Hard Engineering Research Articles

Ultra-wide low-frequency bandgap characteristics of auxeticity-based composite resonator for elastic wave manipulation and machine learning-based inverse structural design

Although auxetic metamaterials are generally light in weight, strong in compression and superior in energy absorption, less research has focused on their low-frequency bandgap realization and inverse structural design. Moreover, broadening the width of bandgap of auxetic metamaterials keep challenging as well in practical low-frequency applications. To broaden their applications, this work provides a new auxeticity-based composite resonator design by filling hard engineering material into the soft auxetic structure perforated by orthogonally-arrayed peanut-shaped holes to achieve ultra-wide low-frequency bandgap. The soft material is silicone rubber and the hard material may be concrete, steel or plumbum. Firstly, the wave propagation mechanics of the present composite structure is studied and then the bandgap characteristics are thoroughly investigated by parameter analysis. On this basis, a machine learning (ML) method combining the standard back-propagation neural network and genetic algorithm is proposed for bandgap prediction and inverse structural design. Results indicate that the present composite structure performs well in generating ultra-wide low-frequency bandgap, i.e. [11.35, 24.07] Hz, and the relative bandgap width reaches 71.76 %. Moreover, the present ML method is effective in the forward prediction of bandgap and the inverse structure design fitting the specific bandgap requirement. For the created optimal designs, the ML method and the finite element simulation can give similar results, and the maximum relative error between them is just about 5 %, which verifies the accuracy of the ML design method. This work provides a new way to realize the structural design of auxeticity-based acoustic metamaterials with low-frequency and broad bandgap.

Enhancing Climate Resiliency Through Improving Ecosystem Services in Shoreline Municipalities – Lessons from Canada

The accelerated impacts of climate change in waterfront areas and the proven inefficacy of the aging hardened shoreline infrastructure have driven shoreline management practices to evolve toward the enhancement of ecosystem services at the land-water interface. Gaining momentum as an adaptive approach in regenerative projects, living shorelines are comprised of natural ecosystem components used in combination or in place of traditional hard engineering methods to provide coastal protective services and erosion mitigation. The success of living shorelines in protecting shoreline property and ecosystem integrity varies based on the biogeomorphology and hydrology of the region and is also heavily reliant on social acceptance of the chosen approach and best practice for implementation. The relatively lower lifecycle cost and associated co-benefits of living shorelines have well positioned them as a promising alternative approach in theory. There are, however, gaps in regional long-term datasets and evidence-based guidelines. This research provides an overview of the underlying geopolitical readiness for integrating nature-based solutions in climate adaptation strategies within shoreline municipalities based on a comprehensive literature review complimented by expert interviews. The synthesized data can inform decisions for minimizing the destructive effects of traditional shoreline erosion prevention approaches and encourage successful implementation of solutions that offer ecological, health, social, and economic benefits.

Transcending disciplinary boundaries: NbS for Caribbean coastal resilience

Caribbean small island developing states are experiencing multiple interconnected crises, including susceptibility to natural hazards, increased vulnerability to climate change, biodiversity loss and reduced accessibility to development funding. Nature-based solutions (NbS) can provide an integrated approach to boost Caribbean coastal resilience as they are economic and practical solutions that capably balance competing interests. This study used a participatory method (group model building) to engage stakeholders across varying disciplines and levels of decision making to collaboratively identify the underlying causes of low uptake of NbS regionally and potential intervention mechanisms. Six overarching factors were found to contribute to low adoption, including data and knowledge limitations, a propensity towards hard engineering, low collaborative engagement and limited implementation capacity. Some areas identified for intervention were comprehensive data collection, reducing uncertainty surrounding the implementation of NbS, effective collaboration, using case studies and best practices, and knowledge translation and dissemination. The outputs demonstrate a critical role for engineers in mainstreaming NbS through adopting a systematic and holistic design approach. Concomitant to this is the need for engineers to operate successfully within transdisciplinary teams to enhance transformative communication skills and ensure that solutions not only minimise environmental impact but also support the conservation of biodiversity and ecosystem services.

