Coral reef sediment dynamics: evidence of sand-apron evolution on a daily and decadal scale

Vila‐Concejo, Ana; Harris, Daniel L.; Shannon, Amelia M.; Webster, Jody M.; Power, Hannah E.

doi:10.2112/si65-103.1

Cited by 17 publications

(13 citation statements)

References 25 publications

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“…Sediment transport processes across coral reef platforms are governed by hydrodynamic processes operating over a range of time scales. Most of the sediment transport is generated by flows directly or indirectly generated by ocean waves, that is, wave orbital velocities and nearshore currents, respectively (Kench, ; Ogston et al, ; Vila‐Concejo et al, ). Tidal currents can also play a significant role, especially when channels are present (Kench & McLean, ), but the main role of the tide is to modulate the ocean‐wave processes (Brander et al, ; Young, ).…”

Section: Introductionmentioning

confidence: 99%

Physical and Numerical Modeling of Infragravity Wave Generation and Transformation on Coral Reef Platforms

et al. 2019

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Wave transformation across reef platforms strongly controls sediment transport processes and coral reef island morphodynamics with infragravity (IG) waves playing an important contributing role. A small‐scale (1:50) laboratory experiment and prototype numerical modeling are used to explore the characteristics of IG wave motion on coral reefs. The slope of the fore reef is the key factor controlling the mechanism of IG wave generation. Steep slopes (>1/10) are dominated by landward and seaward propagating breakpoint‐forced long waves, whereas incoming and then released bound long waves become increasingly important for slopes <1/20. The breakpoint‐forced long wave mechanism is the more effective generator of IG energy, and the most energetic IG motion (normalized by incident wave motion) is generated on reef platforms with a fore reef slope > 1/6. The water level relative to the reef platform hreef is also a key factor, and the largest IG waves are generated for a ratio between hreef and offshore significant wave height Hs,o of −0.25 to 0.75, that is, when most waves break across the reef slope and a fully saturated surf zone extends across the reef platform. An island on the reef platform substantially increases the contribution of IG waves to the total wave spectrum, but increased reef surface roughness reduces IG importance. Under the most optimal conditions, the IG wave height averaged across the platform is 20–30% of the incident offshore wave height. The geomorphic influence of IG waves is considered most significant for reef platforms with energetic waves breaking on the steepest fore reefs.

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Section: Introductionmentioning

confidence: 99%

Physical and Numerical Modeling of Infragravity Wave Generation and Transformation on Coral Reef Platforms

et al. 2019

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“…This is likely due to the lack of simulation of suspended sediment (ReefSAM simulates bedload only) and lack of tidal/lagoonal currents/circulation (the wave-energy only ReefSAM hydrodynamic model does not simulate sufficient shear stress deep enough to distribute sand in the deep parts of the lagoon). Significant wave, wind and tide induced circulation is known to occur in the lagoon (Frith and Mason, 1986;Vila-Concejo et al, 2013) and sedimentation rates of mostly coarse silt to very fine sand (i.e. fine enough that suspended transport is significant) of 1.2 to 2.2 mm/yr have been reported (Kosnik et al, 2014).…”

Section: Best Estimate Simulationmentioning

confidence: 99%

“…Likewise, many of these and other reef features (especially rubble flats and banks) may be formed due to heterogeneity in the energy regime (e.g. swell direction and magnitude) rather than by average or "every day" conditions Vila-Concejo et al, 2013), making their simulation highly challenging. C3D does not simulate these processes or the resulting landforms as it simulates hydrodynamic energy for sediment transport simply as a current of uniform direction across the model space which varies by depth alone.…”

Section: Introductionmentioning

confidence: 99%

Reef Sedimentary Accretion Model (ReefSAM): Understanding coral reef evolution on Holocene time scales using 3D stratigraphic forward modelling

