Global distribution of nearshore slopes with implications for coastal retreat

Athanasiou, Panagiotis; Dongeren, Ap van; Giardino, Alessio; Vousdoukas, Michalis; Gaytan-Aguilar, Sandra; Ranasinghe, Roshanka

doi:10.5194/essd-11-1515-2019

Cited by 76 publications

(60 citation statements)

References 37 publications

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“…Finally, the third scenario (High-end B) follows a worst-model approach; i.e., we selected the outcome of the model showing the highest sea-level projection for every component based on the most recent literature. The shoreline changes induced by the sea-level rise were estimated from the Bruun rule applied to the EUROSION database sandy beach segments, and for which, we considered either the new nearshore slope dataset provided by Athanasiou et al (2019) [52] or a uniform slope of 1%, a common approach used for continental-to-global scale shoreline retreat assessments [61,71].…”

Section: Discussionmentioning

confidence: 99%

Likely and High-End Impacts of Regional Sea-Level Rise on the Shoreline Change of European Sandy Coasts Under a High Greenhouse Gas Emissions Scenario

Thiéblemont¹,

Cozannet²,

Toimil

et al. 2020

Preprint

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<p>Sea-level rise (SLR) is a major concern for coastal hazards such as flooding and erosion in the decades to come. Lately, the value of high-end sea-level scenarios (HESs) to inform stakeholders with low-uncertainty tolerance has been increasingly recognized. Here, we provide high-end projections of SLR-induced sandy shoreline retreats for Europe by the end of the 21st century based on the conservative Bruun rule. Our HESs rely on the upper bound of the RCP8.5 scenario &#8220;likely-range&#8221; and on high-end estimates of the different components of sea-level projections provided in recent literature. For both HESs, SLR is projected to be higher than 1 m by 2100 for most European coasts. For the strongest HES, the maximum coastal sea-level change of 1.9 m is projected in the North Sea and Mediterranean areas. This translates into a median pan-European coastline retreat of 140 m for the moderate HES and into more than 200 m for the strongest HES. The magnitude and regional distribution of SLR-induced shoreline change projections, however, utterly depend on the local nearshore slope characteristics and the regional distribution of sea-level changes. For some countries, especially in Northern Europe, the impacts of high-end sea-level scenarios are disproportionally high compared to those of likely scenarios.</p>

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Section: Discussionmentioning

confidence: 99%

Likely and High-End Impacts of Regional Sea-Level Rise on the Shoreline Change of European Sandy Coasts Under a High Greenhouse Gas Emissions Scenario

Thiéblemont¹,

Cozannet²,

Toimil

et al. 2020

Preprint

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show abstract

Section: Discussionmentioning

confidence: 99%

“…In the absence of global detailed information on nearshore slopes, previous global or continentalscale analysis of erosion using the Bruun rule relied on a constant uniform nearshore slope value assumed to be 1% [61], which corresponds to the average estimate for sandy coasts [70]. Very recently, however, by combining global topo-bathymetric data and global wave reanalysis, Athanasiou et al [52] released the first global dataset of nearshore slopes spaced at 1 km along the global OpenStreetMap (OSM) coastline (the dataset is available at https://doi.org/10.4121/uuid:a8297dcd-c34e-4e6d-bf66-9fb8913d983d). Using a closest-neighbor procedure, we interpolated the Athanasious et al nearshore slopes on the EUROSION sandy coastal segments.…”

Section: The Eurosion Databasementioning

confidence: 99%

“…Our study focuses on beaches, therefore not considering other vulnerable coasts such as non-consolidated cliffs, artificialized coasts and wetlands, and their potential permanent inundation. To do so, we design high-end sea-level scenarios at the European scale that we combined with a database of European coastal settings (EUROSION, 2004) and a recently released nearshore slope dataset [52]. Our sea-level projections account for all relevant regional sea-level component (i.e., sterodynamic, land-water mass transfer, etc.…”

Section: Introductionmentioning

confidence: 99%

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Likely and High-End Impacts of Regional Sea-Level Rise on the Shoreline Change of European Sandy Coasts Under a High Greenhouse Gas Emissions Scenario

