Peer ReviewedPostprint (published version

Calvete Manrique, Daniel

de Swart, Huib E.

Dodd, Nicholas

Falqués Serra, Albert

Garnier, Roland Charles

Ribas Prats, Francesca

English

UPCommons. Portal del coneixement obert de la UPC

CONFERENCE ON MATHEMATICAL GEOPHYSICS 2016 06-10 JUNE, PARIS, FRANCEON THE PHYSICS BEHIND COASTAL MORPHODYNAMIC PATTERNSF. Ribas1, A. Falqués1, H. E. de Swart2, N. Dodd3, R. Garnier4 & D. Calvete11Department of Physics, Universitat Politècnica de Catalunya, Barcelona, Spain2Institute for Marine and Atmospheric research Utrecht, Utrecht University, Utrecht, the Netherlands3Faculty of Engineering, University of Nottingham, Nottingham, UK4Instituto de Hidráulica Ambiental Cantabria, Universidad de Cantabria, Santander, SpainKey words coastal morphodynamic patterns, nearshore sand bars, beach cusps, sand ridges, sediment transport, self-organizationThe focus of this contribution is to understand the physical processes behind the development of a number ofcoastal morphodynamic features that have an alongshore rhythmic pattern: beach cusps, surf zone transverse andcrescentic bars, and shoreface-connected sand ridges. We will present a formulation and methodology, based on theknowledge of the depth-averaged currents and the depth-averaged sediment concentration (DASC, which equals thesediment load divided by the water depth), that has been successfully used to understand the characteristics of thesefeatures ([1] and references therein). These sand bodies, relevant for coastal engineering and other disciplines, arelocated in different parts of the coastal zone and are characterized by different spatial and temporal scales (Figure1) but the same technique can be used to understand them. Since they occur in the presence of depth-averagedcurrents, the sediment transport approximately equals a sediment load times the current. Moreover, it is assumedthat waves essentially mobilize the sediment, and the current increases this mobilization and advects the sediment.In such conditions, knowing the spatial distribution of the DASC and the depth-averaged currents induced bythe forcing (waves, wind, and pressure gradients) over the patterns allows inferring the convergence/divergenceof sediment transport. Deposition (erosion) occurs where the current flows from areas of high to low (low tohigh) values of DASC. The formulation and methodology are especially useful to understand the positive feedbackmechanisms between flow and morphology leading to the formation of those morphological features, but thephysical mechanisms for their migration, their finite-amplitude behavior and their decay can also be explored.Figure 1. Illustration of the (a) incoming waves, (b) depth-averaged sediment concentration profile (DASC), and (c) bed levelon the coastal zone. (d) Satellite image of the coastal zone in front of Duck, North Carolina, USA. Superimposed to it, examplesof (e) beach cusps, (f ) surf zone transverse and (g) crescentic bars, and (h) shoreface-connected sand ridges. Figure from [1].References[1] Ribas, F., A. Falqués, H. E. de Swart, N. Dodd, R. Garnier & D. Calvete (2015), Understanding coastal morphodynamic patterns fromdepth-averaged sediment concentration, Rev. Geophys. 53, 362–410, doi:10.1002/2014RG000457.

On the physics behind coastal morphodynamic patterns

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https://upcommons.upc.edu/bitstream/2117/103092/1/2016_CMG_ribas_abstract.pdf

On the physics behind coastal morphodynamic patterns

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