Discussion About Tsunami Interaction with Fringing Coral Reef

Roger, Jean; Dudon, Bernard; Krien, Yann; Zahibo, Narcisse

doi:10.1007/978-94-007-7269-4_8

Cited by 11 publications

(10 citation statements)

References 39 publications

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“…The fringing reef to the island's north fails to prevent this extensive flooding in the simulations of Buckley et al (2012). In simulations for other places, onshore inundation was found to be reduced by generic reefs (Kunkel et al, 2006) or to vary with reef parameters (Roger et al, 2014), or to increase in onshore height and inundation distance after crossing a fringing reef in American Samoa (Gelfenbaum et al, 2011).…”

Section: Hypothetical Tsunamis From the Puerto Rico Trenchmentioning

confidence: 87%

Extreme waves in the British Virgin Islands during the last centuries before 1500 CE

et al. 2017

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Extraordinary marine inundation scattered clasts southward on the island of Anegada, 120 km south of the Puerto Rico Trench, sometime between 1200 and 1480 calibrated years (cal yr) CE. Many of these clasts were likely derived from a fringing reef and from the sandy flat that separates the reef from the island's north shore. The scattered clasts include no fewer than 200 coral boulders, mapped herein for the first time and mainly found hundreds of meters inland. Many of these are complete colonies of the brain coral Diploria strigosa. Other coral species represented include Orbicella (formerly Montastraea) annu laris, Porites astreoides, and Acropora palmata. Associated bioclastic carbonate sand locally contains articulated cobble-size valves of the lucine Codakia orbicularis and entire conch shells of Strombus gigas, mollusks that still inhabit the sandy shallows between the island's north shore and a fringing reef beyond. Imbricated limestone slabs are clustered near some of the coral boulders. In addition, fields of scattered limestone boulders and cobbles near sea level extend mainly southward from limestone sources as much as 1 km inland. Radiocarbon ages have been obtained from 27 coral clasts, 8 lucine valves, and 3 conch shells. All these additional ages predate 1500 cal yr CE, all but 2 are in the range 1000-1500 cal yr CE, and 16 of 22 brain coral ages cluster in the range 1200-1480 cal yr CE. The event marked by these coral and mollusk clasts likely occurred in the last centuries before Columbus (before 1492 CE). The pre-Columbian deposits surpass Anegada's previously reported evidence for extreme waves in post-Columbian time. The coarsest of the modern storm deposits consist of coral rubble that lines the north shore and sandy fans on the south shore; neither of these storm deposits extends more than 50 m inland. More extensive overwash, perhaps by the 1755 Lisbon tsunami, is marked primarily by a sheet of sand and shells found mainly below sea level beneath the floors of modern salt ponds. This sheet extends more than 1 km southward from the north shore and dates to the interval 1650-1800 cal yr CE. Unlike the pre-Columbian deposits, it lacks coarse clasts from the reef or reef flat; its shell assemblage is instead dominated by cerithid gastropods that were merely stirred up from a marine pond in the island's interior. In their inland extent and clustered pre-Columbian ages, the coral clasts and associated deposits suggest extreme waves unrivaled in recent millennia at Anegada. Bioclastic sand coats limestone 4 m above sea level in areas 0.7 and 1.3 km from the north shore. A coral boulder of nearly 1 m 3 is 3 km from the north shore by way of an unvegetated path near sea level. As currently understood, the extreme flooding evidenced by these and other clasts represents either an extraordinary storm or a tsunami of nearby origin. The storm would need to have produced tsunami-like bores similar to those of 2013 Typhoon Haiyan in the Philippines. Normal faults and a thrust fault provide nearby tsunami ...

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Section: Hypothetical Tsunamis From the Puerto Rico Trenchmentioning

confidence: 87%

Extreme waves in the British Virgin Islands during the last centuries before 1500 CE

et al. 2017

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“…Following a similar logic, some post-inundation field surveys (Fernando et al 2005;McAdoo et al 2011) and modelling studies (Shao et al 2019) have concluded that, due to their structural complexity, coral reef ecosystems impart similar drag-induced attenuation of wave energy on tsunamis. Other field-based studies (McAdoo et al 2009;Fritz et al 2011;Gelfenbaum et al 2011) and modelling work (Kunkel et al 2006;Yao et al 2012;Roger et al 2014) echo these conclusions, but with caveats. For instance, some authors caution that the buffering effect of the reef depends on where the reef is located relative to a coastal community or built asset (McAdoo et al 2009;Fritz et al 2011), and that wider reefs, preferably those with an extensive reef flat, appear to dissipate tsunami energy more effectively than narrower fringing reefs (Kunkel et al 2006;Gelfenbaum et al 2011;Yao et al 2012;Roger et al 2014).…”

