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Abstract: Victoria Beach (Cadiz, Spain) comprises a rocky flat outcrop in its northern zone and a sand-rich southern zone. These natural features allowed for a 5-year monitoring period and subsequent analysis of two different profiles (one in each zone) based on differences in bottom contours. Topo-bathymetric data were analysed using empirical orthogonal functions (EOFs) to determine changes over the short-, medium- and long-term. Several morphologic phenomena were identified (generalised erosion, seasonal or summer?winter tilting of the profile around different hinge points, berm development and its posterior destruction, etc.) in terms of their importance in explaining the variability of the collected data for both profiles. It is worth mentioning that both profiles undergo parallel regression in the medium-term. Thus, the 1st eigenfunction enabled us to identify the true regression of the beach shoreline, independent of seasonal or summer?winter slope changes. Reconstruction of profiles using EOF components demonstrated that though accretion periods in the medium-term were similar for both types of profiles, the accretion speed was much faster in the sand-rich profile than in the reef-protected profile (1.01 m3/day versus 0.33 m3/day). Moreover, the seasonal erosion rate and the subsequent shoreline retreat for the sand-rich profile were much larger than for the reef-protected profile (121 m3/year versus 29 m3/year). Analysis in the short-term (changes induced by a single day's storm) showed an instantaneous tilting of the profile, with the mobilised sand volume being much greater for the sand-rich than for the reef-protected profile (68 m3/m versus 12 m3/m).
In brief, we can assume that the wave energy attenuation provoked by the existence of a reef flat acted as a geological control for profile evolution, which is essentially different for both profiles. Among the most important differences, special attention should be given to the larger slope, smaller mobilised sand volume and slower accretion rate of the reef-flat profile versus the non-protected profile.
Autoría: Muñoz-Perez J.J., Medina R.,
Fuente: Coastal Engineering 2010, 57(3), 241-251
Fecha de publicación: 01/03/2010
Nº de páginas: 11
Tipo de publicación: Artículo de Revista
Proyecto español: REN2003-9640/MAR.
Url de la publicación: https://doi.org/10.1016/j.coastaleng.2009.09.011
JUAN JOSE MUÑOZ PEREZ
RAUL MEDINA SANTAMARIA