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An increase in the global mean sea level is predicted during the twenty-first century, as a consequence of global average rising temperature projections. In addition, changes in the strength of atmospheric cyclonic storms may alter the development of storm surges, exacerbating the risks to coastal communities. Based on the fact that the interest and range of papers on this topic are growing, this study aims to present the status of the global scientific production on studies that have correlated climate change and the impact of storm surges on the coastal zone leading to erosion and flooding (inundation) via a bibliometric analysis. We analyzed 429 papers published in journals between January 1991 and February 2021 from the Scopus database. Through the VOSviewer and Bibliometrix R package, we describe the most relevant countries, affiliations, journals, authors, and keywords. Our results demonstrate that there has been an exponential growth in the research topic and that authors from the USA and the United Kingdom are the most prolific. Among the 1454 authors found, ten researchers published at least five papers on the topic and obtained at least 453 citations in the period. The most represented journals were the Journal of Coastal Research, Climatic Change, and Natural Hazards. We also found and discuss the lack of standardization in the choice of keywords, of which climate change, storm surge, and sea-level rise are the most frequent. Finally, we have written a guide to facilitate the authors' bibliographic review. [ABSTRACT FROM AUTHOR]

This paper investigates the dynamics of the cross-shore extensions of banquettes, a sedimentary structure mostly made by rests of Posidonia oceanica (L.) Delile, in a sandy urban beach located in the Gulf of Cagliari, Italy, western Mediterranean. A video monitoring station was installed above the promontory south of the beach. We analysed a four-year image database and related these dynamics to wave and wind parameters (obtained from the Copernicus and ERA5 databases) from September 2016 to September 2020. Our results showed that banquette deposition occurred in concomitance with the presence of leaf litter in the surf zone associated with mild storm events. Erosion of the banquettes occurred during more intense storms. When leaf litter was not present in the surf zone, banquettes were not deposited even with mild storms. Wind can influence the banquette dynamics: under certain conditions of speed intensity, the banquettes may be removed offshore, supplying litter in the surf zone, or they may be covered by sediment. The permanence of the banquettes on the beaches also depended on their composition: when the banquettes were intertwined with reeds, their removal by the waves did not occur even during intense storms, and this sedimentary structure can protect the beach from flooding. [ABSTRACT FROM AUTHOR]

The impacts of sea level rise under a changing climate negatively affect the world's coastal zones and threaten livelihood opportunities of the dependent communities, thereby highlighting the need for improved coastal adaptation strategies. The study employed a two-step methodology (i.e. bibliometric and systematic review) to analyse the geospatiality of sea level rise impacts and communities' adaptation. In total, 363 papers were retrieved from Scopus and Web of Science databases, and 292 were considered eligible and used for the bibliometric analysis. In the systematic review, the study aimed for specific community adaptation strategies from the 292 papers, and 118 papers were eligible following developed criteria. Results indicate that countries are committed to helping their coastal communities to adapt to sea level rise impacts and the USA has been significant in that regard. Coastal communities adapt to sea level rise impacts by increasing their structural/physical or social options; however, policy/institutional assistance to intensify these options is limited. Also, specific community adaptation strategies to sea level rise impacts have been more of the engineered and built environment (67%) strategies and few on ecosystem-based strategies (7%). More ecosystem-based strategies are, thus, needed considering their socio-ecological benefits. Further research and increased communities-policymakers engagement for enhanced adaptive capacity is required. [ABSTRACT FROM AUTHOR]

In a companion paper (Part 1), the basic concepts are discussed in details. In this paper, the application of the concepts and the proposed methodology in that paper are utilized to set the strategies in order to quantify reliability attributes. The case study is Hunts Point wastewater treatment plant and its sewershed in Bronx, New York City, so that it could function during flood. The strategies are selected and reliability of the Hunts Point plant is estimated before and after using best management practices (BMPs). Therefore, the copula based non-stationary 100–year flood frequency analysis of rainfall and storm surge analyzed in the companion paper (Part 1), are used to obtain the design values of surge and rainfall. A differential evaluation Markov Chain with Bayesian interface is used in that paper for parameter estimation. Because the co-occurrence of surge and rainfall is more critical in coastal areas, the design value resulted from bivariate analysis has been considered in this study. In this Part 2, a multi-criteria decision making (MCDM) approach, which characterized the uncertainty of sub-criteria in load-resistance concept, is applied. The Margin of Safety (MOS) concept is extended to numerically assess a rather non-probabilistic MCDM evaluation of load and resistance to estimate the reliability of the plant. Finally, Effective strategies are selected for flood hazard mitigation to improve the reliability and performance of the plant. The results present an increase of about 46% in reliability after using BMPs. The framework presented in this paper is applicable to other coastal watersheds and could be a platform for addressing some pressing issues in coastal preparedness with impacts on design criteria of coastal infrastructure. [ABSTRACT FROM AUTHOR]

Storm surges due to severe weather events threaten low-land littoral areas by increasing the risk of seawater inundation of coastal floodplains. In this paper, we present recent developments of a numerical modelling system for coastal inundation induced by sea level elevation due to storm surges enhanced by astronomical tides. The proposed numerical code (CoastFLOOD) performs high-resolution (5 m × 5 m) raster-based, storage-cell modelling of coastal inundation by Manning-type equations in decoupled 2-D formulation at local-scale (20 km × 20 km) lowland littoral floodplains. It is fed either by outputs of either regional-scale storm surge simulations or satellite altimetry data for the sea level anomaly. The presented case studies refer to model applications at 10 selected coastal sites of the Ionian Sea (east-central Mediterranean Sea). The implemented regular Cartesian grids (up to 5 m) are based on Digital Elevation/Surface Models (DEM/DSM) of the Hellenic Cadastre. New updated features of the model are discussed herein concerning the detailed surveying of terrain roughness and bottom friction, the expansion of Dirichlet boundary conditions for coastal currents (besides sea level), and the enhancement of wet/dry cell techniques for flood front propagation over steep water slopes. Verification of the model is performed by comparisons against satellite ocean color observations (Sentinel-2 images) and estimated flooded areas by the Normalized Difference Water Index (NDWI). The qualitative comparisons are acceptable, i.e., the modelled flooded areas contain all wet area estimations by NDWI. CoastFLOOD results are also compared to a simplified, static level, "bathtub" inundation approach with hydraulic connectivity revealing very good agreement (goodness-of-fit > 0.95). Furthermore, we show that proper treatment of bottom roughness referring to realistic Land Cover datasets provides more realistic estimations of the maximum flood extent timeframe. [ABSTRACT FROM AUTHOR]

