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The Givetian Balduinstein Reef developed upon mixed felsic lavas and volcaniclastic tuffs. The Givetian age of the reef is proven by conodonts (Polygnathus rhenanus/varcus Zone to the Polygnathus ansatus Zone) and the occurrence of the brachiopod Stringocephalus burtini. Remains of land plants and subaerially ejected volcanic bombs in the vicinity of the outcrops document that the volcano was an emerged island surrounded by a fringing reef in an unstable tectonic environment. Reef development is characterised by a complex interaction of volcanism, erosion and the rate and pattern of sea-level change, which resulted in a variety of facies settings and rock-types. Microfacies analysis and rock-types prove that the fringing reef was backed by a shallow lagoon. A lime mudstone/alkali rhyolitic breccia represents a lava flow, or more probably a dome collapse breccia, which flowed into the lagoonal mud and confirms a contemporaneous occurrence of volcanism and reef growth. Reefs flourished during several episodes of inactivity of the volcano, particularly in the upper part of the sections, suggesting that the reef development kept up with sea-level changes and/or local events. Lithofacies of the upper part of the youngest section point to a regressive phase. The distinctive depositional architecture and evolution of the Balduinstein Reef are interpreted as having been controlled mainly by regional tectonics and volcanism with contributions from eustasy. [ABSTRACT FROM AUTHOR]

The southern fringing reef along Ofu, American Samoa, has been a focus of coral research owing to the presence of super-heated pools on the reef flat, where corals thrive in elevated sea temperatures. Here, we present the first documentation of exceptionally large low-frequency (periods > 100 s) waves over this reef flat. During a large, southerly swell event, low-frequency waves on the inner reef flat had mean heights of 0.7 m and periods of 2–4 min and are estimated to have contributed up to 50% of the total water levels. One observed low-frequency wave had a trough-to-peak vertical height of 1.5 m, possibly representing the largest low-frequency wave ever directly observed on a reef flat. These large, low-frequency waves, which were likely amplified by reef resonance, are important factors in coastal hazards such as flooding and erosion and may also be relevant to coral health and resilience. [ABSTRACT FROM AUTHOR]

This paper presents physical experiments and numerical simulations to study the propagation of focused waves group across hypothetical fringing reef profiles. A wave flume is 69 m long and 1.0 m deep, and the reef cross section is made up of a reef face, a reef flat and a vertical wall. A reef crest of 0.085 m is optionally constructed on the outside to replicate the reef crown. By focusing wave trains of the JONSWAP or constant wave amplitude spectrum, the transient wave group is generated on the reef slope. Free surface elevations and flow velocity are measured over time along the flume's centreline. The focused wave process and the development of higher harmonics as a result of the nonlinear interaction over the reef face are clearly visible in the wavelet and FFT analyses of the observed free surface elevation. Low frequency wave is increasing on the reef flat while these short-period wave motions are primarily absorbed by rapid breaking on reef edge and crest. On the flat, it is discovered that reef crest has the effect of reducing short-period wave motion and increasing long-period wave motion. A numerical multi-layer non-hydrostatic wave model is employed and its ability to describe the propagation of focused wave groups over fringing reef profiles is assessed.

The coral reef ecosystem on Seureudong Island, Sawang Bau Village, Sawang District, South Aceh is very important for the surrounding ecosystem, with the fringing reef type, namely the shape of its growth around the island. This study aims to determine the current condition of coral cover and the types available on Seureudong Island. The Point Intercept Transect (PIT) Method was used. The results showed that the coral forms found at the study site were branching, digitate, encrusting, foliose, massive, mushroom, plates, and submassive. The percentage of the bottom substrate is dominated by hard coral (hard coral) at 45.33%, Dead Coral with Algae/DCA (37.11%), sand (9.89%), rubble of 3.56%, rock (1.56%), algae turf (1.44%), macroalgae (1%) and dead coral (0.11%). At the study site, 25 genera were identified, with Porites (36%) being the most common genus. At the research location, there were also genera with a total presence of less than 1%. These genera were Acanthastrea, Ctenactis, Favia, Favites, Fungia, Gardineroseris, Goniopora, Halimeda, Heliopora, Hydnophora, Leptastrea, Montastrea, Pavona, and Seriatopora. The water quality at the research location still complies with the standards of coral life. The results of these observations must be carried out periodically so that they can always update the condition of coral reefs on Seureudong Island. [ABSTRACT FROM AUTHOR]

The aim of this study is to better understand cross-reef wave-driven current characteristics, which are crucial to biological, ecological, and geomorphological processes within coral reefs. This study reports a set of new wave flume measurements to assess flow along the water depth and across a fringing reef profile under the action of a plunging breaker. Laboratory results are presented in view of cross-reef variations in both the wave height and the mean water level (MWL); the vertical profiles of wave-averaged mean currents below the wave trough and along the reef are also presented. To resolve the two-dimensional vertical (2DV) flow characteristics across the reef, Reynolds-Averaged Navier–Stokes (RANS) equations were solved using k-ω SST closure, modified to improve stability, and a Volume of Fluid (VOF) approach was used to capture the water surface. This numerical model was first validated via experimental measurements in view of waves and flows. It was then used to analyze the cross-reef distributions of the mean flow field, turbulent kinetic energy (TKE), and Reynolds shear stress across the reef. [ABSTRACT FROM AUTHOR]

Dredging materials from reef flats have become an important source of sand and aggregates for meeting the infrastructure needs of coral-lined shores in subtropical and tropical regions, especially for low-lying atoll islands. Dredging at the reef flats can generate artificial excavation pits, which not only have profound influences on coral ecological stability but also deeply affect the hydrodynamic characteristics of coral reefs. To deepen the understanding of the influence of excavation on the wave hydrodynamics of fringing reefs, the wave propagation, wave transformation, wave setup, and wave runup processes of regular waves on fringing reefs with artificial pits have been systematically analyzed using a non-hydrostatic numerical wave solver (NHWAVE). The effects of some significant factors have been carefully investigated. According to the study findings, the existence of artificial pits can result in a slight decrease in the wave height around the artificial pit. The time-mean maximum of wave runup height at the backreef slope can be reduced to some extent when the artificial pit is present. When placed close to the reef edge, the artificial pit can have noticeable effects on the hydrodynamic characteristics of fringing reefs, particularly the wave setup along the reef flat. It is hoped that the study findings can provide further reference for evaluation of the influences of artificial pits on the wave hydrodynamics of fringing reefs. [ABSTRACT FROM AUTHOR]

