1ReportonRebuilding Flood-Conscious Societies
in Small and Medium River Basins
January 2017
Council for Social Infrastructure Development2Contents
1. Introduction - Accelerate Rebuilding Flood-Conscious Societies ............................... 3
2. Typhoons in the Hokkaido and Tohoku regions in August 2016 .................................. 5
2.1 Outline of Torrential Rains ........................................................................................ 5
2.2 Outline of Disaster Damage ....................................................................................... 6
2.3 Features of the Disasters............................................................................................ 7
3. Small and Medium River Basins under Changing Climate and Declining Populations
................................................................................................................................................ 9
4. Key Activities Based on the Report of December 2015................................................ 11
5. Key Challenges to be addressed..................................................................................... 13
6. Measures Needed in Small and Medium River Basins................................................ 15
6.1 Basic Policy................................................................................................................ 15
6.2 Measures to be taken ................................................................................................ 17
7. Conclusion ....................................................................................................................... 2331. Introduction - Accelerate Rebuilding Flood-Conscious Societies
In August 2016, a series of typhoons caused torrential rainfall, bringing about levee
breaches at MLIT-managed rivers in Hokkaido, and inundation around Prefecture
managed rivers in the Tohoku region. Residents at a nursing home were especially
affected, due to the evacuation order being given too late along the Omoto-gawa River,
managed by Iwate Prefecture.
(MLIT: Ministry of Land, Infrastructure, Transport and Tourism)
Three typhoons hit Hokkaido in one year and one typhoon landed on the Pacific
coast in Tohoku, the first time such a series of events have been recorded by the Japan
Meteorological Agency since 1951. Unprecedented crises due to climate change already
seem to have arrived. We are concerned that the frequency and magnitude of flooding
have been growing more severe for some time. Previously unheard-of events will
happen again and again in the future.
Our flood management policy encounters the same issues that our society faces.
Rivers severely affected by typhoons are tributaries of Class A River basins managed
by the MLIT and small and medium river basins managed by prefectural governments.
These have not yet been improved. Moreover, they will be affected by serious
population decline.
After the Kanto-Tohoku Torrential Rain in September 2015, the Council for Social
Infrastructure Development recommended that we keep in mind the inevitability of
large-scale floods that exceed the limited capacity of facilities and that our whole
society must always be prepared for them.
Based on this recommendation, the MLIT embarked on a new policy: Rebuilding
Flood-Conscious Societies in MLIT-managed river basins nationwide, and expanded it
to Prefecture-managed river basins.
The disaster affecting small and medium river basins in 2016 underlined the need to
accelerate policy promotion and fully cover Prefecture-managed river basins. All
possible measures should be implemented without any hesitation, to gain an advantage
before the next flooding season.
Through intensive promotion, we should set targets to eradicate human loss due to
delayed evacuations and to ensure the social functioning of local communities.4The basic policies are:
1) Saving all human life by sharing risk information with local communities,
including nursing homes and other facilities
2) Protecting core facilities through prioritized and intensified investment in
efficient and effective projects, including existing facilities, to support socio-
economic activities
3) Integrating all stakeholders to promote the policy of "no human loss" and the "the
continuity of local communities" through a mutual support network
Adding to the 2015 report, the recommendations should be institutionalized swiftly,
and realize Policy Vision on rebuilding Flood-Conscious Societies in order to save
precious human lives and reduce disaster damage to regional socio-economies as far as
possible.52. Typhoons in the Hokkaido and Tohoku regions in August 2016
2.1 Outline of Torrential Rains
In August 2016, Typhoon No. 7 (Chanthu), No.11 (Kompasu) and No.9 (Mindulle)hit
Hokkaido, and the powerful Typhoon No. 10 (Lionrock) landed on the Pacific coast in
Iwate Prefecture. The succession of typhoons caused intensive rainfalls in the
Hokkaido and Tohoku regions. That month’s precipitation was greatest at 89 of 225
stations in Hokkaido exceeding the average by 2 to 4 times in a wide area of Pacific
coast in Eastern Hokkaido. Record-breaking precipitation was observed at 8 sites for a
24-hour period, and at 19 sites for a 72-hour period in Hokkaido and Tohoku.
