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Infragravity waves play an important role in the nearshore water dynamics and significantly impact coastal processes and port operations. One potential way to reduce the influence of long waves is to take advantage of wave energy converters (WECs) and their ability to alter the downstream wavefield. A small-scale laboratory experiment is used to explore the effect of WECs on the infragravity wave generation over the steep reef platform. The long wave is generated using a bichromatic wave group, and the WECs are designed as oscillating water columns that resonate at the wave group harmonics, providing the greatest impact on the wavefield dynamics. The experiments are conducted in five stages progressively increasing the complexity of the tested set-up. The results demonstrate that the reef platform causes a significant amplification of the infragravity wave amplitude for the tested wave conditions. Placing the WECs upstream of the reef platform reduces the long wave amplitude over the reef flat, where maximum attenuation occurs with the largest number of WECs tested. • In laboratory experiments, long waves are generated using nonlinear wave interaction in the wave group. • Infragravity waves are significantly amplified on the reef platform. • Wave energy converters effectively attenuate infragravity waves by interacting with primary short waves in a wave group. • Oscillating water columns without any orifice effects have the strongest interaction with the incident wave. [ABSTRACT FROM AUTHOR]

Embryonic dunes, continuous dunes and classical beach nourishment are tested as soft coastal protection measures in the vulnerable Trabucador barrier beach located in the NW Mediterranean Sea against different storm conditions. The beach was impacted by severe breaching events during past storms. Evaluation of the performance of the dunes and nourishment as coastal protection measures for the barrier beach is carried out using XBeach model for three different storm events: Storm Isaak being a mid-tier double peak storm, Storm Filomena a typical larger storm of the region and Storm Gloria the largest ever storm to hit the region, with 7, 12 and 60 years of return period respectively. The model showed embryonic dunes and shoreface nourishment systems greatly protect the beach against Storm Isaak and Storm Filomena but did not withstand Storm Gloria considering it being almost 1.5 times larger than the second-highest storm in terms of significant wave height. The study aids in assessing the effectiveness of various mitigation actions for barrier beaches, with the aim of implementing them in practical field applications. • Embryonic dunes have been studied to enhance barrier beach resilience. • Dune behaviour is evaluated for 3 storms and compared to classical interventions. • XBeach model is used to simulate the morphodynamic response. • Embryonic dunes offer a level of protection comparable to shoreface nourishment. • Embryonic dunes are expected to have longer lifetimes due to their emerged location. [ABSTRACT FROM AUTHOR]

• Ecological Infrastructure (EI) is a useful approach for integrating ecosystem services in conservation plans. • Conservation for people and nature requires EI and biodiversity features to be included in planning. • Equitable access to ecosystem services and benefits needs explicit consideration in planning. • Equitable access is achieved by splitting input features into smaller units to spread where targets are met. • Biodiversity features plus EI results in larger, more costly prioritisations, justified by overall benefits. Including human dimensions in conservation practice is increasingly recognized as being essential for creating sustainable and equitable solutions to the current biodiversity crisis. However, including ecosystem services in conservation planning is challenging because services can be intangible and difficult to map, and incorporating equitable access to the resulting benefits of ecosystem services has hardly been considered. Ecological Infrastructure (EI) is a promising framework for integrating ecosystem services into systematic conservation planning (SCP), yet its application remains to be tested. We aimed to quantify the effects of including EI, with and without equitable access, in a biodiversity-based SCP, where EI is the spatial representation of ecosystem services. We took an experimental, scenario-planning approach, running five scenarios in Marxan software with different combinations of input features: biodiversity (n = 135 features), EI (n = 6) and EI with equitable access (hereafter EI*, n = 84) for the South African coastal zone. The resulting conservation networks were compared using multivariate statistics, considering: the proportion of feature targets met; coverage of core areas (areas with 100 % selection frequency for biodiversity features, EI, and EI*); conservation network size and cost; and spatial configuration. Including biodiversity and equitable access drove the dissimilarity among scenarios, and only when all input features were included, were all core areas well covered and all feature targets met. Therefore, biodiversity features were not an adequate surrogate for EI or EI*, and including ecosystem services (via EI*) in SCP is necessary to ensure equitable access to benefits. However, including EI increased the mean size (7.0 % more planning units) and cost (by 9.1 %) of conservation networks. Despite this, the social and economic benefits of investing in EI (e.g., securing dunes for coastal protection) likely outweigh these costs, especially in the longer term. [ABSTRACT FROM AUTHOR]

The integration of wave energy devices and coastal structures may be an innovative and sustainable way to achieve energy production purposes with a secondary benefit of coastal protection, which can increase accessibility and reduce the costs of wave energy technology. In this paper, a 3-D theoretical model was developed to investigate the hydrodynamic efficiency and breakwater function of a periodic array of oscillating buoys embedded in a caisson breakwater. The generalized radiation problem was solved to derive generalized radiation force. The theoretical model was validated using Haskind's relation and energy flux conservation law. The influences of wave/geometrical parameters and PTO damping were revealed. In particular, hydrodynamic phenomenon of multiple orders reflected and transmitted propagating waves and their influence on wave power extraction and coastal protection was examined. Results show that a satisfactory hydrodynamic efficiency and coastal defense are realized simultaneously under oblique waves for this proposed system. A decline of hydrodynamic efficiency is found beyond a critical wavenumber, accompanied by the occurrence of the strong reflection phenomenon. The findings of this paper contribute towards the preliminary design of the hybrid breakwater-WEC system for the synergy effect between the wave energy devices and breakwaters. [ABSTRACT FROM AUTHOR]

In environmental valuation, the issue of the temporal stability of stated preferences to changes in environmental (dis)amenities is important because their results can be employed to inform decision-making. This includes cost–benefit analysis for large infrastructure projects such as coastal protection. A couple of studies have investigated stability of stated preferences over varying time periods. However, less evidence is available for temporal stability of stated preferences for (dis)amenities in uncertain times, i.e., times that are characterized by larger degrees of uncertainty regarding the (near) future. Using a choice experiment on coastal adaptation to climate change, this paper examines the test–retest reliability of individual preferences and resulting welfare estimates over the course of the Covid-19 pandemic. We do so by surveying the same respondents at two points in time five months apart during the ongoing pandemic. Using a latent class model, we find similar preference heterogeneity patterns but different class sizes. While the welfare measure of an adaptation scenario that focuses on safety increases across survey waves, scenarios that centre on recreation or nature have decreasing welfare effects. This suggests that individuals set other priorities in uncertain times. • We study temporal stability of stated preferences during the COVID-19 pandemic. • We record preferences for coastal adaptation to climate change at the Baltic Sea. • We find similar preference heterogeneity patterns for both survey waves. • In the second wave, however, more respondents focus on the heightening of dykes. • Overall, results point to an increased valuation of safety during uncertain times. [ABSTRACT FROM AUTHOR]

A rapid-calculation method O (1 0 3) ∼ O (1 0 4) times faster than a typical BEM (Boundary Element Method) model is presented for optimising an array (farm) of dual-purpose wave-energy converters (WECs) that both generate electricity and protect a coast. It is known that fast semi-analytical descriptions of the wave field are available based on the far-field approach for a widely-spaced wave farm involving point-absorber-type WECs of small sizes, for which scattered waves are negligible. However, these approaches are inept at dealing with "non-small" WECs with non-simple shapes, for which scattered waves can be both complicated and non-negligible. For these devices, this paper demonstrates that a fast semi-analytical description based on a "corrected" version of the far-field approach can still be crafted for an isolated device, with the help of a BEM model. This simple description is then used in an interaction theory for an array of devices, which requires no further input from BEM, hence reducing the computation time drastically. In an example, for an array of eight WECs, 1. 6 × 1 0 5 array configurations are calculated using a laptop computer within seven hours (this time included the time required to set up the far-field model for an isolated device), yielding an array featuring the largest "protection factor", which quantifies wave reduction along a given line downwave of the array. The calculated wave fields around the arrays can be validated against BEM results for the same arrays. Note that the time for searching for an optimum layout can further be reduced by two orders of magnitudes when a standard optimisation routine is used, for the wave farms considered in this paper. • A wave farm model based on far-field waves around an individual device. • Far-field waves are corrected by scattering term and involve nonlinear dissipation. • The wave farm model applies to wave energy devices with non-simple geometry. • The wave farm model is 1000–10000 times faster than a conventional simulation. • The fast model is able to optimise wave farms for coastal protection purposes. [ABSTRACT FROM AUTHOR]

