Coastal Protection Structures Research Articles

Impact Of Seawall Development To The Sulawesi Fishermen Community In Pambusuang Village

A coastal protection structure mostly built to protect human from the detructive wind and wave energy. The various option of type and design has been invented in the development. This study investigates the impact of seawall development in Pambusuang Village, West Sulawesi. This study will examine the fishery activity change after the development of seawall. The benefit and disadvantages of the seawall structure to the community also as well as the community response to address the impact of seawall development will be explored in this study. A mix quantitave and qualitative approach is used in this study. A set of questionnare has been distributed and structured interview to selected infromant were also conducted. The study found that fishermen has changed their docking behavior due to the limited area to docking. Moreover, the respondent believes that seawall has properly function to halt erosion, protect their house and other infrastructure from the wave attack. The other issues is the disharmony between pro and contra seawall development, inundated river flow and damage of natural habitat. The response of the community to addressing some impact of the seawall development such as their adaptation to the sloping gate between the seawall, the use of traditional anti fouling painting and their suggestion to construct breakwater disattached from the shoreline. The findings above has been formed the basis of recommendations to have a participatory development approach and experience sharing between the parties in the community to adapt with the impact of seawall development.

Numerical Modeling of Failure Mechanisms in Articulated Concrete Block Mattress as a Sustainable Coastal Protection Structure

Shoreline protection remains a global priority. Typically, coastal areas are protected by armoring them with hard, non-native, and non-sustainable materials such as limestone. To increase the execution speed and environmental friendliness and reduce the weight of individual concrete blocks and reinforcements, concrete blocks can be designed and implemented as Articulated Concrete Block Mattress (ACB Mat). These structures act as an integral part and can be used as a revetment on the breakwater body or shoreline protection. Physical models are one of the key tools for estimating and investigating the phenomena in coastal structures. However, it does have limitations and obstacles; consequently, in this study, numerical modeling of waves on these structures has been utilized to simulate wave propagation on the breakwater, via Flow-3D software with VOF. Among the factors affecting the instability of ACB Mat are breaking waves as well as the shaking of the revetment and the displacement of the armor due to the uplift force resulting from the failure. The most important purpose of the present study is to investigate the ability of numerical Flow-3D model to simulate hydrodynamic parameters in coastal revetment. The run-up values of the waves on the concrete block armoring will multiply with increasing break parameter (0.5<ξm−1,0<3.3) due to the existence of plunging waves until it (Ru2%Hm0=1.6) reaches maximum. Hence, by increasing the breaker parameter and changing breaking waves (ξm−1,0>3.3) type to collapsing waves/surging waves, the trend of relative wave run-up changes on concrete block revetment increases gradually. By increasing the breaker index (surf similarity parameter) in the case of plunging waves (0.5<ξm−1,0<3.3), the low values on the relative wave run-down are greatly reduced. Additionally, in the transition region, the change of breaking waves from plunging waves to collapsing/surging (3.3<ξm−1,0<5.0), the relative run-down process occurs with less intensity.

Remarks on the Boundary Conditions for a Serre-Type Model Extended to Intermediate-Waters

Numerical models are useful tools for studying complex wave–wave and wave–current interactions in coastal areas. They are also very useful for assessing the potential risks of flooding, hydrodynamic actions on coastal protection structures, bathymetric changes along the coast, and scour phenomena on structures’ foundations. In the coastal zone, there are shallow-water conditions where several nonlinear processes occur. These processes change the flow patterns and interact with the moving bottom. Only fully nonlinear models with the addition of dispersive terms have the potential to reproduce all phenomena with sufficient accuracy. The Boussinesq and Serre models have such characteristics. However, both standard versions of these models are weakly dispersive, being restricted to shallow-water conditions. The need to extend them to deeper waters has given rise to several works that, essentially, add more or fewer terms of dispersive origin. This approach is followed here, giving rise to a set of extended Serre equations up to kh ≈ π. Based on the wavemaker theory, it is also shown that for kh > π/10, the input boundary condition obtained for shallow-waters within the Airy wave theory for 2D waves is not valid. A better estimate for the input wave that satisfies a desired value of kh can be obtained considering a geometrical modification of the conventional shape of the classic piston wavemaker by a limited depth θh, with θ≤ 1.0.

