SUMMARY: Detailed topo-bathymetric levellings were performed biannually for four years at Victoria Beach (Cadiz, Spain) after a beach renourishment carried out in Spring 1991. The subsequent time series were analysed using the Empirical Orthogonal Functions (EOF) method. The evolution of some characteristic longshore contour lines, such as the Highest High Water Level and the Lowest Low Water Level, is studied. The mean coastal line is related to the first spatial EOF mode. Furthermore, an objective criterion for distinguishing between a generalised recession and cyclic accretion-erosion processes due to seasonal sea-swell changes is described, and a uniformly clockwise turn of the shoreline to minimise longshore transport is identified.

Con el fin de identificar y cuantificar los procesos que toman parte en la transmisión de energía entre el oleaje y las estructuras verticales de protección de puertos y costas, se ha analizado la literatura existente y se ha realizado ensayos de laboratorio sobre modelos a escala reducida. Como consecuencia, se ha desarrollado un nuevo método para el cálculo de las acciones del oleaje sobre los espaldones de los diques rompeolas. Dicho método es directamente aplicable onda a onda y al caso de oleaje, aceptando la hipótesis de equivalencia. Se ha aplicado el método a distintos espaldones, y se ha comparado con otros modelos y con ensayos de laboratorio, obteniéndose resultados satisfactorios. Las principales ventajas del método son que (1) es muy simple conceptualmente y en su aplicación, (2) da lugar a espaldones más pequeños y por lo tanto a proyectos más baratos y (3) tiene en cuenta el efecto de la berma del manto principal en las acciones sobre el espaldón.

<p>In hydrological modelling, the identification of hydrological model mechanisms best suited for representing individual hydrological (physical) processes is a major research and operational challenge. We present a statistical hypothesis-testing perspective to identify dominant hydrological mechanism. The method combines: (i) Bayesian estimation of posterior probabilities of individual mechanisms from a given ensemble of model structures; (ii) a test statistic that defines a “dominant” mechanism as a mechanism more probable than all its alternatives given observed data; (iii) a flexible modelling framework to generate model structures using combinations of available mechanisms. The uncertainty in the test statistic is approximated via bootstrap from the ensemble of model structures. Synthetic and real data experiments are conducted using 624 model structures from the hydrological modelling system FUSE and data from the Leizarán catchment in northern Spain. The findings show that the mechanism identification method is reliable: it identifies the correct mechanism as dominant in all synthetic trials where an identification is made. As data/model errors increase, statistical power (identifiability) decreases, manifesting as trials where no mechanism is identified as dominant. The real data case study results are broadly consistent with the synthetic analysis, with dominant mechanisms identified for 4 of 7 processes. Insights on which processes are most/least identifiable are also reported. The mechanism identification method is expected to contribute to broader community efforts on improving model identification and process representation in hydrology.</p>

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Abstract. A system of 15 small-scale finger bars has been observed, by using video imagery, between 23 June 2008 and 2 June 2010. The bar system is located in the intertidal zone of the swell-protected beaches of El Puntal Spit, in the Bay of Santander (Northern coast of Spain). It appears on a planar beach (slope = 1.5%) with fine uniform sand (D50 = 0 .27 mm) and extends 600 m alongshore. The cross-shore span of the bars is determined by the tidal horizontal excursion (between 70 and 130 m). They have an oblique orientation with respect to the low-tide shoreline being up-current oriented with respect to the ebb-flow (mean angle of 26° from the shore normal). Their mean wavelength is 26 m and their amplitude varies between 10 and 20 cm. The full system slowly migrates to the east (opposite to the ebb-flow) with a mean speed of 0.06 m day−1, a maximum speed in winter (up to 0.15 m day−1) and a minimum speed in summer. An episode of merging has been identified as bars with larger wavelength seem to migrate slower than shorter bars. Several forcings can act on the bar dynamics being the wind, blowing predominantly from the west, the main candidate to explain the eastward migration of the system. In particular, the wind can generate waves of up to 20 cm (root-mean-squared wave height) over a fetch that can reach 4.5 km at high tide. The astronomical tide seems to be important in the bar dynamics, as the tidal range conditions the mean (daily) fetch and also the time of exposure of the bars to the marine dynamics. Furthermore, the river discharges could act as input of suspended sediment in the bar system and play a role in the bar dynamics.