Sandy coastlines under threat of erosion

Scientific Reports

Sea level rise (SLR) will cause shoreline retreat of sandy coasts in the absence of sand supply mechanisms. These coasts have high touristic and ecological value and provide protection of valuable infrastructures and buildings to storm impacts. So far, large-scale assessments of shoreline retreat use specific datasets or assumptions for the geophysical representation of the coastal system, without any quantification of the effect that these choices might have on the assessment. Here we quantify SLR driven potential shoreline retreat and consequent coastal land loss in Europe during the twenty-first century using different combinations of geophysical datasets for (a) the location and spatial extent of sandy beaches and (b) their nearshore slopes. Using data-based spatially-varying nearshore slope data, a European averaged SLR driven median shoreline retreat of 97 m (54 m) is projected under RCP 8.5 (4.5) by year 2100, relative to the baseline year 2010. This retreat would translate t...

Journal of Marine Science and Engineering

The dune systems are very important from an environmental, landscape, and coastal defense point of view within coastal areas. Currently, dune systems are significantly reduced compared to a few decades ago and, in Europe alone, dune systems have decreased by 70%. During the same period, intense beach erosion processes have often been observed, and, currently, 30% of the world’s coasts are eroding. These processes have various causes, both natural and anthropogenic, and the knowledge of the causes of the erosive processes are very important for an effective planning and management of coastal areas and to correctly plan any interventions on dunes and beaches. The paper, through a case study, analyzes the beach and dune erosive processes, their causes, and the possible interventions. The case study concerns the archaeological site of Kaulon, located on a dune in the Ionian coast of Calabria (Italy). The beach near the site was affected by erosive processes and during the winter of 2013...

Journal of Marine Science and Engineering

During the second half of the last century, considerable anthropization processes were observed throughout most of the Italian territory. These processes have altered the equilibrium conditions of several river and coastal ecosystems, causing the destruction of numerous dune systems. This issue is particularly important in territories such as Calabria, a region in southern Italy subject to considerable anthropogenic pressures and characterized by over 700 km of coast. The aim of the paper was to evaluate the effects of anthropogenic pressures on the Calabrian dune systems, especially in regard to the triggering of coastal erosion processes. For this purpose, historical and current cartographic data, such as shapefiles, cartography, and satellite imagery, were analyzed using QGIS. This evaluation was carried out through the comparison between the current extension of the dune systems and their extensions after the Second World War, before the anthropogenic pressures. This evaluation ...

Ocean and Coastal Research

In recent years, the identification and economic valuation of ecosystem services have been identified as an important tool to recognize and translate nature's contribution to people's well-being. It is understood that assessing the economic value of ecosystem services contributes to better decision-making process regarding ecosystems, since it helps evaluation of trade-offs in alternative scenarios. Sandy beaches are among the most valuable coastal ecosystems, especially in regards to cultural services; however, they are still commonly subjected to several impacts that compromise the ecosystem integrity and capacity to provide multiple services, especially in the Global South. For this reason, management policies are crucial to reduce negative impacts. Assessing ecosystem services should be seen as a strategic approach to provide empirical support to these policies. We reviewed studies assessing and valuing sandy beach services in Brazil to identify strengths and gaps that could guide future studies. Our analysis showed that, despite Brazil being one of the leading countries in the published literature on sandy beach science, the number of studies assessing and valuing ecosystem services are small. Most of those studies are published in the native language, Portuguese, limiting the possibility of discussion and experience exchange at the international level. The services related to the use of beaches for tourism and leisure are the main category evaluated, and studies seem to focus on tourist beaches, especially those providing monetary evaluation, which follows the global trend. An increase in the number of published studies in recent years suggests a growing interest in the research subject. Based on the literature review, we discuss the results and make recommendations to guide and foster studies assessing beach services in the context of the Ocean Science Decade.

Frontiers in Marine Science

Sandy coasts represent about one-third of the global coastline and are among the most valuable and most vulnerable areas for humans and many other species. Socio-economic development and climate change impacts, together with traditional engineering for shore protection, have pervasively resulted in coastal squeeze, thereby threatening coastal life and economic activities, and the very survival of coastal ecosystems. In the past, the responses to problems such as land loss, coastal erosion and flooding were primarily reactive, through gray engineering solutions, with little interest shown in the ecosystem processes impacted by coastal armoring. In recent decades, coastal management strategies have become more diverse, embracing traditional engineering solutions alongside ecosystem-based measures. Even so, many of these new strategies still fail to meet sustainability criteria. Inspired by Per Bruun’s “The Ten Demands for Coastal Protection” from 1972, this article attempts to conside...

Journal of Marine Science and Engineering

Beachrocks are a window to the past environmental, geological, sedimentological and morphological conditions that were dominant in the coastal zone during their formation. Furthermore, beachrocks have the ability to reduce coastal erosion impact on sandy beaches. This study focuses on the beachrock formation mechanism through the comparison of cement characteristics, mineral chemistry and sedimentology of beachrock occurrences from two different geological and geographical localities: Diolkos, Corinth, Greece and Sumuide, Okinawa, Japan. In addition, in order to investigate a potential soft engineering method to protect coasts from erosion, artificial beachrock samples were created in vitro using sand samples and ureolytic bacteria from both areas under accelerating conditions. For Okinawa artificial beachrock experiments, the bacteria Pararhodobacter sp. was used, and for Diolkos, it was the bacteria Micrococcus yunnainensis sp. For the natural beachrocks, a multi-analytical approa...

Sustainability, 2020

The coastal zone is in a critical state worldwide, due to the loss and fragmentation of its ecosystems. Much of this is caused by long-term anthropic local, regional, or global actions, which drive coastal squeeze processes. Most of the criteria to evaluate the effects of coastal squeeze are focused on merely identifying its effect on the coastal zone. Here, we propose a framework to manage (identify, analyze, quantify, and tackle) the effect of coastal squeeze. This DESCR framework examines the relations between Drivers, Exchanges, and States of the environment to subsequently evaluate the chronic, negative Consequences and determine possible Responses. To illustrate the application of the DESCR framework, the coastal zone of Puerto Morelos, in the Mexican Caribbean, was studied using this approach. We analyzed the systemic interactions among the coastal ecosystems in this area, such as coral reefs, seagrass beds, beach, coastal dunes, and mangroves, which have been altered over th...

Applied Sciences, 2020

Geomorphological changes in recent decades in three estuaries along the Iberian coast were analysed using aerial orthophotographs. A hierarchical classification scheme, based on a literature review representing 26 estuarine eco-geomorphological features relevant to estuarine dynamics and functioning, is described. The estuaries selected were San Vicente de la Barquera (N Spain), Guadiana River (SW border between Spain and Portugal) and the Ebro River Delta mouth (NE Spain). For these systems, a 60-year time series of high-resolution maps was developed, analysing the changes in feature surfaces. The main subsystems analysed were beach, dunes, saltmarshes and the drainage network. The results of the cartographies showed general behaviour common to all transitional systems, relationships among main subsystems and processes inherent to each one. This work illustrates how beaches and dunes serve as a protective barrier for the tidal flats, acting as a sediment buffer for the entire syste...