Intensive Rainfall Caused by Typhoon No.10
Although typhoon No.10 did not land in Hokkaido, a continuing inflow of hot and
humid air caused over 300 mm of rain, especially on the right side of the Tokachi River
basin.
In the Tokachi River basin, 505 mm of cumulative rainfall was recorded from
August 29th to 31st on the upper Tottabetsu. The mean rainfall exceeded its design
rainfall at the upstream basin of Natai-bashi. Flood discharge surpassed the design
flood discharge stipulated in the Satsunai river improvement basic policy.
In addition, on the Sorachi River in the Ishikari River basin, nearly double of the
maximum experienced rainfall was observed, for instance 292mm of rainfall during a
12-hour period at the Kushinai observatory. And at the Kanayama Dam in the
upstream area, the largest inflow was recorded since the Dam had come into operation.
In the Tohoku region, concentrated torrential rains broke the record in the coastal
area of Iwate Prefecture. On the Omoto River, managed by Iwate Prefecture, a record-
high 66mm hourly rainfall was observed at Iwaizumi, and maximum flood discharge
was close to the design flood discharge at Akashika.
Intensive Rainfall Caused by a Series of Typhoons
Typhoons No. 7, 11 and 9 landed in Hokkaido one after another on August 17th, 21st
and 23rd. Moreover, another typhoon, No. 10, approached Hokkaido a week later. These
typhoons brought record heavy rains.
On the Tokoro River, the cumulative rainfall from August 17th in the whole river
basin was at a record-high level. Due to typhoon No. 11, the water rose again after
having dropped temporarily. Flood discharge at Kitami exceeded the designed flood
discharge in the river improvement basic policy. The high water level continued due to
rainfall brought by typhoons No. 9 and 10.62.2 Outline of Disaster Damage
In Hokkaido, four levee breaches and five inundations occurred on the MLIT-
managed sections. Five levee breaches and 73 inundations occurred on Hokkaido-
managed sections. These caused 3 deaths, 2 missing persons, 13 injuries, 30 completely
destroyed houses, 1,019 partially destroyed houses, and 927 flooded houses.
In the Tohoku region, flooding occurred on 20 rivers in 12 river basins managed by
Iwate, Aomori and Miyagi Prefectures. In Iwate Prefecture, extensive damaged
occurred, including 20 deaths, 3 mission persons, 4 injuries, 472 completely destroyed
houses 2,359 partially destroyed houses, and 1,466 flooded houses.
(1) In Hokkaido
Damage in MLIT-Managed River Basins
- A levee breach on the Hokkaido-managing Tottabetsu River caused a flood covering
50 hectares along the Satsunai River.
- On the Sorachi River of Ishikari River basin, a levee breach in the upstream
triggered another breach in the downstream. These caused 130 hectares of
inundation and damage to 183 houses, a food processing factory, and other
properties.
- Four overflows on the Tokoro River and a levee breach on the upper
Shibamyamazawa River caused 504 hectares of inundation and soil erosion on
farmlands.
Damage in Hokkaido-Managed River Basins
- On the Pekerebetu River and Pankeshintoku River of the Tokachi River basin,
rising riverbeds due to sediments caused riverbank erosion to wash houses away.
The channel expanded and washed out the backfilling of a bridge abutment.
Damage to Transportation
- Many bridges on National Highways No. 38 and 274 collapsed, closing off traffic
connections in the Hidaka Mountains and temporarily isolating the Tokachi region.
The Railway network in Eastern Hokkaido was also paralyzed due to collapsed
bridges and other damage.
Damage to Agriculture
- Damage to agriculture amounted to 38,927 hectares of farmland and JPY 54.37billion in total. Half of the damage was to potato and carrot crops that supply 83%
and 92% respectively of the national market. This caused prices to soar nationwide.
