Breakwaters

We carried out experimental studies of a smooth submerged breakwater in a wave channel in order to study such a structure impacts on the changes of statistically and spectrally defined representative wave periods as waves cross it. We discuss the impact of relative submersion, i.e. the relationship between the breakwater crown submersion and the incoming significant wave length Rc/Ls−i, on the representative wave periods. The mean periods, estimated using statistical and spectral methods, were compared in front of and behind the breakwater: the two periods turned out to be identical. Based on the measurements of the spectral mean wave periods in front of and behind the breakwater, an empirical model is derived for estimating the reduction in mean spectral period for submerged and emerged smooth breakwaters. The complete text of the paper is available at http://www.iopan.gda.pl/oceanologia/ 40 D. Carevic, G. Loncar, M. Prsic

Perforated breakwaters are newer generation of vertical breakwaters in which somehow the problems of high wave reflection and forces exerted to the structure have been solved. In this paper the effect of hole shapes of Vertical Perforated Breakwaters on reflection of Solitary Wave s was investigated using numerical method. A single and double walls vertical breakwater with four different hole shapes and four different front wall porosity were considered. The breakwater was modeled in 3D using FVM method of FLOW-3D ® Software. The free surface was modeled using VOF method while RNG k-ε was used to model turbulent effect. The results show that in single wall breakwater as porosity increases the wave reflection increases as well so that a 40% porous wall reflects 90% of incident waves. Furthermore, the reflection coefficient has a fluctuating nature as non-dimensional ratio of B/L increases (B is width of caisson and L is incident wave length). Moreover, double wall breakwater is able to damp wave energy up to 20 to 25% greater than that of the single wall.

A more detailed understanding of porous flow inside a rubble-mound structure may have potential benefits in breakwater design. Numerical models are expected to be a useful additional research tool in this field, provided that their calculation results can be validated against measurements. This paper presents the results of a systematic effort to validate a set of different numerical models for a strongly simplified model set-up. The results of this effort will be used to select models for a next stage in which the complexity of the model set-up is increased. By means of this stepby-step approach a good insight in the capabilities and limitations of the various models is achieved.

The purpose of this Coastal and Hydraulics Engineering Technical Note (CHETN) is to investigate the basic physics and numerical code of GenCade by running a series of simplified test cases and comparing the results to another numerical shoreline evolution model and an analytical solution. The complementary numerical code is the widely used shoreline evolution model LITPACK. The analytical model is the original solution derived by . The underlying assumption in all three approaches is a beach profile of constant shape so that shoreline change is driven by long-shore transport processes and a combination of independent sediment sources or sinks (e.g., sea level change, subsidence). The CHETN presents a descriptive overview of the theory behind the models followed by an inter-comparison using a set of four test cases involving shoreline change in the vicinity of idealized coastal structures and a beach nourishment. GenCade shows good agreement with LITPACK, and both models compare well to the analytical solution for these idealized cases. The GenCade results indicate that the underlying numerical code and basic physical process are consistent with other widely used shoreline modeling systems. INTRODUCTION: Mathematical modeling of shoreline change is a powerful engineering technique for understanding and predicting the long-term evolution of a beach . Mathematical models provide a quantitative means of describing shoreline evolution observed at groins, jetties, and detached breakwaters ).

This report documents a numerical modeling study investigating sediment transport and morphology change adjacent to Merrimack Inlet, Newburyport, and nearshore in the vicinity of Salisbury Beach and Plum Island, Massachusetts. Concerns at the site include beach erosion, shoreline retreat on Plum Island downdrift of and within the inlet, and reduced navigability of the inlet. The numerical modeling evaluation consists of two phases.

