
technical standards and the technological standards on coastal protection
facilities, etc., and considering the impact of climate change as of passed
duration of facilities
(Acceleration of prepared disaster risk reduction)
- Acceleration of prepared disaster risk reduction so far for early
manifestation on the implementation effect
-The "River Basin Disaster Resilience and Sustainability by All" measures
which should be put into effect early are indicated for acceleration of
prepared disaster risk reduction
* For example, the acceleration of prepared disaster risk reduction
combining structural and non-structural measures, by showing the picture
of the measure which should be conducted in the whole basin immediately
in major river basins in the whole country
(Further embankment reinforcement)69-Embankment reinforcement aiming at "persevering embankment" which is
difficult to be burst even when flood and wave overtopping
* Urgent and immediate embankment reinforcement in the narrow part,
bridge upstream, merging section and kink section where it takes some
periods to ease rising water level
* Urgent reinforcement of coastal dyke based on importance in the back
place and the geographical topographical conditions, etc.
(Waterproofing of sewage facilities)
-Deliberate measures based on technological standards setting for
waterproofing on sewage facilities
(Various stakeholder participation from private sectors etc.)
-Reinforcement of the flood control function of existing dams including water
supply reservoir
* A flood control agreement is concluded for preliminary discharge written
in the dam operation rules as well as the clarification of system location of
the water supplier dams and the improvement of facilities when necessary
on dams where certain effect is expected on the flood control function
improvement
* Flood control planning considering the effect of preliminary discharge
* Substantiality of outflow restraint measures and further application in the
country
* Establishment of system and support for further rainwater discharge
restriction including rainwater storage penetration facilities by local
government, the individuals and private sectors and their improvement
* Clarification of systematic placing on the outflow restraint measure as well
as outflow restraint measures which shows the water-related disaster
reduction and prevention effects according to the basin characteristics in
river basins all over the country including the local areas.
* Utilization of green infrastructure using the various functions of the natural
environment
(More risk information on land)
-Blank area of water-related disaster risk information to be canceled
* Prompt designation of expected flood area and early announcement of
water-related disaster risk on middle and small rivers outside the risk
information, coastal area and sewage70* Improvement of the abstraction precision of the district for landslide
disaster hazards
- Utilization of water-related disaster risk information like expected
inundation zones at urban planning
* Promotion of urban planning, housing and flood proofing by mapping and
announcing of multiple flood hazard information such as expected
inundation of external force scale with middle and high frequency, and
cooperating with stakeholders
(Community building and device of how to live)
-Reinforcement of development restraint in the district where water-related
disaster risk is high and promotion of leading policy to the area where the
risk is lower
* Information sharing of water-related disaster risk cooperated with
stakeholders and consideration of land use planning and flood prevention
measures considering water-related disaster risk
- Dissemination of information for the device of how to live based on
water-related disaster risk
* The substantiality of information dissemination and tools so that land and
house dealer can explain right water-related disaster risk, organize
workshops and identify the data of inundation depth by accurate map
(Reinforcement of evacuation system)
- The mechanism to support the independent evacuation ability of the
resident
* Making my timeline which describes the disaster management actions by
each resident in advance and promoting my disaster risk reduction mapping
for evacuation route during the disaster and hazard locations in the map
-Substantiality of disaster prevention information and device
* The substantiality of information to suggest each evacuation behavior and
damage reduction actions, improvement of plain terminology and
improvement of how to disseminate information
-Securement of safe evacuation
* Building of the system and the mechanism to utilize private buildings for
evacuation
* Considering appropriate evacuation cooperated with related agencies
which secure evacuation places and infection measures in the evacuation
places71(Reinforcement of TEC - FORCE)
- Reinforcement and substantiality of national assistance system
* Reinforcement of national support to affected local government by system
reinforcement of MLIT regional development bureaus and capacity building
through training and education etc.
* Establishment of the mechanism where TEC - FORCE staffs take actions on
behalf of affected local government
* Installment and stock of drone, ICT equipment and other materials and
equipment
-Promotion of the TEC-FORCE activities with cooperation of public and
private sectors
* The consideration to secure the system performance of the disaster
agreement
(Support to disaster emergency measure for affected local government)
-Expansion of support of disaster emergency measures for affected local
government by a country
* Expansion of the support rivers where the national government
implements on behalf of affected local governments, the damage survey at
the rivers and river dredging supports
(Substantiality of observation and new development)
-Substantiality of observation system and advance of forecast technology
* Reinforcement of the observation on rainfall, water level and flow, and
monitoring system by CCTV
* Substantiality of dam operation advance and evacuation system by
advancing forecast on rainfall and flow etc.728. Conclusion
Before the River Law was established at Meiji Period, every resident at
community joined the water-related disaster risk reduction collaboratively
through ordinary embankment improvement, ring dikes or secondary dikes
for community protection, flood proofing, temporary evacuation for
community, and flood fighting during flooding.