Our work presents a reliable procedure to obtain real-time assessment of the sea water elevation at the Kaštela Bay site to ensure the a priori warning in the case of expected coastal flooding along the site area. In its origin, the presented procedure relies on relevant data sets which are site-specific and locally observed. Observed data sets are used within the procedure to assess sea water surface elevation when induced by barometric pressure changes and wind-generated waves. Tidal-induced changes are introduced into the assessment procedure by a pre-learned algorithm which relies on long-term sea level oscillations from the relevant tidal gauge. Wind-generated wave heights are determined in the near shore area, following the features of the depth and reflection of the shoreline subsections. By coupling three mechanisms, this paper offers a unique real-time procedure to determine the sea water elevation and assess the possibility for coastline structure to be flooded by the sea. Given information is visualized in a form of mobile application that implements the algorithm and allows end users to set the notifications based on the given ruleset. [ABSTRACT FROM AUTHOR]

AbstractOceanic islands constitute 0.05% of emerged land masses but account for 2% of UNESCO World Heritage Sites. Physical constraints have determined that the history of these remote territories is marked by globally unique forms of colonization and human cultures. A significant part of this heritage, located in coastal areas, is threatened by the mean sea level rise (SLR) due to anthropogenic climate change. This paper presents a regional approach to the risk estimation of SLR in the cultural heritage of oceanic islands, taking the Canary Islands (Spain) as an example. The Canary Islands is one of the most prominent oceanic archipelagos in the world (∼1500 km of coastline), where cultural heritage, preferentially located in the coastal areas (up to 50% in the first 1 km), nicely represents the two major stages of human occupation of islands (aboriginal and European). Through process-based modeling, high resolution flood maps were obtained for 20 climate scenarios and complete coverage of the archipelago. These maps were combined with detailed planimetries of 343 officially designated cultural heritage sites, applying damage functions to relate flood depth with the type of construction and the historical period. The results indicate potential damage to 55 cultural heritage sites of the Canary Islands which could be significant in 15 of them. For these cases, it is recommended to study specific adaptation measures aimed at mitigating the flood risk, such as moving the heritage assets away from the hazard areas or reinforcing and protecting the structures to reduce their vulnerability. [ABSTRACT FROM AUTHOR]

The web-based tool ARClim provides an atlas of climate change-related risk assessments spanning over 50 environmental and productive sectors in Chile. This paper illustrates the implementation of ARClim on two coastal sectors, operational downtime in fishing coves and flooding in coastal settlements, aiming to provide a tool to visualize comparative estimates of risk, which may enable decision makers and stakeholders to prioritize adaptation measures. The risk is calculated as a function of the hazard, exposure, and sensitivity. Exposure and sensitivity are characterized using present day information. To assess the hazard, wave climate for a historical period (1985–2004) and a projection (2026–2045) were modeled with six general circulation models (GCMs) for an RCP8.5 scenario. Similarly, sea-level rise was computed from 21 GCMs. Results show that the flooding hazard is mostly dependent on sea-level rise, with waves playing a minor role. However, the flooding risk is highly variable along the coast, due to differences in the exposure, which strongly depends on the population of each settlement. The analysis of increased operational downtime in fishing coves also shows risk, which is dependent of the size of each site. Lastly, limitations of the analysis and opportunities for improvement are discussed. [ABSTRACT FROM AUTHOR]

Low‐elevation coastal areas are increasingly vulnerable to seawater flooding as sea levels rise and the frequency and intensity of large storms increase with climate change. Seawater flooding can lead to the salinization of fresh coastal aquifers by vertical saltwater intrusion (SWI). Vertical SWI is often overlooked in coastal zone threat assessments despite the risk it poses to critical freshwater resources and salt‐intolerant ecosystems that sustain coastal populations. This review synthesizes field and modeling approaches for investigating vertical SWI and the practical and theoretical understanding of salinization and flushing processes obtained from prior studies. The synthesis explores complex vertical SWI dynamics that are influenced by density‐dependent flow and oceanic, hydrologic, geologic, climatic, and anthropogenic forcings acting on coastal aquifers across spatial and temporal scales. Key knowledge gaps, management challenges, and research opportunities are identified to help advance our understanding of the vulnerability of fresh coastal groundwater. Past modeling studies often focus on idealized aquifer systems, and thus future work could consider more diverse geologic, climatic, and topographic environments. Concurrent field and modeling programs should be sustained over time to capture interactions between physical processes, repeated salinization and flushing events, and delayed aquifer responses. Finally, this review highlights the need for improved coordination and knowledge translation across disciplines (e.g., coastal engineering, hydrogeology, oceanography, social science) to gain a more holistic understanding of vertical SWI. There also needs to be more education of communities, policy makers, and managers to motivate societal action to address coastal groundwater vulnerability in a changing climate. Plain Language Summary: Along the world's coastlines, seawater flooding on the land surface by storms and high tide events can drive the downward infiltration of seawater into coastal aquifers that are an important source of fresh groundwater. Rising sea levels and the intensification of coastal storms are expected to exacerbate seawater flooding events globally. The salinization of fresh groundwater along the coast following floods is often "out of sight, out of mind," but this process threatens freshwater resources that sustain dense coastal human populations and valuable, sensitive ecosystems. This paper reviews prior studies that have applied monitoring and/or computer modeling methods to better understand processes and controls on vertical saltwater intrusion. Our review details how surface flood dynamics, groundwater processes, environmental characteristics, and human activities combine to create complex patterns of salinization and flushing over space and time. From our synthesis we identify future research needs, including long‐term, globally dispersed monitoring and collaboration across scientific disciplines. We further emphasize the need for communication with local stakeholders about this topic to motivate informed management and research initiatives to understand and reduce the vulnerability of coastal fresh groundwater resources in a changing climate. Key Points: Vertical saltwater intrusion following coastal floods threatens fresh groundwater in an age of rising seas and intensifying stormsWe review salinization and flushing processes identified with field and modeling methods and identify future research opportunitiesKnowledge gaps can be addressed through multidisciplinary studies to advance science and inform water resources management and policy [ABSTRACT FROM AUTHOR]

