The Role of Wave Erosion on Sloping and Horizontal Shore Platforms in Macro- and Mesotidal Environments

Trenhaile, Alan S.; Kanyaya, Jacob I.

doi:10.2112/04-0282.1

Cited by 95 publications

(71 citation statements)

References 12 publications

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“…The difference in water depths and modelled wave heights at the toe of the seven sites, however, suggests that the levels of HT ground motion energy recorded at the seven sites during the storm do not represent similarities in wave heights, but instead may indicate similarities in wavecliff face interaction, such as a more uniform pattern of waves breaking onto the cliff toe. At Scots Bay in the Bay of Fundy, another macrotidal site, during storm conditions Trenhaile and Kanyaya (2007) observed narrowing surf zones, lower levels of wave attenuation and more energetic types of breaking waves (plunging breakers) in the upper foreshore during high tides. This was compared to the lower platform during lower tide levels and was attributed to greater water depths and higher platform gradients at the upper foreshore.…”

Section: The Influence Of Foreshore Morphology On Ht Ground Motion Enmentioning

confidence: 99%

“…Stephenson and Kirk, 2000;Trenhaile and Kanyaya, 2007), and have measured the distribution of wave energy cross-shore and the influence of foreshore characteristics (Ogawa et al, 2011(Ogawa et al, , 2016Poate et al, 2016;Stephenson et al, 2017). Such studies have not considered alongshore variability in these foreshore characteristics, the resulting wave energy dissipation and transfer to the cliff.…”

Section: Introductionmentioning

confidence: 99%

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Alongshore variability in wave energy transfer to coastal cliffs

2018

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The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. The alongshore distribution of wave energy is believed to be an important control on the spatial variability of coastal erosion. There is, however, a lack of field data quantifying the alongshore variability in wave energy on rock coasts, whereby the relative control of coastline geometry versus foreshore characteristics on wave energy delivery remains unclear. A number of studies have identified high-frequency cliff-top ground shaking to be generated by wave impacts at the cliff toe during high tides (HT). To capture the variability of wave-cliff impact energy along-coast, we installed an array of cliff-top seismometers along a 1 km stretch of coastline in North Yorkshire, UK. Our aim is to constrain how wave energy transfer to the cliff toe varies, and to examine the relative energy transfer around typical coastline features, including a bay and headlands. Whilst the greatest HT ground motion energy is recorded at a headland and the lowest at the centre of the bay (5% of that observed at the headland), we identify no systematic alongshore variation in the HT ground motion energy that can be related to coastline morphology. We also note considerable variation between features of similar form: the total HT ground motion energy at one headland is only 49% of the next headland 1 km alongshore. Between neighbouring sites within the bay, separated by only 100 m, we observe up to an order of magnitude difference in ground motion energy transfer. Our results demonstrate the importance of the foreshore in driving the variations in energy delivery that we observe. Local alterations in water depth and foreshore topography control the alongshore distribution of wave energy available to generate cliff HT ground motions. Importantly, this apparently local effect overrides the influence of macroscale coastal planform morphology, which has previously been assumed to be the dominant control. The results show that foreshore characteristics that hold influence over wave energy transfer vary significantly over short (~100 m) distances, and so we expect erosion controlled by wave impacts to vary over similar scales.

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Section: The Influence Of Foreshore Morphology On Ht Ground Motion Enmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Alongshore variability in wave energy transfer to coastal cliffs

2018

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“…The effect of discontinuities on rocky coast morphologies and processes has been intensively studied; some recent studies include Benumof et al (2000), Duperret et al (2004), Hénaff et al (2006), Trenhaile & Kanyaya (2007), Cruslock et al (2010), Kennedy (2010) and Naylor & Stephenson (2010). Meso-scale (centimetre to metre order) erosion often occurs on the surface of shore platforms in a short period of time in a mode of 'quarrying' or 'plucking', the removal of blocks bounded by joints and faults, with the erosion scale depending on the dimension of blocks.…”

Section: Discussionmentioning

confidence: 99%

Chapter 12 The rock coast of Japan

Sunamura¹,

Tsujimoto

Aoki

2014

Memoirs

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The Japanese islands, situated in a tectonically unstable region with a highly variable geology, are exposed to high wave energy and microtidal environments in most locations. Rocky coasts are common, most having a steep cliff with coastal recession being primarily driven by wave erosion. A fundamental relationship between recession and wave force is obtained through reanalysis of previous laboratory data. On the basis of this relation a model is constructed for the development of type B platforms, that is, horizontal or subhorizontal platforms that have a steep scarp at the seaward edge. The process of wave attenuation on this type of platform and weathering-induced strength reduction of rocks are incorporated into the model. The model is applied to the southwestern coast of the Kii Peninsula and a platform at Ebisu-jima of the Izu Peninsula. Long-term development rates of platforms in the former area are examined: the model indicates that the rate of erosion when platforms were initiated at 6000 years BP is two orders of magnitude greater than present. At the Ebisu-jima platform, wave-induced erosion processes are explored on a daily basis: the model provides a description of temporal variations in platform growth, although the result is not fully satisfactory.Gold Open Access: This article is published under the terms of the CC-BY 3.0 license.

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“…energy dissipation influences both local downwearing but also backwearing) but provides a convenient picture of main loops at different stages of development. For example, Dickson (2006) and Trenhaile and Kanyaya (2007) suggested that backwearing due to waves is likely to be dominant at early stages of platform development, whereas weathering processes may Fig. 10 Feedback factor strength, g, of a widening platform.…”

Section: Discussionmentioning

confidence: 99%

Feedback structure of cliff and shore platform morphodynamics

Payo

Dickson

Walkden³

2014

J Coast Conserv

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It has been suggested that studies of geomorphological systems should identify potential system feedbacks, determine their direction of influence, and assess their relative importance. In this paper we show how a core set of processes and feedback loops can be distilled from existing literature on rock coast morphodynamics. The structure has been represented using Causal Loop Diagrams and a methodology to estimate the strength of a single feedback loop is presented. The backwearing erosion rate (cliff horizontal erosion) has been found to be controlled by at least four feedback loops; three balancing (cliff toe wave energy depletion, ground-water pore pressure diminution and cliff deposit protection) and one positive loop (abrasion enhancement). The downwearing erosion rate (vertical erosion) has been found to be controlled by at least three balancing feedback loops (weathering limited, shear depletion, cover-protection). Mean sea level directly influences the downwearing rate, through the water depth relative to the wave base, and indirectly influences the backwearing erosion rate through the wave energy dissipation that determines the amount of energy reaching the cliff toe. The offshore wave non-linearity parameter is proposed to capture the complex interaction between waves and shore platform geometries. The strength of the cliff toe energy depletion loop is assessed by reasoning on its causal pathway and found to be O(−10 −10 to −10 −4 ) for poorly lithified rock coasts. By understanding how the individual and overall feedback strengths are influenced by different future environmental and human intervention scenarios we could provide better assessment at the time scales needed for coastal management.

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The Role of Wave Erosion on Sloping and Horizontal Shore Platforms in Macro- and Mesotidal Environments

Cited by 95 publications

References 12 publications

Alongshore variability in wave energy transfer to coastal cliffs

Alongshore variability in wave energy transfer to coastal cliffs

Chapter 12 The rock coast of Japan

Feedback structure of cliff and shore platform morphodynamics

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