Section: Introductionmentioning

confidence: 95%

“…Other field-based studies (McAdoo et al 2009;Fritz et al 2011;Gelfenbaum et al 2011) and modelling work (Kunkel et al 2006;Yao et al 2012;Roger et al 2014) echo these conclusions, but with caveats. For instance, some authors caution that the buffering effect of the reef depends on where the reef is located relative to a coastal community or built asset (McAdoo et al 2009;Fritz et al 2011), and that wider reefs, preferably those with an extensive reef flat, appear to dissipate tsunami energy more effectively than narrower fringing reefs (Kunkel et al 2006;Gelfenbaum et al 2011;Yao et al 2012;Roger et al 2014). Conversely, others have proposed that coral reefs offer marginal to no protective benefit against tsunamis (Baird et al 2005;Uslu et al 2010).…”

Section: Introductionmentioning

confidence: 95%

“…However, the degree of a coral reef's influence cannot be quantified solely from these field-based techniques. As many others have highlighted (Chatenoux and Peduzzi 2005;Kunkel et al 2006;McAdoo et al 2009;Uslu et al 2010;Roger et al 2014;Dilmen et al 2018), several confounding factors can influence tsunami run-up, such as the extent of coral cover, the nature and proximity of the tsunami triggering source, and site-specific variability in coastal bathymetry and topography. Therefore, following a tsunami event, it is difficult to retrospectively ascertain the impact of coral reefs in isolation from these other site-specific factors.…”

Section: Introductionmentioning

confidence: 99%

“…Further still, some field-based (Nott 1997;Peduzzi 2005, 2007;Fritz et al 2011) and modelling work (Roeber et al 2010;Gelfenbaum et al 2011;Yao et al 2012;Ford et al 2014) suggest that reefs can actually exacerbate damage along neighbouring coastlines. While there is near-universal consensus that inter-reef passages (or "gaps/openings" between reefs) can amplify tsunami waves, some argue that these amplification effects, along with other effects such as intra-lagoon resonance and increased shoaling/bore formation over shallow reef platforms, undermine any protective benefit that the presence of the reef would otherwise offer (Chatenoux and Peduzzi 2005;Liu et al 2005;Roeber et al 2010;Gelfenbaum et al 2011;McAdoo et al 2011;Ford et al 2014;Roger et al 2014). Despite the wide variety of methods and case studies employed to investigate this topic, the impact of coral reef ecosystems on tsunami propagation remains unclear.…”

Section: Introductionmentioning

confidence: 99%

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Examining the impact of the Great Barrier Reef on tsunami propagation using numerical simulations

Thran¹,

Brune²,

Webster³

et al. 2022

Preprint

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Coral reefs may provide a beneficial first line of defence against tsunami hazards, though this is currently debated. Using a fully nonlinear, Boussinesq propagation model, we examine the buffering capacity of the Great Barrier Reef against tsunamis triggered by several hypothetical sources: a series of far-field, Solomon Islands earthquake sources of various magnitudes (Mw 8.0, Mw 8.5, and Mw 9.0), a submarine landslide source that has previously been documented in the offshore geological record (i.e. the Gloria Knolls Slide), and a potential future landslide source (i.e. the Noggin Block). We show that overall, the Great Barrier Reef acts as a large-scale regional buffer due to the roughness of coral cover and the complex bathymetric features (i.e. platforms, shoals, terraces, etc.) that corals construct over thousands of years. However, the buffering effect of coral cover is much stronger for tsunamis that are higher in amplitude. When coral cover is removed, the largest earthquake scenario (Mw 9.0) exhibits up to a 31% increase in offshore wave amplitude and estimated run-up. These metrics increase even more for landslide scenarios, where they tend to double. These discrepancies can be explained by the higher bed particle velocities incited by higher-amplitude waves, which leads to greater frictional dissipation at a seabed covered by coral. At a site-specific level, shoreline orientation relative to the reef platforms also determines the degree of protectiveness against both types of tsunamis, where areas situated behind broad, shallow, coral-covered platforms benefit the most. Additionally, we find that the platforms, rather than gaps in the offshore reef structure, tend to amplify wave trains through wave focussing when coral cover is removed from simulations. Our findings have implications for future tsunami hazards along the northeastern Australian coastline, particularly as the physiological stressors imposed by anthropogenic climate change further exacerbate coral die-off and reductions in ecosystem complexity. Therefore, areas that experience a protective benefit by the Great Barrier Reef’s platforms could be disproportionately more vulnerable in the future.

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Examining the impact of the Great Barrier Reef on tsunami propagation using numerical simulations

et al. 2021

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Discussion About Tsunami Interaction with Fringing Coral Reef

Cited by 11 publications

References 39 publications

Extreme waves in the British Virgin Islands during the last centuries before 1500 CE

Extreme waves in the British Virgin Islands during the last centuries before 1500 CE

Examining the impact of the Great Barrier Reef on tsunami propagation using numerical simulations

Examining the impact of the Great Barrier Reef on tsunami propagation using numerical simulations

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