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The article discusses the widespread issue of subsidence, particularly in China's major urban areas, caused by various factors including human activities like groundwater withdrawal. Topics include the considerable subsidence in China's cities, the diverse causes of subsidence, and the need for a systematic approach to assess and mitigate its impacts.

Brown, S.; Nicholls, R.J.; Pardaens, A.K.; Lowe, J.A.; Tol, R.S.J.; Vafeidis, A.T., and Hinkel, J., 2019. Benefits of climatechange mitigation for reducing the impacts of sea-level rise in G-20 countries. Journal of Coastal Research, 35(4), 884–895. Coconut Creek (Florida), ISSN 0749-0208. This paper assesses the potential benefits of climate-change mitigation in reducing the impacts of sea-level rise over the 21st century in G-20 countries (excluding the European Union as a whole), using the Dynamic Interactive Vulnerability Assessment model. Impacts of the expected number of people flooded annually and wetland losses were assessed. To assess the benefits of mitigation, it was assumed that defences were not upgraded during the study. Globally, with a sea-level rise of 0.68 m by the 2080s (with respect to 1980–99), representing a potential future with limited climate-change mitigation, and with the Special Report on Emissions Scenarios A1 socio-economic scenario, 123 million additional people could be flooded annually and 39% of present global wetland stock could be lost. For a 0.19-m rise in sea level, associated with a substantial reduction in emissions, the number of people flooded could be reduced to 13 million/y, with 21% of global wetland stock loss, unless new wetlands emerge. Collectively, non-Annex 1 G-20 countries experience a disproportionately higher number of people flooded in their nations compared with the proportion of population flooded globally. The greatest wetland losses for G-20 countries are projected for Australia, Indonesia, and the United States. Thus, G-20 nations with the highest emissions or gross domestic product frequently do not experience the greatest impacts, despite some of these nations being potentially more able to pay for adaptation. [ABSTRACT FROM AUTHOR]

Regular sediment inputs are required for deltas to maintain their surface elevation relative to sea level, which is important for avoiding salinization, erosion, and flooding. However, fluvial sediment inputs to deltas are being threatened by changes in upstream catchments due to climate and land use change and, particularly, reservoir construction. In this research, the global hydrogeomorphic model WBMsed is used to project and contrast ‘pristine’ (no anthropogenic impacts) and ‘recent’ historical fluvial sediment delivery to the Ganges-Brahmaputra-Meghna, Mahanadi, and Volta deltas. Additionally, 12 potential future scenarios of environmental change comprising combinations of four climate and three socioeconomic pathways, combined with a single construction timeline for future reservoirs, were simulated and analysed. The simulations of the Ganges-Brahmaputra-Meghna delta showed a large decrease in sediment flux over time, regardless of future scenario, from 669 Mt/a in a ‘pristine’ world, through 566 Mt/a in the ‘recent’ past, to 79–92 Mt/a by the end of the 21st century across the scenarios (total average decline of 88%). In contrast, for the Mahanadi delta the simulated sediment delivery increased between the ‘pristine’ and ‘recent’ past from 23 Mt/a to 40 Mt/a (+77%), and then decreased to 7–25 Mt/a by the end of the 21st century. The Volta delta shows a large decrease in sediment delivery historically, from 8 to 0.3 Mt/a (96%) between the ‘pristine’ and ‘recent’ past, however over the 21st century the sediment flux changes little and is predicted to vary between 0.2 and 0.4 Mt/a dependent on scenario. For the Volta delta, catchment management short of removing or re-engineering the Volta dam would have little effect, however without careful management of the upstream catchments these deltas may be unable to maintain their current elevation relative to sea level, suggesting increasing salinization, erosion, flood hazards, and adaptation demands. [ABSTRACT FROM AUTHOR]

To better anticipate potential impacts of climate change, diverse information about the future is required, including climate, society and economy, and adaptation and mitigation. To address this need, a global RCP (Representative Concentration Pathways), SSP (Shared Socio-economic Pathways), and SPA (Shared climate Policy Assumptions) (RCP–SSP–SPA) scenario framework has been developed by the Intergovernmental Panel on Climate Change Fifth Assessment Report (IPCC-AR5). Application of this full global framework at sub-national scales introduces two key challenges: added complexity in capturing the multiple dimensions of change, and issues of scale. Perhaps for this reason, there are few such applications of this new framework. Here, we present an integrated multi-scale hybrid scenario approach that combines both expert-based and participatory methods. The framework has been developed and applied within the DECCMA 1 1 DECCMA ( DEltas , vulnerability and Climate Change: Migration and Adaptation ) project is part of the Collaborative Adaptation Research Initiative in Africa and Asia (CARIAA), with financial support from the UK Government's Department for International Development (DFID) and the International Development Research Centre (IDRC), Canada. For more information, visit the project website: http://www.geodata.soton.ac.uk/deccma/ . project with the purpose of exploring migration and adaptation in three deltas across West Africa and South Asia: (i) the Volta delta (Ghana), (ii) the Mahanadi delta (India), and (iii) the Ganges-Brahmaputra-Meghna (GBM) delta (Bangladesh/India). Using a climate scenario that encompasses a wide range of impacts (RCP8.5) combined with three SSP-based socio-economic scenarios (SSP2, SSP3, SSP5), we generate highly divergent and challenging scenario contexts across multiple scales against which robustness of the human and natural systems within the deltas are tested. In addition, we consider four distinct adaptation policy trajectories: Minimum intervention , Economic capacity expansion , System efficiency enhancement , and System restructuring , which describe alternative future bundles of adaptation actions/measures under different socio-economic trajectories. The paper highlights the importance of multi-scale (combined top-down and bottom-up) and participatory (joint expert-stakeholder) scenario methods for addressing uncertainty in adaptation decision-making. The framework facilitates improved integrated assessments of the potential impacts and plausible adaptation policy choices (including migration) under uncertain future changing conditions. The concept, methods, and processes presented are transferable to other sub-national socio-ecological settings with multi-scale challenges. [ABSTRACT FROM AUTHOR]