Protection and restoration of natural infrastructure are fairly new tactics to reduce coastal flood hazards. Increasingly, floodplain managers and environmental organizations have advanced use of these solutions and communities have embraced them, owing to the perceived multiple benefits derived from these projects. Assessing progress in the use of natural infrastructure solutions requires means to account for projects. One way to measure progress is to track investments made in such projects. This paper analyzes and estimates the United States' investments in natural infrastructure and provides a replicable method for determining whether a project qualifies as an investment in natural infrastructure that could reduce flood hazard and, therefore, have a coastal risk reduction benefit. Estimates of annual investment between 2012 and 2018 indicate increasing, yet variable, annual investment. Better data availability would improve the accuracy of findings. [ABSTRACT FROM AUTHOR]

Coastal flooding is an important current issue due to climate change and due to significant increases in anthropogenic pressures observed in the second half of the last century. Indeed, climate change has been causing an increase in the frequency and the intensity of various natural events such as floods and sea storms; anthropogenic pressures have caused an increase in impermeable surfaces with negative consequences on the vulnerability of territories under the action of natural events. In this paper, we analyze the effects of climate change in terms of possible increases in floodable areas and in terms of population, infrastructure, coastal dunes, and sites of social, economic, and strategic interest exposed along the coasts of the region of Calabria in southern Italy. Calabria was chosen as a case study due to its geomorphological peculiarities and its considerable anthropogenic pressures. These peculiarities cause significant variability of weather and sea conditions among the different coastal areas, which influences the coastal dynamics and the characteristics of meteorological events. The main results show that, in the analyzed areas, the floodable areas double between current and future scenarios, involving both significant percentages of the population and railways, highways, industrial areas, and coastal dunes. [ABSTRACT FROM AUTHOR]

Climate warming, sea level rise, and extreme weather events are creating intensifying and more frequent hazards for human populations inhabiting the coast. In Alaska’s remote coastal communities, flooding and erosion are rapidly increasing due to the combined effect of sea level rise, more frequent storm surges, and increasingly powerful wave action from lack of sea ice. This paper presents survey results documenting socio-economic and psychological livelihood impacts and relocation preferences as reported by residents of a remote coastal Indigenous community. We quantified direct costs of lost or damaged private property, affected community infrastructure, and interruption of public services and found that the resulting financial hardship adds to existing economic challenges and climate stressors. Findings underline a community-level preoccupation with coastal climate threats that manifests primarily in intrusive and distressing thoughts of consequences from storms and other destructive climatic events. We highlight the need to monitor more broadly livelihood impacts to inform the design of innovative risk management tools to moderate financial hardship and strengthen community-driven action. We conclude that new policy responding to the needs of remote Indigenous communities affected by repetitive environmental disasters needs to account for a complex array of community and culture-specific socio-economic, health, and biophysical factors that require frequent co-produced assessments to capture rapidly changing conditions at the local scale. [ABSTRACT FROM AUTHOR]

The intensification of flooding events and the management of ecosystems became global issues. The combination of statistical modelling techniques and geospatial analysis represents a promising strategy to provide a holistic representation of the systems. This paper aimed to develop a strategy to build Spatial Coastal-Flooding Models based on evidence of flooding points and environmental and artificial characteristics of the area. The procedure combines statistical techniques, such as PCA, Cluster analysis, ANOVA, OLS regression, and geospatial data obtained from open databases. The geostatistical strategy was applied in Florianópolis city – Brazil. 108 photographic records of flooding were inventoried. The OLS regression analysis constructed three Spatial Coastal-Flooding Models considering eight factors. The analysis specifies the ability of models to explain the flooding in C1, C2, and C3 sub-regions through calculus (76, 68, and 40%). The results find that relationships between environmental and artificial variables and flooding events are not homogeneous over space. [ABSTRACT FROM AUTHOR]

The devastating impacts of frequent coastal storms, such as Hurricane Katrina in New Orleans in 2005 or Superstorm Sandy in New York City in 2012, in major low-lying metropolitan areas have had repercussions far beyond previously experienced disasters. Two key findings that describe these repercussions related to these events were stated as follows: in the case of Katrina, there was a lack of holistic or system-based thinking, and in the case of Sandy, there was an insufficient integration of critical infrastructure. Among different remediation actions, inland placement of best management practices (BMPs) in order to protect coastal cities from storm surges has received a lot of attention. However, nearshore BMPs as a way of source (wave height) reduction have not yet been thoroughly investigated. Nearshore practices are especially attractive in coastal areas that experience significant wave heights as a total water level component. In this paper, the effects of bathymetric shallowing through an apron on reducing the wave height and water level during storms are investigated in coastal areas. Southern Brooklyn in New York City is selected as the case study. A hydrodynamic model is utilized to generate wave height and storm tide. A water-level hydrograph in ungauged areas of the case study is constructed, which has not been realized before in similar coastal flood studies. Water level variations are investigated to include generated storm surge and wave characteristics. The results show that shallowing can reduce the peak of wave height and water level by 47% and 10%, respectively, in open coastal areas. In a more contained bay area, the reduction of a water level was more than 13%. These figures show the potential of nearshore BMP applications that could significantly improve our flood preparedness plans. The proposed methodology can be applied to other coastal geographical settings. [ABSTRACT FROM AUTHOR]

