200 - Typhoon Committee

TCAR
CHAPTER 1 - TYPHOON COMMITTEE ACTIVITIES 2007
2007
Fig. 2 Outline of aerial laser measurement
In Japan, this issue is being addressed by utilizing aerial
laser measurement that can capture wide-area terrain data
simply with high density. With these measurements, the
channel cross-section of medium- and small-size rivers
is grasped, followed by calculation of flow capacity,
which in turn contributes to surveys and evaluations of
the flood safety of rivers.
Aerial laser measurement is a technology to obtain the
three-dimensional terrain data on the basis of the distance
to the ground determined from the time difference
between the laser irradiation from the air-borne laser
scanner to the ground and the laser reflection from the
ground as well as the location data of aircraft obtained
with GPS locators and IMU (Inertia Measurement Unit).
In turn, the three-dimensional data leads to a channel
cross-section profile or topographical condition of
floodplains, which makes evaluation of the flow capacity
possible.
To evaluate the flood safety of medium- and small-size
rivers by using aerial laser measurement, measurement
of about 50,000 km 2 was made in 2005 on model rivers.
In 2006 and after, aerial laser measurement was made
of about 120,000 km 2 (of 380,000 km 2 of the national
land) for all Class-A rivers. As of July 2007, aerial laser
measurement was nearly done, and a primary evaluation
of the flow capacity was completed for 72 river
systems (of a total 109). Future plans include surveys,
evaluations, and official announcements of flood control
safety, which are scheduled for all Class-A rivers by the
end of fiscal 2007.
2.2 Publication of “Guideline on Warning and Evacuation
for Sediment-Related Disaster Prevention”
It is necessary to mitigate Sediment-Related (S.R.) Disaster
damage by dispensing information warning people about
the degree of risk of S.R. Disasters occurring. Early
Fig. 3 Image of results of evaluation on flood safety of rivers
evacuation of local residents is a key use of the warning
information. For that purpose, the Sabo Department of
the MLIT, Japan formulated a “Guideline on Warning and
Evacuation for Sediment-related Disaster Prevention,”
which was issued in April 2007. Additionally, most
prefectural governments in Japan began issuing warning
and evacuation information this year.
With a focus on lessons learned from recent problems
in warnings and evacuations related to S.R. Disasters,
the Guideline was produced to establish preparedness in
cities, governments and communities at the local level.
The main ideas the Guideline puts forward is that
communities and governments should have a common
understanding of the characteristics of S.R. Disasters
and their role sharing and that they must cooperate
to promote community preparedness. Based on these
ideas, practical procedures involved in “Information
Communication,” “Issuing an Evacuation Advice,” “the
Creation and Operation of an Evacuation Center,”
“Support for the Weak,“ and “Raising Disaster-Prevention
Awareness” are covered in the Guideline.
Today, each city in Japan has begun promoting community
preparedness as recommended by the Guideline. Also,
an English version will be uploaded to the “International
Sabo Network” Web site by the end this year.
“An S.R. Disaster Warning” is issued to support
the judgment of the head of the local authority that
officially announces an evacuation advice and voluntary
evacuation of inhabitants when an S.R. Disaster caused
by heavy rain is likely. Detailed information is also
provided through the homepage. It combines distribution
of hazard-level information and S.R. Disaster hazard
maps to promote an understanding of which areas need
to be evacuated.
Warning services were available in 38 prefectures as
of September 30, 2007, and will be available in all 47
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