- Affected not only by flood damage but by also soil erosion, it took a long time for
local agricultural industries to recover, which deeply affected economy.
(2) Outline of Damage in Iwate Prefecture.
Prefecture-managed River Basins
- Along the Kuji and Akka Rivers, floodwater and driftwood blocked the channel at
bridges and washed away houses along the riverbank.
- On the Omoto River, a great deal of debris and driftwood, combined with intensive
rainfall caused the inundation over an area of 340 hectares, affecting 844 houses.
Damage to Transportation
- Flooding stopped many national and regional roads near rivers, stranding over
1,000 people.
Damage to a Nursing Home
- On the Omoto River, the narrow valley flooded when intensive rainfall caused the
water to rise rapidly. Human suffering due to the slowness of evacuation occurred
at a nursing home.
2.3 Features of the Disasters
The disastrous flooding caused levee breaches and inundation due to overtopping or
erosion of both MLIT-managed and Prefecture-managed rivers. Specific features of the
disaster were:
- Extensive human suffering due to delay in evacuation at a nursing home, which was
caused by inappropriate information distribution and rapidly rising water in the
mountainous area
- Inundation of narrow valleys in mountainous areas, which caused damage to
nursing homes, factories, houses, and other property
- Channel blockages by debris and driftwoods at bridges in small and medium rivers
- Traffic disruptions on the road and rail networks due to channel blockage at bridges
and the erosion of roads, which caused logistics failures and stranded communities.
- Soaring prices of farm products nationwide because of damage to agriculture
production of high-rate market share.8In addition, the Kitagawa River in the Gokase River basin in Miyazaki Prefecture was
hit by flooding caused by Typhoon No.16 (Malakas) in September 2016. The discharge
was on the same scale as that which had occurred in 1997, but the damage was
dramatically smaller because of the flood risk reduction project that was implemented
after 1997, including building open levees and land heightening.93. Small and Medium River Basins under Changing Climate and Declining Populations
The rivers affected by the series of typhoons were tributaries of Class A Rivers
managed by the MLIT and small and medium river basins managed by prefectural
governments.
These small and medium river basins are prone to flooding due a to relatively small
discharge capacity against intensive and frequent torrential rainfall caused by climate
change. In addition, communities along the rivers have less anti-disaster capacity
because of declining and aging populations in this remote mountainous area. These
communities are vulnerable to natural disasters, including flooding.
(1) The Situation of Small and Medium River Basins
Small and medium rivers generally have a small catchment area, steep riverbed
slopes and short channels. The channels normally have a trench-shape or single cross
section between levees, and typically allow the run-off water to rise quickly when there
is intense rainfall. Large-scale flooding upstream often outflows from the channel,
making the valley a whole single channel. Landslides produce debris and driftwood
which may block channels and add to the rise in water level.
River improvement has been carried out in downstream areas of large-scale rivers
which have concentrated populations and assets which can suffer damage caused by
flooding. Therefore, small and medium rivers, which have more scattered populations
and assets, rarely have a river improvement plan, and their improvement is at a low
level.
Prefecture-managed rivers extend to about 113,000 km (77,500 km of class-A rivers
and 35,900 km of class-B rivers), which is much longer than the approximately 10,600
km of MLIT-managed rivers. These remain with insufficient water level observation
and river surveys.
(2) Responses to Climate Change
Regarding climate change adaptation and water-related disasters, the Council for
Social Infrastructure Development discussed countermeasures and presented a report
in August 2015. It suggested taking flexible approaches, taking into account various
influences through:
- Arranging procedures of river improvement to reduce damage if flooding occurs
- Designing levees to prolong time before they breach after overtopping
- Taking a step-by-step approach to deal with higher external forces10The 5th IPCC assessment report assumed that extreme precipitation will occur more
intensively and frequently in mid-latitude areas by the end of the 21st century. This
means that small and medium rivers will suffer from quick and large floods more
frequently, causing more severe damage.