Sustainability, 2022

Households play an important role in reducing coastal vulnerability through individual and collective action. Information provision is a key strategy adopted by governments to support household adaptation. However, there is limited evidence of the effectiveness of the different types of information and their influence on coastal household response. Drawing on case study research in two Australian coastal communities, we explore the types of information shaping household responses to three hazard scenarios: a heatwave, a severe storm, and sea-level rise. We find that passive information informs action in fewer than half of all households. Furthermore, even current attempts at more action-oriented information only informs coping strategies. If coastal adaptation is to achieve the transformational changes vital to manage the impacts of climate change, information provision must transition from passive and generic delivery via traditional modes, to actively communicating adaptation as t...

2020

Shoreline changes are of great importance for evaluating the interaction between humans and ecosystems in coastal areas. They serve as a useful metric for assessing the ecological costs of socioeconomic developmental activities along the coast. In this paper, we present an assessment of shoreline changes along the eastern coast of mainland China from ~1990 to 2019 by applying a novel method recently developed by us. This method which we call the Nearest Distance Method (NDM) is used to make a detailed assessment of shorelines delineated from Landsat Thematic Mapper (TM) and Operational Land Imager (OLI) images. The results indicate a dramatic decline in natural shorelines that correspond to the rapid increase in the construction of artificial shorelines, driven by China’s economic growth. Of the entire coast of mainland China, the biggest change occurred along the Bohai Sea, where artificial shorelines expanded from 42.4% in ~1990 to 81.5% in 2019. Over this period, this study indic...

Geosciences, 2020

One-dimensional (1D) numerical models generally provide reliable results when applied to simulate river hydraulics and morphodynamics upstream of the tidal influence, given the predominantly unidirectional flow conditions. Such models, however, can also be used to reproduce river hydraulics across the fluvial to marine transition zone when specific conditions occur, as during high discharge events, and the results obtained via these simple modeling tools can provide indicative trends that may guide more structured and detailed modeling of a particularly critical area. In this study, the application of a 1D model setup with hydrologic engineering centers river analysis system (HEC-RAS) for simulating the hydro-morphodynamic conditions of a distributary channel of the Po River Delta (Italy) during a flooding event that occurred in Spring 2009 is presented. The channel bathymetry and the grainsize composition was taken from field measurements, while the dimension of the plume offshore ...

Remote Sensing

Remote sensing (RS) enables a cost-effective, extensive, continuous and standardized monitoring of traits and trait variations of geomorphology and its processes, from the local to the continental scale. To implement and better understand RS techniques and the spectral indicators derived from them in the monitoring of geomorphology, this paper presents a new perspective for the definition and recording of five characteristics of geomorphodiversity with RS, namely: geomorphic genesis diversity, geomorphic trait diversity, geomorphic structural diversity, geomorphic taxonomic diversity, and geomorphic functional diversity. In this respect, geomorphic trait diversity is the cornerstone and is essential for recording the other four characteristics using RS technologies. All five characteristics are discussed in detail in this paper and reinforced with numerous examples from various RS technologies. Methods for classifying the five characteristics of geomorphodiversity using RS, as well ...

Journal of Marine Science and Engineering, 2021

Mean sea-level is expected to rise significantly by 2100 in all scenarios, including those compatible with the objectives of the Paris Climate Agreement. Global sea level rise projections indicate devastating implications for populations, ecosystem services and biodiversity. The implications of the sea-level rise (SLR) on low-lying islands and coastal regions and communities are substantial and require deep-rooted coping measures. In the absence of adequate responses for coping, Mozambique is expected to record huge losses, with an impact on the economy and development in many sectors of its coastal regions mainly in northern Mozambique. This research aimed to perform projections on SLR in Mozambique, and to understand its role and implications on the north coast of the country. SLR was estimated through the analysis of model outputs that support the global estimates of the fifth IPCC report near the Mozambican coast, for each of the four representative concentration pathways (RCPs)...

Geosciences, 2022

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Marine Geology, 2022

Multibeam bathymetric and seismic reflection profiles of the southern shelf of Porto Santo Island are used to map its seabed morphology and seismic stratigraphy. In general, the shelf consists of an erosive rocky surface mostly covered by sediments. On the Western and Eastern sectors two sets of submerged erosional terraces have been mapped at different depths (35-45 m, 50-75 m). A pattern of dykes, which are more resistant to erosion that the evolving outcrops, showed directions similar to the structural features outcropping on the island (NNE-SSW and NW-SE). The shelf edge presents an arcuate shape that strongly matches the coastline configuration, suggesting the occurrence of an old large-scale landslide event. Further incisions on the shelf edge imply subsequent and more recent mass-movement processes. The sedimentary cover on the shelf is highly variable both in thickness and internal architecture, mainly due to different shelf width and sediment pathways from the coast.

Remote Sensing

Lipari is the largest and most populated island in the Aeolian Archipelago, a UNESCO site, and a highly frequented touristic destination. As in many other insular settings, the low-lying coastal stretches in the E and NE sectors of Lipari are locally exposed to coastal erosion and flooding, enhanced by subsidence effects leading to local sea level rise. Most of these coastal sectors appear critical, being narrow and increasingly threatened by the risk of permanent inundation and beach disappearance. In this study, this setting is placed in the wider context of the decadal evolution of the main beaches, analysed through a multidisciplinary approach, which includes remote sensing techniques (aero-photogrammetry, unmanned aerial vehicle survey, and satellite data), offshore geophysical surveys (high-resolution multibeam bathymetry), and field observations. The results show a variable interaction in space and time between natural and anthropogenic factors in the long- and mid-term evolu...

Remote Sensing, 2021

Forecasting shoreline evolution for sandy coasts is important for sustainable coastal management, given the present-day increasing anthropogenic pressures and a changing future climate. Here, we evaluate eight different time-series forecasting methods for predicting future shorelines derived from historic satellite-derived shorelines. Analyzing more than 37,000 transects around the globe, we find that traditional forecast methods altogether with some of the evaluated probabilistic Machine Learning (ML) time-series forecast algorithms, outperform Ordinary Least Squares (OLS) predictions for the majority of the sites. When forecasting seven years ahead, we find that these algorithms generate better predictions than OLS for 54% of the transect sites, producing forecasts with, on average, 29% smaller Mean Squared Error (MSE). Importantly, this advantage is shown to exist over all considered forecast horizons, i.e., from 1 up to 11 years. Although the ML algorithms do not produce signifi...

