Assessment of the transport capacity of floating plastics through fluvial systems

Since the early times of plastic production, the relative change increased approximately about 391,050%. It went from a cumulative production of 2 million tons in 1950 to 7.82 billion tons in 2015. Even though there are variable recycling methods at present, not all discarded plastic gets recycled. The vast majority of the waste plastic makes its way to the ocean through specific pathways, with one of the most dominant being transport via fluvial networks. Moreover, a relatively minimal amount of data is available on the transport of riverine plastic. Plastics found in rivers can accumulate, causing flow blockages and potentially affecting flow routing (intensifying flooding and other climate risks). They can also affect water quality and ecology, including biota that may ingest these through the leakage of chemicals. Out of the various types of plastic, buoyant macro plastic is a major polluter, and understanding its flow in rivers can help us reduce plastic pollution in the long run.

This study focuses on getting a better understanding of how floating plastics debris is transported in rivers with aquatic vegetation by undertaking well-controlled lab flume experiments. Specifically, the transport of floating plastic debris in a river system was studied through a series of flume experiments, using instream simulated vegetation. Vegetation patches of different densities were used to assess their effect on the flow field carrying buoyant plastics of variable sizes. The video camera is used to record the transport process of plastic along the flume until they impinge on the simulated vegetation patch. Obtained video files of the flume experiments are analyzed to assess the effect of vegetation density on the transport efficiency of the plastic. Preliminary results focus on using specific transport metrics, particle velocity before contact with the vegetated patch, focusing on the size of plastics being transported. Altered according to various flow conditions and river morphology, the results of this study will help engineers in the future to design and produce more resilient methods of vegetation patches and engineering structures in order to exploit the trapping effects of macro plastics.