Over the past decades, the scientific community has made significant efforts to simulate flooding conditions using a variety of complex physically based models. Despite all advances, these models still fall short in accuracy and reliability and are often considered computationally intensive to be fully operational. This could be attributed to insufficient comprehension of the causative mechanisms of flood processes, assumptions in model development and inadequate consideration of uncertainties. We suggest adopting an approach that accounts for the influence of human activities, soil saturation, snow processes, topography, river morphology, and land‐use type to enhance our understanding of flood generating mechanisms. We also recommend a transition to the development of innovative earth system modeling frameworks where the interaction among all components of the earth system are simultaneously modeled. Additionally, more nonselective and rigorous studies should be conducted to provide a detailed comparison of physical models and simplified methods for flood inundation mapping. Linking process‐based models with data‐driven/statistical methods offers a variety of opportunities that are yet to be explored and conveyed to researchers and emergency managers. The main contribution of this paper is to notify scientists and practitioners of the latest developments in flood characterization and modeling, identify challenges in understanding flood processes, associated uncertainties and risks in coupled hydrologic and hydrodynamic modeling for forecasting and inundation mapping, and the potential use of state‐of‐the‐art data assimilation and machine learning to tackle the complexities involved in transitioning such developments to operation.Plain Language Summary: Every year, a large number of people are affected by flooding and suffer its costly consequences across the world. To properly manage this notorious natural disaster, the physical processes that represent riverine and coastal floods should be well understood and modeled. Over the recent decades, the scientific community has been continuously involved in characterizing the main components of floods and improving flood modeling skills using both types of physical and statistical models. Despite all these efforts, our modeling skill has major limitations which hinder an optimum performance for accurate and efficient flood forecasting. In this article, we provide a thorough review of these past efforts, highlight the main challenges, and provide potential pathways for improved flood characterization and modeling in the future. We specifically discuss the causative mechanisms of floods, physical/statistical methods used to characterize different components of flooding, coupling approaches, methods used to account for uncertainty in different layers of flood modeling, and their benefits for operational flood forecasting systems.Key Points: Causative mechanisms of floods and underlying physical processes in both riverine and coastal floods are thoroughly discussed and reviewedThe weak and selective validation of flood inundation models and the lack of sufficient validation data is a major challengeHybrid methods linking statistical and numerical tools are recommended for efficient and more accurate coastal flood hazard analysis [ABSTRACT FROM AUTHOR]

This study provides a literature‐based comparative assessment of uncertainties and biases in global to world‐regional scale assessments of current and future coastal flood risks, considering mean and extreme sea‐level hazards, the propagation of these into the floodplain, people and coastal assets exposed, and their vulnerability. Globally, by far the largest bias is introduced by not considering human adaptation, which can lead to an overestimation of coastal flood risk in 2100 by up to factor 1300. But even when considering adaptation, uncertainties in how coastal societies will adapt to sea‐level rise dominate with a factor of up to 27 all other uncertainties. Other large uncertainties that have been quantified globally are associated with socio‐economic development (factors 2.3–5.8), digital elevation data (factors 1.2–3.8), ice sheet models (factor 1.6–3.8) and greenhouse gas emissions (factors 1.6–2.1). Local uncertainties that stand out but have not been quantified globally, relate to depth‐damage functions, defense failure mechanisms, surge and wave heights in areas affected by tropical cyclones (in particular for large return periods), as well as nearshore interactions between mean sea‐levels, storm surges, tides and waves. Advancing the state‐of‐the‐art requires analyzing and reporting more comprehensively on underlying uncertainties, including those in data, methods and adaptation scenarios. Epistemic uncertainties in digital elevation, coastal protection levels and depth‐damage functions would be best reduced through open community‐based efforts, in which many scholars work together in collecting and validating these data. Plain Language Summary: One of the main impacts of climate change is sea‐level rise leading to more frequent flooding of low lying coastal areas through higher tides, storm surges and waves. In this context, assessments of current and future coastal flood risk at global to world‐regional scales are needed to inform policy decisions on greenhouse gas reduction targets and finance of adaptation and flood disaster risk reduction. A key requirement for such assessments is that they consider all major uncertainties in models, methods and data applied, because the failure to do so may lead to poor policy outcomes. So far, this key requirement has not been met. To address this limitation, this paper provides the first comparative assessment of uncertainties in global to world‐regional scale studies of current and future coastal flood risks based on the published literature. We find that globally, by far the largest uncertainty concerns how coastal societies will adapt to sea‐level rise, which can influence future flood risk by factors 20–27. Other large global uncertainties are associated with socio‐economic development, digital elevation data, greenhouse gas emissions, and ice sheet evolution, influencing global exposure and flood risk by factors of up to 2 to 6. Key Points: We present the first comparison of uncertainties in global to world‐regional scale assessments of current and future coastal flood riskThe largest uncertainty relates to future coastal adaptation, which can influence future coastal flood risk by factors of 20–27Uncertainties in socioeconomic development, elevation data, defense levels, emissions and ice sheets can affect risks by factors of 2–6 [ABSTRACT FROM AUTHOR]

Sea level rise and high tide events are threatening many coastal cities, which require adequate and sustainable protection measures. The historic city centre of Venice (Italy) is often flooded during very high tide events, especially the area of St. Mark's Island, which is at the lowest elevation among all the islands forming the city. To design cost-effective protection interventions to safeguard the historical heritage, a deep understanding of flooding mechanisms and the relationship between groundwater pressure and tidal oscillations is necessary. Geotechnical survey and analyses play an important role in this process. This paper presents the results of a recent monitoring campaign carried out in St. Mark's Island. A simplified one-dimensional analytical model was derived for saturated conditions to understand the key parameters that govern tidal induced pressure oscillations in soil (material properties, geometrical features, and wave properties). Additional features, such as partially saturated soil conditions and two-dimensional effects, were investigated numerically. Results showed that significant pressure oscillations occur in the subsoil, which should not be neglected when considering the stability of horizontal architectural structures, such as the historical mosaics and paving. However, seepage flow rate is small, and thus its impact on the drainage system is limited in terms of water discharge. [ABSTRACT FROM AUTHOR]