The effectiveness of stringent climate stabilization scenarios for coastal areas in terms of reduction of impacts/adaptation needs and wider policy implications has received little attention. Here we use the Warming Acidification and Sea Level Projector Earth systems model to calculate large ensembles of global sea-level rise (SLR) and ocean pH projections to 2300 for 1.5°C and 2.0°C stabilization scenarios, and a reference unmitigated RCP8.5 scenario. The potential consequences of these projections are then considered for global coastal flooding, small islands, deltas, coastal cities and coastal ecology. Under both stabilization scenarios, global mean ocean pH (and temperature) stabilize within a century. This implies significant ecosystem impacts are avoided, but detailed quantification is lacking, reflecting scientific uncertainty. By contrast, SLR is only slowed and continues to 2300 (and beyond). Hence, while coastal impacts due to SLR are reduced significantly by climate stabilization, especially after 2100, potential impacts continue to grow for centuries. SLR in 2300 under both stabilization scenarios exceeds unmitigated SLR in 2100. Therefore, adaptation remains essential in densely populated and economically important coastal areas under climate stabilization. Given the multiple adaptation steps that this will require, an adaptation pathways approach has merits for coastal areas. [ABSTRACT FROM AUTHOR]

The authors discusses incorporation of Sustainable Development Goals (SDGs) established by the United Nations Framework Convention on Climate Change (UNFCCC) in mitigating of climate change. It states observation of climatic changes in different areas such as deltas along with desertification in semi-arid regions. It mentions several monitoring indicators associated with climate change conditions such as global sea-level rise along with oil extraction activities.

Coastal and shoreline management increasingly needs to consider morphological change occurring at decadal to centennial timescales, especially that related to climate change and sea-level rise. This requires the development of morphological models operating at a mesoscale, defined by time and length scales of the order 10 1 to 10 2 years and 10 1 to 10 2 km. So-called ‘reduced complexity’ models that represent critical processes at scales not much smaller than the primary scale of interest, and are regulated by capturing the critical feedbacks that govern landform behaviour, are proving effective as a means of exploring emergent coastal behaviour at a landscape scale. Such models tend to be computationally efficient and are thus easily applied within a probabilistic framework. At the same time, reductionist models, built upon a more detailed description of hydrodynamic and sediment transport processes, are capable of application at increasingly broad spatial and temporal scales. More qualitative modelling approaches are also emerging that can guide the development and deployment of quantitative models, and these can be supplemented by varied data-driven modelling approaches that can achieve new explanatory insights from observational datasets. Such disparate approaches have hitherto been pursued largely in isolation by mutually exclusive modelling communities. Brought together, they have the potential to facilitate a step change in our ability to simulate the evolution of coastal morphology at scales that are most relevant to managing erosion and flood risk. Here, we advocate and outline a new integrated modelling framework that deploys coupled mesoscale reduced complexity models, reductionist coastal area models, data-driven approaches, and qualitative conceptual models. Integration of these heterogeneous approaches gives rise to model compositions that can potentially resolve decadal- to centennial-scale behaviour of diverse coupled open coast, estuary and inner shelf settings. This vision is illustrated through an idealised composition of models for a ~ 70 km stretch of the Suffolk coast, eastern England. A key advantage of model linking is that it allows a wide range of real-world situations to be simulated from a small set of model components. However, this process involves more than just the development of software that allows for flexible model coupling. The compatibility of radically different modelling assumptions remains to be carefully assessed and testing as well as evaluating uncertainties of models in composition are areas that require further attention. [ABSTRACT FROM AUTHOR]

Abstract: Coastal floodplains are complex regions that form the interface between human, physical and natural systems. This paper describes the development, application and evaluation of a conceptual foundation for quantitative integrated floodplain risk assessments using the recently-developed SPR systems model. The SPR systems model is a conceptual model that combines the well-established Source–Pathway–Receptor (SPR) approach with the concept of system diagrams. In comparison to the conventional approach, the systems model provides spatially explicit quasi-2D descriptions of the floodplain in terms of constituent elements and possible element linkages. The quasi-2D SPR, as it will henceforth be referred to in this paper, is not the final product of this work, but is an important intermediate stage which has been pursued as part of a wider European flood risk project THESEUS (www.theseusproject.eu). Further research is currently on-going to provide full quantification of the quasi-2D SPR, and to add further refinements such that hydraulic assessments could follow on easily and rapidly from the results of these appraisals. The first part of the paper synthesises current conceptual treatment of coastal floodplains and identifies areas for improvement in describing coastal floodplains as complex systems. The synthesis demonstrates that the conceptual foundation of a ‘typical’ flood risk study often achieves a less comprehensive and integrated description of the floodplain than the quantitative models which it informs. From this synthesis, the quasi-2D SPR is identified as a more robust and informative conceptual foundation for an integrated risk assessment. The quasi-2D SPR has been applied to seven European coastal floodplains as part of the THESEUS project. The second part of the paper discusses in detail the application of the quasi-2D SPR to three contrasting floodplain systems — an estuary, a coastal peninsula and a mixed open coast/estuary site. The quasi-2D SPR provides a consistent approach for achieving comprehensive floodplain descriptions that are individual to each coastal floodplain. These are obtained through a robust, participatory model-building exercise, that facilitates developing a shared understanding of the system. The constructed model is a powerful tool for structuring and integrating existing knowledge across multiple disciplines. Applications of the quasi-2D SPR provide key insights into the characteristics of complex coastal floodplains — insights that will inform the quantification process. Finally, the paper briefly describes the on-going quantitative extension to the quasi-2D SPR. [Copyright &y& Elsevier]

Abstract: This paper presents a first assessment of the global effects of climate-induced sea-level rise on the erosion of sandy beaches, and its consequent impacts in the form of land loss and forced migration of people. We consider direct erosion on open sandy coasts and indirect erosion near selected tidal inlets and estuaries, using six global mean sea-level scenarios (in the range of 0.2–0.8m) and six SRES socio-economic development scenarios for the 21st century. Impacts are assessed both without and with adaptation in the form of shore and beach nourishment, based on cost-benefit analysis that includes the benefits of maintaining sandy beaches for tourism. Without nourishment, global land loss would amount to about 6000–17,000km2 during the 21st century, leading to 1.6–5.3million people being forced to migrate and migration costs of US$ 300–1000billion (not discounted). Optimal beach and shore nourishment would cost about US$ 65–220billion (not discounted) during the 21st century and would reduce land loss by 8–14%, forced migration by 56–68% and the cost of forced migration by 77–84% (not discounted). The global share of erodible coast that is nourished increases from about 4% in 2000 to 18–33% in 2100, with beach nourishment being 3–4 times more frequent than shore nourishment, reflecting the importance of tourism benefits. In absolute terms, with or without nourishment, large countries with long shorelines appear to have the largest costs, but in relative terms, small island states appear most impacted by erosion. Considerable uncertainty remains due to the limited availability of basic coastal geomorphological data and models on a global scale. Future work should also further explore the effects of beach tourism, including considering sub-national distributions of beach tourists. [Copyright &y& Elsevier]