Elevating Pakistan’s flood preparedness: a fuzzy multi-criteria decision making approach

In South Asia, Pakistan has a long and deadly history of floods that cause losses to various infrastructures, lives, and industries. This study aims to identify the most appropriate flood risk mitigation strategies that the government of Pakistan should adopt. The assessment of flood risk mitigation strategies in this study is based on certain criteria, which are analyzed using the fuzzy full consistency method. Moreover, flood risk mitigation strategies are evaluated by using the fuzzy weighted aggregated sum product assessment (WASPAS) method, considering previously prioritized criteria. According to the results, lack of governance, lack of funding and resources, and lack of flood control infrastructure are the most significant flood intensifying factors and act as major criteria for assessing flood risk mitigation strategies in Pakistan. Adopting hard engineering strategies (e.g., dams, reservoirs, river straightening and dredging, embankments, and flood relief channels), maintaining existing infrastructure, and adopting soft engineering strategies (flood plain zoning, comprehensive flood risk assessment, and sophisticated flood modeling) are identified as the top three flood risk mitigation strategies by the fuzzy WASPAS method. The highest weight (0.98) was assigned to the adoption of hard engineering strategies to mitigate flood risks. The study introduces a novel dimension by analyzing the real-time impact of the unprecedented 2022 floods, during which approximately one-third of the nation was submerged. This focus on a recent and highly significant event enhances the study’s relevance and contributes a unique perspective to the existing literature on flood risk management. The study recommends that the government of Pakistan should prioritize hard engineering strategies for effective flood risk mitigation. It also recommends that the government should incorporate these strategies in the national policy framework to reduce flood losses in the future.

Evolution of wetlands in the northern part of the Po Delta: The experience of unmanaged realignments

AbstractIt is increasingly recognised that nature‐based solutions in coastal ecosystems provide significant services compared to hard engineering measures. Several restoration projects are now being conducted worldwide to protect coastlines against flood risk and improve the ecosystems' quality. In the case of river deltas, managed realignment through levee breaching is becoming a recognised strategy for coastal wetland restoration. This study focusses on the formation of new wetlands in the Po River Delta after several natural dyke failures that occurred during the last century, when a large part of the land was abandoned and became wetlands. An historical review was performed to quantify the variation of the marsh extent in time developed after natural levee breaching in the easternmost lagoons of the delta and to understand the processes that determined their evolution. The analyses were based on orthophotos from the 1950s to the present‐day integrated with tidal records, water and sediment discharge records, and GPS survey for vegetation distribution. The review indicated that, between the 1950s and 1980s, anthropisation and natural processes caused a strong decline in marsh extent, thus leading to the recent shape of the lagoons. Several breaches and inlets were developed because of a combination of human intervention and erosive processes, and new tidal systems were born. Three main depositional areas connecting the main river branches were identified in three separated lagoons of the delta. These lagoons presented a ‘crevasse splay’ type of deposition which allowed the development of new tidal flats and, in certain cases, of large freshwater marsh systems within less than 8 years after the breach. The newly formed wetland systems (>100 ha) demonstrate the ability of the Po River Delta to build new wetlands, also during periods of human‐induced sediment starvation and high rates of subsidence, suggesting that further levee breaching should be exploited to favour marsh recovery.

