Suspended Sediment Dynamics in a Mesotidal Estuarine Channel Revealed by Numerical Modeling and Remote Sensing of Sediment Concentrations

Process-based sediment transport models can accurately reproduce estuarine sediment dynamics when boundary fluxes, bed properties, and spatially resolved sediment characteristics are well constrained; however, such information is rarely available in most coastal systems. Sediment fluxes at the ocean boundary are commonly unconstrained, riverine sediment inputs are typically estimated from stage–discharge relationships combined with reference concentrations rather than measured continuously, and bottom sediment properties are seldom resolved at high spatial resolution. These limitations hinder robust quantification of suspended sediment redistribution in intertidal estuaries. Here, suspended sediment balance is evaluated in Plum Island Sound (Massachusetts, USA), a mesotidal estuary, by integrating surface suspended sediment concentration (SSC) derived from Sentinel-2 MSI imagery (10 m resolution) with numerical simulations of hydrodynamics. We implemented the depth-integrated suspended sediment balance under quasi-steady conditions during satellite overpasses for erosion-deposition distribution. Six hydrodynamic configurations are analyzed, defined by tidal phase (flood or ebb), river discharge magnitude (high or low), and wind forcing (calm or high wind). The results reveal pronounced tidal asymmetry in sediment redistribution, with flood and ebb tides producing spatially distinct erosion and deposition patterns, particularly within channel bends. Elevated river discharge increases SSC in the upper estuary but does not generate substantial downstream redistribution under calm conditions, whereas wind-driven events induce widespread resuspension and enhanced sediment redistribution across the system. This work demonstrates how coupling remote sensing observations with hydrodynamic modeling enables geomorphologically analysis of suspended sediment balance in estuarine environments.