Evidence for active retreat of a coastal cliff between 3.5 and 12 ka in Cassis (South East France)

Recorbet, F.; Rochette, P.; Braucher, Régis; Bourlès, Didier; Benedetti, Lucilla; Hantz, Didier; Finkel, Robert C.

doi:10.1016/j.geomorph.2009.04.023

Cited by 18 publications

(42 citation statements)

References 33 publications

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“…Sunamura (2015) demonstrated that longer-term records are needed. The return period of coastal mass wasting events, the principal mechanisms of coastal cliff retreat, may in some cases be much longer than these historical records (Recorbet et al, 2010). Methods to estimate long-term rates of cliff retreat are required in order to time average rates across multiple failure events.…”

Section: Introductionmentioning

confidence: 99%

“…Yet, by their very nature, eroding coastlines leave scant evidence of any former state, and their form reflects little about their longterm erosional trajectories (Matsumoto et al, 2016). Cosmogenic isotopes have the potential to reveal the long-term history of coastal change and to quantify process rates along rocky coastlines (Recorbet et al, 2010;Choi et al, 2012;Regard et al, 2012;Rogers et al, 2012;Hurst et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

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Controls on the distribution of cosmogenic <sup>10</sup>Be across shore platforms

2017

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Abstract. Quantifying rates of erosion on cliffed coasts across a range of timescales is vital for understanding the drivers and processes of coastal change and for assessing risks posed by future cliff retreat. Historical records cover at best the last 150 years; cosmogenic isotopes, such as 10 Be could allow us to look further into the past to assess coastal change on millennial timescales. Cosmogenic isotopes accumulate in situ near the Earth surface and have been used extensively to quantify erosion rates, burial dates and surface exposure ages in terrestrial landscapes over the last 3 decades. More recently, applications in rocky coast settings have quantified the timing of mass wasting events, determined long-term averaged rates of cliff retreat and revealed the exposure history of shore platforms. In this contribution, we develop and explore a numerical model for the accumulation of 10 Be on eroding shore platforms. In a series of numerical experiments, we investigated the influence of topographic and water shielding, dynamic platform erosion processes, the presence and variation in beach cover, and heterogeneous distribution of erosion on the distribution of 10 Be across shore platforms. Results demonstrate that, taking into account relative sea level change and tides, the concentration of 10 Be is sensitive to rates of cliff retreat. Factors such as topographic shielding and beach cover act to reduce 10 Be concentrations on the platform and may result in overestimation of cliff retreat rates if not accounted for. The shape of the distribution of 10 Be across a shore platform can potentially reveal whether cliff retreat rates are declining or accelerating through time. Measurement of 10 Be in shore platforms has great potential to allow us to quantify long-term rates of cliff retreat and platform erosion.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Controls on the distribution of cosmogenic <sup>10</sup>Be across shore platforms

2017

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“…2 dN/dt = P-λN λ being the decay constant. Cosmogenic nuclides have recently been used to quantify slowly eroding cliffs (<<10 cm/yr; Recorbet et al, 2010;Le Roux et al, 2009), but until now have not been employed to quantify recession rates of rapidly eroding coastal cliffs. In this paper we propose a simple model for the concentrations of cosmogenic nuclides to be expected in rocks sampled across present-day shore platforms, and compare its predictions against measured concentrations to derive long-term cliff retreat rates.…”

Section: Introductionmentioning

confidence: 99%

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

Regard

Dewez²,

Bourlès

et al. 2012

Quaternary Geochronology

168

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“…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 the coast. It is therefore vital that we obtain longer, reliable records of coastal change to compare with historical observations to understand how coastal erosion may have changed through time, what the drivers are, and how coasts may evolve into the future (5).…”

mentioning

confidence: 99%

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.

103

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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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Evidence for active retreat of a coastal cliff between 3.5 and 12 ka in Cassis (South East France)

Cited by 18 publications

References 33 publications

Controls on the distribution of cosmogenic <sup>10</sup>Be across shore platforms

Controls on the distribution of cosmogenic <sup>10</sup>Be across shore platforms

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

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

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Evidence for active retreat of a coastal cliff between 3.5 and 12 ka in Cassis (South East France)

Cited by 18 publications

References 33 publications

Controls on the distribution of cosmogenic &lt;sup&gt;10&lt;/sup&gt;Be across shore platforms

Controls on the distribution of cosmogenic &lt;sup&gt;10&lt;/sup&gt;Be across shore platforms

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

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

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Resources

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Controls on the distribution of cosmogenic <sup>10</sup>Be across shore platforms

Controls on the distribution of cosmogenic <sup>10</sup>Be across shore platforms