Scoping Review of Paddy Field Dam Studies in Japan

Paddy field dams are one of the nature‐based solutions provided by farmers in Japan for mitigating flood damage. This scoping review analysed 38 papers in the Web of Science Core Collection and J‐STAGE obtained by searching for keywords associated with paddy field dams. Among the 38 selected papers, 31 (approximately 80%) examined the effects of paddy field dams. Knowledge of the effects of paddy field dams, under what conditions, to what extent, how much and what kinds of effects are observed is needed. Studies have revealed that an external force that is too large will cause overflow of water, rendering paddy field dams ineffective. Therefore, it is essential to raise and maintain the ridges of paddy fields. However, no studies have focused on the effects of paddy field dams on crops. The external validity of disseminating paddy field dams is not assured because of bias toward cases in specific regions, and a universal dissemination method for paddy field dams has not been identified. No studies have examined the effectiveness of paddy field dams compared with alternatives or the prioritization of paddy field dams.