Coastal Protection Measures Research Articles

The Variability of the Beach Morphology and the Evolution of the Shoreline in the Strongly Anthropized Sector of Eforie North, the Romanian Coast of the Black Sea

The Eforie Nord sector (between the southern pier of Agigea - Constanta port and the tourist port of Belona), is characterized, from a geomorphological point of view by the presence of high cliffs and narrow beaches. In the mentioned sector, a series of coastal protection works were carried out in several stages, respectively: between 1956 and 1960, 6 groins were placed to etend the perimeter beach; with the epansion of Constanța port, new coastal protection measures were imposed (1981-1986), determined by the erosion processes, made concrete by the eecution of permeable submerged longitudinal dikes in addition to the transversal ones. On long term, the measurements of shore morphological parameters highlighted that the southern sector of the Romanian Black Sea coast is subject to an erosion process, due to the action of both natural and anthropogenic factors, each generating effects with different intensity, depending on local conditions. Within the project “Protection and Rehabilitation of the Southern Part of the Romanian Black Sea Coast, Phase 1” in 2014-2015 period, in the mentioned sector, etended hydrographical works were carried out, including the rehabilitation of dikes, the construction of submerged dikes and beach nourishment. The monitoring of the shore behavior at regular intervals (annual/seasonal) which is essential for an adequate management of the coastal area, highlights both cyclical/seasonal morphological changes (rapid erosion as a result of storms in the cold season and the reconstruction of the beach during summer) and progressive/multiannual changes. The monitoring of morpho dynamic changes at shore level includes the positioning of the shoreline and beach profiles in 6 locations using GPS equipment (geodetic and GIS class). The resulting spatial data were processed and included in the SANDS management system that allows comparative analysis at different time scales. The maps representations were made in the ArcGIS 10.8 system. The data analysis revealed seasonal changes of the shore morphology, both in the longitudinal profile (shoreline) and transversally (beach profiles).

Impacts of coastal protection measures along the coast of Kerala, India (through remote sensing techniques)

ABSTRACT The maritime state, Kerala, is located along the southwest coast of the Indian peninsula, which extends from Trivandrum district (8° 17´ 41.03´´ N, 77° 5´ 37.29´´ E) in the South to Kasaragod district (12° 45´ 20.76´´ N, 74° 51´ 58.92´´ E) in the North, exposed to the waves from the Arabian Sea. The shoreline is extremely dynamic due to the impact of waves, tides, currents, coastal orientation and other associated occasional coastal hazards. The annual climatic calendar for the Kerala coast can be broadly classified as South-West monsoon (June to September), North-East Monsoon (October to December), and Pre-monsoon or Non-Monsoon (January to May). Prior to the 2004 Indian Ocean tsunami, a standardised seawall section had been preferred for highly eroding coastal stretches. The coastal hazards in addition to the tsunami impact paved the way for considering several other structures for coastal protection, of which groyne fields have been predominantly implemented. As it is essential to quantify the performance assessment of these protection measures, an exercise using the DSAS (Digital Shoreline Analysis System) tool was carried out, the results of which are presented and discussed in this paper.

Bayesian extreme value analysis of extreme sea levels along the German Baltic coast using historical information

Abstract. Developed coastlines require considerable investments into coastal protection measures to mitigate the effects of flooding caused by extreme sea levels (ESLs). To maximize the effectiveness of these measures, accurate estimates of the underlying hazard are needed. These estimates are typically determined by performing extreme value analysis on a sample of events taken from tide-gauge observations. However, such records are often limited in duration, and the resulting estimates may be highly uncertain. Furthermore, short records make it difficult to assess whether exceptionally large events within the record are appropriate for analysis or should be disregarded as outliers. In this study, we explore how historical information can be used to address both of these issues for the case of the German Baltic coast. We apply a Bayesian Markov chain Monte Carlo approach to assess ESLs using both systematic tide-gauge observations and historical information at seven locations. Apart from the benefits provided by incorporating historical information in extreme value analysis, which include reduced estimate uncertainties and the reclassification of outliers into useful samples, we find that the current tide-gauge records in the region alone are insufficient for providing accurate estimates of ESLs for the planning of coastal protection. We find long-range dependence in the series of ESLs at the site of Travemünde, which suggests the presence of some long-term variability affecting events in the region. We show that ESL activity over the full period of systematic observation has been relatively low. Consequently, analyses which consider only these data are prone to underestimations.

