Relative influence of antecedent topography and sea-level rise on barrier-island migration

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The response of barrier islands to sea-level rise is modulated by combinations of coastal processes, eco-geomorphic feedbacks, and structural controls, such as antecedent topography. Interactions among these drivers can lead to complex and non-linear changes in island morphology and transitions between migrational, erosional, or progradational states. This study seeks to constrain the morphologic consequences of barrier islands migrating across complex antecedent topography in response to rising sea level. The stratigraphy of four barrier-backbarrier systems along the U.S. Mid-Atlantic coast informs idealized geometries of diverse antecedent substrate. These outcomes are integrated into a cross-shore morphodynamic model of barrier-island migration to quantify the influence of this antecedent geology on barrier-retreat behavior. Additionally, this study explores the future response of specific barrier islands to various rates of sea-level rise over multi-decadal to millennial timescales. The results show antecedent substrate slope plays a central role in barrier morphodynamic behaviour. In particular, migration across a subaqueous backbarrier ridge (e.g., coastal barrier or dune deposits from earlier sea-level highstands) can cause a succession of phase changes in a modern island. For example, the case studies illustrate the steep slopes and decreased backbarrier accommodation associated with antecedent highs greater than 3 m in profile can greatly reduce island migration rates, effectively “pinning” the island in place, even with sea-level rise rates up to 6 mm yr-1. However, once the island migrates over the high, backbarrier accommodation increases, leading to enhanced overwash fluxes, more rapid landward migration, and possible drowning. Additionally, the results indicate that antecedent substrate may slow barrier-island migration by providing sediment through both shoreface and inlet processes. The field and modelling insights from this study are presented as a conceptual model of the relative influence of various antecedent features on barrier-island dynamics along sandy, siliciclastic coasts.

Study Area

Publication type Article
Publication Subtype Journal Article
Title Relative influence of antecedent topography and sea-level rise on barrier-island migration
Series title Sedimentology
DOI 10.1111/sed.12798
Volume 68
Issue 2
Year Published 2021
Language English
Publisher Wiley
Contributing office(s) St. Petersburg Coastal and Marine Science Center
Description 31 p.
First page 639
Last page 669
Country United States
State Maryland, New Jersey, Virginia
Other Geospatial Assateague Island, Brigantine Island, Cedar Island, Edwin B. Forsythe National Wildlife Refuge, Little Beach Island, Parramore Island
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