●Messages from Departments and Centers of NILIM

To reduce damage caused by natural disasters
GOTO KojiChief, Research Center for Disaster Management(Key words) Natural Disaster, reduce damages, monitoring/warning/forecast, evacuation on warning

most serious of all heavy rain disasters since Word

1. Frequent natural disasters
Looking back on natural disasters that occurred inWar II.

2011, Shin-moe-dake of the Kirishima mountains

Approximately 70% of the Japanese land isstarted full-scale volcanic activity on January 26 formountainous or hilly. Its topography is mostly steep,

the first time in about 300 years; and on March 11, awith the geological formation being weak; moreover,gigantic earthquake of magnitude 9.0, the biggest everthere are a large number of active volcanoes, andobserved in Japan, hit the Pacific Ocean side ofearthquakes frequently occur. Besides, we haveTohoku region followed by a huge tsunami causing

explained that Japan has a high risk of naturaldevastating and enormous human and material damage

disasters because it rains heavily beginning with theand seriously affecting social and economic activities

seasonal rain front and when typhoons approach orin broad areas centered on the Pacific coast. Turning

make landfall in Japan. Along with the increase ofto disasters caused by heavy rain, Typhoon No. 6 inintensive rainfall in a short period of time due toJuly caused continuous heavy rain amounting to 1,000

climatemm in the Naharigawa River area in Kochi Prefecture,earthquakes and volcanic activities including the Great

triggering a debris-flow caused by a deep landslide inEast

Kitagawa village, and caused damage to national roads

Shin-moe-dake of the Kirishima mountains

and power plant facilities. Heavy rain in Niigata andhave occurred

Fukushimarecordeddisaster-preventive strength has weakened due to thecontinuous rainfall of 600 mm and more, causing

advance of the aging society and depopulation of

more

mountainous

than

prefectures,

250

also

in

July,

sediment-relateddisasters.

change,Japan

recently

EarthquakeAt

areas,

frequentandthe sameplus

large-scale

theeruption

time,natural/social

ofregionalchanges

Furthermore, Typhoon No. 12, which hit Japan inincluding financial restrictions. For these reasons, weSeptember, brought record rainfall over broad areas

can say that 2011 was a year when we strongly felt

centered on mountainous areas from western tothat the risk of disasters is increasing.

northern parts of Japan, especially in the Kii
Peninsula, where continuous rainfall exceeding 2,000

2. Responding to low-frequency but large scale

mm caused many deep landslides and approximately

disasters

200 sediment-related disasters including 17 landslide

Based on the Great East Japan Earthquake, thedams. Judging from aerial and satellite photographsCouncil for Social Infrastructure Development (Shakai

taken after the typhoon, it is estimated that theShihon Seibi Shingi Kai) and the Transportation

landslides had a volume of approximately 100 million

System3m . The heavy rainfall disaster turned out to be thePlanning

SectionoftheCouncilforTransportation Policies (Kotsu Seisaku Shingi Kai

●Messages from Departments and Centers of NILIM
Kotsu Taikei Bunka Kai Keikaku Bukai) summarized

natural disasters.

an urgent proposal “Concept of town development to(1) Monitoring and alerting people to wide area andprevent tsunami disasters” in July 2011. That proposal

large scale natural disasters

indicated that relatively frequent tsunami of a certain

In the event of a wide-area, large-scale naturallevel and tsunami which occur at an extremely low

disaster, it is essential to get the whole picture of thefrequency but cause large scale disasters are to bedamage situation as soon as possible and to take initial

hypothesized as targets for disaster prevention

responses in a proper manner. One example is the casemeasures based on structures, and that the concept thatof Typhoon No. 12 which hit Japan in September“measures to reduce damage caused by disasters

2011. Concerning landslide(protect human lives and reduce damage as much as

formed in Nara and Wakayama prefectures, the teampossible) are executed to achieve the aim of protecting

startedhuman lives by all means in whatever disasters, theSeptember 4, then on September 8, the team informed

large scale Tsunami may cause.” The proposal also

the affected local governments about predictedpresents the fact that “disasters have no upper limit" as

sediment-related disaster areas and the time they werea lesson, and mentions that the most important goal of

expected in the form of sediment-related disaster

improving social infrastructure is “to protect the lives

warning information. Our team checks the formationand daily life of people” and to consider disasters ofof landslide dams, measures their shapes and performs

all kinds without limiting them to measures against

flooding simulations in a very short time in order totsunamis; and to execute overall disaster prevention

