Sea Level Rise Will Drive Divergent Sediment Transport Patterns on Fore Reefs and Reef Flats, Potentially Causing Erosion on Atoll Islands

Bramante, James F.; Ashton, Andrew D.; Storlazzi, Curt D.; Cheriton, Olivia M.; Donnelly, Jeffrey P.

doi:10.1029/2019jf005446

Cited by 19 publications

(11 citation statements)

References 66 publications

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“…Despite the absence of organized ripples on the reef flat, the phase observations in this study suggests that vortices develop and suspend sediment from the bed, perhaps due to reef flat bed variability (e.g., roughness). Wave nonlinearities such as asymmetric and skewed wave forms (Cheriton et al., 2020) may also contribute to the flux of sediment, particularly closer to the reef crest (Bramante et al., 2020).…”

Section: Discussionmentioning

confidence: 99%

“…It remains unclear from the results of this study how these changes will affect the net cross-reef transport of sediment in suspension. Bramante et al (2020) recently showed, using the nonhydrostatic numerical model XBeach, that for increased sea level the wave height, skewness, and shear stress imposed on the bed are likely to increase cross-reef sediment transport. However, that study also showed that changes to the incident waves on the fore reef would also reduce the sediment transported onto the reef flat from the fore reef.…”

Section: Implications For Future Changes To Sediment Transport Mechanismsmentioning

confidence: 99%

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The Contribution of Currents, Sea‐Swell Waves, and Infragravity Waves to Suspended‐Sediment Transport Across a Coral Reef‐Lagoon System

et al. 2021

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Tropical beaches protect and support communities of hundreds of millions of people globally (Hoegh-Guldberg et al., 2019). These beaches are primarily accumulations of sediment derived from the calcium carbonate skeletal remains of organisms such as coral, crustose coralline algae, and mollusks from adjacent coral reefs (Perry & Hepburn, 2008). When these skeletal remains break down into particle sizes that can Abstract Coral reefs generate substantial volumes of carbonate sediment, which is redistributed throughout the reef-lagoon system. However, there is little understanding of the specific processes that transport this sediment produced on the outer portions of coral reefs throughout a reef-lagoon system. Furthermore, the separate contributions of currents, sea-swell waves, and infragravity waves to transport, which are all strongly influenced by the presence of a reef, is not fully understood. Here, we show that in reef-lagoon systems most suspended sediment is transported close to the seabed and can, at times, be suspended higher in the water column during oscillatory flow transitions (i.e., near slack flow) at sea-swell wave frequencies, and during the peak onshore oscillatory velocity phase at infragravity wave frequencies. While these wave frequencies contribute to the transport of suspended sediment offshore and onshore, respectively, the net flux is small. Mean currents are the primary transport mechanism and responsible for almost 2 orders of magnitude more suspended-sediment flux than sea-swell and infragravity waves. Whilst waves may not be the primary mechanism for the transport of sediment, our results suggest they are an important driver of sediment suspension from the seabed, as well as contributing to the partitioning of sediment grain sizes from the reef to the shoreline. As the ocean wave climate changes, sea level rises, and the composition of reef benthic communities change, the relative importance of mean currents, seaswell waves, and infragravity waves is likely to change, and this will affect how sediment is redistributed throughout reef-lagoon systems. Plain Language Summary Most of the sandy sediment found on coral reef coastlines is produced by organisms living within the reef. This sediment is then transported by waves and currents across the reef and distributed throughout the lagoon. Little is known about these transport processes, including the relative importance of how currents or different types of waves drive transport. This study shows that most of the sediment in the water column (suspended sediment) is transported close to the seabed by mean currents. At times, this sediment can be suspended higher in the water column by short waves (5-25 s) when the flow transitions from being onshore directed to offshore directed, or when the velocities of longer period waves (25-250 s), called infragravity waves, are directed onshore. The timing of the suspension by these waves helps to sort the sediment into different sizes across the system, but the quantity of sediment transported is ...