National infrastructure is as much a priority in countries with a large stock of ageing infrastructural assets as it is for rapidly industrialising economies. Increasing attention is being paid to the risk and opportunities that the growing interdependence between infrastructural systems brings. However, there is no current methodology to enable long-term planning and future performance assessment of interdependent infrastructural systems. This paper makes the case for a long-term, cross-sectoral approach to analysing and planning the performance of national infrastructure systems. Such an approach is required to develop credible long-term visions for infrastructure provision and to analyse system performance across a range of possible futures. A preliminary version of a system-of-systems analysis for the UK is presented as an example. The implementation of a comprehensive, model-based approach is currently well under way. [ABSTRACT FROM AUTHOR]

Coastal change can cause a serious threat to the large populations living in coastal areas around the world and in many situations, appropriate adaptation responses are required. In this paper, the changes, impacts and risks associated with coastal change, especially due to climate change, are reviewed, and a range of the technical options available for addressing resulting coastal flooding and erosion are evaluated. These are classified and compared across three potential adaptation strategies - (1) protect, (2) accommodate and (3) retreat - and considered from developed and developing country perspectives. It is emphasised that adaptation is an ongoing process which requires consideration and assessment of all drivers of risk, and monitoring of the risks and opportunities of the selected risk reduction measures, as well as review of their effectiveness. Further, adaptation needs to be integrated with wider coastal planning and management. [ABSTRACT FROM AUTHOR]

Assessments of changing risks in the future often focus on climate change alone, and ignore other relevant drivers such as socioeconomic changes. If other relevant drivers are considered at all, expert judgment is often used to create scenarios and the underlying logic is not always apparent. In this paper we describe an algorithm-based method for developing quantitative future scenarios of the built environment in East Anglia, England with a focus on a coastal management unit, designated sub-cell 3b. The four UK Foresight socioeconomic storylines were inputs to the study: World Markets, Local Stewardship, Global Sustainability, and National Enterprise. On the basis of estimated regional demand, the distributions of new residential and nonresidential properties were calculated under all scenarios using a GIS-based multicriteria analysis. The buildings are distributed across a large swath of East Anglia using four attraction factors with different weightings to reflect the storylines. The factors are the existing settlements, transport networks, coastline, and floodplain. The results show increases in the number of residential and nonresidential properties within the coastal flood plain of sub-cell 3b under all socioeconomic scenarios, especially under World Markets and National Enterprise. These increases may lead to a significant increase in flood risk and to a lesser extent in the erosion risk in the study site. More importantly, the multicriteria method presented here demonstrates an algorithm-based approach that provides feasible and flexible tools for the development of socioeconomic scenarios in the context of impact and risk assessment. Hence, the scenario assumptions are explicit, reproducible and easily adjustable, as required. [ABSTRACT FROM AUTHOR]

Mombasa is the second largest city in Kenya and the largest international seaport in East Africa, with over 650,000 inhabitants. The city has a history of natural disasters associated with extreme climatic events, most recently, the severe rain-induced flooding in October 2006, which affected about 60,000 people and caused damage to important infrastructure. Because the city is expected to continue to experience rapid growth, the future impacts of such events can only increase. Changes in sea level and storm surges are components of climate change that have the potential to further increase the threats of flooding within the city. This geographic information system-based study provides a first quantitative estimate, both now and through the twenty-first century, of the number of people and associated economic assets potentially exposed to coastal flooding due to sea-level rise and storm surges in Mombasa. The current exposure to a 1 : 100 y extreme water level for the Mombasa district is estimated at 190,000 people and US$470 million in assets. About 60% of this exposure is concentrated in the Mombasa Island division of the city, where about 117,000 people (2005 estimate) live below 10 m elevation. By 2080, exposure could grow to over 380,000 people and US$15 billion in assets, assuming the well-known A1B sea-level and socioeconomic scenario. Future exposure is more sensitive to socioeconomic than climate scenarios. However, there is significant scope within the city limits to steer future development to areas that are not threatened by sea-level rise. Hence, forward planning to focus population and asset growth in less vulnerable areas could be an important part of a strategic response to sea-level rise. The methods used here could be applied more widely to other coastal cities in Africa and elsewhere to better understand present and future exposure and worst-case risks due to climate change and rising sea levels. [ABSTRACT FROM AUTHOR]

Global sea levels have risen through the 20th century. These rises will almost certainly accelerate through the 21st century and beyond because of global warming, but their magnitude remains uncertain. Key uncertainties include the possible role of the Greenland and West Antarctic ice sheets and the amplitude of regional changes in sea level. In many areas, nonclimatic components of relative sea-level change (mainly subsidence) can also be locally appreciable. Although the impacts of sea-level rise are potentially large, the application and success of adaptation are large uncertainties that require more assessment and consideration. [ABSTRACT FROM AUTHOR]

A new global coastal database has been developed within the context of the DINAS-COAST project. The database covers the world's coasts, excluding Antarctica, and includes information on more than 80 physical, ecological, and socioeconomic parameters of the coastal zone. The database provides the base data for the Dynamic Interactive Vulnerability Assessment modelling tool that the DINAS-COAST project has produced. In order to comply with the requirements of the modelling tool, it is based on a data model in which all information is referenced to more than 12,000 linear coastal segments of variable length. For efficiency of data storage, six other geographic features (administrative units, countries, rivers, tidal basins or estuaries, world heritage sites, and climate grid cells) are used to reference some data, but all are linked to the linear segment structure. This fundamental linear data structure is unique for a global database and represents an efficient solution to the problem of representing and storing coastal data. The database has been specifically designed to support impact and vulnerability analysis to sea-level rise at a range of scales up to global. Due to the structure, consistency, user-friendliness, and wealth of information in the database, it has potential wider application to analysis and modelling of the world's coasts, especially at regional to global scales. [ABSTRACT FROM AUTHOR]