A laboratory experiment is carried out to study the generation mechanism and the evolution process of an infragravity wave (IG wave) on a typical permeable fringing reef. Fifteen capacitance wave gauges are installed along the reef model to record the water surface elevation under irregular wave action. Based on the experimental data, both IG wave generation and strong IG wave interaction are systematically analyzed. The experimental results indicate that the IG waves are generated by the time-varying breakpoint mechanism at the reef edge, and the tidal modulations on the IG wave height are mainly influenced by wave breaking and wave dissipation. Around the reef edge, the tidal modulation is controlled by wave breaking and the IG wave height monotonously decreases with the increase of the tide level. At the shoreline, the tidal modulation is controlled by wave dissipation at the low tide level and wave breaking at the high tide level. Therefore, the IG wave height first increases and then decreases with the increase of the tide level, and the maximum IG wave height occurs at the middle tide level. [ABSTRACT FROM AUTHOR]

The low-lying reef islands distributed in the tropical and subtropical coastal regions are highly vulnerable to the devastating damages of surges and waves during the severe weather events. Over the past two decades, extreme waves have caused tremendous loss and damages to the tropical and subtropical coastal regions. Previous research has focused on the wave hydrodynamics of tsunami waves, as well as regular and irregular waves on the fringing reefs. The complex wave hydrodynamics of extreme waves on the fringing reefs are rarely studied. By applying the nonhydrostatic numerical flow solver (NHWAVE), transformation and breaking process of the crest- and trough-focused wave groups on the fringing reef are analyzed in this study. Influences of the major factors, i.e., water depth, significant wave height, peak wave period, forereef slope and backreef slope, and ridge width, are discussed in detail. The results show that there are complex interactions between the fringing reef and the focused wave group. Breaking waves of high intensity can form at the reef crest. Meanwhile, due to the wave breakings at the reef crest and bottom friction of the reef flat, the local wave height can be effectively reduced. Within the complex wave hydrodynamics of focused waves on the fringing reef, most of the wave energy can be dissipated. In addition, hydrodynamic difference between the crest- and trough-focused waves on the fringing reef is very limited. The research results of this study will further help researchers to better understand the wave hydrodynamics of extreme waves over the fringing reefs. [ABSTRACT FROM AUTHOR]

Due to the special topography of coral reefs, most of the energy of incoming waves can be reduced through the wave breakings at the reef edge, thus playing a vital role in protecting the coastal regions behind coral reefs. In severe weather conditions, wind-generated waves tend to propagate in multiple directions in real ocean environment. The abrupt multidirectional wave-focusing mechanisms may result in the formation of huge waves in both deep and shallow waters, threatening the safety of coastal infrastructures and well-being of coastal communities at the reef islands. Therefore, it is crucial to thoroughly examine the complex hydrodynamics of multidirectional extreme waves at the fringing reefs. Previous studies on reef wave hydrodynamics predominantly focus on unidirectional waves. Only a small number of studies have considered the wave hydrodynamics of fringing reefs under multidirectional waves, let alone multidirectional extreme waves. To address the knowledge gap in previous studies, this study analyzes the complex hydrodynamic processes of multidirectional extreme waves at the fringing reef by applying a nonhydrostatic numerical wave model (NHWAVE). Influences of several key factors are analyzed, such as significant wave height, peak wave period, water depth, incident wave angle, and reef topography. It is expected that the research findings of this study will contribute to a deeper understanding of the hydrodynamics of multidirectional extreme waves at the fringing reef. • Complex hydrodynamics of multidirectional extreme waves at the fringing reefs have been numerically investigated by applying a nonhydrostatic wave model. • Influences of major factors, such as significant wave height, peak wave period, water depth, incident wave angle, and reef topography are investigated in detail. • Research results reveal that the wave directionality has strong influences on the wave hydrodynamics of multidirectional extreme waves at the fringing reef. [ABSTRACT FROM AUTHOR]

The aim of this study is to better understand cross-reef wave-driven current characteristics, which are crucial to biological, ecological, and geomorphological processes within coral reefs. This study reports a set of new wave flume measurements to assess flow along the water depth and across a fringing reef profile under the action of a plunging breaker. Laboratory results are presented in view of cross-reef variations in both the wave height and the mean water level (MWL); the vertical profiles of wave-averaged mean currents below the wave trough and along the reef are also presented. To resolve the two-dimensional vertical (2DV) flow characteristics across the reef, Reynolds-Averaged Navier–Stokes (RANS) equations were solved using k-ω SST closure, modified to improve stability, and a Volume of Fluid (VOF) approach was used to capture the water surface. This numerical model was first validated via experimental measurements in view of waves and flows. It was then used to analyze the cross-reef distributions of the mean flow field, turbulent kinetic energy (TKE), and Reynolds shear stress across the reef.

Many post-disaster surveys have reported on the natural function and effectiveness of fringing reef in preventing the shoreline from the inundation caused by severe weather events. Prior studies mainly focus on the wave propagating, transforming, and breaking on the fringing reefs by assuming that ocean waves propagate in an ideal environment where the wind is absent. However, in the real severe ocean environment, huge surges and waves always occur simultaneously with the strong winds. The wave profile can be easily reshaped by the strong winds, which can also significantly affect the way that ocean waves propagate on the fringing reefs. Therefore, it is necessary to study the hydrodynamics of fringing reefs under the combined action of wind and waves. To study the influences of the onshore wind on the hydrodynamics of solitary wave on the fringing reef, the finite volume method is applied to solve the governing equations of two-phase incompressible flow and a high-resolution numerical wind-wave tank is established in this study. Effects of several main factors are analyzed in detail. The research results show that the onshore wind can significantly increase the maximum wave runup height (maximum by 38.49%) and decrease the wave reflection coefficient of solitary wave (maximum by 8.66%). It is hoped that the research results of this study can enhance the understandings on the hydrodynamics of ocean waves on the fringing reefs during severe weather events. [ABSTRACT FROM AUTHOR]

Dredging materials from reef flats have become an important source of sand and aggregates for meeting the infrastructure needs of coral-lined shores in subtropical and tropical regions, especially for low-lying atoll islands. Dredging at the reef flats can generate artificial excavation pits, which not only have profound influences on coral ecological stability but also deeply affect the hydrodynamic characteristics of coral reefs. To deepen the understanding of the influence of excavation on the wave hydrodynamics of fringing reefs, the wave propagation, wave transformation, wave setup, and wave runup processes of regular waves on fringing reefs with artificial pits have been systematically analyzed using a non-hydrostatic numerical wave solver (NHWAVE). The effects of some significant factors have been carefully investigated. According to the study findings, the existence of artificial pits can result in a slight decrease in the wave height around the artificial pit. The time-mean maximum of wave runup height at the backreef slope can be reduced to some extent when the artificial pit is present. When placed close to the reef edge, the artificial pit can have noticeable effects on the hydrodynamic characteristics of fringing reefs, particularly the wave setup along the reef flat. It is hoped that the study findings can provide further reference for evaluation of the influences of artificial pits on the wave hydrodynamics of fringing reefs.

