Examples of Abolished Works and Characteristics of Small Earth Dams for Irrigation in Japan

Abstract

As results of the questionnaires for all prefectures in Japan, a number of abolished works of small earth dams for irrigation had increased rapidly since the new law for small earth dams for irrigation was enacted, and it was likely that the abolished works would continue to be constructed in the future. Therefore, we classified abolished works by surveys systematically at 85 sites in 19 prefectures and indicated these characteristics. The three main abolished works of small earth dam for irrigation included open-cut, underdrainage and filling-up work, and there was also a combination work that combined them. Constructing settling basins in ponds to prevent sediment outflow during drainage, driftwood captures to do the blockade of underdrainage pipes and other devices, it became clear that each prefecture had performed creative ideas to abolish small earth dams for irrigation in spite of the lack of countermeasure works and design guidelines.