Optimal wave reflection as a mechanism for seagrass self-organization

Ecosystems threatened by climate change can boost their resilience by developing spatial patterns. Spatially regular patterns in wave-exposed seagrass meadows are attributed to self-organization, yet underlying mechanisms are not well understood. Here, we show that these patterns could emerge from feedbacks between wave reflection and seagrass-induced bedform growth. We derive a theoretical model for surface waves propagating over a growing seagrass bed. Wave-induced bed shear stress shapes bedforms which, in turn, trigger wave reflection. Numerical simulations show seagrass pattern development once wave forcing exceeds a critical amplitude. In line with Mediterranean Sea field observations, these patterns have half the wavelength of the forcing waves. Our results raise the hypothesis that pattern formation optimizes the potential of seagrass meadows to reflect wave energy, and a clear direction for future field campaigns. If wave-reflecting pattern formation increases ecosystem resilience under globally intensifying wave climates, these ecosystems may inspire nature-based coastal protection measures.

Multi-decadal shoreline changes in Eastern Ghana—natural dynamics versus human interventions

Human infrastructures, such as dams, seawalls, and ports, can affect both the sedimentary budget and nearshore hydrodynamics, enhancing and accelerating the loss or gain of coastal sediments. Understanding the processes and factors controlling beach morphodynamics is essential for implementing adequate adaptation strategies in coastal areas, particularly in those regions where coastal protection measures are scarce. This study analyzes shoreline changes in the Keta Municipal District, located in southeastern Ghana (West Africa). This area is characterized by the sedimentary input of the Volta River, forming a river delta situated to the west, i.e., updrift, of our study site. Following the construction of two dams (Akosombo and Kpong) on the Volta River in 1965 and 1982, groins and revetments have been built along the coast between 2005 and 2015 to reduce the high rates of coastal erosion in this area. Here, we explore the influence of these dams and the hard protection constructions on beach morphodynamics using historical maps and satellite images complemented by a shoreline survey undertaken with a differential GNSS in 2015. The multi-decadal evolution between 1913 and 2015 reconstructed for 90 km of shoreline suggests that local erosion rates in the region predate the construction of the two dams on the Volta River, indicating that these structures might not be the primary driver of coastal erosion in this area, as previously suggested. We emphasize that delta dynamics under conditions of high-energy longshore drift, modified by anthropogenic drivers such as sand mining, play a key role in the long-term evolution of this coast. Our results also show that the infrastructures built to halt coastal erosion result in localized erosion and accretion down-current along the coastline towards the border with Togo, highlighting the need for a transnational perspective in addressing the problems caused by coastal erosion.

Evaluation of seagrass as a nature-based solution for coastal protection in the German Wadden Sea

Global climate change increases the overall risks for coastal flooding and erosion. Meanwhile, nature-based solutions (NbS) are increasingly becoming a focus of coastal protection measures to improve the climate adaptability. In this study, the present and potential future role of seagrass in coastal risk reduction strategies were explored for the highly energetic Wadden Sea area of the German Bight. The methodology in this study combined seagrass coverage data (Zostera marina and Zostera noltei) obtained by field surveys and what-if scenario simulations using the SCHISM unstructured grid model framework, coupling hydrodynamics, waves, sediments, and a seagrass module. The results suggest that the introduction of seagrass meadows locally can reduce both current velocities and significant wave heights in the order of up to 30% in the deeper areas and above 90% in the shallow areas. Reduction in bottom shear stress of a similar relative magnitude significantly reduced sediment mobilisation on the order of 2 g/L in the 95th quantile of bottom layer sediment concentrations. Effectively altering hydromorphodynamic conditions favouring sediment accumulation, seagrass expansion could help tidal flats height growths to keep up with SLR, thus further maintaining the bathymetry-induced tidal dampening and lowering flooding and erosion risks as well the amount of energy at dike infrastructure. The accumulated effect of seagrass under calm weather conditions is considered more important than the increased attenuation in absolute values it provides during extreme conditions. The overall conclusion is that seagrass expansion could be a useful addition to engineered coastal protection measures.

Analysis of data from the full-scale prototype testing of the WASP – A novel wave measuring buoy.