The fringing reefs in Opunohu Bay and Cook's Bay in Moorea, French Polynesia are an important component of Moorea's fringing reef system, as they comprise approximately 20% of the island's perimeter. The two bays are assumed to have differing benthic communities due to differences in onshore land development and freshwater input, but observational studies of their benthic communities are rarely published. To address this information gap, we conducted a quadrat-based benthic survey to determine important drivers of coral spatial variation throughout the bays. Interestingly, we found that coral taxonomic richness and cover did not significantly vary between bays, and corals only declined at the sites nearest freshwater input. Instead, coral richness was significantly greater when the territorial herbivorous damselfish Stegastes nigricans was present. The majority of the corals we documented were relatively small (88% < 10 cm diameter), thus our results support a positive effect of S. nigricans on young coral diversity. Stegastes nigricans could potentially be creating a refuge inside their territories from scraper herbivores for many non-dominant corals, although other potential mechanisms and the context of these benefits warrant further investigation. We conclude that, on the fringing reefs of Moorea's two major bays, spatial variation in coral richness is more strongly associated with patches of S. nigricans territories than larger-scale differences in onshore land development and distance from freshwater input. [ABSTRACT FROM AUTHOR]

Bathymetry and acoustic imagery swath mapping, along with observations and samples from four manned submersible and four ROV dives, confirm that a seafloor slope break on the northern approaches to Kaiwi Channel, between the islands of Oʻahu and Molokaʻi, Hawaiʻi is a former shoreline, now submerged ∼800 m below present sea level. Subaerially emplaced, low-relief basaltic lavas above the slope break transition to submarine morphologies below. The entire region has been tilted about 1° to the SSE (150°), and is cut by an 8–15 m-high, north-facing scarp, 100–400 m south of the slope break. The distribution of platy, table-top, and rarer mounded branching corals indicates the former presence of fringing reefs around low-relief paleo-islands. We infer that the regional tilt resulted from loading by younger Hawaiian volcanoes, compounded by flexural uplift and back tilting away from the unloaded footwall of a flank landslide to the north. Basalt samples collected from both above and below the slope break have petrography, chemical composition, and age (1.64–1.80 Ma) indicating correlation with the (late-shield) Lower Member of the East Molokaʻi Volcanics, rather than with the more proximal volcano of West Molokaʻi. The most likely source of the Kaiwi basalts is a submarine ridge (rift zone) that extends northwest away from ʻĪlio Point on West Molokaʻi. Although the submarine ridge was previously assumed to be an extension of West Molokaʻi's northwest rift, we conclude that regional bathymetry and gravity are consistent with this feature being an extension of the west rift of East Molokaʻi. A corallary of this interpretation is that the shoreline slope break (SSB 7 of Taylor, 2019) in this area is distinct from and younger than the southern SSB 7 formed on West Molokaʻi volcano (∼1.65 Ma vs. ∼1.8 Ma). • A seafloor slope break beneath Kaiwi Channel at ∼800 m below sea level was a shoreline ∼1.65 Ma. • Basalt samples from there are correlative in composition and age with late-shield lavas from East Molokaʻi. • Their most likely source is an extension of the west rift zone of East Molokaʻi along a submarine ridge NW of ʻĪlio Point. [ABSTRACT FROM AUTHOR]

Many atolls in tropical oceans are under the threat of sea‐level rise. Mitigation planning requires reliable estimates of increasing wave runup in response to sea‐level rise and changes in wave climate. However, shoreline dynamics on reef‐lined coasts, particularly the effect of low‐frequency waves, are not yet fully understood. Herein, we present a field study on the southernmost atoll of the Maldives to clarify the variability of shoreline water levels driven by waves and tides. The atoll is located just south of the equator and has a moderate wave climate; it is occasionally impacted by long‐distance swells from the South Indian Ocean. Wave evolution on a reef‐lined coast was observed in situ for a period of seven months. The shallow water depth tightly constrains reef‐flat waves under normal wave conditions; however, this constraint is broken under extreme conditions by low‐frequency waves generated from long‐period swells. Particularly, very low‐frequency waves (<0.005 Hz) are amplified via wave resonance over the reef platform and significantly contribute to shoreline motions. Our observation of shoreline motions confirmed that, under energetic conditions, extreme wave run‐ups are characterized by swell run‐ups riding on crests of low‐frequency waves. A combined approach of observations and analytical modeling revealed the long‐term variability of shoreline water levels, highlighting the stochastic nature of extreme water levels influenced by a joint probability of far‐field swells and high tides. Our results suggested that extreme shoreline water levels would increase at a significantly higher rate than sea‐level rise in the future. Plain Language Summary: An atoll is a ring‐shaped coral reef on which a series of islands (having ground elevations of less than a few meters) have formed. Inhabited atolls in tropical oceans are, therefore, considered to be one of the most vulnerable areas to global sea‐level rise, because this rise will exacerbate wave‐induced flooding in island communities. Adaptation strategies require reliable estimates of increasing wave impacts; however, it is often difficult to assess shoreline water levels driven by waves and tides over actual reef topography of diverse forms. This study investigated wave processes on the southernmost atoll of the Maldives, where there is a strong influence from waves traveling from the South Indian Ocean. Our wave observations revealed that extreme shoreline water levels were driven by short waves riding on crests of relatively long waves that developed over the reef platform. The long‐period waves are generated from a group of high swells over the outer reef platform and are significantly amplified when their period coincides with the natural period of the reef water. The study clarified the shoreline dynamics on the reef‐lined coast and demonstrated that extreme shoreline water levels would increase at a higher rate than sea‐level rise in the future. Key Points: A combination of observations and analytical modeling clarified the variability of shoreline water levels on the atoll of the MaldivesWave runup under energetic conditions is characterized by swell runup modulated by dominant very low‐frequency waves (<0.005 Hz)Extreme shoreline water levels on the reef‐lined coast occur with a joint probability of far‐field energetic swells and high tides [ABSTRACT FROM AUTHOR]