Chapter 1 Introduction configured breakwater project was recently constructed in Cameron Parish in the western part of Louisiana and provides a model for designing a breakwater project at Grand Isle. This task reviewed the observed morphological response at the Cameron Parish project and made comparisons to the proposed project at Grand Isle. The most comprehensive study of Grand Isle is the 1979 U.S. Army Corps of Engineers report on Grand Isle. This report contains extensive information on coastal erosion, coastal processes, and sand resources, and designs for the Corps of Engineers beach erosion and hurricane protection project which was built in 1984. Combe and Soileau (1987) reported on construction details and the successful performance of this project during and after the unusual 1985 hurricane season in which Hurricanes Danny, Elena, and Juan impacted the island. A report related to this investigation of proposed breakwaters at Grand Isle was prepared by engineering firm HNTB under contract for the Louisiana Department of Natural Resources, Coastal Restoration Division (1993). This report reviews Louisiana State Senate Concurrent Resolution Number 83, which urges the Wetlands Conservation and Restoration Authority, the Department of Transportation and Development, and the U.S. Army Corps of Engineers to examine the feasibility and advisability of placing breakwater protection along the coast of Grand Isle, Louisiana. The report provides a good summary of coastal projects constructed at Grand Isle between 1951 and 1991, reviews the performance of the breakwater project at Holly Beach, Louisiana, and proposes a conceptual segmented detached breakwater project design and layout for Grand Isle. This chapter describes procedures and results of the wave data preparation and nearshore wave refraction task of the study. This task consisted of three steps and resulted in the preparation of wave information that was subsequently employed in the numerical shoreline evolution simulations presented in Chapter 3. The first step involved the transformation of hindcast estimates of the offshore wave climate to the Grand Isle project area. In the second step, the time history of wave information at the Grand Isle project area was statistically analyzed and 22 categories of potential wave approach and wave period were identified. The results of the statistical analysis were also used to select a 4-year-long representative time history of wave conditions from the 20-year-long hindcast database. The third step involved the use of a numerical wave refraction model to obtain representative nearshore wave conditions in shallow water at fixed points alongshore. No long-term wave measurements are available for the vicinity of the Grand Isle project. Therefore, the required wave information was generated by means of the Wave Information Study (WIS) hindcast technique. The WIS provides a 20-year hindcast for the U.S. Gulf of Mexico coast for the years 1956 through 1975. The Gulf of Mexico hindcast wave information ) includes a 20-year time history of wave height, wave direction, and wave period at 3-hr intervals for both sea and swell at 50 stations along the Gulf of Mexico coasts of Florida, Alabama, Mississippi, Louisiana, and Texas. Hindcast Station 21 located offshore of Grand Isle at 28.5 deg north latitude and 90.0 deg west longitude was selected for use in this study. Phase 111 transformation. Wave information at WIS Station 21 is representative of wave conditions in 300 ft of water at this geographic location, however, since the location is gulfward of the Mississippi River delta which blocks wave energy approaching from the east, these wave conditions Chapter 2 Wave Refraction Analysis Chapter 3 Long-Term Shoreline Change Chapter 3 Long-Term Shoreline Change zone). If an energy window is open (no diffraction source) on one side, the diffraction coefficient for that side is set equal to 1.0.

This report documents the investigation of coastal processes and development of conceptual alternatives to reduce beach erosion at two sites in Matagorda County. Sargent Beach has experienced the greatest erosion rates on the Texas Coast, prompting study into structural methods to protect beach habitat. Additionally, the three miles of beach to the east of the Mouth of the Colorado River is a candidate for structural stabilization. The proximity of the two project areas provided an opportunity to consider processes on a regional scale in an effort to improve regional shoreline stability and further understanding of regional processes. Sargent Beach is comprised of cohesive sediment overlain by a thin veneer of sand. It is located between an ephemeral inlet to the east and a flood relief inlet to the west. The region includes two major river diversion projects, an eight mile long revetment at Sargent Beach, and many other engineering modifications influencing transport. Because of the complex site, an investigation into coastal processes was conducted to determine alternative development. Understanding of physical processes developed during this investigation was applied to develop potential solutions to reduce erosion, including beach nourishment, groins, breakwaters, and installed bypassing systems. The contents of this report are not to be used for advertising, publication, or promotional purposes. Citation of trade names does not constitute an official endorsement or approval of the use of such commercial products. All product names and trademarks cited are the property of their respective owners. The findings of this report are not to be construed as an official Department of the Army position unless so designated by other authorized documents. DESTROY THIS REPORT WHEN NO LONGER NEEDED. DO NOT RETURN IT TO THE ORIGINATOR.

