Morphological Modeling of Tidal Inlet Migration and Closure

Abstract

Inlet migration and closure Usually occur in micro-tidal, wave-dominated coastal environments with strong seasonal variations in river flow and wave climate. In the last decades, efforts have been undertaken to identify, classify and quantify these phenomena using conceptual models, empirical relationships and behavior-based models. However, to obtain further insight into the dominant physics requires the application of a process-based model. This study investigates the migration and closure of an idealized tidal inlet system due to wave driven longshore sediment transport. The process-based morphodynamic modeling system Delft3D is applied for this purpose. The ratio of wave energy over tidal prism was changed systematically, through varying the tidal amplitude, tidal basin area and wave characteristics, to investigate the morphological response of the inlet (e.g. closure and migration). The results were compared with Bruun's empirical criteria for overall stability and with Escoffier stability concept. The results clearly indicate that a process-based model is able to reproduce a morphological inlet response consistent with Bruun's criteria and Escoffier's closure curve. A typical example of a migrating tidal inlet due to oblique waves is presented which includes features such as ebb channel formation, migration and welding to the downdrift barrier, and bypassing of ebb shoals. In other cases, inlet closure due to prolongation of the inlet channel and infilling with littoral-drift material is also reproduced.