Showing papers on "Breakwater published in 2002"

Design of vertical breakwaters

Abstract: In this book, different types of breakwaters are introduced and their historical development is described in order to understand the advantages and disadvantages associated with each type of breakwater. The failures of breakwaters are then discussed to demonstrate crucial points in their stability design. Finally, the design methods used for vertical are explained including a new design concept of performance design for vertical breakwaters. Since the design methodology for rubble mound breakwaters has been addressed in many textbooks, the design of vertical breakwaters will be concentrated on here.

Experimental Study on the Effect in Reducing Tsunami by the Coastal Permeable Structures

Abstract: In order to understand the tsunami reduction effect of the coastal permeable structures as the coastal forest and the artificial wave dissipating structure, the hydraulic experiment is carried out. The hydraulic experiment for the tsunami of two different amplitudes with five kinds of models; mangrove, coastal forest, wave dissipating block, rock breakwater, houses, with different structure and porosity was carried out in order to measure an effectiveness in reducing tsunami disaster. Wave height, the horizontal velocity, and wave pressure were measured for each model case. The measuring points are arranged by considering the impact of the tsunami due to the existence of permeable structure, and the change of tsunami at the front and rear side of a model, and the reduction effect by model conditions was compared. Comparing with the forest case and the artificial structure case, the quantity of reduction on the forest case is smaller than the artificial structure. Although there is the reduction effect by the forest existence and the coastal forest is effective in the damage mitigation by tsunami. Experimental results suggest that the tsunami reduction effect in the water level, the flow velocity and fluid force in the structure back by the permeable structures was fully expectable.

Simulation of Regional Longshore Sediment Transport and Coastal Evolution - The 'Cascade' Model

Abstract: : A numerical model called Cascade is introduced for simulating regional sediment transport and coastal evolution. Cascade can be applied to stretches of coastline covering hundreds of kilometers where evolution extending to centuries may be of interest. A typical setting encompasses several barrier islands separated by inlets at which sediment is transferred through tidal-shoal complexes. Complex regional trends in shoreline orientation can be represented, as well as sediment sources and sinks, such as beach nourishment, cliff erosion, wind-blown sand, and dredging. Processes are modeled at the local and regional scale, and the interaction between the scales is described in a cascading manner from regional to local. Main components of the model are described, followed by an application to the south shore of Long Island, New York, where the regional sediment transport pattern was simulated, including opening of two inlets and the response of the adjacent shore.

Wave Transmission at Detached Breakwaters for Shoreline Response Modeling

Abstract: : The Coastal and Hydraulics Engineering Technical Note (CHETN) herein evaluates selected available formulas for predicting wave transmission at reef breakwaters and more conventional multilayer structures, leading to recommendations for the most appropriate formulas for shoreline-response modeling. The GENESIS shoreline response numerical model is modified to allow for automated time-dependent calculation of the wave transmission coefficient, and a case study is presented to illustrate the new predictive capability.

Sedimentation Processes at the Navigation Channel of the Damietta Harbour on the Northeastern Nile Delta Coast of Egypt

Abstract: Damietta Harbour is located on the northeastern coast of the Nile delta, Egypt. Two breakwaters were constructed in 1982 to prevent the prevailing NE and SW sediment transport from shoaling the navigation channel, which extends about 20km offshore. However, the harbour channel has experienced continued sedimentation, which has affected navigation. As a result, periodic annual dredging of the channel has being carried out since 1986, averaging of 1.18 x 10 6 m 3 /yr. To provide a basis for evaluating this problem and to provide possible mitigation, an intensive 20-month measurement program was carried out including: intensive hydrographic surveying, waves, longshore currents, littoral drift, currents seaward of the breaker zone, offshore currents and water level variation. Results of this study have led to better understanding of the factors controlling the processes of sedimentation of the navigation channel. The sedimentation process is complex and is influenced by the temporal variability in the direction and intensity of the incoming waves, currents, orientation of coastline and seafloor morphology. Sediments are transported to the sink area including the navigation channel from adjacent coastal sources at Burullus and Ras El Bar as well as from the Damietta offshore shoals by several pathways comprising the opposing NE and SW littoral drift, north-northwest and north-northeast offshore currents as well as from onshore sediment movement. Sediments are dispersed primarily away from sediment sources toward the sink area by both contour-flowing bottom and cross-shelf (seaward-trending currents). The general characteristics and interpretation of depth of closure are applied to evaluate the behavior of the harbour breakwaters versus sediment bypassing and to propose measures to mitigate this problem.

