Shore Protection Structures Research Articles

ЭКОЛОГИЧЕСКИЕ ОСНОВЫ ВЫБОРА БЕРЕГОУКРЕПИТЕЛЬНЫХ СООРУЖЕНИЙ ПРИ РЕКОНСТРУКЦИИ ПЛЯЖЕЙ КРЫМСКОГО ПОБЕРЕЖЬЯ

The relevance of improving the methods of engineering and environmental survey of coastal protection objects is determined by their existing violations, which reduce environmental safety in general and create a danger for the organization of tourism on the coast. The purpose of the study is to substantiate the choice of bank protection structures during the reconstruction of the beaches of the Crimean coast in the conditions of recreational specialization of the region. The nature and extent of deformations of the coastal zone of the sea and shore protection structures on the coast of the Kalamitsky Bay of the Black Sea are described. The authors proposed the design and location of the breakwater, which will make it possible to more effectively cope with the damping of waves during a storm period compared to classical breakwaters. Materials and methods. The study of the state of coastal territories and the solution of problems of coastal protection structures is based on the theory of geomorphology of the surface and underwater parts of the coast, the regularities of the hydrophysical parameters of the sea in the coastal zone, and climatic and seismic conditions. The methods of field observations and experimental studies in the wave basin were used to take into account the influence of natural and anthropogenic factors on the ecological parameters of the coastal zone of the Crimean coast. Results. In 2022, a team of authors carried out a visual survey of the coast in the territory of the Bakhchisaray district of the Republic of Crimea with a total length of 11.5 km. from s. Coastal to with. Angular. As a result of the inspection, sections of the coast that are potentially dangerous to the health and life of people and are not suitable for normal use for recreational purposes were identified. Conclusions. Long-term field observations show that the creation of bank protection in certain local areas, having given only a temporary positive effect for these areas, can have a very negative impact on neighboring and even remote areas; that is why the issue of protecting the coast should be resolved at least on the scale of the coast of settlements, taking into account the conditions of a single system. The shape of the coast protection structure proposed by the authors can make it possible to more effectively dampen waves compared to classical rectangular breakwaters. However, when designing coastal protection measures, it should be taken into account that separate protection of small areas of eroded coastal territories within a large zone of eroded coast is ineffective, since adjacent unprotected shores will recede under the influence of a system of natural factors.

A Dual-Function Design of an Oscillating Water Column Integrated with a Slotted Breakwater: A Wave Flume Study

Wave energy conversion holds promise for renewable energy, but challenges like high initial costs hinder commercialization. Integrating wave-energy converters (WECs) into shore-protection structures creates dual-function structures for both electricity generation and coastal protection. Oscillating water columns (OWCs) have been well studied in the past with their simple generation mechanism and their out-of-water power take-off (PTO) system, which can minimize bio-fouling effects and maintenance costs compared to other submerged WECs. In addition, a slotted barrier allows for better circulation behind the breakwater while dissipating incoming wave energy through viscous damping. This study examines the performance of a new design which combines an OWC with a slotted breakwater. Small-scale (1:49) laboratory tests were performed with a piston-type wave generator. The performance is evaluated in terms of wave transmission, wave energy extraction, and wave loading under various wave conditions while focusing on the effects of the porosity of the slotted barrier and tide level changes. Results show that under larger waves, a decreasing wave transmission, increasing power extraction from the OWC, and energy dissipation from the slotted barrier are observed. On the other hand, under increasing wavelengths, wave transmission is observed to be constant; this is important for harbor design, which means that the breakwater is effective under a wider range of wavelengths. Porosity allows for more transmission while inducing less horizontal force on the structure.

