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1
Van den Bosch, Ilse, Erik Ten Oever, Pieter Bakker, and Markus Muttray. "STABILITY OF INTERLOCKING ARMOUR UNITS ON A BREAKWATER CREST." Coastal Engineering Proceedings 1, no. 33 (October 25, 2012): 11. http://dx.doi.org/10.9753/icce.v33.structures.11.
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The hydraulic stability of single layer, interlocking armour units on low crested and submerged breakwaters was investigated in 2D hydraulic model tests. Displacements of armour units and rocking were monitored and have been applied as indicators for the armour layer stability on the crest, front and rear slope. The effect of freeboard, packing density and wave steepness on the armour layer stability have been investigated. The stability of interlocking concrete armour units on low crested and submerged structures is qualitatively different from rock armour. About 40% to 50% larger armour units are required on the seaward slope and crest of low crested structures (as compared to conventional high crested breakwaters). About 35% larger armour units are required on the rear slope. Larger armour units are not required on submerged breakwaters if the water depth on the crest exceeds 50% of design wave height.
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Koutrouveli, Theofano I., and Athanassios A. Dimas. "WAVE TRANSMISSION OVER LOW-CRESTED POROUS BREAKWATERS." Coastal Engineering Proceedings, no. 36 (December 30, 2018): 15. http://dx.doi.org/10.9753/icce.v36.waves.15.
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Low-crested (LC) rubble mound breakwaters are used for coastal protection. The main advantage of these structures is their mild aesthetic impact on the natural environment. As the waves approach and transmit over these structures, significant hydrodynamic processes occur in their proximal area, such as wave breaking, wave reflection, wave overtopping and transmission (Garcia et al., 2004). Many researchers have studied the hydrodynamics of flow in the vicinity of such structures, as well as the influence of their geometrical characteristics on the flow field. However, in most studies, the structures are either emerged or submerged, while the case in which the crest level of the breakwaters is at the still water level (SWL) has to be further investigated.
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Hassanpour, Nasrin, Diego Vicinanza, and Pasquale Contestabile. "Determining Wave Transmission over Rubble-Mound Breakwaters: Assessment of Existing Formulae through Benchmark Testing." Water 15, no. 6 (March 14, 2023): 1111. http://dx.doi.org/10.3390/w15061111.
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Low-crested and submerged breakwaters are frequently employed as coastal defence structures. Their efficiency is governed by wave energy dissipation, and the wave transmission coefficient can evaluate this parameter. The current study conducts experimental investigations on both low-crested and submerged breakwaters exposed to different wave conditions to compare their performance with that of emerged breakwaters. The current study provides a comprehensive review of existing formulae and highlights the impact of design variables. To evaluate the reliability of each existing formula, four “reference” configurations are used. Having these structures at the same overall volume, the results also provide a useful tool for engineers involved in the lowering operation of existing breakwaters. Nature and magnitude of governing parameters are investigated, and some points of criticism are outlined. The comparison results show that few of the existing equations give reliable estimates of the transmission coefficient for all the models tested in this study. Higher values of root mean square error are related to the emerged breakwater rather than the submerged ones. To obtain information about the transmitted wave energy, spectral analysis is applied as well. Different behaviours of the transmitted spectrum, n terms of shape and peak frequency, are highlighted. The results improve the overall knowledge on formulae that are in the literature, in order to make the user more aware.
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Vanlishout, Valérie, Henk Jan Verhagen, and Peter Troch. "OBLIQUE WAVE TRANSMISSION THROUGH ROUGH IMPERMEABLE RUBBLE MOUND SUBMERGED BREAWATERS." Coastal Engineering Proceedings 1, no. 32 (February 1, 2011): 22. http://dx.doi.org/10.9753/icce.v32.waves.22.
