大規模河道閉塞の緊急工事の考え方について

摘要

2011年9月の紀伊半島大水害時には，深層崩壊により閉塞高が100mに達するような大規模な河道閉塞が複数形成された。我が国では，これまでも2004年に発生した新潟県中越地震や2008年に発生した岩手•宮城内陸地震時にも河道閉塞が形成され，対策を実施してきた。しカゝし，閉塞高は最大でも50m程度であり，紀伊半島大水害時に形成されたような規模の河道閉塞に対しては，近代的な土木工事による対策の経験は無く，従来の対策工事から得られた知見だけでは紀伊半島大水害時に形成された河道閉塞の対策には不十分であつたと言わざるを得ない。%Urgent works, which should be done just after large landslide dam formation, are very important to prevent landslide dam brake, therefore we have to conduct and complete the urgent works in short time although facing many difficulties. But unfortunately we had not haven effective method about like this urgent works against large landslide dam until the terrible disasters, typhoon Talas, Sep. 2011, in which the large landslide dams were caused in Kii peninsula, Nara and Wakayama prefecture, so that it was very hard to get progress and manage the works, and we had to have many trials to complete the urgent works. The review of these trials is necessary to establish the effective way of urgent works against large landslide dam. Therefore I reviewed these works and what methods should be applied to urgent works against large landslide dam. As results, to construct temporary channel effectively, and to get the method to reduce water level of landslide dam lake are important.