The Colonial Beach, Virginia segmented detached breakwater and beach fill project consists of two sites, Central and Castlewood Park Beaches, constructed in October 1982 to protect a cohesive bluff (6 to 10 ft in height) eroding at a preproject rate estimated at 1.5 ft/year. The project sites were cooperatively monitored by the US Army Engineer District, Baltimore, and the US Army Engineer Waterways Experiment Station Coastal Engineering Research Center from October 1982 through June 1985. This report presents the data collected during the monitoring program and documents the bathymetric and shoreline response to the structures. Although the water level increase due to storm conditions was not fully considered in the original design of the beach fills, the project sites have successfully prevented erosion of the beach bluff. Results from the monitoring program were used to modify the Central Beach fill elevation, eliminating inundation of the beach during storms and increasing its r...

This study evaluated the present and future functionality of the Sabine Pass jetties considering planned deepening of the Sabine-Neches Waterway Navigation Channel from 42 to 48 ft mean low water (MLW) and possible rehabilitation of the jetty system. The Sabine Pass jetties were constructed to their full length (East jetty, 25,270 ft; West jetty, 21,860 ft) between 1880 and 1930 and, during the 130 years since construction began, have incurred loss of elevation and damage because of regional subsidence, scour at the base of the structures, storms, disintegration of the original fascine (willow) mats used as foundation for the structures, and consolidation of the underlying substrate. This study evaluated the 2003 condition of the jetties and anticipated functionality in 50 years given change in relative sea level at the site, future consolidation of the underlying substrate, and possible storm damage. Three integrated tasks evaluated 1) the stability of the jetties to storm waves, 2) the decrease in structure elevation through time relative to the mean water level caused by consolidation of the underlying substrate and relative sea level rise, and 3) waves, currents, and potential sediment transport pathways in the vicinity of the jetties and navigation channel. Each task assessed the 2003 "existing" condition, a hypothetical jetty condition in 50 years without rehabilitation, and two repair scenarios that were assumed to occur in 2010 and were assessed after 50 years. The repair scenarios were rehabilitation of the entire length of both jetties vs. rehabilitation of the seaward 4,000 ft. Both alternatives would be constructed to elevations of +9.2 ft MLW (East) and +9.3 ft MLW (West). Shear stresses from numerical calculations of waves, currents, and water levels were applied to indicate the potential for cohesive sediment transport and channel shoaling magnitudes. Recommendations from these analyses were that the jetties should be rehabilitated to +9.2 ft/+9.3 ft MLW to ensure safe navigation and reduce channel shoaling, and that stone size should be increased to approximately 17-18 tons for stability during storms and higher water levels. Repair of the seaward 4,000 ft of both jetties provided similar navigation benefits (reduction in waves and currents, no change in total shoaling) as restoration of the full length of both jetties. Physical model studies are recommended to optimize stone size for rehabilitation. Numerical modeling is recommended to assess the potential for scour of the seabed in the vicinity of the jetties, and to determine magnitudes of channel shoaling for cohesive sediment. Numerical shoreline modeling with anticipated water levels over the project lifetime is recommended to assess the likelihood for structure flanking and minimize adjacent beach erosion. The contents of this report are not to be used for advertising, publication, or promotional purposes. Citation of trade names does not constitute an official endorsement or approval of the use of such commercial products. All product names and trademarks cited are the property of their respective owners. The findings of this report are not to be construed as an official Department of the Army position unless so designated by other authorized documents. DESTROY THIS REPORT WHEN NO LONGER NEEDED. DO NOT RETURN IT TO THE ORIGINATOR.