Coastal resilience and shoreline dynamics: assessing the impact of a hybrid beach restoration strategy in Puducherry, India

Puducherry, a Union Territory of India, has been strongly affected by severe erosion after the construction of the Puducherry port in 1989. To mitigate this cause, the National Institute of Ocean Technology, Chennai, and the Puducherry government implemented a beach restoration strategy involving a hybrid solution in 2017 for coastal protection/stabilization and the restoration of the lost beach. The strategy involved deploying a steel reef into the nearshore sea and implementing beach nourishment processes. To monitor the coastal morphological changes after implementing the coastal protection strategy, the Digital Shoreline Analysis System, was adopted to calculate the rate of shoreline change statistics for the years 2016 to 2022. It uses spatio-temporal shoreline positions from multi-temporal satellite imagery. The shorelines are extracted from the Sentinel-2A satellite images by a Normalized Differential Water Index based semi-automated model. Statistical parameters in DSAS analyze the shorelines to determine the shoreline changes in this area. The results reveal the remarkable resilience of a newly restored beach, where the linear regression rate statistics in Zone A show an average accretional rate of 2.92m/yr. Alternatively, Zone B exhibits an average erosion rate of -0.23m/yr, with intermittent sandy beaches experiencing maximum erosion rates of -1.63m/yr. The influence of longshore current direction and sediment transport on shoreline movement is evident in seasonal analysis, with shoreline development and recession primarily observed near shore protection structures. The study’s outcome provides valuable insights for coastal management, offering a reliable approach for shoreline monitoring post-implementation of mitigation projects.

A Study on Crenulate - Shaped Bays in Coastline of Sri Lanka

Various research studies have been reported in the literature investigating the crenulate-shaped bays that are frequently seen in coastlines all over the world and these coastal bays are recognized as the most stable naturally forming beaches under oblique wave attacks mostly due to swell dominant seas. Although many crenulated bays exist in Sri Lanka coastline, no considerable attention has been given so far to investigate their characteristics. The authors have studied the temporal and spatial variations of crenulated bays in many parts of the coastline of Sri Lanka using Google Earth images. Based on the detailed analysis carried out to investigate the shape of the bay profiles using empirical formulations, a hyperbolic tangent formula has been identified as the best fit for crenulated bays in the coastline of Sri Lanka. Considering various coastal sectors and monsoon seasons, different relationships have been derived between the coefficients a and b of the hyperbolic tangent formula. A relationship that has been developed co-relating the coefficient a with few coastal parameters is also discussed. Since many parts of the Sri Lanka coastline are subjected to severe erosion despite the construction of a variety of shore protection structures in traditional ways, a new approach is suggested for carrying out such work where the coastal structures will be aligned in predetermined directions depending on the coastal stretch so that stable crenulated bays will be naturally formed in between these structures, stabilizing the entire coastal stretch. This approach will be very useful in managing coastal erosion problem in the future.

Spectral analysis of oscillatory wind wave parameters in fetch-limited deep-water conditions at a small reservoir and their prediction: Case Study of the Hulín Reservoir in the Czech Republic

Abstract The dams and banks of small water reservoirs face significant erosion from wind-generated oscillatory waves. Proper design of structure height is crucial to protect such banks against erosion, considering the maximum characteristics of wind waves. Long-term measurements at the Hulín reservoir revealed that the wave spectrum aligns best with the Bretschneider type. This spectrum serves as a basis for simulating oscillatory waves and their impact on shore protection structure design. Empirical models were evaluated using wind and wave data from Hulín reservoir in the Czech Republic. The measured wind speeds attained a maximum of 8 m/s, and wave heights reached up to 15 cm. The Bretschneider (SMB) empirical formula provided the most accurate estimation of wave height (H m 0), with an average underestimate of RMSE = 0.038 m. On the other hand, Wilson revisited (WIL rev.) performed less effectively, with an average RMSE = 0.304 m. For wave period (T) estimation, Bretschneider (SMB) yielded the best results, with an average RMSE = 0.062 s. Conversely, Wilson revisited (WIL rev.) showed poorer performance, with an average underestimate of RMSE = 2.196 s. The discrepancy between the empirical formulas and measured values, particularly in underestimating H m 0, can be attributed to inaccurate determination of fetch length and wind speed.