Based on the 2015 report, in small and medium river basins, structural and non-
structural measures should be implemented flexibly and swiftly to save human lives
and minimize damage.
(3) Responses to Population Decline
Small and medium rivers flow through mountainous areas. These areas will have
difficulty in resilience against natural disasters because a low birthrate, a declining
population and aging communities will affect proper operations during floods such as
sluiceway controls, flood fighting activities, evacuations and other operations.
The National Spatial Strategy (endorsed by the Cabinet in 2015), made the
following recommendations for mountainous areas where there are many small and
medium scale rivers:
- Promote the development of "small hubs" where services and other functions are
concentrated.
- Develop multi-functioning communities to create jobs, operate farmlands, and
prevent disasters.
- Improve safety through land use control in high-risk zones, while taking into account
local conditions.
In accordance with this policy for flood control in small and medium river basins,
river administrators and all stakeholders should share flood risk information, raise
awareness of risk reduction and promote structural measures to protect important
local hubs and take non-structural measures to enable appropriate evacuation behavior.114. Key Activities Based on the Report of December 2015
Based on the report of December 2015, the MLIT formulated a new policy: Rebuilding
Flood-Conscious Societies and established committees to share flood risk reduction
targets among river administrators, municipalities and all stakeholders in each MLIT-
managed river basin in order to promote structural and non-structural measures
integrally.
Flood Risk Reduction Committee
The Flood Risk Reduction Committee had been established in 127 out of a total of 129
areas (98%) by the end of November 2016 and is sharing current flood risk information
and countermeasures. 123 committees (93%) have discussed swift and smooth
evacuation, appropriate flood fighting operations, drainage after inundation, the
operation of facilities, and other matters, and have compiled a Local Action Plan
detailing practical 5-year activities for all stakeholders.
Non-structural Measures
Regarding non-structural measures, the MLIT introduced a Time-series Disaster
Operation Plan which focuses on the issuance of evacuation advisories. 611 out of 730
municipalities (84%) had already installed the plan as of the end of November 2016.
In addition, the MLIT designated house collapse hazard zones where flood waters
might destroy houses, and announced them in 69 of 109 MLIT-managed river basins as
of the end of November 2016.
Moreover, the MLIT improved the web-site Disaster Information on Rivers to provide
live views of rivers and probable inundation zones, adding to the ongoing distribution
of information on river water levels, radar rainfall data and flood warnings. On-site
information is also provided to GPS-equipped smartphone users. Since September 2016,
the MLIT has operated an active information delivery service for the Kinu River in the
Tone River basin (Joso, Ibaraki Prefecture) and the Hiji River (Ohsu, Ehime
Prefecture). There are plans to expand the service area.
In addition, the MLIT has created a video program entitled "Lessons for Mayors in
Flood Fighting Operations" in order to help mayors understand flood management and
disaster information management.
Structural Measures
River administrators are promoting conventional flood disaster preventive measures
such as heightening levees, excavating riverbeds and preventing seepage, on 1,200 km12of prioritized river sections.
In parallel, river administrators have adopted new crisis-management structural
measures which prolong the time before levees are breached in cases of over-topping.
These measures have been introduced at 1,800 km of temporary levees which are risky
but not prioritized due to up and downstream balance and other factors.
As mentioned above, under the policy "Rebuilding Flood-Conscious Societies", the
MLIT and other river administrators are promoting structural and non-structural
measures nationwide mainly to confirm effects in some regions.
On the Tokoro River, where in August 2016 Typhoon No.11 (Kompasu) flooded 215
hectares, the municipality completed a smooth evacuation with nobody left behind
through earlier evacuation advisories depending on the time-series disaster operation
plan and a hot-line from the MLIT, as discussed by the Tokoro River Flood Risk
Reduction Committee.
The MLIT and local committees are publishing such good practices through websites
and social media. It is recommended that river administrators, municipalities,
residents, and private sectors collaborate to promote disaster risk reduction and follow
up the policy.
