Design Standard of Control Structures Against Debris Flow in Japan

Countermeasures to prevent or mitigate sediment-related hazards, debris flow in this paper are classi-fiedasstructuralmeasuresornonstructuralmeasures.ThestructuralmeasuresareSabodams,leadingdikes,and channels for debris flow control. The nonstruc-tural measures are the designation of areas prone todebrisflow, properland useintheareas,thereinforce-ment of houses, the creation of warning systems andthe evacuationof the inhabitants in case ofemergency.A technical standard on debris flow control structuresof Japan was revised in 2007. Major revision is thatcheckdamscalledSabodams constructednearhousesare changed from closed type Sabo dams to open typeSabo dams because the occurrence frequency is lowas once for longer than one hundred years, naturaltorrent environment should be conserved in ordinarydays and sediment trap capacity should be kept untildebris flow occurs. Points changed are explained suchas the opening of open type dams is as equal as themaximum stone size.Keywords: sedimenthazard,countermeasures,structuralmeasures, nonstructural measures, technical standard fordebris flow control