Analysis of the stability of the Kuban river landslide slope involving the materials of landslide hazard monitoring

The article discusses the improvement of methods for calculating the landslide threat in the monitoring of landslide hazard areas on the Kuban River and the study of the possibility of their negative impact on the operated hydraulic structures. The growth of economic activity, intensive use of water resources in the Kuban River basin leads to a decrease in the bearing capacity of slopes and an increase in landslide phenomena. These processes are also observed in the basins of other anthropogenically developed rivers of the Russian Federation. Shore protection structures and their construction are justified on the basis of the limit state method in accordance with the requirements of SR 58.13330.2011. The stability of such structures should be determined by reference to the stability conditions of the entire slope taking into account all acting loads and impacts. To solve this problem it is very effective to use a complex of structures regulating the flow of the river, flow guides (dams made of selected rockfill), slope-strengthening ones, etc. Measures justifying economic activity on a landslide slope are very effective. The right slope of the Kuban River in the suburbs of Armavir, Krasnodar Krai is characterized by the fact that significant (more than 3 m) fluctuations in inter-level and flood flow of rare frequency are observed on this section of the river. Realizing anti-landslide and bank strengthening measures it is necessary to provide for both a reduction in general and local erosion of the left bank and the drainage of groundwater and surface from the anthropogenically developed area adjacent to the right slope of the river Kuban. The purpose of this research is to substantiate the stability of the right slope of the Kuban River in the vicinity of the city of Armavir, Krasnodar Krai, where initial collapses are already taking place in connection with the construction of residential buildings in the immediate vicinity of the bank and the development of general and local erosion of the right bank of the river. The calculation is carried out according to several methods for the basic and special load combinations. These calculations are necessary to substantiate landslide and bank protection measures on the right bank of the Kuban River.

Influence of the permeability of submerged breakwaters on surrounding wave and current fields

ABSTRACT While a submerged breakwater has become one of the preferred options of shore protection structures because of its lower impact on the coastal landscape and environment, it causes complicated hydrodynamic characteristics and sometimes fails to meet the expected coastal protection functions. Accurate prediction of wave and current around the structure is therefore essential for appropriate design of a submerged breakwater. This study focused on the influence of the permeability of the submerged breakwater and newly conducted laboratory experiments using permeable and impermeable breakwaters. The model, Simulate WAves till SHore (SWASH), was then applied to these laboratory experiments and the difference of measured and computed wave and current field around the structure was investigated. It was found that the model qualitatively well represented the horizontal distribution of wave heights and phase-averaged current velocities although it overestimated the shoreward volume flux over the impermeable breakwater, but not over the permeable breakwater. Comparison of these contrasting results between permeable and impermeable breakwaters revealed that the phase-averaged bottom shear stress was underestimated on the crest of the impermeable breakwater. This feature highlighted the importance of the bottom friction forces accounting for the wave current coexisting field for better predictions of wave-induced current field around the submerged breakwaters.

Statistical analysis of shoreline change reveals erosion and baseline are increasing off the northern Tamil Nadu Coasts of India

Many tourists have been recently attracted towards the coasts around the world, especially to the large urban centres and economically significant areas. In the last four decades, there is a significant increase in the key coastal developments and tourist's attractions like major ports, minor ports, fishing harbours, desalination plants, shore protection structures, and many more along the southeast coasts of India, in particular, northern Tami Nadu coastal stretches. The shoreline change study of these regions were carried out using the geospatial technologies (satellite remote sensing and geographical information system) to examine potential modifications occurred during the last 32years between March 1990 and May 2022. This study used Landsat satellite images of spatial resolution 30m to track the shoreline changes which was extracted using the Digital Image Processing software and techniques. In addition, the United States Geological Survey (USGS) developed Digital Shoreline Analysis System (DSAS) v5.2 software, an add-on tool to ArcGIS used for the statistical analysis to compute the shoreline rate of change. The linear regression rate (LRR) and end point rate (EPR) statistics were used to identify the eroding, accreting, and stable shoreline between Kattupalli coast and Kalpakkam coast of the northern Tamil Nadu coasts. This shoreline study of 106km was carried out by dividing it into six zones (zone 1 to zone 6), and the DSAS analysis conveys that the shoreline of zone 1 (Kattupalli) and zone 2 (Ennore) shows erosion compared to other four zones. In locations where the coast is vulnerable, national mitigation measures must be implemented.