Compound flooding, resulting from a combination of riverine and coastal processes, is a complex but important hazard to resolve along urbanized shorelines in the vicinity of river mouths. However, inland flooding models rarely consider oceanographic conditions, and vice versa for coastal flood models. Here, we describe the development of an operational, integrated coastal-watershed flooding model to address this issue of compound flooding in a highly urbanized estuarine environment, San Francisco Bay (CA, USA), where the surrounding communities are susceptible to flooding along the bay shoreline and inland rivers and creeks that drain to the bay. The integrated tributary-coastal forecast model (Hydro-Coastal Storm Modeling System, or Hydro-CoSMoS) was developed to provide water managers and other users with flood forecast information beyond what is currently available. Results presented here are focused on the interaction of the Napa River watershed and the San Pablo Bay at the northern end of San Francisco Bay. This paper describes the modeling setup, the scenario used in a tabletop exercise (TTE), and the assessment of the various flood forecast information products. Hydro-CoSMoS successfully demonstrated the capability to provide watershed and coastal flood information at scales and locations where no such information is currently available and was also successful in showing how tributary flows could be used to inform the coastal storm model during a flooding scenario. The TTE provided valuable feedback on how to guide continued model development and to inform what model outputs and formats are most useful to end-users. [ABSTRACT FROM AUTHOR]

Coastal areas worldwide represent an aggregation of population and assets of growing economic, geopolitical, and sociocultural significance, yet their functions are increasingly challenged by worsening coastal hazards. Vulnerability assessments have been recognized as one way we can better understand which geographic areas and segments of society are more susceptible to adverse impacts from different stressors or hazards. The aims of this paper are to evaluate the state of coastal vulnerability assessment mapping efforts and to identify opportunities for advancement and refinement that will lead to more cohesive, impactful, and policy-relevant coastal vulnerability studies. We conducted a systematic review of the literature that addresses physical and social vulnerability to coastal hazards and contains corresponding mapping products. The content was analyzed for the scale of analysis, location, disciplinary focus, conceptual framework, metrics used, methodological approach, data sources, mapping output, and policy relevance. Results showed that most Coastal Vulnerability Mapping Assessments (CVMAs) are conducted at the local level using a range of methodologies, often with limited inclusion of social considerations and limited discussion of policy relevance. Based on our analysis, we provide seven recommendations for the advancement of this field that would improve CVMAs' methodological rigor, policy relevance, and alignment with other vulnerability assessment paradigms. [ABSTRACT FROM AUTHOR]

Understanding and improving how humans adapt to climate change are priorities in our research community, and coastal settlements are good places to study adaptation. Severe storm events and sea‐level rise are threatening coastal communities with increasing levels of flood damage. Because ownership of coastal assets is distributed among many private and public actors, both individual property owners and public officials must take adaptive actions. This paper introduces an integrated agent‐based and hedonic pricing modeling system to simulate coastal real estate market performance under non‐equilibrium conditions that reflect the effects of storm events. The modeling system, which is used for policy analysis, is calibrated to conditions in two towns in Monmouth County, New Jersey, USA, which were badly damaged by Hurricane Sandy in 2012. The key findings are that (a) coastal real estate markets capitalize flood risk into property values but this discount diminishes rapidly as time passes between storm events, and (b) there is a distinct equity versus efficiency tradeoff in designing public policies to reduce the cost to society of coastal flooding. Stringent regulation of building practices reduces flood damage but drives away poorer home buyers and owners, whereas informational and incentive‐based policies are fairer but less effective. Hands‐off, market‐based retreat from risky areas is socially costly but allows less wealthy people to remain at the shore, albeit in vulnerable situations. Managed retreat should emphasize improved recreational access to coastal amenities while discouraging people from living there. [ABSTRACT FROM AUTHOR]

Navas, F.; Malvárez, G.; Penning-Rowsell, E., and Parker, D.J., 2020. Spreading the use of economic methods in coastal risk management: A simple but insightful "calculator". In: Malvárez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 1217–1222. Coconut Creek (Florida), ISSN 0749-0208. European Directives, such as the EU Floods Directive (2007/60/EC) require that decision makers include objective methodologies, such as benefit-cost analysis, in their assessments of flood risk reduction measures. Methodologies to establish a sustainable knowledge framework addressing the costs and benefits of prevention and response to coastal hazards resulting from hydro-meteorological, hydrographic and other natural events and processes (e.g. flooding, beach erosion, cliff erosion, sea level rise) are not homogeneously implemented in the European Union. Until now, investment decisions in this field have been made more on local political imperatives than logical economic risk assessments. This paper aims to overcome some these limitations by demonstrating the usefulness of a simplified benefit-cost methodology and its application to a coastal case where a number of alternative flood risk reduction schemes are considered. The method allows the economically optimal scheme to be identified. The method is discussed within the context of generally poorly comprehended aspects; issues presented in coupling benefit-cost methods with vulnerability and related assessments; and key data uncertainties. [ABSTRACT FROM AUTHOR]

• Ideology and inclusion are important for spontaneous volunteerism in emergency response. • Spontaneous volunteers in response contributes to emergency management quality. • The inclusion of spontaneous volunteers in emergency response is possible Denmark. The paper studies the response to a coastal flooding in Roskilde Municipality, Denmark, which included a relatively large number of spontaneous volunteers, which is a rare and practically undescribed phenomenon in Denmark. The particular focus of the study is how emergency authorities can embrace and integrate spontaneous volunteers in emergency response. In the paper an analytical model is developed abductively, which suggests that the ideology and inclusion practices of the emergency authorities are important factors that need to be studied more to understand the integration of spontaneous volunteers in emergency response. The study is based on document analysis, media and social media analysis and qualitative interviews. The study concludes that the involvement of spontaneous volunteers in emergency response contributes to emergency management quality if appropriate management approaches are applied. [ABSTRACT FROM AUTHOR]

