Breakwaters

A B S T R A C T This paper reviews the available models for the estimation of mean wave overtopping rate at berm breakwaters. A sensitivity analysis was conducted on selected models in order to study the influence of input variables on estimated overtopping discharge. The dimensionless crest freeboard is the most significant factor influencing the predicted overtopping rate. The sensitivity of overtopping to wave steepness varies from being insensitive, constant, or a function of dimensionless crest freeboard across the formulae analysed. The berm width and berm level (with respect to the still water level) have lower impact on the predicted overtopping compared to that of the crest freeboard. A case study on the sensitivity of predicted overtopping was carried out on Sirevag and Bakkafjordur berm breakwaters and it illustrated that the existing models are most sensitive to the variables of dimensionless crest freeboard, when it is greater than 1.0; and dimensionless berm width, when it is greater than 2.0. Additionally, the case study demonstrated inconsistencies among the models for predicted over-topping. The sensitivities of the estimated overtopping rates to the governing variables were compared with those obtained from experimental data. Among the models, the sensitivity estimations using the artificial neural network of Van Gent et al. (2007) [58] and the Lykke Andersen (2006) [32] formula were found to be in more reasonable agreement with those of the experimental data. The Van der Meer and Janssen (1994) [56] formula showed oversensitivity to the major governing variables. The results of this study throws light on the disparities in accounting the influence of variables, in the estimated overtopping rate at berm breakwaters, using the existing prediction models.

The paper aims at providing a simple model for evaluating piling-up, overtopping, filtration and rip currents for low crested structures. The model is essentially based on mass and momentum balance and on resistance laws that relate piling-up and mass fluxes. A procedure is suggested and validated against 2D and 3D experimental data. This procedure is innovative with respect to existing formulations since it applies both to emerged and submerged structures and it simultaneously accounts for structure permeability, return flow through gaps and dissipative effects.

The entire costal zone of Dubai is currently undergoing a major reshaping. Offshore marine sand is being dredged and deposited where it forms now a great asset to Dubai economy. The reclaimed land is forming the largest offshore development projects world wide. A clear sea view from the reclaimed ground level is one of these developments amenity characteristics which must be preserved. To achieve this goal, the concept of low-crested coastal structures has been utilised. This paper introduces and categorizes the different methods and possibilities for using this concept to fulfil the aesthetic requirements and to produce an economical design. An overview of the functional performance of selected Nakheel developments is also presented, namely Palm Jumeirah, Palm Jebel Ali and the World Islands, in order to illustrate how the low-crested structures concept can be put into practice.

In the year 2011 until 2016, Coastal Erosion news gets the media's attention and the government as they try to find a solution for the erosion problems at Pantai Teluk Lipat, Dungun Terengganu. The beach is listed as among the six severe coastal erosion in Malaysia. It is caused by a heavy storm wave during the northeast monsoon. Moreover, the natural aesthetic value has been destroyed by the geological process and give bad impact on the village settlement at shoreline area. Therefore, this project is to find a solution and implementing the solution for coastal management by using living breakwater system solution to enhance coastal erosion at Pantai Teluk Lipat. Also, to proposed the natural shoreline that necessary for sustaining the coastal landscape by providing long-lasting and viable sustainable landscape design while offering recreation for the public and community. Design implementation is using the coastal management and coastal engineering approach to produce the framework of design which to creating a coastal management solution that will integrate the space of coastal shoreline with constructed the coastal protection breakwater which to be possible of coastal management improvement of coastal erosion. The primary purpose of the solution is to improve the coastal shoreline by providing coastal protection of island breakwater to the local people that will bring new living lifestyle back of breakwater protection. From then that, the new development of coastal management of Pantai Teluk Lipat will bring more excitement to the visitor in recreational and also to the local community about cultural, economic aspects that to help protect the habitat and provide interpretive opportunities.