The low-lying reef islands distributed in the tropical and subtropical coastal regions are highly vulnerable to the devastating damages of surges and waves during the severe weather events. Over the past two decades, extreme waves have caused tremendous loss and damages to the tropical and subtropical coastal regions. Previous research has focused on the wave hydrodynamics of tsunami waves, as well as regular and irregular waves on the fringing reefs. The complex wave hydrodynamics of extreme waves on the fringing reefs are rarely studied. By applying the nonhydrostatic numerical flow solver (NHWAVE), transformation and breaking process of the crest- and trough-focused wave groups on the fringing reef are analyzed in this study. Influences of the major factors, i.e., water depth, significant wave height, peak wave period, forereef slope and backreef slope, and ridge width, are discussed in detail. The results show that there are complex interactions between the fringing reef and the focused wave group. Breaking waves of high intensity can form at the reef crest. Meanwhile, due to the wave breakings at the reef crest and bottom friction of the reef flat, the local wave height can be effectively reduced. Within the complex wave hydrodynamics of focused waves on the fringing reef, most of the wave energy can be dissipated. In addition, hydrodynamic difference between the crest- and trough-focused waves on the fringing reef is very limited. The research results of this study will further help researchers to better understand the wave hydrodynamics of extreme waves over the fringing reefs.

Changes in shoreline positions provide a historical record for identifying causal mechanisms and adaptive responses of coastlines to a wide spectrum of sea-level change that arises either from natural or anthropogenic disturbances. This paper presents a case study of coastal change during a period of the steady rise in sea level that is coupled with frequent storm events. Observations from multiple sources including field survey, topographic map, and series of satellite images were combined and analyzed to determine shoreline changes along the western coast of Calatagan, Batangas from 1979-2018. The Digital Shoreline Analysis System (DSAS) extension tool of ArcGIS was used to estimate magnitudes of shoreline changes, either erosion or accretion. Surface sediment samples were acquired in March and April 2010 to assess the predominant grain size and composition. Historical shoreline positions show that the western coast of Calatagan exhibits discrete erosion, but predominantly coastal accretion trend over a period of nearly 40 years. Both land progradation and the emergence of sand-gravel bars after 1992 occurred in a period of rising sea level across the South China Sea basin, including the West Philippine Sea. Land progradation is attributed to an increase in sediment input to the coast from agricultural activities in unconsolidated volcanic terrain. Notably, overlapping events of storms between 1993--1995 and the 1994 tsunami in the Verde Island Passage (VIP) may have emplaced and reworked a large amount of reef front material onto the reef flat forming emergent bars. Newly accreted lands and emergent bars were subsequently colonized by Avicennia and Sonneratia mangroves. This study highlights that in certain areas, local factors such as increased sediment supply from agricultural activities, storms, and possibly tsunami can modulate shoreline changes in response to modern-day sea-level rise. [ABSTRACT FROM AUTHOR]

Spurs and Grooves (SAG) are coral forereef structures with their main axis normal to the reef crest. The dimensions of SAG vary considerably on a global scale. Despite being common, there are relatively few studies that relate SAG morphology with wave transformation processes. Measurements of wave transformation are presented from Xahuayxol, Quintana Roo, Mexico, across a SAG zone with larger spurs than in previous studies. An array of pressure sensors and current meters sampling at high frequencies were deployed over 8 days. Our results show that SAG structures are more important for wave transformation than previously reported since a high rate of wave energy flux dissipation (up to 0.077 kW/m2) was found and the corresponding wave dissipation friction factor, fw (1.01), was four times higher as compared to other reefs. We also found that the wave dissipation rate over the spurs can be up to three times higher than the adjacent grooves (0.098 vs. 0.028 kW/m2). This study demonstrates that SAG plays a very important role in wave dissipation over coral reefs. Plain Language Summary: Spurs and grooves are a series of ridges (spurs) covered by coral and channels (grooves) covered with sand that are common on reef systems. Research and information on the role of spurs and grooves in energy dissipation remain scarce. Moreover, the dimensions of spurs and grooves are highly variable, for example, the height of the spurs ranges from 1 to 10 m and the distance between spurs can range from 1 to 100 m. Thus, their role in dissipating wave energy may also vary. The objective of this study was to assess the importance of spurs and grooves on wave energy dissipation at Xahauyxol, Mexico, a site that has spurs of different heights from previous studies. Our results showed that spurs and grooves can be more important for wave energy dissipation than previously observed. It was also found that the wave dissipation rate is up to three time higher over the spurs than the grooves. The importance of these findings is that spurs are covered by live coral that it is susceptible to environmental change. Consequently, any loss or change in the structure of the live coral could have consequences for the coastal protection service provided by spurs and grooves. Key Points: High dissipation and wave friction factor observed over spurs and grooves zone by field measurementsWave energy flux dissipation by bottom friction up to three times higher over spur than over groove structures [ABSTRACT FROM AUTHOR]

Many post-disaster surveys have reported on the natural function and effectiveness of fringing reef in preventing the shoreline from the inundation caused by severe weather events. Prior studies mainly focus on the wave propagating, transforming, and breaking on the fringing reefs by assuming that ocean waves propagate in an ideal environment where the wind is absent. However, in the real severe ocean environment, huge surges and waves always occur simultaneously with the strong winds. The wave profile can be easily reshaped by the strong winds, which can also significantly affect the way that ocean waves propagate on the fringing reefs. Therefore, it is necessary to study the hydrodynamics of fringing reefs under the combined action of wind and waves. To study the influences of the onshore wind on the hydrodynamics of solitary wave on the fringing reef, the finite volume method is applied to solve the governing equations of two-phase incompressible flow and a high-resolution numerical wind-wave tank is established in this study. Effects of several main factors are analyzed in detail. The research results show that the onshore wind can significantly increase the maximum wave runup height (maximum by 38.49%) and decrease the wave reflection coefficient of solitary wave (maximum by 8.66%). It is hoped that the research results of this study can enhance the understandings on the hydrodynamics of ocean waves on the fringing reefs during severe weather events.

