Showing papers on "Breakwater published in 2014"

Assessment of the effectiveness of general breakwaters in reducing tsunami inundation in ishinomaki

Abstract: The 2011 Great East Japan Earthquake and Tsunami caused devastation all along the coast of eastern Japan. Ishinomaki City was one of the most severely damaged municipalities, though the height of t...

Area Coastal Protection and the Use of Bamboo Breakwaters in the Mekong Delta

Abstract: The dynamic coastline of Soc Trang Province in the Mekong Delta of Vietnam is in most parts protected from erosion, storms, and flooding by a narrow belt of mangroves However, development and the unsustainable use of natural resources in the coastal zone are threatening the protection function of this forest belt and reducing income for local communities In some places, erosion has destroyed the mangrove forest and is endangering coastal dikes and thus people and infrastructure behind the dike The impacts of climate change further increase these threats to coastal protection and local livelihoods Because of the uncertainties related to the impacts of climate change, a viable coastal protection strategy must include a diverse and site-specific range of approaches to ensure that adaptation conflicts and maladaptations can be avoided In places along the coast of Soc Trang Province, where the coastal floodplains have been eroded and where mangrove forests have been destroyed by erosion, an area coastal protection strategy has been piloted, which uses floodplain management as a sustainable and effective method of coastal erosion and flood protection The design and construction of structural protection measures must be based on numerical modeling which simulates hydrodynamics and shoreline development, as well as physical modeling, to ensure effectiveness and avoid as much as possible negative effects such as downdrift erosion Bamboo T-fences, which were used to close eroded gaps between remaining headlands with mangrove vegetation, have been shown to be successful at restoring eroded coastal floodplains because they significantly reduce wave energy (erosion) and increase sedimentation, which is a precondition for mangrove rehabilitation in erosion sites In places where floodplains provide sites suitable for mangroves to migrate seaward, the subsequent surface elevation could even keep pace with sea level rise to some extent Such a strategy, which combines ecological, hydrological, and morphodynamic elements, also makes a contribution to local livelihoods through cobenefits from an ecosystem-based approach A cost-benefit analysis showed that the wealth benefits are five times higher for the mangrove and earth dike approach than using a dike upgrade as the only element of coastal protection

A floating box-type breakwater with slotted barriers

Abstract: Floating box-type breakwaters are frequently used for small harbours and marinas. This paper reports a comparative experimental study of the performance of a rectangular floating breakwater with and without slotted barriers. Experimental results showed that the slotted barriers attached to the bottom of a floating box-type breakwater could improve the transmission performance without increasing both the heave and surge motion responses. It was also found that the slotted barriers could reduce the pitch motion responses for shorter waves and increase the pitch motion responses for longer waves.

Coastal Erosion Case at Candeias Beach (NE-Brazil)

Abstract: Gomes, G. and Silva, A.C., 2014. Coastal erosion case at Candeias Beach (NE-Brazil). In: Silva, R., and Strusinska-Correia, A. (eds.). The present work is a study of changes in longshore sediment circulation due to the presence of a breakwater which interferes with the beach morphology. The study was done using the SMC software (Sistema de Modelado Costero) as the main tool for simulating the coastal dynamics for the different configurations, as well as for determining the wave climate to be applied at the simulations. The beach environment is a complex dynamic system responsive to the impact of waves and currents through a series of changes that can occur at different time scales and the intervention of human constructions. The focus of the present work is the application of SMC to investigate beach erosion in an area of Candeias Beach, in the metropolitan region of Recife (NE-Brazil), after installation and further modification of a hard coastal structure (breakwater), as well as in a scenario ...

Simulation of Flow within Armour Blocks in a Breakwater

Abstract: Dentale, F.; Donnarumma, G., and Pugliese Carratelli, E., 2014. Simulation of flow within armour blocks in a breakwater. This paper provides some results of a new procedure to analyze the hydrodynamic aspects of the interactions between maritime emerged breakwaters and waves by integrating computer-aided design and computational fluid dynamicsCFD. The structure is modeled in the numerical domain by overlapping individual three-dimensional elements (Xbloc®), very much like the real world or physical laboratory testing. A computational grid is fitted fine enough to provide enough computational nodes within the flow paths. Flow of the fluid within the interstices among concrete blocks is evaluated by integrating the Reynolds averaged Navier–Stokes equations inside the voids instead of using the “porous media” approach. The aim is to investigate the reliability of this approach as a design tool. Therefore, for the results' validation, the numerical run-up and reflection effects on virtual breakwater ...