In this research, the efficiency of a breakwater of caissons supported on piles was studied, as well as erosion around the piles under regular waves. The breakwater's hydrodynamic performance was studied by calculating wave reflection, transmission, energy dissipation, and scour. Many variables have been studied such as the change in the draft (D/h) in addition to the change in wave height (h/L). The transmission coefficient (kt) decreases as the relative wavelengths increase (h/L) and decrease with an increasing relative draft (D/h). The reflection coefficient (kr) has the opposite trend, according to the results. The maximum depth of relative seaward erosion (Dsmax/h) ranged between 0.04 and 0.08 when (D1/h) was changed in the range (0.2-0.6). Empirical equations were developed for estimating the transmission and reflection coefficients. These equations' results were compared to other experimental and theoretical results and were found to be in reasonable agreement. When compared to other breakwater systems, the suggested breakwater type proved efficient.

In this study, erosion around the piles caused by regular monochromatic waves as well as the efficiency of a caisson with slotted supported on piles breakwater was investigated experimentally. By estimating wave reflection, transmission, and energy dissipation, the hydrodynamic performance of the breakwater was investigated. many factors have been studied, including changes in wavelength (h/L) and drafting of slotted (D2/h) towards the seaside. The transmission coefficient (Kt) decreases with increasing relative wavelengths (h/L) and relative drafting (D/h), respectively. The reflection coefficient (Kr) has the opposite trend, the reflection coefficient (Kr) increases with increasing relative wavelength (h/L). For estimating the transmission and reflection coefficients, empirical formulae were created. Results from these equations were compared to those from other experiments and theories, and it was discovered that there was a reasonable amount of agreement. The suggested breakwater type outperformed other breakwater systems in terms of effectiveness.

Groins are one of the most important facilities used to protect coastal regions. In this research, groins made from a concrete cube were tested experimentally. This research investigates the impact of groin length (Lg) of 105, 135, and 165 cm and groin angle with the normal axis of the shoreline (h) of 0 °, 10 °, 20 °, and 30°under different dimensionless wave numbers (khg), from 0.34 to 1.26, with the beach slope of 8:1. The units used to indicate erosion and deposition are dimensionless erosion depth (Smax/h), dimensionless deposition height (Dmax/h), and dimensionless erosion hole length (lsmax/h). The sandy bed changes and wave reflection from the groin were monitored. The results showed that the angle of 30°h ad more impact on beach stability than that of 0°, and more sediments were eroded by short groins than by long ones. The reflection of waves from groins was also studied as a function of the reflection coefficient (kr). As concluded, short groins reflect higher waves than long ones.

In this report, the results of a numerical parameter study on temperature stresses caused by hydration of cement in concrete breakwater elements are shown. Two different geometries were analysed namely hollow cubes and tetrapods. The problem encountered in solid cube breakwaters is the undesirable temperature build up between the core and the outside surface. The main reason for the temperature build up, is the thermal heat, which is generated due to the heat of hydration of cement from the time of casting. This thermal gradient induces eigen-stresses and causes the early age cracking. The choice of a hollow cube is a way to reduce the temperature gradient and thus the eigenstresses. A parameter study is undertaken in order to arrive at an optimum dimension based on the thermal gradient and the eigen-stresses. The variables are the cube dimension (i.e., height H = 2, 3 and 4 m with the inner diameter to the height ratio d,/H = 0.4), the size of the hole (d[ = 0.9, 1.2 and 1.5 m for the 3 m hollow cube only), the cement content (225 and 325 kg/m 3 ), the initial concrete mix temperature (5, 15 and 25 °C) and the degree of isolation (with and without isolation). For the analyses of the tetrapods, two geometries were chosen. The total height H of the tetrapod was 3.11 and 4.15 m with corresponding diameters D = 1.5 and 2 m. The favourable conditions for the reduction in the temperature gradient and the tensile stress peak for the hollow cubes were: the low mix temperature, the larger hole diameter, the low cement content and the smaller hollow cube. From the range of hollow cube specimens analysed, it appears the 2 m hollow cube is the best choice based on the temperature gradient as well as the tensile stress peak generated. v

