Author(s): Megan E. Williams; Lukas WinklerPrins; Raul Flores

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Keywords: Stratified flow; Intertidal flats; Estuarine hydrodynamics; Sediment transport; Waves

Abstract: Bar-built estuaries in Mediterranean and semi-arid climates are characterized by strong gradients, including distinct vertical and longitudinal salinity stratification and associated suspended sediments. These shallow estuaries, with their constricted inlets, typically experience low tidal velocities, which help maintain strong stratification in the absence of other significant mixing forces. One key contributor to increased velocities in such systems is the presence of infragravity waves. While gravity waves break at the beach outside the inlet, infragravity energy (with periods typically ranging between 30 s and 5 min) can propagate past the inlet's shallow threshold, generating oscillatory currents within the estuary. Recent studies have highlighted the impact of these infragravity oscillations on river plume dynamics, such as those observed in the Maipo River estuary in central Chile. In this estuary, field studies have documented the advection of sediments and density gradients, particularly in shallow intertidal flats. This research leverages field measurements to capture the temporal and spatial variability of stratification within the Maipo River estuary. By investigating the role of infragravity motions in the advection and dispersion of salts in stratified intertidal flats, this study aims to better understand how these processes interact with wind stress and influence sediment transport, shedding light on the complex physical dynamics of these unique coastal systems.

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Year: 2025