Current condition of coastal protection structures of Meulaboh, Westcoast of Sumatra Island, Indonesia

Meulaboh is coastal city that has tourism potential. The city has been facing coastal erosion hazard since a long time from high energy wave activity coming from Indian Ocean. To protect the coast from the erosion hazard, a coastal defence structures were built along the city’s coast overlooking the Indian Ocean. Before the 2004 tsunami, hard structures built on the coast that open to waves from the Indian Ocean were damaged by daily wave activity. This study assess effectiveness of the current coastal protection structures protect coastline in the three coastal segments of the city, namely the Padang Seurahet, Ujung Karang and Kampung Pasir, in order to find out if the construction of the structures is the right choice. Related to the tourism potential of Meulaboh City also studied the possibility to expand the function of the structures. The coastal protection structures data for this study were mainly obtained from field observations in June 2021. Effectiveness of the structures protecting coastline were analysed based on technical criteria. Meanwhile, possibility to expand the function of the structures were analysed according to environmental condition of the coastal segments and types of tourism activity. The results of this study show that the hard structure that now exists on Meulaboh coast can protect the city’s coast from the hazard of erosion without negatively impacting the surrounding coastline. In addition, the structure is considered to be expandable to support the development of tourism potential of Meulaboh City. Thus it can be conclude that the choice of hard structure for coastal protection in most of Meulaboh coastline is appropriate.

Modeling of wave processes in closed water areas of shallow water areas

The article presents the developed non-stationary two-dimensional hydrostatic model of wave propagation in the water area of the port of the Bay of Five Hunters, protected by a coastal protection structure in the form of a jetty. The tasks of the work included the development of a model based on the Navier-Stokes and continuity equations and a long-range assessment of the possible impact of the wave situation on marine objects in the port area. At present, the provision of hydrometeorological predictive information is one of the most important factors in the effective operation of port waters. The results are presented graphically using a geographic information system, where different wave heights and maximum wave amplitudes are displayed using a color palette. The consistency of the obtained results is shown, and refraction, diffraction, and interference are noted for the incoming wavefront.

Submerging paddy cultivation area due to coastal flooding in Kuala Kedah, Malaysia

Kuala Kedah is a coastal area where the majority of the community are paddy farmers and fishermen. Almost the entire coastal area is used as a paddy cultivation area. However, this area faces the threat of seawater intrusion into land due to climate change driven sea-level rise. The rising seawater has affected the surrounding area, not only in terms of crop yields but also property and livelihood to the locals. Therefore, this study is designed to detect and analyze the progress of seawater on land at the Kuala Kedah coastal area using a hydrodynamic approach. Mike 21 software was used to simulate the hydrodynamic effects on 2 segments (NA and SA) in this study area by considering two conditions namely Condition 1 (K1) and Condition 2 (K2) which are respectively with and without coastal protection structure. However, this structure was only built along the 2.5 km shoreline in the NA segment and not in the SA segment. The findings show that the coastal protection structure in K2 is effective in reducing 50 % of the impact of sea level rise in year 2100 at NA segment, while only 10 % at SA segment. Therefore, the construction of these structures permanently should be given consideration by local authorities in planning future development to ensure lowland areas are protected from coastal floods.

Modelling the Impact of Climate Change on Coastal Flooding: Implications for Coastal Structures Design

In the present work, the impact of climate change on coastal flooding is investigated through a set of interoperable models developed by the authors, following a modular modelling approach and adapting the modelling sequence to two separate objectives with respect to inundation over large-scale areas and coastal protection structures’ design. The modelling toolbox used includes a large-scale wave propagation model, a storm-induced circulation model, and an advanced nearshore wave propagation model based on the higher order Boussinesq-type equations, all of which are presented in detail. Model capabilities are validated and applications are made for projected scenarios of climate change-induced wave and storm surge events, simulating coastal flooding over the low-lying areas of a semi-enclosed bay and testing the effects of different structures on a typical sandy beach (both in northern Greece). This work is among the few in relevant literature that incorporate a fully non-linear wave model to a modelling system aimed at representing coastal flooding. Results highlight the capabilities of the presented modelling approach and set the basis for a comprehensive evaluation of the use of advanced modelling tools for the design of coastal protection and adaptation measures against future climatic pressures.