Coastal structures, such as groynes and breakwaters, disrupt coastal processes and often promote sediment accumulation updrift and erosion downdrift. However, complex or different groyne designs, such as curved groynes can lead to different behaviours that are still poorly understood. This study investigated the short-term morphological changes caused by the construction of three sinusoidal groynes as a coastal restoration/defence measure at Icaraí Beach, Northeast Brazil. The methodology consisted of monthly field surveys using GNSS-RTK, UAS and high resolution CBERS-4A satellite imagery before, during and after completion of the defence structure. The results were compared with available wave data to provide a comprehensive understanding of the coastal behaviour. The curved shape of the groyne resulted in erosion and accumulation cells that were different (and in some cases opposite) to traditional structures. Beach formation and progradation was observed along a sheltered section of approximately 130 m of shoreline located downdrift, while severe erosion was recorded further downdrift, culminating in the partial loss of a property. The study highlights the challenges facing coastal protection measures and emphasises the need for sustainable solutions to mitigate future risks and prevent coastal degradation. [Display omitted] • Sinusoidal groynes cause beach erosion and deposition in unexpected ways. • Erosion and deposition cells in downdrift areas. • Groyne shadow zone experienced significant beach accumulation. • Further downdrift increased retreat rates in downdrift areas by a factor of 3–4. • Swell waves and rainfall contributed to internal beach success immediately after groyne construction. [ABSTRACT FROM AUTHOR]

This paper presents an analysis of the evolution of the legislation on coasts in Spain using the methodology of the cycle of public policies. This made it possible to recognize important differences in how the issue of coasts entered into the government agenda, the definition of the problem to be addressed and the design of each of the laws analyzed, mainly due to the influence of the political and economic context. The entry into the government agenda ranges from the need to take advantage of the coast to promote tourism, the recovery of State ownership of the maritime-terrestrial public domain (MTPD) and the attempt to recover private ownership of properties released from the MTPD. In the design, two important elements have been maintained in all three cases: the definition of public domain (PD) goods, and the establishment of easements on privately owned land. In the 1988 and 2013 Laws, the publicist and conservationist legal principles have been maintained, as well as the techniques of the PD and the impact on private rights over properties adjoining the MTPD. The implementation of the laws has been very contrasting. The first law was hardly implemented at all, while the two subsequent laws have been resolutely implemented by the state administration. Finally, the most important elements that are recognized in the evolution of the Coastal Laws is the protection of the PD and the affectation of private property through easements. However, that the legal framework is confusing as two current Laws coexist. [ABSTRACT FROM AUTHOR]

Typhoons pose threats to coastal wetlands, but the impacts on carbon stocks remain unclear. This study investigated typhoon effects on salt marsh carbon pools with different vegetation covers (harvested Spartina alterniflora , native Scirpus mariqueter , bare mudflat) in the Yangtze River estuary. During Typhoon Muifa (September 2022), significant erosion occurred in the Scirpus area while the harvested Spartina area experienced sediment deposition, indicating its stronger coastal protection capacity. Grain size analysis validated the geomorphic changes. The harvested Spartina area also captured coarser sediments from the mudflat. Wave data showed the amplified hydrodynamics during typhoons can transport more sediment into marshes. In the Scirpus area, surface sediments (0–15 cm) lost 43% organic carbon and 73% belowground biomass due to erosion. The deposited sediments after typhoons lacked the original high carbon content. In contrast, harvested Spartina areas maintained carbon levels despite intense hydrodynamics. The bare mudflat lost 43% total carbon after experiencing substantial erosion. This study demonstrates harvested Spartina areas effectively mitigated carbon loss and even facilitated carbon sequestration through enhanced sediment trapping during typhoons. With intensifying storm surges, seasonal harvesting of Spartina could balance coastal protection and ecological functions better than complete removal. The carbon sink capacity of sediments with native vegetation is vulnerable to typhoons due to limited resilience. Harnessing bio-geomorphic feedbacks is crucial for preserving blue carbon storage facing climate change. • Sediment sampling and UAV were combined to detect the impact of typhoon on morphological and carbon stock changes in salt marsh. • Harvested Spartina outperformed native Scirpus under storm surges for sedimentation and carbon preservation. • Harvested Spartina can enhance salt marsh carbon sequestration through bio-geomorphic feedbacks. • Salt marshes sensitive to erosion may exacerbate carbon loss during storm surge. • Seasonal Spartina harvesting can balance coastal protection and other ecological roles. [ABSTRACT FROM AUTHOR]

Community support for climate change adaptation projects markedly benefits effective protection. A relevant driver of community support is the perceived attribution of responsibility to individuals. If individuals attribute responsibility for adaptation to others, e.g. public authorities, this reduces the adaptation efforts of the individual, might induce preference uncertainty, and can lead to maladaptation. We study individuals' perceptions of personal responsibility and preferences for coastal protection in a setting in which individuals have little formal responsibility. To do so, we collect data from the Maldives, a small island development state with significant risks of seaborne hazards where responsibility for coastal protection formally rests with the central government without significant involvement of local communities. Using survey measures and a Discrete Choice Experiment (DCE), we investigate respondents' sense of personal responsibility and their preferences for climate change adaptation distinguishing between preferences for hard, man-made structures and soft, working-with-nature protection approaches. The results show that responsibility perception plays an important role for stated willingness to support protective measures. However, they further show a mismatch between formally assigned and perceived responsibility for protection with a majority of respondents having a strong sense of personal responsibility for protection. In addition, the DCE results indicate a misalignment of people's preferences and the measures implemented by the government. While the latter belong to the group of hard protection measures, the majority of respondents show a clear preference for soft protection. We discuss the implications of these findings and highlight the importance of a better understanding of drivers of responsibility perceptions. • We study how formally assigned and perceived responsibility affect coastal protection preferences. • In a DCE we find a significant role of perceived responsibility for protection motivation. • The results show a mismatch between formally assigned and perceived responsibility. • Community preferences are not aligned with implemented government measures. [ABSTRACT FROM AUTHOR]

Inclusion of ecosystem-based approaches in the governmental masterplan for tsunami mitigation in Palu, Indonesia may make the city a rare case study for ecological disaster risk reduction in tropical biodiversity hotspots. Such case studies are a key pillar of the United Nations (UN) Sendai Framework to protect coastal societies globally. [ABSTRACT FROM AUTHOR]

Wave Energy Converters (WECs) have the potential to serve dual purposes, generating power and protecting coastlines. Although traditionally the focus has been on maximizing power generation for cost-effectiveness, growing impacts of climate change have made coastal protection increasingly imperative. However, power production and coastal protection have been addressed separately, missing potential synergies. This paper addresses this gap by conducting a bi-objective analysis to investigate the interactions between power extraction and wave attenuation for a single Oscillating Surge Wave Converter (OSWC) and WEC farms of three and five units. A linear Power Take-Off (PTO) system, with passive and reactive control strategies, is examined. By varying the PTO parameters, we assess their influence on both power production and wave field attenuation. Results demonstrate a significant impact of the PTO choice on wave attenuation, with a similar trend observed for power production. This finding highlights the potential for a trade-off, where maximizing wave attenuation may come at the cost of moderate energy output. Furthermore, the interactions observed within the WEC farms enhance this trend. The study emphasizes the importance of a holistic approach to WEC technology development, promoting sustainable and resilient harnessing of wave energy resources, considering both power generation and coastal protection. [Display omitted] • Bi-objective analysis of power and wave attenuation for wave energy converters. • Analysis of the impact of the PTO on both objective functions. • Progressive analysis from the single WEC to WEC farms layouts. • Power production and wave attenuation interactions might benefit WEC farms. [ABSTRACT FROM AUTHOR]