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There is a growing interest in the application of submerged rubble mound breakwaters as coastal defence structures. As their defensive ability highly depends on the amount of wave energy remaining at their lee side, the accurate prediction of the energy in the lee of such structures is of utmost importance. Past experiments have shown that the behaviour of rough permeable rubble mound structures under oblique wave attack was found to be significantly different from that of smooth impermeable low crested structures. This behavioural difference has led to the research objective of this present study which is to investigate oblique wave transmission by rough impermeable rubble mound submerged breakwaters using 3D physical model tests. This study intentionally uncouples two parameters, being the permeability of the core and the roughness of the breakwater. Analysing the data of this study shows that the permeability of the core has no visible influence on the structure's behaviour with respect to the influence of oblique wave attack. The fully permeable rough rubble mound breakwater behaves analogous to the fully impermeable rough rubble mound breakwater.
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Ahmad Fitriadhy, Sheikh Fakruradzi, Alamsyah Kurniawan, Nita Yuanita, and Anuar Abu Bakar. "3D Computational Fluid Dynamic Investigation on Wave Transmission behind Low-Crested Submerged Geo-Bag Breakwater." CFD Letters 15, no. 10 (August 29, 2023): 12–22. http://dx.doi.org/10.37934/cfdl.15.10.1222.
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Wave transmission characteristics behind low-crested submerged breakwaters involve complex-hydrodynamic interaction of water waves on the structures. To properly comprehend the induced-nonlinear wave transformation, the problem necessitates a trustworthy prediction using a computational fluid dynamic (CFD) technique. The goal of this study is to develop a three-dimensional (3-D) computational model of the hydrodynamic performance of a narrow crest behind a submerged breakwater in order to gain a thorough understanding of the wave transmission coefficient, K_t. The simulation took into account a number of wave parameters such as wave steepness (H_i⁄L), relative submergence depth (H_i⁄h), and crest width (c_w⁄L) of the structure. A numerical wave flume model is included, which is based on the full Navier-Stokes solver and includes a shallow water model to account for nonlinearity in the incident wave field. In addition, laboratory measurements were also conducted using a geo-bag dike model as the main breakwater structure. The result shows that the reduction in transmission coefficient correlates highly with the wave steepness and the relative submergence and crest parameters. This can be attributed to most breaking waves over the submerged breakwater. The steeper the incident wave, the greater the reduction in the transmitted wave. And, the greater the principal dimensions of the breakwater, the greater the drop in transmission coefficient. For validation, the CFD results corroborate satisfactorily with measurements
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Galani, Konstantina A., and Athanassios A. Dimas. "EXPERIMENTAL STUDY OF THE FLOW INDUCED BY WAVES IN THE VICINITY OF A DETACHED LOW-CRESTED (ZERO FREEBOARD) BREAKWATER." Coastal Engineering Proceedings, no. 36 (December 30, 2018): 14. http://dx.doi.org/10.9753/icce.v36.waves.14.
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The combined action of environmental forcing (waves, coastal currents, sediment transport, e.t.c.), the continuously decreasing supply of coastal areas with sediment from rivers, as well as the intense anthropogenic activity, results in the appearance of severe erosion problems in coastal areas and constantly decreasing beach width. A frequently used coastal protection measure is the construction of detached breakwaters parallel to the coastline. Detached breakwaters have a direct effect on the incoming waves, which contributes to the control of coastal sediment transport, hence the morphodynamics of the coastal bed. There are many examples of such structures, the majority of which are emerged breakwaters. Recently, interest has been directed towards the construction of low-crested (LC) and submerged breakwaters due to the reduced construction cost and a more effective harmonization with the natural environment. These structures are characterized by wave overtopping and breaking over their crest in addition to all other coastal processes that are involved with emerged breakwaters. For the proper design of such structures, one critical aspect is the behavior of the induced flow in their vicinity due to their presence. To this purpose, several studies have been carried out in recent years. In particular, Petti et al. (1994) studied experimentally the large scale vortices developed by waves breaking above a submerged breakwater. Mory and Hamm (1997) performed measurements of wave height, surface elevation and wave generated currents around a detached breakwater for incoming regular and irregular waves. Kramer et al. (2005) performed a series of experimental measurements in order to study the waves - LC structure interaction, in terms of flow velocity and turbulence developing around such structures within the European Project DE.LO.S. Garcia et al. (2004), Losada et al. (2005), Johnson et al. (2005) e.t.c. used the database created within the DE.LO.S. project to develop and validate numerical codes for the simulation of wave-induced flow around LC breakwaters. The aim of the present study was the experimental study of the flow developed by waves in the vicinity of an LC rubble mound breakwater with crest level at the water line (zero freeboard). The geometrical scale of the physical model was 1/30. The breakwater was placed on a beach of constant slope 1/15, which is typical of steep beaches in Greece.