Due to changes in atmospheric circulation and warmer winters, the frequency of strong westerly storms associated with high sea level in ice-free sea conditions has increased on the western coast of Estonia. This trend is especially dangerous for the sections of depositional seashores along the eastern coast of the Baltic Sea such as Pärnu Bay and its surroundings. Pärnu is the largest city in SW Estonia being a popular summer resort with excellent sandy beaches and relevant infrastructure for tourism. Extreme events that may occur in the Pärnu Bay region are irregular extensive floods and sea ice attacks but also strong erosion of beaches. During the last 50 years, the city has suffered from two remarkably high storm surges and associated inundations. The aim of the paper was to analyze the best solutions for coastal zone management in Pärnu Bay area using a System Approach Framework (SAF). It is based on some new results of geomorphic surveys performed in the study area in 2015–2017, review of previous work as well as results from stakeholder meetings. Some formerly proposed flood defence projects and ideas were re-analyzed and new ideas were proposed to better inform the people about risks and reduce the damage in case of catastrophic events. Based on the analysis of the collected data and discussions with the stakeholders, we concluded that hard coastal protection measures would be too expensive and therefore not reasonable for implementation. Developing different kinds of adaptation measures and raising awareness of the people are the most applicable response options to high storm surges and extensive inundations in the Pärnu Bay region. [ABSTRACT FROM AUTHOR]

Short‐term changes in sea level can have substantial impacts on coastlines, and increases in coastal flooding have been observed as the mean sea level continues to climb. While extreme events such as hurricanes have been well studied in terms of their impacts on anomalous sea level values, anomalous sea levels due to less extreme atmospheric events have been less well studied, despite the increases in nuisance flood events that have occurred. In this study, we assess the relationship between short‐term atmospheric circulation patterns and anomalous coastal sea level values for all oceanic tidal gauges in the conterminous United States for the period 1979–2016. Atmospheric patterns are depicted using self‐organizing maps for four variables: sea level pressure, 10‐m wind, 850‐mb temperature, and 700‐mb geopotential height. We then reconstruct the time series of anomalous sea level through nonlinear autoregressive models with exogenous input (NARX models), an artificial neural network‐based time series model. Results show that these four atmospheric variables can successfully model sea level, with a correlation between model and observation using a closed‐loop (open‐loop) architecture of 0.83 (0.64), with a median absolute error of 3.34 (4.90) cm. The model generally performs better in winter than summer, and along the Pacific Coast than the Atlantic and Gulf Coasts. By using the NARX methodology, we intend to next assess its utility as a forecasting tool. Plain Language Summary: Coastal flooding is becoming an increasing concern as sea level continues to rise. Beyond extreme events, there are many "blue sky floods" in which atmospheric conditions synergize to produce high sea levels. In this paper, we examined how well we could simulate the time series of anomalous sea level values along the U.S. coast using atmospheric conditions. Our results show significant potential in replicating sea level values. We next plan to evaluate how well our model can be used in a forecasting capacity. Key Points: Atmospheric conditions can have substantial impacts on coastal sea levels beyond extreme eventsClassifications of patterns of several atmospheric variables can be used to reconstruct a time series of anomalous sea level [ABSTRACT FROM AUTHOR]

The intensification of extreme events due climate change and sea-level rise are major challenges to be urgently addressed by Europe's coastal cities. Coastal hazards have the potential to cause significant damage to coastal communities. Nevertheless, various other climate-related hazards also pose imminent threats. This review paper examines the impacts of climate change on ten European coastal cities by means of a participatory process involving the coastal cities and the review of existing literature. Local expertise is included through the novel concept of Coastal City Living Lab. The study also leverages bibliometric analysis of the Scopus and Web of Science databases, along with a desk review of climate-change related institutions and agencies at international, national, regional and local levels. By combining scientific literature analysis with insights from local experts, this research provides a comprehensive overview of the current situation of these diverse cities in relation to multiple climate-related hazards, which can be extrapolated to other cities. There is a scarcity of scientific data for some of the cities, hence collaboration with the CCLLs was crucial. Results serve as a valuable baseline for future works, introducing detail studies focusing on various climate-related challenges. This paper not only contributes novel insights by including the perceptions of local partners but also offers a unique perspective on the complex nature of climate change impacts at city level. • Comprehensive understanding of climate change impacts on coastal cities through multifaceted methodology. • Systematic scientific literature review of Scopus and Web of Science databases. • Local expertise from a collaborative process involving ten diverse European coastal cities. • Unique perspective on the complex nature of climate change impacts at city level. • Baseline for risk assessments and adaptation strategies considering multiple climate-related hazards. [ABSTRACT FROM AUTHOR]

Coastal Virginia, a region with economic and strategic significance at the state and national level, has been experiencing the highest sea-level rise (SLR) on the Atlantic coast of the United States. This has been accompanied by a variety of climate hazards such as flooding and more frequent storms, initiating adaptation planning and decision-making on multiple governance levels. A spatial understanding of climate risk and its associations with socioeconomic vulnerabilities raises essential questions about the underlying roots of such associations and can help local governments prioritize social vulnerabilities in their adaptation efforts. Using coastal flooding as a climate stressor in this region, this paper conducts analyses that strive to help policymakers more effectively utilize social vulnerability in adaptation planning. The analysis reveals significant associations between climate risk, represented by flood risk, and social vulnerability measures such as poverty, access to infrastructure, education, and housing in certain parts of coastal Virginia. The paper then discusses how associations between vulnerability and climate risk in the region could influence policymaking on the local and state level. This research presents several empirical relationships that raise important questions regarding the drivers of social equity in the face of climate adaptation in coastal Virginia. The methodology developed in this study may be modified to assess social equity in climate adaptation in other coastal communities in the United States and possibly other countries. Such modification can help to illuminate the associations between location-specific social vulnerabilities, such as social safety net policies, and climate risks.