The deceleration of early to mid-Holocene (10–7 cal. ka BP) relative sea-level rise (RSLR) played a key role in transforming coastal systems from estuaries to deltas. Palaeoenvironmental reconstruction of coastal evolution provide case studies that can help project the response of modern coastal systems to future RSLR. The response of deltas to future RSLR is particularly important to South, Southeast and East Asia which collectively contain 71% of the global coastal population living below 10 m in elevation and 75% of the global coastal floodplain population. However, few Holocene studies of equatorial delta systems exist. Here, we investigate the early to mid-Holocene coastal response to decelerating rates of RSLR through paleoenvironmental reconstruction of the Kallang River Basin, Singapore. We produce a multi-proxy (sedimentology, stable carbon isotope, XRF elemental ratios) record from sediment core MSBH01B to compare with the Holocene relative sea-level record for Singapore. We identify different phases of coastal response through the interplay between accommodation space (A) driven predominantly by RSLR and sedimentation rate (S). In the early Holocene rapid RSLR coupled with low sedimentation rates (A/S = 5.1 ± 0.3) led to mangrove disappearance in the Kallang River Basin coastal area within ∼300 years (9.5–9.2 cal. ka BP). Estuarine sediments were deposited from 9.2 to 8.8 cal. ka BP during continued high rates of RSLR coupled with highest sedimentation rates (A/S = 3.1 ± 0.8) as the coastline retreated. Prodelta sediments were deposited from 8.8 to 8.2 cal. ka BP during decreasing rate of RSLR and high sedimentation rates (A/S = 4.6 ± 5.2). Delta front sediments were deposited during this delta initiation phase from 8.2 to 7.6 cal. ka BP as during a period of low and consistent RSLR and sedimentation rates (A/S = 1.7 ± 0.2). Finally, a prograding delta started forming from 7.6 to 7.2 cal. ka BP during lowest rates of RSLR and sedimentation rates (A/S = 1.7 ± 0.2). Our record provides a case study of possible responses of modern delta systems under a spectrum of predicted sea-level rise scenarios and accompanying sedimentation rates. This study provides an estimated threshold A/S value of 1.7 for coastal retreat to inform policy and mitigation/adaptation measures for Singapore and a simple methodology to obtain local threshold values of other equatorial cities built on floodplain and/or delta systems. [Display omitted] • First study on the coastal response to Holocene relative sea-level rise (RSLR) for Singapore. • Coastal mangroves locally extinct within 300 years under RSLR of up to 15 mm/yr. • Delta initiation and progradation chronology agrees well with other studies in the region. • Study suggests A/S ratio of 1.7 as tipping point for coastal advance/retreat. • Aids adaptation measures against projected sea-level rise given similar rates during Holocene. [ABSTRACT FROM AUTHOR]

• Attenuation of high water levels (HWL) over restored saltmarshes can be limited. • Inside the MR, half the measurements revealed that HWL's were amplified. • HWL attenuation may be counteracted by MR scheme design and wind conditions. • HWL attenuation over the natural marsh was higher than previous field measurements. The managed realignment (MR) of flood protection on low-lying coasts, and the creation, or re-creation, of intertidal saltmarsh habitat between old and new, more landward sea defence lines is an intervention designed to help protect coastal infrastructure and communities against the impact of storm waves and surges. However, the effectiveness of such schemes has rarely been proven in the field. Environmental monitoring has generally been limited to the first few years after implementation and has focussed on sediment accretion and surface elevation change, vegetation establishment and habitat utilization, to the neglect of the study of biophysical processes, such as wave energy dissipation and High Water Level (HWL) attenuation. We address this knowledge gap by analysing HWL attenuation rates in saltmarshes from within, and in front of, the open coast MR site of Freiston Shore (Lincolnshire, UK). For this purpose, a suite of 16 pressure transducers was deployed along four sections (two within and two outside the MR) of identical setup to measure water level variations during the highest spring tides of the year 2017. Our results show that for the conditions encountered during the field monitoring period, the capacity of the Freiston Shore MR site to provide HWL attenuation was limited. HWL attenuation rates were significantly higher over the natural saltmarsh (in front of the MR), where HWL attenuation ranged between 0 and 101 cm km−1 (mean 46 cm km−1). Within the MR site, rates varied between −102 and 160 cm km−1 (mean −3 cm km−1), with even negative attenuation (i.e. amplification) for about half of the measured tides. We argue that the weak performance of the MR site in terms of HWL attenuation was a result of internal hydrodynamics caused by scheme design and meteorological conditions. The latter may have counteracted the HWL attenuating effect caused by the additional shallow water area provided by the restored saltmarsh. [ABSTRACT FROM AUTHOR]

Along the Upper Gulf of Thailand, coastal fences and breakwaters have been constructed using bamboo since 2005. Despite their potential benefits, bamboo structures disintegrate within seven years releasing floating debris which severely damages mangrove tree stems. The aim of the study was to investigate whether such stem damage resulted in the decline of Avicennia spp. stands along the Upper Gulf of Thailand. Tree health assessments were conducted to assess the probability of crown dieback in damaged and undamaged trees. Satellite-derived time-series of vegetation indices were used to detect long-term forest decline. In contrast to the unaffected landward mangroves, seaward mangroves were unable to recover from insect-induced defoliation events after the collapse of a nearby fence. Furthermore, there was a significantly higher probability that damaged trees showed signs of moderate-to-severe crown dieback. It is recommended that bamboo fences be secured by replacing individual stems before they become detached. • Debris from deteriorating coastal bamboo fences damage stems of mangrove trees. • Damaged trees are more likely show signs of crown dieback. • Seaward mangrove forests are declining. [ABSTRACT FROM AUTHOR]

Abstract Climate change is poised to exacerbate coastal erosion. Recent research has presented a novel strategy to tackle this issue: dual wave farms, i.e., arrays of wave energy converters with the dual function of carbon-free energy generation and coastal erosion mitigation. However, the implications of sea level rise – another consequence of climate change – for the effectiveness of wave farms as coastal defence elements against shoreline erosion have not been studied so far. The objective of this work is to investigate how the coastal defence performance of a dual wave farm is affected by sea level rise through a case study (Playa Granada, southern Iberian Peninsula). To this end, a spectral wave propagation model, a longshore sediment transport formulation and a one-line model are combined to obtain the final subaerial beach areas for three sea level rise scenarios: the present situation, an optimistic and a pessimistic projection. These scenarios were modelled with and without the wave farm to assess its effects. We find that the dual wave farm reduces erosion and promotes accretion regardless of the sea level rise scenario considered. In the case of westerly storms, the dual wave farm is particularly effective: erosion is transformed into accretion. In general, and importantly, sea level rise strengthens the effectiveness of the dual wave farm as a coastal protection mechanism. This fact enhances the competitiveness of wave farms as coastal defence elements. Highlights • Dual wave farms for renewable energy production and coastal protection. • Assessment of the performance of dual wave farms under sea level rise (SLR). • SLR strengthens the effectiveness of wave farms as coastal defence mechanisms. • Better strategy for mitigation of climate change than hard engineering solutions. [ABSTRACT FROM AUTHOR]

This study investigates where coastal green infrastructure (CGI) can provide highest potential coastal protection benefits, while considering its vulnerability to environmental conditions. CGI provides important coastal protection benefits, however, influenced by climate change and human activities, these benefits are highly threatened. This vulnerability of CGI was not considered in the previous studies. This study provides a framework and an indicator-based methodology to fill this gap. A review of the literature was conducted to identify the parameters used to measure CGI's coastal protection benefits and vulnerability. The content of the references that contained specific parameters related to CGI's role in coastal protection and vulnerability were systematically reviewed. A total of 11 indicators were identified and organized into two indices: CGI coastal protection index, and CGI vulnerability index. The indices were synthesized using a 2 × 2 matrix to identify areas with the highest coastal protection potential. Analysis was conducted for the 74 most populated coastal communities in the Salish Sea region. Results indicate that the British Columbia communities in the Salish Sea region have high potential to utilize CGI for coastal protection. CGI in 59% of the communities in British Columbia and 36% in Washington State can provide high coastal protection benefits, even when vulnerability is accounted for. • Coastal green infrastructure (CGI), provides essential flood and erosion protection benefits. • The vulnerability of CGI has mostly been overlooked in the previous studies investigating CGI's protection benefits. • Geomorphology, coastal and land use indicators were used in two indices to identify CGI coastal protection potential. • CGI may not be the ideal tool for protection of large cities and CGI in BC had more potential than in WA. [ABSTRACT FROM AUTHOR]