Thiéblemont

Cozannet

Toimil

et al. 2019

Water

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Sea-level rise (SLR) is a major concern for coastal hazards such as flooding and erosion in the decades to come. Lately, the value of high-end sea-level scenarios (HESs) to inform stakeholders with low-uncertainty tolerance has been increasingly recognized. Here, we provide high-end projections of SLR-induced sandy shoreline retreats for Europe by the end of the 21st century based on the conservative Bruun rule. Our HESs rely on the upper bound of the RCP8.5 scenario "likely-range" and on high-end estimates of the different components of sea-level projections provided in recent literature. For both HESs, SLR is projected to be higher than 1 m by 2100 for most European coasts. For the strongest HES, the maximum coastal sea-level change of 1.9 m is projected in the North Sea and Mediterranean areas. This translates into a median pan-European coastline retreat of 140 m for the moderate HES and into more than 200 m for the strongest HES. The magnitude and regional distribution of SLR-induced shoreline change projections, however, utterly depend on the local nearshore slope characteristics and the regional distribution of sea-level changes. For some countries, especially in Northern Europe, the impacts of high-end sea-level scenarios are disproportionally high compared to those of likely scenarios.2 of 22 gas emissions. Since the release of the IPCC AR5 (Intergovernmental Panel on Climate Change Fifth Assessment Report) in 2013, the debate on long-term projections of GMSL has strongly focused on the potentially very large contribution of the Antarctica ice-sheet [2,[8][9][10][11], which constitutes a deep source of uncertainty.Sea-level changes at the regional scale can substantially differ from GMSL change. Thermal expansion is modulated regionally by changes in ocean circulation, density, and atmospheric pressure [12,13]. In addition, water mass transfer from land to the ocean-due, e.g., to mountain glaciers and ice-sheets melting or groundwater extraction-induces regional changes by altering the Earth's gravity field, Earth rotation, and solid-Earth deformation [14]. Ongoing changes in the solid Earth are also still caused by the viscous adjustment of the mantle to the important mass redistribution that followed the Last Glacial Maximum (named Glacial Isostatic Adjustment; GIA) [15]. At the European scale, the influence of GIA is particularly prominent in the Scandinavian area. Finally, at a local scale, high-resolution oceanic processes [16] and vertical ground motion [17,18] can affect further the relative sea-level.Projections of future regional sea-level are crucial to support adaptation planning. So far, coastal adaptation practitioners have often relied on IPCC sea-level projections, which are provided in the form of a likely range (probability larger than 66%), and do not reflect the whole range of uncertainties of sea-level projections [19][20][21][22][23]. However, as coastal climate services are being developed [24,25], it is increasingly recognized that different types of sea-level projections are requir...

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“…These slope values are characteristic of the highly-reflective West African beaches [46,47] with a highly contrasting rainfall regime, especially in the dry season months when the beach water table is low and the wave regime mild. West Africa has, on average, steep slopes, which can be attributed to the swell dominated wave climate along the coast [48]. In addition, the beach slopes were detected for the intertidal zone that has continuous dynamics.…”

Section: Intertidal Profile Characteristics From Vcs and Uav Datamentioning

confidence: 97%

Application of Shore-Based Video and Unmanned Aerial Vehicles (Drones): Complementary Tools for Beach Studies

et al. 2020

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Video camera systems have been used over nearly three decades to monitor coastal dynamics. They facilitate a high-frequency analysis of spatiotemporal shoreline mobility. Video camera usage to measure beach intertidal profile evolution has not been standardized globally and the capacity to obtain accurate results requires authentication using various techniques. Applications are mostly site specific due to differences in installation. The present study examines the accuracy of intertidal topographic data derived from a video camera system compared to data acquired with unmanned aerial vehicle (UAV, or drone) surveys of a reflective beach. Using one year of 15-min video data and one year of monthly UAV observations, the intertidal profile shows a good agreement. Underestimations of intertidal profile elevations by the camera-based method are possibly linked to the camera view angle, rectification and gaps in data. The resolution of the video-derived intertidal topographic profiles confirmed, however, the suitability of the method in providing beach mobility surveys matching those required for a quantitative analysis of nearshore changes. Beach slopes were found to vary between 0.1 and 0.7, with a steep slope in May to July 2018 and a gentle slope in December 2018. Large but short-scale beach variations occurred between August 2018 and October 2018 and corresponded to relatively high wave events. In one year, this dynamic beach lost 7 m. At this rate, and as also observed at other beaches nearby, important coastal facilities and infrastructure will be prone to erosion. The data suggest that a low-cost shore-based camera, particularly when used in a network along the coast, can produce profile data for effective coastal management in West Africa and elsewhere.

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Global distribution of nearshore slopes with implications for coastal retreat

Cited by 76 publications

References 37 publications

Likely and High-End Impacts of Regional Sea-Level Rise on the Shoreline Change of European Sandy Coasts Under a High Greenhouse Gas Emissions Scenario

Likely and High-End Impacts of Regional Sea-Level Rise on the Shoreline Change of European Sandy Coasts Under a High Greenhouse Gas Emissions Scenario

Likely and High-End Impacts of Regional Sea-Level Rise on the Shoreline Change of European Sandy Coasts Under a High Greenhouse Gas Emissions Scenario

Application of Shore-Based Video and Unmanned Aerial Vehicles (Drones): Complementary Tools for Beach Studies

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