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BACKGROUND AND AIMS: The increased likelihood and severity of storm events has brought into focus the role of coastal ecosystems in provision of shoreline protection by attenuating wave energy. Canopy-forming kelps, including giant kelp (Macrocystis pyrifera), are thought to provide this ecosystem service, but supporting data are extremely limited. Previous in situ examinations relied mostly on comparisons between nominally similar sites with and without kelp. Given that other factors (especially seafloor bathymetry and topographic features) often differ across sites, efforts to isolate the effects of kelp on wave energy propagation confront challenges. In particular, it can be difficult to distinguish wave energy dissipation attributable to kelp from frictional processes at the seabed that often covary with the presence of kelp. Here, we use an ecological transition from no kelp to a full forest, at a single site with static bathymetry, to resolve unambiguously the capacity of giant kelp to damp waves. METHODS: We measured waves within and outside rocky reef habitat, in both the absence and the presence of giant kelp, at Marguerite Reef, Palos Verdes, CA, USA. Nested within a broader kelp restoration project, this site transitioned from a bare state to one supporting a fully formed forest (density of 8 stipes m-2). We quantified, as a function of incident wave conditions, the decline in wave energy flux attributable to the presence of kelp, as waves propagated from outside and into reef habitat. KEY RESULTS: The kelp forest damped wave energy detectably, but to a modest extent. Interactions with the seabed alone reduced wave energy flux, on average, by 12 ± 1.4 % over 180 m of travel. The kelp forest induced an additional 7 ± 1.2 % decrease. Kelp-associated declines in wave energy flux were slightly greater for waves of longer periods and smaller wave heights. CONCLUSIONS: Macrocystis pyrifera forests have a limited, albeit measurable, capacity to enhance shoreline protection from nearshore waves. Expectations that giant kelp forests, whether extant or enhanced through restoration, have substantial impacts on wave-induced coastal erosion might require re-evaluation.

California and most other coastlines around the world are being impacted by both long-term sea-level rise and short-term extreme events. Due to California’s long and intensively developed coastline, it is an important area for evaluating responses to these challenges. The predominant historic approach to coastal erosion in California and globally has been the construction of hard coastal armoring such as seawalls and rock revetments. The concept of living shorelines—defined as using natural elements like plants, sand, or rocks to stabilize the coastline—has been widely proposed as a soft or green response to coastal erosion and flooding. However, these approaches have very limited application in high-energy environments such as California’s 1100-mile-long outer coast and are not realistic solutions for protection from wave attack at high tides or long-term sea-level rise. Each of the state’s coastal communities need to identify their most vulnerable areas, develop adaptation plans, and plan eventual relocation strategies in response to an accelerating sea-level rise.

Different types of social infrastructure, such as roads and bridges, are essential and necessary for supporting our daily lives and economic operations. Because 39% of Japan's road bridges and 27% of its tunnels will have been in use for 50 years or more by 2023, maintaining them has become a significant national concern (Ministry of Land, Infrastructure, Transport and Tourism, White Paper on Land, Infrastructure, Transport and Tourism in Japan (2017), p. 114). Because of the declining birthrate, the deteriorating labor force, and the weakening local economy, the Japanese government must maintain these social infrastructures while facing severe budgetary challenges. And efficient and economical maintenance strategies and plans are required. This paper proposes optimal maintenance policies which consider the unique circumstances of social infrastructure and minimize maintenance costs. By applying these policies to wave-dissipating blocks in Japan, the effectiveness of them is confirmed. [ABSTRACT FROM AUTHOR]

Mangroves are implemented as nature‐based solutions (NbS) for coastal protection, climate change mitigation (carbon sequestration) and other services. They play a core role in providing benefits for biodiversity, livelihoods and human well‐being. Ecological research has informed the use of mangroves as NbS, but failure of NbS projects has often been due to misconceptions about mangrove ecology and the limited use of the wide range of ecological knowledge available. Enhanced knowledge of the spatial and temporal variation in ecological processes, and differentiation among mangrove tree species and assemblages (including fauna and microbial communities) in the provision of ecosystem functions and services, will support successful use of mangroves as NbS. Knowledge of mangrove responses to the interacting pressures of climate change and human uses of the coastal zone will support resilient NbS projects. Synthesis. The success of mangroves as NbS can be improved with increased incorporation of knowledge of the ecology of mangrove plants, animals and microbes and by sharing and co‐producing knowledge within mangrove societies. [ABSTRACT FROM AUTHOR]

Higher wave heights and currents can greatly increase erosion rates. If the coastal region is exposed to long‐term erosion without protective measures, the coastline will irreversibly retreat landwards and endanger coastal assets. One of the solutions is to make use of the natural coastal vegetation, which can both stabilise the soil and contribute to wave attenuation. One of the most important plants for ecosystem services is the Elymus due to its ability to stabilise upper salt marshes and prevent erosion. In order to better predict the fluid‐plant interaction and wave attenuation by vegetation, an experimental characterization has been carried out on Elymus species in this study to determine the bending flexibility and material stiffness of the plants. For this purpose, three‐point and two‐point bending tests were performed on different sections of Elymus collected in March, Jun and September to investigate the seasonal changes in the tissue‐related mechanical behaviour. Based on the structural properties obtained from histological studies of the cross‐sections, the non‐linear material behaviour of Elymus was unravelled from the experimentally measured bending behaviour using the inverse finite element method. The results of these experiments revealed some surprising differences in the flexibility of the stems at different seasons. Furthermore, by comparing the data from the tissue samples and the simulations, valuable insight is gained into how the morphology and mechanical behaviour of plants change throughout the year. The experimental and numerical results obtained will help to predict how plants interact with the fluid and how wave attenuation relates to different vegetation conditions, for example, plant density, stiffness and dimensions. [ABSTRACT FROM AUTHOR]