The time-series disaster operations and the hot-line are proving to be effective in
MLIT-managed rivers and being adapted to prefecture-managed rivers. It is
recommended to develop approaches that meet local needs and conditions in small and
medium river basins.135. Key Challenges to be addressed
Focusing on issues highlighted by the recent series of typhoons, considering the
current situation in small and medium river basins affected by climate change and
population decline, reviewing the new policy of rebuilding flood-conscious societies, the
key challenges to be addressed are as follows:
Structural and Non-structural Measures in Cooperation with Related Organizations
- As Flood Risk Reduction Committees are working effectively in MLIT-managed river
basins, similar approaches are required in Prefecture-managed rivers.
Information Sharing for Appropriate Evacuation
- Errors in communicating to mayors hamper appropriate issuance of evacuation
advisories.
- On rivers not designated as water level warning river, no information to assist in
issuing evacuation advisories is provided.
- Designation of water level warning rivers, to provide local flood risk information, has
not been promoted.
- Flooding information is not fully understood by nursing home administrators.
Practical evacuation plans have not been prepared. Evacuation drills are not being
carried out. As a result, early evacuation of the physically disabled has not been
prepared.
Functional Maintenance of River Facilities
- Due to a low birthrate, an aging and declining population, and changing
communities, it is becoming difficult to secure operators for sluiceways. River
facilities operations will be difficult in the future.
Land use in Accordance with Disaster Risk
- In the recent flooding, a nursing home and several newly-built factories along the
river were damaged. From the viewpoint of security against flooding, the land use
is not appropriate.
Flood Control in Small and Medium River Basins
- Due to up-and-downstream balance, financial constraints, and other factors, the
current level of improvement is not high. The frequency of intensive rainfalls is
increasing. Floods exceeding the capacity of facilities capacity occur in many areas.14- Roads, railways, farmlands, and other property have suffered extensive damage.
Recovery and reconstruction take too long and socio-economic effects extend
beyond the damaged areas.
Support for Municipalities
- Prefecture-managed rivers are numerous and long. Municipalities have decreased
their number of employees and lack experience. When serious situations occur,
disaster response will be problematic in such areas as information management. In
addition, when there is damage in municipalities, it will be impossible to carry out
disaster recovery quickly.
- Due to declining and aging membership of flood fighting teams, local institutional
systems have been weakened. Local disaster resilience has suffered.156. Measures Needed in Small and Medium River Basins
6.1 Basic Policy
Based on major damage caused by the typhoons, the current situation in small and
medium river basins affected by climate change and declining populations, as well as
actions taken so far and issues still to be addressed, with a strong determination never
again to experience such painful damage, we should endeavor to:
- ensure evacuation in order to save all human lives, and eliminate human loss due to
delays in evacuation
- have administrators protect core facilities so as to minimize socio-economic impacts,
and ensure the continuity of communities
We should make efforts to expand and fulfill the policy of "Recreating Flood-
Conscious Societies through the following:
- Ensuring steady-going evacuations to save all human lives, including those of
nursing home residents, through risk information sharing in local
communities
- Protecting core facilities crucial for local socio-economies through prioritized
and intensified investment in efficient and effective projects, including
improvement of existing facilities, for socio-economic activities
- Integrating all stakeholders in order to eradicate human losses and to ensure
local community continuity
Focus of This Report
The rivers damaged by the series of typhoons were tributaries of Class A Rivers
managed by the MLIT and small and medium river basins managed by Prefectures,
where river improvements had been somewhat delayed. Some urbanized rivers had
been covered by the Climate Change Adaptation Policy since 2009. Therefore, this
report focuses on small and medium rivers running through areas with low-density
population and property.
Flood risk information sharing
To promote flood control in each region, firstly, river administrators should provide
flood risk information such as the location of probable inundation zones at normal
times, and a real-time water information system to enable emergency responses such
as evacuation advisories.