NMLONG: Numerical Model for Simulating Longshore Current. Report 2. Wave-Current Interaction, Roller Modeling, and Validation of Model Enhancements

Abstract: : The Numerical Model of the longshore current (NMLong) was orginally developed under the U.S. Army Corps of Engineers Dredging Research Program. It calculates nearshore wave transformation. water level change. and wave-induced longshore current across a single beach profile. under the assumption of longshore uniformity in both the profile and hydrodynamic processes. In considering the nearshore more generally. and the waves at an inlet entrance in particular. both tidal and wind-generated currents can be comparable to or exceed the strength of the wave-generated longshore current. Also. currents produced independently by waves and by wind and tide may be in opposite directions. producing complex distributions of the current across the shore. The capability of representing the action of currents in NMLong and the interaction between the current and waves resulted in a new model with the modified name NMLong-CW. where CW stands for the interaction between currents and waves. The new model includes an algorithm to simulate the contribution of wave rollers generated by breaking waves. improving agreement of calculations to measurements of the longshore current on a beach profile with a longshore bar. This report documents the theoretical developments associated with the enhancement of NMLong that have extended it to NMLong-CW. The new model is validated by sensitivity tests and through comparison of calculations to both field and laboratory measurements of waves and currents. Wave transformation at a long. narrow inlet. resulting in changes in wave steepness as well as wave blocking. is described.

Field and numerical comparisons of the RIBS floating breakwater

Abstract: A new concept in floating breakwaters was successfully field-tested offshore Cape Canaveral, FL in May 1999. The Rapidly Installed Breakwater System (RIBS) has a hybrid design of rigid and membrane components, similar to a ‘Venetian blind’, to permit rapid and expedient deployment. The objective of the RIBS is to reduce Sea State 3 (SS3) wave conditions to Sea State 2 for safe vessel operations. This field study was probably one of the most heavily instrumented floating breakwaters ever deployed. Measured wave transmission coefficients and dynamic wave pressures are compared to two different numerical models. This is the first verification of the numerical model WAMIT with field data.

Environmental impacts of El Arish power plant on the Mediterranean coast of Sinai, Egypt

Abstract: A monitoring program was undertaken to evaluate the adverse impacts of the El Arish power plant on the northeastern Sinai coast of Egypt. This program spanned 28 months and includes intensive hydrographic surveying, measurements of waves, longshore current, littoral drift, currents behind the breaker zone, offshore currents, sea-level variation and water quality. The shoreline dynamics of the region have been substantially disrupted due to the high-intensity longshore transport and the interruption of longshore transport by the shore-perpendicular intake breakwaters. Maximum erosion of 5.5 m/year has been documented east of the breakwater. This erosion has been continuing eastwards, threatening the resort centers on the downcoast beaches. On the other hand, accretion (11.7 m/year) is recorded along the western side of the breakwater, accumulating great volumes of sand which is transported to the east by littoral currents. Part of this sand enters the intake basin, causing sedimentation problems by the easterly and westerly littoral drifts and cross-shore currents. In other respect, an unprotected offshore channel dredged in front of the water discharger, east of the intake, acts as an effective trap for the predominantly easterly sand drift, subsequently interrupting sediments moving from the east, accelerating processes of erosion to the east. The cooling and wastewater discharging from the discharger to the sea are insignificantly warmer than the upcoast water and not contaminated with chemical wastes. The thermal and chemical plume has no significant effect on the quality of the coastal water in the region.