Hurricane Matthew in 2100: effects of extreme sea level rise scenarios on a highly valued coastal area (Palm Beach, FL, USA)

Sea-level rise represents a severe hazard for populations living within low-elevation coastal zones and is already largely affecting coastal communities worldwide. As sea level continues to rise following unabated greenhouse gas emissions, the exposure of coastal communities to inundation and erosion will increase exponentially. These impacts will be further magnified under extreme storm conditions. In this paper, we focus on one of the most valuable coastal real estate markets globally (Palm Beach, FL). We use XBeach, an open-source hydro and morphodynamic model, to assess the impact of a major tropical cyclone (Hurricane Matthew, 2016) under three different sea-level scenarios. The first scenario (modern sea level) serves as a baseline against which other model runs are evaluated. The other two runs use different 2100 sea-level projections, localized to the study site: (i) IPCC RCP 8.5 (0.83 m by 2100) and (ii) same as (i), but including enhanced Antarctic ice loss (1.62 m by 2100). Our results show that the effective doubling of future sea level under heightened Antarctic ice loss amplifies flow velocity and wave height, leading to a 46% increase in eroded beach volume and the overtopping of coastal protection structures. This further exacerbates the vulnerability of coastal properties on the island, leading to significant increases in parcel inundation.

Investigation on the Reflection Coefficient for Seawalls Protected by a Rubble Mound Structure

Sea wave reflection from coastal protection structures is one of the main issues in the coastal design process. Several empirical formulas have been proposed so far to predict reflection coefficient from rubble mound breakwaters and smooth slopes. The aim of this study is to investigate wave reflection from a rubble mound structure placed in front of a vertical concrete seawall. Several experimental tests were performed on a two-dimensional wave flume by reproducing on a rubble mound structure with a steep single primary layer armored with a novel artificial unit. A new approach for the prediction of the reflection coefficient based on dimensional analysis is also proposed, and a new empirical equation is derived. The performance of the proposed equation was compared with widespread existing formulas, and a good accuracy was found.

Spatial distribution of wave-by-wave overtopping behind vertical seawall with recurve retrofitting

Understanding the spatial distribution of wave overtopping water behind coastal protection structures is essential for assessing the safety level of coastal regions behind the coastal defences. The spatial distribution of wave overtopping volume determines the planning and arrangements of critical infrastructures (e.g., railways, roads and buildings) in coastal regions. This study presents a series of laboratory-scale physical modelling experiments to investigate the spatial distribution of wave overtopping volume behind plain vertical seawall and seawall with recurve retrofitting. The hydrodynamic conditions are designed to mimic both swell and storm sea conditions. Tests were conducted for a range of relative freeboard and empirical-based predictive equations were derived for both mean and extreme overtopping events under impulsive and non-impulsive wave conditions. Test results showed that overtopping impact hazard zone reduces up to 87% with the increase of relative freeboard (Rc/Hm0). The hazard zone for extreme overtopping events was found to be up to 3 times of the mean overtopping volumes. The effectiveness of recurve retrofitting on mitigating spatial distribution of wave overtopping were investigated with three recurve prototypes of varying overhang length and recurve's height. It was found that increase in overhang length provides higher reductions in the spatial distribution of hazard zone behind the wall and improve the climate resilience of the seawall. The results highlight that recurve retrofitting is more effective in reducing the length of hazard zone under impulsive wave conditions. The findings of this study provide key data and predictive formulae for robust assessments of the hazard zones behind the key coastal defence infrastructures during mild and extreme climatic events.

Strategies to work towards long-term sustainability and resiliency of nature-based solutions in coastal environments: A review and case studies.

The need for sustainable and resilient long-term strategies for coastal restoration and development projects is largely the result of pressures brought by changing climate conditions and growing human populations along coastal boundaries. As anthropogenic impacts along our coasts increase, the demand for sustainable, nature-based solutions (NbS) will grow commensurately. Trusted approaches are needed for successful implementation of NbS, especially in regions hardest hit by environmental changes. Nearshore strategies for new construction and protection of existing coastal infrastructure are shifting rapidly from hardened approaches to more ecologically aligned techniques that work with natural forces and enhance natural habitat. This paper highlights the benefits of living shorelines composed of ecotypic native plants, wave attenuation structures for coastal protection, and managed retreat to restore coastal environments while supporting and maintaining natural habitats. We review several NbS and present two case studies to illustrate the value of incorporating nature-based approaches to vulnerable coastal environments and highlight the importance of maximizing synergies and understanding trade-offs in their long-term use. Integr Environ Assess Manag 2022;18:123-134. © 2021 SETAC.

