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Jan L. Merkens
Coastal Risks and Sea-Level Rise Research Group, Department of Geography, Christian-Albrechts University Kiel, Ludewig-Meyn-Str. 14, 24098 Kiel, Germany

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Preprint content
Published: 04 March 2021
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Climate-induced sea-level rise and vertical land movements, including natural and human-induced subsidence in sedimentary coastal lowlands, combine to change relative sea levels around the world's coast. Global-average coastal relative sea-level rise was 2.5 mm/yr over the last two decades. However, as coastal inhabitants are preferentially located in subsiding locations, they experience an average relative sea-level rise up to four times faster at 7.8 to 9.9 mm/yr. This first global quantification of relative sea-level rise shows that the resulting impacts, and adaptation needs are much higher than reported global sea-level rise measurements would suggest. Hence, coastal subsidence is an important global issue that needs more assessment and action. In particular, human-induced subsidence in and surrounding coastal cities can be rapidly reduced with appropriate policy measures for groundwater utilization and drainage. This offers substantial and rapid benefits in terms of reducing growth of coastal flood exposure due to relative sea-level rise.

ACS Style

Daniel Lincke; Robert J. Nicholls; Jochen Hinkel; Sally Brown; Athanasios T. Vafeidis; Benoit Meyssignac; Susan E. Hanson; Jan Merkens; Jiayi Fang. A global analysis of subsidence, relative sea-level change and coastal flood exposure. 2021, 1 .

AMA Style

Daniel Lincke, Robert J. Nicholls, Jochen Hinkel, Sally Brown, Athanasios T. Vafeidis, Benoit Meyssignac, Susan E. Hanson, Jan Merkens, Jiayi Fang. A global analysis of subsidence, relative sea-level change and coastal flood exposure. . 2021; ():1.

Chicago/Turabian Style

Daniel Lincke; Robert J. Nicholls; Jochen Hinkel; Sally Brown; Athanasios T. Vafeidis; Benoit Meyssignac; Susan E. Hanson; Jan Merkens; Jiayi Fang. 2021. "A global analysis of subsidence, relative sea-level change and coastal flood exposure." , no. : 1.

Research article
Published: 03 May 2019 in Natural Hazards and Earth System Sciences
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This study explores the uncertainty introduced in global assessments of coastal flood exposure and risk when not accounting for water-level attenuation due to land-surface characteristics. We implement a range of plausible water-level attenuation values for characteristic land-cover classes in the flood module of the Dynamic and Integrated Vulnerability Assessment (DIVA) modelling framework and assess the sensitivity of flood exposure and flood risk indicators to differences in attenuation rates. Results show a reduction of up to 44 % in area exposure and even larger reductions in population exposure and expected flood damages when considering water-level attenuation. The reductions vary by country, reflecting the differences in the physical characteristics of the floodplain as well as in the spatial distribution of people and assets in coastal regions. We find that uncertainties related to not accounting for water attenuation in global assessments of flood risk are of similar magnitude to the uncertainties related to the amount of sea-level rise expected over the 21st century. Despite using simplified assumptions to account for the process of water-level attenuation, which depends on numerous factors and their complex interactions, our results strongly suggest that an improved understanding and representation of the temporal and spatial variation of water levels across floodplains is essential for future impact modelling.

ACS Style

Athanasios T. Vafeidis; Mark Schuerch; Claudia Wolff; Tom Spencer; Jan L. Merkens; Jochen Hinkel; Daniel Lincke; Sally Brown; Robert J. Nicholls. Water-level attenuation in global-scale assessments of exposure to coastal flooding: a sensitivity analysis. Natural Hazards and Earth System Sciences 2019, 19, 973 -984.

AMA Style

Athanasios T. Vafeidis, Mark Schuerch, Claudia Wolff, Tom Spencer, Jan L. Merkens, Jochen Hinkel, Daniel Lincke, Sally Brown, Robert J. Nicholls. Water-level attenuation in global-scale assessments of exposure to coastal flooding: a sensitivity analysis. Natural Hazards and Earth System Sciences. 2019; 19 (5):973-984.

Chicago/Turabian Style

Athanasios T. Vafeidis; Mark Schuerch; Claudia Wolff; Tom Spencer; Jan L. Merkens; Jochen Hinkel; Daniel Lincke; Sally Brown; Robert J. Nicholls. 2019. "Water-level attenuation in global-scale assessments of exposure to coastal flooding: a sensitivity analysis." Natural Hazards and Earth System Sciences 19, no. 5: 973-984.