To assess the viability of locations for wave energy farms, and design effective coastal protection measures, knowledge of local wave regimes is required. Current regime-measuring devices are expensive, and the aim of the WASP Project is to develop a low-cost, self-powering wave-measuring device. The Wave-Activated Sensor Power Buoy (WASP) comprises a floating body with a moonpool. The relative motion of the water level in the moonpool to the buoy will pressurise and depressurise the air above the water column, which will be used to drive a bidirectional turbine in the manner of an oscillating water column, which will operate in conjunction with a generator to recharge an on-board battery pack. It has previously been demonstrated through tank testing of scale-models that a sea-state may be estimated from measurements of the pressure within the air above the water column under controlled conditions [1]. Important statistical parameters relating to the sea state, such as the significant wave height, zero-cross period et cetera. may then be estimated from the spectral moments of the wave spectrum [2].
 This paper seeks to validate the use of measurements taken of the pressure in a volume of air contained in a chamber above an oscillating water column (OWC) (which is in communication with the ocean) to estimate the sea state which induces motion of the water column.
 The WASP was deployed from March to July 2019 at the Smart Bay test facility in Galway Bay, Ireland. The ¼ Scale test site was previously characterised by B Cahill UCC 2011 [3] using data captured by the Marine Institute Datawell WaveRider buoy from 2006 to 2011. Pressure signal data recorded by the WASP at a frequency of 8Hz was processed in to 30-minutes blocks to reflect the presented data from the WaveRider buoy, from which the WASP was moored a distance of 400m from during deployment. Power Density Spectra for 6,500 thirty-minute sea states were generated and an inverse transfer function between the WASP and the WaveRider produced. This allowed for the calculation of the associated significant wave height, Hs, and zero-crossing period, Tz, from the WASP pressure data for each thirty-minute block of data. At this time, outliers and bimodal spectra were removed to simplify the analysis, and the data was binned based on Hs and Tz ranges. For each bin, average inverse transfer functions were generated. A Bretschneider Spectrum [4] was produced using the Hs and Tz values from the WaveRider data for the respective binned WASP data. An average transfer function was then generated between the Bretschneider models and the corresponding sea states for the WASP. Using this final transfer function, a scatter plot of Hs and Tz for the test site was generated and compared against the previously produced scatter plot from the initial resource characterisation of the Galway Bay Test Site in 2011 in order to determine if the WASP is capable of measuring sea-states through measurement of time series pressure signals in the volume of air above the water column in the OWC.

MULTI-SCALE WAVE MODELLING; FIELD VALIDATION IN FAXE BAY, DENMARK

Access to local nearshore wave climate conditions on a detailed spatial scale is important for many coastal engineering practices. These include assessing the flood risk of coastal infrastructure, designing coastal protection measures, and estimating sediment transport processes and wave run-up. The present study displays a multi-scale wave modelling approach using the numerical wave model SWAN (Booij et al., 1999) together with field data applied in the southern Baltic Sea. The main objective of the study was to investigate the possibility of employing a single wave model for seamless simulations over several scales in time and space, from offshore to nearshore, including the effects of grid size and resolution. Validation with extensive field data was a crucial part of the study.

Hydrodynamic Model Tests for Seaweed as a Source of Energy Reduction during Extreme Events

One fifth of the world’s population and critical infrastructures are close to the coast and regions of high-risk sea level rise elevation. The last decades have been characterized by increasing extreme events, including storm surges, flooding, coastal erosion, enhanced coastal vulnerability with associated livelihood, and economic losses. Nature-based engineering solutions are being adopted as sustainable solutions for helping existing technologies live their design life and providing climate change adaptation and resilience for coastal and riverine communities. This paper involves the investigation of nature-based eco-hydraulic soft coastal engineering to cultivate seaweed for coastal protection. In this context, the present study involves an advanced risk evaluation performed by conducting an extreme bore interaction with seaweed as a soft engineering coastal protection measure. The load reduction on the inland structure during extreme flooding conditions, incorporating seaweed, is addressed. The present study indicates that the load on inland structures can be reduced by as much as 14% in extreme flooding conditions in the presence of seaweed with two rows of seaweed, indicating the usage of seaweed as a part of coastal protection over existing site protection infrastructure for improved coastal mitigation.