In recent years, dredging reef sand and aggregate as building materials for infrastructures has become a common practice in many atoll islands, which can significantly reshape the wave hydrodynamic environment at the fringing reef. Hence, it becomes necessary to evaluate the hydrodynamic impacts of excavation pits at fringing reef. However, previous research adopted a simplified two-dimensional (2D) excavation pit model, which ignores the influences of 3D geometric characteristics of excavation pit. This study performs a three-dimensional (3D) numerical study on the hydrodynamic impacts of 3D excavation pit on tsunami-like wave at fringing reef by using a nonhydrostatic wave model (NHWAVE). Impacts of several main factors, such as water depth, wave height, pit location, geometric dimensions of pit, the spacing between two serially connected pits and the spacing between two parallel connected pits are carefully discussed. Research results reveal that 3D excavation pit can significantly reshape the wave hydrodynamic environment at the fringing reef, especially the local wave height at the pit. In addition to wave breaking at the reef edge, the 3D excavation pit can further damp out a portion of energy of the breaking surge bore, which can reduce the maximum value of wave runup height at centerline of computational domain. However, maximum value of wave runup height near the two sides of pit are slightly increased to some extent. • Hydrodynamic impacts of 3D excavation pit on wave transformation and runup processes of tsunami-like wave at fringing reef have been numerically investigated. • Influences the water depth, wave height, pit location, geometric dimensions of pit, spacing distances and arrangements of two pits are investigated in detail. • Research findings reveal the 3D excavation pit can damp out a great portion of energy of the breaking surge bore, reducing the maximum value of wave runup height at centerline of domain. [ABSTRACT FROM AUTHOR]

India is endowed with exceptionally enriched coastal and marine biodiversity in its peninsular coastal regions, island ecosystems as well as EEZ zones along with four major reef areas and other patchy reef areas. Being one of the major reef areas of India, Andaman and Nicobar Islands are considered the prime treasure-trove marine biodiversity with mostly fringing type reefs and one barrier reef. Comprehensive studies were carried out in the coral reef ecosystems of Andaman and Nicobar Islands for more than a decade to explore the coral reefs and associated faunal communities along with the estimation and monitoring of their health status. During the surveys, the live colonies of Acropora teres (Verrill, 1866) were recorded from North Reef Island in 2009 while all the colonies were found dead due to the bleaching event of 2010. None of the colonies showed resilience due to the arrival of biogenic habitat during the post-bleaching period. None of the live colonies were seen in other areas of the Andaman and Nicobar Islands. Hence, it is presumed that A. teres faced regional vulnerability. [ABSTRACT FROM AUTHOR]

Storms strongly affect coral reefs; one unstudied but potentially important outcome may be a decrease in herbivory, presumably through changes to freshwater, sediment and nutrient influx. Algal turfs are sensitive early indicators of reef condition, and experimental evidence demonstrates low sediment loads and strong herbivory maintain short, healthy turf. While unknown, storms likely disrupt these controlling forces. We have observed storms that generate frequent, visible sediment plumes in Moorea, French Polynesia. To evaluate the effects of storms on herbivory, we conducted a set of field experiments manipulating herbivore access to naturally occurring turf under three rainfall regimes: no rain, light rain, and heavy rain that generated a plume event. We found strong effects of herbivores except following the storm, indicating disruption of typically strong top-down control by herbivores on algal turfs. Further research into the underlying mechanisms is critical as storm intensities and watershed development increase in many tropical regions. [ABSTRACT FROM AUTHOR]

Many coral reefs around the Ryukyu Islands are “fringing” reefs which grow adjacent to the land. This makes them highly susceptible to impacts from the land. In recent years, the regional coral reefs have been decreasing because of bleaching caused by elevated water temperatures. In addition, red soil runoff from nearby rivers and groundwater nutrients continue to degrade the coral reef environment. This study examines the vulnerabilities that fringing coral reefs are exposed to, using the Shiraho Coral Reef of Ishigaki Island as a case study. The Shiraho Coral Reef has a wide shallow lagoon 800 m in width from the shore and a well-developed reef crest running parallel to the shore from north to south. The 3-meter-deep reef extends between the beach and the ocean, whereas the ocean-facing ridge divides the ocean from the shallow lagoon. The ridge dries out when the water level drops below mid-tide and acts as a barrier to the ocean waves. This creates a calm and closed-off area where the reef’s shallow lagoon is unaffected by the waves. Large colonies of blue coral reside in the reef at Shiraho. However, the area has low coral species diversity because the location makes it difficult for many coral species to survive. It is believed that the blue coral’s resistance to high water temperatures enables it to survive in this environment. Although various coral species inhabit the northern side of the reef, the number of species is now significantly decreasing across the entire Shiraho reef. The Todoroki River to the north and the Miyara River to the south-west meet the coral reefs as they enter the ocean. The basins of both the rivers are home to large expanses of pasture for cows and agricultural fields for sugar cane. In monsoon, red soil flows from the rivers to the reef. This river runoff has continued for many years. Furthermore, as coral typically survives in oligotrophic environments, the eutrophication of the ocean habitat also contributes to its reduction. As such, in addition to the red soil, the nutrient water resulting from eutrophication from river runoff is causing a decline in the corals. Moreover, the land adjacent to the reefs is calcareous, which gives it excellent water permeability. It is now clear that human activities add nutrient water to the ground water, which runs off into the ocean. As described above, the Shiraho Coral Reef, which is adjacent to a land, is vulnerable to impact from river and underground runoff of red soil and nutrient water. In addition, there has been a recent increase in the number of tourists visiting Okinawa. When residents offer snorkeling tours of the reefs and other sightseeing activities, there are concerns that the coral can be damaged by the tourists entering the water and that the substances contained in sunblock are affecting the coral ecosystem. The land-adjacent coral reefs of Shiraho are susceptible to a wide variety of impacts from the land. Although coral reef environments face further declines because of global warming, it will be necessary to explicitly elucidate the negative pressures on coral reefs in various regions and to devise conservation measures tailored to each area. [ABSTRACT FROM AUTHOR]

Abstract. Zooplankton is an essential component of every coral reef system, not only because it is the base of many marine food chains, but also because it is an important stage in many marine animals’ life cycles. While by definition plankton is free floating, zooplankton ha been known to move in predictable patterns. This includes a daily diel vertical migration towards the surface at night and back to the depths during the day and fluctuations in abundance over the lunar cycle, usually peaking around the full moon. This study aimed to look at the amount of control plankters have in choosing their horizontal position over the reef by looking at substrate preferences of demersal zooplankton in the fringing reef. It was found that zooplankton emerge in the largest numbers from branching coral followed by coral rubble and sand and in significantly lower numbers from smooth coral. This suggests that demersal zooplankton is able to select the substrate on which it seeks shelter during the day. Little evidence was found suggesting specific taxa prefer specific substrates. The study also compared plankton emerging from the substrate of the reef with those in the water above it. A zooplankton from the genus Lucifer was found to be dominant in the water column above the reef, but was not seeking shelter in the reef substrate during the day. Lastly, fluctuations in abundance were observed throughout the lunar cycle with a peak in numbers occurring 6-11 days after the full moon.