Preprint content
Published: 21 December 2018
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This study explores the uncertainty introduced in global assessments of coastal flood exposure and risk when not accounting for water level attenuation due to land-surface characteristics. We implement a range of plausible water-level attenuation values for characteristic land-cover classes in the flood module of the Dynamic and Integrated Vulnerability Assessment (DIVA) modelling framework and assess the sensitivity of flood exposure and flood risk indicators to differences in attenuation rates. Results show a reduction of up to 47 % in area exposure and even larger reductions in population exposure and expected flood damages when considering water level attenuation. The reductions vary by country, reflecting the differences in the physical characteristics of the floodplain as well as in the spatial distribution of people and assets in coastal regions. We find that uncertainties related to not accounting for water attenuation in global assessments of flood risk are of similar magnitude to the uncertainties related to the amount of SLR expected over the 21st century. Despite using simplified assumptions to account for the process of water level attenuation, which depends on numerous factors and their complex interactions, our results strongly suggest that an improved understanding and representation of the temporal and spatial variation of water levels across floodplains is essential for future impact modelling.

ACS Style

Athanasios T. Vafeidis; Mark Schuerch; Claudia Wolff; Tom Spencer; Jan L. Merkens; Jochen Hinkel; Daniel Lincke; Sally Brown; Robert J. Nicholls. Water-level attenuation in broad-scale assessments of exposure to coastal flooding: a sensitivity analysis. 2018, 2018, 1 -19.

AMA Style

Athanasios T. Vafeidis, Mark Schuerch, Claudia Wolff, Tom Spencer, Jan L. Merkens, Jochen Hinkel, Daniel Lincke, Sally Brown, Robert J. Nicholls. Water-level attenuation in broad-scale assessments of exposure to coastal flooding: a sensitivity analysis. . 2018; 2018 ():1-19.

Chicago/Turabian Style

Athanasios T. Vafeidis; Mark Schuerch; Claudia Wolff; Tom Spencer; Jan L. Merkens; Jochen Hinkel; Daniel Lincke; Sally Brown; Robert J. Nicholls. 2018. "Water-level attenuation in broad-scale assessments of exposure to coastal flooding: a sensitivity analysis." 2018, no. : 1-19.

Article
Published: 16 November 2018 in Climatic Change
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Large-area coastal exposure and impact analysis has focussed on using sea-level rise (SLR) scenarios and has placed little emphasis on socioeconomic scenarios, while neglecting spatial variations of population dynamics. We use the Dynamic Interactive Vulnerability Assessment (DIVA) Framework to assess the population exposed to 1 in 100-year coastal flood events under different population scenarios, that are consistent with the shared socioeconomic pathways (SSPs); and different SLR scenarios, derived from the representative concentration pathways (RCPs); and analyse the effect of accounting for regionalised population dynamics on population exposure until 2100. In a reference approach, we use homogeneous population growth on national level. In the regionalisation approaches, we test existing spatially explicit projections that also account for urbanisation, coastal migration and urban sprawl. Our results show that projected global exposure in 2100 ranges from 100 million to 260 million, depending on the combination of SLR and population scenarios and method used for regionalising the population projections. The assessed exposure based on the regionalised approaches is higher than that derived from the reference approach by up to 60 million people (39%). Accounting for urbanisation and coastal migration leads to an increase in exposure, whereas considering urban sprawl leads to lower exposure. Differences between the reference and the regionalised approaches increase with higher SLR. The regionalised approaches show highest exposure under SSP5 over most of the twenty-first century, although total population in SSP5 is the second lowest overall. All methods project the largest absolute growth in exposure for Asia and relative growth for Africa.

ACS Style

Jan-Ludolf Merkens; Daniel Lincke; Jochen Hinkel; Sally Brown; Athanasios Thomas Vafeidis. Regionalisation of population growth projections in coastal exposure analysis. Climatic Change 2018, 151, 413 -426.

AMA Style

Jan-Ludolf Merkens, Daniel Lincke, Jochen Hinkel, Sally Brown, Athanasios Thomas Vafeidis. Regionalisation of population growth projections in coastal exposure analysis. Climatic Change. 2018; 151 (3-4):413-426.

Chicago/Turabian Style

Jan-Ludolf Merkens; Daniel Lincke; Jochen Hinkel; Sally Brown; Athanasios Thomas Vafeidis. 2018. "Regionalisation of population growth projections in coastal exposure analysis." Climatic Change 151, no. 3-4: 413-426.

