Barrier islands such as the Wadden Islands can drown or migrate landward in response to sea level rise, depending on their ability to move sediment to the back barrier. The potential magnitude of this landward sediment flux over decadal to centennial time scales, however, is poorly constrained.
Here we use a new barrier inlet environment (BRIE) model combined with remote sensing to quantify potential overwash and flood-tidal delta deposition rates (Fig. 1a) (Nienhuis & Lorenzo‐Trueba, 2019a, 2019b). The BRIE model integrates existing overwash and shoreface formulations with alongshore sediment transport, inlet stability (de Swart & Zimmerman, 2009), inlet migration, and flood-tidal delta deposition. Within BRIE, inlets can open, close, migrate, merge with other inlets, and build flood-tidal delta deposits. We use 34 years of remote sensing observations of barrier island change to parameterize overwash fluxes. The model accounts for feedbacks between overwash and inlets through their mutual dependence on barrier geometry.
Model results suggest that flood-tidal delta deposition can be a significant component of the long-term landward sediment flux keeping barrier islands above sea-level. For highly developed barrier islands such as the Wadden Islands (Fig. 1b) where protection against storms limits overwash deposition, tidal inlets might be crucial to provide a platform for long-term island transgression.
Figure 1 (a) BRIE model of barrier island transgression, (b) Wadden Islands along the Dutch and German coast.
Nienhuis, J. H., & Lorenzo-Trueba, J. (2019a). Can Barrier Islands Survive Sea-Level Rise? Quantifying the Relative Role of Tidal Inlets and Overwash Deposition. Geophysical Research Letters, 46(24), 14613–14621. https://doi.org/10.1029/2019GL085524
Nienhuis, J. H., & Lorenzo-Trueba, J. (2019b). Simulating barrier island response to sea level rise with the barrier island and inlet environment (BRIE) model v1.0. Geoscientific Model Development, 12(9), 4013–4030. https://doi.org/10.5194/gmd-12-4013-2019
de Swart, H. E., & Zimmerman, J. T. F. (2009). Morphodynamics of Tidal Inlet Systems. Annual Review of Fluid Mechanics, 41, 203–229. https://doi.org/10.1146/annurev.fluid.010908.165159