What controls the Geometry of Rocky Coasts at the Local Scale?

Swirad, Zuzanna; Rosser, Nick; Brain, Matthew J.; Jones, E. C. Vann

doi:10.2112/si75-123.1

Cited by 8 publications

(4 citation statements)

References 10 publications

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“…The bedding dip results in three sandstone beds (B1-B3: Fig. 1b) exposed along the foreshore surface, which each terminate with abrupt breaks in slope, herein referred to as steps at the termini of beds B1 (0.80-m thick) and B2 (0.75-m thick), and a seaward edge at the terminus of B3 29 . Submerged layers of sedimentary rocks are present seawards from the platform edge, but are not considered here.…”

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Cosmogenic exposure dating reveals limited long-term variability in erosion of a rocky coastline

et al. 2020

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Predicted sea-level rise and increased storminess are anticipated to lead to increases in coastal erosion. However, assessing if and how rocky coasts will respond to changes in marine conditions is difficult due to current limitations of monitoring and modelling. Here, we measured cosmogenic 10 Be concentrations across a sandstone shore platform in North Yorkshire, UK, to model the changes in coastal erosion within the last 7 kyr and for the first time quantify the relative long-term erosive contribution of landward cliff retreat, and downwearing and stripping of rock from the shore platform. The results suggest that the cliff has been retreating at a steady rate of 4.5 ± 0.63 cm yr −1 , whilst maintaining a similar profile form. Our results imply a lack of a direct relationship between relative sea level over centennial to millennial timescales and the erosion response of the coast, highlighting a need to more fully characterise the spatial variability in, and controls on, rocky coast erosion under changing conditions.

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confidence: 99%

Cosmogenic exposure dating reveals limited long-term variability in erosion of a rocky coastline

et al. 2020

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“…The platform surface is characterized by a heterogeneous cover of intertidal algae and patches of barnacles, which are typically found in topographic lows that retain water during low tides, and on the most seaward portions of the platform which are less frequently exposed (Figure D). Closer to the cliff toe the algae and barnacle cover becomes more sparse, concentrating in niches, included joints and rock pools (Figure B) (Swirad et al, ).…”

Section: Study Sitementioning

confidence: 99%

Identifying mechanisms of shore platform erosion using Structure‐from‐Motion (SfM) photogrammetry

Swirad

Rosser

Brain

2019

Earth Surf Processes Landf

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Shore platforms control wave energy transformation which, in turn, controls energy delivery to the cliff toe and nearshore sediment transport. Insight into shore platform erosion rates has conventionally been constrained at millimetre‐scales using micro‐erosion metres, and at metre‐scales using cartographic data. On apparently slowly eroding coasts, such approaches are fundamentally reliant upon long‐term observation to capture emergent erosion patterns. Where in practise timescales are short, and where change is either below the resolution or saturates the mode of measurement, the collection of data that enables the identification of the actual mechanisms of erosion is hindered. We developed a method to monitor shore platform erosion at millimetre resolution within metre‐scale monitoring plots using Structure‐from‐Motion photogrammetry. We conducted monthly surveys at 15 0.25 m2 sites distributed across the Hartle Loup platform in North Yorkshire, UK, over one year. We derived topographic data at 0.001 m resolution, retaining a vertical precision of change detection of 0.001 m. We captured a mean erosion rate of 0.528 mm yr‐1, but this varied considerably both across the platform and through the year. We characterized the volume and shape of eroded material. The detachment volume–frequency and shape distributions suggest that erosion happens primarily via removal of shale platelets. We identify that the at‐a‐point erosion rate can be predicted by the distance from the cliff and the tidal level, whereby erosion rates are higher closer to the cliff and at locations of higher tidal duration. The size of individual detachments is controlled by local micro‐topography and rock structure, whereby larger detachments are observed on more rough sections of the platform. Faster erosion rates and larger detachments occur in summer months, rather than in more energetic winter conditions. These results have the potential to form the basis of improved models of how platforms erode over both short‐ and long‐timescales. © 2019 John Wiley & Sons, Ltd.

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“…Rockfall, or the removal of individual and superficial rocks from a cliff face [1,2], is a significant geohazard, particularly on coastal cliffs where the exposure of people and assets is often high [3,4]. Rock coasts account for much of the world's coastline [5], yet our understanding of their evolution remains limited by progressive time-dependent failure processes [6], geological and geometric settings [7][8][9], increasing environmental extremes [10,11], and the appropriateness of the available…”

Section: Introductionmentioning

confidence: 99%

Decoding Complex Erosion Responses for the Mitigation of Coastal Rockfall Hazards Using Repeat Terrestrial LiDAR

Westoby

Lim

Hogg³

et al. 2020

Remote Sensing

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A key factor limiting our understanding of rock slope behavior and associated geohazards is the interaction between internal and external system controls on the nature, rates, and timing of rockfall activity. We use high-resolution, monthly terrestrial light detection and ranging (LiDAR) surveys over a 2 year monitoring period to quantify rockfall patterns across a 0.6 km-long (15.3 × 103 m2) section of a limestone rock cliff on the northeast coast of England, where uncertainty in rates of change threaten the effective planning and operational management of a key coastal cliff top road. Internal system controls, such as cliff material characteristics and foreshore geometry, dictate rockfall characteristics and background patterns of activity and demonstrate that layer-specific analyses of rockfall inventories and sequencing patterns are essential to better understand the timing and nature of rockfall risks. The influence of external environmental controls, notably storm activity, is also evaluated, and increased storminess corresponds to detectable rises in both total and mean rockfall volume and the volumetric contribution of large (>10 m3) rockfalls at the cliff top during these periods. Transient convergence of the cumulative magnitude–frequency power law scaling exponent (ɑ) during high magnitude events signals a uniform erosion response across the wider cliff system that applies to all lithologies. The tracking of rockfall distribution metrics from repeat terrestrial LiDAR in this way demonstrably improves the ability to identify, monitor, and forecast short-term variations in rockfall hazards, and, as such, provides a powerful new approach for mitigating the threats and impacts of coastal erosion.

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What controls the Geometry of Rocky Coasts at the Local Scale?

Cited by 8 publications

References 10 publications

Cosmogenic exposure dating reveals limited long-term variability in erosion of a rocky coastline

Cosmogenic exposure dating reveals limited long-term variability in erosion of a rocky coastline

Identifying mechanisms of shore platform erosion using Structure‐from‐Motion (SfM) photogrammetry

Decoding Complex Erosion Responses for the Mitigation of Coastal Rockfall Hazards Using Repeat Terrestrial LiDAR

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