A closed-form solution to the linear shallow-water wave equation for wave reflection by a finite periodic array of widely spaced trapezoidal bars on a fringing reef flat is presented. It is shown that, when the total number, height, or top width of the trapezoidal bars increases, the strength of the Bragg resonance increases but the downward shift of the resonance phase becomes more pronounced. When the width of the reef face increases or when the reef face changes from a concave profile to a convex profile, the strength of the Bragg resonance decreases and the downward shift of the resonance phase also becomes more pronounced. Especially, it is found that the location of trapezoidal bars plays an important role in the strength and occurrence condition of the Bragg resonant reflection. Finally, the optimal collocation of the location and width of trapezoidal bars is investigated. Considering both construction cost and reflecting capacity, the relative width is recommended to be within 0. 4 ≤ w b / d ≤ 0. 6 and the distance from the reef edge to trapezoidal bars is suggested to be equal to the spacing of trapezoidal bars. • A closed solution for linear long wave reflection by trapezoids on a fringing reef flat is derived. • Effects of various geometrical parameters on the Bragg reflection are systematically examined. • The location of trapezoids has a key effect on the strength and occurrence of Bragg reflection. • The location and width are two critical parameters in the optimization of trapezoids on a reef flat. [ABSTRACT FROM AUTHOR]

This paper presents flume experiments and numerical simulations of focused wave group propagation over an idealized fringing reef profile and its impact on the vertical wall mounted on reef flat. The large transient wave group is produced over the steep fore-reef slope by focusing JONSWAP wave trains. The numerical simulations are performed using the compressible two-phase OpenFOAM model. Wavelet and FFT analysis of the surface elevation time histories clearly show wave focusing process and the generation of higher harmonics due to the nonlinear wave-wave interactions. For the high peak frequency cases, the low frequency wave motion increases gradually after wave breaking, but the peak frequency motion still dominates energy spectrum partially due to wave defocusing and reformation of broken waves. However, the magnitude of low frequency wave motion is higher than those around peak frequency and high harmonics for the lower peak frequency cases. It is found that the contribution of low frequency wave motion to the total force exerted on the wall is comparable to or higher than peak frequency wave motion. The effect of geometry characters of fringing reef and focusing position on the maximum horizontal force on the vertical wall is investigated utilizing the validated OpenFOAM model. • New experiments for focused wave propagation and evolution over a fringing reef are conducted. • The surface elevation, TKE and energy spectrum as the focused wave group propagates over a fringing reef is reported. • The impacts on the vertical wall exerted by the broken focused wave group are investigated. • The excellent agreements between CFD simulation and experimental data are obtained. [ABSTRACT FROM AUTHOR]

This paper presents physical experiments and numerical simulations to study the propagation of focused waves group across hypothetical fringing reef profiles. A wave flume is 69 m long and 1.0 m deep, and the reef cross section is made up of a reef face, a reef flat and a vertical wall. A reef crest of 0.085 m is optionally constructed on the outside to replicate the reef crown. By focusing wave trains of the JONSWAP or constant wave amplitude spectrum, the transient wave group is generated on the reef slope. Free surface elevations and flow velocity are measured over time along the flume's centreline. The focused wave process and the development of higher harmonics as a result of the nonlinear interaction over the reef face are clearly visible in the wavelet and FFT analyses of the observed free surface elevation. Low frequency wave is increasing on the reef flat while these short-period wave motions are primarily absorbed by rapid breaking on reef edge and crest. On the flat, it is discovered that reef crest has the effect of reducing short-period wave motion and increasing long-period wave motion. A numerical multi-layer non-hydrostatic wave model is employed and its ability to describe the propagation of focused wave groups over fringing reef profiles is assessed., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors.)

Microplastic pollution of coral reef ecosystems has received increasing attention since the discovery that several typical coral types have the ability to ingest (micro-) plastics. However, data on the distribution of microplastics in coral reef ecosystems are still very limited. The study reported here selected sands/sediments from coral reef islands located in the South China Sea as a representative study site. The abundance of microplastics was found to reach 90 ± 5 items/kg and 530 ± 7 items/kg at the Weizhou Island and Sanya Lu Hui Tou (LHT) sites (fringing reef), respectively. Each of these qualities are lower than the quantity of microplastics collected from the Xisha Islands (atoll) (60 ± 3 to 610 ± 11 items/kg), which experiences less human activity and pollution. Moreover, further investigation demonstrated that the differences in the microplastics in the sands of these atolls and fringing reefs were determined not only by their sources, but were also dependent on their water exchange rates. The primary type and color of the microplastics found in these four sampling zones was red polypropylene and there was a greater proportion of smaller size particles (<1 mm) in the remote atolls of the Nansha and Xisha islands than in the other fringing reef sites. Additionally, there were no obvious differences found in the abundance of microplastics and the compositions/structures of coral sand in the Weizhou Island and Sanya LHT sites. Unlabelled Image • Firstly determination of microplastic in the sand of coral island at South China Sea • Higher content of microplastic was detected in the Xisha Islands than coastal sites. • Human activities were not the only source for microplastic in the sand of coral island. • Mineral type was one of the dominant factor affect the distribution of microplastics. • No obviously differences were found between the sand in reef flat and ragoon zones. [ABSTRACT FROM AUTHOR]

Wave-induced set-up brings severe impacts on the safety of the land area behind the reef through increase of the mean water level on the fringing reef flat. Flume experiments were carried out under irregular wave conditions to study the wave-induced set-up on reef flat. The experimental tests were carried out with 3 reef flat depths,4 significant wave heights and 4 spectral peak periods. It was found that:① Stable hydrodynamic conditions on reef flat can be achieved only when the sampling time lasts for more than 200 peak periods;② Irregular wave trains have more complex breaking process than that of regular wave trains,in that the larger waves in the same wave train break on the fore-reef slope in plunging manner,while smaller waves break on the reef flat in spilling manner or do not break;③ The maximum set-up on reef flat was found to increase with the increase of the peak period,and decrease with the increase of the water depth on the reef flat,and be proportional to the significant wave heights. The formula,proposed by Gourlay for estimating set-up on reef flat under regular wave conditions,was extended to irregular wave conditions. It was found that the maximum set-up can be well predicted by replacing the regular wave height and period in the formula with the significant wave heights and peak periods for irregular waves,respectively. [ABSTRACT FROM AUTHOR]

