The tidal trap – seasonal transport of floating macro-debris in the bi-directional chao phraya river network entering the gulf of thailand
Year: 2024
Type: conference-paper
Abstract: Models estimate that rivers transport 0.3–4 million tonnes of plastic waste per year into the world's ocean. Such models are mostly calibrated with Eulerian flux data taken kilometres upstream of river mouths. This neglects a Lagrangian understanding of particle transport which is particularly important in highly seasonal and tidal estuaries. To address this gap we analysed the trajectories of grapefruit-sized floating GPS drifters (n = 63) along the final ∼80 km of the Chao Phraya River network in Bangkok. The drifters were deployed in three seasonal batches during 2022–2023. In all seasons, the bi-directional tidal river flow resulted in dozens of kilometres of up- and downstream drifter oscillations. Drifters alternated their flow direction up to 23 times, passing a single river location up to 10 times. We demonstrate that drifters tend to follow the outside radius in river curves most likely impacted by the helical water motion. One third of the drifters transitioned between main river and tributary canals. Single drifters traversed up to three different canals exhibiting up to five in-and-out transitions at a time. Remarkably, in the dry and hot seasons median net drifter transport was in the upstream direction at –5 km and –0.5 km, respectively. Only during the rainy season, we observed net downstream transport (+11 km). It was also during the latter season that the only drifter out of the 63 deployed reached the Gulf of Thailand. Our results highlight the complex waterway interactions, seasonal transport and temporary retention of floating debris in tidal estuaries. The spatiotemporal implications of this study shall inform prevention and cleanup measures against macro-pollution of major waterways and their connecting oceans. Furthermore, this study enriches the discourse on tidal estuary debris transport and supports modelling in refining regional and global ocean emission calculations. Also see: https://micro2024.sciencesconf.org/558746/document
Language: English
Subfield: Pollution
Field: Environmental Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7125963130