The Modern Nile Delta Continental Shelf, with an Evolving Record of Relict Deposits Displaced and Altered by Sediment Dynamics

The most extensive coverage of surficial sediment samples collected to date on Egypt’s Nile Delta coast and shelf is needed to better define sediment dispersal patterns across this setting’s rapidly eroding margin. Changes in time are now induced by River Nile sediment cutoff by dams, sea level rise, marked shelf subsidence, and regional climate changes, which have altered the amounts and components of sediments; these require replacement, along with the implementation of more effective coastal protection measures. Multiple computer-generated offshore maps depict the distributions and proportions of sand, silt, and mud; the mean grain size and standard deviation (sorting); heavy mineral concentrations; and carbonate content. Heavy mineral lobes at the coast and offshore identify former Nile branch sites. Channel lobes extending seaward resulted from their progradational phase and from the delta’s altered sedimentation from the early to late Holocene. The progressive deposition and erosion of these fossil fluvial lobes, and of two active Nile channels, selectively removed their quartz and less dense minerals, thus concentrating heavy minerals on the coast and inner shelf. The prolonged dispersal of original sediment effluence from relict and recent Nile tributaries induced variable depositional patterns on the present shelf. These coastal depocenters, along with extensive sand, silt, and mud from shelf sediments, were reworked further seaward and dispersed by bottom currents, thus masking most previous onshore-to-offshore transport patterns. The major surficial features document long-term responses to the diverse dispersal that influenced the shoreline to the outer shelf deposits from the Pleistocene to the present.

Decadal shoreline changes and effectiveness of coastal protection measures post-tsunami on 26 December 2004

Decadal shoreline changes and effectiveness of coastal protection measures post-tsunami on 26 December 2004

Potential of Transplanted Seagrass Meadows on Wave Attenuation in a Fetch-Limited Environment

In this paper, the effectiveness of transplanted (either created or restored) seagrass meadows as a coastal protection measure is assessed through a five-step methodology. The analysis is focused on a stretch of the Catalan coast (NW Mediterranean) which is a fetch-limited environment. The results show that even considering conservative values for the meadow parameters (plant diameter, meadow density and canopy height), significant reductions of the annual average wave heights reaching the beach may be obtained, reducing flooding and erosion risks. Therefore, the investment in the conservation and restauration of seagrass meadows for protecting coastal areas from erosion and flooding is a measure that must be considered, due to the multiple benefits that they provide including ecosystem services. In addition, the proposed methodology may be a useful tool for coastal managers to help them in the design of seagrass meadows for coastal protection.

The Coastal Protection Measures and Techniques for Shoreline of Visakhapatnam

Globally, most coastlines' rapid erosion is seen as a serious issue. Anthropogenic activities and coastal hydrodynamics are the major culprits. Along with difficulties related to pollution, accretion, sedimentation, and climate change, the coastal zone also experiences these issues Climate change will accelerate sea level rise, saltwater incursions, and storm surges. To safeguard homes, infrastructure, and cultivated land, significant effort has been made to mitigate coastal erosion issues and restore coastal capacity. Different kinds of hard structures were used to solve these issues, but the majority of these solutions had limited success since they failed to consider the complete ecological situation. This encouraged the coastal engineers to consider new designs for environmentally friendly constructions that would better fit the surrounding ecosystem. This report reviews global protection measures and categorizes them primarily into four groups: hard, soft, combination, and novel approaches. Each type's use and negative effects are briefly described. It is obvious that using soft engineering, eco-engineering approaches, or a mix of these to improve the ecological condition is the preferred strategy. This article's aim is to suggest practical remedies for this problematic situation in Visakhapatnam by examining reviews and a few global case studies.

