Many tidal basins associated with barrier coasts worldwide infilled over the past millennia due to the combination of sediment supply, wave-tidal sediment transport, and eco-engineering effects of plants. However, the biogeomorphological interactions between saltmarsh and the morphodynamics of an entire coastal barrier system are poorly understood, especially under sea level rise. Here we study the evolution of a barrier coast for combinations of mud availability, presence of vegetation and sea level rise. We developed a novel biogeomorphological model of an idealized barrier coast enclosing a tidal basin with sandy-clayey sediments that was subjected to tides and waves for 100 years. The morphodynamic Delft3D model was coupled to a vegetation code which accounts for the dynamics of marsh-type vegetation.
The model data includes input files and output as a timeseries of maps of the Delft3D model and of the vegetation model for 8 scenarios and 77 timesteps per scenario. Furthermore, detailed timeseries at predefined observation points and cross-sections are reported for 3649 timesteps over the same model duration.
Initially, vegetation contributed to reducing the tidal prism while sediment was imported. However, with SLR this trend was reversed and the tidal basins started to export sediment for vegetated runs after about 50-60 years while the unvegetated scenarios continued to infill in pace with the SLR. The sediment export was caused by cascading morphodynamic feedback effects triggered by vegetation which modified channel and shoal dynamics. Even under higher mud supply, the SLR resulted in vegetation collapse. The hypsometries, similar to natural systems, show that vegetated systems converge into an alternative equilibrium condition. We conclude that, although the short-term tendency of tidal basins to import sediment is increased by mud availability and vegetation, the long-term trapping capacity can be reduced by the cascading large-scale effects of vegetation on the morphodynamics of barrier coasts. Contact person: Maarten Kleinhans - m.g.kleinhans@uu.nl
