Abstract
Rice paddy dam initiatives are attracting attention as part of river basin flood control measures. In this study, we quantitatively evaluated the effectiveness of the rice paddy dam introduction in controlling runoff at the dam basin scale, focusing on the upper reaches of the Hiji River basin, including the Uwa Basin (Nomura Dam basin). In the runoff analysis using the storage function method considering the presence or absence of rice paddy dams, it was confirmed that by expanding the basin to the Aza-scale level, a similar approach to the conventional storage function method (with a model parameter k=2.4) could be applied. Furthermore, in the runoff analysis considering factors such as land use ratio in the dam basin, it was possible to reproduce the actual inflow volume to the Nomura Dam. By conducting runoff analysis at the dam basin scale using various probabilistic rainfall events and rainfall patterns, it was possible to identify the conditions under which the introduction of rice paddy dams effectively reduces the peak runoff volume.