Abstract Background Shallow, tropical coral reefs face compounding threats from climate change, habitat degradation due to coastal development and pollution, impacts from storms and sea-level rise, and pulse disturbances like blast fishing, mining, dredging, and ship groundings that reduce reef height and complexity. One approach toward restoring coral reef physical structure from such impacts is deploying built structures of artificial, natural, or hybrid (both artificial and natural) origin. Built structures range from designed modules and repurposed materials to underwater sculptures and intentionally placed natural rocks. Restoration practitioners and coastal managers increasingly consider incorporating – and in many cases have already begun to incorporate – built structures into coral reef-related applications, yet synthesized evidence on the ecological (coral-related; e.g., coral growth, coral survival) and physical performance of built structures in coral ecosystems across a variety of contexts (e.g., restoration, coastal protection, mitigation, tourism) is not readily available to guide decisions. To help fill this gap and inform management decisions, we systematically mapped the global distribution and abundance of published evidence on the ecological (coral-related) and physical performance of built structure interventions in shallow (≤ 30 m), tropical (35°N to 35°S) coral ecosystems. Methods To identify potentially relevant articles, we used predefined and tested strategies to search two indexing platforms, one bibliographic database, two open discovery citation indexes, one web-based search engine, one novel literature discovery tool, 19 organizational websites, and information requested from stakeholders. Discovered articles were screened according to preset eligibility criteria first by title and abstract and second by full text. Articles included during full text screening were coded to extract metadata following a predefined framework. We analyzed and visualized the evidence base to answer our primary and secondary research questions and to identify knowledge clusters and gaps. Findings are reported in a narrative synthesis. Results Our search discovered > 20,000 potentially relevant unique articles, of which 258 were included in the systematic map. The evidence base spans 50 countries, and the volume of evidence increased over the past five decades. Built structures were most commonly installed for coral restoration (61%) or coastal protection (12%). Structures were predominately characterized as artificial (87%), with fewer hybrid or natural interventions. Evidence clusters existed for intentionally designed artificial structures and outcomes associated with coral-related ecological performance, including coral mortality, growth, recruitment, cover, and diversity. Pronounced evidence gaps occurred at the intersection of several ecological coral-related performance outcomes (e.g., connectivity, microbiome) across all types of built structures; gaps also existed across most ecological coral-related outcomes for artwork and repurposed artificial structures. Physical performance of built structures was most frequently evaluated for outcomes related to waves (n = 14) and sediment and morphology (n = 11) with pervasive evidence gaps across other outcomes like storm surge and water level. Conclusions While the systematic map highlighted several evidence clusters, it also revealed pronounced evidence gaps surrounding the coral-related ecological and physical performance of built structures in coral ecosystems. The compiled evidence base will help inform policy, management, and future consideration of built structures in reef-related applications, including habitat restoration, environmental mitigation, and coastal protection. Map findings also point to promising future research avenues, such as investigating seascape-scale ecological effects of and the physical performance of built structures.

Brett, J.; Samuell, M.; Augstein, B.; Parra, S.; Hancock, E.; Saunders, C.; Wunsch, S.; Winstead, N., and Boothby, J., 2024. Nature-based coastal protection: Measuring and modeling flow reduction by oysters. Journal of Coastal Research, 40(4), 647–660. Charlotte (North Carolina), ISSN 0749-0208. Natural coastal infrastructure protects coast lines from climate hazard impacts, such as erosion and flooding. Laboratory and modeling studies presented here examine the utility of oyster reefs as a form of natural coastal protection. Oyster reefs are known to provide both water quality improvements and erosion protection. Experiments were conducted to determine the effects of oysters on flow parameters in a recirculating flow channel. A cage of eastern oysters, Crassostrea virginica, was placed in the flow channel, blocking a portion of the flow, to imitate cultured oysters in the ocean. Particle image velocimetry was used to measure the flow behind the oyster cage to examine the impact of the oysters compared with a control test with an empty cage. Average velocities were reduced by 15%, with velocities directly behind the cage reduced 70% in fresh water and reversed in salt water. A setup similar to the laboratory experiments was simulated in a Coupled Ocean–Atmospheric–Wave–Sediment Transport (COAWST) model. In the COAWST model, the oyster reef was simulated as stiff vegetation with a drag coefficient of 8, reproducing the 70% reduction measured in the lab experiments. Finally, a regional model is presented, which demonstrates the impact of an oyster reef on waves and currents at a larger scale with a drag coefficient of 1.5, the highest numerically stable value found. Within the oyster vegetation patch, depth-averaged currents were reduced 14% and bottom currents were reduced 97%. Significant wave heights were reduced by 62% above the reef and 23% shoreward of the reef. The results here suggest that regional modeling such as COAWST can be an effective tool for assessing the impact of potential coastal resilience strategies to mitigate climate hazard impacts in a climate-changed world. [ABSTRACT FROM AUTHOR]

High-energy events such as tsunamis pose significant threats to coastal infrastructure and buildings, necessitating effective mitigation strategies to minimize damage. Compared to massive construction measures, buffer blocks are increasingly recognized as a potential solution for reducing the impact of such events. Understanding their effectiveness and optimizing their placement configurations is crucial for enhancing coastal resilience. The present study aims to experimentally evaluate the influence of buffer blocks on the depth of tsunami inundation. By comparing different configurations of buffer blocks, this study seeks to identify the most effective one for reducing the inundating flow depth. The laboratory tests revealed that the buffer blocks significantly influence flow depth and its characteristics. For ratios of flow depth to block height (R) below 1.5, the buffer blocks exhibited a delay in the arrival of the flow and effectively reduced the flow depths. However, for R values greater than 1.5, the effectiveness reduced as the flow began to overtop the obstructions. The increase in the flow depth at the buffer blocks was the least for a single-row configuration, while the multiple-row configurations with wider spacing offered higher flow resistance and increased the flow depths in front of the blocks. These findings suggest that strategically configured buffer blocks can substantially enhance coastal protection against high-energy flow events during natural coastal hazards. This study provides critical insights into the design and optimization of buffer block configurations, contributing to improved coastal infrastructure resilience and disaster mitigation strategies. [ABSTRACT FROM AUTHOR]

The Smoothed Particle Hydrodynamic (SPH) method has been extensively used in coastal engineering applications, including coastal protection optimization. This paper presents a systematic literature review of research studies that have utilized SPH method for coastal protection optimization. The review covers various applications of SPH method, such as optimizing breakwaters, studying wave-structure interactions, modelling wave-induced erosion, simulating tsunami run-up and inundation, and optimizing artificial reefs. The review demonstrates the versatility of SPH method in coastal engineering applications and highlights the importance of its capabilities in simulating complex coastal processes. The limitations and challenges of using SPH method are also discussed in the context of coastal protection optimization. The review provides a comprehensive overview of the current state of research on SPH method for coastal protection optimization, which can serve as a valuable reference for researchers and practitioners in the field. [ABSTRACT FROM AUTHOR]

Humans have always lived with and around algae. At times, algae enable life, and at others, render life difficult. This article examines two sites suffering from atypical—and potentially harmful—algae blooms: Lake Erie in Ohio (USA) and the Riviera Maya (Mexico). Referring to ethnographic fieldwork, as well as to newspaper articles, policy papers, and online fora, we demonstrate how the narratives around algae have changed over time and shed light on how changes in these narratives opened the discussion of wetland repair and coastal integrity. We argue that conceptualizing algae as the "unwanted" unifies people, brings them together, and makes the treatment of lake eutrophication and coastal protection actionable. [ABSTRACT FROM AUTHOR]