Analysis of wave performance through pile–rock breakwaters:

Abstract: This study gives an analytical solution of wave interaction with a new-type pile–rock breakwater in the context of linear potential theory. The pile–rock breakwater consists of two rows of closely spaced piles and a rock core between them. The matched eigenfunction expansion method is used to obtain the analytical solution. The analytical solution is confirmed by other solutions for several limiting cases of the present structure. The solution is also validated by a multi-domain boundary element method solution. The reflection coefficient, the transmission coefficient and the energy loss coefficient of the pile–rock breakwater are examined. Their significance for practical engineering is discussed.

Risk assessment of coastal erosion of Karasu coast in Black Sea

Abstract: Coastal erosion occurs as a result of human ac tivity and natural phenomena. Coastal erosion causes significant economic and ecological problem. There is continuing serious coastal erosion along the Karasu coastline. This study reports on the process of determining the extent of the coastal erosion using satellite images from different time periods and the analysis of the risk to the environment. The change in the coastline over a 26-year period from 1987 to 2013 was determined using satellite images. In this study, significant coastline movements were detected for a 26-year period. For this study, the Karasu coastline was subdivided into 7 sections for analyses the coastal erosion risk. The risk of each section can be determined by using the classic risk. The results showed that both sides of the river outfall and the coastline have a moderate risk level with the area of the breakwater has a low risk.

Temporal analysis of coastal erosion in Turkey: a case study Karasu coastal region

Abstract: Coastal erosion may be caused by natural causes as well as human factors. Karasu town of the city of Sakarya in Turkey which is a touristic region on the Black Sea coast has been experienced a drastic coastal erosion. In recent years, this erosion reached the threatening dimensions for the structures in the settlement. According to the temporal analyses of Landsat satellite images, the maximum erosion on the coastline was detected 100 m between 1987–2013. The results of the study show that the harbour construct on the Karasu coast has the major impact on this event. The secondary factor is that the amount of the sediment carried by the Sakarya River was decreased in time due to different reasons. To prevent the coastal erosion, a series of offshore breakwaters were planned after the failed application of groins on the coastline. In this study, temporal changes of the coastline are investigated by the Landsat satellite data and land surveys, possible reasons of the erosion are discussed and the solutions are proposed regarding the coastal structures.

Effects of Submerged Breakwater on Hydrodynamics and Shoreline Change of the East Beach of Beidaihe, Bohai Bay, China

Abstract: Kuang, C.; He, L.; Gu, J.; Pan, Y.; Zhang, Y.; Yang, Y.; Qiu, R., and Zhang, J., 2014. Effects of submerged breakwater on hydrodynamics and shoreline change of the East Beach of Beidaihe, Bohai Bay, China. The beaches in Beidaihe of Bohai Bay of China have been eroded since 1950s, clearly evidenced by sand coarsening, rock outcropping, and slope steepening. Beach nourishment is a common coastal management strategy used to protect beaches from erosion along sandy coastlines, and it has already been applied to recover several beaches of Beidaihe since 2008. In this paper, the effects of a submerged breakwater used as part of a beach nourishment project on hydrodynamics and shoreline changes of the East Beach of Beidaihe are presented. First, the brief descriptions of phase I and phase II of the beach nourishment project of East Beach are given. And then numerical models, including tidal current model, wave model, and one-line model for simulating hydrodynamics (tidal currents and waves) and shoreli...

Management Of Shoreline Morphological Changes Consequent To Breakwater Construction

Abstract: The coastal stretch from Veli to Varkala along Thiruvananthapuram coast, which was in dynamic equilibrium, has two identifiable sediment cells separated by the Muthalapozhi inlet with harbour breakwaters on either side of the inlet. Construction of breakwaters to develop a fishing harbour at Muthalapozhi has caused erosion immediately north of the inlet and beach build up south of the inlet. In addition, the harbour mouth gets blocked due to deposition of sand, virtually making the harbour unusable. In the present study, the processes of shoreline morphological changes along the high energy coast are analyzed using numerical models to propose management options to tackle morphological modifications. Shoreline changes, nearshore processes and beach characteristics along this sector are studied through extensive field observations. The data is used to calibrate and validate sediment transport and shoreline change models for this coast. Sediment transport and shoreline changes are simulated using different modules of LITPACK model. The LITDRIFT module is used to calculate annual sediment transport. The LITLINE module is used for shoreline evolution during fair season and the behaviour of coast during monsoon is simulated using the module LITPROF. The calibration of the model is done with field observations. It is found that beach sediments get deposited on southern side of the breakwater and bypassed sediment gets deposited at the inlet mouth. The model after validation is used to simulate the processes with different designs and a groin field of smaller transitional lengths comparable with the surf zone width. The groins having lengths 40, 30 and 20 m at 120, 220 and 300 m south of breakwater, has been found best suited to control the chocking of harbour mouth due to sediment deposition during beach building period.