Akurasi pengukuran gelombang di laboratorium merupakan faktor penting penentu kualitas hasil pengujian. Penelitian ini mengevaluasi akurasi pengukuran tinggi gelombang di depan model pemecah gelombang terapung menggunakan metode kombinasi dua dan tiga titik wave probe. Nilai akurasi ditentukan dengan membandingkan hasil tersebut terhadap pengukuran metode enam wave probe. Gelombang teratur dibangkitkan dari satu sisi tangki gelombang dengan panjang 25 m, lebar 1 m dan kedalaman 1,2 m yang dilengkapi dengan generator gelombang tipe flap. Peredaman gelombang di ujung lainnya dibangun dari tumpukan batu. Enam titik wave probe (HR Wallingford 8 saluran) ditempatkan di sepanjang gelombang di depan model berjarak 0,2L. Pembangkit gelombang membangkitkan fluktuasi muka air yang meningkat hingga mencapai ketinggian gelombang yang diinginkan. Setelah beberapa gelombang datang, gelombang pantul kemudian menurunkan fluktuasi muka air hingga mencapai kondisi gelombang stabil (yang bentuk dan tinggi puncaknya relative sama) yang menunjukkan bahwa gelombang yang dihasilkan adalah gelombang linear. Nilai R-square digunakan untuk mengevaluasi akurasi pengukuran gelombang. Metode tiga titik dengan jarak wave probe gelombang 0,2L adalah metode terbaik untuk mengukur tinggi gelombang.Kedua metode tersebut dibandingkan dengan metode umum untuk mendapatkan yang sesuai untuk setiap kasus. Kinerja pembangkit gelombang dapat ditingkatkan dengan mengurangi refleksi gelombang. Sementara pengaruh jarak wave probe juga memberikan pengaruh terhadap akurasi pengukuran tinggi gelombang.

Wave run-up on a rubble mound breakwater is investigated. Prototype measurements are carried out on the Zeebrugge breakwater. Two 2D (1:30) and one 3D (1:40) scale models are tested. Measured prototype storms are simulated and parametric tests are performed. Wave run-up is detected by a novel step gauge allowing to detect wave run-up more accurately. In prototype, wave run-up is measured by two different measuring devices: a so-called 'spiderweb system' and a run-up gauge. Both instruments yield comparable results. A clear difference between prototype measurement and physical modelling results is noticed. Also differences between the results of the different laboratories are seen. Various factors leading to these differences are highlighted.

This report discusses the application of detached single and segmented breakwaters for shore protection and beach stabilization. Four single detached breakwaters and six segmented breakwater systems in the United States are reviewed. Based on this review, the performance of breakwaters in other countries, and general knowledge of coastal processes, the implementation and design of breakwaters are discussed. General guidance is presented for the design of detached breakwaters and several design examples are presented.-- This report is published to provide coastal engineers with information and guidance on the use of detached breakwaters for shore protection and beach stabilization. The material is based on an extensive literature review and the analysis of existing projects constructed for these purposes.

This paper describes the numerical modeling of waves, currents, and sediment transport at Pillar Point Harbor, CA. The Coastal Modeling System (CMS), developed at the US Army Engineer Research and Development Center (ERDC) with fully integrated wave, current, and sedimentation models (Demirbilek and Rosati, 2011), was applied to calculate the coastal processes at the harbor and adjacent beaches. The model simulations include both the present-day bathymetry with breakwaters and pre-harbor condition without breakwaters. The model results indicate the construction of Pillar Point Harbor in 1960s have adversely affected local sediment transport and shoreline change while aged breakwaters have caused more sand accumulation inside harbor.

