2024 Volume 37 Issue 2 Pages 142-154
Because of recent shifts in policy toward integrated flood control in basins, the use of "paddy field dams," an approach that draws on rice paddies for flood control, has become increasingly popular. This method is effective at reducing the peak discharge of tributary rivers and at preventing flood inundation during heavy rains. This study was conducted to evaluate the peak discharge mitigation rates in several tributary rivers in the Kuma River upper left side in Kumamoto prefecture, where agricultural land is predominant. The model used for the study accounted for unique agricultural water utilization facilities in this region, such as main canals and discharge mechanisms to tributary rivers during heavy rainfalls. Findings revealed that the peak discharge mitigation rate varied depending on the rice paddy field ratio and the paddy field dam implementation rate in the tributary river watersheds. Additionally, a simple equation was estimated as describing the two factors’ mutual relation. The main canal in this area functions as a drainage channel, enhancing drainage during heavy rainfalls. Implementation of the presented approach not only decreased the tributary river peak flow rates; it also prevented overflow of the channel itself.
