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

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.

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Simulating barrier island response to sea level rise with the barrier island and inlet environment (BRIE) model v1.0

Geoscientific Model Development ◽

10.5194/gmd-12-4013-2019 ◽

2019 ◽

Vol 12 (9) ◽

pp. 4013-4030 ◽

Cited By ~ 3

Author(s):

Jaap H. Nienhuis ◽

Jorge Lorenzo-Trueba

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Barrier Island ◽

Barrier Islands ◽

Emergent Behavior ◽

Tidal Inlets ◽

Rise Rate ◽

Ecological Importance ◽

Alongshore Sediment Transport

Abstract. Barrier islands are low-lying coastal landforms vulnerable to inundation and erosion by sea level rise. Despite their socioeconomic and ecological importance, their future morphodynamic response to sea level rise or other hazards is poorly understood. To tackle this knowledge gap, we outline and describe the BarrieR Inlet Environment (BRIE) model that can simulate long-term barrier morphodynamics. In addition to existing overwash and shoreface formulations, BRIE accounts for alongshore sediment transport, inlet dynamics, and flood–tidal delta deposition along barrier islands. Inlets within BRIE can open, close, migrate, merge with other inlets, and build flood–tidal delta deposits. Long-term simulations reveal complex emergent behavior of tidal inlets resulting from interactions with sea level rise and overwash. BRIE also includes a stratigraphic module, which demonstrates that barrier dynamics under constant sea level rise rates can result in stratigraphic profiles composed of inlet fill, flood–tidal delta, and overwash deposits. In general, the BRIE model represents a process-based exploratory view of barrier island morphodynamics that can be used to investigate long-term risks of flooding and erosion in barrier environments. For example, BRIE can simulate barrier island drowning in cases in which the imposed sea level rise rate is faster than the morphodynamic response of the barrier island.

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The complex influences of back-barrier deposition, substrate slope and underlying stratigraphy in barrier island response to sea-level rise: Insights from the Virginia Barrier Islands, Mid-Atlantic Bight, U.S.A.

Geomorphology ◽

10.1016/j.geomorph.2015.06.014 ◽

2015 ◽

Vol 246 ◽

pp. 334-350 ◽

Cited By ~ 24

Author(s):

Owen T. Brenner ◽

Laura J. Moore ◽

A. Brad Murray

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Barrier Island ◽

Barrier Islands ◽

Deposition Substrate

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Statistical modeling of the long-range-dependent structure of barrier island framework geology and surface geomorphology

Earth Surface Dynamics ◽

10.5194/esurf-6-431-2018 ◽

2018 ◽

Vol 6 (2) ◽

pp. 431-450 ◽

Cited By ~ 6

Author(s):

Bradley A. Weymer ◽

Phillipe Wernette ◽

Mark E. Everett ◽

Chris Houser

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Long Range ◽

Moving Average ◽

Quantitative Measure ◽

Barrier Island ◽

Barrier Islands ◽

Wave Number ◽

Statistical Parameters ◽

Padre Island

Abstract. Shorelines exhibit long-range dependence (LRD) and have been shown in some environments to be described in the wave number domain by a power-law characteristic of scale independence. Recent evidence suggests that the geomorphology of barrier islands can, however, exhibit scale dependence as a result of systematic variations in the underlying framework geology. The LRD of framework geology, which influences island geomorphology and its response to storms and sea level rise, has not been previously examined. Electromagnetic induction (EMI) surveys conducted along Padre Island National Seashore (PAIS), Texas, United States, reveal that the EMI apparent conductivity (σa) signal and, by inference, the framework geology exhibits LRD at scales of up to 101 to 102 km. Our study demonstrates the utility of describing EMI σa and lidar spatial series by a fractional autoregressive integrated moving average (ARIMA) process that specifically models LRD. This method offers a robust and compact way of quantifying the geological variations along a barrier island shoreline using three statistical parameters (p, d, q). We discuss how ARIMA models that use a single parameter d provide a quantitative measure for determining free and forced barrier island evolutionary behavior across different scales. Statistical analyses at regional, intermediate, and local scales suggest that the geologic framework within an area of paleo-channels exhibits a first-order control on dune height. The exchange of sediment amongst nearshore, beach, and dune in areas outside this region are scale independent, implying that barrier islands like PAIS exhibit a combination of free and forced behaviors that affect the response of the island to sea level rise.

