Relation between beachface morphology and wave climate at Trafalgar beach (Cádiz, Spain) (original) (raw)
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Relation between beachface morphology and wave climate at Trafalgar beach (C�diz, Spain)
Geomorphology, 2008
Two years of offshore wave data and daily time exposure images from Trafalgar beach, a 2-km-long sandy beach located on the southwest coast of Spain that frequently exhibits rhythmic features, were used to (1) explore the variability of the beachface morphology and (2) determine environmental conditions associated with the different morphological states. The beachface morphology at three distinct alongshore sectors was analyzed and classified and five different morphological states were found that are related with the presence or absence of beach cusps and a berm: (1) large beach cusps, (2) small beach cusps, (3) low-tide terrace; (4) plane beach berm and (5) plane beach. The predominant beachface morphology is characterized by the presence of large beach cusps, and the main wave climate consisted of offshore significant wave heights ranging from 0.5-1 m and wave periods between 4 and 12 s. An alongshore variation of the morphology is found which might be related to the nearshore wave variability (SWAN wave model results). The morphologies are, in some cases, well-correlated with the daily offshore incident wave climate (described by the daily maximum significant wave height and the corresponding period), particularly for the moderate to high energy wave conditions. Small beach cusps appear under short period waves, whereas when the wave periods are longer the morphology tends to change to large beach cusps. This transition only occurs if the forcing is maintained as constant for a certain duration, which depends itself on the wave energy. It is concluded that correlations over 90% are only found for the highest wave energy conditions or under long wave periods. For the remainder, it is not possible to generally correlate the beachface morphology based only on the wave forcing because the previous morphological state cannot be ignored.
Morphodynamics of a wave dominated embayed beach on an irregular rocky coastline
Brazilian Journal of Oceanography
Wave-dominated embayed beaches on irregular rocky coastlines are highly appreciated for their landscapes and tourism potential. Yet our understanding about the interaction of the oceanographic processes with the geological inheritance in this type of beaches still needs further investigation to better understand their natural balance. In this study, we apply the classical approach of morphodynamics to describe for the first time the variations in the Boiçucanga beach morphology, an embayed beach located in São Sebastião City on an irregular rocky coastline that is well known for its beautiful beaches embedded in the valleys of Serra do Mar. Field surveys were performed over 15 months, between April 2008 and September 2009, seeking to evaluate the interactions among the morphology, sediments and hydrodynamic characteristics at Boiçucanga. All data generated during the field surveys have supported the application of the following morphodynamic models: Classification of morphological b...
Journal of Coastal …, 2003
We present a morphodynamic study of an apparently homogeneous rectilinear coast in SW Spain. The study area covers 14 km of mesotidal sandy beaches, interrupted in some places by rocky-shore platforms. The method used consisted of a monthly monitoring of 12 beach profiles during two years. According to the results obtained from the study, which also include granulometric analyses and in situ determination of the beach disturbance depth, three main beach classes have been differentiated: low-reflective beaches, dissipative beaches and rocky-shore platform beaches. Their longitudinal distribution is not linked to their distance to the main source of sediments in the area (mouth of the river Guadalquivir). Instead, a very irregular long-shore variation of morphodynamic beach states appears. It is deduced that this long-shore variation is mainly linked to local contouring conditions (e.g. the presence of rocky shoals which affect wave-breaking processes), and not to the regional long-shore currents prevailing in the zone.
Wave Power and Beach-Stages: A Global Model
Coastal Engineering Proceedings, 1978
A three-dimensional morphodynamic model of sequential beach changes Is presented. The model Is based on variations in breaker wave power generating a predictable sequence of beach conditions. The spectrum of beach conditions from fully eroded-dissipatlve to fully accreted reflective is characterised by ten beach-stages. Using the breaker wave power to beach-stage relationship the model Is applied to explain temporal, spatial and global variations In beach morphodynamlcs.
Beach Morphodynamics and Profile Sequence for a Headland Bay Coast
2001
This paper presents a sequence of beach profile for a headlands and bay coast. Shape analyses of the embayed beach, identification of the predominant wave direction, beach and nearshore profiles, sedimentology characteristics, hydrodynamic conditions at the beaches, morphodynamics and morphometric data for 17 beaches on central-north coast of Santa Catarina, Brazil, were obtained. Beaches are classified in three main groups: (1) exposed; (2) semi-exposed; and (3) sheltered. The exposed beaches had an indentation ratio smaller than 0.39 and the dominant south waves are approximately parallel to the coast (angle smaller than 40°). The beaches can be divided into three mainly groups. (a) Reflective beaches have coarse sand (0.59mm-0.94mm) and steeper nearshore slope (1:40) associated with a very narrow coastal plain <1Km). (b) Intermediate beaches with one nearshore bar have medium sand (0.30mm-0.45mm) and gentle nearshore slope (1:100-1:200) and a developed coastal plain-island bar...
