Temporal and spatial variations of chalk cliff retreat in East Sussex, 1873 to 2001

Dornbusch, Uwe; Robinson, David A.; Moses, Cherith; Williams, R. B. G.

doi:10.1016/j.margeo.2007.12.005

Cited by 84 publications

(72 citation statements)

References 14 publications

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“…2C) (7). Extrapolating this range of historical retreat rates back in time, a ∼350-m platform (widest observed subaerially exposed platform at the study site) can form in between 450 and 7,000 y, and therefore certainly within the Holocene.…”

Section: Significancementioning

confidence: 84%

“…Although there are no active interventions protecting the studied coastline, engineering activities since the late 19th century, designed to protect several kilometers of the coastline 2-15 km to the west (updrift), have reduced the supply of littoral sediment along the studied coastline; beach widths have been observed to be declining or been lost along the length East Sussex coastline (7). Numerical modeling has demonstrated that shoreline interventions can result in significant nonlocal impact many kilometers downdrift from the protected sites (3,34).…”

Section: Discussionmentioning

confidence: 99%

“…At the junction between cliff and platform there are intermittent fringing beaches composed of flint pebbles and cobbles mixed with sand. These are known to have been more continuous and of larger volume during the 19th century (7). Frequent cliff failures result in aprons of chalk debris that are subsequently reworked by wave action.…”

Section: Significancementioning

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.

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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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Section: Significancementioning

confidence: 84%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

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.

Self Cite

103

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“…Observations of beach cover can be made from historical data (e.g. Dornbusch et al, 2008) but are limited to the length of the historical record (ca. 150 years maximum) and may be influenced by human intervention at the coast.…”

Section: Discussionmentioning

confidence: 99%

“…Dornbusch et al, 2008), but there is little information about how beaches may have changed over millennial timescales. However, exposed shore platforms are most likely to be associated with locations with little or declining beach cover, since if beaches were accumulating, the platform would not be exposed and cliff retreat rates might be expected to drop.…”

Section: Interpreting Rates Of Cliff Retreat From 10 Be Concentrationsmentioning

confidence: 99%

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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Relict landscape resistance to dissection by upstream migrating knickpoints

Brocard

Willenbring

Miller

et al. 2016

J. Geophys. Res. Earth Surf.

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Expanses of subdued topographies are common at high elevation in mountain ranges. They are often interpreted as relict landscapes and are expected to be replaced by steeper topography as erosion proceeds. Preservation of such relict fragments can merely reflect the fact that it takes time to remove any preexisting topography. However, relict fragments could also possess intrinsic characteristics that make them resilient to dissection. We document here the propagation of a wave of dissection across an uplifted relict landscape in Puerto Rico. Using 10Be‐26Al burial dating on cave sediments, we show that uplift started 4 Ma and that river knickpoints have since migrated very slowly across the landscape. Modern detrital 10Be erosion rates are consistent with these long‐term rates of knickpoint retreat. Analysis of knickpoint distribution, combined with visual observations along the streambeds, indicates that incision by abrasion and plucking is so slow that bedrock weathering becomes a competing process of knickpoint retreat. The studied rivers flow over a massive stock of quartz diorite surrounded by an aureole of metavolcanic rocks. Earlier studies have shown that vegetation over the relict topography efficiently limits erosion, allowing for the formation of a thick saprolite underneath. Such slow erosion reduces streambed load fluxes delivered to the knickpoints, as well as bed load grain size. Both processes limit abrasion. Compounding the effect of slow abrasion, wide joint spacing in the bedrock makes plucking infrequent. Thus, the characteristics of the relict upstream landscape have a direct effect on stream incision farther downstream, reducing the celerity at which the relict, subdued landscape is dissected. We conclude that similar top‐down controls on river incision rate may help many relict landscapes to persist amidst highly dissected topographies.

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Temporal and spatial variations of chalk cliff retreat in East Sussex, 1873 to 2001

Cited by 84 publications

References 14 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

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

Relict landscape resistance to dissection by upstream migrating knickpoints

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Temporal and spatial variations of chalk cliff retreat in East Sussex, 1873 to 2001

Cited by 84 publications

References 14 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

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

Relict landscape resistance to dissection by upstream migrating knickpoints

Contact Info

Product

Resources

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