Coastal Protection Research Articles

Mediterranean seagrasses provide essential coastal protection under climate change

Seagrasses are vital in coastal areas, offering crucial ecosystem services and playing a relevant role in coastal protection. The decrease in the density of Mediterranean seagrasses over recent decades, due to warming and anthropogenic stressors, may imply a serious environmental threat. Here we quantify the role of coastal impact reduction induced by seagrass presence under present and future climate. We focus in the Balearic Islands, a representative and well monitored region in the Mediterranean. Our results quantify how important the presence of seagrasses is for coastal protection. The complete loss of seagrasses would lead to an extreme water level (eTWL) increase comparable to the projected sea level rise (SLR) at the end of the century under the high end scenario of greenhouse gases emissions. Under that scenario, the eTWL could increase up to ~ 1.4 m, with 54% of that increase attributed to seagrass loss. These findings underscore the importance of seagrass conservation for coastal protection.

Unveiling the bacterial diversity and potential of the Avicennia marina ecosystem for enhancing plant resilience to saline conditions

BackgroundAvicennia marina ecosystems are critical for coastal protection, water quality enhancement, and biodiversity support. These unique ecosystems thrive in extreme saline conditions and host a diverse microbiome that significantly contributes to plant resilience and growth. Global food security is increasingly threatened by crop yield losses due to abiotic stresses, including saline soils. Traditional plant breeding for salt tolerance is both costly and time-consuming. This study explores the potential of bacteria from A. marina to enhance plant growth under saline conditions, emphasizing their ecological significance.ResultsWe analyzed the microbiome of A. marina from the Red Sea coast using high-throughput Illumina sequencing and culture-dependent methods across various compartments (bulk soil, rhizosphere, rhizoplane, roots, and leaves). Our findings revealed distinct compartment-specific microbial communities, with Proteobacteria being the dominant phylum. Functional predictions indicated diverse microbial roles in metal uptake and plant growth promotion (PGP). Remarkably, our culture-dependent methods allowed us to recover 56% of the bacterial diversity present in the microbiome, resulting in the isolation and characterization of 256 bacterial strains. These isolates were screened for PGP traits, including salt and heat tolerance, siderophore production, and pectinase activity. Out of the 77 bacterial isolates tested, 11 demonstrated a significant ability to enhance Arabidopsis growth under salt stress.ConclusionsOur study highlights the ecological significance of mangrove microbiomes and the potential of culture collections in offering innovative solutions for ecological restoration and crop production in saline conditions. The unique collection of mangrove bacteria, particularly from the rhizosphere and endophytes, showcases significant PGP traits and stress tolerance capabilities. These findings emphasize the importance of functional traits, such as salt tolerance, in the recruitment of endophytic bacteria by plants over taxonomic affiliation. The identified bacterial strains hold potential not only for developing biofertilizers to improve crop productivity but also for ecological restoration projects aimed at rehabilitating saline-degraded lands, thereby contributing to overall ecosystem health and sustainability.

Field survey of the 2024 Noto Peninsula Earthquake and Tsunami in Japan: Characteristics of damage patterns to coastal communities

On January 1st, 2024, a major earthquake near the Noto Peninsula, Japan, triggered tsunami waves that impacted coastal communities in the region. This study reports findings from two field surveys conducted four days and two months after the event to understand the tsunami's mechanisms and effects, respectively. The proximity of the epicenter to land and the complex topography of the Noto Peninsula caused spatial variability in the observed damage. The observed tsunami inundation and run-up heights along the peninsula ranged from 1.02 to 4.10 m, with the maximum of 6.64 m measured at Naoetsu, located approximately 100 km away from the peninsula. However, areas experiencing earthquake-induced land uplift of up to 4 m observed no coastal inundation. Coastal protection structures were crucial in mitigating damage; areas behind breakwaters suffered minimal impact, while unprotected locations and weak points in hydraulic structures allowed increased damage. The relatively infrequent occurrence of large tsunamis on the Japan Sea side, compared to the Pacific side, may have led to lower preparedness levels. However, despite the limited time for evacuation of less than 10 min, one community experienced no casualties, highlighting the effectiveness of prompt evacuation and increased social awareness following the 2011 Tohoku Earthquake Tsunami.