Coastal erosion, extreme climate events, and the loss of biodiversity are important consequences of climate change that directly impact our society. The needs to develop effective engineering practices using nature as model and mentor are now emerging aimed to develop high-performance coastal infrastructures integrating and sustaining local marine ecosystems. In this scenario, the present article describes the concept development and preliminary experimentation of simplified bioinspired models to evaluate their hydraulic performances. This study is part of a future vision to develop submerged barriers, printed with eco-friendly materials, characterized by high hydraulic performances and cable of supporting local biodiversity. Following a top-down approach, the functional features of key organisms were abstracted and transferred to create three bioinspired models. The hydraulic performance of these models is analyzed in terms of wave transmission, reflection, and dissipation under various wave conditions. Under certain circumstances, the bioinspired barriers demonstrate wave attenuation comparable to traditional submerged breakwaters. A method based on skin friction and drag-related processes provides a simple heuristic explanation of how the shape of the models affect the transmission coefficient. The results achieved offer valuable insights for the design of future coastal defense systems that are inspired by, and integrated with, natural ecosystems. [ABSTRACT FROM AUTHOR]

Background: Shallow, tropical coral reefs face compounding threats from climate change, habitat degradation due to coastal development and pollution, impacts from storms and sea-level rise, and pulse disturbances like blast fishing, mining, dredging, and ship groundings that reduce reef height and complexity. One approach toward restoring coral reef physical structure from such impacts is deploying built structures of artificial, natural, or hybrid (both artificial and natural) origin. Built structures range from designed modules and repurposed materials to underwater sculptures and intentionally placed natural rocks. Restoration practitioners and coastal managers increasingly consider incorporating – and in many cases have already begun to incorporate – built structures into coral reef-related applications, yet synthesized evidence on the ecological (coral-related; e.g., coral growth, coral survival) and physical performance of built structures in coral ecosystems across a variety of contexts (e.g., restoration, coastal protection, mitigation, tourism) is not readily available to guide decisions. To help fill this gap and inform management decisions, we systematically mapped the global distribution and abundance of published evidence on the ecological (coral-related) and physical performance of built structure interventions in shallow (≤ 30 m), tropical (35°N to 35°S) coral ecosystems. Methods: To identify potentially relevant articles, we used predefined and tested strategies to search two indexing platforms, one bibliographic database, two open discovery citation indexes, one web-based search engine, one novel literature discovery tool, 19 organizational websites, and information requested from stakeholders. Discovered articles were screened according to preset eligibility criteria first by title and abstract and second by full text. Articles included during full text screening were coded to extract metadata following a predefined framework. We analyzed and visualized the evidence base to answer our primary and secondary research questions and to identify knowledge clusters and gaps. Findings are reported in a narrative synthesis. Results: Our search discovered > 20,000 potentially relevant unique articles, of which 258 were included in the systematic map. The evidence base spans 50 countries, and the volume of evidence increased over the past five decades. Built structures were most commonly installed for coral restoration (61%) or coastal protection (12%). Structures were predominately characterized as artificial (87%), with fewer hybrid or natural interventions. Evidence clusters existed for intentionally designed artificial structures and outcomes associated with coral-related ecological performance, including coral mortality, growth, recruitment, cover, and diversity. Pronounced evidence gaps occurred at the intersection of several ecological coral-related performance outcomes (e.g., connectivity, microbiome) across all types of built structures; gaps also existed across most ecological coral-related outcomes for artwork and repurposed artificial structures. Physical performance of built structures was most frequently evaluated for outcomes related to waves (n = 14) and sediment and morphology (n = 11) with pervasive evidence gaps across other outcomes like storm surge and water level. Conclusions: While the systematic map highlighted several evidence clusters, it also revealed pronounced evidence gaps surrounding the coral-related ecological and physical performance of built structures in coral ecosystems. The compiled evidence base will help inform policy, management, and future consideration of built structures in reef-related applications, including habitat restoration, environmental mitigation, and coastal protection. Map findings also point to promising future research avenues, such as investigating seascape-scale ecological effects of and the physical performance of built structures. [ABSTRACT FROM AUTHOR]

Griggs, G., 2024. Can we make coastal communities resilient to sea-level rise? Journal of Coastal Research, 40(3), 571–576. Charlotte (North Carolina), ISSN 0749-0208. "Resilient" is a term that has gotten increasingly widespread usage in recent years as a solution or response for coastal communities to the well-documented global rise in sea level. The message that is usually conveyed seems to be that if we can make coastal communities resilient, everything will be fine and we will have solved the challenge of how to adapt to a rising sea. The federal government and some coastal state government agencies are providing grant money to encourage coastal communities to develop plans to become more resilient. This is an appropriate time to ask what would a resilient coastal community look like and can we actually make a community resilient to future sea-level rise, and if so, for how long? [ABSTRACT FROM AUTHOR]

This dataset quantifies storm intensity of approximately 130 unique historical storms along the New Jersey coastline from 1980 to 2014 for three separate sea level conditions. Namely, (1) as observed in the historical record; (2) detrended to 1997 mean sea level and (3) adjusted to the 2050 and 2100 sea level rise scenarios presented in the International Panel on Climate Change's (IPCC) Sixth Assessment Report (AR6). Projected sea level scenarios are adjusted to include local vertical land movement. Storm intensity is quantified in terms of erosion potential, considering the combination of total water level, wave heights, and storm duration. The observational dataset includes both tropical and extratropical storms and quantifies both the cumulative (duration) and peak (single hour) storm intensity for each storm and sea level rise (SLR) condition. Additionally, hourly time series of wave characteristics and water levels are provided at 13 locations along the New Jersey coast, facilitating hydrodynamic forcing of nearshore models. The dataset provides the means and methods to directly compare historical storms under future SLR conditions.

Coastal erosion is a growing problem worldwide and seriously threatens coastal infrastructure ecosystems and communities, particularly in areas where urban development has encroached on natural shorelines. Salty urbanism, an approach to urban design that incorporates natural features and works in harmony with coastal environments, offers a promising solution to this problem. This review explores strategies for coastal erosion reduction, particularly emphasizing community participation within the context of salty urbanism. By investigating the advantages of incorporating salty urbanism and community engagement in coastal management through a literature study, this paper explores a case study-Paradeep, a coastal city in India. The aim is to comprehend how salty urbanism principles have been assimilated into coastal erosion initiatives in Paradeep and to identify potential opportunities for further integration to maximize benefits. The results emphasize the importance of integrating salty urbanism and community participation into coastal erosion management strategies, especially in coastal areas where these principles are either lacking or only minimally incorporated, often without a clear recognition of the term "salty urbanism" itself. Utilizing a mixed-methods research approach, the study integrates primary data from case studies and interviews, along with inferences from literature studies to gain valuable insights from coastal community residents and stakeholders. The findings will provide a significant contribution to advancing strategies and initiatives that advocate for sustainable coastal development and management by suggesting ways to incorporate a community participation-based salty urbanism approach in similar contexts.

