Numerical data of hydrodynamics and sediment transport for three reference scenarios: N1, P, and N2

The residual sediment transport in tidally energetic estuarine channels is
investigated by means of idealized cross‐sectional modeling. The lateral
bathymetric variation follows a Gaussian profile, assuming longitudinal
uniformity. The total along‐channel residual sediment flux is decomposed
into contributions from an advective flux and a tidal pumping flux. Two
important mechanisms are found to modify the tidal covariance between
sediment concentration and current velocity, thereby contributing to the
tidal pumping of sediment. First, longitudinal and lateral straining of
salinity leads to tidal asymmetries in stratification and thus sediment
resuspension. Second, lateral circulations directly redistribute suspended
sediments within the cross section, which are then differentially
transported by the along‐channel tidal currents. A general relationship
between the phasing of the lateral circulations and the resulting
lateral‐advection‐driven tidal pumping is proposed. Reduced‐physics
experiments with lateral sediment advection turned off provide the first
evidence that lateral‐advection‐driven tidal pumping plays a leading role
in sediment transport for tidally energetic estuaries with nonnegligible
lateral depth gradients. Additionally, a temporal decomposition breaks
down the cross‐sectionally averaged tidal pumping flux into individual
contributions from different tidal phases (early tide, peak tide, late
tide), providing a new perspective on tidal asymmetry in sediment
resuspension and settling. The direction and strength of tidal pumping
(both stratification‐driven and lateral‐advection‐driven) are shown to
depend on lateral bathymetry, sediment grain size, and longitudinal
buoyancy gradient forcing.