Coasts

Coastal erosion is a common phenomenon along the world’s coasts. Studying it is complex because such studies must cover large portions of land, and it is necessary to understand the multiple processes that interact in each area, so it is important to recognize regional patterns that allow for defining representativeness in relation to the surrounding dynamics. Spatial statistics can be used in coastal geomorphology to identify and quantify trends in coastal morphodynamics. This study analyzes and interprets the spatio-temporal patterns present in the changes in a shoreline, that is, the processes of erosion and coastal sedimentation in the Pacific and the Colombian Caribbean. The results are derived from the detection of significant changes in the coastline via satellite images. For this study, the shoreline of Colombia was digitized for the years 1986 and 2016, thus obtaining changes in the shoreline at a medium temporal scale. The Global Moran’s Index, Local Moran’s Index and Geti...

Applied Sciences

Many coasts suffer from prevailing erosion, with them being particularly vulnerable to predicted climate change impacts, threatening coastal ecosystems, their services, infrastructures and populations. Understanding coastal morpho-sedimentary dynamics is thus essential for coastal management. However, coastal vulnerability may differ locally, depending on exposure/protection and local geological and morpho-hydrodynamical features, suggesting that a local approach to erosion risk assessment is needed to identify and understand local patterns. Digital elevation models of a 14 km long coastal stretch in northern Portugal that were extracted from aerial surveys obtained between November 2008 and February 2019 were analysed to quantify changes in shoreline position and sediment budgets, both for the whole study area and for distinct beach segments. The observed dynamics were subsequently analysed by considering prevailing wave and wind intensities and directions. Overall and during the d...

Nature Climate Change, 2022

The African coast contains heritage sites of ‘Outstanding Universal Value’ that face increasing risk from anthropogenic climate change. Here, we generated a database of 213 natural and 71 cultural African heritage sites to assess exposure to coastal flooding and erosion under moderate (RCP 4.5) and high (RCP 8.5) greenhouse gas emission scenarios. Currently, 56 sites (20%) are at risk from a 1-in-100-year coastal extreme event, including the iconic ruins of Tipasa (Algeria) and the North Sinai Archaeological Sites Zone (Egypt). By 2050, the number of exposed sites is projected to more than triple, reaching almost 200 sites under high emissions. Emissions mitigation from RCP 8.5 to RCP 4.5 reduces the number of very highly exposed sites by 25%. These findings highlight the urgent need for increased climate change adaptation for heritage sites in Africa, including governance and management approaches, site-specific vulnerability assessments, exposure monitoring, and protection strateg...

Journal of Coastal Conservation, 2021

The coast, as the interface between land and sea, is a highly dynamic area, endangered by erosion and flooding, particularly at times of sea-level rise. At the present context of climate change, the use of scientific knowledge to understand coastal dynamics and coastal evolution assessment through time is essential to find a suitable management response for a successful adaptive coastal governance. It is proposed that the obtained high-resolution and long-term coastline change dataset is of crucial importance to improve the knowledge on mesoscale evolution of the Portuguese southeastern coast, from Ancão to Vila Real de Santo António (VRSA), a 55 km long coastal stretch. The evolutionary trend, from 1950 to 2015, points to a general seaward progradation at the western (Barreta island) and eastern (Cacela peninsula-VRSA) sectors, and mostly an erosional trend at the central barrier island system (Culatra, Tavira and Cabanas islands). Moreover, a considerable average landward displacement of approximately 130 m is observed at Cabanas island. Regarding overall coastline movement, seaward displacement prevails, with a prograding coastline occupying approximately 54% of the studied sector even though this is mostly associated with human intervention on the coast. The exception is the Manta Rota-Monte Gordo sector where accumulation is likely related to natural processes. Considering the significant influence man-made interventions have had on the coastline evolution, it is believed that the natural evolutionary pattern would point to an overall erosional trend in the islands sector and a progradational trend from Manta Rota to VRSA beach.

Perspectives in Ecology and Conservation, 2021

h i g h l i g h t s • Changes in the Brazilian semi-arid coast reveal key questions to advance research. • Changes in the semi-arid coast can have consequences in the ecological stability and connectivity. • Modifications of the coastal dynamics can impact structure and function of adjacent marine ecosystems. • Semi-arid coast community dynamics under ongoing climate change should be monitored. • Beaches and nearshore mangroves erosion contrast with mangrove expansion inland.

Natural Hazards and Earth System Sciences

Nature-based solutions are increasingly suggested for mitigating coastal flood risks in the face of climate change. Managed realignment (MR), a coastal adaptation strategy that entails the landward realignment of coastal defences to restore coastal habitats (often salt marshes), plays a pivotal role in implementing nature-based solutions in the coastal zone. Across Europe, more than 130 sites have been implemented so far, often to harness their potential to mitigate coastal flood risks while restoring coastal habitats (ABPmer, 2021). However, local communities often oppose MR projects, not only because they are seen as returning hard-won land to the sea but also because their coastal protection function is less trusted than traditional hard engineering techniques. This scepticism has foundation. The proclaimed coastal protection function of MRs is based on a broad body of literature on the protective function of natural salt marshes. However, contrary to natural salt marshes, MRs are often semi-enclosed tidal basins with narrow breaches to the open sea/estuary. Recent studies indicate that MR-internal hydrodynamics may significantly reduce their coastal protection, depending on their engineering design. To successfully implement MR, a much-improved scientific knowledge base is needed, as well as a process for addressing community concerns and genuinely engaging stakeholders in decision-making beyond the usual obligatory consultancy approach. Here, we propose the co-production of scientific knowledge with local communities and stake-holders to optimize the success of coastal nature-based solutions and promote community acceptance.

Frontiers in Marine Science, 2021

Increasing sea level rise (SLR), and frequency and intensity of storms, paired with degrading ecosystems, are exposing coastal areas to higher risks of damage by storm events. Coastal natural habitats, such as dunes or saltmarshes, can reduce exposure of coastlines to these events and help to reduce the impacts and the potential damage to coastal property. The goal of our study was to evaluate the current vulnerability of the Portuguese northern coast to erosion and flooding caused by extreme events and to assess the contribution of natural habitats in reducing both vulnerability and property damages considering SLR scenarios. The Integrated Valuation of Environmental Services and Trade-offs (InVEST) Coastal Vulnerability model was used to produce an Exposure Index (EI) for the northern Portuguese coastline, for the current situation, and for future International Panel for Climate Change (IPCC) scenarios Representative Concentration Pathway (RCP) 2.6, RCP4.5, and RCP8.5, considering...