However, water level observation is insufficient in small and medium river basins.
Even in such regions, river administrators should install simplified water gauges,16conduct river surveys, simulate probable inundations, and share as much information
with communities as possible. Roadside indicators of past water depth are also an
effective way to raise residents’ awareness in their daily lives.
In addition, administrators in charge of disaster management, social welfare, and
medical care should properly understand the shared information, consider
countermeasures and implement them in normal times before flooding occurs.
Steady-going Evacuation of Nursing Homes
In the nursing home affected on this occasion, the manager did not understand the
flood risks, thus exacerbating the damage. River administrators and other stakeholders
should raise the awareness of the management of every facility.
Because nursing care recipients require considerable time for evacuation, the facility
managers should prepare practical evacuation plans and carry out evacuation drills in
cooperation with local communities. Preparation on a daily basis is recommended in
order to ensure smooth evacuations.
Prioritization and Implementation of River Improvement
River improvement has been promoted intensively in urban areas located
downstream. The flooding hit small and medium river basins where river improvement
had been delayed due to concerns about up-and-downstream balance and financial
constraints. River administrators should invest in these areas to ensure a balance of
safety between upstream and downstream.
Therefore, river administrators should prioritize and concentrate on projects that
secure lives and property efficiently, utilize natural topography as much as possible,
select localized countermeasures such as ring levees and land heightening, and
revitalize existing facilities for maximum retarding functions.
River administrators should also promote structural measures that assist swift and
smooth evacuations. It is important to build evacuation centers and routes with local
communities and to stop water flows using continuous embankments and natural hills.
Land Use
In this flooding disaster, a narrow valley was inundated, and a nursing home and
newly built factories were damaged. For better land use, river administrators should
actively provide flood risk information and each community should review the locations
of nursing homes, taking into account flood risks and daily needs. If a community
decides to build a nursing home in a probable inundation zone, it is necessary to17consider how to act in case of emergency. It is also important to consider using new
nursing homes as evacuation centers and community communication sites.
Cooperation among Relevant Administrators and Support for Municipalities
As recommended in the 2015 report, frequent floods exceeding the capacity of present
facilities have recently occurred; climate change may exacerbate the situation. It is
very difficult to deal with this only through conventional measures. River
administrators and all stakeholders in river basins should take measures together.
Because of climate change and declining populations in particular, municipalities will
face further difficulties in emergency response, flood fighting and disaster recovery due
to both of financial and institutional limitations.
To a build safe and secure society, the MLIT and municipalities should fulfill their
respective roles and fully cooperate in dealing with the issues. It is urgent to enhance
interdependence among all stakeholders, and establish institutional support for
municipalities, and for the MLIT to actively provide flood risk information, utilizing
the Flood Risk Reduction Committee.
6.2 Measures to be taken
Based on the basic policies, the following measures should be implemented in small
and medium river basins:
6.2.1 Structural and Non-structural Measures in Cooperation with Relevant
Organizations
(1) Flood Risk Reduction Committee to Rebuild Flood-Conscious Societies
Prefecture-managed river basins require an institutional framework to share
flood risk information and risk reduction targets during normal times, and to
promote structural and non-structural measures integrally and systematically.
It is recommended that river administrators and local mayors establish a Flood
Risk Reduction Committee, as well as a cooperative mechanism in order for a wide
range of stakeholders to carry out continuous and effective actions.
6.2.2 Steady-going Evacuations through Flood Risk Information Sharing
(1) Support for Issuing Evacuation Advisories
1) Review by Flood Risk Reduction Committees
To ensure appropriate evacuation advisories by municipalities, Flood Risk
Reduction Committees should review and recommend criteria and a time-series18disaster operation plan.
2) Hot-line between River Administrators and Mayors
To ensure appropriate evacuation advisories at Prefecture-managed river basins,
river administrators and mayors should establish a hot-line in order to share river
information directly. Furthermore, it is recommended that they compile guidelines
for confirming run-off features and local conditions.
