Leveraging the Interdependencies Between Barrier Islands and Backbarrier Saltmarshes to Enhance Resilience to Sea-Level Rise

Abstract

Barrier islands and their backbarrier saltmarshes have a reciprocal relationship: aeolian and storm processes transport sediment from the beaches and dunes to create and build marshes along the landward fringe of the island. In turn, these marshes exert a stabilizing influence on the barrier by widening the barrier system and forming a platform onto which the island migrates, consequently slowing landward barrier migration and inhibiting storm breaching. Here, we present a novel framework for applying these natural interdependencies to managing coastal systems and enhancing barrier-island resilience. Further, we detail application of these principles through a case study of the design of a marsh creation project that showcases the interdisciplinary engagement of scientists, engineers, stakeholders, and policymakers. Specifically, we describe: (1) the ecologic, sedimentologic, stratigraphic, and morphologic data obtained from the southern 4 km of Cedar Island (Virginia, United States) and nearby backbarrier tidal channels, tidal flats, and flood-tidal deltas, and (2) the use of those data to develop an engineering and design plan for the construction of a high (46 ha) and low (42 ha) fringing marsh platform located behind the island, proximal to a former ephemeral inlet. Additionally, we chronicle the process used to narrow five initial alternative designs to the optimal final plan. This process involved balancing best-available existing science and models, considering design and financial constraints, identifying stakeholder preferences, and maximizing restoration benefits of habitat provision and shoreline protection. Construction of this marsh would: (1) provide additional habitat and ecosystem benefits, (2) slow the rapid migration (up to 15 m/yr at present) of the barrier island, and (3) hinder island breaching. Ultimately, this project – presently at the final design and permitting stage – may enhance the storm and sea-level rise resilience of the island, backbarrier marshes and lagoons, and the mainland town community; and provide an example of a novel science-based approach to coastal resilience that could be applied to other global barrier settings.

Can a small island nation build resilience? The significance of resource‐use patterns and socio‐metabolic risks in The Bahamas

“…Coastal wetlands have the potential to grow with climate change‐driven sea level rise and expand in area. However, this is only possible if enough inland accommodation space is given to coastal wetlands (e.g., through elevation management of the coastal topography, or through a process of “managed retreat” in which wetlands can form as inundation occurs) and these areas are protected such as with upland nature reserves (Bridges et al., 2021; Hein et al., 2021; Schuerch et al., 2018; Zhu et al., 2010). However, these approaches have to be considered cautiously so they do not heighten the existing dependency on material imports and do not add to the current coastal squeeze effect.…”

Shoreface erosion counters blue carbon accumulation in transgressive barrier-island systems

“… 12 , however, we account for lagoon sediment OC in our erosion terms, quantifying a maximum blue carbon loss term for erosion of the entire Holocene unit. Except where replaced by inlet fills, lagoon deposits ubiquitously underlie both transgressive and progradational islands within the VBI chain 35 , 36 , 39 , 41 . Thus, lagoon sediment volume loss is approximated by multiplying the shoreline length, L shoreline (m) (Supplementary Table 1 ), by the island-specific shoreline-change rate, SCR (m yr −1 ) (Supplementary Table 2 ).…”

Undeveloped and developed phases in the centennial evolution of a barrier-marsh-lagoon system: The case of Long Beach Island, New Jersey

“…groins, revetments) engineering structures (Kolodin et al, 2021;Janoff, 2021;Janoff et al, 2020). Additionally, morphological changes in backbarrier environments have been often counteracted with engineering efforts such as hardening of marsh shorelines to prevent marsh-edge erosion, removal of embankments in previously reclaimed saltmarsh land, opening dikes, (re)creating or deepening tidal channels, or vegetating intertidal dredge disposal areas (Weinstein et al, 2001;Teal and Weishar, 2005;Wolters et al, 2005;Hein et al, 2021). It is unclear, however, what the relative effect of these anthropogenic changes is on the evolution of barrier-marsh-lagoon systems over decadal to centennial time scales.…”