Many breakwaters and jetties have become permeable to sand transport and wave transmission, a condition that results in increased operations and maintenance dredging costs and increased risks and delays to navigation. First-cost savings could be realized by applying grouting techniques and sealing procedures developed for closing voids and fractures, instead of the more expensive method of applying layers of chinking and armor stone to the existing structure. The longevity of such grouts and sealants placed in voids of rubble-mound structures exposed to wave and current conditions is not well known. The term 'sealant' is used here to describe any material that closes voids and include grouts and very stiff, aggregate-containing cementitious and asphalt materials. This problem was separated into two parts; an evaluation of the effectiveness of materials already being used the development of guidance on sealant hole drilling, quantities to inject, techniques of injection, and ...

The present case study serves the two-fold objective of firstly addressing the less documented design context of single layer armoured breakwaters nearby a curved step-like bathymetric feature, while secondly striving for accurate design wave boundary conditions after numerical modelling of wave transformations on a fine spatial grid near the step-like feature to account for the localized effects on the design waveheights. A detailed extremal analysis was performed on hindcast wave results verified against buoy and satellite data, investigating the goodness of fit for a large number of candidate long-term probability distributions. Numerical modelling results show an amplification of waveheights due to the combined shoaling and focusing effects of nearshore bathymetry for certain sectors of wave approach, including the direction of the highest deep-water waves, while for other directions exacerbated dispersion results in further reduction of the refracted waveheights. Preliminary hydraulic design of the breakwaters was undertaken prior to further study by physical modelling.

The geographic location of the ancient Ptolemaic harbor settlement situated on the border of Pamphylia and Cilicia Trachea was first identified by Beaufort, with reference to Strabo. The current settlement was documented as an ancient Ptolemaic settlement situated in the Pamphylia region by the studies focusing on the relationship between Egypt and Anatolia during the Hellenistic Period. The ancient Ptolemais harbor settlement is situated on the Cape Fığla Peninsula, which is 20 km to the west of Alanya District in Antalya Province. At present, the ancient breakwater structure is partially observed around the Aynalıgöl Bay, which is located in the southeastern end of the peninsula. The Aynalıgöl Bay is open to southeasterly winds such as the samiel, and the imbat due to its natural topography. With its arc length of 1 radian, its larger portion rising above the water, and its particularly well-preserved condition, the breakwater structure that extends from the east section of the Aynalıgöl Bay to the southwest, makes the bay a well-sheltered harbor. A 62 m long portion observed above the water reaches to a total lenght of 78 m, including the inclining submerged end portion that extends into the bay. The four courses of a wall system consisting of stone blocks in different sizes ranging from 214x118 cm to 96x82 cm is partly observed. Dovetail joints were used on the first three courses of blocks. The dovetail groove that remained is 51 cm long and 17 cm wide, and has a neck width of 7 cm and a depth of 6 cm. The breakwater structure was reinforced by stone blocks placed perpendicular to the south direction, facing the sea alongside the platform.

Landsat Enhanced Thematic Mapper imagery (ETM) of 2002 and aerial photography of 1955, combined with published charts and field observations were used to interpret geomorphological changes in the coastal zone between Kitchener drain and Damietta spit in the northeastern Nile delta previously recognized as a vulnerable zone to the effects of any sea-level rise resulting from global warming. The interpretation resulted in recognition of several changes in nine identified geomorphological land types: beach and coastal flat, coastal dunes, agricultural deltaic land, sabkhas, fish farms, Manzala lagoon, saltpans, marshes and urban centers. Reclamation of vast areas of the coastal dunes and of Manzala lagoon added about 420 km 2 to the agricultural deltaic land. About 48 km 2 of sand dunes, marshes, sabkhas and salt pans have been converted to productive fish farms. The main urban centers have expanded, and new urban centers (Damietta harbor and the New Damietta city) have been constructed at the expense of vast areas of Manzala lagoon, coastal dunes, and backshore flats. As the consequence of human activities the size of Manzala lagoon has been reduced to less than 50%. Short-term shoreline changes along the coast of the study area established from beach profile survey, spanning the years of 1990 to 2000, reveal longshore patterns of erosion versus accretion. The rate of shoreline retreat has increased in the downdrift side of Damietta harbor (- 14 m/year), whereas areas of accretion exist within the embayment of Gamasa and in the shadow of Ras El Bar detached breakwater system, with a maximum shoreline advance of ~ 15 m/year. A sandy spit, 12 km long, has developed southeast of Damietta promontory. These erosion/accretion patterns denote the natural processes of wave-induced longshore currents and sediment transport, in addition, the impact of man-made coastal protection structures.