Using Field Data to Improve the Settlement Prediction Model of a Breakwater on Soft Soil

Abstract: The need for an improved harbor access resulted in the construction of two new rubble mound breakwaters in Ostend, Belgium. In the past, a specific dredging technique was used to maintain the required depth of the access channel to the harbor. This has resulted in a complex soil layering underneath the northern part of the new western breakwater with locally very thick soft soil layers. As an alternative for an expensive soil remediation, a very strong geotextile was included into the breakwater core, reinforcing the structure. In addition a staged construction was necessary, allowing the soft layers to consolidate and preventing undrained failure during construction. Because of the complexity of the situation, a numerical model was used to get an estimate of the settlements and the consolidation process during and after construction of the breakwater. Extensive field measurements of the settlements were performed during construction and are still performed at this moment (early 2013). Comparison ...

Overtopping on rubble mound breakwaters for low steepness waves in deep and depth limited conditions

Abstract: In this paper, the investigation of overtopping on rubble mound breakwaters for low steepness waves in both deep and shallow-water conditions are presented. The existing formulae provide quite different results for long waves for both conventional and berm breakwaters. Therefore, new model tests with focus on long waves have been performed for both types of breakwaters. The new model tests showed some deviation from the formulae. Therefore, limitations in the use of the present methods and an update for one of the methods are presented.

The Effect of Porosity of Submerged and Emerged Breakwater on Wave Transmission

Abstract: Porous breakwaters offer an alternative to conventional solid breakwater to create a tranquil water basin for the berthing of vessels by dissipate the energy of incoming waves. The efficiency of the porous breakwaters is governed by their porosity and their depth of submergence. In this study, experimental investigation has been carried out in a two-dimensional wave flume to investigate the effect of porosity on submerged and emerged porous breakwaters under various wave conditions. At 50 cm still water depth, interactions between regular waves (wave period, T= 1.5 sec, 1.6 sec, 1.8 sec and 2.0 sec) and the fixed vertical porous breakwater of three different porosity (n= 0.45, 0.51 and 0.7) having three different structure heights (hb= 40 cm, 50 cm and 60 cm) have been studied experimentally. Experimental results reveal that, minimum transmission co-efficient (Kt = 0.261) is obtained for breakwater with lowest porosity (n= 0.45) and with emerged condition (when hb/h= 1.2) for short wave, i.e. when T = 1.5 sec. Minimum reflection co-efficient (Kr = 0.089) is obtained for breakwater with highest porosity (n=0.7) and with minimum submerged (hb/h=0.8) condition. It is noticed that porosity has effect on the wave energy loss co-efficient also.

Geometrical design of berm breakwaters

Abstract: Cooperation between the authors has led to a number of papers on main design parameters for berm breakwaters. These were the recession at the berm of a berm breakwater for assumed design conditions and main armour rock class, as well as the functional behaviour (wave overtopping and reflection), where often allowable overtopping rates determine the crest height of the structure. They also gave guidance on how some geometrical aspects may influence the recession. For example a flatter down slope, a higher berm level and a higher toe level all decrease the expected recession. Expected recession and expected wave overtopping (or requested crest height) are only two parameters that influence the design of the cross-section of a berm breakwater. In order to design a complete cross-section many more design decisions have to be taken into account. In the past clear design rules on determining a full cross-section of a berm breakwater were lacking and design was based on the experience with earlier designs (in Iceland and Norway)or simply on good reasoning and then testing the structure in a hydraulic laboratory. This paper gives guidance on all relevant geometrical design parameters.