Barrett

Webster

2017

Marine Geology

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A detailed understanding of the development of coral reefs and their internal structure has important applications for predicting future reef trajectories in light of climate changes, petroleum exploration and reconstructing past environmental changes such as sea level. Numerical computer modelling provides a quantitative means of testing and understanding reef processes and better predicting past and future reef development. However, most existing carbonate stratigraphic forward models (SFMs) focus on the platform scale and several limitations in their simulation of important reef processes and reef-scale features (e.g. patch reefs, sand aprons) have been previously identified. We present the Reef Sedimentary Accretion Model (ReefSAM)-a new carbonate SFM designed to test new approaches to modelling processes important at the reef scale, with the goal of better simulating reef features and evolution at higher temporal and *Manuscript Click here to download Manuscript: MARGO6160_R2_clean.docx Click here to view linked References Barrett and Webster 2017-Marine Geology 2 spatial resolutions. Specific developments include a sediment transport model which calculates deposition based on a range of grain sizes, and additional controls on coralgal growth including wave energy and surface substrate specificity, and model outputs showing categorized paleo-conditions (composition, paleo-depth and paleoenergy) along with numerous quantitative measures for objective comparison of model results to real-world observational data, which is often more abundant for modern/Holocene reefs than buried ancient reefs Simulations of the well-studied Holocene One Tree Reef (OTR), in the southern Great Barrier Reef (GBR) showed improvements upon previous modelling attempts in both quantitative measures (e.g. lagoon size or reef sea level catch-up time), and ability to produce more realistic reefscale morphological features (e.g. lagoonal patch-reefs, mostly sand-filled lagoon) and reef development characteristics (e.g. transition from mostly vertical aggradation during sea level catch-up to horizontal progradation afterwards). Controls on reef maturity/lagoonal filling identified in previous modelling experiments were corroborated. Sensitivity testing also revealed a very high sensitivity to reef drowning. These results indicate the new modelling approaches are viable and provide a way forward for future Holocene reef evolution model development.

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“…Once reef platforms attain a stable elevation with respect to sea‐level, sediment dynamics become the primary constructional process on coral reefs (Kench, ). Thus, sediment dynamics largely govern the response of coral reefs to sea‐level fluctuations (Vila‐Concejo et al ., ). Analysis of sediment transport pathways, rates of sediment transport and process mechanisms driving transport is therefore fundamental to the management of reef‐associated sedimentary landforms and a better understanding of the long‐term evolution of geomorphic features on coral reefs.…”

Section: Introductionmentioning

confidence: 97%

“…Once broken down, carbonate sediments derived from the peripheral reef slopes and productive reef flats are entrained and transported by refracted waves and deposited at focal points (Smithers & Hopley, ). These depositional sinks include rubble ridges and spits on the reef flat (Harris & Vila‐Concejo, ; Shannon et al ., ), sand aprons (Vila‐Concejo et al ., , ; Harris et al ., ) and within lagoon basins (Perry et al ., ).…”

Section: Introductionmentioning

confidence: 99%

Linking pattern to process in reef sediment dynamics at Lady Musgrave Island, southern Great Barrier Reef

et al. 2016

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Linking surficial sediment patterns in reef environments to the processes that underlie their depositional dynamics enables predictions to be made of how environmental changes will influence reef-associated sedimentary landforms, such as islands and beaches. Geomorphic linkages between sediment deposition patterns and the biophysical processes that drive them are often poorly resolved, particularly at broad landscape scales where tangible statements can be made about structural changes to landforms. The present study applies geospatial techniques to link patterns in reef sediment dynamics at Lady Musgrave Island to the underlying processes driving them. In situ calcification is characterized by developing a high resolution map of the surficial calcium carbonate producing communities inhabiting the reef platform, and associated sediments across the reef flat are analysed for grain size, kurtosis, sorting and threshold bed shear stress to explore transport pathways across the reef flat and lagoon. Wave energy is modelled across the entire reef platform as a potential driver of sediment dynamics, and morphometric linkages are empirically defined between wave energy and grain size. Findings indicate that carbonate sediments are primarily sourced from calcifying communities colonizing the outer periphery of the reef platform and that sediment grain size can be reliably linked to wave energy by virtue of a linear model.

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Coral reef sediment dynamics: evidence of sand-apron evolution on a daily and decadal scale

Cited by 17 publications

References 25 publications

Physical and Numerical Modeling of Infragravity Wave Generation and Transformation on Coral Reef Platforms

Physical and Numerical Modeling of Infragravity Wave Generation and Transformation on Coral Reef Platforms

Reef Sedimentary Accretion Model (ReefSAM): Understanding coral reef evolution on Holocene time scales using 3D stratigraphic forward modelling

Linking pattern to process in reef sediment dynamics at Lady Musgrave Island, southern Great Barrier Reef

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