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Long-Term Community Dynamics Reveal Different Trajectories for Two Mid-Atlantic Maritime Forests

Forests ◽

10.3390/f12081063 ◽

2021 ◽

Vol 12 (8) ◽

pp. 1063

Author(s):

Natasha N. Woods ◽

Philip A. Tuley ◽

Julie C. Zinnert

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Basal Area ◽

Barrier Island ◽

Barrier Islands ◽

Complete Loss ◽

Forest Community ◽

Morella Cerifera ◽

Geographic Position ◽

Maritime Forest

Maritime forests are threatened by sea-level rise, storm surge and encroachment of salt-tolerant species. On barrier islands, these forested communities must withstand the full force of tropical storms, hurricanes and nor’easters while the impact is reduced for mainland forests protected by barrier islands. Geographic position may account for differences in maritime forest resilience to disturbance. In this study, we quantify two geographically distinct maritime forests protected by dunes on Virginia’s Eastern Shore (i.e., mainland and barrier island) at two time points (15 and 21 years apart, respectively) to determine whether the trajectory is successional or presenting evidence of disassembly with sea-level rise and storm exposure. We hypothesize that due to position on the landscape, forest disassembly will be higher on the barrier island than mainland as evidenced by reduction in tree basal area and decreased species richness. Rate of relative sea-level rise in the region was 5.9 ± 0.7 mm yr−1 based on monthly mean sea-level data from 1975 to 2017. Savage Neck Dunes Natural Area Preserve maritime forest was surveyed using the point quarter method in 2003 and 2018. Parramore Island maritime forest was surveyed in 1997 using 32 m diameter circular plots. As the island has been eroding over the past two decades, 2016 Landsat imagery was used to identify remaining forested plots prior to resurveying. In 2018, only plots that remained forested were resurveyed. Lidar was used to quantify elevation of each point/plot surveyed in 2018. Plot elevation at Savage Neck was 1.93 ± 0.02 m above sea level, whereas at Parramore Island, elevation was lower at 1.04 ± 0.08 m. Mainland dominant species, Acer rubrum, Pinus taeda, and Liquidambar styraciflua, remained dominant over the study period, with a 14% reduction in the total number of individuals recorded. Basal area increased by 11%. Conversely, on Parramore Island, 33% of the former forested plots converted to grassland and 33% were lost to erosion and occur as ghost forest on the shore or were lost to the ocean. Of the remaining forested plots surveyed in 2018, dominance switched from Persea palustris and Juniperus virginiana to the shrub Morella cerifera. Only 46% of trees/shrubs remained and basal area was reduced by 84%. Shrub basal area accounted for 66% of the total recorded in 2018. There are alternative paths to maritime forest trajectory which differ for barrier island and mainland. Geographic position relative to disturbance and elevation likely explain the changes in forest community composition over the timeframes studied. Protected mainland forest at Savage Neck occurs at higher mean elevation and indicates natural succession to larger and fewer individuals, with little change in mixed hardwood-pine dominance. The fronting barrier island maritime forest on Parramore Island has undergone rapid change in 21 years, with complete loss of forested communities to ocean or conversion to mesic grassland. Of the forests remaining, dominant evergreen trees are now being replaced with the expanding evergreen shrub, Morella cerifera. Loss of biomass and basal area has been documented in other low elevation coastal forests. Our results indicate that an intermediate shrub state may precede complete loss of woody communities in some coastal communities, providing an alternative mechanism of resilience.

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Simulating barrier island response to sea-level rise with the barrier island and inlet environment (BRIE) model v1.0

10.5194/gmd-2019-10 ◽

2019 ◽

Author(s):

Jaap H. Nienhuis ◽

Jorge Lorenzo-Trueba

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Barrier Island ◽

Barrier Islands ◽

Tidal Inlets ◽

Emergent Behaviour ◽

Rise Rate ◽

Ecological Importance ◽

Alongshore Sediment Transport

Abstract. Barrier islands are low-lying coastal landforms vulnerable to inundation and erosion by sea-level rise. Despite their socio-economic and ecological importance, their morphodynamic response to sea-level rise or other hazards is poorly understood. To tackle this knowledge gap, we outline and describe the BarrieR Inlet Environment (BRIE) model that can simulate long-term barrier morphodynamics. In addition to existing overwash and shoreface formulations, BRIE accounts for alongshore sediment transport, inlet dynamics, and flood-tidal delta deposition along barrier islands. Inlets within BRIE can open, close, migrate, merge with other inlets, and build flood-tidal delta deposits. Long-term simulations reveal complex emergent behaviour of tidal inlets resulting from interactions with sea-level rise, and overwash. BRIE also includes a stratigraphic module, which demonstrates that barrier dynamics under constant sea-level rise rates can result in stratigraphic profiles composed of inlet fill, flood-tidal delta and overwash deposits. In general, the BRIE model represents a process-based exploratory view of barrier island morphodynamics that can be used to investigate long-term risks of flooding and erosion in barrier environments. For example, BRIE can simulate barrier island drowning in cases where the imposed sea-level rise rate is faster than the morphodynamic response of the barrier island.

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Tracking Barrier Island Response to Early Holocene Sea-level Rise: High Resolution Study of Estuarine Sediments in the Trinity River Paleovalley

10.31223/x5vp7q ◽

2021 ◽

Author(s):

Jacob Burstein ◽

John Goff ◽

Sean Gulick ◽

Christopher Lowery ◽

Patricia Standring ◽

...

