Modeling cyclic recession of cohesive clay coasts: Effects of wave erosion and bluff stability

Castedo, Ricardo; Fernández, Marta; Trenhaile, Alan S.; Paredes, Carlos

doi:10.1016/j.margeo.2012.11.001

Cited by 51 publications

(39 citation statements)

References 47 publications

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“…In spite of the difficulties of acquiring geotechnical data accurate enough to be representative of the strength variations of the rock masses that compose the cliffs, approaches have been made using physically based slope stability evaluation methods, including different types of cliff instability (e.g. Fall et al, 2006), or specifically for cliffs mainly composed of clays (Castedo et al, 2013). One of the most common shortcomings of these approaches lies in the limited or absent validation of results using standard methods.…”

Section: F M S F Marques Et Al: Sea Cliff Instability Susceptibimentioning

confidence: 99%

Sea cliff instability susceptibility at regional scale: a statistically based assessment in the southern Algarve, Portugal

Marques

Matildes

Redweik

2013

Nat. Hazards Earth Syst. Sci.

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Abstract. Sea cliff evolution is dominated by the occurrence of slope mass movements of different types and sizes, which are a considerable source of natural hazard, making their assessment a relevant issue in terms of human loss prevention and land use regulations. To address the assessment of the spatial component of sea cliff hazards, i.e. the susceptibility, a statistically based study was made to assess the capacity of a set of conditioning factors to express the occurrence of sea cliff failures affecting areas located along their top.The study was based on the application of the bivariate information value and multivariate logistic regression statistical methods, using a set of predisposing factors for cliff failures, mainly related to geology (lithology, bedding dip, faults) and geomorphology (maximum and mean slope, height, aspect, plan curvature, toe protection), which were correlated with a photogrammetry-based inventory of cliff failures that occurred in a 60 yr period . The susceptibility models were validated against the inventory data using standard success rate and ROC curves, and provided encouraging results, indicating that the proposed approaches are effective for susceptibility assessment. The results obtained also stress the need for improvement of the predisposing factors to be used in this type of study and the need for detailed and systematic cliff failure inventories.

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Section: F M S F Marques Et Al: Sea Cliff Instability Susceptibimentioning

confidence: 99%

Sea cliff instability susceptibility at regional scale: a statistically based assessment in the southern Algarve, Portugal

Marques

Matildes

Redweik

2013

Nat. Hazards Earth Syst. Sci.

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“…Fine sediment eroded from the cliff and platform may be removed from the system as suspended sediment, whereas beach-grade sediment may be deposited at the cliff toe. Beach sediments might impede direct wave attack, reducing backwearing rates, and cover the shore platform reducing downwearing rates (Castedo et al 2012;Trenhaile 2005;Walkden and Hall 2005). & Abrasion enhancement loop.…”

Section: Feedback Loop Structure Of Cliff Dynamicsmentioning

confidence: 99%

“…& Feedback loop between pore pressure release and backwearing erosion rate. The build-up and release of pore pressure has been identified (measured and modelled) as a balancing feedback of backwearing rate (Castedo et al 2012;Fort et al 2000). The associated zone of depressed pore pressure to cliff backwearing prevents the pore pressure build-up over time.…”

Section: Feedback Loop Structure Of Cliff Dynamicsmentioning

confidence: 99%

“…The influence of the debris at the toe of the cliff on the backwearing erosion rate is lately included within the overall feedback loop structure. The rainfall accumulated as groundwater increases the pore pressure eventually triggering the shear failure of the cliff (Castedo et al 2012). Fort et al (2000) found that the associated unloading resulted in a zone of the depressed pore pressures which temporarily prevent deep-seated instability of the oversteepened cliff.…”

Section: Feedback Loop Structure Of Cliff Dynamicsmentioning

confidence: 99%

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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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“…Physically-based slope stability methods have also been applied, in spite of the difficulties involved in the acquisition of geotechnical data of the cliffs rock masses (e.g., [7,21,22]), for cliffs mainly composed of clays [23], or cliffs made of fairly homogeneous and weak rock masses as chalk [24]. However, in spite of the amount of work and diversity of data acquisition techniques used in these studies, there is limited or absent validation of their results with actual cliff failures inventories.…”

Section: Introductionmentioning

confidence: 99%

Regional Scale Sea Cliff Hazard Assessment at Sintra and Cascais Counties, Western Coast of Portugal

Marques

2018

Geosciences

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Abstract:Mass movements of different types and sizes are the main processes of sea cliff evolution, being a considerable natural hazard, the assessment of which is a relevant issue in terms of human loss prevention and land use regulations. To predict the occurrence of future failures affecting the cliff top in slow retreating cliffs, a study was made using the logistic regression statistical method, a set of predisposing factors mainly related with geology (lithology, structure, faults), geomorphology (maximum, mean and standard variation of slope angle, height, aspect, curvatures, toe protection) and near offshore mean annual wave power, which were correlated with an aerial photo interpretation based inventory of cliff failures occurred in a 63 years period ). The susceptibility model was validated against the inventory data using standard Receiver Operator Curves, which provided area under the curve (AUC) values higher than 0.8. In spite of the room for improvement of cliff failure inventories and predisposing factors to be used in these types of studies, namely those related to the rock mass strength and wave power nearshore, the results obtained indicate that the proposed approach is an effective contribution for objective and quantitative hazard assessment.

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Modeling cyclic recession of cohesive clay coasts: Effects of wave erosion and bluff stability

Cited by 51 publications

References 47 publications

Sea cliff instability susceptibility at regional scale: a statistically based assessment in the southern Algarve, Portugal

Sea cliff instability susceptibility at regional scale: a statistically based assessment in the southern Algarve, Portugal

Feedback structure of cliff and shore platform morphodynamics

Regional Scale Sea Cliff Hazard Assessment at Sintra and Cascais Counties, Western Coast of Portugal

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