Abstract
AbstractBarrier island response to sea‐level rise depends on their ability to transgress and move sediment onto and behind the barrier, either through flood‐tidal delta deposition or via overwash. Our understanding of these processes over decadal or longer timescales, however, is limited. Here we use a recently developed barrier island model (BRIE) to better understand the interplay between tidal dynamics, overwash fluxes, and sea‐level rise on barrier coasts and barrier island stratigraphy. Model results suggest that in microtidal environments with large alongshore sediment transport fluxes, tidal inlets are ephemeral and migrate rapidly. These conditions lead to effective deposition of flood‐tidal deltas and allow inlets to constitute most of the landward sediment flux. Whether barrier islands can survive sea‐level rise depends on the combined landward sediment flux from overwash and flood‐tidal delta deposition, likely making barrier islands with artificially stabilized inlets (via jetty construction or maintenance dredging) more vulnerable to sea‐level rise.
Highlights
Low‐lying coastal barriers face an uncertain future in coming decades as sea levels are projected to rise (IPCC, 2014)
We find a relation with offshore wave height; larger net alongshore transport increases flood‐tidal delta deposition, which adds to the maximum potential landward flux of overwash deposition alone and makes barrier islands able to remain subaerial under higher sea‐level rise (SLR) rates
We present a morphodynamic model for barrier island evolution (BRIE), in which inlets can form and contribute to barrier island landward migration
Summary
Low‐lying coastal barriers face an uncertain future in coming decades as sea levels are projected to rise (IPCC, 2014). Given the socioeconomic and ecological importance of barrier islands and their associated back‐barrier environments, a number of models have been developed to better understand their response to SLR (Lorenzo‐Trueba & Ashton, 2014; Lorenzo‐Trueba & Mariotti, 2017; Masetti et al, 2008; Moore et al, 2010; Stolper et al, 2005; Storms, 2003) These models, do not explicitly include tidal inlets even though tidal inlets and flood‐tidal delta deposition can represent a significant fraction of the landward‐ directed sediment flux (Armon & McCann, 1979; Pierce, 1969; Simms et al, 2006). This allows us to compare observed barrier facies (e.g., Mallinson et al, 2010) to centennial timescale overwash and flood‐tidal delta deposition
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