The measures to improve the safety level have been mainly the
improvement of river and sewage facilities by the administrators while the
developers in the basin have played some roles on establishing storage
facilities for discharge restriction in the basin where the change of rainfall
and its discharge characteristics has exceeded the flood prevention facilities
because of rapid urbanization after the WWII.
However, the torrential rainfalls all over the country, influenced certainly
by yearly increased impact of climate change, will further mightier from now
on. The research on the change of external force because of climate change,
its impact on water-related risk and measures, the effective measure in
field, should be promoted and further updated based on the various
accumulated observation data and developed research and development in
the future. There will be no room around a question that the necessity on
effective flood prevention facilities increases. Further, more device and
community participation will be desired in order to reduce the damages of
more frequent torrential rainfalls even a little.
A basin can be a family. It is desirable that all stakeholders in the basin
can cooperate than before, and think what they can do for the total damage
reduction, under the recognition of each resident membership.
On the other hand, recently, the planned suspension of railroad service and
the other actions preparing for the risk have become recognized widely for
promptly responding to the normal. Such movements should be connected
with each action by upgrading the social recognition to water-related
disaster risk and its dissemination, and further raising the social
understanding on water-related disaster risk.
During the argument for this council report, COVID-19 infection
expanded coincidently. Under the emergency declaration all over the
country, various actions have been taken place for the reduction of contact
opportunity. When a disaster occurs, evacuation is essential to avoid the
hazards, as well as to advance the actions for infectious risk reduction as
possible. While new lifestyle was proposed and remote-working rapidly
spread, people’s values of thinking changed dramatically and the society
including their way of work and living may also change. Both COVID-1973infection and large-scale water-related disaster occur in very low frequency,
but load quite heavily on the social system comparing to the normal once
they occur. The concept on the management for both events are similar, and
the whole society should well consider preparation in advance and measures
for early response and recovery in order to minimize the damage by
simulating the worst case scenario in this country vulnerable to natural
disaster.
The efforts toward more severe water-related disaster considering
climate change should be a long battle. During the efforts, there might be
unexpected various change such as social change, people’s change on their
value conception and technical innovation. However, there is no room for a
doubt that sustainable and inclusive response are always necessary as well
as continued investment for disaster risk reduction and prevention. Rather,
these new challenges should be considered as the opportunity for
sustainable economic growth and people ’ s abundance rise during the
matured steady growth period, for more privileged and rich society in the
world stepping forward toward future generation.
The policy and technology in this council report should become reality as
early as possible, under the strong belief for water-related disaster
prevention, and hopefully upgraded to better policy and technology under
continued validation.74National Land Development Council, River subcommittee
Water-related disaster risk reduction considering climate change Working
Group
Member Lists
Akita Noriko, Chiba University
Asahi Chisato, Tokyo Metropolitan University
Ikeuchi Koji, University of Tokyo
Onishi Kazufumi, Mayor of Kumamoto
Oohashi Hiroshi, University of Tokyo
Oki Taikan, University of Tokyo
Kato Takaaiki, University of Tokyo
Koike Toshio, ICHARM (Chair)
Shimizu Yoshihiko, Gunma University
Shuin Yasuhiro, Utsunomiya University
Suzuki Eikei, Governor of Mie Prefecture
Takahashi Koichi, Sompo
Tajima Yoshimitsu, University of Tokyo
Tanaka Risa, The Graduate School of Project Design
Nakakita Eiichi, Kyoto University
Noguchi Kikumi, Hitotsubashi University
Fujisawa Kumi, SophiaBank
Furumai Hiroaki, University of Tokyo
Motomura Yukiko, Mainichi Newspaper
Yamori Katsuya, Kyoto University
WG sessions
- 18 October 2019 MLIT asked for the Council
- 24 October 2019 Council asked for the River subcommittee
- 22 November 2019 WG1
- 17 January 2020 WG2
- 17 March 2020 WG3
- 26 May 2020 WG4
- 26 June 2020 WG5