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Título:
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Self-organization mechanisms for the formation on nearshore crescentic and transverse sand bars
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Autor/a:
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Caballeria, Miquel; Coco, G.; Falqués, Albert; Huntley, D.A.
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Otros autores:
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Universitat de Vic. Escola Politècnica Superior; Universitat de Vic. Grup de Recerca de Medi Ambient |
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Notas:
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The formation and development of transverse and crescentic sand bars in the coastal
marine environment has been investigated by means of a nonlinear numerical model
based on the shallow-water equations and on a simpli ed sediment transport parameterization.
By assuming normally approaching waves and a saturated surf zone,
rhythmic patterns develop from a planar slope where random perturbations of
small amplitude have been superimposed. Two types of bedforms appear: one is a
crescentic bar pattern centred around the breakpoint and the other, herein modelled
for the rst time, is a transverse bar pattern. The feedback mechanism related to the
formation and development of the patterns can be explained by coupling the water
and sediment conservation equations. Basically, the waves stir up the sediment and
keep it in suspension with a certain cross-shore distribution of depth-averaged concentration.
Then, a current flowing with (against) the gradient of sediment concentration
produces erosion (deposition). It is shown that inside the surf zone, these currents
may occur due to the wave refraction and to the redistribution of wave breaking
produced by the growing bedforms. Numerical simulations have been performed in
order to understand the sensitivity of the pattern formation to the parameterization
and to relate the hydro-morphodynamic input conditions to which of the patterns
develops. It is suggested that crescentic bar growth would be favoured by high-energy
conditions and ne sediment while transverse bars would grow for milder waves and
coarser sediment. In intermediate conditions mixed patterns may occur. |
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Materia(s):
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-Hidràulica
-Mecànica de fluïds |
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Derechos:
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(c) Cambridge University Press
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Tipo de documento:
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Artículo
Artículo - Versión publicada |
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Editor:
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Cambridge University Press
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Compartir:
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