[M-IS21] Understanding plastic pollution: The reality and countermeasures

[MIS21-P03] Enhancing Beach Litter Prediction Accuracy: Evaluating Leeway Drift Effects in Wind Tunnel Tank Experiments

*Fukushige Hiroki¹, Shinichiro Kako^1,2, Tetsuya Taneda¹, Akira Tsujimoto³, Atsuhiko Isobe⁴ (1.Kagoshima University, 2.Japan Agency for Marine-Earth Science and Technology, 3.Shimane University, 4.Research Institute for Applied Mechanics, Kyushu University)

Keywords:Beach litter, Beach litter prediction experiment, Wind tunnel tank , Leeway drift, Particle tracking experiment, Webcam

Accurate prediction of the variation of marine debris abundance is crucial for effective marine debris management. To this end, we conduct forecasting experiments on marine debris abundance using a regional ocean model in conjunction with particle tracking experiments, focusing specifically on marine debris unaffected by leeway drift. However, many types of drifting litter, such as plastic bottles and buoys, exhibit high buoyancy and are significantly influenced by leeway drift. Therefore, to enhance the accurately of the abundance of marine debris forecasting, it is essential to develop a hindcasting/forecasting model that incorporates the effects of leeway drift. In the present study, wind tunnel tank experiments were conducted to quantitatively assess the influence of leeway drift on drifting litter. Litter with different projected area ratios in air and water was floated in a wind tunnel under different wind velocity conditions, and its drifting velocity was measured. The effect of leeway drift was determined by subtracting the ambient current velocity from the observed drifting velocities. Based on these experimental results, particle tracking experiments were conducted to compare the modeled accumulation of drifted litter with the observed abundance of marine debris washed ashore on Mitsu Beach, Izumo City, Shimane Prefecture. In these numerical simulations, particles were initially released from multiple locations along the East China Sea, and forward particle tracking experiment were conducted to determine the origin and timeframes of debris washed ashore on Mitsu Beach. To validate the accuracy of the model, the modeled results were compared with the results of in-situ surveys conducted on Mitsu Beach, as well as with the time series of the beach litter abundance estimated from webcam images. The detailed findings and implications of the present study will be presented and discussed.