Highlights • A new set of laboratory data for spectral wave processes over an idealized fringing reef is reported. • Different reef morphologies with/without reef crest, lagoon and reef surface roughness are examined. • Infragravity (IG) waves on reef flat are confirmed to be generated by the breakpoint forcing mechanism. • IG wave resonance on reef flat is identified by a spectral analysis of shoreline wave records. • A Boussinesq model is applied to investigate varying fore-reef slopes, reef-crest widths, lagoon widths, and reef roughness coefficients. Abstract Many low-lying tropical and sub-tropical atolls fringed by coral reefs are susceptible to coastal inundation during extreme wave events. Previous studies have shown that the infragravity (IG) wave is the dominant component of shoreline run-up compared to the sea and swell (SS) wave and the wave-induced setup. To better understand both the SS and IG wave dynamics over a fringing reef with various morphologies, a series of laboratory experiments were conducted in a wave flume based on an idealized fringing reef profile. The shoreline responses of waves to different reef morphologies with/without the reef crest, the lagoon and the reef surface roughness were examined. IG wave resonance on the reef flat was identified by a spectral analysis of the shoreline wave records. Subsequently, a numerical model based on the Boussinesq equations was validated by the experimental data. The model was then applied to investigate the impacts of varying reef morphologic features (fore-reef slope, reef-crest width, lagoon width, and reef roughness coefficient) on the shoreline wave motions. [ABSTRACT FROM AUTHOR]

Abstract: Sediment produced on fringing coral reefs that is transported along the bed or in suspension affects ecological reef communities as well as the morphological development of the reef, lagoon, and adjacent shoreline. This study quantified the physical process contribution and relative importance of sea‐swell waves, infragravity waves, and mean currents to the spatial and temporal variability of sediment in suspension. Estimates of bed shear stresses demonstrate that sea‐swell waves are the key driver of the suspended sediment concentration (SSC) variability spatially (reef flat, lagoon, and channels) but cannot fully describe the SSC variability alone. The comparatively small but statistically significant contribution to the bed shear stress by infragravity waves and currents, along with the spatial availability of sediment of a suitable size and volume, is also important. Although intratidal variability in SSC occurs in the different reef zones, the majority of the variability occurs over longer slowly varying (subtidal) timescales, which is related to the arrival of large swell waves at a reef location. The predominant flow pathway, which can transport suspended sediment, consists of cross‐reef flow across the reef flat that diverges in the lagoon and returns offshore through channels. This pathway is primarily due to subtidal variations in wave‐driven flows but can also be driven alongshore by wind stresses when the incident waves are small. Higher frequency (intratidal) current variability also occurs due to both tidal flows and variations in the water depth that influence wave transmission across the reef and wave‐driven currents. [ABSTRACT FROM AUTHOR]

This study investigates infragravity motions on a two-dimensional fringing reef with a concave topography using a wave-resolving nonlinear Boussinesq wave model. The effect of bathymetric nonlinearity on spatial variations of infragravity waves is studied from shore-normal incident random waves. The model is first verified from cross-shore/alongshore significant wave height, wave setup and infragravity wave height measured in laboratory experiments. The modeled velocity is further examined to elucidate the infragravity-wave current field. Wavenumber-frequency velocity spectra show that cross-shore infragravity motions are controlled by the leaky waves, while alongshore infragravity motions exhibit edge waves characteristics. Additionally, high-mode edge waves prevail on the entire infragravity frequency band while low-mode edge waves are dominant at very low frequencies. Furthermore, the model results illustrate the spatial and temporal variability of wave-induced nearshore currents, alongshore and cross-shore flows accompanying with circulation cells and rip currents. The infragavity-wave current field is nearly identical to the mean current field and the circulations develop at the same spatial scale as the reef flat. [ABSTRACT FROM AUTHOR]

Geological heterogeneity of the subsurface, caused by both discrete features and spatially distributed hydraulic conductivity fields, affects the flow of coastal groundwater. It influences the shape and the position of the interface between saltwater and freshwater, as well as the location and flux rate of freshwater discharge to the ocean. Fringing reefs lead to a bimodal regime of freshwater discharge, with discharge at the beach face and through deeper, submarine springs. Impermeable vertical flow barriers (dykes) lead to an impoundment of fresh groundwater and a compartmentalization of the aquifer but also to a delayed expulsion of saline water. Spatially distributed conductivity fields affect the shape of the interface and the geometry of the saltwater wedge. Higher effective conductivities lead to a further landward intrusion of the wedge toe. These flow characteristics can be important for groundwater extraction, the delineation of protection zones and the assessment of contaminant transport to coastal ecosystems. [ABSTRACT FROM AUTHOR]

After the 2004 Indian Ocean tsunami, the effectiveness of fringing reefs in protecting coastlines from tsunami-induced inundation has aroused great attention in the post-tsunami surveys. To better understand the role of fringing reefs in the mitigation of a tsunami hazard, laboratory experiments were conducted in a wave flume to study the transformation and run-up of tsunami-like solitary waves over various fringing reef profiles. The effects of incident wave height, reef-flat submergence, lagoon width and reef surface roughness were examined. Cylinder arrays were employed to create artificial roughness elements on the reef surface. Empirical formulas based on the experimental data were also proposed for the wave run-up. The ratio of the reef flat submergence to the incident wave height was always found to be the dominant parameter to characterize the wave run-ups over various tested reef profiles. Subsequently, a numerical model based on the improved Boussinesq equations including the drag effect of roughness elements was validated by the experimental data. The validated model was then applied to investigate the impacts of variations of reef morphologies (fore-reef slope, back-reef slope, reef-flat width, reef-crest width) on the solitary wave run-up. [ABSTRACT FROM AUTHOR]

The characteristics of wave breaking in shallow waters that are of interest include whether a wave will break, the type of breaking that will occur, the breaking wave height, breaking depth, the position of breaking, the wave setup, and the transformation of the broken wave for given offshore wave characteristics and given bottom profile. Various methods have been proposed in the literature to estimate these wave-breaking characteristics. Deo et al. (2003) used a neural network approach to predict the breaking wave height and breaking depth for waves transforming over a range of simply sloped bottoms. The Deo et al. approach is extended here to predict other characteristics of wave breaking, including the type of wave breaking, the position of breaking, the wave setup, and the rate of dissipation of wave energy, in the case of waves impinging on a fringing reef. Observations from a series of specially conducted laboratory experiments involving monochromatic waves impinging on an idealized reef are used to develop and train respective models. The input parameters to the neural network models are the ratio of offshore wave height to the shallow-water depth of the flat section of the reef, H 1 / h s and the wave frequency parameter f H 1 / g . The breaker type classification model developed predicts the type of breaker with a success rate of 96 % , outperforming previously used criteria for classifying breaker types. The numeric prediction models for the dimensionless position of wave breaking for plunging and spilling breakers, for wave setup, and for the reduction in energy flux across the reef have performance ratings characterized by respective correlation coefficients of 0.99, 0.82, 0.89, and 0.94. The modest value for the correlation between prediction and the actual result for the position of breaking of spilling breakers is believed to be associated with inaccuracies in determination of the exact position of breaking and to difficulty in visually capturing spilling breakers in observations. High correlation between predicted and actual values of the reduction in energy flux across the reef is achieved in spite of the fact the model was trained using data from a wave tank that included partial reflection (characterized by 7% mean deviation among non-breaking waves) from the downstream end of the tank. The method can be extended to provide predictive models for consideration of a range of natural coastal conditions, random waves, and various bottom profiles and complex geometry, based on training and testing of the models using representative laboratory, field, and/or flow simulation, in support of accurate prediction of near-shore wave phenomena. [ABSTRACT FROM AUTHOR]