Large parts of the coasts of Great Britain (including England, Wales, and Scotland) already experience a number of problems, including sediment starvation and erosion, loss/degradation of coastal ecosystems, and significant exposure to coastal flooding. Sea-level rise and other potential climate change will exacerbate all of these issues. Coastal management is embracing sea-level rise and climate change as one of the long-term issues that must be addressed, while recent nonstatutory guidelines are encouraging decision makers and actors alike to promote integrated coastalzone management. Hence, preparations for adaptation to sea-level rise are more advanced than in most European coastal countries. In England and Wales, it is recommended that new coastal defences consider an allowance for accelerated sea-level rise. Strategic shoreline management plans have also been prepared, which include proposals for managed retreat (termed managed realignment) in flood-prone areas with low levels of development, and allowing continued erosion of retreating cliffs. More strategic tools for coastal management are also being developed. Future needs include a better response to the uncertainties of climate change, better guidance on managing the interaction between river flooding and sea-level rise in coastal lowlands, regional analyses of changes in coastal ecosystem stocks, and flood management for London and the Thames River. Scotland requires more basic assessment to define the key issues and needs. [ABSTRACT FROM AUTHOR]

This study comprises a first-order evaluation of the implications of accelerated sea-level rise and some other aspects of climate change for Turkey's coastal areas. Global sea-level rise during the 20th century has been estimated between 10 and 20 cm and similar changes appear to have occurred along Turkish coasts, although available data is poor. Coastal cities cover less than 5% of the total surface area of Turkey, but they have over 30 million inhabitants and are growing rapidly. The Marmara region around Istanbul has the highest population density of all regions. At the same time, more than 60% of the Turkish Gross National Product (GNP) is produced in the coastal strip from Tekirdag to Kocaeli (along the northern shoreline of the Marmara Sea). Analysis suggests that the effects of a 1-m rise in sea level could be significant and adaptation costs substantial. This preliminary assessment suggests a capital loss of about 6% of current GNP, whereas simple protection/adaptation could cost 10% of current GNP. Continued urbanisation and tourist development will further increase exposure to sea-level rise. Currently, the consequences of sealevel rise and climate change are ignored in coastal management, and although strengthening of coastal management mechanisms is required for a number of reasons, sea-level rise and climate change should be considered an important long-term issue. To assist this, detailed case studies are recommended around Turkey's diverse coast, starting with the strategically important Istanbul area. [ABSTRACT FROM AUTHOR]

Over the centuries, London has progressively encroached into the tidal Thames River as it has developed into a ''World City''. This encroachment has exacerbated the flood risk to new and adjacent land, despite continual upgrading of flood defences. The pressure for further encroachment remains, despite the new threat of human-induced climate change—that is, the combined effect of (1) increased peak river flow in the winter, (2) more intense precipitation events, (3) accelerated sea-level rise, and possibly (4) more severe storms and resulting storm surges. Costly upgrade of defences is inevitable to manage the increased flood risk, and this has caused a re-evaluation of the Thames Estuary's flood defence program. For the first time, managed realignment in urban areas is being considered as a flood management tool. This offers a range of potential benefits including (1) increasing storage for floodwater, (2) improving ecological functioning, (3) improving riverside access for people, and (4) reversing the long-term trend of encroachment into the river. Planned managed realignment can widen the scope for future defence upgrade, but has been limited in urbanised areas. Several projects in London (e.g., Tate Modern and Millennium Dome) have shown that realignment can achieve the benefits described above, which supports the government's recent ''Making Space for Water'' policy. This study investigates the feasibility of managed realignment in the Thames Estuary. Fragmentation between flood defence and spatial development policies, lack of political support, and riverside encroachment continue to delay urban realignment projects. Successful application will require long-term planning (over decades) that exploits all opportunities for landward realignment offered by redevelopment. With the uncertainties behind climate change and more development in the ''Thames Gateway'', further research is needed to understand the contribution of urban realignment to any flood management strategy that may be applied to other coastal urban areas. [ABSTRACT FROM AUTHOR]

Managed realignment has aroused increasing interest over the past decade, reflecting a growing awareness of the high cost of holding the line, the widespread trend of coastal squeeze, and the potentially adverse effects of accelerated sea level rise. This comparative study of England's and Germany's approaches to managed realignment sought to explore similarities and differences and hence provide insights on its future use. Although consideration of managed realignment is widely perceived as a positive development, important and sometimes surprising differences were found concerning its application. This reflects various factors ranging from the physical landscape and the state of coastal defences to cultural factors. Existing schemes are mostly concentrated on the coasts of eastern England and the German federal states of Lower Saxony and Mecklenburg-Western Pomerania. Managed realignment in England, and to some extent on Germany's Baltic Sea coast, seems driven by longer term factors, such as the desire to create more sustainable flood defences and to provide new intertidal habitats, although these are often combined with the more immediate need to upgrade defences. On Germany's well-defended North Sea coast, managed realignment has only been undertaken for specific compensation reasons, although broader conservation concerns might become an important future driver for managed realignment in summer polders. Thus managed realignment is now firmly on the agenda in both countries, reflecting a radical departure from the recent past, in which protection was the only possible response. However, application is likely to differ significantly both between and within these countries. [ABSTRACT FROM AUTHOR]

A coherent approach to structuring reference units for coastal vulnerability analysis is often required for large-scale analyses of the coastal system. However, a review of existing spatial reference frameworks within vulnerability analyses demonstrates that our use of coastal space within large-scale models remains relatively poor. This paper examines a series of challenges to spatial modeling that have emerged from the development of a national to global impact tool, DIVA (Dynamic Interactive Vulnerability Assessment). The paper addresses how best to utilize the limited data to develop a reference framework for modeling vulnerability within the global coastal environment. It outlines the approach to spatial modeling that has been developed for use within the DIVA tool: segmenting the coastal zone into a series of relatively homogenous reference units at the scale of DIVA, based on the behavior of the physical, social, and economic systems within the zone. The importance of effective spatially defined models is emphasized within the paper. Encouraging greater spatial recognition and definition of the behavioral environment of the coast is critical to modeling space within the coastal system. By decreasing spatial uncertainties in the creation of reference units for vulnerability analysis, the accuracy of modeling within large-scale coastal environments can be further improved. [ABSTRACT FROM AUTHOR]