Performance characteristics of a conical pile head breakwater: An experimental study

Breakwaters are constructed for dissipating the wave energy and safeguarding the coastline from destructive wave forces. Conventional pile breakwater built using prismatic circular piles has been proven to provide partial protection efficiently. In the present study, the conventional pile breakwater is modified by widening the pile's cross-sectional area at the surface level in a conical shape. The concept of introducing the conical shape is to attenuate the concentrated wave energy, mainly focusing at the surface. The influence of the structural parameters such as diameter, height and clear spacing of the conical pile head is investigated experimentally for various monochromatic wave climatic conditions. The investigation is also focused on determining the influence of the second row on performance characteristics. The analysis shows that the least transmission coefficient (Kt) of 0.662 for the configuration of D/Hmax = 0.4, Y/Hmax = 1.5 and b/D = 0.1 for a single row of piles. Further, the second row of piles' inclusion resulted in improved attenuation characteristics of conical pile head breakwater (CPHB) with the least Kt of 0.582 at an optimal B/D of 0.4. The performance of the CPHB is compared with the theoretical solutions of conventional pile breakwater. The results indicate that the introduction of pile head on conventional pile breakwater is beneficial in improving wave attenuation. A set of empirical equations is developed based on the experimental values for quick prediction of Kt and Kr. The estimated values of Kt and Kr are in line with the experimental data with a coefficient of determination (R2) of 0.91 and 0.90, respectively. The overall performance of the CPHB is found to be promising as a potential coastal protection structure.

Coastal Structures as Beach Erosion Control and Sea Level Rise Adaptation in Malaysia: A Review

The shoreline of Malaysia is exposed to threats of coastal erosion and a rise of sea level. The National Coastal Erosion Study, 2015 reported that 15% of an 8840 km shoreline is currently eroding, where one-third of those falls under the critical and significant categories that require structural protection. The Study of Sea Level Rise in Malaysia, 2017 presented a sea-level increase of 0.67–0.74 mm on average yearly. This study reviewed selected coastal protection structures along the shoreline of Malaysia as an erosion control and sea-level rise adaptation based on coastal management strategies. Hard structures such as rock revetment and breakwater are commonly used as erosion protection systems in the “hold the line” strategy. Increased platform level of seawalls and earth bunds, considered as an “adaptation” approach, are effective in erosion protection and are adaptive to sea-level rise. Mangrove replanting is suitable as a “limited intervention” approach in minimizing the long-term impact of both threats. However, offshore breakwater, groyne, and geotextile tubes are solely for protection purposes and are not as effective for sea-level rise adaptation. As the sea level is continuously increasing, their function as coastal protection will also become less effective. In summary, this comprehensive review on coastal protection in Malaysia will benefit the related agencies on the future assessment.

Coastal Erosion in The Unprotected and Protected Sections At Berakas

The coast at Berakas in the Brunei-Muara district of Brunei Darussalam suffers from erosion caused by a combination of fluvial and marine processes. This paper investigates the rate and pattern of erosion along a 1.8-km stretch of coast to compare the difference between the unprotected and protected sections. We used (i) image and spatial analysis and (ii) field geomorphology. The Digital Shoreline Analysis System (DSAS) in ArcGIS was used to compare the study area using two Google Earth images. The study found that the unprotected section had receded by 4.6 m between 2009 and 2019, while the protected section had advanced by 8.0 m over the same period; intense gullying and slumping of cliff continued at both sections. The detached headland breakwaters in the protected section were effective in stabilizing the coast. A concrete drain installed parallel to the cliff edge appears to be capable of intercepting storm runoff, but its effectiveness was undermined by lack of maintenance. We conclude that terrestrial-fluvial processes continue to erode coastal land and cause slumping of the cliff face at Berakas. However, coastal protection structures that curb the marine process could stabilize the coastline, even where sediment transport is active.

Определение расчетных параметров границ затопления поймы реки Терек на основе инженерно-гидрологических расчетов

When using rivers and lakes as communication routes, the shape of the underwater relief should be studied. The irrigation capacity of the rivers is determined by the measured water discharge. The main dimensions of hydraulic structures and the dimensions of water-pass structures on roads and railways depend on the flow rate of water in the river. Consequently, in the construction design of coastal protection structures, information is needed on flows, depths, as well as the corresponding marks of the water surface (levels). Keywords: FLOW RATE, WATER DEPTH, DRAINAGE AREA, ANALOGUE RIVER, COEFFICIENT, RIVER FLOOD

Prediction and reconstruction of ocean wave heights based on bathymetric data using LSTM neural networks

