Estimates of longshore sediment transport rates along Macumba and Recreio-Barra da Tijuca sandy beaches (Rio de Janeiro, southeastern Brazil)

Abstract

Due to the complex nature of coastal dynamics, several models were developed to estimate longshore sediment transport (LST) rates. The Coastal Engineering Research Center (CERC), Kamphuis, and Bayram models are among the most used and were applied to three east–west oriented sandy urban beaches from Rio de Janeiro (southeastern Brazil): Macumba, Recreio, and Barra da Tijuca. The wave record from oceanographic buoys and the WaveWatch III (WW3) model were used to identify fairweather periods and increased storminess between 2016 and 2018. Eastwards, median sediment grain-size grades from coarse to medium sand, and is associated with decreasing beach slopes in the same direction. The magnitude of the estimated LST rates varied significantly between the models (Δ ≈ 1,000 m³/day, p < 0.001), although the time-averaged LST rates obtained from the four models indicate eastward transport. The four models identified areas of convergence and divergence of sediment transport with increasing rates to the east. The modeling results may support effective coastal management initiatives when integrated with topographic profiles, numerical modeling, satellite imagery, and historical information.