2020 年 76 巻 1 号 p. 295-303
In recent years, to mitigate the flood disaster caused by the increasing intensity and frequency of torrential rain events, some places have adjusted the retention of the paddy field by installing the runoff control device called paddy field dam. In comparison with other flood control facilities, the installation cost is much lower mainly for drainage control devices at the drain outlet of the paddy field, while the expected effect is significant since paddy fields are widely distributed in Japan. Therefore, this research aims to evaluate the potential flood mitigation effect of the paddy field dam for typhoon 19th in October 2019 in the Naruse River basin using the Rainfall-Runoff-Inundation model. To consider the potential effect of all paddy fields inside the basin, a simple one-dimensional paddy field dam model was developed, which can be applied for the whole basin. Moreover, the scenario analysis was conducted for different heights of free-drain and proportion of application. In conclusion, the paddy field could store about 90 million m3 water in whole paddy fields in the basin using 15 cm height of free-drain, and it significantly mitigated flood in the downstream of the Naruse River basin.