Understanding sediment and carbon accumulation in macrotidal minerogenic saltmarshes for climate resilience

Coastal saltmarshes play an essential role in providing services such as sediment and carbon storage, coastal protection and support for biodiversity. Despite their importance, understanding the factors controlling sediment and carbon accumulation in these minerogenic saltmarshes remains challenging due to their diversity and site-specific characteristics. Understanding the respective role of these drivers is essential for effective coastal management, particularly for mitigating the impacts of climate change. This study evaluates the control of forcing factors on the lateral and vertical morphological evolution and carbon burial rates of three minerogenic saltmarshes located on the French Atlantic coast (Pertuis Charentais region). By focusing on these sites, the study isolates specific factors such as wind and wave exposure, inundation frequency, and sediment availability, while minimizing confounding influences like climate and tidal range. Results reveal significant lateral expansion of saltmarsh boundaries towards the sea across all sites, with the highest rates of progradation observed in the protected areas influenced by geomorphological features such as sand spits and sheltered bay heads. Sediment and mass accumulation rates (SAR; MAR), derived from 210Pb and 137Cs profiles of sediment cores (n = 14), range from 0.48 to 2.22 cm yr−1, among the highest reported globally, with notable variability within and between sites. Inundation frequency and accommodation space explain SAR variability within sites, while sediment availability predominantly determines spatial differences in vertical accumulation rates between sites. Organic carbon burial rates range from 75 to 345 gC m−2 yr−1, and show a strong correlation with SAR (r = 0.9, p < 0.001, n = 13) but no dependence on carbon content or density (r = 0.2, p > 0.05, n = 13). This highlights the role of sediment input in the accumulation and sequestration of carbon by minerogenic saltmarshes. Furthermore, isotopic analysis indicates a marine source dominance in organic carbon sediment. This research provides insights into how different environmental conditions affect saltmarsh morphological evolution and carbon sequestration rates, informing targeted coastal management strategies focused on enhancing ecosystem resilience and climate resilience.

The impact of a storm on the microtidal flat in the Yellow River Delta

Strong hydrodynamic forces generated by storms are key in shaping coastal tidal flats. Most tidal flats achieve equilibrium by adapting to hydrodynamic conditions and sediment inputs. However, high-energy wave activity during storms disrupts this equilibrium, causing rapid and significant changes, particularly in tidal flats, especially in microtidal flats, which are characterized by low tidal ranges. In this study, we conducted an 11-d field campaign on a microtidal flat in the Yellow River Delta (YRD), capturing data during both stormy and calm weather conditions. We measured tidal currents, wave activity, suspended sediment concentrations and sediment grain sizes. The results demonstrated that the tidal flat maintained equilibrium under calm conditions, with minimal fluctuations in bed level (within ±2 mm). Contrastingly, severe erosion and sediment removal during the storm significantly altered the equilibrium of the area. The storm-induced high shear stresses, ranging from 1.02 to 1.48 , along with alongshore sediment transport, resulted in an elevation change of -10 mm. Furthermore, the subsequent bed level recovery was minimal and insufficient to offset the erosion. Compared to that of the mesotidal and macrotidal flats, post-storm recovery on microtidal flats was limited due to shorter inundation periods and weaker hydrodynamic forces. Therefore, frequent storms may lead to continuous shoreline retreat on microtidal coasts. Conclusively, the present findings underscore the significant impact of storm-induced erosion on the evolutionary processes of microtidal flats and suggest that greater attention should be given to protecting these areas during storms in the Yellow River Delta. The insights can guide the development of more effective coastal protection strategies, highlighting the need for enhanced measures to mitigate erosion and promote resilience in microtidal regions.