Since climate change impacts threaten the coastal regions of the North Sea, consistent sea state time series are essential for building coastal protection or offshore structures. Vast gaps in buoy data, caused by false measurements or maintenance periods, require reconstruction and forecasting of ocean waves. Morphodynamic changes of the Ebb-Tidal Delta (ETD) sandbanks exert a huge impact on the local wave climate off the island of Norderney, Germany. Therefore, the objective of this paper is to develop a machine learning model based on Long Short-Term Memory (LSTM) neural networks for reconstruction and short- and long-term prediction of nearshore significant wave height (SWH), integrating bathymetric data for the first time. Time series of sea state and weather data of adjacent buoys as well as bathymetric data of the ETD sandbanks from 2004 to 2017 were used and the networks were tuned with Bayesian hyperparameter optimization. Including the bathymetries improved the performance of the LSTM for SWH reconstruction, short-, and long-term predictions by 16.7%, 7.4–11.7%, and 8.8–9.1% in terms of RMSE, respectively. The LSTM outperformed deep feed-forward neural networks and other state-of-the-art machine learning algorithms. With an RMSE of 0.069 m, a parallel LSTM structure (P-LSTM) is the proposed method for SWH reconstruction.

Fine Spatial Scale, Frequent Morphological Monitoring of Urbanised Beaches to Improve Coastal Management

Between 1959 and 2010, a coastline retreat of 2.4 m/year and erosion of up to 174 m were recorded around Turbo, in northern Colombia. This degraded coastal system is the result of a poorly planned coastal defence scheme, combined with a lack of formal technical methodologies for diagnosis and monitoring. The coastal system cannot provide the protection services required by the local community. From 2017 to 2019, the group monitored urban beach profiles in a small area close to the town of Turbo, in the wet and the dry seasons, as part of a coastline analysis to identify morphodynamic trends in the area. The results show a net shoreline accretion of up to 30 m and positive sedimentary accumulation of up to 45.8 m3/m. To the north of the study area, sediment accumulation is evident at the Turbo River Delta. The 34 coastal protection structures in the study area have a high k index (~0.7), suggesting that they are the main drivers controlling the trend of sediment accumulation. The correlation of geomorphological, oceanographic, and anthropic variables related to the presence of coastal structures, is necessary in order to set up efficient coastal protection schemes.

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.

The 16 September 2015 Illapel Earthquake and Tsunami: Post-Event Tsunami Inundation, Building and Infrastructure Damage Survey in Coquimbo, Chile

The 16 September 2015 MW8.3 Illapel Earthquake generated a tsunami that caused severe building and infrastructure damage in Coquimbo, Chile. Initial reports indicated numerous buildings, transport, energy, water and coastal protection structures sustained varying levels of damage in response to tsunami exposure. A digital ‘census style’ survey was carried out in Coquimbo to measure and record tsunami hazard characteristics and associated buildings and infrastructure network component damage. Flow depths measured from 655 watermarks ranged from 0.1 to 4.7 m, with a 1.47 m mean and 1.02 m standard deviation. Over 3000 damage samples were recorded for tsunami exposed buildings and infrastructure components. Damage levels for 545 buildings showed most sustained partial but repairable damage at tsunami flow depths up to 2 m. A further 2544 damage samples were collected for transport, energy, water infrastructure network components and coastal protection structures. We observed undamaged infrastructure components in high proportions and observed that complete component damage was often caused by secondary hazards (e.g. debris) or cascading impacts where seawall and stormwater culvert failures damaged co-located roads, pathways and utility poles. Future investigations of the hydrodynamic tsunami characteristics influencing infrastructure component fragility will support the analysis of physical damage to single components and cascading impacts across multiple infrastructure networks.

Experimental characterisation and three-dimensional modelling of Elymus for the assessment of ecosystem services

To make a significant contribution to the fundamental understanding of how the internal tissue structure of the Elymus culm is related to the culm stiffness and flexibility with respect to its section height, the present work uses state-of-the-art methods such as three‐-/two-point bending experiments, histological investigations, and numerical optimisation/identification modelling. The combination of these methods generates a knowledge that is needed, to adequately model the degree of bending and associated drag forces in hydrodynamic models used to predict wave loads on landward lying coastal protection structures. In addition, it is possible to predict the likely plant culm stresses that will ultimately lead to plant breakage and removal, and thus to a temporary reduction in coastal protection. The results of this study show that knowledge of the geometric cross sectional information (cross sectional area and area moment of inertia) is indispensable for an adequate description of the mechanical behaviour of the grass culm. Especially the area moment of inertia was often overestimated in previous studies. It also becomes clear that the histological plant characteristics in the form of tissue compositions explain the differences in stiffness and thus in bending behaviour that exist between the different stem sections (bottom, middle, top). The methodology presented here, combining experimental investigations and numerical methods, has the potential to make a significant contribution to the elucidation of plant load transfer and wave-vegetation interaction in the future.