Coastal erosion is a growing problem worldwide and seriously threatens coastal infrastructure ecosystems and communities, particularly in areas where urban development has encroached on natural shorelines. Salty urbanism, an approach to urban design that incorporates natural features and works in harmony with coastal environments, offers a promising solution to this problem. This review explores strategies for coastal erosion reduction, particularly emphasizing community participation within the context of salty urbanism. By investigating the advantages of incorporating salty urbanism and community engagement in coastal management through a literature study, this paper explores a case study-Paradeep, a coastal city in India. The aim is to comprehend how salty urbanism principles have been assimilated into coastal erosion initiatives in Paradeep and to identify potential opportunities for further integration to maximize benefits. The results emphasize the importance of integrating salty urbanism and community participation into coastal erosion management strategies, especially in coastal areas where these principles are either lacking or only minimally incorporated, often without a clear recognition of the term "salty urbanism" itself. Utilizing a mixed-methods research approach, the study integrates primary data from case studies and interviews, along with inferences from literature studies to gain valuable insights from coastal community residents and stakeholders. The findings will provide a significant contribution to advancing strategies and initiatives that advocate for sustainable coastal development and management by suggesting ways to incorporate a community participation-based salty urbanism approach in similar contexts. [ABSTRACT FROM AUTHOR]

Political attention for and research on nature-based solutions in coastal flood an erosion risk management has increased significantly in recent years. Literature suggests that there remains a historical inertia towards nature-based solutions due to the continued predominance of classical grey infrastructures like dikes and stone revetments. In this regard, Schleswig–Holstein can act as a living laboratory as it has a long tradition of applying grey and green infrastructures as well as nature-based measures like salt marsh enhancement techniques to protect against coastal flooding and erosion. Based on an assessment of structural and non-structural coastal flood and erosion risk management measures in Schleswig–Holstein, this paper elaborates on the prospects of grey and green infrastructures in the context of stronger sea level rise. This article concludes that nature-bases solutions for coastal flood and erosion risk management are not a recent development. Nature-based management of green infrastructures can significantly improve their functionality, also with regard to the expected stronger SLR, and includes non-structural measures like codes and prohibitions. Green infrastructures and their nature-based management successfully complement and support grey infrastructures i.e., as green as possible, as grey as necessary. However, with the exception of dunes as natural flood defenses, green infrastructures cannot render grey infrastructures superfluous. [ABSTRACT FROM AUTHOR]

Coastal erosion is a pervasive global phenomenon, exemplified by the Hel Peninsula situated in the Gulf of Gdańsk, the southern Baltic Sea. The geological constitution of the Hel Peninsula, characterized by sandy and loosely consolidated material, predisposes its coastal zones to continual morphological changes. The peninsula's limited width and elevation exacerbate shoreline erosion, particularly during periods of heightened storm activity. This study scrutinizes the effectiveness of coastal nourishment interventions, with a specific focus on segments influenced by the Władysławowo port and the Kuźnica vicinity, over several years. This specific section of the coast serves as a significant case study due to its role as a transit zone for sand transport along the whole peninsula. Protective measures, including shore nourishments and coastal groynes, aim to mitigate erosion impacts. Utilizing Airborne Laser Scanning (ALS) data spanning from 2008 to 2022, erosion dynamics were analyzed. The analysis reveals significant erosion patterns coinciding with the frequency and volume of nourishment material deposition, particularly evident in heavily nourished areas proximate to Władysławowo and Kuźnica. Despite persistent monitoring endeavors, persistent erosive trends pose imminent threats to Kuźnica's infrastructure, necessitating further research into the efficacy of implemented coastal protection measures. [ABSTRACT FROM AUTHOR]

This article reviews the literature covering the period from 1965 to 2020 dedicated to the issue of artificial beach nourishment along the Polish coast, with a particular focus on the Hel Peninsula. The primary sources used in this work include 34 reports from unpublished case studies and projects implemented by the Department of Maritime Hydrotechnics, Maritime Institute in Gdańsk, between 1971 and 2020. This paper also presents detailed information about the total fill volume in cubic meters of dredged material deposited along the Polish coast and lagoon shores in 1980–2020. During these 40 years, approximately 40.5 million m3 of sediment was deposited along the Polish coast and lagoon shores. Particular consideration was given to beach fills along the Hel Peninsula, which was at actual risk of breaking in its basal and central sections after intense storms at the turn of 1988 and 1989. The survey materials collected enabled the assessment of the coastal morphodynamics of the peninsula under the Coastal Protection Program through the prism of changes in the fill volume along the coastal sections, which were replenished with material coming from submarine deposits. The peninsula's stability was also assessed, taking into account the ongoing climate change. Moreover, this article discusses the proposed rules and terms for protecting the Polish coast by way of artificial nourishment. [ABSTRACT FROM AUTHOR]

Ecosystems vary broadly in their responses to disturbance, ranging from highly impacted to resilient or resistant. We conducted a large‐scale analysis of hurricane disturbance effects on coastal marshes by examining 20 years of data from 10 sites covering 100,000 ha at the Georgia Coastal Ecosystems Long‐Term Ecological Research site distributed across gradients of salinity and proximity to the ocean. We analyzed the impacts of Hurricanes Matthew (in 2016) and Irma (in 2017) on marsh biota (plants, crabs, and snails) and physical attributes (erosion, wrack deposition, and sedimentation). We compared these variables prior to the storms (2000–2015) to years with storms (2016, 2017) to those after the storms (2018–2020). Hurricanes generated storm surges that increased water depth and salinity of oligotrophic areas for up to 48 h. Biological variables in the marsh showed few effects of the hurricanes. The only physical variable affected was creek bank slumping; however, slumping had already increased a year before the hurricanes, suggesting that slumping could have a different cause. Thus, our study uncovered only minor, ephemeral impacts on Georgia coastal marshes, highlighting their resistance to hurricane disturbance of the lower magnitude that typically confronts this region of coastline. [ABSTRACT FROM AUTHOR]