Ocean & Coastal Management, 2020

Shoreline armoring has repercussions on coastal processes, including reducing the width and height of sandy beaches, which affect coastal ecosystems and ecosystem services. This project, consisting of two parts, was carried out in the Canadian province of Quebec, on the coasts of the St. Lawrence Estuary and Gulf, which cover the territory of 21 coastal Regional County Municipalities (RCM). The objectives were to characterise shoreline armoring in Eastern Quebec, to determine the role played by coastal managers, coastal citizens, and coastal engineers in the coastal defence decision-making process, and to identify possible actions to be taken by each stakeholder to improve coastal engineering development. First, over 3300 km of shoreline were segmented and characterised, allowing the mapping of what proportion of the shoreline was covered by artificial structures. In 2017, coastal defence measures (CDM) occupied about 10% of the shoreline, and 97.6% of them were reflective rigid structures. The second part of the project involved three different consultations carried out in 2017 and 2018 with 300 coastal managers, 494 coastal residents and 51 professionals from environmental and engineering firms to assess their knowledge of CDM types and functions, and to discuss about the decision process leading to the CDM identification. Results of the consultations show a significant change in the type of desired solutions compared to previous studies where rigid structures were clearly preferred. But despite a greater prioritization of soft techniques by professionals from municipalities, ministries' managers and coastal citizens, the rigid structures continue to be the type of solution mostly implemented along Quebec's coasts. This difference can be explained by a number of factors: a lack of specialized knowledge; a lack of funding; a lack of collaborative process; and regulations that are too restrictive for innovative CDM. In addition to an increase of funding for preventive CDM, for long term CDM monitoring and maintenance, for case studies and pilot projects, the main solutions proposed were interdisciplinary projects based on consultation, adjustment of environmental regulations, and development of a tool that would enable decision-makers to evaluate each option in a particular context, so as to identify the most appropriate solutions and make better decisions for the long term.

Antiquity

The Intergovernmental Panel on Climate Change has documented wide-ranging changes to the world's coasts and oceans, with significant further change predicted. Impacts on coastal and underwater heritage sites, however, remain relatively poorly understood. The authors draw on 30 years of research into coastal and underwater archaeological sites to highlight some of the interrelated processes of deterioration and damage. Emphasising the need for closer collaboration between, on one hand, archaeologists and cultural resource managers and, on the other, climate and marine scientists, this article also discusses research from other disciplines that informs understanding of the complexity of the interaction of natural and anthropogenic processes and their impacts on cultural heritage.

Journal of Geophysical Research: Earth Surface, 2021

 Ensemble-based simulations of future shoreline evolution to 2100, including sea-level rise driven erosion, are performed and analysed  Future shoreline projections uncertainties are initially controlled by modelling assumptions and after 2060 by sea-level rise uncertainties  The choice of wave-driven equilibrium modelling approach and incident wave chronology are critical to short/mid-term shoreline projections

Coastal Engineering

Coastal communities are currently facing the challenge of climate change and coastal retreat. While scientists are moving towards ensemble-modelling approaches to address uncertainties on shoreline evolution predictions, they rarely account for the stochastic nature of wave conditions across a variety of temporal scales (e.g., daily, weekly, seasonal, and interannual). In this contribution, we investigate the effects of the inherent variability of wave conditions on past and future multi-decadal shoreline evolution at the, cross-shore transport dominated, beach of Truc Vert (France). Using a climate-based wave emulator and variance decomposition method, we address the relative impacts of uncertain wave chronology, sea-level rise and model free parameters on modelled shoreline change, while accounting for possible correlations and interactions among the input variables. This work is done for two different wave-driven equilibrium models. The results show that the equilibrium shoreline models respond differently to the ensemble wave forcing, with strong implications on the long-term variability of modelled shoreline. We find that the modelled shoreline variance is primarily driven by the uncertain wave chronology until mid-21 st century, while the uncertainties on future sea-level rise become dominant after 2060 in all the simulated scenarios. We also found that interactions and correlations among the uncertain variables can affect the estimation of shoreline predictions uncertainties. Finally, we provide a perspective on the application of non-stationary wave-related model parameters as future research avenue for understanding uncertainties in modelled shoreline.

Remote Sensing

Hurricanes are one of the most devastating earth surface processes. In 2020 and 2021, Hurricanes Zeta and Ida pounded the Mississippi River Delta in two consecutive years, devastated South Louisiana, and raised tremendous concerns for scientists and stakeholders around the world. This study presents a high-resolution spatial-temporal analysis incorporating planialtimetric data acquired via LIDAR, drone, and satellite to investigate the shoreline dynamics near Port Fourchon, Louisiana, the eye of Ida at landfall, before and after the beach nourishment project and recent hurricane landfalls. The remote sensing analysis shows that the volume of the ~2 km studied beachfront was reduced by 240,858 m3 after consecutive landfalls of Hurricanes Zeta and Ida in 2020 and 2021, while 82,915 m3 of overwash fans were transported to the backbarrier areas. Overall, the studied beach front lost almost 40% of its volume in 2019, while the average dune crest height was reduced by over 1 m and the sho...

Geoplanning: Journal of Geomatics and Planning

Sandy beaches are most popular tourists and fish landing sites, and serve as habitat for several endangered species. However, sandy beaches more vulnerable to coastal erosion, particularly those along open oceans. Assessment of shoreline change using reliable dataset aid in understanding the morphology of coastal landforms, the processes associated with their occurrence and support decision making. This paper analysed available multi-temporal spatial dataset and field observations using GNSS techniques to assess the shoreline change along the study area. The shoreline features were extracted from 1974 topographic map and 2005 orthophotographs using the High Water Line (HWL) in conjunction with 2020 spatial data. Shoreline change statistics were computed using DSAS. A geodatabase was created, transects were cast and the shoreline change rates computed using EPR, LRR and WLR methods. Both accretion and erosion were recorded with mean erosion rate of 0.97 m/year. It was observed that s...

Mitigation and Adaptation Strategies for Global Change

Coastal cities are under severe threat from the impacts of climate change, such as sea-level rise, extreme weather events, coastal inundation, and ecosystem degradation. It is well known that the ocean, and in particular coastal environments, have been changing at an unprecedented rate, which poses increasing risks to people in small island developing states, such as Fiji. The Greater Suva Urban Area, the capital and largest metropolitan area of Fiji, is expected to be largely impacted by climate-related risks to its socioeconomic , cultural, and political positions. In the face of these threats, creating a resilient city that can withstand and adapt to the impacts of climate change and promote sustainable development should be guided by a holistic approach, encompassing stakeholders from the government, the private sector, civil society organizations, and international institutions. This study assesses the risk profile of Suva city using an innovative risk information tool, the climate and ocean risk vulnerability index (CORVI), which applies structured expert judgment to quantify climate-related risks in data-sparse environments. Through comparative quantification of diverse risk factors and narrative analysis, this study identifies three priority areas for Suva's future climate-resilient actions: development of climate risk-informed urban planning, harmonized urban development and natural restoration, and enhancing the climate resilience to the tourism sector.