Recent improvements in mapping of global population distribution makes it possible to estimate the number and distribution of people near coasts with greater accuracy than previously possible, and hence consider the potential exposure of these populations to coastal hazards. In this paper, we combine the updated Gridded Population of the World (GPW2) population distribution estimate for 1990 and lighted settlement imagery with a global digital elevation model (DEM) and a high resolution vector coastline. This produces bivariate distributions of population, lighted settlements and land area as functions of elevation and coastal proximity. The near-coastal population within 100 km of a shoreline and 100 m of sea level was estimated as 1.2 × 10[sup 9] people with average densities nearly 3 times higher than the global average density. Within the near coastal-zone, the average population density diminishes more rapidly with elevation than with distance, while the opposite is true of lighted settlements. Lighted settlements are concentrated within 5 km of coastlines worldwide, whereas average population densities are higher at elevations below 20 m throughout the 100 km width of the near-coastal zone. Presently most of the near-coastal population live in relatively densely-populated rural areas and small to medium cities, rather than in large cities. A range of improvements are required to define a better baseline and scenarios for policy analysis. Improving the resolution of the underlying population data is a priority. [ABSTRACT FROM AUTHOR]

Resilience is widely seen as a desirable system property in environmental management. This paper explores the concept of resilience to natural hazards, using weather-related hazards in coastal megacities as an example. The paper draws on the wide literature on megacities, coastal hazards, hazard risk reduction strategies, and resilience within environmental management. Some analysts define resilience as a system attribute, whilst others use it as an umbrella concept for a range of system attributes deemed desirable. These umbrella concepts have not been made operational to support planning or management. It is recommended that resilience only be used in a restricted sense to describe specific system attributes concerning (i) the amount of disturbance a system can absorb and still remain within the same state or domain of attraction and (ii) the degree to which the system is capable of self-organisation. The concept of adaptive capacity, which has emerged in the context of climate change, can then be adopted as the umbrella concept, where resilience will be one factor influencing adaptive capacity. This improvement to conceptual clarity would foster much-needed communication between the natural hazards and the climate change communities and, more importantly, offers greater potential in application, especially when attempting to move away from disaster recovery to hazard prediction, disaster prevention, and preparedness. [Copyright &y& Elsevier]

Analysis of the response to climate change and sea-level rise requires a link from climate change science to the resulting impacts and their policy implications. This paper explores the impacts of sea-level rise, particularly increased coastal flooding due to storm surges. In particular, it asks the simple question “how much will projected global sea-level rise exacerbate coastal flood problems, if ignored?” This is an important question to the intergovernmental process considering climate change. Further many countries presently ignore sea-level rise in long-term coastal planning, even though global sea levels are presently slowly rising.Using the model of Nicholls et al. [Global Environmental Change 9 (1999) S69], the analysis considers the flood impacts of sea-level rise on an “IS92a world” based on a consistent set of scenarios of global-mean sea-level rise, subsidence (where appropriate), coastal population change (usually increase), and flood defence standards (derived from GDP/capita). Two of the protection scenarios consider the possible upgrade of flood defences, but no allowance for global-mean sea-level rise is allowed to ensure consistency with the question being investigated. This model has been validated against national- and regional-scale assessments indicating that the relative results are reasonable, and the absolute results are of the right order of magnitude.The model estimates that 10 million people experienced flooding annually in 1990. It also predicts that the incidence of flooding will change without sea-level rise due to changes to the other three factors. Taking the full range of scenarios considered by 2100 the number of people flooded could be from 0.4 to 39 million/year. All the sea-level rise scenarios would cause an increase in flooding during the 21st century if measures to adapt to sea-level rise are not taken. However, there are significant uncertainties and the number of people who are estimated to experience flooding in 2100 is 16–388 million for the mid (55-cm) global-mean sea-level rise scenarios, and up to 510 million people/year for the high (96-cm) scenario. These results suggest that sea-level rise could be a significant problem if it is ignored, and hence it needs to be considered within the policy process considering climate change in terms of mitigation (reducing greenhouse gas emissions) and adaptation (improved coastal management and planning) needs. [Copyright &y& Elsevier]

Discusses technologies that can help reduce the vulnerability of coastal zones to climate change. Coastal zone management; Development of information and awareness for adaptation in coastal zones; Recognition of the benefits of soft protection.

Climate and socio-economic change impacts are likely to cross traditional sectoral and regional boundaries with cascading indirect, and potentially far-reaching, repercussions. This is particularly important for the food-water-land-ecosystems (FWLE) nexus, which is fundamental for the achievement of at least six of the seventeen Sustainable Development Goals (SDGs). A holistic understanding of the FWLE nexus interactions and how and to what extent various exogenous drivers of change affect them is therefore central to cross-sectoral adaptation planning. Here, we present such an integrated assessment for Europe applying a regional Integrated Assessment Platform (IAP). The study explores a wide range of future climate and socio-economic scenarios using more than 900 model simulations. The results show that food production is likely to be the main driver of Europe's future landscape change dynamics (with or without climate change). Agriculture and land use allocation is often driven by complex cross-sectoral interactions with cascading effects on other sectors such as forestry, biodiversity, and water under the various scenarios. The modelling also highlighted that while sustaining current levels of food production at the European level could be achievable under most climate and socio-economic scenarios, there are significant regional differences with winners and losers. The analysis raises the question of whether current production and consumption policies are sustainable in the long-term. Such systematic integrated model-based analysis plays a crucial role in informing development of cross-sectoral policies that maximise synergies and minimise trade-offs across nexus sectors, regions, and scenarios. This is essential to achieve the SDGs. Unlabelled Image • We present a systematic integrated model-based analysis of the complex FWLE nexus interactions in Europe. • Over 900 stylised scenarios of key climatic and non-climatic drivers are explored sampling a large uncertainty space. • Findings highlight key nexus synergies and trade-offs and the need for cross-sectoral adaptation planning. • The study has important implications for achieving the SDGs. [ABSTRACT FROM AUTHOR]