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Kim, Taeyoon, Soonchul Kwon, and Yongju Kwon. "Prediction of Wave Transmission Characteristics of Low-Crested Structures with Comprehensive Analysis of Machine Learning." Sensors 21, no. 24 (December 8, 2021): 8192. http://dx.doi.org/10.3390/s21248192.
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The adoption of low-crested and submerged structures (LCS) reduces the wave behind a structure, depending on the changes in the freeboard, and induces stable waves in the offshore. We aimed to estimate the wave transmission coefficient behind LCS structures to determine the feasible characteristics of wave mitigation. In addition, various empirical formulas based on regression analysis were proposed to quantitatively predict wave attenuation characteristics for field applications. However, inherent variability of wave attenuation causes the limitation of linear statistical approaches, such as linear regression analysis. Herein, to develop an optimization model for the hydrodynamic behavior of the LCS, we performed a comprehensive analysis of 10 types of machine learning models, which were compared and reviewed on the prediction accuracy with existing empirical formulas. We found that, among the 10 models, the gradient boosting model showed the highest prediction accuracy with MSE of 1.0 × 10−3, an index of agreement of 0.996, a scatter index of 0.065, and a correlation coefficient of 0.983, which indicates a performance improvement over the existing empirical formulas. In addition, based on a variable importance analysis using explainable artificial intelligence, we determined the significant importance of the input variable for the relative freeboard (RC/H0) and the relative freeboard to water depth ratio (RC/h), which confirms that the relative freeboard was the most dominant factor for influencing wave attenuation in the hydraulic behavior around the LCS. Thus, we concluded that the performance prediction method using a machine learning model can be applied to various predictive studies in the field of coastal engineering, deviating from existing empirical-based research.
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Archetti, Renata, and Maria Gabriella Gaeta. "WAVE RUN-UP OBSERVATION AND 2DV NUMERICAL INVESTIGATION ON BEACHES PROTECTED BY STRUCTURES." Coastal Engineering Proceedings 1, no. 33 (December 14, 2012): 20. http://dx.doi.org/10.9753/icce.v33.currents.20.
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The main parameter for the assessment of coastal vulnerability and sediment transport is the wave run-up on the beach, defining the limit of maximum flooding, but also hydrodynamic properties in the Swash Zone (SZ) are trivial for the comprehension of hydro-morphodynamic processes. Several studies have been carried out on the SZ but few literature is still available on the run-up and on SZ flows on beaches protected by Low Crested Structures (LCSs), where flow motion is driven by a combination of low frequency infra-gravity waves and incident waves. In presence of breakwaters, swash incident waves are transmitted through the structure. In the transmission area behind the structures, wave energy is shifted to higher frequencies with respect to the incident wave spectrum and in general its mean period considerably decreases with respect to the incident one. Collecting in situ run-up measurements during storms is essential to understand the SZ processes and properly calibrate their both empirical and numerical models but measuring extreme run-up is difficult, due to the severe sea conditions and due to unexpected nature of storms. The present paper present a numerical and experimental analysis of the wave run-up and of the flow properties on a beach: the study shows the different behavior of unprotected and protected beach, subjected to the same wave conditions. In particular the paper shows that submerged breakwaters reduce in general the run-up height, on the basis of the calibrated 2DV numerical simulations, under extreme wave conditions (TR >50 years), the effect of submerged breakwaters seems to be negligible on the run-up height. Moreover a preliminary empirical equation for run-up with protected beach is proposed
9
Dassanayake, Darshana T., and H. Oumeraci. "Engineering Properties of Geotextile Sand Containers and Their Effect on Hydraulic Stability and Damage Development of Low-Crested / Submerged Structures." International Journal of Ocean and Climate Systems 3, no. 3 (September 2012): 135–50. http://dx.doi.org/10.1260/1759-3131.3.3.135.