Journal of Marine Science and Engineering

The coastal zone may be considered as the location where the marine and land environments interact dynamically and coexist with human societies. Globally, natural and human systems are being severely threatened by the sea level rise related to climate change. The outcome between the dynamic relationship of coastal environments and marine processes, and the future sea level rise as predicted by scientific reports, is the vulnerability of coastal areas such as sandy beaches, pocket beaches and low-lying coastal areas. The current research aims to assess the coastal vulnerability of Ios Island, Cyclades, Greece for the next 100 years and to identify areas that are comparatively more vulnerable to future sea level changes. Moreover, the seasonal changes concerning sedimentological and morphological characteristics of two pocket beaches of Ios Island, Mylopotas and Magganari, are also examined. From the application of the Coastal Vulnerability Index, 92.37% of the total length of the coa...

Water

The Port of Klaipėda, located at the Klaipėda strait, divides the Lithuanian coast into two different geomorphological parts: southern—the coast of the Curonian Spit, and northern—the mainland coast. Port jetties interrupt the main sediment transport path along the South-Eastern Baltic Sea’s coast. Port of Klaipėda reconstruction in 2002 and the beach nourishment project which started in 2014 significantly influenced the northern part of the coast, which led to changes in the coastal zone evolution. The measurements in various periods are essential for cross-shore profile elevation to analyze seabed morphology and sedimentation patterns. These data highlight our understanding of the scale and timing of seabed erosion or sedimentation processes scale and timing. This study evaluates the impact of anthropogenic pressure and natural factors on coastal geomorphology and dynamics. In order to assess the latter changes, the cross-shore profile evolution and sediment budget were analyzed a...

Geosciences

Shoreline change and coastal erosion resulting from natural events such as sea level rise and negative anthropogenic activities continue to be problems in many of the world’s coastal regions. Many coastal socio-ecological systems have become vulnerable as a result, especially in developing countries with less adaptive capacity. We utilized the systematic method to understand the research progress and policy recommendations on shoreline change and coastal erosion in West Africa. A total of 113 documents were retrieved from Scopus and the Web of Sciences databases, and 43 documents were eligible following established criteria. It was revealed that research on shoreline change and coastal erosion has progressed substantially since 1998, with most research studies originating from the Ghanaian territory. Again, most of the shoreline change and erosion problems in West Africa result from natural events such as sea level rise. However, there was evidence of anthropogenic influences such a...

Journal of Marine Science and Engineering

Beach slope is a critical parameter to, e.g., beach safety, wave reflection at the coast and longshore transport rate. However, it is usually considered as a time-invariant and profile-average parameter. Here, we apply a state-of-the-art equilibrium model to hindcast beach slope variability from the time scales of days to years at the high-energy meso-macrotidal sandy beach of Truc Vert, southwest France. We use 9 years of bimonthly beach surveys to compute beach slope time series at different elevations. Results show that beach slope exhibits an equilibrium response with contrasting behaviors along two distinct areas of the beach profile. From 0 to 2 m above mean sea level, which is located under the berm crest, a slope response predominantly at the storm time scale is observed. The beach slope steepens under low energy waves, with the equilibrium model explaining up to 40% of the observed beach slope variability. In contrast, from 2.5 to 4 m above mean sea level, which is above th...

Science of The Total Environment, 2020

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Frontiers in Marine Science

At coasts, sandy beach-dune systems act as natural barriers to environmental forcing, preventing coastal flooding and protecting coastal communities. In the context of coastal studies, it is fundamental to identify beach-dune sectors exposed to wave impact to support coastal management and suggest soft engineering interventions. This work examines the morphodynamics of the Mira beach-dune system on the northern-central littoral of Portugal over the winter 2016-2017. Coupling topographic data with the estimation of wave runup and total water level (TWL) timeseries, we proposed an operational framework to spot the beach-dune system sectors most vulnerable to dune collision and overwash. The highest topographic variations occurred in the northern sector of the study area, where overwash events occurred due to low dune crest (DC) elevation. The dune toe (DT) was frequently collided by waves in the central sector, where the upper beach profile was the most variable during winter. Overall...

Sustainability

Direct and indirect impacts of climate change are alarming in the coastal areas of the world, including the Mediterranean coasts. Extreme events (such as marine storms, medicanes, etc.) are likely to increase the coastal risks in the region (e.g., erosion, flooding, and inundation), resulting in a significant socio-economic impact, loss of natural biodiversity and ecosystem services, and damage to cultural heritage along the affected coasts. Therefore, climate-related risk assessment procedures are crucial for the management and sustainable development of coastal areas. The purpose of this paper is to review and analyze the literature on the assessment of both the long- and short- term effects of climate change on coastal Mediterranean areas. It emphasizes methods and techniques to evaluate coastal vulnerability and sea level rise risk. This paper presents an overview of relevant scientific literature on the matter with a focus on approaches used in addressing the issues on climate ...

Water

Sandy beaches are fragile and dynamic coastal areas exposed to numerous environmental forcings. Systematic long-term data acquisition programs and exhaustive data series analyses are fundamental for a comprehensive understanding of the coastal processes. The software CoastSat was implemented to detect the shoreline position at beaches located to the south of Mar del Plata city (Buenos Aires Province, Argentina), by means of satellite images (period: 1986–2020). Tides in this area are mixed semidiurnal with a mean range of 1.74 m. The most frequent waves are characterized by significant wave heights from 0.5 to 2 m and periods of around 8 s propagating mainly from SSE. Seasonal and interannual variability and long-term trends of the shoreline position were investigated at Punta Mogotes (PM) bay, Faro Norte (FN) bay, and Ensenada Mogotes (EM). Seasonal cycles were noticed in the beach width variation series. In general, maximum accumulation was observed in summer and maximum erosion i...

Communications Earth & Environment

The analysis of extreme wave conditions is crucial for understanding and mitigating coastal hazards. As global wave reanalyses allow to extend the evaluation of wave conditions to periods and locations not covered by in-situ measurements, their direct use is common. However, in coastal areas, the accuracy of global reanalyses is lower, particularly for extreme waves. Here we compare two leading global wave reanalyses against 326 coastal buoys, demonstrating that both reanalyses consistently underestimate significant wave height, 50-year return period and mean wave period in most coastal locations around the world. Different calibration methods applied to improve the modelled extreme waves, resulting in a 53% reduction in the underestimation of extreme wave heights. Importantly, the 50-year return period for significant wave height is improved on average by 55%. Extreme wave statistics determined for coastal areas directly from global wave reanalyses require careful consideration, wi...

