Coastal vulnerability of a pinned, soft-cliff coastline, II: assessing the influence of sea walls on future morphology

Barkwith, Andrew; Hurst, Martin D.; Thomas, Chris W.; Ellis, Michael A.; Limber, Pat; Murray, A. Brad

doi:10.5194/esurf-2-233-2014

Cited by 11 publications

(8 citation statements)

References 27 publications

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“…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%

“…Rising sea levels and increased storminess may lead to accelerated coastal erosion rates in the future, potentially increasing hazard exposure (2)(3)(4)(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.…”

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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.

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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: Discussionmentioning

confidence: 99%

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.

Self Cite

103

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“…There is societal need to assess the rates, and the change of rates, at which cliffed coastlines will erode in the face of changing sea levels and wave climates that may result in more energetic coasts (Bray and Hooke, 1997;Trenhaile, 2010;Ashton et al, 2011;Barkwith et al, 2014). The lack of long-term records of cliff and shore-platform erosion rates is a key problem to address (Trenhaile, 2014).…”

Section: Introductionmentioning

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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“…Thus, although sea‐level and wave height having equal footing in the Hackney et al . () model employed in this study, it is wave height that has the largest effect on coastal erosion (Figure ), suggesting that for studies focused over the meso‐scale (~100 years) more focus should be paid to changes in wave heights in future studies of coastal erosion, particularly in cliffed environments where energy delivery to the cliff foot is likely the key driver of coastal erosion (Hackney et al ., ; Barkwith et al ., , ).…”

Section: Discussionmentioning

confidence: 97%

“…These interactions may produce responses in landscape evolution which are difficult to constrain in the currently available suite of terrestrial LEMs, none of which explicitly represent coastal geomorphic processes. Although coastal evolution models (CEMs; Ashton et al ., ; Barkwith et al ., , b) exist which are capable of modelling the dynamic evolution of shorelines, the inclusion of coastal processes as a boundary condition to a terrestrial LEM would be a useful and timely addition to this area of landscape modelling.…”

Section: Introductionmentioning

confidence: 99%

Landscapes on the edge: examining the role of climatic interactions in shaping coastal watersheds using a coastal–terrestrial landscape evolution model

Hackney

Darby

Leyland

2014

Earth Surf Processes Landf

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Incised coastal gullies (ICGs) are dynamic features found at the terrestrial‐coastal interface. Their geomorphic evolution is driven by the interactions between processes of fluvial knickpoint migration and coastal cliff erosion. Under scenarios of future climate change the frequency and magnitude of the climatological drivers of both terrestrial (fluvial and hillslope) and coastal (cliff erosion) processes are likely to change, with an adjunct impact on these types of coastal features. Here we explore the response of an incised coastal gully to changes in both terrestrial and coastal climate in order to elucidate the key process interactions which drive ICG evolution. We modify an extant landscape evolution model, CHILD, to incorporate processes of soft‐cliff erosion. This modified version, termed the Coastal‐Terrestrial‐CHILD (CT‐CHILD) model, is then employed to explore the interactions between changing terrestrial and coastal driving forces on the future evolution of an ICG found on the south‐west Isle of Wight, UK. It was found that the magnitude and frequency of storm events will play a key role in determining the future trajectory of ICGs, highlighting a need to understand the role of event sequencing in future projections of landscape evolution. Furthermore, synergistic (positive) and antagonistic (negative) interactions were identified between coastal and terrestrial parameters, such as wave height intensity and precipitation duration, which act to modulate the impact of changes in any one parameter. Of note was the role played by wave height intensity in driving coastal erosion, which was found to play a more important role than sea‐level rise in determining rates of coastal erosion. This highlights the need for a greater focus on wave height in studies of soft‐cliff erosion. Copyright © 2014 John Wiley & Sons, Ltd.

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Coastal vulnerability of a pinned, soft-cliff coastline, II: assessing the influence of sea walls on future morphology

Cited by 11 publications

References 27 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

Landscapes on the edge: examining the role of climatic interactions in shaping coastal watersheds using a coastal–terrestrial landscape evolution model

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Coastal vulnerability of a pinned, soft-cliff coastline, II: assessing the influence of sea walls on future morphology

Cited by 11 publications

References 27 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

Landscapes on the edge: examining the role of climatic interactions in shaping coastal watersheds using a coastal–terrestrial landscape evolution model

Contact Info

Product

Resources

About

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