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Brancasi, Alberica, Elisa Leone, Antonio Francone, Giulio Scaravaglione, and Giuseppe Roberto Tomasicchio. "On Formulae for Wave Transmission at Submerged and Low-Crested Breakwaters." Journal of Marine Science and Engineering 10, no. 12 (December 13, 2022): 1986. http://dx.doi.org/10.3390/jmse10121986.
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Submerged and low-crested breakwaters are nearshore barriers with an underwater or slightly emergent crest, designed to reduce the energy of wave attacks and, consequently, to protect the coast from erosion and flooding. Their performance in reducing the wave energy can be evaluated by the value of the wave transmission coefficient, which thus requires accurate prediction. In the last few decades, several experimental investigations allowed the development of several formulae to predict this coefficient that agreed well within the given range of validity. In the present study, a comprehensive review of the existing formulae has been reported and the influence of input design variables has been highlighted. Moreover, an extensive set of experimental data has been collected and critically examined and re-analyzed to obtain a homogenous up-to-date database. Special attention has been addressed to the assessment of the reliability of each existing formula for and to evaluate its performance beyond the validity limits for which it was developed.
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Lye, Leonard M., and James J. Sharp. "Hydrotechnical studies of Peter's River." Canadian Journal of Civil Engineering 21, no. 1 (February 1, 1994): 131–40. http://dx.doi.org/10.1139/l94-012.
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Peter's River in central Newfoundland supplies water to the town of Botwood from an intake located at a point just upstream of a right-angled bend. The pumphouse is situated on the outer bank of the river and is constructed on a foundation of sandy silt. In 1983, a large flood eroded part of the bank and removed vegetation which had provided a protective cover. Progressive erosion then threatened the pumphouse and forced an engineering assessment of the situation. This was conducted in the winter of 1984–1985 and included the prediction of the 50- and 100-year floods from the minimal data (4 years of records) which were then available. Estimates were made of velocities and flood levels, and various protection schemes were considered.The installation of a revetment in 1986 stabilized the bank, but icing on the intake had always caused problems and these continued unabated. In winter, frazil ice adhered to the submerged intake structure and was drawn into the pumps causing frequent shutdowns. Various solutions, including electrical heating, were considered. However, in 1991, a decision was made to install infiltration pipes below the stream bed, to raise water levels with a small broad crested weir and to disconnect the existing intake. Flow estimates were again required, both for construction purposes and for responding to the Department of Fisheries requirement that there would be no immediate or long-term harm to fish habitat.This paper provides a brief description of the general problems, but focuses primarily on the methods used, 8 years apart, to estimate flood data. These methods were intended to be relatively unsophisticated, but were consistent with the magnitude of the river and the relatively small scale of the proposed works. In the study conducted in 1984–1985, only 4 years of records were available and the estimation of the 50- and 100-year floods relied strongly on the use of regional equations, the development of unit hydrographs, and one large recorded flood. The more extensive record available in 1991 permitted some more sophisticated statistical techniques. However, the large flood which occurred in 1983 still caused considerable difficulty, and the results of the analysis varied according to how this flood was included. Despite these difficulties, it was shown that the estimates made in 1984 were not unreasonable. Key words: Peter's River, Newfoundland, flood estimation, regional equations, censored maximum likelihood method, low gauging ratios.