Public perceptions of nature-based coastal solutions in the UK

Coastal scientists are increasingly advocating for nature-based coastal solutions (NBCS) to ensure long-term coastal sustainability. Implementing NBCS will change coastal landscapes, necessitating consultation with the wider public as such changes directly affect the socio-cultural values of coastal zone residents and users. We, therefore, investigate public willingness to support, preferences for, and perceived effectiveness of coastal management solutions, nature-based and otherwise, focusing on the UK as a case study. We do this through an online survey of >500 UK residents, capturing their demographics, place of residence, and coastal management perceptions. We apply inductive coding, statistical, and geospatial techniques to analyse our survey data. While we find consensus on the need for coastal management, there are divergent coastal management preferences and perceptions: NBCS are most preferred while hard defences are considered most effective. We find that people with coastal management and/or engineering experience are more convinced by NBCS effectiveness, while coastal residents believe in hard defences. Although NBCS may have several environmental benefits (e.g., coastal protection, carbon sequestration, greater biodiversity), we find that public knowledge on their likely effectiveness is limited. Therefore, if NBCS is deemed to be the way forward for coastal sustainability, more local stakeholder engagement on NBCS will be needed, potentially through systems mapping, in order to facilitate more robust and inclusive coastal management policies.

Evaluating the feasibility of coastal protection scenarios on a city scale across plausible pathways scenarios for both sea level rise and urban development

Coastal flood risk accelerates rapidly due to rising sea levels and urban expansion in low-lying areas. Many strategies based on the widespread application of hard protection have been developed. However, the implementation of such measures has raised concerns due to their environmental impact, high costs, and a potential increase in exposure.This study focuses on the economic implications of coastal flood protection at the local level, examining impacts on small to medium-sized cities, which reflects many coastal communities around the world. We introduce a framework for assessing the economic burden or benefit of flood protection strategies on local communities and municipalities. We derive standardized values for protection costs, flood risk, and socioeconomic development for typical coastal topologies, i.e., the data usually used for cost-benefit analyses of coastal protection.Based on two illustrative examples of coastal cities in different topographies, we demonstrate that cost-effective protection strategies can lead to lock-in situations because their implementation cost likely exceeds local willingness to pay, and we argue that this risk needs to be considered when designing flood adaptation pathways.

Transformasi Gelombang Reguler Akibat Pemecah Gelombang Tiang Pancang Dua Baris Selang-Seling

Hydraulic experiments in a two-dimensional physical laboratory were conducted to evaluate the performance of pile breakwaters in reducing wave energy. The piles on the breakwater were arranged in a staggered pattern in two rows. A total of seventy-two simulation scenarios were run based on variations in the incoming wave height and period, and the spacing between the piles, using a 1:10 model scale. The data from the hydraulic tests were then processed using a spectral method that could separate the energy spectra of reflected and transmitted waves. These changes result in reflected and transmitted waves. The laboratory test data were used to estimate the values of the transmission coefficient and reflection coefficient. Both coefficients were then used to validate semi-empirical formulas for the two coefficients. The semi-empirical formulas for the two coefficients were developed based on a model for estimating the spatial porosity of pile breakwaters. The porosity estimation model takes into account the dimensions of the piles and the dimensional components of the breakwater, including the arrangement, number of rows, and spacing between the piles. The validation results of the semi-empirical formulas with the laboratory test data showed a coefficient of determination of 0.917 and a root mean square of 0.077. The staggered arrangement improves the effectiveness of the breakwater in reducing the transmission wave height. The developed semi-empirical model can be used to design the pile dimensions to achieve optimal reflected and transmitted wave heights for coastal protection. Keywords: pile breakwater, coastal protection, hydraulic experiment, physical wave simulation, wave transmission new formula

Hydrodynamic Assessment of Seashell Blocks for Coastal Protection

Hydrodynamic Assessment of Seashell Blocks for Coastal Protection

Impacts of Sea Level Rise on Danish Coastal Wetlands - a GIS-based Analysis.