The use of shoreline change mapping in coastal engineering project assessment

Abstract: An important tool in assessment of coastal engineering problems is the understanding of shoreline evolution. The U.S. Army Corps of Engineers is responsible for the safe navigation at inlets and coastal harbor entrances and providing shore protection projects to protect the coastal infrastructure from damage due to coastal storms, Shoreline change studies have been a useful tool in evaluating the success of these projects. On a national scale, several shoreline change studies have been done by the Corps to evaluate the erosion potential and identify areas of critical erosion on a national or regional scale. In 1971, the Corps published the National Shoreline Study to compile an analysis of the Nations shorelines and develop shore protection management guidelines. Areas of critical erosion were identified for future shore protection needs. In the 1980's, a joint NOAA-CERC cooperative shoreline movement study provided a series of long-term shoreline change maps of four coastal regions and analysis of selected shoreline change rates and patterns. A new National Shoreline Management Study is being initiated to pursue an interagency effort to update the study of coastal erosion and to improve future coastal sediment management issues. Information from the study will be used to develop recommendations regarding Federal and non-Federal participation in shore protection and use of a systems approach to sand management on a national scale. On a more local scale, shoreline change mapping has been applied to many coastal engineering projects to improve design and management of resources. Three selected projects are used to show tools and techniques from recent studies to evaluate shoreline trends on the project scale in both navigation and shore protection applications. The use of a Geographic Information System (GIS) has facilitated integration of various shoreline formats into a usable product. A complex evolution of a new inlet formation was evaluated using aerial photography derived shorelines to assess adjacent barrier island movements and resulting impacts to navigation channel management. Hot and Cold spots of erosion and accretion were identified and measured by shoreline change analysis along a beach nourishment project to improve renourishment design. A shoreline change analysis of an experimental nearshore prefabricated breakwater indicated a complex interaction of natural nearshore hardbottom and sand wave movement controlled shoreline change more than the breakwater. Shoreline change analysis has been carried out on the national and project specific scale. Each study has improved understanding of how shoreline evolution has changed with both natural and engineering practices and its relationship to coastal engineering problems.

Analysis of Hydro-elastic Response of Pontoon-type VLFS Coupled With Floating Breakwaters Using a Higher-Order Boundary Element Method

Abstract: Ocean space utilization using VLFS(Very Large Floating Structures) can provide environmental impact free space by allowing sea water to flow freely below the floating structure. Use of Pontoon type VLFS for that purpose necessitates the construction of breakwaters for reduction of wave effects. Therefore, in order to maximize advantage of environmental impact free structure, the breakwater should allow water to flow through it. In this paper hydro-elastic response of a pontoon type structure is analyzed considering breakwaters which allow water flow through its opening at bottom of the structure. Mode superposition technique is used for solving equation of flexible body while interactions between the pontoon and breakwaters is considered based on the generalized mode concept. Bi-quadratic, nine-node, higher-order boundary element method is adopted for a more accurate numerical treatment near sharp edged body shape. The effects of various combinations of breakwaters are investigated.

Effects of Mean Wave Drift Force on Mooring Tension and Performance of a Moored Floating Breakwater

Abstract: This paper is a numerical investigation of incident wave interactions with a moored, pontoon-type floating breakwater We employ a boundary element method to solve the diffraction and radiation boundary value problems describing the situation of a moored floating breakwater in waves The numerical model includes the hydrodynamic and mooring analyses, verified by the previous numerical and experimental results Using the numerical model, we are able to assess the hydrodynamic performance of a moored single and dual pontoon floating breakwaters in regular waves In particular, the effects of the mean wave drift force on the mooring system and wave attenuation characteristics are examined The numerical results show that mooring tensions are significantly influenced by the mean wave drift force However, the effect of the drift force on the performance of the floating breakwater in regular waves is not as significant

Stability of armour units on rubble mound breakwater under multi-directional waves

Abstract: An extensive 3D model test program has been performed to study the effects of wave obliquity and multidirectionality on the stability of armour units on rubble mound breakwater. Four types of armour units — dolosse, Accropode, hollow-square and quarry stones were tested under five angles of wave attack (0°, 15°, 30°, 45° and 60°) for both long-crested waves and directional waves. Two wave steepnesses (sop = 0.05 and 0.03) and three directional spreading (s = 10, 40 and ∞) were chosen for the test. A method is proposed to take into account the effects of wave obliquity and multidirectionality on the armour unit stability.

