non-structural measures against landslides and debris ... · non-structural measures against...
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Non-structural measures against landslides and debris flows in Japan
Keigo NAKAMURA, Ph.D
8 Sep. 2009Sabo (Erosion and Sediment Control) Department,
Ministry of Land, Infrastructure, Transport and Tourism (MLIT)
Earthquake country~20% of the world’s earthquakes
Distribution of epicenters of earthquakes with M=3.0 or
more in 1998-2000
Volcanic country~10% of the world’s active volcanoes (108 active volcanoes)
Japan: the hot spot of landslides and debris flows
Depth of hypocenter (km)
Magnitude of earthquake (M)
Vulnerable and steep geologyWith many faults and complex geology, the Japanese islands are vulnerable to collapses.
Japan: the hot spot of landslides and debris flows
Rainy countryHeavy rains caused by the rainy season and typhoons.
台
16台
6
台
4
台
18
台
15
台
11
台
10
台
21 台
22
台
23
Landfalls of typhoons in 2004
0
200
400
600
800
1000
1200
1400
1600
平成13年 平成14年 平成15年 平成16年 平成17年 平成18年 平成19年
539
897
2,537
814
2500
509
1,441
1400
10
20
4 4
23
30
25 30
Num
ber of the dead and missing: person
Number of the dead and missing
Number of disasters
60
50
40
62
0
Num
ber o
f sed
imen
t-rel
ated
dis
aste
rs: c
ase
Landslides and debris flows in recent years
966
2001 2005 2006 20072002 2003 2004
Three major categories against landslides and debris flows mitigation
Hard
Warning &
Evacuation
Restriction&
regulation
Non structural measures
Structural measures
Essences of Public Warning
Timingand
Area
AREA
Hazard area Special hazard area100m
Presumed maximum force
Height of debris flow
Warning area designated by the Landslides and Debris flows Prevention Law
• An area prone to landslides and debris flows shall be designated as a landslides and debris flows hazard area (Yellow Zone).
• In the Yellow Zone, – Early warning systems must be established,– Hazard map against landslides and debris flows
should be produced.– But NO RESTRICTION ON LANDUSE
Landslides and debris flows Hazard Area
• An area in serious hazards shall be designated as a special landslides and debris flows hazard area (Red Zone).
Special landslides and debris flows Hazard Area
Landslides and debris flows hazard map
TIMING
Warning information on landslides and debris flows(Sediment Disaster Alert)
•Warning information on landslides and debris flows (WILD) based on rainfall intensity and duration was launched in 2008 all through Japan in collaboration with JMA.
40
20
0
Rai
n in
tens
ity (m
m h
-1)
Index on soil moisture
Critical line (CL): Threshold for landslides or debris flows
How WILD works?
Disaster baseAnnouncement base
~12% of WILD announcement predicted landslides or debris flows.
138
991 # of landslidesand debris flow
Total 1129announcements
295
121
# of WILDannouncements
~70% of landslides and debris flows was picked up by WILD.
Total 416disasters
Notify weather advisory, warnings and WILD through diverse media
Push based mobile services
土砂災害危険度情報(5kmメッシュ)
7月19日 15時00分現在
・ 前の画面へ戻る・ 市町別発表状況へ・ TOPへ
1時間前を表示
■ レベル3(現在土砂災害警戒避難基準に達している区域)■ レベル2(1時間以内に警戒避難基準に達すると想定される区域)■ レベル1(2時間以内に警戒避難基準に達すると想定される区域)
【危険度情報】
loudspeaker broadcasting
Individual receiver
Urgency of time Rumbling of mountain, rumbling of ground
Abnormal turbidity of flowing water
Driftwood, sound of rolling rocks in the stream
Debris flow
Slope failure Increase in spring water
Turbidity of spring water
Cracks
Constant fall of small stones
Debris flow
Slope failure
Landslide
Landslide
Frequent fall of small stones
Cracks Turbidity of well water
Rumbling of mountain, rumbling of ground
Increase in spring water
Abrupt decrease in water level
Education on symptoms of landslides and debris flows