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Debris flow and its countermeasures in Japan

  • Hiroshi Ikeya
Article

Summary

Japan is an island lying off the east border of the Asian Continent. Its total area is about 370,000 km2 75% of the whole land area of Japan is mountainous. The lowlands, chiefly plains and alluvial fans, that constitute the remaining 25% are formed from sediments which have flowed there from the mountains in the past. In these lowlands live 85% of our population of 110 million people. Geologically, japan is extremely fragile and her topography is very steep. Under these conditions, sediment disasters caused by debris flow have occurred by torrential downpours, typhoons or the seasonal rain front in every year somewhere in Japan. These sediment disasters are the most harmful natural disaster to human life and property in Japan. For this reason the Sabo Law (Erosion Control Law) was enacted in 1897, and the government has exerted every effort to prevent such disasters. Thus Japan is one of the most advanced countries with regard to the study and research of sediment disasters and to the development of countermeasures.

Keywords

Debris Flow Sediment Discharge Hazard Area Debris Flow Deposit Sediment Flow 

Les laves torrentielles au Japon—Mesures préventives

Résumé

Soixante quinze pour cent des 370 000 km2 du Japon sont des régions montagneuses. Les basses terres, essentiellement des plaines et des dépôts de piedmont, qui représentent les 25% restants, sont formés de sédiments qui se sont répandus dans le passé depuis les zones montagneuses, 85% des 110 millions d'habitants vivent dans ces régions. Le Japon est très fragile et sa topographie est très accentuée. Dans ces conditions des désastres dus aux laves torrentielles provoquées par des orages violents, des typhons ou des pluies saisonnières abondantes se produisent tous les ans quelque part dans le pays. Ce sont les catastrophes naturelles qui provoquent le plus grand nombre de pertes en vies humaines et en biens matériels dans le pays. Pour cette raison, une loi sur le Contrôle de l'Erosion a été adoptée en 1897 (Loi Sabo) et le gouvernement déploie de grands efforts pour éviter de telles catastrophes. Le Japon est ainsi devenu un des pays où l'étude de ces phénomènes, ainsi que la mise au point de mesures préventives a été la plus poussée.

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Copyright information

© International Association of Engineering Geology 1989

Authors and Affiliations

  • Hiroshi Ikeya
    • 1
  1. 1.Sabo Dept. River BureauMinistry of ConstructionTokyoJapan

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