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Abstract
This thesis presents the results of a beach monitoring program of the littoral between Chipiona and Rota, North of Cadiz Bay (SW Spain), in order to obtain a better knowledge of the natural dynamics of these environments. This is important to design adequate beach nourishment works or coastal structures to contrast coastal retreat.
Wave climate evolution during the study period was analyzed. Wave height, period and steepness have been obtained from the buoy “Sevilla 1”, located at 10 m water depth in front of Chipiona. The data have a great importance for the comprehension of morphological changes.
Historical evolution of the study littoral was reconstructed from previous works carried out through the analysis of aerial photographs of different years. Coastal dune and cliff retreat was also measured with a seasonal periodicity. Historical retreat rates have been obtained for different parts of the study area.
Beach evolution was assessed through a topographic monitoring program that was carried out with a monthly periodicity. Twelve topographic profiles were realized from the dry-beach to a closure dept equivalent with the low tide sea level. As a result, beach morphology was characterized and studied beaches were grouped into four classes: low reflective beaches, dissipative, low-tide terrace and rocky-shore beaches. The morphological monitoring program also allowed obtaining bar morphology and morphometry as well as spatial and temporal bar distribution. Through informatics applications, volumetric changes in beach sediments were calculated. Sediments were recollected in the beach and statistical parameters were calculated. Few temporal and spatial variations were observed.
To study small topographic changes that take place in beach face during a single tidal cycle, roods and plugs of coloured sand were inserted onto the beach surface. Tracers were used to evaluate longshore sediment transport. Great values of disturbance depth were observed in low reflective beaches while low values prevailed in dissipative beaches.
To describe and parameterize beach morphodynamics, several bibliographic parameters and indexes have been employed. These parameters are based on wave height, period and wave steepness and sediment grain size. The obtained parameters result quite useful to predict the beach morphodynamic state and agree very well with field observations.
Last but not lists, in order to explain the longshore distribution of beach states, several cases of wave propagation have been reconstructed. All these information allowed explaining the presence of littoral cells along study coast.