Integrating Oyster Castles into Living Shorelines to promote coastal bays resilience to Sea Level Rise

Abstract. Sea-level rise (SLR) not only increases the threat of coastal flooding, but also may change tidal regimes in estuaries and coastal bays. To investigate such nearshore tidal responses to SLR, a hydrodynamic model of the European Shelf is downscaled to a model of a Dutch coastal bay (the Eastern Scheldt) and forced by SLR scenarios ranging from 0 to 2 m. The results indicate that SLR induces larger increases in tidal amplitude and stronger nonlinear tidal distortion in the bay compared to the adjacent shelf sea. Under SLR, the basin shifts from a mixed flood- and ebb-dominant state to complete ebb-dominance, causing enhanced sediment export and accelerated loss of tidal flats. In this case study, we find that local impacts of SLR can be highly spatially-varying and nonlinear depending on basin geometry. Our model downscaling approach is widely applicable for establishing local SLR projections in estuaries and coastal bays.

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Integrating biogeomorphic feedbacks in the coastal zone to bolster coastal resiliency

10.5194/egusphere-egu21-5669 ◽

2021 ◽

Author(s):

Cindy Palinkas ◽

Lorie Staver

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Management Strategy ◽

Environmental Changes ◽

Sediment Supply ◽

Coastal Protection ◽

Coastal System ◽

Living Shorelines ◽

Accretion Rates ◽

Created Marshes

<p>Living shorelines, defined in this study as narrow marsh fringes with adjacent sills, have been gaining traction as the preferred management strategy to mitigate shoreline erosion. These nature-based features provide the same ecosystem services as natural marshes while protecting coastlines. However, they also are threatened by the same environmental changes (sea-level rise, changing sediment supply) as natural marshes and may change characteristics of adjacent subtidal sediments. This study evaluates the role of plants in both the created marshes of living shorelines and, where present, beds of submersed aquatic vegetation (SAV) in the adjacent subtidal in the effectiveness, impacts, and resiliency of living shorelines over ~10 years in mesohaline Chesapeake Bay. At study sites, there is a net seaward movement of shorelines with living shoreline installation due to construction technique. This movement replaces shallow-water habitat immediately adjacent to the pre-existing shoreline; farther offshore, sedimentological changes vary among sites but do not appear to drive changes in the presence/absence of subtidal SAV. While current accretion rates in the created marshes are greater than local relative sea-level rise, there is evidence that accretion rates increase with marsh age, suggesting that living shorelines are most vulnerable in the first few years after installation. Because nutrient burial is maximized when SAV occur next to living shorelines, a management strategy that considers the subtidal and intertidal as integrated components of the coastal system is needed to optimize co-benefits of coastal protection.</p>

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Effects of sea-level rise on tides and sediment dynamics in a Dutch tidal bay

Ocean Science ◽

10.5194/os-16-307-2020 ◽

2020 ◽

Vol 16 (2) ◽

pp. 307-321 ◽

Cited By ~ 1

Author(s):

Long Jiang ◽

Theo Gerkema ◽

Déborah Idier ◽

Aimée B. A. Slangen ◽

Karline Soetaert

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Bottom Topography ◽

Tidal Asymmetry ◽

Meteorological Forcing ◽

Coastal Bays ◽

Dominant State ◽

Shelf Sea ◽

Load Transport ◽

Coastal Bay

Abstract. Sea-level rise (SLR) not only increases the threat of coastal flooding, but may also change tidal regimes in estuaries and coastal bays. To investigate such nearshore tidal responses to SLR, a hydrodynamic model of the European Shelf is downscaled to a model of a Dutch coastal bay (the Oosterschelde, i.e., Eastern Scheldt) and forced by SLR scenarios ranging from 0 to 2 m. This way, the effect of SLR on tidal dynamics in the adjacent North Sea is taken into account as well. The model setup does not include meteorological forcing, gravitational circulation, and changes in bottom topography. Our results indicate that SLR up to 2 m induces larger increases in tidal amplitude and stronger nonlinear tidal distortion in the bay compared to the adjacent shelf sea. Under SLR up to 2 m, the bay shifts from a mixed flood- and ebb-dominant state to complete ebb dominance. We also find that tidal asymmetry affects an important component of sediment transport. Considering sand bed-load transport only, the changed tidal asymmetry may lead to enhanced export, with potential implications for shoreline management. In this case study, we find that local impacts of SLR can be highly spatially varying and nonlinear. The model coupling approach applied here is suggested as a useful tool for establishing local SLR projections in estuaries and coastal bays elsewhere. Future studies should include how SLR changes the bed morphology as well as the feedback effect on tides.