Abstract Increased coastal development and rising sea levels as a result of continuing climate-change put coastal regions at risk from flooding and inundation. A common mitigation response is the construction and upgrade of hard coastal protection structures, such as breakwaters, seawalls, and groynes. The alteration of the coast, together with the introduction of novel materials into coastal waters can negatively impact adjacent habitats and associated organisms. The implementation of management plans that involve scientists, as well as a variety of other stakeholders offer an opportunity to minimise adverse effects to biodiversity or even enhance it, while still protecting infrastructure and people. This study examines the management of an Australian breakwater upgrade and the progressive design finding process, including stakeholder engagement, determination of assessment criteria, and environmental impact assessment. In the course of the latter, scientific research led to the rediscovery of a presumed extinct algal species, Nereia lophocladia , which created an additional challenge and temporarily halted the upgrade. To accommodate this, the breakwater design solution was modified to avoid any impacts on the algal population and, in order to maximise the species' survival, novel ecological engineering approaches were proposed as mitigation strategies. Our case study underpins the value of evidence-based conservation and cooperation among stakeholders as important tools for minimising ecological impacts from coastal infrastructure upgrades. Highlights • Improved coastal protection is needed to safeguard coastal assets from rising sea levels and storms. • Existing coastal protection structures can be improved through engineering upgrades. • Upgrades to coastal protection structures can impact biodiversity and threatened species. • Evidence-based management can improve environmental outcomes of coastal protection structure upgrades. • Ecological engineering can contribute to conservation efforts when multidisciplinary management is utilised. [ABSTRACT FROM AUTHOR]

Ocean wave energy is a rapidly developing sector and has the potential to contribute a significant share to the global green energy transformation. However, nearshore coastal regions, in which energy harvesting devices are most commonly installed, experience low wave energy densities compared with offshore regions. This is a significant impediment to the commercialisation of the wave energy sector. This study proposes a low cost solution to these low wave energy density distributions at nearshore environments whilst simultaneously providing an effective coastal protection system. A parabolic energy concentrator wall is coupled with an oscillating water column wave energy converter. The parabolic concentrator reflects and consolidates the incident wave energy to a focal point, at which the wave energy convertor is positioned. Experimental investigations, supported by numerical modelling results confirm energy conversion performances significantly exceeding hitherto recorded wave energy converter efficiencies, with wave-to-wire conversion efficiency in the laboratory model exceeding 70%. Furthermore, the parabolic concentrator wall has an ancillary purpose to act as a shoreline protection barrier. The simplicity of design, high energy conversion efficiencies, and inherent shoreline defensive aspect of the proposed system deems it particularly suitable for deployment to remote island nations, or coastal communities vulnerable to coastal erosion that presently rely on fossil fuel consumption for energy generation. • A novel OWC WEC-parabola-breakwater system is developed. • The parabolic breakwater focusses the wave energy to the OWC WEC. • Physical experiments are supported by compressible numerical modelling. • The system achieves capture-width-ratios exceeding 2.0. • Wave-to-wire efficiencies of 0.7 are revealed. [ABSTRACT FROM AUTHOR]

Coastal water pollution has a significant impact on sedimentary environments, altering the microstructure of clay-rich sediments and further destabilizing river-dominated delta strata. However, the understanding of the microstructure of clay sediment, influenced by burial depth and pore water chemistry, remains limited due to challenges in quantitatively analyzing clay texture at varying depths. The perturbable of clay microstructures, and the cost of deep sampling have hindered such efforts. To address this issue, this study aims to quantitatively analyze the clay anisotropy at different depths and pore water chemistry through laboratory-simulated sediment samples by using centrifugal modeling and 2DXRD technology. The results suggest that 1DXRD (Orientation index) is prone to generating incorrect conclusions, whereas 2DXRD (pole density) yields more precise and reliable results. Specifically, the results indicated that the introduction of salt ions promoted clay precipitation and stabilized the oriented microstructure at shallower depths. In acidic solutions, clay sediment still contained a certain proportion of edge to face (EF) microstructure at depths less than 6 m, suggesting higher soil thixotropy and lower strength than that of clay sediments in other types of solutions. Overall, our findings provide valuable insights into the relationship between water pollution, delta disappearance, and ocean acidification, highlighting the urgent need for effective environmental management strategies to prevent further damage to fragile coastal ecosystems. [Display omitted] • The shrinking of deltas is closely related to ocean acidification. • Pore water chemistry still significantly influences the microstructure of sediment even at deep burial depths. • 2DXRD provides accurate evaluation of kaolinite sediment microstructure anisotropy compared to 1DXRD. • "pH - NaCl ion concentration - burial depth" spatial fabric map of kaolinite was first developed. [ABSTRACT FROM AUTHOR]

Assessing the influence of marshes on mitigating flooding along estuarine shorelines under the pressures of sea level rise requires understanding wave transformation across the marsh. A numerical model was applied to investigate how vegetated marshes influence wave transformation. XBeach non-hydrostatic (XB-NH) was calibrated and validated with high frequency pressure data from the marsh at China Camp State Park in San Pablo Bay, California (USA). The model was used to examine how marsh and hydrodynamic characteristics change the potential for marshes to mitigate wave driven flooding. Model results demonstrate that hydrodynamics, vegetation, and marsh width influence wave transformation most, while marsh morphology parameters such as elevation and slope had least effect. Results suggest that in the range of settings explored here (incident wave heights ranging from 0.5 to 3 m and water levels ranging from current mean higher high water to 3 m above current mean higher high water), in comparison to wave propagation over an unvegetated mudflat, marsh vegetation reduces runup by a median of 40 cm and wave height by a median of 35 cm. Results illustrate how marshes can be strategically utilized to provide flood reduction benefits. • We examined how marsh and hydrodynamic characteristics change the potential for marshes to mitigate wave driven flooding. • Hydrodynamics, vegetation, and marsh width influence wave transformation most. • Marsh morphology parameters such as elevation and slope had least effect. • Marsh vegetation reduced runup by a median of 40 cm and wave height by a median of 35 cm. • Results illustrate how marshes can be strategically utilized to provide flood reduction benefits. [ABSTRACT FROM AUTHOR]

Understanding how saltmarshes and mangroves reduce movement inland of high water levels resulting from storm surges and tsunamis is vital for disaster planning and predicting impacts of sea level rise. This has been examined using both site-specific hydrodynamic models and field measurement, but an overarching theoretical framework is lacking. To address this, we provide a simple analytical solution for the propagation of a surge across a uniform wetland surface. The distance that flooding penetrates inland is reduced by the presence of vegetation and increases with both surge height and duration. After 4 h, 1 m and 5 m floods will travel 5.5 and 19.1 km inland over saltmarshes respectively. Penetration distances are approximately 2.5 times smaller for mangroves and are lower for short duration events, emphasising the effectiveness of mangroves in reducing impacts of tsunamis. The (absolute) reduction in water level per km depends strongly on surge duration and vegetation type, but only weakly on surge height. In a surge rising by 2m over 1 h, the reduction in water level over a saltmarsh can be as high as 45 cm/km, but reduces as surge duration increases or where the width of the low-lying land is small enough for the surge to fill "the bathtub". So water level reductions will be greatest during short duration events or when large widths of wetland are maintained. Several studies report much higher rates of attenuation, but these involve up to 50-fold extrapolation from measurements made over short distances or misinterpretations of primary sources. Once these are excluded, field data are consistent with our model results. • Saltmarshes and mangroves reduce inland movement of water during surges and tsunamis. • Water level reductions are greatest for short duration events. • Flood protection, particularly by mangroves, is substantial for tsunamis. • Protection against storm surges requires wetlands that are several to many km wide. • Extrapolation of measurements over short distances grossly exaggerate water level reductions per km. [ABSTRACT FROM AUTHOR]

Training walls to improve navigability at river mouths alter natural sediment transport regimes, occasioning morphological changes in the nearby littoral zone. In addition, harbor channels and shorelines are susceptible to on-going changes in global circulation conditions and large-scale engineering interventions. Here we present a process-based modeling approach to determine the relationship between spatial patterns of erosion and deposition, seasonal river discharge, and the geometry of coastal defenses. The study uses the Magdalena River delta as an example, where the redistribution of freshwater and sediments after the construction of the "Tajamar" training wall heralded significant morphological changes in the area. The numerical experiments are used to describe how the erosion and deposition patterns within the estuary and delta of the Magdalena River are linked to the seasonal cycle of the Magdalena River and to the geometry of the hard structures. We demonstrate that the construction of the Tajamar and complementary hard structures would have decreased depositional fluxes in the littoral zone, leading to the observed shoreline retreat and disappearance of an extensive coastal lagoon system. It is shown that an aperture in the training walls may help restore the wetlands without compromising navigability. In addition, projected increases in mean sea level are shown to decrease velocities within the lower estuary, potentially causing increased sedimentation within the channel and more complex conditions for the management of safe navigation over the Magdalena River estuary. • Seawall construction on the Magdalena River, Colombia, resulted in the redistribution of freshwater and sediments. • Numerical experiments provide evidence that shoreline retreat was caused by the altered sedimentation regime. • A diversion system in the training walls may help restore sediment supply to the shorelines without risking navigability. • Sea level rise may increase rates of sedimentation within the estuary. [ABSTRACT FROM AUTHOR]