This paper introduces the collection of papers on impacts of sea-level rise on a number of European countries, and presents some overarching conclusions. [ABSTRACT FROM AUTHOR]

Coastal erosion and flooding are projected to increase during the 21st century due to sea-level rise (SLR). To prevent adverse impacts of unmanaged coastal development, national organizations can apply a land protection policy, which consists of acquiring coastal land to avoid further development. Yet, these reserved areas remain exposed to flooding and erosion enhanced by SLR. Here, we quantify the exposure of the coastal land heritage portfolio of the French Conservatoire du littoral (Cdl). We find that 30% (~40%) of the Cdl lands owned (projected to be owned) are located below the contemporary highest tide level. Nearly 10% additional surface exposure is projected by 2100 under the high greenhouse gas emissions scenario (SSP5-8.5) and 2150 for the moderate scenario (SSP2-4.5). The increase in exposure is largest along the West Mediterranean coast of France. We also find that Cdl land exposure increases more rapidly for SLR in the range of 0–1 m than for SLR in the range 2–4 m. Thus, near-future uncertainty on SLR has the largest impact on Cdl land exposure evolution and related land acquisition planning. Concerning erosion, we find that nearly 1% of Cdl land could be lost in 2100 if observed historical trends continue. Adding the SLR effect could lead to more than 3% land loss. Our study confirms previous findings that Cdl needs to consider land losses due to SLR in its land acquisition strategy and start acquiring land farther from the coast. [ABSTRACT FROM AUTHOR]

Five cases of ports in Japan and Indonesia that have subsided by a metre or more were analysed. The findings suggest that there are no unsurmountable technological, cost-benefit, financial and social limits to the progressive raising of these ports, at least for the magnitude of climate-induced sea-level rise expected during the 21st century. In Indonesia observed adaptation is a sequential process: only part of the port is raised at one time, allowing port operations to continue elsewhere and spreading costs in time. Jumps in unit costs are apparent as the elevation height increases. In addition, the possibility of sea-level rise triggering innovative changes in port design to lower costs (e.g., a move to floating ports) is being considered. For traditional ports to upgrade by up to 1 metre, unit costs are found to be somewhere between 50–360 USD/m3 rise (not including the cost of piling). Nevertheless, such adaptation costs would represent a significant burden and adaptation is often reactive rather than proactive, leading to significant damage costs, as in the case of Hurricane Katrina's impact on Gulf Coast Ports. [ABSTRACT FROM AUTHOR]

Deltas are precarious environments experiencing significant biophysical, and socio-economic changes with the ebb and flow of seasons (including with floods and drought), with infrastructural developments (such as dikes and polders), with the movement of people, and as a result of climate and environmental variability and change. Decisions are being taken about the future of deltas and about the provision of adaptation investment to enable people and the environment to respond to the changing climate and related changes. The paper presents a framework to identify options for, and trade-offs between, long term adaptation strategies in deltas. Using a three step process, we: (1) identify current policy-led adaptations actions in deltas by conducting literature searches on current observable adaptations, potential transformational adaptations and government policy; (2) develop narratives of future adaptation policy directions that take into account investment cost of adaptation and the extent to which significant policy change/political effort is required; and (3) explore trade-offs that occur within each policy direction using a subjective weighting process developed during a collaborative expert workshop. We conclude that the process of developing policy directions for adaptation can assist policy makers in scoping the spectrum of options that exist, while enabling them to consider their own willingness to make significant policy changes within the delta and to initiate transformative change. [ABSTRACT FROM AUTHOR]

Owing to globalization, the potential impacts of climate change/sea-level rise in one country/region are likely to affect and be felt elsewhere. Such indirect impacts could be significant but have received a limited analysis. This deficiency is addressed here using the indirect impacts on coastal infrastructure for the UK as an example. National opportunities and threats are identified. Potential indirect national threats include disruption of supply chains, security threats due to forced migration, a decline in national prestige, and impacts on the finance and insurance industries. Potential opportunities include export of world-leading coastal hazard and management expertise, and benefits to national prestige conferred by a strong response to climate change. Such opportunities and threats depend on several distinct dimensions of change, especially the magnitude of climate and socio-economic change, and the success/failure of appropriate responses. Promoting adaptation and climate mitigation is important to exploit the opportunities and address the threats. Adaptation should deal with more than the effects of climate change and link to the wider development agenda. These lessons are transferable to other developed countries and, indeed, many of the actions will be strengthened by collective action. Policy relevance National-level measures to address these indirect impacts will make a positive contribution to the global effort in addressing climate change (e.g. supporting emissions reductions). Countries should include the indirect effects of climate change in national assessments so that the national context and useful responses can be identified. Cooperation between nations is also important; countries must act together to more effectively address the direct and indirect effects of climate change (e.g. promoting a widespread adaptation response). International initiatives (such as the Belmont Forum initiative on Coastal Vulnerability) should be promoted and global environmental change research shared (e.g. within multilateral institutions). [ABSTRACT FROM PUBLISHER]

The Dynamic Interactive Vulnerability Assessment Wetland Change Model (DIVA_WCM) comprises a dataset of contemporary global coastal wetland stocks (estimated at 756 × 10 3 km 2 (in 2011)), mapped to a one-dimensional global database, and a model of the macro-scale controls on wetland response to sea-level rise. Three key drivers of wetland response to sea-level rise are considered: 1) rate of sea-level rise relative to tidal range; 2) lateral accommodation space; and 3) sediment supply. The model is tuned by expert knowledge, parameterised with quantitative data where possible, and validated against mapping associated with two large-scale mangrove and saltmarsh vulnerability studies. It is applied across 12,148 coastal segments (mean length 85 km) to the year 2100. The model provides better-informed macro-scale projections of likely patterns of future coastal wetland losses across a range of sea-level rise scenarios and varying assumptions about the construction of coastal dikes to prevent sea flooding (as dikes limit lateral accommodation space and cause coastal squeeze). With 50 cm of sea-level rise by 2100, the model predicts a loss of 46–59% of global coastal wetland stocks. A global coastal wetland loss of 78% is estimated under high sea-level rise (110 cm by 2100) accompanied by maximum dike construction. The primary driver for high vulnerability of coastal wetlands to sea-level rise is coastal squeeze, a consequence of long-term coastal protection strategies. Under low sea-level rise (29 cm by 2100) losses do not exceed ca. 50% of the total stock, even for the same adverse dike construction assumptions. The model results confirm that the widespread paradigm that wetlands subject to a micro-tidal regime are likely to be more vulnerable to loss than macro-tidal environments. Countering these potential losses will require both climate mitigation (a global response) to minimise sea-level rise and maximisation of accommodation space and sediment supply (a regional response) on low-lying coasts. [ABSTRACT FROM AUTHOR]