Analytical Model for Response of Seabed beneath Composite Breakwater to Wave

Abstract: The response of a breakwater and the underlying seabed in the presence of waves has been recognized as an important design problem in the field of harbor and coastal engineering. In this research, an analytical model is proposed for the response of a composite-type breakwater and seabed to sinusoidal standing waves. In the proposed analytical model, the problem of the response is decomposed into the wave mode, called a scattering problem, and the caisson motion mode, called a radiation problem. The analytical model is characterized by solving each decomposed problem using a complex Fourier series technique. It is verified, first, by comparison with an analytical solution of the simpler problem of a caisson on a seabed, and secondly, by comparing it with a finite-element solution for the response of a composite-type breakwater (caisson on a rubble mound base). In both cases, the comparisons are in good agreement for pore-water pressure. The proposed analytical model is superior to a numerical model in requ...

Periodic Inspection of Nawiliwili Harbor Breakwater, Kauai, Hawaii

Abstract: : Selected coastal navigation structures are periodically monitored under the "Periodic Inspections" work unit of the Monitoring Completed Navigation Projects Program. Such monitoring is done to gain an understanding of the long-term structural response of unique structures to their environment. Periodic data sets are used to improve knowledge in design, construction, and maintenance of the existing and proposed coastal navigation projects. The Nawiliwili Harbor breakwater, Hawaii, was nominated for periodic monitoring by the U.S. Army Engineer District, Honolulu. The positions of the above-water, concrete armor units (tribars and dolosse) on the breakwater were initially obtained in 1995 through limited ground surveys, aerial photography, and photogrammetric analysis. An inventory of broken armor units on the breakwater also as obtained. The structures were revisited in 2001 to determine changes that had occurred. Results indicated negligible movement of The concrete armor units and minimal armor unit breakage on the breakwater. The site will again be revisited in the future and the long-term structural response of the structure to its environment will continue be tracked. This data set will facilitate engineering decisions concerning whether or not closer surveillance and/or repair of the breakwater might be required to reduce its chance of failing catastrophically. The periodic inspection methods developed and validated for the Nawiliwili Harbor breakwater may also be used to gain insight into other Corps structures.

Water sealing method for controlled revetment

Abstract: PROBLEM TO BE SOLVED: To improve reliability for water sealability by constructing an impervious wall using steel sheet piles and impervious materials at a waste disposal plant against a breakwater of a caisson installed in the sea side when constructing the controlled revetment using the impervious wall. SOLUTION: A caisson 11 is arranged in the same way with the conventional construction method when constructing a controlled revetment 1 and the revetment body 10 is constructed and then a perpendicular impervious wall 15 is constructed so as to penetrate by a specified depth into an impermeable ground layer 3 in the waste disposal plant site to isolate the reclaimed site from the sea side. Two rows of impervious walls 15 made of steel sheet piles are erected with a specified distance and an asphalt mixture or the like is filled between the steel sheet piles. In this way, the strength and reliability at the time when the perpendicular impervious wall is constructed are improved. COPYRIGHT: (C)2004,JPO&NCIPI

Positioning of cubes on a breakwater slope

Abstract: Recent research has shown that it is possible to use concrete cubes as a single armour layer on breakwaters. However, this is only possible in case a placing density of at least 70 % is achieved. In lab-tests it is no problem to place cubes with this density, however it is questionable if such a placing density can be achieved in prototype situations. A number of tests have been carried out in order to determine the requirements for dropping concrete blocks from a crane onto a breakwater slope. The conclusion is that at a waterdepth of approximately 10 times the block size this just can be achieved and that at smaller depth this placing density can be reached without too many difficulties. However, in all cases a good quality toe is vital for a high placing density. Blocks have to be placed at an angle of 45° with respect to the breakwater axis; blocks placed parallel to the breakwater axis will lead to large voids.

Comparison of Hydrodynamic Parameters for a Floating Breakwater

Abstract: The U. S. Army Engineer Research and Development Center is in the process of developing a Rapidly Installed Breakwater System (RIBS) for use in Joint Logistics Over the Shore Operations (JLOTS). The objective of RIBS is to reduce Sea State 3 (SS3) wave conditions to Sea State 2 for safe vessel operations. The first ocean-scale RIBS was deployed off Cape Canaveral, FL, in May 1999. In this paper, we compare wave transmission coefficients and dynamic pressure distributions predicted by two numerical models with the measured values from the XM99 prototype.