have local governments issue evacuation warnings andmeasures by resorting to all possible “hardware” andinstructions. The initial investigations when a disaster“soft” measures for reducing damage by low

occurs are mainly investigations by helicopters or

frequency but large scale natural disasters including

taking/analyzing photographs by aircrafts; but thosebiginvestigations

earthquakes,

stormsandflood

damages/investigating

face

thedams which weredamagechallenges

situation

becauseonnight

sediment-related disasters caused by typhoons, ininvestigations are impossible or the investigations areorder to build up a strong foundation for the national

impossible under bad weather conditions. As one

land. Besides steadily improving disaster preventive

method to permit investigations of the extent offacilities, it is becoming more and more necessary anddamage even under bad conditions, we are developing

important to improve capabilities to deal withan investigation technology that uses synthetic

situations caused by disasters and think of “soft”

aperture radar (SAR), which is capable of observing

measures to support the evacuation of residents.

disaster damage even during the night or under badweather conditions, to monitor large scale landslides,

3. For the improvement of risk management

landslide dams, flooded areas, and areas withorganization

concentrated damage toThe following presents research and development

infrastructure.

which the Research Center for Disaster Management

Furthermore, in order to grasp the occurrence of deep

conducts in the midst of the increasing need forlandslides as early as possible, we are developing ameasures on the “soft” side - including the early grasp“Large scale landslide monitoring and warning systemof the damage situation, and monitoring and warning(tentative name)" which combines high precisionsystems for the purpose of reducing damage caused byrainfall monitoring by the above mentioned satellite

buildings and public

●Messages from Departments and Centers of NILIM
remote sensing technology and X Band MP radar, andand especially complex natural disasters from excess

seismometers to sense ground vibration that isexternal force, earthquake, flooding beyond ourgenerated when a landslide occurs, etc.

expectations which have not been well considered, weIn addition, to reduce damage caused by flooding innow review damage caused and the structure of thesmall to medium size rivers caused by local intensive

influence of such a disaster, construction methods for

rainfall, consideration is being given to a “Monitoringdisaster scenarios, and disaster risk and impact

and forecasting system against flood damage” which

evaluations etc.; and we are considering how risk

combines providing real time monitoring devices for

management against excess external force andan entire drainage basin, inundation inside the leveecomplex natural disasters should be done or how

and inundation by river water; rainfall monitoringhighly robust basic facilities for disaster prevention

using X Band MP radar; and river water level forecast

should be planned.

through a distributed rainfall-runoff model and soforth.

4. Improvement of regional disaster-prevention(2) Technology for the immediate estimation ofcapacity

earthquake damage

We have introduced initiatives from the perspectives

Inspections will be made of facilities underof understanding damage status, and of collecting andmanagement immediately after the occurrence of aanalyzing disaster information. To reduce damage

large scale earthquake, but it is predicted that it shouldcaused by large-scale natural disasters, communities

take longer to grasp the whole picture of the damage

and residents, who receive this disaster related

in a case where an earthquake occurs at night or in a

information,case where the damage is spread over broader areas

information and take adequate and efficient actions

and where the damage is severe. For example, after

without losing time. For that purpose, it is necessary tothe Southern Hyogo Prefecture Earthquake or theimprove

Niigata Prefecture Chuetsu earthquake, it took 10communities and residents through disaster preventive

hours or longer to grasp the entire facility damage

training, practical disaster preventive drills, passing onstatus, resulting in a period with an information blank.

the disaster preventive culture to later generations andIn order to realize quicker initial responses toso forth. For the future, we would like to work on

disasters, we are now developing methods to estimate

further deepening our considerations about improving

the distribution of seismic motion from strong motion

area disaster preventive capacity and construct reliable

earthquake records (seismic intensity, acceleration, SI

warning and evacuation systems.

theneedtodisaster

properlyunderstandprevention

capacity

thisofvalue etc.) received from the network of seismometers
immediately after the occurrence of an earthquake,[Reference]and methods to estimate damages status to facilities

1) [Concept of town development to prevent tsunami

under our own control such as river facilities or roaddisasters] proposed urgently by Council for Social

facilities from seismic motion distribution.

Infrastructure Development (Shakai Shihon Seibi(3) In preparation for excess external force andShingi Kai), Transportation System Planning Section

complex natural disasters

in the Council for Transportation Policies (Kotsu

With the focus on natural disasters including
earthquakes, heavy rainfall and volcanic activities,

Seisaku Shingi Kai Kotsu Taikei Bunka Kai Keikaku
Bukai) in July 2011.