Amidst escalating global changes and heightened human activities, tidal flats worldwide are facing a transition from accretion to erosion. In order to quantify the growth pattern of tidal flats and its response to changes in multiple external driving factors, here we established a geometric model, in combination with field surveys, to study the historical behavior (1127–1990) and future trends (2100) of a typical tidal flat system on the Jiangsu coast, China. The results indicate that sediment supply and relative sea level change determine the accretion‐erosion status and the eventual morphological pattern of the tidal flat. If these two factors remain stable and sediment supply can compensate for the increase in sediment accommodation space caused by sea level change, the tidal flat will continue to accrete until its growth limit is reached. Otherwise, tidal flats will face erosion risk, which can be further enhanced by localized land subsidence. Furthermore, changes in the coastal profile show a trend of progressive retreating, with the lower part of intertidal zone being eroded more rapidly than its upper part. This demonstrates that the sediment supply has been reduced to such a level that the present "in‐transition" evolution pattern of central Jiangsu coast will soon be replaced by severe inundation and erosion. Hence, we advocate for a comprehensive, multi‐tiered coastal protection strategy focusing on wave suppression, enhancement of sediment retention, and increased storm resistance. This strategy underscores fundamental underlying mechanisms of the accretion‐erosion transition, which is crucial for the future safeguarding of coastal wetlands globally. Plain Language Summary: Tidal flats are important potential land resources. Over the Holocene period, under increased sediment from rivers has led to rapid growth in most coastal areas, supporting the prosperity of coastal cities. However, uncertainties exist regarding the limits of this growth, and global changes and human activities are causing tidal flats worldwide to shift from growth to erosion. To understand the tidal flats growth patterns and their response to future challenges, we developed a geometric model based on key processes. Field surveys and a millennium‐scale study in eastern China support the model's reliability. Our findings highlight sediment supply and relative sea‐level change as key factors in tidal flat evolution, with growth limitations even with sustained sediment supply. We propose a protective scheme based on tidal flat evolution mechanisms to enhance coastal resilience against global change. Key Points: Geometric modeling is employed to simulate the evolution of a transitional tidal flat system and tested against historical processesThe central coast of Jiangsu, China, is anticipated to reach its growth limit and become eroding around 2065A stepped green protection scheme, designed in a manner progressing from sea to land, is established to safeguard coastal wetlands [ABSTRACT FROM AUTHOR]

With rising sea level and climate change, coastal protection against natural hazards such as typhoons and storm surges becomes increasingly important in densely populated areas. Yet, how to integrate necessary engineering structures for coastal protection with development of a healthy socio-ecological system represents a realistic question challenging both the science community and practitioners. This study is motivated to examine the role and influence of diverse dimensions in the construction of seawalls for coastal protection and sustainability. Focusing on a case along the Qiantang River in China, we structured an indicator framework based on technical standards and literature for guiding the design and construction of ecological seawalls. We explored and illustrated the application of a multi-criteria decision making (MCDM) method to analyze proposed indicators as design factors and their influence in practice as reflected by expert evaluation. Our empirical analysis revealed a heterogeneous role and influence of different indicators and their asymmetric interaction in seawall construction aimed to deliver structural safety, ecological functions and social development. This study provides important insights into the design and management of seawalls as an integrated, nature-based solution for coastal protection and sustainability, informing practice improvement and contributing to the literature. [ABSTRACT FROM AUTHOR]

This paper provides a comprehensive overview on coastal protection and hazard mitigation by mangroves. Previous studies have made great strides to understand the mechanisms and influencing factors of mangroves' protection function, including wave energy dissipation, storm surge damping, tsunami mitigation, adjustment to sea level rise and wind speed reduction, which are systematically summarized in this study. Moreover, the study analyzes the extensive physical models, based on indoor flume experiments and numerical models, that consider the interaction between mangroves and hydrodynamics, to help our understanding of mangrove-hydrodynamic interactions. Additionally, quantitative approaches for valuing coastal protection services provided by mangroves, including index-based and process-resolving approaches, are introduced in detail. Finally, we point out the limitations of previous studies, indicating that efforts are still required for obtaining more long-term field observations during extreme weather events, to create more real mangrove models for physical experiments, and to develop numerical models that consider the flexible properties of mangroves to better predict wave propagation in mangroves having complex morphology and structures. [ABSTRACT FROM AUTHOR]

Aims: Latitudinal gradients in plant communities are well studied, yet how these fundamental ecological patterns influence ecosystem recovery after extreme weather events remains largely unknown. In coastal foredunes, we investigated how the cover of a key dune‐building grass (Uniola paniculata), vegetation diversity and vegetation cover vary along a short latitudinal gradient during recovery from hurricane disturbance. Location: Southeastern USA. Methods: We surveyed 24 sites, from central Florida to north Georgia (>400 km), four times over 18 months. General linear mixed‐effect models were used to unravel patterns of vegetation responses across latitude. Results: Vegetation properties showed countervailing patterns across the latitudinal gradient. While vegetation richness, functional diversity and total cover generally declined, Uniola cover increased with increasing latitude. Further, the latitude–richness relationship strengthened while the latitude–functional diversity relationship was invariant with increasing time since the hurricane disturbance. Meanwhile, the latitude–Uniola association was seasonally dependent and strongest in the summer. Latitude also influenced diversity–cover relationships: vegetation cover was positively related to species richness at lower latitudes, while it was positively associated with functional diversity only at northern sites. We found no relationship between species richness or functional diversity and increases in cover between time steps; however, recruitment of new species and functional groups was associated with increases in vegetation cover between time steps at northern sites. Conclusions: Our study highlights the temporal dynamism and contrasting patterns along latitudinal gradients exhibited by key engineering species and overall plant diversity in foredunes — a crucial line of coastal protection — exposed to hurricane disturbances. These results suggest a need for greater integration of latitudinal and diversity effects into our understanding of coastal dune resilience. They also highlight the potential benefits of enhancing dune plant biodiversity, particularly in areas where the dune‐building grasses that are classically employed in restoration (e.g., Uniola) are unfavoured, to accelerate the re‐establishment of well‐vegetated dunes. [ABSTRACT FROM AUTHOR]

Estimating maritime climate accurately is essential to ensure the safety of marine structures. The most reliable data are in situ measurements, but due to the lack of this kind of data in both time and space, other datasets, from reanalyses and wave models, have to be used. In this study, data from the three main databases of the Spanish Mediterranean Sea used for the design of maritime structures (ERA5, Waverys and SIMAR-WANA) were compared with buoy data from Valencia, Alicante, and Cabo de Palos. A statistical analysis, using Python, MATLAB, and the Ameva tool, was performed on both the entire historic record (20,362,032 data) and the most extreme data distribution (95th percentile). Then, further analysis was performed to assess the consequences of using these datasets in the design of coastal protection and their reliability. Waverys performed slightly better than the in situ measurements and SIMAR-WANA underestimated the extreme values of significant wave height the least. Regarding the consequences on the design of coastal protection structures, the estimation of extreme events proved to be of particular interest, with the databases typically underestimating the values of extreme events, which was determined to have the potential to lead to errors in the design of coastal protection structures by up to 60%. [ABSTRACT FROM AUTHOR]

In parallel with many other countries, the government of Japan has started to tackle coastal adaptations to climate change. In 2020, the national Basic Policy for Coastal Protection was revised to add the statement that coastal management should account for future changes in coastal hydrodynamic conditions due to climate change. Following this policy, the management body of each coast is requested to revise the Basic Plan for Coastal Protection by 2025. This paper first reviews the current legal frameworks and measures of coastal protection and conservation, such as disaster prevention and mitigation against stormy waves, storm surges and tsunamis, beach conservation, and maintenance of coastal protection facilities. Second, the paper outlines the recent actions taken for coastal adaptation to climate change. With example cases in Osaka and Tokyo bays, it is described how design conditions such as design waves and water levels should account for the influence of climate change. It is also described how adaptive beach management should be implemented accounting for projections of future beach changes. Finally, the paper discusses future challenges in coastal adaptation strategies to climate change in Japan, such as introduction of integrated coastal zone management and other potential options that have not been implemented in Japan. [ABSTRACT FROM AUTHOR]