Sustainability

Economic costs associated to coastal erosion are projected in 45 sandy beaches in Chilean coasts. We compare mid-century (2026–2045) and end-of-century projections (2081–2100) of wave climate and sea-level rise (SLR) with a historical period (1985–2004) using several General Circulation Models for the RCP 8.5 scenario. Offshore wave data are then downscaled to each site, where shoreline retreat is assessed with Bruun rule for various berm heights and sediment diameters. Results indicate that mid-century retreat would be moderate (>13 m) while larger end-of-century projections (>53 m) are explained by SLR (0.58 ± 0.25 m). A small counterclockwise rotation of long beaches is also expected. To assess the costs of shoreline retreat, we use the benefit transfer methodology by using adjusted values from a previous study to the sites of interest. Results show that, by mid-century, beach width reduction would be between 2.0% and 68.2%, implying a total annual loss of USD 5.6 [5.1–6.1]...

Journal of Maritime Archaeology

Syria’s coastal and nearshore zone contains a significant, but under-researched, record of maritime cultural heritage (MCH) ranging from prehistory to the present. This is exemplified by a lack of underwater investigations, but also limited investigation of key onshore maritime sites such as ports and harbours. There is also a lack of specialist in-country management regarding maritime cultural heritage research and protection. This situation has been worsened by the ongoing conflict (since 2011), which has reduced (already limited) field investigation. To assist in the advancement of Syrian maritime archaeology, this paper presents a baseline assessment which makes use of a geospatial database generated from satellite imagery as well as both published and grey literature. This assessment reviews past coastal environment changes affecting the Syrian littoral, and then highlights past disturbances and potential future threats impacting the MCH. This is done through analysis of all co...

Geosciences

Coastal erosion is a major coastal hazard in Greece. This work aimed to assess the perceptions of citizens about coastal erosion. We developed a questionnaire containing 25 questions that was distributed online and filled out by 1636 respondents. A surprising find was that 33% of the respondents were not aware of the phenomenon of coastal erosion. On the other hand, among those respondents who are aware of coastal erosion, there is a basic understanding of the major factors promoting erosion and its impacts. Responses also highlighted a lack of information and awareness from the media and public authorities, while the vast majority considered that protecting the coast from erosion should be important or a priority. Our findings stress the need for awareness-raising activities about this important natural hazard.

Scientific Reports

A common inference in research studies of observed and projected changes in global ocean wave height and storm surge, is that such changes are potentially important for long-term coastal management. Despite numerous studies of the impacts of anthropogenic climate change on trends in global wind and waves, a clear link to impacts on sandy coastlines, at global scale, is yet to be demonstrated. This study presents a first-pass assessment of the potential link between historical trends in global wave and storm surge values and recession/progradation rates of sandy coastlines since the 1980s. Global datasets of waves, surge and shoreline change rate are used for this purpose. Over the past 30 + years, we show that there have been clear changes in waves and storm surge at global scale. The data, however, does not show an unequivocal linkage between trends in wave and storm surge climate and sandy shoreline recession/progradation. We conclude that these long-term changes in oceanographic ...

Journal of Marine Science and Engineering

Understanding the dynamics of beach–dune systems is crucial for effective coastal management. The cellular automata model DuBeVeg provides a powerful tool for simulating and understanding the bio-geomorphological evolution of these systems, capturing key interactions of aeolian, hydro-, and vegetation dynamics in a simplified manner. In this study, we present an alternative representation of the aeolian transport component in DuBeVeg, aiming to better capture the saltation transport mode that prevails on beaches. This new representation is compared with the original aeolian transport representation in DuBeVeg, which is inspired by ripple migration. For three beach width scenarios, we considered the effects of the different aeolian transport representations on the predicted foredune morphology after 50 years, as well as the spatio-temporal evolution of the beach–dune system leading to that morphologic state. The saltation transport representation resulted in a more realistic simulati...

Geosciences, 2021

Along the Baltic coastline of Germany, drifting vegetation and beach cast create overlays at the otherwise sandy or stony beaches. These overlays influence the morphodynamics and structures of the beaches. To better understand the influence of these patchy habitats on coastal environments, regular monitoring is necessary. Most studies, however, have been conducted on spatially larger and temporally more stable occurrences of aquatic vegetation such as floating fields of Sargassum. Nevertheless, drifting vegetation and beach cast pose a particular challenge, as they exhibit high temporal dynamics and sometimes small spatial extent. Regular surveys and mappings are the traditional methods to record their habitats, but they are time-consuming and cost-intensive. Spaceborne remote sensing can provide frequent recordings of the coastal zone at lower cost. Our study therefore aims at the monitoring of drifting vegetation and beach cast on spatial scales between 3 and 10 m. We developed an...

Journal of Marine Science and Engineering, 2023

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Remote Sensing

A prerequisite for solving issues associated with surf zone variability, which affect human activity in coastal zones, is an accurate estimation of the effects of coastal protection methods. Therefore, performing frequent monitoring activities, especially when applying new nature-friendly coastal defense methods, is a major challenge. In this manuscript, we propose a pipeline for performing low-cost monitoring using RGB images, accessed by an unmanned aerial vehicle (UAV) and a four-level analysis architecture of an underwater object detection methodology. First, several color-based pre-processing activities were applied. Second, contrast-limited adaptive histogram equalization and the Hough transform methodology were used to automatically detect the underwater, circle-shaped elements of a hybrid coastal defense construction. An alternative pipeline was used to detect holes in the circle-shaped elements with an adaptive thresholding method; this pipeline was subsequently applied to ...

Scientific Reports

Sea level rise has accelerated during recent decades, exceeding rates recorded during the previous two millennia, and as a result many coastal habitats and species around the globe are being impacted. This situation is expected to worsen due to anthropogenically induced climate change. However, the magnitude and relevance of expected increase in sea level rise (SLR) is uncertain for marine and terrestrial species that are reliant on coastal habitat for foraging, resting or breeding. To address this, we showcase the use of a low-cost approach to assess the impacts of SLR on sea turtles under various Intergovernmental Panel on Climate Change (IPCC) SLR scenarios on different sea turtle nesting rookeries worldwide. The study considers seven sea turtle rookeries with five nesting species, categorized from vulnerable to critically endangered including leatherback turtles (Dermochelys coriacea), loggerhead turtles (Caretta caretta), hawksbill turtles (Eretmochelys imbricata), olive ridley...

Scientific Reports, 2023

Coral reefs offer natural coastal protection by attenuating incoming waves. Here we combine unique coral disturbance-recovery observations with hydrodynamic models to quantify how structural complexity dissipates incoming wave energy. We find that if the structural complexity of healthy coral reefs conditions is halved, extreme wave run-up heights that occur once in a 100-years will become 50 times more frequent, threatening reef-backed coastal communities with increased waves, erosion, and flooding.

Water

The coastal zone, situated at the sensitive interface between land and sea, serves as a pivotal area of human economic activities. As one of China’s economic special zones, Xiamen exemplifies the comprehensive trajectory of coastal governance in China. However, there are still research gaps in the human ecological transitions in coastal governance. This study adopts the research approach of scale politics and the local state, with the purpose of explaining the governance model of the coastal zone transformation. Sources include interviews with fishers, direct observation, participant observation, and content analysis. The study demonstrates how local governments strive to maximize the profits of scenic tourism, by (1) appropriating the international scale, absorbing international aid and technical assistance; (2) confiscating the access rights of the coastal zone; and (3) vertically integrating all relationships from local to international organizations to create new governance patt...

