Scientia Marina, Vol 74, No 3 (2010)

Beach cusps and inner surf zone processes: growth or destruction? A case study of Trafalgar Beach (Cádiz, Spain)


https://doi.org/10.3989/scimar.2010.74n3539

Roland Garnier
Environmental Fluid Mechanics Research Centre, Process and Environmental Division, Faculty of Engineering, University of Nottingham - Instituto de Hidráulica Ambiental (IH), Universidad de Cantabria, E.T.S., United Kingdom

Miguel Ortega-Sánchez
Centro Andaluz de Medio Ambiente, Universidad de Granada, Spain

Miguel A. Losada
Centro Andaluz de Medio Ambiente, Universidad de Granada, Spain

Albert Falqués
Departament de Física Aplicada, Universitat Politècnica de Catalunya, Spain

Nicholas Dodd
Environmental Fluid Mechanics Research Centre, Process and Environmental Division, Faculty of Engineering, University of Nottingham, United Kingdom

Abstract


Large beach cusps (LBC, wavelength of ~ 30 m) are intertidal features that can alternately exist in the swash and in the inner surf zone due to tidal sea level changes. They have a larger cross-shore extent (up to 50 m) than traditional cusps. This extent has been explained by a shift of the swash zone during falling tide. The cusps immerse at rising tide and previous studies indicate that surf zone processes are exclusively destructive. Here, the behaviour of large beach cusps in the inner surf zone is investigated by using a 2DH morphological numerical model applied to Trafalgar Beach (Cádiz, Spain). The model results indicate that the inner surf zone processes do not always destroy the cusps but can in fact reinforce them by considering neither the swash processes nor the tidal changes. More generally, in conditions favouring the presence of the LBC the surf zone of a beach can be unstable, leading to the formation of transverse/oblique sand bars that can have characteristics similar to the LBC. Thus, in principle, the LBC could emerge not only due to swash zone morphodynamics but also due to surf zone morphodynamics or a combination of both.

Keywords


beach cusps; surf zone; sand bars; instability; beach morphology; beach features; rip currents; wave processes on beaches

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