On the diffusivity in coastline dynamics

Falqués, Albert

doi:10.1029/2003gl017760

Cited by 51 publications

(60 citation statements)

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“…The diffusivity is positive provided that the angle between wave fronts and the coastline at breaking is smaller than 45-. Since this is typically the case because of the refraction of the waves as they approach the coast, the diffusivity in this model is always positive (Falqués, 2003;Falqués and Calvete, 2005). This has the important implication that the rectilinear coastline is stable, any perturbation tending to diffuse away.…”

Section: Introductionmentioning

confidence: 95%

Wave driven alongshore sediment transport and stability of the Dutch coastline

Falqués

2006

Coastal Engineering

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Section: Introductionmentioning

confidence: 95%

Wave driven alongshore sediment transport and stability of the Dutch coastline

Falqués

2006

Coastal Engineering

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“…As a consequence, the correct formulation for shoreline evolution includes a diffusivity that changes magnitude and sign as wave angle changes Murray, 2006a, 2006b;Ashton et al, 2001;Falqués, 2003]. This shoreline diffusivity is positive when wave angles are smaller than the maximum in alongshore sediment transport (tending to smooth the coast) and negative for larger angles (meaning a straight shoreline configuration would be unstable) (Figure 2a).…”

Section: Introductionmentioning

confidence: 99%

Wave-angle control of delta evolution

Ashton

Giosan

2011

Geophys. Res. Lett.

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[1] Wave-influenced deltas, with large-scale arcuate shapes and demarcated beach ridge complexes, often display an asymmetrical form about their river channel. Here, we use a numerical model to demonstrate that the angles from which waves approach a delta can have a first-order influence upon its plan-view morphologic evolution and sedimentary architecture. The directional spread of incoming waves plays a dominant role over fluvial sediment discharge in controlling the width of an active delta lobe, which in turn affects the characteristic rates of delta progradation. Oblique wave approach (and a consequent net alongshore sediment transport) can lead to the development of morphologic asymmetry about the river in a delta's plan-view form. This plan-form asymmetry can include the development of discrete breaks in shoreline orientation and the appearance of selforganized features arising from shoreline instability along the downdrift delta flank, such as spits and migrating shoreline sand waves-features observed on natural deltas. Somewhat surprisingly, waves approaching preferentially from one direction tend to increase sediment deposition updrift of the river. This 'morphodynamic groin effect' occurs when the delta's plan-form aspect ratio is sufficiently large such that the orientation of the shoreline on the downdrift flank is rotated past the angle of maximum alongshore sediment transport, resulting in preferential redirection of fluvial sediment updrift of the river mouth.

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“…In addition, changes in shoreline shape that occur on time scales shorter than the characteristic time for the whole shoreface to respond will not necessarily be reflected in the contours on the deeper portions of the shoreface. To address the evolution of shoreline features on these smaller time and space scales, wave transformation over contours that do not reflect the shoreline shapes of interest needs to be considered [5,6,28]. For example, the smaller the alongshore scales of a coastline undulation, and the shallower the undulations affecting the seabed (and the longer the wave period), the greater the dominance of high-angle waves at the offshore extent of the shoreface needs to be to cause the high-angle coastline instability [7,11].…”

Section: Discussionmentioning

confidence: 99%

Instability and finite-amplitude self-organization of large-scale coastline shapes

Murray

Ashton

2013

Phil. Trans. R. Soc. A.

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Recent research addresses the formation of patterns on sandy coastlines on alongshore scales that are large compared with the cross-shore extent of active sediment transport. A simple morphodynamic instability arises from the feedback between wave-driven alongshore sediment flux and coastline shape. Coastline segments with different orientations experience different alongshore sediment fluxes, so that curvatures in coastline shape drive gradients in sediment flux, which can augment the shoreline curvatures. In a simple numerical model, this instability, and subsequent finite-amplitude interactions between pattern elements, lead to a wide range of different rhythmic shapes and behaviours—ranging from symmetric cuspate capes and bays to alongshore migrating ‘flying spits’—depending on the characteristics of the input wave forcing. The scale of the pattern coarsens in some cases because of the merger of migrating coastline features, and in other cases because of non-local screening interactions between coastline protrusions, which affect the waves reaching other parts of the coastline. Features growing on opposite sides of an enclosed water body mutually affect the waves reaching each other in ways that lead to the segmentation of elongated water bodies. Initial tests of model predictions and comparison with observations suggest that modes of pattern formation in the model are relevant in nature.

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On the diffusivity in coastline dynamics

Cited by 51 publications

References 7 publications

Wave driven alongshore sediment transport and stability of the Dutch coastline

Wave driven alongshore sediment transport and stability of the Dutch coastline

Wave-angle control of delta evolution

Instability and finite-amplitude self-organization of large-scale coastline shapes

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