A long-term dataset of reported flooding based on reports from the UK Met Office and the UK Centre for Ecology and Hydrology is described. This is possibly a unique dataset as the authors are unaware of any other 100+ year records of flood events and their consequences on a national scale. Flood events are classified by severity based upon qualitative descriptions. There is an increase in the number of reported flood events over time associated with an increased exposure to flooding as floodplain areas were developed. The data was de-trended for exposure, using population and dwelling house data. The adjusted record shows no trend in reported flooding over time, but there is significant decade to decade variability. This study opens a new approach to considering flood occurrence over a long time scale using reported information (and thus likely effects on society) rather than just considering trends in extreme hydrological conditions.Editor Z.W. Kundzewicz Associate editor Not assigned [ABSTRACT FROM AUTHOR]

Coastal compound flooding events occur when extreme events of rainfall, river discharge and sea level coincide and collectively increase water surface elevation, exacerbating flooding. The meteorological conditions that generate these events are usually low‐pressure systems that generate high winds and intense rainfall. In this study, we identify the types of synoptic atmospheric conditions that are typically associated with coastal compound events using a weather‐type approach, for the North Atlantic coastlines (encompassing northwest Europe and the east coast of the United States). Compound events are identified along the estuaries of the study region from 1980 to 2014 based on an impact function defined by water surface elevation that resulted from the combination of river discharge and sea level. We find that compound events are more frequent along European as opposed to U.S. coastlines. In both cases, they are associated with a few dominant weather patterns. European hotspots of compound events are concentrated in the west coast of United Kingdom, the northwest coast of the Iberian Peninsula and around the Strait of Gibraltar. These areas share the same weather patterns which represent the main pathways of storms that cross the North Atlantic Ocean. In the case of U.S. locations, the areas with highest number of compound events are located mainly in the Gulf of Mexico and along Mexico and along the mid‐eastern U.S. coastlines. In these areas, compound events are produced by transitional weather patterns, which describe storms that travel northward parallel to the coastline. Splitting the occurrence of compound events in the corresponding weather types discriminates the interannual variability based on the relationship with dominant climate indices in the North Atlantic Ocean. [ABSTRACT FROM AUTHOR]

Soft cliff retreat has often triggered a hard adaptation response by the building of seawalls and groynes. On adjacent undefended coasts erosion continues, resulting in set-backs. This paper examines the impact of coastal defences on the adjacent coast from historic records and present practices, and explores possible future response. Continued set-back often leads to outflanking of defences, making them ineffective at their extremities, particularly at the down-drift end where it is most severe. Solutions to outflanking usually involve extending defences, initiating a cycle of set-back, outflanking and further extensions. Multiple defence extensions and continued retreat of the unprotected adjacent coast results in artificial headland formation. Over several decades, headlands experience foreshore steepening and reduced sediment availability, making them more difficult and expensive to defend. Shoreline management plan policies of managed retreat advocate selective defence abandonment, which may change the nature of artificial headland formation. Defence abandonment and new engineering works must be planned, anticipating the processes described in this paper. This will reduce unexpected changes and reduce maintenance and emergency work costs. [ABSTRACT FROM AUTHOR]

The cost of upgrading and raising coastal defences is an important consideration in societal response to sea-level rise. Currently available unit cost estimates have a limited empirical basis. This article presents new information on the unit costs of adapting coastal defences for three specific case studies in low-lying delta regions: The Netherlands, New Orleans, and Vietnam. Typical measures include dikes, flood walls, storm surge barriers, and nourishment. These unit cost estimates are significantly higher than earlier estimates that are still the main source of costs for global vulnerability assessments. Factors affecting these unit costs include local economic factors (material and labour costs), design choices related to the alignment of the system, and the types of measures for implementation of the system in an urban or rural environment. On the basis of an example for a Dutch sea dike, it is shown that the material quantities and associated costs are expected to rise linearly, in the case of depth-limited wave breaking, for the range of sea-level rise rates that are expected in the coming century. However, other factors, such as increasing costs for implementation of wider coastal defences in an urban environment and future changes in material and labour costs, could contribute to a nonlinear increase of the costs. Further collection and analysis of project information for coastal defence projects in other regions is recommended to strengthen the empirical basis of the cost estimates that are used for regional and global assessments. [ABSTRACT FROM AUTHOR]

The threat of sea-level rise and climate change means that coastal managers are being increasingly asked to make long-term assessments of potential coastal impacts and responses. In the UK, shoreline management planning (for flood and erosion hazards) and spatial planning now takes a 100 year perspective. An integrated framework across a wide range of physical and social issues is required for the assessment of coastal impacts and consequently for making sound management decisions. This paper provides an overview of the development of the 'Tyndall Coastal Simulator' including the underlying philosophy that is being followed. The Simulator is based on a series of linked climate models (CM) within a nested framework which recognises three spatial scales: (i) the global (GCM) scale; (ii) the regional scale and (iii) the Simulator Domain (a physiographic unit, such as a coastal sub-cell). Within the nesting, the larger scale provides the boundary conditions for the smaller scale. The models feed into each other and describe a range of relevant processes: sea level, tides, surges, waves, sediment transport and coastal morphology. Different climate scenarios, as well as the range of uncertainty, are being explored. Communication of results is a major issue and the Simulator includes a dedicated GIS-based user interface that allows a wide range of queries of model outputs. The paper demonstrates the possibility of developing an integrated framework that is multi-scale and capable of linking various models in order to simulate complex coastal processes and consequently allowing long-term assessments that are useful for setting future management plans. [ABSTRACT FROM AUTHOR]