(2) Flood risk Information Sharing
1) Promotion of water level warning river scheme
It is recommended to promote the water level warning river scheme by clarifying
designating criteria. Even before designation, in the absence of flood simulations,
flood risk information should be shared in a simple manner, utilizing data on
previous inundation areas and water depths.
2) Water Level Monitoring for Evacuation
It is recommended to develop simplified and inexpensive water level gauges and
a monitoring network to increase the number of water level observatories in small
and medium river basins.
3) Flood Risk Information Sharing (out of the designated scheme)
Without designation of a water level warning river scheme, the Flood Risk
Management Act doesn’t enforce the disclosure of probable inundation zones.
However, municipalities and river administrators should investigate past flood
records and utilize them as flood risk information.
4) Rainfall Information (out of the designated scheme)
Rivers not included in the water level warning scheme have a short run-off time.
Municipalities should utilize rainfall information for issuing evacuation advisories
so as to gain lead times for evacuation.
(3) Steady-going Evacuations of Nursing Homes
1) Awareness-raising among Facility Management
River administrators and other stakeholders should hold briefing sessions for
nursing homes to provide disaster information and evacuation information. To
deepen the understanding of administrators and staff, it is recommended that they19prepare practical evacuation plans and carry out evacuation drills in cooperation
with local communities.
2) Practical Evacuation Planning
It is recommended to ensure an evacuation system for nursing homes through
the practical evacuation plans and evacuation drills. In model districts, all
relevant stakeholders should make up practical evacuation plans and share
lessons learned nationwide. In addition, municipalities should check the
effectiveness and sustainability of their plans, utilizing inspection manuals.
6.2.3 Functional Maintenance of River Facilities
(1) Functional Maintenance of River Facilities
1) Reliable Operation of Sluicegates and Sluiceways
Due to a low birthrate, an aging and declining population, and change in
communities, it has become difficult to secure operators for river facilities. River
administrators should install operation-free sluice gates and outsource
maintenance to local organizations in order to promote more reliable operations.
2) Sophistication of river management
River administrators should sophisticate river management using the state-of-the-
art ICT technology, such as land and underwater laser surveys using drones.
6.2.4 Appropriate Land Use
(1) Appropriate Land Use
1) Flood risk Information for Appropriate Land Use
River administrators should encourage land use in low-risk areas by distributing
flood risk information in cooperation with the relevant agencies.
2) Designation of Disaster Hazard Zones
River administrators should encourage municipalities to designate flood hazard
zones where inundation can be allowed, and building ring levees in cooperation
with the relevant agencies.206.2.5 Prioritization of Flood Management Measures
(1) Flood Management in Low-density Areas
1) Prioritization Based on Local Conditions
To improve safety in areas where populations and properties are widely spread
out, and considering financial constraints, it is recommended that administrators
intensively protect core facilities, such as those concerned with disaster
management and public services.
River Administrators should proceed with efficient localized measures against
flooding, such as ring levees and residential land heightening with the
understanding of local residents gained through flood risk information sharing.
Flood Risk Reduction Committees should discuss evacuation centers and routes
in order to develop them collaboratively among the relevant stakeholders. For
example, gravel excavated from rivers may be used in land reclamation. Also,
continuous embankments and natural hills are useful for stopping floodwater flow.
2) Run-off Control in Rural areas
It is recommended that administrators promote run-off control in rural areas,
not only in urbanized areas. To maximize water storage capacity, reservoirs and
paddy fields should maintain their retarding functions with the consensus of the
owners.
3) Countermeasures against Driftwood and Debris
Driftwood captured by bridges in narrow sections of small and medium rivers,
dams up the upstream water. River administrators should share the risk with the
communities and take responsibility for preventing such occurrences with relevant
stakeholders. Debris from slope collapses also raises the water level in small and
medium rivers. River administrators should research debris flow on riverbeds. It is
recommended that they prevent problems caused by sediment in upstream basins.