Nature Communications, 2020

Extreme sea levels (ESLs) in Europe could rise by as much as one metre or more by the end of this century due to climate change. This poses significant challenges to safeguard coastal communities. Here we present a comprehensive analysis of economically efficient protection scenarios along Europe's coastlines during the present century. We employ a probabilistic framework that integrates dynamic simulations of all ESL components and flood inundation, impact modelling and a cost-benefit analysis of raising dykes. We find that at least 83% of flood damages in Europe could be avoided by elevating dykes in an economically efficient way along 23.7%-32.1% of Europe's coastline, specifically where high value conurbations exist. The European mean benefit to cost ratio of the investments varies from 8.3 to 14.9 while at country level this ranges between 1.6 and 34.3, with higher efficiencies for a scenario with high-end greenhouse gas emissions and strong socioeconomic growth.

Scientific Reports

Shoreline position is a key parameter of a beach state, often used as a descriptor of the response of the system to changes in external forcing, such as sea-level rise. Changes in shoreline position are the result of coupled hydrodynamic and morphodynamic processes happening in the nearshore and acting at different temporal scales. Due to this complexity, methodologies aimed at reproducing shoreline evolution at decadal time scale require many simplifications. Simpler methods usually consider an equilibrium beach profile whose shape depends only on beach morphology, and whose location varies depending on incoming forcing. Here, we derive a general equation for shoreline evolution using equilibrium beach profiles. We particularize it based on several common assumptions, and evaluate changes on shoreline position caused by sea-level rise, combined with simultaneous wave and high-frequency sea-level forcing. We compare our model against other analytical equilibrium beach profile-based ...

Journal of Maritime Archaeology

Tropical cyclones are among the most detrimental hazards to the environment, societies, and economies, each year affecting millions of people and resulting in substantial casualties and material destructions in coastal communities. In this context, maritime cultural heritage, encompassing material evidence for the engagement of people with the sea, both on land and under water, is particularly vulnerable. Despite the significant number of archaeological sites exposed to tropical cyclones and other extreme sea-level events, maritime cultural heritage in the MENA region is rarely included in coastal vulnerability indices or incorporated in mitigation strategies, disaster management, sustainability, and resilience policies. In this study we examine the impact of tropical cyclones on the maritime archaeology of Oman with emphasis on the Dhofar region. This paper builds on existing coastal research in the Dhofar region—an area identified as the most cyclone-prone administrative region in...

Corals - Habitat Formers From the Shallow to the Deep [Working Title]

Survival of coral reefs from globally rising temperature, sea level, and pollution requires new regeneration methods that greatly increase coral growth rates, survival, and resistance to accelerating extreme environmental stresses. Electric (“Biorock”) limestone reefs can be grown in any size or shape, get stronger with age, grow back if damaged, and increase settlement, growth, survival, and stress resistance of all marine organisms examined. Electrified corals survive repeated severe bleaching events when over 90% of corals on nearby reefs die. Electric reefs are open mesh frameworks with more vertical levels of holes and surfaces than natural reefs, which can be grown in places where natural reefs cannot grow due to lack of substrate or unsuitable physical and chemical conditions. They strongly enhance reef physical structure, wave absorption, ecological function, biodiversity, productivity, and habitat and ecosystem services including shore protection, sand generation, and fishe...

Marine Geology, 2021

Predicting change to shorelines globally presents an increasing challenge as sea level rise (SLR) accelerates. Many shoreline prediction models use the simplistic 'Bruun rule' for dealing with SLR profile translation, in-part due to alternative approaches being too complex and time-consuming to implement. To address this, we introduce ShoreTrans: a simple, rules-based, user-input driven, shoreface translation and sediment budgeting model, that applies the surveyed 2D-profile (not a parameterization), for estimating change to realistic coastlines, resulting from SLR and variations in sediment supply, while accounting for armouring, hard-rock cliffs and outcropping rocks. The tool can be applied to sand, gravel, rock and engineered coasts at a temporal scale of 10-100 years, accounting for shoreline trends as well as variability. The method accounts for: (1) dune encroachment/accretion; (2) barrier rollback; (3) non-erodible layers; (4) seawalls; (5) lower shoreface transport; (6) alongshore rotation; and (7) other sources and sinks. Uncertainty is accounted for using a probabilistic distribution for inputs and Monte Carlo simulations. We provide a first-pass assessment of two macrotidal UK embayments: Perranporth (sandy, dissipative, cross-shore dominant transport) and Start Bay (gravel, reflective, bi-directional alongshore dominant), then use idealised profiles to investigate the relative importance of forcing controls on shoreline recession and beach width. For the dissipative sandy site, the primary modes of coastal change are predicted to be short-term storm erosion and SLR translation while long-term trends may be important but are highly uncertain. For the reflective gravel site, the primary mode is multi-decadal longshore sediment flux, while shortterm alongshore rotation and SLR translation are secondary. Relative to the ShoreTrans approach, the Bruun rule under-predicts shoreline recession in front of cliffs, seawalls and for low barriers that rollback, and overpredicts where large erodible dunes are present. ShoreTrans directly addresses change in beach width, with beaches in front of seawalls and cliffs predicted to shrink, such that narrow beaches (<50 m width) may disappear under 1-m SLR. As a standalone tool, ShoreTrans is transferable to many coast types and will provide coastal practitioners with a simple first-pass estimate of how the 2D appearance of a complex profile may change under SLR. A future benefit will be to combine this approach with existing hybrid modelling techniques to augment SLR translation predictions.

Frontiers in Marine Science, 2021

Sea-level rise induces a permanent loss of land with widespread ecological and economic impacts, most evident in urban and densely populated areas. Potential coastline retreat combined with waves and storm surges will result in more severe damages for coastal zones, especially over insular systems. In this paper, we quantify the effects of sea-level rise in terms of potential coastal flooding and potential beach erosion, along the coasts of the Balearic Islands (Western Mediterranean Sea), during the twenty-first century. We map projected flooded areas under two climate-change-driven mean sea-level rise scenarios (RCP4.5 and RCP8.5), together with the impact of an extreme event defined by the 100-year return level of joint storm surges and waves. We quantify shoreline retreat of sandy beaches forced by the sea-level rise (scenarios RCP4.5 and RCP8.5) and the continuous action of storm surges and waves (modeled by synthetic time series). We estimate touristic recreational services decrease of sandy beaches caused by the obtained shoreline retreat, in monetary terms. According to our calculations, permanent flooding by the end of our century will extend 7.8-27.7 km 2 under the RCP4.5 scenario (mean sea-level rise between 32 and 80 cm by 2100), and up to 10.9-36.5 km 2 under RCP8.5 (mean sea-level rise between 46 and 103 cm by 2100). Some beaches will lose more than 50% of their surface by the end of the century: 20-50% of them under RCP4.5 scenario and 25-60% under RCP8.5 one. Loss of touristic recreational services could represent a gross domestic product (GDP) loss up to 7.2% with respect to the 2019 GDP.