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R.A. VAN GENT, MARCEL. "Low-Crested Structures In Front Of Rubble Mound Breakwaters." CoastLab 2024: Physical Modelling in Coastal Engineering and Science, April 30, 2024. http://dx.doi.org/10.59490/coastlab.2024.711.
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Climate adaptation of coastal structures has become more important due to climate change, resulting in sea level rise and increased wave loading for coastal structures with depth-limited wave conditions. If sea level rise causes wave loading that becomes too severe, one of the options is to reduce the wave loading before the waves reach the existing coastal structure (see for instance Van Gent, 2019, and Van Gent and Teng, 2023). This can be achieved by increasing the foreshore (e.g. sand nourishment) or by constructing a low-crested structure in front of the coastal structure. In this study the climate adaptation measure to add a submerged low-crested structure in front of an existing (emerged) coastal structure has been studied. Between the two structures, structure-induced wave set-up occurs. This structure-induced wave set-up has been studied based on wave flume tests. The effects of structure-induced wave set-up on wave transmission at the low-crested structures and the effects on wave overtopping at the emerged coastal structure were also measured and analyzed. To evaluate the performance of submerged low-crested structures Van Gent et al (2023) performed wave flume tests to examine wave transmission at various types of submerged low-crested structures, without an emerged structure behind the low-crested structures. For a submerged low-crested structure in front of an emerged coastal structure, the transmitted waves can be used as incident waves for estimates of wave overtopping at a rubble mound breakwater, using wave overtopping expressions described in Van Gent et al (2022). However, to verify whether the expressions for wave transmission and wave overtopping can be applied for submerged low-crested structures in front of rubble mound breakwaters, new physical model tests have been performed at Deltares. The new wave flume tests were performed with impermeable and permeable low-crested structures in front of impermeable and permeable emerged structures (see Figure 1 for permeable structure).
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Van Gent, Marcel R. A. "Submerged low-crested structures in front of coastal structures." Journal of Coastal and Hydraulic Structures 4 (March 8, 2024). http://dx.doi.org/10.59490/jchs.2024.0033.
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Climate adaptation of coastal structures has become more important due to climate change, resulting in sea level rise and increased wave loading on coastal structures with depth-limited wave conditions. One of the climate adaptation measures to ensure that existing coastal structures continue to perform their function after unforeseen sea level rise, is to reduce the wave loading before the waves reach the existing coastal structure. This can be achieved by constructing a low-crested structure in front of the existing structure. Between the two structures, structure-induced wave set-up occurs. This structure-induced wave set-up has been studied based on wave flume tests. The effects of structure-induced wave set-up on wave transmission at the low-crested structures and the effects on wave overtopping at the emerged coastal structures were also measured and analyzed.The structure-induced wave set-up depends on the freeboard, wave steepness, and permeability of the low-crested structure. For configurations with impermeable low-crested structures, this wave-set-up does not depend on the distance between the two structures. Empirical expressions to estimate structure-induced wave set-up are derived for impermeable and permeable low-crested structures.The measurements indicate that the effect of structure-induced wave set-up on the wave transmission coefficients is negligibly small.The structure-induced wave set-up increases the wave overtopping discharges at the emerged coastal structure. This effect can be taken into account in wave overtopping estimates by reducing the freeboard with the structure-induced wave set-up.
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ESCUDERO, MIREILLE, JORGE MOLINES, and JOSEP R. MEDINA. "Sustainable And Bioengineered Concrete For Armor Units Of Low-Crested Structures." CoastLab 2024: Physical Modelling in Coastal Engineering and Science, April 29, 2024. http://dx.doi.org/10.59490/coastlab.2024.695.