Coral reefs are among the most biodiverse habitats on Earth, but knowledge of their associated marinemicrobiome remains limited. To increase the understanding of the coral reef ecosystem in the lower Gulf of Thailand, this study utilized 16S and 18S rRNA gene-based pyrosequencing to identify the prokaryotic and eukaryotic microbiota present in the reef water at Kham Island, Trat province, Thailand (N6.97 E100.86). The obtained result was then compared with the published microbiota from different coral reef water and marine sites. The coral reefs at Kham Island are of the fringe type. The reefs remain preserved and abundant. The community similarity indices (i.e., Lennon similarity index, Yue & Clayton similarity index) indicated that the prokaryotic composition of Kham was closely related to that of Kra, another fringing reef site in the lower Gulf of Thailand, followed by coral reef water microbiota at GS048b (Cooks Bay, Fr. Polynesia), Palmyra (Northern Line Islands, United States) and GS108b (Coccos Keeling, Australia), respectively. Additionally, the microbial eukaryotic populations at Kham was analyzed and compared with the available database at Kra. Both eukaryotic microbiota, in summer and winter seasons, were correlated. An abundance of Dinophysis acuminata was noted in the summer season, in accordance with its reported cause of diarrhoeatic shellfish outbreak in the summer season elsewhere. The slightly lower biodiversity in Kham than at Kra might reflect the partly habitat difference due to coastal anthropogenic activities and minor water circulation, as Kham locates close to the mainland and is surrounded by islands (e.g., Chang and Kut islands). The global marine microbiota comparison suggested relatively similar microbial structures among coral sites irrespective of geographical location, supporting the importance of coral-associated marine microbiomes, and Spearman’s correlation analysis between community membership and factors of shore distance and seawater temperature indicated potential correlation of these factors (p-values < 0.05) with Kham, Kra, and some other coral and coastal sites. Together, this study provided the second marine microbial database for the coral reef of the lower Gulf of Thailand, and a comparison of the coral-associated marine microbial diversity among global ocean sites.

We investigated the dynamics of carbonate system which was greatly modulated by a river plume and coastal upwelling in July 2014 and July 2015 at the east coast of Hainan Island where a fringing reef distributes inshore. By using a three end-member mixing model, we semiquantitatively estimated the removal of dissolved inorganic carbon (DIC) mediated by biological production in the river plume and upwelled water to be 13 ± 17 and 15 ± 16 μmol kg−1, respectively. The enhanced organic production was mainly responsible for these DIC consumptions in both two regimes, however, nearly a half of DIC removal was attributed to biocalcification in the plume system while it was negligible in the upwelling system. Furthermore, the modeled results over reefs revealed that river plume and coastal upwelling were two major threats of acidification to coral communities at the east coast of Hainan Island during cruises. In comparison, the biological contribution to acidification was limited for balancing between organic production and biocalcification during July 2014 cruise, whereas the acidification was greatly intensified by organic degradation during July 2015 cruise. It was verified that naturally local acidification (physical and biological processes) played a major role in great pH decreases on a short-term scale, leading to coastal waters more vulnerable to anthropogenic 'ocean acidification' (uptake of atmospheric CO2) by reducing buffering capacity of waters. Finally, effects of acidification associated with other local threats on a fringing reef were further depicted with a conceptual model. [ABSTRACT FROM AUTHOR]

It has been well observed that a reef crest (ridge) may be present at the reef edge, but so far very few published studies focusing on the effects of such reef-crest on the wave dynamics over fringing reefs. To understand the role of a reef-crest configuration in determining breaking-wave induced setup over the reef flat, a series of experiments were carried out in a wave flume using an idealized fringing reef model with a reef crest. Experimental results were reported for a trapezoidal reef crest with five reef-crest widths under a series of monochromatic waves. Also examined was the reef without a reef crest. Data analysis shows that larger energy dissipation associated with smaller surfzone width around the reef edge occurred with a wider reef crest. The maximum wave-induced setup on the reef flat in the presence of the reef crest was significantly larger than that without, and it also increased with increasing reef-crest width. The reef-crest submergence was found to be a primary parameter controlling the magnitude of wave setup on the reef flat provided that the reef crest was sufficient wide. An alternative semi-analytical 1DH model based on the balance of cross-shore momentum was proposed. The model was validated by present laboratory data as well as three existing 1DH laboratory studies. Comparing with other two representative semi-analytical models in the literature showed that the proposed model was capable of better reproducing the maximum wave-induced setup on the reef flat for a variety of reef profiles with/without a reef crest, different reef-crest water levels, as well as both monochromatic and spectral waves. The model parameter was physically related to the two characteristic lengths in the surf zone and its value was dependent on the fore-reef slope as well as the presence of a reef crest. The 1DH model was also satisfactorily applied to a fringing reef in field conditions where the effects of fore-reef friction and back-reef lagoon were not important. [ABSTRACT FROM AUTHOR]

Engineering characteristics of calcareous soils are more peculiar due to the grain geometries, hardness and intraparticle voids. In the fringing reef in Sanya, calcareous soils were mixed with some terrestrial deposits, such as quartz sand and clay. In this paper, a series of laboratory and in-situ tests are conducted on calcareous soils to investigate the engineering characteristics and the effect of water saturation: laboratory large-scale direct shear tests, large-scale oedometer tests, X-Ray diffraction experiments, in-situ Plate Load Tests (PLTs) and Dynamic Cone Penetration Tests (DCPTs). The results showed that: (i) apparent cohesion of calcareous soils is quite higher than that of quartz sand but decreases significantly due to the softening effect of water; (ii) the bearing capacity decreases by 43% and deformation modulus decreases by 31% at the presence of 20% clay minerals; (iii) deformation modulus reduces 80% in saturated condition compared to dry condition; (iv) the relationship between N 63.5 and bearing capacity of calcareous soils was established; therefore, engineers can decrease the amount of PLTs and increase DCPTs in the site exploration of fringing coral reef according to the testing results. [ABSTRACT FROM AUTHOR]