Late Holocene seacliff retreat recorded by 10Be profiles across a coastal platform: Theory and example from the English Channel

Regard, Vincent; Dewez, Thomas; Bourlès, Didier; Anderson, Robert S.; Duperret, Anne; Costa, Stéphane; Léanni, Laëtitia; Lasseur, Éric; Pedoja, Kévin; Maillet, Grégoire

doi:10.1016/j.quageo.2012.02.027

Cited by 67 publications

(210 citation statements)

References 44 publications

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“…The technique has recently been applied to rocky coasts to estimate rates of cliff retreat (10,11) and to understand the Quaternary history of exposure, inheritance, and reoccupation of shore platforms (12). Here we report a long-term record of cliff retreat in the relatively soft chalk cliffs of East Sussex, United Kingdom, which have been observed to be eroding at rates of 10-80 cm·y −1 over the last 150 y (7).…”

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confidence: 96%

“…In this study, we derived retreat rates of chalk cliffs on the south coast of Great Britain over millennial time scales by coupling high-precision cosmogenic radionuclide geochronology and rigorous numerical modeling. Measured 10 Be concentrations on rocky coastal platforms were compared with simulations of coastal evolution using a Monte Carlo approach to determine the most likely history of cliff retreat. The 10 Be concentrations are consistent with retreat rates of chalk cliffs that were relatively slow (2-6 cm·y −1 ) until a few hundred years ago.…”

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confidence: 99%

“…Measured 10 Be concentrations on rocky coastal platforms were compared with simulations of coastal evolution using a Monte Carlo approach to determine the most likely history of cliff retreat. The 10 Be concentrations are consistent with retreat rates of chalk cliffs that were relatively slow (2-6 cm·y −1 ) until a few hundred years ago. Historical observations reveal that retreat rates have subsequently accelerated by an order of magnitude (22-32 cm·y −1 ).…”

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confidence: 99%

“…Measurement of in situ concentrations of 10 Be provide a versatile geochronometer for geomorphic studies, which facilitates dating of surface exposure and the deposition and burial of sediments and estimation of weathering and erosion rates (9). The technique has recently been applied to rocky coasts to estimate rates of cliff retreat (10,11) and to understand the Quaternary history of exposure, inheritance, and reoccupation of shore platforms (12).…”

mentioning

confidence: 99%

“…Here we report a long-term record of cliff retreat in the relatively soft chalk cliffs of East Sussex, United Kingdom, which have been observed to be eroding at rates of 10-80 cm·y −1 over the last 150 y (7). Our long-term record was generated by coupling high-precision measurement of concentrations of 10 Be on a coastal platform with a numerical and statistical model that inverts these data for rates of cliff retreat at millennial time scales.…”

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confidence: 99%

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Recent acceleration in coastal cliff retreat rates on the south coast of Great Britain

Hurst

Rood

Ellis

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

105

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Rising sea levels and increased storminess are expected to accelerate the erosion of soft-cliff coastlines, threatening coastal infrastructure and livelihoods. To develop predictive models of future coastal change we need fundamentally to know how rapidly coasts have been eroding in the past, and to understand the driving mechanisms of coastal change. Direct observations of cliff retreat rarely extend beyond 150 y, during which humans have significantly modified the coastal system. Cliff retreat rates are unknown in prior centuries and millennia. In this study, we derived retreat rates of chalk cliffs on the south coast of Great Britain over millennial time scales by coupling high-precision cosmogenic radionuclide geochronology and rigorous numerical modeling. Measured 10 Be concentrations on rocky coastal platforms were compared with simulations of coastal evolution using a Monte Carlo approach to determine the most likely history of cliff retreat. The 10 Be concentrations are consistent with retreat rates of chalk cliffs that were relatively slow (2-6 cm·y −1 ) until a few hundred years ago. Historical observations reveal that retreat rates have subsequently accelerated by an order of magnitude (22-32 cm·y −1 ). We suggest that acceleration is the result of thinning of cliff-front beaches, exacerbated by regional storminess and anthropogenic modification of the coast.geomorphology | coasts | cosmogenic radionuclides | erosion | cliffs R ocky coasts are "erosional environments formed as a result of the landward retreat of bedrock at the shoreline" (1). They leave scant evidence of any previous state, making it difficult to interpret their history. Cliff retreat is driven by a combination of wave-driven cliff-base erosion, subaerial weathering, and mass wasting processes, whose efficiencies are dependent on lithology and climate. Sediment generated by mass wasting processes such as abrasion, plucking, landslides, and rockfalls tends to be reworked and transported away by waves and currents, particularly for softer rock types.Cliff erosion due to mass wasting threatens livelihoods and both public and private clifftop infrastructure and development; quantitative estimates of the rate of cliff retreat are necessary to assess the associated risk. Rising sea levels and increased storminess may lead to accelerated coastal erosion rates in the future, potentially increasing hazard exposure (2-5). To accurately assess coastal hazards in the face of future climate and land-use changes, it is necessary to understand the dynamics of cliff erosion over length and time scales relevant to the processes that drive change. To establish the context for modern change, we must quantify the natural variability and the long-term behavior of cliff retreat. Historical records are too short to allow us to do this: they typically span no longer than ∼150 y (6, 7), which can be less than the characteristic return period of significant coastal failures (8), and they coincide with the period over which humans have significantly modified th...

