The influence of riverine outputs from the Tuy River on the coastal processes of near sandy beaches was assessed by measuring the physical and chemical characteristics of water and sediment samples at eight sites along the north central Venezuelan coast and from the rivers that flow through this región into the sea (Tuy, Capaya, Curiepe) during two field surveys. In addition, the behavior of the Tuy River discharge plume was evaluated using remote sensors, and its effect on the population abundance and size structure of the clam Tivela mactroides was determined. Of the three rivers evaluated, the Tuy River had the highest impact on the coastal zone (789.15 ± 190.63 km²) in terms of flow rate (246.39 m³ s-1), nutrients (659.61 ± 503.27 g s-1total nitrogen; 52 ± 53.09 g s-1 total phosphorus) and sedimentary material (9320.84 ± 9728.15 g s-1). The variables measured (salinity, total nitrogen and phosphorus, pH, turbidity, and total organic carbon) showed a spatial gradient along the coast. Tivela mactroides had the highest biomass and density (9126.8 ± 1562 g m-2; 9222.22 ± 1976.72 ind m-2 ) at the sites farthest from the river mouths and smaller sizes (< 13 mm long) at sites close to the river mouths. The Tuy River plume modifies the functioning of the coastal system processes by discharging large amounts of nutrients and sedimentary material into the water column, which are then distributed by marine currents and alongshore transport. These contributions are used by T. mactroides populations, which show high abundances and differentiation in size structure along this coastline.