108 research outputs found
Traversing Erosion Beam data, Warden Point, Kent, 2005 to 2015
No full textTitle: Intertidal cohesive foreshores: Erosion rates and processes illustrated by a shore platform at Warden Point, Kent, UK.
Authors: Cherith A. Moses and David A. Robinson
Description: platform downwearing data, measured using the Traversing Erosion Beam (TEB), on the London Clay foreshore at Warden Point, Kent, UK.
Technical details for the TEB construction and installation of fixed measurement points in the platform are detailed in Charman et al. (2007) as is the procedure for recording measurements and their accuracy and reproducibility.
Erosion rates are presented and discussed in Moses and Robinson (under review). Measurement sites are as follows: upper site (WA1 and WA2); mid site (WB1 and WB2); lower site (WC1 and WC2).
Data collection: Initial data collection in 2005 to 2006, was carried out as part of the ‘Understanding cohesive foreshores’ project, funded by DEFRA and the Environment Agency Joint R&D Programme (project number FD 1915). Details can be found in Brew (2007). Continuation of the field measurements over the following years has been carried out by the authors with the help of a number of colleagues and students, whose assistance with the TEB and surveying is gratefully acknowledged: Rendel Williams, Richard Charman, Jerome Curoy, Hanna Kauppila, Jessica Jordan, and Christopher Gordon. The authors thank English Nature (now Natural England) for permission to install the measurement sites into the shore platform.
References:
Brew, D. S. 2007. Understanding and Predicting Beach Morphological Change Processes Associated with the Erosion of Cohesive Foreshores. DEFRA-Flood Management Division Technical Report FD1926/TR.
Charman, R., Cane, T., Moses, C. and Williams, R., 2007. A device for measuring downwearing rates on cohesive shore platforms. Earth Surface Processes and Landforms, 32, 14: 2212-2221.
Moses, C.A. and Robinson, D.A. (under review) Intertidal cohesive foreshores: Erosion rates and processes illustrated by a shore platform at Warden Point, Kent, UK. Marine Geology
Chapter 4 The rock coast of the British Isles: shore platforms
No full textRock shore platforms, present on at least half of the 20 500 km-long coastline of the British Isles, are usually backed by cliffs of varying heights. They form in a range of material types from soft cohesive sediment to sedimentary and metamorphic rocks of varying strengths to very resistant igneous rocks. Lithology influences platform erosion rates: glacial till > London Clay > chalk > schist > limestone > basalt and granite. Chalk platform erosion rates adjacent to engineering structures are significantly higher than elsewhere on the platform. There are no published reports of erosion rates on British platforms developed in igneous rocks such as basalt and granite because they have proved too resistant to record values using a micro-erosion meter. The most intensively studied shore platforms in the British Isles are on Blue Lias limestone in south Wales and Cretaceous chalk in SE England and there is a need for more detailed studies on additional rock types, particularly for understanding key controls on platform morphology and rates of erosion. The issue of whether the shore platforms exposed at present day mean sea-level are inherited from earlier periods remains. The role of platform erosion in helping to drive cliff retreat is understudied and evidence that engineering structures may enhance platform erosion rates comes from only one rock type. Predicted climate change and sea-level rise scenarios combined with more intensive management of coastal systems mean that it is important to improve understanding of platform systems and their link to cliffs. There is much scope, using established and new methods of investigation, to address the issues raised by existing studies of shore platforms of the British Isles.</p
Observations on coastal biokarst, Hells Gate, Lord Howe Island, Australia
No full textMany studies of limestone coasts in the Tropics and sub-Tropics are concerned with intertidal form and process, neglecting the supra-tidal zone. Meso- and micromorphologies are described for a supratidal calcarenite coastal platform at Hells Gate, Lord Howe Island. Three morphological zones are identified and field and laboratory investigations elucidate their relation to process zonation. Pinnacles, similar to those described as phytokarst at other sub-tropical sites, are investigated and the role of biological processes in their formation is examined. Evidence for selective biodisintegration is presented. The pinnacles at Hells Gate cannot be described as phytokarst but have biokarstic properties. This study contributes to ongoing discussions on the role of biological weathering in coastal environments.</p
Field rock block exposure trials
No full textThe exposure of rock blocks to monitor environmental controls on rock weathering and erosion processes and rates has become an established technique in geomorphology. Such exposure trials using rock blocks, ranging in size from discs of diameter 20 mm and 5 mm thickness to large blocks of dimensions 200 mm x 200 mm x 200 mm, are used to examine weathering and erosion rates over a variety of different spatial and temporal scales. This paper discusses the original design and purpose of rock block exposures and the range of environments in which they have been used. Subsequent modifications of the original technique have been used to measure not just erosion rates, but also rates of accumulation of travertine, rates of solute uptake and to monitor rock surface temperature changes. Two examples are given of field trials in which weathering gradients have been determined using a range of rock block exposure types. Little research has been carried out to correlate weathering and erosion rates determined from rock tablet exposure and other techniques, though one study suggests that there is an order of magnitude difference between solution rates measured using this technique and water hardness methods. Rock blocks, however, are often used to give a more detailed picture of spatial and temporal variations in weathering and erosion rates that would otherwise be masked by such indirect mass balance approaches.</p
How to explain variations in sea cliff erosion rates? Insights from a literature synthesis
No full textChalk coast dynamics: Implications for understanding rock coast evolution
No full textRock cliffs and shore platforms are linked components of the world's coastal zone. Understanding of the dynamics of their relationships has been hindered by the often imperceptible changes that occur within human time scales. The Cretaceous Chalk coasts of northwest Europe, and particularly those of southeast England, are among the most dynamic, and most intensively studied, cliffed rock coasts in the world. Perceptible changes to both cliffs and platforms have been measured on monthly, seasonal, annual and decadal time scales. Through a review of previously published data and the addition of data not previously published, average cliff retreat rates are calculated as 0.49±0.38my-1 and platform erosion rates 3.999±3.208mmy-1. This paper highlights some of the interactions over time and space between process and measurement that continue to limit our understanding of the dynamics of rock coasts; in particular the link between rates of cliff retreat and platform erosion. It concludes by identifying fruitful areas for future research.</p
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Tropical rock coasts:Cliff, notch and platform erosion dynamics
No full textRock coasts are widespread in the tropics and exhibit particular morphologies that may be specific to their tropical, micro-tidal location. Notches are particularly well developed, often linked to onshore cliffs and fronted by subhorizontal platforms. Through a review of previously published data across the tropics, average cliff face erosion rates are calculated as 2.15 ± 2.62 mm a-1, intertidal erosion rates 3.03 ± 7.50 mm a-1 and subtidal erosion rates 0.96 ± 0.44 mm a-1. Intertidal erosion rates are variable within and across latitudinal ranges: within 10°N and S of the equator average rates are 1.42 ± 1.22 mm a-1; between latitudes of 10°and 20°, 0.88 ± 1.16 mm a-1 and between latitudes of 20°and 30°, 2.04 ± 2.57 mm a-1. A consideration of temporal variations in intertidal erosion rates provides insights into the potential impacts of climate change on the erosion dynamics of rock coasts in the tropics. This paper highlights some of the interactions over time and space between process and measurement that continue to limit our understanding of, and ability to model, the erosion dynamics of tropical rock coasts. It concludes by identifying potentially fruitful areas for future research.</p
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