北広島町出原地区における地域貢献研究--土砂災害の調査と自主防災のための雨量観測の試み

概要

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Sediment-related disasters occurred two times in Idebara area in Kita-Hiroshima Town, Hiroshima Prefecture. This area is covered by weathered granite and rhyolite, and located around the watershed of Idebara-river, which is one tributary of the most upper region of Gonokawa-river. Since the disaster in 2006, some investigation were executed to become clear a danger degree of sediment-related disasters, and to make up some countermeasures for disaster prevention and mitigation. According to this investigation, debris-flows occurred repeatedly in a few sub-watersheds and a very dangerous sub-watershed, where a new debris-flow would occur in near future, was detected. There are a lot of debris-materials in the area, which were composed of some sediment transported by past slope-failures and debris-flows. The surfacesoil is very wet and trees on it are disorderly inclined. These conditions of the investigated area and the importance of rainfall information were explained to the residents in Idebara. After the explanation meeting, a trial rainfall observation by residents themselves was started. It was verifi ed that this system was very functional and useful for people there through the torrential rainfall in July, 2010.