Intergovernmental Panel on Climate Change (IPCC) scenarios run by an ensemble of models developed by the Coupled Model Intercomparison Project (CMIP) projects an average sea level rise (SLRs) of 0.6 to 1.2 m for the low and high emission scenarios (SSP1-1.9, SSP5-8.5), during the next century (IPCC 2021). The coastal zone will experience an increase in the flooding of terrestrial habitats and the depth of marine productive areas, with potential negative consequences for these ecosystems. The coast in Denmark is highly modified due to anthropogenic uses. Dikes, dams, and other coastal infrastructure are widespread, causing a coastal squeeze that prevents natural coastal development and inland migration of coastlines. We performed a national-scale analysis on the impacts of mean sea level rise (MSLR) in 2070 and 2120, and a 1 in 10-year storm surge water level (10SS) in 2120 MSLR for the Danish coast. Our study shows extensive permanent flooding of coastal habitats (~14%), whereas only 1.6% of urban areas will be flooded. Finally, very large agricultural areas (~191,000 ha) will be frequently flooded by 10SS if no extra protective measures are planned. With the present coastal protection structures, key habitats will be affected by permanent flooding or coastal squeeze while even larger extents will be subjected to intermittent marine flooding. About 45% (199 km2) of all Danish coastal wetlands will be permanently flooded by 2120, while areas occupied by forest, lakes and freshwater wetlands will be more frequently flooded by marine water. This study highlights the importance of including coastal habitats as dynamic elements in climate adaptation plans. Conservation and restoration of key habitats such as coastal wetlands should be prioritized in management plans. If Denmark does not change its current priorities, it may face the complete loss of coastal wetlands habitat in the 22nd century.

Evolution of flood protection levels and flood vulnerability in Europe since 1950 estimated with vine-copula models

AbstractThe magnitude of flood impacts is regulated not only by hydrometeorological hazard and exposure, but also flood protection levels (primarily from structural flood defenses) and vulnerability (relative loss at given intensity of hazard). Here, we infer the variation of protection levels and vulnerability from data on historical riverine, coastal, and compound floods and associated impacts obtained from the HANZE database, in 42 European countries over the period 1950–2020. We contrast actual damaging floods, which imply flood protection was locally inadequate, with modelled potential floods, i.e. events that were hydrologically extreme but did not lead to significant impacts, which imply that flood protection was sufficient to prevent losses. Further, we compare the reported magnitude of impacts (fatalities, population affected, and economic losses) with potential impacts computed with depth-damage functions. We finally derive the spatial and temporal drivers of both flood protection and vulnerability through a multivariate statistical analysis. We apply vine-copulas to derive the best predictors out of a set of candidate variables, including hydrological parameters of floods, exposure to floods, socioeconomic development, and governance indicators. Our results show that riverine flood protection levels are much lower than assumed in previous pan-European studies. North-western Europe is shown to have better riverine protection than the south and east, while the divide is not so clear for coastal protection. By contrast, many parts of western Europe have relatively high vulnerability, with lowest value observed in central and northern Europe. Still, a strong decline in flood vulnerability over time is also observed for all three indicators of relative losses, suggesting improved flood adaptation. Flood protection levels have also improved since 1950, particularly for coastal floods.

Coming to light: How effective are sediment gravity flows in removing fine suspended carbonate from reefs?