(2) Flood Management in the Upstream of Main Stream and Tributaries
1) Safety Improvement Upstream and Downstream Balance
River administrators should discuss and promote structural and non-structural
measures for keeping an upstream and downstream balance.212) Review of River Improvement Plans
River administrators should review present river improvement plans through
assessment of the effects of recent heavy rainfalls.
3) Flood Control in the Upstream
River improvement should be promoted in small and medium river basins, where
improvement level is currently relatively low, to increase total safety level of the
whole river basins.
River administrators should promote pinpoint (smaller) projects which have less
impact on the downstream, and revitalize existing facilities by enhancing the flood
control functions of reservoirs or revising operational rules in accordance with
downstream river improvement. Especially in river basins damaged recently, dam
operators should consider temporary operational rules.
In Prefecture-managed river basins, it is recommended to install new technical
support for the MLIT to carry out difficult projects, such as dam upgrades, instead
of the actual administrators.
(3) Protection of Facilities Influential on the Socio-economy
1) Collaboration with Core Facility Administrators
In order to minimize the socio-economic impact of floods, river administrators
and administrators of important facilities should collaboratively enhance measures
for disaster risk reduction. River administrators should promote river
improvement and the administrators of core facilities should maintain the
functions of their facilities by themselves. For this purpose, river administrators
should share flood risk information with the administrators through the Flood
Risk Reduction Committee.
6.2.6 Supporting Municipalities in Disaster Recovery and Flood Fighting
(1) Support in Quick Recovery
1) Technical Support for Disaster Recovery
River administrators should enhance collaboration with municipalities in
capacity development through training, drills, and equipment provision.
The Technical Emergency Force (TEC-FORCE), in addition to damage
investigation, should support municipalities with a number of disaster recovery
works such as recovery planning, financial support applications and procurement
work.22In Prefecture-managed river basins, especially, it is recommended that
administrators install new technical support system which enables the MLIT
(central government) to conduct urgent and difficult works for the quickest
recovery instead of prefectures.
(2) Support in Disaster Information Management
1) Warning Stage
As large-scale and devastating disasters cause confusion and delay emergency
response, preparatory work is important. However, disaster simulation and
information management require advanced technical skills. River administrators
should support municipalities in the warning stage before disasters occur.
In addition, river administrators should prepare time-series disaster operational
plans to simulate disaster response in Prefecture-managed river basins.
2) Human Resource Training for Flood Response
Because large-scale and devastating disasters cause damage also to MLIT-
managed rivers, MLIT staff may not be able to support municipalities.
Municipalities should rely on specialists with experience of TEC-FORCE and
disaster damage assessment or on those licensed in river management. It is
recommended that municipalities promote better human resource utilization
through training programs and by listing professional careers.
(3) Support for Flood Fighting Operations
1) Involvement of the Private Sector
Because flood fighting teams suffer from personnel and financial shortages, river
administrators should support flood fighting operations such as sandbag piling,
river monitoring and evacuation guidance, involving private sector actors such as
civil contractors.237. Conclusion
This report summarizes the measures to be implemented toward "Rebuilding Flood-
Conscious Societies" in small and medium river basins, in terms of both structural and
non-structural measures, based on the social situation in areas around the rivers.
In particular, the following measures should be promoted promptly, in order not to
repeat past disasters in the next flooding season:
- Steady going evacuation at nursing homes in order to avoid repeating the tragedy of
the last flood
- Flood Risk Reduction Committee to promote risk reduction sharing good practices
- Technical assistance for disaster recovery requested by many stakeholders
In parallel, measures having a deep impact, such as flood control and land use
planning, should be discussed with careful consideration from a long-term perspective.
Currently, based on the report of December 2015, "Rebuilding Flood-Conscious
Societies" is ongoing, mainly in MLIT-managed river basins. This policy is also
effective in small and medium river basins, and is expected to be implemented
nationwide. We hope to establish a safe and secure society with no further delay.