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Uchida - vajont 2013

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International Conference Vajont2013 - 8 October

International Conference Vajont2013 - 8 October

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  • 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
  • 30. MATION WIDE MONITORING
  • 31. Monitoring sites
  • 32.    Dimensionless bedload                        Shear stress v.s. bedload        Dimensionless shear stress