AbstractCoral reefs are hard calcified structures, mainly found in warm tropical water. These ecosystems serve important roles as, for example, a source of food, shelter and nursery for different organisms, and in coastal protection. Reef‐building organisms have evolved to inhabit a narrow ecological niche and thus are particularly susceptible to rapid changes in their environment, for example, under predicted climate‐change scenarios. Anthropogenic climate change is widely accepted as the leading cause of rising ocean temperatures, sea water acidity and sedimentation rate, which all affect a coral's productivity, health and, to some extent, skeletal strength. High‐energy weather events, such as storms and hurricanes, can erode reefs, thereby increasing the amount of suspended sediment and consequently the turbidity of the water. The removal of suspended sediment from the reef is vital for the health of reef producers, and a natural process that removes suspended sediment from reefs are sediment gravity flows. A key factor that controls the ability of sediment gravity flows to transport sediment is cohesion, as cohesion determines the run‐out distance of a flow through changes in its rheological properties. This study examines the cohesive nature of sediment gravity flows laden with fine‐grained CaCO3. These gravity flows laden with mud‐grade calcite are compared with flows carrying non‐cohesive, silt‐sized, silica flour, weakly cohesive kaolinite clay and strongly cohesive bentonite clay, by means of laboratory experiments. The results of these experiments show that the mud‐grade calcite flows behave more akin to the silica‐flour flows by reaching maximum mobility at considerably higher volumetric suspended sediment concentrations (47% for silica flour and 53% for CaCO3) than the kaolinite and bentonite flows (22% for kaolinite and 16% for bentonite). Fine CaCO3 gravity flows can therefore be regarded as physically non‐cohesive, and their high mobility may constitute an effective mechanism for removing suspended sediment from coral reefs, especially at locations where a slope gradient is present, such as at the reef front and forereef. However, biological cohesion, caused by ‘sticky’ extracellular polymer substances produced by micro‐organisms, can render mud‐grade calcite cohesive and sediment gravity flows less mobile. The present study should therefore be seen as a first step towards a more comprehensive analysis of the efficiency of removal of suspended sediment from coral reefs.

Disrupted Sand Flows, Artisanal Fishers, and the Making of Coastal Protection in Southern India

&lt;p&gt;Flowing parallel to the sea, sand is subject to erosive, accretive, and extractive processes and is intertwined with the socio-ecological dynamics at the land–sea interface. Human interventions, climate change, and societal responses to it are constantly reshaping the morphology of coastal areas and thus disrupting sand flows, for example, through the construction of harbours or groins to prevent erosion. In this article, we ask how disrupted sand flows shape the interaction and social dynamics between different coastal actors in the making of coastal protection. Empirically, we ground our research in the Pondicherry region of southern India, characterised by a sandy morphology and numerous fishing communities. Building on the literature on “geosocialities,” we argue that engaging with the materialities of ocean sand and the social implications of sediment loss for artisanal fishers is crucial to reducing maladaptation. Following sand as a non-human actor unravels the social entanglements with ocean sand that underpin the implementation of protective measures and that shape access to sandy beaches for artisanal fishers. By exploring these contestations, we show how the reclamation of sand through groins is embedded in unequal power relations over shrinking beaches. While migration to other sandy beaches becomes a necessary means of adaptation, this leads to local conflicts over coastal space. We conclude by highlighting the need to understand coastal adaptation as a geophysical and socially intertwined process, in which ocean sand must be critically considered for future adaptation strategies.&lt;/p&gt;

Assessment of electricity production and coastal protection of a nearshore 500 MW wave farm in the north-western Portuguese coast

Wave energy can contribute towards the “green” energy transition, but complementary applications like coastal protection are equally pertinent. However, viable commercialization should entice large wave energy farms of significant capacity, which may raise conflicts with coastal industries and/or protected areas. Such matters are addressed in this paper's numerical case study of a dual wave farm for a nearshore Portuguese site. It incorporates two parks of 75 bottom-fixed oscillating flap units, each. The farm's configuration, orientation, layout, and rating were evaluated for varying wave conditions and water levels, based on a statistically representative clustering technique. The farm's location was selected to minimize marine space conflicts. The numerical modelling was executed with SNL-SWAN, from which it was found that a staggered configuration – “W” – would yield better results than an aligned configuration – “III”. The “shadowing” effect of one park onto the other was equally observed, but with limited impact. Greater farm unit spacing and rated power benefited the annual energy production, with values of nearly 345 GWh/yr being achieved. However, the capacity factors were generally greater for lower power ratings, as pondered mean values varied between 0.078 (3.332 MW) to 0.144 (1 MW). Wave power absorption ratios between wave farms and cumulative standalone units (q-factors) were always below 1, pointing towards a destructive interference pattern. Important significant wave height reductions were observed (above 30 %, at times), albeit increments were punctually identified near two shallow water areas. Lastly, increasing the tidal level did not impact the farm's performance considerably, but benefited the nearshore impact.

