International Conference Vajont2013 - 8 October

1. Oct, 2013
Vajont 2013
Possibility of Early-warning of
Large-scale Landslides
using Hydrological and Sediment
Transport Observations
in Mountain Rivers
A. Okamoto, T. Uchida, S. Hayashi,
T. Suzuki, and J. Kanbara

2. Large scale landslide
More than 1100
people were killed
on Leyte Island,
Philippines, in 2006
More than 400 people
at Shaolin Village,
Taiwan, in 2009

3. Large scale landslide
Rainfall
Snowmelt
Earthquake
Gravitational deep-seated
deformation
Volcanic activity
Human impact

4. Disasters by Typhoon Tales,
2011
Ui
umano river

5. Rainfall (mm/h)
時間雨量（ m ）
m
0
2000
40
1 600
30
1 200
20
800
10
400
0
累積雨量（ m ）
m
50
Total rainfall (mm)
1 8:00
1 2:00
00
6:
9/4 00
0:
1 8:00
1 2:00
00
6:
9/3 00
0:
1 8:00
1 2:00
6:00
9/2 00
0:
1 8:00
1 2:00
00
6:
9/1 0:
00
1 8:00
1 2:00
6:00
8/31 00
0:
Disasters by Typhoon Tales,
2011

6. Disasters by Typhoon Tales,
2011 2:00LT Sep. 4
0
1000 m
7:10LT Sep. 4
18:45 to
20:15LT Sep. 3
2:00LT Sep. 4
Kaarabi River
16 :20LT Sep. 4
Large scale
landslide
23:00LT Sep. 2
11:00LT Sep. 3
3:00LT Sep. 4
10:45LT Sep. 4
23:00LT Sep. 2
Sediment
discharge

7. Rainfall (mm/h)
時間雨量（ m ）
m
0
2000
40
1 600
30
1 200
20
800
10
400
0
累積雨量（ m ）
m
50
Total rainfall (mm)
1 8:00
1 2:00
00
6:
9/4 00
0:
1 8:00
1 2:00
00
6:
9/3 00
0:
1 8:00
1 2:00
6:00
9/2 00
0:
1 8:00
1 2:00
00
6:
9/1 0:
00
1 8:00
1 2:00
6:00
8/31 00
0:
Disasters by Typhoon Tales,
Local government and Japan Metrological
2011
Agency alerted the special warning of
sediment disasters based on the rainfall
threshold

8. Rainfall (mm/h)
時間雨量（ m ）
m
0
2000
40
1 600
30
1 200
20
800
10
400
0
累積雨量（ m ）
m
50
Total rainfall (mm)
1 8:00
1 2:00
00
6:
9/4 00
0:
1 8:00
Alert the special warning
1 2:00
change of dangerousness
00
6:
9/3 00
0:
1 8:00
1 2:00
6:00
9/2 00
0:
1 8:00
1 2:00
00
6:
9/1 0:
00
1 8:00
1 2:00
6:00
8/31 00
0:
Disasters by Typhoon Tales,
Long
2011 time lag
Difficult to recognize
Large landslides

9. Rainfall (mm/h)
時間雨量（ m ）
m
0
2000
40
1 600
30
1 200
20
800
10
400
0
累積雨量（ m ）
m
50
Total rainfall (mm)
1 8:00
1 2:00
00
6:
debris flow form streams
Alert the special warning
9/4 00
0:
1 8:00
1 2:00
00
6:
9/3 00
0:
1 8:00
1 2:00
6:00
9/2 00
0:
1 8:00
1 2:00
00
6:
9/1 0:
00
1 8:00
1 2:00
6:00
8/31 00
0:
Disasters by Typhoon Tales,
2011
Sediment discharge and small
Large
landslides

10. Lessons from the disasters
 There was long time lag between the warning
and the occurrence of large scale landslide,
since the current rainfall threshold for the
warning determined by past ordinal-scale
landslides and debris flows.
 Sediment discharge from relatively small
tributaries occurred before the large-scale
landslide occurrence. Moreover, the time lag
between the occurrence of sediment
discharge and large-scale landslide was
relatively short

11. Lessons from the disasters
• If we were able to detect
sediment discharge early, the
information about sediment
discharge could prove useful in
ensuring effective early warning
systems for large-scale
landslides.

12. Problems
Can we monitor sediment discharge
easily?
Can we detect extra-ordinal
sediment discharge from ordinal
sediment discharge?

13. MONITROING DEVICE
Japanese Pipe-type Geophone
(Hydrophone)

14. Hydrophone?
Japanese Pipe-type Geophone
Vibrations of the air,
砂礫の衝突音を
generated by collision
計測する
are detected by a
microphone.
データ
ロガー
Data
logger
Sediment particles
金属管
Steel
増幅器・
マイクロフォン
変換器
Microphone
preamplifier
converter
pipe

15. Hydrophone
50cm
12 mm
Upstream
24 mm
Mortar
Pipe
Downstream
48.6 mm
Riverbed
3 mm

16. Integrated sound pressure method
Sound data
Field ex.
Numerical sim.
Bedload amount
Grain size of bedload

17. FIELD INVESTIGATION

18. Can we monitor bedload
using hydrophone?

19. Yotagiri

20. Downstream
Hydrophone
Sediment trap for
direct sampling

21. 0
5
10
15
20
25
10,000
1,000
(a)
Rain
(b)
Bedload (hydrophone)
Bedload (direct sampling)
Flow depth
100
1
1
0.5
0.1
a
o
l
d
e
B
2
1.5
10
0.01
100
2.5
0
(c)
10
)
(
r
t
e
m
a
i
D
1
0.1
0:00LT
9/19
0:00LT
9/20
0:00LT
9/21
0:00LT
9/22
0:00LT
9/23
)
m
(
h
t
p
e
d
w
o
l
F
m
c
(
3/
)
s
m
)
h
/
m
(
l
f
n
i
a
R
Hydrophone v.s. Direct sampling

22. Can we detect extra-ordinal
sediment discharge from
ordinal sediment discharge?

23. Yotagiri
Omukawa

24. )
h
/
m
(
l
f
n
i
a
R
8 month data in Omukawa
1.2
0.8
)
m
(
v
l
r
e
t
a
W
0.4
0
m s
( 3/
)
m
0.005
a
o
l
d
e
B
0

25. Dimensionless bedload
100
Meyer-Peter and Muller
芦田・
道上式(u*e/u*=1.0)
芦田・
道上式(u*e/u*=0.8)
芦田・
高橋・
水山式
H23 0529
H23 0719
H23 0831
H23 0920
Transport capacity limit
10
1
0.1
0.01
量
砂
流
元
次
無
Supply limit
0.001
0.0001
0.00001
0.000001
0.001
(L=0.5m ) d 60
0.01
0.1
無次元掃流力
1
Dimensionless shear stress
10

26. Start of rainfall
Alert warning/caution
time
Exceed
rainfall
threshold
Time lag
Large-scale landslide occurrence

27. Start of rainfall
time
Exceed
rainfall
threshold
Alert warning/caution
Hydrologic and
sediment transport
observation
Sediment
discharge
Alert new warning
Large-scale landslide occurrence

28. Conclusion
We demonstrated
the applicability of hydrophones and
new calibration method in detection
of sediment discharge.
the possibility that hydrophones
could help to improve early warning
systems for large-scale landslide.

29. THANK YOU for YOUR ATTENTION

31. MATION WIDE
MONITORING

32. Monitoring sites

33. Dimensionless
bedload
Shear stress v.s. bedload
Dimensionless shear stress