Marine structures, such as groins, coastal walls, and detached breakwaters are built to improve and protect the coast against erosion resulting from changes in patterns of waves and currents on the coasts. Thus, marine mechanisms for hydraulic structures need serious study. Breakwaters are among the most important structures for coastal protection. The most substantial hydraulic performance of breakwaters is to control current along the coast, decrease the destructive effects of the waves, and create a safe condition for the port environment. Now, the coastline reaction to these structures is not well-determined. Nowadays, simulation and computer models are used for sediment transport patterns and coast morphology near the marine structure to alleviate the application of experimental and laboratory assessments. The purpose of this study is to examine the interaction between waves, coast, and breakwater, and to model the sedimentation and current regime model based on the mathematical MIKE 21 models and computations in the southern margin of the Caspian Sea within the breakwater area of Anzali Port's (Bandar-e Anzal) development plan. According to conducted studies, it is found that sediment accumulation will appear after breakwater construction in the coastal area.

One of the usual methods of building breakwaters in Iran is to use rock mass structures. Most of the rocks in the south of Iran are sedimentary (limestone, sandstone and lomashell). Most of the regulations in present codes regarding the usage of stone in hydraulic protection structures in other countries are mostly according to the availability and abundance of igneous rocks, as well as their own specific different geological conditions, so they have criteria's that are more suitable for these types of rocks. In 2009, the regulations for the use of stone in breakwaters and protection structures were prepared to provide a codified standard for quality control during construction due to the extreme poverty of desirable stones in the south of Iran. Despite the promulgation of this regulation , the quality of construction in the majority of rock mass structures is still not favorable, the reasons for which can be attributed to: high abundance of harmful clay minerals within the range of extractable depth of the existing formations, high heterogeneity in the quality of the extracted rock, The extension of the life of the constructed structures beyond the initial assumptions of the design, the insufficiency of the existing standards for medium and long term serviceability, and in general the dominant effect of mineralogy on the overall performance of sedimentary rocks in rock mass structures. With regard to the mentioned cases, in this article, a new criterion for the classification of sedimentary rocks has been proposed.

The European Manual for the Assessment of Wave Overtopping (“EurOtop”) was issued free on the internet in 2007 and is now used worldwide. The manual and the accompanying Neural Network give guidance on all aspects of wave overtopping. It was the result of synthesis of existing Dutch, UK and German guidance and new research findings arising out of projects such as the EC FP7 “CLASH” project. During and since writing, the manual team has identified gaps and areas in which other improvements and clarifications could be made. This paper presents a summary of new analysis of existing data on vertical and very steep walls. A companion paper revisits sloping structures (Van der Meer et al., 2013).

Introduction and problem definition Allowable overtopping very often determines the crest height of a structure during the functional design. And for given structures overtopping under extreme conditions is required to say anything on the hazard. Overtopping formulae for sloping structures have been developed in the past, see the Dutch TAW guidance (TAW, 2002 – by Van der Meer) and the UK Environment Agency Overtopping Manual (EA Manual, 1999 – by Besley). Rough structures are included by using the same formulae, but giving these structures a roughness coefficient. It becomes very complicated if the structure consists of several parts with different roughness, but this is often the case in reality. For example a coastal protection or dike often consists of a rock berm around normal water level, a fairly, but not completely, smooth revetment and an upper part of asphalt or grass. Figure 1 gives such an example, where not only a rock berm is present around swl, but also a higher (at d...

The present paper deals with stability of berm breakwaters designed to be hardly or sometimes partly reshaping. Burcharth (2008, 2011) showed by comparison to the performance of a prototype berm breakwater that the Van der Meer formulae for stability of conventional rock armour including low crests could predict the deformations of the front slope in terms of the eroded area. The present paper verifies the method by comparison to model test results. It is found that the Van der Meer formula for plunging waves predicts very well the eroded area of the reshaped profile, even if it is applied in the surging wave area. Moreover, a simple method to estimate the erosion area based on recession formulae and the depth of intersection of reshaped and initial profile is presented and is applicable for hardly reshaping to fully reshaping. Even when using the only very simple and inaccurate estimate of the depth of intersection the last method leads to scatter quite similar to the first method ...