Abstract A common form of coastal protection in New South Wales, Australia, is the rubble mound breakwater. This consists of quarried rock or unreinforced concrete armour units. However, increased impact forces on these structures due to greater storm surge levels that are predicted by global warming models, suggest that they will require strengthening. Traditionally steel bar reinforcement is used to strengthen concrete; however, as steel is particularly susceptible to corrosion in aggressive coastal environments, it is not a robust solution. This paper reports on the potential of using macro-synthetic fibre reinforcement in reinforcing of breakwater armour units, in lieu of traditional steel reinforcing bars. To this end, a programme to ascertain the tensile capacity of 0.6 percent and 1.0 percent by volume of concrete reinforced with macro-synthetic fibres was implemented. The behaviour of this synthetic fibre reinforced concrete in Dolos type breakwater armour units was then examined using the finite element analysis software ATENA. The results of the numerical analysis indicate that the addition of synthetic fibres at these volume percentages into concrete armour units improves the post peak response under impact loading by a factor of two to three, compared with unreinforced units. Furthermore, the addition of fibres significantly reduced the maximum crack width for the same number of impact loadings and allows the units to withstand larger crack widths before failure. Highlights • This paper assesses the effectiveness of Dolosse concrete armour units reinforced with 0.6 percent and 1.0 percent of macro-synthetic fibres. • An experimental programme was developed to investigate the post crack capacity of the synthetic FRC. • The experimental results were used to simulate the properties of synthetic FRC in Dolosse breakwater armour units. • The addition of fibres significantly improves the breakwater armour unit's capacity to withstand higher and more numerous impact loads. [ABSTRACT FROM AUTHOR]

Highlights • Coastal and marine infrastructure are typically built with little consideration to the nature of urban marine habitats they generate. • This study demonstrates application of environmentally sensitive technologies for ecological enhancement of coastal infrastructure. • Innovative bio-enhancing concrete mix, surface textures and designs were integrated into the design of constructive ECO seawall panels. • The ECO panels significantly increased the habitat value, diversity and richness compared to standard concrete seawalls. • Findings highlight the importance ecological engineering considerations in future planning and design of coastal development schemes. Abstract With nearly 60% of the human population concentrated around the coastlines, alongside growing threats from sea level rise and increased storminess, accelerated coastal development is inevitable. As most marine flora and fauna reside in coastal areas, anthropogenic changes to coastlines are a key reason for loss of coastal habitats, and associated ecosystem services. While coastal infrastructure such as seawalls or breakwaters add significant amounts of hard substrate for marine organisms, they do not support similar species assemblages to those of natural habitats. This is mainly due to design features related to steep slopes, low structural complexity, and high homogeneity, all of which are rarely found in natural habitats. This study provides an example for seascape architecture of coastal structures using ecologically sensitive designs and concrete technologies that enhance the structures’ biological and ecological value while contributing to structural integrity. Four 1.5 mx0.8 m seawall panels made of bio-enhancing concrete with high structural complexity were deployed in an active marina (Herzliya, Israel). The panels, spanned from the Mean High Higher Water (MHHW) down to the sublittoral zone, were surveyed 2, 7, 12, 18 and 22 months post deployment using 0.3 × 0.3 m quadrats in both intertidal and sublittoral zones of each panel. Bio-enhanced panels were compared to fixed control quadrats comprised of scraped sections of the original concrete marina seawall. Results demonstrated the effectiveness of applying ecological considerations for biological and ecological enhancement of active infrastructure. All community parameters examined (live cover, richness, biodiversity) were significantly higher on bio-enhanced panels compared to controls. Moreover, mobile invertebrates and resident fish species were clearly enhanced through design aspects (holes and crevices) of the bio-enhanced panels. The study provides an example of an emerging approach of assimilating ecological considerations into the design and construction of working waterfronts and active coastal infrastructure, thus reducing their ecological footprint without compromising their operational performance. [ABSTRACT FROM AUTHOR]

Abstract A dune restoration program was initiated by the City of South Padre Island, Texas in 2010 consisting primarily of plantings of Sea Oats, Uniola paniculata , and Bitter Panicum, Panicum amarum , and has continued annually thereafter. These restoration efforts were evaluated by comparing selected metrics of ecosystem structure and function among reference and restoration plots ranging in age (time after planting) from 2 to 5 years. Plant and animal communities were examined using a combination of quadrat sampling, funnel traps, pit-falls, and sweep nets. Soil organic content and soil electrical conductivity were also measured. Dune volumes and heights were calculated using a 2013 Lidar DEM. Plant communities were similar across 2 and 4 year-old plots but differed markedly among 2 and 5 year-old plots and between all restoration plots and undisturbed reference plots. After 5 years, restoration plots had 15 plant species, while reference plots had 19. Animal communities followed a similar trend in which all restoration plots differed from the reference plots with the exception of 5 year-old plots which were similar. More time seems necessary for restored dunes to accumulate soil organic matter at levels similar to natural dunes which is still about three times higher. There was a significant positive correlation between plot age and dune heights. These results suggest the native dune plant revegetation as implemented by the City of South Padre Island from 2010 to 2015 is successful in fostering plant and animal community succession and potentially increasing coastal resiliency. Highlights: - Revegetation efforts quickly improve habitat for most local dune plant and animal species. - Plant community in restored dunes remains different compared to references dunes. - Soil organic matter is much lower in restored dunes after five years. - Revegetation with few foundation species fosters the return of native dune communities. [ABSTRACT FROM AUTHOR]

While sea-level rise could flood and displace hundreds of millions of people, a range of studies have shown that adaptation in the form of coastal protection can be very effective and cost-efficient in reducing coastal impacts. All of these studies have, however, investigated adaptation decisions within one given sea-level rise and one given socio-economic scenario, which is at odds with the actual decision problem coastal planers are facing in that they need to decide across scenarios. This study takes first steps at filling this gap by assessing for which parts of the global coastline coastal protection is economically robust across 21st century global mean sea-level rise from 0.3 m to 2.0 m, the five Shared Socio-economic Pathways and discount rates from 0 to 6%. We find that for 92,500 km of the global coastline it is economically robust to invest in protection (i.e. protection is cheaper than not protecting under every scenario considered). While these 92,500 km cover only 13% of the global coastline, they account for 90% of global coastal floodplain population and for 96% of assets in the global coastal floodplain. For 451,000 km of the global coastline (65%) covering 0.2% of coastal floodplain population and 0.2% of coastal floodplain assets globally, it is economically robust not to invest in protection. Our results suggest bifurcating coastal futures. On the one hand, richer, densely populated and urban areas are likely to be protected through higher and higher dikes. On the other hand, poorer rural areas will struggle to maintain safe human settlements and are likely to eventual retreat from the coast, raising difficult policy questions concerning transfer payments, compensation and liability for loss and damage. [ABSTRACT FROM AUTHOR]

Wave attenuation is a central process in the mechanics of a healthy salt marsh. Understanding how wave attenuation varies with vegetation and hydrodynamic conditions informs models of other marsh processes that are a function of wave energy ( e.g. sediment transport) and allows for the incorporation of marshes into coastal protection plans. Here, we examine the evolution of wave height across a tidal salt marsh in San Francisco Bay. Instruments were deployed along a cross-shore transect, starting on the mudflat and crossing through zones dominated by Spartina foliosa and Salicornia pacifica . This dataset is the first to quantify wave attenuation for these vegetation species, which are abundant in the intertidal zone of California estuaries. Measurements were collected in the summer and winter to assess seasonal variation in wave attenuation. Calculated drag coefficients of S. foliosa and S. pacifica were similar, indicating equal amounts of vegetation would lead to similar energy dissipation; however, S. pacifica has much greater biomass close to the bed (<20 cm) and retains biomass throughout the year, and therefore, it causes more total attenuation. S. foliosa dies back in the winter, and waves often grow across this section of the marsh. For both vegetation types, attenuation was greatest for low water depths, when the vegetation was emergent. For both seasons, attenuation rates across S. pacifica were the highest and were greater than published attenuation rates across similar ( Spartina alterniflora ) salt marshes for the comparable depths. These results can inform designs for marsh restorations and management plans in San Francisco Bay and other estuaries containing these species. [ABSTRACT FROM AUTHOR]