Shoreline change on a tropical island beach, Seven Mile Beach, Grand Cayman: The influence of beachrock and shore protection structures

Contemporary and near-future shoreline change is widely regarded as an issue on small tropical islands. While it is widely anticipated that sea-level rise will precipitate shoreline recession on tropical islands, studies to date record both accretion and recession at historical timescales. This study of Seven Mile Beach, Grand Cayman presents a case study of historical shoreline change in which the local geomorphic setting is shown to be an important influence on shoreline behaviour. Consistent with its leeside setting, historic shoreline analysis (1958–2019) reveals erosion on the margins and accretion in the central part of the headland-embayment beach where no beachrock is present. The beach comprises five discrete, but interlinked subcells delineated by low headlands of exposed beachrock. These headlands have emerged through shoreline recession post-1971 but once exposed have become loci of persistent erosion, suggesting a positive feedback between beachrock and waves. A Category 5 Hurricane generated waves directly opposed to long-term modes and throughout the beach, long-term patterns of shoreline change were temporarily reversed, however, the historic pattern of shoreline change was restored within 2 years. The contemporary patterns of erosion and cell development suggest a reduction in sediment supply leading to cannibalization of relict beachridges on the margins of the embayment and emergence of formerly buried beachrock. The effects of coastal structures and erosion abatement measures were assessed and recommendations for coastal management, including development setback lines are presented.

Consolidation of loose foundation soil for esplanade project in Kaliningrad

The article presents the practical experience of pre-construction compaction of loose water-saturated clay foundation soils during the construction of Paradnaya Embankment in Kaliningrad. The engineering and geological conditions of the embankment construction site were complicated by the occurrence of a significant thickness (up to 15 m) of highly compressible flowing silts from the surface. The base preparation was carried out by preliminary compaction of loose soils with the ballasting embankment using vertical geodrains. The geotechnical monitoring system at the site was implemented after the construction of the ballasting embankment, in connection with which the designers made a premature conclusion that 90% of the degree of consolidation of soft soils according to the readings of pore pressure sensors was reached only 2 months after the filling of the ballasting embankment. The authors of the article analyzed the calculation methods of the consolidation process used in the design and the results of geotechnical monitoring. A repeated prediction of deformations of the soil mass from its compaction by the ballasting embankment was performed by a numerical method, taking into account the nature of the transfer of the load to the foundation, as well as the presence of shore protection structures of the embankment. A non-standard method was used to assess the total settlement of the ballasting embankment and the degree of consolidation of the foundation in the absence of correct monitoring data, which consists in determining the top elevations of loose soils by drilling control observation wells and comparing them with the results of engineering and geological surveys performed before the start of construction.

Current State of the Northeast Black Sea Coast along the Russian Caucasus

Kosyan, R.D.; Krylenko, M.V., and Krylenko, V.V., 2023. Current state of the northeast Black Sea coast along the Russian Caucasus. Journal of Coastal Research, 39(2), 317–327. Coconut Creek (Florida), ISSN 0749-0208. This paper describes the state of the NE Black Sea coasts in the 21st century. The modern development and economic use of these coasts in the conditions of climate change and anthropogenic load are analyzed. A geomorphological feature of the Black Sea coast of the Caucasus is the predominance of denudation processes over accumulative ones. There is only one large accumulative sandy section—the Anapa Bay-Bar. Abrasion shores with narrow beaches are widespread in the NE part of the Russian Black Sea coast. There is no united longshore sediment flux. Local lithodynamic cells on concave sections of the shore are characteristic. The conditions of these shores are favorable for the use of local coast protection. In the SE section, the dynamics of the shores in natural conditions were determined by the sediment balance. The active abrasive processes were combined with a large volume of beach-forming sediments carried out by rivers. Up to the middle of the 20th century, there was a single longshore sediment flux toward the SE and broad beaches near river mouths. The Imereti Lowland was formed between the mouths of the Mzymta and the Psou rivers. Irrational and excessive technogenic transformation of the shoreline and river basins in 20th century resulted in a progressive lack of sediment supply. Since the beginning of the 21st century, the width of the beaches has been decreasing throughout the entire area, and the stability of the coast has been maintained artificially by shore protection structures. The Russian sector of the Caucasus Black Sea coast is now densely populated and is an important recreational and economic zone. The main problems that had to be solved in the past and will have to be solved in the future are the shortage of beaches and the protection of the coast and objects located on it from wave impacts.