The coastal zone is a fascinating place that comprises the interface between sea and land. This interface, which is both very dynamic and sensitive, has been affected by strong urban and industrial pressures, and an increase in both traffic and recreational uses, leading to the deterioration of natural habitats and the growing instability of residential areas. Added to this disruption is ongoing climate change, which will lead to rising sea levels and increased wave action. Another problem we are increasingly concerned about is ocean pollution, which has been one of the main causes of threats to deep-water coral reef areas. The main sources of pollution include oil spills and offshore oil drilling. The effects of pollution caused by oil spills can not only seriously affect the global environmental balance of our planet but can also, on a different scale, seriously affect the economy of countries whose main resources depend heavily on the sea. Wave energy has the potential to alleviate the world's dependence on depleting fossil energy resources. With regard to coastal protection, the development of ecological solutions to preserve ecosystems and address coastal processes as an alternative to traditional coastal protection structures (seawalls, groins and breakwaters) is becoming increasingly important. These structures, generally referred to as passive measures, are usually built to alter the effects of sea waves, currents and the movement of sand along the coastline, with the aim of protecting beaches, ports and harbors. The concerns outlined are critically addressed throughout this review article. All of them are highly relevant today and, as demonstrated throughout this article, are expected to grow even more and with much more pronounced consequences starting from the middle of the current century. [ABSTRACT FROM AUTHOR]

With the recent development from grey infrastructures to green infrastructures, artificial reefs become more popular in coastal protection projects. To investigate the responses of beach profile evolution to the presence of an artificial reef, a non-hydrostatic model is established. Both hydrodynamic and morphodynamic evolution for the beach with and without an artificial reef are compared under regular wave conditions. In addition, the protected beach profile evolution by an artificial reef is discussed under irregular wave conditions. Three key parameters in non-hydrostatic simulation are considered for sensitivity analysis, including maximum wave steepness criterium (maxbrsteep), water depth factor (depthscale), and equilibrium sediment concentration factor (sedcal). The numerical results under regular wave conditions indicate that the artificial reef enhances wave attenuation by inducing wave breaking. In addition, the artificial reef reduces local flow velocity and offshore sediment transport by 51%, therefore decrease the total erosion by 53%. Over the artificial reef, wave skewness and asymmetry go through a drastic change. Under irregular wave conditions, short waves contribute to the wave energy mainly and reflection-induced standing wave effects decline considerably. It demonstrates that the artificial reef can protect the beach from regular and irregular waves by reducing erosion and offshore transport of suspended sediments. Moreover, in the wave breaking area, the increase of maximum wave steepness criterium may give arise to the wave height. The morphological evolution is more sensitive to water depth factor than equilibrium sediment concentration factor, because the former is a controlling factor for beach profile characteristics while the latter forms the sandbar varying irregularly in shape. [ABSTRACT FROM AUTHOR]

Seagrass ecosystem is an important component of the coastal and marine biodiversity, yet seagrasses remain in decline in the Philippines. This study carried out spatial assessment on seagrass ecosystem in Maribojoc Bay. The spatial dataset consists of geographic, ecological and social data. Particularly, this study determined the spatial associations across environmental variables with seagrass biotic variables. Seven species of seagrass were identified and the occurrence ranged from Thalassia-Enhalus bed to a maximum of seven species in mixed communities. Maribojoc Bay had a "fair" seagrass condition. The findings of the study provide spatial data demonstrating that seagrass ecosystem in Maribojoc Bay was influenced by several environmental factors and land-use practices. Land-use related to human development had the most important impact on seagrass biological variables in the present study. Seagrass beds adjacent to human development showed lower seagrass density, species richness, percent cover and Th shoot density. Hence, the nature of coastal land is an important determinant of seagrass health and condition. The findings of the study suggest that mitigating human activities on land adjacent to seagrass communities is more important for maintaining seagrass biodiversity. It is therefore important to consider both marine and land-based strategies for mitigating declines in seagrasses and degradation. [ABSTRACT FROM AUTHOR]

Abstract Ecosystems vary broadly in their responses to disturbance, ranging from highly impacted to resilient or resistant. We conducted a large‐scale analysis of hurricane disturbance effects on coastal marshes by examining 20 years of data from 10 sites covering 100,000 ha at the Georgia Coastal Ecosystems Long‐Term Ecological Research site distributed across gradients of salinity and proximity to the ocean. We analyzed the impacts of Hurricanes Matthew (in 2016) and Irma (in 2017) on marsh biota (plants, crabs, and snails) and physical attributes (erosion, wrack deposition, and sedimentation). We compared these variables prior to the storms (2000–2015) to years with storms (2016, 2017) to those after the storms (2018–2020). Hurricanes generated storm surges that increased water depth and salinity of oligotrophic areas for up to 48 h. Biological variables in the marsh showed few effects of the hurricanes. The only physical variable affected was creek bank slumping; however, slumping had already increased a year before the hurricanes, suggesting that slumping could have a different cause. Thus, our study uncovered only minor, ephemeral impacts on Georgia coastal marshes, highlighting their resistance to hurricane disturbance of the lower magnitude that typically confronts this region of coastline.

Abstract Amidst escalating global changes and heightened human activities, tidal flats worldwide are facing a transition from accretion to erosion. In order to quantify the growth pattern of tidal flats and its response to changes in multiple external driving factors, here we established a geometric model, in combination with field surveys, to study the historical behavior (1127–1990) and future trends (2100) of a typical tidal flat system on the Jiangsu coast, China. The results indicate that sediment supply and relative sea level change determine the accretion‐erosion status and the eventual morphological pattern of the tidal flat. If these two factors remain stable and sediment supply can compensate for the increase in sediment accommodation space caused by sea level change, the tidal flat will continue to accrete until its growth limit is reached. Otherwise, tidal flats will face erosion risk, which can be further enhanced by localized land subsidence. Furthermore, changes in the coastal profile show a trend of progressive retreating, with the lower part of intertidal zone being eroded more rapidly than its upper part. This demonstrates that the sediment supply has been reduced to such a level that the present “in‐transition” evolution pattern of central Jiangsu coast will soon be replaced by severe inundation and erosion. Hence, we advocate for a comprehensive, multi‐tiered coastal protection strategy focusing on wave suppression, enhancement of sediment retention, and increased storm resistance. This strategy underscores fundamental underlying mechanisms of the accretion‐erosion transition, which is crucial for the future safeguarding of coastal wetlands globally.