Experimental Investigation on Wave Dissipation of Perforated Pipe Breakwater Under Regular Wave Conditions

The permeable breakwater is an innovative, eco-friendly coastal protection structure that reduces wave impact while minimizing “dead water” and environmental harm. This study introduces a perforated pipe breakwater design with an increasing pipe diameter from top to bottom, evaluated through physical model tests using transmission coefficient Kt and reflection coefficient Kr serving as the primary parameters. The results indicate that Kt decreases as the relative width (B/L), wave steepness (H/L), and relative water depth (h/L) increase, but rises with a steeper breakwater slope. When B/L exceeds 0.3, H/L surpasses 0.06, or the h/L ratio is greater than 0.3, Kt gradually declines until reaching a stable state, resulting in a more pronounced wave reduction. As B/L and H/L increase, the coefficient Kr initially drops, then rises. The slope ratio of 1:1.5 demonstrates the most effective wave energy dissipation, with primary dissipation occurring on the front slope. The mixed pipe diameter design shows superior wave absorption over a uniform diameter. Compared to a porous horizontal plate, the perforated pipe breakwater exhibits better wave absorption. These findings offer valuable guidance for designing eco-friendly coastal protection projects.

Experimental Investigation on Wave and Bed Profile Evolution in a Sandbar-Lagoon Coast with Submerged Vegetation

Better understanding of the hydro- and morphodynamic processes within vegetated sandbar-lagoon coasts is important for assessing the coastal protection capability of vegetation meadow for the coastal environments. Eighteen flume tests were conducted in a mobile-bed sandbar-lagoon with mimicked submerged vegetation under different water depths and wave conditions. It was found that wave attenuation by submerged vegetation near the breaking point is significant. An empirical linear expression for the total wave energy change ratio is proposed with a determination coefficient of 0.84. Moreover, the quantitative formulae for the erosion volume and maximum erosion thickness of sandbars and foredunes, as well as the total sediment transport volume, were proposed to demonstrate the implications of submerged vegetation meadows. These findings provide scientific references for coastal management and conservation planning, especially for sandbar-lagoon coasts. Nevertheless, additional physical experiments or field data are necessary to further validate those formulae.

Nature-based solution for coastal erosion protection in the muddy coasts: Empirical perceptibility from the Upper Gulf of Thailand

Coastal erosion presents a significant challenge for muddy coasts worldwide. Aggravated by climate change and local factors, protecting against erosion has proven to be a complex task. The delicate sedimentary composition and the interplay of natural forces and human intervention render these muddy coasts particularly vulnerable. The choice between traditional engineering solutions and nature-based approaches is often dichotomous and entails risks for the coastline, ecology, livelihoods, and coastal management. Hence, comprehensive research on tangible, environment-friendly protection strategies with a holistic approach to muddy coastal contexts is scanty. This article aims to critically reveal the hegemonic situation around coastal erosion and protection challenges, and perceptible nature-based modalities for erosion protection in the distinctive and socio-ecologically contested atypical peri-urban muddy coastal context of the upper Gulf of Thailand. A mixed-methods approach has been applied to gain an in-depth understanding. Empirical research findings critically divulged that coastal erosion protection is extremely challenging due to the vulnerable situation espoused by the interplay of exogenous and endogenous factors in the community, feeble governance, and leadership crises. The muddy coasts require holistic considerations for a plausible and dynamic nature-based erosion protection modality that is environment-friendly, science-based, long-term, people-oriented, knowledge-driven, and based on collaborative adaptive coastal management approaches. Nature-based solutions are crucial to ensure coastal stability, management, and climate-resilient development in the fragile muddy coasts in Thailand and elsewhere in similar contexts.