A coupled model for sediment transport dynamics and prediction of seabed morphology with application to 1DH/2DH coastal engineering problems

Coastline retreat poses a threat to nearshore environment and the assessment of erosion phenomena is required to plan the coastal engineering works. The hydro-morphodynamic response of a beach to natural and artificial forcing factors differ considerably, as the nearshore processes are especially complex and depended on a multitude of parameters, including prevailing wave and hydrodynamic conditions, beach topography, sediment characteristics and the presence of coastal protection works. The present study serves the purpose of numerically evaluating nearshore morphological processes and ultimately assessing the capacity of coastal defence structures to control beach erosion. For this reason, a new sediment transport model including unsteady effects and swash zone morphodynamics, was coupled to the highly nonlinear Boussinesq wave model FUNWAVE-TVD, providing integrated predictions of bed level evolution, across various timescales of interest. The compound model was validated thoroughly against laboratory data and other numerical investigations. Overall, a good agreement between experimental and numerical results was achieved for a number of test cases, investigating the effects of different types of shore protection structures. The proposed integrated model can be a valuable tool for engineers and scientists desiring to obtain accurate bed level predictions, over complex mildly and steeply sloping sea bottoms composed of non-cohesive sediment particles.

Calculation of coast-protecting structure from wave influence

A coupled system consisting of a shore protection structure, a soil base and an aquatic environment is considered. The influence of the aquatic environment on the oscillations of the structure was taken into account. The wave processes arising in the system from the action of surfing and breaking waves were investigated. The developed methodology and software package allow the calculation of various structures interacting with a deformable soil environment from the action of static and dynamic loads, taking into account the real properties of their materials, such as elasticity, viscosity and plasticity. The theory of plastic flow was used. Discretization of the computational area was performed by the finite element method. Studies were carried out on the basis of the obtained schemes of plastic zones, diagrams of stresses and oscillations at various points of the structure.

Coastal protection structures influence on diffraction and reflection of waves simulation based on 3D wave hydrodynamics model

The work describes research of wave processes in the presence of shore protection and coastal structures using 3D wave hydrodynamics model. The model presented in the article gives realistic description of the physical wave process near the coastline. The influence of coastal protective structures on the diffraction and reflection of waves is investigated on the basis of 3D wave hydrodynamics model.

Waves in Western Long Island Sound: A Fetch‐Limited Coastal Basin

AbstractThis paper summarizes the statistics of observations of wind and surface gravity waves in Long Island Sound, a large estuarine embayment in southern New England. We examine the relationship between significant wave height and wind speed and direction and show that the significant wave height and dominant period in western Long Island Sound have an asymmetric response to the wind direction. Waves are larger and have longer periods when the wind is from the east than when the same stress is directed from the west. The data are consistent with the predictions of empirical parameterizations of fetch limited wave growth when the wind is from the west. However, for easterly winds, the westward narrowing of the Sound limits wave growth and requires that an effective fetch of approximately 30 km be used in the empirical formulae. An examination of the extreme values in the time series shows that previous estimates based on simulations significantly underestimates the occurrence of large waves with the important consequence that design guidance for shore protection structures may underestimate wave heights during severe storms. We speculate that earlier work has not adequately represented the consequences of fetch asymmetry on wave growth.

Numerical simulation of bottom topography transformation taking into account the coastal shore protection structures

The article presents the results of studies and modeling the dynamics of nonlinear processes of sediment transport and the diagnostics of changes in shallow water relief, taking into account underwater structures that are widely used for coastal protection. The study of these processes was carried out on the basis of 2D model of sediment transport and 3D model of wave hydrodynamics, taking into account the geometry of the bottom topography and the function of elevating the level of the aquatic environment. A discrete model of sediment transport is obtained by approximating the corresponding linearized continuous model. Particular attention is paid to the creation of effective software for conducting hydrodynamic computational experiments. The developed software package allows predicting the dynamics of bottom surface behavior, the appearance of marine braids and ridges, their growth and transformation.