Marine self-support equipment for large-sized floating body structure

Abstract: PROBLEM TO BE SOLVED: To provide marine self-support equipment for a large-sized floating body structure capable of being stably moored even in a sea area having the deep depth of water and self-supporting energy such as required power and water. SOLUTION: The large-sized floating structure 10 installed on the sea is installed by being connected with a floating breakwater bank 20 in a breakwater sea area of the floating breakwater bank 20 moored and installed at the bottom of the sea and equipment for self-supporting required power is constituted by mounting power generation equipment using natural energy usable in the breakwater bank 20 and the large-sized floating body structure 10. As a result, a mooring rope for installing the large-sized structure 10 becomes unnecessary, the large-sized floating structure 10 can be installed in a breakwater sea area, the structure 10 can be installed in an offing having the deep depth of water, a vessel is capable of approaching and coming alongside the pier, and power is self-supported by mounting the power generation equipment using natural energy usable on the sea on the floating breakwater bank and the large-sized floating structure.

Breakwater structure and construction method thereof

Abstract: PROBLEM TO BE SOLVED: To provide a breakwater structure for a revetment such as a breakwater and a quay wall formed into the shape having a high non-overflow wave characteristic and facilitated in construction and stabilized after the construction thereof. SOLUTION: This breakwater structure has a breakwater shape having a part projecting toward the offshore in an upper part of an offshore side wall in order to hit back the wave coming from the offshore. This breakwater structure is constructed by fastening several blocks 8 (a lower stage block 13, a middle stage block 14 and an upper stage block 15) arranged in any one direction of the direction along the shore and the vertical direction at a position in rear of the offshore side wall.

Periodic Inspections of Kahului and Laupahoehoe Breakwaters, Hawaii

Abstract: : Selected coastal navigation structures are periodically monitored under the "Periodic Inspections" Work Unit of the monitoring Completed Navigation Projects Program. Such monitoring is done to gain an understanding of the long-term structural response of unique structures to their environment. Periodic data sets are used to improve knowledge in design, construction, and maintenance of both existing and propose coastal navigation projects. The Kahului Harbor breakwaters and the Laupahoehoe boat-launching facility breakwater, HI, were nominated for periodic monitoring by the U.S. Army Engineer District, Honolulu. The positions of the above-water, concrete armor units (tetrapods, tribars, and/or dolosse photogrammetric analysis. The structures were revisited in 2001 to determine changes that had occurred. Results indicated that some armor units had moved along the seaward quadrant of the head of the Kahului east breakwater. These units were intact, however, and are still functional. Armor unit movements on the Kahului west breakwater and the Laupahoehoe breakwater were minimal. A detailed inventory of broken armor units on these structures was obtained. The sites will be revisited in the future and the long-term structural response of the structures to their environment will continued to be tracked. These data sets will facilitate engineering decisions concerning whether or not closed surveillance and/or repair of the breakwaters might be required to reduce their chances of failing catastrophically. The periodic inspection methods developed and validated for the Hawaii breakwaters may also be used to gain insight into other Corps structures.

Berm Breakwaters—Design, Construction and Monitoring

Abstract: The philosophy of the fieldwork of Berm breakwaters was applied in Iceland. A few case histories were described with emphasis on quarry investigations, design, construction and monitoring. The aim of the design of a berm breakwater was to construct a berm with high wave energy absorption, to minimize wave reflection from the trunk and especially from the breakwater head for navigational reasons and to minimize wave overtopping during its live time.

Inner-Bank Erosion Processes and Solutions at Coastal Inlets

Abstract: : This Coastal and Hydraulics Engineering Technical Note (CHETN) provides information on erosion which occurs on the banks (or shoulders) of tidal inlets stabilized with jetties. The causes for initiation of this erosion area are discussed, and potential solutions for reducing/preventing the erosion are presented.

Estimating Surface Currents Using Dyes and Drogues

Abstract: : The Coastal and Hydraulics Engineering Technical Note (CHETN) described herein provides information about simple, inexpensive field techniques for quantifying current patterns in the vicinity of coastal structures such as breakwaters, jetties, and groins. Although these techniques cannot produce a complete picture of the flow regime, they do provide reliable information that can be included with other analyses to understand and solve coastal engineering problems. The techniques are illustrated by application to Aguadilla Harbor, Puerto Rico.