The purpose of this study was to analyze the December 1993 breach at Grays Harbor, WA, and assess the threat to the Federal Navigation Project had the breach not been filled the following fall. The study was conducted by quantifying evolution of breach morphology; numerically simulating the ocean wave and water level conditions producing the current through such a breach, including investigation of wide-area implications for the current in Grays Harbor; and numerical modeling breach evolution. Available data on the breach evolution were analyzed with a Geographic Information System. The width of the breach and erosion of the adjacent shoreline are quantified from aerial photographs. Shoreline position and bottom configurations in the vicinity of the now-closed breach are the basis of numerical modeling of wave- and tide-driven currents. Estimates are made of the wave and current climate at South Beach, Pt. Chehalis, and in Half Moon Bay under the assumption of a breach at the jetty....

In 1995, Suh and Park developed a numerical model that computes the reflection of regular waves from a fully perforated-wall caisson breakwater. This paper describes how to apply this model to a partially perforated-wall caisson and irregular waves. To examine the performance of the model, existing experimental data are used for regular waves, while a laboratory experiment is conducted in this study for irregular waves. The numerical model based on a linear wave theory tends to overpredict the reflection coefficient of regular waves as the wave nonlinearity increases, but such an over-prediction is not observed in the case of irregular waves. For both regular and irregular waves, the numerical model slightly over-and under-predicts the reflection coefficients at larger and smaller values, respectively, because the model neglects the evanescent waves near the breakwater. q

This report documents a study performed for the U.S. Army Engineer District, Seattle to identify and evaluate feasible methods for reducing annual maintenance dredging in the outer Federal navigation channel at Grays Harbor, WA, by modification of the north jetty. Main interest was in potential reduction of southward sand bypassing the north jetty and preservation of the jetty should the neighboring beach erode. Considerable information and predictive capability were generated concerning the behavior of the Federal navigation channel and adjacent coastal and inlet shorelines. The study was conducted as a coordinated multi-disciplinary approach involving field measurement, physical modeling of the hydrodynamics and potential sediment pathways, geomorphic analysis and sediment budget formulation, and numerical modeling of waves, circulation and sediment transport, including modeling of shoreline change and bypassing. Numerous alternatives were considered and subjected to a screening p...

This paper compares the output from four methods used to predict the mean overtopping discharge at the root of the South Breakwater of Póvoa de Varzim Harbour ͑Portugal͒: two numerical models AMAZON, based on solving the nonlinear shallow-water equations, and COBRAS-UC, based on the Reynolds averaged Navier-Stokes equations, Pedersen's empirical formula, and the neural network tool NN_Overtopping. Output from the methods is considered alongside data from two-dimensional ͑2D͒ physical model tests.

Publié le 29 avril 2022 sur https://archeorient.hypotheses.org/18350.
Les ruines du brise-lame principal du port forment les façades ouest et sud du port extérieur. Les blocs de couronnement de cet ouvrage culminent aujourd’hui à -2.5 à -3.5 m sous le niveau actuel de la mer. Par ailleurs, les ruines d’une plateforme submergée à l’intérieur du port extérieur sont à -5 m sous le niveau actuel de la mer. Si on relevait ces niveaux de 6 m, le brise-lame culminerait donc à environ +3 m au-dessus du niveau actuel de la mer et la plateforme serait à +1 m. Ces deux niveaux seraient alors corrects pour un brise-lame et pour un quai. La question est donc de savoir comment une subsidence de 6 m a pu se produire dans le port extérieur, avec une subsidence de seulement 1 m dans le port central.
Après avoir acté que la surélévation du niveau de la mer depuis 2000 ans est d’environ 0.50 m, des chercheurs ont commencé par évoquer l’option tectonique selon laquelle une faille nord-sud située à la limite entre le port extérieur et le port central serait le plan de rupture d’un effondrement tectonique du port extérieur, mais cette option est rejetée aujourd’hui par Galili (2021).
Quelles autres explications peut-on avancer ?