Research Square (Research Square), 2022

Coral reefs offer natural coastal protection by attenuating incoming waves. Here we combine unique coral disturbance-recovery observations with hydrodynamic models to quantify how structural complexity dissipates incoming wave energy. We find that if the structural complexity of healthy coral reefs conditions is halved, extreme wave run-up heights that occur once in a 100-years will become 50 times more frequent, threatening reef-backed coastal communities with increased waves, erosion, and flooding. By March 2020, the world's human population grew to more than 7.8 billion people 1 , with most of the growth taking place in coastal areas where population density is highly concentrated 2 . As a result, the number of people exposed to intense coastal storms and flooding also markedly increased 3 . Climate change is expected to further exacerbate the risks of flooding due to rising seas 4,5 and changes in weather patterns . In response, societies are called to design effective coastal protection schemes 9 , which preserve or strengthen the current natural protection offered in the form of ecosystem services 10 . This is particularly true in tropical areas, where more than 500 million people are protected by coral reefs 11 . Shallow water coral reefs act as natural breakwaters , and can attenuate up to 98% of the incoming wave energy 13 . However, coral reefs are being rapidly degraded by intensifying anthropogenic stressors, including ocean acidification, rising seas, pollution, and sedimentation 14 . Such perturbations usually reduce living coral cover and subsequently habitat structural complexity, thereby leading to reef flattening, a process observed worldwide . Such trends reduce the natural protective capacity of reefs, further intensifying coastal flood and erosion risks . Although the link between wave attenuation and reef structural complexity is widely accepted among scientists in theory, quantitative examinations of the protective capacity of reefs under real world conditions as anticipated for the near future are yet limited . Indeed, most of the studies investigated the wave energy dissipation in conditions where coral reefs would be entirely wiped out or not , while others chose a wider geomorphologybased approach exploring flooding risk as a function of reef proximity or geologic structure . Here we report field observations and numerical models to quantify the natural protection offered by coral reefs at a high-energy site in Mo' orea, French Polynesia. First, we monitor changes in coral community abundance and size-distribution over a 10-year full cycle of disturbance and recovery (2005-2016), and quantify the associated reef structural complexity (see "Materials and methods" for details). Second, we use in situ hydrodynamic measurements to link the structural complexity levels with the wave energy dissipation capacity of the reef, and to calibrate a Boussinesq wave propagation model, which simulates the interplay between hydrodynamics and reef topography on the site. Third, we apply a probabilistic framework that assesses a coral reef 's capacity to attenuate incoming wave energy, applying our model under all possible wave and structural complexity conditions for the study site. We evaluate the resulting 10,000 runs by using as proxies wave overwash, impact, and flooding, the significant wave run-up, and finally, the 2% exceedance wave run-up height (R 2% ).

Journal of Marine Science and Engineering

Climate change is an increasingly critical issue impacting coasts and coast structures, leading to erosion, flooding, sea level rise, etc. These significantly impact not only the environment and society, but also the regional infrastructure and economy. This study focused on assessing the costs associated with climate change along the coast of Catalonia. An innovative tool in Python called GCIFS (Georeferenced Impact Forecast System) was developed for the assessment, which is based on LiDAR measurements, cartography, and online databases to predict future coastlines and economic impacts. The proposed methodology considered unique beach-specific scenarios, and multiple direction and altitude vectors to identify difficult-to-erode areas and existing protections were generated. Seven approaches based on forecasted sea-level rise with and without coastal geomorphology were applied to 262 beaches. Local impact factors and potential protection, using detailed data on infrastructure and bu...

Frontiers in Marine Science, 2021

The fate of the beaches around the world has paramount importance as they are one of the main assets for touristic activities and act as a natural barrier for coastal protection in front of marine storms. Climate change could put them at risk as sea levels rise and changes in the wave characteristics may dramatically modify their shape. In this work, a new methodology has been developed to determine the flooding of sandy beaches due to changes in sea level and waves. The methodology allows a cost-effective and yet accurate estimation of the wave runup for a wide range of beach equilibrium profiles and for different seagrass coverage. This, combined with regional projections of sea level and wave evolution, has allowed a quantification of the future total water level and coastline retreat for 869 beaches across the Balearic Islands for the next decades as a function of greenhouse gases emission scenario. The most pessimistic scenario (RCP8.5) at the end of the century yields an averaged percentage of flooded area of 66% under mean conditions which increases up to 86% under extreme conditions. Moreover, 72 of the 869 beaches of the region would permanently disappear while 314 would be completely flooded during storm episodes. Under a moderate scenario of emissions (RCP4.5), 37 beaches would permanently disappear while 254 would disappear only during storm episodes. In both cases, the average permanent loss of beach surface at the end of the century would be larger than 50%, rising over 80% during storm conditions. The results obtained for the Balearic Islands can be extrapolated to the rest of the Mediterranean as the beaches in all the regions have similar characteristics and will be affected by similar changes in sea level and wave climate. These projections indicate that adaptation plans for beach areas should be put in place as soon as possible.

Meandering channels are ubiquitous features in intertidal mudflats and play a key role in the eco-morphosedimentary evolution of such landscapes. However, the hydrodynamics and morphodynamic evolution of these channels are poorly known, and direct flow measurements are virtually nonexistent to date. Here, we present new hydroacoustic data collected synchronously at different sites along a mudflat meander located in the macrotidal Yangkou tidal flat (Jiangsu, China) over an 8-day period. The studied bend exhibits an overall dominance of flood flows, with velocity surges of about 0.8 m/s occurring immediately below the bankfull stage during both ebb and flood tides. Unlike salt-marsh channels, velocities attain nearly-constant, sustained values as long as tidal flows remain confined within the channel, and reduce significantly during overbank stages. In contrast, curvatureinduced cross-sectional flows are more pronounced during overbank stages. Thus, a phase lag exists between streamwise and cross-stream velocity maxima, which limits the transfer of secondary flows and likely hinders the formation of curvature-induced helical flows along the entire meander length. Our results support earlier suggestions that the morphodynamics of intertidal mudflat meanders does not strongly depend on curvature-induced helical flows, and is most likely driven by high velocities and sustains seepage flows at late-ebb stages, as well as by other non-tidal processes such as waves and intense rainfall events. By unraveling complex flow structures and intertwined morphodynamic processes, our results provide the first step toward a better understanding of intertidal mudflat meanders, with relevant implications for their planform characteristics and dynamic evolution.

Resources, Conservation and Recycling, 2021

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