Optimizing coastal protection: Nature-based engineering for longitudinal drift reversal and erosion reduction

Traditional hard engineering solutions have shown weaknesses in mitigating erosion processes in vulnerable coastal areas, contributing in some cases to their aggravation, which makes it necessary to study innovative nature-based engineering solutions. This research deals with an in-depth analysis of hydro-morphodynamic modelling results for optimizing the geometry of maritime structures under longitudinal drift reversal conditions by mimicking and manipulating natural processes to promote wave energy dissipation and sediment retention through wave deformation due to obstacle interposition. The solutions draw inspiration from the full-scale observation data of two examples of longitudinal drift reversal. Additionally, numerical simulations were developed for predicting wave climate near the Iberian Peninsula shoreline under different scenarios. Hydrodynamics and morphodynamics modelling results are discussed based on the impact of a specific storm, considering different characteristics of protection structures, followed by parametric sensitivity analysis and comparative studies performed with an optimized solution. Results indicated this solution contributed to sediment accumulation downdrift near the shoreline, as there is no interruption of the longitudinal drift compared to traditional protection structures. At the alignment, the structure also improved nearshore sediment accretion, reduced areas of erosion relative to a no-structure scenario and exhibited behaviour akin to an emerged structure with its crest level. Compared to wholly submerged structures, it becomes a relevant coastal protection alternative, as it guarantees excellent protection on the adjacent coastal zone by safeguarding against tidal variations induced by storm surges and mean sea level rise due to climate change. Furthermore, there is a positive effect to help promote biodiversity whenever the structure is located in an intertidal zone. Despite the enormous computational effort required in the hydro-morphodynamic modelling process, this study shows that it is possible to create innovative engineering coastal solutions to induce longitudinal drift reversal and reduce erosion near the shoreline.

Microscopic investigation on micro electric discharge milling of AA6063-SiC composites

Metal matrix composites (MMC) have found applications in places where the utilization of conventional materials is limited. This also includes areas of micro- and meso-applications. However, micromachining of metal matrix composites by conventional methods poses difficulties due to the heterogeneous nature of the material and the presence of hard reinforcement particles. Micro-ED milling is a versatile micromachining process used to machine hard engineering materials. It employs a simple cylindrical cross-section tool, which is rotated and fed in predefined paths to generate intricate 3D features with good dimensional accuracy and surface finish. In order to study the machining performance of micro-ED milling process on metal matrix composites, micro-ED milling of AA6063-4 wt.% SiC composite fabricated by ultrasonic-assisted stir casting was carried out. The tool feed rate and tool rotation speed are important parameters as they aid in debris evacuation and influence material removal. So, the effect of tool feed rates, tool rotation speeds and discharge energies on the surface morphology and surface roughness of the machined channels were studied. The surface roughness parameters, namely Sa and Sq, were considered for the study. The least surface roughness, Sa and Sq, was observed at 2 µm/s for all the investigated discharge energies.

Seagrass as a nature-based solution for coastal protection

Our coasts are facing a growing threat from rising sea levels and detrimental storm events. Nature-based solutions are gaining interest for their potential to provide multiple ecosystem services, including coastal protection. Seagrass can influence coastal sediment transport and wave propagation, however, whether seagrass can be used as an effective intervention for coastal protection is unclear. Using the Delft3D model, this study looks at how seagrass affects coastal hydrodynamics in a macrotidal bay, under idealised scenarios that simulate a rise in sea level and storm wave heights, emulating projected sea conditions under climate change. Through the use of a habitat suitability model, a seagrass patch in Morecambe Bay was simulated, based on a location within the bay that is most suitable for seagrass species Zostera marina. Hydrodynamic simulations were run for a number of scenarios for a domain with and without a seagrass patch. Scenarios included variable boundary wave heights, sea levels and vegetation parameters, to test the influence of seagrass in future climates. Results show that there is a reduction in mean and maximum wave height inside and behind the seagrass patch, with the largest changes in wave dissipation observed during higher boundary wave conditions. In these conditions the maximum wave height reduced by over a half within the patch. Simulations examining the influence of seagrass density and canopy height found that a lower density seagrass patch reduced maximum wave height more substantially than higher density patches. Although alternative hard engineered solutions are able to attenuate wave energy more effectively than seagrass, these results demonstrate seagrass could play an important role in conjunction with salt marsh restoration or existing hard engineering solutions, helping to mitigate the risk of flooding and erosion, whilst providing additional ecosystem services such as carbon sequestration and habitat provision.