Growth and expansion in construction has increased recently and especially in coastal areas. In Alexandria, Egypt, mega projects such as El-Max Port Project (Middle Port), Port of ABU QIR (EG AKI), hotels, and restaurants were spread along the coastal lines, thus, it will need a high electrical energy. Although, the great economic benefits of such projects, it will have some negative impacts, such as overloading on the present grid. According to recommendations of COP 27, Egypt is one of the countries targeting to increase the dependency on green energy to minimize the production of greenhouse gases. This study is interested in wave energy as a renewable source of energy. Using a machine learning model that predicts wave height and wave period through the year 2030 in three separate places (Alamein, Alexandria, and Mersa-Matruh), this study will try to estimate the future amount of wave energy along Egypt's coast. Hourly measurements of the significant height and the mean wave period for the period 1979–2023 have been utilized for this. An extractor for wave energy can also be built on the Overtopping Breakwater for Energy Conversion (OBREC) in order to use this energy to fill the hole in the electric grid. The machine learning model was developed using hourly wave height and period data from three buoys, and as a result, the results have a root mean square error (RMSE) of 0.52. The amount of energy taken, wave power, and system efficiency at each place were then fully determined using a mathematical model for each of the three locations. The area along the coast of Alamein had the highest energy extraction rates, followed by Alexandria and Mersa-Matruh in that order. The results of the mathematical model indicate that the yearly power generation for Alamein, Alexandria, and Mersa-Matruh is 25287 MWhr, 14713 MWhr, and 4865 MWhr, respectively.

Mangroves, the distinctive coastal ecosystems of the tropics and sub-tropics, serve as crucial intersections between terrestrial and marine environments. In this review, we delve into the manifold roles of mangroves, showcasing their significance in environmental engineering and sustainable ecosystem practices. Historically undervalued, mangroves have undergone a renaissance in perception, with increasing recognition of their indispensable ecological services, ranging from coastal protection and blue carbon sequestration to fostering biodiversity and supporting sustainable fisheries. As we explore their potential in phytoremediation, bioremediation, urban resilience, and ecosystem-based adaptation, the synergistic relationships between mangroves and their resident microorganisms are highlighted, offering innovative avenues for environmental restoration. Additionally, the review underscores the importance of collaborative partnerships for mangrove conservation, emphasizing the need for a harmonized approach between stakeholders. In an era marked by rapid environmental changes, this review accentuates the multifunctional capability of mangroves as nature's coastal architects, advocating for their conservation and integration into sustainable ecosystem management strategies.

Abstract Background Shallow, tropical coral reefs face compounding threats from habitat degradation due to coastal development and pollution, impacts from storms and sea-level rise, and pulse disturbances like blast fishing, mining, dredging, and ship groundings that reduce coral reefs’ height and variability. One approach toward restoring coral reef structure from these threats is deploying built structures. Built structures range from engineered modules and repurposed materials to underwater sculptures and intentionally placed natural rocks. Restoration practitioners and coastal managers increasingly consider incorporating built structures, including nature-based solutions, into coral reef-related applications. Yet, synthesized evidence on the ecological and physical performance of built structure interventions across a variety of contexts (e.g., restoration, coastal protection, mitigation, tourism) is not readily available to guide decisions. To help inform management decisions, here we aim to document the global evidence base on the ecological and physical performance of built structures in shallow (≤ 30 m) tropical (35° N to 35° S latitude) coral ecosystems. The collated evidence base on use cases and associated ecological and physical outcomes of built structure interventions can help inform future consideration of built structures in reef restoration design, siting, and implementation. Method To discover evidence on the performance of built structures in coral reef-related applications, such as restoration, mitigation, and coastal protection, primary literature will be searched across indexing platforms, bibliographic databases, open discovery citation indexes, a web-based search engine, a novel literature discovery tool, and organizational websites. The geographic scope of the search is global, and there is no limitation to temporal scope. Primary literature will be screened first at the level of title and abstract and then at the full text level against defined eligibility criteria for the population, intervention, study type, and outcomes of interest. Metadata will be extracted from studies that pass both screening levels. The resulting data will be analyzed to determine the distribution and abundance of evidence. Results will be made publicly available and reported in a systematic map that includes a narrative description, identifies evidence clusters and gaps, and outlines future research directions on the use of built structures in coral reef-related applications.

High-energy events such as tsunamis pose significant threats to coastal infrastructure and buildings, necessitating effective mitigation strategies to minimize damage. Compared to massive construction measures, buffer blocks are increasingly recognized as a potential solution for reducing the impact of such events. Understanding their effectiveness and optimizing their placement configurations is crucial for enhancing coastal resilience. The present study aims to experimentally evaluate the influence of buffer blocks on the depth of tsunami inundation. By comparing different configurations of buffer blocks, this study seeks to identify the most effective one for reducing the inundating flow depth. The laboratory tests revealed that the buffer blocks significantly influence flow depth and its characteristics. For ratios of flow depth to block height (R) below 1.5, the buffer blocks exhibited a delay in the arrival of the flow and effectively reduced the flow depths. However, for R values greater than 1.5, the effectiveness reduced as the flow began to overtop the obstructions. The increase in the flow depth at the buffer blocks was the least for a single-row configuration, while the multiple-row configurations with wider spacing offered higher flow resistance and increased the flow depths in front of the blocks. These findings suggest that strategically configured buffer blocks can substantially enhance coastal protection against high-energy flow events during natural coastal hazards. This study provides critical insights into the design and optimization of buffer block configurations, contributing to improved coastal infrastructure resilience and disaster mitigation strategies.

Climate change-induced sea level rise has exacerbated coastal change putting millions of people at risk from coastal hazards, such as flooding and coastal erosion. Nature-based solutions have been recognised as an opportunity to simultaneously address the coastal hazard risks and achieve biodiversity goals. While such solutions are included in climate adaptation strategies, “hard” engineered solutions are still often preferred by those implementing the schemes. We sought to explore the diverse perspectives on UK coastal flood risk management among interested and/or affected groups by utilising the Q-methodology. We identified five perspectives: (1) The Pro-Green Practitioners; (2) The Future-Planning Relocators; (3) The Case-by-Case Thinkers; (4) The Cautious Practitioners and (5) The Climate Change Concerned. All five perspectives strongly valued the co-benefits of nature-based solutions and their role in coastal risk reduction. None of the perspectives prioritised hard-engineered solutions as the primary flood protection strategy in the UK, though they recognised their role in protecting essential infrastructure. The main disagreements between perspectives were (1) on the need for relocation strategies, and (2) whether nature-based solutions could cause social inequalities. The Q-methodology does not identify how prevalent such perspectives are, thus further research is needed to assess the social acceptance of nature-based solutions.