Keyword(s):

High Resolution ◽

Sea Level Rise ◽

Sea Level ◽

Barrier Island ◽

Barrier Islands ◽

Sediment Supply ◽

Incised Valley ◽

Trinity River ◽

Island System ◽

The Trinity

Understanding how barrier islands respond to factors such as variations in sediment supply, relative sea-level rise, and accommodation is valuable for preparing coastal communities for future impacts of climate change. Increasingly, the underlying antecedent topography has been observed to have a significant control on the evolution of the barrier island system by providing increased elevation, decreased accommodation, and sediment supply for the barrier to rework and anchor upon. However, less attention has been focused on how back barrier sediments respond to this decreased accommodation, and how this may affect barrier island evolution. Additionally, the control in which the geometry of the underlying valley itself has on the initiation of barrier islands is poorly understood. Here we examine the stratigraphic framework of the Trinity River incised valley, offshore Galveston, Texas in order to investigate the role of antecedent topography in the evolution of an ancient barrier island system. We present high-resolution imaging of the Trinity incised valley fill using over 1200 km2 of 3D seismic, <700 km of 2D envelope and full waveform chirp data, along with 2 piston cores, 4 gravity cores, 1 platform boring, with associated grain size, foraminiferal, and radiocarbon data. We find that the geometry and elevation of the underlying antecedent topography plays a central role in the evolution of the barrier island system, promoting both initiation and stabilization. This study provides a methodology to investigate the evolution of a relict barrier island system where little to none of the barrier is preserved. With this methodology, we revise the established Holocene paleoshoreline model for the Trinity incised valley.

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Statistical modeling of the long-range dependent structure of barrier island framework geology and surface geomorphology

10.5194/esurf-2018-5 ◽

2018 ◽

Cited By ~ 1

Author(s):

Bradley A. Weymer ◽

Phillipe Wernette ◽

Mark E. Everett ◽

Chris Houser

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Long Range ◽

Moving Average ◽

Quantitative Measure ◽

Barrier Island ◽

Barrier Islands ◽

Auto Regressive ◽

Padre Island ◽

Dune Height

Abstract. Shorelines exhibit long-range dependence (LRD) and have been shown in some environments to be described in the wavenumber domain by a power law characteristic of scale-independence. Recent evidence suggests that the geomorphology of barrier islands can, however, exhibit scale dependence as a result of systematic variations of the underlying framework geology. The LRD of framework geology, which influences island geomorphology and its response to storms and sea level rise, has not been previously examined. Electromagnetic induction (EMI) surveys conducted along Padre Island National Seashore (PAIS), Texas, USA, reveal that the EMI apparent conductivity σa signal and, by inference, the framework geology exhibits LRD at scales up to 101 to 102 km. Our study demonstrates the utility of describing EMI σa and LiDAR spatial series by a fractional auto-regressive integrated moving average process that specifically models LRD. This method offers a robust and compact way for quantifying the geological variations along a barrier island shoreline using three parameters (p,d,q). We discuss how ARIMA (0,d,0) models that use a single parameter d provide a quantitative measure for determining free and forced barrier island evolutionary behavior across different scales. Statistical analyses at regional, intermediate, and local scales suggest that the geologic framework within an area of paleo-channels exhibits a first order control on dune height. The exchange of sediment amongst nearshore, beach and dune in areas outside this region are scale-independent, implying that barrier islands like PAIS exhibit a combination of free and forced behaviors that affect the response of the island to sea level rise.

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Assessing the Effectiveness of Nourishment in Decadal Barrier Island Morphological Resilience

Water ◽

10.3390/w13070944 ◽

2021 ◽

Vol 13 (7) ◽

pp. 944

Author(s):

Davina L. Passeri ◽

Matthew V. Bilskie ◽

Scott C. Hagen ◽

Rangley C. Mickey ◽

P. Soupy Dalyander ◽

...

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Barrier Height ◽

Barrier Island ◽

Barrier Islands ◽

Sandy Beaches ◽

Integrated Models ◽

Short Term ◽

Moderate Amount ◽

Coastal Resilience

Nourishment has shown to be an effective method for short-term storm protection along barrier islands and sandy beaches by reducing flooding, wave attack and erosion. However, the ability of nourishment to mitigate the effects of storms and sea level rise (SLR) and improve coastal resilience over decadal time scales is not well understood. This study uses integrated models of storm-driven hydrodynamics, morphodynamics and post-storm dune recovery to assess the effectiveness of beach and dune nourishment on barrier island morphological resilience over a 30-year period, accounting for storms and a moderate amount of SLR. Results show that at the end of the 30 years, nourishment contributes to maintaining island volumes by increasing barrier height and width compared with a no-action scenario (i.e., no nourishment, only natural recovery). During storms where the collision regime was dominant, higher volumes of sand were lost from the wider beach in the nourishment scenario than in the no-action scenario. During stronger storms, nourishment reduced dune overtopping compared with the no-action scenario, allowing the island to maintain height and width. Additionally, nourishment was particularly effective in reducing breaching during back-to-back storms occurring in the same year.

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