Experimental study on wave attenuation and beach profile evolution under the protection of submerged flexible vegetation

Coastal protection methods are evolving from hard engineering techniques to natural enhancement approaches. Aquatic vegetation provides an environmentally friendly solution by effectively dissipating waves and resisting erosion. Laboratory flume experiments were conducted to investigate the effect of submerged flexible vegetation on the regular wave attenuation and cross-shore profiles on the artificial plane beach under varying hydraulic conditions. Variations in the waveform, wave spectrum, and wave height were analysed in the vegetation zone. Results show vegetation distorts the waveform and accelerates the attenuation process of the wave energy, and wave height evolution behaves differently from the theoretically obtained attenuation by Mendez and Losada (2004) due to the underestimating vegetation-induced attenuation and neglecting sediment-induced attenuation. Additionally, the formation process of the winter and summer profiles of the vegetated beach was analysed by the screenshots. Regenerated wave breaking becomes more apparent with increasing wave periods. The critical surf similarity parameter of the vegetated beaches was found to be lower than that of a smooth, impermeable slope because of the energy dissipation. Vegetation did not alter the type of the beach profiles, as compared to the final profiles and their characteristic parameters of the unvegetated beaches. Instead, it reduced the erosion depth and brought the eroded area closer to the shoreline. Dimensionless parameters were formulated to characterize the response of the cross-shore beach profile under the shelter of flexible vegetation, and an empirical equation about maximum erosion depth was developed within the scope of the experiment.

Sand dune restoration as sustainable natural architectural design for coastal protection along seasonal storm-prone beach

Monsoonal storms cause coastal erosion of worldwide sandy beaches, including coasts in Malaysia. Although hard engineering structures are effective in mitigating erosion, those constructions can create several environmental issues such as down-drift erosion. The Effective Sand Fence (also known as E-Fence) is considered one of the sustainable alternative structures to protect beach erosion. Therefore, the objective of the current study is to identify the effectiveness of E-Fence for dune restoration. In this study, we measured beach profile survey, grain size distribution, and wind speed. In addition, XBeach simulation was used to determine sediment accumulation under the E-Fence protection. Results of the beach profile survey (i.e., slope and dune volume) indicate dune restoration in protected areas of the E-Fence. Grain size distribution and wind speed suggest the decreasing of wind velocities from the swash zone to the backshore. Accordingly, the E-Fence acts as a barrier, and the reduction of energy leads to accumulate sediments by passing through gaps in the structure. The E-Fence is thus capable of sustaining against wave attack and can maintain stable coastal ecosystems. Consequently, this coastal protection structure assists in developing cheaper coastal erosion mitigation strategies in Malaysia and elsewhere.

Evolution of trends in Sri Lankan mangrove research and future prospects

The trend of sporadic surveys and qualitative descriptions of Sri Lankan mangrove flora in the first half of the 20th century has gradually changed to include quantitative studies on floristics, nevertheless, studies on quantification of fauna associated closely with mangrove ecosystems are scarce. Microbial diversity, especially in soil, and its ‘contribution to the detritus cycle are the least studied. The tendency to engage in short-term research at convenient sites affects the quality and relevance of research output with some redundancy, resulting in a marginal contribution to the knowledge base on mangrove ecology. Studying mangrove ecosystem functions/ services demands long-term collection of data that would have made them less attractive research ventures. Research on trophic relationships, detritus and nutrient cycling, habitat and pollination functions too have had the same fate. The Indian Ocean tsunami in 2004 triggered a considerable interest in the coastal protection function of mangroves, as it was evident that mangroves and other coastal vegetation provided superior resistance to tsunami waves than hard engineering coastal protective structures. This has led to an unprecedented trend of mangrove afforestation for coastal defense, more than to research on planting techniques and maintenance to enhance the survival and growth of seedlings. This is still an under-researched aspect. Escalating recognition of blue carbon as a climate-smart solution and the development of market mechanisms for blue carbon trading have induced a considerable research interest in quantifying the mangrove blue carbon stocks, especially in the soil. Research on atmospheric carbon removal capacity/rates of mangrove plants/forests through photosynthesis however, lags behind for the reason that it requires data collection for a longer period that demands greater financial and labour investment. The urgency created by the current climate change crisis for effective solutions to reduce atmospheric greenhouse gases may provide a conducive environment for mangrove research.

