未圃場整備地区における「田んぼダム」の洪水緩和機能の評価

抄録

The Paddy Field Dam, a flood mitigation measure taking advantage of the ponding function of paddy fields, has been introduced as a complementary function to the existing drainage facilities to countermeasure a recent increase in the frequency and magnitude of heavy rainfall events. The core facility of the Paddy Field Dam is the runoff control device, which shrinks the drain orifice and restricts the volume of surface water runoff from a paddy field plot. Although this technology was originally developed for modernized paddy fields equipped with concrete-made drainage boxes, authors contrived the runoff control device to be applicable to unimproved paddy fields without drainage boxes being equipped. The purpose of this study is to quantitively evaluate the flood mitigation performance of the paddy fields installed with the newly developed device in an unimproved paddy field area. The evaluation was conducted by an integrated simulation model. The result of the simulation shows that the Paddy Field Dam in the study area would have the effect reducing the inundation damage due to 30-year return period rainfall event to almost that due to 10-year return period rainfall event.