This Supplementary Data complements the research article "Three Rivers to the Test: Lessons for Global Plastic Transport Modelling". In this piece, we investigate plastic fluxes and ocean emissions in three global rivers: (1) the Rio Ozama, Dominican Republic; (2) the Umgeni River, South Africa and (3) the Chao Phraya, Thailand. Combining Eulerian (camera arrays on multiple bridges) and Lagrangian (GPS drifters) data we calibrate and validate a hydrologically driven debris flux model.