STUDY OF LUBRICANT ADDITIVES FOR EXPANSION PIPE EXPANSION IN MONODIAMETER WELLS

There is a need to improve well design and completion in order to reduce material intensity while maintaining sufficient casing cross-sections. One of the possible solutions for this is the construction of mono-diameter wells using expandable casing technology. The technology of drilling wells with the same fixed bore diameter from the wellhead to the productive formation could solve many problems and limitations in the construction of wells, opening up opportunities for the development of large oil and gas reserves that are currently classified as difficult to recover or inaccessible. The technology of drilling monodiameter wells also reduces drilling volumes, reduces the adverse impact on the environment and, ultimately, leads to minimization of construction costs.For purposeful choice of flushing fluid components, especially reagents of complex action and lubricating additives necessary for drilling of mono-diameter wells, their preliminary laboratory tests on experimental installations providing physical similarity of interaction processes (wear) of friction pairs in relation to drilling technology are required. The task of this article is to study lubricating additives for reaming of reaming pipe in mono-diameter wells for subsequent selection of the most optimal of them. The experiments were carried out on the wellknown universal machine II 5018, designed for testing friction and wear of metals and alloys, hard engineering plastics and composites. The loading system and the II 5018 work unit were upgraded to simulate the processes being studied. During the experiments, the friction coefficient and wear rate of the sample were measured. To carry out the research, various lubricating and cooling media used in drilling technology were selected.

Effects of coastal protection structures in controlling erosion and livelihoods

The fiscal and social cost of ameliorating the impact of coastal erosion resulting from climate change is an increasing burden for coastal states, and in developing nations the physical interventions implemented may present a double agony – increasing debt levels and potentially obstructing livelihoods in the rural coasts. Against this background, this study was conducted to explore the impact of hard-engineered coastal protection on coastal vulnerability and community livelihoods in Ghana using a combination of Unmanned Aerial Vehicles (UAV), geographic information system tools and social survey. Shoreline change analysis by the application of the Digital Shoreline Analysis System (DSAS) with aerial photographs from 2005 to 2022 reveals an average statistical rate of change of −1 m/year in shoreline erosion of the beaches. A computation of coastal vulnerability indices for fourteen beaches, incorporating coastal protection as an additional parameter shows that from east to west, hard-engineered coastal protection structures slowed the rate of erosion, whereas unprotected beaches have highly eroded, stressing the importance of coastal protection. In consequence, coastal protection has dire livelihood-reduction implications for coastal inhabitants who are predominantly artisanal fishers. A lack of acceptable consultation with the communities exacerbates the effects from these hard-engineering interventions. The beaches of high vulnerability concerns are Dzita, Ada, Sakumono, Glefe, Apam, Anlo, and Busua. To safeguard the livelihoods of vulnerable coastal communities, we support a shift from hard engineering to more integrated and nature-based coastal management approaches on a national scale since most parts of the coast are now susceptible to erosion in contrast to what was previously observed that only the eastern part of the coast was highly vulnerable.