This paper presents a new approach to guiding coastal stakeholders about making informed decisions about Disaster Risk Reduction (DRR) measures and alternatives. As part of the RISC-KIT project and tool box, the paper presents a holistic DRR measure approach including the biophysical environment, governance aspects and practical examples from coastal areas in Europe and elsewhere. The guide (see: www.coastal-management.eu ) is addressed to a wide variety of coastal stakeholders with a different level of knowledge about DRR measures with the aim to provide guidance and information. The paper gives an overview of the overall structure of the guide. [ABSTRACT FROM AUTHOR]

Ecosystem-based coastal protection by means of conserving, restoring or creating intertidal ecosystems that attenuate waves and stabilize shorelines, offers a promising way to climate proof coastlines for the future. The Pacific oyster ( Crassostrea gigas ) is an ecosystem engineering species, which is known for its wave attenuating and sediment trapping ecosystem services, but it remains unknown to which extent this is conditional. We aim to test the hypothesis that the ecosystem engineering effect concerning sediment trapping and stability by oyster reefs is conditional, and can be predicted based on i) local physical forcing, ii) morphological characteristics of the tidal flat, and iii) biological characteristics of the oyster reef. Analyses of long-term sediment accretion patterns on natural intertidal oyster reefs at the Oosterschelde basin (The Netherlands) showed that this ecosystem engineering effect is strongest on tidal flats under erosional conditions, lower aspect ratio (i.e., relative long and narrow reefs), relatively closed reefs (i.e., few open patches) and higher coverage of oysters within reef patches. The ability of C. gigas to shape the environment thus depends both on biotic and abiotic conditions, meaning that oyster reefs only work under specific conditions for erosion control. Overall, our results provide baseline understanding for ecosystem management aimed at affecting sediment dynamics, thereby contributing to a better understanding for designing ecosystem-based solutions under different abiotic and biotic conditions. In addition, present study provides a clear example of how we need to gain a better understanding of the conditionality of ecosystem services in general, to be able to create and restore ecosystems for obtaining their services. [ABSTRACT FROM AUTHOR]

While there is considerable literature on coastal adaptation, there is less scholarly attention for how social capital, interactive governance, and ecosystem-based approaches can be combined to promote inclusive development. Hence, this paper examines contemporary efforts to protect coasts in Demak, northern Java, Indonesia, which are threatened by coastal erosion induced flooding, through large-scale planting of mangroves. We argue that the success of such ecosystem-based approaches depends on wide-spread civil society participation. Our analysis of the structure of bonding, bridging and linking capital in Demak reveals that although some local groups may lack bonding and bridging capital, their ability to acquire linking capital enables them to monopolise resources from the state and international NGOs for mangrove plantings; this negatively effects the cohesion of the coastal protection program and therefore its effectiveness and inclusiveness as mangrove groups protect their own areas. The paper shows that an understanding of the social capital of different local groups can enable a better understanding of how to engage them in ecosystem based governance. [ABSTRACT FROM AUTHOR]

Decision-making in a coastal socio-ecological system involves managing a site-specific complexity arising not only from the interaction between hydrodynamic and morphological conditions, but also from the interactions between human structures and ecological systems, as well as the conflicting needs and interests of local actors. In addition, the projections of climate change impacts on coastal systems have a degree of uncertainty, which increases the general unpredictability of coastal dynamic behaviour, and adds a layer of complexity to the decision-making process. Scientific knowledge can help reduce some of the inherent uncertainties, and is essential when it comes to making sound decisions on the choice of appropriate coastal defence measures (CDMs) that are adapted to specific coastal environments and improve the resilience of coastal communities. This paper is based on a meta-analysis of 355 CDMs case studies drawn from 301 publications. From these published case studies, the objectives were to analyze the geographical and physical contexts in which CDMs monitoring was carried out and, based on the findings, to recommend areas of improvement necessary to help make sound decisions in any type of coastal environment. The meta-analysis showed that study sites are not evenly distributed around the world. Most originate from Europe (n = 106), the USA (n = 151) and Australia (n = 30), while few studies have been carried out in Africa and Asia where dense population resides in high-risk zones. Also noticeable is the absence of sites in high latitude climates where ice plays a major role in the erosion process. Five basic variables (coastal type, sediment type, wave characteristics, tidal range, and currents or sediment transport characteristics) are used in publications to characterize study sites according to their physical components. However, only 13 of the 355 sites included a complete characterization using the 5 variables, of which coastal and sediment types are the most frequently identified (77.2% and 72.7% respectively). In general, CDMs are studied in the context of unconsolidated low shore (59.4%) and in sandy environments (74.6%). Information on tidal range, wave climate, and currents, or sediment transport characteristics, is much scarcer. Since 1990, 3 of the 10 CDMs identified in the studies have received more attention than the others; these are beach nourishments, seawalls and breakwaters, with respective cumulative study sites of 164, 67 and 50. The geomorphological effects of CDMs are the most studied (55.1%), followed by ecological (31.2%), hydrodynamic (9.1%), and social (4.6%). Overall, this meta-analysis helped identify knowledge gaps regarding geographical and physical contexts in which CDMs monitoring was held. It also gave an indication of the kind of improvement necessary for global-scale adaptation planning, and for a better decision-making process to reduce coastal risks in the most vulnerable coastal communities. Finally, the analysis shows that 4.4% of the studies on defence measures include monitoring of their effects on the coastal zone. A conceptual scheme is proposed for the evaluation of adaptation solutions based on the global monitoring of coastal zones to measure coastal change trajectories in the context of climate change. [ABSTRACT FROM AUTHOR]

Beach ecosystem provides services that produce substantial economic value. Different functions of beach resources (recreation and tourism, amenity, coastal protection, biodiversity, etc.) perform inherently different characteristics and contribute diversely to human welfare and fortune. Yet, there have been rare quantification estimations for economic contributions of beaches to human life. Here, framework of beach ecosystem services based on key functions is established, then a series of integrated quantification methods are summarized by published literature and a few novel estimations. Economic contributions of beach resources are obtained through application in fifty-nine coastal cities of China in recent ten years. Spatial added values in real estate benefiting from beaches are separated out economically for the first time. In China, beach resources of 3100 km generate an economic value of at least ¥4.00 × 1012 ($579.60 × 109) during the time interval 2010–2019. Furthermore, legislation, international tourism competitiveness, beach nourishment and restoration issues are discussed; dynamic pattern and healthy-recycled beach economy are creatively proposed according to the needs of sustainable development. This study explores the interface between ecosystem services and economics for beach resources, provides straight recognition upon beaches' economic contribution (least estimation), and promotes understanding of social and natural impacts on China's beach economy. • A holistic framework of economic estimation for beach resources is established and applied with time and space in national scale. • Spatial added value in real estate benefiting from beach resources is separated out of housing price in China's coastal cities for the first time. • Dynamic pattern and healthy-recycled beach economy are creatively proposed according to the needs of sustainable development. [ABSTRACT FROM AUTHOR]

Management and restoration of mangrove forests to protect coasts are promoted in many countries, including Indonesia. Indonesian mangrove forests are actively restored and managed by local communities for their ecosystem services, including coastal protection. Whether community-based mangrove management (CBMM) is effective is still debated. Our study analysed the effectiveness of different CBMM practices in four Central Javan communities by analysing the capacity of their mangrove forests to protect against coastal hazards. We used complementary interviews, field assessments and literature reviews to collect the necessary information. The overall CBMM performance and success significantly differed for each community's mangrove rehabilitation effort and the resulting coastal protection service. Of the four communities, Bedono performed best in terms of mangrove coverage, forest structure and restored coastal protection service. This is explained by multiple factors, such as application of long-term and integrated CBMM approaches, involving appropriate maintenance and additional measures to reduce wave energy. Our results can help governments, practitioners and communities to better understand the factors that contribute to CBMM's success and failure when restoring and managing mangrove forests and protecting coasts. • Community-Based Mangrove Management can achieve enhanced coastal protection. • Long-term and integrated approaches are needed for enhancing coastal protection. • Additional protective measures are necessary for eroding coastal areas. • Strategic collaboration between institutions is critical for sustainable results. [ABSTRACT FROM AUTHOR]