Journal article
Published: 05 September 2018 in Sustainability
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Broad-scale impact and vulnerability assessments are essential for informing decisions on long-term adaptation planning at the national, regional, or global level. These assessments rely on population data for quantifying exposure to different types of hazards. Existing population datasets covering the entire globe at resolutions of 2.5 degrees to 30 arc-seconds are based on information available at administrative-unit level and implicitly assume uniform population densities within these units. This assumption can lead to errors in impact assessments and particularly in coastal areas that are densely populated. This study proposes and compares simple approaches to regionalize population within administrative units in the German Baltic Sea region using solely information on urban extent from the Global Urban Footprint (GUF). Our results show that approaches using GUF can reduce the error in predicting population totals of municipalities by factor 2 to 3. When assessing exposed population, we find that the assumption of uniform population densities leads to an overestimation of 120% to 140%. Using GUF to regionalise population within administrative units reduce these errors by up to 50%. Our results suggest that the proposed simple modeling approaches can result in significantly improved distribution of population within administrative units and substantially improve the results of exposure analyses.

ACS Style

Jan-Ludolf Merkens; Athanasios Vafeidis. Using Information on Settlement Patterns to Improve the Spatial Distribution of Population in Coastal Impact Assessments. Sustainability 2018, 10, 3170 .

AMA Style

Jan-Ludolf Merkens, Athanasios Vafeidis. Using Information on Settlement Patterns to Improve the Spatial Distribution of Population in Coastal Impact Assessments. Sustainability. 2018; 10 (9):3170.

Chicago/Turabian Style

Jan-Ludolf Merkens; Athanasios Vafeidis. 2018. "Using Information on Settlement Patterns to Improve the Spatial Distribution of Population in Coastal Impact Assessments." Sustainability 10, no. 9: 3170.

Preprint content
Published: 07 September 2017 in Natural Hazards and Earth System Sciences Discussions
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This study explores the uncertainty introduced in global assessments of coastal flood exposure and risk by not accounting for water level attenuation due to land–surface characteristics. We implement a range of plausible water level attenuation values in the flood module of the Dynamic Interactive Vulnerability Assessment (DIVA) modelling framework and assess the sensitivity of flood exposure and flood risk indicators to differences in attenuation rates. Results show a reduction of up to 47 % in area exposure and even larger reductions in population exposure and expected flood damages. Despite the use of a spatially constant rate for water attenuation the reductions vary by country, reflecting the differences in the physical characteristics of the floodplain as well as in the spatial distribution of people and assets in coastal regions. We find that uncertainties related to the omission of this factor in global assessments of flood risk are of similar magnitude to the uncertainties related to the amount of SLR expected over the 21st century. Despite using simplified assumptions, as the process of water level attenuation depends on numerous factors and their complex interactions, our results strongly suggest that future impact modelling needs to focus on an improved representation of the temporal and spatial variation of water levels across floodplains by incorporating the effects of relevant processes.

ACS Style

Athanasios T. Vafeidis; Mark Schuerch; Claudia Wolff; Tom Spencer; Jan L. Merkens; Jochen Hinkel; Daniel Lincke; Sally Brown; Robert J. Nicholls. Water-level attenuation in broad-scale assessments of exposure to coastal flooding: a sensitivity analysis. Natural Hazards and Earth System Sciences Discussions 2017, 2017, 1 -18.

AMA Style

Athanasios T. Vafeidis, Mark Schuerch, Claudia Wolff, Tom Spencer, Jan L. Merkens, Jochen Hinkel, Daniel Lincke, Sally Brown, Robert J. Nicholls. Water-level attenuation in broad-scale assessments of exposure to coastal flooding: a sensitivity analysis. Natural Hazards and Earth System Sciences Discussions. 2017; 2017 ():1-18.

Chicago/Turabian Style

Athanasios T. Vafeidis; Mark Schuerch; Claudia Wolff; Tom Spencer; Jan L. Merkens; Jochen Hinkel; Daniel Lincke; Sally Brown; Robert J. Nicholls. 2017. "Water-level attenuation in broad-scale assessments of exposure to coastal flooding: a sensitivity analysis." Natural Hazards and Earth System Sciences Discussions 2017, no. : 1-18.