Estimation of the main parameters of wave action on the gentle slopes of the banks of large water bodies

When designing coastal protection measures, special attention is paid to the creation and expansion of a natural beach slope on the coast of a water body. To assign geometric dimensions to relatively stable beach slopes, it is necessary to evaluate the relationship of waves, taking into account the level regime characteristic of a given section of the coast. The aim of the research is to explore the features of the transformation of the wave profile in shallow water and to conduct a comparative analysis of theory and experiment. The studies were carried out in a wave tray, where the waves were reproduced by a swinging shield. The features of the transformation of the wave profile at decreasing depths of the shallow water of a large water body are considered. An assessment is given of the change in the kinematic characteristics of a wave incident in a shallow water zone on an unfortified beach slope with a depth of 10, 20 and 30. The results of experimental studies are presented and analyzed, as a result of which the influence of the wave steepness on the kinematic characteristics and features of wave transformation in shallow water is revealed. A comparative analysis of theoretical solutions and experimental data with an assessment of the area of their applicability is carried out. On the whole, the wave profile and the horizontal component of the orbital velocity during the passage of the wave crest are in satisfactory agreement with the calculations according to the Stokes theory at relative depths of more than 0.07. It has been established that for shallow water conditions the relative height of the wave crest affecting the beach slope of the near-shore zone of the coast of a large water body is most noticeably affected by the slope, with an increase from 10 to 30 the magnitude of the wave steepness can increase by 1.2 times.

Shoreline change detection along North Sebou–Moulay Bousselham, based on remote sensing analysis

Sustainable management of the shoreline is crucial. Shoreline mapping is very essential to investigate the impact of the dynamic nature of the coastal area over a certain period. Coastal zone at the north Sebou estuary experience some issues as shoreline retreats as well as shoreline advancement in some locations. Shoreline mapping along the northern area of Sebou estuary was implemented by applying remote sensing technology to detect and analyze shoreline changes.Multi-temporal satellite images with different periods during the last 37 years (1984–2021) were used to detect changes as well as analyze shoreline change rates. Landsat images (Landsat 5–TM, Thematic Mapper TM, Landsat7 ETM+, Landsat 8 OLI_TIRS) were corrected from geometric and radiometric perspectives, then classified by assigning six different classes for analyzing the evolution of the coastal zone from 1984 to 2021. To detect changes in both land use and land cover, the Support Vector Machine algorithm supervised classification was executed to classify the images. As a powerful statistical analysis tool, DSAS was used to assess the rate of shoreline change by EPR technique and to anticipate the required coastal protection measures along the coastline.The classification results show that agricultural land, bare land, and sand-dune beaches have decreased by −8.26%, −5.92%, and −4.53% respectively. On the other hand, statistical analysis of DSAS shows that the northern area of Sebou estuary experienced an average accretion rate of (+0.96 m/yr) while erosion rates achieved an average of (−1.04 m/yr). A drastic erosion was noticeable at the right side of the estuary with (−3.1 m/yr). The decision matrix by EPR method has been developed. It illustrates the evolution, risk level, and proposed decision at each sector along the shorelines during the preceding three decades. The final goal of this study is to support decision-makers in implementing preventive management techniques in the most vulnerable locations.

Quantitative assessment of the shoreline protection performance of geotextile sandbags at an in-situ coastal experimental station

The coast of China is periodically impacted by tropical cyclones and storm surges, and has experienced significant coastal erosion problems. Traditional “hard engineering” coastal protection measures used to protect Chinese sandy coasts from storm erosion are found to be expensive and less environmental and even make sandy beach disappearing. In this study, geotextile system as a more flexible material was developed and qualitatively compared with the traditional coastal protection measures. An in-situ permanent revetment was applied with durable geotextile sandbags on the coast of Chudao in China from October 2018 to October 2020, and it was designed for three different testing segments to optimize the stability and construction cost of geotextile sandbags. The field surveys were carried out to collect the in-situ data on beach profiles, wave dynamics, material durability, and sandbag revetment stability. In analyzing the two-year field data collected, it is found that the testing segment-2 wrapped with sheet of plastic geogrids is the most effective of the three testing segments in terms of their coat, structural stability and material durability, and that both the slope of the seabed and the design thickness of geotextile sandbag are the dominate factors responsible for the failure of sandbag structures.

Environmental problems of the Crimean coast territories

The article describes the nature and degree of deformations of the coastal zone of the sea and coastal protection structures on the coast of the Kalamitsky Gulf of the Black Sea. In 2022, a team of authors made a visual survey of the coast on the territory of the Bakhchisarai district of the Republic of Crimea with a total length of 11.5 km. from the village of Beregovoe to the village of Uglovoye. As a result of the inspection, coast areas potentially dangerous for human health and life that are not suitable for normal use for recreational purposes were identified. Long-term field observations show that the creation of coastal protection in certain local areas, giving only a temporary positive effect for these areas, can have a very negative impact on neighboring and even remote areas; that is why the coastal protection issue should be solved at least on the scale of the coast of settlements, considering the conditions of a single system. When designing coastal protection measures, it is necessary to consider that separate protection of small areas of erodible coastal territories within a large area of the eroded coast is ineffective, since adjacent unprotected shores will recede under the action of a system of natural factors.