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Divergence of Sediment Fluxes Triggered by Sea‐Level Rise Will Reshape Coastal Bays

Geophysical Research Letters ◽

10.1029/2020gl087862 ◽

2020 ◽

Vol 47 (13) ◽

Cited By ~ 1

Author(s):

Xiaohe Zhang ◽

Nicoletta Leonardi ◽

Carmine Donatelli ◽

Sergio Fagherazzi

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Coastal Bays ◽

Sediment Fluxes

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Communicating Managed Retreat in California

Water ◽

10.3390/w13060781 ◽

2021 ◽

Vol 13 (6) ◽

pp. 781

Author(s):

Wendy Karen Bragg ◽

Sara Tasse Gonzalez ◽

Ando Rabearisoa ◽

Amanda Daria Stoltz

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Review Process ◽

Program Review ◽

Property Management ◽

Short Term ◽

Living Shorelines ◽

Defensive Strategies ◽

Management Plans ◽

Imminent Risk

California cities face growing threats from sea-level rise as increased frequency and severity of flooding and storms cause devastating erosion, infrastructure damage, and loss of property. Management plans are often designed to prevent or slow flooding with short-term, defensive strategies such as shoreline hardening, beach nourishment, and living shorelines. By contrast, managed retreat focuses on avoiding hazards and adapting to changing shorelines by relocating out of harm’s way. However, the term “managed retreat” can be controversial and has engendered heated debates, defensive protests, and steady resistance in some communities. Such responses have stymied inclusion of managed retreat in adaptation plans, and in some cases has resulted in complete abandonment of the policy review process. We examined the Local Coastal Program review process in seven California communities at imminent risk of sea-level rise and categorized each case as receptive or resistant to managed retreat. Three prominent themes distinguished the two groups: (1) inclusivity, timing, and consistency of communication, (2) property ownership, and (3) stakeholder reluctance to change. We examined use of terminology and communication strategies and provided recommendations to communicate “managed retreat” more effectively.

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Economic evaluation of sea-level rise adaptation strongly influenced by hydrodynamic feedbacks

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2025961118 ◽

2021 ◽

Vol 118 (29) ◽

pp. e2025961118

Author(s):

Michelle A. Hummel ◽

Robert Griffin ◽

Katie Arkema ◽

Anne D. Guerry

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

San Francisco ◽

Economic Assessment ◽

The United States ◽

Coastal Communities ◽

Coastal Bays ◽

Shoreline Protection ◽

Sea Level Rise Adaptation ◽

Shared Risk

Coastal communities rely on levees and seawalls as critical protection against sea-level rise; in the United States alone, $300 billion in shoreline armoring costs are forecast by 2100. However, despite the local flood risk reduction benefits, these structures can exacerbate flooding and associated damages along other parts of the shoreline—particularly in coastal bays and estuaries, where nearly 500 million people globally are at risk from sea-level rise. The magnitude and spatial distribution of the economic impact of this dynamic, however, are poorly understood. Here we combine hydrodynamic and economic models to assess the extent of both local and regional flooding and damages expected from a range of shoreline protection and sea-level rise scenarios in San Francisco Bay, California. We find that protection of individual shoreline segments (5 to 75 km) can increase flooding in other areas by as much as 36 million m3 and damages by $723 million for a single flood event and in some cases can even cause regional flood damages that exceed the local damages prevented from protection. We also demonstrate that strategic flooding of certain shoreline segments, such as those with gradually sloping baylands and space for water storage, can help alleviate flooding and damages along other stretches of the coastline. By matching the scale of the economic assessment to the scale of the threat, we reveal the previously uncounted costs associated with uncoordinated adaptation actions and demonstrate that a regional planning perspective is essential for reducing shared risk and wisely spending adaptation resources in coastal bays.

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Glacial Contributions to 21st Century Sea Level Rise

Eos ◽

10.1029/2020eo143700 ◽

2020 ◽

Vol 101 ◽

Author(s):

Kate Wheeling

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

21St Century ◽

Mass Change ◽

Sources Of Uncertainty

Researchers identify the main sources of uncertainty in projections of global glacier mass change, which is expected to add about 8–16 centimeters to sea level, through this century.

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