Morphodynamic classification of sandy beaches in
2007
Morphodynamic classification of beaches has achieved widespread acceptance in both geological and geomorphological literature. In this sense, the present work classifies twelve Mediterranean low energetic beaches according to the dimensionless fall parameter (Ω) parameter in the Island of Mallorca. Propagation of 44 years of wave data as well as a detailed sediment study allows to provide probabilities for morphodynamical beach state on annual and seasonal basis. Consequently, beaches in Mallorca fall between three major categories which are (a) truly reflective, (b) reflective skewed to intermediate and (c) intermediate beaches. The mallorcan beach position in the morphodynamical scheme is close related to the physiographical and geological framework. Comparison of observed values with those obtained in the analysis leads that for gross beach classification there is agreement between predicted and real state. However on a seasonal classification, mainly during summer, there is no agreement between the predicted state and the real one. As the model does not incorporate the role of summer sea breezes, beach reflective states are highlighted. Real beach configurations correspond to more energetic wave dynamic conditions and to intermediate state scenarios.
Coastal Dynamics 2005, 2006
This contribution presents the results of intensive field surveys executed during late spring and summer 2004 along two pocket beaches located in the northwestern and eastern coast of the Faial island (Azores archipelago, Portugal). The main purpose of this study was to characterize the morphodynamics of these two beaches by associating the short-term evolution of a couple of beach profiles, monitored on a fortnight basis, with the wave climate and wave refraction model output. Study shows that both these beaches are undergoing rapid and significant phases of accretion/erosion during summer time in relation with growing sea state. Also, fast beach rotation has been noted. Although these two beaches are located to the west and to the east of the island and despite the prominence of westward waves and winds, their evolution appears simultaneous. This manuscript constitutes the first step towards achieving a comprehensive understanding of beach morphodynamics in the Azores.
Geological control of beach morphodynamic state
Marine Geology, 2005
The concept of beach morphodynamic states has achieved widespread acceptance in the coastal geological literature since its inception in the mid-1980s and expansion in the 1990s. Much of the pioneering work was undertaken in Australia under a range of environmental conditions in microtidal environments and a close empirical relationship between beach 3-dimensional morphology and the Dean's parameter (H b /W s T) was established. Subsequently, the Relative Tidal Range parameter (H b /TR) was extended to beaches of all tidal ranges.
Morphodynamic variability of surf zones and beaches: A synthesis
Marine Geology, 1984
A synthesis of some results obtained over the period 1979-1982 from a study of beach and surf zone dynamics is presented. The paper deals with the different natural beach states, the process signatures associated with these states, environmental controls on modal beach state, and the temporal variability of beach state and beach profiles. Hydrodynamic processes and the relative contributions of different mechanisms to sediment transport and morphologic change differ dramatically as functions of beach state, that is depending on whether the surf zone and beach are reflective, dissipative or in one of several intermediate states. Depending on beach state, near bottom currents show variations in the relative dominance of motions due to: incident waves, subharmonic oscillations, infragravity oscillations, and mean longshore and rip currents. On reflective beaches, incident waves and subharmonic edge waves are dominant. In highly dissipative surf zones, shoreward decay of incident waves is accompanied by shoreward growth of infragravity energy; in the inner surf zone, currents associated with infragravity standing waves dominate. On intermediate states with pronounced bar-trough (straight or crescentic) topographies, incident wave orbital velocities are generally dominant but significant roles are also played by subharmonic and infragravity standing waves, longshore currents, and rips. The strongest rips and associated feeder currents occur in association with intermediate transverse bar and rip topographies. Long-term consecutive surveys of different beaches with contrasting local environmental conditions provide the data sets for empirical-statistical assessment of beach mobility, direction of change and response to environmental conditions. Conditions of persistently high wave energy combined with abundant and/or fine grained sediment results in maintaining highly dissipative states which exhibit very low mobility. Relatively low mobility is also associated with persistently low-steepness waves acting on coarsegrained beach sediments. In such cases, the modal beach state is reflective. The greatest degree of mobility is associated with intermediate but highly changeable wave conditions, medium grained sediment and a modest or meager sediment supply. Under such conditions, the beach and surf zone tend to alternate among the intermediate states and to exhibit well-developed bar trough and rhythmic topographies. A good association is *Contribution No. 1135 from the Virginia Institute of Marine Science.
Marine Geology, 2008
Morphodynamic classification of sandy beaches in low energetic marine environment. Mar. Geol. 242, pp. 235-246] used the Wright and Short beach classification scheme fed with hindcasted wave and sediment settling velocity data to classify the morphodynamic states of a group of lowenergy Mediterranean beaches (Mallorca, Spain). Here, we use morphodynamic data obtained from an Argus video station and a morphodynamic model to assess the validity of this type of model for predicting beach states under typical Mediterranean wave conditions. The results show that Ω-values alone do not provide a realistic prediction of beach states statistics and that the intensity of the forcing, represented by the wave energy level and the duration of the events, must also be taken into account.