Wave overtopping nearshore coastal structures, such as shore-parallel breakwaters, can significantly alter the current circulation and sediment transport patterns around the structures, which in turn affects the formation of tombolos and salients in the nearshore area. This paper describes the implementation of a wave overtopping module into an existing depth-averaged coastal morphological mode: COAST2D and model applications to investigate the effect of wave overtopping on the hydrodynamics and morphodynamics around a group of shore-parallel breakwaters. The hydrodynamic aspects of the model were validated against a series of laboratory conditions. The model was then applied to a study site at Sea Palling, Norfolk, UK, where 9 shore-parallel segmented breakwaters including 4 surface-piercing and 5 low-crested breakwaters are present, for the storm conditions in Nov 2006. The model results were compared with laboratory data and field measurements, showing a good agreement on both hydrodynamics and morphological changes. Further analysis of wave overtopping effect on the nearshore hydrodynamics and morphodynamics reveals that wave overtopping has significant impacts on the nearshore circulation, sediment transport and the resulting morphological changes within such a complex breakwater scheme under the storm and macro-tide conditions. The results indicate the importance of including the wave overtopping in modelling nearshore morphodynamics with the presence of coastal structures.

The weather and environment have changed drastically after the Vizhinjam International deep water Multipurpose Seaport construction began. The fishermen have lost their sense of safety. The direction of the waves has shifted. The journalist has exposed the severe problems faced by the sea and the coast.

This study proposes a new technique to separate incident and reflected higher harmonic waves using four or more spatially separated probes. Both the free and locked modes in the higher harmonics of the regular waves can be isolated. The complex waves are decomposed into individual frequency components using the Fourier transform. The least squares method is applied to minimize the error caused by possible signal noise and to obtain the equations for solving the unknown parameters related to the wave amplitudes. Probe spacing condition for preventing singularity in the calculation is provided. The accuracy of this method is verified by applying it to resolve artificial waves with arbitrarily selected amplitudes. The sensitivity of this method to the noise inevitably associated with the experiments is also tested. The free surface elevation data collected from probes located upstream and downstream of a submerged breakwater in a numerical wave tank are analyzed to demonstrate the applicability of this method. The results are compared with those obtained using the methods of Goda and Suzuki Estimation of incident and reflected waves in random wave experiments. Proc. 15th Costal Eng. Conf., ASCE, pp. 828 -845] and Mansard and Funke [Mansard, E.P.D., Funke, E.R., 1980. The measurement of incident and reflected spectra using a least squares method. Proc. 17th Costal Eng. Conf., ASCE,. The comparison indicated that this method gives exactly the same first harmonic incident and reflected wave amplitudes as the other two methods. The full modes in the higher harmonics can be determined using this method, while the higher harmonics are presumed to be free waves in the other two methods.

Numerical and physical modeling studies were performed by the Coastal Inlets Research Program (CIRP) of the U.S. Army Corps of Engineers to investigate the spatial and temporal behavior of waves and wave-induced currents near jetties of an idealized coastal inlet. Hydrodynamics were examined in the vicinity of two extreme types of jetty structure: a highly absorbing jetty (resembling fairly porous rock rubble structure) and a fully reflective jetty (resembling a vertical sheet pile or caisson type breakwater). Laboratory experiments in a Froude scale of 1:50 were conducted with regular and irregular shore-normal (0 • ) and obliquely incident (20 • ) unidirectional waves. Current and wave measurements were made on the up-wave side and inside the inlet as well as in the bay, along a number of cross-shore and along-shore transects. Wave directions were measured by a remote-sensing video-camera system and Acoustic Doppler Velocimeters (ADV). Numerical modeling was performed with the Coastal Modeling System (CMS) consisting of a two-dimensional circulation model coupled to a spectral wave model. Calculated current and wave fields from CMS in the area around and between absorbing or reflected jetties were compared to measurements. The highly reflecting jetty created a circulation cell on the up-wave side of the inlet, whereas the absorbing jetty did not.

