Coupled Hydrodynamic-wave Modeling of Dry-Season Sediment Dynamics in a Narrow Tropical Estuary in Arosbaya, Indonesia

Abstract The sediment transport dynamics of small tropical estuaries are still poorly understood. A coupled hydrodynamic-wave numerical modeling (MIKE 21/3 FM) was used to investigate the sediment transport pattern in the narrow Arosbaya Estuary (below 10 m wide) during dry season. Field data was integrated into the model such as, bathymetry, bed sediment samples, and tidal currents, including wind-waves data from reanalysis model. Model validation showed good agreement with MAPE values of 34% for current speed, 22% for current direction, and water level below 1%. The results showed that tidal currents dominate in the sediment transport patterns during dry season, with simulation showing the velocities 0.1 – 0.25 m/s of longshore transport current move toward south-west. The simulations revealed a sedimentation rate up to 0.12 m over 40 days, primarily near aquaculture canals and the river mouth. In addition, the next critical step is to apply this validated model to simulate wet season conditions with higher river discharge in order to provide a complete picture of sediment dynamics throughout the year.