Особенности литодинамики галечных пляжей южного берега Крыма

The results of the study of the peculiarities of lithodynamics of pebble beaches of the South Coast of Crimea based on the long-term monitoring of the state of beaches performed at the Black Sea Hydrophysical Subsatellite Proving Ground of the Marine Hydrophysical Institute of the Russian Academy of Sciences in the settlement of Katsiveli are presented. Long-term changes of the beach of Limensky Bay since 1950 and of beaches of the shore protection structures since 1988 are characterized. The volume of income and outcome of pebbles during the change of wind-wave regimes was estimated by the example of Limensky Bay beach and the artificial beaches of the coast protection structures in the coastline section from Katsiveli to Ponizovka settlement. The most influential factor in the formation of the pebble beaches of the Southern Coast of Crimea is the change in alongshore wind-wave regimes in the “days-months” time scale, which leads to significant fluctuations in sea level near the coast and a corresponding change in the directions of the bottom current velocity components perpendicular to the shoreline. The largest expense and income of beach-forming material (up to 1 m3/day per linear meter of beach) occurs during storms, respectively, with wind-wave regimes of the eastern and western directions. The largest irreversible removal of the mass of beach-forming materials during the change in wind-wave regimes occurs from the eastern and central sections of the bays and artificial beaches of coastal protection structures, and partial restoration of beaches—on their western sections. Natural underwater reefs in the coastal waters of bays and artificial beaches of shore protection structures contribute to the preservation of beaches in them. The reason for the gradual average long-term degradation of beaches may be the predominance of eastern storm winds over western ones in conditions of blocking the natural income of beach-forming materials from the coast by the coastal infrastructure objects.

Operational Experience of Gabion Shore Protection Structures on Mountain Rivers and Some Suggestions for their Improvement

The paper presents the accumulated experience in the construction and operation of gabions. The results of field surveys of gabions, their advantages and disadvantages, which must be taken into account in environmental practice, are presented. Innovative developments of sloping fasteners made of semi-cylindrical gabions and their construction technologies are presented. Variants of flexible retaining walls of semi-cylindrical gabions are proposed, with lower specific pressures on the soil of the base and enhanced bearing capacity on the action of bending moments. Experimental studies of prismatic and cylindrical gabion models have been carried out for a comparative assessment of their work.

СПОСІБ ЗВЕДЕННЯ БЕРЕГОЗАХИСНИХ СПОРУД З ГАБІОНІВ

Abstract. The shores of seas, lakes, bays and reservoirs under the action of wind waves, drifting level ice, rainwater, wind erosion and other factors are subject to intensive destruction. As a result of this, the areas of valuable agricultural land and other lands are reduced. The destruction of the coasts is accompanied by landslides, which reduce the area of settlements where residential buildings, urban buildings, industrial enterprises, park areas, roads and other communications are located. In such cases there is a need for the construction of special protection structures, which will protect coasts from destruction. There are two methods of coastal protection ‒ active and passive. Experience in coastal protection shows, that in many cases, these methods can be successful when applied jointly. The types of structures of shore protection structures are diverse. Therefore, the main task of designers is to choose the most optimal of them, taking into account the climatic, hydrological and engineering-geological conditions of the region construction. The aim of this work is to create a progressive method of construction of shore protection structures on shallow shores of the seas and in shallow reservoirs. This paper considers the existing and innovative designs of shore protection structures made of various materials, the conditions of their use and technical and economic characteristics are analyzed. Based on the analysis, a progressive method of construction of shore protection structures from gabions is proposed. The using of the proposed method for the construction of shore protection structures from a box type gabion will speed up the construction process of such structures, as well as reduce the volume of material at the base, which will lead to a significant reduction in the cost of construction. The mass of gabions in each project should be determined on the parameters of the waves of the design storm in accordance to the recommendations of standards.

Investigation on hydrodynamic performance of an environmentally friendly pile breakwater

In this paper, a type of pile breakwater is studied in a configuration that can provide an effective shore protection structure. While, the rubble mound breakwaters are the most common type, but they suffer from a number of shortcomings including the interruption of water that may lead to deterioration of water quality and corresponding environmental problems. The breakwater of this study with rows of piles can be used against sea waves, as an alternative. Its hydraulic performance, including wave reflection and transmission, shear stresses, pressure measurements, drag and inertia coefficients are investigated. In the first step, the hydrodynamics around the mono-piles with square cross-sections are inspected. The parametric equations are developed to measure the optimal orientation of the piles. As evidenced in the literature, relatively limited works have been carried out on this kind of piles. Also, the performance of the considered pile breakwaters are evaluated. To do this, the numerical results are calibrated and validated by experimentation. It is observed that the group piles with the square cross-section in optimum conditions, could have a higher value of reflection almost between 7 even to almost 30 percent, than other considered conditions with mild and short waves. It can be related to the effect of the square piles edges on the separation process of the flow.