Global patterns and drivers of tidal marsh response to accelerating sea-level rise

Abstract The vulnerability of the world’s tidal marshes to sea-level rise threatens their substantial contribution to fisheries, coastal protection, biodiversity conservation and carbon sequestration. Feedbacks between relative sea-level rise (RSLR) and the rate of mineral and organic sediment accumulation in tidal wetlands, and hence elevation gain, have been proposed to ameliorate this risk. Here we report on changes in tidal marsh elevation and shoreline position in relation to our network of 387 fixed benchmarks in tidal marshes on four continents measured for an average of 10 years. During this period RSLR at these marshes reached on average 6.6 mm yr-1, compared to 0.34 mm yr-1 over the past millenia. While the rate of sediment accretion corresponded to RSLR, the loss of elevation to shallow subsidence increased in proportion to the accretion rate. This caused a deficit between elevation gain and RSLR which increased consistently with the rate of RSLR regardless of position within the tidal frame, suggesting that long-term in situ tidal marsh survival is unlikely. While higher tidal range (>3m) conferred a greater stability in measures of shoreline change and vegetation cover, other regions showed a tendency towards instability and retreat.

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Biogeomorphic modeling to assess resilience of tidal marsh restoration to sea level rise and sediment supply

10.5194/esurf-2021-66 ◽

2021 ◽

Author(s):

Olivier Gourgue ◽

Jim van Belzen ◽

Christian Schwarz ◽

Wouter Vandenbruwaene ◽

Joris Vanlede ◽

...

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Tidal Marsh ◽

Model Performance ◽

Suspended Sediments ◽

Sediment Supply ◽

Tidal Marshes ◽

Marsh Restoration ◽

Tidal Marsh Restoration ◽

Increasing Demand

Abstract. There is an increasing demand for creation and restoration of tidal marshes around the world, as they provide highly valued ecosystem services. Yet, tidal marshes are strongly vulnerable to factors such as sea level rise and declining sediment supply. How fast the restored ecosystem develops, how resilient it is to sea level rise, and how this can be steered by restoration design, are key questions that are typically challenging to assess. In this paper, we apply a biogeomorphic model to a planned tidal marsh restoration by dike breaching. Our modeling approach integrates tidal hydrodynamics, sediment transport and vegetation dynamics, accounting for relevant fine-scale flow-vegetation interactions (less than 1 m2) and their impact on vegetation and landform development at the landscape scale (several km2) and on the long term (several decades). Our model performance is positively evaluated against observations of vegetation and geomorphic development in adjacent tidal marshes. Model scenarios demonstrate that the restored tidal marsh can keep pace with realistic rates of sea level rise and that its resilience is more sensitive to the availability of suspended sediments than to the rate of sea level rise. We further demonstrate that restoration design options can steer marsh resilience, as it affects the rates and spatial patterns of biogeomorphic development. By varying the width of two dike breaches, which serve as tidal inlets to the restored marsh, we show that a larger difference in the width of the two inlets leads to more diversity in restored habitats. This study showcases that biogeomorphic modeling can support management choices in restoration design to optimize tidal marsh development towards sustainable restoration goals.

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An Assessment of Coastal Vulnerability of Pahang’s Coast Due to Sea Level Rise

International Journal of Engineering & Technology ◽

10.14419/ijet.v7i3.14.16880 ◽

2018 ◽

Vol 7 (3.14) ◽

pp. 176 ◽

Cited By ~ 1

Author(s):

Fazly Amri Mohd ◽

Khairul Nizam Abdul Maulud ◽

Othman A. Karim ◽

Rawshan Ara Begum ◽

Md Firoz Khan ◽

...

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Local Community ◽

Climate Extremes ◽

Shoreline Change ◽

Vulnerability Index ◽

Peninsular Malaysia ◽

Tidal Range ◽

Coastal Vulnerability ◽

Physical Variables

Climate change interacts in a different way with varieties of human activities and other drivers of change along coastlines. Sea level rise (SLR) is one of the major impacts of global warming. Changes in climate extremes and SLR may impact the critical infrastructures such as coastal road, jetty and chalets as well as the local community. The population and assets exposed to coastal risks will increase significantly due to population growth, economic development and urbanization in the future. As most of the cities in Malaysia are situated near the coast, immediate actions are needed to minimize the undesired outcome due to the SLR. The main objective of this study is to identify physical variables that may have impacts on the coastal area, thus develop a coastal vulnerability index (CVI) for the East Coast of Peninsular Malaysia. Seven (7) physical variables have been identified to assess the CVI that consists of geomorphology, coastal slope, shoreline change rate, mean significant wave height, mean tidal range, relative sea level rate and land use. A comprehensive CVI was obtained by integrating the differential weighted rank values of the variables. The outcome of this study is useful as a tool for coastal disaster management.