The Fresnel integrals in the diffraction analyses of Penny and Price [Penny, W.G., Price, A.T., 1944. Diffraction of water waves by breakwaters. Misc. Weapons Development Technical History 26, Artificial Harbors, Sec. 3D; Philos. Trans. R. Soc. London, Ser. A, 244 (1952) 236] are replaced by polynomial approximations for positive arguments in the range of zero to infinity. The approximations over this range of arguments have an error that is less than, or equal to, 0.002. The value of using the approximations is twofold: first, the use of polynomials is computationally efficient; second, the relative simplicity of the polynomial approximations allows for field engineering computations by hand calculators in the determination of the theoretical values of diffraction coefficients and phase relationships. The diffraction coefficient values determined for demonstration purposes are those for diffraction caused by both totally reflective or totally absorbent breakwaters, the latter referred to as a ''cushion'' type by Penny and Price. For either case, the breakwaters can be finite or semi-infinite. Examples are presented. D

Las ondas de infragravedad, conocidas también como ondas largas o de baja frecuencia, dominan el espectro de energía del oleaje en aguas poco profundas y en la zona de lavado, lo que juega un papel importante en el transporte de sedimentos cercano a la costa, así como en la inundación y los procesos erosivos de las playas ante eventos extremos.
Los rompeolas son obras diseñadas para proteger la costa o abrigar un área de agua de la acción del oleaje, generalmente ubicados paralelos a la costa, siendo catalogados por su cota de coronación como emergidos (rebasables o no rebasables) y sumergidos.
En las últimas décadas los rompeolas sumergidos han incrementado su popularidad debido al bajo impacto que desde el punto de vista estético y paisajístico introducen en las playas. Sin embargo, estudios recientes muestran que en la mayoría de los casos donde fueron construidos se reportaron procesos erosivos, demostrando que los mecanismos hidrodinámicos y de transporte de sedimentos son completamente diferentes a los que se generan ante los rompeolas emergidos y que los criterios que actualmente se emplean para predecir la respuesta de la costa ante la construcción de rompeolas emergidos no pueden utilizarse en su diseño.

The unsteady two-dimensional Navier -Stokes equations and Navier -Stokes type model equations for porous flows were solved numerically to simulate the interaction between a solitary wave and a submerged porous breakwater. The free surface boundary conditions and the interfacial boundary conditions between the water and the porous media are in complete form. A piston-type wavemaker, set-up in the computational domain, generated the incident solitary wave. The accuracy of the numerical model was verified by comparing the numerical results with the experimental data. Having verified the accuracy of the numerical model, the effects of several parameters on the interaction of a solitary wave and a submerged breakwater were systematically investigated. These parameters include the incident wave height, the aspect ratio of the breakwater, and the porosity including the impermeable case. The flow fields near the breakwater are discussed in terms of the velocity vectors, the vortex shedding and the trajectories of the fluid particles. The pressure drag acting on the breakwater was also calculated. The numerical results reveal that if the breakwater width is small compared with the effective wave length, the structure permeability has no apparent effect on wave transformation. For wide porous breakwaters, if the structure porosity is small, the increase in the porosity results in the reduction of the transmission coefficient; otherwise the transmission coefficient increases with porosity. D