Inhabitants of coastal areas are constantly confronted with minor or major events such as storms, erosion or flooding. This article investigates the predictors of coping willingness among citizens exposed to coastal flooding. Coping can be defined as a set of cognitive and behavioral efforts to master, reduce or tolerate a given risk and these strategies are generally regrouped into two different categories: active coping strategies oriented toward the risk to reduce or master it, and passive coping strategies focused on the reduction of internal tensions such as anxiety or fear. In this paper, we focus especially on how place identity, perceived self-efficacy, anxiety-state and coastal flooding risk perception shape both active and passive coping willingness. Data were obtained from different areas at risk of coastal flooding located in France. The sample is composed of 315 adult participants (mean age = 47; SD = 15). Two competing models were tested using path modeling. We expected a direct relation between risk perception and the willingness to cope actively and that a higher perceived self-efficacy would increase active coping willingness. Concerning passive coping strategies, we expected that a higher anxiety-state increases passive coping willingness, and that place identity would act as a mediator and increases the relation between anxiety-state and passive coping willingness. Results suggest that place identity increased when the living place is threatened and that the use of passive coping strategies also increased. Also, we demonstrated a direct relation between risk perception and active coping willingness but it appeared that self-efficacy has no effect on this relation. Model fit indices suggest the good fit of our model and Bayesian model comparison reveals a very strong evidence of the best fit of this model compared to its saturated and independent equivalents. [ABSTRACT FROM AUTHOR]

The main aim of this paper is to present a new methodology to determine coastal susceptibility to erosion and flooding processes by means of an index-based method. The proposed indices take into account physical parameters, such as dune and beach geomorphologic characteristics, shoreline evolution, local significant wave height and relative run-up. The coastal susceptibility has been estimated by elaboration of spatial input data into a GIS environment. The method has been tested in Valdelagrana area, a sandy spit located in SW Spain. The spit includes several morpho-sedimentary environments: sandy beach, discontinuous embryo dunes and foredunes, mud flats and wide areas of vegetated salt marshes. The Northernmost sector is densely urbanized whilst the rest is part of a natural protected area belonging to the Bahía de Cádiz Natural Park. The results obtained showed how the Southern part of the spit presented a high susceptibility due to an elevated erosion rate and the presence of low and discontinuous dune ridges. [ABSTRACT FROM AUTHOR]

The generalised sea level and temperature rise, along with the increasing frequency and intensity of storms and temperature extremes, trigger a variety of climate-change-related impacts on coastal communities, such as coastal flooding and erosion, pluvial and river flooding, heat waves, cold spells, droughts, and landslides. These events can rapidly cascade into additional challenges and have a profound impact on the coastal zone. Many studies have focused on the causes and consequences of climate change for coastal cities in the past decades. As a result, the number of forecasts, risk assessments, literature reviews, and methodologies has increased. This comprehensive review comprises the key findings of a systematic analysis of the scientific literature on extreme impacts of climate change on coastal cities. After a bibliometric analysis, which yields 2321 papers in 470 journals from 1976 to 2021, a scientometric analysis is carried out. There is wide geographical diversity, with publications from 97 countries. In terms of numbers and nationalities, the USA was followed by China, UK, Australia, and Indonesia. The scarcity of papers from developing countries is apparent. "Storm" and "risk assessment" are the top keywords regarding frequency of occurrence and relationships with other keywords. The main research areas for this topic are risk assessment, climate-change-related hazards and their drivers, modelling tools, disaster control and prevention measures, climate change policies and urban planning. Finally, research gaps are identified, and future research directions proposed, e.g., emerging integrated coastal zone management tools and the impacts on climate change on developing countries. [ABSTRACT FROM AUTHOR]

National weather forecasting agencies routinely issue a range of hazard warnings. But to our knowledge, along sandy coastlines where storm waves and storm surge can result in widespread but location-specific beach erosion and beachfront flooding, no national-scale early warning service for these hazards is presently operational. This paper outlines the scientific basis and implementation of a new framework for large area coastal storm hazards forecasting, currently being tested along the southwest (Indian Ocean) and southeast (Pacific Ocean) coasts of Australia. The system provides 7-day rolling predictions of localized beach erosion and/or coastal flooding linked to forecasted extreme weather events. Coastal setting influences the nature and occurrence of these hazards, with sandy beaches along wave-dominated coasts more prone to erosion and at surge-dominated coasts to flooding. An existing nearshore water-level forecasting system and a new inshore wave modeling capability are used to forecast beach erosion and coastal flooding at every 100 m along the shore. At the regional scale O(100–1 000 km of coastline), a threshold-based decision tree model categorises the predicted extent, location, and severity of erosion and flooding. At a more local scale O(100–1 000 m), physics-based modeling using XBeach focuses on vulnerable or high-value locations, providing specific storm hazard indicators tailored to local needs. This two-tier approach is feasible for national implementation due to the reduced computational effort, limiting intensive modeling to pre-identified critical locations. Delft-FEWS manages the data and modeling workflow, ensuring scalability and compatibility with existing forecast infrastructure. Initial evaluations of the system are promising, with a detailed 2-year evaluation in progress. Future enhancements could include the use of satellite imagery for real-time beach width and dune topography assimilation and exploring alternative modeling approaches to further improve forecast accuracy. • A framework for coastal storm hazards early warning over very large areas is developed. • The severity of hazards is predicted every 100 m alongshore by parametric modeling. • Site-specific storm hazard indicators at vulnerable sites are predicted by XBeach. • 7-day rolling forecasts of storm hazards are communicated via a web portal. [ABSTRACT FROM AUTHOR]

This paper explains the process of increasing coastal vulnerability in response to coastal flooding, from the property market viewpoint. Rooted in knowledge about housing submarket-based neighborhood change, this study adds new understandings of how housing obsolesces influence vulnerability following rapid land use changes, which are currently studied as a new exposure by many researchers. We employ six years of house sales transaction data (n = 1,029) in a spatial data-driven delineation with k-means, through which the submarket shift can be visualized. This approach addresses weaknesses in the existing methods to measure neighborhood change. We find that second-hand houses purchased by low-income people tend to cluster close together in newly formed submarkets in at-risk areas creating submarkets for western-inner city and distressed properties. Our data series also show that the geographical growth of the submarket for distressed properties is expanding, creating further blight in the submarket for western-inner city. Consequently, the submarket for distressed properties tends to transform into an area characterized by substandard housing conditions or slum living. Bearing in mind that the consequences of a flood will cover a wide range of issues, such as the future of public services, and the welfare of citizens in general, disaster risk management is fundamental to socio-economic development of a country. This study can enrich discussions around housing vulnerability and neighborhood change and support the current debate over spatial adaptation and climate change. [ABSTRACT FROM AUTHOR]