Numerical Analysis on Influences of Emergent Vegetation Patch on Runup Processes of Focused Wave Groups

During severe weather, the runup of the devasting surges and waves can cause extensive damages to the coastal facilities and results in significant loss of life. Therefore, it becomes necessary to find reliable measures to reduce the wave runup in coastal regions. As a natural barrier to the shorelines, coastal vegetation has great potential to attenuate wave runup and to prevent the coastal communities from extreme floodings and huge land loss. This study numerically discusses the influences of the emergent vegetation patch on the runup processes of extreme wave groups by applying a nonhydrostatic flow solver. Influences of the major factors, i.e., water depth, peak wave period, significant wave height, and density and length of the vegetation patch, are analyzed in detail. Research findings indicate that the presence of the emergent vegetation patch can substantially dissipate most of the incident wave energy and effectively reduce the maximum wave runup heights of extreme wave groups at the sloped beach. It is hoped that the research results of this study will be helpful to the design of coastal soft protection measures.

Assessment of the Geomorphological and Sedimentological Changes in Mamaia Sector after the Implementation of the Coastal Protection Measures

"The paper analyses the changes in the beach sector of Mamaia resort from a geomorphological and sedimentological point of view in the context of coastal protection works carried out in 2014-2015 and 2021 (measures to reduce wave energy, beach protection with structures to stabilize the sand and beach nourishment). The Mamaia sector, with a length of about 12 km, is geomorphologically constituted mainly by sandy barrier of Lake Siutghiol representing a transition unit between the northern unit (deltaic and lagoon shore) and the southern unit (small pocket rocks-beaches in front, separated by small coastal sandbars). From an economic point of view, the sector is important for coastal tourism both in terms of the number of tourists and the existing of infrastructure generating significant revenues. Since the 1950s, the sector has been severely affected by the construction of the dikes of the Midia Port in the north, which have affected the longitudinal transport of sediments and accentuated the erosion of the submerged and backshore beach. To counteract the effects of erosion, a longitudinal and transversal coastal protection system was built between 1960 and 1990, which proved to be ineffective in the long term. The data collected in the field (topographic profiles of the backshore, shoreline, sediment samples) before and after the recent coastal protection works were processed using a dedicated software (ArcGIS 10.x and Gradistat v8) and represented in the form of maps and graphics. The spatial analysis highlighted the modification of the coastal system components, the trends of the beach evolution in longitudinal and transversal profile and the changes in the structure and distribution of sediments determined by the impact of the coastal protection works."

Effectiveness of grey and green engineered solutions for protecting the low-lying muddy coast of the Chao Phraya Delta, Thailand

Coastal protection measures can be categorized into grey and green solutions in terms of their ecosystem impacts. As the use of grey solutions has become a serious issue due to environmental consequences during the last few decades, green/nature-based solutions have become prioritized. This study evaluates the effectiveness of grey and green solutions applied along the eastern Chao Phraya Delta (ECPD) based on historical shoreline change analysis and coastal observations using Light Detection and Ranging technology. The results from shoreline analysis indicate that nearshore breakwaters installed 100–250 m from the shoreline have successfully reclaimed the coastline with a sedimentation rate of 17–23 cm/y. Meanwhile, sand-sausage-submerged breakwaters were ineffective at stabilizing the coastline during 2002–2010 due to land subsidence. With a low subsidence rate, the rubble-mound-submerged breakwaters can reduce the shoreline retreat rate with a vertical deposition rate of about 5 cm/y. In contrast, use of a bamboo fence, a green solution widely used along muddy coasts, traps sediment at a rate of less than 1.3 cm/y and typically lasts only for 2–3 years after installation. Decomposed bamboo causes environmental degradation so local communities disapprove of the approach. Results reveal that grey solutions are more effective for stabilizing the ECPD coastline and result in less coastal environmental impact than the nature-based solution using a bamboo fence.