Shore platform downwearing in eastern Canada: Micro-tidal Gaspé, Québec

Porter, Neil J.; Trenhaile, Alan S.; Prestanski, Kyle J.; Kanyaya, Jacob I.

doi:10.1016/j.geomorph.2009.10.010

Cited by 52 publications

(25 citation statements)

References 29 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Porter et al (2010a) concluded that there was no apparent relationship between downwearing rates and elevation at Scots Bay or Burntcoat Head, but this was not tested statistically nor were trends analysed within the upper, central and lower portions of the intertidal zone. Porter et al (2010b) found no relationship between downwearing rates and elevation at Mont Louis, where the platform surface is irregular but essentially quasi-horizontal.…”

Section: Introductionmentioning

confidence: 77%

“…Rates of downwearing for the argillaceous rocks on the upper intertidal shore platform at Mont Louis are faster, for approximately the same elevations, than in the sea water experiments. This has been attributed to weaker rocks having been selected for the experiments than the harder outcrops on which most of the TMEMs were installed (Porter et al, 2010b).…”

Section: Discussionmentioning

confidence: 99%

“…The other three study sites were in the micro-to mesotidal St Lawrence Estuary and Gulf of St Lawrence (Figures 1 and 2, and Figure 5 in Porter et al, 2010b) The subhorizontal shore platform at Mont Louis consists primarily of Ordovician siltstones, mudstones, and shales (Enos, 1969;Trenhaile et al, 2006;Porter et al 2010b). The platform is from about 140 to 180 m in width, and it is at an elevation at, or slightly above, the mid-tidal level.…”

Section: The Study Areasmentioning

confidence: 99%

See 2 more Smart Citations

Patterns of surface downwearing on shore platforms in eastern Canada

Porter

Trenhaile

Prestanski

et al. 2010

Earth Surf Processes Landf

Self Cite

View full text Add to dashboard Cite

Downwearing rates were measured on shore platforms at about 200 transverse micro-erosion meter (TMEM) stations, over periods ranging from 2 to 6 years. There were seven study areas in eastern Canada. The platforms were surveyed and a Schmidt Rock Test Hammer was used to measure rock hardness. More than 1200 rock samples from three of the study areas were also subjected each day, over a 3 year period, to two tidal cycles of immersion and exposure, which simulated the central intertidal zone. A further 840 samples were subjected to longer periods of exposure and immersion, over a 1 year period, which represented different elevations within the upper and lower intertidal zone, respectively. These experiments suggested that tidally generated weathering and debris removal is an effective erosional mechanism, particularly at the elevation of the lowest high tides. In the fi eld, mean rates of downwearing for each study area ranged from 0·24 mm yr −1 to more than 1·5 mm yr . Rates tended to increase with elevation in the fi eld, with maxima in the upper intertidal zone. This trend in the fi eld cannot be attributed entirely to the tidally induced weathering processes that were simulated in the laboratory, and must refl ect, in part, the effect of waves, frost, ice, and other mechanisms. It is concluded that there are no strong spatial downwearing patterns on shore platforms, and that downwearing rates in the intertidal zone are the result of a number of erosional mechanisms with different elevationeffi cacy characteristics. Furthermore, even if only one or two mechanisms were dominant in an area, any resulting relationship between downwearing rates and elevation would be obscured or eliminated by the effect of variations in the chemical and physical characteristics of the rocks.

show abstract

Section: Introductionmentioning

confidence: 77%

Section: Discussionmentioning

confidence: 99%

Section: The Study Areasmentioning

confidence: 99%

See 1 more Smart Citation

Patterns of surface downwearing on shore platforms in eastern Canada

Porter

Trenhaile

Prestanski

et al. 2010

Earth Surf Processes Landf

Self Cite

View full text Add to dashboard Cite

show abstract

“…This model is constructed on the premise that the lithology is so vulnerable to abrasive processes and subaerial weathering that the platform surface is easily lowered (e.g. Porter et al 2010). This facilitates wave propagation across the platform, allowing for waves to attack the landward cliff and cause erosion.…”

Section: Rocky Coast Evolution Models Under Uplift Conditionsmentioning

confidence: 99%

Chapter 12 The rock coast of Japan

Sunamura¹,

Tsujimoto

Aoki

2014

Memoirs

View full text Add to dashboard Cite

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.

show abstract

“…This is represented as a positive link between intertidal exposure time and weathering rate. Downwearing of the intertidal platform, in the absence of abrasive material and bioerosional organisms, has been attributed generally to weathering and removal of the fine-grained debris by waves (Porter et al 2010). Most of the mechanical downwearing of the submerged platform is due to breaking waves, the downwearing erosion rate has been often conceptualized as a decaying function of water depth (Sunamura 1992;Trenhaile 2005).…”

Section: Feedback Loop Structure Of Cliff Dynamicsmentioning

confidence: 99%

Feedback structure of cliff and shore platform morphodynamics

Payo

Dickson

Walkden³

2014

J Coast Conserv

View full text Add to dashboard Cite

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.

show abstract

Shore platform downwearing in eastern Canada: Micro-tidal Gaspé, Québec

Cited by 52 publications

References 29 publications

Patterns of surface downwearing on shore platforms in eastern Canada

Patterns of surface downwearing on shore platforms in eastern Canada

Chapter 12 The rock coast of Japan

Feedback structure of cliff and shore platform morphodynamics

Contact Info

Product

Resources

About