This paper gives first an elaboration of berm recession equations for berm breakwaters and then new deterministic design rules for the Icelandic-type berm breakwater. Safety optimization calculations have been performed for a mild depth limited wave climate and for a situation at deep water. Repair strategies and possible failure with corresponding downtime have been taken into account, as well as actual market prices (in Iceland and Norway) for rock material and construction. Calculations show that low stability numbers for the largest rock armour layer give the optimal safety level.

A 2-phases neural prediction method for wave overtopping is developed. The 'classifier' predicts whether overtopping occurs or not, i.e. q = 0 or q N 0. If the classifier predicts overtopping q N 0, then the 'quantifier' is used to determine the mean overtopping discharge. The overtopping database set up within the EC project CLASH (

This paper describes a major programme of small-scale physical model tests to establish better the influence of armour type and configuration on overtopping. Specifically, 179 tests determined the relative difference in overtopping behaviour for 13 types/configurations of armour. Roughness factors γ f were determined for rock (two layers), cubes (single layer and two layers), Tetrapod, Antifer, Haro, Accropode, Core-Loc™ and Xbloc™. These roughness influence factors have been included in the CLASH database and are for use in the neural network prediction of overtopping. Individual wave-by-wave overtopping volumes were analysed and found to compare well with current prediction methods. Measured reflection coefficients for the different units are also presented and compared with recent formulae.

Recently, the investigations on the hydrodynamic performance of floating breakwaters have great interest to researchers because of its high advantages in protecting marinas and small craft harbors. For the purpose of improving the hydrodynamic performance of the stepped-slope floating breakwater type, this research had been carried out as an approach to investigate experimentally the resulting hydrodynamic performance of a composite pile supported breakwater consists of a stepped-slope floating body moving only in heave motion overlying a fixed submerged horizontal plate in a constant water depth, d = 30 cm. The transmission, reflection and losses coefficients had been determined individually for each of the stepped-slope floating, fixed submerged horizontal plate and the composite breakwaters. The results showed that the performance of the stepped-slope floating breakwater tested using different relative draft values, Df /d, of the floating body had been significantly improved and achieved extra wave damping by reducing the transmission coefficients by a ratio range between 23 % to 52 %, when using the submerged fixed horizontal plate underneath the floating body, with definite improvement value depends on plate relative submergence depth, dp /d and plate relative thickness, tp /d. For a composite breakwater using two relative submergence depths of the plate, it had been found that a significant higher wave attenuation takes place with a configuration using dp /d = 0.33 than that obtained when using dp /d = 0.50. Furthermore, plate relative thickness achieved wave attenuation improvement for the composite breakwater especially for the configuration using dp /d = 0.33 and tp /d = 4%.

This paper describes a major programme of small-scale physical model tests to establish better the influence of armour type and configuration on overtopping. Specifically, 179 tests determined the relative difference in overtopping behaviour for 13 types/configurations of armour. Roughness factors γ f were determined for rock (two layers), cubes (single layer and two layers), Tetrapod, Antifer, Haro, Accropode, Core-Loc™ and Xbloc™. These roughness influence factors have been included in the CLASH database and are for use in the neural network prediction of overtopping. Individual wave-by-wave overtopping volumes were analysed and found to compare well with current prediction methods. Measured reflection coefficients for the different units are also presented and compared with recent formulae.