Analyses of land area and population distribution in the Low Elevation Coastal Zone (LECZ) and their potential susceptibility to future sea level rise have been used to derive first-order assessments of areas and populations at risk. Variations in results are shown to be highly dependent on the input datasets. In this paper we explore differences in land and population distribution estimates in the LECZ resulting from the use of three digital elevation models and two population datasets at global, continent, and country levels. Results at the global scale show differences of up to 150% in area estimates, depending on the elevation model used. The differences are most extreme below 1 m elevation and diminish at higher elevation increments. On the continent level, the use of different elevation models produced area estimate differences ranging from more than 1200% at an elevation of 1 m to 160% in the LECZ. Country-level differences are even higher. Similarly, substantial differences in population distribution can arise with the use of different population datasets. Population counts below 1 m elevation range from 1% to 2.3% of the total global population. In the LECZ, estimates vary from 9.2% to 10.9% of the total global population. Differences at continental and country levels are also significant depending on the elevation model and the population dataset used. These large differences indicate that results of such analyses should be regarded with caution and within the context of the methods and materials used. [ABSTRACT FROM AUTHOR]

Adaptation is defined as the planned or unplanned, reactive or anticipatory, successful or unsuccessful response of a system to a change in its environment. This paper examines the current status of adaptation to sea-level rise and climate change in the context of European coasts. Adaptation can greatly reduce the impact of sea-level rise (and other coastal changes), although it requires adjustment of coastal management policies to changing circumstances. Consequently, adaptation is a social, political, and economic process, rather than just a technical exercise, as it is often conceived. The Synthesis and Upscaling of sea-level Rise Vulnerability Assessment Studies project has shown that adaptation to sea-level rise is widely divergent among European countries. Crudely, four groups of countries were identified: 1. Those that do not worry about accelerated sea-level rise and should not as their coasts are not susceptible 2. Those that do not worry as they have more urgent problems 3. Those that do not worry but probably should 4. Those that do worry and have started to adapt At the European Union level, while coastal management is a focus, this effort is mainly targeted at today's problems. Hence, this paper suggests the need for a concerted effort to address adaptation in coastal zones across Europe. Sharing of experience among countries would facilitate this process. [ABSTRACT FROM AUTHOR]

Sandy coastlines adjacent to tidal inlets are highly dynamic and widespread landforms, where large changes are expected due to climatic and anthropogenic influences. To adequately assess these important changes, both oceanic (e.g., sea-level rise) and terrestrial (e.g., fluvial sediment supply) processes that govern the local sediment budget must be considered. Here, we present novel projections of shoreline change adjacent to 41 tidal inlets around the world, using a probabilistic, reduced complexity, system-based model that considers catchment-estuary-coastal systems in a holistic way. Under the RCP 8.5 scenario, retreat dominates (90% of cases) over the twenty-first century, with projections exceeding 100 m of retreat in two-thirds of cases. However, the remaining systems are projected to accrete under the same scenario, reflecting fluvial influence. This diverse range of response compared to earlier methods implies that erosion hazards at inlet-interrupted coasts have been inadequately characterised to date. The methods used here need to be applied widely to support evidence-based coastal adaptation. [ABSTRACT FROM AUTHOR]

Climate change is and will continue altering the world's coasts, which are the most densely populated and economically active areas on earth and home for highly valuable ecosystems. While there is considerable relevant research, in the authors' experience this problem remains challenging for coastal engineering. This paper reviews important challenges in this respect and identifies three key actions to address them: (a) refocusing traditional practice towards more climate-aware approaches; (b) developing more comprehensive risk frameworks that include the multi-dimensionality and non-stationarity of their components and consideration of uncertainty; and (c) building bridges between risk assessment and adaptation theory and practice. We conclude that the way forward includes numerous activities including increased observations; the attribution of coastal impacts to their drivers; enhanced climate projections and their integration into impact models; more impact assessments at the local scale; dynamic projections of spatially-distributed exposure and vulnerability; and the exploration of inherently adaptive options. Given the complexity of the possible solutions, more practical guidance is required. • Reviews the challenges of climate change risks and adaptation in coastal areas. • Suggests refocusing traditional practice towards more climate-aware approaches. • Proposes multi-dimensional and non-stationary risk frameworks. • Emphasises the need to consider uncertainty. • Explores bridges between risk assessment and adaptation theory and practice. [ABSTRACT FROM AUTHOR]

Resource-based livelihoods are uncertain and potentially unstable due to variability over time, including seasonal variation: this instability threatens marginalised populations who may fall into poverty. However, empirical understanding of trajectories of household well-being and poverty is limited. Here, we present a new household-level model of poverty dynamics based on agents and coping strategies–the Household Economy And Poverty trajectory (HEAP) model. HEAP is based on established economic and social insights into poverty dynamics, with a demonstration of the model calibrated with a qualitative and quantitative household survey in coastal Bangladesh. Economic activity in Bangladesh is highly dependent on natural resources; poverty is widespread; and there is high variability in ecosystem services at multiple temporal scales. The results show that long-term decreases in poverty are predicated more on the stability of, and returns from, livelihoods rather than their diversification. Access to natural resources and ecosystem service benefits are positively correlated with stable income and multidimensional well-being. Households that remain in poverty are those who experience high seasonality of income and are involved in small scale enterprises. Hence, seasonal variability in income places significant limits on natural resources providing routes out of poverty. Further, projected economic trends to 2030 lead to an increase in well-being and a reduction in poverty for most simulated household types. [ABSTRACT FROM AUTHOR]

Global models of tide, storm surge, and wave setup are used to obtain projections of episodic coastal flooding over the coming century. The models are extensively validated against tide gauge data and the impact of uncertainties and assumptions on projections estimated in detail. Global "hotspots" where there is projected to be a significant change in episodic flooding by the end of the century are identified and found to be mostly concentrated in north western Europe and Asia. Results show that for the case of, no coastal protection or adaptation, and a mean RCP8.5 scenario, there will be an increase of 48% of the world's land area, 52% of the global population and 46% of global assets at risk of flooding by 2100. A total of 68% of the global coastal area flooded will be caused by tide and storm events with 32% due to projected regional sea level rise. [ABSTRACT FROM AUTHOR]