Tidal inlet channel stability in long term process based modelling

The Dutch Waddenzee is characterised by a large number of tidal inlets between sandy barrier islands. The general morphodynamics and hydrodynamics of tidal inlets are relatively well understood, but the detailed interactions remain a prominent research interest. Recent studies have used process-based computer models as a tool to investigate the long term mechanisms, interactions and morphologic development. One of the major problems identified in these models is an unrealistic development of tidal channels. The exact reasons for this inconsistency are not yet know. The aim of this report is to improve the model performance by using more natural “morphological” boundary conditions instead of currently used schematizations. An idealized representation of the Ameland inlet was used to evaluate different modelling strategies. It was found that the incorporation of the TRANSPOR 2004 sediment transport predictor and a space and time dependent bedform roughness led to a reduced incision and more stable channels over a 40 year period, without additional tuning parameters. Further potential improvement in channel stability was found with a more complex transverse bedslope predictor. The outcome of the modelling contributes the development of tidal inlet models that are able to produce more valid long term morphologic simulation in order to study the inlet sensitivity to future sea level rise and determine sound nourishment strategies.