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Recent acceleration in coastal cliff retreat rates on the south coast of Great Britain

Hurst

Rood

Ellis

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

105

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Mapping Coastal Erosion of a Mediterranean Cliff with a Boat‐Borne Laser Scanner: Performance, Processing, and Cliff Erosion Rate

Giuliano

Dewez

Lebourg

et al. 2022

3D Digital Geological Models

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Terrestrial laser scanners (TLS) are well known for providing an efficient means to monitor coastal cliff erosion. Cliffs along micro-tidal coasts, however, have often escaped quantification because the narrow or absent coastal platforms do not offer stable and embracing vantage points. To circumvent this issue, mobile laser scanning surveys from a boat can be used. We present a case study from Provence-Alpes-Côte-d'Azur (Mediterranean coastsouthern France) to quantify cliff erosion in such micro-tidal environments. Three surveys were sub-contracted over a period of 17 months to monitor a 3.5-km-long cliff of Carry-le-Rouet (15km west of Marseille). Data quality was check independently using man-made planar walls positioned above the cliff face, to retrieve survey precision and change detection thresholds.Boat-borne mobile lidar system was capable of describing planar features with a precision of 3-4 cm (epoch 1 and 2) and improved to 2.6 cm (epoch 3) with point densities around 100 pts/m². Absolute positioning accuracy varied between 0.1 cm and 0.3 cm. Because the coastline is very sinuous, we describe a method to unfold the point clouds using a continuous analytical surface made of vertical planes joined by arcs of cylinders and perform the analysis in 2.5D.Change was detected using a unique, conservative, threshold of 14 cm (99% quantile estimated on plane change) on grids of 10 x 10 cm pixels. Integrated over the entire cliff face, the average annual cliff recession rate at Carry-le-Rouet is 1.1cm/year. In 17 months, erosion was three times more effective in sandstone and marls layers than in calcarenites and conglomerates.Erosion varies vertically with erosion three times more effective in the lower 25 m of the cliffs than above. Despite imperfections, boat-borne laser scanning system are capable of delivering meaningful erosion data even in this low erosion context.

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Shore platform lowering due to frost shattering during the 2009 winter at mesnil Val, English channel coast, NW France

Dewez

Regard

Duperret

et al. 2015

Earth Surf Processes Landf

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In 2008–2009, a severe cold snap affected the otherwise temperate mid‐latitude coasts of the English Channel of France. In March 2009, we gathered rock spalling observations at Mesnil Val, NW France, to document the effect of frost on platform lowering in macro‐tidal environments. Six epochs of frost were recorded in 2 months, the two longest lasted 16 and 8 days, with minimum air temperature dropping to –9.5°C. Semi‐diurnal tides flood the entire platform, imposing up to 25 freeze–thaw cycles below –2.5°C, the freezing temperature of seawater. 19 cycles occurred at neap tidal elevation lasting at most 3.5 h. Our integrated observations indicate that these frost cycles were responsible for a platform lowering of about 0.8±0.5 mm during a single winter. No clear spatial trend appears, nor do macroscopic chalk types clearly stand out as being more susceptible to erosion. Assuming that the long‐term platform retreat model preserves a constant slope, frost shattering would then account for 10 to 20% of the expected annual platform erosion rate. Under more contrasted climates, frost is thus likely to be a prominent shaping process for rocky coastal platforms. Copyright © 2015 John Wiley & Sons, Ltd.

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Late Holocene seacliff retreat recorded by 10Be profiles across a coastal platform: Theory and example from the English Channel

Cited by 67 publications

References 44 publications

Recent acceleration in coastal cliff retreat rates on the south coast of Great Britain

Recent acceleration in coastal cliff retreat rates on the south coast of Great Britain

Mapping Coastal Erosion of a Mediterranean Cliff with a Boat‐Borne Laser Scanner: Performance, Processing, and Cliff Erosion Rate

Shore platform lowering due to frost shattering during the 2009 winter at mesnil Val, English channel coast, NW France

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