The hydrodynamic efficiency of a proposed type of breakwaters was studied using numerical and physical models. The breakwater consists of caisson supported on a pile system and thin plates suspended on the piles under the caisson. A Flow-3D software which is based on the finite differences and volumes was used to examine the hydrodynamic efficiency of the suggested breakwater system. The efficiency of the breakwater was presented as a function of wave transmission, reflection and energy dissipation coefficients. Regular waves with different wave heights and periods and constant water depth were investigated. In addition, different characteristics of the caisson structure, the plates and the pile system were tested. It was found that the transmission coefficient (k t) decreases with the relative caisson draft (D 1 /h), the relative plate depths (D 2 /h and D 3 /h), the relative breakwater width (B/h), and the distance between piles (S) and piles diameters (d) and with decreasing the pile gap-diameter ratio (G/d).Also the reflection coefficient(k r) and the energy dissipation coefficient (k L) increases with the relative caisson draft (D 1 /h), the relative plate depths (D 2 /h and D 3 /h), the relative breakwater width (B/h), the distance between piles (S) and the pile diameter (d) and with decrease of the pile gap-diameter ratio (G/d). The study shows that we can get (k t) values less than 0.25 when D 1 /h≥0.5, and also when D 2 /h,D 3 /h≥0.4at D 1 /h=0.1. The reflection coefficient (k r) values were between 15 to 55 % for all studied models. The proposed breakwater dissipates about 10 to 30 % of the incident wave energy. In addition, the study shows that the proposed breakwater model has about 75 % efficiency compared with other suspended floating breakwaters. RÉSUMÉ L'efficacité hydrodynamique d'un type brise-lames a été étudiée à l'aide de modèles numériques et physiques. Le brise-lames se compose d'un caisson appuyé sur le système de apile et plaques minces en suspension sur les pieux sous le caisson. Un logiciel Flow-3D qui s'appuie sur les différences et les volumes finis a été utilisée pour examiner l'efficacité hydrodynamique du système de brise-lames proposé. L'efficacité de la digue a été présentée comme une fonction de transmission d'onde, les coefficients de réflexion et de dissipation d'énergie. Vagues régulières avec différentes hauteurs et périodes vagues et la profondeur de l'eau constante ont été étudiés. En outre, les différentes caractéristiques de la structure de caisson, les plaques et le système de pile sont testés. On a constaté que le coefficient de transmission (kt) diminue avec l' ébauche par rapport à caisson (D1 / h) , la profondeur de la plaque relatifs (D2 / h et D3 / h), la largeur de la digue rapport (B / h) , et la distance entre les piles (S) et des diamètres de pieux (d) et avec la diminution du rapport écart-diamètre pile (G / d). Aussi le coefficient de réflexion (kr) et le coefficient de dissipation d'énergie (kL) augmente avec le projet de caisson rapport (D1 / h) , la profondeur de la plaque par rapport (D2 / h et D3 / h), la largeur de la digue rapport (B / h), la distance entre les piles (S) et le diamètre du pieu (d) et avec diminution du rapport de poil écart de diamètre (G / D). L'étude montre que nous pouvons obtenir (kt) des valeurs inférieures à 0,25 quand D1 / h ≥ 0,5 , et aussi quand D2 / h , D3 / h ≥ 0.4at D1 / h = 0,1. Le coefficient de réflexion (kr) des valeurs comprises entre 15 à 55% pour tous les modèles étudiés. Le brise-lames dissipe environ 10 à 30 % de l'énergie de l'onde incidente. En outre, l'étude montre que le modèle de brise-lames a environ 75 % d'efficacité par rapport aux autres brise-lames flottants suspendus.

The world is heavily dependent on fossil fuels since most of its energy requirements are fulfilled by conventional methods of burning these fuels. The energy demand is increasing by day with growing population. The energy production by fossil fuels is devastating the environment and survival of life on globe is endangered. The renewal energy technologies are vital to ensure future energy sustenance and environmental issues. Ocean is a vast resource of renewable energy. The technology today makes it possible to extract energy from tides. The growing interest in exploring tidal current technologies has compelling reasons such as security and diversity of supply, intermittent but predictable and limited social and environmental impacts. The purpose of this study is to present a comprehensive review of tidal current technologies to harness ocean energy. The ocean energy resources are presented. The author discusses tidal energy technologies. The tidal current turbines are discussed in d...

