Closure of Secondary Basins Causes Channel Deepening in Estuaries With Moderate to High Friction

Abstract

Estuaries are often characterized by the presence of secondary basins (side embayments), which affect the estuarine hydrodynamics and sediment dynamics. Many of these basins have disappeared due to land reclamations, which might influence the estuarine morphodynamics. This study addresses how the presence and closure of secondary basins affect the estuarine channel depth using the Delft3D model. Results reveal that channels in estuaries with secondary basins are shallower than those in which these basins are absent, regardless of their location, length, or number. This shallowing is more pronounced for basins that are located at the northern estuarine margin due to the Coriolis force. The shallowing of channels increases if more secondary basins are present. Channels deepen after the closure of secondary basins, resulting from a decrease of the landward directed sediment transport that is driven by tidal asymmetry. Model results apply to estuaries with moderate to high friction.