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Section: Discussionmentioning

confidence: 99%

Section: Implications For Future Changes To Sediment Transport Mechanismsmentioning

confidence: 99%

The Contribution of Currents, Sea‐Swell Waves, and Infragravity Waves to Suspended‐Sediment Transport Across a Coral Reef‐Lagoon System

et al. 2021

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“…Suspended sediment transport seems to be controlled by mean currents on the reef flat, although sediment suspension is triggered through swell- and infragravity waves ( Pomeroy et al, 2021 ). Notably, such mechanisms that induce sediment transport from the reef to the shoreline are likely to alter with future sea-level rise and related changes in reef flat topography ( Bramante et al, 2020 ; Pomeroy et al, 2021 ). Accordingly, divergent patterns of sediment redistribution might induce unintended shoreline erosion and deposition, as seen in development projects in the waters of Abu Dhabi ( Van Lavieren et al 2011 ).…”

Section: Survey Methodologymentioning

confidence: 99%

Ecosystem design as an avenue for improving services provided by carbonate producing marine ecosystems

Westphal

Murphy

Doo

et al. 2022

PeerJ

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Ecosystem Design (ED) is an approach for constructing habitats that places human needs for ecosystem services at the center of intervention, with the overarching goal of establishing self-sustaining habitats which require limited management. This concept was originally developed for use in mangrove ecosystems, and is understandably controversial, as it markedly diverges from other protection approaches that assign human use a minor priority or exclude it. However, the advantage of ED lies within the considered implementation of these designed ecosystems, thus preserving human benefits from potential later disturbances. Here, we outline the concept of ED in tropical carbonate depositional systems and discuss potential applications to aid ecosystem services such as beach nourishment and protection of coastlines and reef islands at risk from environmental and climate change, CO2 sequestration, food production, and tourism. Biological carbonate sediment production is a crucial source of stability of reef islands and reef-rimmed coastlines. Careful implementation of designed carbonate depositional ecosystems could help counterbalance sea-level rise and manage documented erosion effects of coastal constructions. Importantly, adhering to the core ethos of ED, careful dynamic assessments which provide a balanced approach to maximizing ecosystem services (e.g., carbonate production), should identify and avoid any potential damages to existing functioning ecosystems.

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“…SedBudget has potential for application on a stand-alone basis for supporting reef-shoreline sediment linkage studies, to help parametrise coastal vulnerability (e.g., Storlazzi et al, 2011) and reef-to-island sediment models (Morgan and Kench, 2014;Bramante et al, 2020;Masselink et al, 2020), and/or to be used alongside ReefBudget for more complete biogenic carbonate budget assessments.…”

Section: Introductionmentioning

confidence: 99%

Quantifying reef-derived sediment generation: Introducing the SedBudget methodology to support tropical coastline and island vulnerability studies

Perry¹,

Lange²,

Stuhr³

2023

Camb. prisms Coast. futures

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The development and maintenance of reef-fronted tropical shorelines and reef islands is strongly dependent upon the supply of biogenic sediments produced on the adjacent coral reefs. It is well established that a wide array of reef-dwelling plants and animals either directly (e.g., in the form of their shelly remains) or indirectly (e.g., as a byproduct of their feeding) contribute to the production of this sedimentary material. However, we lack standardised methodologies that can enable estimates of both the amounts and types of sediment being generated and the sediment size-class fractions to which this material contributes. Sediment composition and grain size are both important controls on shoreline sediment supply because they impact sediment hydrodynamic behaviour. Reliable estimates of production are thus needed to better support shoreline sediment transport and supply modelling. Here we introduce a new census-based method called SedBudget that has been set up to address this challenge. Based on a proposed set of consistent taxaspecific methodologies it generates estimates of total sediment production from reef taxa, and the types and size-class fractions of sediment generated. We then apply this data to several reef sites in the northern Chagos Archipelago to illustrate the nature of the data produced. Such data not only have potential to support coastal sediment transport modelling studies through the acquisition of site-level production estimates, but also to contribute to more integrated datasets capturing total site-level biogenic carbonate production that can

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Sea Level Rise Will Drive Divergent Sediment Transport Patterns on Fore Reefs and Reef Flats, Potentially Causing Erosion on Atoll Islands

Cited by 19 publications

References 66 publications

The Contribution of Currents, Sea‐Swell Waves, and Infragravity Waves to Suspended‐Sediment Transport Across a Coral Reef‐Lagoon System

The Contribution of Currents, Sea‐Swell Waves, and Infragravity Waves to Suspended‐Sediment Transport Across a Coral Reef‐Lagoon System

Ecosystem design as an avenue for improving services provided by carbonate producing marine ecosystems

Quantifying reef-derived sediment generation: Introducing the SedBudget methodology to support tropical coastline and island vulnerability studies

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