STRENGTHENING COASTAL DEFENCE WITH ARTIFICIAL DUNES

The Belgian coast is primarily sandy and is locally subject to erosion (Deronde, 2004). Traditionally, erosion was counteracted using hard engineering structures like groynes, seawalls and sea dikes. Nowadays, the Belgian government uses a different strategy by adopting a more soft and dynamic approach where possible. Many ‘soft’ managing activities at the Belgian coast are carried out in the form of regular and routine sand nourishments to cope for future flooding risks and coastal erosion (Houthuys, 2012). This method gives room to a new approach for coastal management where the natural elements and processes facilitate the development of new engineered dune areas at locations where traditional dike structures currently protect the hinterland. In the context of climate change and strict requirements for water safety, these hard to adapt engineering structures will not resist future flood events and more innovative solutions like dune in front of a dike principles to deal with rising sea level are receiving considerable attention. As a result, concepts are worked out in which traditional sea dikes are reinforced with newly created dune systems, offering a high level of protection of coastal infrastructure and at the same time offering a more natural appearance and higher ecological and socio economical values. In the framework of the SARCC project, one pilot site is realized in Raversijde. Besides the coastal defense function of the artificial dune, a second benefit is achieved: mitigating the nuisance, created by aeolian sand transport and preventing roads and tram tracks at the dike crest to be buried in sand.

Field-based monitoring of instream leaky barrier backwater and storage during storm events

Engineered leaky barriers are increasingly used as natural flood management methods providing ecosystem and water quality benefits in addition to flood attenuation, complementing hard engineering flood defences. Field-based monitoring of a natural flood management site, Wilde Brook in the Corvedale catchment, England (UK) studied the rainfall-runoff relationship for a 5.36 km reach with 105 leaky barriers over two years. Paired pressure transducers were placed upstream and downstream of three channel spanning leaky barriers, allowing evaluation of upstream backwater rise relative to rainfall intensity, storm magnitude, and frequency. By increasing backwater rise, the leaky barriers caused overbank flows, resulting in a reduction in the cross-sectional area velocity after the event. The incidence of overbank flow depended on the local stream cross-sectional profile, barrier properties, location in the reach, and storm magnitude. Barrier operational flow conditions were classified into five modes according to relative bank inundation and barrier submergence extent. The backwater rise magnitude depended on barrier physical properties and evolution over time through cycles of accretion and build-up of brash and leafy material in the barrier, in addition to local bedload sediment transport dynamics, where instances of scour around the barriers were observed. Backwater rise and net volume hydrographs showed rapid filling up behind the barriers on the rising limb and slower water release on the falling limb. For a ∼ 4 yr return period storm event, results indicated that one leaky barrier increased storage volume by up to 102 m3, which translates to an overall net volume increase of ∼ 10,700 m3 for the full reach. These new findings provide quantitative evidence of leaky barrier backwater and storage performance, and leaky barrier design recommendations for storms up to a 4 yr return period. This evidence can be used to develop and validate flood modelling generalised approaches for smaller, more frequent storms, and work towards the development of an approach for modelling leaky barriers for larger storm magnitudes.

Using salt marshes for coastal protection: Effective but hard to get where needed most

Abstract Salt marshes fronting coastal structures, such as seawalls and dikes, may offer important ecosystem‐based coastal defence by reducing the wave loading and run‐up levels during storms. We question (i) how the long‐term salt marsh development in the Dutch Wadden Sea relates to the tidal‐flat foreshore bathymetry and (ii) how the wave run‐up onto dikes, which enhances the risk of dike failure, depends on foreshore bathymetry, the presence/absence of marshes, marsh vegetation properties, tidal range and wind exposure. We analysed 15 years of vegetation and bathymetry maps along the entire Dutch Wadden Sea coast, in combination with detailed process‐based measurements at five locations during 3 years, to understand where salt marshes naturally form and what features determine their contribution to coastal protection. The horizontal extent of marshes along the dikes remained relatively stable over the past decade. The presence of marshes was associated with higher elevations of adjacent tidal flats (above ~0.5 m NAP), while landward‐directed marsh retreat was associated with surface erosion of the fronting tidal flats. Wave run‐up during storms was lower at sites with wider marshes and higher foreshore elevations. This was attributed to the marsh attenuation effect, which led to a reduction in wave heights at the dike toe. As the tidal range varies across the Dutch Wadden Sea, areas to the East with generally higher water levels experienced higher wave run‐up. Synthesis and applications. We found that (i) marshes, where present, effectively protected the dikes from wave loading and (ii) the sites where marshes typically do not develop spontaneously were the most vulnerable to high wave run‐up. This catch‐22 problem implies that increasing reliance on nature‐based coastal defences along soft‐bottom coasts may require human interventions to stimulate marsh formation at the locations where it is most needed. Alternatively, ‘hard engineering’ solutions may remain necessary where implementing nature‐based solutions are either too costly, unachievable, or at the expense of other ecological values, such as causing the loss of mudflats that are important for migratory birds.

