Proof of concept for a global semi-autonomous river plastic monitoring system

Understanding, predicting and preventing anthropogenic debris transport through rivers benefits from monitoring and comprehension of the dynamics of plastic transport from an hourly to multi-annual scale. Existing methodologies for the monitoring of plastic transport are not suited for long, continuous observation periods or lack a rigorous comparability between locations. This paper proposes and tests a strategy and methodology for the monitoring and quantification of floating macroplastic transport in rivers, that is suitable for multi-year periods and comparable between locations. Camera deployments on bridges that focus on longevity and standardization of data collection in combination with object detection and tracking techniques resulted in high-frequency data of plastic and plastic transport from 11 locations worldwide spanning multiple years. This tracking and detection methodology can be transferred to new locations with low effort in model retraining. Comparison to visual counting measurements show that we can measure the same dynamics and ranges of transport. We also demonstrate that this technique allows us to measure the surface flow speed and tidal fluctuations of plastic debris in rivers as well as identify high intensity plastic transport events, such as floods. This paper offers a complete monitoring method for the transport of floating macroplastic debris which can be used to improve plastic transport models and measure the effects of policy and mitigation strategies of plastic waste in rivers.