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Success of coastal wetlands restoration is driven by sediment availability

Communications Earth & Environment ◽

10.1038/s43247-021-00117-7 ◽

2021 ◽

Vol 2 (1) ◽

Author(s):

Zezheng Liu ◽

Sergio Fagherazzi ◽

Baoshan Cui

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Coastal Wetlands ◽

Coastal Wetland ◽

Meta Analysis ◽

Regional Scale ◽

Global Strategy ◽

Sediment Supply ◽

Tidal Range ◽

Coastal Protection

AbstractShorelines and their ecosystems are endangered by sea-level rise. Nature-based coastal protection is becoming a global strategy to enhance coastal resilience through the cost-effective creation, restoration and sustainable use of coastal wetlands. However, the resilience to sea-level rise of coastal wetlands created under Nature-based Solution has been assessed largely on a regional scale. Here we assess, using a meta-analysis, the difference in accretion, elevation, and sediment deposition rates between natural and restored coastal wetlands across the world. Our results show that restored coastal wetlands can trap more sediment and that the effectiveness of these restoration projects is primarily driven by sediment availability, not by wetland elevation, tidal range, local rates of sea-level rise, and significant wave height. Our results suggest that Nature-based Solutions can mitigate coastal wetland vulnerability to sea-level rise, but are effective only in coastal locations where abundant sediment supply is available.

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Sediment Accumulation, Elevation Change, and the Vulnerability of Tidal Marshes in the Delaware Estuary and Barnegat Bay to Accelerated Sea Level Rise

Estuaries and Coasts ◽

10.1007/s12237-021-00972-9 ◽

2021 ◽

Author(s):

LeeAnn Haaf ◽

Elizabeth Burke Watson ◽

Tracy Elsey-Quirk ◽

Kirk Raper ◽

Angela Padeletti ◽

...

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Sediment Accumulation ◽

Tidal Marshes ◽

Delaware Estuary ◽

Elevation Change ◽

Barnegat Bay

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Sediment accumulation, elevation change, and the vulnerability of tidal marshes in the Delaware Estuary and Barnegat Bay to accelerated sea level rise

10.1101/821827 ◽

2019 ◽

Author(s):

LeeAnn Haaf ◽

Elizabeth Burke Watson ◽

Tracy Elsey-Quirk ◽

Kirk Raper ◽

Angela Padeletti ◽

...

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Sediment Accumulation ◽

High Water ◽

Tidal Marshes ◽

Delaware Estuary ◽

Elevation Change ◽

Barnegat Bay ◽

Mean High Water ◽

Elevation Capital

AbstractTidal marshes protect coastal communities from the effects of sea level rise and storms, yet they are vulnerable to prolonged inundation and submergence. Uncertainty regarding their vulnerability to sea level rise motivated the establishment of a monitoring network in the Delaware Estuary and Barnegat Bay. Using data collected through these efforts, we determined whether rates of tidal marsh sediment accumulation and elevation change exceeded local sea level rise and how these dynamics varied along geographic and environmental gradients. Marker horizons, surface elevation tables, elevation surveys, water level data, and water column suspended sediment concentrations were used to evaluate sea level rise vulnerability. Of 32 study sites, 75% had elevation change that did not keep pace with long-term rising sea levels (1969–2018) and 94% did not keep pace with recent sea level rise (2000–2018). Mean high water rose most rapidly in the freshwater tidal portion of the Delaware Estuary with rates nearing 1 cm yr-1 from 2000–2018. We noted that greater sediment accumulation rates occurred in marshes with large tidal ranges, low elevations, and high water column suspended sediment concentrations. We found correlations between rates of shallow subsidence, increasing salinity, and decreasing tidal range. Marsh elevation and water level surveys revealed significant variability in elevation capital and summer flooding patterns (12–67% inundation). However, rapid increases in mean high water over the past 19 years suggests that all marsh platforms currently sit at or below mean high water. Overall, these data suggest that tidal marshes in the Delaware Estuary and Barnegat Bay are vulnerable to submergence by current rates of sea-level rise. While we observed variability in marsh elevation capital, the absence of strong correlations between elevation trends and environmental parameters makes it difficult to identify clear patterns of sea level rise vulnerability among wetlands.

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Analysis of the Makran Coastline of Iran’s Vulnerability to Global Sea-Level Rise

Journal of Marine Science and Engineering ◽

10.3390/jmse9080891 ◽

2021 ◽

Vol 9 (8) ◽

pp. 891

Author(s):

Ezatollah Ghanavati ◽

Majid Shah-Hosseini ◽

Nick Marriner

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Global Climate ◽

Shoreline Change ◽

Vulnerability Index ◽

Sandy Beaches ◽

Tidal Range ◽

Rocky Shores ◽

Mangrove Forests ◽

Global Sea Level

The SE coast of Iran is of great economic and environmental importance. Global climate change affects this coastline through sea level rise (SLR), compounded by a decrease in sediment budgets in coastal areas. This study developed a Coastal Vulnerability Index (CVI) for the SE coast of Iran using satellite, instrumental and field data. Eight risk variables were defined: coastal slope, regional coastal elevation, mean tidal range, mean significant wave height, rate of relative sea-level change, rate of shoreline change, environmental sensitivity and socio-economic sensitivity. The coast was divided into 27 segments based on geomorphic, environmental and socioeconomic traits. Coastal segments were categorized based on their vulnerability to each risk factor using a CVI. The resulting maps highlighted the vulnerability of each coastal segment to SLR. Approximately 50% of the coast is comprised of mostly rocky shores, which are less vulnerable to SLR. Approximately 33% of the coastal length, including sandy beaches, tidal flats and mangrove forests, were determined to be highly vulnerable to SLR. Approximately 12% of the coastline was determined to be moderately vulnerable. Population centers and infrastructure were ranked as highly-to-moderately vulnerable to SLR. This study highlighted the high vulnerability of low-lying areas, such as lagoons and mangroves, in the western part of the Iranian coast of Makran. Proper coastal management and mitigation plans are essential in the future to protect coastal societies and environments.

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