We investigated how lateral erosion control, measured by novel photogrammetry techniques, is modified by the presence of Spartina spp. vegetation, sediment grain size, and the nutrient status of salt marshes across 230 km of the Italian Northern Adriatic coastline. Spartina spp. vegetation reduced erosion across our study sites. The effect was more pronounced in sandy soils, where erosion was reduced by 80% compared to 17% in silty soils. Erosion resistance was also enhanced by Spartina spp. root biomass. In the absence of vegetation, erosion resistance was enhanced by silt content, with mean erosion 72% lower in silty vs . sandy soils. We found no relevant relationships with nutrient status, likely due to overall high nutrient concentrations and low C:N ratios across all sites. Our results contribute to quantifying coastal protection ecosystem services provided by salt marshes in both sandy and silty sediments. [ABSTRACT FROM AUTHOR]

A management policy adopted by the Kien Giang Province, Vietnam, is to allocate mangroves areas using contracts with local community members who are dependent on mangrove resources for both mangrove protection and livelihood improvement. However, community members have not made the best use of the allocated areas, and mangroves have not been well protected. The policy is due to be revised in late 2016, as is legally required. This study used mixed methods to review the policy and its implementation with respect to mangrove protection requirements and use of mangroves for livelihood improvement and to provide recommendations for sustainable mangrove management in Kien Giang. The policy and its implementation is demonstrated to be a constraint to achieving its goal. Limited understanding of the policy of contractees resulted in ineffective and inefficient aquaculture and mangrove protection in almost all areas. Permitted thinning and selective harvests led to the creation of substantial gaps and disconnections in the established mangroves, making the entire coastline vulnerable to coastal erosion. Improper technical guidance on the configuration of mangrove allocations, and mangrove protection and transplantation methods resulted in the mangrove protected areas being fragmented and vulnerable to erosion. Permitted thinning and selective harvest practices should be reviewed to ensure adequate resilience and protection of mangrove areas, especially on critically eroding areas. Proper law enforcement should be put in place to ensure contracts are adequately implemented. Allocation and/or transferal of areas less than 1 ha must be discontinued in the future to avoid further defragmentation and degradation. Technical guidance on configuring allocated mangrove areas should be established and incorporated into the updated policy that would help improve the effectiveness of the policy, and address problems relating to strengthening resilience and protection of mangrove areas in Kien Giang Province, Vietnam. Similar programs using mangrove area allocation to individuals and households in response to mangrove area loss exist elsewhere in the Mekong delta. Understanding the reasons for the very limited success of the Kien Giang program and local co-investigation in drawing lessons learnt can help guide other similar programs elsewhere in the Mekong Delta region. [ABSTRACT FROM AUTHOR]

To fulfil international conservation commitments, governments have begun to recognise the need for more proactive marine planning policies, advocating sensitive engineering design that can deliver secondary benefits above and beyond the primary purpose of developments. In response, there is growing scientific interest in novel multi-functional coastal defence structures with built-in secondary ecological and/or socio-economic benefits. To ensure research efforts are invested effectively, it is first necessary to determine what secondary benefits can potentially be built-in to engineered coastal defence structures, and further, which of these benefits would be most desirable. It is unlikely that secondary benefits are perceived in the same way across different stakeholder groups. Further, their order of priority when evaluating different options is unlikely to be consistent, since each option will present a suite of compromises and trade-offs. The aim of this study was to investigate stakeholder attitudes towards multi-functional coastal defence developments across different sector groups. A preliminary questionnaire indicated unanimous support for implementing multi-functional structures in place of traditional single-purpose ones. This preliminary survey informed the design of a Delphi-like study, which revealed a more nuanced and caveated level of support from a panel of experts and practitioners. The study also elicited a degree of consensus that the most desirable secondary benefits that could be built-in to developments would be ecological ones - prioritised over social, economic and technical benefits. This paper synthesises these findings, discusses the perceived barriers that remain, and proposes a stepwise approach to effective implementation of multi-functional coastal defence developments. [ABSTRACT FROM AUTHOR]

The risks from climate change are ever-growing, especially in more vulnerable and exposed regions such as coastlines. The rise in sea level and increase in the frequency and intensity of climate-induced coastal hazards are threatening the increasing coastal populations. Brazil, with its 8,500 km of coast, is one of the countries most at risk from coastal flooding and erosion. Nature-based solutions have been suggested as climate adaptation strategies with the greatest potential to counteract coastal hazards stemming from sea-level rise and safeguard coastal cities. However, there is still a knowledge gap in the scientific literature on the effectiveness of nature-based solutions, especially at large spatial scales in Central and South America. Here, we assessed the risks from climate-induced hazards of coastal erosion and flooding related to sea-level rise on the Brazilian coast, and the effectiveness of nature-based solutions as climate adaptation strategies. We reveal that nature-based shoreline protection can reduce by 2.5 times the risks to the Brazilian coastline. The loss of existing natural habitats would substantially increase the area and population at risk from these climate-induced hazards. Worrisomely, legal mechanisms to protect these natural habitats are few and being weakened. Only 10% of the coastal natural habitats are within protected areas, and these alone do not ensure coastal protection, as our results indicate that the loss of unprotected natural habitats has about the same risk as the total absence of natural habitats. Our results warn of the severe consequences of the continued loss of natural habitats along the coast. Thus, actions towards the maintenance and protection of coastal habitats are paramount for climate adaptation and to ensure the well-being and livelihoods of coastal populations. Brazil has a central role in demonstrating the benefits of strategies based on nature-based solutions for shoreline protection, favoring their implementation worldwide. We provide both the natural habitat maps and the maps with model results with spatial and numerical information so readers can explore the relations between the natural habitats and coastal risk indexes at a sub-national level and foster their use by local stakeholders. [ABSTRACT FROM AUTHOR]

Under uncertainty about the kind, extent, or time frames of coastal threats, efficient protection requires measures that are effective in time and flexible enough to assure protection even if conditions change over time. Existing protection options are unable to offer both attributes simultaneously, creating a trade-off between short-term and long-term effectiveness in protection choice. This paper investigates the role played by differences in the temporal effectiveness of coastal protection measures in the choice of protection modes. Results from a discrete-choice experiment implemented in Papua New Guinea suggest that respondents have a strong preference for long-term over short-term effectiveness; an urgency to protect cannot be identified. Using incentivized preference measures for patience and risk-aversion as well as sociodemographic controls, we account for taste heterogeneity and validate the robustness of our results. • Adaptation to climate change requires decision making under intertemporal uncertainty. • Our DCE focuses on the role of temporal effectiveness in a developing country context. • Results suggest strong preferences for long-term over short-term effectiveness. • An urgency to protect cannot be identified. • Results are robust to including revealed preference measures for patience and risk. [ABSTRACT FROM AUTHOR]

Among the many activities in the recent efforts to evaluate coastal resiliency is the study of the capacity of wetlands and coastal marshes to attenuate storm surge. The development of an acceptable index or attenuation rate for coastal flooding is complicated by the many factors that contribute to maximum surge elevation, inundation extent and duration, including storm characteristics (e.g. track, size, forward speed, duration, central low pressure) and local features including topo-bathymetry, land-cover, barrier islands, channels, lagoons and inlets. For this study, we investigated the impact of spatial scaling, mesh resolution, storm characteristics and bottom friction on storm surge in wetland areas in the barrier island system of the Delmarva Peninsula using the coupled hydrodynamic-wave model (ADCIRC + SWAN). Synthetic storms derived from hindcasts of historical storms affecting this region were used for model forcing through multi resolution meshes recreating the complex wetland areas exposed to varying degrees of ocean surge through natural breaks in the barrier islands. Sensitivity to mesh resolution and bottom friction were evaluated for regional attributes and storm characteristics, confirming the results of previous studies. Results suggest inlet configuration and exposure to ocean surge are dominant factors for surge propagation through small scale wetlands and barrier island systems for weak to moderate storms. Attenuation rates observed for weaker storms, were influenced secondarily by the complex geometry of channels, lagoons and the presence and continuity of marshes. Results evaluating greater surge produced by stronger storms, even of less than a meter of storm surge increase, indicate that the mitigating impacts of local features are greatly diminished. Our results indicate that although the back bays systems in the Delmarva Peninsula and similar ecosystems in the US East Coast could provide storm surge attenuation for annual storm events, its use in coastal engineering protection may require a case by case analysis due to the high dependence on local characteristics. [ABSTRACT FROM AUTHOR]