James Island and Barren Island, in Maryland waters, are among the few remaining eastern shore islands in mid-Chesapeake Bay. Both islands are eroding at a rapid rate due to wave and storm action, as well as to relative sea level rise. These two islands are considered as potential candidate restoration sites as a beneficial use of clean dredged material from the Baltimore Harbor and Channels Federal Navigation Project. The island restoration project requires the construction of protective dikes to contain the dredged material. The restoration work should provide efficient protection to the existing islands, shelter sandy beaches and the shoreline from severe erosion, and improve water quality and surrounding environment for submerged aquatic vegetation. This report describes establishment and operation of a suite of numerical modes to evaluate alternative designs as an initial study for restoration and modification of James Island and Barren Island. The predicted wave climate along the mainland shore was also estimated for the alternatives. Both typical and storm hydrodynamic conditions were assessed. In support of the numerical modeling, sediment samples were taken and bathymetric surveys made in key areas, together with assemblage of relevant data sets such as aerial photographs of the shoreline, wind, and presence and vulnerability of submerged aquatic vegetation. Data from the modeling and other data sets assembled and collected were compiled on a DVD.

The design of breakwater armour units against tsunami attacks has received little attention in the past because of the comparative low frequency of these events and the rarity of structures designed specifically to withstand them. However, field surveys of recent events, such as the 2011 Great Eastern Japan Earthquake Tsunami and the 2004 Indian Ocean Tsunami, have shown flaws in the design of protection structures. During these extreme events, many breakwaters suffered partial or catastrophic damage. Although it is to be expected that most normal structures fail due to such high order events, practicing engineers need to possess tools to design certain important breakwaters that should not fail even during level 2 events. Research into the design of critical structures that only partially fail (i.e., "resilient" or "tenacious" structures) during a very extreme level 2 tsunami event should be prioritized in the future, and in this sense the present paper proposes a formula that allows the estimation of armour unit damage depending on the tsunami wave height.

The measurement of wave-induced impacts on structures involves significant scientific and engineering challenges. Regular nearly breaking pgbgand broken waves generated following cnoidal and first-order Stokes wavemaker theory have been considered to study the variability of wave impacts on vertical breakwaters. Four small-scale hydraulic experiments were carried out and repeated 120 times using high-speed pressure and force measurement equipment. High variability in the measured pressure field and total force were observed, reflecting the random nature of the studied phenomena. The force variability was similar for the nearly breaking and broken waves. The maximum measured force was between 166 and 177% of the minimum measured force. In relation to the force distribution and maximum pressure points, the observed variability is higher for broken waves. To deal with such variability in the observations, suitable probability distributions for forces (GEV) and pressures (Gamma) are proposed.

This paper presents a new low-reflectivity quay wall caisson based on the formation of cell circuits. The cell circuit lengths can be adapted to the specific wave climate conditions at the construction site to obtain the best performance. Results from physical model tests of conventional and cell circuit caissons are described, as well as the construction process and steel reinforcement, which turns out to be quite similar to highly reflective conventional caissons. Neural Network (NN) models are used to describe the nonlinear relationship observed between experimental coefficients of reflection (CR) and the structural and wave conditions for the new low reflectivity quay wall caisson.

This paper presents the results from a new set of 3-D physical model tests performed in a 6.5 m wide flume at the Centre for Harbour and Coastal Studies in Madrid. These results will contribute to enhance the existing knowledge obtained in previous studies. Among other variables, they cover concrete-cubes armours and the submergence is increased, with a higher model scale. Damage criterions are discussed and proposed for both types of armour. The latter takes into account the different damage growth observed between rock and cubes-armours. Lower thresholds are proposed for cubes in order to increase the safety, though still allowing some movements before considering the damage is reached.

A new semi-empirical model is used to estimate the coefficient of reflection for single-and double-perforated chambers in Jarlan-type breakwaters. This semi-empirical model is based on a potential flow theoretical model which was modified with specific, empirical formulas to obtain a much better agreement with the experimental tests. Single-chamber and double-chamber slotted and perforated Jarlan-type breakwaters were tested with 1500 regular wave and 160 random wave runs. Pruned Neural Network models with Evolutionary Strategies were used to identify the nonlinear relationships between the structural and wave climate parameters and the Jarlan-type breakwater reflectivity. This new semi-empirical model is valid for regular and random waves on single-chamber and double-chamber Jarlan-type breakwaters, providing estimations of the coefficient of reflection with a relative mean squared error lower than 10% for all experimental observations used to calibrate the model.