Nuclear power plant breakwater overtopping impact simulation method based on mixed model

Abstract: The invention discloses a nuclear power plant breakwater overtopping impact simulation method based on a mixed model. The method includes the following steps that at first, a three-dimensional entity finite element model of a fine structure of a breakwater is established; secondly, a breakwater structure rigid body model and a neighboring environment entity model are established; thirdly, initial stress is added to the established three-dimensional mixing finite element model of the nuclear power plant breakwater to simulate the initial operating condition to obtain the initial state of the nuclear power plant breakwater under the action of gravity and seawater pressure; finally, after distribution of initial stress of the nuclear power plant breakwater is obtained, the impact state and the overtopping state of the nuclear power plant breakwater under the action of waves are obtained, and integral simulation of the breakwater is achieved. According to the method, simulation analysis of numerical simulation of the super-large-scale nuclear power plant breakwater is achieved, response rules of an overall model can be contained, meanwhile local structures can be finely analyzed, local dangerous positions are obtained, and reference bases are provided for engineering design of the nuclear power plant breakwater.

Shoreline Change due to Construction of the Artificial Headland with Submerged Breakwaters

Abstract: Kim, I.H.; Lee, H.S.; Kim, J.H.; Yoon, J.S., and Hur, D.S., 2014. Shoreline change due to construction of the artificial headland with submerged breakwaters. The littoral drift cell of Bongpyeong Beach in Gyeongsangbuk-do ranges from Jukbyeon harbor to Goljang harbor. The beach erosion has largely occurred due to the expansion construction of Jukbyeon harbor. Headlands were installed as a countermeasure, however, the effectiveness of headland was not good as expected because of complicated coastal hydraulic phenomena. Furthermore, the headlands spoil the coastal landscape. Therefore, in this study, the field investigation of the shoreline and beach profile was conducted to analyze the characteristics around Bongpyeong Beach from 2013 through 2014. The causes of the beach erosion were identified by physical oceanographic investigation and numerical analysis. As a result, the complicated flow characteristics due to the construction of headlands and submerged breakwaters appear. The results also sho...

Adaptation of coastal structures to mean sea level rise

Abstract: With the mean sea level (MSL) rise, coastal defence structures will be exposed to wave height, which are larger than the design values, in particular for all the structures built in shallow waters where the depth imposes the maximal wave height due to bathymetric breaking. If MSL rise is one meter, the crest of these structures will have to be raised between two and three meters in order to keep the same overtopping volumes. Moreover the structures will have more severe damages and mass of armour units should be doubled. Statistics moderate the first conclusions because it keeps into account the whole set of events, including in particular shoaling waves. Schematically with the increase of damages, according to the severity of changes the stakeholders will adopt one of the following scenarios: a) repairing the structures as it is b) reinforcing the structures c) demolishing and redesigning the structures d) accepting coastal realignment. Three axes of reinforcement of structures are presented: limiting overtopping by modifying for example the crown wall, improving armour stability by adding an armour layer or by using milder armour slope and reducing the incident wave energy by building a detached low-crested breakwater or by sand nourishment. A curved parapet wall is a very efficient solution for impervious structures. This solution must often be completed by an additional armour layer for pervious structures. The front reservoir is also a promising solution. Cost benefice analysis (CBA) applied to the city of Le Havre shows that reinforcement becomes economically justified in district of Malraux when MSL rise is 1 m. Redesign and coastal realignment as far as they are concerned are acceptable when MSL rise exceeds 2 m.

Beach Erosion in San Benito Chiapas, Mexico: Assessment and Possible Solution

Abstract: Delgadillo-Calzadilla, M.A.; Mendoza, E.; Silva, R.; Gonzalez-Vazquez, J.A., and Infante-Mata, D., 2014. Beach erosion in San Benito Chiapas, Mexico: Assessment and possible solution. The study area is on the Gulf of Tehuantepec, where a harbour was built at San Benito, near Tapachula, Chiapas, in 1972. Two breakwaters, of 630 m and 800 m, respectively, were constructed to provide protection to the harbour channel. Erosion problems were detected near the harbour even before it was opened to trade. The original design had many flaws as no wave climate analysis had been done and littoral drift had not been taken into account. In 1975, 17 groins were built with the aim of reducing the erosion on the adjacent beach. These were unsuccessful and, in 1980, a rock armour apron was built at the most seriously eroded section in a further attempt to minimize the problem and to protect the population. However, the erosion continues at a rate of around 25 m per year in some sections. Commercial and navigation...