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In the last two decades, Eco-engineering has emerged to mitigate and compensate the environmental impacts of man-made structures while integrates benefits to society, being concrete the most widely alternative material used to natural rocks for construction of artificial coastal structures. Over the past three decades, an extensive literature has documented different supplementary cementitious materials (SCMs) to reduce CO2 emissions from Portland cement, with common SCMs used in marine and coastal structures such as fly ashes, ground granulated blast furnace slags, pozzolanas and limestones. However, there is a need to further investigate the suitability of SCMs for the construction of Low-Crested Structures (LCS) to decrease carbon footprint from concrete production and improve the bioreceptivity of concrete armor units during the breakwater lifetime. A literature review conducted in this study shows several advantages of slag cements compared to other SCMs to reduce carbon emissions and enhance biological colonization and durability of concrete submerged in seawater, identifying surface roughness as the most effective factor in design of bioreceptive concrete. This study also highlights the importance of the type and quantity of cement used in concrete mixes to reduce carbon footprint of the manufacture of concrete armor units of LCS and the implementation of long-term monitoring plans to fully understand the functioning of local communities that develop on concrete surfaces of artificial structures, and thus, to improve the integration of environmental parameters in the field of coastal engineering.
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HASSANPOUR, NASRIN, PASQUALE CONTESTABILE, JAVIER L. LARA, and DIEGO VICINANZA. "Analisis Of Upgrading Low-Crested Structures As An Adaptation Measure To Climate Change For Coastal Protection: A Hybrid Approach." CoastLab 2024: Physical Modelling in Coastal Engineering and Science, May 7, 2024. http://dx.doi.org/10.59490/coastlab.2024.770.
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Coastal zones have consistently been among the most appealing settlement areas due to their proximity to the sea, rich natural resources, and the high quality of life they offer (Lamberti et al., 2005). However, these regions are affected by climate change impacts, such as sea-level rise, storm surges, and an increased intensity of extreme weather events (Burcharth et al., 2014). Traditional low-crested rubble mound breakwaters are commonly used to protect coastal areas from wave damage. However, it is expected that the variability of climate conditions will induce a loss of functionality and structural integrity in the coming decades. Coastal communities and coastal managers, within the framework of sustainable development, are demanding new approaches that include not only the preservation of the hydraulic performance of the breakwaters, but also other factors, including social and environmental impacts. These requests significantly affect the traditional way to conceive those structures to be integrated into the coastal landscape. To cope with the variation of climate drivers, existing low-crested breakwaters must be adapted to accommodate social demands and environmental issues. Therefore, upgrading and maintaining the existing rubble-mound breakwater is a hot topic in coastal engineering, and deserves special attention due to the possible intensification of external loads resulting from the impacts of climate change (Stagnitti et al., 2023). Upgrading can be done by modifying the structure profile and/or adding structure elements (Burcharth et al., 2014). In 2011, Cappietti provided curves for the functional design of submerged breakwaters to be used in place of preexisting emergent breakwaters. Burcharth et al. (2014) explained that the best way to improve the structure is to put an additional layer of protection on the front slope, as long as the foreshore has a mild slope of around 1:100. But if the foreshore becomes steeper because of erosion, then a front berm will also be needed. Stagnitti et al. (2022) introduced a novel methodology based on the calculation of the failure probability during a lifetime due to independent failure modes. Their method was employed to evaluate the performance of upgraded breakwaters in response to climate change. Estimating the wave overtopping of both existing and upgraded breakwaters is essential for designing upgrade options that can ensure the safety of port operations. Stagnitti et al. (2023) applied the numerical model IH2VOF, which was calibrated using experimental data, to study the wave overtopping of damaged and upgraded rubble-mound breakwaters. The present work examines the feasibility of converting emerged rubble-mound breakwaters into submerged breakwaters to minimize their detrimental environmental effects. To achieve this goal, an investigation was conducted to evaluate the hydraulic performance of submerged breakwaters that are created by lowering the crest of existing emerged breakwaters. Additionally, two-dimensional numerical simulations were performed using IH2VOF to investigate wave interactions with the structures.