Catastrophic flooding associated with sea-level rise and change of hurricane patterns has put the northeastern coastal regions of the United States at a greater risk. In this paper, we predict coastal flooding at the east bank of Delaware Bay and analyze the resulting impact on residents and transportation infrastructure. The three-dimensional coastal ocean model FVCOM coupled with a two-dimensional shallow water model is used to simulate hydrodynamic flooding from coastal ocean water with fine-resolution meshes, and a topography-based hydrologic method is applied to estimate inland flooding due to precipitation. The entire flooded areas with a range of storm intensity (i.e., no storm, 10-, and 50-year storm) and sea-level rise (i.e., current, 10-, and 50-year sea level) are thus determined. The populations in the study region in 10 and 50 years are predicted using an economic-demographic model. With the aid of ArcGIS, detailed analysis of affected population and transportation systems including highway networks, railroads, and bridges is presented for all of the flood scenarios. It is concluded that sea-level rise will lead to a substantial increase in vulnerability of residents and transportation infrastructure to storm floods, and such a flood tends to affect more population in Cape May County but more transportation facilities in Cumberland County, New Jersey. [ABSTRACT FROM AUTHOR]

Design-flood levels with associated exceedance probabilities are usually determined for coastal flood protection projects. Rising sea level introduces another design feature that needs to be combined with the design-flood level. However, most sea-level projections do not have exceedance probabilities that can be used in conjunction with the design flood to obtain total flood levels. This paper shows how to combine design-flood levels with sea-level rise projections that have exceedance probabilities, such as those of the Intergovernmental Panel for Climate Change, to obtain total elevations at desired exceedance probabilities over particular intervals. [ABSTRACT FROM AUTHOR]

ABSTRACT Palginõmm, V.; Orviku, K.; Suursaar, Ü.; Kont, A.; Tõnisson, H., and Rivis, R., 2018. Lessons Learned from Record-High Storm Surges and Associated Inundations in Pärnu, SW Estonia. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 1391–1395. Coconut Creek (Florida), ISSN 0749-0208. Due to changes in atmospheric circulation and warmer winters, the frequency of strong westerly storms associated with high sea level in ice-free sea conditions has increased over the last half-century on the western coast of Estonia including in Pärnu City. During the last 50 years Pärnu has suffered from two remarkably high storm surges and associated inundations – in 1967 (2.53 m above mean sea level) and in 2005 (2.75 m). This paper addresses the problem of coastal floods in Pärnu, analyzing different action plans in order to protect the city against floods, which may get even more disastrous due to climate change induced sea level rise. Our analysis showed that application of adaptation measures seems to be the most reasonable option for Pärnu, while the expenses on building a protective dam exceeds the potentially avoidable losses. A managed retreat was not acceptable either because the city would lose its identity as a famous summer resort with excellent sandy beaches. Dissipation of storm surge water over adjacent low-lying uninhabited territories would not give any clear effect reducing the high water level only by 5 centimetres as maximum. In case of adapting to temporary extensive floods, a more efficient warning system and better communication between the authorities and the local people are needed. [ABSTRACT FROM AUTHOR]

The run-up and overtopping by sea waves are two of the main processes that threaten coastal structures, leading to flooding, destruction of both property and the environment, and harm to people. To build early warning systems, the consequences and associated risks in the affected areas must be evaluated. It is also important to understand how these two types of spatial information integrate with sensor data sources and the risk assessment methodology. This paper describes the relationship between consequences and risk maps, their role in risk management and how the HIDRALERTA system integrates both aspects in its risk methodology. It describes a case study for Praia da Vitória Port, Terceira Island, Azores, Portugal, showing that the main innovations in this system are twofold: it represents the overtopping flow and consequent flooding, which are critical for coastal and port areas protected by maritime structures, and it works also as a risk assessment tool, extremely important for long-term planning and decision-making. Moreover, the implementation of the system considers possible known variability issues, enabling changes in its behaviour as needs arise. This system has the potential to become a useful tool for the management of coastal and port areas, due to its capacity to effectively issue warnings and assess risks. [ABSTRACT FROM AUTHOR]

Coastal areas are at a higher risk of flooding, and novel changes in the climate are induced to raise the sea level. Flood acceleration and frequency have increased recently because of unplanned infrastructural conveniences and anthropogenic activities. Therefore, the assessment of flood susceptibility mapping is considered the most significant flood management model. In this paper, flood susceptibility identification is performed by applying the innovative Multi-criteria decision-making model (MCDM) called Analytical Hierarchy Process (AHP) by ensembles with Support vector machine (AHP-SVM) and Decision Tree (AHP-DT). This model combines two Representation concentration pathway (RCP) scenarios such as RCP 2.6 & RCP 8.5. The factors influencing the coastal flooding in Bandar Abbas, Iran, identified through Flood susceptibility mapping. Multi-criteria decision-making (MCDM) has been applied to evaluate the Coastal flood conditioning factors, and ensemble machine learning (ML) approaches are employed for Coastal risk factor (CRF) prediction and classification. The statistical variances are measured through Friedman and Wilcoxon signed rank tests and statistical metrics such as Accuracy, sensitivity, and specificity. Among the models, AHP-DT obtained an improved AUC value of ROC as 0.95. After applying the ML models, the northern and western park of Raidak Basin River recognises very low and low flood susceptibility because of their topographic characteristics. The eastern part of the middle section fell very high and high CFSM. Observed from this result analysis, the people living nearer to the coastline are distributed by the low to medium exposure in the region of the west and middle of the considered study area. The results of this study can help decision-makers take necessary risk reduction approaches in the high-risk flooding zones of the coastal system. • Coastal areas are facing an increased risk of flooding due to rising sea levels and the impact of climate change. • Floods increased due to unplanned infrastructure and human activities. • The AHP-SVM-DT combination for flood susceptibility mapping is a notable flood management model. • The study uses flood susceptibility mapping to examine Bandar Abbas, Iran, to identify factors impacting coastal flooding. • AHP-DT model achieved AUC 0.95, effectively predicting and classifying coastal flood risk factors. [ABSTRACT FROM AUTHOR]