Climate change has been recognised as a major concern in coastal hotspots exposed to multiple climate hazards under regionally specific characteristics of vulnerability. We review the emerging research and current trends in the academic literature on coastal climate risk and adaptation from a human security perspective. The ecological and socioeconomic developments are analysed for key risk areas, including coastal infrastructure; water, food and fisheries; health; human mobility; and conflict, taking the different geographical contexts of coastal areas in islands, megacities and deltas into consideration. Compounding and cascading interactions require integrative research and policy approaches to address the growing complexity. Governance mechanisms focus on coastal management and adaptation, nature-based solutions and community-based adaptation, considering their synergies and trade-offs. This perspective allows for a holistic view on climate risks to human security and vicious circles of societal instability in coastal systems and the interconnectedness of different risk dimensions and systems necessary for sustainable and transformative adaptation solutions for the most affected coastal hotspots.

Background: Shallow, tropical coral reefs face compounding threats from habitat degradation due to coastal development and pollution, impacts from storms and sea-level rise, and pulse disturbances like blast fishing, mining, dredging, and ship groundings that reduce coral reefs' height and variability. One approach toward restoring coral reef structure from these threats is deploying built structures. Built structures range from engineered modules and repurposed materials to underwater sculptures and intentionally placed natural rocks. Restoration practitioners and coastal managers increasingly consider incorporating built structures, including nature-based solutions, into coral reef-related applications. Yet, synthesized evidence on the ecological and physical performance of built structure interventions across a variety of contexts (e.g., restoration, coastal protection, mitigation, tourism) is not readily available to guide decisions. To help inform management decisions, here we aim to document the global evidence base on the ecological and physical performance of built structures in shallow (≤ 30 m) tropical (35° N to 35° S latitude) coral ecosystems. The collated evidence base on use cases and associated ecological and physical outcomes of built structure interventions can help inform future consideration of built structures in reef restoration design, siting, and implementation. Method: To discover evidence on the performance of built structures in coral reef-related applications, such as restoration, mitigation, and coastal protection, primary literature will be searched across indexing platforms, bibliographic databases, open discovery citation indexes, a web-based search engine, a novel literature discovery tool, and organizational websites. The geographic scope of the search is global, and there is no limitation to temporal scope. Primary literature will be screened first at the level of title and abstract and then at the full text level against defined eligibility criteria for the population, intervention, study type, and outcomes of interest. Metadata will be extracted from studies that pass both screening levels. The resulting data will be analyzed to determine the distribution and abundance of evidence. Results will be made publicly available and reported in a systematic map that includes a narrative description, identifies evidence clusters and gaps, and outlines future research directions on the use of built structures in coral reef-related applications. [ABSTRACT FROM AUTHOR]

Different countries practice various approaches to coastal erosion management, which have characteristics strengths and weaknesses. Protection of the land from coastal erosion is a complex task, and it depends on many socioeconomic and environmental factors. Asian countries have unique cultural, social, environmental, and political behaviors. Therefore, the objectives of this study are to analyze the current status of coastal management in Thailand, Malaysia, and Sri Lanka, and to synthesize a common coastal management framework for those countries. In this study, we analyzed the situation of coastal erosion, and the existing responsible government department and their legal authorities in Thailand, Malaysia, and Sri Lanka. After that, we evaluated specific challenges and common issues in the management of coastal erosion. The main challenges can be summarized as rapid urbanization and the construction of infrastructure along the coasts, rising sea levels as a consequence of climate change, inadequate coastal zone planning and management framework, a deficit of sediment supply compared to erosion rates, and face constraints in terms of financial and technical resources for coastal erosion management. A multi-faceted approach is required to address these challenges, and it combines both structural and non-structural measures. For example, this approach involves (i) sustainable coastal zone planning, (ii) the implementation of nature-based solutions, (iii) restoration of natural coastal features, (iv) regulation of coastal development activities, and (v) the integration of climate change considerations into coastal management practices. Finally, collaborative efforts among government agencies, researchers, local communities, and international organizations are crucial for successful coastal erosion management in Thailand, Malaysia, Sri Lanka, and potentially other Asian regions. [ABSTRACT FROM AUTHOR]

Shoreline changing position along the coast is an immediate and long-term indicator determined by the interplaying driving forces across the dry and wet parts of coastal areas. Extreme waves, such as tsunamis, may result in a remarkable shift of shoreline position and a change of sediment transport regime, thus potentially inducing coastal hazards. This work investigates the multi-temporal changes and development of shorelines at the tsunami-affected coast nearly two decades after the Indian Ocean tsunami on 26 December 2004. Additionally, the dynamic responses of the coast to the man-made coastal structures as a means of protection measures during the observed period are also evaluated. This study uses the US Army's Digital Shoreline Analysis System (DSAS) extension in the ArcGIS to calculate the multi-temporal shoreline changes and erosion/accretion rates. Multi-temporal shoreline vectors delineated from the LANDSAT satellite images are utilized to calculate the Net Shoreline Movement (NSM), End Point Rate (EPR), and Linear Regression Rate (LRR) for the respective short-term and decadal-term shoreline change analysis. The shoreline change rates are examined at the three shoreline segments at Aceh coast, the north tip of Sumatra Island of Indonesia. The results show that Segment A has the highest erosion rate due to the 2004 tsunami (− 395.19 m/year) compared to Segment B (− 26.46 m/year) and Segment C (− 74.26 m/year). The 2004 tsunami has changed the coastal states from erosional coast prior to the tsunami to accretional coast in Segment A and C, and the eastern side of Segment B in almost two decades since the tsunami. Consequently, ignoring such phenomena in designing coastal protection measures may lead to structural failures such the ones identified in the investigated coast. Thus, a thorough investigation of shoreline change is fundamental for coastal managers, particularly in determining appropriate coastal protection measures. [ABSTRACT FROM AUTHOR]

Natural climate changes like global warming and changes in the sea natural phenomena have led to numerous challenges, including changed regional flow patterns and, therefore, coastal erosion and sedimentation. Sediment transport management is an essential factor in coastal management and ecosystem conservation plans. Using forest cover is an environmentally shore-oriented strategy, which can reduce wave-induced sediment transport through the flow blockage and turbulence changes. In this study, the effect of forest cover configuration and density on sediment trapping efficiency was evaluated by implementing a model of coastal forest cover. A flume with an installed acoustic Doppler velocimeter and an output valve for the transported sediment was used, and the experiments were performed at different densities ranging from 12 to 273 stem/m2 of forest cover in both staggered and parallel patterns. The results demonstrated a rising trend in the sediment trapping efficiency following the increase in the cover density so that it reached from 20% in the lowest density to 84% in the highest. The staggered pattern was found to perform better than the parallel pattern in increasing sediment trapping efficiency; however, the difference was not significant (averagely 10%). An equation with an acceptable accuracy was also proposed for determining the sediment transport rate affected by the flow hydraulic and forest cover density. [ABSTRACT FROM AUTHOR]