Referensi Sabo Dam [PDF]

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There have been a lot of disaster by debris flow throughout Japan in recent years. The disasters related to debris flow have also occurred repeatedly in our prefecture. Sabo works are construction of sabo dam, which collects and deposits sediments, and groundsel and revetment works which prevents eroding river bed and bank and fixs mountains. In our prefecture, sabo work, which was based on Sabo Law, was started at 1908 (Meiji 41). The recent Sabo works consider the environment of moutain stream.



Before the occurrence of debris flow



Debris flow has occurred



Sabo dam prevents debris floe behind a residential section (Nakanotani Sabo dam, Susami Town)



Revetment works which considered surrounding environment (River Daiya sabo works for environmental maintenance, Negoro temple, Iwade-cho)



The sediment related disaster of Higashinokawa at Kumanogawa Town



The Sabo dam of Fudotanigawa



If there is not sabo dam, a lot of sediments will flow quickly to a lower stream of a river.



Construction of sabo dam contributes to be gentle channel gradient, resulting in less hillside landslide of river bank.



In the case of sediments are discharged by heavy rainfall, sabo dam holds large sediments temporally.



Temporal depositions of excessive sediments flow to lower stream gradually. As a result, the initial condition"2"is obtained.



Introduction of Sabo Works



| Introduction of Sabo Works | Debris flow Control -Sabo Works- | | Landslide Control-Landslide Control Works | | Cliff collapse control -Slope failure control works- | Measures for the weak against disaster | | Non-structural ("soft") measure |



Copyright (C) 2002 Wakayama Pref. All Rights Reserved.



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Definition of Technical Term



Debris Flow



Part of soil, stone and gravel making up a hillside and river bed is intermingled with water from long-continuing or localized rainfall, becomes slushy like porridge and is carried downstream at a dash. The flow is called a "debris flow".



The debris flow that occurred at Kamikamihori valley in Mt.Yakedake (August 3, 1976)



The debris flow that occurred in the Nojiri river in Sakurajima, Kagoshima Prefecture (July 2-3, 1985)



Debris flow disasters occar frequently in recent years Debris flow disaster occurred under the influence of the Bai-u front along Yamatetani river in Matsuyama City (June 20, 2001)



The debris flow flowing, involving woody debris, down the Aratani River at Saeki Ward. Hiroshima City, Hiroshima Prefecture (June, 1999).



A debris flow caused by a torrential rainfall in Nishi-machi, Kochi City (September 25, 1998)



Preventive measures against debris flows Sabo dam as preventive measures against debris flows Sabo dams built in the upstream areas of mountain streams accumulate sediment and suppress production and flow of sediment. Those built at the exits of valleys work as a direct barrier to a debris flow which has occurred. A sabo dam with slits is particularly effective in capturing a debris flow because it has a larger capacity of sand pool under normal conditions. In case that there is a fear of flow-down of driftwood, a slit sabo dam is built as a preventive measure. Function of slit type sabo dam



(1)The dam allows sediment to flow downstream under normal conditions. areas.



(2)When a large scale debris flow occurs, sediment is captured and temporarily held here to prevent disasters in downstream