Habitat suitability modelling for restoration of intertidal seagrass, Zostera noltei: A case study from the Greater Thames Estuary, UK

Seagrasses are marine flowering plants that play crucial roles in blue carbon capture and coastal protection, as well as providing a critical feeding and nursery habitat for several species. However, the extent of seagrass meadows has drastically decreased around the UK coastline since the 1930s. As such, restoration of Zostera spp. seagrasses is a growing field for academics and practitioners, yet for Zostera noltei (dwarf eelgrass) in particular, restoration is hampered by knowledge of current distributions and where to restore. Habitat suitability modelling is a valuable tool for mapping and can be applied by practitioners at a site-specific scale to identify potential areas for restoration. Here we have created a Maximum Entropy (maxent) habitat suitability model to predict Z. noltei suitability in the Greater Thames Estuary based on seven environmental variables at a 10-m resolution within an intertidal boundary. Using areas of higher suitability to identify restoration potential, our results indicate 602.9 Ha of “good” suitable habitat for potential restoration around existing Z. noltei beds in the Thames, Medway and Swale Estuaries. Despite reasonable predictive accuracy, our model was limited by the availability, resolution and extent of important environmental variables such as sediment type. Nonetheless, we believe this is a valuable tool for practitioners in the initial stage of site selection at a local scale for Z. noltei restoration projects in the UK.

Cost‐efficiency and effectiveness of coral restoration pathways

Coral reefs play a crucial role in supporting over half a billion human livelihoods through their contributions to fisheries, tourism, and coastal protection. In light of substantial global declines in coral cover and the deterioration of reef habitats due to climate change and other human‐driven influences, the urgency of coral reef restoration has escalated to help preserve their vital ecosystem services. Comprehending the economic costs associated with existing and potential future coral restoration approaches has become time‐sensitive. The median cost of coral reef restoration is estimated to be 400,000 USD/ha (at base year 2010). This estimate comes with limitations due to its reliance on reported project costs associated with various techniques. Here we look to standardize expenses through uniform costing of reported efforts based on the time invested to estimate specific per‐unit costs for restoration methods. We complement literature‐extracted values with independent estimates based on real‐world operations. Using this approach, we decipher comparative costs of different nursery and outplanting approaches and identify incorporated dependencies. To gain insights into the impact of labor costs on global coral reef restoration expenditures, we examine variations in the costs of labor in two coral reef regions. Overall, our data‐based approach identifies limitations within the most commonly practiced restoration pathways, opportunities to reduce operational costs, and points toward priorities for future research and development.

Predicting the drag coefficient of coastal trees using Support Vector Machines and boosting ensemble models

The effect of green belts on wave absorption is a critical aspect of coastal protection strategies. The effectiveness of green belts in wave absorption is influenced by factors such as the type of vegetation used, the density and width of the green belt, and the topography of the coastline. The current study aims to explore the performance of various intelligent tools, including SVM (Support Vector Machine), ABR (Ada Boost Regression), ETR (Extra Trees Regression), GBR (Gradient Boosting Regression), and RF (Random Forest), to forecast drag coefficients of coastal trees (CD). In this direction, four dimensionless parameters of relative wave height (H/d), vegetation density (D), coastal shoreline slope (S), and wave propagation velocity (u/ξE/ρ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sqrt{\\xi E/\\rho }$$\\end{document}) were assumed as input parameters, and CD was considered as the target. To evaluate the performance of developed soft computing models, various statistical indicators and graphical plots including Violin, Tylor, and Scatter were applied. The results revealed that the ETR method outperforms existing machine learning techniques with statistical results of R2 = 0.996, RMSE = 0.003, MAE = 0.002, and SI = 0.014. In addition, the Tylor diagram indicates that the distance index obtained using the ETR model exhibited a high alignment with actual data, especially in comparison with alternative tools.