Two-dimensional modelling of wave dynamics and wave forces on fringing coral reefs

Baldock, Tom E.; Shabani, Behnam; Callaghan, David P.; Hu, Zhifang; Mumby, Peter J.

doi:10.1016/j.coastaleng.2019.103594

Cited by 24 publications

(5 citation statements)

References 42 publications

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“…The results show that narrower and deeper reef flats are linked greater erosion rates. This is in agreement with previous studies focused on the hydrodynamics over reef flats and nearshore coastal processes (Péquignet et al, 2011;Quataert et al, 2015;Reguero et al, 2018;Baldock et al, 2019Baldock et al, , 2020. The distance that the wave breaking zone is from the coastline was found to be a significant parameter to describe the coastal change, as previously characterized for shoreline response with artificial submerged structures.…”

Section: Discussionsupporting

confidence: 91%

“…In contrast, Pearson et al (2017) found that the beach slope and the sea bottom roughness due to the presence or absence of corals were less important parameters to estimate water levels and rup-up on reef-lined coasts, whereas water depth over reef flats, reef flat widths and incident wave conditions resulted as essential factors. Yet, among the remaining gaps that need to be addressed is how different reef morphologies influence the erosion potential at the shoreline (Elliff and Silva, 2017;Reguero et al, 2018;Baldock et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

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Coral Reef Geometry and Hydrodynamics in Beach Erosion Control in North Quintana Roo, Mexico

et al. 2021

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Coral reefs are increasingly recognized for their shoreline protection services. The hydrodynamic performance of this ecosystem is comparable to artificial low-crested structures often used in coastal protection, whose objective is to emulate the former. Coral reefs also provide other important environmental services (e.g., food production, habitat provision, maintenance of biodiversity and social and cultural services) and leave almost no ecological footprint when conservation and restoration actions are conducted to maintain their coastal protection service. However, studies have focused on their flood protection service, but few have evaluated the morphological effects of coral reefs through their ability to avoid or mitigate coastal erosion. In this paper, we investigate the relation between shoreline change, reefs’ geometry and hydrodynamic parameters to elucidate the physics related to how the Mesoamerican Reef in Mexico protects sandy coastlines from erosion. Using numerical wave propagation and historical shoreline change calculated from satellite imagery, a direct correlation was found between shoreline movement, the depths and widths of reef flats, changes in the wave energy flux, and the radiation stresses of breaking waves. The findings indicate that the most remarkable efficacy in preventing beach erosion is due to reefs with shallow crests, wide reef flats, a dissipative lagoon seabed, located at ∼300 m from the coastline. The results provide essential insights for reef restoration projects focused on erosion mitigation and designing artificial reefs in microtidal sandy beaches. Results are limited to wave-dominated coasts.

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Section: Discussionsupporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Coral Reef Geometry and Hydrodynamics in Beach Erosion Control in North Quintana Roo, Mexico

et al. 2021

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“…Recent numerical modeling of idealized geometries has demonstrated that for reefs with finite length protruding from a straight coast, refraction from the lateral edges of the reef can increase wave heights at the center of reef flats relative to what 1‐D wave models would predict (Baldock et al, 2020). This effect is limited for shallow, narrow reef flats like that studied here but becomes more pronounced for deeper reef flats or with SLR.…”

Section: Discussionmentioning

confidence: 99%

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

et al. 2020

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Atoll reef islands primarily consist of unconsolidated sediment, and their ocean-facing shorelines are maintained by sediment produced and transported across their reefs. Changes in incident waves can alter cross-shore sediment exchange and, thus, affect the sediment budget and morphology of atoll reef islands. Here we investigate the influence of sea level rise and projected wave climate change on wave characteristics and cross-shore sediment transport across an atoll reef at Kwajalein Island, Republic of the Marshall Islands. Using a phase-resolving model, we quantify the influence on sediment transport of quantities not well captured by wave-averaged models, namely, wave asymmetry and skewness and flow acceleration. Model results suggest that for current reef geometry, sea level, and wave climate, potential bedload transport is directed onshore, decreases from the fore reef to the beach, and is sensitive to the influence of flow acceleration. We find that a projected 12% decrease in annual wave energy by 2100 CE has negligible influence on reef flat hydrodynamics. However, 0.5-2.0 m of sea level rise increases wave heights, skewness, and shear stress on the reef flat and decreases wave skewness and shear stress on the fore reef. These hydrodynamic changes decrease potential sediment inputs onshore from the fore reef where coral production is greatest but increase potential cross-reef sediment transport from the outer reef flat to the beach. Assuming sediment production on the fore reef remains constant or decreases due to increasing ocean temperatures and acidification, these processes have the potential to decrease net sediment delivery to atoll islands, causing erosion.

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“…Previous studies that have investigated alongshore variations in reefs [18][19][20] usually addressed barrier reef-lagoon systems rather than the more common fringing reefs, and focused on setup differences and flushing times rather than the waves, water levels, and resulting runup at the shoreline. The one study that specifically investigated two-dimensional (2-D) wave processes on fringing reef platforms [21] used a sea-swell ("S", periods < 25 s) wave model that did not include the effects of longer infragravity ("IG", 25 s < periods < 250 s) and low-frequency ("VLF", periods > 250 s) waves, which are important for wave-driven water levels and runup on such reef morphologies [3,4,8].…”

Section: Introductionmentioning

confidence: 99%

A Numerical Study of Geomorphic and Oceanographic Controls on Wave-Driven Runup on Fringing Reefs with Shore-Normal Channels

Storlazzi

Rey

Dongeren

2022

JMSE

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Many populated, tropical coastlines fronted by fringing coral reefs are exposed to wave-driven marine flooding that is exacerbated by sea-level rise. Most fringing coral reefs are not alongshore uniform, but bisected by shore-normal channels; however, little is known about the influence of such channels on alongshore variations on runup and flooding of the adjacent coastline. We conducted a parametric study using the numeric model XBeach that demonstrates that a shore-normal channel results in substantial alongshore variations in waves, wave-driven water levels, and the resulting runup. Depending on the geometry and forcing, runup is greater either on the coastline adjacent to the channel terminus or at locations near the alongshore extent of the channel. The impact of channels on runup increases for higher incident waves, lower incident wave steepness, wider channels, a narrower reef, and shorter channel spacing. Alongshore variation of infragravity waves is predominantly responsible for large-scale variations in runup outside the channel, whereas setup, sea-swell waves, and very-low frequency waves mainly increase runup inside the channel. These results provide insight into which coastal locations adjacent to shore-normal channels are most vulnerable to high runup events, using only widely available data such as reef geometry and offshore wave conditions.

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Two-dimensional modelling of wave dynamics and wave forces on fringing coral reefs

Cited by 24 publications

References 42 publications

Coral Reef Geometry and Hydrodynamics in Beach Erosion Control in North Quintana Roo, Mexico

Coral Reef Geometry and Hydrodynamics in Beach Erosion Control in North Quintana Roo, Mexico

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

A Numerical Study of Geomorphic and Oceanographic Controls on Wave-Driven Runup on Fringing Reefs with Shore-Normal Channels

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