Original article
Published: 21 July 2017 in Regional Environmental Change
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Existing narratives and population projections of the global-scale Shared Socioeconomic Pathways (SSPs) do not capture regional differences in socioeconomic development in the Mediterranean region. In this study, we regionalize the global SSPs to account for differences in coastal population development between northern, eastern, and southern countries of the region. First, we develop coastal SSP narratives that include region-specific elements and differentiate between geographical regions. Based on these narratives, we derive coastal population growth rates that vary for each SSP as well as between coastal, inland, rural, and urban areas. We apply these growth assumptions to observed population growth patterns in a spatially explicit manner. The Mediterranean coastal SSPs thereby reflect socioeconomic development patterns across countries as well as coastal versus inland development within countries. Our results show that coastal population in the Mediterranean increases across SSPs 2–5 by 3% to 130% until 2100 except for SSP1, where population declines by almost 20% compared to 2010. We observe considerable differences between geographical regions and countries. In the Mediterranean north, coastal population declines in SSP1, SSP3, and SSP4 and experiences the highest increase of more than 100% in SSP5. In southern and eastern Mediterranean countries, the highest increase in coastal population takes place in SSP3 and amounts to almost 180% by 2100. The regionalized SSP narratives and population projections are intended for assessing future exposure, vulnerability, and impacts of population to coastal hazards and sea-level rise but can also be of use for a wider range of Impact, Adaptation, and Vulnerability (IAV) studies.

ACS Style

Lena Reimann; Jan-Ludolf Merkens; Athanasios T. Vafeidis. Regionalized Shared Socioeconomic Pathways: narratives and spatial population projections for the Mediterranean coastal zone. Regional Environmental Change 2017, 18, 235 -245.

AMA Style

Lena Reimann, Jan-Ludolf Merkens, Athanasios T. Vafeidis. Regionalized Shared Socioeconomic Pathways: narratives and spatial population projections for the Mediterranean coastal zone. Regional Environmental Change. 2017; 18 (1):235-245.

Chicago/Turabian Style

Lena Reimann; Jan-Ludolf Merkens; Athanasios T. Vafeidis. 2017. "Regionalized Shared Socioeconomic Pathways: narratives and spatial population projections for the Mediterranean coastal zone." Regional Environmental Change 18, no. 1: 235-245.

Journal article
Published: 01 October 2016 in Global and Planetary Change
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Existing quantifications of the Shared Socioeconomic Pathways (SSP) used for climate impact assessment do not account for subnational population dynamics such as coastward-migration that can be critical for coastal impact assessment. This paper extends the SSPs by developing spatial projections of global coastal population distribution for the five basic SSPs. Based on a series of coastal migration drivers we develop coastal narratives for each SSP. These narratives account for differences in coastal and inland population developments in urban and rural areas. To spatially distribute population, we use the International Institute for Applied Systems Analysis (IIASA) national population and urbanisation projections and employ country-specific growth rates, which differ for coastal and inland as well as for urban and rural regions, to project coastal population for each SSP. These rates are derived from spatial analysis of historical population data and adjusted for each SSP based on the coastal narratives. Our results show that, compared to the year 2000 (638 million), the population living in the Low Elevated Coastal Zone (LECZ) increases by 58% to 71% until 2050 and exceeds one billion in all SSPs. By the end of the 21st century, global coastal population declines to 830–907 million in all SSPs except for SSP3, where coastal population growth continues and reaches 1.184 billion. Overall, the population living in the LECZ is higher by 85 to 239 million compared to the original IIASA projections. Asia expects the highest absolute growth (238–303 million), Africa the highest relative growth (153% to 218%). Our results highlight regions where high coastal population growth is expected and will therefore face an increased exposure to coastal flooding

ACS Style

Jan-Ludolf Merkens; Lena Reimann; Jochen Hinkel; Athanasios Vafeidis. Gridded population projections for the coastal zone under the Shared Socioeconomic Pathways. Global and Planetary Change 2016, 145, 57 -66.

AMA Style

Jan-Ludolf Merkens, Lena Reimann, Jochen Hinkel, Athanasios Vafeidis. Gridded population projections for the coastal zone under the Shared Socioeconomic Pathways. Global and Planetary Change. 2016; 145 ():57-66.

Chicago/Turabian Style

Jan-Ludolf Merkens; Lena Reimann; Jochen Hinkel; Athanasios Vafeidis. 2016. "Gridded population projections for the coastal zone under the Shared Socioeconomic Pathways." Global and Planetary Change 145, no. : 57-66.