In response to flood risk from rising and stormier seas, increasing amounts of natural coastline worldwide are being replaced by a proliferation of coastal defence structures. While the primary role of defence structures is protecting the coastline, consideration should be given to the biological coastal communities they support. Artificial structures are currently seen as poor habitats for marine organisms. They are constructed in harsh coastal environments, lack structural complexity, and are subjected to episodic disturbance from maintenance, reducing their suitability as habitats for coastal species. Recent work has focused on mitigating the impacts of coastal defence structures, through secondary routes such as enhancing biodiversity by encouraging colonisation of marine biota. Research thus far has focused on enhancements to improve structural complexity on the external surfaces of coastal defences. Many structures are porous with internal compartments. To date no work has been undertaken on the habitat provided by the internal surfaces of the blocks used in building structures. We investigated the role of porous coastal defence structures in habitat provision. Taking advantage of a groyne reduction from 45 m to 20 m length, we surveyed the internal environment of the structure. We also considered the impacts of maintenance activity on coastal assemblages. Our work shows that the internal environment of artificial structures provides functional habitat space supporting higher species richness and diversity than external surfaces. The more benign environment of internal surfaces protects from desiccation stress and is probably less scoured by mobile sediments, and as such is of unrealised importance to coastal assemblages. External surfaces are also subject to high levels of disturbance from maintenance activities, further limiting the potential ecological contribution this area of the artificial habitat might otherwise develop. These findings reveal the multifunctional role of porous coastal defence structures, acting as engineering protection and habitats for coastal assemblages. [ABSTRACT FROM AUTHOR]

Geotextile tubes are widely used in coastal protection and beach restoration. The objective of this study is to evaluate the internal shear strength of geotextile tubes using a miniature cone in a small-scale model test. Sandy soils with different particle size distributions are used as fill materials in the geotextile tubes. Each fill material with high water content is injected into the geotextile tube using a sand pump. After injecting the fill material, cone penetration tests are conducted using a miniature cone to characterize the internal strength profile of the geotextile tube. The experimental results indicate that fill materials with fines content have smaller cone tip resistances than those without. Moreover, the cone tip resistances near the inlet of the geotextile tube are smaller than those far from the inlet in the longitudinal direction. The strength characterization approach using a miniature cone may be promising for evaluating the internal stability of geotextile tubes. • Geotextile tubes (GTs) are used for coastal protection and beach restoration. • Internal shear strength of geotextile tubes is investigated using a miniature cone. • Sandy soils with various particle size distributions are used as fill materials. • Cone tip resistance profiles of GTs depend on particle size distribution of fill materials. [ABSTRACT FROM AUTHOR]

Climate-induced natural disasters such as floods and storms are expected to become more frequent and intense in the coming years. From 2017 till 2020, a pilot project was set up where mussel reefs were established as a nature-based solution to mitigate coastal erosion off the Belgian Coast. These subtidal mussel reefs were created by applying a longline mussel aquaculture technique consisting of filamentous and non-filamentous dropper lines of different materials. In this study, several biological aspects of the Nature-based Solution (NbS) set-up were examined: the suitability of the set-up as a whole, the suitability of the seven dropper line types, distribution of biofouling organism on the dropper lines and the spatio-temporal evolution of the mussel reef and its impact on the underlying benthic communities. Only during the summer months, a mussel reef could be established under the dropper line structure. Filamentous and non-filamentous dropper lines harbored different mussel densities and sizes, leading to a possible different effect on the underlying mussel reef. The biofouling community on the dropper lines was also defined in this study with amphipod species such as Jassa sp. and Monocorophium sp. as the dominant species. The impact of the NbS set-up on the macrofaunal communities remained low for the study period. First indications of a shift towards a less diverse and oligochaete dominated community was observed, although longer time series and an optimized sampling protocol will be needed. This pilot study showed the application of using a mussel longline technique in order to establish a subtidal mussel reef in a soft-sediment environment. • A mussel reef could be established during the summer months. • Choice of dropper line structure depends on the site-specific challenges. • Wave forcing, predation and sediment instability may limit mussel bed development. • In the short term, macrobenthos was not affected by the longline mussel set-up. • Recommendations to improve the longline technique for coastal defense are proposed. [ABSTRACT FROM AUTHOR]

Resilience of a beach is often defined by return period (RP) of a designed storm. During extreme events some correlation exists between storm parameters, such as wave height (H s) and surge (S), and these parameters are also stochastic in nature. Thus, numerous combinations of H s and S occurs for the same level of RP. The objective of this study is to demonstrate if a same level of joint RP with different combination of H s and S would produce similar beach erosion, considering wave directions and orientation of coastline. To achieve this, a non-directional Joint Probability (JP) of storm H s and S is integrated with a morphological model. Three scenarios along a JP contour are selected and erosions are estimated. The selected JP scenarios are converted into a synthetic storm time-series for morphological simulations. The results demonstrated that JP with a high H s and low S scenario produced more erosion than other scenarios under constant direction. Regarding wave direction, for the same H s and S , the shore-normal wave direction produced highest erosion. Thus, shore-normal wave with high H s and low S produces the highest erosion than other combinations. This study demonstrates the importance of consideration various JP and wave directions in assessing resilience of a beach. • Integrate a joint probability method with a morphological model for extreme beach erosion analysis. • Beach erosion can vary despite analysing the same joint return period of wave heights and water surface elevations. • Wave heights are more important than water surface elevations for erosion on a wave dominated, micro-tidal coastline. • A joint high wave height and low water surface elevation from shore normal direction produced the highest erosion. [ABSTRACT FROM AUTHOR]

This paper analyses the effect of vegetation on wave damping under severe storm conditions, based on a combination of field measurements and numerical modelling. The field measurements of wave attenuation by vegetation were performed on two salt marshes with two representative but contrasting coastal wetland vegetation types: cordgrass ( Spartina anglica ) and grassweed ( Scirpus maritimus ). The former is found in salty environments, whereas the latter is found in brackish environments. The measurements have added to the range with the highest water depths and wave heights presented in the literature so far. A numerical wave model (SWAN) has been calibrated and validated using the new field data. It appeared that the model was well capable of reproducing the observed decay in wave height over the salt marsh. The model has been applied to compute the reduction of the incident wave height on a dike for various realistic foreshore configurations and hydraulic loading conditions. Additionally, the efficiency of vegetated foreshores in reducing wave loads on the dike has been investigated, where wave loads were quantified using a computed wave run-up height and wave overtopping discharge. The outcomes show that vegetated foreshores reduce wave loads on coastal dikes significantly, also for the large inundation depths that occur during storms and with the vegetation being in winter state. The effect of the foreshore on the wave loads varies with wave height to water depth ratio on the foreshore. The presence of vegetation on the foreshore extends the range of water depths for which a foreshore can be applied for effective reduction of wave loads, and prevents intense wave breaking on the foreshore to occur. This research demonstrates that vegetated foreshores can be considered as a promising supplement to conventional engineering methods for dike reinforcement. [ABSTRACT FROM AUTHOR]

Mangroves provide vital climate change mitigation and adaptation (CCMA) ecosystem services (ES), yet have suffered extensive tropics-wide declines. To mitigate losses, rehabilitation is high on the conservation agenda. However, the relative functionality and ES delivery of rehabilitated mangroves in different intertidal locations is rarely assessed. In a case study from Panay Island, Philippines, using field- and satellite-derived methods, we assess carbon stocks and coastal protection potential of rehabilitated low-intertidal seafront and mid- to upper-intertidal abandoned (leased) fishpond areas, against reference natural mangroves. Due to large sizes and appropriate site conditions, targeted abandoned fishpond reversion to former mangrove was found to be favourable for enhancing CCMA in the coastal zone. In a municipality-specific case study, 96.7% of abandoned fishponds with high potential for effective greenbelt rehabilitation had favourable tenure status for reversion. These findings have implications for coastal zone management in Asia in the face of climate change. [ABSTRACT FROM AUTHOR]

Friction properties at geotextile interfaces play an important role in the stability of geotextile encapsulated-sand systems in coastal protection. The stabilising action of the frictional force is important to oppose sliding along the contact surface and to prevent deformations, which may lead to structural failures. This paper presents a set of experiments, based on large-scale direct shear tests performed under both cyclic loading and cyclic displacement conditions, examining friction at interfaces between geotextile specimens, sand-filled geosystem elements, and between a sand layer and a sand-filled geosystem element. The results presented here indicate that the friction parameters (i.e., shear strength and friction angle) derived from geotextile specimens are below those obtained for sand-filled elements, which suggests that using the former for the stability analysis is conservative. The tests carried out with a sand layer surface showed that a modification to the shear plane slope is likely to occur – for the sand-filled geosystem element buries into the sand layer. This deformation can result in toe instability, ultimately leading to progressive damage or even collapse of the entire structure. [ABSTRACT FROM AUTHOR]