Shoreline Change Analysis of the Eastern Coast of Ghana between 1991 and 2020

The Eastern Coastline of Ghana is facing intense natural and anthropogenic disturbances, which pose a serious threat to the coastal community, ecosystem, and livelihoods. This study assessed the shoreline changes occurring along the Eastern Coast of Ghana stretching 149 km from Laloi Lagoon West of Prampram to Aflao, Ghana. The study utilizes satellite images from Landsat 4TM, Landsat 7 ETM+, and Landsat 8 OLI taken between 1991 and 2020. Data pre-processing techniques using ENVI 5.3 included calibration, layer stacking, mosaicking, and supervised classification. Post-classification shorelines were extracted using ArcGIS 10.7, and the DSAS tool was used to determine the rate of change over the 29-year period. The results showed that the coastline experienced an average erosion rate of 9 m/y and a maximum rate of 24 m/y, however, the accretion rate (3 m/y) was much lower, reflecting general coastline retreat. Thus, some 25 coastal communities are highly exposed to shoreline erosion. Sustaining the coastal area may require coastline re-engineering interventions. This study recommends continuous monitoring of the shorelines to ensure the protection of livelihoods. Implementation of both hard engineering and ecosystem-based adaptation strategies may be required to achieve holistic results toward sustainable coastal management.

Setback zones can effectively reduce exposure to sea-level rise in Europe

Coastal space is one of the most valuable assets of the EU coastal member states, as the coast is highly urbanized. Hard engineering has traditionally been employed to protect communities in coastal lowlands, but as this alternative becomes less sustainable and more costly, coastal managers are increasingly turning to landuse planning strategies, such as setback zones or managed retreat. To explore the efficiency of these planning tools in reducing future urban exposure to sea-level rise and associated hazards, we developed spatially explicit projections of urban extent that account for different socio-economic futures and various types of setback zones. We find that the establishment of coastal setback zones can reduce the exposure of new urban development by at least 50% in the majority of EU countries by 2100. Our results emphasize that future urban exposure to sea-level rise will be significantly influenced by the ways in which we plan, design, and develop urban space in the EU coastal lowlands.

Socio-Economic Assessment of Ecosystem-Based and Other Adaptation Strategies in Coastal Areas: A Systematic Review

Coastal areas are highly vulnerable to climate-change hazards (e.g., sea-level rise, flooding, coastal erosion), which can lead to significant impacts at the ecosystem and societal level. Interest in ecosystem-based adaptation (EbA) is gaining importance due to its potential multiple benefits, including social and environmental aspects, when compared to more traditional approaches such as hard engineering interventions. When assessing EbA strategies, further understanding of the nature–society functions, processes, values, and benefits is needed to increase its application. This study contributes to better knowledge of EbA and other adaptation strategies by developing a systematic literature review of studies performing socio-economic assessments of climate-change adaptation in coastal areas. The analysis of 54 publications revealed that cost–benefit analysis was applied in most studies, followed by multi-criteria analysis and other techniques. Hybrid adaptation strategies based on different combinations of hard, soft, and EbA interventions were considered as potential optimal solutions in a significant part of the assessments. This study shows some potential co-benefits of EbA, such as livelihood diversification or biodiversity conservation, but also stresses the need for further research on this topic, as well as on evaluating how EbA performs in the long term under changing climate-condition scenarios.

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

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