: This Coastal and Hydraulics Engineering Technical Note (CHETN) provides improved predictive equations for coastal rubble-mound stone-armor stability. The engineering methods outlined apply to breakwaters and revetments exposed to wave loading. The stability equations are based on the concept that the maximum wave force causing armor instability is proportional to the maximum wave momentum flux near the structure toe. This concept introduces a more physics-based first principles approach to estimation of armor stability. The new equations explicitly include the effects of nearshore wave height, wave period, water depth, and storm duration as well as the characteristics of wave breaking on the structure.

Abstract: The renewal energy technologies are increasingly popular to ensure future energy sustenance and address environmental issues. The tides are enormous and consistent untapped resource of renewable energy. The growing interest in exploring tidal energy has compelling reasons such as security and diversity of supply, intermittent but predictable and limited social and environmental impacts. The tidal energy industry is undergoing an increasing shift towards diffuser augmented turbines. The reason is the higher power ...

The world is heavily dependent on fossil fuels since most of its energy requirements are fulfilled by conventional methods of burning these fuels. The energy demand is increasing by day with growing population. The energy production by fossil fuels is devastating the environment and survival of life on globe is endangered. The renewal energy technologies are vital to ensure future energy sustenance and environmental issues. Ocean is a vast resource of renewable energy. The technology today makes it possible to extract energy from tides. The growing interest in exploring tidal current technologies has compelling reasons such as security and diversity of supply, intermittent but predictable and limited social and environmental impacts. The purpose of this study is to present a comprehensive review of tidal current technologies to harness ocean energy. The ocean energy resources are presented. The author discusses tidal energy technologies. The tidal current turbines are discussed in detail. The author reviews today's popular tidal current technologies. The present status of ocean energy development is also reported.

Climate change is considered one of the hottest global environmental problems
facing the world community. The sea level rising (SLR) is a associated phenomena to
this climate change. This phenomenon has directly affected on many sectors such as
water  resources, coastal  zones, agriculture, rangeland  and  livestock,  human  health,
human  settlements,  energy,  forest  and  bio-diversity.  Without  serious  adaptation
measures, millions of peoples will be displaced from their homes. In addition to the
loss  of productive  land  will  have  serious  implications  on  job  opportunities,  food
availability and population movement.
In this study, the hydrodynamic efficiency of a porous seawall, may be used in
protecting  coasts  from  probable  SLR,  is  experimentally  studied  using  physical
models.  The  seawall  consists  of  front  steel  screen,  back  solid  wall  and  filled with
rock-core. A submerged breakwater with different parameters is installed in front of
the seawall to decrease the wave action on the seawall. The wave run-up, the wave
reflection  and the  wave  transmission  due  to  the  seawall  with  or  without  the
submerged breakwater are investigated.
The main results are: the run-up and reflection coefficients due to the seawall
only decrease with increasing of the relative water depth (h/L), the wave steepness
(Hi
/L), the relative seawall width (b/h) and the seawall porosity (n). The submerged
breakwater decreases the run-up on the seawall and the wave reflection coefficients
by  about  20-60%  and 40-70% respectively. This  means  that  the  proposed  system
significantly  helps  in  reducing  the  wave  run  up  on  the  seawall which  facing the
probable  sea  level  rise. In  addition,  the  submerged  breakwater  is  achieving  low
transmission coefficients with increasing of the relative breakwater height (D/h) and
the relative breakwater width (B/h).

A comparative assessment of available formulae for the water setup inshore of submerged breakwaters is made on the basis of a wide and varied dataset derived from basin and flume laboratory experiments. Formulae derived from a simplified view which does not account for the horizontal flow circulation provide a large overestimate ͑up to one order of magnitude͒ of the smaller setup values. A much better overall approximation of the measured data is obtained through formulae that consider the setup as part of a complete flow description, be it partially or fully accounting for the horizontal flow motion.