INFLUENCE OF WIND AND TIDES ON FLOATING DEBRIS IN THE NEYA RIVER SYSTEM

Abstract

 To clarify the behavior of floating debris in the Neya River system in Osaka, we conducted continuous detection of floating debris using the object detection model YOLOv5 applied to water surface images captured by fixed-point cameras. We then analyzed the influence of wind and tides on this behavior. The results revealed that in the Neya River system, the density of floating debris was higher near the tidal limit, suggesting accumulation due to the cessation of flow during high tide, which allows debris transported from upstream and downstream to accumulate. Long-term observations focused on Suminodo, where a high number of floating debris were detected, showed that both wind and tides significantly contributed to the abundance of floating debris. Despite low precipitation periods, a considerable amount of floating debris was detected, indicating transportation upstream by westerly winds and prolonged drift in the tidal area. Moreover, the amount of floating debris varied according to the lunar cycle, with an increase during spring tide compared to neap tide. This study's findings on wind and tide effects on floating debris behavior are expected to contribute to effective measures to reduce floating debris.